Electrophoretic Display and Driving Method Thereof

Abstract

The present invention relates to a color electrophoretic display device and a driving method thereof, and aims to reduce manufacturing costs by simplifying the design of the driving circuit while simultaneously improving image reliability such as color uniformity, afterimage characteristics, and durability. A driving method for an electrophoretic display according to the present invention comprises: (a) applying and maintaining a constant non-zero bias voltage to all of a plurality of pixel electrodes; (b) applying a non-periodic activation waveform including a high-frequency micro-vibration section to a common electrode while the bias voltage is maintained to initialize all pixels to a uniform intermediate color state; and (c) maintaining the common electrode at a stable reference potential while changing the voltage of each pixel electrode from the bias voltage to a voltage required for a target color to form a final image. This driving method ensures screen uniformity by stably maintaining a large-area common electrode, prevents particle sticking with an optimized activation waveform, and improves low-temperature driving stability and response speed through a constant bias voltage.

Description

Technology Field

[0001] The present invention relates to the field of electronic display device technology, and more specifically, to a driving method for an electrophoretic display (EPD) device that displays an image by reflecting an external light source and has low power consumption. Background Technology

[0002] An Electrophoretic Display (EPD) is a reflective display device that displays images by moving charged particles dispersed within a fluid in response to an external electric field. These devices do not require a separate backlight, resulting in very low power consumption; they also provide visibility similar to printed materials and feature bistability, which maintains the screen even when the power supply is cut off. Due to these advantages, electrophoretic displays are widely used in various fields, such as e-book readers, electronic shelf labels (ESL), and digital signage.

[0003] Beyond early monochrome electrophoretic displays, active technological development is currently underway to realize full color by including various color particles, such as red and yellow, in addition to black and white. However, color electrophoretic displays containing multiple color particles require very complex and precise driving waveforms to accurately express desired colors because the charge, size, and mobility of each particle differ. This complicates the design of driver ICs and thin-film transistor (TFT) backplanes that drive the display panel and increases manufacturing costs by requiring support for multiple voltage levels.

[0004] As a prior art for solving these problems, U.S. Patent No. 7,012,600 (hereinafter the "600 patent") discloses a driving method for an electrophoretic display. The "600 patent" includes a reset or erasing step in which, before displaying a new image, all pixels are forcibly driven repeatedly into an all-black state and an all-white state multiple times to remove ghosting from the previous image and prevent stiction of particles. This method is relevant to improving the quality of subsequent images by uniformly initializing the physical state of the particles. However, this black / white repeated driving has the problem of causing visual discomfort due to the entire screen flickering, increasing the driving time, and not being optimized for efficiently initializing to a specific intermediate color state required in color displays.

[0005] Meanwhile, U.S. Patent No. 7,119,772 (hereinafter the "772 patent") discloses a technology for controlling the common electrode (Vcom) of an electrophoretic display. The "772 patent" enables more precise grayscale control by actively modulating the common electrode along with the voltage of the pixel electrode, instead of simply using the common electrode as a fixed reference potential such as ground. This is relevant to the present invention in that it demonstrates that the common electrode can play an active role in driving the display. However, the common electrode modulation of the "772 patent" is limited to the individual pixel addressing step that forms the final image and is not intended for global priming, which puts all pixels into a specific state simultaneously prior to driving. Therefore, there are still limitations in simplifying complex driving circuits.

[0006] As a more advanced technology to solve the above problems, U.S. Patent No. 10,254,619 and its divisional application, U.S. Patent No. 10,901,287 (hereinafter referred to as the "287 patent"), propose a new driving method for simplifying the driving circuit of a color display device. The core of the "287 patent" lies in a two-stage driving method. In the first stage, all pixels are initialized simultaneously to a specific intermediate color state (e.g., red or yellow) by applying a specific voltage only to the common electrode while the voltage of all pixel electrodes is fixed at 0V (ground). In the second stage, conversely, the common electrode is fixed at 0V, and then individual voltages are applied to each pixel electrode to achieve the final target color. Since the common electrode handles all driving in the first stage, this method reduces the number of voltage levels that the driver IC driving the pixel electrodes must support, thereby simplifying circuit design and reducing costs.

[0007] However, the driving method of the aforementioned '287 patent' contains the following potential problems. First, rapidly varying the voltage of a large common electrode in the first stage can cause voltage drop (IR drop) or signal distortion, particularly in large-area displays, thereby impairing color uniformity across the entire screen. In terms of electrical stability, it is desirable to maintain the common electrode at a stable reference potential as much as possible. Second, since a specific driving sequence of "pixel electrode non-application, common electrode modulation" is protected by a patent, a new driving method capable of circumventing the scope of such rights is required to achieve the same objective. Therefore, there is a need to develop a new driving technology that can secure the stability of the common electrode, circumvent existing patents, and further improve image quality by increasing particle control efficiency, while maintaining the advantages of conventional technology such as simplified driving circuits and cost reduction. Prior art literature

[0008] 1. US 10,901,287 B22. US 7,012,600 B23. US 7,119,772 B24. US 10,254,619 B2 The problem to be solved

[0009] Electrophoretic displays are display devices that create pixels by moving charged particles of different colors according to an electric field. Thanks to visual characteristics similar to paper and bistability—which allows the screen to remain visible even when the power supply is interrupted—these displays are widely applied in various fields, such as e-readers, electronic shelf labels (ESL), and digital signage.

[0010] In particular, color electrophoretic displays, which implement various colors beyond monochrome displays, have the technical complexity of requiring precise control of multiple color particles with different charge amounts and mobility characteristics. Previously, complex multi-stage driving voltages had to be applied to pixel electrodes to express desired colors, which complicated the design of driver ICs and backplanes and became a major cause of increased manufacturing costs.

[0011] Accordingly, the present invention relates to a new driving technology field that simplifies the driving circuit of such a color electrophoretic display while simultaneously improving the accuracy and uniformity of color expression and ensuring long-term driving reliability.

[0012] More specifically, the present invention belongs to the field of a new concept of electrophoretic display driving technology, which controls the initial response state of particles by constantly applying a constant non-zero bias voltage to the pixel electrodes, and at the same time applies a complex and aperioditic activation waveform designed in advance to the common electrode to prevent particle stiction and maximize color separation.

[0013] The present invention has been devised to solve the problems of the prior art as described above. The main objective of the present invention is to provide a new driving method that simplifies the driving circuit of a color electrophoretic display to reduce manufacturing costs while avoiding the scope of rights of existing patents.

[0014] Another objective of the present invention is to provide a driving method that solves problems of voltage drop or signal distortion that may occur, particularly in large-area displays, by maintaining a common electrode at a stable reference potential during the driving sequence, thereby improving image quality reliability, such as color uniformity across the entire screen.

[0015] Another objective of the present invention is to provide an electrophoretic display driving method capable of realizing clearer and more accurate colors by effectively preventing particle sticking and maximizing color separation through the introduction of an optimized activation waveform that considers the physical characteristics of particles, rather than a simple square wave driving voltage.

[0016] In conclusion, the present invention provides an innovative electrophoretic display driving method that can simultaneously solve technical challenges such as simplifying the driving circuit, avoiding existing patents, and improving image quality and reliability through a new two-stage driving method in which a constant non-zero bias voltage is applied to all pixel electrodes at all times, and a complex and non-periodic activation waveform is applied to a common electrode in this state to initialize all pixels simultaneously. means of solving the problem

[0017] A driving method for an electrophoretic display according to one aspect of the present invention for solving the above-mentioned technical problem comprises: the electrophoretic display including an electrophoretic fluid containing particles of first, second, third, and fourth types, and a plurality of pixels located between a common electrode (Vcom) and a pixel electrode (Vpixel); and the driving method may include the following steps: (a) applying and maintaining a non-zero constant bias voltage (Vbias) to all of the plurality of pixel electrodes; (b) while the bias voltage is maintained, including a control step of a complex driving waveform and an equipotential section that maintains the potential of the pixel electrodes in synchronization with the potential of the common electrode, thereby controlling the actual potential difference to change to a target voltage corresponding to a target color to form a final image.

[0018] A driving method for an electrophoretic display characterized by applying a driving waveform including a non-periodic driving waveform or an activation waveform for preventing particle adhesion in at least one of the above steps (a) or (b).

[0019] A driving method for an electrophoretic display characterized by changing the voltage of the pixel electrode to a voltage level substantially identical to the bias voltage in order to maintain the pixel in a first color state.

[0020] To drive the pixel to the color state of the first type of particle, a first voltage having the same polarity as the charge polarity of the first type of particle can be applied to the pixel electrode.

[0021] To drive the pixel to the color state of the fourth type of particle, a second voltage having the same polarity as the charge polarity of the fourth type of particle can be applied to the pixel electrode.

[0022] To drive the pixel to the color state of the second type of particle, a first low voltage having the same polarity as the charge polarity of the second type of particle and having an absolute value smaller than the second voltage can be applied to the pixel electrode.

[0023] Prior to step (a) above, a step of applying a shaking waveform to reset the initial state of the particles may be further included.

[0024] The above non-periodic activation waveform may include a high-frequency micro-vibration section for resolving particle adhesion; a medium-amplitude random pulse section for rearranging particles; and a low-frequency strong driving pulse section for aligning all pixels to the first color state.

[0025] The above bias voltage may have a magnitude of 5% to 20% relative to the maximum absolute value of the target voltages of step (b).

[0026] The first type of particle may be a black particle having a strong positive charge, the second type of particle may be a yellow particle having a strong negative charge, the third type of particle may be a red particle having a weak positive charge, and the fourth type of particle may be a white particle having a weak negative charge.

[0027] When driven by the above-described driving method of the electrophoretic display, the maximum color difference (ΔE*ab) may be 1.5 or less when the electrophoretic display is driven in a single color.

[0028] When driven by the above-described driving method of the electrophoretic display, when the electrophoretic display displays a black and white grid pattern for 30 minutes and then updates to gray, the difference in luminance (ΔL*) between the previous black area and the white area may be 1.0 or less.

[0029] In a driving method for a color electrophoretic display according to one aspect of the present invention, the color electrophoretic display comprises a plurality of pixels, each pixel is located between a common electrode and a pixel electrode, and the driving method may include the following.

[0030] (a) a step of initializing all pixels to a uniform color state, wherein a non-zero constant bias voltage is applied to all pixel electrodes, and the step of actively controlling the actual potential difference by including an equipotential control section that maintains the potential of the pixel electrodes in synchronization with the potential change of the common electrode; and (b) a step of driving all pixels to a desired color state by maintaining the common electrode in a ground state and applying different target voltages starting from the bias voltage to the pixel electrodes.

[0031] In at least one of the above steps (a) or (b), a driving waveform including a non-periodic driving waveform or an activation waveform for preventing particle adhesion may be applied.

[0032] The above non-periodic activation waveform includes a high-frequency micro-vibration section in the frequency range of 1 kHz to 5 kHz, and the bias voltage may have a magnitude of 5% to 20% relative to the maximum absolute value of the target voltage.

[0033] An electrophoretic display according to one aspect of the present invention comprises: an electrophoretic fluid comprising a plurality of charged particles; a common electrode and a plurality of pixel electrodes; and a driving circuit connected to the common electrode and the plurality of pixel electrodes, wherein the driving circuit is configured to supply a non-zero constant bias voltage to all of the plurality of pixel electrodes while simultaneously supplying a non-periodic activation waveform to the common electrode, and the electrophoretic fluid may be enclosed inside a plurality of microcapsules or filled inside a space partitioned by a partition wall. Effects of the invention

[0034] The electrophoretic display and the driving method according to the present invention provide the following remarkable effects.

[0035] First, by simplifying the driving sequence into a global activation step and an optional write step without the need to apply complex multi-stage voltages to the pixel electrodes as in conventional technology, the circuit design of the display driver IC and backplane can be simplified and manufacturing costs can be significantly reduced.

[0036] Second, by maintaining a large common electrode at a stable reference potential (ground) for most of the driving sequence, it fundamentally prevents voltage drop (IR Drop) or signal distortion issues that may occur in large-area panels. This ensures superior color uniformity and minimizes boundary phenomena occurring during partial screen refresh, thereby improving overall image quality reliability.

[0037] Third, by introducing a non-periodic activation waveform designed considering the physical properties of particles, particle stiction caused by the history of previous images is very effectively eliminated. This dramatically improves ghosting characteristics and minimizes performance degradation even during long-term repetitive operation, thereby extending the durability and lifespan of the display.

[0038] Fourth, a constant non-zero bias voltage is continuously applied to all pixel electrodes to keep the particles always in a 'reaction-ready state'. This not only improves response speed but also enables stable operation and color expression even in low-temperature environments where fluid viscosity increases, thereby expanding the range of product usage environments.

[0039] In conclusion, the present invention provides an innovative solution that effectively avoids existing patented technologies while simultaneously achieving technical challenges such as cost reduction, image quality improvement, and reliability enhancement, thereby elevating the commercial competitiveness of electrophoretic display technology to the next level. Brief explanation of the drawing

[0040] FIG. 1 is a cross-sectional view of an electrophoretic display including a 3-particle system according to one embodiment of the present invention. (a) shows a pixel structure (microcup), and (b) shows a microcapsule structure. FIG. 2 is a cross-sectional view of an electrophoretic display including a 4-particle system according to another embodiment of the present invention. (a) shows a pixel structure (microcup), and (b) shows a microcapsule structure. FIG. 3a illustrates Phase I (initialization phase), which is a driving waveform of an electrophoretic display according to the prior art compared with the present invention. FIG. 3b illustrates Phase II (individual driving stage), which is a driving waveform diagram of an electrophoretic display according to the prior art compared with the present invention. FIG. 4 illustrates the activation phase of the driving waveform diagram of an electrophoretic display according to one embodiment of the present invention. FIG. 5 illustrates a cross-sectional structure of an electrophoretic display showing the final activation completion state according to particle behavior during the activation phase of the 4-particle system of the present invention. (a) illustrates a pixel structure (microcup), and (b) illustrates a microcapsule structure. Specific details for implementing the invention

[0041] The present invention will be described in detail below through specific manufacturing examples, but these are merely examples to aid in understanding the invention and the scope of the invention is not limited thereto.

[0042] The core of the present invention is to provide a new two-stage driving method for driving a color electrophoretic display, wherein (1) a constant pixel bias voltage that is not zero is maintained in a basic state at all pixel electrodes, (2) a complex and aperiodic activation waveform is applied to a common electrode in this state to uniformly initialize all pixels to a specific intermediate color state, and (3) individually drive to a final target color.

[0043] An electrophoretic display used in one embodiment of the present invention has a panel structure composed of a common electrode and a plurality of pixel electrodes. A plurality of particles having different colors and charge characteristics are dispersed in the fluid inside each pixel. For example, as disclosed in U.S. Patent No. 10,254,619, a 4-particle system composed of a black (K) particle with a strong positive charge, a yellow (Y) particle with a strong negative charge, a red (R) particle with a weak positive charge, and a white (W) particle with a weak negative charge can be assumed. The present invention is not limited to this specific particle system and is applicable to any electrophoretic display comprising two or more types of particles.

[0044] In addition, the present invention can be equally applied not only to 4-particle systems but also to electrophoretic displays using a smaller number of particles, such as 3-particle systems. Hereinafter, a method for manufacturing an electrophoretic display including a 3-particle system will be described.

[0045] The driving method of the present invention can be applied to various types of displays depending on the structure containing the electrophoretic fluid. Representative examples include a pixel structure (or microcup structure) in which each pixel is physically partitioned by a partition wall, and a microcapsule structure in which the electrophoretic fluid is encased in a polymer shell. The present invention can be effectively applied to both of these structures. Below, a method for manufacturing an electrophoretic display including each structure is described.

[0046] 1. Manufacturing of Pixel Structure (Microcup) Electrophoretic Displays

[0047] (1) Preparation of electrophoretic fluid

[0048] The electrophoretic particles according to the present invention may have a simple coated particle, an uncoated particle, or a triple structure of Core-Shell-Corona.

[0049] white particles It consists of a white inorganic pigment that has a high refractive index and effectively scatters light. Preferably, titanium dioxide (TiO₂) is used, and the crystal structure may be rutile or anatase. In addition, zinc oxide (ZnO), barium sulfate (BaSO₄), zirconia (ZrO₂), etc., may be used.

[0050] black particles : It consists of pigments that absorb light of specific wavelengths in the visible light region. Iron oxide (Fe₃O₄) or carbon black was used. In addition, organic black pigments such as copper chromite black spinel or aniline black can also be used.

[0051] colored particles : It consists of high-saturation organic pigments to realize the three primary colors of subtractive color mixing.

[0052] Cyan: Pigment Blue 15:3, a copper phthalocyanine pigment, was used. In addition, Pigment Blue 15:4, Pigment Blue 16, etc. can also be used.

[0053] Magenta: Pigment Red 122, a quinacridone-based pigment, was used. In addition, Pigment Red 202, Pigment Violet 19, etc., can be used to achieve similar colors.

[0054] Yellow: Pigment Yellow 12 (PY 12), Pigment Yellow 13 (PY 13), Pigment Yellow 14 (PY 14), and Pigment Yellow 83 (PY 83) are used as Arylide Yellow (Diarylide Yellow). Pigment Yellow 151 (PY 151) and Pigment Yellow 154 (PY 154) are used as Benzimidazolone Yellow. Pigment Yellow 110 (PY 110) and Pigment Yellow 139 (PY 139) are used as Isoindolinone Yellow, and Pigment Yellow 138 (PY 138) is used as Quinophthalone Yellow.

[0055] In addition to the pigments specified above, pigments having various CI (Color Index) numbers may be used depending on the desired color and durability. The average particle size of the core particles is generally selected in the range of 100 nm to 500 nm.

[0056] An electrophoretic fluid containing four types of particles is prepared. A dispersant and a charge control agent are added to a non-conductive fluid solvent (e.g., an isoparaffin-based hydrocarbon). Pigment particles, each imparted with specific charge characteristics through different surface treatments, are dispersed in this fluid. In one embodiment, a weak negative charge is imparted to titanium dioxide (TiO₂)-based white (W) particles, a strong positive charge to iron oxide (Fe2O3)-based black (K) particles, a weak positive charge to quinacridone-based red (R) particles, and a strong negative charge to arylide-based yellow (Y) particles. A uniform colloidal solution is prepared using an ultrasonic disperser or the like to ensure the dispersion stability of each particle.

[0057] (2) Pixel structure formation and fluid filling:

[0058] A photosensitive resin (photoresist) is applied to a backplane on which a TFT (Thin Film Transistor) array is formed, and a partition wall pattern defining each pixel area is formed through a photolithography process. The partition wall structure formed in this way constitutes a microcup array. Subsequently, an electrophoretic fluid prepared using precision coating equipment, such as inkjet printing or slit coating, is quantitatively filled into each microcup.

[0059] (3) Top bag and panel completion:

[0060] An upper transparent substrate (or film) with a transparent conductive film (e.g., ITO) deposited thereon is laminated onto a lower substrate filled with fluid. In this process, the transparent conductive film of the upper substrate acts as the common electrode (Vcom). A sealant is applied to the edges, and the upper and lower substrates are completely sealed through UV curing or thermal curing processes to protect the fluid from the external environment. Finally, the driving circuit (driver IC) and the backplane are connected, and a polarizing film or anti-reflective film is attached to complete the electrophoretic display panel.

[0061] 2. Fabrication of Microcapsule Structure Electrophoretic Displays

[0062] (1) Preparation of microcapsules:

[0063] Microcapsules are prepared using the electrophoretic fluid prepared above. The electrophoretic fluid is added to an aqueous solution in which a polymer precursor (e.g., gelatin, gum arabic) is dissolved in water, and the solution is vigorously stirred to form fine oil droplets. Subsequently, a polymer shell is formed on the surface of each oil droplet through in-situ polymerization or complex coacervation. Through this process, a large number of microcapsules with a diameter of several tens of micrometers are obtained, each containing an electrophoretic fluid encapsulated with four types of colored particles inside.

[0064] (2) Manufacturing of electronic ink film (Front Plane Laminate, FPL):

[0065] The manufactured microcapsules are mixed with a binder resin to produce a coating slurry, namely e-ink. This e-ink is uniformly coated onto a transparent conductive film (common electrode) formed on a transparent plastic film (e.g., PET) and dried. An adhesive layer is additionally coated on top to complete the front plane laminate (FPL).

[0066] (3) Panel completion:

[0067] A manufactured FPL is attached to a lower substrate on which a TFT array is formed by pressing it through a lamination process. At this time, the adhesive layer of the FPL is electrically insulated from the pixel electrodes of the lower substrate while being physically and firmly bonded. In this structure, a microcapsule layer is positioned between each pixel electrode of the lower substrate and the common electrode of the FPL. Subsequently, a driving circuit is connected and necessary optical films are attached, similar to the pixel structure, to complete the electrophoretic display panel.

[0068] As described above, the driving method of the present invention can be equally applied to both a pixel structure that partitions a fluid with partitions and a structure that encapsulates a fluid with microcapsules. This is because both structures share the common principle that particles are driven by an electric field between a common electrode and a pixel electrode. An electrophoretic display used in one embodiment of the present invention may include any one of the above structures, and the particle composition also assumes a 4-particle system including black (K) with a strong positive charge, yellow (Y) with a strong negative charge, red (R) with a weak positive charge, and white (W) with a weak negative charge, but the present invention is not limited thereto.

[0069] 3. Fabrication of an electrophoretic display using a 3-particle system

[0070] (1) Preparation of electrophoretic fluid (3-particle type):

[0071] The electrophoretic fluid of a 3-particle system generally consists of white (W), black (K), and one colored particle (e.g., red R or magenta M). In one embodiment, negatively charged (-) white (W) particles and positively charged (+) black (K) particles are dispersed in a non-conductive fluid solvent. To this, red (R) particles are additionally dispersed, which are positively charged (+) as the black particles but have a weaker charge amount. That is, the system consists of one negatively charged particle (W) and two positively charged particles (K, R) with different charge amounts. A homogeneous colloidal solution is prepared through the same process as the 4-particle system to ensure stable dispersion of each particle.

[0072] (2) Manufacturing of pixel structure (microcup) display (3-particle type):

[0073] The manufacturing process of a pixel structure display using a 3-particle system is fundamentally the same as the manufacturing process of a 4-particle system described above. The difference is that the fluid filled inside the microcup array is an electrophoretic fluid containing 3 types of particles instead of 4 types. A partition is formed on the lower TFT substrate, and after filling each microcup with the manufactured 3-particle electrophoretic fluid, the panel is completed by sealing it with an upper substrate having a common electrode formed thereon.

[0074] (3) Manufacturing of microcapsule structure display (3-particle type):

[0075] The manufacturing process of a microcapsule structure display using a 3-particle system also follows the same principle as the manufacturing process of the 4-particle system described above. Microcapsules containing an electrophoretic fluid containing three types of particles (W, K, R) are manufactured using interfacial polymerization or a complex coacervation method. These microcapsules are mixed with a binder to create electronic ink, which is then coated onto a transparent film with a common electrode to produce an upper laminated film (FPL). Finally, the manufactured FPL is bonded to a TFT lower substrate to complete the final display panel.

[0076] As described above, the driving method of the present invention can be widely applied regardless of the number of particles used (4-particle, 3-particle, etc.) or the physical structure of the display (pixel structure, microcapsule structure). This is because the present invention is based on the fundamental principle of an electrophoretic display that drives charged particles by controlling the electric field between a common electrode and a pixel electrode. The embodiments described below are described based on a 4-particle system, but this is for convenience of explanation and the scope of the present invention is not limited thereto.

[0077] FIGS. 1(a) and (b) illustrate the cross-sectional structure of a 3-particle system electrophoretic display to which the present invention can be applied.

[0078] The display consists of an upper transparent substrate (20) and a lower TFT substrate (30). A common electrode (Vcom, 21) is formed on the upper substrate, and a pixel electrode (Vpixel, 31) and a TFT switching element that control each pixel are formed on the lower substrate. Particles in the electrophoretic fluid are driven by the electric field between the common electrode (21) and the pixel electrode (31).

[0079] FIG. 1(a) shows a pixel structure. A partition (33) is formed on a lower substrate (30) to physically partition each pixel area. Inside this partitioned space, three types of particles—namely, negatively charged white particles (W) (102), strongly positively charged black particles (K) (103), and weakly positively charged red particles (R) (104)—are filled together with a fluid (40).

[0080] FIG. 1(b) shows a microcapsule structure. Three identical types of particles (W, K, R) and a fluid (40) are wrapped by a polymer shell to form a microcapsule (110). These microcapsules are placed between a lower substrate (30) and an upper substrate (20) together with a binder (111).

[0081] FIG. 2 illustrates a cross-sectional structure of a 4-particle system electrophoretic display to which the present invention can be applied, and the basic structure is the same as that of FIG. 1. However, it differs in that four types of particles are included in the electrophoretic fluid: a white particle with a weak negative charge (W), a black particle with a strong positive charge (K), a red particle with a weak positive charge (R), and a yellow particle with a strong negative charge (Y) (105). (a) shows a pixel structure, and (b) shows a microcapsule structure.

[0082] FIGS. 3a and 3b are driving waveform diagrams of the prior art (U.S. Patent No. 10,901,287) illustrated for comparison. In the initialization phase (Phase I) of FIG. 3a, the pixel electrode (Vpixel) is fixed at 0V and the common electrode (Vcom) is sequentially modulated to bring all pixels into a specific intermediate state. Subsequently, in the individual driving phase (Phase II) of FIG. 3b, Vcom is fixed at 0V and individual voltages are applied to Vpixel.

[0083] Figure 4 is a waveform diagram showing the core driving principle of the present invention. The driving sequence of the present invention is broadly divided into an activation phase and a writing phase.

[0084] In the activation phase, all pixel electrodes (Vpixel) are maintained at a preset constant bias voltage (Vbias), e.g. +2V, as the default value throughout the driving sequence, rather than 0V. In this state, a non-periodic activation waveform (50) is applied to the common electrode (Vcom). This waveform (50) is not a simple square wave, but may consist of (1) a high-frequency micro-vibration section (51) that releases the particles from sticking, (2) a medium-amplitude random pulse section (52) that strongly shakes and rearranges the particles, and (3) a low-frequency strong driving pulse section (53) that forcibly aligns all particles to a specific intermediate color state.

[0085] In the writing phase, the common electrode (Vcom) is fixed at a stable reference potential (0V), and the voltage of each pixel electrode (Vpixel) is changed from Vbias to the voltage level (V_target) required for the target color.

[0086] FIG. 5 illustrates a cross-sectional structure of an electrophoretic display showing the final activation completion state according to particle behavior during the activation phase of the 4-particle system of the present invention. (a) illustrates a pixel structure (microcup), and (b) illustrates a microcapsule structure.

[0087] In the initial state, particles are mixed in a disordered manner or some are adhered to the electrode surface due to the influence of the previous image. K (black) and Y (yellow) particles may adhere to the electrode surface.

[0088] In the activation waveform application step, when an activation waveform is applied to Vcom while Vpixel maintains Vbias, a complex dynamic electric field is formed. Due to this electric field, all particles (W, K, R, Y) are violently shaken and rearranged, and separated from the surface. It may consist of (1) a high-frequency micro-vibration section (51) that releases the adhesion of particles, (2) a medium-amplitude random pulse section (52) that strongly shakes and rearranges the particles, and (3) a low-frequency strong driving pulse section (53) that forcibly aligns all particles to a specific intermediate color state.

[0089] An activation waveform is a highly sophisticated, controlled sequence of waveforms that leverages the difference in particle mobility.

[0090] The driving principle is the 'overshoot and pull-back' technique, and the final stage of the activation waveform is actually a sequence of at least two fine pulses combined, operating as follows.

[0091] Step 1: Overshoot - Strong particle priority movement

[0092] A short, strong negative (-) voltage pulse is applied to the common electrode (Vcom). All positively charged particles within the electric field are attracted toward Vcom. At this time, the black (K) particle, which has the strongest charge and the highest mobility, reaches the surface of Vcom first. It is followed by the red (R) particle, which has a weak positive charge. At this moment, the observation surface temporarily appears close to black.

[0093] Step 2: Pull-back & Settling - Exploiting Mobility Differences. Immediately after the 'overshoot' pulse, a weaker, shorter positive (+) voltage pulse is applied to Vcom. Since Vcom has now become positive, a force acts to push the positively charged particles attached to the surface of Vcom downwards (towards the pixel electrode). This is where a key physical phenomenon occurs.

[0094] Black (K) particle: Since it has the strongest charge, it reacts most sensitively to this 'return' electric field and returns downwards the fastest.

[0095] Red (R) particle: Since it has a weak charge, it responds relatively insensitively to the 'return' electric field. It does not move downward sufficiently while a short pulse is applied and remains near the observation surface.

[0096] When this sophisticated sequence of 'overshoot' and 'return' ends in the final activation complete state, the following particle distribution is finally formed.

[0097] In the final activation complete state, all pixels are aligned into a uniform intermediate color state by the last strong driving pulse of the activation waveform. For example, weakly positively charged red particles (R) move to the top (observation plane), strongly positively charged K (black) particles are located at the top-center, strongly negatively charged Y (yellow) particles are located at the center-bottom, and negatively charged W (white) particles are located at the bottom. This state becomes a very stable and uniform starting point for the next write step.

[0098] In conclusion, the core technology of the activation waveform of the present invention is to utilize the basic principle that "particles with a stronger charge move faster" in reverse, intentionally overshooting the strong particles to the target point, and then selectively pulling back only the strong particles with a weak force in the opposite direction, thereby finally leaving the particles with a weak charge at the desired location (observation surface).

[0099] The writing step details the process of implementing each target color from the state where activation is complete (a). In this step, Vcom is fixed at 0V.

[0100] (b) Black driving: A strong positive voltage (e.g., +15V) is applied to the pixel electrode (Vpixel). Due to the strong potential difference with Vcom (0V), all negative charge particles (W, Y) are strongly pulled down toward Vpixel, and all positive charge particles (K, R) move toward Vcom. At this time, the black particle (K), which has the strongest charge, rises to the top, and black is visible on the observation surface.

[0101] (c) White Driving: A strong negative voltage (e.g., -15V) is applied to the pixel electrode (Vpixel). Conversely, all positively charged particles (K, R) move toward Vpixel, and all negatively charged particles (W, Y) move toward Vcom. At this time, the white particles (W), which have a weaker charge, rise to the top, making white visible. (Depending on the system design, particle size or mobility is adjusted so that the yellow particles (Y), which have a strong negative charge, are positioned below the white particles (W).)

[0102] (d) Yellow driving: A weak negative voltage (e.g., -10V) is applied to the pixel electrode (Vpixel). This voltage pushes the yellow particles (Y) with strong negative charges upward, but is not strong enough to completely push the white particles (W) with weak negative charges upward. As a result, the yellow particles (Y) are positioned at the top to represent yellow.

[0103] (e) Red state maintenance: The voltage of the pixel electrode (Vpixel) is maintained at a weak voltage similar to the initial activation state (e.g., +2V, i.e., Vbias) or adjusted to be close to 0V. In this case, the red particle (R) already located at the top hardly moves, so the red state is maintained.

[0104] As such, the driving method of the present invention can be applied to physically different structures (pixels, microcapsules) and different particle systems (3-particles, 4-particles), and solves the problems of the prior art through unique activation and writing steps, and provides improved image quality and reliability.

[0105] 4. Performance Evaluation and Verification of Effectiveness

[0106] To objectively prove the superiority of the present invention, four experimental groups were established as follows and comparative tests were performed on five items.

[0107] Example 1 (E1): The driving method of the present invention (normal bias voltage + non-periodic activation waveform) was applied to a 4-particle system panel.

[0108] Example 2 (E2): The driving method of the present invention (normal bias voltage + non-periodic activation waveform) was applied to a 3-particle system panel.

[0109] Comparative Example 1 (C1): A driving method of the prior art (US Patent No. 10,901,287) (Vpixel=0V, Vcom square wave modulation) was applied to a 4-particle system panel.

[0110] Comparative Example 2 (C2): A driving method of the prior art (US Patent No. 10,901,287) (Vpixel=0V, Vcom square wave modulation) was applied to a 3-particle system panel.

[0111] (All panels have the same 5.8-inch size and resolution, and use an optimized driving voltage for each system.)

[0112] Test Example 1: Color Uniformity Evaluation

[0113] Test Objective: Evaluate the effect of the driving method on color uniformity by measuring the color deviation according to location when the entire panel is driven in a single color.

[0114] Test Design: After driving the panels of each group full screen with representative chromatic colors (4-particle: red, 3-particle: red), the color coordinates (CIE Lab*) at a total of 5 points—the center and the four corners of the panel—are measured using a high-precision colorimeter. The Maximum Color Difference (ΔEab) between the values ​​measured at the 5 points is calculated. A smaller ΔEab value indicates better uniformity.

[0115] graph 1: Color Uniformity Evaluation Results Table

[0116]

[0117] Result Analysis: Examples 1 and 2 showed a significantly lower maximum color difference of less than 1 / 3 compared to Comparative Examples 1 and 2. This demonstrates that while the conventional Vcom modulation method caused a minute voltage drop (IR Drop) over a large area, resulting in positional color deviation, the stable Vcom (0V) maintenance and optimized activation waveform of the present invention initialize the particles very uniformly, thereby securing excellent color uniformity. In other words, the color uniformity of the present invention (E1, E2) improved by approximately 66–71% compared to the Comparative Examples (C1, C2). (ΔE*ab < 2.0: indicates excellent uniformity at a level difficult to detect with the human eye.) Furthermore, it is possible to realize uniform particle placement through the composite waveform of the activation step.

[0118] Test Example 2: Evaluation of Ghosting Characteristics

[0119] Test Objective: Evaluate the particle control and reset capabilities of each driving method by measuring how much the history of the previous image influences the next image.

[0120] Test design: After displaying a black and white grid pattern on the panel for 30 minutes, the entire screen is immediately refreshed to 50% gray. Immediately thereafter, the difference in luminance (ΔL*) between the previously black area and the previously white area is measured. The smaller the ΔL* value, the less afterimage there is.

[0121] graph 2: Evaluation of Ghosting Characteristics

[0122]

[0123] Result Analysis: The afterimage levels of Examples 1 and 2 were excellent, at approximately one-quarter the level of the Comparative Example group. In other words, the afterimage of the present invention (E1, E2) was reduced by approximately 76–81% compared to the Comparative Examples (C1, C2). (ΔL* < 1.0: Excellent performance at a level difficult for the user to perceive.) This demonstrates that while the simple square wave initialization method of the Comparative Examples makes it difficult to completely resolve particle stiction, the high-frequency micro-vibration components included in the non-periodic activation waveform of the present invention effectively physically separate the particles, thereby eliminating image history to near perfection. Furthermore, the previous pattern can be completely removed through the complete rearrangement of particles during the activation step.

[0124] The non-periodic composite waveform of the activation phase (high-frequency vibration + random pulse + strong driving pulse) uniformly rearranges the particles of all pixels, completely eliminating the history effect of the previous image, thereby significantly reducing afterimage phenomena compared to conventional technology.

[0125] Test Example 3: Evaluation of Low-Temperature Operation Stability

[0126] Test Objective: To evaluate the degree of color distortion occurring during operation in a low-temperature (-10°C) environment, and to verify the robustness of the drive method against environmental changes.

[0127] Test design: After leaving the panels of each group in a low-temperature chamber (-10°C) for 1 hour, the color coordinates are measured by driving them with the same waveform as the reference red measured at room temperature (25°C). The color difference (ΔE*ab) at low temperature compared to room temperature is calculated.

[0128] Table 3: Low-temperature operation stability evaluation results

[0129]

[0130] Result Analysis: In low-temperature environments, fluid viscosity increases, causing a rapid decrease in particle mobility. The example group exhibited significantly less color distortion compared to the comparative example group. In other words, the present invention (E1, E2) demonstrated 65–69% superior stability in low-temperature environments compared to the comparative examples (C1, C2). (ΔE*ab < 5.0: An acceptable level of color is maintained even in low-temperature environments.) This is attributed to the fact that the constant bias voltage (Vbias) of the present invention keeps the particles in a 'reaction-ready state' at all times, thereby reducing initial driving resistance at low temperatures, and the activation waveform effectively moves the particles even within a highly viscous fluid. The non-periodic composite waveform (high-frequency vibration + random pulse + strong driving pulse) used in the activation step of the present invention effectively removed particle adhesion and maintained the activated state even in low-temperature environments. As a result, low-temperature driving stability was dramatically improved compared to conventional technology, thereby ensuring display stability in extreme environments.

[0131] Test Example 4: Partial Update Performance Evaluation

[0132] Test Objective: Evaluate the border phenomenon occurring at the boundary between the updated and non-updated areas and the degree of image quality degradation when repeating partial screen refresh, which updates only a portion of the screen.

[0133] Test design: Only a 1 / 4 area in the center of the screen is subjected to black-and-white switching (partial update) repeated 100 times. Afterward, the entire screen is updated to grayscale, and the difference in luminance (ΔL*) between the updated area and the non-updated area and the change in color (ΔE*ab) in the non-updated area are measured.

[0134] Table 4: Partial Update Performance Evaluation Results Table

[0135]

[0136] Result Analysis: In the comparative example group, the voltage applied to the common electrode (Vcom) during partial updates caused electrical crosstalk in surrounding non-updated areas, leading to severe boundary phenomena and color changes. In contrast, the present invention maintained a stable Vcom at 0V even during partial updates, resulting in minimal impact on surrounding areas. This suggests that the present invention is significantly more suitable for applications where only price information changes frequently, such as Electronic Shelf Labels (ESL). The present invention (E1, E2) demonstrates 74–82% superior partial screen update performance compared to the comparative examples (C1, C2). (ΔL* < 1.0, ΔE*ab < 2.0: Boundary effects are minimized even during partial updates.)

[0137] By uniformly arranging the particles of all pixels in the activation step of the present invention, the boundary effect between the updated area and the non-updated area during partial updates is minimized to an extreme degree. This effectively prevents screen quality degradation during dynamic content display or real-time updates, thereby dramatically improving the user experience.

[0138] Test Example 5: Long-term Durability Evaluation

[0139] Test Objective: Evaluate the impact of the driving method on panel lifespan by measuring the degree of performance degradation compared to the initial state after prolonged, repetitive operation under harsh conditions.

[0140] Test design: An accelerated life test is conducted on each group of panels for 500 hours by repeatedly updating random images at 1-minute intervals. The rate of decrease in white state luminance (L*) and the rate of increase in afterimage (ΔL*) are measured before and after the test.

[0141] Table 5: Long-term Durability Evaluation

[0142]

[0143] Result Analysis: The example group showed significantly less performance degradation compared to the comparative example group. This implies that the activation waveform of the present invention performs a 'recovery' role that prevents particle clumping or permanent adhesion during every operation, thereby greatly improving the long-term durability of the panel. The present invention (E1, E2) demonstrates 75–81% superior long-term durability compared to the comparative examples (C1, C2). Brightness reduction is 2% or less (industry standard within 5%), and afterimage increase is within 35% (industry standard within 50%). By completely rearranging particles during every update cycle through a non-periodic composite waveform in the activation stage of the present invention, particle adhesion, aggregation, and degradation are extremely suppressed. As a result, excellent durability is achieved with a brightness reduction of within 2% and an afterimage increase of within 35% even after 1 million screen updates, demonstrating 75–81% superior long-term reliability compared to conventional technology. This improves practicality in long-term usage environments such as e-book readers, smart labels, and digital signage.

[0144] Test Example 6. Critical Significance of the Normal Bias Voltage (Vbias) Range

[0145] Test Objective: To demonstrate that when the magnitude of the bias voltage deviates from the 5% to 20% range, low-temperature driving stability rapidly deteriorates or power consumption increases unnecessarily.

[0146] Test design: Based on a driving voltage of ±15V, the 4-particle panel (E1) is driven by setting Vbias to 0V (comparative example), +0.375V (2.5%), +0.75V (5%), +1.5V (10%), +3.0V (20%), and +3.75V (25%), respectively. Color distortion (ΔE*ab) in a low temperature (-10°C) environment and total energy consumption (mJ) per screen refresh at room temperature (25°C) are measured.

[0147] Table 6. Test Results Table of Critical Significance of Normal Bias Voltage (Vbias) Range

[0148]

[0149] Result Analysis (Critical Significance)

[0150] Criticality of the lower limit (5%): Color distortion (9.7) was still very high when Vbias was 2.5%, but the color distortion improved sharply to 4.8 the moment it reached 5%. This suggests that 5% is the minimum critical voltage to overcome the initial driving resistance of the particle at low temperatures. Below 5%, the effect of creating a 'ready state' is negligible.

[0151] Criticality of the upper limit (20%): Even when Vbias was increased from 20% to 25%, low-temperature color distortion was not further improved (remaining the same at 4.5). On the other hand, total energy consumption increased sharply from 35.2 mJ to 40.1 mJ. This implies that a bias voltage exceeding 20% ​​is an inefficient range that causes only unnecessary power consumption without performance improvement. Therefore, 5% to 20% is the optimal range that satisfies both low-temperature performance and power efficiency. The optimal ratio of the high frequency (HF) section within the activation waveform is 10 to 20% (absolute time: 20 ms to 40 ms), and the optimal range of the normal bias voltage (Vbias) is 10 to 20% of the reference voltage (absolute value ±1.5 V to ±3.0 V). In this range, low-temperature color distortion was minimized to 4.5–4.6 ΔE*ab (65% improvement compared to the comparative example), and energy consumption was minimized to 35.2–35.5 mJ (8.6% decrease compared to the comparative example).

[0152] In other words, maintaining the particle activation state ensures particle mobility in low-temperature environments, while excessive bias (over 25%) resulted in a counterproductive effect of increased energy consumption. Settings within this range simultaneously optimize the performance, efficiency, and reliability of the display.

[0153] Test Example 7. Critical Significance of the Time Ratio of the High Frequency (HF) Section in the Activation Waveform

[0154] Test Objective: To demonstrate that when the time ratio of the high-frequency section within the activation waveform falls outside the range of 10% to 30%, the afterimage removal effect is negligible or the total driving time becomes inefficiently long.

[0155] Test design: After fixing the total activation time to 200ms, the 4-particle panel (E1) is driven by changing the time ratio occupied by the high frequency (3kHz) micro-vibration section within it to 5%, 10%, 20%, 30%, and 40%. The afterimage characteristic (ΔL*) and the minimum total activation time required to achieve the same afterimage performance (ΔL*<1.0) are measured.

[0156] Table 7. Test Results Table on the Critical Significance of the Time Ratio of the High Frequency (HF) Section in the Activation Waveform

[0157]

[0158] Result Analysis (Critical Significance)

[0159] Criticality of the lower limit (10%): When the HF interval ratio was 5%, the afterimage target (ΔL*<1.0) could not be achieved no matter how much the activation time was increased. However, when the ratio became 10%, the target was achieved in 200ms, and performance improved rapidly in a non-linear manner. This demonstrates that 10% is the minimum physical time required to effectively separate particle adhesion.

[0160] Criticality of the upper limit (30%): Even when the ratio was increased from 30% to 40%, the afterimage removal performance did not improve further (remaining the same at 0.7). Rather, the minimum total activation time required to achieve the same performance unnecessarily increased from 200ms to 250ms. This implies that the HF section exceeding 30% is an inefficient section that no longer contributes to afterimage removal and only delays the overall driving time. Therefore, 10% to 30% is the critical range that optimizes both the afterimage removal effect and the driving speed. The optimal ratio of the high frequency (HF) section within the activation waveform is 10–20% (absolute time: 20ms to 40ms). In this range, with a fixed activation of 200ms, the afterimage is 0.7–0.9 ΔL* (excellent level), and the minimum time to achieve ΔL* < 1.0 is 180–200ms (very efficient), thereby optimizing the removal of particle surface adhesion using high-frequency vibration. In particular, 20% (40ms) was the "golden ratio" and represented the optimal balance of high-frequency vibration and subsequent random / strong pulse intervals with the lowest afterimage level (ΔL* = 0.7) and the shortest activation time (180ms).

[0161] Less than 5% is inefficient because the high-frequency vibration is insufficient to completely remove particle adhesion, and more than 40% is inefficient because the high-frequency range is excessive.

[0162] Test Example 8. Critical Significance of the High Frequency (HF) Section Frequency Range within the Activation Waveform

[0163] Test Objective: To demonstrate that the afterimage removal effect decreases sharply when the frequency of high-frequency micro-vibrations falls outside the range of 1 kHz to 5 kHz.

[0164] Test design: The 4-particle panel (E1) is driven by changing only the frequency to 0.5 kHz, 1 kHz, 3 kHz, 5 kHz, and 7 kHz while keeping the time ratio of the HF section fixed at 20%. The afterimage characteristic (ΔL*) is measured under each condition.

[0165] Table 8. Test Results Table of Critical Significance of the High Frequency (HF) Section Frequency Range within the Activation Waveform

[0166]

[0167] Result Analysis (Critical Significance)

[0168] Criticality of the lower limit (1 kHz): When the frequency was 0.5 kHz, the afterimage (3.2) was very severe. This is because the frequency is too low to effectively 'vibrate' the particles and they only 'move'. However, when the frequency reached 1 kHz, the afterimage was greatly improved to 0.9. This indicates that 1 kHz is the critical frequency that overcomes the inertia of the particles and induces effective micro-vibrations.

[0169] Criticality of the upper limit (5kHz): Excellent afterimage removal performance was observed within the frequency range of 15kHz. However, when the frequency exceeded 5kHz to 7kHz, the afterimage actually worsened again to 2.1. This is because when the frequency becomes too high, the particles cannot follow changes in the electric field due to the viscous resistance of the fluid and the inertia of the particles, and as a result, the energy transfer efficiency decreases, reducing the sticking separation effect. Therefore, 1kHz to 5kHz is a critical frequency range that produces an effect similar to 'resonance' optimized for the physical response characteristics of the particles.

[0170] The optimal frequency range for the high frequency (HF) section within the activation waveform is 1–5 kHz, with peak performance achieved particularly at 3 kHz. At the optimal frequency of 3 kHz, the lowest afterimage is ΔL* = 0.7 (best), demonstrating the highest particle adhesion removal efficiency and optimal system stability. In the acceptable range of 1–5 kHz, excellent performance was observed within 0.9 ΔL*. 0.5 kHz is too low and inefficient (ΔL* = 3.2), while 7 kHz is too high and inefficient (ΔL* = 2.1). At low frequencies, the electrostatic adhesion force of particles cannot be overcome, while at high frequencies, particle movement becomes unstable, reducing effectiveness. The 1–5 kHz range corresponds to the natural resonance characteristics of particles, resulting in the highest adhesion removal efficiency.

[0171] The present invention relates to a color electrophoretic display device and a driving method thereof, and aims to significantly improve image reliability, such as color uniformity, afterimage characteristics, low-temperature driving performance, and long-term durability, while simplifying the design of the driving circuit and reducing manufacturing costs.

[0172] A driving method for an electrophoretic display according to the present invention comprises: a step of applying and maintaining a non-zero constant bias voltage having a magnitude of 5% to 20% of the driving voltage to all pixel electrodes; a step of initializing all pixels to a uniform intermediate color state by applying a non-periodic activation waveform including a high-frequency micro-vibration section in a frequency range of 1 kHz to 5 kHz to a common electrode while the bias voltage is maintained; and a step of forming a final image by changing the voltage of each pixel electrode from the bias voltage to a voltage required for a target color while maintaining the common electrode at a stable reference potential.

[0173] This driving method provides a combination of effects, such as ensuring screen uniformity through a stable common electrode (maximum color difference ΔEab ≤ 1.5), preventing particle sticking with an optimized activation waveform to eliminate afterimages (luminance difference ΔL ≤ 1.0), and improving low-temperature driving stability and response speed through a constant bias voltage.

Claims

Claim 1 A driving method for an electrophoretic display, wherein the display comprises an electrophoretic fluid containing particles of first, second, third, and fourth types, and a plurality of pixels located between a common electrode (Vcom) and a pixel electrode (Vpixel), and the driving method is characterized by comprising the following steps: (a) applying and maintaining a non-zero constant bias voltage (Vbias) to all of the plurality of pixel electrodes; (b) while the bias voltage is maintained, including a control step of a complex driving waveform and including an equipotential section that synchronizes and maintains the potential of the pixel electrodes with the potential of the common electrode, wherein the equipotential section has a time range of 20ms to 60ms, thereby controlling a substantial potential difference to change to a target voltage corresponding to a target color to form a final image. Claim 2 A driving method for an electrophoretic display according to claim 1, characterized in that a driving waveform including a non-periodic driving waveform or an activation waveform for preventing particle adhesion is applied in at least one of step (a) or step (b). Claim 3 A driving method for an electrophoretic display according to claim 2, characterized in that, in order to maintain the pixel in a first color state, the voltage of the pixel electrode is changed to a voltage level substantially identical to the bias voltage. Claim 4 A driving method for an electrophoretic display according to claim 2, characterized by applying a first voltage having the same polarity as the charge polarity of the first type particle to the pixel electrode in order to drive the pixel to the color state of the first type particle. Claim 5 A driving method for an electrophoretic display according to claim 2, characterized by applying a second voltage having the same polarity as the charge polarity of the fourth type particle to the pixel electrode in order to drive the pixel to the color state of the fourth type particle. Claim 6 A driving method for an electrophoretic display according to claim 5, characterized by applying a first low voltage to the pixel electrode having the same polarity as the charge polarity of the second type particle and having an absolute value smaller than the second voltage, in order to drive the pixel to the color state of the second type particle. Claim 7 A driving method for an electrophoretic display according to claim 2, further comprising, prior to step (a), a step of applying a shaking waveform to reset the initial state of the particles. Claim 8 A driving method for an electrophoretic display according to claim 3, wherein the aperiodic activation waveform comprises: a high-frequency micro-vibration section for resolving particle adhesion; a medium-amplitude random pulse section for rearranging particles; and a low-frequency strong driving pulse section for aligning all pixels to the first color state. Claim 9 A driving method for an electrophoretic display according to claim 2, wherein the bias voltage has a magnitude of 5% to 20% relative to the maximum absolute value of the target voltages of step (b). Claim 10 A driving method for an electrophoretic display according to claim 1, wherein the first type of particle is a black particle having a strong positive charge, the second type of particle is a yellow particle having a strong negative charge, the third type of particle is a red particle having a weak positive charge, and the fourth type of particle is a white particle having a weak negative charge. Claim 11 A driving method for an electrophoretic display according to claim 10, characterized in that when the electrophoretic display is driven by the driving method of the electrophoretic display, the maximum color difference (ΔE*ab) is 1.5 or less when the electrophoretic display is driven by a single color. Claim 12 A driving method for an electrophoretic display according to claim 10, characterized in that when the electrophoretic display is driven by the driving method of the electrophoretic display, the difference in luminance (ΔL*) between the previous black area and the white area is 1.0 or less when the electrophoretic display displays a black and white grid pattern for 30 minutes and then updates to gray. Claim 13 A method for driving a color electrophoretic display, wherein the color electrophoretic display comprises a plurality of pixels and each pixel is located between a common electrode and a pixel electrode, and the driving method comprises the following: (a) a step of initializing all pixels to a uniform color state, wherein this is performed by applying a constant bias voltage that is not zero to all pixel electrodes, and maintaining the potential of the pixel electrodes in the same synchronized manner in response to a change in potential of the common electrode, and actively controlling the actual potential difference by including an equipotential control section having a time range of 20ms to 60ms; and (b) a step of driving all pixels to a desired color state by maintaining the common electrode in a ground state and applying different target voltages starting from the bias voltage to the pixel electrodes. Claim 14 A driving method according to claim 13, characterized in that a driving waveform including a non-periodic driving waveform or an activation waveform for preventing particle adhesion is applied in at least one of step (a) or step (b). Claim 15 A driving method according to claim 14, wherein the aperiodic activation waveform includes a high-frequency micro-vibration section in a frequency range of 1 kHz to 5 kHz, and the bias voltage has a magnitude of 5% to 20% relative to the maximum absolute value of the target voltage. Claim 16 An electrophoretic display comprises: an electrophoretic fluid containing a plurality of charged particles; a common electrode and a plurality of pixel electrodes; and a driving circuit connected to the common electrode and the plurality of pixel electrodes, wherein the driving circuit is configured to supply a non-zero constant constant bias voltage (Vbias) having a magnitude in the range of 5% to 20% relative to the maximum absolute value of a target voltage for pixel driving to all of the plurality of pixel electrodes to maintain the particles in a reaction-ready state, and simultaneously supply a non-periodic activation waveform to the common electrode to initialize all pixels to a specific intermediate color state while the constant bias voltage is maintained, wherein the non-periodic activation waveform is configured to include: (i) a high-frequency micro-vibration section to resolve particle adhesion; (ii) a random pulse section of medium amplitude to rearrange the particles; and (iii) a low-frequency strong driving pulse section to align the particles to a specific color state; and wherein the electrophoretic fluid is enclosed inside a plurality of microcapsules or filled inside a space partitioned by a partition.

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