CN114815432A - Dielectrophoretic display and method for controlling display thereof - Google Patents

Abstract

The invention discloses a dielectrophoretic display, which is composed of a reflector as a substrate, a first driving electrode array, a first hydrophobic layer, an emulsion layer and a transparent cover plate in order from bottom to top, wherein the emulsion layer is composed of an emulsion, and the The emulsion includes an outer phase as a continuous phase, inner phase droplets and one or more particles located in the inner phase droplets, and the first drive electrode array generates an AC electric field across the inner phase droplets by applying an AC voltage and The particles in the internal phase droplets are driven to move. According to the dielectrophoretic display of the present invention, a multi-state display can be realized by applying an alternating voltage to a pair of electrodes at least. Since the driving force is mainly dielectrophoretic force, there is no specific requirement for particle surface charge. Combined with internal phase droplets and colored particles, as well as multi-state controllable dynamic switching, a multi-color continuously adjustable display effect can be achieved and a bistable display can be realized.

Description

A kind of dielectrophoretic display and method for controlling its display

technical field

The invention belongs to the technical field of information display, and in particular relates to a dielectrophoretic display and a method for controlling the display of information on the dielectrophoretic display.

Background technique

Reflective display technology: Different from traditional display technology, it relies on luminescent materials or backlight sources to form display effects. Reflective display technology relies on dynamic adjustment of display materials, natural lighting/ambient lighting conditions, and uses the principle of light reflection to form a display effect. Reflective display technology has the advantages of high definition and eye protection in strong light/outdoor environments.

Existing reflective display technologies mainly include Reflective LCD, Bistable LCD, Electrophoretic Electronic Paper (EPD), Optical Interference Modulation (iMod Mirasol) and Electrowetting Display (EWD). Among them, electrophoresis and optical interference modulation have been successfully industrialized. Optical interferometric modulation displays have high color saturation, but their complex processes and low yield lead to high production costs, thus limiting their commercialization. Electrowetting display technology is still in the stage of material development and display sample development. Electrophoretic electronic paper technology (including microcapsule type and microcup type, such as Chinese patent CN200810109116.3) is based on the distribution of solid particles in the capsule to control the reflection or transmission of light, with bistable characteristics, color contrast and color Saturation is good, it has been successfully commercialized, and is widely used in e-book readers, electronic tags, electronic watches and other products. The successful industrialization of electrophoretic electronic paper displays illustrates the multiple advantages of particles as reflective displays.

At present, the commercialized electrophoretic electronic paper products are only black-and-white and black-and-white color electronic paper displays. , in order to maintain the bistable characteristics, the density of the particles should be kept consistent, which brings great challenges to the material. In addition, the distribution adjustment among various particles requires sophisticated driver IC design and complex multi-amplitude driving waveforms. Therefore, it is difficult to experiment for practical application.

Patent US 9664978 B2 proposes an electrophoretic display. The pixel units can be composed of pixel units, microcapsules or droplets. Electrophoresis works in conjunction with dielectrophoresis and involves at least one type of charged particle. The particles are moved laterally to the side of the droplet by the positive dielectrophoretic force, and the up and down movement of the particles is mainly driven by the electrophoresis generated by the DC electric field formed by the upper and lower sandwich electrodes. The technology uses the combined action of dielectrophoresis and electrophoresis, and the particle surface needs to be charged, and the driving system combines DC and AC systems, which is relatively complex. In addition, the technology consists of display units composed of microcapsules, and the outer phase has higher conductivity and higher dielectric constant, so microcapsules and even droplet systems usually result in droplets that will move away from areas of high field strength, so to some extent The field strength distribution inside the microcapsules or droplets is weakened, and there are problems of low refresh rate of the display or high driving voltage.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, according to one aspect of the present invention, an object of the present invention is to provide a dielectrophoretic display, which consists of a reflector as a substrate, a first driving electrode array, a first hydrophobic layer, Emulsion layer and transparent cover plate,

wherein the emulsion layer consists of an emulsion comprising an outer phase as a continuous phase, inner phase droplets and one or more particles located in the inner phase droplets,

The reflector is used to reflect the transmitted incident light,

The first driving electrode array generates an AC electric field across the inner phase droplets by applying an AC voltage and drives the particles in the inner phase droplets to move,

The first hydrophobic layer is located on the upper surface of the first driving electrode array and is in contact with the surface of the inner phase droplet.

Preferably, the lower surface of the transparent cover plate is subjected to hydrophobic treatment or a second hydrophobic layer is provided on the lower surface of the transparent cover plate.

Preferably, a second driving electrode array is disposed between the second hydrophobic layer and the transparent cover plate, and the shape of the second driving electrode array is consistent with that of the first driving electrode array.

Preferably, the outer phase, the inner phase droplets and the particles located in the inner phase droplets may be transparent and colourless, black and white or coloured.

Preferably, the reflective plate can be formed from diffuse reflective materials (such as white paper), metals, etc., or by coating the substrate with white titanium dioxide coating, barium sulfate coating, reflective coating material, reflective mirror surface material, etc. form.

Preferably, the diameter of the inner phase droplets ranges from 10 microns to 1000 microns.

Preferably, a pixel wall structure is formed in the emulsion layer space, the thickness of the pixel wall structure is in the range of 1-100 microns, the height is in the range of 10-300 microns, and the length of the pixel wall is in the range of 10-500 microns In between, the inner phase droplets are formed into droplet arrays.

Preferably, the external phase is selected from silicone oil, dodecane, hexadecane, olive oil, castor oil, mineral oil and the like.

Preferably, the dielectric constant of the inner phase droplets is greater than that of the outer phase, the components of the inner phase droplets are immiscible or very slightly soluble with the outer phase, and the components of the inner phase droplets are selected from pure water, organic solvents , or a mixed solution of pure water and a water-soluble organic solvent, a water-soluble polymer compound, the organic solvent is selected from carbon tetrachloride, acetic acid, phenol, dichloroethane, etc., and the water-soluble organic solvent is selected from glycerol, Acetone, acetic acid, etc., the water-soluble polymer compound is selected from sodium alginate, hydroxymethyl cellulose, polyethylene glycol and derivatives thereof.

Preferably, the particles have a lower electrical conductivity and a higher dielectric constant than the internal phase droplets, or the particles have a lower dielectric constant and a higher electrical conductivity than the internal phase droplets , the particles are selected from titanium dioxide, silicon dioxide, polystyrene (PS) polymers, mineral materials, composite core-shell particles, etc., and the particle diameters range from 500 nanometers to 50 micrometers.

Preferably, the mineral material is selected from chlorite, illite, etc., montmorillonite, etc., the composite core-shell particles are metal-wrapped silica microspheres, and the ratio of shell thickness to core radius is less than 1:10.

Preferably, the external phase may further include a silicone oil emulsifier, a surfactant, and a thickener.

Preferably, the silicone oil emulsifier is selected from EM90, MC-215 and the like.

Preferably, the inner phase droplets may further include a density control agent, a conductivity control agent, a cosolvent, and the like.

Preferably, the density control agent is selected from glucose, sucrose and the like.

Preferably, the conductivity control agent is selected from sodium chloride, potassium chloride and the like.

Preferably, the color dyes that can be used for the outer phase, the inner phase droplets and the particles located in the inner phase droplets are selected from ionic dyes, disperse dyes, acid dyes, basic dyes and the like.

More preferably, the color dyes that can be used for the inner phase droplets are selected from malachite green dyes, orange yellow dyes, Bengal red dyes, brilliant blue dyes, amaranth dyes, methyl red dyes, alizarin yellow dyes , Rhodamine B, yield dye, etc.

Preferably, the first hydrophobic layer and the second hydrophobic layer are selected from Teflon, Hyflon and other materials.

According to another aspect of the present invention, another object of the present invention is to provide a method of controlling the display of information by the dielectrophoretic display, the method being performed as follows: applying no application to the first and/or second driving electrode arrays Or applying an alternating voltage to form an alternating electric field in the emulsion layer, the amplitude of the alternating electric field is controlled to be 0Vpp-200Vpp, and the frequency range of the alternating electric field is 100kHz-10MHz, thereby controlling one or more of the inner phase droplets the state of the particle.

beneficial effect

Compared with the prior art, the invention has the following advantages and positive effects:

1) According to the dielectrophoretic display of the present invention, a multi-state display can be realized by applying an AC voltage to a pair of electrodes at least. Since the driving force is mainly dielectrophoretic force, there is no specific requirement for the surface charge of the particles, only the particles can be dispersed, which simplifies the complexity of particle production and expands the types of applicable particles.

2) Compared with the microcapsule electrophoresis display in the prior art, the emulsification system used in the dielectrophoresis display method is used as the display material, the formation method is simple, and the system complexity is low. The emulsification system has the characteristics of flexibility, and is not afraid of the microcapsule rupture problem caused by external force extrusion, improves the stability of the device, and is easy to realize a flexible display that can be bent at a large angle.

3) The emulsion droplets can be subjected to positive dielectrophoresis force and dielectric wetting under the AC electric field, which can automatically align the electrode gap and increase the contact area with the electrode surface or the hydrophobic layer in the corresponding area of the electrode surface. The uniformity of driving between display pixels is improved, the driving voltage is reduced, and the refresh rate of the display is improved.

4) Colorized display can be realized. Combined with internal phase droplets and colored particles, as well as multi-state controllable dynamic switching, a multi-color continuously adjustable display effect is achieved.

5) The processing technology is simple, which can effectively reduce the manufacturing cost.

6) Using micron particles as the display driving material, the increase in particle size can reduce the Brownian motion effect, and through density matching, bistable display can be achieved.

Description of drawings

In order to illustrate the specific embodiments of the present invention or the technical solutions in the prior art more clearly, the following will briefly introduce the accompanying drawings used in the description of the specific embodiments or the prior art. Obviously, the accompanying drawings in the following description The drawings are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative efforts. In order to clarify the present invention, parts irrelevant to the description are omitted in the drawings, and the same or similar parts are denoted by the same reference numerals throughout the specification. In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, and thus the present invention is not necessarily limited to those shown in the drawings.

1 is a schematic diagram showing a single pixel structure of a dielectrophoretic display according to the present invention;

Figure 2 is a schematic diagram showing that particles form different distributions under the action of an electric field to display different colors and particle forces;

3 is a schematic diagram showing the shape of the internal phase droplet, the relationship between the electrode and the position of the droplet;

FIG. 4 is a schematic diagram showing the arrangement of droplets of a dielectrophoretic display;

5 is a schematic diagram showing the dispersion state of particles in a droplet when at least two kinds of particles are contained;

6 is a schematic diagram of a dielectrophoresis display according to Example 1;

7 is a schematic diagram of a dielectrophoretic display according to Example 2;

8 is a schematic diagram of a dielectrophoretic display according to Example 3;

9 is a schematic diagram showing that dielectrophoresis shows bistability according to Example 3;

Reference numerals: 1-reflective plate, 2-first driving electrode array, 3-transparent cover plate, 4-external phase, 5-internal phase droplet, 6-particle, 7-pixel wall.

Detailed ways

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before describing, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to their ordinary and lexicographical meanings, but should be based on principles that allow the inventor to define terms appropriately for the best explanation, based on corresponding Explain the meaning and concept of the present invention at the technical level. Accordingly, the descriptions herein are preferred examples for illustrative purposes only and are not intended to limit the scope of the invention, and it should be understood that other equivalent implementations and modifications may be made without departing from the spirit and scope of the invention.

The dielectrophoretic force is generated in a non-uniform electric field. When both the object and the medium around the object can be polarized by the electric field, the dielectrophoretic force will be generated and act on the interface between the particle and the surrounding medium, so that the object will follow the direction of the electric field gradient. Low electric field strength region motion. For microparticles within a droplet, dielectrophoresis acts on the particles, causing the particles to move from the bottom of the droplet to the top of the droplet. Dielectrophoresis display is based on the principle of dielectrophoresis, which relies on the electric field to control the movement and distribution of particles in a specific area of the medium to realize the reflective display process and control.

The terms "first", "second" and the like used herein are used to explain various constituent elements, and they are only used for the purpose of distinguishing one constituent element from another.

Also, the terminology used herein is for explaining exemplary embodiments only, and is not intended to limit the present invention. Singular expressions also include their plural expressions, unless the context clearly indicates otherwise. Terms such as "comprising," "equipped with," or "having" as used herein are used to designate the presence of a practical characteristic, number, step, constituent element, or combination thereof, and should be understood as not excluding one or more The possibility of addition or existence of other characteristics, numbers, steps, constituent elements or combinations thereof.

Also, if a layer or an element is referred to as being formed "on" or "over" a "layer" or "element", it means that each layer or element is formed directly on the layer or element, or on Additional layers or elements may be formed between the layers, bodies or substrates.

As used herein, the terms "comprising", "including", "having", "containing" or any other similar terms are open-ended transitional phrases intended to cover non-exclusive inclusions. For example, a composition or article of manufacture containing a plurality of elements is not limited to only those elements listed herein, but can also include other elements not expressly listed, but which are generally inherent to the composition or article of manufacture. Otherwise, unless expressly stated to the contrary, the term "or" refers to an inclusive "or" rather than an exclusive "or". For example, the condition "A or B" is satisfied by any of the following: A is true (or present) and B is false (or absent), A is false (or absent) and B is true (or present), Both A and B are true (or exist). In addition, in this document, the terms "comprising", "including", "having", "containing" should be interpreted as having specifically disclosed and encompassing both "consisting of" and "substantially consisting of" and other closures Formal or semi-closed connectives.

Throughout the specification, when it is mentioned that an element is "connected" to another element, it includes not only "direct connection" but also "indirect connection" between other elements. Additionally, when it is referred to that an element "comprises" a certain component, it means that the element can further include other components rather than exclude other components, unless expressly stated to the contrary.

The invention provides a reflective display based on the principle of dielectrophoresis. The display has simple requirements for display materials, can achieve three display states through a single particle system, simplifies driving circuit design, reduces display production costs and reduces driving time. The display refresh rate can reach about 400ms (345 micron pixels), and can be further improved depending on the material system and pixel size. At the same time, the display can achieve bi-stable characteristics and reduce display power consumption. In addition, the display is based on dielectrophoresis technology, and the driving mode is AC voltage mode, which will not cause the ghosting problem caused by DC imbalance due to the polarization of ions or molecules of display devices and materials after long-term DC power-on, so as to ensure Good display effect and prolong life of display device. The display material adopts an emulsification system, which can be prepared by the existing mechanical emulsification method, film emulsification or microfluidic method, and the range of optional materials is wide, so that the display effect of this display technology is not easily limited by multiple constraints on the selection of display materials. .

Referring to FIG. 1, FIG. 1 shows a schematic diagram of a single pixel structure of a dielectrophoretic display according to the present invention, an emulsion layer space is formed between the transparent cover plate 3 and the first driving electrode array 2, wherein the first hydrophobic layer and the second hydrophobic layer are formed. Layers not shown, the emulsions used in the present invention form emulsions (such as water-in-oil) from two-phase immiscible fluids, wherein the outer phase is typically a dielectric fluid, such as an organic solvent or an oil phase, preferably a non-volatile liquid, Provides protection for internal phase droplets from volatilization or reaction with air. The inner phase liquid can be dyed by adding dyes, for example, dissolving color dyes in the inner phase liquid, and the color dyes can be ionic dyes, disperse dyes, acid dyes, basic dyes, and the like. Dyes dissolved in the outer phase liquid should be insoluble in the inner phase liquid, and dyes dissolved in the inner phase liquid should be insoluble in the outer phase liquid. The diameter of the inner phase droplets ranges from 10 microns to 1000 microns.

The selected particles must be able to be driven by the dielectrophoretic force under an alternating electric field of a certain frequency. There is no specific requirement for the surface charge of the particles, as long as the particles can be dispersed without serious agglomeration. Colored particles are dispersed in the inner phase droplets. The color of the particles is different from that of the inner phase droplets. Compared with the inner phase droplets, the particles have lower electrical conductivity or dielectric constant. The particles mainly include titanium dioxide and silicon dioxide. , polystyrene (PS) and other polymers, mineral materials, composite core-shell particles (such as metal-coated silica microspheres, etc.), etc., with a diameter ranging from 500 nanometers to 50 micrometers. Preferably, under different electric field frequencies, the magnitude and direction (positive and negative dielectrophoretic forces) of the dielectrophoretic force that the particles are subjected to may change. For example, polystyrene particles of about 1-4 microns may be subjected to positive dielectrophoresis force under low-frequency electric field because the surface conductivity may be higher than that of liquid in water-phase droplets. However, under the high-frequency electric field, the particle polarization properties depend on the dielectric constant, and the polystyrene particles are smaller than the dielectric constant of the aqueous liquid, so they are affected by the negative dielectrophoretic force. The color of the colored particles is not limited to a single color.

The emulsion multiphase system described above is used as a display material system in a dielectrophoretic display. Figure 2 is a schematic diagram showing that the particles form different distributions under the action of an electric field to show different colors and the force on the particles. Referring to Figure 2, under the action of an AC electric field, the inner phase droplets are subjected to positive dielectrophoresis force at a specific frequency, and the automatic It is positioned at the electrode gap to improve the synchronization and controllability of display pixel driving. Moreover, under the action of AC electric field, the droplet will undergo dielectric wetting phenomenon. The dielectric wetting phenomenon can increase the AC electric field strength of the internal phase droplets, which in turn helps to reduce the driving voltage and increase the particle motion rate.

The particles in the inner phase droplets may be affected by positive or negative dielectrophoretic forces under the action of an electric field. When the particles are subjected to the negative dielectrophoretic force, they can move upward from the bottom of the droplet and form a structure with curved curvature along the sidewall of the droplet, with various distribution states. In Fig. 2, taking a single particle system (the inner phase droplet contains only a single type of colored particles) as an example, when no electric field is applied or the applied electric field is small, the particles accumulate at the bottom of the droplet to form state 1; the electric field and frequency are sufficient to drive When the particles move upward, the particles move to the vicinity of the equatorial line of the inner phase droplet, forming the state 2 distribution; when the particles move further upward to the top of the droplet, they will gather at the top of the droplet to form the state 3. These three states only show the symbolic state of particle distribution. In fact, in the process of changing from state 1 to state 3, there are various states (gray scales) that vary infinitely. Each and multiple states (grayscales) may correspond to one or more display colors or display grayscales. When the particles are subjected to positive dielectrophoretic forces, they can move from top to bottom within the droplet, returning from state 3 to state 2, and from state 2 to state 1.

In order to avoid mutual fusion between adjacent inner phase droplets or no curvature at the interface between the inner phase droplet and the outer phase hindering the upward movement of particles to form state 3, the lower surface of the top transparent cover plate and the upper surface of the first driving electrode array respectively form the first state 3. The hydrophobic layer and the second hydrophobic layer (not shown in the figure), or the lower surface of the transparent cover plate and the upper surface of the first driving electrode array are subjected to hydrophobic modification treatment (for example, the transparent cover plate is treated by physical, chemical and other methods). The lower surface is hydrophobically modified). The internal phase droplets must be in contact with the first and second hydrophobic layers. The inner phase droplet is between the first hydrophobic layer and the second hydrophobic layer, and can be squeezed to form a flatter droplet shape, as shown in FIG. 3 . The side of the droplet needs to ensure a certain curvature towards the center of the sphere to ensure that the particles can slide from the bottom along the curved sidewall to the top. The contact area between the bottom of the droplet and the electrode surface or the hydrophobic layer on the electrode surface can be affected by the applied AC voltage, and the dielectric wetting effect will change the contact area. The top of the inner phase droplet may not be in contact with the first hydrophobic layer, or may have a certain contact area, and the contact angle should be greater than or equal to 90 degrees.

From a top view, the positional relationship between the distribution area of the first driving electrode array at the bottom and the inner phase droplets is shown, and the distribution area of the first driving electrode array needs to overlap with the droplets (Fig. 3), that is, the droplets partially cover electrode surface. The shape of the electrode is not particularly limited, as long as it can generate an AC electric field across the inside of the droplet after an AC voltage is applied. It is preferable to use transparent conductive electrode materials, such as indium tin oxide materials, etc. The patterning of the electrodes provides a non-uniform strong electric field for the emulsion as a display material, so that the particles inside the inner phase droplets are subjected to the dielectrophoretic force. The first driving electrode array is distributed on the reflective plate, and the electrode pattern is not specifically limited, and a pair of electrodes should correspond to at least one pixel unit of the driveable display.

Referring to Figures 2 and 3, when in state 1, the particles accumulate at the bottom of the dyed internal phase droplets, and when the incident light passes through the dyed internal phase droplets, according to the principle of color transmission, other than the color of the dyed internal phase droplets themselves. The incident light of other wavelengths is absorbed by the dyed internal phase droplets, and the incident light of the remaining wavelength bands further acts on the particle surface, and the particle material absorbs the incident light of other wavelengths except its own color, including the wavelength of the color of the dyed internal phase droplet. incident light. Therefore, the incident light is reflected by the particles and absorbs almost all wavelengths of visible light, that is, the color corresponding to state 1 is a mixed color. When an AC electric field is applied to the electrode, the particles can move upward along the sidewall of the inner phase droplet, forming a dispersed state of state 2 near the equator of the inner phase droplet. In state 2, the opening ratio of the inner phase droplet (the ratio of the light-transmitting area of the droplet to the maximum cross-sectional area of the droplet in a top view) can be adjusted. After the incident light passes through the internal phase droplet, it is reflected by the reflector, and then returns through the droplet and the transparent cover. Since the incident light is blocked by the small particle area, the color of the reflected light at this time is mainly the color of the dyed internal phase droplets, that is, the color of the internal phase droplets corresponding to state 2. When the particles move to the top of the inner phase droplet under the action of dielectrophoretic force, the incident light forms reflected light mainly based on particle color under the action of particle reflection, that is, the color of solid particles corresponding to state 3. In this state, the displayed color and color saturation are affected by the coverage of the surface of the inner phase droplet by the particles.

The electrodes in the first driving electrode array and the second driving electrode array are arranged in coplanar electrode pairs, which generate a high electric field strength between the respective electrode pairs and form an electric field strength (electric field gradient) that continuously decays outward from the electrode gap. The electrode pattern geometry of the coplanar electrode is not limited, and can be designed and adjusted according to application needs. When an AC voltage is applied to the first driving electrode, the particles are moved to the top of the droplet by the negative dielectrophoretic force, corresponding to the display switching from state 1 to state 2, or from state 2 to state 3. When an AC voltage is applied to the second driving electrode, the particles are moved to the bottom of the droplet by the negative dielectrophoretic force, and the corresponding display state is switched from state 3 to state 2, or from state 2 to state 1.

The electrode power-on method can be the method of applying alternating current signals alternately. Figure 4 is a schematic diagram showing the arrangement of phase droplets in the DEP display. The 2-column electrodes (common electrodes) are grounded. A second drive electrode array is arranged between the transparent cover plate and the second hydrophobic layer. The structure and pattern of the second drive electrode array and the first drive electrode array are mirror-symmetrical, so as to provide an upper electric field for the particles and improve the accuracy of the particles. control ability. For example: when the particle is under the action of an alternating current field of a certain frequency, only the negative dielectrophoretic force is applied. The particles move upward only when an alternating voltage is applied to the first pair of drive electrode arrays. When an alternating electric field is applied only to the second drive electrode array pair, the particles move downward. The distance control between the reflector and the transparent cover can be achieved by any method, such as a photoresist layer, an adhesive tape layer, solid particles, etc., to form a pixel wall as a support structure.

The arrangement of the droplet array is shown in Figure 4. Due to the positive dielectrophoretic force, the inner phase droplets will be positioned in the high field strength area of the electrode gap. And the inner phase droplets are in contact with the first hydrophobic layer and the second hydrophobic layer under the action of dielectric wetting, so as to ensure that the particles inside the inner phase droplets can be controlled by the AC electric field generated by the surrounding electrodes. The arrangement of the droplets is not specifically limited, and can be adjusted according to the structure of the electrode array and the size of the droplets. The internal phase droplets can be independent of each other by means of the liquid-liquid interface, arranged into droplet arrays that can be isolated by solid substances, or isolated from each other by micron "pixel wall" structures made of materials such as photoresist. The thickness of the pixel wall is in the range of 1-100 microns, the height of the pixel wall is in the range of 10-300 microns, and the length of the pixel wall (top view) is in the range of 10-500 microns.

Furthermore, the species of particles within the internal phase droplets may not be limited to a single species. The inner phase droplet can contain more than two kinds of particles. The color and dielectric properties of the first kind of particles are different from those of the second kind of particles, so the droplets can show different colors under the condition of applying electrical signals of different frequencies. As shown in Fig. 5, when no electric field is applied, both particle 1 and particle 2 are located at the bottom of the inner phase droplet, showing mixed colors at this time. When an electrical signal of frequency 1 is applied, the dielectrophoretic force of the two kinds of particles is different. Among them, the particle 2 is subjected to a stronger negative dielectrophoresis force and moves to the top of the droplet rapidly. Under the action of electrophoretic force, it is still located at the bottom of the inner phase droplet, and the color is the color of particle 2 at this time. When an electrical signal of frequency 2 is applied, both particle 1 and particle 2 are affected by the negative dielectrophoretic force, and both can move to the equator of the inner phase droplet, showing the color of the inner phase droplet at this time. When the electrical signal of frequency 3 is applied, the particle 1 is subjected to a stronger negative dielectrophoresis force and moves to the top of the inner phase droplet, while the particle 2 is subjected to a weak negative or positive dielectrophoresis force and is located at the bottom of the inner phase droplet , the color of particle 1 appears at this time. Particle 1 and Particle 2 satisfying the above conditions may have the following properties: Particle 1 has a relatively high electrical conductivity relative to the internal phase droplets, and has a relatively low dielectric constant relative to the internal phase droplets (eg, a particle size of about 4 microns or less). of polystyrene particles, etc.). The particles 2 have a lower electrical conductivity relative to the internal phase droplets, and have a relatively high dielectric constant relative to the internal phase droplets (eg, particles of insulating material of high dielectric constant materials such as titanium dioxide particles).

The following examples are only listed as examples of the embodiments of the present invention, and do not constitute any limitation to the present invention. Those skilled in the art can understand that modifications within the scope of the spirit and concept of the present invention are all within the protection of the present invention. scope. Unless otherwise specified, the reagents and instruments used in the following examples are commercially available products.

Example 1

The device display pixel unit of the dielectrophoretic display in this embodiment is composed of a reflective plate, a first driving electrode array, a first hydrophobic layer, an emulsion layer, a second hydrophobic layer and a transparent cover plate in order from bottom to top, and the reflective plate is composed of It is made of glass coated with white titanium dioxide or barium sulfate. Photolithography technology is used on the reflector, and the pattern of driving electrode array is photoetched with positive glue, and then the ITO driving electrode array is obtained by etching process. Then, a Teflon material is coated on the driving electrode array layer to form a first hydrophobic layer with a thickness of 10-1000 nanometers (if it is suitable, please modify it at your discretion). In order to avoid the fusion between the internal phase droplets, a pixel wall (dam) structure is formed on the first hydrophobic layer with SU8 series photoresist material, and the area enclosed by each pixel wall includes a fixed and consistent electrode pattern . The pixel walls are 10-150 microns in height, 345 microns in side length, and 20 microns in space between the pixel walls, so as to separate the internal phase droplets and improve the stability of the display device. The transparent cover plate is made of silica glass or ITO glass, and the lower surface of the transparent cover plate is coated with a second hydrophobic layer. An emulsion layer is formed by injecting an emulsion between the driving electrode array and the transparent cover plate. At least one internal phase droplet is contained in the area enclosed by the pixel wall.

The outer phase of the emulsion system of the emulsion layer is silicone oil, and a small amount of surfactant (MC-215 or EM90 emulsifier) is added to the silicone oil at 0.5-2% v/v. Deionized water with low conductivity is used as the inner phase droplet, and 0.03-0.09 wt % of malachite green dye and 8-12 wt % of red polystyrene particles (1-7 microns) are added. The inner phase suspension containing the dye and red polystyrene particles was added to the silicone oil as the outer phase and emulsified by mechanical stirring. After emulsification, droplets of the inner phase encapsulated by silicone oil are formed. The emulsion is uniformly filled into the emulsion layer between the first driving electrode array and the transparent cover plate, so that the area enclosed by the pixel wall contains at least one internal phase droplet. The transparent cover is then covered to complete the preparation of the display.

The movement of the polystyrene particles in the inner phase droplet (water) is realized by applying an alternating current signal to the first driving electrode array, thereby realizing a dynamic display effect. Referring to Figure 6, when an alternating current signal is applied, the internal phase droplet undergoes a certain deformation under the action of polarization and under the action of dielectric wetting. State 1 is the initial state when no electrical signal is applied, state 2 is the state where the amplitude of the AC electric field is 40Vpp, and state 3 is the state where the amplitude of the AC electric field is 120Vpp, and the frequency range of the AC electric field is 100kHz-10MHz to ensure that the particles can move At the same time, the strong electrothermal effect of the emulsion system is avoided. The display of this embodiment can display dark red (state 1), blue (state 2), and light red (state 3) by driving the red polystyrene particles.

Example 2

Using the device structure similar to that in Example 1, changing the formulation of the emulsion material, the display color can be further expanded, and the yellow-dark blue display effect can be realized. As shown in Figure 7. A small amount of silicone oil emulsifier (MC-215 or EM90 emulsifier) of 0.5-2% v/v is added to the silicone oil of the emulsion system. The inner phase droplets use deionized water with low conductivity, and add 0.03-0.09 wt% of orange-yellow IV dye and 8-12 wt% of blue polystyrene particles. As shown in Figure 7, applying different alternating current signals to electrodes in different regions can display yellow letters "S" and "U" and a blue background area; conversely, changing the driving alternating current signal can display a yellow background area and a blue background area. Color letters "C" and "N". The applied electrical signal amplitude is 30Vpp and the frequency is 400kHz when the pattern is displayed.

Example 3

Using a device structure similar to that in Example 1, an alternating current signal is applied to a specific area of the first driving electrode array in the dielectrophoretic display as required to drive, as shown in Figure 8, the pattern "flower" and the number "7" can be presented , and the display effect of the pattern "heart". Tilt the screen from 0-75 degrees, the quality of the displayed content is not significantly affected, and the colors presented are not sensitive to the viewing angle, so the monitor has the characteristics of a wide viewing angle.

Example 4

Using the same device structure as in Example 1, a second driving electrode array is additionally arranged between the second hydrophobic layer and the transparent cover plate, and the pattern of the second driving electrode array is the same as that of the first driving electrode. The arrays are exactly aligned and correspond.

The emulsion system is formed by water-in-silicon oil, and a small amount of 0.5-2% v/v silicone oil emulsifier (MC-215 or EM90 emulsifier) is added to the silicone oil. The inner phase droplet adopts deionized water with low conductivity, and adds 0.01-0.85 wt% of orange-yellow dye and 8-12 wt% of colored polystyrene particles with a diameter of 7 microns. And add a density control agent (sucrose) to the inner phase droplets to adjust the density of the water (adjusted to a density similar to the particle, about 1.06 g/cm3), so that the polystyrene particles can be suspended and significantly slow down sedimentation, which can be After the display pattern is refreshed, the pattern is kept unchanged to realize the bistable characteristic of the dielectrophoretic display.

Since the particles are difficult to settle, the corresponding driving mode also needs to be adjusted. The alternating current signal is applied to the second driving electrode array to control the downward movement of the polystyrene particles, and the alternating current signal is applied to the first driving electrode array to control the polystyrene particles. The styrene particles move upward. The dielectrophoretic display according to the present embodiment can achieve a bistable effect for about 10 minutes. As shown in Figure 9, after the electrodes are applied with voltage, the driving part appears yellow, such as the large yellow area on the left and the yellow "box" pattern on the right corresponding to 0 minutes. Dark blue pixels are not powered and therefore remain blue. After a power failure, the yellow driven pixels can remain displayed for a long time. At 10 minutes of power-off, a gradual transition from the yellow state to the blue state can be observed, but the "box" pattern can still be clearly observed.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention. Included within the scope of protection of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (10)

1. A dielectrophoretic display consisting of a reflector as a substrate, a first driving electrode array, a first hydrophobic layer, an emulsion layer and a transparent cover plate in order from bottom to top, wherein the emulsion layer consists of an emulsion comprising an outer phase as a continuous phase, inner phase droplets and one or more particles located in the inner phase droplets, The reflector is used to reflect the transmitted incident light, The first driving electrode array generates an AC electric field across the inner phase droplets by applying an AC voltage and drives the particles in the inner phase droplets to move, The first hydrophobic layer is located on the upper surface of the first driving electrode array and is in contact with the surface of the inner phase droplet. 2 . The dielectrophoretic display according to claim 1 , wherein the lower surface of the transparent cover plate is subjected to hydrophobic treatment or a second hydrophobic layer is provided on the lower surface of the transparent cover plate; 3 . Preferably, a second driving electrode array is disposed between the second hydrophobic layer and the transparent cover plate, and the shape of the second driving electrode array is consistent with that of the first driving electrode array. 3 . The dielectrophoretic display according to claim 1 , wherein the reflector can be formed of materials such as diffuse reflection materials (such as white paper), metals, or the like, or by coating the substrate with a white titanium dioxide coating, sulfuric acid, and the like. 4 . Barium coating, reflective coating material, reflective mirror material, etc. are formed. 4 . The DEP display according to claim 1 , wherein a pixel wall structure is formed in the emulsion layer space, and the thickness of the pixel wall structure ranges from 1 to 100 μm and the height ranges from 10 to 10 μm. 5 . Between 300 microns and pixel wall lengths ranging from 10-500 microns, the inner phase droplets form droplet arrays. 5 . The DEP display according to claim 1 , wherein the external phase is selected from the group consisting of silicone oil, dodecane, hexadecane, olive oil, castor oil, mineral oil and the like. 6 . 6. The DEP display of claim 1, wherein the outer phase, the inner phase droplets and the particles located in the inner phase droplets can be transparent and colorless, black and white or colored. 7 . The DEP display of claim 1 , wherein the inner phase droplet has a diameter ranging from 10 μm to 1000 μm; 8 . Preferably, the dielectric constant of the inner phase droplets is greater than that of the outer phase, the components of the inner phase droplets are immiscible or very slightly soluble with the outer phase, and the components of the inner phase droplets are selected from pure water, organic solvents , or a mixed solution of pure water and a water-soluble organic solvent, a water-soluble polymer compound, the organic solvent is selected from carbon tetrachloride, acetic acid, phenol, dichloroethane, etc., and the water-soluble organic solvent is selected from glycerol, Acetone, acetic acid, etc., the water-soluble polymer compound is selected from sodium alginate, hydroxymethyl cellulose, polyethylene glycol and derivatives thereof. 8 . The dielectrophoretic display of claim 1 , wherein the particles have lower conductivity and higher dielectric constant than the internal phase droplets, or the particles have a higher dielectric constant than the internal phase droplets. 9 . The droplets have lower dielectric constant and higher conductivity, the particles are selected from titanium dioxide, silica, polystyrene (PS) polymers, mineral materials, composite core-shell particles, etc., and the particle diameters range from 500 nanometers to 50 microns; Preferably, the mineral material is selected from chlorite, illite, etc., montmorillonite, etc., the composite core-shell particles are metal-wrapped silica microspheres, and the ratio of shell thickness to core radius is less than 1:10. 9 . The dielectrophoretic display according to claim 1 , wherein the external phase can further comprise a silicone oil emulsifier, a surfactant, and a thickener; 10 . Preferably, the silicone oil emulsifier is selected from EM90, MC-215, etc.; Preferably, the inner phase droplets may further include a density control agent, a conductivity control agent, a cosolvent, and the like; Preferably, the density control agent is selected from glucose, sucrose, etc.; Preferably, the conductivity control agent is selected from sodium chloride, potassium chloride, etc.; Preferably, the color dyes that can be used for the outer phase, the inner phase droplets and the particles located in the inner phase droplets are selected from ionic dyes, disperse dyes, acid dyes, basic dyes, and the like; More preferably, the color dyes that can be used for the inner phase droplets are selected from malachite green dyes, orange yellow dyes, Bengal red dyes, brilliant blue dyes, amaranth dyes, methyl red dyes, alizarin yellow dyes , Rhodamine B, yield dye, etc.; Preferably, the first hydrophobic layer and the second hydrophobic layer are selected from Teflon, Hyflon and other materials. 10. A method of controlling the display of information in a dielectrophoretic display according to any one of claims 1 to 9, the method being performed by applying no or applying an alternating current to the first and/or second array of drive electrodes voltage to form an AC electric field in the emulsion layer, the amplitude of the AC electric field is controlled at 0Vpp-200Vpp, and the frequency range of the AC electric field is 100kHz-10MHz, so as to control one or more of the particles in the inner phase droplets status.

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