CN107367835B - Electrowetting display and preparation method thereof - Google Patents
Electrowetting display and preparation method thereof Download PDFInfo
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- CN107367835B CN107367835B CN201710686589.9A CN201710686589A CN107367835B CN 107367835 B CN107367835 B CN 107367835B CN 201710686589 A CN201710686589 A CN 201710686589A CN 107367835 B CN107367835 B CN 107367835B
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- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/004—Optical devices or arrangements for the control of light using movable or deformable optical elements based on a displacement or a deformation of a fluid
- G02B26/005—Optical devices or arrangements for the control of light using movable or deformable optical elements based on a displacement or a deformation of a fluid based on electrowetting
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Abstract
The invention discloses an electrowetting display and a preparation method thereof.A magnetic solid particle is added into a filling fluid, in the process of applying voltage, the conductive fluid drives ink to move, the thinnest part of an oil film determines the breaking point and the moving direction of the oil film, and the thinner the oil film, the lower the required pixel opening voltage is, the magnetic solid particle introduced into a pixel wall can change the thickness distribution of the oil film in the pixel wall, thereby achieving the beneficial effect of controlling the moving direction of the ink. The preparation method provided by the invention is simple in process and easy to realize, and the prepared electrowetting display can effectively control the movement direction of the ink.
Description
Technical Field
The invention relates to the technical field of displays, in particular to an electrowetting display and a preparation method thereof.
Background
Electro-wetting Display (EWD) utilizes an external electric field to control the surface tension of a polar liquid in a Display unit, thereby controlling the contraction and spreading of ink, and realizing the controllability of an optical switch. To obtain a good color display, the position of the ink break and the direction of movement must be reliably controlled.
The existing ink motion control modes are two types: one is through forming the local hole or defect of the driving electrode layer (such as ITO) in a corner of the pixel unit, utilize the local unevenness of the applied electric field, realize the ink movement shrinks to a corner of the pixel, because in the thinnest place of ink thickness, the ink breaks preferentially, the threshold voltage that the ink breaks and needs depends on the thickness of the thinnest place of ink, therefore the local defect formed can control the position of the contraction end point of the ink, but can't control the ink breaking point effectively, and in carrying on the etch manufacturing defect process to the conductive backplane (such as common ITO glass), apt to appear the irregular jaggy edge, while exerting the voltage drive, the electric charge will tend to gather to the irregular edge, form the local high charge density, cause the insulating layer to break down very easily, destroy the device, reduce the life time of the device; the other is to use two kinds of photoresists with different hydrophilicities to manufacture a pixel wall, so that the thickness of the ink on the more hydrophilic side is thinner, and the position of ink fracture is changed, so that the ink moving direction is controlled, but the final ink shrinkage position can be any one of two corners of the pixel wall on the other side, so that the final ink shrinkage position cannot be controlled by adopting the method, and the two kinds of photoresists with different hydrophilicities are used, the requirement on alignment precision is high by using a secondary photoetching method, and the insulating layer at the bottom is easily damaged by carrying out dry etching twice.
Disclosure of Invention
The invention aims to solve the technical problem of providing an electrowetting display device and a preparation method thereof, and aims to solve the problem that the movement direction of ink in a pixel grid of the display device is uncontrollable.
The technical scheme adopted by the invention is as follows:
the invention provides an electrowetting display, which comprises an upper substrate and a lower substrate which are oppositely arranged, wherein the upper substrate and the lower substrate are packaged to form a closed cavity, a first fluid and a second fluid which are mutually immiscible are filled in the closed cavity, the lower substrate comprises a lower conductive substrate, a hydrophobic dielectric layer and a pixel wall which are sequentially arranged, the pixel wall encloses a plurality of pixel grids, and each pixel grid is filled with the first fluid and magnetic solid particles.
Preferably, the first fluid is a non-polar liquid and the second fluid is an electrolytic liquid. The first fluid is a non-polar liquid immiscible with the second fluid, such as hexadecane, silicone oil or a mixture of the two. The first fluid absorbs at least a part of the light spectrum, which may be transmissive for a part of the light spectrum, thereby forming a color filter. Preferably, the viscosity of the first fluid 5 is in the range of 5 to 30cps, and the surface tension is in the range of 15 to 45 mN/cm. The second fluid is an electrolyte liquid, such as a polar solvent, ionic liquid, salt solution, etc., and may be a transparent, black or colored absorptive or reflective liquid, preferably a transparent absorptive or reflective liquid.
Preferably, the magnetic solid particles are ferromagnetic or antiferromagnetic materials.
Preferably, the surface wettability of the magnetic solid particles is rendered lipophilic or hydrophilic, the contact angle of the surface water of the magnetic solid particles being <70 ° or >110 °. The surfaces of the magnetic solid particles are hydrophilic through hydrophilic modification and lipophilic through hydrophobic modification.
Preferably, the magnetic solid particles are spherical in shape.
Preferably, the magnetic solid particles are an alloy or a metal oxide, the alloy is a magnetic material containing at least one of iron, cobalt and nickel, and the metal oxide is at least one of iron oxide, cobalt oxide and nickel oxide.
Preferably, the particle size of the magnetic solid particles is 1-100 μm.
Preferably, the magnetic solid particles have a relative magnetic permeability of 200 to 200000.
The invention also provides a preparation method of the electrowetting display, which comprises the step of filling the magnetic solid particles into the pixel grids.
Preferably, the specific steps of filling the pixel cells with the magnetic solid particles include: dispersing the magnetic solid particles in the first fluid, and filling the magnetic solid particles into the pixel cells simultaneously with the first fluid.
Further, the magnetic solid particles and the first fluid are simultaneously filled into the pixel cells by any one of a vertical inlet filling method, an ink jet printing method, a liquid separation filling method, a slit coating method, and an interface self-assembly method.
Preferably, the method further comprises the step of fixing the magnetic solid particles in the pixel cells by using an external magnetic field. After the magnetic solid particles are filled into the pixel grids and the upper substrate and the lower substrate are completely packaged, the magnetic solid particles are moved and fixed at a specific position in the pixel grids, which can be the middle or the corner of the pixel grids, through an external magnetic field, and then the external magnetic field is removed, and the original specific position of the magnetic solid particles can be maintained due to the surface tension effect of the filled ink and the conductive liquid.
The invention has the beneficial effects that:
aiming at the problem that the movement direction of the ink is uncontrollable in the prior art, magnetic solid particles are added into the filling fluid, the conductive fluid drives the ink to move in the process of applying voltage, the thinnest part of the oil film determines the breaking point and the movement direction of the oil film, and the pixel opening voltage required by the thinner oil film is lower. The preparation method provided by the invention is simple in process and easy to realize, and the prepared electrowetting display can effectively control the movement direction of the ink.
Drawings
FIG. 1 is a schematic diagram of an electrowetting display;
FIG. 2 is a graph showing the effect of magnetic solid particles of different sizes on varying oil film thickness;
FIG. 3 is an optical microscope photograph of magnetic solid particles of different sizes to change the thickness of an oil film;
fig. 4 is a flow chart of a process for manufacturing an electrowetting display.
Detailed Description
The conception, the specific structure, and the technical effects produced by the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings to fully understand the objects, the features, and the effects of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.
Example 1
The invention provides an electrowetting display, the structural schematic diagram of which is shown in fig. 1, and the electrowetting display comprises an upper substrate 9 and a lower substrate 10 which are oppositely arranged, wherein the lower substrate 10 comprises a lower conductive substrate 1, a hydrophobic dielectric layer 2 and a pixel wall 3 which are sequentially arranged, the pixel wall 3 encloses a plurality of pixel grids, a first fluid 4 and magnetic solid particles 6 are filled in the pixel grids, the upper substrate 9 and the lower substrate 10 are packaged by a glue material 8 to form a closed cavity 7, and the closed cavity 7 is filled with the first fluid 4 and a second fluid 5 which are mutually immiscible.
FIG. 2 shows the effect of varying the thickness of the oil film by the magnetic solid particles of different particle diameters, where the magnetic solid particles 61 and 62 have the same surface wettability (contact angle θ)1＝θ2) The oil film of the ink at the position of the magnetic solid particles gradually becomes thicker along with the increase of the particle size of the magnetic solid particles. Referring to fig. 3, fig. 3(a), 3(b) and 3(c) are optical microscopic views of a magnetic solid particle having a small particle diameter changing the thickness of an oil film, and fig. 3(d), 3(e) and 3(f) are electron microscopic views of a magnetic solid particle having a large particle diameter changing the thickness of an oil film, in which when the particle diameter of the magnetic solid particle is small, the oil film on the side of the magnetic solid particle is thin, and when a voltage is applied, ink moves toward the opposite side of the magnetic solid particle, and when the particle diameter of the magnetic solid particle is large, the ink on the side of the magnetic solid particle is thick, and when a voltage is applied, ink moves toward the same side as the magnetic solid particle, and since the thinnest point of the oil film determines the direction of the oil film, the direction of the ink contraction movement can be controlled by controlling the particle diameter of the magnetic solid particle.
The invention also provides a preparation method of the electrowetting display, and the preparation process flow is shown in figure 4. The hydrophobic dielectric layer 2 is prepared on the lower conductive substrate 1 in a manner of spin coating, roll coating, screen printing, dip coating, spray coating, blade coating, slit coating and the like, the hydrophobic dielectric layer 2 can be AF1600 and AF1600X of DuPont company or Cytop of AGC company or Hyflon of Solvay Plastics and the like, drying is carried out to obtain the hydrophobic dielectric layer 2, and the dry film thickness of the formed hydrophobic dielectric layer 2 is 200 nm-800 nm.
The first fluid 4 and the magnetic solid particles 6 are filled in the pixel grid: adding ultrapure water and absolute ethyl alcohol into Invar alloy powder in sequence for washing, separating, drying in a vacuum drying oven at 60 ℃ for 2 hours, and grinding into powder by using an agate mortar to obtain magnetic solid particles 6, wherein the particle size of the magnetic solid particles 6 is 1-100 microns. The magnetic solid particles 6 prepared above are dispersed in a first fluid 4 to form a dispersion liquid, the first fluid 4 is an electrolyte liquid such as a polar solvent, an ionic liquid, a salt solution and the like, the dispersion liquid is filled into a pixel cell by a vertical entry filling method, an ink jet printing method, a liquid separation filling method, a slit coating method, an interfacial self-assembly method or by using an ink filling device such as that in CN104932096A, and then a second fluid 5 is filled into the pixel cell, the second fluid 5 is a non-polar liquid which is immiscible with the first fluid 4, such as hexadecane, silicone oil or a mixture of the two, the second fluid absorbs at least a part of a spectrum and can be transmissive for a part of the spectrum, thereby forming a color filter, preferably, the viscosity range of the second fluid 5 to 30cps, and the surface tension range of the second fluid 5 to 45 mN/cm. Finally, the upper substrate 9 and the lower substrate 10 are encapsulated by the glue material 8 to form an electrowetting display device, before voltage is applied, the magnetic solid particles 6 are fixed at specific positions in the pixel cells, which can be the middle or the corners of the pixel cells, by an external magnetic field, and then the external magnetic field is removed, so that the magnetic solid particles 6 can maintain the initial specific positions due to the surface tension of the filled first fluid 4 and the second fluid 5.
In some embodiments of the present invention, the magnetic solid particles are Invar alloy particles, the magnetic solid particles 6 added in practice may be an alloy or a metal oxide, the alloy is a magnetic material containing at least one of iron, cobalt and nickel, the metal oxide is at least one of iron oxide, cobalt oxide and nickel oxide, the magnetic solid particles 6 have a relative magnetic permeability of 200 to 200000, and the shape thereof is arbitrary, preferably regular spherical.
Example 2
This embodiment provides an electrowetting display having substantially the same structure as in embodiment 1, except that: the magnetic solid particles are Fe with oleophilic surface3O4And (3) granules. The preparation process comprises the following steps: dissolving coupling agent LD-139-2 in ethanol to obtain 2% coupling agent LD-139-2 ethanol solution, and adding 500mgFe into the solution3O4And (3) placing the powder on a rolling stirrer, stirring for 12h, magnetically separating out the powder, adding absolute ethyl alcohol, washing, then placing in a vacuum drying oven, drying for 2h at 60 ℃, and grinding into powder by using an agate mortar to obtain the lipophilic magnetic solid particles.
The magnetic solid particles can be subjected to hydrophilic or hydrophobic modification by using a chemical reagent, the wettability of the surfaces of the modified magnetic solid particles is hydrophilic or lipophilic, and the contact angle of water on the surfaces of the magnetic solid particles<70 DEG or>110 deg., the chemical agent may be titanate chemical modifier, such as TC-311 of Chen chemical industry or LD-139-2 of Lida gum. When the magnetic solid particles are subjected to hydrophilic modification, the oil film on one side of the magnetic solid particles is thinner, and when the magnetic solid particles are magneticAfter the solid particles are subjected to hydrophobic modification, the oil film on one side of the magnetic solid particles is thick, and the thinnest part of the oil film determines the breaking point and the moving direction of the oil film, so that the ink shrinkage moving direction can be controlled by controlling the surface wettability of the magnetic solid particles. This example uses Fe3O4For example, the magnetic solid particles added in practice may be an alloy or a metal oxide, the alloy is a magnetic material containing at least one of iron, cobalt and nickel, and the metal oxide is at least one of iron oxide, cobalt oxide and nickel oxide. And filling the modified hydrophilic or lipophilic magnetic solid particles and the first fluid into the pixel grids, and sealing and packaging to obtain the electrowetting display.
Example 3
This embodiment provides an electrowetting display having substantially the same structure as in embodiment 1, except that: the magnetic solid particles are permalloy particles with hydrophilic surfaces. The preparation process comprises the following steps: and (3) calcining 1g of permalloy powder in a muffle furnace at 500 ℃ for 6h, cooling to room temperature in air, and grinding into powder by using an agate mortar to obtain the hydrophilic magnetic solid particle I.
In this embodiment, permalloy is taken as an example, and the magnetic solid particles added in practice may be an alloy or a metal oxide, the alloy is a magnetic material containing at least one of iron, cobalt and nickel, and the metal oxide is at least one of iron oxide, cobalt oxide and nickel oxide. And filling the hydrophilic magnetic solid particles and the first liquid into the pixel cells, and sealing to obtain the electrowetting display.
Example 4
This embodiment provides an electrowetting display having substantially the same structure as in embodiment 1, except that: the magnetic solid particles are iron-nickel-cobalt alloy particles with hydrophilic surfaces. The preparation process comprises the following steps: and (3) calcining 1g of iron-nickel-cobalt alloy powder in a muffle furnace at 500 ℃ for 6h, cooling to room temperature in air, and grinding into powder by using an agate mortar to obtain the hydrophilic magnetic solid particles II.
Claims (10)
1. The utility model provides an electrowetting display, includes relative upper substrate and infrabasal plate that sets up, the upper substrate with the infrabasal plate encapsulation forms a sealed chamber, sealed intracavity is filled with first fluid and the second fluid of mutual incompatibility, the infrabasal plate is including the lower conducting substrate, hydrophobic dielectric layer and the pixel wall that set gradually, the pixel wall encloses into a plurality of pixel check, its characterized in that, each the pixel check are filled with first fluid and magnetic solid particle, first fluid is nonpolar liquid.
2. An electrowetting display according to claim 1, wherein said magnetic solid particles are of a ferromagnetic or antiferromagnetic material.
3. Electrowetting display according to claim 1, wherein the surface wettability of the magnetic solid particles is rendered lipophilic or hydrophilic, the contact angle of the surface water of the magnetic solid particles being >110 ° or <70 °.
4. An electrowetting display according to any of claims 1-3, wherein said magnetic solid particles are an alloy being a magnetic material containing at least one of iron, cobalt, nickel or a metal oxide being at least one of an iron oxide, a cobalt oxide, a nickel oxide.
5. An electrowetting display according to any of claims 1-3, wherein the magnetic solid particles have a particle size of 1-100 μm.
6. An electrowetting display according to any of claims 1-3, wherein the magnetic solid particles have a relative magnetic permeability of 200-200000.
7. A method of manufacturing an electrowetting display according to any one of claims 1 to 6, including the step of filling the pixel cells with magnetic solid particles.
8. The method of claim 7, wherein the step of filling the pixel cells with the magnetic solid particles comprises: dispersing the magnetic solid particles in the first fluid, and filling the magnetic solid particles into the pixel cells simultaneously with the first fluid.
9. The method of manufacturing an electrowetting display according to claim 7, wherein the filling of the magnetic solid particles and the first fluid into the pixel cells is performed by any one of a vertical entry filling method, an inkjet printing method, a liquid separation filling method, a slit coating method, and an interfacial self-assembly method.
10. A method of manufacturing an electrowetting display according to claim 7, further comprising the step of fixing the magnetic solid particles in the pixel cells using an applied magnetic field.
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| WO2002068821A2 (en) * | 2001-02-28 | 2002-09-06 | Lightwave Microsystems Corporation | Microfluidic control using dieletric pumping |
| US8093064B2 (en) * | 2008-05-15 | 2012-01-10 | The Regents Of The University Of California | Method for using magnetic particles in droplet microfluidics |
| CN104108248A (en) * | 2013-04-19 | 2014-10-22 | 中国科学院理化技术研究所 | Liquid metal ink-jet printing equipment and printing method |
| CN104614853B (en) * | 2015-01-27 | 2017-11-10 | 华南师范大学 | Electrowetting substrate and preparation method thereof, Electrowetting module |
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Patent Citations (5)
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|---|---|---|---|---|
| CN101004423A (en) * | 2006-01-19 | 2007-07-25 | 博奥生物有限公司 | Card, kit system in use for analyzing sample of liquid |
| CN103984088A (en) * | 2014-05-14 | 2014-08-13 | 华南师范大学 | Electric wetting displayer and drive method thereof |
| CN104570326A (en) * | 2015-01-27 | 2015-04-29 | 深圳市国华光电科技有限公司 | Method for improving packaging performance of electrowetting device and electrowetting device |
| CN105204155A (en) * | 2015-09-07 | 2015-12-30 | 华南师范大学 | Display device based on surface acoustic wave technology and method thereof |
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