A low voltage driven electrowetting display device and a method for preparing the same

Abstract

The present invention discloses a low-voltage driven electrowetting display device and a preparation method thereof, wherein the low-voltage driven electrowetting display device comprises a first conductive substrate and a second conductive substrate arranged opposite to each other, wherein a hydrophobic insulating layer is provided on the second conductive substrate on a side facing the first conductive substrate, and a pixel wall is provided on the hydrophobic insulating layer, wherein the pixel wall encloses a plurality of pixel grids; conductive columns are provided between the second conductive substrate and the hydrophobic insulating layer and in the area corresponding to each pixel grid, and the conductive columns are provided on one side of the pixel grid away from the central area of ​​the pixel grid. In the above manner, the electrowetting display device of the present invention can realize low-voltage driving and controllable pixel opening direction.

Description

Technical Field

[0001] The present invention relates to the technical field of electrowetting display, and in particular to a low-voltage driven electrowetting display device and a preparation method thereof. Background Art

[0002] Electrowetting display has the characteristics of low energy consumption, high reflectivity, high contrast ratio, fast response speed, wide viewing angle, etc., and the display effect is not affected by the gap between the panels. It has great potential in the development of flexible display screens and bistable devices. Compared with existing display technologies, it shows great advantages and is expected to replace existing liquid crystal displays and become the next generation of mainstream displays. Electrowetting display devices were first realized by Philips, where RA Haye and others worked. Electrowetting display (EFD) technology uses the competition between electrowetting force and liquid interfacial tension to control the contraction and spreading of color inks, thereby achieving the effect of grayscale regulation of pixel switching agents. A typical electrowetting display device consists of a conductive backplane (electrode), a dielectric layer or insulating layer, a hydrophilic pixel wall, a non-polar solution (usually a colored ink), and a polar conductive liquid (usually water) from bottom to top. Its display principle is as follows: Figure 1 When no power is applied, the ink is spread in each pixel unit according to the interface characteristics of the pixel wall to display the ink color. Figure 1 As shown in (a); when an external electric field is applied, the electrostatic force at the oil / water interface breaks the original interface balance and changes the wettability of the polar liquid conductive liquid (water) on the insulating substrate. Its contact angle is based on the Young-Lippmann equation (where θ0, θ U They represent the contact angles before and after power is applied, ε0 and ε represent the dielectric constant of vacuum and the effective dielectric constant of the dielectric layer, U represents the applied voltage, d represents the effective thickness of the hydrophobic dielectric layer, and σ LV The surface tension between the droplet and the air) changes, causing the non-polar solution (ink) to rupture, shrink, and rearrange along the pixel wall. Therefore, natural light passes through the pixel substrate and reflects the color of the substrate. By controlling the voltage to achieve functions such as pixel opening rate, response time, and grayscale control, the purpose of display is achieved. Figure 1 As shown in (b); when the voltage is removed, the hydrophobic insulating layer recovers its hydrophobic properties. At this time, the ink re-covers the hydrophobic insulating layer under the action of surface potential energy, and the pixel unit is closed, as shown in FIG. Figure 1 As shown in (c).

[0003] Traditional electrowetting display devices have the following problems: 1) The driving voltage is high, and the high driving voltage is easy to cause the breakdown of the dielectric layer, which greatly reduces the service life of the electrowetting display device; 2) After the voltage is applied, the opening and movement of the ink are uncontrollable, and it is possible to move to any corner of the pixel grid. The opening direction is inconsistent and random, which affects the display effect. In terms of controlling the direction of ink movement, the commonly used methods currently include pattern electrode design and an additional "pinning" structure with a guiding function; among them, the pattern electrode design requires that the wettability of the pixel wall is weakly oleophobic in the oil-water phase, and its contact angle is not greater than 90° (for the water phase), the material requirements are relatively strict, and the threshold voltage is also high; and the physical principle of the additional "pinning" structure with a guiding function is that the "pinning" structure can reduce the local thickness of the ink in the pixel unit. Although this method can achieve the function of guiding the movement of the ink, the driving voltage of the structure needs to be above 20V, and it is impossible to reduce the driving voltage. Therefore, it is now urgent to provide an electrowetting display device that can achieve low-voltage driving and controllable pixel opening direction. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a low-voltage driven electrowetting display device and a preparation method thereof, wherein the low-voltage driven electrowetting display device can realize low-voltage driving and controllable pixel opening direction.

[0005] The technical solution adopted by the present invention is:

[0006] According to a first aspect of the present invention, there is provided a low-voltage driven electrowetting display device, comprising a first conductive substrate and a second conductive substrate arranged opposite to each other, wherein a hydrophobic insulating layer is provided on the second conductive substrate on a side facing the first conductive substrate, and pixel walls are provided on the hydrophobic insulating layer, wherein the pixel walls enclose a plurality of pixel grids; conductive columns are provided in the area between the second conductive substrate and the hydrophobic insulating layer and in the area corresponding to each pixel grid, and the conductive columns are provided on one side of the pixel grid away from the central area of ​​the pixel grid.

[0007] According to some embodiments of the present invention, each pixel grid is square, the conductive column is arranged close to a pixel wall on one side of the pixel grid, and the shortest horizontal distance between the conductive column and the pixel wall is less than or equal to 1 / 4 of the side length of the pixel wall in the corresponding pixel grid;

[0008] Alternatively, each pixel grid is rectangular, the conductive column is arranged close to a short side pixel wall on the pixel grid, and the shortest horizontal distance between the conductive column and the short side pixel wall is less than or equal to 1 / 4 of the side length of the long side pixel wall on the corresponding pixel grid.

[0009] According to some embodiments of the present invention, one or more conductive pillars are provided in the area corresponding to each pixel grid between the second conductive substrate and the hydrophobic insulating layer; if multiple conductive pillars are provided in the area corresponding to each pixel grid between the second conductive substrate and the hydrophobic insulating layer, each conductive pillar is provided on the same side of the pixel grid.

[0010] According to some embodiments of the present invention, the top of the conductive column is located between 1 / 3 of the height of the pixel wall and the top of the pixel wall. Preferably, the top of the conductive column is located between 1 / 2 of the height of the pixel wall and the top of the pixel wall.

[0011] According to some embodiments of the present invention, the height of the conductive pillar is 2.5 um to 4.5 um.

[0012] According to some embodiments of the present invention, the areas corresponding to each pixel grid, the conductive pillars between the second conductive substrate and the hydrophobic insulating layer are arranged in the same manner.

[0013] According to some embodiments of the present invention, the conductive pillar is a metal conductive pillar; or the conductive pillar includes a non-conductive pillar-shaped structure and a metal conductive layer covering a surface of the non-conductive pillar-shaped structure.

[0014] According to some embodiments of the present invention, the distance between the first conductive substrate and the pixel wall is 50-80 um.

[0015] According to some embodiments of the present invention, the first conductive substrate includes a first substrate and a first conductive layer provided on a surface of the first substrate facing the second conductive substrate; the second conductive substrate includes a second substrate and a second conductive layer provided on a surface of the second substrate facing the first conductive substrate.

[0016] The second aspect of the present invention provides a method for preparing any one of the low-voltage driven electrowetting display devices provided in the first aspect of the present invention, comprising the following steps:

[0017] S1, disposing conductive pillars on one side surface of the second conductive substrate to form a conductive pillar array;

[0018] S2, providing a hydrophobic insulating layer on one side surface of a conductive column provided on the second conductive substrate and on the conductive column;

[0019] S3, setting a pixel wall on the hydrophobic insulating layer;

[0020] S4, filling the packaging liquid, and bonding and packaging the first conductive substrate and the second conductive substrate.

[0021] The beneficial effects of the embodiments of the present invention are:

[0022] The embodiment of the present invention provides a low-voltage driven electrowetting display device, which is based on the principle of spatial electric field distortion and the principle of redistribution of non-polar solution after the device is turned on. By setting a conductive column between the second conductive substrate and the hydrophobic insulating layer and in the area corresponding to each pixel grid, and setting the conductive column away from the central area of ​​the pixel grid on one side of the pixel grid, the local (conductive column setting position and its vicinity) thickness of the non-polar solution (usually ink) can be reduced while enhancing the local electric field at the conductive column setting position and its vicinity, so as to facilitate the rupture of the non-polar solution, so that the ink can be driven to rupture and move to realize pixel opening at a lower voltage; and the non-polar solution can be guided to move to the side opposite to the conductive column setting side in the pixel grid, so as to achieve the reduction of the driving voltage and the controllable direction of the non-polar solution rupture movement in the pixel grid (i.e., the pixel opening direction). The driving voltage of the electrowetting display device can be reduced to below 20V, and even in the range of 10 to 15V. In addition, the conductive column is arranged between the second conductive substrate and the hydrophobic insulating layer, the conductive column is not easy to fall off, and the structure is stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for describing the embodiments are briefly described below.

[0024] Figure 1 This is the display principle diagram of a traditional electrowetting display device.

[0025] Figure 2 This is a diagram showing the research results of the rupture position of the non-polar solution in the pixel grid when the electrowetting display device with different pixel grid sizes is powered on;

[0026] Figure 3 It is a structural schematic diagram of an embodiment of a low-voltage driven electrowetting display device of the present invention;

[0027] Figure 4 yes Figure 3 Schematic diagram of the positional relationship between the conductive pillars and the pixel walls in the pixel grid in the low-voltage driven electrowetting display device shown;

[0028] Figure 5 yes Figure 3 A simulation diagram of the spatial electric field distribution near the conductive pillar in the low-voltage driven electrowetting display device shown;

[0029] Figure 6 It is a structural schematic diagram of the preparation process of an embodiment of a method for preparing a low-voltage driven electrowetting display device of the present invention;

[0030] Figure 7 This is an experimental result diagram of the effect of the conductive column position setting on the device pixel opening direction. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the concept, specific structure and technical effects of the present invention in combination with the embodiments and drawings, so as to fully understand the purpose, scheme and effect of the present invention. It is understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Descriptions such as up, down, left, and right used in the present invention are merely relative to the relative positions of the components of the present invention in the drawings, and the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions.

[0033] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments and features in the embodiments in this application may be combined with each other without conflict.

[0034] Based on the working principle of the electrowetting display device: when voltage is applied, a large amount of space charge accumulates at the oil-water interface of the device, and due to the different pressure gradients, the non-polar solution (usually ink) ruptures to realize the function of pixel opening. The inventors established a rupture model and applied voltage to the electrowetting display devices with different pixel grid sizes to conduct research experiments on the rupture position of the non-polar solution in the pixel grid.

[0035] Specifically, for a typical electrowetting display system, if the pixel grid is rectangular, L x Indicates the shorter side in the pixel grid, L y Indicates the longer side; if the pixel grid is square, L x and L y Represents two adjacent sides; for any of the above electrowetting display devices with fixed geometric pixel unit sizes, under a certain voltage, the rupture mode of the non-polar solution is represented by the number of peaks and troughs that appear on the shorter side and the longer side, respectively. The rupture mode is recorded as [m, n], where m represents the number of peaks and troughs that appear on the shorter side of the pixel grid, and n represents the number of peaks and troughs that appear on the longer short side of the pixel grid. Combined with the above rupture model, the rupture position of the non-polar solution ink in the pixel grid was observed and simulated by electrowetting display devices with pixel grid sizes of 150μm×150μm, 150μm×315μm, and 67.5μm×315μm under voltage, and the results are as follows Figure 2 shown. Figure 2 (a), (b), and (c) respectively represent the distribution diagrams of the rupture points of the non-polar solution in the electrowetting display device with pixel grid sizes of 150μm×150μm, 150μm×315μm, and 67.5μm×315μm when powered on. Figure 2 (d) in the figure shows a simulated diagram of the height distribution of the non-polar solution after power is applied. Experiments show that for electrowetting display devices with different pixel grid sizes, the non-polar solution in the pixel grid is broken in the [1, 2] mode, and the rupture position of this rupture mode deviates from the central area of ​​the pixel grid and is located on one side of the pixel grid; specifically, the length of the long side of the pixel grid is represented by L, and the rupture point of the [1, 2] mode rupture is generally located within 1 / 4L of the short side of the pixel grid (if the pixel grid is a square, L represents the side length of the pixel grid, and the rupture point of the [1, 2] mode rupture is generally located within 1 / 4L of the side pixel wall of the pixel grid).

[0036] Based on the above principle research, the present invention makes full use of the characteristics of the rupture of non-polar solutions under pressure, and combines it with the principle of spatial electric field distortion to propose an electrowetting display device.

[0037] See also Figure 3 , Figure 3 Schematic diagram of the structure of an embodiment of a low voltage driven electrowetting display device of the present invention. Figure 3 As shown, the low-voltage driven electrowetting display device of this embodiment includes a first conductive substrate 1 and a second conductive substrate 2 arranged opposite to each other, a hydrophobic insulating layer 3 is provided on the side of the second conductive substrate 1 facing the first conductive substrate 1, pixel walls 4 are provided on the hydrophobic insulating layer 3, and the pixel walls 4 enclose a plurality of pixel grids; conductive columns 5 are provided between the second conductive substrate 2 and the hydrophobic insulating layer 3 and in the area corresponding to each pixel grid, and the conductive columns 5 are arranged on one side of the pixel grid away from the central area of ​​the pixel grid.

[0038] In this embodiment, the first conductive substrate 1 includes a first substrate 11 and a first conductive layer 12 provided on a side surface of the first substrate 11 facing the second conductive substrate 2; the second conductive substrate 2 includes a second substrate 21 and a second conductive layer 22 provided on a side surface of the second substrate 21 facing the first conductive substrate 1. The first substrate 11 and the second substrate 21 can be glass substrates or polymer material substrates, such as PET, PI, etc.; can be rigid substrates or flexible substrates; and the first substrate 11 and the second substrate 21 can be substrates of the same material or substrates of different materials. The first conductive layer 12 and the second conductive layer 22 can independently use gold, silver or ITO (indium tin oxide) conductive layers, preferably ITO conductive layers.

[0039] Of course, the first conductive substrate 1 and the second conductive substrate 2 are not limited to the above-mentioned structural arrangement. In other embodiments, other forms of the first conductive substrate and the second conductive substrate may also be used.

[0040] The thickness of the hydrophobic insulating layer 3 is generally 1±0.2um. The material of the hydrophobic insulating layer 3 can be a fluorine-containing polymer material, specifically, an amorphous fluorine-containing polymer material with low surface energy such as AF1600, AF1600x, Cytop, Teflon, etc., preferably AF1600 or AF1600x. The pixel wall 4 has weak hydrophilicity, and can be specifically prepared by slit coating, spin coating, etc. using a weak hydrophilic photoresist (such as SU-8, etc.). The thickness of the pixel wall 4 is generally 5 to 8μm.

[0041] Each pixel grid is square, and the conductive column 5 in the corresponding area of ​​each pixel grid is arranged close to the pixel wall 4 on one side of the pixel grid, and the shortest horizontal distance between the conductive column 5 and the pixel wall 4 is less than or equal to 1 / 4 of the side length of the pixel wall 4 in the corresponding pixel grid. Figure 4 As shown. The top of the conductive column 5 is located between 1 / 3 of the height of the pixel wall 4 and the top of the pixel wall 4. The height of the pixel wall 4 is the distance from the contact surface with the hydrophobic insulating layer 3 to the end surface on the side away from the hydrophobic insulating layer 3. Specifically, the height of the conductive column 5 is generally 2.5um to 4.5um. The height of the conductive column 5 is the distance from the contact surface with the second conductive substrate 2 to the end surface on the side away from the second conductive substrate 2. The conductive column 5 is specifically a metal conductive column, and its material can be Ag, Al, Au, Ti and other conductive materials. Of course, the conductive column 5 can also be set to include a non-conductive columnar structure and a metal conductive layer covering the surface of the non-conductive columnar structure. The material of the metal conductive layer can also be Ag, Al, Au, Ti, etc.

[0042] In this embodiment, the number of the conductive pillars 5 in the area corresponding to each pixel grid is one, and the area corresponding to each pixel grid and the conductive pillars 5 between the second conductive substrate 2 and the hydrophobic insulating layer 3 are arranged in the same manner; preferably, the conductive pillars 5 are arranged in the corner area of ​​the corresponding pixel grid. In other embodiments, the number of the conductive pillars 5 in the area corresponding to each pixel grid may also be multiple, such as 2, 3, 4, 5, 7, etc. The area corresponding to each pixel grid and the conductive pillars 5 between the second conductive substrate 2 and the hydrophobic insulating layer 3 generally adopt the same arrangement, but may also be arranged differently.

[0043] In addition, in other embodiments, the pixel grid may be set in other shapes, such as a rectangular pixel grid. If the pixel grid is rectangular, the conductive column 5 is generally arranged close to a short side pixel wall of the pixel grid, and the shortest horizontal distance between the conductive column 5 and the short side pixel wall is less than or equal to 1 / 4 of the side length L of the long side pixel wall on the corresponding pixel grid.

[0044] The first conductive substrate 1 and the second conductive substrate 2 are sealed and closed by the packaging structure 6 to form a sealed chamber. The height of the packaging structure 6 is generally 50 to 80 μm, and the height of the packaging structure 6 is the distance between the first conductive substrate 1 and the pixel wall 4. The packaging structure 6 can be specifically a packaging glue, and the packaging glue can be a pressure-sensitive material, a heat-sensitive material, a photosensitive material, a microwave polymerization material, etc., among which UV-curable acrylate pressure-sensitive adhesive is preferably used. The sealed chamber is filled with a packaging liquid, which is a polar electrolyte solution 7 and a non-polar solution 8, and the two solutions are incompatible with each other. Among them, the polar electrolyte solution 7 can be water, a sodium chloride aqueous solution, etc., and the non-polar solution 8 is usually ink, specifically a solution of non-polar dye small molecules in an oil solution.

[0045] The above electrowetting display device is based on the principle of spatial electric field distortion and the [1, 2] rupture mode of the non-polar solution in the pixel grid after the device is turned on. It follows the rupture law of the non-polar solution and sets the conductive pillar 5 at or near the conventional rupture position of the non-polar solution in the pixel grid after the device is turned on. The local electric field intensity gradient (such as Figure 5 As shown), the driving voltage is reduced; at the same time, the local (conductive column setting position and its vicinity) thickness of the non-polar solution 8 (usually ink) can be reduced to facilitate the rupture of the non-polar solution 8, further reducing the driving voltage; and the non-polar solution 8 can be guided to move to the side opposite to the side where the conductive column 5 is set in the pixel grid; specifically, if a single conductive column 5 is set in a corner area of ​​the corresponding pixel grid in the above manner, then after the driving voltage is applied, the non-polar solution 8 in the pixel grid tends to move to the corner opposite to the setting position of the conductive column 5 in the pixel grid; if a plurality of conductive columns 5 are set on one side of the pixel grid (generally close to the short side pixel wall of the pixel grid) away from the center of the pixel grid, after the driving voltage is applied, the non-polar solution 8 in the pixel grid tends to move to the side opposite to the setting position of the conductive column 5 in the pixel grid. Through the above method, the driving voltage can be reduced and the rupture and movement direction of the non-polar solution 8 in the pixel grid (i.e., the pixel opening direction) can be controlled. The driving voltage can be reduced to below 20V, or even in the range of 10 to 15V; and the conductive column 5 is arranged between the second conductive substrate 2 and the hydrophobic insulating layer 3. The conductive column 5 is not easy to fall off, and the structure is stable and reliable.

[0046] The present invention also provides a method for preparing a low voltage driven electrowetting display device. Figure 6 , Figure 6 FIG. 1 is a schematic diagram of a preparation process of a method for preparing a low-voltage driven electrowetting display device according to an embodiment of the present invention. Figure 6 As shown, the preparation method specifically comprises the following steps:

[0047] S1. Prepare a second conductive layer on a second substrate to prepare a second conductive substrate.

[0048] Specifically, the second substrate can be a glass substrate or a substrate of other materials, such as a polymer material substrate, which can be a flexible substrate or a rigid substrate. The preparation of the second conductive layer can be carried out by depositing a conductive layer such as gold, silver or ITO (indium tin oxide) on the second substrate by magnetron sputtering or the like. The thickness of the second conductive layer can be controlled by the time of magnetron sputtering, and the thickness is usually controlled to be 25 to 800 nm.

[0049] S2. Disposing conductive pillars on a surface of the second conductive layer facing away from the second substrate to form a conductive pillar array.

[0050] Specifically, transparent conductive metal (such as Ag, Al, Au, Ti and other light-transmitting conductive materials) can be arranged on the surface of the second conductive layer facing away from the second substrate to form a conductive column array corresponding to each preset pixel grid area by photolithography, screen printing, inkjet printing and other methods. The height of the conductive column is generally 2.5um to 4.5um.

[0051] S3. A hydrophobic insulating layer is provided on one side surface of a conductive column on the second conductive layer and on the conductive column.

[0052] Specifically, amorphous fluorine-containing polymer materials with low surface energy such as AF1600 and AF1600X can be used as raw materials, and perfluoro solvent 7100 can be used as solvent to prepare a hydrophobic insulating layer solution with a mass fraction of 3-5%; then the hydrophobic insulating layer solution is coated on the side surface of the second conductive layer where the conductive column is provided and on the conductive column by spin coating, screen printing, slit coating and other methods, and then heat curing treatment is performed, specifically, it can be placed in an 85°C oven for baking and curing for 90 minutes to form a hydrophobic insulating layer.

[0053] S4. Setting a pixel wall on the hydrophobic insulating layer.

[0054] Specifically, a layer of weak water photoresist (such as SU-8, etc.) can be coated on the surface of the hydrophobic insulating layer by slit coating or spin coating, and the thickness can be 5-8μm. After heat drying, a weak hydrophilic pixel wall is obtained by photolithography and development process under the action of the mask plate, and a pixel grid is formed between each pixel wall. The pixel wall is set according to the setting position of the conductive column and the shape of the conductive column array, so that the setting position of the conductive column deviates from the central area of ​​the pixel grid and is set on one side of the preset pixel grid. In addition, the shape of the pixel grid generally corresponds to the shape of the conductive column array. If the conductive column array is a square array, the pixel grid is generally a square pixel grid, the conductive column is arranged close to a pixel wall on one side of the pixel grid, and the shortest horizontal distance between the conductive column and the pixel wall in the pixel grid is less than or equal to 1 / 4 of the side length of the pixel wall in the corresponding pixel grid; if the conductive column array is a rectangular array, the pixel grid is generally a rectangular pixel grid, the conductive column is arranged close to a short side pixel wall of the pixel grid, and the shortest horizontal distance between the conductive column and the short side pixel wall is less than or equal to 1 / 4 of the side length of the pixel wall in the corresponding pixel grid.

[0055] S5. Prepare a first conductive substrate and a packaging rubber frame.

[0056] Specifically, a first conductive layer is prepared on the first substrate to form a first conductive substrate. The preparation method of the first conductive substrate is similar to the preparation method of the second conductive substrate, which will not be described in detail. Then, a packaging frame (i.e., a packaging structure) is prepared on the first conductive layer. Specifically, it can be prepared by screen printing of ultraviolet curing pressure-sensitive adhesive. In this embodiment, UV acrylate pressure-sensitive adhesive is used. According to the size of the electrowetting display device, the UV acrylate pressure-sensitive adhesive is graphically printed on the surface of the first conductive layer away from the first substrate by screen printing. The UV acrylate pressure-sensitive adhesive is 100 mj / cm 2 The sealant frame was obtained by curing under ultraviolet light for 10 seconds.

[0057] S5, filling with liquid and packaging.

[0058] Specifically, the encapsulation liquid is filled, and then the first conductive substrate provided with the encapsulation glue frame is bonded and encapsulated with the second conductive substrate to obtain an electrowetting display device. The process of filling the encapsulation liquid is specifically completed in a polar electrolyte solution environment, and the non-polar solution is filled in the pixel grid through the adsorption of the surface of the hydrophobic insulating layer to the non-polar solution; the weakly hydrophilic pixel wall is hydrophilic, and the non-polar solution can be separated so that it can be filled in each pixel grid separately, and the polar electrolyte solution continuously covers the non-polar solution and the pixel wall.

[0059] The above method for preparing a low-voltage driven electrowetting display device is based on the principle of spatial electric field distortion and the [1, 2] rupture mode of the non-polar solution in the pixel grid after the device is turned on, and follows the rupture law of the non-polar solution. The prepared electrowetting display device can reduce the driving voltage and control the rupture movement direction of the non-polar solution in the pixel grid (i.e., the pixel opening direction).

[0060] In addition, the inventors also conducted experiments on the influence of the conductive pillars and their position settings on reducing the voltage drive and the device pixel opening direction by adjusting the specific setting positions of the conductive pillars. The experimental results of the influence of the conductive pillar position settings on the pixel opening direction are shown as follows: Figure 6 According to the number and position of the conductive pillars, the grouping experiment is carried out as follows:

[0061] Experimental group 1: a single conductive column is arranged on the same side (specifically the upper right corner area) of the corresponding square pixel grid of different electrowetting display devices, and each conductive column is arranged at different positions within a range where the shortest horizontal distance from the pixel wall on that side is less than or equal to 1 / 4 of the side length of the pixel grid, such as Figure 7 As shown in (a1);

[0062] Experimental group 2: A single conductive column is set at different positions in the center area of ​​the square pixel grid corresponding to different electrowetting display devices, such as Figure 7 As shown in (b1);

[0063] Experimental group 3: Two conductive pillars (one group) are arranged on the same side of the corresponding square pixel grid of different electrowetting display devices, and each group of conductive pillars is dispersedly arranged at a position where the shortest horizontal distance from the pixel wall on that side is less than or equal to 1 / 4 of the side length of the pixel grid, such as Figure 7 As shown in (c1).

[0064] The minimum driving voltage for the electrowetting display devices in the above experimental groups to achieve pixel opening was measured respectively, and the movement direction of the non-polar solution in the pixel opening process (i.e., the pixel opening direction) was observed. It was detected that the driving low voltage of each group of electrowetting display devices was less than 20V, and the driving voltage of the electrowetting display devices in experimental groups 1 and 3 was less than that in experimental group 2. The driving voltage of the electrowetting display devices in experimental groups 1 and 3 was in the range of 10 to 15V. It can be seen that the setting of the conductive column can enhance the gradient of the electric field strength and reduce the thickness of the non-polar solution, thereby reducing the driving voltage; and setting the conductive column at a position where the shortest horizontal distance from the pixel wall in the pixel grid is less than or equal to 1 / 4 of the side length of the pixel grid can follow the rupture mode of the non-polar solution and further reduce the driving voltage. In addition, the movement direction of the non-polar solution in the pixel opening process of the electrowetting display devices in each experimental group is as follows Figure 7 As shown in (a2) to (c2), Figure 7The schematic diagrams of the movement and contraction direction of the non-polar solution shown in (a2) to (c2) correspond to the settings of the conductive columns in the electrowetting display devices of experimental groups 1 to 3. Figure 7 It can be seen that by arranging the conductive column on one side of the pixel grid away from the central area of ​​the pixel grid, the non-polar solution can be guided to move to the side opposite to the side where the conductive column is arranged in the pixel grid, so as to achieve controllable rupture and movement direction of the non-polar solution in the pixel grid (i.e., the pixel opening direction).

[0065] In addition, the inventor further adjusted the setting position of the voltage conductive column, specifically setting the conductive column on the first conductive substrate (i.e., the upper conductive substrate), the end surface of the conductive column facing the second conductive substrate is lower than the end surface of the pixel wall facing the first conductive substrate, the surface of the conductive column is oleophobic, and the other structures are similar to Figure 3 The structure of the electrowetting display device shown is similar. An electrowetting display device in which a conductive column is arranged on a first conductive substrate is prepared; then the driving voltage of the electrowetting display device is tested and studied. The study shows that the driving voltage still needs to be above 20V to open the pixel unit, and low-voltage driving cannot be achieved. This is because the strong capillary force on the conductive column structure in the electrowetting display device increases the difficulty of breaking the non-polar solution, so a higher driving voltage is still required to achieve driving.

[0066] Although the present invention has been specifically shown and described in conjunction with preferred embodiments, it should be understood by those skilled in the art that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined in the claims, all of which are within the scope of protection of the present invention.

Claims

1. A low voltage driven electrowetting display device, characterized in that: The invention comprises a first conductive substrate and a second conductive substrate which are arranged opposite to each other, a hydrophobic insulating layer is arranged on the second conductive substrate on a side facing the first conductive substrate, a pixel wall is arranged on the hydrophobic insulating layer, and the pixel wall encloses a plurality of pixel grids; the first conductive substrate and the second conductive substrate are sealed and closed by a packaging structure to form a sealed chamber, and the sealed chamber is filled with a packaging liquid, and the packaging liquid is a polar electrolyte solution and a non-polar solution; a conductive column is arranged between the second conductive substrate and the hydrophobic insulating layer and in an area corresponding to each pixel grid, and the conductive column is arranged on one side of the pixel grid away from the central area of ​​the pixel grid; Each pixel grid is square, and the side length of the pixel grid is L. When the device is powered on, the non-polar solution in the pixel grid is broken in a [1, 2] mode, and 1 and 2 in the [1, 2] mode respectively represent the number of peaks and troughs appearing on the two adjacent sides of the pixel grid. The rupture point of this rupture mode is within 1 / 4L of the side pixel wall of the pixel grid; the conductive column is arranged close to one side pixel wall in the pixel grid, and the shortest horizontal distance between the conductive column and the pixel wall is less than or equal to 1 / 4 of the side length of the pixel wall in the corresponding pixel grid, and the conductive column is located at or near the rupture point; Alternatively, each pixel grid is rectangular, the long side of the pixel wall is L, and when the device is powered on, the non-polar solution in the pixel grid is broken in a [1, 2] mode, 1 and 2 in the [1, 2] mode respectively represent the number of peaks and troughs on the short side and long side of the pixel grid, and the rupture point of this rupture mode is within 1 / 4L of the short side of the pixel grid; the conductive column is arranged near a short side pixel wall of the pixel grid, and the shortest horizontal distance between the conductive column and the short side pixel wall is less than or equal to 1 / 4 of the side length of the long side pixel wall on the corresponding pixel grid, and the conductive column is located at or near the rupture point.

2. The low voltage driven electrowetting display device according to claim 1, characterized in that: One or more conductive pillars are provided in the area corresponding to each pixel grid between the second conductive substrate and the hydrophobic insulating layer; if multiple conductive pillars are provided in the area corresponding to each pixel grid between the second conductive substrate and the hydrophobic insulating layer, each conductive pillar is provided on the same side of the pixel grid.

3. The low voltage driven electrowetting display device according to claim 1, characterized in that: The top of the conductive column is located between a 1 / 3 height position of the pixel wall and the top of the pixel wall.

4. The low voltage driven electrowetting display device according to claim 3, characterized in that: The height of the conductive pillar is 2.5um to 4.5um.

5. The low-voltage driven electrowetting display device according to any one of claims 1 to 4, characterized in that: The areas corresponding to each pixel grid, the conductive pillars between the second conductive substrate and the hydrophobic insulating layer are arranged in the same manner.

6. The low voltage driven electrowetting display device according to any one of claims 1 to 4, characterized in that: The conductive column is a metal conductive column; or the conductive column includes a non-conductive columnar structure and a metal conductive layer covering the surface of the non-conductive columnar structure.

7. The low voltage driven electrowetting display device according to any one of claims 1 to 4, characterized in that: The distance between the first conductive substrate and the pixel wall is 50-80 um.

8. The low voltage driven electrowetting display device according to any one of claims 1 to 4, characterized in that: The first conductive substrate includes a first substrate and a first conductive layer disposed on a surface of the first substrate facing the second conductive substrate; the second conductive substrate includes a second substrate and a second conductive layer disposed on a surface of the second substrate facing the first conductive substrate.

9. The method for preparing a low voltage driven electrowetting display device according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, disposing conductive pillars on one side surface of the second conductive substrate to form a conductive pillar array; S2, providing a side surface of a conductive column on the second conductive substrate and providing a hydrophobic insulating layer on the conductive column; S3, setting a pixel wall on the hydrophobic insulating layer; S4, filling the packaging liquid, and bonding and packaging the first conductive substrate and the second conductive substrate.

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