Patterned electrode structure for electrowetting device

Abstract

An embodiment of the present invention provides a pattern electrode structure for an electrowetting device, comprising: a first branch electrode disposed in a direction perpendicular to any plane perpendicular to a plane defined by the pattern electrode structure, and a base pattern electrode disposed in a direction perpendicular to any plane defined by the pattern electrode structure; the base pattern electrode is disposed in a region above an upper end of the first branch electrode and is connected to an electrode connection portion configured to receive a voltage, in which an interval between the first branch electrode and the base pattern electrode is equal to or larger than a diameter of a droplet to be removed.

Description

Technical Field

[0001] The present invention relates to an electrode structure for an electrowetting device. Background Art

[0002] The electrowetting phenomenon refers to the phenomenon that the contact angle between a solid and an electrolyte changes due to the potential difference between the solid and the electrolyte.

[0003] This phenomenon can be used to control the surface tension of a droplet placed on an electrode coated with an insulator, thereby controlling the deformation / movement of microfluids below the microliter (μl) unit.

[0004] In addition, since a separate external driver is not required to operate the application product, the application product can be lightweight. Since the insulator applied to the electrode restricts the flow of current, the electric power consumption is low and the response speed is fast. Therefore, the electrowetting phenomenon has attracted much attention in various industrial fields.

[0005] Examples of the use of electrowetting in industry include new generation electronic devices that operate differently from previous technologies, such as Lab-on-a-chip, fluidic lenses and displays.

[0006] In addition, electrowetting devices can be used to move, deform and remove droplets formed on glass. Therefore, electrowetting devices can be installed on vehicle windshields, rearview mirrors, cameras, etc. to remove rain and dew.

[0007] The information disclosed in the above background art is only for helping understanding the background of the present invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0008] The present invention relates to an electrode structure for an electrowetting device. The specific embodiment relates to an electrode structure that uses a pattern structure that utilizes the electrowetting phenomenon.

[0009] Therefore, embodiments of the present invention provide a pattern electrode structure for an electrowetting device, which can more effectively exhibit self-cleaning performance by preventing liquid droplets from stagnating at the upper end of the pattern in a structure using a vertical pattern.

[0010] As a preferred embodiment, a pattern electrode structure for an electrowetting device is stacked between a substrate and a dielectric layer of the electrowetting device, and includes a first branch electrode formed in a direction perpendicular to any plane perpendicular to the plane defined by the pattern electrode structure, and a base pattern electrode formed in an area above the upper end of the first branch electrode and connected to an electrode connection portion configured to receive a voltage, wherein the spacing between the first branch electrode and the base pattern electrode is equal to or greater than the diameter of a droplet to be removed.

[0011] More specifically, an interval between the first branch electrodes and the base pattern electrode may be equal to or greater than 1.93 mm.

[0012] In this case, the first branch electrodes and the base pattern electrodes may have different polarities.

[0013] In addition, the pattern electrode structure may further include second branch electrodes alternately formed with the first branch electrodes in a width direction of the pattern electrode structure, and the second branch electrodes are different in polarity from the first branch electrodes.

[0014] Meanwhile, the upper end of the first branch electrode may be formed as a concave portion.

[0015] Alternatively, the upper end of the first branch electrode may be formed as a convex portion.

[0016] Alternatively, the upper end of the first branch electrode may include a cutting-edge portion.

[0017] Meanwhile, a dummy pattern may be formed in a space between the first branch electrodes and the base pattern electrode.

[0018] In electrowetting glass, if a droplet stays in a specific narrow space and oscillates or moves repeatedly in place, charges and ions will move in the droplet due to the periodic change of voltage, and the charges and ions will be concentrated in a specific position, which will cause burning due to exceeding the yield voltage of the dielectric layer on the glass surface.

[0019] However, according to an embodiment of the present invention, the droplets may be directed to a region to which a low periodic voltage or no periodic voltage is applied, thereby preventing the dielectric layer from being burned.

[0020] Therefore, according to the embodiments of the present invention, the working life of the electrowetting glass can be significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figures 1 to 3 is a diagram for explaining a general electrowetting device.

[0022] Figure 4 is a view showing a pattern structure of an electrowetting device.

[0023] Figures 5 to 11 It is a view for explaining the limitation of the technology according to the pattern structure in the related art.

[0024] Fig.12 This is a view showing a part of a pattern structure of an electrowetting device according to an embodiment of the present invention.

[0025] Fig.131 is a diagram showing an overall pattern structure of an electrowetting device according to an embodiment of the present invention.

[0026] Fig.14 and Fig.15 It is a diagram showing the experimental results of the pattern structure of the electrowetting device according to the embodiment of the present invention.

[0027] Fig.16 1 is a diagram showing the specifications of a pattern structure of an electrowetting device according to an embodiment of the present invention.

[0028] Figures 17 to 19 : are views showing application examples according to pattern shapes.

[0029] Fig. 20 1 and 2 are views showing additional application examples of the pattern structure of the electrowetting device according to the embodiment of the present invention.

[0030] Fig.21 It is a view for explaining the effect of the pattern structure of the electrowetting device according to the embodiment of the present invention. DETAILED DESCRIPTION

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to exemplary drawings, and the present invention is not limited to the embodiments described herein because these embodiments as examples can be implemented in various forms by those skilled in the art to which the present invention pertains.

[0032] For a fuller understanding of the embodiments of the present invention, operating advantages of the embodiments of the present invention, and objectives achievable by implementing the embodiments of the present invention, reference is made to the accompanying drawings which illustrate exemplary embodiments of the present invention and the contents disclosed therein.

[0033] Furthermore, in the description of the embodiments of the present invention, when it is determined that the description of the known prior art will unnecessarily obscure the subject matter of the embodiments of the present invention, the repeated description thereof will be reduced or omitted.

[0034] Embodiments of the present invention relate to self-cleaning technology utilizing the electrowetting phenomenon.

[0035] Figure 1 A basic electrowetting self-cleaning device is shown, in which an electrode layer 10, a dielectric layer 30, and a water-repellent layer 40 are stacked on glass 20 as a substrate.

[0036] The type of the substrate 20 is not limited, but transparent glass may be used to facilitate mounting the substrate 20 on a product that transmits visible light, such as a camera.

[0037] The electrode layer 10 is a transparent electrode pattern layer and needs to be located at the lower end of the dielectric layer, and the performance of the electrode layer 10 improves as the conductivity increases.

[0038] The electrode layer 10 does not necessarily need to be transparent, but in order to mount the electrode layer 10 on a product that transmits visible light, it is necessary to use a transparent substrate 20. As representative materials, oxide-based ITO, polymer-based PEDOT:PSS, oxide-polymer composite materials (FTO), etc. can be used.

[0039] The performance can be improved due to the high dielectric constant and thin thickness of the dielectric layer 30. The durability and life are improved due to the high dielectric breakdown strength and low defects of the dielectric layer 30. As the dielectric layer 30 becomes more uniform, more homogenous, and more continuous, the deviation in performance and durability is reduced.

[0040] The dielectric layer 30 may be configured as a single layer or a multi-layer. As a representative material, an oxide / nitride-based material such as SiO 2 、TiO 2 、Al 2 O 3 、CeO 2 , HfO 2 、ZrO 2 , ZnO, SiON and Si 3 N 4 , and polymer-based materials such as polyparaxylene-C, cycloolefin polymer (COP) and polymethyl methacrylate (PMMA). As a deposition method, wet processes (spraying, spin coating, inkjet, etc.) and dry processes (electron beam, sputtering, CVD, etc.) can be used.

[0041] If the outermost layer of the dielectric layer has a sufficiently large contact angle, the water-repellent layer 40 is not an essential element and may be omitted.

[0042] A fluorine compound is used as a representative material, and a coating process is performed by a method such as electron beam spin coating.

[0043] When a voltage is applied to a transparent electrode on the glass surface of an electrowetting device, the contact angle of a droplet around the electrode changes.

[0044] The droplets around the electrodes may move in response to changes in the polarity of the voltage applied to the electrodes, or oscillate in response to changes in the magnitude of the voltage.

[0045] According to the Lippmann-Young equation, the contact angle changes greatly when the following three conditions are met.

[0046] (1) The dielectric coating material has a high dielectric constant and a thin thickness;

[0047] (2) The interfacial tension of the hydrophobic coating material is low (= large contact angle);

[0048] (3) The applied voltage is high.

[0049] The mobility of a droplet on the surface of an electrowetting device varies depending on the frequency and / or magnitude of the applied voltage.

[0050] That is to say, Figure 2 As shown, when DC voltages having different polarities are applied to two adjacent electrodes, a droplet is attracted (dragged) by the attractive force between the electrodes having polarities opposite to that of the droplet, thereby causing the droplet to move.

[0051] Furthermore, if a half-wave rectified current with a phase difference of 180 degrees is continuously applied to two adjacent electrodes, the droplet repeatedly shrinks and expands in opposite polarity directions. Figure 3 As shown, oscillation occurs and the adhesion to the bottom surface decreases.

[0052] That is, when an external force is applied to a droplet, the droplet can easily move in the direction of the external force (adhesion force reduction + gravity = dripping).

[0053] Figure 4 An example of an electrode pattern structure is shown. The electrode pattern structure includes a first electrode portion and a second electrode portion. The first electrode portion includes a first electrode connection portion 111, a first base pattern electrode 112, and a first branch electrode 113. The second electrode portion includes a second electrode connection portion 121, a second base pattern electrode 122, and a second branch electrode 123.

[0054] Generally, a liquid droplet on an electrowetting surface is moved in the length direction of the branch electrodes by applying an alternating current (AC) to induce oscillation, under the influence of gravity.

[0055] Therefore, vertical patterns are usually used to minimize the droplet distance and time. However, if a comb-like vertical pattern structure is used when an AC voltage is applied, the droplet may stagnate when crossing the electrode at the upper end of the pattern.

[0056] As mentioned above, Figure 4 is a view showing a pattern structure of an electrowetting device, Figures 5 to 10 It is a view for explaining the limitation of the technology according to the pattern structure in the related art.

[0057] The embodiments of the present invention can prevent a liquid droplet from stagnating at the upper end of a vertical pattern without dripping in a structure using a vertical pattern.

[0058] Figures 5 to 7 The case where the size of the droplet D spans two or less electrodes is shown. Figure 5 and Figure 6 A droplet D is shown spanning the first branch electrode 113 and the second branch electrode 123 , and a balanced relationship between the forces is shown. Figure 7 The behavior of an actual droplet D when an AC voltage is applied in this case is shown.

[0059] Figures 8 to 10 The case where the size of the droplet D spans more than three electrodes is shown. Figure 8 and Fig. 9 The droplet D is shown to span the first branch electrode 113 and two second branch electrodes 123 disposed on opposite sides of the first branch electrode, and a balanced relationship between the forces is shown. Fig.10 The behavior of an actual droplet D when an AC voltage is applied in this case is shown.

[0060] In the case where the droplet stays at a specific position for a long period of time without moving as described above, applying a high potential difference between the droplet and the driving electrode disposed under the insulating layer for a long period of time may cause insulation breakdown of the insulating layer.

[0061] The insulation breakdown occurs after the smoke appears and leads to the separation of the insulation layer and the overall separation.

[0062] An insulating layer with a high dielectric breakdown strength may be applied. However, since the dielectric breakdown strength and the dielectric constant are inversely proportional to each other, the cleaning performance will be significantly deteriorated as the dielectric constant decreases.

[0063] Therefore, it is advantageous to prevent droplets from sticking to a specific location for a long time.

[0064] Fig.11 Shows the situation where the droplet sticks.

[0065] Fig.11 A case is shown in which a droplet D is stuck between the first branch electrode 113 and the second base pattern electrode 122 at the upper end of the first branch electrode 113 and repeatedly moves in place at a fixed position. Fig.11 The right side of shows a portion of the droplet located on the second base pattern electrode 122 but away from the camera's field of view.

[0066] When the droplets stick as described above, the dielectric layer may be burned.

[0067] That is, when an AC voltage is applied in this case, the droplet moving downward toward the first branch electrode 113 by the electric attraction is moved upward toward the second base pattern electrode 122 by the electric attraction by polarity switching. For this reason, the droplet repeatedly moves and oscillates in a narrow space, and the charge and ion flow in the droplet are concentrated in the narrow space, which causes damage to the dielectric layer.

[0068] The embodiments of the present invention can prevent the droplets from adhering to the upper ends of the branch electrodes as described above.

[0069] Fig.12 This is a view showing a part of a pattern structure of an electrowetting device according to an embodiment of the present invention.

[0070] The following will refer to Fig.12 A pattern electrode structure of an electrowetting device according to an embodiment of the present invention is described.

[0071] like Figure 1 As shown, in the electrowetting self-cleaning device according to the embodiment of the present invention, an electrode layer 10, a dielectric layer 30 and a water-repellent layer 40 are stacked on a glass 20. The water-repellent layer 40 may be a hydrophobic coating.

[0072] like Figure 4 As shown, the pattern structure of the electrowetting device according to the embodiment of the present invention includes a first electrode portion and a second electrode portion. The first electrode portion includes a first electrode connecting portion 111, a first base pattern electrode 112 and a first branch electrode 113. The second electrode portion includes a second electrode connecting portion 121, a second base pattern electrode 122 and a second branch electrode 123.

[0073] The pattern structure shown may be a quadrilateral as a whole, but may also be a circle or an ellipse as a whole. That is, the overall shape is irrelevant to the subject matter of the embodiments of the present invention.

[0074] In addition, the pattern electrode structure of the embodiment of the present invention realizes self-cleaning by receiving an AC voltage to make the droplets oscillate and drop on the electrode. The plane defined by the overall structure needs to be a plane perpendicular to the horizontal plane, or needs to be a plane inclined at a predetermined angle.

[0075] The first electrode connection part 111 and the second electrode connection part 121 are connected to a power source to receive a voltage. The first base pattern electrode 112 and the second base pattern electrode 122 are connected to the first electrode connection part 111 and the second electrode connection part 121, respectively, and define the periphery of the entire pattern electrode structure. That is, a predetermined area of ​​the periphery is defined by the first base pattern electrode 112, and the remaining area of ​​the periphery is defined by the second base pattern electrode 122.

[0076] The first branch electrodes 113 and the second branch electrodes 123 branch out from the first base pattern electrode 112 and the second base pattern electrode 122, respectively, and are arranged along one direction on the electrode structure, which is defined as a direction perpendicular to any plane perpendicular to the electrode structure.

[0077] In addition, the first branch electrodes 113 and the second branch electrodes 123 are alternately arranged in the width direction.

[0078] Fig.12A portion of a pattern electrode structure according to an embodiment of the present invention is shown, and a portion including the upper ends of branch electrodes and a base pattern electrode arranged on the upper portion of the pattern electrode structure is shown. In the embodiment of the present invention, the arrangement of the electrode pattern is used to prevent the dielectric layer on the upper portion of the glass of the electrowetting device from burning.

[0079] In this case, the interval between the first branch electrode 113 and the second base pattern electrode 122 is represented by G 2b The diameter of the droplet D is represented by Φ d express.

[0080] Since the second base pattern electrode of the prior art electrode pattern is spaced apart from the first branch electrode pattern by a distance G 2b The defined distances are adjacent to each other, so the droplet D may cross the second base electrode and the first branch electrode pattern, which causes the droplet to be stuck.

[0081] In an embodiment of the present invention, Fig.13 As shown, the interval G 2b The spacing is designed to be larger than that in the prior art so that a droplet cannot exist between the pattern of the second base pattern electrode 122 and the pattern of the first branch electrode 113. As a result, Fig.14 As shown, it can be determined that when using a 10 μl droplet and applying 100 V rms and the 100 Hz voltage did not change during the experiment.

[0082] That is to say, Fig.15 As shown, it can be determined that the interval area G 2b The droplets in the tube do not oscillate or move downward, so burning due to insulation breakdown does not occur.

[0083] In order to obtain such a result, under the condition that the droplet does not contact the first branch electrode 113, the vibration of the droplet is weakened and no burning occurs. Fig.16 As shown, the interval G 2b Need to be equal to or larger than the diameter of the droplet D d .

[0084] Table 1 below shows the droplet radius relative to the droplet volume.

[0085] Table 1

[0086]

[0087] More specifically, referring to Table 1, on a surface with a contact angle of 115 degrees, the minimum volume of a droplet that does not slide naturally is 3 μl. In an embodiment of the present invention, the range of the droplet to be removed is 0.2 μl to 3 μl.

[0088] Refer to Table 1, droplet diameter Φ d The range is as follows:

[0089] 0.658~0.782mm≤Φ d ≤1.748~1.93mm.

[0090] Due to the need to meet G 2b ≥Φ d , so we can deduce that G 2b Results ≥1.93mm, but there is no maximum limit as long as space allows.

[0091] As described above, the spacing condition between the first branch electrode 113 and the second base pattern electrode 122 for preventing the droplet from stagnating at the upper portion has been derived.

[0092] In addition, if Figures 17 to 19 As shown, the branch electrodes according to the embodiment of the present invention may have various shapes, thereby making it easier to prevent the droplets from stagnating at the upper portion.

[0093] The upper end of the branch pattern in the above embodiment is in a straight line shape. Due to the angular shape of the edge, when the droplet reaches the edge of the upper end, the droplet can return to the upper end of the first branch electrode 113, or move repeatedly while moving to a position where there is a symmetric ratio between the first branch electrode 113 and the second branch electrode 123.

[0094] Therefore, the embodiment of the present invention further provides an application example of changing the shape of the upper end of the first branch electrode 113 .

[0095] Fig.17 and Fig.18 1 shows an example in which the upper ends of the first branch electrodes 113 have a downwardly concave shape, wherein: Fig.17 An example is shown in which the upper end of the first branch electrode 113 has a circular shape. Fig.18 An example is shown in which the upper end of the first branch electrode 113 has a pointed concave shape.

[0096] also, Fig.19 An example is shown in which the upper end of the first branch electrode 113 has a shape that is convex upward.

[0097] As described above, since the areas of the droplet D on the first branch electrode 113 and the second branch electrode 123 are different, compared with the shape in the prior art, the movement of the droplet can be further increased.

[0098] Next, Fig. 20 1 and 2 are views showing additional application examples of the pattern electrode structure according to the embodiment of the present invention.

[0099] Compared with the prior art, the embodiment of the present invention increases the interval (gap) between the first branch electrode 113 and the second base pattern electrode 122 in the upward direction.

[0100] The gap space may be an empty space. However, the gap space may be a dummy pattern to which no voltage is applied. Since the dummy pattern may be electrically isolated, the same effect as setting a partition space may be achieved, and visibility may be compensated.

[0101] The influence of the above-mentioned interval between the second base pattern electrode and the first branch electrodes of the pattern electrode structure according to the embodiment of the present invention will be described below.

[0102] refer to Fig.21 , when the droplet spans the two electrodes because the interval between the second base pattern electrode 122 and the first branch electrode 113 is smaller than the size of the droplet, the droplet is placed as shown in the first to fourth cases, so that the droplet is periodically subjected to downward and upward forces.

[0103] Therefore, the droplet cannot leave the boundary portion, which may cause the surface dielectric layer to burn out.

[0104] In the case of the fifth example shown in the figure, since the droplet only crosses a single electrode, the force on the droplet is small and will not cause burning of the dielectric layer, but the frequency is very low.

[0105] In contrast, when the interval between the second base pattern electrode 122 and the first branch electrode 113 is designed to be equal to or larger than the droplet size, when the droplet crosses the first branch electrode 113, the droplet is subjected to a downward force and slides, as shown in the sixth and seventh cases. When the droplet crosses only the second base pattern electrode 122 as in the eighth and ninth cases, as in the fifth case, the force on the droplet is reduced, so that the dielectric layer is not burned.

[0106] Although the embodiments of the present invention have been described with reference to the exemplary drawings, it is obvious to those skilled in the art that the embodiments of the present invention are not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, the examples of changes or modifications belong to the scope of the claims of the present invention, and the scope of the present invention should be interpreted based on the attached claims.

Claims

1. A pattern electrode structure for an electrowetting device, the pattern electrode structure comprising: a first branch electrode disposed in a direction perpendicular to any plane perpendicular to the plane defined by the pattern electrode structure; and a base pattern electrode disposed in an area above the upper end of the first branch electrode and connected to an electrode connection portion configured to receive a voltage, Wherein, the interval between the first branch electrode and the base pattern electrode is equal to or greater than the diameter of the droplet to be removed.

2. The pattern electrode structure according to claim 1, wherein: An interval between the first branch electrode and the base pattern electrode is equal to or greater than 1.93 mm.

3. The pattern electrode structure according to claim 1, wherein: The polarity of the first branch electrode is different from the polarity of the base pattern electrode.

4. The pattern electrode structure according to claim 3, further comprising second branch electrodes arranged alternately with the plurality of first branch electrodes in a width direction of the pattern electrode structure, wherein: The polarity of the second branch electrode is different from the polarity of the first branch electrode.

5. The pattern electrode structure according to claim 1, further comprising second branch electrodes arranged alternately with the plurality of first branch electrodes in a width direction of the pattern electrode structure, wherein: The polarity of the second branch electrode is different from the polarity of the first branch electrode.

6. The pattern electrode structure according to claim 1, wherein: The upper end of the first branch electrode includes a concave portion.

7. The pattern electrode structure according to claim 1, wherein: The upper end of the first branch electrode includes a convex portion.

8. The pattern electrode structure according to claim 1, wherein: The upper end of the first branch electrode includes a pointed portion. 9 . The pattern electrode structure of claim 1 , further comprising a dummy pattern provided in a space between the first branch electrode and the base pattern electrode.

10. An electrowetting device comprising: Base material; a dielectric layer on the substrate; and An electrode layer stacked between the substrate and the dielectric layer, the electrode layer comprising a patterned electrode structure, the patterned electrode structure comprising: a first branch electrode disposed in a direction perpendicular to any plane perpendicular to the plane defined by the pattern electrode structure; and a base pattern electrode disposed in an area above the upper end of the first branch electrode and connected to an electrode connection portion configured to receive a voltage, Wherein, the interval between the first branch electrode and the base pattern electrode is equal to or greater than the diameter of the droplet to be removed.

11. The electrowetting device according to claim 10, wherein: An interval between the first branch electrode and the base pattern electrode is equal to or greater than 1.93 mm.

12. The electrowetting device according to claim 10, wherein: The polarity of the first branch electrode is different from the polarity of the base pattern electrode.

13. The electrowetting device according to claim 12, further comprising second branch electrodes arranged alternately with the plurality of first branch electrodes in the width direction of the pattern electrode structure, wherein: The polarity of the second branch electrode is different from the polarity of the first branch electrode.

14. The electrowetting device according to claim 10, further comprising second branch electrodes arranged alternately with the plurality of first branch electrodes in a width direction of the pattern electrode structure, wherein: The polarity of the second branch electrode is different from the polarity of the first branch electrode.

15. The electrowetting device according to claim 10, wherein: The upper end of the first branch electrode includes a concave portion.

16. The electrowetting device according to claim 10, wherein: The upper end of the first branch electrode includes a convex portion.

17. The electrowetting device according to claim 10, wherein: The upper end of the first branch electrode includes a pointed portion. 18 . The electrowetting device of claim 10 , further comprising a dummy pattern disposed in a space between the first branch electrode and the base pattern electrode.

19. A pattern electrode structure for an electrowetting device, the pattern electrode structure comprising: The first electrode portion includes: a first electrode connecting portion; a first base pattern electrode connected to the first electrode connecting portion; and a first branch electrode branching from the first base pattern electrode, and The second electrode portion comprises: a second electrode connecting portion; a second base pattern electrode connected to the second electrode connecting portion; and a second branch electrode branching from the second base pattern electrode, Wherein, the first electrode connection portion and the second electrode connection portion are both connected to a power source to receive a voltage, The first branch electrodes and the second branch electrodes are alternately arranged in the width direction and are arranged in the same direction perpendicular to any plane perpendicular to the pattern electrode structure, and Wherein, the interval between the first branch electrode and the second base pattern electrode is equal to or greater than the diameter of the droplet to be removed.

20. The pattern electrode structure according to claim 19, wherein: The upper end of the first branch electrode includes a concave portion, a convex portion or a pointed portion.

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