Electro-wetting pixel unit and driving method thereof, display panel

Abstract

The application relates to an electrowetting pixel unit and a driving method thereof and a display panel, wherein the upper substrate, the first pixel wall, the lower substrate and the second pixel wall in the electrowetting pixel unit are sequentially connected to form a closed space; a first transparent electrode is arranged at a position where the closed space is attached to the upper substrate; a first super-hydrophobic insulating layer is arranged at a position where the closed space is attached to the first transparent electrode; a second super-hydrophobic insulating layer is arranged at a position where the closed space is attached to the lower substrate; the first super-hydrophobic insulating layer, the second super-hydrophobic insulating layer, the first pixel wall and the second pixel wall form an electrowetting fluid chamber in the closed space; a second transparent electrode is arranged in the electrowetting fluid chamber and divides the electrowetting fluid chamber into two independent fluid chambers, and the second transparent electrode forms an asymmetric microstructure with the upper substrate and the lower substrate.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to an electrowetting pixel unit and its driving method, and a display panel. Background Technology

[0002] The principle of electrowetting electronic paper displays is as follows: by applying electricity to droplets, the wettability of the solid-liquid interface is changed, thereby controlling the shrinkage and spreading of colored ink, and ultimately realizing the switching of pixels and the adjustment of grayscale. Existing electrowetting electronic paper has the following problems: grayscale control is usually controlled along the falling edge of the voltage. When a pixel is powered on, the ink needs to be pushed to the corners before spreading to a specific aperture ratio. The voltage is high during the process of pushing the ink to the corners, and the polar fluid fluctuations are violent, which can easily cause the ink to overflow into adjacent pixel cells, resulting in display abnormalities. Summary of the Invention

[0003] This application provides an electrowetting pixel unit and its driving method, as well as a display panel, to solve the problem in the prior art where, when the pixels in electrowetting electronic paper are powered on, the ink is pushed to the corners by a large voltage, and the polar fluid fluctuations are violent, causing the ink to flip over to adjacent pixel grids, resulting in display abnormalities.

[0004] In a first aspect, this application provides an electrowetting pixel unit, including an upper substrate, a lower substrate, a first superhydrophobic insulating layer, a second superhydrophobic insulating layer, a first pixel wall, a second pixel wall, a first transparent electrode, and a second transparent electrode; the upper substrate, the first pixel wall, the lower substrate, and the second pixel wall are sequentially connected to form a closed space; the first transparent electrode is disposed in the closed space at a position attached to the upper substrate; the first superhydrophobic insulating layer is disposed in the closed space at a position attached to the first transparent electrode; the second superhydrophobic insulating layer is disposed in the closed space at a position attached to the lower substrate; the first superhydrophobic insulating layer, the second superhydrophobic insulating layer, the first pixel wall, and the second pixel wall form an electrowetting fluid chamber in the closed space; the second transparent electrode is disposed in the electrowetting fluid chamber and divides the electrowetting fluid chamber into two independent fluid chambers, the second transparent electrode forming an asymmetric microstructure with the upper substrate and the lower substrate; a polar fluid is disposed in the fluid chamber above the second transparent electrode, and ink is disposed in the fluid chamber below the second transparent electrode.

[0005] Optionally, the angle between the second transparent electrode and the upper substrate is the target angle, or the angle between the second transparent electrode and the lower substrate is the target angle, wherein the target angle is greater than zero and less than 90°.

[0006] Optionally, when the electrowetting pixel unit is not powered on, the polar fluid remains on the side with the higher cross-sectional height in the fluid chamber, and the ink remains on the side with the higher cross-sectional height in the fluid chamber.

[0007] Optionally, the target angle ranges from 3° to 15°.

[0008] Optionally, the second transparent electrode is a flexible electrode.

[0009] Optionally, when the electrowetting pixel unit is energized, an electric field is generated between the first transparent electrode and the second transparent electrode to drive the polar fluid to move to the other side of its position in the fluid chamber, so as to compress the second transparent electrode to deform and then compress the ink to move to the other side of its position in the fluid chamber.

[0010] Optionally, a reflective layer is deposited on the lower substrate.

[0011] The second aspect provides a method for driving the electrowetting pixel unit described in the first aspect, the method comprising: when the electrowetting pixel unit is energized, driving the polar fluid to move to the other side of its position in a fluid chamber based on an electric field generated between the first transparent electrode and the second transparent electrode; using the movement of the polar fluid to compress the second transparent electrode to deform, and then using the deformed second transparent electrode to compress the ink to move to the other side of its position in the fluid chamber, thereby achieving grayscale control.

[0012] Optionally, different gray levels correspond to different spreading areas of the ink in the fluid chamber.

[0013] Thirdly, a display panel is provided, including the electrowetting pixel unit described in the first aspect.

[0014] Compared with the prior art, the technical solution provided in this application has the following advantages: One electrowetting fluid chamber in the electrowetting pixel unit is divided into two independent fluid chambers by a second transparent electrode, and the two independent fluid chambers respectively hold the polar fluid and the ink. In other words, in this application embodiment, a dual-chamber design is achieved through the second transparent electrode, with the polar fluid and ink placed separately in independent chambers, thus eliminating direct contact. Based on this, the pixel's driving method is changed from the existing method of water-fracturing ink forcing contraction to a method where the polar fluid squeezes the electrode and, in conjunction with asymmetric interfacial tension, causes the ink to expand. Therefore, when the ink moves to the leftmost end, it is blocked and stops moving, preventing ink from overflowing. Even if the polar fluid fluctuates violently, the ink will not overflow into adjacent pixel cells. Attached Figure Description

[0015] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 This is a schematic diagram of the existing electrowetting electronic paper display principle; Figure 2 A schematic diagram of an electrowetting pixel unit in an electrowetting electronic paper provided in an embodiment of this application; Figure 3 This is one of the schematic diagrams of ink movement provided in the embodiments of this application; Figure 4 This is a second schematic diagram of ink movement provided in the embodiments of this application; Figure 5 This is the third schematic diagram of ink movement provided in the embodiments of this application; Figure 6 A comparative illustration of existing inks and inks in this application at the corners, provided for the purposes of this application; Figure 7 This is a flowchart illustrating a method for driving electrowetting pixel units in electrowetting electronic paper, as provided in an embodiment of this application.

[0019] Explanation of reference numerals in the attached drawings: Transparent electrode-101, Water-102, Colored ink-103, Pixel wall-104, Hydrophobic insulating layer-105, Transparent electrode-106, Substrate-107; Upper substrate-210, Lower substrate-211, First superhydrophobic insulating layer-220, Second superhydrophobic insulating layer-221, First pixel wall-230, Second pixel wall-231, First transparent electrode-240, Second transparent electrode-241, Polar fluid-250, Ink-260. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed.

[0022] The principle of electrowetting electronic paper displays is as follows: by applying electricity to droplets, the wettability of the solid-liquid interface is changed, thereby controlling the shrinkage and spreading of colored inks, and ultimately realizing the switching of pixels and the adjustment of grayscale. A typical electrowetting electronic paper pixel structure is as follows: Figure 1 The two-phase fluid system within the pixel unit shown is controlled by applying an electric field to control the movement of the oil-water interface, thus achieving grayscale adjustment. (a) represents the un-electrified state, and (b) represents the energized state. Additionally, as... Figure 1 As shown, the bottom TFT electrode layer uses an oleophilic and hydrophobic insulating layer, and pixel walls are constructed using photoresist. Then, an ink layer is applied to the bottom of the pixel grid, and the entire substrate is placed in a polar fluid (such as water) and encapsulated with the upper ITO glass layer to form a display screen. When the pixel grid is not powered, the ink covers the bottom of the pixel grid, and the pixel grid displays the color of the ink. When power is applied to the upper ITO glass layer and the lower TFT substrate, the ink is pushed away by the water, and the pixel displays the color of the bottom of the pixel grid (usually white). Thus, the pixel grid color can be switched by applying voltage.

[0023] To address the problem in existing electrowetting electronic paper technology where, during pixel energization, the high voltage pushes the ink to the edges, causing violent fluctuations in the polar fluid and resulting in ink overflowing into adjacent pixel cells and causing display abnormalities, this application provides an electrowetting pixel unit, such as... Figure 2 As shown, the electrowetting pixel unit includes an upper substrate 210, a lower substrate 211, a first superhydrophobic insulating layer 220, a second superhydrophobic insulating layer 221, a first pixel wall 230, a second pixel wall 231, a first transparent electrode 240, and a second transparent electrode 241. The upper substrate 210, the first pixel wall 230, the lower substrate 211, and the second pixel wall 231 are sequentially connected to form a closed space; the first transparent electrode 240 is disposed in the closed space at a position attached to the upper substrate 210; the first superhydrophobic insulating layer 220 is disposed in the closed space at a position attached to the first transparent electrode 240; and the second superhydrophobic insulating layer 221 is disposed in the closed space at a position attached to the lower substrate 211. The first superhydrophobic insulating layer 220, the second superhydrophobic insulating layer 221, the first pixel wall 230, and the second pixel wall 231 form an electrowetting fluid chamber in a closed space; the second transparent electrode 241 is disposed in the electrowetting fluid chamber and divides the electrowetting fluid chamber into two independent fluid chambers; the second transparent electrode 241 forms an asymmetric microstructure with the upper substrate 210 and the lower substrate 211; a polar fluid 250 is disposed in the fluid chamber above the second transparent electrode 241, and an ink 260 is disposed in the fluid chamber below the second transparent electrode 241.

[0024] As can be seen, in this embodiment, the second transparent electrode 241 divides one electrowetting fluid chamber in the electrowetting pixel unit into two independent fluid chambers, with the polar fluid and ink placed in the two independent fluid chambers respectively. In other words, this embodiment achieves a dual-chamber design through the second transparent electrode 241, with the polar fluid and ink placed separately in independent chambers, thus eliminating direct contact between them. Based on this, the pixel's driving method changes from the existing method of water-fracturing ink forcing contraction to a method where the polar fluid squeezes the electrode and, in conjunction with asymmetric interfacial tension, causes the ink to expand. Therefore, when the ink moves to the leftmost end, it is blocked and stops moving, preventing ink from overflowing. Even with violent fluctuations in the polar fluid, the ink will not overflow into adjacent pixel cells.

[0025] In other words, existing electrowetting pixels operate with high voltage and rapid voltage rise during the water-pressure fracturing process of the ink, which easily causes ink splitting and failure to merge in time, resulting in ink residue. However, the dual-chamber design in this embodiment places the ink and polar fluid separately. During pixel operation, the polar fluid does not directly contact the fracturing ink, but rather drives the ink through the second transparent electrode of the dielectric, avoiding ink splitting caused by fluctuations and disturbances in the polar fluid during rapid pressurization, thus effectively preventing ink residue.

[0026] In an optional embodiment of this application, the angle between the second transparent electrode 241 and the upper substrate 210 is the target angle, or the angle between the second transparent electrode and the lower substrate 211 is the target angle, and the target angle is greater than zero and less than 90°.

[0027] As can be seen, in the embodiments of this application, the asymmetric microstructure formed by the second transparent electrode 241 with the upper substrate 210 and the lower substrate 211 means that the second transparent electrode 241 is not parallel to the upper substrate 210 and the lower substrate 211, specifically as follows: Figure 2 As shown, the angle between the second transparent electrode 241 and the lower substrate 211 is the target angle, i.e., from... Figure 2 It can be seen that the cross-sectional height of the cavity formed by the second transparent electrode 241 and the first superhydrophobic insulating layer 220 gradually decreases from left to right, while the cross-sectional height of the cavity formed by the second transparent electrode 241 and the second superhydrophobic insulating layer 221 gradually increases from left to right. Of course, Figure 2 This only illustrates one scenario where the second transparent electrode 241 forms an asymmetric microstructure with the upper substrate 210 and the lower substrate 211. Another scenario is where the angle between the second transparent electrode 241 and the upper substrate 210 is the target angle. If it is still related to... Figure 2 Similar to this illustration, the angle between the second transparent electrode 241 and the upper substrate 210 is the target angle. This means that the height of the cavity cross-section formed by the second transparent electrode 241 and the first superhydrophobic insulating layer 220 gradually increases from left to right, while the height of the cavity cross-section formed by the second transparent electrode 241 and the second superhydrophobic insulating layer 221 gradually decreases from left to right. In a specific example, the target angle can range from 3° to 15°. The specific value of the target angle can be set according to actual needs.

[0028] In this embodiment, when the electrowetting pixel unit is not energized, the polar fluid remains on the side with the higher cross-sectional height within its fluid chamber, and the ink also remains on the side with the higher cross-sectional height within the fluid chamber. Specifically, as follows... Figure 2 As shown, when the electrowetting pixel unit is not energized, the ink in the lower chamber (the fluid chamber where the ink is located) will move in the direction of decreasing chamber cross-sectional height under the action of capillary force and surface tension. Figure 2 (From center to left). However, due to the unequal height of the chamber cross-sections, the direction with higher cross-sections provides a greater surface tension, thus causing the ink to remain on the... Figure 2 At a higher cross-sectional height on the right side of the middle section. Correspondingly, the polar fluid in the upper chamber (the fluid chamber where the polar fluid resides) will remain at the upper... Figure 2 At a higher section height on the left side of the middle.

[0029] It should be noted that the second transparent electrode in this embodiment is a flexible electrode. Therefore, when the electrowetting pixel unit is energized, an electric field is generated between the first transparent electrode 240 and the second transparent electrode 241. This electric field can drive the polar fluid to move to the other side of its position within the fluid chamber, thereby compressing the second transparent electrode to deform and then compressing the ink to move to the other side of its position within the fluid chamber. In this regard, Figure 2As shown in the example, when no power is applied, the polar fluid is on the left and the ink is on the right. After power is applied to the pixel unit, the second transparent electrode 241 and the first transparent electrode 240 generate an electric field, and the polar fluid moves towards the right side of the upper cavity under the action of the electrodes. Since the cross-sectional height of the cavity gradually narrows and the second transparent electrode 240 is flexible, the polar fluid inevitably compresses the second transparent electrode 240 during its movement, thereby indirectly compressing the ink, thus disrupting the static ink force balance, and thus compressing the ink to move to the left side of the lower cavity. Specifically... Figures 3 to 5 The ink movement process shown is as follows: Figure 3 As shown, when the current is initially applied, the polar fluid begins to move, which compresses the second transparent electrode 240 and causes it to deform. At this point, the deformation of the second transparent electrode 240 is not obvious, and the ink has just begun to move. As the current continues to flow, the polar fluid continues to compress the second transparent electrode, and its deformation becomes more pronounced. Figure 4 As shown, the ink moves from right to left to the middle position, and the polar fluid continuously presses against the second transparent electrode, causing the ink to move from the rightmost to the leftmost position.

[0030] Therefore, the magnitude of the pressure exerted by the polar fluid on the second transparent electrode 240 can control the ink spreading area in the lower chamber, thereby achieving grayscale control. Different ink spreading areas within the chamber correspond to different grayscale levels. In other words, the electrowetting pixel unit in this embodiment can better control the grayscale of pixel units in electronic paper. Furthermore, the lower substrate 211 in this embodiment can deposit a reflective layer, which further enhances the display effect of the pixel unit.

[0031] Additionally, in the embodiments of this application, such as Figure 6 The left side shows a partial schematic diagram of the pixel structure ink in existing electrowetting electronic paper when it is at the corners, such as... Figure 6 The right side of the image shows a partial schematic diagram of the pixel structure ink in the electrowetting electronic paper provided in this application when it is at the corner. Due to the independent chamber design in this embodiment, the height of the chamber cross-section is usually lower than the cross-sectional width of the existing electrowetting structure. As a result, the ink adheres to the superhydrophobic insulating layer between the second transparent electrode 240 and the lower substrate 211 due to surface tension. Compared with the existing electrowetting pixel structure ink being squeezed and piled up at the corner, the method in this embodiment makes the ink occupy less space, that is, occupy a smaller cross-sectional width, and correspondingly improves the pixel aperture ratio.

[0032] This application embodiment also provides a method for driving the above-mentioned electrowetting pixel unit, such as... Figure 7 As shown, the steps of this method include: Step 701: When the electrowetting pixel unit is energized, an electric field is generated between the first transparent electrode and the second transparent electrode to drive the polar fluid to move to the other side of its position in the fluid chamber. Step 702: Based on the movement of the polar fluid, the second transparent electrode is deformed by pressure. The deformed second transparent electrode then presses the ink to move to the other side of its position in the fluid chamber, thereby achieving grayscale control.

[0033] In response, Figure 2 As shown in the example, when no power is applied, the polar fluid is on the left and the ink is on the right. After power is applied to the pixel unit, the second transparent electrode 241 and the first transparent electrode 240 generate an electric field, and the polar fluid moves towards the right side of the upper cavity under the action of the electrodes. Since the cross-sectional height of the cavity gradually narrows and the second transparent electrode 240 is flexible, the polar fluid inevitably compresses the second transparent electrode 240 during its movement, thereby indirectly compressing the ink, thus disrupting the static ink force balance, and thus compressing the ink to move to the left side of the lower cavity.

[0034] It should be noted that in existing electrowetting electronic paper drives, the threshold voltage Vth for ink rupture is typically very high. Rapidly applying pressure to Vth often causes the ink to vibrate violently and rupture, easily resulting in ink residue. This can lead to grayscale modulation inaccuracies, thereby reducing display contrast and color gradation. Through the embodiments of this application, the pixel driving method is changed from the existing method of forcing ink to contract using water-fracturing ink to a method of polar fluid extruding electrodes and coordinating with asymmetric interfacial tension to expand the ink. Due to the change in driving method, the voltage driving ink expansion is lower than the voltage of fracturing ink, significantly reducing the threshold voltage Vth for ink rupture and its driving voltage, thus improving pixel driving performance.

[0035] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0036] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented using software plus a general-purpose hardware platform, or of course, using hardware. Based on this understanding, the above technical solutions, in essence or the parts that contribute to the related technology, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0037] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also include the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0038] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An electrowetting pixel unit, characterized in that, It includes an upper substrate, a lower substrate, a first superhydrophobic insulating layer, a second superhydrophobic insulating layer, a first pixel wall, a second pixel wall, a first transparent electrode, and a second transparent electrode; The upper substrate, the first pixel wall, the lower substrate, and the second pixel wall are connected in sequence to form a closed space; The first transparent electrode is disposed in the closed space at a position where it is attached to the upper substrate; the first superhydrophobic insulating layer is disposed in the closed space at a position where it is attached to the first transparent electrode; The second superhydrophobic insulating layer is disposed in the closed space at the position where it is attached to the lower substrate; The first superhydrophobic insulating layer, the second superhydrophobic insulating layer, the first pixel wall, and the second pixel wall form an electrowetting fluid chamber in the closed space; the second transparent electrode is disposed in the electrowetting fluid chamber and divides the electrowetting fluid chamber into two independent fluid chambers; the second transparent electrode forms an asymmetric microstructure with the upper substrate and the lower substrate; a polar fluid is disposed in the fluid chamber above the second transparent electrode and ink is disposed in the fluid chamber below the second transparent electrode.

2. The electrowetting pixel unit according to claim 1, characterized in that, The angle between the second transparent electrode and the upper substrate is the target angle, or the angle between the second transparent electrode and the lower substrate is the target angle, wherein the target angle is greater than zero and less than 90°.

3. The electrowetting pixel unit according to claim 1, characterized in that, When the electrowetting pixel unit is not powered on, the polar fluid remains on the side with the higher cross-sectional height in the fluid chamber, and the ink remains on the side with the higher cross-sectional height in the fluid chamber.

4. The electrowetting pixel unit according to claim 2, characterized in that, The target angle ranges from 3° to 15°.

5. The electrowetting pixel unit according to claim 1, characterized in that, The second transparent electrode is a flexible electrode.

6. The electrowetting pixel unit according to claim 5, characterized in that, When the electrowetting pixel unit is energized, an electric field is generated between the first transparent electrode and the second transparent electrode to drive the polar fluid to move to the other side of its position in the fluid chamber, so as to compress the second transparent electrode to deform and then compress the ink to move to the other side of its position in the fluid chamber.

7. The electrowetting pixel unit according to claim 1, characterized in that, A reflective layer is deposited on the lower substrate.

8. A method for driving the electrowetting pixel unit of any one of claims 1 to 7, characterized in that, The method includes: When the electrowetting pixel unit is energized, an electric field is generated between the first transparent electrode and the second transparent electrode, driving the polar fluid to move to the other side of its location in the fluid chamber; The movement of the polar fluid compresses the second transparent electrode to deform it, and the deformed second transparent electrode then compresses the ink to move to the other side of its position in the fluid chamber, thereby achieving grayscale control.

9. The method according to claim 8, characterized in that, Different gray levels correspond to different spreading areas of the ink in the fluid chamber.

10. A display panel, characterized in that, Includes the electrowetting pixel unit according to any one of claims 1 to 7.

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