An electrowetting display device and its preparation method and application

Abstract

The present invention discloses an electrowetting display device and its preparation method and application. The electrowetting display device includes a first substrate, a second substrate and a plurality of display units arranged between the first substrate and the second substrate, the display unit includes a sealed cavity, the sealed cavity is filled with a polar fluid and a non-polar fluid, when no voltage is applied between the first substrate and the second substrate, the arrangement direction of the polar fluid and the non-polar fluid forms an angle θ with the arrangement direction of the first substrate and the second substrate, θ>0°. The polar fluid, the non-polar fluid and the surface of the first substrate or the second substrate in the present invention will form a three-phase contact line, on which only a very low potential energy is needed to achieve the movement or rewetting of the fluid, so that the opening voltage of the electrowetting display device is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrowetting display, and in particular relates to an electrowetting display device and a preparation method and application thereof. Background Art

[0002] The basic structure of the conventional electrowetting display device is as follows: Figure 1 As shown, the basic structure is a sealed cavity formed by filling a specific solution in the upper and lower substrates. The specific solution contains two immiscible polar electrolyte solutions 04 and non-polar liquids 05. The upper substrate contains a support plate 01 and a first electrode 02, and the lower substrate contains a support plate 09, a second electrode 08, a hydrophobic insulating layer 07 and a pixel wall 06. The two substrates are connected by a specific solution and sealed by a sealant 03. Each pixel grid in the pixel wall 06 is evenly filled with non-polar liquids 05. Since the material of the pixel wall 06 is hydrophilic, the adjacent non-polar liquids 05 are separated by the pixel wall 06, and the mobile phase polar electrolyte solution 04 covers the pixel wall 06. Since the polar electrolyte solution 04 is connected to the first electrode 02, when a voltage is applied between the first electrode 02 and the second electrode 08, the wetting properties of the polar electrolyte solution 04 change from the original hydrophobic state to the hydrophilic state, so that the polar electrolyte solution 04 wets the surface of the hydrophobic insulating layer 07, and the non-polar liquid 05 in each pixel grid is squeezed to a corner. On the contrary, when the first electrode 02 and the second electrode 08 are not under pressure, the polar electrolyte solution 04 remains in a hydrophobic state, covering the pixel wall 06, and the non-polar liquid 05 is in a spreading state. That is, the display device is in an open state by applying pressure, and the display device is in a closed state when no pressure is applied. Since the polar electrolyte solution 04 and the non-polar liquid 05 in the traditional electrowetting display device are stacked up and down, when a voltage is applied, enough potential energy is required to cause the rupture of the non-polar liquid 05 film layer and then wet the surface of the hydrophobic insulating layer 07 by the polar electrolyte solution 04, so the opening voltage is relatively high. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides an electrowetting display device having the characteristic of low opening voltage.

[0004] The invention also provides a method for preparing the electrowetting display device.

[0005] The present invention also proposes the application of the electrowetting display device.

[0006] According to a first aspect of the present invention, an electrowetting display device is proposed, comprising a first substrate, a second substrate and a plurality of display units arranged between the first substrate and the second substrate, wherein the display unit comprises a sealed cavity filled with a polar fluid and a non-polar fluid, and when no voltage is applied between the first substrate and the second substrate, the arrangement direction of the polar fluid and the non-polar fluid forms an angle θ with the arrangement direction of the first substrate and the second substrate, and θ>0°.

[0007] The electrowetting display device according to the embodiment of the present invention has at least the following beneficial effects:

[0008] In the present invention, the arrangement direction of the polar fluid and the non-polar fluid forms an angle greater than zero with the arrangement direction of the first substrate and the second substrate, and the polar fluid, the non-polar fluid and the surface of the first substrate or the second substrate form a three-phase contact line. Only very low potential energy is required on this contact line to achieve fluid movement or rewetting, thereby reducing the opening voltage of the electrowetting display device and having a lower opening voltage.

[0009] In some embodiments of the present invention, 90°≥θ≥60°.

[0010] In some more preferred embodiments of the present invention, θ=90°.

[0011] Through the above-mentioned implementation mode, compared with the upper and lower stacking structure of polar fluid and non-polar fluid in the traditional electrowetting display device (consistent with the arrangement direction of the first substrate and the second substrate), when no voltage is applied between the first substrate and the second substrate of the electrowetting display device in the present invention, the polar fluid and the non-polar fluid are arranged left and right (horizontally arranged, perpendicular to the arrangement direction of the first substrate and the second substrate), and the opening voltage is significantly reduced.

[0012] In some embodiments of the present invention, the first substrate and the second substrate are parallel.

[0013] In some embodiments of the present invention, the polar fluid has a color. The polar fluid in each display unit independently has different or the same color, including but not limited to yellow, red, blue, magenta (or fuchsia) or cyan, etc.

[0014] In traditional electrowetting display devices, polar fluids are usually transparent, and non-polar fluids are black or colored non-polar solutions. Among them, the colored solutes in the non-polar solution are mostly anthraquinone, azo or perylene small molecule compounds, and in order to meet the light absorption of the special band in the range of 400-800nm, metal ions are added for molecular design. However, this type of molecule can easily cause the positive and negative charge centers to not coincide. From the perspective of the entire molecule, the charge distribution is uneven and asymmetric. Such molecules are polar molecules, which are easily polarized under the action of an electric field, which has a certain interference with the display effect of the display device, making it impossible to achieve grayscale control of the display device. Specifically, in traditional electrowetting display devices, such as Figure 1 As shown in the figure, when a voltage is applied between the first electrode 02 and the second electrode 08, the polar electrolyte solution 04 changes the wettability on the surface of the hydrophobic insulating layer 07 under the action of the electric field, so that the non-polar liquid 05 is pushed to the corner of the pixel grid. However, because the polar molecules contained in the non-polar liquid 05 also produce polarization under the action of the electric field, the surface of the hydrophobic insulating layer 07 is re-wetted. When the electrowetting display device is in the on state, the non-polar liquid 05 cannot be stably maintained in a corner of the pixel grid, which has a certain interference with the display effect, thereby failing to achieve grayscale control of the display device. In severe cases, the pixel aperture ratio and reflectivity of the device will be greatly affected.

[0015] In the present invention, the polar fluid has color, and the non-polar fluid is transparent. The present invention first improves the filling solution, changes the original colored non-polar liquid into a transparent non-polar fluid, and changes the original transparent polar electrolyte solution into a colored polar fluid. The present invention avoids the rewetting phenomenon between the polar molecules in the non-polar liquid and the upper and lower substrates of the traditional electrowetting device under the pressurized state, so that the performance of the electrowetting display device is improved, and the display device can maintain the stable state of the image grayscale during the driving process, and maintain its grayscale controllability when it is in the working state. When the electrowetting display device in the present invention is applied to text display, the display can be changed from white before pressurization to black after pressurization, which is more in line with the daily use habits of traditional paper. For example, when displaying text content, more than about 80% of the pixels of the electrowetting display device in the present invention are in the off state, which has certain energy saving. The traditional electrowetting display needs to pressurize the non-text image part pixel grid to white, and the voltage of the corresponding pixel grid is turned off to display the corresponding pattern. In comparison, the energy consumption of the traditional electrowetting display device is relatively large.

[0016] In some embodiments of the present invention, the polar fluid is a polar electrolyte solution.

[0017] In some preferred embodiments of the present invention, the polar electrolyte solution comprises a dye and a polar solvent.

[0018] In some more preferred embodiments of the present invention, the polar solvent includes water or an alcohol solvent; preferably, the dye includes a water-soluble dye.

[0019] In some more preferred embodiments of the present invention, the alcohol solvent includes ethylene glycol.

[0020] In some embodiments of the present invention, the non-polar fluid is a transparent fluid.

[0021] In some embodiments of the present invention, the non-polar fluid comprises an alkane substance. Preferably, the non-polar fluid is an alkane substance.

[0022] Through the above-mentioned implementation mode, a water-soluble dye is added to the polar electrolyte solution, and the non-polar fluid remains a simple alkane solvent, thereby avoiding the re-wetting phenomenon between the polar molecules in the non-polar fluid and the second substrate (such as including an insulating hydrophobic layer) under pressurized state, thereby improving the performance of the electrowetting display device and enabling the display to maintain a stable state of image grayscale during the driving process.

[0023] The colored polar electrolyte solution, transparent non-polar fluid and the surface of the hydrophobic insulating layer will form a three-phase contact line. On this contact line, only very low potential energy is needed to make the polar electrolyte solution wet the surface of the hydrophobic insulating layer, thereby reducing the opening voltage of the device.

[0024] When the present invention is applied to text display, the display changes from white before pressure to black after pressure, which is more in line with the daily use habits of traditional paper. For example, when displaying text content, more than 80% of the pixels of the electrowetting device in the present invention are in a closed state, which has certain energy saving properties. Traditional electrowetting displays require pressure to make the non-text and graphic part of the pixel grid white, and turn off the voltage of the corresponding pixel grid to display the corresponding pattern. In comparison, traditional electrowetting display devices have a large energy consumption.

[0025] In some preferred embodiments of the present invention, the non-polar fluid comprises at least one of C6-C14 alkanes.

[0026] In some more preferred embodiments of the present invention, the non-polar fluid comprises at least one of octane, heptane, decane, undecane or dodecane.

[0027] In some more preferred embodiments of the present invention, the non-polar fluid is decane.

[0028] In some embodiments of the present invention, the first substrate comprises a first base plate and a first electrode layer which are arranged in sequence. The first electrode layer is located on a side of the first base plate close to the second substrate. Preferably, the first electrode layer is in contact with the non-polar fluid.

[0029] In some preferred embodiments of the present invention, the first substrate includes a first base plate and a first electrode layer which are stacked in sequence.

[0030] In some embodiments of the present invention, the second substrate comprises a second base plate and a hydrophobic insulating layer which are arranged in sequence. The hydrophobic insulating layer is located on a side of the second base plate close to the first substrate. Preferably, the hydrophobic insulating layer is in contact with the polar fluid.

[0031] When no voltage is applied between the first substrate and the second substrate, a three-phase contact line is formed between the polar fluid, the non-polar fluid and the hydrophobic insulating layer.

[0032] In some preferred embodiments of the present invention, a second electrode layer is provided between the second base plate and the hydrophobic insulating layer.

[0033] In some preferred embodiments of the present invention, the second substrate includes a second base plate, a second electrode layer and a hydrophobic insulating layer which are stacked in sequence.

[0034] In some embodiments of the present invention, the display unit further includes a pixel wall assembly, and the sealed cavity includes a first sealed cavity and a second sealed cavity that are interconnected, the first sealed cavity is formed between components of the pixel wall assembly, and the second sealed cavity is formed between the pixel wall assembly and the first substrate and the second substrate.

[0035] It should be noted that the first sealed cavity is formed between the internal components in the pixel wall assembly. Specifically, a group of the pixel wall assemblies includes a plurality of components, and the first sealed cavity is formed between the components of the group of the pixel wall assemblies. In addition, taking the group of the pixel wall assemblies as a whole, the second sealed cavity is formed between the pixel wall assembly and the first substrate and the second substrate.

[0036] In some preferred embodiments of the present invention, the first sealed cavity is filled with a polar fluid, and the second sealed cavity is filled with a non-polar fluid.

[0037] In some preferred embodiments of the present invention, the pixel wall assembly includes a first hydrophilic component and a second hydrophilic component spaced apart between the first substrate and the second substrate, a set distance is provided between the first hydrophilic component and the second substrate, and the hydrophilicity of the second hydrophilic component is greater than that of the first hydrophilic component.

[0038] The set distance between the first hydrophilic member and the second substrate means that the first hydrophilic member and the second substrate are not in contact, and there is a certain distance between the two. The distance can be set according to actual conditions and a suitable distance size can be selected. The first hydrophilic member and the second hydrophilic member are both insulating hydrophilic members. Preferably, a group of the pixel wall components includes a first hydrophilic member and a second hydrophilic member adjacent to each other.

[0039] In some more preferred embodiments of the present invention, the first sealed cavity is formed between adjacent first hydrophilic components and second hydrophilic components.

[0040] Since the first hydrophilic member and the second hydrophilic member are arranged in an interval manner, specifically, the first substrate, the adjacent first hydrophilic member and the second hydrophilic member, and the second substrate form the first sealed cavity.

[0041] In some more preferred embodiments of the present invention, the first hydrophilic component is connected to the first substrate; or, there is a set distance between the first hydrophilic component and the first substrate.

[0042] The set distance between the first hydrophilic component and the first substrate means that the first hydrophilic component and the first substrate are not in contact with each other, and there is a certain distance between them. The distance can be set according to actual conditions and a suitable distance can be selected.

[0043] In some more preferred embodiments of the present invention, the second hydrophilic member is connected to the second substrate.

[0044] In some more preferred embodiments of the present invention, the second hydrophilic component is connected to the first substrate; or, there is a set distance between the second hydrophilic component and the first substrate.

[0045] The set distance between the second hydrophilic component and the first substrate means that the second hydrophilic component and the first substrate are not in contact with each other, and there is a certain distance between them. The distance can be set according to actual conditions and a suitable distance can be selected.

[0046] In some more preferred embodiments of the present invention, two ends of the second hydrophilic member are connected to the first substrate and the second substrate respectively.

[0047] In some more preferred embodiments of the present invention, the first hydrophilic member includes a first pixel wall.

[0048] In some more preferred embodiments of the present invention, the second hydrophilic member includes a second pixel wall.

[0049] In some preferred embodiments of the present invention, a conductive member is provided in the first sealed cavity, and the conductive member is electrically connected to the first substrate. Preferably, the conductive member is connected to the first electrode layer. Preferably, the conductive member is a conductive column. Preferably, the conductive column is a conductive glue layer column. Preferably, the conductive member is located between the adjacent first hydrophilic member and the second hydrophilic member.

[0050] In some more preferred embodiments of the present invention, there is a set distance between the conductive member and the second substrate. The set distance between the conductive member and the second substrate means that the conductive member and the second substrate are not in contact with each other, and there is a certain distance between the two. The distance can be set according to actual conditions and a suitable distance can be selected.

[0051] In some embodiments of the present invention, each of the display units includes two groups of symmetrically arranged pixel wall components.

[0052] Through the above implementation mode, each display unit includes two groups of pixel wall components symmetrically arranged, which means that each display unit includes two first hydrophilic parts (first hydrophilic part I and first hydrophilic part II), two second hydrophilic parts (second hydrophilic part I and second hydrophilic part II), two conductive pillars (conductive pillar I and conductive pillar II), two first sealed cavities (first sealed cavity I and first sealed cavity II) and one second sealed cavity, and in each display unit: between the first substrate and the second substrate, from one end of the first substrate to the other end thereof, the second hydrophilic part I, the conductive pillar I, the first hydrophilic part I, the first hydrophilic part II, the conductive pillar II, and the second hydrophilic part II are sequentially arranged at intervals, and the sealed cavity of the display unit includes the first sealed cavity I, the second sealed cavity and the first sealed cavity II which are sequentially connected, wherein the first sealed cavity I is formed between the second hydrophilic part I, the first hydrophilic part I, the first substrate and the second substrate; the second sealed cavity is formed between the first hydrophilic part I, the first hydrophilic part II, the first substrate and the second substrate; the first sealed cavity II is formed between the first hydrophilic part II, the second hydrophilic part II, the first substrate and the second substrate.

[0053] In some embodiments of the present invention, the electrowetting display device further comprises a plurality of partitions spaced between the first substrate and the second substrate, the first substrate and the second substrate facing each other are respectively connected to the partitions, and the partitions are arranged vertically to the pixel wall assembly. Preferably, the partitions are vertically connected to the second hydrophilic member. Preferably, the partitions are connected to both the first electrode layer of the first substrate and the hydrophobic insulating layer of the second substrate.

[0054] Through the above-mentioned implementation manner, in the middle part of the electrowetting display device: the first substrate, two adjacent partitions, the second substrate and two second hydrophilic parts located at the edge of a display unit together form the display unit; the edge part of the electrowetting display device: the first substrate, two adjacent partitions (or one partition), the second substrate and one to two second hydrophilic parts located at the edge of a display unit together form the display unit, or / and, the first substrate, one partition, the second substrate and two second hydrophilic parts (or one second hydrophilic part) located at the edge of a display unit together form the display unit.

[0055] In some preferred embodiments of the present invention, the first hydrophilic member is connected to the side surfaces of two adjacent partitions, and the second hydrophilic member is connected to the side surfaces of two adjacent partitions.

[0056] In some embodiments of the present invention, the electrowetting display device further comprises a sealing frame, and the first substrate and the second substrate are connected around the sealing frame.

[0057] Through the above implementation, the edge portion of the electrowetting display device: the first substrate, the partition, the second hydrophilic member, the second substrate and the sealing frame together form the display unit.

[0058] In some preferred embodiments of the present invention, the first substrate and the second substrate are bonded together by a sealant, and the sealant forms a sealant frame.

[0059] A second aspect of the present invention further provides a method for preparing an electrowetting display device, comprising the following steps: assembling a first substrate and a second substrate to obtain the electrowetting display device.

[0060] In some embodiments of the present invention, the preparation method comprises the following steps:

[0061] S1, taking a first substrate;

[0062] S2, taking a second substrate with a pixel wall assembly;

[0063] S3, taking the first substrate obtained in step S1 and the second substrate obtained in step S2, assembling them to obtain the electrowetting display device.

[0064] In some preferred embodiments of the present invention, step S2 includes preparing a second substrate with a pixel wall assembly, wherein the second substrate with the pixel wall assembly is prepared by using a sacrificial layer.

[0065] In some preferred embodiments of the present invention, the second substrate includes a second base plate, a second electrode layer and a hydrophobic insulating layer which are stacked in sequence.

[0066] In some preferred embodiments of the present invention, the pixel wall assembly includes a first hydrophilic member and a second hydrophilic member. In step S2, preparing a second substrate with the pixel wall assembly includes the following operations:

[0067] S2-1, performing hydrophilic modification on the hydrophobic insulating layer of the second substrate;

[0068] S2-2, spin-coating photoresist I on the hydrophilically modified hydrophobic insulating layer to obtain a deposited structure layer, and etching the deposited structure layer to obtain a hydrophilically modified hydrophobic insulating layer with a second hydrophilic component;

[0069] S2-3, preparing a sacrificial layer on the hydrophilic-modified hydrophobic insulating layer obtained in step S2-2, and then spin-coating photoresist II on the sacrificial layer to obtain a hydrophilic-modified hydrophobic insulating layer with a first hydrophilic component;

[0070] S2-4, modifying the hydrophilic-modified hydrophobic insulating layer obtained in step S2-3 by heating to obtain a hydrophobic insulating layer having a first hydrophilic component and a second hydrophilic component.

[0071] In step S2-1, the hydrophobic insulating layer is modified to make the layer more hydrophilic, which is convenient for the subsequent production of pixel wall components (such as the first hydrophilic component and the second hydrophilic component).

[0072] In some more preferred embodiments of the present invention, in step S2-2, the photoresist I includes Surflon material and / or Novec material.

[0073] In some more preferred embodiments of the present invention, in step S2-3, photoresist II is spin-coated on the sacrificial layer, and the sacrificial layer is removed to obtain a hydrophilic-modified hydrophobic insulating layer with a first hydrophilic component.

[0074] In some more preferred embodiments of the present invention, in step S2-4, the heating temperature is higher than the glass transition temperature of the hydrophobic insulating layer.

[0075] In some preferred embodiments of the present invention, in step S2, a second substrate is first prepared, and then a pixel wall assembly is prepared on the second substrate, wherein the method for preparing the second substrate comprises the following operations: taking a second base plate, coating a raw material liquid of a hydrophobic insulating layer, and curing to obtain a second substrate. Preferably, the coating method is spin coating, and the raw material liquid comprises a fluorine-containing coating or a Hyflon material.

[0076] In some preferred embodiments of the present invention, in step S1, a conductive member is prepared on the first substrate to obtain the first substrate connected with the conductive member. Preferably, preparing the conductive member specifically comprises the following steps: spin coating a conductive photoresist on the first substrate, pre-baking, photolithography, post-baking, and developing to obtain the conductive member. Preferably, the first substrate is electrically connected to the conductive member.

[0077] In some more preferred embodiments of the present invention, in step S1, preparing a conductive element on the first substrate specifically includes the following steps:

[0078] S1-1, spin coating: spin coating a conductive photoresist on the first substrate to obtain an intermediate member I;

[0079] S1-2, pre-baking: heating and pre-baking the intermediate part I to obtain the intermediate part II;

[0080] S1-3, photolithography: performing exposure processing on the intermediate piece II in a photolithography machine to obtain the intermediate piece III;

[0081] S1-4, post-baking: heating and post-baking the intermediate part III to obtain the intermediate part IV;

[0082] S1-5, developing: developing the intermediate piece IV in a developing machine to obtain the intermediate piece V;

[0083] S1-6, curing: curing the intermediate component V to obtain a first substrate with a conductive component.

[0084] In some more preferred embodiments of the present invention, in step S1-1, the conductive photoresist is a negative conductive photoresist.

[0085] In some more preferred embodiments of the present invention, in step S1-1, the spin coating thickness is 30-2000 nm.

[0086] In some more preferred embodiments of the present invention, in step S1-1, the spin coating speed is 500-2000 r / min.

[0087] In some more preferred embodiments of the present invention, in step S1-2, the pre-baking temperature is 100-120° C., and the pre-baking time is 2-4 min.

[0088] In some more preferred embodiments of the present invention, in step S1-3, the exposure light intensity is 15.0-22.0 mW / cm 2 , the photolithography time is 15-20s.

[0089] In some more preferred embodiments of the present invention, in step S1-4, the post-baking temperature is 100-120° C., and the post-baking time is 2-4 min.

[0090] In some more preferred embodiments of the present invention, in step S1-5, the development treatment includes immersing the intermediate member IV in 0.4% KOH for 1 min, shaking it for 1 min, rinsing it with 0.4% KOH for 10 s, shaking it for 20 s, and rinsing it with water for 1 min.

[0091] In some embodiments of the present invention, in step S3, the second substrate with the pixel wall assembly obtained in step S2 includes a first sealed cavity precursor and a second sealed cavity precursor, and the first sealed cavity precursor and the second sealed cavity precursor are filled with a polar fluid and a non-polar fluid, respectively, and assembled with the first substrate obtained in step S1 and sealed with a sealant to obtain a first sealed cavity and a second sealed cavity, thereby obtaining the electrowetting display device.

[0092] The third aspect of the present invention proposes the application of the above-mentioned electrowetting display device in the field of electrowetting display, LED or LCD display technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0094] Figure 1 It is a schematic diagram of the structure of a traditional electrowetting display device;

[0095] Figure 2 is a schematic cross-sectional structural diagram of an electrowetting display device according to Embodiment 1 of the present invention;

[0096] Figure 3 Schematic diagram of the cross-sectional structure of a display unit of an electrowetting display device according to Embodiment 1 of the present invention;

[0097] Figure 4 It is a top view schematic diagram of the electrowetting display device in the unpowered state according to Example 1 of the present invention;

[0098] Figure 5 This is a schematic diagram comparing the changes of a single pixel before and after voltage application of the electrowetting display device according to Example 1 of the present invention;

[0099] Figure 6 It is a schematic top view comparing the changes of the electrowetting display device before and after pressurization according to Example 1 of the present invention;

[0100] Figure 7 This is a schematic cross-sectional structural diagram of a first substrate with conductive pillars in an electrowetting display device according to Example 1 of the present invention;

[0101] Figure 8 This is a schematic diagram of the preparation process of a pixel wall assembly in an electrowetting display device according to Example 1 of the present invention;

[0102] Fig. 9 This is a schematic cross-sectional structural diagram of a second substrate with a pixel wall assembly in an electrowetting display device according to Example 1 of the present invention;

[0103] Fig.10 Schematic diagram of the cross-sectional structure of a single display unit in the electrowetting display device of Example 1 of the present invention Figure 1 ;

[0104] Fig.11 Schematic diagram of the cross-sectional structure of a single display unit in the electrowetting display device of Example 1 of the present invention Figure 2 ;

[0105] Fig.12 Schematic diagram of the cross-sectional structure of a single display unit in the electrowetting display device of Example 1 of the present invention Figure 3 ;

[0106] Fig.13 It is a schematic diagram of the cross-sectional structure of the electrowetting display device according to Example 2 of the present invention.

[0107] Figure numerals: 1. first base plate; 2. first electrode layer; 3. sealing rubber frame; 4. polar electrolyte solution; 5. non-polar liquid; 7. hydrophobic insulating layer; 8. second electrode layer; 9. second base plate; 10. first hydrophilic part; 11. conductive rubber layer column; 12. second hydrophilic part; 13. three-phase contact line; 14. partition; 16. sacrificial layer. DETAILED DESCRIPTION

[0108] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0109] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0110] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0111] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0112] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific content of the technical solution.

[0113] The experimental methods in the following examples without specifying specific conditions are generally carried out according to conventional conditions in the art or conditions recommended by the manufacturers; the raw materials and reagents used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets.

[0114] Example 1

[0115] This embodiment discloses an electrowetting display device, and its cross-sectional schematic diagram is shown in FIG. Figure 2 As shown, the electrowetting display device includes a first substrate, a second substrate, and a plurality of display units disposed between the first substrate and the second substrate.

[0116] The first substrate is parallel to the second substrate, and the first substrate includes a first base plate 1 and a first electrode layer 2 which are stacked in sequence, and the first electrode layer 2 is located on the side of the first base plate 1 close to the second substrate. A conductive column 11 is provided in the first sealed cavity, which is a conductive glue layer column, and the conductive column is connected to the first electrode layer 2. The second substrate includes a second base plate 9, a second electrode layer 8 and a hydrophobic insulating layer 7 which are stacked in sequence. The hydrophobic insulating layer 7 is located on the side of the second base plate 9 close to the first substrate.

[0117] The display unit includes a sealed cavity and a pixel wall assembly, the sealed cavity includes a first sealed cavity and a second sealed cavity that are interconnected, a second sealed cavity is formed between the pixel wall assembly and the first substrate and the second substrate, the pixel wall assembly includes a first hydrophilic component 10 (first pixel wall) and a second hydrophilic component 12 (second pixel wall) that are spaced between the first substrate and the second substrate, a set distance (the set distance may be 20-100 μm) is provided between the first hydrophilic component 10 and the second substrate, and the hydrophilicity of the second hydrophilic component 12 is greater than that of the first hydrophilic component 10. A first sealed cavity is formed between the first hydrophilic component 10 and the second hydrophilic component 12. Specifically, the display unit includes two groups of pixel wall components that are symmetrically arranged, and a cross-sectional schematic diagram thereof is shown in FIG. Figure 3As shown. In each display unit, between the first substrate and the second substrate, along the direction from one end to the other end of the first substrate, the second hydrophilic member 12, the conductive column, the first hydrophilic member 10, the first hydrophilic member 10, the conductive column, the second hydrophilic member 12 are sequentially arranged (the hydrophilic members and the conductive columns are arranged transversely in the aforementioned order), and the sealed cavity of the display unit includes the first sealed cavity I, the second sealed cavity and the first sealed cavity II which are connected in sequence. Specifically, as Figure 3 As shown, in a display unit, from left to right, a first sealed cavity I is formed between the first second hydrophilic component, the first first hydrophilic component and the first substrate, and the second substrate; a second sealed cavity is formed between the first first hydrophilic component, the second first hydrophilic component and the first substrate, and the second substrate; a first sealed cavity II is formed between the second first hydrophilic component, the second second hydrophilic component and the first substrate, and the second substrate.

[0118] The first sealed cavity is filled with a polar fluid, and the second sealed cavity is filled with a non-polar fluid. The polar fluid is a polar electrolyte solution 4 with color. The polar electrolyte solution 4 in each display unit independently has different or the same colors, including but not limited to yellow, red, blue, magenta (or fuchsia), cyan or black, etc. The polar electrolyte solution 4 includes a water-soluble dye and a polar solvent (such as water or an alcohol solvent, wherein the alcohol solvent is such as ethylene glycol, etc.). The non-polar fluid is a transparent non-polar liquid 5, which is decane (C6-C14 alkanes). Among them, the soluble dye can be a dye that is soluble in water but insoluble in the non-polar fluid, such as yellow, magenta, blue or black, etc. The water-soluble dye specifically used in this embodiment can be obtained from commercial channels such as conventional markets, and can be selected from but not limited to: acid yellow, Aladdin, A330858; acid magenta, Aladdin, A104916; acid black 24, Aladdin, A355221. In the polar electrolyte solution 4, the mass percentage of the water-soluble dye may be 5-10%.

[0119] The electrowetting display device further includes a plurality of partitions 14 spaced apart between the first substrate and the second substrate, the first substrate and the second substrate facing each other are respectively connected to the partitions 14, and the partitions are vertically arranged with the pixel wall assembly. Specifically, the partitions 14 are vertically connected with the second hydrophilic member 12, the partitions 14 are connected with the first electrode layer 2 of the first substrate, and the partitions 14 are connected with the hydrophobic insulating layer 7 of the second substrate.

[0120] Specifically, in the middle part of the electrowetting display device: the first substrate, two adjacent partitions 14, the second substrate and two second hydrophilic parts 12 located at the edge of a display unit together form the display unit; the edge part of the electrowetting display device: the first substrate, two adjacent partitions 14 (or one partition 14), the second substrate and one (or two) second hydrophilic parts 12 located at the edge of a display unit together form the display unit, or / and, the first substrate, one partition 14, the second substrate and two second hydrophilic parts 12 (or one second hydrophilic part 12) located at the edge of a display unit together form the display unit.

[0121] The first hydrophilic member 10 is not connected to the first electrode layer 2 and the hydrophobic insulating layer 7, and is connected to the sides of the two adjacent partitions 14. The first hydrophilic member 10 is a first pixel wall (a hydrophilic material). When no voltage is applied between the first substrate and the second substrate, the top and bottom of the first hydrophilic member 10 are in contact with the polar electrolyte solution 4. The bottom of the second hydrophilic member 12 is connected to the hydrophobic insulating layer 7, and the top is in contact with the polar electrolyte solution 4. The second hydrophilic member 12 is connected to the sides of the two adjacent partitions 14, and the second hydrophilic member 12 is a second pixel wall (a strongly hydrophilic material).

[0122] The electrowetting display device further comprises a sealing frame 3, the first substrate and the second substrate are connected around by the sealing frame 3, the first substrate and the second substrate are bonded by a sealant, and the sealant forms the sealing frame 3. The edge portion of the electrowetting display device: the first substrate, the partition 14, the second hydrophilic member 12, the second substrate and the sealing frame together form the display unit.

[0123] When no voltage is applied between the first substrate and the second substrate, the arrangement directions of the polar fluid and the non-polar fluid form an angle θ with the arrangement directions of the first substrate and the second substrate, θ=90°, and a three-phase contact line 13 is formed between the polar fluid, the non-polar fluid and the hydrophobic insulating layer 7.

[0124] The driving and display principles of the electrowetting display device are as follows Figure 4-6 As shown:

[0125] Figure 4It is a top view of the electrowetting display device in the unpowered state, and each small grid represents a pixel grid (i.e., a display unit). In each pixel grid, the left and right sides will be filled with a colored polar electrolyte solution 4, and the middle will be filled with a transparent non-polar liquid 5. The pixel wall contains two materials: a strong hydrophilic material and a hydrophilic material, which are the second hydrophilic part 12 and the first hydrophilic part 10 respectively. The pixel grid is generally made of hydrophilic material, the second hydrophilic part 12 is made of a strong hydrophilic material, and the first hydrophilic part 10 is made of a hydrophilic material. Among them, the second hydrophilic part 12 mainly uses a strong hydrophilic negative photoresist HN-018N. This type of material can increase a certain hydrophilic property due to the fluorine-loving group and hydrophilic group contained therein, so that its contact angle is between 50 degrees and 65 degrees, while the hydrophilic photoresist HN-0081N negative photoresist is used in the first hydrophilic part 10, and the contact angle is between 70 degrees and 108 degrees. Among them, HN-018N and HN-0081N photoresists were purchased from Weifang Xingtai Microelectronic Materials Co., Ltd.

[0126] The transparent non-polar liquid 5 is more inclined to stay in the cavity surrounded by the first hydrophilic component 10 (the second sealed cavity) due to the oleophilic and hydrophobic properties of the surface of the hydrophobic insulating layer 7. The colored polar electrolyte liquid 4 is more inclined to stay in the two side walls (the first sealed cavity) due to the strong hydrophilicity of the second hydrophilic component 12 and the capillary force formed by the second hydrophilic component 12 and the first hydrophilic component 10. When the first electrode layer 2 and the second electrode layer 8 on the electrowetting display device are pressurized, the colored polar electrolyte solution 4 wets the surface of the hydrophobic insulating layer 7 under the action of the electric field and replaces the non-polar liquid 5 in the surface area of ​​the hydrophobic insulating layer 7 to display the open state, as shown in FIG. Figure 5 , 6 Medium color polar electrolyte solution 4'. Among them, Figure 5 Middle: The left picture is a state diagram of a single pixel grid when the first electrode layer 2 and the second electrode layer 8 are not pressurized, and the right picture is a state diagram of a single pixel grid when the first electrode layer 2 and the second electrode layer 8 are pressurized. Figure 6 Middle: The left figure is a schematic top view of the electrowetting display device when the first electrode layer 2 and the second electrode layer 8 are not pressurized, and the right figure is a schematic top view of the electrowetting display device when the first electrode layer 2 and the second electrode layer 8 are pressurized.

[0127] Regarding the conductive glue layer column 11, whether a forward voltage or a reverse bias is applied, the contact angle of the droplet on the surface of the hydrophobic insulating layer 7 will continue to decrease with the continuous increase of the voltage, and the contact angle will be reduced from the initial hydrophobic state to the hydrophilic state. Before the voltage is applied, the droplet is usually in a state of equilibrium of the static contact angle. After the voltage is applied, under the action of the electrowetting force, the spreading of the entire droplet is dominated by the advancing angle until the advancing angle at the mechanical equilibrium near the three-phase contact line 13 in the powered state is reached. When the voltage is removed, the entire contraction process of the droplet under the action of the surface tension is dominated by the receding angle until the receding angle in the unpowered state is reached. The conductive glue layer column 11 can expand the contact area with the polar electrolyte solution 4 to a certain extent, speed up the reaction speed, and reduce the hysteresis effect of the electrowetting effect. In addition, the establishment of the conductive glue layer column 11 can increase the range of the contact angle regulated by electrowetting, and ensure the reversibility of electrowetting to a certain extent.

[0128] In the present invention, a water-soluble dye is added to the polar electrolyte solution 4, and decane is selected from the non-polar liquid 5, so as to avoid the re-wetting phenomenon caused by the polar molecules in the non-polar liquid and the insulating hydrophobic layer under the pressurized state, improve the performance of the electrowetting display device, and enable the display to maintain the stable state of the image grayscale during the driving process. The polar electrolyte solution 4 and the non-polar liquid 5 are arranged left and right, and a three-phase contact line 13 is formed on the surface of the polar electrolyte solution 4, the non-polar liquid 5 and the hydrophobic insulating layer 7. Only a very low potential energy is required on this contact line to make the polar electrolyte solution 4 wet the surface of the hydrophobic insulating layer 7, thereby reducing the opening voltage of the device. Therefore, the performance of the electrowetting display device in the present invention is improved, so that the display can maintain the stable state of the image grayscale during the driving process, so that the opening voltage of the electrowetting display device is reduced while maintaining its grayscale controllability when it is in the working state.

[0129] Regarding the preparation process of the electrowetting display device in this embodiment,

[0130] The preparation of the colored polar electrolyte solution 4 and the transparent non-polar liquid 5 is mainly carried out in the early stage of manufacturing the device. Different from the general electrowetting device materials, in this embodiment, a colored solute is added to the polar electrolyte solution 4 so that the polar electrolyte solution 4 has a specific color, and no colored substance is added to the non-polar liquid 5 to keep it transparent. The implementation of this step makes the display mode of the electrowetting display device in this embodiment opposite to that of the traditional electrowetting display device at the time of opening and closing. In this embodiment, when the screen is white, the display device is in the closed state, and when the screen is in color, the display device is in the open state.

[0131] Specifically, the preparation process of the electrowetting display device in this embodiment includes the following steps:

[0132] 1. The steps for preparing the first substrate are the same as those of the conventional electrowetting display device: a conductive layer (used as the first electrode layer 2) is provided on the glass substrate. On this basis, the conductive glue layer column 11 is prepared by spin coating conductive photoresist and photolithography process. The preparation of the first substrate containing the conductive glue layer column specifically includes the following operations:

[0133] (1) Cleaning: Cleaning the ITO glass substrate to remove organic and inorganic impurities to obtain a first substrate;

[0134] (2) Spin coating: Spin coating the first substrate with a conductive photoresist, using a negative conductive photoresist with a thickness of generally about 500 nm and a corresponding spin coating speed of 1000 r / min;

[0135] (3) Pre-baking: After spin coating, pre-bake on a hot plate for a certain period of time. Set the hot plate temperature to 110°C and the time to 2 min 30 s.

[0136] (4) Photolithography: The first substrate obtained in step (3) is placed in a photolithography machine for exposure processing, and the light intensity is set to 16 mW / cm 2 , the photolithography time is 16s;

[0137] (5) Post-baking: Post-baking is used to eliminate certain standing wave effects. The hot plate temperature is set to 110°C and left for 2 min 30 s.

[0138] (6) Development: The first substrate obtained in step (5) is placed in a developer for development treatment, and developed using a 0.4% KOH solution. The substrate is immersed in 0.4% KOH for 1 minute and then shaken for 1 minute. The substrate is then rinsed with 0.4% KOH for 10 seconds, shaken for 20 seconds, and then rinsed with pure water for 1 minute. The preparation of the conductive column 11 structure is completed.

[0139] (7) Curing: Finally, it is cured to enhance the mechanical strength and complete the preparation of the upper substrate.

[0140] The schematic diagram of the structure of the first substrate with conductive pillars finally obtained is as follows: Figure 7 shown.

[0141] 2. The steps of preparing the second substrate with the pixel wall assembly specifically include the following operations:

[0142] (1) Cleaning: Cleaning the ITO glass substrate to remove organic and inorganic impurities to obtain a second base plate containing a second electrode layer;

[0143] (2) Spin coating: Spin coating the raw material liquid of the hydrophobic insulating layer 7. The material of the raw material liquid is preferably AF or Hyflon material. The thickness is generally about 600 nm. The spin coating speed is generally 1400 r / min for AF material and 1000 r / min for Hyflon material. The spin coating time is about 65 s. After the spin coating is completed, it is placed on a hot plate for pre-curing treatment (110° C., 2 min 30 s);

[0144] (3) Modification: The second substrate obtained in step (2) is placed in a reactive ion etcher for modification, with the equipment power set to 6 W and the time set to 5 s. This step is used to improve the wettability of its surface, which is beneficial to the subsequent uniform film formation of the photoresist.

[0145] (4) Preparation of pixel wall and partition: The pixel wall is prepared on the modified hydrophobic insulating layer 7, and the second hydrophilic member 12, the first hydrophilic member 10 and the partition 14 are mainly prepared by using a sacrificial layer or the like. The cross-sectional schematic diagram of the pixel wall preparation process is shown in FIG. Figure 8 As shown (the partition 14 is not shown), specifically comprising:

[0146] a) spin coating a strongly hydrophilic photoresist HN-018N on the modified second substrate as a deposition structure layer based on the second hydrophilic member (strongly hydrophilic material) 12;

[0147] b) etching the deposited structure layer so that only the second hydrophilic member (strongly hydrophilic material) 12 and the partition 14 remain on the second substrate;

[0148] c) depositing a sacrificial layer 16 near the second hydrophilic member 12;

[0149] d) depositing a first hydrophilic member (hydrophilic material) 10 on the sacrificial layer 16;

[0150] e) releasing the excess sacrificial layer;

[0151] (5) High temperature treatment: The second substrate on which the pixel wall is prepared is subjected to high temperature treatment, and the temperature needs to exceed the Tg temperature of the hydrophobic insulating layer 7 to restore its initial hydrophobic properties.

[0152] The cross-sectional schematic diagram of the finally obtained second substrate with the pixel wall assembly is as follows: Figure 8 shown.

[0153] 3. Fill the colored polar electrolyte solution 4 and the transparent non-polar liquid 5 into the cavities formed by the pixel wall respectively by inkjet printing: the first sealed cavity and the second sealed cavity, and align and press the first substrate with the sealant 3 and the first electrode layer 2 with the second substrate to complete the preparation process of the electrowetting device. The final finished product schematic diagram is shown in FIG. Fig. 9 shown.

[0154] Fig.10 This is a cross-sectional view of the area where a single pixel grid is located, from which the pixel wall and the distribution structure of the mixed solution filled in the pixel wall can be clearly seen. The transparent non-polar liquid 5 is mainly gathered in the cavity formed by the first hydrophilic member (hydrophilic material) 10 (the second sealed cavity), and the colored polar electrolyte solution 4 is mainly gathered in the wall formed by the second hydrophilic member (strongly hydrophilic material) 12 and the first hydrophilic member (hydrophilic material) 10 (the first sealed cavity).

[0155] Example 2

[0156] This embodiment discloses an electrowetting display device, which is different from the embodiment 1 in that the cross-sectional schematic diagram of the electrowetting display device is as shown in FIG. Fig.13 As shown: the top of the second hydrophilic component 12 is connected to the first electrode layer 2 ; the top of the first hydrophilic component 10 is connected to the first electrode layer 2 .

[0157] Example 3

[0158] This embodiment discloses an electrowetting display device, which differs from Embodiment 1 in that: in this embodiment, there is a set distance between the top of the second hydrophilic component 12 and the first electrode layer 2 (the set distance may be 20-100 μm); the top of the first hydrophilic component 10 is connected to the first electrode layer 2.

[0159] Example 4

[0160] This embodiment discloses an electrowetting display device, which differs from Embodiment 1 in that: in this embodiment, the top of the second hydrophilic component 12 is connected to the first electrode layer 2; there is a set distance between the top of the first hydrophilic component 10 and the first electrode layer 2 (the set distance may be 20-100 μm).

[0161] In summary, in the present invention, in order to improve the performance of the electrowetting display device, the display can maintain a stable state of image grayscale during the driving process. First, the two-phase fluid is improved for the polarization effect, a water-soluble dye is added to the polar electrolyte solution 4, and the non-polar liquid maintains a simple alkane solvent, preferably decane, to avoid the rewetting phenomenon caused by the polar molecules in the non-polar liquid and the insulating hydrophobic layer under the pressurized state. Secondly, in order to reduce the opening voltage, the polar electrolyte solution and the non-polar liquid are arranged left and right, and a three-phase contact line is formed on the surface of the polar electrolyte solution, the non-polar liquid and the hydrophobic insulating layer. Only a very low potential energy is needed on this contact line to make the polar electrolyte solution wet the surface of the hydrophobic insulating layer. That is, in general, while the opening voltage of the electrowetting display device in the present invention is reduced, its grayscale controllability is maintained when it is in the working state.

[0162] In addition, when the electrowetting display device of the present invention is applied to text display, the display device changes from white before pressure to black after pressure, which is more in line with the daily use habits of traditional paper. For example, when displaying text content, more than 80% of the pixels of the electrowetting device of the present invention are in a closed state, which has certain energy saving properties. Traditional electrowetting displays need to pressurize the pixels of non-text and graphic parts to turn white, and turn off the voltage of the corresponding pixels to display the corresponding pattern. In comparison, traditional electrowetting display devices have a large energy consumption.

[0163] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. An electrowetting display device, characterized in that: The invention comprises a first substrate, a second substrate and a plurality of display units arranged between the first substrate and the second substrate, wherein the display unit comprises a sealed cavity filled with a polar fluid and a non-polar fluid, and when no voltage is applied between the first substrate and the second substrate, the arrangement direction of the polar fluid and the non-polar fluid forms an angle θ with the arrangement direction of the first substrate and the second substrate, and θ>0°; The display unit also includes a pixel wall assembly, and the sealed cavity includes a first sealed cavity and a second sealed cavity that are interconnected. The first sealed cavity is formed between components of the pixel wall assembly, and the second sealed cavity is formed between the pixel wall assembly and the first substrate and the second substrate. The first sealed cavity is filled with a polar fluid, and the second sealed cavity is filled with a non-polar fluid.

2. The electrowetting display device according to claim 1, characterized in that: The polar fluid has a color.

3. The electrowetting display device according to claim 1, characterized in that: The polar fluid includes a dye and a polar solvent.

4. The electrowetting display device according to claim 1, characterized in that: The non-polar fluid is a transparent fluid.

5. The electrowetting display device according to claim 1, characterized in that: The non-polar fluid includes alkane substances.

6. The electrowetting display device according to claim 1, characterized in that: The non-polar fluid includes at least one of C6-C14 alkanes.

7. The electrowetting display device according to claim 1, characterized in that: The pixel wall assembly includes a first hydrophilic member and a second hydrophilic member spaced between the first substrate and the second substrate, a set distance is provided between the first hydrophilic member and the second substrate, and the hydrophilicity of the second hydrophilic member is greater than that of the first hydrophilic member.

8. The electrowetting display device according to claim 7, characterized in that: The second hydrophilic component is connected to the second substrate.

9. The electrowetting display device according to claim 1, characterized in that: A conductive member is disposed in the first sealed cavity, and the conductive member is electrically connected to the first substrate.

10. The electrowetting display device according to claim 1, characterized in that: The display unit includes two groups of pixel wall components which are symmetrically arranged.

11. The electrowetting display device according to claim 1, characterized in that: The electrowetting display device further comprises a sealing frame, and the first substrate and the second substrate are connected around each other via the sealing frame.

12. A method for preparing the electrowetting display device according to claim 1, characterized in that: The method comprises the following steps: assembling a first substrate and a second substrate to obtain the electrowetting display device.

13. Application of the electrowetting display device according to any one of claims 1 to 11 or the electrowetting display device prepared by the method according to claim 12 in the field of electrowetting display, LED or LCD display technology.

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