Flexible electrowetting display device with double-layer structure and preparation method thereof

Abstract

The invention discloses a double-layer structure flexible electrowetting display device and a preparation method and application thereof.The display device comprises an upper conductive substrate and a lower conductive substrate which are oppositely arranged, the lower conductive substrate is sequentially provided with a hydrophobic insulating layer and a plurality of pixel walls distributed at intervals in the direction facing the upper conductive substrate, and the hydrophobic insulating layer is arranged on the lower conductive substrate. A pixel grid is enclosed by the adjacent pixel walls, each pixel wall comprises a first pixel wall layer and a second pixel wall layer which are stacked, the first pixel wall layer is connected with the hydrophobic insulating layer, the sections of the first pixel wall layer and the second pixel wall layer in the height direction are trapezoidal, and at least the first pixel wall layer is in an inverted trapezoidal shape. By means of the double-layer pixel wall layer structure, the high-pixel wall is achieved, the phenomenon that printing ink of a single high-wall structure grabs and turns over is effectively avoided, meanwhile, the filling amount of the printing ink and the problem that the printing ink in adjacent pixel grids is gathered together are controlled, and the reliability of the printing ink of the electrowetting optical device is improved.

Description

Technical Field

[0001] The present invention relates to the technical field related to electrowetting display, and in particular to a double-layer structure flexible electrowetting display device and a preparation method thereof. Background Art

[0002] Electrowetting display refers to a technology that changes the voltage applied between the liquid-solid electrodes, changes the surface tension between the liquid and the solid, and thus changes the contact angle of the liquid on the solid surface to achieve a change in liquid distribution, ultimately achieving the function of optical switching of transmitted light or reflected light and completing the display. Its basic principle can be summarized as follows: through the precise control of the applied voltage, the contact angle of the liquid in the display unit is changed, thereby guiding the change in liquid distribution, and ultimately achieving the function of effectively switching the transmitted light or reflected light. Electrowetting display technology has shown great application potential in the display field due to its advantages such as low energy consumption, fast response speed, and rich color expression.

[0003] However, the electrowetting devices currently prepared face a major challenge in practical applications - the "ink flipping over the wall" phenomenon is prone to occur. This problem is particularly prominent in flexible electrowetting devices, because flexible electrowetting devices are made of flexible substrates and have good bendability. However, due to improper design of the pixel structure height, the too low pixel structure can easily cause the middle part to collapse during the bending process of the device, thereby squeezing the ink and causing the ink flipping over the wall problem.

[0004] Therefore, it is of great significance to develop a new flexible electrowetting display device that can solve the problem of ink wall overflow and ink aggregation in adjacent pixel grids and improve the reliability of ink movement in electrowetting optical devices. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a double-layer structure flexible electrowetting display device, which can effectively solve the problem of ink wall overflow and ink aggregation in adjacent pixel grids.

[0006] The present invention also provides a method for preparing the electrowetting display device.

[0007] According to one aspect of the present invention, a double-layer structure flexible electrowetting display device is proposed, comprising an upper conductive substrate and a lower conductive substrate arranged opposite to each other, wherein the lower conductive substrate is sequentially provided with a hydrophobic insulating layer and a plurality of spaced pixel walls along a direction toward the upper conductive substrate, adjacent pixel walls form a pixel grid, the pixel wall comprises a first pixel wall layer and a second pixel wall layer stacked, the first pixel wall layer is connected to the hydrophobic insulating layer, and the cross-sections of the first pixel wall layer and the second pixel wall layer in the height direction are both trapezoidal, and at least the first pixel wall layer is an inverted trapezoidal.

[0008] According to a preferred embodiment of the present invention, at least the following beneficial effects are achieved: the scheme of the present invention achieves effective suppression of the ink wall-over phenomenon by adopting a double-layer pixel wall structure. This design successfully solves the problem of easy wall-over of ink under a single high wall structure and effectively solves the problem of ink aggregation in adjacent pixel grids, significantly improving the reliability of ink use in electrowetting optical devices. Specifically, the present invention designs the first pixel wall layer as an inverted trapezoidal structure, which can better suppress the occurrence of ink wall-over phenomenon and further enhance the stability of ink in high-pixel walls. In addition, by setting the pixel wall layer as a stepped structure, not only the effective control of the ink filling amount required for the high-pixel wall is achieved, but also the capillary force of the low-pixel wall of the stepped structure is utilized to effectively suppress the accumulation, wall climbing and shear flow of ink at the angle of the pixel wall, thereby further improving the reliability of ink movement in electrowetting optical devices. In summary, the double-layer pixel wall structure of the present invention and its special design not only effectively solve the problem of ink wall-over and aggregation, but also significantly improve the performance of electrowetting optical devices, while also enhancing the bending performance and stability of flexible devices.

[0009] In some embodiments of the present invention, the first pixel wall layer and the second pixel wall layer are both in an inverted trapezoidal shape. The first and second pixel wall layers are both in an inverted trapezoidal shape to further prevent the problem of ink overflowing the wall.

[0010] In some embodiments of the present invention, the bottom angle of the first pixel wall layer is between 90° and 100°, and the bottom angle of the second pixel wall layer is between 95° and 100°.

[0011] In some embodiments of the present invention, the bottom angle of the second pixel wall layer is not less than the bottom angle of the first pixel wall layer. When the bottom angle of the second pixel wall layer is larger, the problem of ink overflowing the wall can be better prevented.

[0012] In some embodiments of the present invention, the bottom angle of the inverted trapezoid is not less than 95°. When the bottom angle of the trapezoid is above 95°, the amount of non-polar liquid required for the high pixel wall can be better controlled, and the wall climbing phenomenon of the ink can be suppressed.

[0013] In some embodiments of the present invention, the base angle of the inverted trapezoid is between 95° and 135°.

[0014] In some embodiments of the present invention, the overall height of the pixel wall is 6 to 30 times the height of the first pixel wall layer.

[0015] In some embodiments of the present invention, the overall height of the pixel wall is 1.2 to 1.7 times the height of the second pixel wall layer.

[0016] In some embodiments of the present invention, the overall height of the pixel wall is 20 to 30 μm. Setting a high pixel wall can better suppress the wall-over and wall-climbing shear flow phenomenon of the ink, control the ink filling amount, improve the reliability of ink movement in the electrowetting optical device, and improve the bending performance and stability of the flexible device.

[0017] In some embodiments of the present invention, the height of the first pixel wall layer is 3-5 μm.

[0018] In some embodiments of the present invention, the height of the second pixel wall layer is 17-25 μm.

[0019] In some embodiments of the present invention, a sealed cavity is formed between the upper conductive substrate and the lower conductive substrate, and the sealed cavity is filled with mutually immiscible polar liquid and non-polar liquid.

[0020] In some embodiments of the present invention, the overall height of the pixel wall is 6 to 30 times the thickness of the non-polar liquid when it is spread.

[0021] In some embodiments of the present invention, the thickness of the non-polar liquid is 3-5 μm.

[0022] In some embodiments of the present invention, the thickness of the non-polar liquid is not greater than the height of the first pixel wall layer.

[0023] In some embodiments of the present invention, the non-polar liquid is ink. Using ink as the non-polar liquid has good color saturation and light stability.

[0024] In some embodiments of the present invention, the polar liquid includes at least one of water, ethylene glycol, polyethylene glycol, propylene glycol, glycerol or other mixed solutions. The polar liquid can be water, propylene glycol, ethylene glycol, polyethylene glycol or other conductive fluids.

[0025] In some embodiments of the present invention, the non-polar liquid is injected into the pixel grid by inkjet printing. During the filling process, the filling amount of the non-polar liquid can be better controlled, and at the same time, the non-polar liquid can be prevented from contacting the side of the pixel wall, which can better suppress the shear flow phenomenon. Furthermore, the injection filling is more conducive to the point-to-point alignment of the first layer of the pixel wall structure and the second layer of the pixel grid structure in the dual-pixel structure of the present invention, thereby improving the bending performance and stability of the flexible device.

[0026] In some embodiments of the present invention, the pixel wall is prepared by photolithography.

[0027] In some embodiments of the present invention, both the upper conductive substrate and the lower conductive substrate are flexible light-transmitting conductive substrates.

[0028] In some embodiments of the present invention, the lower conductive substrate includes a lower substrate layer and a conductive layer I stacked from outside to inside.

[0029] In some embodiments of the present invention, the upper conductive substrate includes an upper substrate layer and a conductive layer II stacked from outside to inside.

[0030] In some embodiments of the present invention, the materials of the first and second pixel wall layers are independently selected from hydrophilic polymer materials.

[0031] In some embodiments of the present invention, the material of the first pixel wall layer is selected from at least one of SU-8 photoresist, HN-008 photoresist or HN-018 photoresist.

[0032] In some embodiments of the present invention, the material of the second pixel wall layer is selected from at least one of SUN-130P photoresist, SUN-120P photoresist or SUN-350P photoresist.

[0033] The hydrophilicity of the HN series is stronger than that of the Su-8 series and the SUN series.

[0034] In some embodiments of the present invention, the contact angle of the hydrophobic insulating layer is 110° to 130°.

[0035] According to another aspect of the present invention, a method for preparing the above-mentioned double-layer structure flexible electrowetting display device is provided, comprising the following steps:

[0036] S1, removing the conductive substrate, filling the pixel grid with a non-polar liquid, and filling the pixel grid with a polar liquid above the non-polar liquid;

[0037] S2. Take the upper conductive substrate, set a sealing frame on the upper conductive substrate, set an opening on the sealing frame, cover the lower conductive substrate on top of the upper conductive substrate, apply pressure to the lower conductive substrate so that excess non-polar liquid flows out from the opening, and seal the opening.

[0038] The preparation method according to a preferred embodiment of the present invention has at least the following beneficial effects: the preparation method of the present invention is easy to operate and has good application prospects.

[0039] In some embodiments of the present invention, the non-polar liquid is injected into the pixel grid by inkjet printing.

[0040] In the description of the present invention, if I and II are described, they are only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the sequence of the indicated technical features.

[0041] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0043] Figure 1 It is a schematic structural diagram of the electrowetting display device according to Example 1 of the present invention.

[0044] Figure 2 This is a schematic diagram of ink spreading of the electrowetting display device of Example 1 of the present invention when no voltage is applied.

[0045] Figure 3 It is a schematic diagram of ink shrinkage when voltage is applied to the electrowetting display device of Example 1 of the present invention.

[0046] Figure 4 It is a schematic diagram of the structure of the electrowetting display device according to Example 2 of the present invention.

[0047] Figure 5 This is a schematic diagram of ink spreading of the electrowetting display device of Example 2 of the present invention when no voltage is applied.

[0048] Figure 6 It is a schematic diagram of ink shrinkage when voltage is applied to the electrowetting display device of Example 2 of the present invention.

[0049] Figure numerals: 1, lower substrate layer; 2, conductive layer I; 3, hydrophobic insulating layer; 4, conductive layer II; 5, upper substrate layer; 6, non-polar liquid; 7, polar liquid; 8, first pixel wall layer; 9, second pixel wall layer; 10, sealing frame; 20, lower conductive substrate; 30, upper conductive substrate. DETAILED DESCRIPTION

[0050] 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, rather than all of them. Based on the embodiments of the present invention, other embodiments obtained by technicians in this field without creative work are all within the scope of protection of the present invention. The test methods used in the embodiments are conventional methods unless otherwise specified; the materials, reagents, etc. used, unless otherwise specified, can be reagents and materials obtained from commercial channels. Unless otherwise specified, the same parameter in each embodiment has the same value. The embodiments described below are exemplary and are only used to explain the present invention, and cannot be understood as limitations on the present invention.

[0051] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0052] In some embodiments of the present invention, the polar liquid may be ethylene glycol, propylene glycol, or both.

[0053] Example 1

[0054] In this example, a double-layer flexible electrowetting display device was prepared. Figure 1 As shown, the specific structure includes an upper conductive substrate 30 and a lower conductive substrate 20, wherein the lower conductive substrate 20 is sequentially provided with a lower substrate layer 1, a conductive layer I2, a hydrophobic insulating layer 3 and a plurality of pixel walls from the outside to the inside, the pixel walls are spaced and distributed on the hydrophobic insulating layer 3, and a pixel grid is formed between adjacent pixel walls, and each pixel wall is composed of a first pixel wall layer 8 and a second pixel wall layer 9, the cross section of the first pixel wall layer 8 along the height direction is an inverted trapezoid, and the cross section of the second pixel wall layer 9 along the height direction is a regular trapezoid, wherein the bottom angle of the inverted trapezoid is 95°, and the bottom angle of the regular trapezoid is 85°. The upper conductive substrate 30 is sequentially provided with an upper substrate layer 5 and a conductive layer II 4 from the outside to the inside, and a sealed cavity is formed between the upper conductive substrate 30 and the lower conductive substrate 20 through a sealing frame 10, and the sealed cavity is filled with mutually immiscible polar liquid 7 and non-polar liquid 6.

[0055] The preparation process is:

[0056] 1. Prepare the conductive substrate

[0057] 1.1 Take the upper and lower conductive substrates for use. Both the upper and lower conductive substrates are flexible light-transmitting conductive glass, specifically ultra-thin glass UTG (commercially available).

[0058] 2. Apply hydrophobic insulating layer 3

[0059] 2.1 Coat 2 mL of Hyflon on the surface of the lower conductive substrate 20 (including the lower substrate layer 1 and the conductive layer I 2) and spin coat for 65 seconds at a rotation speed of 325 rpm to form a film; then heat at about 55°C (45°C-60°C) for 5 minutes, stop heating immediately, and cool naturally to room temperature to form a Hyflon hydrophobic insulating layer.

[0060] 2.2 Place the lower conductive substrate 20 obtained in step 2.1 into an ion etching machine with a power of 5W, and change the hydrophobicity of the hydrophobic insulating layer 3 to hydrophilicity (the contact angle with pure water is about 90°, 80°-100° is acceptable).

[0061] 3. Prepare pixel wall

[0062] 3.1 Spin coat 2mL of HN-008n, 50cp, at a speed of 1100rpm for 65s on the surface of the treated hydrophobic insulating layer 3, and heat it on a heating plate at about 105℃ (110℃-120℃ is acceptable) for 3min, then stop heating immediately and cool naturally;

[0063] 3.2 Place the film in the photolithography machine and use the mask with the selected pattern to perform point-to-point alignment with the first pixel wall structure and expose it to UV light for 18 seconds; place it on a heating plate and heat it at 110°C for 3 minutes, stop heating immediately, and cool it naturally;

[0064] 3.3 Prepare two boxes with 0.4wt% KOH solution, place them in the developer for 60s, and then gently shake them for 60s. Gently shake them for 50s in a third box with clean water, rinse the lower conductive substrate with flowing water for 50s, and then blow the lower conductive substrate 20 clean with nitrogen to obtain the lower conductive substrate 20 with the first pixel wall layer 8 structure, with a pixel wall height of about 4 microns (3-5 microns is acceptable);

[0065] 3.4 Spin-coat 2 mL of SUN-1170P, 3600 cp, 1800 rpm, for 90 s on the surface of the first pixel wall layer 8 structure, place on a heating plate at about 100 ° C (90 ° C -110 ° C) and heat for 6 min, stop heating immediately, and cool naturally;

[0066] 3.5 Place it in the photolithography machine and use the mask of the selected pattern to align it and expose it to UV light for 62 seconds; place it on the heating plate and heat it at 100℃ for 6 minutes, stop heating immediately, and cool it naturally;

[0067] 3.6 Prepare two boxes with 2.38wt% TMAH developer, gently shake for 60s in the developer and for 30s in a third box with clean water, rinse the lower conductive substrate 20 with flowing aqueous solution for 50s, and then blow the lower conductive substrate 20 clean with nitrogen to obtain a lower conductive substrate 20 with a second pixel wall layer 9 structure, with a pixel wall height of about 23 microns (20 microns-25 microns are acceptable);

[0068] 3.7 Place the lower conductive substrate 20 with the pixel wall structure obtained in step 3.6 into an ion etcher to decompose the photoresist remaining at the bottom of the pixel grid;

[0069] 3.8 Place the lower conductive substrate 20 obtained in step 3.7 into a heating furnace and heat it under reflux at about 200° C. (170° C. to 220° C. is acceptable) for 1.5 hours, and then cool it naturally.

[0070] 4. Fill

[0071] 4.1 Inkjet printing is performed on the lower conductive substrate 20 with the pixel wall structure obtained in step 3. The pixel cells of the lower conductive substrate 20 are filled with ink using an inkjet printer. The thickness of the oil film is lower than that of the first pixel wall layer 8, and the thickness is about 4 microns (3 to 5 microns).

[0072] 5. Packaging

[0073] 5.1 Place the polar liquid 7 and the lower conductive substrate 20 filled with ink (the ingredients are tetradecane and magenta dye, wherein the mass proportion of magenta dye is 5wt%) on a condenser at a temperature of -5°C to -30°C, cool for 2 to 3 minutes, and spread the polar liquid 7 on the pixel grid filled with ink.

[0074] 5.2 Use a UV cleaning machine to treat the upper conductive substrate 30 (including the upper substrate layer and the conductive layer II 4) for 5 minutes, and adhere the pressure-sensitive adhesive to the conductive layer II 4;

[0075] 5.3 Align the packaging glue frame with the pixel grid filled by inkjet printing on the lower conductive substrate 20, and bond the upper and lower conductive substrates together with pressure to obtain a double-layer structure flexible electrowetting display device, such as Figure 2 As shown (since the top of the pixel wall is directly attached to the upper conductive substrate 30 when the upper and lower conductive substrates are attached, the preparation step of the support column is not included).

[0076] The driving mode of the above-mentioned electrowetting display structure during application is as follows: when the upper conductive substrate and the lower conductive substrate are powered on, the electric field formed forces the positively charged polar liquid 7 to produce polarization and move toward the negative charge accumulation at the bottom. The polar fluid 7 pushes the non-polar liquid 6 aside, and the pixel shows the color of the bottom.

[0077] like Figure 3As shown, when the conductive layer I2 is connected to the negative power supply and the conductive layer II4 is connected to the positive power supply, and the applied voltage is greater than the threshold voltage (30V) of the non-polar fluid 6, the non-polar fluid 6 begins to deform, changing from the initial wet state to the contracted state, and the thickness of the ink after contraction will not exceed the second pixel wall layer; when the applied voltage is less than the threshold voltage (30V) of the non-polar fluid 6, the non-polar fluid 6 is still in the wet state, locked in the middle of the first layer of pixel grids, and different forms of the non-polar fluid 6 can be achieved by controlling different voltages. In the single-layer structure of the traditional scheme, the ink will climb up along both sides in the pixel grid, so that the amount of ink needs to be increased. The structure of the scheme of the present invention cleverly limits the problem of ink eversion through the double-layer structure, effectively saving the amount of ink filling.

[0078] Example 2

[0079] In this example, a double-layer flexible electrowetting display device was prepared. Figure 4 As shown, the specific structure includes an upper conductive substrate 30 and a lower conductive substrate 20, wherein the lower conductive substrate 20 is sequentially provided with a lower substrate layer 1, a conductive layer I2, a hydrophobic insulating layer 3 and a plurality of pixel walls from the outside to the inside, the pixel walls are spaced and distributed on the hydrophobic insulating layer 3, and a pixel grid is formed between adjacent pixel walls, each pixel wall is composed of a first pixel wall layer 8 and a second pixel wall layer 9, and the cross-section of the first and second pixel wall layers along the height direction is an inverted trapezoid, wherein the bottom angle of the first pixel wall layer is 95°, and the bottom angle of the second pixel wall layer is 97°. The upper conductive substrate 30 is sequentially provided with an upper substrate layer 5 and a conductive layer II 4 from the outside to the inside, and a sealed cavity is formed between the upper conductive substrate 30 and the lower conductive substrate 20 through a sealing frame 10, and the sealed cavity is filled with mutually immiscible polar liquid 7 and non-polar liquid 6.

[0080] The preparation process is:

[0081] 1. Prepare the conductive substrate

[0082] 1.1 Take the upper and lower conductive substrates for use. Both the upper and lower conductive substrates are flexible light-transmitting conductive glass, specifically ultra-thin glass UTG (commercially available).

[0083] 2. Apply hydrophobic insulating layer 3

[0084] 2.1 2 mL of Hyflon is coated on the surface of the lower conductive substrate 20 (including the lower substrate layer 1 and the conductive layer I 2), and the film is formed by spin coating at a rotation speed of 325 rpm for 65 seconds; then, it is heated at about 55°C (45°C-60°C) for 5 minutes, and the heating is immediately stopped, and it is naturally cooled to room temperature to form a Hyflon hydrophobic insulating layer 3.

[0085] 2.2 Place the lower conductive substrate 20 obtained in step 2.1 into an ion etching machine with a power of 5W, and change the hydrophobicity of the hydrophobic insulating layer 3 to hydrophilicity (the contact angle with pure water is about 90°, 80°-100° is acceptable).

[0086] 3. Prepare pixel wall

[0087] 3.1 Spin coat 2mL of HN-008n, 50cp, at a speed of 1100rpm for 65s on the surface of the treated hydrophobic insulating layer 3, and heat it on a heating plate at about 105℃ (110℃-120℃ is acceptable) for 3min, then stop heating immediately and cool naturally;

[0088] 3.2 Place the film in the photolithography machine and use the mask with the selected pattern to perform point-to-point alignment with the first pixel wall structure and expose it to UV light for 18 seconds; place it on a heating plate and heat it at 110°C for 3 minutes, stop heating immediately, and cool it naturally;

[0089] 3.3 Prepare two boxes with 0.4wt% KOH solution, place them in the developer for 60s, and then gently shake them for 60s. Gently shake them for 50s in a third box with clean water, rinse the lower conductive substrate with flowing water for 50s, and then blow the lower conductive substrate 20 clean with nitrogen to obtain the lower conductive substrate 20 with the first pixel wall layer 8 structure, with a pixel wall height of about 4 microns (3-5 microns is acceptable);

[0090] 3.4 Spin-coat 2 mL of HN-018n, 150 cp, at a speed of 180 rpm for 90 s on the surface of the first pixel wall layer 8 structure, place on a heating plate and heat at about 115°C (110°C-120°C) for 6 min, stop heating immediately, and cool naturally;

[0091] 3.5 Place it in the photolithography machine and use the mask of the selected pattern to align it and expose it to UV light for 40 seconds; place it on the heating plate and heat it at 110℃ for 6 minutes, stop heating immediately and cool it naturally;

[0092] 3.6 Prepare two boxes with 0.4wt% KOH developer, place them in the developer for 90s, and then gently shake them for 60s respectively. Gently shake them for 50s in a third box with clean water, rinse the lower conductive substrate with flowing water for 50s, and then blow the lower conductive substrate 20 clean with nitrogen to obtain the lower conductive substrate 20 with the second pixel wall layer 9 structure, with a pixel wall height of about 23 microns (20 microns-25 microns are acceptable);

[0093] 3.7 Place the lower conductive substrate 20 with the pixel wall structure obtained in step 3.6 into an ion etcher to decompose the photoresist remaining at the bottom of the pixel grid;

[0094] 3.8 Place the lower conductive substrate 20 obtained in step 3.7 into a heating furnace and heat it under reflux at about 200° C. (170° C. to 220° C. is acceptable) for 1.5 hours, and then cool it naturally.

[0095] 4. Fill

[0096] 4.1 Inkjet printing is performed on the lower conductive substrate 20 with the pixel wall structure obtained in step 3. The pixel cells of the lower conductive substrate 20 are filled with ink using an inkjet printer. The thickness of the oil film is lower than that of the first pixel wall layer 8, and the thickness is about 4 microns (3 to 5 microns).

[0097] 5. Packaging

[0098] 5.1 Place the polar liquid 7 and the lower conductive substrate 20 filled with ink (the ingredients are tetradecane and magenta dye, wherein the mass proportion of magenta dye is 5wt%) on a condenser at a temperature of -5°C to -30°C, cool for 2 to 3 minutes, and spread the polar liquid 7 on the pixel grid filled with ink.

[0099] 5.2 Use a UV cleaning machine to treat the upper conductive substrate 30 (including the upper substrate layer 5 and the conductive layer II 4) for 5 minutes, and adhere the pressure-sensitive adhesive to the conductive layer II 4;

[0100] 5.3 Align the packaging glue frame with the pixel grid filled by inkjet printing on the lower conductive substrate 20, and bond the upper and lower conductive substrates together with pressure to obtain a double-layer structure flexible electrowetting display device, such as Figure 5 As shown (since the top of the pixel wall is directly attached to the upper conductive substrate 30 when the upper and lower conductive substrates are attached, the preparation step of the support column is not included).

[0101] The driving mode of the above-mentioned electrowetting display structure during application is as follows: when the upper conductive substrate and the lower conductive substrate are powered on, the electric field formed forces the positively charged polar liquid 7 to produce polarization and move toward the negative charge accumulation at the bottom. The polar fluid 7 pushes the non-polar liquid 6 aside, and the pixel shows the color of the bottom.

[0102] like Figure 6As shown, when the conductive layer I is connected to the negative power supply and the conductive layer II is connected to the positive power supply, and the applied voltage is greater than the threshold voltage (30V) of the non-polar fluid 6, the non-polar fluid 6 begins to deform, changing from the initial wet state to the contracted state, and the thickness of the ink after contraction will not exceed the second pixel wall layer; when the applied voltage is less than the threshold voltage (30V) of the non-polar fluid 6, the non-polar fluid 6 is still in the wet state, locked in the middle of the first layer of pixel grids, and different forms of the non-polar fluid 6 can be achieved by controlling different voltages. In the single-layer structure of the traditional scheme, the ink will climb up along both sides in the pixel grid, so that the amount of ink needs to be increased. The structure of the scheme of the present invention cleverly limits the problem of ink eversion through the double-layer structure, effectively saving the amount of ink filling.

[0103] Example 3

[0104] This example prepares a double-layer flexible electrowetting display device, which differs from Example 1 in that the second pixel wall structure is in an inverted trapezoidal shape. In the traditional single-layer structure, the ink will climb up along both sides in the pixel grid, thus requiring an increase in the amount of ink. The structure of the present invention cleverly limits the problem of ink eversion through a double-layer structure, effectively saving the amount of ink filling.

[0105] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A double-layer flexible electrowetting display device, characterized in that: The invention comprises an upper conductive substrate and a lower conductive substrate which are arranged opposite to each other, wherein the lower conductive substrate is provided with a hydrophobic insulating layer and a plurality of pixel walls which are distributed at intervals in sequence along a direction toward the upper conductive substrate, and the adjacent pixel walls form a pixel grid, and the pixel walls comprise a first pixel wall layer and a second pixel wall layer which are stacked, the first pixel wall layer is connected to the hydrophobic insulating layer, and the cross-sections of the first pixel wall layer and the second pixel wall layer in the height direction are both trapezoidal, and at least the first pixel wall layer is an inverted trapezoidal.

2. The double-layer structure flexible electrowetting display device according to claim 1, characterized in that: The first pixel wall layer and the second pixel wall layer are both in an inverted trapezoid; preferably, the bottom angle of the first pixel wall layer is between 90°-100°, and the bottom angle of the second pixel wall layer is between 95°-100°; more preferably, the bottom angle of the second pixel wall layer is not less than the bottom angle of the first pixel wall layer.

3. The double-layer structure flexible electrowetting display device according to claim 1, characterized in that: The base angle of the inverted trapezoid is not less than 95°; preferably, the base angle of the inverted trapezoid is between 95° and 135°.

4. The double-layer flexible electrowetting display device according to claim 1, characterized in that: The overall height of the pixel wall is 6 to 30 times the height of the first pixel wall layer; and / or the overall height of the pixel wall is 1.2 to 1.7 times the height of the second pixel wall layer.

5. The double-layer flexible electrowetting display device according to claim 1, characterized in that: The overall height of the pixel wall is 20-30 μm; and / or the height of the first pixel wall layer is 3-5 μm; and / or the height of the second pixel wall layer is 17-25 μm.

6. The double-layer structure flexible electrowetting display device according to claim 1, characterized in that: A sealed cavity is formed between the upper conductive substrate and the lower conductive substrate, and is filled with mutually immiscible polar liquid and non-polar liquid. The thickness of the non-polar liquid is 3 to 5 μm. Preferably, the thickness of the non-polar liquid is not greater than the height of the first pixel wall layer.

7. The double-layer structure flexible electrowetting display device according to claim 1, characterized in that: The material of the first pixel wall layer is selected from at least one of SU-8 photoresist, HN-008 photoresist or HN-018 photoresist; and / or the material of the second pixel wall layer is selected from at least one of SUN-130P photoresist, SUN-120P photoresist or SUN-350P photoresist.

8. The double-layer structure flexible electrowetting display device according to claim 1, characterized in that: The contact angle of the hydrophobic insulating layer is 120° to 305°.

9. The method for preparing a double-layer flexible electrowetting display device according to any one of claims 1 to 8, characterized in that: The steps include: S1, removing the conductive substrate, filling the pixel grid with a non-polar liquid, and filling the pixel grid with a polar liquid above the non-polar liquid; S2. Take the upper conductive substrate, set a sealing frame on the upper conductive substrate, set an opening on the sealing frame, cover the lower conductive substrate on top of the upper conductive substrate, apply pressure to the lower conductive substrate so that excess non-polar liquid flows out from the opening, and seal the opening.

10. The preparation method according to claim 9, characterized in that: The non-polar liquid is injected into the pixel grid by inkjet printing.

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