Lower substrate, electrowetting display device and manufacturing method of lower substrate

Abstract

The invention discloses a lower substrate, an electrowetting display device with the lower substrate and a manufacturing method for manufacturing the lower substrate, and the lower substrate comprises a lower plate body, a first electrode is arranged on the side surface of the lower plate body; the convex part is arranged on the first electrode, and the convex part is gradually shrunk in the protruding height direction of the convex part; the hydrophobic insulating layer is arranged on one side, close to the convex part, of the first electrode and covers the convex part; and the pixel wall is arranged on one side, far away from the first electrode, of the hydrophobic insulating layer, a plurality of pixel grids are defined by the pixel wall, and the convex parts are arranged in each pixel grid. According to the invention, the gradually-shrunk convex parts are arranged in the pixel grids, so that the turn-on voltage required by ink cracking can be reduced, the consistency of the shrinkage motion direction of ink in each pixel grid is improved, and the light characteristic of the display device is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of displays, and in particular to a lower substrate, an electrowetting display device and a method for manufacturing the lower substrate. Background Art

[0002] In an electrowetting display, the surface tension between the liquid and the solid in the pixel grid is changed by changing the voltage applied between the liquid and the substrate electrode, so that the ink in the pixel grid changes from the original spreading state to the contracted state, thereby achieving the functions of pixel switching and grayscale control.

[0003] In the prior art, a pixel grid and a cylindrical protrusion are provided on the electrode of the substrate. The cylindrical protrusion is located in the pixel grid. The ink thickness at the position of the cylindrical protrusion in the pixel grid is the thinnest. When a voltage is applied to the electrode of the substrate, the rupture position of the ink occurs preferentially at the thinnest part of the ink, so that the ink in the pixel grid changes from the original spreading state to the contracted state.

[0004] However, as the voltage increases, the rupture opening rate of the ink at the cylindrical protrusion undergoes a mutation process and does not change with the increase in voltage, making it impossible for the ink to shrink in a directional manner. There are large differences in the shrinkage direction of the ink within each pixel grid, resulting in poor pixel switching and grayscale control effects. 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 provides a lower substrate that can reduce the turn-on voltage required for ink rupture, improve the consistency of the ink shrinkage movement direction in each pixel grid, and improve the optical characteristics of the display device.

[0006] The present invention also provides an electrowetting display device having the above-mentioned lower substrate.

[0007] The present invention also provides a method for manufacturing the above-mentioned lower substrate.

[0008] According to a first aspect of the present invention, a lower substrate includes: a lower plate body, a first electrode is arranged on the side surface; a convex portion is arranged on the first electrode, and the convex portion is gradually tapered along the height direction of its own convexity; a hydrophobic insulating layer is arranged on the side of the first electrode close to the convex portion and covers the convex portion; a pixel wall is arranged on the side of the hydrophobic insulating layer away from the first electrode, the pixel wall defines a plurality of pixel grids, and the convex portion is arranged in each of the pixel grids.

[0009] A lower substrate according to an embodiment of the present invention has at least the following beneficial effects: 1. The present invention arranges convex portions so that each pixel grid is arranged with convex portions, so that the thinnest position of the ink in the pixel grid is on the convex portions. When a voltage is applied to drive the ink in the pixel grid, the ink on the convex portions is preferentially broken, and the convex portions gradually shrink along the height direction of their own protrusions, so that the surface transition in the height direction of the convex portions is smooth. As the applied voltage increases, the opening rate of the ink rupture and shrinkage also increases with the increase in voltage, that is, the ink gradually separates from the inclined surface of the convex portion, avoiding the situation in which the ink movement direction suddenly changes due to fault changes during the ink separation process from the surface of the cylindrical convex structure. The convex portions are used to control the movement direction of the ink, so that the movement direction of the ink in each pixel grid is controllable, ensuring that the movement direction of the ink in each pixel grid is consistent.

[0010] 2. The present invention separates the convex portion and the pixel wall by covering the convex portion with a hydrophobic insulating layer. The convex portion and the pixel wall are formed separately, so that the height and shape of the convex portion and the pixel wall are precise, so that the convex portion in each pixel grid accurately induces the directional movement of the ink, greatly improving the consistency of the ink movement in each pixel grid.

[0011] 3. Compared with the existing cylindrical protrusion structure, the present invention can reduce the opening voltage, improve the consistency of the ink contraction movement direction in each pixel grid, improve the photoelectric performance of the device, increase the electric field response speed, reduce power consumption, and optimize the device stability by adopting a tapered protrusion.

[0012] According to a lower substrate of an embodiment of the first aspect of the present invention, the pixel grid has a first symmetry axis and a second symmetry axis, the first symmetry axis and the second symmetry axis are perpendicular to each other, a first area is formed between the inner side wall of the pixel grid, the first symmetry axis and the second symmetry axis, and the convex portion is located within the first area.

[0013] According to a lower substrate of an embodiment of the first aspect of the present invention, the maximum height of the protrusion is 10% to 30% of the height of the pixel wall.

[0014] According to a lower substrate of an embodiment of the first aspect of the present invention, the convex portion is a truncated cone structure, a hemispherical structure or a conical structure.

[0015] According to a lower substrate of an embodiment of the first aspect of the present invention, one convex portion is arranged in each pixel grid.

[0016] An electrowetting display device according to an embodiment of the second aspect of the present invention comprises: a lower substrate as described in any one of claims 1 to 5; a polar liquid and a non-polar liquid, wherein the polar liquid and the non-polar liquid are filled in the pixel grid; an upper substrate, comprising an upper plate body and a second electrode arranged on the side surface of the upper plate body, wherein the upper plate body is connected to the pixel wall on a side close to the second electrode.

[0017] An electrowetting display device according to an embodiment of the present invention has at least the following beneficial effects: 1. The present invention arranges convex portions so that each pixel grid is arranged with convex portions, so that the thinnest position of the ink in the pixel grid is on the convex portions. When a voltage is applied to drive the ink in the pixel grid, the ink on the convex portions is preferentially broken, and the convex portions gradually shrink along the height direction of their own protrusions, so that the surface transition in the height direction of the convex portions is smooth. As the applied voltage increases, the opening rate of the ink rupture and shrinkage also increases with the increase in voltage, that is, the ink gradually separates from the inclined surface of the convex portion, avoiding the situation in which the ink movement direction suddenly changes due to fault changes during the ink separation process from the surface of the cylindrical convex structure. The convex portions are used to control the movement direction of the ink, so that the movement direction of the ink in each pixel grid is controllable, ensuring that the movement direction of the ink in each pixel grid is consistent.

[0018] 2. The present invention separates the convex portion and the pixel wall by covering the convex portion with a hydrophobic insulating layer. The convex portion and the pixel wall are formed separately, so that the height and shape of the convex portion and the pixel wall are precise, so that the convex portion in each pixel grid accurately induces the directional movement of the ink, greatly improving the consistency of the ink movement in each pixel grid.

[0019] 3. Compared with the existing cylindrical protrusion structure, the present invention can reduce the opening voltage, improve the consistency of the ink contraction movement direction in each pixel grid, improve the photoelectric performance of the device, increase the electric field response speed, reduce power consumption, and optimize the device stability by adopting a tapered protrusion.

[0020] A method for manufacturing a lower substrate according to an embodiment of the third aspect of the present invention is used to manufacture a lower substrate as described in any one of claims 1 to 5, characterized in that it includes the steps of: S1, manufacturing the first electrode on the lower plate body; S2, manufacturing the protrusion on the first electrode; S3, manufacturing a hydrophobic insulating layer on the side of the first electrode close to the protrusion; S4, manufacturing a pixel wall on the side of the hydrophobic insulating layer away from the protrusion.

[0021] A method for manufacturing a lower substrate according to an embodiment of the present invention has at least the following beneficial effects: 1. The present invention arranges convex portions so that each pixel grid is arranged with convex portions. Therefore, the thinnest position of the ink in the pixel grid is on the convex portions. When a voltage is applied to drive the ink in the pixel grid, the ink on the convex portions is preferentially broken, and the convex portions gradually shrink along the height direction of their own protrusions, so that the surface transition in the height direction of the convex portions is smooth. As the applied voltage increases, the opening rate of the ink rupture and shrinkage also increases with the increase in voltage. The convex portions are used to control the movement direction of the ink, so that the movement direction of the ink in each pixel grid is controllable, avoiding the situation where the movement direction of the ink is suddenly changed due to the use of a cylindrical convex structure to control the movement of the ink, thereby ensuring that the movement direction of the ink in each pixel grid is consistent.

[0022] 2. The present invention makes the protrusions and the pixel walls separately, and can use photoembossing technology to make the protrusions and the pixel walls. First, the protrusions of a certain height and shape are made, then the hydrophobic insulating layer is made, and then the pixel walls are made, so that the protrusions and the pixel walls are formed separately, and the protrusions and the pixel walls are not affected by each other during the production process, so that the height and shape of the protrusions and the pixel walls are accurate, so that the protrusions in each pixel grid accurately induce the directional movement of the ink, thereby greatly improving the consistency of the ink movement in each pixel grid.

[0023] 3. Compared with the existing cylindrical protrusion structure, the present invention can reduce the opening voltage, improve the consistency of the ink contraction movement direction in each pixel grid, improve the photoelectric performance of the device, increase the electric field response speed, reduce power consumption, and optimize the device stability by adopting a tapered protrusion.

[0024] According to a method for manufacturing a lower substrate in an embodiment of the third aspect of the present invention, S2 comprises the steps of: Prepare a first mask having a light-transmitting area matching the shape of the protrusion; spin-coat a layer of first photoresist on the first electrode, heat-cured the first photoresist, and cooled to room temperature; use the first mask to expose the first photoresist, and then post-bake and cure it to form the protrusion.

[0025] According to a method for manufacturing a lower substrate of an embodiment of the third aspect of the present invention, S3 includes the step of spin-coating a hydrophobic insulating material on the surface of the first electrode and covering the protrusion to form a hydrophobic insulating layer.

[0026] According to a method for manufacturing a lower substrate in an embodiment of the third aspect of the present invention, S4 includes the steps of: preparing a second mask, the second mask having a light-transmitting area matching the shape of the pixel wall; spin coating a layer of second photoresist on the surface of the hydrophobic insulating layer away from the protrusion, the second photoresist being heated and cured, and cooled to room temperature; exposing the second photoresist using the second mask, and then post-baking and developing to form the pixel wall.

[0027] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 This is a schematic structural diagram of an electrowetting display device according to an embodiment of the present invention; Figure 2 for Figure 1 A schematic diagram of the structure of a pixel wall of a lower substrate viewed from above is shown; Figure 3 for Figure 1 A schematic structural diagram of a pixel grid of a lower substrate is shown; Figure 4 for Figure 1 A schematic diagram of the structure of a state in which ink shrinks after a voltage is applied to an electrowetting display device is shown; Figure 5 for Figure 1 A schematic structural diagram of a convex portion of a lower substrate is shown; Figure 6 for Figure 1 A manufacturing flow chart of a lower substrate is shown; Figure 7 for Figure 1 A schematic structural diagram of a manufacturing process of a lower substrate is shown.

[0030] Figure numerals: 100 - lower plate, 110 - first electrode, 120 - convex portion, 130 - hydrophobic insulating layer, 140 - pixel wall, 150 - pixel grid, 160 - first axis of symmetry, 170 - second axis of symmetry, 180 - first region, 190 - upper plate, 200 - second electrode, 210 - first mask, 220 - second mask. DETAILED DESCRIPTION

[0031] 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.

[0032] In the description of the present invention, it is necessary to understand that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the 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 cannot be understood as a limitation on the present invention.

[0033] In the description of the present invention, "several" means one or more, "more" 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 and second, this is only for the purpose of distinguishing the 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 order of the indicated technical features.

[0034] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation, connection and connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] A lower substrate, an electrowetting display device and a method for manufacturing the lower substrate according to embodiments of the present invention will be described below with reference to the accompanying drawings.

[0036] The present invention aims to provide an embodiment of a lower substrate, an electrowetting display device and a method for manufacturing the lower substrate.

[0037] In terms of structure, refer to Figure 1 , an electrowetting display device mainly includes a lower substrate, a polar liquid, a non-polar liquid and an upper substrate.

[0038] It should be noted that the non-polar liquid is usually ink.

[0039] A lower substrate according to an embodiment of the present invention includes a lower plate body 100, a convex portion 120, a hydrophobic insulating layer 130 and a pixel wall 140. A first electrode 110 is disposed on a side surface of the lower plate body 100; the convex portion 120 is disposed on the first electrode 110, and the convex portion 120 is gradually reduced in a height direction of its own convexity; the hydrophobic insulating layer 130 is disposed on a side of the first electrode 110 close to the convex portion 120 and covers the convex portion 120; the pixel wall 140 is disposed on a side of the hydrophobic insulating layer 130 away from the first electrode 110, refer to Figure 2 The pixel wall 140 defines a plurality of pixel grids 150 , and a convex portion 120 is arranged in each pixel grid 150 .

[0040] Furthermore, polar liquid and non-polar liquid are filled in the pixel grid 150 , and the upper substrate includes an upper plate body 190 and a second electrode 200 disposed on a side surface of the upper plate body 190 . The upper plate body 190 is connected to the pixel wall 140 on one side close to the second electrode 200 .

[0041] In some embodiments of the present invention, reference Figure 3 The pixel grid 150 has a first symmetry axis 160 and a second symmetry axis 170 , which are perpendicular to each other. A first region 180 is formed between the inner side wall of the pixel grid 150 , the first symmetry axis 160 and the second symmetry axis 170 , and the convex portion 120 is located in the first region 180 .

[0042] It can be understood that the protrusion 120 is arranged in the first area 180, that is, the protrusion 120 is arranged at the corner position of the pixel grid 150. When a voltage is applied to drive the ink from a spreading state to a contracted state, the ink at the position of the protrusion 120 breaks. As the voltage increases, the ink contracts and moves from one side of the pixel grid 150 to the other side, which helps to control the consistent direction of ink movement in each pixel grid 150.

[0043] In some embodiments of the present invention, a convex portion 120 is disposed in each pixel grid 150 .

[0044] When voltage is applied to drive the ink, it is necessary to ensure that the ink breaks only at one convex portion 120 . By gradually increasing the voltage, the ink shrinks and moves in a directional manner, ensuring that the ink movement direction in each pixel grid 150 is consistent.

[0045] It should be noted that if there is more than one convex portion 120 in the pixel grid 150, when a voltage is applied to drive the ink, multiple ink ruptures will appear in the pixel grid 150. The multiple ink ruptures and contractions will cause the ink to shrink and move in a disordered manner.

[0046] In some embodiments of the present invention, the protrusion 120 is a truncated cone structure, a hemispherical structure or a conical structure.

[0047] It is understandable that the convex portion 120 may have various tapered forms. The convex portion 120 may be made into a truncated cone structure, a hemispherical structure, or a conical structure.

[0048] Preferably, the protrusion 120 is a truncated cone structure, referring to Figure 5 The truncated cone-shaped protrusion 120 has a certain inclination, which can avoid sudden changes in the ink shrinkage and movement process and make it easier to control the directional shrinkage and movement of the ink.

[0049] In some embodiments of the present invention, the maximum height of the protrusion 120 is 10% to 30% of the height of the pixel wall 140 .

[0050] Furthermore, the maximum height of the protrusion 120 is ≤10 um.

[0051] Since the height of the protrusion 120 is limited by the thickness of the ink, it is necessary to ensure that the height of the protrusion 120 is less than the thickness of the ink. If the height of the protrusion 120 is less than 10% of the height of the pixel wall 140, the turn-on voltage required for the ink to rupture may be larger, which is not conducive to controlling power consumption; if the height of the protrusion 120 exceeds 30% of the height of the pixel wall 140, the thickness of the ink must be increased. When a voltage is applied to drive the ink, the ink may shrink and move over the pixel wall 140.

[0052] Therefore, a lower substrate of the present invention is provided with a convex portion 120 so that each pixel grid 150 is provided with a convex portion 120. Therefore, the thinnest position of the ink in the pixel grid 150 is on the convex portion 120. Figure 4 When a voltage is applied to drive the ink in the pixel grid 150, the ink on the protrusion 120 breaks first, and the protrusion 120 gradually shrinks along the height direction of its own protrusion, so that the surface transition of the protrusion 120 in the height direction is smooth. As the applied voltage increases, the opening rate of the ink rupture and shrinkage also increases with the increase of voltage, that is, the ink gradually separates from the inclined surface of the protrusion 120, avoiding the situation where the ink movement direction suddenly changes due to the fault change during the surface separation of the cylindrical protrusion structure. The convex portion 120 is used to control the movement direction of the ink, so that the movement direction of the ink in each pixel grid 150 is controllable, ensuring that the movement direction of the ink in each pixel grid 150 is consistent.

[0053] In terms of manufacturing, a lower substrate of the present invention is manufactured using a technique called photoembossing, which is based on moving material on a substrate rather than removing material from it like photolithography. The technique is able to create complex textures because it uses a latent image, so multiple exposures can be made before development. A unique feature of the process is the contactless unfolding of the undulating structure by heating. Unlike traditional patterning techniques, photoembossing does not require contact with a mold or solvent, but uses heat.

[0054] It is understood that patterned UV exposure is applied to the photopolymer to produce a latent image, which can be exposed through a photolithography mask. During the patterned exposure, the monomer begins to polymerize. Due to the low mobility of the reactive species in the solid photopolymer layer at room temperature, the polymerization reaction is limited, and a latent image is obtained.

[0055] Heating the sample increases the molecular mobility within the photopolymer, which enhances the polymerization reaction and the diffusion of the active species into the exposed areas. The diffusion leads to a local increase in volume in the exposed areas, which manifests as a surface relief structure.

[0056] Based on the above technology, refer to Figure 6 and Figure 7 A method for manufacturing a lower substrate according to an embodiment of the present invention comprises the following steps: S1 , manufacturing a first electrode 110 on the lower plate 100 .

[0057] S2 , forming a protrusion 120 on the first electrode 110 .

[0058] S3 , forming a hydrophobic insulating layer 130 on a side of the first electrode 110 close to the protrusion 120 .

[0059] S4 , manufacturing the pixel wall 140 on the side of the hydrophobic insulating layer 130 away from the protrusion 120 .

[0060] Furthermore, S2 includes the steps of: preparing a first mask 210, the first mask 210 having a light-transmitting area matching the shape of the protrusion 120; spin coating a layer of first photoresist on the first electrode 110, the first photoresist being heated and cured on a hot plate and cooled to room temperature; exposing the first photoresist using the first mask 210, and heating and curing the first photoresist again on a hot plate, i.e., post-baking, to form the protrusion 120.

[0061] It should be noted that the first photoresist is one of SU-8 photoresist, Fujifilm SC-450 photoresist and HN-022N negative photoresist.

[0062] Furthermore, S3 includes the steps of: spin coating a hydrophobic insulating material on the surface of the first electrode 110 and covering the protrusion 120 to form a hydrophobic insulating layer 130; after the spin coating is completed, heating and curing it on a hot plate; baking it in an oven and cooling it to room temperature; after cooling, placing it in a reactive ion etcher for modification so that the hydrophobic insulating layer 130 is changed from a hydrophobic state to a hydrophilic state.

[0063] Further, S4 includes the steps of: preparing a second mask 220, the second mask 220 having a light-transmitting area matching the shape of the pixel wall 140; spin-coating a layer of second photoresist on the surface of the hydrophobic insulating layer 130 away from the protrusion 120, the second photoresist being heated and cured on a hot plate and cooled to room temperature; exposing the second photoresist using the second mask 220, and then heating and curing it on the hot plate again, i.e., post-baking, and then cooling it to room temperature; finally, developing it to remove excess second photoresist material remaining on the hydrophobic insulating layer 130, thereby forming a pixel wall 140, and using the pixel wall 140 to define a plurality of pixel grids 150, ensuring that each pixel grid 150 has and only has one protrusion 120.

[0064] It should be noted that the second photoresist used is HN-022N photoresist.

[0065] A method for manufacturing an electrowetting display device according to an embodiment of the present invention comprises the following steps: Make the lower substrate.

[0066] The filling process fills the non-polar liquid and the polar liquid into the pixel grid 150 .

[0067] The upper substrate and the lower substrate are laminated together.

[0068] Therefore, the present invention makes the protrusion 120 and the pixel wall 140 separately, and can adopt the photoembossing technology to make the protrusion 120 and the pixel wall 140, first make the protrusion 120 of a certain height and shape, then make the hydrophobic insulating layer 130, and then make the pixel wall 140, so that the protrusion 120 and the pixel wall 140 are formed separately, and the protrusion 120 and the pixel wall 140 are not affected by each other during the manufacturing process, so that the height and shape of the protrusion 120 and the pixel wall 140 are accurate, so that the protrusion 120 in each pixel grid 150 accurately induces the directional movement of the ink, and the consistency of the ink movement in each pixel grid 150 is greatly improved.

[0069] A driving method of an electrowetting display device according to an embodiment of the present invention is as follows: When the upper and lower substrates are energized, the generated electric field causes the positively charged polar liquid to move toward the negatively charged area at the bottom, and the polar liquid pushes the non-polar liquid to one side, causing the pixel to display the color at the bottom.

[0070] Specifically, a negative electrode is applied to the first electrode 110 and a positive electrode is applied to the second electrode 200. When the applied voltage is higher than the turn-on voltage of the non-polar fluid, the non-polar fluid will undergo a morphological change from an initial wet state to a contracted state. In this state, the thickness of the ink will also remain within the range of the pixel wall 140; when the voltage is lower than the turn-on voltage of the non-polar fluid, the non-polar fluid will remain in a spreading state.

[0071] Therefore, the morphology change of nonpolar fluids can be controlled by adjusting the voltage.

[0072] In the description of this specification, the description with reference to the terms "one embodiment, some embodiments, illustrative embodiments, examples, specific examples or some examples" etc. 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.

[0073] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and 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 lower substrate, characterized in that: include: A lower plate body (100) having a first electrode (110) disposed on a side surface thereof; A convex portion (120) is arranged on the first electrode (110), and the convex portion (120) is arranged to be gradually reduced along a height direction of the convex portion; a hydrophobic insulating layer (130), arranged on a side of the first electrode (110) close to the convex portion (120) and covering the convex portion (120); A pixel wall (140) is arranged on a side of the hydrophobic insulating layer (130) away from the first electrode (110), the pixel wall (140) defining a plurality of pixel grids (150), and the convex portion (120) is arranged in each of the pixel grids (150).

2. A lower substrate according to claim 1, characterized in that: The pixel grid (150) has a first symmetry axis (160) and a second symmetry axis (170), the first symmetry axis (160) and the second symmetry axis (170) being perpendicular to each other, a first area (180) being formed between the inner side wall of the pixel grid (150), the first symmetry axis (160) and the second symmetry axis, and the convex portion (120) is located in the first area (180).

3. A lower substrate according to claim 1, characterized in that: The maximum height of the protrusion (120) is 10% to 30% of the height of the pixel wall (140).

4. The lower substrate according to claim 1, characterized in that: The convex portion (120) is a truncated cone-shaped structure, a hemispherical structure or a conical structure.

5. The lower substrate according to claim 1, characterized in that: One convex portion (120) is arranged in each pixel grid (150).

6. An electrowetting display device, characterized in that: include: A lower substrate according to any one of claims 1 to 5; A polar liquid and a non-polar liquid, wherein the polar liquid and the non-polar liquid are filled in the pixel grid (150); The upper substrate comprises an upper plate body (190) and a second electrode (200) arranged on a side surface of the upper plate body (190); a side of the upper plate body (190) close to the second electrode (200) is connected to the pixel wall (140).

7. A method for manufacturing a lower substrate, used for manufacturing a lower substrate according to any one of claims 1 to 5, characterized in that: Includes steps: S1, manufacturing the first electrode (110) on the lower plate (100); S2, manufacturing the convex portion (120) on the first electrode (110); S3, forming a hydrophobic insulating layer (130) on a side of the first electrode (110) close to the protrusion (120); S4, manufacturing a pixel wall (140) on a side of the hydrophobic insulating layer (130) away from the protrusion (120).

8. The method for manufacturing a lower substrate according to claim 7, characterized in that: S2 includes the steps: Preparing a first mask, wherein the first mask has a light-transmitting area matching the shape of the convex portion (120); Spin coating a layer of first photoresist on the first electrode (110), wherein the first photoresist is cured by heating and then cooled to room temperature; The first photoresist is exposed using the first mask, and then post-baked and cured to form the protrusion (120).

9. The method for manufacturing a lower substrate according to claim 7, characterized in that: S3 includes the following steps: A hydrophobic insulating material is spin-coated on the surface of the first electrode (110) and covers the protrusion (120) to form a hydrophobic insulating layer (130).

10. The method for manufacturing a lower substrate according to claim 7, characterized in that: S4 includes the steps: Preparing a second mask, wherein the second mask has a light-transmitting area matching the shape of the pixel wall (140); Spin coating a layer of second photoresist on the surface of the hydrophobic insulating layer (130) away from the convex portion (120), wherein the second photoresist is heated and cured, and then cooled to room temperature; The second photoresist is exposed using the second mask, and then post-baked and developed to form the pixel wall (140).

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