Method for manufacturing display panel and display panel

Abstract

The application provides a display panel preparation method and a display panel. The display panel comprises a plurality of pixel units, each of which comprises at least two sub-pixels of different colors. The preparation method comprises the following steps: providing a driving substrate, an anode corresponding to a sub-pixel of different colors is formed on the driving substrate, and the height of each anode is different; preparing a light-emitting material layer of each color in order from low to high: applying a liquid drop containing a target color light-emitting material to a pixel unit area where a target sub-pixel is located; applying a voltage to the target sub-pixel anode and at least part of the electrodes of other sub-pixels in the same pixel unit to drive the liquid drop to move to the target anode by the electrowetting effect; and solidifying the liquid drop moved to the target anode to form a light-emitting layer; wherein when the light-emitting layer of the same color is prepared, the liquid drop and voltage application operations are performed for multiple times, and each time, the pixel units where the target sub-pixels are located are not adjacent to each other. The application can reduce the printing precision requirement and improve the yield.

Description

Technical Field

[0001] This application belongs to the field of display technology, specifically relating to a method for preparing a display panel and the display panel itself. Background Technology

[0002] With the development of optoelectronic display technology, organic light-emitting diode (OLED) display panels have been widely used in various electronic devices due to their advantages such as self-illumination, thinness, and flexibility. In the fabrication process of OLED display panels, in addition to vapor deposition, inkjet printing technology can also be used to form organic light-emitting material layers. This inkjet printing technology has attracted increasing attention due to its advantages such as high material utilization and the absence of fine masks.

[0003] However, limited by the precision of current inkjet printing equipment, when the pixel density (PPI) of the display panel is high and the area of ​​a single subpixel is small, it is difficult to precisely control the droplet's landing point on the target subpixel anode. This easily leads to printing errors such as droplets falling into adjacent, different-colored subpixel areas, for example, red luminescent material droplets falling into green or blue subpixel positions. This color mixing phenomenon results in abnormal emission colors, severely reducing product yield and thus limiting the widespread application of inkjet printing technology in the manufacturing of high-resolution organic light-emitting diode (OLED) display panels. Summary of the Invention

[0004] The purpose of this application is to provide a method for manufacturing a display panel and a display panel that can reduce the requirements for printing accuracy and improve the production yield of the display panel.

[0005] The first aspect of this application provides a method for fabricating a display panel, the display panel including a plurality of pixel units, each pixel unit including at least two sub-pixels of different colors, the fabrication method including: providing a driving substrate, on which a plurality of anodes corresponding to the sub-pixels of different colors are formed, wherein the anodes of the sub-pixels of different colors have different heights; sequentially performing a process of fabricating a light-emitting material layer on the sub-pixels of different colors in order of anode height from low to high, the fabrication process including: applying a droplet containing a light-emitting material of a target color to the pixel unit region corresponding to the target sub-pixel; applying a voltage to the anode of the target sub-pixel and the electrodes of at least some other sub-pixels located in the same pixel unit as the target sub-pixel, so as to drive the droplet to move toward the anode of the target sub-pixel through an electrowetting effect; and solidifying the droplet that has moved onto the anode of the target sub-pixel to form a light-emitting material layer of the target sub-pixel; wherein, when forming a light-emitting material layer of the same color, the operations of applying the droplet and applying the voltage are performed multiple times, and the pixel units where the target sub-pixel is located are not adjacent to each other in each operation.

[0006] In one exemplary embodiment of this application, the step of providing a driving substrate includes: providing a planarization layer; forming a padding layer on at least a portion of the sub-pixel regions of the planarization layer, the padding layer having different thicknesses in sub-pixel regions of different colors; and forming the plurality of anodes on the padding layer or the planarization layer to make the plurality of anodes have different heights.

[0007] In one exemplary embodiment of this application, the padding layer has a ramp formed between adjacent sub-pixels that have differences, and adjacent anodes are connected through the ramp; after forming the padding layer and before forming the anode, the fabrication method further includes: forming a reflective layer on the ramp, the reflective layer being electrically insulated from the anode and used to reflect light emitted from the low-position sub-pixel.

[0008] In one exemplary embodiment of this application, the at least two different color sub-pixels include a first color sub-pixel, a second color sub-pixel, and a third color sub-pixel, and the anode height of the first color sub-pixel, the anode height of the second color sub-pixel, and the anode height of the third color sub-pixel increase sequentially; when preparing the light-emitting material layer of the first color sub-pixel, the step of applying voltage includes: applying a first positive voltage to the anode of the target first color sub-pixel, applying a second positive voltage to the anodes of other sub-pixels within the same pixel unit, and the first positive voltage being greater than the second positive voltage.

[0009] In an exemplary embodiment of this application, the preparation method further includes: after preparing a light-emitting material layer of one color, forming a cathode on the light-emitting material layer; when preparing the light-emitting material layer of the second color sub-pixel or the third color sub-pixel, the step of applying voltage includes: applying a positive voltage to the anode of the second color sub-pixel or the third color sub-pixel, and applying a negative voltage to at least one formed cathode, wherein the formed cathode is located on a sub-pixel within the same pixel unit where the light-emitting material layer has been prepared.

[0010] In one exemplary embodiment of this application, when preparing the luminescent material layer of the second color sub-pixel or the third color sub-pixel, a positive voltage is also applied to the anode of other sub-pixels in the same pixel unit that have not yet formed a luminescent material layer, and the amplitude of the applied positive voltage is less than the amplitude of the positive voltage applied to the anode of the target sub-pixel.

[0011] In one exemplary embodiment of this application, the operation performed in multiple steps includes a first operation and a second operation, wherein the pixel unit where the target sub-pixel is located in the first operation and the pixel unit where the target sub-pixel is located in the second operation are alternately arranged in the row direction or column direction.

[0012] A second aspect of this application provides a display panel, comprising: a plurality of pixel units, each pixel unit including at least two different colors of sub-pixels; a planarization layer; a padding layer disposed on the planarization layer, the padding layer having different thicknesses in the sub-pixel regions of different colors, and the padding layer forming an inclined surface between adjacent sub-pixels; a plurality of anodes disposed on the padding layer and respectively corresponding to the sub-pixels of different colors, the anodes of the sub-pixels of different colors having different heights; a light-emitting material layer disposed on each of the anodes; and a reflective layer disposed on the inclined surface, the reflective layer being electrically insulated from the anodes and used to reflect light emitted from the lower-position sub-pixels.

[0013] In one exemplary embodiment of this application, the display panel further includes: a cathode disposed on the light-emitting material layer; and an encapsulation layer covering the cathode.

[0014] In one exemplary embodiment of this application, the at least two different colored sub-pixels include a red sub-pixel, a green sub-pixel, and a blue sub-pixel, wherein the anode height of the red sub-pixel, the anode height of the green sub-pixel, and the anode height of the blue sub-pixel increase sequentially.

[0015] The method for manufacturing the display panel and the display panel described in this application have at least the following beneficial effects:

[0016] The fabrication method of this application involves preparing luminescent material layers sequentially by varying the height of the anodes of different color sub-pixels, from lowest to highest anode height. This allows the droplet to converge towards the lower target anode after being applied to the pixel unit region, utilizing the height difference and reducing the difficulty of subsequent driving. Simultaneously, applying voltage to the target anode and other sub-pixel electrodes within the same pixel unit actively drives the droplet towards the target anode through electrowetting, effectively mitigating color mixing issues caused by droplet position deviations and significantly relaxing the requirements for initial droplet accuracy. Furthermore, preparing the luminescent material layer for the same color sub-pixel multiple times, with each target sub-pixel being a non-adjacent pixel unit, reduces electric field interference caused by simultaneous voltage application to adjacent pixel units, ensuring that the droplet is not mistakenly adsorbed onto non-target anodes and further improving pixel positioning accuracy. Therefore, this method significantly reduces printing errors, improves the process window, and increases production yield without requiring increased droplet application accuracy.

[0017] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0018] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0020] Figure 1 A flowchart of a display panel fabrication method provided in an embodiment of this application is shown.

[0021] Figure 2 This illustration shows a cross-sectional structure diagram of anodes of different heights formed on a driving substrate, as provided in an embodiment of this application.

[0022] Figure 3 A schematic flowchart illustrating the preparation process of the red luminescent material layer provided in an embodiment of this application is shown.

[0023] Figure 4 A schematic flowchart illustrating the preparation process of the green luminescent material layer provided in the embodiments of this application is shown.

[0024] Figure 5 A schematic flowchart illustrating the preparation process of the blue luminescent material layer provided in the embodiments of this application is shown.

[0025] Figure 6 A cross-sectional structural diagram of the display panel provided in an embodiment of this application is shown.

[0026] Explanation of reference numerals in the attached figures: 100, Display panel; 110, Pixel unit; 111, First color subpixel; 112, Second color subpixel; 113, Third color subpixel; 120, Driving substrate; 130, Pad layer; 131, Bevel; 140, Reflective layer; 150, Anode; 160, Light-emitting material layer; 170, Cathode; 180, Encapsulation layer. Detailed Implementation

[0027] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this application more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art.

[0028] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0029] In this application, unless otherwise expressly specified and limited, the terms "assembly," "connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0030] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0031] Example 1 See Figure 1 and Figure 2 As shown, this application provides a method for manufacturing a display panel 100. The display panel 100 includes a plurality of pixel units 110, and each pixel unit 110 may include at least two different colors of sub-pixels. The following embodiment uses a first color sub-pixel 111 (red sub-pixel), a second color sub-pixel 112 (green sub-pixel), and a third color sub-pixel 113 (blue sub-pixel) as examples for illustration, but this application is not limited to this. In different embodiments, the color types and arrangements of the sub-pixels may be different. The manufacturing method includes the following steps: Step S100: A driving substrate 120 is provided.

[0032] First, a driving substrate 120 is provided, on which a backplane structure including a thin-film transistor (TFT) array, multiple insulating layers, and a planarization layer is formed. The TFTs can be manufactured using processes such as low-temperature polycrystalline silicon (LTPS), low-temperature polycrystalline oxide (LTPO), or indium gallium zinc oxide (IGZO). The planarization layer material is an organic insulating material, such as polyimide (PI), acrylic (PMMA), or epoxy resin-based photoresist, with a thickness of approximately 1 to 3 μm, used to cover the TFTs and wiring, providing a flat surface. The backplane fabrication process described above can follow conventional OLED backplane processes and will not be detailed here.

[0033] A padding layer 130 is formed on the planar layer. This padding layer 130 can be used to make the subsequently formed anode 150 have different heights in different color sub-pixel regions.

[0034] For example, an organic insulating material, such as polyimide (PI) or polymethyl methacrylate (PMMA), is coated onto the planarization layer surface. The thickness can be designed according to the required maximum height difference, for example, 2 to 5 μm. Then, exposure is performed using a multi-tone photomask (such as a halftone or grayscale mask), followed by development to differentially thin different sub-pixel regions. The lowest height sub-pixel region (such as the red sub-pixel) may not have a padding layer 130 formed, i.e., the padding layer 130 thickness is zero; the anode 150 is formed directly on the planarization layer in this region; the green (G) region retains a medium thickness (e.g., 1.5 to 2.5 μm); and the blue (B) region retains the thickest thickness (close to the initial thickness), such as... Figure 2 As shown. At this time, the height difference between the red sub-pixel anode 150 and the green sub-pixel anode 150 is determined by the thickness of the padding layer 130 below the green sub-pixel.

[0035] In other embodiments, the padding layer 130 of the red (R) subpixel region may be kept to a minimum thickness (e.g., 0.3 to 0.8 μm), while the green and blue subpixel regions retain padding layers 130 of the corresponding thickness.

[0036] It is worth mentioning that a slope 131 with a certain gradient (tilt angle of about 10° to 70°) can be formed between adjacent sub-pixels by gradient exposure or isotropic etching with developer. This slope 131 smoothly connects the top surfaces of padding layers 130 at different heights. In embodiments where there is no padding layer 130 in the red sub-pixel area, the slope 131 is naturally formed by the sidewall of the padding layer 130, that is, the slope formed by the padding layer 130 at the edge of the green / blue sub-pixels, which can also be used to set the reflective layer 140.

[0037] It should be noted that the formation of the padding layer 130 is not limited to photolithography etching. It can also be achieved by using a fully additive process such as inkjet printing or screen printing to directly pattern and deposit materials of different thicknesses, and utilize the liquid phase leveling properties to form a transition slope 131.

[0038] In addition, the material for the padding layer 130 can also be other photosensitive organic insulators such as SU-8 photoresist, benzocyclobutene (BCB), or inorganic materials such as spin-coated glass (SOG) to obtain more precise morphology control. If inorganic materials such as silicon dioxide are used, the entire surface can be deposited first, and then the stepped structure can be achieved through multiple photolithography and chemical mechanical polishing (CMP).

[0039] In other embodiments, the padding layer 130 may also employ a multi-layer structure. For example, the padding layer 130 may consist of two or more layers of material, with a thicker, low-cost organic layer (such as PI) as the bottom layer and a thinner, more hydrophilic organic layer (such as polyacrylic acid materials) as the top layer. The hydrophilic top layer enhances the wettability of droplets in the anode 150 region, assisting in faster droplet spreading and stabilization, while the bottom layer retains its original height difference and slope 131 morphology. Furthermore, the multi-layer structure can introduce a stress-buffering layer to reduce peeling of the padding layer 130 due to bending in flexible displays.

[0040] In other embodiments, an auxiliary drive electrode may be embedded within or on the bottom surface of the pad layer 130. For example, a layer of transparent conductive material (such as an indium tin oxide (ITO) mesh) may be embedded in or formed on the bottom surface of the pad layer 130. This auxiliary electrode is electrically insulated from the anode 150 and can also be used for voltage application during the electrowetting drive phase. This improves the direct application of the drive voltage to the anode 150, prevents electrochemical corrosion of the anode 150 material, and extends device life. The auxiliary electrode can also be reused as a touch electrode or a shielding layer, further enhancing integration.

[0041] In some other embodiments, the padding layer 130 can also be directly integrated with the pixel definition layer (PDL). That is, the padding layer 130 also has the function of defining the light emission opening of the sub-pixel, and its thicker area naturally forms the sub-pixel boundary, thereby saving a photolithography process. Furthermore, the use of the inclined surface 131 of the padding layer 130 to replace the inverted trapezoidal PDL structure simplifies the process and reduces costs.

[0042] In some embodiments, prior to forming the anode 150, a reflective layer 140 is also formed on the slope 131 of the pad layer 130.

[0043] For example, a high-reflectivity metal layer, such as silver (Ag), magnesium (Mg), aluminum (Al), or their alloys, with a thickness of 80 to 200 nm, is first deposited using physical vapor deposition (PVD). Then, an inorganic insulating protective layer, such as SiNx or SiOx, with a thickness of 50 to 150 nm, is deposited to provide electrical isolation. The reflective layer 140 is then patterned using photolithography, ensuring it remains only on the bevel 131, physically disconnected and insulated from the subsequent anode 150.

[0044] Understandably, when a low-position sub-pixel (such as R) emits light, its large-angle emitted light may be absorbed or blocked by the sidewall of the padding layer 130 of the high-position sub-pixels (such as G, B). By using the reflective layer 140, this light can be reflected back to the light-emitting surface, improving light extraction efficiency and viewing angle.

[0045] Furthermore, the reflective layer 140 can also be a distributed Bragg reflector (DBR) composed of multiple dielectric films, such as stacked SiNx / SiO2 films, which has higher reflectivity for specific wavelengths (such as red light); or it can be formed using metal, dielectric, and metal structures to create a microcavity effect. In addition, the reflective layer 140 can also form a pixel isolation structure together with the pixel definition layer, without the need for an additional insulating layer.

[0046] In some other embodiments, the reflective layer 140 may also function as a black matrix. For example, a low-reflectivity light-shielding metal (such as Cr, Mo) or black resin layer may be superimposed on the metal layer (such as Ag) of the original reflective layer 140, so that while reflecting light from the low-position sub-pixels, it absorbs stray light from the environment or adjacent pixels, reduces light crosstalk, and improves display contrast.

[0047] Then, an anode 150 is formed on the pad layer 130. A transparent conductive material, such as indium tin oxide (ITO) or indium zinc oxide (IZO), is deposited with a thickness of approximately 50 to 150 nm, and anode 150 patterns corresponding to each sub-pixel are formed by photolithography. The anode 150 is connected to the drain of the underlying TFT through vias penetrating the planarization layer and the pad layer 130 to enable independent voltage application. Due to the thickness difference of the pad layer 130 in different color regions, the finished anode 150 has a predetermined height difference. Among them, the red sub-pixel anode 150 has the lowest height, followed by the green one, and the blue one has the highest height. The anodes 150 of adjacent sub-pixels are naturally connected by the bevel 131 of the pad layer 130 (which can be continuous or discontinuous), ensuring the continuity of the substrate surface and reducing the adverse effects of abrupt steps on subsequent film deposition.

[0048] Step S200: Prepare the luminescent material layer 160 of the first color sub-pixel 111.

[0049] Taking a red sub-pixel with a height of 150 as the lowest anode as an example, a red luminescent material layer 160 is first prepared. This embodiment assumes that the pixel arrangement order is R / G / B side by side, but this application is not limited to this, and other arrangements are also possible.

[0050] A solution or dispersion containing red organic light-emitting material is sprayed as droplets onto the pixel unit 110 containing the target red sub-pixel using a droplet application device (such as a piezoelectric or thermal inkjet printhead). The solution may contain the host material, dopants, and high-boiling-point solvents (such as cyclohexylbenzene, benzoic acid esters, etc.), with a viscosity controlled between 2 and 20 cP and a surface tension between 25 and 40 mN / m. This step has relatively relaxed requirements for droplet placement accuracy; it is only necessary to ensure that the droplets fall within the perimeter of the target pixel unit 110, without needing to precisely hit the surface of the red anode 150. Therefore, the droplets may initially be distributed on the red anode 150 within the pixel unit 110, or they may fall on the green anode 150, blue anode 150, or even in the gaps between sub-pixels.

[0051] To concentrate droplets onto the red anode 150, droplet manipulation is achieved using the electrowetting effect. The electrowetting effect refers to the change in the apparent surface energy of the solid when a voltage is applied to the solid-liquid interface, resulting in a decrease in the liquid contact angle and an increase in wettability.

[0052] For example, see Figure 3 As shown, through the TFT driving circuit, a first positive voltage V1 (e.g., +10 to +30 V) is applied to the anode 150 of the target red sub-pixel, while a second positive voltage V2 (e.g., +3 to +10 V) is applied to the anodes 150 of the green and blue sub-pixels located in the same pixel unit 110, and V1 > V2. Since the red anode 150 has the lowest height and the highest potential, the droplet tends to flow to the lower position under the assistance of gravity. At the same time, the electrowetting effect on the surface of the red anode 150 is the strongest, the contact angle is greatly reduced, and the surface affinity for the droplet increases sharply. On the other hand, the green and blue anodes 150 have lower potentials and are located at higher positions, driving the droplets to move from these areas toward the red anode 150 and converge. For example, when a droplet initially falls on the slope 131 or gap of the pad 130 in the blue sub-pixel area, the component of gravity along the slope 131 will cause it to slide downhill; at the same time, the high potential of the red anode 150 forms a potential gradient with the surrounding area. With the assistance of the electrowetting effect, the droplet is continuously attracted and overcomes the small frictional force to move towards the red anode 150. Once it comes into contact with the high potential area of ​​the red anode 150, the stronger wetting gradient will lock it in and spread it completely across the entire surface of the red anode 150.

[0053] It is understood that, in embodiments employing an auxiliary driving electrode, the aforementioned driving voltage may also be applied to the embedded pad layer 130 or to the auxiliary electrode formed on its bottom surface, instead of being applied directly to the anode 150, thereby providing a more uniform electric field distribution while protecting the anode 150 material and further enhancing the driving capability of the droplets on the inclined surface 131.

[0054] It is worth mentioning that, in order to reduce electric field cross-interference when adjacent pixel units 110 operate simultaneously (for example, a droplet flowing towards the red anode 150 in a pixel unit 110 is mistakenly attracted by the electric field of the red anode 150 in the adjacent pixel unit 110 and deviates from the target, and then moves to the red anode 150 in the adjacent pixel unit), this application divides the preparation of the same color sub-pixel into at least two batches, and the pixel units 110 where the target sub-pixel is located in each operation are not adjacent to each other.

[0055] In one alternative embodiment, the first operation applies droplet application and voltage driving only to the odd-numbered rows (or odd-numbered columns) of pixel units 110. After the batch of droplets has completed aggregation, the second operation applies the same operation to the even-numbered rows (or even-numbered columns) of pixel units 110.

[0056] Understandably, batch division can also adopt a more sparse arrangement with multiple rows or columns, such as taking one out of every three rows; for non-standard arrangements such as Pentile, they can be grouped according to sub-pixel rendering groups (logical pixels). The basic principle is to ensure that there is at least one unoperated sub-pixel of the same color between each target sub-pixel that is simultaneously driven by voltage as an isolation, or that the physical distance between them is far enough that the electric field strength has decayed to a level that is insufficient to cause the droplet to move erroneously.

[0057] After all the droplets in the pixels of this batch have been stably gathered on the red anode 150, the solvent is removed by heating (substrate temperature of about 40 to 80°C for 1 to 10 minutes), vacuum drying (1 to 100 Pa), or infrared irradiation, so that the droplets are solidified into a solid red light-emitting film with a thickness of about 20 to 100 nm.

[0058] After all batches of red light-emitting layers have been prepared, a cathode 170 is deposited only in the red sub-pixel region using a metal mask, for example by thermally evaporating and depositing a Mg / Ag alloy (ratio 10:1, thickness approximately 10 to 20 nm) to form a local cathode 170.

[0059] Understandably, this local cathode 170 can be used as a negative voltage application terminal when subsequently electrowetting other color subpixels.

[0060] Step S300: Prepare the luminescent material layer 160 of the second color sub-pixel 112.

[0061] See Figure 4 As shown, after completing the red subpixel, the green (G) subpixel is then prepared. The green anode 150 is centered in height, higher than the red but lower than the blue.

[0062] Accordingly, droplets containing green luminescent material are sprayed onto the pixel unit 110 region where the target green sub-pixel is located using a droplet application device. The initial droplet distribution may cover the red (already containing the luminescent layer and cathode 170), green, and blue regions.

[0063] Then, a relatively large positive voltage V is applied to the anode 150 of the target green sub-pixel. G (e.g., +15 to +35V); apply a negative voltage -V to the local cathode 170 of the red sub-pixel already prepared within the same pixel unit 110. C (e.g., -5 to -20V); simultaneously, a small positive voltage V is applied to the anode 150 of the blue sub-pixel (where the light-emitting layer has not yet been fabricated). B (For example, +3 to +10V). With this voltage configuration, a value equal to (V) is formed between the negative potential of the red cathode 170 and the positive potential of the green anode 150. G +|V C The large pressure difference between the green and red anodes (150) is significantly greater than that between the anodes alone. This means that the strong electric field generates a highly significant electrowetting effect, overcoming the potential energy barrier caused by the height difference between the green and red anodes (150), allowing droplets to climb along the surface of the red region onto the green anode (150). Meanwhile, the small positive pressure of the blue anode (150) provides a gentle repulsive or guiding effect, preventing excessive migration of droplets towards the blue region and ensuring that they eventually accumulate on the green anode (150).

[0064] In some other embodiments, the cathode 170 region may also be divided into multiple sub-regions, and a negative voltage may be selectively applied by the circuit to form a finer electric field distribution, optimize the droplet climbing path, and reduce the excessive spread of droplets to adjacent sub-pixels.

[0065] Similarly, the preparation of green sub-pixels is also divided into multiple batches, and the pixel units 110 processed in the same batch are not adjacent to each other. The operation principle is the same as that of red, and will not be described in detail here.

[0066] After the droplets have assembled, they are solidified again by heating or other methods to form a green luminescent material layer 160. Subsequently, a mask is used to deposit a local cathode 170 only in the green sub-pixel region. At this point, both red and green have their own independent cathode electrodes 170.

[0067] Step S400: Prepare the luminescent material layer 160 of the third color sub-pixel 113.

[0068] See Figure 5 As shown, the blue (B) sub-pixel is finally prepared, with the highest anode height of 150. When the droplet is located in the red or green sub-pixel, the droplet must climb up from the lower red or green area, which is the most difficult to drive.

[0069] After droplets of blue luminescent material are applied, a large positive voltage V is applied to the target blue sub-pixel anode 150. B' (e.g., +20 to +40V) A negative voltage -V is simultaneously applied to the completed red sub-pixel cathode 170 and green sub-pixel cathode 170 within the pixel unit 110. C' (e.g., -5 to -20V). A strong electric field is formed between the blue anode 150 and the two low-potential cathodes 170, with a value equal to (V). B' +|V C' |), easily driving droplets to climb from the lowest red area and the middle green area to the highest blue anode 150 surface, achieving precise convergence.

[0070] The batch operation principle is the same as before. After the droplets solidify to form a blue luminescent material layer 160, a local cathode 170 can be deposited in the blue area as needed, or it can be covered together when the entire surface of the cathode 170 is formed subsequently. This application does not limit the final structure of the cathode 170, as long as it meets the electrical connection requirements of the step-by-step preparation process.

[0071] Step S500: Complete the packaging and subsequent processes.

[0072] After the luminescent material layers 160 of all colors and the corresponding cathodes 170 are prepared, thin-film encapsulation (TFE) layers are prepared according to relevant technologies, such as alternating deposition of inorganic layers (e.g., SiNx, Al2O3, 50 to 200 nm thick) and organic layers (e.g., polymer films, 1 to 5 μm thick), forming 2 to 5 cycles of stacking. Following this, subsequent processes such as cutting and bonding are performed to finally obtain the OLED display panel 100, such as... Figure 6 As shown.

[0073] Example 2 Embodiment 2 of this application provides a display panel 100, which can be manufactured by any of the methods described above, but is not limited thereto.

[0074] See Figure 2 and Figure 6 As shown, the display panel 100 may include a plurality of pixel units 110 arranged in an array, each pixel unit 110 containing at least two different colors of sub-pixels.

[0075] For example, consider red (R), green (G), and blue (B) sub-pixels. Each sub-pixel includes an anode 150, a light-emitting material layer 160 located on the anode 150, and a cathode 170 covering the light-emitting material layer 160.

[0076] In addition, described from bottom to top along the film structure, the display panel 100 may also include a driving substrate 120, a planarization layer, a padding layer 130, a reflective layer 140, an anode 150, a light-emitting material layer 160, a cathode 170, and an encapsulation layer 180.

[0077] The driving substrate 120 is provided with a TFT driving circuit and multiple insulating layers (such as buffer layer, gate insulating layer, interlayer dielectric layer, etc.) to provide a hardware foundation for active matrix driving.

[0078] A planarization layer, made of polyimide (PI) or acrylic, covers the uppermost surface of the drive substrate 120, providing a flat reference surface and protecting the circuitry below.

[0079] See Figure 2 As shown, the padding layer 130 is disposed on the planarization layer. The padding layer 130 has different thicknesses for sub-pixel regions of different colors; for example, the red sub-pixel region has a first thickness, the green region has a second thickness, and the blue region has a third thickness, with the first thickness < the second thickness < the third thickness. Since the subsequent anode 150 is disposed on the padding layer 130, the anode 150 above it also exhibits a height difference, with the red sub-pixel anode 150 having the lowest height, the green one in the middle, and the blue one the highest. The padding layer 130 forms a transition slope 131 between adjacent sub-pixels to make the height of the anode 150 change smoothly.

[0080] In some embodiments, see Figure 2 As shown, the first thickness is zero, meaning that the red sub-pixel area does not have a padding layer 130, and the anode 150 of the red sub-pixel is formed directly on the planarization layer. At this time, the padding layer 130 only exists in the green and blue sub-pixel areas.

[0081] In other embodiments, the padding layer 130 may also employ a multi-layer structure, including a bottom layer and a hydrophilic top layer, to enhance droplet spreading ability.

[0082] In other embodiments, the padding layer 130 is integrally formed with the pixel definition layer (PDL), that is, the padding layer 130 simultaneously defines the light-emitting opening area of ​​the sub-pixel, and its thicker portion naturally forms a pixel isolation structure.

[0083] It is worth mentioning that an auxiliary electrode, such as an ITO electrode, can be embedded inside or on the bottom surface of the pad layer 130 to provide an electrowetting drive voltage and reduce the voltage stress directly borne by the anode 150.

[0084] A reflective layer 140 is disposed on the inclined surface 131 of the pad layer 130, and is composed of a highly reflective metal layer and an insulating layer covering it, and is electrically insulated from the anode 150. The reflective layer 140 can reflect large-angle light emitted from the low-position sub-pixel upwards, reducing the loss of light due to absorption or blockage by the high-position structure, and improving the light extraction efficiency.

[0085] In some other embodiments, the reflective layer 140 is further integrated with a black matrix layer, for example, by superimposing a low-reflectivity light-shielding material (such as Cr, black resin) on the reflective metal layer to absorb stray light and improve contrast.

[0086] In other embodiments, the reflective layer 140 may also employ a distributed Bragg mirror (DBR) structure to enhance the reflectivity of specific wavelengths.

[0087] The anode 150 is located above the pad layer 130 and patterned to correspond to each sub-pixel. The material is ITO or a stacked structure (such as ITO / Ag / ITO). It is connected to the TFT drain through vias that penetrate the pad layer 130 and the planarization layer.

[0088] The luminescent material layer 160 contains red, green, and blue organic luminescent materials, respectively, and is located on the anode 150 of the corresponding color sub-pixels. It has a uniform thickness and clear boundaries, and the film layer formed by the above method is accurately positioned and free from color mixing.

[0089] The cathode 170 is located on the light-emitting material layer 160.

[0090] It is understandable that sub-pixels of different colors can have discrete local cathode 170 patterns, or they can form a full-surface common cathode 170 on all sub-pixels (depending on the process selection). The cathode 170 material is Mg / Ag alloy, Ag, Al, or transparent conductive oxide, etc.

[0091] The encapsulation layer 180 covers the cathode 170 to block water and oxygen and extend the device life.

[0092] In addition, the display panel 100 may also include a pixel definition layer (PDL) for defining the opening area of ​​the sub-pixels. The PDL can be prepared after the pad layer 130 and before the anode 150, or the pad layer 130 material itself can be used as the pixel definition layer, depending on the degree of process integration.

[0093] Understandably, the padding layer 130 and the pixel definition layer can be integrated into the same film layer, which can both create a height difference and isolate pixels, simplifying the manufacturing process.

[0094] This display panel 100, with an anode height difference of 150 and a reflective layer of 140 on a slope of 131, combined with the sequential fabrication method of this application from low to high, can achieve high-yield, high-resolution color inkjet-printed OLEDs, and is especially suitable for small and medium-sized display products with a pixel density of ≥300 PPI, such as smartphone screens, virtual reality (VR) devices, etc.

[0095] Based on the above technical solution, firstly, by making the anodes 150 of different color sub-pixels have different heights, and strictly preparing the light-emitting material layers 160 in order from low to high anode height, the gravitational potential energy of the droplets can assist them to naturally converge towards the lower target anode 150 after the droplets are applied, reducing the difficulty of electrowetting drive; at the same time, the voltage difference between the target anode 150 and other sub-pixel electrodes in each pixel unit 110 is used to generate an electrowetting effect, which can actively drive the droplets that initially fall in the non-target area to the surface of the target anode 150, fundamentally compensating for the landing point deviation of inkjet printing and significantly relaxing the requirements for printing accuracy.

[0096] Based on this, the luminescent material layer 160 of the same color sub-pixel is prepared in multiple batches, and it is ensured that the pixel unit 110 where the target sub-pixel is located in each operation is not adjacent to each other. This completely reduces the electric field cross-interference between adjacent pixel units 110 due to the simultaneous application of voltage, prevents droplets from being mistakenly adsorbed, and ensures the accuracy of pixel-level positioning. When preparing color sub-pixels at higher positions, a negative voltage is applied to them using the already formed sub-pixel cathode 170, creating a larger potential difference between it and the higher target anode 150. This provides sufficient driving force for the droplets to overcome gravity and climb, maintaining effective driving of each color sub-pixel.

[0097] Furthermore, a reflective layer 140 electrically insulated from the anode 150 is provided on the inclined surface 131 between adjacent sub-pixels of the padding layer 130. This layer reflects the light emitted from the lower-position sub-pixels back to the light-emitting surface, reducing shading losses from the higher-position sidewalls and improving light extraction efficiency and brightness uniformity. The above solution fully utilizes the existing anode 150 and cathode 170 of the organic light-emitting diode as electrowetting driving electrodes, eliminating the need for additional dedicated electrodes. The process is highly compatible with existing production lines, effectively improving the production yield of the high-resolution display panel 100 without significantly increasing costs.

[0098] In summary, the display panel 100 manufacturing method and the display panel 100 provided in this application effectively improve the color mixing defects caused by droplet displacement in high-resolution inkjet printed OLEDs while maintaining low cost. It has multiple advantages such as large process window, high yield, and excellent optical performance, and is especially suitable for high-end display applications such as mobile terminals, wearable devices, and VR / AR.

[0099] In the description of this specification, references to terms such as "some embodiments," "exemplarily," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. The illustrative expressions of the above terms in this specification do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0100] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application. Therefore, any changes or modifications made in accordance with the claims and description of this application should fall within the scope of this patent application.

Claims

1. A method for manufacturing a display panel, the display panel comprising a plurality of pixel units, each pixel unit comprising at least two sub-pixels of different colors, characterized in that, The preparation method includes: A driving substrate is provided, on which a plurality of anodes corresponding to sub-pixels of different colors are formed, wherein the anodes of the sub-pixels of different colors have different heights; Following the order of anode height from low to high, the luminescent material layer fabrication process is performed sequentially on sub-pixels of different colors. The fabrication process includes: A droplet containing a target color luminescent material is applied to the pixel unit region of the corresponding target sub-pixel; A voltage is applied to the anode of the target sub-pixel and the electrodes of at least some other sub-pixels located in the same pixel unit as the target sub-pixel to drive the droplet toward the anode of the target sub-pixel through an electrowetting effect; The droplets that move onto the anode of the target sub-pixel are solidified to form a light-emitting material layer of the target sub-pixel; In this process, when forming a light-emitting material layer of the same color, the operations of applying droplets and applying voltage are performed multiple times, and the pixel units of the target sub-pixels targeted by each operation are not adjacent to each other.

2. The preparation method according to claim 1, characterized in that, The step of providing the driving substrate includes: Provide a flattening layer; A padding layer is formed in at least a portion of the sub-pixel regions on the flat layer, and the padding layer has different thicknesses in sub-pixel regions of different colors; The plurality of anodes are formed on the pad layer or the flat layer such that the plurality of anodes have different heights.

3. The preparation method according to claim 2, characterized in that, The padding layer has a ramp formed between adjacent sub-pixels that have differences, and adjacent anodes are connected through the ramp; After forming the pad layer and before forming the anode, the preparation method further includes: A reflective layer is formed on the inclined surface. The reflective layer is electrically insulated from the anode and is used to reflect light emitted from the low-position sub-pixel.

4. The preparation method according to claim 1, characterized in that, The at least two different color sub-pixels include a first color sub-pixel, a second color sub-pixel, and a third color sub-pixel, and the anode height of the first color sub-pixel, the anode height of the second color sub-pixel, and the anode height of the third color sub-pixel increase sequentially. When preparing the luminescent material layer of the first color sub-pixel, the step of applying voltage includes: applying a first positive voltage to the anode of the target first color sub-pixel, applying a second positive voltage to the anode of other sub-pixels within the same pixel unit, wherein the first positive voltage is greater than the second positive voltage.

5. The preparation method according to claim 4, characterized in that, The preparation method further includes: After preparing a light-emitting material layer of one color, a cathode is formed on the light-emitting material layer; When preparing the luminescent material layer of the second color sub-pixel or the third color sub-pixel, the step of applying voltage includes: applying a positive voltage to the anode of the second color sub-pixel or the third color sub-pixel, and applying a negative voltage to at least one formed cathode, wherein the formed cathode is located on a sub-pixel within the same pixel unit on which the luminescent material layer has been prepared.

6. The preparation method according to claim 5, characterized in that, When preparing the luminescent material layer of the second color sub-pixel or the third color sub-pixel, a positive voltage is also applied to the anode of other sub-pixels in the same pixel unit that have not yet formed a luminescent material layer, and the amplitude of the applied positive voltage is less than the amplitude of the positive voltage applied to the anode of the target sub-pixel.

7. The preparation method according to claim 1, characterized in that, The operation performed in multiple steps includes a first operation and a second operation. The pixel unit where the target sub-pixel is located in the first operation and the pixel unit where the target sub-pixel is located in the second operation are arranged alternately in the row or column direction.

8. A display panel, characterized in that, include: Multiple pixel units, each pixel unit containing at least two different colors of subpixels; Planarization layer; A padding layer is disposed on the flat layer. The padding layer has different thicknesses in sub-pixel regions of different colors, and the padding layer forms a slope between adjacent sub-pixels. Multiple anodes are disposed on the pad layer and are respectively set for sub-pixels of different colors, and the anodes of the sub-pixels of different colors have different heights; A light-emitting material layer is disposed on each of the anodes; A reflective layer is disposed on the inclined surface. The reflective layer is electrically insulated from the anode and is used to reflect light emitted from the low-position sub-pixel.

9. The display panel according to claim 8, characterized in that, The display panel also includes: A cathode is disposed on the light-emitting material layer; and An encapsulation layer is applied over the cathode.

10. The display panel according to claim 9, characterized in that, The at least two different colored sub-pixels include red sub-pixels, green sub-pixels, and blue sub-pixels, wherein the anode height of the red sub-pixels, the anode height of the green sub-pixels, and the anode height of the blue sub-pixels increase sequentially.

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