A method of preventing propagation of edge cracks in a panel

Abstract

This invention discloses a method for preventing the propagation of cracks at the edge of a display panel, belonging to the field of display panel manufacturing technology. The method includes: forming a non-uniformly arrayed stress-relieving pore pattern in the edge region of the brittle layer or flexible film material of the panel through a patterning process; the pores include main holes and circumferential grooves on the sidewalls; setting coaxial stress-buffering micropillars at the bottom of the pores; and coating the inner wall of the pores and the panel edge with a gradient functional coating whose modulus gradually changes from the inside to the outside. This invention achieves gradual dissipation of crack energy through a multi-level synergistic mechanism of "circumferential grooves guiding crack direction → stress-buffering micropillars absorbing impact → gradient coating preventing cracking," solving the problems of existing technologies such as a single crack arrest mechanism, easy interface peeling, and low protection efficiency. It significantly improves dynamic bending life and interface bonding strength, and the process is compatible with existing mass production processes. It is suitable for edge crack protection of flexible OLEDs and various flexible display panels, and has good industrialization prospects.

Description

Technical Field

[0001] This invention relates to the field of display panel manufacturing technology, and in particular to a method for preventing the propagation of cracks at the edges of a panel. Background Technology

[0002] With the rapid development of display technology, flexible OLED display panels, due to their bendable and foldable characteristics, are widely used in smartphones, wearable devices, and foldable screen terminals. Throughout the entire process of production, assembly, transportation, and use of flexible panels, the panel edges are highly susceptible to microcracks due to equipment movement, manual handling and impacts, laser cutting / film cutting processes, and stress concentration effects from long-term bending. These microcracks can gradually propagate inwards, ultimately leading to display failure or product scrap.

[0003] To address the aforementioned technical problems, various edge crack protection solutions have been proposed in the prior art. For example, buffer units are added between the glass adhesive and the substrate to disperse cutting stress; partitions are set on the inorganic layer to block the crack propagation path; or isolation pillar structures are set in the panel transition area, using a composite layer structure of metal layer and inorganic insulating part to prevent cracks from invading the display area; other solutions involve coating the panel edge with an elastic adhesive layer or setting protective protrusions to absorb bending stress.

[0004] However, the above-mentioned existing technologies all have the following shortcomings: First, the crack arrest mechanism is simple and can only play a limited role under static working conditions, and its effect on inhibiting fatigue crack propagation under dynamic bending conditions is significantly insufficient; second, the interface compatibility is poor, the difference in thermal expansion coefficient between the coating or adhesive layer and the substrate is large, and the interface is prone to peeling after repeated bending, resulting in poor protective stability; third, the synergistic characteristics of the multi-layer heterogeneous structure of the panel are not considered, and there is a lack of multi-level energy dissipation mechanism, resulting in low protective efficiency.

[0005] In summary, existing technologies have not yet provided a protection solution that can simultaneously achieve multi-level energy dissipation, robust interface bonding, and high compatibility with existing manufacturing processes. Therefore, there is an urgent need to develop a novel method and structure for protecting panel edge cracks to address the industry pain point of crack propagation at the edges of flexible panels. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preventing the propagation of cracks at the edge of a panel. By constructing a synergistic protection system of "three-dimensional stress trap pores + stress buffer micropillars + gradient functional coating", the method utilizes a multi-level mechanism of circumferential grooves to guide cracks to dissipate energy, stress buffer micropillars to absorb impact energy, and gradient coatings to block residual cracks, thus systematically solving the problem of crack propagation at the edge of the panel.

[0007] To achieve the above objectives, the present invention provides a method for preventing the propagation of cracks at the edge of a panel, comprising the following steps: Step 1: In the edge region of at least one brittle layer or flexible film material of the panel, an array of stress relief pores is formed by a patterning process; the stress relief pores include a main hole that penetrates the brittle layer or flexible film material along the thickness direction, and at least one circumferential groove provided on the sidewall of the main hole. Step 2: Set stress buffer micropillars at the bottom of the stress relief pore. The stress buffer micropillars are coaxial with the main hole and their height is less than the depth of the main hole, so that there is a gap between the top of the micropillar and the opening of the main hole. When the crack extends to the bottom of the pore, the stress buffer micropillars absorb the impact energy of the crack through their own deformation, preventing the crack from penetrating the bottom of the pore and continuing to extend. Step 3: Apply a gradient functional coating to the inner wall of the stress relief pores, the inner wall of the circumferential groove, and the edge surface of the panel. The modulus of the gradient functional coating gradually decreases from the inside to the outside. The array arrangement of stress-relieving pores is non-uniform according to the stress distribution at the edge of the panel, with the pore spacing in the stress concentration area being smaller than that in the non-stress concentration area.

[0008] Preferably, the main hole is a stepped hole structure, with the hole diameter decreasing in a stepped manner from the surface of the panel to the interior, forming at least two steps. The stepped hole structure can release crack propagation energy at different depth levels, thereby improving crack arrest efficiency.

[0009] Preferably, the depth of the circumferential groove is 5% to 20% of the diameter of the main hole, and the cross-sectional shape of the circumferential groove is semi-circular, V-shaped or rectangular. The main function of the circumferential groove is to introduce the crack tip that is propagating in a straight line into the groove, forcing the crack propagation direction to deflect, thereby consuming the crack propagation energy.

[0010] Preferably, the spacing between adjacent stress relief pores is 0.5 to 2 times the pore diameter; the pore spacing in the stress concentration area is 50% to 80% of that in the non-stress concentration area.

[0011] Preferably, the stress-buffered micropillars have a cross-shaped, star-shaped, or honeycomb-shaped cross-section, and their surfaces are provided with axially extending microgrooves to guide crack energy dissipation along the micropillar axis and prevent energy from concentrating at a single point.

[0012] Preferably, the gradient functional coating comprises an inorganic nanoparticle reinforcement layer and a high-toughness organic layer arranged sequentially from the inside out.

[0013] Preferably, the inorganic nanoparticle reinforcing layer comprises nano-silica, nano-alumina, or nano-boron nitride dispersed in the organic matrix, with a modulus of 5-15 GPa, for forming a good interface match with the brittle substrate; the high-toughness organic layer is a polyimide, polyurethane, or acrylate polymer, with a modulus of 0.5-2 GPa.

[0014] Preferably, the gradient functional coating contains two-dimensional nanomaterials, such as graphene oxide or boron nitride nanosheets, which are used to enhance the crack-blocking ability of the coating.

[0015] Preferably, when the panel includes multiple brittle layers and / or flexible film materials (such as inorganic encapsulation layers, polarizers, cover windows, etc.), the stress relief pores in each layer are staggered in planar position, and the lateral misalignment distance between pores in adjacent layers is 0.5 to 1.5 times the pore diameter.

[0016] Preferably, a structure for preventing the propagation of cracks at the edge of a panel, prepared using the above method, comprises: Panel substrate; At least one brittle layer or flexible film material formed in the edge region of the panel substrate; An array of stress-relieving pores is set in the edge region of the brittle layer or flexible membrane material. The stress-relieving pores include a main hole and an circumferential groove set on the side wall of the main hole. The bottom of the main hole is provided with a stress-buffering micro-pillar coaxial with the main hole, and the height of the stress-buffering micro-pillar is less than the depth of the main hole. A gradient functional coating is applied to the inner wall of the stress relief pores, the inner wall of the circumferential grooves, and the edge surface of the panel. The modulus of the gradient functional coating gradually decreases from the inside to the outside. Among them, the stress relief pores are arranged non-uniformly according to the stress distribution at the edge of the panel, and the pore spacing in the stress concentration area is smaller than that in the non-stress concentration area. When the panel contains multiple brittle layers and / or flexible membranes, the stress relief pores of each layer are staggered in planar position.

[0017] Therefore, the method for preventing the propagation of cracks at the edge of a panel according to the present invention has the following beneficial effects: (1) This invention utilizes a multi-level energy dissipation mechanism, namely “circumferential grooves guiding crack direction → stepped holes releasing energy in layers → stress-buffered micropillars absorbing impact → gradient coating interface blocking,” to gradually consume crack propagation energy at multiple levels. In addition, compared to smart materials that rely on external triggers, the stress-buffered micropillars of this invention employ a physical structure design, absorbing crack impact energy through their own deformation, without relying on external triggering conditions such as temperature or stress waves, resulting in high reliability and low manufacturing difficulty.

[0018] (2) This invention optimizes the pore array non-uniformly based on the actual stress distribution at the panel edge, densifying the pores in stress concentration areas. This ensures crack protection while avoiding excessive weakening of the panel's mechanical strength, achieving the best balance between protection and structural strength. The gradient coating design with gradually changing modulus eliminates abrupt stress at the interface, and the anchoring structure on the inner wall of the pores achieves mechanical interlocking between the coating and the substrate, improving the interface bonding strength and significantly enhancing long-term reliability.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the arrangement of stress relief pore array at the edge of the panel in Embodiment 1 of the present invention; Figure 2 This is a schematic cross-sectional view of the stress relief pore structure in Embodiment 1 of the present invention; Figure 3 The diagram shows the cross-sectional shape of the stress-buffered micropillars in Embodiments 1 and 2 of the present invention; wherein, (a) is cross-shaped and (b) is honeycomb-shaped. Figure 4 This is a schematic diagram of the staggered arrangement of pores in the multilayer membrane material in Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of the layered structure of the gradient functional coating in Embodiment 1 of the present invention; Figure label: 1. Panel substrate; 2. Inorganic encapsulation layer; 3. Main hole; 31. Circumferential trench; 4. Stress buffer micropillar; 5. Gradient functional coating; 51. Inorganic nanoparticle reinforcement layer; 52. High-toughness organic layer; 6. Flexible film material. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0023] Example 1 This embodiment implements three-dimensional stress trap pore protection and gradient coating protection for the inorganic encapsulation layer. First, a flexible OLED panel substrate 1 with a thickness of 0.5mm and a diameter of 100mm × 100mm is selected. The panel substrate 1 contains silicon nitride (SiN). x Inorganic encapsulation layer 2 (i.e., brittle layer), with a thickness of approximately 1 μm.

[0024] Step 1: Formation of three-dimensional stress trap pores: A perforation pattern is defined at the edge of the inorganic encapsulation layer 2 using photolithography. The main holes 3 are circular in shape, 60 μm in diameter, and arranged in a single row along the edge of the panel substrate 1. Figure 1As shown. In this embodiment, the main hole 3 is configured as a coaxially connected upper wide hole and lower narrow hole. Inductively coupled plasma etching (ICP) is used, with an etching gas ratio of SF6:O2 = 3:1 and an etching power of 200W. First, the main hole 3 is formed by vertical etching. Then, by alternately changing the etching parameters, two circumferential trenches 31 are formed on the sidewall of the main hole 3. The circumferential trenches 31 are 8μm deep and have a semi-circular cross-section, as shown. Figure 2 As shown, an inorganic layer of approximately 0.2 μm thickness is retained at the bottom of the main hole 3 as a substrate.

[0025] Step 2, Setting up stress-buffered micropillars 4: A stress-buffered micropillar 4 with a cross-shaped cross-section was deposited at the center of the bottom of the pore using a focused ion beam assisted deposition process. The cross-sectional shape is as follows: Figure 3 As shown in (a), the micropillar is 0.5 μm high, with a 0.3 μm gap between its top and the bottom of the main hole 3. Microgrooves extending axially are formed on the surface of the micropillar by adjusting the deposition parameters, which guide the dissipation of crack energy along the micropillar axis.

[0026] Step 3: Non-uniform optimization layout: The stress distribution at the panel edge under bending conditions was obtained through finite element analysis. The pore spacing was set to 80 μm in stress concentration areas (the four corners of the panel and near the neutral layer during bending) and 120 μm in non-stress concentration areas. The spacing between adjacent pores was 1.3 to 2 times the pore diameter, and the spacing in stress concentration areas was 67% of that in non-stress concentration areas.

[0027] Step 4: Coating of gradient functional coating 5: A gradient functional coating 5 is applied to the panel edges and inner walls of pores using a spin coating process. For example... Figure 5 As shown, the coating consists of two layers: Bottom layer (inorganic nanoparticle reinforcement layer 51): epoxy acrylate matrix + 10wt% nano-silica, modulus of about 8GPa, thickness of 1.5μm; Surface layer (high-toughness organic layer 52): polyurethane acrylate, modulus approximately 1 GPa, thickness 2 μm.

[0028] During the coating process, a vacuum-assisted permeation process (vacuum degree 100Pa, holding time 15min) is used to ensure that the coating fully fills the inner wall of the pores and the circumferential groove 31, forming an anchoring structure.

[0029] Comparative Example 1 This comparative example uses a traditional anti-crack hole scheme, employing a circular through hole with a diameter of 60μm, without circumferential grooves or gradient coating.

[0030] The three-point bending method was used to test the panels treated in Example 1 and Comparative Example 1, as well as the untreated panel. The results showed that the average bending strength of the untreated panel was 85 MPa; the average bending strength of the panel treated with the conventional anti-crack hole scheme in Comparative Example 1 was 120 MPa; and the average bending strength of the panel treated in the steps of Example 1 was about 165 MPa.

[0031] Dynamic bending tests were conducted on three types of panels under the conditions of a bending radius of 3mm and a bending frequency of 30 times / minute. The number of bends in which the crack extended to the display area was recorded: the untreated panel showed crack penetration after about 80,000 bends; the traditional anti-crack hole solution in Comparative Example 1 showed crack penetration after about 220,000 bends; and the treated panel in Example 1 did not show crack penetration after more than 600,000 bends, at which point the test was terminated.

[0032] Comparative Example 2 This comparative example uses the same 100mm × 100mm flexible OLED panel with a thickness of 0.5mm as in Example 1. The panel contains silicon nitride (SiN). x An inorganic encapsulation layer, approximately 1 μm thick, is applied to the panel edges using a spin-coating process.

[0033] The panels treated in Example 1 and Comparative Example 2 were tested under conditions of -40°C to 85°C and 1000 cycles to observe coating peeling and crack propagation. In Comparative Example 2, microcracks appeared at the edge of the adhesive layer after 300 cycles, and localized peeling occurred after 800 cycles; while in Example 1, the coating remained intact after 1000 cycles, with no peeling or crack propagation. The adhesion between the coating and the substrate was tested using the cross-cut adhesion test (ASTM D3359). In Comparative Example 2, the conventional adhesive application method resulted in a grade 2 (partial peeling); in Example 1, the panel achieved a grade 0 (completely no peeling).

[0034] Example 2 In this embodiment, the pore protection and interlayer misalignment design of the flexible film material are carried out. A polarizer (thickness 50μm) and a cover window film (thickness 80μm) are selected as the flexible film material 6 to be processed. The two will be sequentially bonded to the OLED panel substrate 1.

[0035] Step 1, Polarizing film aperture processing: An array of stress-relieving pores was fabricated on the edge of the polarizer using an ultrafast laser cutting process (10 ps pulse width, 355 nm wavelength). The main pore 3 is elliptical, with a major axis of 300 μm and a minor axis of 150 μm. V-shaped circumferential grooves 31, 20 μm deep, are formed on the sidewalls of the main pore 3 through laser parameter modulation. The pore spacing was set based on stress analysis results: 200 μm in the bending zone and 400 μm in the non-bending zone.

[0036] Step 2, Processing the pores of the covering window film: A die-cutting process is used to create holes of the same shape along the edge of the film covering the window, but these holes are staggered in planar position from those of the polarizer holes, such as... Figure 4 As shown, the misalignment distance is 150μm.

[0037] Step 3, Setting up stress buffer micropillars 4: Using nanoimprinting technology, stress-reducing micropillars 4 with a honeycomb-shaped cross-section are formed at the bottom of the pores, with a cross-sectional shape as shown in the figure. Figure 3 As shown in (b), the height of the micropillar is 8 μm.

[0038] Step 4, Gradient Functional Coating 5: A dip-coating process is used, in which the edge of the membrane material is immersed in a gradient coating solution at a pull-out speed of 2 mm / s, forming a coating approximately 5 μm thick. The coating consists of two layers: The bottom layer is epoxy resin + 8wt% nano boron nitride, with a modulus of about 12 GPa; the top layer is polyurethane, with a modulus of about 1 GPa; and the middle layer is a gradient transition zone.

[0039] The processed polarizer and the cover window film are then sequentially bonded onto the OLED panel.

[0040] Comparative Example 3 This comparative example compares two film materials: a polarizer (50μm thick) and a cover window film (80μm thick). Both materials are treated with single-layer pores, with no misalignment or gradient coating, and then they are sequentially bonded to the OLED panel.

[0041] Comparative Example 4 Using a polarizer (50μm thick) and a cover window film (80μm thick), without any pore processing or coating treatment, the film is directly bonded to the OLED panel.

[0042] The panels processed in Example 2, Comparative Example 3, and Comparative Example 4 were tested under the conditions of a bending radius of 2 mm and a bending frequency of 40 times / minute: The untreated Comparative Example 4 panel showed polarizer cracks extending to the display area after approximately 50,000 cycles; the Comparative Example 3 panel with single-layer pore treatment showed crack penetration after approximately 180,000 cycles; and the panel of Embodiment 2 of the present invention showed no crack penetration after more than 750,000 cycles.

[0043] This indicates that the interlayer misalignment design prevents the crack from directly entering the corresponding position of the covering window film after passing through the polarizer apertures. It must extend laterally by about 150 μm before encountering the next layer of apertures. This lateral extension process further consumes crack energy, thus extending the crack propagation lifetime.

[0044] Therefore, the present invention provides a method for preventing the propagation of cracks at the edge of a panel. By constructing a multi-layered synergistic protection system of "three-energy coating" and combining it with non-uniform optimized arrangement and interlayer misaligned stress trap pores + stress buffer micropillars + gradient work design, it achieves significantly better technical effects than existing technologies in multiple dimensions such as static strength, dynamic bending life, interface reliability, and environmental adaptability, and has good industrialization prospects.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preventing the propagation of cracks at the edge of a panel, characterized in that, Includes the following steps: Step 1: In the edge region of at least one brittle layer or flexible film material of the panel, an array of stress relief pores is formed by a patterning process; the stress relief pores include a main hole that penetrates the brittle layer or flexible film material along the thickness direction, and at least one circumferential groove provided on the sidewall of the main hole. Step 2: Set stress buffer micropillars at the bottom of the stress relief pores. The stress buffer micropillars are coaxial with the main hole and their height is less than the depth of the main hole, so that there is a gap between the top of the micropillar and the opening of the main hole. Step 3: Apply a gradient functional coating to the inner wall of the stress relief pores and the edge surface of the panel. The modulus of the gradient functional coating gradually decreases from the inside to the outside. The array arrangement of stress-relieving pores is non-uniform according to the stress distribution at the edge of the panel, with the pore spacing in the stress concentration area being smaller than that in the non-stress concentration area.

2. The method for preventing the propagation of cracks at the edge of a panel according to claim 1, characterized in that: The main hole has a stepped hole structure, with its diameter decreasing in a stepped manner from the surface of the panel inward, forming at least two steps.

3. The method for preventing the propagation of cracks at the edge of a panel according to claim 2, characterized in that: The depth of the circumferential groove is 5% to 20% of the main hole diameter, and the cross-sectional shape of the circumferential groove is semi-circular, V-shaped or rectangular.

4. The method for preventing the propagation of cracks at the edge of a panel according to claim 3, characterized in that: The spacing between adjacent stress relief pores is 0.5 to 2 times the pore diameter.

5. The method for preventing the propagation of cracks at the edge of a panel according to claim 4, characterized in that: The cross-section of the stress-buffered micropillars is cross-shaped, star-shaped, or honeycomb-shaped.

6. The method for preventing the propagation of cracks at the edge of a panel according to claim 5, characterized in that: The gradient functional coating consists of an inorganic nanoparticle reinforcement layer and a high-toughness organic layer arranged sequentially from the inside out.

7. A method for preventing the propagation of cracks at the edge of a panel according to claim 6, characterized in that: The inorganic nanoparticle reinforcing layer contains nano-silica, nano-alumina, or nano-boron nitride dispersed in the organic matrix; the high-toughness organic layer is a polyimide, polyurethane, or acrylate polymer.

8. The method for preventing the propagation of cracks at the edge of a panel according to claim 7, characterized in that: The gradient functional coating contains two-dimensional nanomaterials, which are graphene oxide or boron nitride nanosheets.

9. The method for preventing the propagation of cracks at the edge of a panel according to claim 1, characterized in that: When the panel comprises multiple brittle layers and / or flexible membranes, the stress-relieving pores in each layer are staggered in planar position.

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