Preparation method of defective pixel repairable composite material optical packaging film for MLED, packaging film, MLED packaging method and defective pixel repairing method

Abstract

The invention discloses a preparation method of a defective pixel repairable composite material optical packaging film for an MLED, a packaging film, an MLED packaging method and a defective pixel repairing method, and belongs to the field of miniature light-emitting diodes. The problem that defective pixels are difficult to repair after an existing MLED display module is packaged is solved. According to the technical scheme, the method comprises the steps that a black protection solution is prepared, a release film is coated with the black protection solution to form a black protection layer, the black protection layer is coated with a thermal response bonding solution, a thermal response bonding layer is formed on the black protection layer after drying and curing treatment, and an optical regulation and control layer is prepared. The optical control layer forms a microstructure on the surface of the optical control layer through a surface processing technology, the optical control layer is attached to the thermal response bonding layer, the optical control layer and the thermal response bonding layer are compounded through hot pressing, and breakthrough improvement of repairability and optical performance of the packaging film is achieved through a material system and technology innovation of the black protection layer and the thermal response bonding layer; the invention is applied to the MLED.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro light-emitting diode packaging, in particular to a preparation method of a bad point repairable composite optical packaging film for MLED, a packaging film, an MLED packaging method and a bad point repair method. BACKGROUND

[0002] As a new generation of display technology, MLED (Mini / Micro LED, micro light-emitting diode) has been widely used in high-end televisions, commercial displays, vehicle displays and other fields due to its advantages of high brightness, high contrast, high refresh rate and long service life. However, at the same time, its precise microstructure and complex working environment have put forward strict requirements on the weather resistance, optical performance and repairability of the packaging material. However, the traditional packaging film mainly uses single functional materials, which has obvious shortcomings in actual application. The specific problems are as follows: 1. Difficulty and high cost in repairing bad points: destructive peeling of the packaging film is required when repairing bad points, which directly leads to a decrease in product yield and a significant increase in production cost; 2. Incomplete functional coverage: the existing packaging layer (such as the epoxy film mentioned in Chinese patent CN115632002B) cannot meet the functional requirements of optical regulation (including light diffusion, brightness enhancement, etc.) and mechanical protection (including moisture resistance, puncture resistance, etc.) at the same time; 3. Poor matching of thermal stability: the thermal stability of the optical regulation layer and the adhesive layer is not uniform, and the two layers of materials are prone to delamination in high-temperature process environment, affecting the packaging effect.

[0003] In the prior art, the packaging method of a low-warp mini LED display screen disclosed in Chinese patent CN115632002B can reduce the warping problem by optimizing the components of the epoxy film, but due to the single-layer structure design, this technology cannot realize the bad point repair function and lacks the necessary optical regulation ability, and still cannot fully meet the packaging needs of MLED display technology. SUMMARY

[0004] In order to solve at least one of the above technical problems, the present application proposes a preparation method of a bad point repairable composite optical packaging film for MLED, a packaging film, an MLED packaging method and a bad point repair method, which solves the problem of repairing bad points after packaging the MLED display module and optimizes the optical performance.

[0005] In order to solve the above technical problems, the technical solution adopted by the present application is as follows: a preparation method of a bad point repairable composite optical packaging film for MLED, comprising the following steps: Step S11, preparing a black protective solution, and coating the black protective solution on a release film to form a black protective layer; Step S12, coating a thermal response adhesive solution on the black protective layer, forming a thermal response adhesive layer on the black protective layer after drying and curing treatment, and the peel strength of the thermal response adhesive layer at 80-150℃ is reduced to 20% or less of the normal temperature value; Step S13, making an optical control layer, and forming a microstructure on the surface of the optical control layer through a surface processing process; Step S14, attaching the optical control layer to the thermal response adhesive layer, and compounding them by hot pressing to make the composite structure of the optical control layer and the thermal response adhesive layer reach a preset thickness, and finally obtaining a composite material optical packaging film capable of repairing the bad points of the MLED display module.

[0006] Further, the composition of the black protective layer includes thermosetting resin, black filler and curing agent; The composition of the thermal response adhesive solution includes thermal expansion microspheres and low-melting-point polymers; The composition of the optical control layer includes light diffusion microparticles.

[0007] Further, the method for making the black protective layer includes the following steps: Step A1, mixing the thermosetting resin, black filler and curing agent to form a black protective solution; Step A2, coating the black protective solution on the release film, pre-curing for a first set time, then heating to the target temperature for further curing for a second set time, and forming a hard black protective layer with uniform thickness.

[0008] Further, the method for making the thermal response adhesive layer includes the following steps: Step B1, dissolving EVA and thermal expansion microspheres in toluene to form a thermal response adhesive solution; Step B2, coating the thermal response adhesive solution on the black protective layer, and forming a thermal response adhesive layer on the black protective layer after drying treatment.

[0009] Further, the method for making the optical control layer includes the following steps: D1, substrate preparation: selecting any of the following systems to prepare the substrate layer: System A: combining silica microspheres with PMMA substrate to form a substrate layer; System B: taking polycarbonate particles and silica microparticles in a set weight ratio, melt blending and calendering to form a substrate layer; D2, surface processing: processing the surface of the substrate layer to form a microstructure, and obtaining an optical control layer.

[0010] Further, the thermosetting resin is epoxy resin or polyimide material; The black filler is nano carbon black or black metal oxide; the thermal expansion microspheres are acrylic shell / hydrocarbon core microspheres; and the light diffusion microparticles are silica microparticles or silicone microspheres.

[0011] Further, the microstructure is a prism array structure or a diffuse reflection texture structure.

[0012] Further, the pencil hardness of the black protective layer is greater than or equal to 3H, and the elastic modulus of the black protective layer is 1-5 Gpa.

[0013] Further, the thickness of the hard black protective layer matches the height of the chip of the MLED display module to be repaired, and the thickness of the hard black protective layer is 80%-95% of the height of the chip.

[0014] Further, the diameter of the thermal expansion microspheres ranges from 10 to 100 microns, and the volume expansion rate of the thermal expansion microspheres is greater than or equal to 300% at 80-150 DEG C.

[0015] Further, the haze of the optical regulation layer ranges from 70 to 100%, and the light transmittance is greater than or equal to 80%.

[0016] The packaging film is prepared by the method for preparing the composite optical packaging film for repairing a defective MLED.

[0017] The MLED packaging method comprises the following steps: Step S21, preparing the packaging film as described above; Step S22, attaching the packaging film to the PCBA board on which the chip is packaged, to ensure that the black protective layer of the packaging film is pierced by the chip, and the optical regulation layer covers the surface of the chip; Step S23, firmly adhering the optical regulation layer to the PCBA board by a hot pressing process, and completing the packaging process after drying and curing treatment.

[0018] The defective point repair method comprises the following steps: Step S31, heating the packaging film as described above packaged on the PCBA board of the MLED display module, to make the heat-responsive adhesive layer of the packaging film lose adhesion; Step S32, repairing the defective point of the MLED display module after peeling off the optical regulation layer of the packaging film; Step S33, reattaching the optical regulation layer to the black protective layer through the heat-responsive adhesive layer after repairing the defective point of the MLED display module.

[0019] The present application has the following beneficial effects compared with the prior art: Repairability: the synergistic effect of the heat-responsive adhesive layer and the black protective layer realizes the non-destructive peeling of the optical regulation layer, and the repair cost is reduced by 60%. Mechanical protection: the high hardness (3H-5H) of the black protective layer can effectively protect the circuit on the PCBA board, and the yield is improved to 99.5%; Optical performance: the microstructure of the optical control layer can improve the light efficiency of the MLED display module by 18%, and the color gamut coverage rate NTSC is 105%.

[0020] Through the material system and process innovation of the black protective layer, the heat responsive adhesive layer and the optical control layer, the repairability of the packaging film and the breakthrough improvement of the optical performance are realized, and the packaging film has significant industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0021] The application will be further described below in combination with the drawings: Figure 1 It is a cross-sectional schematic diagram of the packaging film of the application; Figure 2 It is a structural schematic diagram of the packaging film of the application covering on the PCBA board; Figure 3 It is a structural schematic diagram of the packaging film of the application and the bad point on the PCBA board cooperating with each other; Figure 4 It is a structural schematic diagram of the packaging film of the application and the PCBA board cooperating with each other after peeling off the optical control layer in the heating process; Figure 5 It is a schematic diagram of the process of repairing the bad point by laser heating the black protective layer of the application; Figure 6 It is a structural schematic diagram of the packaging film of the application and the PCBA board cooperating with each other after repairing the bad point; In the figure: 1 is the black protective layer, 2 is the heat responsive adhesive layer, 3 is the optical control layer, 4 is the thermal expansion microsphere, 5 is the solder pad, 6 is the PCBA board, 7 is the chip, 9 is the bad point, 10 is the laser heating device. DETAILED DESCRIPTION

[0022] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate relative positional or location relationship, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second" and the like are only for description purpose and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features referred to. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0023] In the description of the present application, it needs to be understood that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium, or internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0024] As shown in Figures 1 to 6 The present application provides a preparation method of a bad point repairable composite optical packaging film for MLED, which comprises the following steps: Step S11, preparing a black protective solution, and coating the black protective solution on a release film to form a black protective layer 1.

[0025] Specifically, the following steps are included: Step A1, mixing the thermosetting resin, black filler and curing agent to form a black protective solution. The thermosetting resin preferably uses epoxy resin or polyimide material, which provides high rigidity and pencil hardness through cross-linking structure, preventing scratching of PCBA circuit during assembly. The black filler is nano carbon black (particle size 20-50 nm) or black metal oxide (such as Fe3O4, Cr2O3), and the addition amount is 15-30 wt%, ensuring that the ink consistency is > 99%, and at the same time avoiding the increase of brittleness caused by excessive black filler.

[0026] Step A2, the black protective solution is coated on the release film, pre-cured at 80°C for 2 hours, and then heated to 15°C for 4 hours to form a hard black protective layer 1 with uniform thickness (CV < 5%). The pencil hardness of the black protective layer 1 is ≥ 3H, the elastic modulus of the black protective layer 1 is 1-5 Gpa, the thickness of the hard black protective layer 1 matches the height of the Micro / Mini LED chip 7 of the MLED display module to be repaired (usually 20-150 μm), and the thickness of the hard black protective layer 1 is 80-95% of the height of the Micro / Mini LED chip 7 of the MLED display module. This structure can ensure that when the black protective layer 1 is pierced by the Micro / Mini LED chip 7 of the MLED display module, the interlayer stress of the black protective layer 1 is evenly distributed, avoiding edge warping.

[0027] Step S12, a thermal response adhesive solution is coated on the black protective layer 1, and a thermal response adhesive layer 2 is formed on the black protective layer 1 after drying and curing. The peel strength of the thermal response adhesive layer 2 decreases to 20% or less of the normal temperature value at 80-150°C, and the thermal response adhesive layer has flowability at 80-150°C.

[0028] Specifically includes the following steps: B1, the thermal expansion microspheres 4 and EVA are dissolved in toluene in a certain mass ratio to form a thermal response adhesive solution, and the material selection and mechanism are as follows: Thermal expansion microspheres 4: preferably acrylic shell / hydrocarbon core microspheres (diameter 10-100 μm), volume expansion rate ≥ 300% at 80-150°C, and the voids formed after expansion make the adhesion force drop to 20% or less of the normal temperature.

[0029] Low-melting-point polymer: ethylene-vinyl acetate copolymer (EVA, melting point 80-100°C) or polycaprolactone (PCL, melting point 60-90°C), which loses adhesion after melting, achieving non-destructive peeling.

[0030] Synergistic effect: thermal expansion microspheres 4 and EVA are compounded in a mass ratio of 3:7, which not only ensures the adhesion strength at normal temperature (peel strength ≥ 5 N / cm), but also quickly fails after heating.

[0031] B2, the thermal response adhesive solution is coated on the black protective layer 1, and a thermal response adhesive layer 2 (thickness 20-50 μm) is formed on the black protective layer 1 after drying at 60°C.

[0032] Step S13, making an optical control layer 3, and forming a microstructure on the surface of the optical control layer 3 by surface processing technology. Specifically includes the following steps: D1, substrate preparation: select any of the following systems to prepare the substrate layer: System A: silica microspheres (particle size 2-20 μm) are compounded with PMMA base material to form a base material layer; System B: polycarbonate particles and silica particles are taken in a set weight ratio, melt blended, and then calendered into a base material layer; The light transmittance of the PMMA base material or polycarbonate particles is ≥80%, the yellowing resistance index ΔE is <1.5 (1000 h aging test); the silica particle addition amount is 5-15 wt%, the haze is adjusted to 70-100%, and the light cross talk between MLED display module pixels is eliminated; D2, surface processing: the surface of the base material layer is processed to form a microstructure, and an optical regulation layer 3 with a haze of 70-100% and a light transmittance of ≥80% is obtained; The microstructure is a prism array structure or a diffuse reflection texture structure, the prism array structure has a height of 10-50 μm to increase the light extraction efficiency by 15-20%, and the diffuse reflection texture structure has a roughness Ra=0.2-2 μm to achieve uniform light emission in a wide viewing angle.

[0033] Step S14, the optical regulation layer 3 is attached to the heat-responsive adhesive layer 2, and the two are compounded by hot pressing to make the composite structure of the optical regulation layer 3 and the heat-responsive adhesive layer 2 reach a preset thickness, and finally a composite material optical packaging film for repairing bad points of an MLED display module is obtained.

[0034] To make the structure features, technical means and specific purposes and functions of the present application clearer, the present application will be further described in detail below with reference to the drawings and specific examples: Example 1:

[0035] Manufacture of the black protective layer 1: 70 wt% of epoxy resin (EPON828), 25 wt% of carbon black (VXC-72R) and 5 wt% of curing agent are mixed to form a black protective solution, the black protective solution is coated on a release film to form a black protective layer 1 with a thickness of 50 μm and a pencil hardness of 4H; Manufacture of the heat-responsive adhesive layer 2: 70 wt% of EVA (VA content 28%) and 30 wt% of acrylic microspheres (Expancel 051DU40) are dissolved in toluene to form a heat-responsive adhesive solution, the heat-responsive adhesive solution is coated on the surface of the black protective layer 1 and then dried and cured to form a heat-responsive adhesive layer 2 with a thickness of 30 μm; Fabrication of optical regulation layer 3: silica microspheres (particle size 5 pm) are compounded with PMMA substrate to form a substrate layer, a prism array structure is formed on the surface of the substrate layer by UV imprinting, the surface prism height is 30 pm, the haze is 85%, the light transmittance is 91%, and the optical regulation layer 3 is compounded with the heat-responsive adhesive layer 2 by hot pressing process (pressure 0.5 MPa, temperature 80°C, time 10 s), so that the thickness of the composite structure composed of the optical regulation layer 3 and the heat-responsive adhesive layer 2 reaches 130 pm.

[0036] The encapsulation film fabricated by the method of Example 1 is used to repair the bad points of the MLED display module, the MLED display module is heated at a temperature of 120°C for 10 minutes, and the residual condition of the black protective layer 1 is detected by weight method (or image analysis method) after the optical regulation layer 3 is peeled off. The results show that the residual rate of the black layer is 99.3%, indicating that the heating process can realize the lossless peeling of the optical layer, and the black layer has good integrity. After the new chip 7 is laser welded by the laser heating device 10, the optical regulation layer 3 is reattached to the heat-responsive adhesive layer 2, and the brightness uniformity difference is less than 3%. Example 2:

[0037] Fabrication of black protective layer 1: mix epoxy resin E44 (100 parts by weight), carbon black (15 parts), and curing agent methyl tetrahydrophthalic anhydride (25 parts) to form a black protective solution, coat the black protective solution on a PET release film, and cure to form a black protective layer 1 with a thickness of 100 pm, a curing temperature of 12°C, and a curing time of 2 hours; Fabrication of heat-responsive adhesive layer 2: dissolve acrylic pressure-sensitive adhesive (80 parts) and heat-expandable microspheres 4 (20 parts, 5 times volume expansion at 90°C) in toluene to form a heat-responsive adhesive solution, coat the heat-responsive adhesive solution on the surface of the black protective layer 1, and dry and cure to form a heat-responsive adhesive layer 2 with a thickness of 30 pm. Fabrication of optical regulation layer 3: melt and blend polycarbonate particles (95 wt%) and silica particles (5 wt%, diameter 2 pm) to form a film, which is a substrate layer, form a prism array structure on the surface of the substrate layer by UV imprinting, the surface prism has a haze of 85% and a light transmittance of 91%, and the optical regulation layer 3 is compounded with the heat-responsive adhesive layer 2 by hot pressing process (pressure 0.5 MPa, temperature 80°C, time 10 s), so that the thickness of the composite structure composed of the optical regulation layer 3 and the heat-responsive adhesive layer 2 reaches 120 pm.

[0038] When the encapsulating film prepared by the method of Example 2 is used to repair the bad point 9 on the MLED display module, the MLED display module board is heated at 100℃ for 15 minutes, and the residual condition of the black protective layer 1 is detected by weight method (or image analysis method) after the optical regulation layer 3 is peeled off. The result shows that the residual rate of the black layer is 99.9%, indicating that the heating process can realize the lossless peeling of the optical layer, and the black layer has good integrity. After the new chip 7 is laser welded by the laser heating device 10, the optical regulation layer 3 is reattached to the heat-responsive adhesive layer 2, and the brightness uniformity difference is less than 3%.

[0039] Peeling force test: The peeling strength tester (such as GB / T2792-2014 standard) is used to test the peeling force of the optical regulation layer 3 and the heat-responsive adhesive layer 2 in a normal temperature environment, and the result is 5.2N / cm; the temperature of the test environment is increased to 100℃, and the peeling force at the same position is tested again, and the result is reduced to 0.8N / cm, indicating that the optical regulation layer 3 has the temperature response characteristics of “high adhesion at normal temperature and easy peeling at high temperature”; The encapsulating film prepared by the method of repairing the MLED bad point of the composite material optical encapsulating film.

[0040] The MLED encapsulating method provided by the application comprises the following steps: Step S21, preparing the encapsulating film described above; Step S22, attaching the encapsulating film to the PCBA board 6 encapsulating the chip 7, and the hot pressing parameters are 120℃ / 1MPa / 30s, so as to ensure that the black protective layer 1 of the encapsulating film is pierced by the chip 7 on the PCBA board 6, the heat-responsive adhesive layer 2 fully wets the solder pad 5 of the PCBA board 6, and the optical regulation layer 3 covers the surface of the chip 7 on the PCBA board 6; Step S23, firmly adhering the optical regulation layer 3 to the PCBA board 6 by the hot pressing process, and the encapsulating process is completed after drying and curing treatment.

[0041] The bad point repairing method provided by the application comprises the following steps: Step S31, heating (heating temperature: 80-150℃) the encapsulating film described above encapsulating the PCBA board 6 of the MLED display module, so that the heat-responsive adhesive layer 2 of the encapsulating film is in a molten state, so that the heat-responsive adhesive layer 2 loses adhesion; the heating temperature in this embodiment is 120℃.

[0042] Step S32, removing the optical regulation layer 3 of the encapsulating film, and repairing the bad point 9 of the MLED display module by laser.

[0043] When the optical regulation layer 3 of the encapsulation film is peeled off, the mechanism is as follows: after the encapsulation film encapsulated on the MLED display module PCBA board is heated, the hydroxyl (-OH) in the molecular structure of the thermosetting resin in the black protective layer 1 of the encapsulation film will form a stable hydrogen bond with the carbonyl oxygen (C=O) or ether oxygen (-O-) in the low-melting-point polymer (such as EVA) molecules in the heat-responsive adhesive layer 2, and the heating environment not only drives the formation of the hydrogen bond, but also further promotes the diffusion movement of the molecular chains in the black protective layer 1 and the heat-responsive adhesive layer 2 and accelerates the chemical reaction between the two layers. This series of changes at the molecular level will significantly enhance the bonding strength of the adhesive interface between the two layers, providing a structural basis for the stable peeling of the optical regulation layer 3. At the same time, if the heat-responsive adhesive layer 2 is pre-plasma treated, the surface polarity of the heat-responsive adhesive layer 2 can be effectively improved. This increase in polarity can further strengthen the interaction between the heat-responsive adhesive layer 2 and the thermosetting resin in the black protective layer 1, not only enhancing the hydrogen bond between the two layers, but also promoting the formation of chemical bonds, thereby further optimizing the bonding performance of the two layers. Therefore, after heating, the bonding force between the heat-responsive adhesive layer 2 and the black protective layer 1 will be significantly improved. If further improvement of the bonding effect is needed, an additional plasma treatment step can be added during the film formation of the heat-responsive adhesive layer 2 and the black protective layer 1.

[0044] In combination with the above-mentioned strengthening effect of heating and plasma treatment on the bonding force of the heat-responsive adhesive layer 2 and the black protective layer 1, the non-destructive peeling of the optical regulation layer 3 can be further ensured. During the operation of peeling off the optical regulation layer 3, the problem of "accidental peeling" caused by insufficient bonding force can be effectively avoided, ensuring that the heat-responsive adhesive layer 2 will not fall off from the surface of the black protective layer 1 with the peeling of the optical regulation layer 3, thereby maintaining the stability of the encapsulation structure.

[0045] Step S33, after the bad point 9 of the MLED display module is repaired, the optical regulation layer 3 is reattached to the black protective layer 1 through the heat-responsive adhesive layer 2. When reattaching, the residual adhesion (recovery rate > 85%) of the heat-responsive adhesive layer 2 is used to realize secondary adhesion.

[0046] It should be noted that the connection relationship between the components and modules of the present application is determined and can be realized. Except for the special description in the embodiments, the specific connection relationship can bring about the corresponding technical effects, and based on the premise of not relying on the corresponding software program execution, the technical problems proposed by the present application are solved. The model of the components, modules, specific elements, the connection mode between them, and the conventional use method and the expected technical effects brought by the above technical features, except for the specific description, all belong to the public content that can be obtained by the prior art before the application date, such as patents, journal papers, technical manuals, technical dictionaries, textbooks, or belong to the existing technology of the conventional technology and common knowledge in the art, and do not need to be described in detail. The technical solutions provided in the present application are clear, complete, and can be realized, and the corresponding entity products can be reproduced or obtained according to the technical means.

[0047] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a composite optical encapsulation film for MLEDs that can repair defects, characterized in that: The method comprises the following steps: Step S11, a black protective solution is prepared, and the black protective solution is coated on a release film to form a black protective layer (1); Step S12, a thermal response adhesive solution is coated on the black protective layer (1), and a thermal response adhesive layer (2) is formed on the black protective layer (1) after drying and curing treatment, and the peel strength of the thermal response adhesive layer (2) at 80-150 DEG C is reduced to 20% or less of the normal temperature value; Step S13, an optical control layer (3) is prepared, and a microstructure is formed on the surface of the optical control layer (3) through a surface processing process; Step S14, the optical control layer (3) is attached to the thermal response adhesive layer (2), and the two are compounded by hot pressing, so that the composite structure of the optical control layer (3) and the thermal response adhesive layer (2) reaches a preset thickness, and finally a composite material optical packaging film of a bad point (9) of a repairable MLED display module is obtained.

2. The method of claim 1, wherein the method further comprises: The black protective layer (1) comprises a thermosetting resin, a black filler and a curing agent; The thermal response adhesive solution comprises thermal expansion microspheres (4) and a low-melting-point polymer; The optical control layer (3) comprises light diffusion particles.

3. The method of claim 2, wherein the method further comprises: The method for preparing the black protective layer (1) comprises the following steps: Step A1, the thermosetting resin, the black filler and the curing agent are mixed to form a black protective solution; Step A2, the black protective solution is coated on a release film, pre-cured for a first set time, heated to a target temperature for a second set time for curing, and a hard black protective layer (1) with uniform thickness is formed.

4. The method of claim 2, wherein the method further comprises: The method for preparing the thermal response adhesive layer (2) comprises the following steps: Step B1, the EVA and the thermal expansion microspheres (4) are dissolved in toluene to form a thermal response adhesive solution; Step B2, the thermal response adhesive solution is coated on the black protective layer (1), and a thermal response adhesive layer (2) is formed on the black protective layer (1) after drying treatment.

5. The method of claim 1, wherein the method further comprises: The method for preparing the optical control layer (3) comprises the following steps: D1, substrate preparation: any of the following systems is selected to prepare a substrate layer: System A: silica microspheres are combined with a PMMA substrate to form a substrate layer; System B: polycarbonate particles and silica particles are taken in a set weight ratio, melt blended and calendered into a substrate layer; D2, surface processing: the surface of the substrate layer is processed to form a microstructure, and an optical control layer (3) is obtained.

6. The method of claim 2, wherein the method further comprises: The thermosetting resin is an epoxy resin or a polyimide material; The black filler is nano carbon black or a black metal oxide; the thermal expansion microspheres (4) are acrylic shell / hydrocarbon core microspheres; and the light diffusion particles are silica particles or silicone microspheres.

7. The method of claim 1, wherein the method further comprises: The microstructure is a prism array structure or a diffuse reflection texture structure.

8. The method of claim 1, wherein the method further comprises: The black protective layer (1) has a pencil hardness of 3H or more, and an elastic modulus of 1-5 Gpa.

9. The method of claim 1, wherein the method further comprises: The thickness of the hard black protective layer (1) matches the height of a chip (7) of an MLED display module to be repaired, and the thickness of the hard black protective layer (1) is 80%-95% of the height of the chip (7).

10. The method of claim 2, wherein the method further comprises: The thermal expansion microspheres (4) have a diameter ranging from 10 to 100 μm, and a volume expansion rate ≥ 300% at 80-150 ℃.

11. The method of claim 1, wherein the method further comprises: The optical regulation layer (3) has a haze ranging from 70 to 100% and a light transmittance ≥ 80%.

12. An encapsulation film, characterized by The encapsulation film is prepared by the method of claim 1-11.

13. A method of packaging MLEDs, characterized by, The method comprises the following steps: Step S21, preparing the encapsulation film of claim 12; Step S22, attaching the encapsulation film to the PCBA board (6) encapsulating the chip (7), ensuring that the black protective layer (1) of the encapsulation film is pierced by the chip (7) and the optical regulation layer (3) covers the surface of the chip (7); Step S23, firmly adhering the optical regulation layer (3) to the PCBA board (6) by a hot pressing process, and completing the encapsulation process after drying and curing treatment.

14. A bad pixel repair method characterized by, The method comprises the following steps: Step S31, heating the encapsulation film of claim 12 encapsulated on the PCBA board (6) of the MLED display module, so that the thermal response adhesive layer (2) of the encapsulation film loses adhesion; Step S32, repairing the bad point (9) of the MLED display module after peeling off the optical regulation layer (3) of the encapsulation film; Step S33, re-attaching the optical regulation layer (3) to the black protective layer (1) through the thermal response adhesive layer (2) after repairing the bad point (9) of the MLED display module.

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