An LED packaging structure, an LED display module, a preparation method of the LED display module, and a display screen

Abstract

This invention belongs to the field of LED display technology, and particularly relates to an LED packaging structure, an LED display module, its manufacturing method, and a display screen. Compared with the prior art, this invention, by setting a black-doped high-refractive-index layer between the substrate and the LED chip, utilizes its light absorption properties to effectively absorb ambient stray light and lateral light leakage from the chip, significantly reducing the surface reflection brightness when the screen is black, thereby greatly improving the contrast of the display screen; by setting a matte hydrophobic layer on the outermost layer, a special micro-fine surface rough structure is constructed, which transforms the strong ambient light illuminating the screen surface from specular reflection into soft diffuse reflection, thereby effectively eliminating glare, avoiding strong light glare, and improving the viewing comfort and image readability of viewers in different lighting environments; by combining a dense epoxy encapsulation layer and a low surface energy matte hydrophobic layer, a double protective barrier is constructed, thereby significantly improving the reliability and service life of the display screen in humid, rainy, or dusty environments.

Description

Technical Field

[0001] This invention belongs to the field of LED display technology, and particularly relates to an LED packaging structure, an LED display module, its preparation method, and a display screen. Background Technology

[0002] As LED display technology advances towards smaller pitches and higher pixel density, COB (Chip on Board) technology, by directly bonding LED chips onto a PCB and encapsulating them as a whole, offers advantages such as high protection, high reliability, and the ability to achieve high density, and has been widely used in the Mini / Micro LED display field. However, in practical applications, COB-LED displays still have several common problems in terms of display effect and environmental reliability, especially in areas such as contrast ratio, black screen consistency (black screen consistency), anti-glare, and waterproof protection, where the following issues remain:

[0003] 1) Contrast and black screen consistency issues

[0004] The contrast ratio of a COB display depends not only on the brightness and driving capability of the LED chip, but also on the reflectivity of the screen surface in a dark environment. Since COB packaging typically uses a transparent or semi-transparent encapsulating adhesive (such as epoxy resin or silicone) to cover the chip and PCB surface, and the PCB substrate, circuit pads, and traces often have different background colors such as green, black, or white, they are prone to surface reflection under ambient light, resulting in insufficient black levels and reduced overall screen contrast. Although COB packaging eliminates the SMD support structure, structurally increasing the "black area," in actual products, differences in PCB background color, metallic reflections from pads and traces, and the non-uniformity of encapsulating adhesive thickness and refractive index all cause significant differences in blackness and brightness in different areas when the screen is black. This results in poor color consistency, creating visible "mosaic" or blocky color differences, severely affecting the overall appearance and display integrity.

[0005] 2) Anti-glare issues

[0006] COB (Chip-on-Board) encapsulation typically results in a smooth or slightly rough transparent gel layer. Under strong ambient light (such as natural light, stage lighting, and office lighting), this layer is prone to specular or strong directional reflection, producing noticeable glare. Glare not only reduces image readability but also causes eye strain, impacting the viewing experience over extended periods. In existing technologies, some manufacturers reduce specular reflection by applying a matte film, AG (Anti-Glare) coating, or adding matting agents to the encapsulation gel, thus reducing glare by causing diffuse reflection of incident light. However, simply introducing a matte layer or matting agent to reduce glare often comes at the cost of decreased resolution and sharpness, as well as degradation of anti-glare performance due to coating wear, contamination, or aging over long-term use. A balance between sharpness, anti-glare, and durability is difficult to achieve.

[0007] 3) Waterproofing and stain resistance issues

[0008] While COB packaging offers better moisture and dust resistance compared to SMD packaging, it still faces risks from rain, moisture, salt spray, and cleaning liquids in outdoor or semi-outdoor applications. Traditional epoxy or silicone encapsulation layers, although possessing some water resistance, have relatively high surface energy, making water droplets spread easily and difficult to slide off. In prolonged humid and hot environments, moisture may penetrate along the colloid-PCB interface, leading to circuit corrosion, solder joint oxidation, and decreased reliability. Furthermore, the high surface energy makes it easy for dust and oil to adhere, making cleaning difficult and further affecting display quality and appearance. Summary of the Invention

[0009] In view of this, the technical problem to be solved by the present invention is to provide an LED packaging structure, an LED display module and a display screen that simultaneously have high optical performance, surface protection performance and environmental adaptability.

[0010] This invention provides an LED packaging structure, comprising a black-doped high-refractive-index layer, an epoxy encapsulation layer, and a matte hydrophobic layer stacked together;

[0011] The black-doped high-refractive-index layer is formed by black-doped high-refractive-index adhesive;

[0012] The black-doped high-refractive-index adhesive comprises a first multifunctional polyurethane acrylate, a high-refractive-index acrylate, surface-treated high-refractive-index nanoparticles, melanin particles, and a first photoinitiator.

[0013] The mass of the first multifunctional polyurethane acrylate is 30% to 70% of the mass of the black-doped high-refractive-index adhesive;

[0014] The mass of the high refractive index acrylate is 10% to 30% of the mass of the black-doped high refractive index adhesive;

[0015] The mass of the surface-treated high-refractive-index nanoparticles is 20% to 40% of the mass of the black-doped high-refractive-index adhesive;

[0016] The mass of the melanin particles is 0.01% to 0.1% of the mass of the black-doped high-refractive-index adhesive;

[0017] The mass of the first photoinitiator is 1% to 10% of the mass of the black-doped high-refractive-index adhesive;

[0018] The matte hydrophobic layer is formed by matte hydrophobic adhesive;

[0019] The matte hydrophobic adhesive comprises a second multifunctional polyurethane acrylate, a multifunctional acrylate monomer, matte particles, a hydrophobic additive, and a second photoinitiator.

[0020] The mass of the second multifunctional polyurethane acrylate is 50% to 70% of the mass of the matte hydrophobic adhesive;

[0021] The mass of the multifunctional acrylate monomer is 5% to 20% of the mass of the matte hydrophobic adhesive;

[0022] The mass of the matte particles is 5% to 20% of the mass of the matte hydrophobic adhesive;

[0023] The mass of the hydrophobic additive is 1% to 10% of the mass of the matte hydrophobic adhesive;

[0024] The mass of the second photoinitiator is 1% to 10% of the mass of the matte hydrophobic adhesive;

[0025] The functionality of the first multifunctional polyurethane acrylate and the second multifunctional polyurethane acrylate is each independently greater than or equal to 6.

[0026] The high-refractive-index acrylate has a refractive index greater than or equal to 1.55;

[0027] The high refractive index nanoparticles have a refractive index greater than or equal to 1.9;

[0028] The functionality of the multifunctional acrylate monomer is greater than or equal to 2.

[0029] Preferably, the functionality of the first multifunctional polyurethane acrylate and the second multifunctional polyurethane acrylate is independently 6 to 10.

[0030] The first multifunctional polyurethane acrylate and the second multifunctional polyurethane acrylate are each independently selected from aliphatic polyurethane acrylates.

[0031] The functionality of the multifunctional acrylate monomer is 2 to 6;

[0032] The high refractive index acrylate is selected from one or more of o-phenylphenoxyethyl acrylate, biphenylmethanol acrylate, bicyclophenoxyethyl acrylate, bisphenol A epoxy diacrylate, bisphenol F epoxy diacrylate, and ethoxylated bisphenol fluorene diacrylate.

[0033] Preferably, the first multifunctional polyurethane acrylate and the second multifunctional polyurethane acrylate are each independently selected from one or more of the following: Arkema's CN9276, CN9667, CN9013, CN9018, CN991; IGM Resins' Photomer6720, Photomer6892, Photomer6008, Photomer6010, Photomer6210; Allnex's EBECRYL8701, EBECRYL8703, EBECRYL8314, EBECRYL8606, EBECRYL896; and MIWON's MIRAMERPU600, MIRAMERPU610, MIRAMERPU620, MIRAMERPU900, and MIRAMERM600.

[0034] The multifunctional acrylate monomer is selected from one or more of the following: 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, dipropylene glycol diacrylate, cyclohexanediol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, and dipentaerythritol penta / hexaacrylate.

[0035] The high refractive index nanoparticles are selected from one or more of metal oxides, metal oxide composite particles and metal sulfides; the volume median particle size D50 of the high refractive index nanoparticles is 5~100 nm, and the particle size distribution PDI≤0.3.

[0036] The original particle size of the melanin particles is 10~30 nm; the average particle size of the aggregates of the melanin particles in the high refractive index glue is 80~200 nm.

[0037] The first photoinitiator and the second photoinitiator are each independently selected from one or more of the following: biphenyl ketal photoinitiators, α,α-dialkoxyacetophenone photoinitiators, α-hydroxyalkylphenyl ketone photoinitiators, α-aminoalkylphenyl ketone photoinitiators, and acylphosphine oxide photoinitiators;

[0038] The median particle size of the matte particles is 1~12 μm, and the particle size distribution (PDI) is ≤1.5.

[0039] The hydrophobic additive is selected from UV-curable silicone hydrophobic additives and / or UV-curable fluorinated hydrophobic additives.

[0040] Preferably, the epoxy encapsulation layer is formed of epoxy encapsulant; the epoxy encapsulant includes epoxy resin, epoxy toughening agent and curing agent; the mass of epoxy resin is 40% to 50% of the mass of epoxy encapsulant; the mass of epoxy toughening agent is 5% to 20% of the mass of epoxy encapsulant; and the mass of curing agent is 40% to 50% of the mass of epoxy encapsulant.

[0041] Preferably, the epoxy equivalent of the epoxy resin is 0.25~1 eq / 100 g;

[0042] And / or, the epoxy toughening agent is selected from one or more of the following: carboxyl-terminated butadiene-acrylonitrile copolymer, amino-terminated butadiene-acrylonitrile copolymer, core-shell rubber particles, epoxy resin masterbatch containing core-shell rubber particles, long-chain aliphatic flexible epoxy compound, cycloaliphatic flexible epoxy compound, epoxy-terminated polyurethane toughening agent, and epoxy-terminated polyurethane prepolymer toughening agent.

[0043] And / or, the curing agent is selected from anhydride thermosetting agents.

[0044] Preferably, the thickness of the black-doped high-refractive-index layer is 10~100 μm;

[0045] The thickness of the epoxy encapsulation layer is 100~300 μm;

[0046] The thickness of the matte hydrophobic layer is 5~50 μm.

[0047] Preferably, the black-doped high-refractive-index layer has an average refractive index of 1.6 to 1.8 in the visible light band;

[0048] The water contact angle of the matte hydrophobic layer is greater than or equal to 110°;

[0049] The haze of the matte hydrophobic layer is 10%~50%;

[0050] The pencil hardness of the matte hydrophobic layer is greater than or equal to 3H.

[0051] The present invention also provides an LED display module, including the above-described LED packaging structure.

[0052] The present invention also provides a method for manufacturing the above-mentioned LED display module, comprising the following steps:

[0053] S1) Provide a semi-finished LED display module; the semi-finished LED display module includes a substrate and a plurality of LED chips disposed on the substrate;

[0054] S2) Transfer the black-doped high-refractive-index adhesive to the substrate surface and the gaps between several LED chips, and cure it to form a black-doped high-refractive-index layer;

[0055] S3) Transfer the epoxy encapsulant to the surface of the black-doped high-refractive-index layer and cure it to form an epoxy encapsulant layer;

[0056] S4) Transfer the matte hydrophobic adhesive to the surface of the epoxy encapsulation layer, allow it to stand and level, and cure to obtain the LED display module.

[0057] The present invention also provides a display screen, including the LED display module described above.

[0058] Compared with the prior art, the LED packaging structure provided by the present invention has the following advantages:

[0059] 1) Improve contrast and ink color consistency: This invention sets a black-doped high-refractive-index layer between the substrate and the LED chip. The light absorption properties of this layer effectively absorb ambient stray light and lateral light leakage from the chip, significantly reducing the surface reflection brightness when the screen is black, thereby greatly improving the contrast of the display screen. At the same time, through the whole-surface coating and uniform design of this layer, the visual differences caused by substrate color difference and pad reflection are eliminated, ensuring that the whole screen presents a highly consistent deep ink color in black screen or dark field state, solving the display defects such as uneven ink color and mosaic effect of traditional COB screens.

[0060] 2) Effective anti-glare: This invention achieves effective glare reduction by creating a matte hydrophobic layer on the outermost layer, constructing a special micro-rough surface structure. This transforms strong ambient light incident on the screen surface from specular reflection into soft diffuse reflection, effectively eliminating glare, avoiding harsh light, and improving viewing comfort and image readability under different lighting conditions. Simultaneously, this matte hydrophobic layer is UV-cured, achieving a hardness ≥3H, significantly enhancing its mechanical strength.

[0061] 3) Enhanced Waterproofing, Stain Resistance, and Weather Resistance: This invention constructs a dual protective barrier by combining a dense epoxy encapsulation layer with a low surface energy matte hydrophobic layer. The epoxy layer provides a basic physical seal to prevent moisture penetration; the matte hydrophobic layer utilizes its hydrophobic properties, with a water contact angle ≥120°, making it difficult for water droplets to adhere and easy to roll off. It also possesses self-cleaning functions, including dustproofing, oil resistance, and easy cleaning, thereby significantly improving the reliability and lifespan of the display screen in humid, rainy, or dusty environments.

[0062] 4) Balancing light efficiency and display quality: While improving contrast and protection performance, this invention optimizes light path transmission and reduces total internal reflection loss by using high refractive index materials as the encapsulation substrate. This ensures that the display screen maintains high blackness and high protection without sacrificing or even improving light output efficiency and brightness, achieving a perfect balance between high image quality and high reliability.

[0063] Experimental results show that the LED display module prepared by this invention has a corrected display brightness of 800 nits and a static contrast ratio of ≥15000:1; good black screen consistency and no obvious color difference visible to the naked eye; surface haze of 25%~45%, good anti-glare performance; surface hardness ≥3H, surface water contact angle ≥120°, good protective performance; after 500 h of damp heat aging test (85℃, RH85%) and 500 cycles of cold and thermal shock test (-40℃~80℃), the brightness loss is ≤3%, the static contrast ratio is ≥15000:1, and the static contrast ratio loss rate after aging is ≤3%. Attached Figure Description

[0064] Figure 1 This invention provides a schematic diagram of the structure of a specific LED display module;

[0065] Figure 2 This invention provides a schematic diagram of a specific LED display module manufacturing process.

[0066] Figure 3 This is a physical image of the LED display module obtained in Embodiment 1 of the present invention. Detailed Implementation

[0067] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0068] This invention provides an LED packaging structure, comprising a black-doped high-refractive-index layer, an epoxy encapsulation layer, and a matte hydrophobic layer stacked together; the black-doped high-refractive-index layer is formed by a black-doped high-refractive-index adhesive; the black-doped high-refractive-index adhesive comprises a first multifunctional polyurethane acrylate, a high-refractive-index acrylate, surface-treated high-refractive-index nanoparticles, melanin particles, and a first photoinitiator; the mass of the multifunctional polyurethane acrylate is 30%~70% of the mass of the black-doped high-refractive-index adhesive; the mass of the high-refractive-index acrylate is 10%~30% of the mass of the black-doped high-refractive-index adhesive; the mass of the surface-treated high-refractive-index nanoparticles is 20%~40% of the mass of the black-doped high-refractive-index adhesive; the mass of the melanin particles is 0.01%~0.1% of the mass of the black-doped high-refractive-index adhesive; the mass of the first photoinitiator is 1%~10% of the mass of the black-doped high-refractive-index adhesive; the matte hydrophobic layer is formed by a matte hydrophobic adhesive. The matte hydrophobic adhesive comprises a second multifunctional polyurethane acrylate, a multifunctional acrylate monomer, matte particles, a hydrophobic additive, and a second photoinitiator; the mass of the second multifunctional polyurethane acrylate is 50% to 70% of the mass of the matte hydrophobic adhesive; the mass of the multifunctional acrylate monomer is 5% to 20% of the mass of the matte hydrophobic adhesive; the mass of the matte particles is 5% to 20% of the mass of the matte hydrophobic adhesive; the mass of the hydrophobic additive is 1% to 10% of the mass of the matte hydrophobic adhesive; the mass of the second photoinitiator is 1% to 10% of the mass of the matte hydrophobic adhesive; the functionality of the first multifunctional polyurethane acrylate and the second multifunctional polyurethane acrylate is independently greater than or equal to 6; the refractive index of the high-refractive-index acrylate is greater than or equal to 1.55; the refractive index of the high-refractive-index nanoparticles is greater than or equal to 1.9; and the functionality of the multifunctional acrylate monomer is greater than or equal to 2.

[0069] In this invention, there are no special restrictions on the source of any raw materials; they can be commercially available.

[0070] The bottom layer of the LED packaging structure provided by the present invention is a black-doped high refractive index layer; the thickness of the black-doped high refractive index layer is preferably 10~100 μm; optionally, the thickness of the black-doped high refractive index layer is 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or any two of the above values.

[0071] In this invention, the black-doped high-refractive-index layer is formed by black-doped high-refractive-index adhesive to improve contrast and ink color consistency. It needs to be uniformly filmed in the gaps between LED chips and on the surface of the substrate, and must take into account optical properties such as high refractive index and moderate light absorption, as well as mechanical reliability such as hardness, adhesion, and weather resistance. Through a UV curing system of a first multifunctional polyurethane acrylate, a high-refractive-index acrylate, surface-treated high-refractive-index nanoparticles, melanin particles and a first photoinitiator, the requirements of fast speed, low temperature, high crosslinking and suitability for inorganic nanoparticle composites can be met simultaneously.

[0072] In this invention, the black-doped high-refractive-index adhesive uses a first multifunctional polyurethane acrylate with a functionality of 6 or greater as the main oligomer (film-forming resin), providing the coating with mechanical properties and matrix properties. The high functionality enables the formation of a UV-curable network with high cross-linking density, resulting in higher hardness, abrasion resistance, and solvent resistance, making it suitable as a framework for optical functional layers. The polyurethane acrylate combines the toughness and elasticity of polyurethane with the rapid photocuring characteristics of acrylate, achieving a balance between hardness and adhesion, and preventing brittleness. In one specific embodiment of this invention, optionally, the mass of the first multifunctional polyurethane acrylate is 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% of the mass of the black-doped high-refractive-index adhesive, or a range between any two of the above values.

[0073] In a specific embodiment of the present invention, the functionality of the first multifunctional polyurethane acrylate is 6 to 10; specifically, it can be 6, 7, 8, 9 or 10; the first multifunctional polyurethane acrylate is preferably an aliphatic polyurethane acrylate, more preferably one or more of Arkema's CN9276, CN9667, CN9013, CN9018, CN991, IGM Resins' Photomer6720, Photomer6892, Photomer6008, Photomer6010, Photomer6210, Allnex's EBECRYL8701, EBECRYL8703, EBECRYL8314, EBECRYL8606, EBECRYL896, MIWON's MIRAMERPU600, MIRAMERPU610, MIRAMERPU620, MIRAMERPU900 and MIRAMERM600.

[0074] In this invention, the black-doped high-refractive-index adhesive uses high-refractive-index acrylate monomers as reactive diluents and refractive index-enhancing components to reduce system viscosity. This facilitates the uniform dispersion and leveling of high-refractive-index particles and melanin particles. Furthermore, while maintaining transparency, it can further enhance the overall refractive index of the cured film, enabling it to participate in UV free radical copolymerization and become part of the crosslinking network, without volatilization or migration. In one specific embodiment of this invention, optionally, the mass of the high-refractive-index acrylate is 10%, 15%, 20%, 25%, 30% of the mass of the black-doped high-refractive-index adhesive, or any two of the above values.

[0075] In one specific embodiment of the present invention, the refractive index of the high refractive index acrylate is preferably greater than or equal to 1.55, and more preferably one or more of o-phenylphenoxyethyl acrylate, biphenylmethanol acrylate, bicyclophenoxyethyl acrylate, bisphenol A epoxy diacrylate, bisphenol F epoxy diacrylate and ethoxylated bisphenol fluorene diacrylate.

[0076] In this invention, by adding surface-treated high-refractive-index nanoparticles to the black-doped high-refractive-index adhesive and dispersing them in the resin, the average refractive index of the composite film is significantly increased, which is beneficial for enhancing light removal efficiency. Furthermore, the surface treatment of the high-refractive-index nanoparticles improves their compatibility and dispersion stability with the resin matrix, reduces agglomeration and scattering losses, thereby maintaining sufficient transparency while increasing the refractive index. In one specific embodiment of this invention, optionally, the mass of the surface-treated high-refractive-index nanoparticles is 20%, 25%, 30%, 35%, 40% of the mass of the black-doped high-refractive-index adhesive, or a range between any two of the above values.

[0077] In a specific embodiment of the present invention, the refractive index n of the high refractive index nanoparticles at a wavelength of 589 nm is preferably 1.9~2.5, more preferably 2.0~2.4; specifically, the high refractive index nanoparticles are preferably one or more of metal oxides, metal oxide composite particles, and metal sulfides; the metal oxides are preferably titanium dioxide and / or zirconium dioxide, more preferably rutile titanium dioxide and / or zirconium dioxide; the metal oxide composite particles include metal oxides and silicon dioxide; the silicon dioxide and metal oxide in the metal oxide composite particles can be doped or coated, without any special limitations; the metal sulfides are preferably zinc sulfide; the surface-treated high refractive index nanoparticles are preferably high refractive index nanoparticles surface-treated with organic materials, more preferably high refractive index nanoparticles surface-treated with silane coupling agents.

[0078] In a specific embodiment of the present invention, the volume median particle size D50 of the high refractive index nanoparticles is preferably 5~100 nm, more preferably 10~80 nm, even more preferably 10~60 nm, and most preferably 10~50 nm; optionally, the volume median particle size D50 of the high refractive index nanoparticles is 10 nm, 20 nm, 30 nm, 40 nm, 50 nm or any two of the above values; the particle size distribution PDI of the high refractive index nanoparticles is ≤0.3.

[0079] In a specific embodiment of the present invention, when the high emissivity nanoparticles are rutile titanium dioxide, the surface-treated high refractive index nanoparticles can be one or more of the following: Changzhou Kenada's KND-TH50, Hangzhou Jiupeng New Materials' CY-T15, Suzhou Youzirconium's UG-T25, Daxinong's DXN-TC20, and Zhongke Leiming's DK-TiO2-T30; when the high emissivity nanoparticles are zirconium dioxide, the surface-treated high refractive index nanoparticles can be one or more of the following: Shanghai Yingcheng New Materials' YC-G30, Nanjing Baoket's BKT-Z30, Hangzhou Hengna New Materials' HN-R30, Suzhou Youzirconium's UG-Z30, and Shanghai Puzhen Biotechnology's PR-Z50; when the high emissivity nanoparticles are zinc sulfide, the surface-treated high refractive index nanoparticles can be one or more of the following: Yunfu Hongzhi New Materials' S-20 / S-10, and Sachtolith® from SACHTLEBEN (Germany). HD-S, XH-ZnS30 from Shanghai Xiaohuang Nanotechnology, and GRIRET-ZnS40 from GRINM Resources and Environment; when the high refractive index nanoparticles are metal oxide composite particles, the surface-treated high refractive index nanoparticles may be one or more of Evonik's AEROXIDE® TiO2 / SiO2 P250, Suzhou Youzirconium's UG-TZ30, Shanghai Aoke New Materials' AZ-ZS30, Nanjing Baoket's BKT-ZS40, and Hangzhou Jiupeng New Materials' CY-ZS25.

[0080] In this invention, the black-doped high-refractive-index adhesive provides the necessary light absorption (black) function by adding melanin particles, mainly absorbing stray light and ambient light in non-light-emitting areas and lateral light paths, thereby improving contrast and ink color consistency. Even with a very low addition amount, the optical density (OD) of the layer in the visible light band can be significantly increased, achieving a deeper black effect. Combined with nanoscale particle size and good dispersion, it mainly absorbs lateral and scattered light, while minimizing absorption in the vertically emitted main light path to avoid a significant decrease in brightness. In one specific embodiment of this invention, optionally, the mass of the melanin particles is 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1% of the mass of the black-doped high-refractive-index adhesive, or a range between any two of the above values.

[0081] In one specific embodiment of the present invention, the melanin particles are preferably carbon black and / or surface-treated carbon black; the carbon black may specifically be channel black, furnace black or a mixture thereof; the surface-treated carbon black may specifically be carbon black that has undergone oxidation treatment, silane coupling agent treatment or polymer grafting treatment.

[0082] In a specific embodiment of the present invention, the native particle size of the melanin particles is preferably 10-30 nm; optionally, the native particle size of the melanin particles is 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, or any two of the above values; the melanin particles used in the present invention have a narrow particle size distribution, specifically, the particle size distribution polydispersity index (PDI) of the melanin particles is preferably less than 1.5, more preferably less than 1.2; since the melanin nanoparticles dispersed in the adhesive will aggregate, thus forming aggregates, the average particle size of the aggregates of melanin particles in the high refractive index adhesive is preferably 80-200 nm, more preferably 100-180 nm, and even more preferably 100-150 nm; optionally, the average particle size of the aggregates of melanin particles in the high refractive index adhesive is 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, or any two of the above values.

[0083] By employing surface-treated melanin with the aforementioned specific particle size range and narrow distribution, extremely high blackness and light absorption efficiency can be achieved with very low addition amounts, thereby effectively reducing the black screen brightness of LED modules and significantly improving contrast. The narrow particle size distribution and excellent surface treatment ensure uniform dispersion of the melanin in the resin matrix.

[0084] In one specific embodiment of the present invention, the melanin particles may include the following grades from Orion: COLOUR BLACK FW200, COLOUR BLACK FW2V, COLOUR BLACK FW285, SPECIAL BLACK 4A (SB4A), SPECIAL BLACK 6 (SB6), Colour Black S160; the following grades from Cabot: MOGUL L, VULCANX C72R, BLACK PEARLS 880; the following grades from Borra Carbon Black: Raven 5000 Ultra, Raven 3500, Raven 2500; the following grades from Furui Specialty Carbon Black: FR-H10, FR-M20, FR-L30; and the following grades from Derui New Materials: DR-12, DR-20.

[0085] In this invention, the addition of a first photoinitiator to the black-doped high-refractive-index adhesive to absorb UV light and generate free radicals (or cations) initiates the polymerization and crosslinking of the acrylate / polyurethane acrylate system, which is key to achieving rapid curing. In a specific embodiment of this invention, the mass of the first photoinitiator is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the mass of the black-doped high-refractive-index adhesive, or any two of the above values.

[0086] In a specific embodiment of the present invention, the first photoinitiator is preferably one or more of the following: biphenyl ketal photoinitiators, α,α-dialkoxyacetophenone photoinitiators, α-hydroxyalkylacetophenone photoinitiators, α-aminoalkylacetophenone photoinitiators, and acylphosphine oxide photoinitiators; the biphenyl ketal photoinitiator includes, but is not limited to, α,α-dimethoxy-α-phenylacetophenone; the α,α-dialkoxyacetophenone photoinitiator includes, but is not limited to, 2,2-diethoxyacetophenone; the α-hydroxyalkylacetophenone photoinitiator includes, but is not limited to, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, and 1-[4-(2-hydroxyethoxy)-phenyl]-2- One or more of hydroxy-2-methyl-1-propanone; the α-aminoalkylphenyl ketone photoinitiator includes, but is not limited to, 2-methyl-1-(4-methylmercaptophenyl)-2-morpholino-1-propanone (MMMP) and / or 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (BDMB); the acylphosphine oxide photoinitiator includes, but is not limited to, one or more of 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO), ethyl 2,4,6-trimethylbenzoyl phenylphosphine acid (TPO-L), 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO) and phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO).

[0087] In this invention, there are no special restrictions on the preparation method of the black-doped high refractive index adhesive. Specifically, the black-doped high refractive index adhesive can be obtained by mixing and stirring a first multifunctional polyurethane acrylate, a high refractive index acrylate, surface-treated high refractive index nanoparticles, melanin particles and a first photoinitiator evenly and then degassing.

[0088] In one specific embodiment of the present invention, the average refractive index of the black-doped high refractive index layer in the visible light band (380~780 nm) is preferably 1.6~1.8, more preferably 1.65~1.75.

[0089] In a specific embodiment of the present invention, a high refractive index layer with the same thickness and composition but without added melanin particles is used as a reference layer. The increase in light loss of the black-doped high refractive index layer in the visible light band is preferably no more than 10%, and more preferably no more than 5%.

[0090] In this invention, an epoxy encapsulation layer is disposed on the black-doped high-refractive-index layer to protect the chip and bonding wires. The thickness of the epoxy encapsulation layer is preferably 100~300 μm; optionally, the thickness of the epoxy encapsulation layer is 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 220 μm, 250 μm, 280 μm, 300 μm, or any two of the above values.

[0091] In this invention, epoxy resin is used as the main component of the epoxy encapsulation layer. After curing, it forms a three-dimensional cross-linked network, providing mechanical strength, electrical insulation properties, and chemical barrier properties, protecting the underlying LED chip, bonding wires, and black-doped high-refractive-index layer from external environmental corrosion (moisture, dust). The epoxy encapsulation layer is formed from epoxy encapsulant. In a specific embodiment of this invention, the mass of the epoxy resin is 40%, 42%, 45%, 48%, 50% of the mass of the epoxy encapsulant, or any two of the above values.

[0092] In a specific embodiment of the present invention, the epoxy equivalent of the epoxy resin is preferably 0.25~1 eq / 100 g, corresponding to an epoxy equivalent weight (EEW) of 100 g / eq~400 g / eq. This equivalence range is selected to ensure a suitable crosslinking density during reaction with the curing agent. Too low an equivalence (too few active groups) may lead to insufficient curing or performance degradation; too high an equivalence (too many active groups) may lead to excessively rapid reaction, intense exothermic reaction, or excessive internal stress. This range balances processability (viscosity, pot life) with the heat resistance and mechanical strength of the final cured product. Optionally, the epoxy equivalent of the epoxy resin is preferably 0.25 eq / 100 g, 0.3 eq / 100 g, 0.4 eq / 100 g, 0.5 eq / 100 g, 0.6 eq / 100 g, 0.7 eq / 100 g, 0.8 eq / 100 g, 0.9 eq / 100 g, 1 eq / 100 g, or a range between any two of the above values.

[0093] In a specific embodiment of the present invention, the epoxy resin is preferably a glycidyl ether type epoxy resin, more preferably a bisphenol A type epoxy resin and / or a cresol-formaldehyde epoxy resin; more specifically, the epoxy resin may include the following grades from Huntsman-Araldite: Araldite GY 250, Araldite CY 225, Araldite 502, Araldite ECN 1299; the following grades from Dow Chemical: DER 383, DER 331; the following grades from Pelnox Japan: ME-512 / HV-512, ME-562 / HV-562; the following grades from Changchun Chemical: BE188 / BE188EL, EPS-201, EPS-211; and the following grades from Sumitomo Bakelite Japan: SUMIKON® EME-1100, SUMIKON® EME-1200, SUMIKON® One or more of EME-2100, SUMIKON® EME-2500, and SUMIKON® EME-5961.

[0094] In this invention, an epoxy toughening agent is added to the epoxy encapsulating adhesive to reduce internal stress and improve crack resistance: pure epoxy resin is brittle after curing, with high hardness but poor toughness. In COB encapsulation, due to the inconsistency in the coefficients of thermal expansion (CTE) of the PCB board (usually FR-4 or aluminum substrate), chip (silicon / sapphire), and adhesive, the display screen will generate thermal stress when switching lights on and off or when the ambient temperature changes. The addition of the toughening agent can introduce flexible segments or form "island structures" in the epoxy network, absorbing and dissipating these stresses and preventing the adhesive from cracking or peeling off from the chip / PCB. In a specific embodiment of this invention, optionally, the mass of the epoxy toughening agent is 5%, 8%, 10%, 12%, 15%, 18%, 20% of the mass of the epoxy encapsulating adhesive, or a range between any two of the above values.

[0095] In a specific embodiment of the present invention, the epoxy toughening agent is preferably one or more of the following: carboxyl-terminated butadiene-acrylonitrile copolymer, amino-terminated butadiene-acrylonitrile copolymer, core-shell rubber particles, epoxy resin masterbatch containing core-shell rubber particles, long-chain aliphatic flexible epoxy compound, cycloaliphatic flexible epoxy compound, epoxy-terminated polyurethane toughening agent, and epoxy-terminated polyurethane prepolymer toughening agent; specifically, the epoxy toughening agent includes, but is not limited to, Hycar / HYPRO® 1300×8, 1300×9, 1300×13 CTBN, 1300×16, 1300×21, 1300×42ATBN, KANE ACE™ MX-153, MX-257, GENIOPERL® M23A, PARALOID™ EXL-2314, EXL-2650A / J, TMS-2670J, ALBIPOX® series, and HELOXY™ 116, one or more of DER™ 732, 736 and ERL-4221.

[0096] In this invention, the role of the curing agent in the epoxy encapsulant is to react chemically with the epoxy groups in the epoxy resin, transforming the liquid resin into a solid network structure. In a specific embodiment provided by this invention, the mass of the curing agent is 40%, 42%, 45%, 48%, 50% of the mass of the epoxy encapsulant, or any two of the above values.

[0097] In a specific embodiment of the present invention, the curing agent is preferably an acid anhydride thermosetting agent, more preferably hexahydrophthalic anhydride and / or methylhexahydrophthalic anhydride.

[0098] In this invention, there are no special restrictions on the preparation method of epoxy encapsulant. Specifically, epoxy encapsulant can be obtained by mixing epoxy resin, epoxy toughening agent and curing agent evenly and then vacuum degassing.

[0099] In a specific embodiment of the present invention, the epoxy encapsulation layer is formed by thermosetting epoxy encapsulating adhesive; the thermosetting includes pre-curing and post-curing; the pre-curing is preferably high-temperature molding curing; the pre-curing temperature is preferably 100℃~120℃; the pre-curing time is preferably 3~10 min; the post-curing temperature is preferably 130℃~150℃; the post-curing time is preferably 150~250 min; optionally, the post-curing time is 150 min, 180 min, 200 min, 220 min, 250 min or any two of the above values.

[0100] In this invention, a matte hydrophobic layer is provided on the epoxy encapsulation layer, which is used for anti-glare and waterproofing, and is formed by matte hydrophobic adhesive; the thickness of the matte hydrophobic layer is preferably 5~50 μm; optionally, the thickness of the matte hydrophobic layer is 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or any two of the above values.

[0101] In this invention, the second multifunctional polyurethane acrylate is the main component of the matte hydrophobic layer. As the main film-forming resin (skeleton), it determines the physical and mechanical properties (such as hardness, abrasion resistance, and flexibility) and adhesion of the cured coating. It provides a high crosslinking density through its high functionality, where functionality represents the number of double bonds on a molecule that can participate in the photocuring reaction. High functionality means that an extremely dense three-dimensional network structure can be formed after curing. It provides durability: polyurethane acrylate (PUA) itself combines the toughness of polyurethane with the hardness of acrylic resin. High-functionality PUA can impart extremely high hardness, scratch resistance, and excellent chemical solvent resistance to the coating, ensuring that the screen is not easily worn during long-term wiping and use. In one specific embodiment of this invention, optionally, the mass of the second multifunctional polyurethane acrylate is 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70% of the mass of the matte hydrophobic adhesive, or a range between any two of the above values.

[0102] In a specific embodiment of the present invention, the functionality of the second multifunctional polyurethane acrylate is 6 to 10; specifically, it can be 6, 7, 8, 9 or 10; the second multifunctional polyurethane acrylate is preferably an aliphatic polyurethane acrylate, more preferably one or more of Arkema's CN9276, CN9667, CN9013, CN9018, CN991, IGM Resins' Photomer6720, Photomer6892, Photomer6008, Photomer6010, Photomer6210, Allnex's EBECRYL8701, EBECRYL8703, EBECRYL8314, EBECRYL8606, EBECRYL896, MIWON's MIRAMERPU600, MIRAMERPU610, MIRAMERPU620, MIRAMERPU900 and MIRAMERM600.

[0103] In this invention, the addition of multifunctional acrylate monomers to the matte hydrophobic adhesive is primarily used to adjust the system viscosity and simultaneously participate in curing. Unlike ordinary inactive diluents (such as solvents), these monomers are reactive; their multifunctionality indicates that they are not only diluents but also crosslinking agents. Unlike monofunctional monomers, which merely act as chain terminators reducing strength, they participate in the curing network, maintaining or even increasing the coating's hardness and crosslinking density. Furthermore, they can adjust properties: by selecting monomers with different chain lengths, the coating's flexibility and adhesion can be fine-tuned. In one specific embodiment of this invention, optionally, the mass of the multifunctional acrylate monomer is 5%, 8%, 10%, 12%, 15%, 18%, 20% of the mass of the matte hydrophobic adhesive, or a range between any two of these values.

[0104] In one specific embodiment of the present invention, the functionality of the multifunctional acrylate monomer is greater than or equal to 2, preferably 2 to 6; specifically, the functionality of the multifunctional acrylate monomer can be 2, 3, 4, 5 or 6.

[0105] In a specific embodiment of the present invention, the multifunctional acrylate monomer is preferably one or more selected from 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, dipropylene glycol diacrylate, cyclohexanediethanol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, and dipentaerythritol penta / hexaacrylate.

[0106] In this invention, matte particles are added to the matte hydrophobic adhesive to construct a micro-rough structure (anti-glare core). The matte particles are dispersed in the coating and, after curing, float on or protrude from the surface, forming a micron-level uneven structure. When light shines on this uneven surface, diffuse reflection (scattering) occurs, dispersing strong specular reflections and thus eliminating glare, providing a softer visual experience. In one specific embodiment of this invention, the mass of the matte particles is preferably 5%, 8%, 10%, 12%, 15%, 18%, 20% of the mass of the matte hydrophobic adhesive, or a range between any two of these values.

[0107] In a specific embodiment of the present invention, the matte particles are preferably one or more of the following: silica micropowder, organosilicon microspheres, cross-linked acrylate microspheres, cross-linked polymethyl methacrylate microspheres, cross-linked polyurethane micropowder, and surface-treated materials. Specifically, the surface-treated materials are one or more of the following: surface-treated silica micropowder, surface-treated organosilicon microspheres, surface-treated cross-linked acrylate microspheres, surface-treated cross-linked polymethyl methacrylate microspheres, and surface-treated cross-linked polyurethane micropowder. The surface treatment method can be any method well known to those skilled in the art and is not particularly limited, including but not limited to silane coupling agent treatment, amino modification, or polymer grafting treatment.

[0108] In a specific embodiment of the present invention, the median weight particle size D50 of the matte particles is preferably 1~12 μm, more preferably 2~10 μm, even more preferably 2~8 μm, and most preferably 2~5 μm; optionally, the median weight particle size D50 of the matte particles is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm or any two of the above values; the polydispersity index (PDI) of the particle size distribution of the matte particles is preferably not greater than 1.5, more preferably not greater than 1.2.

[0109] In one specific embodiment of the present invention, the matte particles may include the following brands from Evonik: ACEMATT® OK412, ACEMATT® OK500, ACEMATT® OK607, ACEMATT® 3600, ACEMATT® HK520; the following brands from Grace: SYLOID® 7000, SYLOID® ED30, SYLOID® RAD2105, SYLOID® 670; the following brands from Tosoh: Nipsil® E-1011, Nipsil® E-200A, Nipsil® K-300; the following brands from Dow Corning: DOWSIL™ EP-5518, DOWSIL™ MB50-001, DOWSIL™ TS-610; and the following brands from Lingwei Technology: HOMSIL® 8800, HOMSIL® 9900, HOMSIL® 7700; The following grades of ultra-high molecular weight polymers: LC-3000, LC-5000, LC-4000.

[0110] In this invention, adding a hydrophobic additive to the matte hydrophobic adhesive reduces surface energy (the core of waterproofing). The hydrophobic additive has extremely low surface energy; during film formation, it spontaneously migrates and accumulates on the coating surface, forming a hydrophobic layer. This causes water droplets to form spherical shapes (high contact angle) on the surface, making them easy to roll off, thus achieving waterproofing, stain resistance (anti-ink pen), and easy cleaning. In one specific embodiment of this invention, optionally, the mass of the hydrophobic additive is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the mass of the matte hydrophobic adhesive, or a range between any two of the above values.

[0111] In a specific embodiment of the present invention, the hydrophobic additive is preferably one or more of fluorosilanes, fluorocarbon resins, and modified nano-silica, more preferably UV-curable organosilicon hydrophobic additives and / or UV-curable fluorinated hydrophobic additives; specifically, the hydrophobic additives may include one or more of Shin-Etsu's KY-1203, KY-1206, KY-1211, KY-1213, and X-22-164A, and DAIKIN's OPTOOLDAC-100, OPTOOLDAC-HP, OPTOOLDAC-MOPTOOL, and DAC-L UV-F200.

[0112] In one specific embodiment of the present invention, optionally, the mass of the second photoinitiator is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the mass of the matte hydrophobic adhesive, or a range between any two of the above values.

[0113] In a specific embodiment of the present invention, the second photoinitiator is preferably one or more of the following: biphenyl ketal photoinitiators, α,α-dialkoxyacetophenone photoinitiators, α-hydroxyalkylacetophenone photoinitiators, α-aminoalkylacetophenone photoinitiators, and acylphosphine oxide photoinitiators; the biphenyl ketal photoinitiator includes, but is not limited to, α,α-dimethoxy-α-phenylacetophenone; the α,α-dialkoxyacetophenone photoinitiator includes, but is not limited to, 2,2-diethoxyacetophenone; the α-hydroxyalkylacetophenone photoinitiator includes, but is not limited to, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, and 1-[4-(2-hydroxyethoxy)-phenyl]-2- One or more of hydroxy-2-methyl-1-propanone; the α-aminoalkylphenyl ketone photoinitiator includes, but is not limited to, 2-methyl-1-(4-methylmercaptophenyl)-2-morpholino-1-propanone (MMMP) and / or 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (BDMB); the acylphosphine oxide photoinitiator includes, but is not limited to, one or more of 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO), ethyl 2,4,6-trimethylbenzoyl phenylphosphine acid (TPO-L), 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO) and phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO).

[0114] In this invention, there are no special restrictions on the preparation method of the matte hydrophobic adhesive. Specifically, it can be obtained by mixing and stirring the second multifunctional polyurethane acrylate, multifunctional acrylate monomer, matte particles, hydrophobic additives and the second photoinitiator evenly and stirring continuously; continuous stirring can prevent the matte particles from settling.

[0115] In one specific embodiment of the present invention, the water contact angle of the matte hydrophobic layer is preferably greater than or equal to 110°, and more preferably greater than or equal to 120°.

[0116] In one specific embodiment of the present invention, the haze of the matte hydrophobic layer is preferably 10% to 50%, more preferably 25% to 45%.

[0117] In one specific embodiment of the present invention, the pencil hardness of the matte hydrophobic layer is preferably greater than or equal to 3H; the adhesion of the matte hydrophobic layer is 5B.

[0118] The present invention also provides an LED display module, including the above-described LED packaging structure.

[0119] In one specific embodiment of the present invention, the LED display module includes a substrate, a plurality of LED chips disposed on the substrate, gaps between the plurality of LED chips, a black-doped high refractive index layer on the surface of the substrate excluding the LED chip area, an epoxy encapsulation layer disposed on the black-doped high refractive index layer away from the substrate surface, and a matte hydrophobic layer disposed on the epoxy encapsulation layer away from the substrate surface.

[0120] In one specific embodiment of the present invention, the surface of the plurality of LED chips is also provided with a black-doped high refractive index layer, which is integrally formed with the black-doped high refractive index layer disposed between the plurality of LED chips and on the surface of the substrate excluding the LED chip area.

[0121] In this invention, the substrate can be any substrate known to those skilled in the art, and there are no special restrictions. In this invention, a PCB substrate is preferred.

[0122] In one specific embodiment of the present invention, the LED display module is specifically a COB-LED display module.

[0123] In a specific embodiment provided by the present invention, the structural schematic diagram of the LED display module is shown below. Figure 1 As shown, 1 is the substrate, 2 is the LED chip, 3 is the black-doped high refractive index layer, 4 is the epoxy encapsulation layer, and 5 is the matte hydrophobic layer.

[0124] In a specific embodiment of the present invention, the static contrast ratio of the LED display module is greater than or equal to 15000:1; the static contrast ratio of the LED display module after 500 cycles of extreme temperature difference from -40℃ to 80℃ is greater than or equal to 15000:1; and the static contrast ratio loss rate of the LED display module after 500 cycles of extreme temperature difference from -40℃ to 80℃ is less than or equal to 3%, preferably less than or equal to 2.5%.

[0125] The LED display module provided by this invention includes the above-mentioned packaging structure, which enables the display product to have comprehensive advantages such as high contrast, high color consistency, low glare and high protection level, meeting the stringent requirements of high-end command centers, commercial displays and outdoor media for high-quality LED displays.

[0126] The present invention also provides a method for preparing the above-mentioned LED display module, comprising the following steps: S1) providing a semi-finished LED display module; the semi-finished LED display module includes a substrate and a plurality of LED chips disposed on the substrate; S2) transferring black-doped high-refractive-index adhesive to the surface of the substrate and the gap between the plurality of LED chips, and curing it to form a black-doped high-refractive-index layer; S3) transferring epoxy encapsulant to the surface of the black-doped high-refractive-index layer, and curing it to form an epoxy encapsulation layer; S4) transferring matte hydrophobic adhesive to the surface of the epoxy encapsulation layer, allowing it to stand and level, and curing it to obtain the LED display module.

[0127] See Figure 2 , Figure 2 This is a schematic diagram illustrating a specific manufacturing process of an LED display module provided by the present invention.

[0128] In this invention, there are no special restrictions on the source of any raw materials; they can be commercially available or self-made.

[0129] In a specific embodiment of the present invention, the LED display module semi-finished product is preferably prepared by the following method: a substrate with circuit lines arranged on its surface is provided, LED chips are die bonded at preset pad positions on the substrate, and wire bonded by gold or aluminum wires to form a die bonded COB-PCB board with a light-emitting chip array.

[0130] In a specific embodiment of the present invention, the LED display module semi-finished product is preferably subjected to surface treatment first to improve the surface layer and adhesion; the surface treatment method can be any method known to those skilled in the art and there are no special limitations, specifically it can be plasma treatment or corona treatment.

[0131] Then, the black-doped high-refractive-index adhesive is transferred to the substrate surface and the gaps between several LED chips, specifically, it is also transferred to the surface of several LED chips simultaneously, and cured to form a black-doped high-refractive-index layer. The transfer method can be any method well-known to those skilled in the art, specifically one or more of the following: precision dispensing, array spraying, stencil / stencil printing, squeegee application, slot coating, and inkjet printing. The curing is preferably UV curing; the wavelength of the UV curing is preferably 200~400 nm; and the energy density of the UV curing is preferably 500~1500 mJ / cm². 2 Optionally, the energy density of the UV curing is 500 mJ / cm². 2 800 mJ / cm 2 1000 mJ / cm 2 1200 mJ / cm 2 1500 mJ / cm 2 Or the range between any two of the above values.

[0132] In one specific embodiment of the present invention, after the black-doped high-refractive-index adhesive is transferred to the substrate surface and the gap between several LED chips, vacuum degassing is preferably used to allow the adhesive to flow fully and eliminate air bubbles before curing.

[0133] In one specific embodiment of the present invention, the black-doped high refractive index composition is first injected into the gap between the LED chip and the substrate by high-precision dispensing and then pre-cured by UV. The composition is then coated on the entire board surface by stencil printing and leveling and UV main curing to form a black-doped high refractive index layer with uniform thickness.

[0134] Epoxy encapsulant is transferred to the surface of a black-doped high-refractive-index layer and cured to form an epoxy encapsulation layer. The transfer is preferably performed via molding, covering the surface of the black-doped high-refractive-index layer and the LED chip with the epoxy encapsulant. Curing is preferably thermosetting; the thermosetting includes pre-curing and post-curing. Pre-curing is preferably high-temperature molding curing, which can be performed during the transfer process. The pre-curing temperature is preferably 100℃~120℃; the pre-curing time is preferably 3~10 min; the post-curing temperature is preferably 130℃~150℃; the post-curing time is preferably 150~250 min; optionally, the post-curing time is 150 min, 180 min, 200 min, 220 min, 250 min, or any two of the above values.

[0135] In a specific embodiment of the present invention, it is preferable to perform surface treatment on the LED display module semi-finished product that forms a black-doped high refractive index layer to improve the surface layer and adhesion, and then transfer epoxy encapsulant to the surface of the black-doped high refractive index layer; the surface treatment method can be any method known to those skilled in the art and there are no special limitations, specifically it can be plasma treatment or corona treatment.

[0136] A matte hydrophobic adhesive is transferred to the surface of an epoxy encapsulation layer, allowed to stand and level, and then cured to obtain an LED display module. The transfer method is preferably one or more of spraying, dip coating, and immersion coating. The standing and leveling time is preferably 10-30 seconds. The curing is preferably UV curing. The wavelength of the UV curing is preferably 200-400 nm. The energy density of the UV curing is preferably 500-1500 mJ / cm². 2 Optionally, the energy density of the UV curing is 500 mJ / cm². 2 800 mJ / cm 2 1000mJ / cm 2 1200 mJ / cm 2 1500 mJ / cm 2Or the range between any two of the above values.

[0137] In a specific embodiment of the present invention, the LED display module semi-finished product forming the epoxy encapsulation layer is preferably subjected to surface treatment to improve the surface layer and adhesion, and then a matte hydrophobic adhesive is transferred to the surface of the epoxy encapsulation layer; the surface treatment method can be any method known to those skilled in the art and there are no special limitations, specifically it can be plasma treatment or corona treatment.

[0138] In one specific embodiment of the present invention, matte hydrophobic adhesive is preferably transferred to the surface of epoxy encapsulation layer under continuous stirring, allowed to stand and level, and cured to obtain an LED display module.

[0139] The present invention also provides a display screen, including the LED display module described above.

[0140] To further illustrate the present invention, the following describes in detail, with reference to embodiments, an LED packaging structure, an LED display module, its preparation method, and a display screen provided by the present invention.

[0141] All reagents used in the following examples are commercially available.

[0142] Example 1

[0143] 1.1 The materials and formulations used in the black-doped high refractive index layer, epoxy encapsulation layer and UV matte hydrophobic layer are shown in Tables 1 to 3.

[0144] Table 1. Batching Table for Black-Doped High Refractive Index Layer

[0145]

[0146] Table 2 Epoxy Encapsulation Layer Raw Material List

[0147]

[0148] Table 3 Raw Material List for UV Matte Hydrophobic Layer

[0149]

[0150] 1.2 The preparation method of the display module is as follows:

[0151] S1) Provides die-bonded COB-PCB boards

[0152] A PCB substrate with circuit lines already arranged on its surface is provided. LED chips (with a chip height of 20~40 μm) are die-bonded at preset pad positions on the PCB substrate and wire bonded by gold or aluminum wire to form a die-bonded COB-PCB board with a light-emitting chip array. The COB pitch is 0.9 mm.

[0153] S2) Formation of a black-doped high-refractive-index layer

[0154] Ingredients: Weigh the materials according to the component ratios described in Table 1, and use vacuum stirring to remove bubbles to obtain UV-curable adhesive;

[0155] Surface treatment: The surface of the COB-PCB board is subjected to plasma treatment (oxygen gas, power 120 W, time 10 min) to improve surface energy and adhesion;

[0156] Coating / filling: The UV-curable adhesive is applied to the surface of the die-bonded COB-PCB board using inkjet printing technology;

[0157] Pre-leveling: Vacuum degassing is used to ensure the adhesive is fully leveled and air bubbles are eliminated;

[0158] UV curing: Cured by UV light irradiation, energy density 1000 mJ / cm³ 2 This forms a black-doped high-refractive-index layer with a thickness of 40 μm.

[0159] S3) Forming an epoxy encapsulation layer

[0160] An epoxy encapsulation layer is prepared on the cured black-doped high-refractive-index layer. This layer is used to protect the chip and bonding wires. The specific steps are as follows:

[0161] Ingredients: Weigh the materials according to the component ratios described in Table 2, and use vacuum stirring to degas the materials to obtain the epoxy encapsulating adhesive solution;

[0162] Surface treatment: The surface of the black-doped high refractive index layer is subjected to plasma treatment (gas is oxygen, power is 120W, time is 10 min) to improve surface energy and adhesion.

[0163] Encapsulation and molding: The epoxy encapsulating adhesive is applied to the black-doped high refractive index layer and the LED chip using a molding process, with a thickness of 200 μm.

[0164] Thermosetting: Pre-curing temperature of molding is 100℃ for 5 min, and post-curing temperature is 130℃ for 180 min.

[0165] S4) Forms a UV matte hydrophobic layer

[0166] A UV matte hydrophobic layer is prepared on the surface of the cured epoxy encapsulation layer. This layer serves to prevent glare and provide waterproofing and hydrophobicity. The specific steps are as follows:

[0167] Surface treatment: The surface of the epoxy encapsulation layer is subjected to plasma treatment (gas is oxygen, power is 120 W, time is 10 min) to improve surface energy and adhesion;

[0168] Ingredients: Weigh the materials according to the composition ratios described in Table 3, and use vacuum stirring to degas the materials and prevent the matte particles from settling.

[0169] Spraying: A precision spraying process is used to uniformly apply the mixed adhesive to the surface of the epoxy encapsulation layer, controlling the wet film thickness to be 20~50 μm and the dry film thickness to be 20 μm.

[0170] Leveling: Allow to stand at room temperature for 30 seconds to level;

[0171] UV curing: Curing is performed under nitrogen protection or air environment using UV light irradiation, with an energy density of 1500 mJ / cm³. 2 This forms a matte hydrophobic layer with a rough surface and hydrophobic properties.

[0172] A physical image of the LED display module obtained in Example 1 is shown below. Figure 3 As shown.

[0173] Refractive index test of the black-doped high refractive index layer: The well-dispersed black-doped high refractive index adhesive was pre-coated on the silicon wafer. A gyroscope was used to form a thin layer of adhesive of about 300 nm on the silicon wafer. After curing, the refractive index of the epoxy-organosilicon hybrid resin composition was tested with an ellipsometry, and the refractive index n=1.70 was obtained.

[0174] The brightness, contrast, surface hardness, and surface haze of the LED display module obtained in Example 1 were tested, and the results are shown in Table 4. The brightness and contrast were tested according to the SJ / T 11281 standard (Test Method for Light Emitting Diode (LED) Display Screen); the surface hardness was tested according to GB / T 2411-2008; and the haze test was based on the standard GB / T 2410 "Determination of Light Transmittance and Haze of Transparent Plastics".

[0175] Aging test:

[0176] The cured module was lit and placed in a device at 85℃ and 85% humidity for 500 hours. Then, a thermal shock test was performed with a temperature of -40 to 80℃, a cold shock time of 30 minutes, and a hot shock time of 30 minutes. This constituted one cycle, and a total of 500 cycles were performed. The test brightness results are shown in Table 4.

[0177] Table 4 Performance test results of the LED display module obtained in Example 1

[0178]

[0179] Example 2

[0180] 2.1 The materials and formulations used in the black-doped high refractive index layer, epoxy encapsulation layer and UV matte hydrophobic layer are shown in Tables 5 to 7.

[0181] Table 5. Raw material list for black-doped high-refractive-index layer

[0182]

[0183] Table 6. Raw Material List for Epoxy Encapsulation Layer

[0184]

[0185] Table 7 UV Matte Hydrophobic Layer

[0186]

[0187] 2.2 The preparation method of the display module is as follows:

[0188] S1) Provides die-bonded COB-PCB boards

[0189] A PCB substrate with circuit lines already arranged on its surface is provided. LED chips (with a chip height of 20~40 μm) are die-bonded at preset pad positions on the PCB substrate and wire bonded by gold or aluminum wire to form a die-bonded COB-PCB board with a light-emitting chip array. The COB pitch is 0.9 mm.

[0190] S2) Formation of a black-doped high-refractive-index layer

[0191] Ingredients: Weigh the materials according to the component ratios described in Table 5, and use vacuum stirring to remove bubbles to obtain UV-curable adhesive;

[0192] Surface treatment: The surface of the COB-PCB board is subjected to plasma treatment (oxygen gas, power 120 W, time 10 min) to improve surface energy and adhesion;

[0193] Coating / filling: The UV-curable adhesive is applied to the surface of the die-bonded COB-PCB board using inkjet printing technology;

[0194] Pre-leveling: Vacuum degassing is used to ensure the adhesive is fully leveled and air bubbles are eliminated;

[0195] UV curing: Cured by UV light irradiation, energy density 1000 mJ / cm³ 2 This forms a black-doped high-refractive-index layer with a thickness of 40 μm.

[0196] S3. Forming an epoxy encapsulation layer

[0197] An epoxy encapsulation layer is prepared on the cured black-doped high-refractive-index layer. This layer is used to protect the chip and bonding wires. The specific steps are as follows:

[0198] Ingredients: Weigh the materials according to the component ratios described in Table 6, and use vacuum stirring to degas the materials to obtain the epoxy encapsulating adhesive solution;

[0199] Surface treatment: The surface of the black-doped high refractive index layer is subjected to plasma treatment (gas is oxygen, power is 120W, time is 10 min) to improve surface energy and adhesion.

[0200] Encapsulation and molding: The epoxy encapsulating adhesive is applied to the black-doped high refractive index layer and the LED chip using a molding process, with a thickness of 200 μm.

[0201] Thermosetting: Pre-curing temperature of molding is 100℃ for 5 min, and post-curing temperature is 130℃ for 180 min.

[0202] S4) Forms a UV matte hydrophobic layer

[0203] A UV matte hydrophobic layer is prepared on the surface of the cured epoxy encapsulation layer. This layer serves to prevent glare and provide waterproofing and hydrophobicity. The specific steps are as follows:

[0204] Surface treatment: The surface of the epoxy encapsulation layer is subjected to plasma treatment (gas is oxygen, power is 120 W, time is 10 min) to improve surface energy and adhesion;

[0205] Ingredients: Weigh the materials according to the composition ratios described in Table 7, and use vacuum stirring to degas the materials and prevent the matte particles from settling.

[0206] Spraying: A precision spraying process is used to uniformly apply the mixed adhesive to the surface of the epoxy encapsulation layer, controlling the wet film thickness to be 20~50μm and the dry film thickness to be 20μm.

[0207] Leveling: Allow to stand at room temperature for 30 seconds to level;

[0208] UV curing: Curing is performed under nitrogen protection or air environment using UV light irradiation, with an energy density of 1500 mJ / cm³. 2 This forms a matte hydrophobic layer with a rough surface and hydrophobic properties.

[0209] The test results of the LED display module in Example 2 were obtained by testing according to the test method of Example 1, as shown in Figure 8.

[0210] The refractive index of the black-doped high-refractive-index layer is n=1.65.

[0211] Table 8 Performance test results of the LED display module obtained in Example 2

[0212]

[0213] Comparative Example 1

[0214] The preparation method is the same as in Example 1, except that no melanin particles are added, and 1-hydroxycyclohexylphenyl ketone is used to supplement the melanin.

[0215] The test results of the LED display module in Comparative Example 1 were obtained by testing according to the test method of Example 1, as shown in Figure 9.

[0216] The refractive index of the high refractive index layer is n=1.70.

[0217] Table 9 Performance test results of the LED display module obtained in Comparative Example 1

[0218]

[0219] Comparative Example 2

[0220] The preparation method is the same as in Example 1, except that the high-refractive nanoparticles UG-Z30 are not added.

[0221] The test results of the LED display module in Comparative Example 2 were obtained by testing according to the test method of Example 1, as shown in Figure 10.

[0222] The refractive index of the high refractive index layer is n=1.53.

[0223] Table 10 Performance test results of the LED display module obtained in Comparative Example 2

[0224]

[0225] Comparative Example 3

[0226] The preparation method is the same as in Example 1, except that bisphenol fluorene diacrylate ester is replaced with pentaerythritol triacrylate ester.

[0227] The test results of the LED display module in Comparative Example 4 were obtained by testing according to the test method of Example 1, as shown in Figure 11.

[0228] The refractive index of the high refractive index layer is n=1.63.

[0229] Table 11 Performance test results of the LED display module obtained in Comparative Example 3

[0230]

[0231] In summary, the LED display module provided by this invention has the following advantages:

[0232] 1) Breaking through the bottleneck of the trade-off between contrast and brightness, achieving a balance between ultra-high static contrast and high brightness: This invention introduces a specially designed black-doped high-refractive-index layer. The high-refractive-index component effectively reduces total internal reflection loss at the chip-medium interface, significantly improving light extraction efficiency, enabling the module to achieve a high brightness of 800-1000 nits under standard driving conditions. Simultaneously, the melanin component efficiently absorbs ambient stray light and lateral light leakage from the chip, greatly reducing surface reflection brightness when the screen is black. The direct effect of this synergistic design of light absorption and light guidance is that the module's static contrast ratio is ≥15000:1. This invention successfully resolves the technical contradiction in traditional technologies where increasing contrast comes at the cost of sacrificing brightness, or maintaining brightness without significantly improving black depth.

[0233] 2) Completely solves the problem of color difference (mosaic) on black screens, achieving seamless black color consistency: Existing COB technology often results in obvious blocky color differences (mosaic effect) on black screens due to PCB substrate color differences, pad reflections, or uneven encapsulation colloid thickness. This invention forms an optically uniform black substrate by uniformly covering the gaps between the PCB and the chip with a black-doped high-refractive-index layer, physically masking the material differences at the underlying layer. Actual testing shows that modules using this structure have no obvious color difference visually, exhibit excellent black screen consistency, and present a seamless, high-end texture, greatly enhancing the visual unity and premium feel of large-screen splicing.

[0234] 3) Achieves the best balance between anti-glare and image clarity.

[0235] The outermost UV matte hydrophobic layer of this invention precisely controls the surface haze between 25% and 45% by controlling the content and dispersion process of matte particles. The lower limit of haze (>25%) ensures sufficient diffuse reflection capability to eliminate specular reflection glare under strong light, thus improving viewing comfort; the upper limit of haze (<45%) avoids blurry or out-of-focus images caused by excessive scattering. This allows the module to maintain high definition and high contrast image reproduction while possessing excellent anti-glare performance.

[0236] 4) Combining high hardness and superhydrophobicity, the protection level is significantly improved.

[0237] The UV matte hydrophobic layer of this invention utilizes a high-crosslinking-density polyurethane acrylate system with a functionality of ≥6, giving the coating a high hardness of ≥3H, effectively resisting scratches and wear during daily cleaning. Simultaneously, the compounded hydrophobic additives result in a surface water contact angle of ≥120°, exhibiting an excellent lotus leaf effect. Water droplets are difficult to adhere to, easily rolling off and carrying away stains, achieving not only waterproofing and stain resistance but also significantly reducing maintenance costs in outdoor or high-humidity environments. This combination of hardness and hydrophobicity solves the problems of traditional coatings being either too soft and not wear-resistant or too hard and not hydrophobic.

[0238] 5) Excellent environmental reliability and long-term stability: Rigorous aging tests verified the long-term reliability of the invention's structure: Moisture and heat resistance: After 500 hours at 85℃ / 85% RH, the brightness loss was ≤3%, indicating strong hydrolysis resistance of the encapsulation material and no significant yellowing or transmittance reduction. Thermal shock resistance: After 500 cycles of extreme temperature differences from -40℃ to 80℃, the module's static contrast ratio remained ≥15000:1, with a static contrast ratio loss of less than or equal to 2.5%, indicating tight bonding between layers, no cracking or delamination, and no phase separation or performance degradation in the black doped layer. This demonstrates that the module prepared by this invention can operate stably for a long time in harsh outdoor or industrial environments, exhibiting an extremely long service life and extremely low maintenance requirements.

[0239] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An LED packaging structure, characterized in that, It includes a stacked black-doped high-refractive-index layer, an epoxy encapsulation layer, and a matte hydrophobic layer; The black-doped high-refractive-index layer is formed by black-doped high-refractive-index adhesive; The black-doped high-refractive-index adhesive comprises a first multifunctional polyurethane acrylate, a high-refractive-index acrylate, surface-treated high-refractive-index nanoparticles, melanin particles, and a first photoinitiator. The mass of the first multifunctional polyurethane acrylate is 30% to 70% of the mass of the black-doped high-refractive-index adhesive; The mass of the high refractive index acrylate is 10% to 30% of the mass of the black-doped high refractive index adhesive; The mass of the surface-treated high-refractive-index nanoparticles is 20% to 40% of the mass of the black-doped high-refractive-index adhesive; The mass of the melanin particles is 0.01% to 0.1% of the mass of the black-doped high-refractive-index adhesive; The mass of the first photoinitiator is 1% to 10% of the mass of the black-doped high-refractive-index adhesive; The matte hydrophobic layer is formed by matte hydrophobic adhesive; The matte hydrophobic adhesive comprises a second multifunctional polyurethane acrylate, a multifunctional acrylate monomer, matte particles, a hydrophobic additive, and a second photoinitiator. The mass of the second multifunctional polyurethane acrylate is 50% to 70% of the mass of the matte hydrophobic adhesive; The mass of the multifunctional acrylate monomer is 5% to 20% of the mass of the matte hydrophobic adhesive; The mass of the matte particles is 5% to 20% of the mass of the matte hydrophobic adhesive; The mass of the hydrophobic additive is 1% to 10% of the mass of the matte hydrophobic adhesive; The mass of the second photoinitiator is 1% to 10% of the mass of the matte hydrophobic adhesive; The functionality of the first multifunctional polyurethane acrylate and the second multifunctional polyurethane acrylate is each independently greater than or equal to 6. The high-refractive-index acrylate has a refractive index greater than or equal to 1.55; The high refractive index nanoparticles have a refractive index greater than or equal to 1.9; The functionality of the multifunctional acrylate monomer is greater than or equal to 2.

2. The LED packaging structure according to claim 1, characterized in that, The functionality of the first multifunctional polyurethane acrylate and the second multifunctional polyurethane acrylate is independently 6 to 10. The first multifunctional polyurethane acrylate and the second multifunctional polyurethane acrylate are each independently selected from aliphatic polyurethane acrylates. The functionality of the multifunctional acrylate monomer is 2 to 6; The high refractive index acrylate is selected from one or more of o-phenylphenoxyethyl acrylate, biphenylmethanol acrylate, bicyclophenoxyethyl acrylate, bisphenol A epoxy diacrylate, bisphenol F epoxy diacrylate, and ethoxylated bisphenol fluorene diacrylate.

3. The LED packaging structure according to claim 2, characterized in that, The first multifunctional polyurethane acrylate and the second multifunctional polyurethane acrylate are each independently selected from one or more of the following: Arkema's CN9276, CN9667, CN9013, CN9018, CN991; IGM Resins' Photomer6720, Photomer6892, Photomer6008, Photomer6010, Photomer6210; Allnex's EBECRYL8701, EBECRYL8703, EBECRYL8314, EBECRYL8606, EBECRYL896; and MIWON's MIRAMERPU600, MIRAMERPU610, MIRAMERPU620, MIRAMERPU900, and MIRAMERM600. The multifunctional acrylate monomer is selected from one or more of the following: 1,6-hexanediol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, neopentyl glycol diacrylate, dipropylene glycol diacrylate, cyclohexanediol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, and dipentaerythritol penta / hexaacrylate. The high refractive index nanoparticles are selected from one or more of metal oxides, metal oxide composite particles and metal sulfides; the volume median particle size D50 of the high refractive index nanoparticles is 5~100 nm, and the particle size distribution PDI≤0.

3. The original particle size of the melanin particles is 10~30 nm; the average particle size of the aggregates of the melanin particles in the high refractive index glue is 80~200 nm. The first photoinitiator and the second photoinitiator are each independently selected from one or more of the following: biphenyl ketal photoinitiators, α,α-dialkoxyacetophenone photoinitiators, α-hydroxyalkylphenyl ketone photoinitiators, α-aminoalkylphenyl ketone photoinitiators, and acylphosphine oxide photoinitiators; The median particle size of the matte particles is 1~12 μm, and the particle size distribution (PDI) is ≤1.

5. The hydrophobic additive is selected from UV-curable silicone hydrophobic additives and / or UV-curable fluorinated hydrophobic additives.

4. The LED packaging structure according to claim 1, characterized in that, The epoxy encapsulation layer is formed of epoxy encapsulant; the epoxy encapsulant includes epoxy resin, epoxy toughening agent and curing agent; the mass of epoxy resin is 40% to 50% of the mass of epoxy encapsulant; the mass of epoxy toughening agent is 5% to 20% of the mass of epoxy encapsulant; the mass of curing agent is 40% to 50% of the mass of epoxy encapsulant.

5. The LED packaging structure according to claim 4, characterized in that, The epoxy equivalent of the epoxy resin is 0.25~1 eq / 100 g; And / or, the epoxy toughening agent is selected from one or more of the following: carboxyl-terminated butadiene-acrylonitrile copolymer, amino-terminated butadiene-acrylonitrile copolymer, core-shell rubber particles, epoxy resin masterbatch containing core-shell rubber particles, long-chain aliphatic flexible epoxy compound, cycloaliphatic flexible epoxy compound, epoxy-terminated polyurethane toughening agent, and epoxy-terminated polyurethane prepolymer toughening agent. And / or, the curing agent is selected from anhydride thermosetting agents.

6. The LED packaging structure according to claim 1, characterized in that, The thickness of the black-doped high-refractive-index layer is 10~100 μm; The thickness of the epoxy encapsulation layer is 100~300 μm; The thickness of the matte hydrophobic layer is 5~50 μm.

7. The LED packaging structure according to claim 1, characterized in that, The black-doped high-refractive-index layer has an average refractive index of 1.6 to 1.8 in the visible light band; The water contact angle of the matte hydrophobic layer is greater than or equal to 110°; The haze of the matte hydrophobic layer is 10%~50%; The pencil hardness of the matte hydrophobic layer is greater than or equal to 3H.

8. An LED display module, characterized in that, Includes the LED packaging structure described in any one of claims 1 to 7.

9. A method for manufacturing an LED display module according to claim 8, characterized in that, Includes the following steps: S1) Provide a semi-finished LED display module; the semi-finished LED display module includes a substrate and a plurality of LED chips disposed on the substrate; S2) Transfer the black-doped high-refractive-index adhesive to the substrate surface and the gaps between several LED chips, and cure it to form a black-doped high-refractive-index layer; S3) Transfer the epoxy encapsulant to the surface of the black-doped high-refractive-index layer and cure it to form an epoxy encapsulant layer; S4) Transfer the matte hydrophobic adhesive to the surface of the epoxy encapsulation layer, allow it to stand and level, and cure to obtain the LED display module.

10. A display screen, characterized in that, Includes the LED display module as described in claim 8 or the LED display module prepared by the preparation method described in claim 9.

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