Nanocomposite modified encapsulation adhesive, preparation method thereof and LED display screen

Abstract

The application provides a nanocomposite modified packaging adhesive, a preparation method thereof and an LED display screen. The packaging adhesive comprises a base resin, nanometer inorganic fillers, an ultraviolet absorber, an antioxidant and a curing agent. The base resin comprises a terminal vinyl methyl phenyl modified organic silicon resin. The nanometer inorganic fillers comprise coupling agent modified nanometer silicon dioxide, nanometer aluminum oxide powder and silane modified nanometer calcium carbonate. The terminal vinyl methyl phenyl modified organic silicon resin is compounded with specific multistage nanometer inorganic fillers and additives, so that the anti-yellowing performance of the adhesive in a long-term ultraviolet irradiation environment is improved. The combined action of the various nanometer inorganic fillers enhances the interfacial adhesion between the cured adhesive layer and the substrate, disperses and buffers the thermal stress generated by high-low temperature switching, reduces the delamination and cracking risk of the material in a cold-hot alternating environment, and meets the weather resistance requirement of high-density display screen mask-free long-term packaging.

Description

Technical Field

[0001] This invention relates to the field of encapsulating adhesives, specifically to a nanocomposite modified encapsulating adhesive, a method for preparing the encapsulating adhesive, and an LED display screen. Background Technology

[0002] With the continuous advancement of LED display technology, the pixel pitch of high-density displays (such as Mini LED) is becoming increasingly smaller. To ensure the consistency of displayed colors, traditional processes usually require the addition of a mask, but this assembly process is difficult to implement at extremely small pitches, and maskless encapsulation is gradually becoming the mainstream.

[0003] Faceless encapsulation typically uses epoxy resins for potting, but these materials are prone to yellowing under prolonged exposure to outdoor ultraviolet radiation. Furthermore, these resins have limited weather resistance in harsh environments such as extreme cold, and their interfacial adhesion to the circuit board substrate is insufficient. Especially in complex encapsulation structures and environments with alternating hot and cold temperatures, the adhesive layer is susceptible to microcracks caused by thermal stress, leading to detachment or peeling failure between the adhesive layer and the substrate. Summary of the Invention

[0004] In view of the aforementioned problems, this application is made to provide a nanocomposite modified encapsulant, a method for preparing the same, and an LED display screen that overcomes or at least partially solves the aforementioned problems, comprising: A nanocomposite modified encapsulant includes a base resin, nano-inorganic fillers, ultraviolet absorbers, antioxidants, and curing agents; The matrix resin comprises a terminal vinyl methyl phenyl modified organosilicon resin; The nano-inorganic fillers include coupling agent-modified nano-silica, nano-alumina powder, and silane-modified nano-calcium carbonate.

[0005] According to one embodiment of the present invention, the components in the nanocomposite modified encapsulant are as follows, by weight: 70 to 85 parts of matrix resin, 1 to 4 parts of coupling agent modified nano silica, 0.5 to 2 parts of nano alumina powder, 0.3 to 1.5 parts of silane modified nano calcium carbonate, 0.2 to 1 part of ultraviolet absorber, 0.1 to 0.8 parts of antioxidant, and 3 to 8 parts of curing agent.

[0006] According to one embodiment of the present invention, the ultraviolet absorber is a benzotriazole ultraviolet absorber, the antioxidant is a hindered amine antioxidant, and the curing agent is a platinum-based addition curing agent.

[0007] According to one embodiment of the present invention, the method further includes a leveling and defoaming agent, wherein the leveling and defoaming agent is an organosilicone leveling and defoaming agent; the organosilicone leveling and defoaming agent is present in parts by weight of 0.1 to 0.5 parts.

[0008] According to one embodiment of the present invention, the viscosity of the nanocomposite modified encapsulant at 25°C before curing is between 8000 and 15000 mPa·s.

[0009] A method for preparing a nanocomposite modified encapsulating adhesive as described in any of the preceding claims, comprising the following steps: Pretreatment step: The matrix resin is put into a mixing device for pre-stirring; Dispersion step: The nano-inorganic filler is added to the pre-stirred matrix resin for dispersion treatment until the powder is completely wetted and no agglomerates, forming a mixed matrix material; Addition and degassing steps: The mixed base material is cooled, the ultraviolet absorber and the antioxidant are added, and then the first vacuum degassing treatment is performed; Curing preparation steps: The curing agent is mixed into the degassing system and stirred until homogeneous. A second vacuum degassing process is then performed to obtain the finished adhesive.

[0010] According to one embodiment of the present invention, the stirring device is a vacuum stirring vessel; In the pretreatment step, the matrix resin is heated to 35°C to 45°C and then pre-stirred for a time of 10 to 20 minutes. In the dispersion step, the nano-inorganic filler is added in stages, and the dispersion treatment time is set to 25 to 40 minutes.

[0011] According to one embodiment of the present invention, the raw materials of the nanocomposite modified encapsulating adhesive further include a leveling and defoaming agent; In the addition and defoaming step, the leveling and defoaming agent is added to the system before the first vacuum defoaming treatment is performed.

[0012] According to one embodiment of the present invention, in the addition and degassing step, the mixed base material is cooled to 20°C to 30°C, and the time for the first vacuum degassing treatment is set to 15 minutes to 25 minutes; In the curing preparation step, the curing agent is mixed in by stirring, and the time for the secondary vacuum degassing treatment is set to 3 to 8 minutes.

[0013] An LED display screen includes a substrate, LED chips disposed on the substrate, and an encapsulating adhesive layer; The encapsulating adhesive layer covers the LED chip, and the encapsulating adhesive layer is formed by curing the nanocomposite modified encapsulating adhesive as described in any of the above claims.

[0014] This application has the following advantages: In the embodiments of this application, the nanocomposite modified encapsulant improves the anti-yellowing performance of the colloid under ultraviolet irradiation by compounding terminal vinyl methyl phenyl modified organosilicon resin with nano-inorganic fillers and additives. Simultaneously, the combined effect of various nano-inorganic fillers enhances the interfacial adhesion between the encapsulant layer and the substrate, reducing the risk of delamination and cracking under alternating hot and cold environments, allowing it to maintain structural stability over a wide temperature range after curing. Furthermore, this encapsulant maintains suitable rheological viscosity and visible light transmittance after curing, ensuring the optical performance of the light-emitting device while meeting the encapsulation and wetting requirements for small gaps. Attached Figure Description

[0015] To more clearly illustrate the technical solution of this application, the drawings used in the description of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart of a method for preparing a nanocomposite modified encapsulating adhesive according to an embodiment of this application; Figure 2 This is a schematic diagram of the structure of an LED display screen provided in one embodiment of this application; Figure 3 This is a product image of the nanocomposite modified encapsulating adhesive provided in one embodiment of this application; Figure 4 This is a physical example of an LED display screen (encapsulated with the nanocomposite modified encapsulant of this application) provided in one embodiment of this application. Figure 1 ; Figure 5 This is a physical example of an LED display screen (encapsulated with the nanocomposite modified encapsulant of this application) provided in one embodiment of this application. Figure 2 . Detailed Implementation

[0017] To make the objectives, features, and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0018] The inventors, through analysis of existing technologies, discovered that current maskless encapsulation processes generally use conventional epoxy resins and other materials as the main potting matrix. These polymer segments are prone to photodegradation under prolonged exposure to outdoor ultraviolet radiation, resulting in irreversible yellowing and reduced light transmittance and optical consistency of the display screen. Simultaneously, the interfacial adhesion between the encapsulating material and the substrate is insufficient. Especially in extreme outdoor environments such as extreme cold or alternating hot and cold conditions, the increased thermal stress caused by the difference in thermal expansion coefficients between the adhesive layer and the substrate leads to microcracks, delamination, or peeling failure of the adhesive layer.

[0019] One embodiment of this application provides a nanocomposite modified encapsulant, comprising a base resin, nano-inorganic fillers, ultraviolet absorbers, antioxidants, and curing agents.

[0020] The matrix resin is the continuous phase of the nanocomposite modified encapsulant, forming a three-dimensional cross-linked framework after the colloid is molded. The matrix resin contains vinyl-terminated methylphenyl-modified silicone resin. The vinyl groups at both ends of the resin molecular chain have reactive sites, which can undergo addition curing reactions with the curing agent to form a polymeric spatial network structure. At the same time, the methylphenyl groups introduced into the molecular chain improve the cohesive energy of the matrix resin after curing and its resistance to external thermal stress through their steric hindrance effect and conjugated structure, thus providing structural stability for the nanocomposite modified encapsulant.

[0021] Nano-inorganic fillers, as dispersed phases, are distributed within the continuous phase composed of the matrix resin. In this embodiment, the nano-inorganic fillers include coupling agent-modified nano-silica, nano-alumina powder, and silane-modified nano-calcium carbonate.

[0022] The modified groups grafted onto the surface of the coupling agent-modified nano-silica can interact with the terminal vinyl methyl phenyl-modified organosilicon resin at the interface, weakening the high surface energy of the nanoparticles, preventing particle aggregation, and achieving dispersion within the organosilicon framework. Nano-alumina powder is embedded in the gaps formed by the coupling agent-modified nano-silica and resin segments, increasing the density of the colloidal internal structure. Silane-modified nano-calcium carbonate forms a direct connection with the matrix resin through silane molecular segments on its surface. When the matrix resin is subjected to external deformation or thermal stress, the aforementioned surface-modified inorganic particles can play a role in stress transfer and dispersion within the matrix resin. The three inorganic fillers with different properties work together in the matrix resin to enhance the overall mechanical strength of the nanocomposite modified encapsulant by improving interfacial bonding.

[0023] Ultraviolet absorbers and antioxidants are dispersed in the matrix resin and the nano-inorganic fillers. When the nanocomposite modified encapsulant is cured and in working condition, the ultraviolet absorbers absorb ultraviolet radiation irradiating the interior of the encapsulant, reducing the damage of ultraviolet radiation to the matrix resin. The antioxidants consume free radicals generated in the photothermal environment, thereby blocking the photo-oxidative degradation reaction of the polymer chains. The curing agent is distributed in the matrix resin. Under set curing conditions, the curing agent promotes the cross-linking reaction of the active end groups of the vinyl methyl phenyl-terminated silicone resin, causing the adhesive to cure and fixing the nano-inorganic fillers, ultraviolet absorbers, and antioxidants in the cured cross-linked network structure.

[0024] In the embodiments of this application, the nanocomposite modified encapsulant improves the anti-yellowing performance of the colloid under ultraviolet irradiation by compounding terminal vinyl methyl phenyl modified organosilicon resin with nano-inorganic fillers and additives. Simultaneously, the combined effect of various nano-inorganic fillers enhances the interfacial adhesion between the adhesive layer and the substrate, reducing the risk of delamination and cracking of the material under alternating hot and cold environments, allowing it to maintain physical structural stability over a wide temperature range after curing. Furthermore, this nanocomposite modified encapsulant maintains suitable rheological viscosity and visible light transmittance after curing, ensuring the optical performance of the light-emitting device while meeting the encapsulation and wetting requirements for small gaps.

[0025] In some embodiments of the present invention, the components in the nanocomposite modified encapsulant are, by weight, 70 to 85 parts of matrix resin, 1 to 4 parts of coupling agent modified nano silica, 0.5 to 2 parts of nano alumina powder, 0.3 to 1.5 parts of silane modified nano calcium carbonate, 0.2 to 1 part of ultraviolet absorber, 0.1 to 0.8 parts of antioxidant, and 3 to 8 parts of curing agent.

[0026] Specifically, the content of the base resin is in the range of 70 to 85 parts. This range ensures that the nanocomposite modified encapsulant has suitable rheological properties before curing, avoiding the problem of difficulty in molding due to excessively high system viscosity. At the same time, in combination with 3 to 8 parts of the curing agent, it ensures that the stoichiometric ratio of active groups in the system is within an appropriate range during the curing reaction stage. If the amount of curing agent added is less than 3 parts, the curing crosslinking will be incomplete, leading to stickiness or a decrease in physical strength of the adhesive layer. If the amount of curing agent added is more than 8 parts, it will lead to a high crosslinking density and increased internal stress in the cured adhesive layer, making it prone to brittle cracking under alternating hot and cold environments. For the nano-inorganic fillers, 1 to 4 parts of coupling agent-modified nano-silica are mainly used to adjust the thixotropy of the adhesive and provide basic reinforcing points in the cross-linked network structure; 0.5 to 2 parts of nano-alumina powder are dispersed in the matrix resin to fill the micro-gap, improving the density and thermal conductivity of the cured adhesive layer; 0.3 to 1.5 parts of silane-modified nano-calcium carbonate mainly play a role in stress dispersion and toughening when the system is under stress. The above three inorganic fillers, when compounded in this proportion, form a tiered filler structure within the matrix resin. In specific applications, when high penetration and leveling properties are required for the nanocomposite modified encapsulant (e.g., for circuit board encapsulation with extremely small pitch), the lower limit of the above-mentioned nano-inorganic filler part ratio range can be used; when higher structural hardness of the cured adhesive layer is required, the upper limit of the above-mentioned range can be used accordingly. This ratio achieves structural reinforcement of the matrix resin while maintaining the fluidity of the adhesive.

[0027] For the additives, the addition of 0.2 to 1 part of UV absorber and 0.1 to 0.8 parts of antioxidant achieved a balance of dissolution and distribution in the matrix resin. This addition range provides the system with sufficient active groups to absorb external UV radiation and consume internal free radicals, avoiding the precipitation of additives in the crosslinking network or plasticization of the resin structure due to excessive additive addition; while protecting against photothermal aging, it maintains the visible light transmittance of the nanocomposite modified encapsulant before and after curing.

[0028] By adopting the above-mentioned component ratios by weight, the components produce a synergistic effect during physical mixing and cross-linking molding, enabling the nanocomposite modified encapsulant to have fluid properties suitable for wetting before curing, and to have a moderate cross-linking network density and multi-level filler reinforcement structure after curing, thus balancing the processing requirements of injection molding and the mechanical and weather resistance stability of the finished product in complex environments.

[0029] In a preferred embodiment of the present invention, the ultraviolet absorber is a benzotriazole ultraviolet absorber, the antioxidant is a hindered amine antioxidant, and the curing agent is a platinum-based addition curing agent.

[0030] Benzotriazole-based UV absorbers are dispersed within the matrix resin, and the hydroxyl groups in their molecular structure can form intramolecular hydrogen bonds with nitrogen atoms. When exposed to outdoor UV light, they convert absorbed high-energy UV photons into low-energy heat energy through proton transfer and release it, preventing photochemical breakage of the polymer chains in the matrix resin. Preferably, the UV absorber is 2-(2'-hydroxy-5'-methylphenyl)benzotriazole. Optionally, hindered phenolic antioxidants can also be used to achieve free radical scavenging, but hindered amine antioxidants are preferred; because they possess the chemical property of capturing free radicals and then regenerating them, and their molecules do not contain chromophores, they are more suitable for maintaining the initial high light transmittance of the maskless encapsulation layer for a long time.

[0031] Under specified heat curing conditions, the vinyl groups in the catalytically modified vinyl methyl phenyl silicone resin undergo a hydrosilylation reaction. During formulation, to prevent premature local cross-linking of the adhesive, the platinum-based addition curing agent is incorporated during the low-speed mixing stage before the secondary vacuum degassing process. This catalytic addition reaction is completed through direct chemical bond addition, and no anhydrous or low-molecular-weight byproducts are released during the curing stage, ensuring the integrity of the interface morphology at the substrate bonding site.

[0032] The above-mentioned additives further improve the anti-yellowing effect of the nanocomposite modified encapsulant. The cross-linking reaction without by-products improves the density of the cured adhesive layer structure, reduces the scattering interference of internal micropores on visible light transmission, and ensures long-term optical stability.

[0033] In some embodiments of the present invention, the nanocomposite modified encapsulant further includes a leveling and defoaming agent, wherein the leveling and defoaming agent is an organosilicon leveling and defoaming agent; the organosilicon leveling and defoaming agent is 0.1 to 0.5 parts by weight.

[0034] The organosilicon leveling and defoaming agent is uniformly dispersed in the mixed system composed of the matrix resin and nano-inorganic filler, and through the low surface energy siloxane structure contained in its molecular chain, it undergoes directional migration to the gas-liquid interface when the colloid is in the liquid phase.

[0035] Preferably, the silicone leveling and defoaming agent is polyether-modified polydimethylsiloxane. Alternatively, acrylate or fluorocarbon leveling agents can also be used. The silicone leveling and defoaming agent has better chemical compatibility with the silicone resin as the continuous phase, preventing phase separation after curing. During formulation, after being added to the mixed base material, the silicone leveling and defoaming agent, through the fluid shear force of stirring, breaks down the walls of the tiny air bubbles formed inside the system, causing the internal air to merge, rise, and rupture towards the surface, while simultaneously reducing the surface tension of the adhesive during spreading.

[0036] In addition, the amount of the silicone leveling and defoaming agent added is controlled between 0.1 and 0.5 parts. If the amount added is less than 0.1 parts, the surface tension inside the system is insufficient, making it difficult to meet the venting requirements during micro-gap injection molding. If it exceeds 0.5 parts, the free agent molecules are prone to excessive accumulation on the surface of the adhesive layer, hindering the interfacial bonding between the cured adhesive layer and the substrate, and may cause local precipitation leading to an increase in optical haze.

[0037] Preferably, the viscosity of the nanocomposite modified encapsulant at 25°C before curing is between 8000 and 15000 mPa·s. This viscosity range is determined by the initial molecular chain length of the silicone resin and the content of the nano-inorganic filler. At room temperature (25°C), the uncrosslinked mixed base system exhibits moderate pseudoplastic fluid characteristics.

[0038] During encapsulation, this viscosity range allows the adhesive to thin appropriately under injection shear forces, enabling it to flow smoothly along the flow path and, relying on rheological properties and capillary action, directly penetrate and wet the tiny gaps between high-density chips on the substrate. When the viscosity is below 8000 mPa·s, the fluid's thixotropy is insufficient, easily leading to sedimentation of nano-inorganic fillers and edge overflow during injection molding. If the viscosity is above 15000 mPa·s, the flow friction resistance increases dramatically, making it difficult to overcome the venting resistance between chips and easily causing unwetted voids in the bottom area. The aforementioned viscosity range meets the wetting requirements of injection molding in tiny gaps, balancing the adhesive's anti-settling stability with its penetration and spreading performance within tiny gaps, and reducing the risk of structural defects within the adhesive layer.

[0039] This invention also provides a method for preparing a nanocomposite modified encapsulant, used to prepare the nanocomposite modified encapsulant described in the above embodiments. The preparation method includes: S101, Pretreatment step: The matrix resin is put into a mixing device for pre-stirring.

[0040] In some embodiments, the stirring device is a vacuum stirring vessel; in this pretreatment step, the matrix resin is heated to 35°C to 45°C and then pre-stirred, the pre-stirring time is set to 10 to 20 minutes, preferably, pre-stirring at low speed at 40°C for 15 minutes. Specifically, a double planetary vacuum stirring vessel is selected, and by matching the heating range with the stirring time, the polymer chain segments undergo initial deentanglement and the internal frictional resistance of the fluid is reduced.

[0041] S102. Dispersion step: The nano-inorganic filler is added to the pre-stirred matrix resin for dispersion treatment until the powder is completely wetted and no agglomeration occurs, forming a mixed matrix.

[0042] In some embodiments, the dispersion step involves adding the nano-inorganic filler in stages, and the dispersion time is set to 25 to 40 minutes, preferably 30 minutes.

[0043] The phased addition method involves sequentially or alternately adding coupling agent-modified nano-silica, nano-alumina powder, and silane-modified nano-calcium carbonate. A high-speed rotating dispersion disk generates fluid shear force within the matrix resin, disrupting the agglomeration structure between the nanoparticles. After a set dispersion period, the micro-particles are uniformly embedded within the gaps between the siloxane backbone chains, completing the solid-liquid interface relationship.

[0044] S103, Addition and Degassing Steps: Cool the mixed base material, add the ultraviolet absorber and the antioxidant, and then perform the first vacuum degassing treatment.

[0045] In some embodiments, the raw materials of the nanocomposite modified encapsulant further include a leveling and defoaming agent; in the addition and defoaming step, the leveling and defoaming agent is added to the system before performing the first vacuum defoaming treatment. In the addition and defoaming step, the mixed base material is cooled to 20°C to 30°C, and the first vacuum defoaming treatment time is set to 15 to 25 minutes. Preferably, the mixed base material is cooled to 25°C, and the vacuum defoaming treatment is performed for 20 minutes. Controlling the temperature within this range can prevent the subsequent addition of additives from volatilizing or thermally degrading. Under negative pressure, the tiny air bubbles in the system expand in volume and rise to the liquid surface and burst under the action of buoyancy and the leveling and defoaming agent, achieving preliminary degassing and structural densification of the system.

[0046] S104. Curing preparation step: Mix the curing agent into the degassing system and stir until homogeneous. Perform a second vacuum degassing process to obtain the finished adhesive.

[0047] In some embodiments, the curing agent is incorporated by stirring and mixing, and the secondary vacuum degassing treatment time is set to 3 to 8 minutes. To prevent premature local crosslinking reaction, the curing agent is incorporated by stirring at a low speed; the subsequent short secondary vacuum degassing treatment aims to remove trace amounts of air bubbles introduced during the incorporation of the curing agent and to control the system residence time, ensuring that the finished adhesive maintains fluid properties suitable for micro-gap wetting when it exits the reactor.

[0048] The preparation method of this application adopts a combination of segmented temperature-controlled mixing and dual vacuum degassing process, which reduces microscopic pores and hard agglomeration defects in the process of compounding high viscosity resin and nanoparticles, ensures the homogeneous distribution of nano-inorganic reinforcing phase and additives in the colloidal three-dimensional structure, and improves the optical properties and interfacial adhesion of the final cured adhesive layer.

[0049] This invention also provides an LED display screen, including a substrate 10, an LED chip 20 disposed on the substrate 10, and an encapsulating adhesive layer 30. The encapsulating adhesive layer 30 covers the LED chip 20, and the encapsulating adhesive layer 30 is formed by curing a nanocomposite modified encapsulating adhesive as described in any of the preceding embodiments.

[0050] To make the objectives, technical solutions, and technical effects of this application clearer and more complete, the nanocomposite modified encapsulating adhesive and its preparation method described in detail below with reference to specific embodiments and comparative examples. All raw material components used in the embodiments and comparative examples of this application can be obtained commercially, and unless otherwise specified, the amount of each component is by weight.

[0051] The encapsulating adhesives of Examples 1 to 5 and Comparative Examples 1 to 2 of this application were all prepared using the aforementioned preparation method, and the specific steps of unloading and curing were consistent. The specific component ratios of each example and comparative example are shown in Table 1.

[0052]

[0053] The finished adhesives and cured adhesive layers prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were subjected to performance tests. The specific test methods and conditions are as follows: I. Viscosity test before curing: The initial viscosity of the uncrosslinked finished adhesive was measured using a rotational viscometer under a constant temperature environment of 25℃.

[0054] II. Optical Performance Testing: The finished adhesive is cross-linked and cured to form a test film of uniform thickness. The transmittance and haze values ​​in the visible light band are measured using a transmittance / haze meter.

[0055] III. UV Aging Resistance (Yellowing Resistance) Test: The cured adhesive layer sample was placed in a UV accelerated aging test chamber and continuously irradiated for 1000 hours. After irradiation, the color difference of the adhesive layer before and after aging was measured using a spectrophotometer, and the yellowing index ΔE was calculated.

[0056] IV. Thermal Shock Peel Test: The finished adhesive was completely encapsulated onto the PCB test substrate containing the Mini LED chip using a potting process. After curing, it was placed in a thermal shock test chamber. The cyclic test conditions were set from -40℃ to 85℃, and the test was run 1000 times under alternating high and low temperatures. After the cycle, the interface between the adhesive layer and the PCB test substrate was observed and recorded using a high-magnification microscope to determine whether peeling, delamination, warping, or microcracks occurred.

[0057] The test data for various performance indicators of the above embodiments and comparative examples are shown in Table 2.

[0058]

[0059] As shown in Table 2, the encapsulating adhesives prepared in Examples 1 to 5 of this application have a rheological viscosity controlled within the range of 8000 to 15000 mPa·s at 25°C before curing, ensuring that the adhesive can smoothly wet the high-density micron-level chip gaps during the maskless filling stage. The cured adhesive layer has high visible light transmittance (≥92.2%) and low haze characteristics, meeting the optical consistency output requirements of the light-emitting device.

[0060] In the weathering test, after 1000 hours of accelerated UV aging, the yellowing index ΔE of Examples 1 to 5 was less than 1.5, indicating that the vinyl methyl phenyl-modified silicone resin and additives effectively inhibited the photodegradation reaction of the polymer backbone. Furthermore, after 1000 cycles of high and low temperature thermal shock, no interfacial peeling or cracking occurred in Examples 1 to 5.

[0061] Based on the data from Comparative Example 1, it can be found that under the same matrix resin conditions, if the coupling agent modified nano-silica, nano-alumina powder, and silane modified nano-calcium carbonate in the formulation of this application are not used, the cured adhesive layer will have insufficient interfacial adhesion to the PCB test substrate when facing the internal stress generated by alternating hot and cold temperatures. This is due to the lack of stress dispersion and interfacial interaction of the multi-level inorganic filler network. After thermal shock, the adhesive layer will peel up at the edges and the chip will fall off.

[0062] Based on the data from Comparative Example 2, it can be seen that although the initial viscosity and some optical properties of the traditional epoxy resin encapsulation system are acceptable, its chain segments are prone to photo-oxidation under strong outdoor ultraviolet radiation, resulting in a yellowing index ΔE as high as 12.5. Furthermore, under thermal shock, it is prone to network microcracks and delamination failure due to its high brittleness.

[0063] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0064] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0065] The above provides a detailed description of a nanocomposite modified encapsulating adhesive, its preparation method, and an LED display screen provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A nanocomposite modified encapsulating adhesive, characterized in that, It includes matrix resin, nano-inorganic filler, ultraviolet absorber, antioxidant and curing agent; The matrix resin comprises a terminal vinyl methyl phenyl modified organosilicon resin; The nano-inorganic fillers include coupling agent-modified nano-silica, nano-alumina powder, and silane-modified nano-calcium carbonate.

2. The nanocomposite modified encapsulating adhesive according to claim 1, characterized in that, By weight, the components in the nanocomposite modified encapsulant are as follows: 70 to 85 parts of matrix resin, 1 to 4 parts of coupling agent modified nano silica, 0.5 to 2 parts of nano alumina powder, 0.3 to 1.5 parts of silane modified nano calcium carbonate, 0.2 to 1 part of ultraviolet absorber, 0.1 to 0.8 parts of antioxidant, and 3 to 8 parts of curing agent.

3. The nanocomposite modified encapsulating adhesive according to claim 1, characterized in that, The ultraviolet absorber is a benzotriazole ultraviolet absorber, the antioxidant is a hindered amine antioxidant, and the curing agent is a platinum-based addition curing agent.

4. The nanocomposite modified encapsulating adhesive according to claim 1, characterized in that, It also includes a leveling and defoaming agent, wherein the leveling and defoaming agent is an organosilicon leveling and defoaming agent; the organosilicon leveling and defoaming agent is present in parts by weight of 0.1 to 0.5 parts.

5. The nanocomposite modified encapsulating adhesive according to claim 1, characterized in that, The viscosity of the nanocomposite modified encapsulant at 25°C before curing is 8000 to 15000 mPa·s.

6. A method for preparing a nanocomposite modified encapsulating adhesive as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Pretreatment step: The matrix resin is put into a mixing device for pre-stirring; Dispersion step: The nano-inorganic filler is added to the pre-stirred matrix resin for dispersion treatment until the powder is completely wetted and no agglomerates, forming a mixed matrix material; Addition and degassing steps: The mixed base material is cooled, the ultraviolet absorber and the antioxidant are added, and then the first vacuum degassing treatment is performed; Curing preparation steps: The curing agent is mixed into the degassing system and stirred until homogeneous. A second vacuum degassing process is then performed to obtain the finished adhesive.

7. The preparation method according to claim 6, characterized in that, The stirring equipment is a vacuum stirring tank; In the pretreatment step, the matrix resin is heated to 35°C to 45°C and then pre-stirred for a time of 10 to 20 minutes. In the dispersion step, the nano-inorganic filler is added in stages, and the dispersion treatment time is set to 25 to 40 minutes.

8. The preparation method according to claim 6, characterized in that, The raw materials for the nanocomposite modified encapsulating adhesive also include leveling and defoaming agents; In the addition and defoaming step, the leveling and defoaming agent is added to the system before the first vacuum defoaming treatment is performed.

9. The preparation method according to claim 6, characterized in that, In the addition and degassing steps, the mixed base material is cooled to 20°C to 30°C, and the time for the first vacuum degassing treatment is set to 15 to 25 minutes; In the curing preparation step, the curing agent is mixed in by stirring, and the time for the secondary vacuum degassing treatment is set to 3 to 8 minutes.

10. An LED display screen, characterized in that, It includes a substrate, an LED chip disposed on the substrate, and an encapsulating adhesive layer; The encapsulating adhesive layer covers the LED chip, and the encapsulating adhesive layer is formed by curing the nanocomposite modified encapsulating adhesive as described in any one of claims 1 to 5.

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