Resin composition for preparing packaging adhesive film and application thereof

Abstract

The invention provides a resin composition for preparing a packaging adhesive film and application thereof, and the resin composition comprises the following components in parts by weight: 10-20 parts of UV resin, 30-70 parts of epoxy resin, 25-45 parts of a modified amine curing agent, 0.5-2 parts of a curing accelerator, 0.1-2 parts of a photoinitiator and 10-20 parts of light diffusion powder. The modified amine curing agent comprises a long-chain alkyl compound modified amine curing agent; the molecular structure of the long-chain alkyl compound contains an epoxy group. The packaging adhesive film prepared from the resin composition has excellent storage stability and water resistance, is low in curing temperature and short in curing time, and also has relatively high strength and toughness.

Description

Technical Field

[0001] This invention belongs to the field of encapsulation film technology, specifically relating to a resin composition for preparing encapsulation films and its applications. Background Technology

[0002] Mini LED direct-view displays use 50μm LED chips directly as display pixels, serving as the basic unit for image display. Their advantages lie in inheriting the high efficiency, high brightness, high reliability, and fast response time of inorganic LEDs, while also being self-emissive and requiring no backlight. They are small, thin, and easily achieve energy savings. Traditional Mini LED direct-view display encapsulation technology uses two-component epoxy resin molding compound for compression molding. This process is cumbersome, requiring the addition of diffusion powder to mix the adhesive before encapsulation; the molding process requires maintaining high temperature and pressure for 2-3 hours to ensure the molding compound cures and sets, resulting in a time-consuming process, low product yield, and difficulty in rework.

[0003] In recent years, encapsulation films for Mini LED screens have been gradually replacing two-component epoxy resin molding adhesives. This process is quick, simple, and yields high-quality products. The encapsulation film only requires roller bonding or molding. The bonding process involves a pressure of 0.1-0.3 MPa, a temperature of 50-80℃, and a bonding time of 3-5 minutes. Afterward, high-pressure degassing is performed in batches, followed by heat curing at 120℃ for 1.5 hours to complete the Mini LED screen encapsulation process.

[0004] In the current field of Mini LED screen packaging, the commonly used encapsulating films mainly employ anhydride curing agents. However, this system has several technical bottlenecks. Anhydride curing agents typically require high temperatures to initiate the curing reaction, and to lower the curing temperature, curing accelerators are often added. This approach introduces new problems. At room temperature, the encapsulating film undergoes a slow curing reaction. This slow curing process causes the film viscosity to gradually increase, significantly shortening its storage time and causing great inconvenience to the storage and transportation of the encapsulating film.

[0005] Furthermore, acid anhydride curing agents are highly hygroscopic. In the air, they absorb moisture. Water molecules can penetrate and diffuse into the encapsulated film, potentially damaging the chemical bonds within it. This hygroscopicity not only affects the chemical stability of the encapsulated film but may also lead to performance degradation in the encapsulated Mini LED screen.

[0006] Therefore, to meet the high-quality requirements of Mini LED screen packaging, it is particularly important to develop an encapsulating film with excellent storage stability and water resistance. This film needs to have excellent stability at room temperature to extend storage time; at the same time, it needs to have good water resistance to prevent water molecules from damaging the internal structure of the film, thereby ensuring that the encapsulated Mini LED screen maintains stable performance under various environmental conditions. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a resin composition for preparing encapsulating films and its application; the encapsulating film prepared by the resin composition has excellent storage stability and water resistance, low curing temperature and short curing time, and also has high strength and toughness.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a resin composition for preparing an encapsulating film, wherein, by weight, the resin composition comprises 10-20 parts of UV resin, 30-70 parts of epoxy resin, 25-45 parts of modified amine curing agent, 0.5-2 parts of curing accelerator, 0.1-2 parts of photoinitiator, and 10-20 parts of light diffusing powder; wherein the modified amine curing agent comprises an amine curing agent modified with a long-chain alkyl compound; and wherein the molecular structure of the long-chain alkyl compound contains epoxy groups.

[0010] Existing primary amine curing agents have significant drawbacks: First, their mechanical properties (including toughness and impact resistance) and weather resistance are poor, which limits their application scenarios; second, they pose safety hazards such as high toxicity, volatility, and hygroscopicity; third, when directly applied to Mini LED encapsulation film systems, they can cause premature gelation of the film, a sharp decline in storage stability (significantly shortened shelf life), and severe water absorption in the encapsulation edge area.

[0011] This invention modifies primary amine curing agents using long-chain alkyl compounds. Compared with traditional primary amine systems, the modified product exhibits three significant advantages: (1) enhanced fracture resistance due to improved molecular chain flexibility; (2) hydrolytic stability conferred by the hydrophobic long-chain structure; (3) reduced active sites and decreased reactivity after long-chain alkyl grafting modification, thus improving long-term storage stability. Therefore, by using modified amine curing agents with specific structures as latent curing agents, the prepared encapsulating film not only has excellent storage stability and water resistance, low curing temperature, and short curing time, but also has high strength and toughness. Furthermore, it avoids the potential safety hazards of high volatility and toxicity of amine curing agents.

[0012] In this invention, 10 to 20 parts of UV resin can be, for example, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, etc.

[0013] In this invention, 30 to 70 parts of epoxy resin can be, for example, 32 parts, 35 parts, 38 parts, 40 parts, 42 parts, 45 parts, 48 ​​parts, 50 parts, 52 parts, 55 parts, 58 parts, 60 parts, 62 parts, 65 parts, 68 parts, etc.

[0014] In this invention, 25 to 45 parts of modified amine curing agent can be, for example, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, etc.

[0015] In this invention, 0.5 to 2 parts of curing accelerator can be, for example, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, etc.

[0016] In this invention, 0.1 to 2 parts of photoinitiator can be, for example, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.8 parts, 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, etc.

[0017] In this invention, 10 to 20 parts of light diffusing powder, for example, can be 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, etc.

[0018] Preferably, the long-chain alkyl compound has the structure shown in Formula I.

[0019] Formula I.

[0020] In Formula I, R is selected from straight-chain or branched alkyl groups with ≥8 carbon atoms; for example, it can be a straight-chain or branched alkyl group with 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms.

[0021] Preferably, the long-chain alkyl compound includes at least one of octyl glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether, and octadecyl glycidyl ether.

[0022] Preferably, the amine curing agent includes at least one of aliphatic polyamine curing agents, alicyclic polyamine curing agents, aromatic polyamine curing agents, and polyamide curing agents.

[0023] In this invention, the aliphatic polyamine curing agent includes ethylenediamine (EDA), hexamethylenediamine (HDA), triethylenetetramine (TETA), etc.; the alicyclic polyamine curing agent includes 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane (DMDC), N,N-dimethylcyclohexylamine, isophorone diamine (IPDA), etc.; and the aromatic polyamine curing agent includes m-phenylenediamine (MPDA), 4,4′-diaminodiphenylmethane (DDM), diaminodiphenyl sulfone (DDS), etc.

[0024] In this invention, the preparation method of the modified amine curing agent includes: reacting the amine curing agent with a long-chain alkyl compound at 50~70℃ for 2~4h to obtain the modified amine curing agent.

[0025] Preferably, the UV resin includes at least one of modified polybutadiene resin, polyurethane modified acrylate resin, epoxy acrylate resin, and silicone modified polyurethane acrylate resin.

[0026] Preferably, the modified polybutadiene resin has a functionality of 2 to 4, for example, 3; a number average molecular weight of 3000 to 6000, for example, 3500, 4000, 4500, 5000, 5500, etc.; and a viscosity at 25°C of 6500 to 18000 cps, for example, 7000 cps, 8000 cps, 10000 cps, 12000 cps, 14000 cps, 16000 cps, etc.

[0027] Preferably, the polyurethane-modified acrylate resin includes aromatic polyurethane-modified acrylate resin and / or aliphatic polyurethane-modified acrylate resin.

[0028] Preferably, the aromatic modified polyurethane acrylate resin has a functionality of 2-3 and a viscosity of 30,000-60,000 cps at 60°C, such as 35,000 cps, 40,000 cps, 45,000 cps, 50,000 cps, 55,000 cps, etc.; and an acid value of <2 mgKOH / g, such as 0.2 mgKOH / g, 0.4 mgKOH / g, 0.6 mgKOH / g, 0.8 mgKOH / g, 1 mgKOH / g, 1.2 mgKOH / g, 1.4 mgKOH / g, 1.6 mgKOH / g, 1.8 mgKOH / g, etc.

[0029] Preferably, the aliphatic modified polyurethane acrylate resin has a functionality of 2 to 4, for example, 3; a viscosity at 60°C of 9000 to 15000 cps, for example, 10000 cps, 11000 cps, 12000 cps, 13000 cps, 14000 cps, etc.; and an acid value < 2 mgKOH / g, for example, 0.2 mgKOH / g, 0.4 mgKOH / g, 0.6 mgKOH / g, 0.8 mgKOH / g, 1 mgKOH / g, 1.2 mgKOH / g, 1.4 mgKOH / g, 1.6 mgKOH / g, 1.8 mgKOH / g, etc.

[0030] Preferably, the epoxy acrylate resin has a functionality of 2-3 and a viscosity of 500-700 cps at 60°C, for example, 520 cps, 550 cps, 580 cps, 600 cps, 620 cps, 650 cps, 680 cps, etc.; and an acid value <5 mgKOH / g, for example, 0.2 mgKOH / g, 0.4 mgKOH / g, 0.6 mgKOH / g, 0.8 mgKOH / g, 1 mgKOH / g, 1.2 mgKOH / g, 1.4 mgKOH / g, 1.6 mgKOH / g, 1.8 mgKOH / g, 2 mgKOH / g, 2.2 mgKOH / g, 2.5 mgKOH / g, 2.8 mgKOH / g, 3 mgKOH / g, 3.2 mgKOH / g, 3.5 mgKOH / g, 4 mgKOH / g, 4.5 mgKOH / g, etc. mgKOH / g, etc.

[0031] Preferably, the functionality of the organosilicon-modified polyurethane acrylate resin is 2 to 6, for example, 3, 4, 5, etc.; the viscosity at 60°C is 2200 to 4500 cps, for example, 2400 cps, 2600 cps, 2800 cps, 3000 cps, 3200 cps, 3500 cps, 3800 cps, 4000 cps, 4200 cps, 4400 cps, etc.; and the acid value is <1 mgKOH / g, for example, 0.2 mgKOH / g, 0.4 mgKOH / g, 0.6 mgKOH / g, 0.8 mgKOH / g, etc.

[0032] Preferably, the epoxy resin includes at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, biphenyl type epoxy resin, polyurethane modified epoxy resin, polyether modified epoxy resin, organosilicon modified epoxy resin, and dimer acid modified epoxy resin.

[0033] Preferably, the viscosity of the polyurethane-modified epoxy resin at 60°C is 2000~7000 cps, for example, 2500 cps, 3000 cps, 3500 cps, 4000 cps, 4500 cps, 5000 cps, 5500 cps, 6000 cps, 6500 cps, etc.; and the epoxy equivalent is 250~300 g / eq, for example, 260 g / eq, 270 g / eq, 280 g / eq, 290 g / eq, etc.

[0034] In this invention, the polyurethane-modified epoxy resin is a pale yellow transparent liquid with a volatile content of <0.1%.

[0035] Preferably, the viscosity of the polyether-modified epoxy resin at 25°C is 3000~8000 cps, for example, 3500 cps, 4000 cps, 4500 cps, 5000 cps, 5500 cps, 6000 cps, 6500 cps, 7000, 7500, etc.; and the epoxy equivalent is 305~410 g / eq, for example, 310 g / eq, 320 g / eq, 340 g / eq, 360 g / eq, 380 g / eq, 400 g / eq, etc.

[0036] In this invention, the polyether-modified epoxy resin is a pale yellow to colorless transparent liquid.

[0037] Preferably, the viscosity of the silicone-modified epoxy resin at 25°C is 500~1500 cps, for example, 600 cps, 800 cps, 1000 cps, 1200 cps, 1400 cps, etc.; and the epoxy equivalent is 180~200 g / eq, for example, 185 g / eq, 190 g / eq, 195 g / eq, etc.

[0038] In this invention, the organosilicon-modified epoxy resin is a pale yellow to colorless transparent liquid.

[0039] Preferably, the viscosity of the dimer acid modified epoxy resin at 25°C is 500~6000 cps, for example, 600 cps, 800 cps, 1000 cps, 1500 cps, 2000 cps, 3000 cps, 4000 cps, 5000 cps, 5500 cps, etc.; and the epoxy equivalent is 250~500 g / eq, for example, 300 g / eq, 350 g / eq, 400 g / eq, 450 g / eq, etc.

[0040] In this invention, the dimer acid modified epoxy resin is a pale yellow transparent liquid.

[0041] Preferably, the bisphenol A type epoxy resin has a viscosity of 500~2500 cps at 25°C, for example, 600 cps, 800 cps, 1000 cps, 1200 cps, 1500 cps, 1800 cps, 2000 cps, 2200 cps, 2400 cps, etc.; and an epoxy equivalent of 170~250 g / eq, for example, 180 g / eq, 200 g / eq, 220 g / eq, 240 g / eq, etc.

[0042] In this invention, the bisphenol A type epoxy resin is a pale yellow to colorless transparent liquid.

[0043] Preferably, the viscosity of the aliphatic epoxy resin at 25°C is 3500~8000 cps, for example, it can be 4000 cps, 4500 cps, 5000 cps, 5500 cps, 6000 cps, 6500 cps, 7000 cps, 7500 cps, etc.; the epoxy equivalent is 305~335 g / eq, for example, it can be 310 g / eq, 315 g / eq, 320 g / eq, 325 g / eq, 330 g / eq, etc.

[0044] In this invention, the aliphatic epoxy resin is a pale yellow to colorless transparent liquid.

[0045] In this invention, the resin composition further includes 5 to 15 parts of reactive diluent by weight, for example, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, 10.5 parts, 11 parts, 11.5 parts, 12 parts, 12.5 parts, 13 parts, 13.5 parts, 14 parts, 14.5 parts, etc.

[0046] Preferably, the reactive diluent includes at least one of polyester polyol, polyether polyol, polycarbonate polyol, and glycidyl ether.

[0047] Preferably, the viscosity of each of the polyester polyol, polyether polyol, and polycarbonate polyol at 25°C is independently 200~1000 cps, for example, 300 cps, 400 cps, 500 cps, 600 cps, 800 cps, 900 cps, etc.; and the hydroxyl value is independently 50~300 mgKOH / g, for example, 100 mgKOH / g, 150 mgKOH / g, 200 mgKOH / g, 250 mgKOH / g, etc.

[0048] In this invention, the polyester polyol, polyether polyol, and polycarbonate polyol are all light-colored to transparent liquids with a moisture content of <0.2%.

[0049] Preferably, the glycidyl ether comprises monofunctional glycidyl ether and / or difunctional glycidyl ether.

[0050] Preferably, the monofunctional glycidyl ether has an epoxy equivalent of 150~300 g / eq, for example, 160 g / eq, 180 g / eq, 200 g / eq, 220 g / eq, 240 g / eq, 260 g / eq, 280 g / eq, etc.; and a viscosity of 2~50 cps at 25°C, for example, 4 cps, 8 cps, 12 cps, 16 cps, 20 cps, 25 cps, 30 cps, 35 cps, 40 cps, 45 cps, etc.

[0051] Preferably, the bifunctional glycidyl ether has an epoxy equivalent of 100~300 g / eq, for example, 120 g / eq, 150 g / eq, 180 g / eq, 200 g / eq, 220 g / eq, 250 g / eq, 280 g / eq, etc.; and a viscosity of 10~50 cps at 25°C, for example, 15 cps, 20 cps, 25 cps, 30 cps, 35 cps, 40 cps, 45 cps, etc.

[0052] Preferably, the curing accelerator includes at least one of imidazole accelerator, organic urea accelerator, and phosphorus-containing accelerator.

[0053] In this invention, a curing accelerator and a modified amine curing agent are combined to effectively reduce the curing temperature and shorten the curing time of the encapsulation film, thus avoiding the risk of burning out the Mini LED chip due to excessively high temperature and long curing time during the encapsulation process.

[0054] Preferably, the light-diffusing powder includes at least one of organosilicon microspheres and fumed silica.

[0055] In this invention, the photoinitiator can be any conventional photoinitiator in the art, including but not limited to the photoinitiator TPO.

[0056] In this invention, the preparation method of the resin composition includes: stirring and dispersing UV resin, epoxy resin, photoinitiator, and optional reactive diluent at 1500-2000 rpm for 5-20 minutes under light-protected conditions; then adding modified amine curing agent, light diffusing powder, and curing accelerator, followed by degassing and stirring dispersion at 1000-2000 rpm for 1-10 minutes to obtain the resin composition.

[0057] In a second aspect, the present invention provides an encapsulating film comprising the resin composition described in the first aspect.

[0058] Preferably, the thickness of the encapsulating film is 100~200μm, for example, it can be 120μm, 150μm, 180μm, etc.

[0059] In this invention, the method for preparing the encapsulating film includes: coating a resin composition onto the surface of a substrate, curing it, and then covering the cured resin composition surface with another substrate to obtain the encapsulating film; the substrate may be a release film; the coating may be performed using a two-roller coater; the coating spacing is 100~200μm, and the coating speed is 1~3m / min; the curing is carried out under ultraviolet light irradiation; the UV light wavelength is 365nm, and the UV light energy is 3000~4000mj / cm. 2 .

[0060] Thirdly, the present invention provides a Mini LED display screen, the Mini LED display screen comprising the resin composition described in the first aspect or the encapsulating film described in the second aspect.

[0061] Fourthly, the present invention provides a display device, the display device comprising the MiniLED display screen described in the third aspect.

[0062] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

[0063] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0064] The resin composition for preparing encapsulating films provided by this invention uses a specific modified amine curing agent as a latent curing agent, effectively avoiding premature curing reactions during storage, significantly extending the storage time of the encapsulating film at room temperature, and improving the storage stability of the encapsulating film. Secondly, the modified amine curing agent also has excellent water resistance, low affinity for water molecules and non-absorption, effectively inhibiting the potential destructive effect of water molecules on the internal chemical bonds of the film, thereby significantly improving the water resistance of the film and preventing melting under high temperature and high humidity conditions. Thirdly, the modified amine curing agent can also improve the fracture resistance of the film, giving it high strength and toughness, avoiding the disadvantages of high volatility and toxicity of amine curing agents and the high brittleness of the cured product. At the same time, the compounded curing accelerator enables the film to complete curing in a relatively low and short time, ensuring that the encapsulated Mini LED screen maintains stable performance under various environmental conditions. Detailed Implementation

[0065] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0066] All materials used in this invention can be purchased commercially or prepared using conventional methods. Unless otherwise specified, the materials used in this invention are as follows.

[0067] UV resin

[0068] Polyurethane modified acrylate resin: Guangdong Boxin New Material Technology Co., Ltd., B-216.

[0069] Organosilicon-modified polyurethane acrylate resin: Guangdong Boxin New Material Technology Co., Ltd., B-828.

[0070] Epoxy acrylate resin: Guangdong Boxin New Material Technology Co., Ltd.; B-151.

[0071] Epoxy resin

[0072] Bisphenol A epoxy resin: Suzhou Sanmu Group, SM827H.

[0073] Aliphatic epoxy resin: Guangdong Zhongke Zhiyuan New Material Technology Co., Ltd., ZK-1815.

[0074] Reactive diluent: Shanghai Fushun Guojin Trading Co., Ltd., 1,4-Butanediol glycidyl ether.

[0075] Photoinitiator: Zhejiang Yangfan New Material Co., Ltd., TPO.

[0076] Organosilicon microspheres: Shin-Etsu Chemical Industry Co., Ltd., KMP-601.

[0077] Curing accelerator: Guangzhou Weichuang High-Tech Materials Technology Co., Ltd., WE-15.

[0078] Modified amine curing agent A1: 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane modified with dodecyl glycidyl ether; the preparation method includes: weighing 2.384 g of 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane (DMDC) into a three-necked flask (250 mL), and slowly adding 7.269 g of dodecyl glycidyl ether dropwise to the three-necked flask of DMDC under stirring at room temperature. After the addition is complete, the temperature is raised to 60 °C and reacted for 3 h to obtain a colorless and transparent modified amine curing agent A1; the specific synthetic route is shown below.

[0079]

[0080] Modified amine curing agent Ad1: 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane modified with propylene oxide; the preparation method includes: weighing 2.384 g of 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane (DMDC) into a three-necked flask (250 mL), and slowly adding 1.742 g of propylene oxide dropwise to the three-necked flask of DMDC under stirring at room temperature. After the addition is complete, the temperature is raised to 60 °C and reacted for 3 h to obtain a colorless and transparent modified amine curing agent Ad1.

[0081] In this invention, other modified amine curing agents are prepared using a similar method, only requiring the replacement of the corresponding raw materials.

[0082] Specifically:

[0083] Modified amine curing agent A2: Octyl glycidyl ether modified DMDC.

[0084] Modified amine curing agent A3: octadecyl glycidyl ether modified DMDC.

[0085] Modified amine curing agent A4: Dodecyl glycidyl ether modified ethylenediamine (EDA).

[0086] Modified amine curing agent Ad2: Nonylphenyl glycidyl ether modified DMDC.

[0087] Examples 1-8, Comparative Examples 1-6

[0088] Examples 1-8 and Comparative Examples 1-6 each provide a resin composition, the formulation of which is shown in Table 1 by weight. The preparation method of the resin composition includes: adding UV resin, epoxy resin, reactive diluent, and photoinitiator into a container and stirring at 1800 rpm for 10 minutes. Then, adding modified amine curing agent, light diffusing powder, and curing accelerator, and stirring and dispersing at 1500 rpm for 5 minutes to obtain the resin composition.

[0089] Table 1

[0090]

[0091] Table 2

[0092]

[0093] Application examples

[0094] A Mini LED encapsulation film is prepared by means of: coating a resin composition onto one surface of a first release film (heavy release film), coating it into a film using a two-roll coater, curing it under UV light to obtain an adhesive layer, and then covering the adhesive layer with a second release film (light release film) to obtain an encapsulation film with a length of 250 mm, a width of 150 mm, and a thickness of 150 μm; wherein the coating spacing is 150 μm, the coating speed is 1.5 m / min, the UV light wavelength is 365 nm, and the UV light energy is 3500 mJ / cm². 2 The thickness of the first and second release films is 100 μm; the resin compositions are provided in the examples and comparative examples, respectively.

[0095] In this invention, a resin composition is coated onto a heavy release film, and after UV resin curing, a light release film is applied to obtain an encapsulating film. When using the encapsulating film, the light release film is removed, and the heavy release film is removed after heat curing.

[0096] Performance testing

[0097] (1) High temperature and high humidity test

[0098] The encapsulating film was applied to the panel and placed in an environment of 25℃ / 60% humidity for 12 hours. The panel was then placed in a 150℃ oven for 2 hours to cure, and after cooling, it was placed in a thermal shock chamber at 85℃ and 85% humidity for 2 days. The edges were observed for melting. No melting was marked as "none" and melting was marked as "yes".

[0099] (2) Storage stability test

[0100] ① The initial viscosity of the resin compositions provided in the examples and comparative examples was tested using a rheometer and recorded as n0; then the resin compositions were stored at room temperature for 7 days, and the viscosity after storage was tested daily and recorded as nt; viscosity change rate

[0101] Among them, a viscosity change rate of less than 10% after 7 days of storage is rated as excellent; a viscosity change rate of more than 40% after 1 day of storage is rated as poor.

[0102] ② The initial release force of the encapsulating film was tested using a computer-controlled peel force tester (manufacturer: Shenzhen Zhongzheng Instrument Co., Ltd.), and recorded as F0. The encapsulating film was then stored in a constant temperature and humidity chamber (25℃ / 50%RH) for 7 days, and the release force after storage was tested daily and recorded as Fn; the release force change rate...

[0103] Among them, the release force change rate after 7 days of storage is less than 10%, which is recorded as excellent; the release force change rate after 1 day of storage is greater than 100%, which is recorded as poor.

[0104] (3) Tensile strength and elongation at break: The obtained encapsulating film was cured in an oven at 150℃ for 2 hours. After cooling to room temperature, a dumbbell-shaped test strip was obtained using a sampler (manufacturer: Siberon hand-press sampler). The tensile strength and elongation at break were tested using a computer-controlled peel force tester (manufacturer: Shenzhen Zhongzheng Instrument Co., Ltd.) according to the national standard GB / T 30776-2014. The tensile rate was 10 mm / min.

[0105] (4) Hardness: Place the sample on a horizontal platform, hold the hardness tester, and ensure the indenter surface is completely and smoothly in contact with the sample surface. Apply sufficient force vertically without impact to ensure close contact between the indenter and the sample. Within 1 second after the indenter makes full contact with the sample, immediately read the hardness value on the dial or display screen. (Manufacturer: Shanghai Siwei Instrument Manufacturing Co., Ltd.). Unless otherwise specified, all values ​​refer to Shore D hardness. The Shore A hardness obtained in Comparative Example 5 is Shore A hardness.

[0106] (5) Curing temperature and curing time test: Differential scanning calorimetry (DSC) was used to determine the curing characteristics of the adhesive film. First, a dynamic temperature rise test (10℃ / min) was performed to determine the curing temperature: initial temperature, peak temperature and total reaction enthalpy (ΔH). Then, based on the curing temperature (such as 140℃, 150℃ or 210℃) determined by the temperature rise DSC test results, an isothermal test was performed. The time required to reach a curing rate of 99% was determined by integrating the heat flow-time curve and calculating the reaction conversion rate. The entire test was conducted using 5-10mg of sample under nitrogen protection (instrument manufacturer: Hitachi High Technology Co., Ltd.).

[0107] The specific test results are shown in Table 3. Among them, Comparative Example 4, which uses DMDC as a curing agent, will cause UV curing failure, fail to form a film, and make it impossible to measure data; Comparative Example 5 cannot be heat-cured, and some properties cannot be tested.

[0108] Table 3

[0109]

[0110] As shown in Table 3, the resin composition provided by this invention, using a specific modified amine curing agent as a latent curing agent, produces an encapsulating film with excellent storage stability and water resistance, low curing temperature, short curing time, and high strength and toughness. Examples 1-3, 5, and 8 show that the encapsulating film containing the resin composition exhibits no edge melting after 2 days in a thermal shock chamber at 85°C and 85% humidity; after 7 days of storage, the release force change rate is less than 10%, the tensile strength is greater than 18 MPa, the elongation at break is greater than 18%, and the curing temperature and time are low. Examples 1 and 4 show that, with the total amount of UV resin remaining constant, the combination of polyurethane-modified acrylate resin, silicone-modified polyurethane acrylate resin, and epoxy acrylate resin can effectively improve the flexibility of the encapsulating film.

[0111] As can be seen from Examples 1-3, the more modified amine curing agent added, the shorter the curing time required, and the greater the elongation at break of the cured film.

[0112] As can be seen from Examples 1, 6, and 7, the encapsulating film obtained by using amine curing agents modified with specific modifiers can balance strength and toughness.

[0113] Compared with Example 1, in Comparative Example 1, the modified amine curing agent was replaced with methyltetrahydrophthalic anhydride, resulting in poor film storage stability; the viscosity of the adhesive changed by more than 40% after one day of storage at room temperature, the release force of the adhesive film changed by more than double, and the high temperature and high humidity performance was poor.

[0114] Compared with Example 1, no curing accelerator was added in Comparative Example 2, and the thermal curing temperature and time of the adhesive film were significantly increased.

[0115] Compared with Example 1, in Comparative Example 3, the modified amine curing agent A1 was replaced with the modified amine curing agent Ad1, and the toughness of the cured film decreased significantly. This is because the selected alkyl glycidyl ether alkane chain segment is significantly longer than that of propylene oxide, and the improved molecular chain flexibility leads to enhanced fracture resistance.

[0116] Compared with Example 1, in Comparative Example 6, the modified amine curing agent A1 was replaced with modified amine curing agent Ad2, and the toughness of the cured film decreased significantly.

[0117] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A resin composition for preparing an encapsulating film, characterized in that, The resin composition comprises, by weight, 10-20 parts UV resin, 30-70 parts epoxy resin, 25-45 parts modified amine curing agent, 0.5-2 parts curing accelerator, 0.1-2 parts photoinitiator and 10-20 parts light diffusing powder; The modified amine curing agent includes an amine curing agent modified with a long-chain alkyl compound; the long-chain alkyl compound contains an epoxy group in its molecular structure.

2. The resin composition according to claim 1, characterized in that, The long-chain alkyl compound has the structure shown in Formula I; Equation I; In Formula I, R is selected from straight-chain or branched alkyl groups with ≥8 carbon atoms; Preferably, the long-chain alkyl compound includes at least one of octyl glycidyl ether, dodecyl glycidyl ether, tridecyl glycidyl ether, tetradecyl glycidyl ether, and octadecyl glycidyl ether; Preferably, the amine curing agent includes at least one of aliphatic polyamine curing agents, alicyclic polyamine curing agents, aromatic polyamine curing agents, and polyamide curing agents.

3. The resin composition according to claim 1 or 2, characterized in that, The UV resin includes at least one of modified polybutadiene resin, polyurethane modified acrylate resin, epoxy acrylate resin, and silicone modified polyurethane acrylate resin. Preferably, the modified polybutadiene resin has a functionality of 2 to 4, a number-average molecular weight of 3000 to 6000, and a viscosity of 6500 to 18000 cps at 25°C. Preferably, the polyurethane-modified acrylate resin includes aromatic polyurethane-modified acrylate resin and / or aliphatic polyurethane-modified acrylate resin. Preferably, the aromatic polyurethane modified acrylate resin has a functionality of 2 to 3, a viscosity of 30,000 to 60,000 cps at 60°C, and an acid value of <2 mg KOH / g. Preferably, the aliphatic polyurethane modified acrylate resin has a functionality of 2 to 4, a viscosity of 9000 to 15000 cps at 60°C, and an acid value of <2 mgKOH / g. Preferably, the epoxy acrylate resin has a functionality of 2 to 3, a viscosity of 500 to 700 cps at 60°C, and an acid value of <5 mg KOH / g; Preferably, the organosilicon-modified polyurethane acrylate resin has a functionality of 2-6, a viscosity of 2200-4500 cps at 60°C, and an acid value of <1 mgKOH / g.

4. The resin composition according to any one of claims 1 to 3, characterized in that, The epoxy resin includes at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, alicyclic epoxy resin, aliphatic epoxy resin, biphenyl type epoxy resin, polyurethane modified epoxy resin, polyether modified epoxy resin, organosilicon modified epoxy resin, and dimer acid modified epoxy resin. Preferably, the polyurethane-modified epoxy resin has a viscosity of 2000~7000cps at 60°C and an epoxy equivalent of 250~300g / eq. Preferably, the polyether-modified epoxy resin has a viscosity of 3000~8000cps at 25°C and an epoxy equivalent of 305~410g / eq. Preferably, the silicone-modified epoxy resin has a viscosity of 500~1500 cps at 25°C and an epoxy equivalent of 180~200 g / eq. Preferably, the dimer acid modified epoxy resin has a viscosity of 500~6000cps at 25°C and an epoxy equivalent of 250~500g / eq; Preferably, the bisphenol A type epoxy resin has a viscosity of 500~2500cps at 25°C and an epoxy equivalent of 170~250g / eq; Preferably, the aliphatic epoxy resin has a viscosity of 3500~8000cps at 25°C and an epoxy equivalent of 305~335g / eq.

5. The resin composition according to any one of claims 1 to 4, characterized in that, The resin composition further comprises 5 to 15 parts by weight of an active diluent; Preferably, the reactive diluent includes at least one of polyester polyol, polyether polyol, polycarbonate polyol, and glycidyl ether; Preferably, the viscosity of each of the polyester polyol, polyether polyol, and polycarbonate polyol at 25°C is independently 200~1000cps, and the hydroxyl value is independently 50~300mgKOH / g. Preferably, the glycidyl ether comprises a monofunctional glycidyl ether and / or a difunctional glycidyl ether; Preferably, the monofunctional glycidyl ether has an epoxy equivalent of 150~300 g / eq and a viscosity of 2~50 cps at 25°C; Preferably, the difunctional glycidyl ether has an epoxy equivalent of 100~300 g / eq and a viscosity of 10~50 cps at 25°C.

6. The resin composition according to any one of claims 1 to 5, characterized in that, The curing accelerator includes at least one of imidazole accelerator, organic urea accelerator, and phosphorus-containing accelerator; Preferably, the light-diffusing powder includes at least one of organosilicon microspheres and fumed silica.

7. An encapsulating film, characterized in that, The encapsulating film comprises the resin composition according to any one of claims 1 to 6.

8. The encapsulating film according to claim 7, characterized in that, The thickness of the encapsulating film is 100~200μm.

9. A Mini LED display screen, characterized in that, The Mini LED display screen comprises the resin composition as described in any one of claims 1 to 6 or the encapsulating film as described in claim 7 or 8.

10. A display device, characterized in that, The display device includes the Mini LED display screen as described in claim 9.

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