High-transmittance mled packaging glue and high-transmittance mled packaging membrane

Abstract

This invention discloses a high-transmittance MLED encapsulating film and a high-transmittance MLED encapsulating sheet. The high-transmittance MLED encapsulating adhesive comprises: a photocurable main chain resin, a DA reaction donor, a DA reaction acceptor, and a photoinitiator. The photoinitiator photocures the photocurable main chain resin under ultraviolet light. The DA reaction donor and acceptor are used to achieve a reversible DA reaction, which is a cycloaddition reaction between a conjugated diene and an unsaturated double bond. The cycloaddition occurs at temperatures below 100°C, and the reverse ring-opening reaction occurs at temperatures above 110°C. This invention combines double bond radical addition with a DA reaction. The double bond addition satisfies the requirements for surface drying and winding of the film after photocuring. The presence of the DA reaction allows the film to have fluidity at a certain temperature. Increased film fluidity squeezes the residual adhesive on the front side of the LED chip to the sides, reducing the adhesive's absorption of light emitted from the chip and thus increasing the light extraction rate.

Description

Technical Field

[0001] This invention relates to the field of MLED technology, and in particular to a high-transmittance MLED encapsulating adhesive and a high-transmittance MLED encapsulating film. Background Technology

[0002] With the rapid penetration of MLED display technology in high-end TVs, automotive displays, tablets, and VR / AR devices, higher demands are being placed on the optical performance and appearance consistency of display modules. Among these, black color uniformity (i.e., black state uniformity) and high light output (i.e., white state brightness and luminous efficacy) are core indicators determining the visual quality of end products. To achieve high contrast and wide color gamut, the industry generally adopts a design scheme combining local dimming with a precision optical packaging structure. The encapsulating film, as a key functional layer covering the surface of the MLED chip, directly affects the display effect due to its optical characteristics, curing method, and process adaptability. MLED is a collective term for two next-generation LED display technologies: Mini LED and Micro LED. Its core is the miniaturization and arraying of LED chips to achieve the ultimate display effect of self-illumination, high brightness, long lifespan, and low power consumption.

[0003] Currently, some technical solutions employ a photo-thermal dual curing system, such as the one proposed in CN202310913173.1. This involves first using UV curing to create a semi-cured film from a photosensitive epoxy composite adhesive, and then using thermosetting to roll-press and encapsulate the film onto a direct-view display panel to create a direct-view screen. However, this type of system has significant drawbacks: First, it suffers from poor pressing stability. The film undergoes a slow pre-reaction at room temperature, resulting in differences in fluidity at high temperatures, making it difficult to control the pressing effect. Second, it requires strict storage conditions. Generally, thermosetting systems require frozen storage to extend the film's usability, and material requisition also involves steps such as material requisition and rewarming, placing higher demands on the production process and storage conditions.

[0004] Therefore, there is an urgent need to develop a new type of encapsulation film material and supporting process that can achieve excellent ink color consistency and high light output, as well as good room temperature storage stability and simple hot pressing processing characteristics, so as to meet the industrialization needs of MLED display modules for high performance, high yield and low cost packaging.

[0005] Therefore, existing technologies have shortcomings and need to be improved. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high light transmittance MLED encapsulating adhesive and a high light transmittance MLED encapsulating film to solve the problems mentioned in the background art.

[0007] The technical solution of the present invention is as follows: A high-transmittance MLED encapsulating adhesive is provided, comprising: a photocurable main chain resin, a DA reaction donor, a DA reaction acceptor, and a photoinitiator; the photoinitiator photocures the photocurable main chain resin under ultraviolet light; the DA reaction donor and DA reaction acceptor are used to achieve a reversible DA reaction, which is a cycloaddition reaction between a conjugated diene and an unsaturated double bond, undergoing a forward cyclization at <100℃ and a reverse ring-opening reaction at >110℃; by mass, the main chain resin is added at 20-90% of the total mass, the DA reaction donor at 1%-60% of the total mass, the DA reaction acceptor at 1%-60% of the total mass, and the photoinitiator at 0.1%-5% of the total mass.

[0008] The high-transmittance MLED encapsulating adhesive of this invention combines double-bond free radical addition with a reversible Diels-Alder reaction (hereinafter referred to as the DA reaction). The double-bond addition satisfies the conditions for surface drying and winding of the adhesive film after photocuring, while the presence of the DA reaction allows the adhesive film to have fluidity at a certain temperature, thereby enabling the encapsulation of LED panels via hot pressing. The improved film fluidity squeezes the residual adhesive on the front of the LED chip to the sides, reducing the absorption of light emitted by the chip by the adhesive and its pigments, thus increasing the light extraction efficiency. The reversible DA reaction is a cycloaddition reaction between a conjugated diene and an unsaturated double bond. At temperatures below 100°C, it undergoes a forward addition ring-forming reaction, while at high temperatures (above 110°C), it undergoes a reverse ring-opening reaction.

[0009] Furthermore, the main chain resin is an acrylate compound, and the photoinitiator is at least one selected from hydroxy ketone, acylphosphine oxide, α-amino ketone, iodonium salt, and thiodonium salt.

[0010] Further, the acrylate compound is at least one of polyurethane acrylate, aliphatic polyurethane acrylate, polyether acrylate, polyester acrylate, silicone-modified acrylate, and epoxy acrylate; the functionality of the acrylate is 2 to 8.

[0011] Furthermore, the high-transmittance MLED encapsulating adhesive further includes: pigments (i.e., colorants), wherein the amount of pigment added is 0.1% to 5% of the total mass; the pigments include: black pigments and / or blue pigments; the black pigments include inorganic black and / or organic black, wherein the inorganic black is at least one of: carbon black, iron oxide black, copper chromium black, iron chromium black, cobalt black, manganese iron black, and titanium black, and the organic black is at least one of aniline black, perylene black, and solvent black; the blue pigments include: inorganic blue and / or organic blue, wherein the inorganic blue is at least one of ultramarine, cobalt blue, and iron blue, and the organic blue is at least one of phthalocyanine blue and indanthrene blue.

[0012] Further, the DA reaction donor is at least one of 2-furanyl acrylate, 2-furanyl methacrylate, bisfuranyl acrylate, and 2-(acryloyloxymethyl)furan; the DA reaction acceptor is at least one of monofunctional maleimide, difunctional maleimide, polyfunctional maleimide, polyethylene glycol bismaleimide, and maleic anhydride.

[0013] Furthermore, the high-transmittance MLED encapsulating adhesive further includes: a flexibility-adjusting monomer; the amount of the flexibility-adjusting monomer added is 1% to 40% of the total mass; the flexibility-adjusting monomer is at least one of acrylate monomers and furan monomers. The flexibility-adjusting monomer is used to adjust the flexibility of the high-transmittance MLED encapsulating adhesive after photocuring, preventing it from being insufficiently flexible after photocuring. When the flexibility-adjusting monomer is an acrylate monomer, the principle is that the acrylate monomer undergoes a polymerization reaction with the photocurable main chain resin, reducing the reaction between the photocurable main chain resins, thereby reducing the degree of polymerization and adjusting the flexibility; similarly, when the flexibility-adjusting monomer is a furan monomer, the furan monomer reacts with the DA reaction acceptor, reducing the reaction between the DA reaction donor and the DA reaction acceptor, thereby adjusting the flexibility.

[0014] Furthermore, when the flexible regulating monomer is an acrylate monomer, the acrylate monomer is at least one selected from polyethylene glycol acrylate, octyl acrylate, butyl acrylate, lauryl acrylate, and isobornyl acrylate; when the flexible regulating monomer is a furan monomer, the furan monomer is at least one selected from tetrahydrofurfuryl acrylate, furfuryl alcohol, furfurylamine, furan-terminated polyethylene glycol, furan-terminated polycaprolactone, and furan-modified polyurethane acrylate.

[0015] Furthermore, the high-transmittance MLED encapsulating adhesive further includes: a heat stabilizer, wherein the amount of the heat stabilizer added is 0.05% to 2% of the total mass; the heat stabilizer is at least one of Irganox 1010, Irgafos 168, Ultranox 626, Irganox 1076, BHT, Tinuvin 1130, and Chimassorb 944.

[0016] Furthermore, the high-transmittance MLED encapsulating adhesive further includes a toughening agent, wherein the toughening agent is added at a rate of 1% to 10% of the total mass; the toughening agent is at least one selected from maleic anhydride-grafted SEBS, core-shell rubber particles, polycaprolactone acrylate, polylactic acid diacrylate, amino-terminated nitrile rubber acrylate, carboxyl-terminated nitrile rubber modified acrylate, and polypropylene glycol diacrylate. The toughening agent is used to improve the toughness of the high-transmittance MLED encapsulating adhesive after photocuring, preventing the film from being easily torn after photocuring.

[0017] Furthermore, the present invention also provides a high-transmittance MLED encapsulation film, which is manufactured by the following method, including: S1: Coating preparation; prepare the aforementioned high light transmittance MLED encapsulating adhesive.

[0018] S2: Coating and film formation and winding; The high-transmittance MLED encapsulating adhesive is coated onto the lower release film, with a wet film thickness of 30~150μm. Then, a release film is placed over the adhesive film, and UV curing is performed. The cumulative radiation energy of the UV curing is 100~2000mJ / cm². 2 .

[0019] S3: Curing of the roll material; let the coated roll material stand at 20℃-90℃ for 0.5~48h to cure.

[0020] S4: After allowing to stand and mature, store at room temperature. In this method, room temperature is 4℃-40℃.

[0021] To reduce the impact of die-cutting on the roll material, step S4 further includes: slicing the cured roll material into the required shapes, such as circles, squares, and rectangles, and then storing it at room temperature. When needed, there is no need for die-cutting again; the pre-cut film can be directly heat-pressed onto the MLED display module.

[0022] Using the above-described scheme, this invention provides a high-transmittance MLED encapsulating adhesive and a high-transmittance MLED encapsulating film. Based on double-bond free radical addition, a reversible DA reaction is incorporated. The double-bond addition satisfies the conditions for surface drying and winding of the adhesive film after photocuring, while the presence of the DA reaction allows the adhesive film to have fluidity at a certain temperature, thereby enabling the encapsulation of LED light panels through hot pressing. The improved fluidity of the adhesive film squeezes the residual adhesive on the front side of the LED chip to the sides, reducing the absorption of light emitted by the chip by the adhesive and its pigments, thus increasing the light extraction efficiency. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the principle of UV-initiated free radical addition polymerization of acrylic resin according to the present invention.

[0024] Figure 2 This is a schematic diagram illustrating the principle of cyclization and ring-opening of furan and maleimide in this invention.

[0025] Figure 3 This is a schematic diagram illustrating the changes in the internal structure of the high-transmittance MLED encapsulating adhesive during the coating, curing, and hot-pressing processes of the adhesive film according to the present invention.

[0026] Figure 4 Microscopic photograph of the chip on an unpackaged miniLED module.

[0027] Figure 5 Microscopic images of the chipset after hot-pressing and encapsulation of the miniLED module using the film prepared in Example 1.

[0028] Figure 6 This is a microscope image of the chipset after the miniLED module is thermo-press-packaged using the diaphragm in Comparative Example 1.

[0029] Figure 7 Microscopic images of the chipset after the miniLED module is thermo-press-packaged using the diaphragm in Comparative Example 2.

[0030] Figure 8 The image shows a microscopic photograph of the miniLED module after it has been thermo-pressed and packaged using a film prepared in Example 1 for 10 days.

[0031] Figure 9 This is a microscope image of the miniLED module after it has been thermo-pressed and packaged, 10 days after the film of Comparative Example 1 was placed.

[0032] Figure 10 This is a microscope image of the miniLED module after it has been thermo-pressed and packaged, 10 days after the film of Comparative Example 2 was placed.

[0033] Figure 11 The image shows a microscopic photograph of the miniLED module after it has been thermo-pressed and packaged using a film prepared in Example 1 for 20 days.

[0034] Figure 12 This is a microscope image of the miniLED module after it has been thermo-pressed and packaged, 20 days after the film of Comparative Example 1 was placed.

[0035] Figure 13 This is a microscope image of the miniLED module after it has been thermo-pressed and packaged, 20 days after the film of Comparative Example 2 was placed.

[0036] Figure 14 A macroscopic photograph of an unpackaged miniLED module.

[0037] Figure 15This is a macroscopic photograph of the packaged miniLED module. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0039] Please see Figures 1-3 This invention provides a high-transmittance MLED encapsulating adhesive, comprising: a photocurable main chain resin, a DA reaction donor, a DA reaction acceptor, and a photoinitiator; the photoinitiator photocures the photocurable main chain resin under ultraviolet light; the DA reaction donor and DA reaction acceptor are used to achieve a reversible DA reaction, which is a cycloaddition reaction between a conjugated diene and an unsaturated double bond, performing a forward cyclization at <100°C and a reverse ring-opening reaction at >110°C; by mass, the main chain resin accounts for 20-90% of the total mass, the DA reaction donor accounts for 1%-60% of the total mass, the DA reaction acceptor accounts for 1%-60% of the total mass, and the photoinitiator accounts for 0.1%-5% of the total mass.

[0040] The high-transmittance MLED encapsulating adhesive of this invention combines double-bond free radical addition with a reversible Diels-Alder reaction (hereinafter referred to as the DA reaction). The double-bond addition satisfies the conditions for surface drying and winding of the adhesive film after photocuring, while the presence of the DA reaction allows the adhesive film to have fluidity at a certain temperature, thereby enabling the encapsulation of LED panels via hot pressing. The improved film fluidity squeezes the residual adhesive on the front of the LED chip to the sides, reducing the absorption of light emitted by the chip by the adhesive and its pigments, thus increasing the light extraction efficiency. The reversible DA reaction is a cycloaddition reaction between a conjugated diene and an unsaturated double bond. At temperatures below 100°C, it undergoes a forward addition ring-forming reaction, while at high temperatures (above 110°C), it undergoes a reverse ring-opening reaction.

[0041] When UV radiation initiates free radical addition, the high electronegativity of the carboxyl groups on acrylic resin results in a strong electron-withdrawing effect. Due to this electron-deficient effect, the unsaturated double bonds in acrylic resin are preferentially attacked by free radicals, forming stable secondary carbon free radicals, which promote chain growth. While maleimide also has electron-deficient double bonds, its steric hindrance is significant, and the resulting free radicals are unstable. Furthermore, the conjugated double bonds in furan possess aromaticity; free radical addition would destroy this aromaticity, resulting in high-energy and unstable intermediates. Therefore, the free radical reactivity of maleimide and furan is far lower than that of acrylic double bonds. Thus, during coating, UV radiation-induced free radical addition primarily results in chain growth of the acrylic double bonds, with almost no competition between the conjugated double bonds of furan and the unsaturated double bonds of maleimide.

[0042] Benefits of incorporating DA reaction design into the composition of high transmittance MLED encapsulant: (1) The finished encapsulant film has completed double bond photocuring crosslinking and DA reaction forward ring-forming crosslinking, with high crosslinking degree and high curing degree. Without unpacking, there are no special requirements for storage conditions, and it can be stored at room temperature for more than 1 year; while conventional photothermal dual-curing films usually need to be stored at low temperature and have a short shelf life, usually only 1 to 6 months, which puts forward relatively high production management and storage requirements. (2) When using encapsulant film to encapsulate mini LED modules, the hot pressing process of existing encapsulant film equipment is used. The hot pressing temperature reaches the reverse ring-opening temperature of DA reaction. Heating for a very short time can open the DA ring in the entire film structure, generate conjugated dienes and maleimides, reduce the overall crosslinking degree, and make it fluid and filling at this temperature, which can be matched with existing hot pressing equipment.

[0043] The main structure of the high-transmittance MLED encapsulating adhesive of this invention utilizes unsaturated double bonds. During coating, UV radiation initiates free radical addition polymerization, forming a linear resin structure to achieve surface drying, facilitating subsequent film coating and winding. The formulation simultaneously contains donor and acceptor functional groups capable of DA reactions. These two functional groups can undergo forward cyclization reactions at room temperature or slightly above room temperature, increasing the crosslinking degree of the adhesive film. The adhesive film changes from a linear long chain to a network structure, ensuring the stability of the adhesive film during room temperature storage. At high temperatures, reverse ring-opening reactions can occur, reducing the crosslinking degree of the adhesive film. The adhesive film changes from a network structure back to a linear long chain, and the temperature reaches the Tf temperature (flow temperature) of the adhesive film under linear structure, changing from a highly elastic state to a viscous flow state. Therefore, the adhesive film has good flowability and filling properties during hot pressing.

[0044] The main chain resin is an acrylate compound, and the photoinitiator is at least one of hydroxy ketone, acylphosphine oxide, α-amino ketone, iodonium salt, and thiodonium salt.

[0045] The acrylate compound is at least one of polyurethane acrylate, aliphatic polyurethane acrylate, polyether acrylate, polyester acrylate, silicone-modified acrylate, and epoxy acrylate; the functionality of the acrylate is 2 to 8.

[0046] The high-transmittance MLED encapsulating adhesive further includes: pigments (i.e., colorants), wherein the amount of pigment added is 0.1% to 5% of the total mass; the pigments include: black pigments and / or blue pigments; the black pigments include inorganic black and / or organic black, wherein the inorganic black is at least one of: carbon black, iron oxide black, copper chromium black, iron chromium black, cobalt black, manganese iron black, and titanium black, and the organic black is at least one of aniline black, perylene black, and solvent black; the blue pigments include: inorganic blue and / or organic blue, wherein the inorganic blue is at least one of ultramarine, cobalt blue, and iron blue, and the organic blue is at least one of phthalocyanine blue and indanthrene blue.

[0047] The DA reaction donor is at least one of 2-furanyl acrylate, 2-furanyl methacrylate, bisfuranyl acrylate, and 2-(acryloyloxymethyl)furan; the DA reaction acceptor is at least one of monofunctional maleimide, difunctional maleimide, polyfunctional maleimide, polyethylene glycol bismaleimide, and maleic anhydride.

[0048] The high-transmittance MLED encapsulant further includes: a flexibility-adjusting monomer; the amount of the flexibility-adjusting monomer added is 1% to 40% of the total mass; the flexibility-adjusting monomer is at least one of acrylate monomers and furan monomers. The flexibility-adjusting monomer is used to adjust the flexibility of the high-transmittance MLED encapsulant after photocuring, preventing it from being insufficiently flexible after photocuring. When the flexibility-adjusting monomer is an acrylate monomer, the principle is that the acrylate monomer undergoes a polymerization reaction with the photocurable main chain resin, reducing the reaction between the photocurable main chain resins, thereby reducing the degree of polymerization and adjusting the flexibility; similarly, when the flexibility-adjusting monomer is a furan monomer, the furan monomer reacts with the DA reaction acceptor, reducing the reaction between the DA reaction donor and the DA reaction acceptor, thereby adjusting the flexibility.

[0049] When the flexible regulating monomer is an acrylate monomer, the acrylate monomer is at least one selected from polyethylene glycol acrylate, octyl acrylate, butyl acrylate, lauryl acrylate, and isobornyl acrylate; when the flexible regulating monomer is a furan monomer, the furan monomer is at least one selected from tetrahydrofurfuryl acrylate, furfuryl alcohol, furfurylamine, furan-terminated polyethylene glycol, furan-terminated polycaprolactone, and furan-modified polyurethane acrylate.

[0050] The high-transmittance MLED encapsulating adhesive further includes: a heat stabilizer, wherein the amount of the heat stabilizer added is 0.05% to 2% of the total mass; the heat stabilizer is at least one of Irganox 1010, Irgafos 168, Ultranox 626, Irganox 1076, BHT, Tinuvin 1130, and Chimassorb 944.

[0051] The high-transmittance MLED encapsulating adhesive further includes a toughening agent, wherein the toughening agent is added at a rate of 1% to 10% of the total mass; the toughening agent is at least one selected from maleic anhydride-grafted SEBS, core-shell rubber particles, polycaprolactone acrylate, polylactic acid diacrylate, amino-terminated nitrile rubber acrylate, carboxyl-terminated nitrile rubber modified acrylate, and polypropylene glycol diacrylate. The toughening agent is used to improve the toughness of the high-transmittance MLED encapsulating adhesive after photocuring, preventing the film from being easily torn after photocuring.

[0052] The present invention also provides a high-transmittance MLED encapsulation film, which is manufactured by the following method, including: S1: Coating preparation; prepare the aforementioned high light transmittance MLED encapsulating adhesive.

[0053] S2: Coating and film formation and winding; The high-transmittance MLED encapsulating adhesive is coated onto the lower release film, with a wet film thickness of 30~150μm. Then, a release film is placed over the adhesive film, and UV curing is performed. The cumulative radiation energy of the UV curing is 100~2000mJ / cm². 2 .

[0054] In one embodiment, the lower release film (coating substrate) is a PET (polyethylene terephthalate) release film with a thickness of 25-125 micrometers and a release force of 15-100 g / inch; the upper release film (coating) is one of PET, PC, PE, PP, or CPP release films with a thickness of 25-125 micrometers and a release force of 30-150 g / inch; the curing method is light radiation curing, and the light source is one of a mercury lamp or an LED lamp, with the mercury lamp having a power of 3-10 kW and the LED lamp having a wavelength of 245-420 nm and a light power of 1000-25000 mW; the coating machine speed is 3-20 m / min; the coating head type is one of a slot coating head, a doctor blade coating head, or a gravure coating head; the wet thickness of the coating is 30-150 micrometers; and the cumulative radiation energy during coating is 100-2000 mJ / cm². 2 The coating length of a single roll of film shall not exceed 1000m.

[0055] S3: Curing of the roll material; let the coated roll material stand at 20℃-90℃ for 0.5~48h to cure.

[0056] S4: After allowing to stand and mature, store at room temperature. In this method, room temperature is 4℃-40℃.

[0057] To reduce the impact of die-cutting on the roll material, step S4 further includes: slicing the cured roll material into the required shapes, such as circles, squares, and rectangles, and then storing it at room temperature. When needed, there is no need for further die-cutting; the pre-cut film is directly heat-pressed onto the MLED. Specifically, the die-cutting method includes one of round-to-round die-cutting, flat-to-flat die-cutting, and laser cutting, with flat-to-flat die-cutting being preferred.

[0058] The following description is based on specific embodiments.

[0059] Example 1 Coating formulation: All figures are by weight. Polyether polyurethane acrylic resin 40% (Sartomer CN9007), 2-furan acrylic acid 8% (Aladdin, CAS No.: 539-47-9), aliphatic bismaleimide 12% (Lonza, BMI-1000), TPO-L 0.5% (Guangdong Jihe New Materials), isoborneol acrylate 10% (Taiwan Changxing, EM70C), carbon black 0.5% (Mitsubishi, MA100), heat stabilizer 1% (BASF, Irganox 1010), CTBN modified acrylate 8% (Emerald Kalama, Hypro® R-45AHTLO).

[0060] Example 2 Coating formulation: All figures are by weight. Polyether polyurethane acrylic resin 60% (Sartomer CN9007), 2-furan acrylic acid 8% (Aladdin, CAS No.: 539-47-9), aliphatic bismaleimide 12% (Lonza, BMI-1000), TPO-L 0.5% (Guangdong Jihe New Materials), isoborneol acrylate 18% (Taiwan Changxing, EM70C), carbon black 0.5% (Mitsubishi, MA100), heat stabilizer 1% (BASF, Irganox 1010).

[0061] Example 3 Coating formulation: All figures are by weight. Polyether polyurethane acrylic resin 60% (Sartomer CN9007), 2-furan acrylic acid 8% (Aladdin, CAS No.: 539-47-9), N,N'-1,3-phenylenebismaleimide 12% (Shanghai Aoji Chemical), TPO-L 0.5% (Guangdong Jihe New Materials), isobornyl acrylate 10% (Taiwan Changxing, EM70C), carbon black 0.5% (Mitsubishi, MA100), heat stabilizer 1% (BASF, Irganox 1010), CTBN modified acrylate 8% (Emerald Kalama, Hypro® R-45AHTLO).

[0062] Comparative Example 1 Coating formulation: All figures are by weight. Polyurethane acrylic resin 60% (Sartomer CN9016), epoxy resin 20% (Nanya, NPEF 170), TPO-L 0.5% (Guangdong Jihe New Materials), HDI trimer 10% (Covestro, N3300), isoborneol acrylate 8% (Taiwan Chang Hsing, EM70C), carbon black 0.5% (Mitsubishi, MA100), heat stabilizer 1% (BASF, Irganox 1010).

[0063] Comparative Example 2 Commercially available MLED encapsulation black film, Dongguan Yimei Technology, YMF1065B. The instruction manual requires storage at 0-10℃, and storage at 20-30℃ for no more than 7 days.

[0064] Examples 1-3 and Comparative Example 1 all used doctor blade coating at a speed of 8 m / min and were cured using a UV LED lamp with a wavelength of 395 nm and a radiation energy of 1500 mJ / cm². 2 The wet film thickness was 50 micrometers, the light release film was 100 micrometers with a release force of 5-8g, and the heavy release film was 50 micrometers with a release force of 30-40g. After coating, the films were cut into slices using flat-to-flat die-cutting to obtain the encapsulation films for each example.

[0065] The following experiments were conducted using Examples 1-3 and Comparative Example 1: DMA stretching mode test to confirm the optimal flow temperature window for each embodiment at the lowest modulus plateau temperature; Elongation at break test to confirm the brittleness of the film at room temperature; For different examples, the MLED modules were thermo-pressed at their optimal flow temperature, with a pressure of 0.5 MPa, a vacuum degree of -99 kPa, a vacuum period of 60 s, and a pressing period of 60 s, and the light output was compared. Place the above examples at room temperature for a period of time and test the light output rate after encapsulation.

[0066] Using Comparative Example 2: (1) Pressing was performed using the pressing conditions recommended in the instruction manual: 140°C, 1.5MPa, 60s vacuum, and 120s pressing. The light output rate was recorded. (2) Place it at room temperature for a period of time, and press it using the pressing conditions recommended in its instruction manual: 140℃, 1.5MPa, 60s vacuum, and 120s pressing. Record the light output rate. The data is shown in the table below:

[0067] It can be seen that the elongation at break of Examples 1, 2, and 3 is significantly higher than that of Comparative Example 1, and the flexibility at room temperature is better. The elongation at break is Example 2 > Example 1 > Example 3, indicating that Example 2 has the best flexibility.

[0068] Please see Figures 4-15 Taking miniLED as an example, Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 were all stored at room temperature and then applied to miniLED for bonding tests. It can be seen that room temperature storage has no significant effect on the bonding effect of Examples 1, 2, and 3; however, the light output rate of Comparative Example 1 and Comparative Example 2 decreased significantly with the increase of time. In addition, the instruction manual of Comparative Example 2 also indicated that the film stored at room temperature should be used within 7 days, indicating that room temperature storage will affect the bonding effect of Comparative Example 2.

[0069] In summary, this invention provides a high-transmittance MLED encapsulating adhesive and a high-transmittance MLED encapsulating film. Based on double-bond radical addition, it incorporates a reversible Diels-Alder reaction (hereinafter referred to as the DA reaction). The double-bond addition satisfies the conditions for surface drying and winding of the adhesive film after photocuring, while the presence of the DA reaction allows the adhesive film to have fluidity at a certain temperature, thereby enabling the encapsulation of LED light panels through hot pressing. The improved fluidity of the adhesive film squeezes the residual adhesive on the front side of the LED chip to the sides, reducing the absorption of light emitted by the chip by the adhesive and its pigments, thus increasing the light extraction efficiency.

[0070] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-transmittance MLED encapsulation adhesive, characterized in that, include: The product comprises a photocurable main-chain resin, a DA reaction donor, a DA reaction acceptor, and a photoinitiator. The photoinitiator photocures the main-chain resin under ultraviolet light. The DA reaction donor and acceptor are used to achieve a reversible DA reaction, which is a cycloaddition reaction between a conjugated diene and an unsaturated double bond. The cycloaddition occurs at temperatures below 100°C, and the reverse ring-opening reaction occurs at temperatures above 110°C. By mass, the main-chain resin accounts for 20-90% of the total mass, the DA reaction donor accounts for 1%-60% of the total mass, the DA reaction acceptor accounts for 1%-60% of the total mass, and the photoinitiator accounts for 0.1%-5% of the total mass.

2. The high light transmittance MLED encapsulating adhesive according to claim 1, characterized in that, The main chain resin is an acrylate compound, and the photoinitiator is at least one of hydroxy ketone, acylphosphine oxide, α-amino ketone, iodonium salt, and thiodonium salt. The acrylate compound is at least one of polyurethane acrylate, aliphatic polyurethane acrylate, polyether acrylate, polyester acrylate, silicone-modified acrylate, and epoxy acrylate. The functionality of the acrylate is 2 to 8.

3. The high light transmittance MLED encapsulating adhesive according to claim 1, characterized in that, Also includes: The pigments are added at an amount of 0.1% to 5% of the total mass; the pigments include: black pigments and / or blue pigments; the black pigments include inorganic black and / or organic black, wherein the inorganic black is at least one of: carbon black, iron oxide black, copper chromium black, iron chromium black, cobalt black, manganese iron black, and titanium black, and the organic black is at least one of aniline black, perylene black, and solvent black; the blue pigments include: inorganic blue and / or organic blue, wherein the inorganic blue is at least one of ultramarine, cobalt blue, and iron blue, and the organic blue is at least one of phthalocyanine blue and indanthrene blue.

4. The high light transmittance MLED encapsulating adhesive according to claim 1, characterized in that, The DA reaction donor is at least one of 2-furanyl acrylate, 2-furanyl methacrylate, bisfuranyl acrylate, and 2-(acryloyloxymethyl)furan; the DA reaction acceptor is at least one of monofunctional maleimide, difunctional maleimide, polyfunctional maleimide, polyethylene glycol bismaleimide, and maleic anhydride.

5. The high light transmittance MLED encapsulating adhesive according to claim 1, characterized in that, Also includes: Flexible regulating monomer; The amount of the flexible regulating monomer added is 1% to 40% of the total mass; The flexible regulating monomer is at least one of acrylate monomers and furan monomers.

6. The high light transmittance MLED encapsulating adhesive according to claim 5, characterized in that, When the flexible regulating monomer is an acrylate monomer, the acrylate monomer is at least one selected from polyethylene glycol acrylate, octyl acrylate, butyl acrylate, lauryl acrylate, and isobornyl acrylate; when the flexible regulating monomer is a furan monomer, the furan monomer is at least one selected from tetrahydrofurfuryl acrylate, furfuryl alcohol, furfurylamine, furan-terminated polyethylene glycol, furan-terminated polycaprolactone, and furan-modified polyurethane acrylate.

7. The high light transmittance MLED encapsulating adhesive according to claim 1, characterized in that, Also includes: The heat stabilizer, by mass, is added at a rate of 0.05% to 2% of the total mass; the heat stabilizer is at least one of Irganox 1010, Irgafos 168, Ultranox 626, Irganox 1076, BHT, Tinuvin 1130, and Chimassorb 944.

8. The high light transmittance MLED encapsulating adhesive according to claim 1, characterized in that, Also includes: The toughening agent, by mass, is added in an amount of 1% to 10% of the total mass; the toughening agent is at least one of maleic anhydride-grafted SEBS, core-shell rubber particles, polycaprolactone acrylate, polylactic acid diacrylate, amino-terminated nitrile rubber acrylate, carboxyl-terminated nitrile rubber modified acrylate, and polypropylene glycol diacrylate.

9. A high-transmittance MLED encapsulation film, characterized in that, It is made by the following methods, including: S1: Coating preparation; Formulating the high light transmittance MLED encapsulating adhesive as described in any one of claims 1-8; S2: coating and film forming and winding; coating the high light transmittance MLED packaging adhesive on the lower release film, the wet thickness of the adhesive film is 30-150 μm, then covering the upper release film on the adhesive film, and performing light curing by ultraviolet rays, the cumulative radiation energy of the light curing is 100-2000 mJ / cm 2 ; S3: Curing of the roll material; let the coated roll material stand at 20℃-90℃ for 0.5~48h to cure. S4: After allowing to stand and mature, store at room temperature.

10. The high transmittance MLED encapsulation film according to claim 9, characterized in that, Step S4 also includes slicing the cured roll material.

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