Phosphorus-nitrogen-containing UV-curable flame-retardant coating, LED display module and preparation method thereof

Abstract

The invention belongs to the technical field of LED display screens, and particularly relates to a phosphorus-nitrogen-containing UV curing flame-retardant coating, an LED display module and a preparation method of the phosphorus-nitrogen-containing UV curing flame-retardant coating. Compared with the prior art, the UV curing prepolymer containing phosphorus and nitrogen is a cyclotriphosphazene functionalized product, contains phosphorus and nitrogen, and is endowed with an excellent flame retardant effect due to high nitrogen and phosphorus content; the flame-retardant coating has the advantages that the flame-retardant coating contains acryloyloxy which can be cured through UV, each molecular structure contains six curable functional groups, and the overall structural compactness can be improved after curing, so that the heat resistance of the molecular structures is improved, and the flame-retardant coating is applied to LED display modules and displays, can reach UL-94V-0 and 5VA standards and can also reach the BS476-7Class 1 standard; moreover, the coating can be cured by UV, equipment is simple, consumed time is short, production efficiency can be improved, and cost can be saved.

Description

Technical Field

[0001] This invention belongs to the field of LED display technology, and particularly relates to a phosphorus-nitrogen UV-curable flame-retardant coating, an LED display module, and a method for preparing the same. Background Technology

[0002] LED display modules need to meet safety protection requirements when used indoors and outdoors. Although traditional encapsulation processes can meet the requirements for dust and water resistance, they also have the following drawbacks: the adhesives used for encapsulation are usually epoxy or silicone polymers, which do not have flame retardant properties and pose a fire risk in the event of a fire; the encapsulation uses thermosetting adhesives, which take a long time to form using molding or film methods and require post-curing, resulting in low production efficiency. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a phosphorus-nitrogen-containing UV-curable flame-retardant coating and an LED display module, and a method for preparing the same.

[0004] This invention provides a phosphorus-nitrogen-containing UV-curable flame-retardant coating, comprising:

[0005] Phosphorus-nitrogen UV-curable prepolymer, UV-curable monomer, photoinitiator and nanofiller;

[0006] The phosphorus-nitrogen-containing UV-curable prepolymer has the structure shown in formula (I) and / or formula (II):

[0007]

[0008]

[0009] Where m and n are each independently selected from integers from 0 to 5;

[0010] X is selected from O or N;

[0011] R is selected from H or C1 to C5 alkyl groups.

[0012] Preferably, m and n are each independently selected from 0 or 1; X is selected from O or N; and R is selected from H or methyl.

[0013] Preferred, including:

[0014]

[0015] Preferably, the phosphorus-nitrogen-containing UV-curable prepolymer is prepared according to the following method:

[0016] Under the conditions of a protective atmosphere and the presence of a catalyst, the compound represented by formula (A) or formula (B) is reacted with the isocyanate compound represented by formula (B) in an organic solvent to obtain a phosphorus-nitrogen UV-curable prepolymer.

[0017]

[0018] Preferably, the catalyst is selected from organotin catalysts; the mass of the catalyst is 0.2% to 0.5% of the mass of the compound shown in formula (A) or formula (B); the reaction temperature is 60°C to 75°C; and the reaction time is 3 to 6 hours.

[0019] Preferably, the UV curing monomer is selected from one or more of phosphate ester UV curing monomers, phosphite UV curing monomers, and UV curing monomers containing triazine rings;

[0020] The photoinitiator is selected from phosphorus-containing photoinitiators and / or nitrogen-containing photoinitiators;

[0021] The nanofiller is selected from inorganic oxides and / or inorganic oxides modified with silane coupling agents;

[0022] The particle size of the nanofiller is 10–100 nm.

[0023] Preferably, the UV-curable monomer is selected from one or more of monomers 1 to 5;

[0024] And / or, the photoinitiator is selected from one or more of photoinitiator TPO, photoinitiator 819, photoinitiator 369 and photoinitiator 907;

[0025] And / or, the inorganic oxide is selected from one or more of nano-alumina, nano-magnesium oxide and nano-silica;

[0026] And / or, the inorganic oxide modified by the silane coupling agent is selected from one or more of the following: nano-alumina modified by silane coupling agent, nano-magnesium oxide modified by silane coupling agent, and nano-silica modified by silane coupling agent.

[0027] The silane coupling agent is selected from one or more of 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 8-methacryloxyoctyltrimethoxysilane;

[0028]

[0029] Preferably, the silane coupling agent-modified inorganic oxide is prepared according to the following method:

[0030] A1) Mix the silane coupling agent with an alcohol-water mixed solvent and adjust the pH to 4.5-5.5 to hydrolyze, obtaining a silanol active intermediate solution;

[0031] A2) The silanol active intermediate solution is sprayed onto the surface of the inorganic oxide, stirred at high speed, and then dried to obtain the inorganic oxide modified with silane coupling agent.

[0032] The present invention also provides an LED display module, including a substrate, a plurality of LED light-emitting chips disposed on the substrate, and a flame-retardant coating disposed between the plurality of LED light-emitting chips and on the surface away from the substrate; the flame-retardant coating is formed by the above-mentioned UV-cured flame-retardant coating.

[0033] This invention also provides a method for manufacturing an LED display module, comprising the following steps:

[0034] S1) Transfer the UV-curable flame-retardant coating according to any one of claims 1 to 8 to the surface of the release film, and perform UV pre-curing to obtain a pre-cured UV flame-retardant coating;

[0035] S2) The pre-cured UV flame retardant coating is attached to the surface away from the release film onto the surface of a substrate with several LED light-emitting chips, and UV curing is continued to obtain an LED display module.

[0036] This invention provides a phosphorus-nitrogen-containing UV-curable flame-retardant coating, comprising: a phosphorus-nitrogen-containing UV-curable prepolymer, a UV-curable monomer, a photoinitiator, and nanofillers; the phosphorus-nitrogen-containing UV-curable prepolymer has the structure shown in formula (I) and / or formula (II). Compared with the prior art, the phosphorus-nitrogen-containing UV-curable prepolymer used in this invention is a product of cyclotriphosphazene functionalization, containing phosphorus and nitrogen elements. The high nitrogen and phosphorus content endows it with excellent flame-retardant effect; furthermore, it contains acryloyloxy groups that can be cured by UV, and each molecular structure contains six curable functional groups, which can improve the overall structural density after curing, thereby improving the heat resistance of the molecular structure. Thus, the flame-retardant coating can be applied to LED display modules and displays, meeting UL-94V-0 and 5VA standards, as well as BS476-7 Class 1 standards; moreover, this coating can be cured by UV, which requires simple equipment, is time-saving, improves production efficiency, and saves costs.

[0037] Furthermore, the UV-curing monomer and photoinitiator used in this invention also contain phosphorus and / or nitrogen elements, which give full play to the synergistic effect of phosphorus and nitrogen flame retardants, and the addition of highly heat-resistant fillers further improves the flame retardancy of the coating. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the manufacturing process of the LED display module provided by the present invention;

[0039] Figure 2 This is a structural diagram of the prepolymer of formula 1 prepared in Example 1 of the present invention;

[0040] Figure 3 This is a structural diagram of the prepolymer of formula 2 prepared in Example 2 of the present invention. Detailed Implementation

[0041] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] This invention provides a phosphorus-nitrogen-containing UV-curable flame-retardant coating, comprising: a phosphorus-nitrogen-containing UV-curable prepolymer, a UV-curable monomer, a photoinitiator, and nanofillers; the phosphorus-nitrogen-containing UV-curable prepolymer has the structure shown in formula (I) and / or formula (II):

[0043]

[0044] Where m and n are each an independent integer from 0 to 5; X is O or N; R is H or a C1 to C5 alkyl group.

[0045] In a specific embodiment of the present invention, m and n are each preferably integers from 0 to 3, more preferably 0 or 1.

[0046] In a specific embodiment of the present invention, R is preferably H or a C1-C3 alkyl group, more preferably H or a C1-C2 alkyl group, and even more preferably H or a methyl group.

[0047] In a specific embodiment of the present invention, the substituents on the benzene ring in formulas (I) and (II) can be ortho, meta, or para, without any particular limitation, but para is preferred.

[0048] This phosphorus-nitrogen UV-curable prepolymer contains both phosphorus and nitrogen elements, allowing it to function as both a phosphorus-based and nitrogen-based flame retardant. The phosphorus-based flame retardant exerts its flame-retardant effect through gas-phase and condensation phase mechanisms. In the condensed phase, it often decomposes to generate acidic substances such as phosphoric acid, metaphosphoric acid, and polyphosphoric acid, promoting the dehydration and carbonization of the resin matrix, improving its char-forming properties, and protecting the matrix from combustion. In the gas phase, the phosphorus-based flame retardant decomposes to generate phosphorus-oxygen free radicals, which can quench the active free radicals generated during combustion, terminating the combustion chain reaction and inhibiting the material's decomposition and combustion behavior. The nitrogen-based flame retardant, upon thermal decomposition, often releases non-flammable gases such as ammonia, oxides, and water vapor. The release of these gases dilutes the concentration of combustible gases and oxygen, acting as a gas-phase dilution agent. Furthermore, the endothermic processes of flame retardant decomposition and sublimation at certain temperatures lower the polymer's temperature, resulting in excellent flame-retardant performance.

[0049] In a specific embodiment of the present invention, the phosphorus-nitrogen-containing UV-curable prepolymer is prepared by the following method: under a protective atmosphere and in the presence of a catalyst, the compound represented by formula (A) or formula (B) is reacted with the isocyanate compound represented by formula (C) in an organic solvent to obtain the phosphorus-nitrogen-containing UV-curable prepolymer.

[0050]

[0051] In one specific embodiment of the present invention, the compound represented by formula (A) or formula (B) is hexa(4-hydroxymethylphenoxy)-cyclotriphosphazene or hexa(p-aminophenoxy)-cyclotriphosphazene.

[0052] In one specific embodiment of the present invention, the isocyanate compound represented by formula (C) is preferably ethyl isocyanate acrylate.

[0053] In a specific embodiment of the present invention, the protective atmosphere can be any protective atmosphere known to those skilled in the art and is not particularly limited; nitrogen is preferred in the present invention. The catalyst is preferably an organotin catalyst, including but not limited to dibutyltin dilaurate (DBTDL). The mass of the catalyst is preferably 0.2% to 0.5% of the mass of the compound shown in formula (A) or formula (B); optionally, the mass of the catalyst is preferably 0.2%, 0.3%, 0.4%, 0.5% of the mass of the compound shown in formula (A) or formula (B), or a range between any two of the above values. The organic solvent can be any organic solvent known to those skilled in the art and is not particularly limited; tetrahydrofuran is preferred in the present invention, and anhydrous tetrahydrofuran is more preferred. The reaction temperature is preferably 60°C to 75°C; optionally, the reaction temperature is 60°C, 65°C, 70°C, 75°C, or a range between any two of the above values. The reaction time is preferably 3 to 6 hours; optionally, the reaction time is 3 hours, 4 hours, 5 hours, 6 hours, or a range between any two of the above values.

[0054] In a specific embodiment of the present invention, X is O; the reaction temperature is preferably 70℃~75℃; and the reaction time is preferably 4~6h.

[0055] In one specific embodiment of the present invention, X is N; the reaction temperature is preferably 60℃~70℃; and the reaction time is preferably 3~5h.

[0056] In one specific embodiment of the present invention, since the reaction needs to be carried out under anhydrous conditions, it is preferable to pretreat the raw materials first, specifically by mixing the compound shown in formula (A) or formula (B) with anhydrous organic solvent to obtain a phosphazene compound solution; and dehydrating the isocyanate compound shown in formula (B) using a molecular sieve to prevent hydrolysis.

[0057] In one specific embodiment of the present invention, in a protective atmosphere, the isocyanate compound represented by formula (B) is added dropwise to a phosphazene compound solution, and then a catalyst is added and heated to react, thereby obtaining a phosphorus-nitrogen UV-curable prepolymer. To avoid local overheating, the isocyanate compound represented by formula (B) is preferably added dropwise within 20 to 40 minutes, more preferably within 25 to 35 minutes, and even more preferably within about 30 minutes.

[0058] In a specific embodiment of the present invention, after the reaction is completed, the mixture is preferably cooled to room temperature to remove the solvent, and then washed, filtered, and dried to obtain a phosphorus-nitrogen UV-curable prepolymer. The method for removing the solvent can be any method well-known to those skilled in the art and is not particularly limited. In this invention, vacuum distillation is preferred to remove the solvent. Ethyl acetate is preferred for washing. Vacuum drying is preferred. The drying temperature is preferably 40℃~80℃. Optionally, the drying temperature is 40℃, 50℃, 60℃, 70℃, 80℃, or any two of the above values. The drying time is preferably 8~24h. Optionally, the drying time is 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, or any two of the above values.

[0059] In this invention, the phosphorus-nitrogen UV-curable prepolymer is a product of cyclotriphosphazene functionalization. The high nitrogen and phosphorus content gives it excellent flame retardant effect. Furthermore, it contains acryloyloxy groups that can be cured by UV. Each molecular structure contains six curable functional groups, which improves the overall structural density after curing, thereby improving the heat resistance of the molecular structure. It performs better when burned by a high-temperature radiation source of BS476-7, and can reduce the flame spread distance.

[0060] To improve the flame retardancy of UV-cured flame-retardant coatings and the nitrogen and / or phosphorus content in the coatings, the UV-curing monomer is preferably one or more of phosphate ester UV-curing monomers, phosphite ester UV-curing monomers, and triazine ring-containing UV-curing monomers, more preferably one or more of monomers 1 to 5, wherein monomer 1 is triallyl cyanurate, monomer 2 is triallyl phosphite, and monomers 3, 4, and 5 are respectively a monocondensate, dicondensate, and tricondensate of phosphoric acid and hydroxyethyl methacrylate.

[0061]

[0062]

[0063] To improve the flame retardancy of UV-cured flame-retardant coatings and the nitrogen and / or phosphorus content in the coatings, the photoinitiator is selected from phosphorus-containing photoinitiators and / or nitrogen-containing photoinitiators, more preferably one or more of photoinitiator TPO, photoinitiator 819, photoinitiator 369 and photoinitiator 907.

[0064] The structural formula of the photoinitiator TPO is as follows:

[0065]

[0066] The structural formula of photoinitiator 819 is:

[0067]

[0068] The structural formula of photoinitiator 369 is:

[0069]

[0070] The structural formula of photoinitiator 907 is:

[0071]

[0072] In this invention, the nanofiller serves two purposes: firstly, it reduces the internal stress generated during the curing of phosphorus-nitrogen UV-curable prepolymers; secondly, it improves heat resistance. High-film-thickness UV coatings experience significant shrinkage during curing, easily generating internal stress. Therefore, nanofillers are needed to reduce shrinkage and eliminate curing stress. Furthermore, during the BS476-7 test, a high-temperature radiant heat source continuously radiates heat, necessitating improved heat resistance of the coating; the nanofiller also fulfills this function. Therefore, the nanofiller in this invention is preferably a heat-resistant nanofiller, more preferably an inorganic oxide modified with an inorganic oxide and / or a silane coupling agent; the inorganic oxide includes, but is not limited to, one or more of nano-alumina, nano-magnesium oxide, and nano-silica; the nanofiller should be modified to improve its dispersibility and reactivity with UV-curable flame-retardant coatings, and is therefore preferably an inorganic oxide modified with a silane coupling agent, including, but not limited to, one or more of nano-alumina modified with a silane coupling agent, nano-magnesium oxide modified with a silane coupling agent, and nano-silica modified with a silane coupling agent; the silane coupling agent is preferably a silane coupling agent containing methacryloyloxy group, including, but not limited to, one or more of 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-methacryloyloxypropyltriethoxysilane, and 8-methacryloyloxyoctyltrimethoxysilane.

[0073] In a specific embodiment of the present invention, the inorganic oxide modified by the silane coupling agent is prepared by the following method: A1) the silane coupling agent is mixed with an alcohol-water mixed solvent and the pH value is adjusted to 4.5-5.5 for hydrolysis to obtain a silanol active intermediate solution; A2) the silanol active intermediate solution is sprayed onto the surface of the inorganic oxide, stirred at high speed, and then dried to obtain the inorganic oxide modified by the silane coupling agent.

[0074] In a specific embodiment of the present invention, the alcohol-water mixed solvent is preferably an ethanol-water mixed solvent; the volume ratio of alcohol to water in the alcohol-water mixed solvent is preferably (92-98):(2-8); optionally, the volume ratio of alcohol to water in the alcohol-water mixed solvent is 92:8, 94:6, 95:5, 96:4, 98:2 or any two of the above ratios.

[0075] In one specific embodiment of the present invention, the mass concentration of the silane coupling agent in the mixture after mixing the silane coupling agent with the alcohol-water mixed solvent is preferably 1% to 5%; optionally, the mass concentration of the silane coupling agent in the mixture is 1%, 2%, 3%, 4%, 5% or any two of the above values.

[0076] In one specific embodiment of the present invention, after mixing, the pH value is adjusted to 4.5-5.5 using acetic acid; optionally, after mixing, the pH value is adjusted to 4.5, 5, 5.5 or any two of the above values.

[0077] In one specific embodiment of the present invention, the mass ratio of the silane coupling agent to the inorganic oxide is preferably 1:(1-10); optionally, the mass ratio of the silane coupling agent to the inorganic oxide is 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 or any two of the above ratios; in some embodiments of the present invention, the mass ratio of the silane coupling agent to the inorganic oxide is 1:(3-5).

[0078] In a specific embodiment of the present invention, the inorganic oxide is preferably dried first, and then the silanol active intermediate solution is sprayed onto the surface of the dried inorganic oxide; the drying process specifically involves mixing the inorganic oxide under heating conditions to reduce its water content to below 0.3%; the heating temperature is preferably 100℃~110℃; the mixing is preferably carried out in a high-speed mixer; and the mixing time is preferably 10~15min.

[0079] In a specific embodiment of the present invention, the rotation speed of the high-speed stirring is preferably greater than or equal to 1000 rpm; optionally, the rotation speed of the high-speed stirring is 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, 10000 rpm or any two of the above values; the high-speed stirring time is preferably 10 to 30 minutes; optionally, the high-speed stirring time is 10 minutes, 20 minutes, 30 minutes or any two of the above values.

[0080] In a specific embodiment of the present invention, the drying temperature is preferably 100℃ to 150℃; optionally, the drying temperature is 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, or any two of the above values; the drying time is preferably 1 to 5 hours; optionally, the drying time is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or any two of the above values. After drying, a stable chemically bonded layer can be formed.

[0081] In one specific embodiment of the present invention, the particle size of the nanofiller is preferably 10–100 nm; nanofillers smaller than this size are difficult to disperse and prone to agglomeration, while nanofillers larger than this size weaken the function of relieving internal stress. Optionally, the particle size of the nanofiller is 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any two of the above values.

[0082] In one specific embodiment of the present invention, the UV-curable flame-retardant coating comprises:

[0083]

[0084] Optionally, the content of the phosphorus-nitrogen-containing UV-curable prepolymer in the UV-curable flame-retardant coating is 35 parts by weight, 40 parts by weight, 45 parts by weight, 50 parts by weight, 55 parts by weight, or any two of the above values.

[0085] Optionally, the content of the UV-curable monomer in the UV-curable flame-retardant coating is 20 parts by weight, 22 parts by weight, 25 parts by weight, 28 parts by weight, 30 parts by weight, or any two of the above values.

[0086] Optionally, the content of the photoinitiator in the UV-cured flame-retardant coating is 1 part by weight, 3 parts by weight, 5 parts by weight, 8 parts by weight, 10 parts by weight, or any two of the above values.

[0087] Optionally, the content of the nanofiller in the UV-curable flame-retardant coating is 20 parts by weight, 22 parts by weight, 25 parts by weight, 28 parts by weight, 30 parts by weight, or any two of the above values.

[0088] Additives can improve certain properties of UV-cured flame-retardant coatings, such as improving the leveling, uniformity, and adhesion of the coating. In this invention, the additives preferably include one or more of leveling agents, silane coupling agents, and defoamers.

[0089] According to the present invention, the leveling agent includes one or more of silicone leveling agents, acrylate leveling agents, and fluorocarbon leveling agents; the silicone leveling agent includes, but is not limited to, polyether-modified polysiloxane, polyester-modified polysiloxane, long-chain alkyl-modified polysiloxane, etc.; the acrylate leveling agent includes, but is not limited to, pure acrylate leveling agents, fluorinated acrylate leveling agents, etc.

[0090] According to the present invention, the silane coupling agent includes, but is not limited to, one or more of vinyl silane coupling agents, epoxy silane coupling agents, amino silane coupling agents, ureosilane coupling agents, and mercaptosilane coupling agents; the vinyl silane coupling agent includes, but is not limited to, vinyltriethoxysilane, vinyltrimethoxysilane, etc.; the epoxy silane coupling agent includes, but is not limited to, 2-(3,4-epoxycyclohexyl)ethoxytrimethoxysilane, 3-glycidyl etheroxypropylmethyldimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, and 3-glycidyl etheroxypropylmethyldiethoxysilane. The aminosilane coupling agents include, but are not limited to, γ-aminopropyltriethoxysilane (KH550), N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH792), and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH602); the ureosilane coupling agents include, but are not limited to, γ-ureopropyl-trimethoxysilane and γ-ureopropyl-methyldimethoxysilane; and the mercaptosilane coupling agents include, but are not limited to, 3-mercaptopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane.

[0091] According to the present invention, the defoamer includes silicone defoamers and / or non-silicone defoamers; the silicone defoamers include, but are not limited to, polydimethylsiloxane defoamers, polyether-modified silicone defoamers, etc.; the non-silicone defoamers include, but are not limited to, mineral oil-based defoamers, polyether defoamers, alcohol defoamers, etc.

[0092] In this invention, the UV-curable flame-retardant coating can be prepared according to methods well known to those skilled in the art, without any special limitations. Preferably, the UV-curable flame-retardant coating is prepared by mixing a phosphorus-nitrogen-containing UV-curable prepolymer, a UV-curable monomer, a photoinitiator, and a nanofiller through vacuum stirring and degassing. The mixing method can be any method well known to those skilled in the art, without any special limitations. In this invention, a vacuum high-speed stirring and degassing machine is preferably used. The mixing speed is preferably 1000-2000 rpm. The mixing time is preferably 10-20 min. After mixing, it is preferable to allow the mixture to stand for 10-20 min.

[0093] The present invention also provides an LED display module, including a substrate, a plurality of LED light-emitting chips disposed on the substrate, and a flame-retardant coating disposed between the plurality of LED light-emitting chips and on the surface away from the substrate; the flame-retardant coating is formed by the above-mentioned UV-cured flame-retardant coating.

[0094] In one specific embodiment of the present invention, the thickness of the flame-retardant coating is preferably 150-250 μm; optionally, the thickness of the flame-retardant coating is 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm or any two of the above values.

[0095] The present invention also provides a method for preparing the above-mentioned LED display module, comprising the following steps: S1) transferring the above-mentioned UV-curable flame retardant coating to the surface of a release film and performing UV pre-curing to obtain a pre-cured UV flame retardant coating; S2) attaching the surface of the pre-cured UV flame retardant coating away from the release film to the surface of a substrate on which a plurality of LED light-emitting chips are disposed, and continuing UV curing to obtain an LED display module.

[0096] See Figure 1 , Figure 1 This is a schematic diagram of the manufacturing process of the LED display module provided by the present invention.

[0097] In this invention, there are no special restrictions on the source of any raw materials; they can be commercially available.

[0098] In one specific embodiment of the present invention, the UV-curable flame-retardant coating is preferably transferred to the surface of the release film by a two-roller coating process; the thickness of the coating is controlled by controlling the gap between the two rollers and the pressure during the transfer process.

[0099] In one specific embodiment of the present invention, the light source used for the UV pre-curing is preferably a high-pressure mercury lamp; the light intensity for the UV pre-curing is preferably 100–300 mW / cm². 2 Optionally, the UV pre-curing light intensity is 100 mW / cm². 2 150mW / cm 2 200mW / cm 2 250mW / cm 2 300mW / cm 2 Or the range between any two of the above values; the UV pre-curing exposure is preferably 100–300 mJ / cm. 2 Optionally, the UV pre-curing exposure is 100 mJ / cm². 2 150mJ / cm 2 200mJ / cm2 250mJ / cm 2 300mJ / cm 2 Or the range between any two of the above values.

[0100] In one specific embodiment of the present invention, for the convenience of storage and use, after UV pre-curing, it is preferable to attach another release film to the surface of the pre-cured UV flame retardant coating away from the release film.

[0101] In one specific embodiment of the present invention, a pre-cured UV flame retardant coating has release films on both sides. After removing the release film on one side, it is attached to the surface of a substrate on which a plurality of LED light-emitting chips are disposed, and UV curing is continued to obtain an LED display module.

[0102] In one specific embodiment of the present invention, the substrate with a plurality of LED light-emitting chips is preferably fixed on a preset molding fixture after being plasma cleaned, and then bonded to the surface of the pre-cured UV flame-retardant coating away from the release film.

[0103] In one specific embodiment of the present invention, vacuum bonding is preferably used for bonding.

[0104] In one specific embodiment of the present invention, the light source used for continued UV curing is preferably a high-pressure mercury lamp; the light intensity for continued UV curing is preferably 100–300 mW / cm². 2 Optionally, the light intensity for the continued UV curing is 100 mW / cm². 2 150mW / cm 2 200mW / cm 2 250mW / cm 2 300mW / cm 2 Or any two of the above values; the preferred exposure for continued UV curing is 1000–1500 mJ / cm. 2 Optionally, the exposure amount for continued UV curing is preferably 1000 mJ / cm. 2 1100mJ / cm 2 1200mJ / cm 2 1300mJ / cm 2 1400mJ / cm 2 1500mJ / cm 2 Or the range between any two of the above values.

[0105] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a phosphorus-nitrogen-containing UV-curable flame-retardant coating and an LED display module and their preparation method provided by the present invention.

[0106] All reagents used in the following examples are commercially available.

[0107] Example 1

[0108] Table 1 Formulation of Flame Retardant Coating in Example 1

[0109] Component Name Component proportion Prepolymer structural formula 1 55％ melamine-traceryl 20％ Photoinitiator TPO 5％ 30nm aluminum oxide 20％

[0110] 1.1 Preparation of prepolymer structure 1

[0111] (1) Raw material pretreatment

[0112] Dissolve 40g of hexa(4-hydroxymethylphenoxy)-cyclotriphosphazene in 60g of anhydrous tetrahydrofuran and stir until completely dissolved to obtain a phosphazene compound solution; pre-treat 40g of ethyl isocyanate acrylate with molecular sieves to prevent hydrolysis.

[0113] (2) Mixing and Catalytic Reaction

[0114] Under nitrogen protection, ethyl isocyanate acrylate was slowly added dropwise to the phosphazene compound solution over a period of about 30 minutes to avoid local overheating; 0.1 g of catalyst DBTDL was added, the temperature was raised to 75°C, and the reaction was stirred for 5 hours.

[0115] (3) Post-processing

[0116] The solvent was removed by vacuum distillation after cooling to room temperature. The residue was washed with ethyl acetate and filtered. The filter cake was dried in a vacuum drying oven at 60°C for 12 hours to obtain the target polymer.

[0117] 1.2 nanometer alumina modification

[0118] (1) Drying treatment of nano-alumina

[0119] Take 50g of 30nm alumina powder and place it in a high-speed mixer. Preheat the mixer to 100℃ and stir for 10 minutes to reduce the moisture content of the filler to below 0.3%.

[0120] (2) Preparation of coupling agent solution

[0121] An alcohol-water system (ethanol:water = 95:5) was used, and 10g of silane coupling agent 3-methacryloyloxypropylmethyldimethoxysilane was added. The concentration of the coupling agent was 5wt%. Then, the pH value was adjusted to 4.5 with acetic acid, and the mixture was stirred and hydrolyzed for 5 minutes to form a silanol active intermediate.

[0122] (3) Nano-alumina surface modification

[0123] The silanol active intermediate was uniformly sprayed onto the surface of the pretreated nano-alumina and stirred at high speed for 30 minutes (5000 rpm). After treatment, the filler was transferred to a 120℃ oven and dried for 2 hours to form a stable chemical bond layer, thus obtaining the modified nano-alumina.

[0124] 1.3 Add the ingredients from the ingredient list to the mixing tray according to the proportions, and use a vacuum high-speed mixer to stir and degas at 1000 rpm for 10 minutes. Let the dispersed material stand for 10 minutes to obtain the flame-retardant coating.

[0125] 1.4 Pre-curing of adhesive

[0126] The coating is transferred onto the substrate release film using a two-roll coating process. The coating thickness is controlled by adjusting the gap and pressure between the two rollers, with a selected thickness of 150 μm. Following this, UV pre-curing is performed using a high-pressure mercury lamp with an illuminance of 100 mW / cm². 2 Exposure 100mJ / cm 2 After pre-curing, the coating is bonded to another release film.

[0127] 1.5 LED Display Module Fabrication

[0128] After plasma cleaning, the LED board with attached LED chips and driver ICs is fixed onto a pre-designed molding fixture. The release film on one side of the pre-cured coating is peeled off, and the coating is then bonded to the LED chips using a vacuum bonding device. UV curing is then performed using a high-pressure mercury lamp with an illuminance of 100 mW / cm². 2 Exposure level 1000mJ / cm 2 After curing, it forms an LED display module.

[0129] Performance testing

[0130] Flame retardancy test: Cut the cured LED module into strips of 125mm in length and 13mm in width, and conduct flame retardancy test according to UL 94 standard. The flame retardancy afterflame and afterburn test results are shown in Table 2. Prepare LED modules with specifications of 270mm×295mm, and conduct flame retardancy test according to BS 476-7 standard. The flame spread results are shown in Table 2.

[0131] Module aging test: The cured module was lit up and placed in a device with a temperature of 85℃ and a humidity of 85% for a total of 168 hours. The display effect was observed to see if there were any abnormalities, and whether there were any cracks, bubbles or other appearance abnormalities on the lamp surface. The results are shown in Table 2.

[0132] Thermal shock test: The cured module is lit and subjected to thermal shock test at a temperature of -40 to 80℃. The cold shock time is 30 minutes and the hot shock time is 30 minutes. This is one cycle. A total of 500 cycles are performed. The display effect is observed for any abnormalities, and the lamp surface is checked for cracks, bubbles, or other appearance abnormalities. The results are shown in Table 2.

[0133] Table 2 Test results of Example 1

[0134]

[0135]

[0136] Note: The numbers in Table 2 refer to the numbers of multiple samples in different tests. Samples with the same number in different tests are not necessarily the same sample.

[0137] Example 2

[0138] Table 3 Formulation of Flame Retardant Coating in Example 2

[0139] Component Name Component proportion Prepolymer structural formula 2 35％ Triallyl phosphite 30％ Photoinitiator 369 5％ 10nm magnesium oxide 30％

[0140] 2.1 Preparation of prepolymer structure 2

[0141] (1) Raw material pretreatment

[0142] Dissolve 40g of hexa(p-aminophenoxy)-cyclotriphosphazene in 60g of anhydrous THF and stir until completely dissolved; pre-treat 45g of ethyl isocyanate acrylate with molecular sieves to prevent hydrolysis.

[0143] (2) Mixing and Catalytic Reaction

[0144] Under nitrogen protection, ethyl isocyanate acrylate was added dropwise to a solution of hexa(p-aminophenoxy)-cyclotriphosphazene, and the addition rate was slow (about 30 minutes) to avoid local overheating; 0.2 g of catalyst DBTDL was added, the temperature was raised to 60 °C, and the reaction was stirred for 3 hours.

[0145] (3) Post-processing

[0146] The solvent was removed by vacuum distillation after the reaction solution was cooled to room temperature; the product was washed with ethyl acetate and filtered, and the filter cake was dried in a vacuum drying oven at 60°C for 12 hours to obtain the target polymer.

[0147] 3.2 nanometer magnesium oxide modification

[0148] (1) Drying treatment of nano magnesium oxide

[0149] Place 50g of 10nm magnesium oxide powder in a high-speed mixer, preheat to 100℃ and stir for 10 minutes to reduce the moisture content of the filler to below 0.3%.

[0150] (2) Preparation of coupling agent solution

[0151] An alcohol-water system (ethanol:water = 95:5) was used, and 15g of silane coupling agent 3-methacryloyloxypropyltrimethoxysilane was added. The concentration of the coupling agent was 3wt%. Then, the pH value was adjusted to 5.5 with acetic acid, and the mixture was stirred and hydrolyzed for 5 minutes to form a silanol active intermediate.

[0152] (3) Surface modification of nano-magnesium oxide

[0153] The silanol active intermediate was uniformly sprayed onto the surface of the pretreated nano-magnesium oxide and stirred at high speed for 30 minutes (5000 rpm). After treatment, the filler was transferred to a 120℃ oven and dried for 2 hours to form a stable chemical bond layer, thus obtaining the modified nano-magnesium oxide.

[0154] 2.3 Add the ingredients from the ingredient list to the mixing tray according to the proportions, and use a vacuum high-speed mixer to stir and degas at 1000 rpm for 10 minutes. Let the dispersed material stand for 10 minutes to obtain the flame-retardant coating.

[0155] 2.4 Pre-curing of adhesive

[0156] The coating is transferred onto the substrate release film using a two-roll coating process. The coating thickness is controlled by adjusting the gap and pressure between the two rollers, with a selected thickness of 200 μm. Following this, UV pre-curing is performed using a high-pressure mercury lamp with an illuminance of 200 mW / cm². 2 Exposure 300mJ / cm 2 After pre-curing, the coating is bonded to another release film.

[0157] 2.5 LED Display Module Fabrication

[0158] After plasma cleaning, the LED board with attached LED chips and driver ICs is fixed onto a pre-designed molding fixture. The release film on one side of the pre-cured coating is peeled off, and the coating is then bonded to the LED chips using a vacuum bonding device. UV curing is then performed using a high-pressure mercury lamp with an illuminance of 200 mW / cm². 2 Exposure: 1500 mJ / cm 2 After curing, it forms an LED display module.

[0159] Performance testing

[0160] Flame retardancy test: Cut the cured LED module into strips of 125mm in length and 13mm in width, and conduct flame retardancy test according to UL 94 standard. The flame retardancy afterflame and afterburn test results are shown in Table 4. Prepare LED modules with specifications of 270mm×295mm, and conduct flame retardancy test according to BS 476-7 standard. The flame spread results are shown in Table 4.

[0161] Module aging test: The cured module was lit and placed in a device with a temperature of 85℃ and a humidity of 85% for a total of 168 hours. The display effect was observed for any abnormalities, and the appearance of the lamp surface was checked for cracks, bubbles, or other abnormalities. The results are shown in Table 4.

[0162] Thermal shock test: The cured module is lit and subjected to thermal shock test at a temperature of -40 to 80℃. The cold shock time is 30 minutes and the hot shock time is 30 minutes. This is one cycle. A total of 500 cycles are performed. The display effect is observed for any abnormalities, and the lamp surface is checked for cracks, bubbles, or other appearance abnormalities. The results are shown in Table 4.

[0163] Table 4 Test results of Example 2

[0164]

[0165]

[0166] Note: The numbers in Table 4 refer to the numbers of multiple samples in different tests. Samples with the same number in different tests are not necessarily the same sample.

[0167] Comparative Example 1

[0168] Without prepolymerization, a mixture of hexa(4-hydroxymethylphenoxy)cyclotriphosphazene, ethyl isocyanate, and catalyst DBTDL in a mass ratio of 4:4:0.01 was used to replace the prepolymer structure in Example 1, and the rest was the same as in Example 1.

[0169] The results were obtained by testing according to the detection method in Example 1, as shown in Table 5.

[0170] Table 5 shows the test results of Comparative Example 1.

[0171]

[0172]

[0173] Note: The numbers in Table 5 refer to the numbers of multiple samples in different tests. Samples with the same number in different tests are not necessarily the same sample.

[0174] Comparative Example 2

[0175] Without prepolymerization, a mixture of hexa(p-aminophenoxy)cyclotriphosphazene, ethyl isocyanate, and catalyst DBTDL in a mass ratio of 4:4.5:0.02 was used to replace the prepolymer structure in Example 2, and the rest was the same as in Example 2.

[0176] The results obtained by testing according to the detection method in Example 2 are shown in Table 6.

[0177] Table 6 shows the test results of Comparative Example 2.

[0178]

[0179] Note: The numbers in Table 6 refer to the numbers of multiple samples in different tests. Samples with the same number in different tests are not necessarily the same sample.

[0180] Comparative Example 3

[0181] Same as Example 1, except that the particle size of the nanofiller alumina is 150 nm.

[0182] The results were obtained by testing according to the detection method in Example 1, as shown in Table 7.

[0183] Table 7 shows the test results of Comparative Example 3.

[0184]

[0185] Note: The numbers in Table 7 refer to the numbers of multiple samples in different tests. Samples with the same number in different tests are not necessarily the same sample.

[0186] Comparative Example 4

[0187] Same as Example 1, except that it does not contain the nanofiller alumina.

[0188] The results were obtained by testing according to the detection method in Example 1, as shown in Table 8.

[0189] Table 8 shows the test results of Comparative Example 4.

[0190]

[0191] Note: The numbers in Table 8 refer to multiple sample numbers in different tests. Samples with the same number in different tests are not necessarily the same sample. Data from Tables 2, 4, and 5-8 show that using cyclotriphosphazene-functionalized products as phosphorus-nitrogen UV-curable prepolymers improves the overall structural density after curing, thereby enhancing the heat resistance of the molecular structure. Furthermore, the high nitrogen and phosphorus content imparts excellent flame retardant properties, resulting in flame-retardant coatings with high flame retardant performance. Consequently, LED display modules can not only meet UL-94V-0 and 5VA standards but also BS476-7 Class 1 standards.

[0192] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A phosphorus-nitrogen-containing UV-curable flame-retardant coating, characterized in that, include: The phosphorus-nitrogen-containing UV-curable prepolymer, UV-curable monomer, photoinitiator, and nanofiller; the phosphorus-nitrogen-containing UV-curable prepolymer has the structure shown in formula (I) and / or formula (II): Where m and n are each independently selected from integers from 0 to 5; X is selected from O or N; R is selected from H or C1 to C5 alkyl groups.

2. The UV-curable flame-retardant coating according to claim 1, characterized in that, The m and n are each independently selected from 0 or 1; X is selected from O or N; R is selected from H or methyl.

3. The UV-curable flame-retardant coating according to claim 1, characterized in that, include:

4. The UV-curable flame-retardant coating according to claim 1, characterized in that, The phosphorus-nitrogen-containing UV-curable prepolymer was prepared according to the following method: Under the conditions of a protective atmosphere and the presence of a catalyst, the compound shown in formula (A) or formula (B) is reacted with the isocyanate compound shown in formula (C) in an organic solvent to obtain a phosphorus-nitrogen UV-curable prepolymer.

5. The UV-curable flame-retardant coating according to claim 4, characterized in that, The catalyst is selected from organotin catalysts; the mass of the catalyst is 0.2% to 0.5% of the mass of the compound shown in formula (A) or formula (B); the reaction temperature is 60℃ to 75℃; and the reaction time is 3 to 6 hours.

6. The UV-curable flame-retardant coating according to claim 1, characterized in that, The UV curing monomer is selected from one or more of phosphate ester UV curing monomers, phosphite UV curing monomers, and triazine ring-containing UV curing monomers; The photoinitiator is selected from phosphorus-containing photoinitiators and / or nitrogen-containing photoinitiators; The nanofiller is selected from inorganic oxides and / or inorganic oxides modified with silane coupling agents; The particle size of the nanofiller is 10–100 nm.

7. The UV-curable flame-retardant coating according to claim 6, characterized in that, The UV-curing monomer is selected from one or more of monomers 1 to 5; And / or, the photoinitiator is selected from one or more of photoinitiator TPO, photoinitiator 819, photoinitiator 369 and photoinitiator 907; And / or, the inorganic oxide is selected from one or more of nano-alumina, nano-magnesium oxide and nano-silica; And / or, the inorganic oxide modified by the silane coupling agent is selected from one or more of the following: nano-alumina modified by silane coupling agent, nano-magnesium oxide modified by silane coupling agent, and nano-silica modified by silane coupling agent. The silane coupling agent is selected from one or more of 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 8-methacryloxyoctyltrimethoxysilane; 8. The UV-curable flame-retardant coating according to claim 6, characterized in that, The silane coupling agent-modified inorganic oxide is prepared according to the following method: A1) Mix the silane coupling agent with an alcohol-water mixed solvent and adjust the pH to 4.5-5.5 to hydrolyze, obtaining a silanol active intermediate solution; A2) The silanol active intermediate solution is sprayed onto the surface of the inorganic oxide, stirred at high speed, and then dried to obtain the inorganic oxide modified with silane coupling agent.

9. An LED display module, characterized in that, The invention includes a substrate, a plurality of LED light-emitting chips disposed on the substrate, and a flame-retardant coating disposed between the plurality of LED light-emitting chips and on the surface away from the substrate; the flame-retardant coating is formed by the UV-curable flame-retardant coating according to any one of claims 1 to 8.

10. A method for manufacturing an LED display module, characterized in that, The following steps are involved: S1) Transfer the UV-curable flame-retardant coating according to any one of claims 1 to 8 to the surface of the release film, and perform UV pre-curing to obtain a pre-cured UV flame-retardant coating; S2) The pre-cured UV flame retardant coating is attached to the surface away from the release film onto the surface of a substrate with several LED light-emitting chips, and UV curing is continued to obtain an LED display module.

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