The Preparation And Performance Of Ultra-High Hardness Methyl Phenyl Silicone Film For Mini LEDd Encapsulation

In recent years,Mini LED displays devices have attracted more and more attention due to its advantages of higher brightness,higher resolution,longer durability and lower cost compared with OLED displays.Different from other common LEDs,the chip size of Mini LED is greatly reduced,resulting in the exponential increase in the number of chips on the same display panel and a significant decrease in chip spacing.Because of this,the heat and radiation from LED displays increases greatly,demanding for higher performance encapsulants to protect chip from environmental effects.Addition-cure silicone materials exhibit high transparency,good thermal stability,great flexibility and excellent resistance against raddition,which makes it ideal LEDs encapsulation material.However,the low mechanical strength of silicone materials cannot protect the chip from enternal impact well.This shortcome is enlarged further in the Mini LED application,negatively affecting the long-term work of displays.Therefore,it's urgent to develop silicone materials with high mechanical strength for Mini LED packaging.This paper focused on the preparation of an ultra-high-hardness silicon film for Mini LED encapsulation.Firstly,a new dealcoholization method was proposed to synthesize vinyl silicone resins.Secondly,the long chain network structure hydrogen-containing silicone resins were synthesized in two steps.Then,the prepared silicone resins were carried out addition reaction to attain packaging materials to verify the effect of the above process.Base on the resins preparation process,the ultra-high-hardness silicone film was prepared successfully.The thesis can be divided into the following five parts:(1)The development status and characteristics of Mini LED encapsulants were reviewed.The components of addition-cure packaging materials were introduced in details.(2)Methyltrimethoxysilane,instead of ?-glycidoxypropylmethyldimethoxysilane,was used to eliminate hydroxyl groups in silicone resins.Methylphenyldimethoxysilane,vinyltrimethoxysilane and phenyltrimethoxysilane were used as raw maerials to synthesize vinyl methyl phenyl silicone resins with terminal hydroxyl groups(HVMPS)through hydrolysis condensation reaction.Then,HVMPS carried out a dealcoholization reaction with methyltrimethoxysilane to synthesize vinyl methyl phenyl silicone resins(VMPS-1).The preparation process of these two silicone resins was optimized.Under the optimal process,the characteristic peaks of hydroxyl groups in VMPS-1 disappeared and the vinyl content was3.06%.Compared with the 61.5% vinyl loss in the dealcoholization reaction of ?-glycidoxypropylmethyldimethoxysilane,the vinyl loss of methyltrimethoxysilane was only14.5%.(3)A two step method was used to synthesize long chain hydrogem-containing methyl phenyl silicone resins with high refractive and high hydrogen-containg.Firstlt,phenyltrimethoxysilane,methylphenyldimethoxysilane and diphenyldimethoxysilane were carried out hydrolysis condensation reaction to synthesize methyl phenyl silicone resins with terminal-hydroxyl groups(HMPS).Then,tetramethylcyclotetrasiloxane was used as hydrogen donor,while 1,1,3,3-tetramethyldisiloxane was used as end-capping agent.A series of hydrogen-containing methyl phenyl silicone resins(HMPS*)were synthesized through the condensation of HMPS,tetramethylcyclotetrasiloxane and 1,1,3,3-tetramethyldisiloxane.The preparation process of these two silicone resins was optimized.Under the optimal conditions,the hydrogen content of silicone resins achieved up to 0.49%,while the refractive index achieved up to 1.50.What's more,the number average molecular weight was above1500 and the molecular distribution coefficient was below 2.(4)VMPS-1 was cured with commeicial hydrogen-containing silicone resins to prepare methyl phenyl silicone materials(MPS-1)under the catalyst of VMPS-1.Due to the significant reduction of vinyl loss during the dealcoholization reaction,MPS-1 showed better mechanical performance and better resistance to heat and radiation.The hardness of MPS-1reached 51 shore D,while the 5% mass loss temperature achieved up to 435 ?C.In addition,the lumen depreciation after 168 h work was only 3.26%.VMPS-1 was carried out addition reaction with the three HMPS* to prepared methyl phenyl silicone materials(MPS-1*,MPS-2*,MPS-3*)respectively.The hardness of cured silicone materials achieved up to 51 shore D,while the 5% mass loss temperature reached 386 ?C without reinforcement.Moreover,the lumen depreciation after 168 h aging test was less than 6%.This illustrated that VMPS-1 and HMPS* improved the performance of silicone materials effectively.(5)The above-mention dealcoholization process and hydrogen-containing silicone resins process were used to synthesize vinyl silicone resins(VMPS-3)and hydrogen-containing silicone resins(HMPS-4*)respectively.The vinyl content of VMPS-3was 10.24% and the hydrogen content of HMPS-4* was 0.80*.VMPS-3,HMPS-4*,vinyl MQ silicone resins,long chain vinyl methyl silicone oil,silicone tackifier,Pt catalyst and acetylene ring hexanol was mixed in a certain proportion.Then,the mixture was cured to prepare methyl phenyl silicone film through dam method and the mixture formula was optimized.At last,the smooth silicone film with a hardness of 76 shore D was successfully attain.