Study On The Preparation Of Organic-inorganic Composite Materials For Led Encapsulation

Solid-state lighting,represented by light-emitting diodes(LED),has outstanding characteristics such as low energy consumption,high efficiency,and long life,and is an effective way to achieve energy saving and emission reduction.The internal quantum efficiency of LEDs has been significantly improved in the past few decades.The increase in efficiency has made it widely used in various high-quality lighting products,leading the development direction of lighting devices.The encapsulation material is the key support material in the LED lighting devices.It is not only used to isolate water and oxygen to protect the chip,but also needs to have a higher light permeability and a higher refractive index to improve the external light extraction efficiency of the LED lighting device.Due to the difference in refractive index between the chip and the encapsulation material,light tends to be totally reflected at the chip encapsulation interface.Therefore,when evaluating encapsulation materials or other optical materials,the retractive index value is considered to be one of the most important parameters.Traditional epoxy resin and silicone encapsulation materials have limited for improvement in increasing the refractive index.The combination of high refractive index inorganic nanoparticles and organic resins can improve the external light extraction efficiency of LEDs,which is the focus of current LED encapsulation materials research and development.The key scientific issue involved in this field is how to realize the controllable preparation of high refractive index inorganic nanoparticles and to make the nanoparticles uniformly dispersed in organic resin materials.In view of this,this work mainly uses silicone and epoxy resin as substrates.First,a variety of functional nanoparticles and their liquid dispersions are designed,and various nanocomposite processes such as solution blending and in-situ compounding are used to prepare nanocomposite material with high refractive index and high transparency is obtained and used in LED encapsulation to improve performance.The main research contents and innovations of the full text are as follows:1.Using zirconium(?)carbonate basic as a raw material,a cubic phase nano-zirconia aqueous dispersion is prepared by a combination of hydrothermal method and alkaline hydrogen peroxide method,which solves the raw material problem of inorganic functional nanoparticles in organic-inorganic composite encapsulation materials.The study found that the optimal reaction conditions in the hydrothermal method are the reaction temperature of 110?,the reaction time of 6 h,and the reaction mole ratio of Na/C=3.06.At this time,the cubic zirconia grain size is 4 nm,and the agglomerate size is 1000 nm.Afterwards,the agglomerates were treated with alkaline hydrogen peroxide to prepare a cubic zirconia aqueous dispersion,and the optimal reaction conditions were determined to be 4 M sodium hydroxide and 0.4 M hydrogen peroxide.At this time,the hydrated particle size of the aqueous dispersion of zirconia is 5 nm.2.The aqueous nano-zirconia dispersion was obtained by hydrothermal method and alkaline hydrogen peroxide treatment.The dispersibility of the aqueous phase nano-zirconia was further analyzed using Hansen solubility parameters,and it was found that the nanoparticles can be dispersed in water,methanol,ethanol,glycol and glycerol.Among them,the highest solid content of the nanoparticles that can be dispersed in water is 37.6 wt%,and they exist stably within six months without any obvious agglomeration.3.Using zirconium(?)carbonate basic as a raw material,a high-solid content organic phase zirconia dispersion was prepared by a high-gravity assisted method combined with a two-step modification method.The study found that the zirconia nanoparticles obtained by the high-gravity method are pure cubic phases with a size distribution in the range of 3-5 nm,which similar to the conventional method.However,the hydrated particle size of the zirconia nanoparticles obtained by the high gravity method is 124 nm,which is much smaller than the 1000 nm prepared in a conventional stirred tank,which makes the zirconia nanoparticles prepared by this method easy to surface modification.Two-step surface modification with butyric acid and KH570 has obtained liquid zirconia dispersions with high transparency in various organic solvents(such as toluene,chloroform,tetrahydrofuran,etc.)and epoxy resins.The zirconia nanodispersion can be used for LED encapsulation.Compared with a device encapsulated by pure epoxy resin,when the doping content of zirconia nanoparticles is 20 wt%,the light extraction efficiency of the LED device is increased by 10%.4.Using tetrabutyl titanate as a raw material,a solvothermal method combined with active design of the zirconate coupling agent was used to prepare a transparent and dispersed organic phase titanium oxide dispersion.Studies have found that the optimal ratio of zirconate coupling agent to titanium oxide is 1:10,and the coated titanium oxide nanoparticles have better thermal stability and dispersibility.Zirconate coupling agent coating the surface of titanium oxide nanoparticles can also reduce the original photocatalytic properties of titanium oxide nanoparticles,and at the same time has good compatibility with silicone resins.When the amount of titanium oxide added is 50 wt%,the transmittance of the silicone composite film is higher than 90%.Adding the surface passivation titanium oxide nanoparticles to the silicone resin can increase the refractive index of the composite film to 2.01.5.Using n-Propyl zirconate as a raw material,a zirconium oxide/silicon composite film with high transparency,high thermal stability and high refractive index was directly prepared by a high-gravity in-situ synthesis method.The composite material prepared by the method can be used for LED encapsulation,and has the effects of improving light extraction efficiency and reducing blue light exposure.Studies have found that in-situ grown zirconia nanoparticles can be formed on the silicone chains in a high-gravity rotating packed bed,with an average particle size of 2-3 nm.Micro-uniform mixing in a supergravity reactor can form ultra-small zirconia nanoparticles in the organosilicon chain,and the result is better than that of conventional reactors.Furthermore,the transmittance of the zirconium oxide/silicon composite film in the visible light region is higher than 90%,and at the same time,it has lower haze,higher thermal stability,and stronger UV resistance and aging resistance.Compared with commercial silicone-encapsulated LED devices,the luminous flux of LED devices packaged with nano-zirconia/silicone(containing 5 wt%n-Propyl zirconate)is significantly increased(from 13.28 to 31.34),and the proportion of blue light is reduced(from 3.1%to 1.8%),while getting a lower color temperature(4573 K).