Fabrication And Properties Of Anti-reflection Coating With PMMA/PBA Latex Blend

An anti-reflection coating(AR coating)is a dielectric thin-film coating applied to an optical surface in order to reduce the optical reflectivity of that surface in a certain wavelength range.AR coating has a wide range of applications including energy,optical imaging and military stealth.Currently,the preparation methods are etching,dissolving with selective solvent and inorganic particle packing.These methods have the disadvantages of low preparation efficiency,high selectivity to substrate and structural instability.In this thesis,a new method for the preparation of AR coatings based on cross-linked poly(methyl methacrylate)(PMMA)and poly(butyl acrylate)(PBA)blends were proposed and studied.As the latex blend is baked,the PMMA particle still has a spherical morphology,and is adhered to the surface of the substrate with the aid of PBA latex film.In the coating,air fills among PMMA particles,so that the refractive index of the coating is greatly reduced.It can effectively reduce the substrate reflectivity of light.Based on this idea,PMMA latex and PBA latex with different particle size were prepared by emulsion polymerization technology in chapter 2.In chapter 3,the effects of mass ratio of PMMA to PBA,the particle size of PBA and the solid content of latex blend on the antireflection properties of the coating were investigated.Then,the applicability of the existing antireflection theory to the latex blend coating was investigated,and a new model is proposed.In Chapter 4 and Chapter 5,the effects of PMMA latex particle size on the antireflection properties and structural stability of the coatings were investigated.The followings are concluded:1.The effect of mass ratio of PMMA to PBA on the anti-reflectivity of the coating was studied: the anti-reflection efficiency grew with the increase of the mass ratio of PMMA to PBA until the mass ratio achieved 97:3.2.The anti-reflectivity of coating depended on the particle size of both PBA and PMMA(DPBA and DPMMA):(1)With the decrease in DPBA,the distance between PMMA particle decreases accordingly.The scattering of incident light is reduced especially in the case of DPBA less than 85 nm;(2)The increase in the solid content of latex blend lead to the surface density increase of PMMA particles in the coating,which finally lead to PMMA stacking.In the case of single PMMA layer coating,the maximum of surface coverage Smax is 78.54%.It corresponds to a coating with refractive index of 1.23.The wavelength(?max)at the highest transmission equals to 4*1.23*DPMMA;(3)The reflective index of the coating decreases with the decrease in the surface coverage(S).However,the ?max remains 4* 1.23*DPMMA,indicating the deviation from the Fresnel model for homogeneous film.(4)A new model for coating with S less than 78.54% is proposed: ?T/?Tmax=S/Smax.(5)The structure and antireflection properties of the coating remains stable even after 20 cycles of 180�bending.3.The antireflection behavior of coating prepared from mixture of PBA and PMMA with two kinds of particle size was also studied,in which DPBA=55 nm;DPMMA,B=134nm;DPMMA,Sm is 54 nm,84nm and 112 nm,respectively.Research shows:(1)The transmission curves of the coating combined the properties of both PMMA,B and PMMA,Sm.However,the curve can be obtained from the curves of PMMA,B and PMMA,Sm,exclusively when PMMA,B and PMMA have a similar size(DPMMA,B=134nm,DPMMA,Sm=112nm);(2)With the increase in the number ratio of PMMA,B to PMMA,Sm,?max has been totally determined by DPMMA,B since a low NB/Sm of less than 1.