An Easy Fabrication Method to Prepare Inexpensive UV–Cured Transparent Silicone Modified Polyacrylate Coatings with Good Adhesion and UV Resistance

High Refractive Index Diphenyl Sulfide Photopolymers for Solar Cell Antireflection Coatings

The anti-reflection film can effectively reduce the surface reflectivity of solar photovoltaics, increase the transmittance of light, and improve the photoelectric conversion efficiency. The high refractive index coating is an important part of the anti-reflection film. However, the traditional metal oxide coating has poor stability and complicated processes. To address this issue, we prepared two organic high refractive index (HRI) photopolymers by modifying epoxy acrylic acid with 4,4′-thiodibenzenethiol, which can be surface patterned by nanoimprinting to prepare antireflection coatings. As a result, two modified photopolymers with high refractive index (n > 1.63), high optical transmittance (T > 95%), and thermal stability (Tg > 100 °C) are obtained after curing. In particular, the diphenyl sulfide photopolymer modified by ethyl isocyanate acrylate has a refractive index up to 1.667 cured by UV light. Our work confirms that the organic HRI photopolymer can be obtained by introducing high molar refractive index groups, with potential to be applied as a PV cell power conversion efficiency material.

UV-Cured Transparent Silicone Materials with High Tensile Strength Prepared from Hyperbranched Silicon-Containing Polymers and Polyurethane-Acrylates

Flexibility and mechanical performance are essential for transparent silicone materials applied in some optical and electronic devices; however, the tensile strength of transparent silicone materials is fairly low. To overcome this problem, a kind of UV-cured transparent flexible silicone material with quite a high tensile strength and elongation at break was developed through UV-initiated thiol-ene reaction by hyperbranched silicon-containing polymers (HBPs) with a thiol substitute and acrylate-terminated polyurethanes. Unexpectedly, it is found that both the tensile strength and elongation at break of the transparent silicone materials are extraordinarily high, which can reach 3.40 MPa and 270.0%, respectively. The UV-cured materials have good UV resistance ability because their transmittance is still as high as 93.4% (800 nm) even when aged for 40 min in a UV chamber of 10.6 mW cm-2. They exhibit outstanding adhesion to substrates, and the adhesion to a glass slide, wood, and a tin plate is grade 1. The promising results encourage us to further improve the mechanical performance of flexible transparent silicone materials by effective chemical modification strategies with HBPs. An attempt was made to apply the UV-cured materials in a Gel-Pak box and it could be proved that the UV-cured materials may be one of the good candidates for use as packaging or protecting materials of optical or electronics devices such as the Gel-Pak product.

High Efficiency and Low Migration Hyperbranched Silicone Contain Macrophotoinitiators for UV-Cured Transparent Coatings

A kind of hyperbranched silicone containing macrophotoinitiators (HBSMIs) were synthesized from 2-hydroxy-2-methyl-1-phenyl propanone (HMPP) and the UV-curing behaviors of HBSMIs were investigated in UV-cured transparent polyurethane-acrylate (PUA) coatings. HBSMIs show higher UV-initiating efficiency than HMPP. The migration of HBSMIs from the UV-cured coatings can be as low as 1.7–6.0 wt%, which is obviously lower than the migration of HMPP. There is a remarkable improvement of the tensile strength of the UV-cured materials initiated by HBSMI in comparison to that of the materials prepared with the same PUA initiated by HMPP. Especially for the UV-cured materials prepared from PUA with 20 wt% 1,1,1-tris(hydroxymethyl)propane (TMP), the tensile strength and the strain at break increased from 6.81 MPa to 12.14 MPa and from 43.0% to 71.9%, respectively. The fraction of improvement for the tensile strength and the strain at break is as high as 78.9% and 67.2%, respectively. The coatings prepared with HBSMI also have better UV resistance ability than those coatings prepared with HMPP because they turn slightly yellow when they are aged by UV for about 15 min while the coating prepared with 4 wt% of HMPP will turn yellow only aged by UV for 2 min. These results suggest that preparation hyperbranched silicone containing macrophotoinitiators will be one of the good strategies to improve the curing efficiency of the UV-curing system, reduce the migration of UV initiator from cured material, improve the mechanical and UV resistance performance of UV-cured materials.