UV/UV step-curing of optically clear acrylate adhesives for mobile devices

Abstract

In order to overcome the issues of rework and height difference in the manufacturing of smart devices, UV/UV stepwise curing was conducted on acrylate-based optically clear adhesives. Photo differential scanning calorimetry was used to confirm the results of curing of samples that were processed both with and without acrylic acid, over a range of UV light exposure times for a primary curing process. The samples processed at 0.6 J/cm 2 of UV energy with and without acrylic acid showed the highest amount of residual monomers after primary curing. The amount of residual monomers observed in primary-cured samples decreased as the amount of UV light energy increased, from 0.9 to 1.5 J/cm 2. After secondary curing, only the samples cured at 0.6 J/cm 2 showed small amounts of residual monomers, while the samples exposed to other UV energies showed very few residual monomers, implying that these samples were completely cured during the secondary curing step. Adhesion properties were evaluated using peel and tack tests, while the viscoelastic properties of the samples were confirmed by dynamic mechanical analysis. Our results indicate that uniform physical properties were achieved after secondary curing. The effects of stepwise curing are demonstrated by the difference in gel fractions determined after primary and secondary curing.

Free-Radical Bulk-Photopolymerization Process as a Method of Obtaining Thermally Curable Structural Self-Adhesive Tapes and Effect of Used Type I Photoinitiators

“…Relatively rarely the photopolymerization method is used to obtain a liquid polymer or polymer solutions. Admittedly, in the last decade several publications have been published ‘regarding the method of obtaining acrylate syrups via the photoinduced polymerization process that occurs in large amounts of monomers’ mixture and with a mechanical mixing [ 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. Obtained products were mainly used as transparent pressure-sensitive adhesives.…”

Influence of radical photoinitiators on features of polyacrylate syrups and self-adhesives

“…After UV-crosslinking of such composition, finished product is achieved. Using this method, in the last few years, a group of scientists from Dankook University (Republic of Korea) obtained acrylate binders for optically clear pressure-sensitive adhesives (PSA's) [20,[23][24][25][26][27]. Researchers focused on obtaining optically clear adhesives using new monomers (tetrahydrofurfuryl acrylate, acryloyl morpholine, menthyl acrylate and derivatives of monosaccharides) and mainly in the presence of 1-hydroxy-cyclohexyl-phenyl-ketone as photoinitiator and 1-dodecanethiol as chain transfer agent.…”

The Effect of Type-I Photoinitiators on the Kinetics of the UV-Induced Cotelomerization Process of Acrylate Monomers and Properties of Obtained Pressure-Sensitive Adhesives

“…Instead, Beak at al. showed the free radical bulk photopolymerization process as a method of obtaining acrylic syrups to prepared PSAs [ 12 , 13 , 14 , 15 , 16 , 17 ]. However, the resulting reaction products (prepolymers/syrups) had a high content of unreacted monomers, so the PSA film was UV-cured in the presence of volatile compounds and must be covered with a transparent release film to avoid oxygen inhibition.…”