Studies on the near infrared laser induced photopolymerization employing a cyanine dye–borate complex as the photoinitiator

Laser diodes are small, cheap and easy to operate, so the near infrared laser diode induced photopolymerization has potential applications in computer-to-plates, erasable computer compact discs and photolithography technology. In this paper, a novel cyanine dye–borate complex (CBC), 1,3,3,1′,3′,3′-hexamethyl-11-chloro-10,12-propylene-tricarbocyanine triphenylbutyl borate, was employed as the photoinitiator, and a near infrared laser diode emitting at 796 nm was used as the irradiation source of photopolymerization. The influence of various irradiation parameters, such as the CBC content, light intensity and sample thickness, on the photopolymerization kinetics of different acrylate monomers, with or without a binder, was investigated in detail by real-time FTIR. The maximum photopolymerization quantum yield was about 21.2 mol einstein−1 for TMPTA with a sample thickness of 20 μm and a CBC content of 2.0 wt% under 0.5 mW cm−2 laser irradiation. It was found that CBC was indeed capable of initiating the polymerization of acrylate monomers under the irradiation of a 796 nm laser. However, the dependence of polymerization rate Rp on the light intensity in the infrared laser induced process was not as pronounced as that induced by conventional UV/Vis light. Moreover, neat TMPTA gave a double bond conversion compared with the system including a solid binder under the same irradiation conditions.