Visible laser lights in photoinduced polymerization. VI. Thioxanthones and ketocoumarins as photoinitiators

Abstract

SYNOPSISThe efficiency of thioxanthones and ketocoumarins as photoinitiators has been checked in visible laser light-induced polymerization reactions and discussed in terms of excited-state reactivity (as revealed by time-resolved laser spectroscopy). These compounds undergo fast electron transfer reactions in the presence of amines and onium salts. Transient absorption spectra and rate constants of the processes involved have been determined. The combination photoinitiator-amine-onium salt appears as very promising for the design of efficient photosensitive systems.

A mechanistic investigation of the three-component radical photoinitiator system Eosin Y spirit soluble,N-methyldiethanolamine, and diphenyliodonium chloride

“…A similar result was observed for the system ketocoumarin dye/MDEA/ diphenyliodonium hexafluoroantimonate by Fouassier and Wu. 6 The results shown in Figure 4 suggest that the three-component initiation system displays two distinct timescales in photobleaching: a short timescale representing the EYss/DPI reaction and a long timescale representing the EYss/ MDEA reaction. The data shown in Figure 4 come from an experiment with data points spaced ϳ1 s apart.…”

Visible Laser Recordable Photopolymer Based on Poly(p-hydroxystyrene) and Acidolysis of Crosslinked Vinyl Ether.

“…[3] For the reaction mechanism between sensitizing dyes and TAZ 114, DITS and DITFMS, we consider that it was electron transfer reaction as several reports. [1][2][3][4] When TAZI 14 is used as PAG, the relative order of sensitization of the sensitizing dye was acridine orange > KCD > thioxanten-9-one > rose bengal. However, there is a disadvantage that acridine orange reacts with TAZ 114 in dark.…”

“…In both cases, the reactivity in the excited states will govern the efficiency of the photosensitive systems. [1,2] From this concept, the negative and positiveworking photoresists sensitive to visible light have been developed. Hotta et al [3] reported that the negative-working photoresist consisting of PHS and hexamethoxy methylmelamine crosslinker and photoacid generator (PAG), which is high sensitivity to 488-nm argon ion Jr light based on cationic polycondensation.…”

1,3‐dioxane methylcoumarin as a novel photoinitiator for free radical polymerization

“…Triplet coumarin dyes are well‐known high‐efficient photosensitizers in UV–vis curable systems. When excited by light, they can transfer electrons with high efficiencies to coinitiators, such as iodonium salts or hexaarylbisimidazoles 14–18…”