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Effect of white pigments on UV curing of inks
Author(s) -
Otsubo Yasufumi,
Amari Takeshi,
Watanabe Koichiro
Publication year - 1988
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1988.070350620
Subject(s) - materials science , curing (chemistry) , refractive index , photoinitiator , composite material , ultraviolet , pigment , scattering , irradiation , cure rate , radiation , optics , polymer , optoelectronics , chemistry , organic chemistry , medicine , nuclear physics , physics , surgery , monomer
The dynamic viscosity of ultraviolet (UV) inks during curing was measured by the use of an oscillating plate rheometer and the cure rate was determined rheologically. The effect of white pigments on the cure rate is discussed in relation to absorption and scattering of UV radiation by the pigments. In white inks, the scattering, which depends primarily on the difference in refractive index between the pigment and the vehicle, has an important role in controlling the cure rate. A pigment with a refractive index very close to that of the vehicle has little adverse effect on the cure rate. Thin films of ink containing a pigment with a high refractive index are rapidly cured because of the increase in optical path length by scattering. However, the cure rate is greatly reduced when the thickness is increased due to the rapid decay of UV radiation with depth in the film. The absorption of UV radiation by the photoinitiator in a film which absorbs and scatters radiation is calculated, from which the cure rate is predicted. The theoretical prediction shows good agreement with the experimental results.