Direct Evaluation Method of UV Curing Process on the Basis of Conductivity Change of UV Ink.

A novel direct evaluation method is proposed for UV curing. The method is based on the measurement of the photodecrease of conductivity which is caused by the photopolymerization of aclylate monomer during the curing process of the ink film. The amount of photochange of sample current is related to the amount of photopolymerization of curable monomer. The current changing rate by UV irradiation is in proportion to relative hardness of ink layer in surface type cell. The measured photochange data of sample current contain the information of both cured and non-cured portions of UV curable material layer in surface type cell. The evaluation of sensitivity and curing mechanism of UV curable materials is possible by the measurement of photochange of sample current in either surface or sandwich type cell. In practical measurement of negative photocurrent of UV curable materials, the sample and electroded cell are simple and easy, and the measured current data may contain the informations of both cured and non-cured portions of UV curable material layer.