Synthesis and applications of near-infrared absorbing additive copper hydroxyphosphate

The use of copper hydroxyphosphate (Cu2PO4OH), also called libethenite, as a near-infrared (NIR) absorbing additive has been investigated. Samples were synthesized by using a hydrothermal treatment or simple wet chemical processing, which was later easily upscaled. All synthesized samples showed a strong absorption in the NIR region. Trials were conducted to produce laser-marked plastic plates and security IR ink printing tests. It was found that when incorporated in plastic and ink formulation, Cu2PO4OH added good NIR absorption properties without influencing other finished product properties too much, which confirms that it is a suitable additive that can be readily manufactured at room temperature and without pressured equipment.