Study On Preparation And Properties Of Fluorescent Offset Printing Ink

Photochromic anti-counterfeiting offset printing ink was prepared by using new BaGd₂(MoO₄)₄ based inorganic photochromic materials as pigment, phenolic resin solution as ink vehicle, and adding other additives. Printing ink marks are colorless in general light source, and show red color if excited by 395nm ultraviolet laser, and green if done by 980 infrared laser, and recovery as colorless if the exciting stopped. It demonstrates excellent photochromic anti-counterfeiting property. In the present research, the synthesis technology of BaGd₂(MoO₄)₄:Eu³⁺,Yb³⁺,Er³⁺ pigment was determined and the crystal structure as well as luminescence spectra were characterized. Also, the composition of photochromic anti-counterfeiting offset printing ink was determined and its luminescent characteristics and rheological properties were detailed by experiments. The results are given as: (1) the ingredients ratio of Eu³⁺ , Er³⁺ , Yb³⁺ doped BaGd₂(MoO₄)₄ photochromic materials was BaGd₂(MoO₄)₄:0.6Eu³⁺,0.06Er³⁺,0.2Yb³⁺ , synthesized by kept the ingredients at 850℃for 5 hours. The synthesized BaGd₂(MoO₄)₄ is well crystallized. It emits 613 nm orange-red light if excited by by 395nm ultraviolet laser, and luminescences 523 nm 545 nm green light if excited by 980 infrared laser.(2) the optimized formulation of the photochromic anti-counterfeiting offset printing ink is (wt%): photochromic materials 35%,varnish2%,dispersing agent2%,antioxygen1%,phenolic resin ink vehicle 60%. The viscosity of the prepared ink is 190.7Pa·S. The maximum relative intensity is 299 a. u. . (3)The rheological properties of the ink prepared by the present inorganic pigment is similar to those of the other three monochrome commercial offset printing inks, which is prepared by organic pigments. It indicted that the dispersion-aggregation structure in the prepared ink is similar to those of the commercial offset printing inks, too. The initial viscosity of the prepared ink is large enough and the shear viscosity is sufficient small. The thixotropic, viscoelastici properties and offset printing ability of the prepared ink are favourable.