Heat-induced inkless eco-printing inspired by paper discoloration: A review

Abstract

In this paper, the art-of-the-state of heat-induced inkless eco-printing (HIEP) technology in recent years was summarized and prospected, mainly from the printing effect, degree of carbonization, environmental impact and feasibility. The main results were as following: (1) The paper used in HIEP is predominantly yellow in color, which enables a practical printing effect. (2) After HIEP, the paper exhibits no significant carbonized microstructure and keeps its high strength. (3) HIEP is an ecologically and environmentally preferable technology. Only a small amount of toxic products is generated, and no carcinogens are emitted. (4) No significant damage to the paper is evident following HIEP, as the degree of heat experienced during HIEP is far below that experienced during a thermogravimetric (TG) experiment. Additionally, the evaporated water has a buffering effect. Based on the previous research results, this paper finally pointed out the possible research direction in terms of discoloration mechanism and printing effect, environmental impact improvement, paper damage mechanism and strength during HIEP, high-temperature printing head installation and relevant techniques, optimization of printing process parameters.