The importance of anti-counterfeiting measures for banknotes goes without saying. This article explains how to identify the authenticity of banknotes based on the features of optically variable ink. Taking the Chinese currency as an example, there are many anti-counterfeiting features incorporated in the banknotes, and here we focus on the visual features produced by the optically variable ink.

Visual features can generally be divided into watermark features and overprinting features. Watermarks on Chinese banknotes are usually made of white watermarks and multi-level watermarks. The white watermark has a higher brightness than ordinary watermarks, while the multi-level watermark has a multi-level gray effect, which can create a relief-like pattern. The watermark features are produced by using optically variable ink for printing, which reduces the accumulation of paper fibers and the height difference in the watermark area. The pattern of the watermark can be observed under backlighting.

In the process of banknote printing, offset printing is generally used. The overprinting feature is achieved by using optically variable ink to print different partial patterns on the front and back of the banknote, so that when viewed under transmitted light, the two patterns can be displayed simultaneously and form a complete pattern. This printing method for optically variable ink has strict requirements on the printing process.