Ink made from fluorescent pigments and coloring agents is called fluorescent ink. The main characteristic of printing with fluorescent ink is that it can convert short-wave ultraviolet light into longer visible light and reflect brilliant colors, which provides good anti-counterfeiting effects. The coloring agents used in fluorescent ink (usually pigments or dyes) have different properties than ordinary coloring agents: 1) reflecting visible light, and 2) absorbing short-wave light (such as violet, blue, and green light) and reflecting it as visible fluorescence. When stimulated by sunlight or ultraviolet light, the printed coloring material exhibits fluorescence, showing brilliant fluorescent colors. Whether fluorescent ink can produce a bright fluorescent effect mainly depends on the persistence status of atomic groups in the molecular structure of the coloring agent.

Fluorescent ink is mainly divided into two types: phosphorescent fluorescent ink and colorless fluorescent ink. They are briefly introduced below:

1. Basic characteristics of phosphorescent fluorescent ink

After printing with phosphorescent fluorescent ink, when the printed pattern is irradiated with ultraviolet light, it reflects visible light in the long wave band, and it can also show brilliant colors in the dark without any light, which is the result of the action of sulfides such as zinc, cadmium, and strontium in the coloring agent.

2. Characteristics of colorless fluorescent ink

The most important characteristic of colorless fluorescent ink is that it can be mixed with the same type of four-color ink to form other colored fluorescent inks. The color and amount of ink added will affect the fluorescence color and brightness of the fluorescent ink. Improper mixing will also affect the ink printing performance. Red and yellow fluorescent inks can produce obvious fluorescent colors because their transmitted wavelength is significantly different from that of ultraviolet fluorescence. For green fluorescent ink to achieve ideal fluorescent effect, the ink layer needs to reach a certain thickness when printed on a light or white background.

3. Application of fluorescent ink

Fluorescent ink is widely used in securities, stamps, trademarks, labels, scratch cards, invoices, navigation markers, and other packaging and decoration printing products. Because it can produce a brilliant effect in color printing, its application prospects are extremely broad.