4.1 Introduction

The printing of security documents is a threefold matter. First, there is an abundance of security printing inks, such as fugitive inks, metameric inks, luminescent inks, and iridescent inks, discussed in Section 4.2. Second, there are various ways of transferring these inks to the substrate, the most important of which are intaglio printing, offset printing, letterpress printing, and screen printing, discussed in Section 4.3. Finally, there is a like abundance of printed security patterns, such as guilloches, latent images, see-through registers, and various modulated screens, which are the subject of Chapter 5.

Printing inks must be adapted to the printing technique used to apply them to the substrate, but this is not the subject of this chapter. Rather, a discussion of the optical characteristics of security inks is of interest in this context. For further reading, reference is made to [1].

4.2 Printing Inks