Flexo printing, also known as flexographic printing, is a technique that employs the use of flexible printing sleeves of plates. Traditionally, rubber plates were used. However, over recent years, flexible photopolymer printing plates have become the order of the day. Flexographic printing is considered a modern version of letterpress printing and an example of complex direct printing technology. The difference is that it uses flexo printing ink and a wide range of substrates.
This technique is currently the most vigorously evolving areas in the entire printing market. This can be attributed to the continuous and widespread application of this technique in different parts of the world. The substrates and flexo printing plates are some of the most crucial elements of this technique. However, flexographic ink is the center of the printing process.
Features of flexographic printing inks
The technique uses different ink types specifically designed to work correctly with the different types of substrates and carriers within the process. Below are some unique features of flexographic printing inks:
Flexo printing technology utilized low-viscosity inks. These inks allow for regular flow within the printing unit. The average viscosity for the ink used in this technique is between 0.05-0.5 Pa . s. Note that these inks are usually manufactured as concentrates of solvent and water-based inks. This is the root behind the unique viscosity of the inks.
2. Surface tensions
Naturally, inks usually flow to higher dyne levels. In this technique, proper surface tension configurations are applied to allow as much ink as possible to be transferred to the substrate. The configured surface tension also provides for an even and full wet out of the substrate.
3. Drying rate
One of the advantages of flexo printing technology is that it is speedy. The types of inks used in the process are partly responsible for this advantage. The inks are typically fast drying. This allows the substrate to move from one plate to the next without allocating any ink’s drying time.
Types of flexographic printing inks
There are four main types of flexo printing inks. They are;
These inks are mostly made up of water and pigment. They also include various additives that are responsible for the fast drying rate. They have a high surface tension, and they are commonly applied in the corrugated packaging market.
These contain alcohols, pigments, and acetates. They have a lower surface tension as compared to the latter. They are commonly applied in the manufacture of plastic shopping bags or films.
They consist of hydrocarbons, pigments, and sometimes mineral oils. They are highly recommended for the publication printing market.
They contain pigments, monomers, prepolymers, and photoinitiators. They have require exposure to an electron beam or UB light for them to dry or adhere to a solvent. They are also highly viscous and eco-friendly since they are resistant to the ozone. UV or EB flexo printing inks are commonly used in the food packaging industry.
Note that flexographic inks are usually transferred to the substrate through the plates. The inks play a significant role in this printing technique’s popularity because they are cost-efficient and eco-friendly.