Screen Printing

Screen Printing Today

Screen printing has come a long way over time with the introduction to new equipment and materials; screen emulsions inks, and solvents, surfactants, caustics and oxidizers. the essential tools used are the screen (or porous mesh), the squeegee and the ink. The stencil image can be made manually or photochemically. The thickness of the ink layer depends on the diameter of the threads and the thread count of the mesh; it will determine how much ink is deposited.

Today, we have the privilage of automatic presses that do screen printing by machine. The development of the rotary screen press allows for continuous operation of the press by placing the screen on a conveyer belt.

Rotary press is just one type of press. There are flat, cylinder and rotary presses for screen printing. Flat and cylinder are similar in that you simply press the screen down, squeegee and lift and these machines are designed for a flat or cylinder surface. Rotary involves thin cylinders that are filled with ink to keep a steady flow of color in the screen. Inside the bar is a magnetic squeegee whose pressure is monitored by magnets below the press bed. This method is best suited for textiles, wallpaper, and other products that require unbroken continuous patterns.

The most recent advancement in screen print technology is UV curable inks. These have liquid prepolymers, monomers and initiators that when exposed to UV light instantly polymerizes the ink to a dry, tough thermosetting resin. This method is better than gas or electric driers, for it is not as hazordous and it also saves a lot of money. This is energy efficient for it reduces energy consumption by 40-50%! Old methods use mercury lamps which are more hazardous and emit more heat.

Some inks like solvent inks result in VOC emissions. It is also known that water based inks may still emit small amounts of VOC from additives. A search for a "clean ink" may be underway.