Screen printing Applications

Applications

Screen printing is arguably the most versatile of all printing processes. It can be used to print on a wide variety of substrates, including paper, paperboard, plastics, glass, metals, fabrics, and many other materials. including paper, plastics, glass, metals, nylon and cotton. Some common products from the screen printing industry include posters, labels, decals, signage, and all types of textiles and electronic circuit boards. The advantage of screenprinting over other print processes is that the press can print on substrates of any shape, thickness and size.

A significant characteristic of screen printing is that a greater thickness of the ink can be applied to the substrate than is possible with other printing techniques. This allows for some very interesting effects that are not possible using other printing methods. Because of the simplicity of the application process, a wider range of inks and dyes are available for use in screen printing than for use in any other printing process.

Utilization of screenprinting presses has begun to increase because production rates have improved. This has been a result of the development of the automated and rotary screenprinting press, improved dryers, and U.V. curable ink. The major chemicals used include screen emulsions, inks, and solvents, surfactants, caustics and oxidizers used in screen reclamation. The inks used vary dramatically in their formulations (GATF 1992b).

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Tips To Improve Screen Printing Quality

Tips To Improve Screen Printing Quality

Ink Quality: The consistency of ink is a critical factor in the quality of screen printing. Inks can be classified as stiff or loose depending on their consistency. Some printers try to adjust the squeegee angle and pressure to compensate for the consistency of ink. This is likely to make the screen printing process much more difficult and if the process is manual, can even lead to carpel tunnel syndrome or sore joints.

The correct way to modify the way an ink prints is by using two products known as soft hand clear or extender base and curable reducer. The soft hand clear is used to adjust the pigmentation in the ink. In addition to adjusting the percentage of pigment in the ink, the soft hand clear also makes the ink more creamy and easier to screen print. The soft hand clear ink requires less squeegee pressure than regular ink and hence improves screen printing quality.

Curable reducer changes the adhesive quality of the ink and can be used anywhere from 2-4% to 10% depending on its texture. The curable reducer allows the ink to shear easily and thus print better.

Thus it is important to modify the inks as required so that you not only screen print easier and faster but also save ink and get better registration.

Screens: The rule of thumb with screens and meshes is that the tighter they are, the better the quality of output. The benefits of a tight mesh include a decreased likelihood of the mesh moving out of registration during printing and lesser chances of one color bleeding into another.

Tight screens also offer lower resistance when pulling the squeegee thereby reducing labor and cutting the ink cleanly.

A tight mesh also deposits the ink evenly onto the substrate. A soft mesh may have deposits of ink towards the edges thus printing with more ink in the center and less towards the corners. The uneven deposit of ink results in lowered printing quality.

Squeegee: It is vital that the blade of the squeegee is straight and sharp. The squeegee should be sharpened every day if need be to allow for even spreading of the ink.

Press: To get good quality screen printing, the platen must never move during printing. Even if you do everything else right and the platen shifts, the quality of the print will suffer. Also the color arm must not deflect when it in or out of the registration gate.

Curing: You cannot substitute the amount of time that the ink is cured for by increasing the heat. Sometimes inks need to be cured at lower heat for longer time for the ink to fuse with the fabric and get a full cure.

Thus, keep these tips in mind when screen printing to ensure high quality screen printing.

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Screen Printing Inks

Screen Printing

UV Curable

UV curable inks consist of liquid prepolymers, monomers, and initiators which upon being exposed to large doses of U.V. Radiation instantly polymerize the vehicle to a dry, tough thermosetting resin. They also require less energy, overall, to dry or "cure" compared to gas or electric driers.

The down side of UV inks is they can cost as much as three times that of regular inks and must be handled differently than conventional inks due to safety issues. Additionally, solvents are required for clean-up which results in some VOC emissions.

Plastisol Inks

Plastisol inks (both solvent and water based) are used in textile screen printing.

Solvent Inks & Water Inks

Solvent and water based screen printing inks are formulated with primarily solvent or water. The solvent evaporates and results in VOC emissions. Water based inks, though they contain significantly less, may still emit VOC’s from small amounts of solvent and other additives blended into the ink. The liquid waste material may also be considered hazardous waste.

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