Screen Printing or Digitally Printing PVC or Vinyl Banners; No Painting Allowed on Vinyl
I have received several questions regarding vinyl (flexible PVC) banners that I am going to answer over the next few articles. The first is, “What type of paint does one use on vinyl banners?”
The answer is that we don’t use “paint” per se on vinyl banners, although there may be some craft type stores that sell such a product. Coming from the commercial side of vinyl banners, though, there are about three main methods to print banners.
The first method, and the oldest method of these three printing styles is screen printing. In screen printing, there is a frame, or several frames if it is a multi-color print, with an image that is created by exposing, like old-fashioned picture film, certain elements of the print to an ultra-violet or similar type of lamp.
Once the light has been applied for a pre-determined period of time, the film positive, the image that is printed on a digital printer (this is the current method although older methods are still in use in many print shops), is removed, and the screen is taken to a washout tank and using pressurized water, the non-exposed photo-sensitive emulsion is washed away from the screen, leaving the image to be printed.
After the screen and frame are completely dry, the frame is moved to a screen printing press, typically a “clam shell” style press that, as it prints, the front end come up so the press operator is able to insert the next substrate onto the flat print bed. In the case of vinyl banners, because they will typically be larger, the larger screen printing presses will not be clam shell style printers, but rather the mechanisms will lift the screen up entirely, allowing the screen to remain in a flat position.
Automatic loading and unloading apparatus are also available on many of these presses to speed up production and reduce the risk of mucking a print due to human error in handling the substrate.
The type of ink used for air dry printing is a vinyl ink that “burns” itself into the PVC banner material so that it will last a long time. However, it is not chemical resistant by any means, and a chemical such as lacquer thinner or xylene, if accidentally splashed on the banner, will ruin the print.
Over the past couple of decades or a little longer, new inks were developed that had lower VOC’s than the old harsh vinyl inks that were lacquer-based. These newer inks are known as UV curable inks, or just UV ink. UV stands for “ultra-violet,” and are chemically reactive to UV light.
And they’re still applied by many print shops using screen printing presses, except now the substrate, in this case PVC vinyl banners, are moved from the press to a conveyor belt that moves the banner underneath a set of UV lights that cure the ink instantly. There is much less odor, and less chance for dust to get in the ink or other issues with this ink as it is much more resistant to problems that the old vinyl inks that were air or infra-red dried.
The final method of printing is digital printing, which uses either solvent-based, water-based, or UV inks. More and more shops are going to the UV digital printers, which dry instantly as the light passes over the fresh print just behind the print heads.
So, to answer your question, commercially we don’t use “paint,” per se, but hopefully you now have a pretty good idea of how we print on vinyl PVC banners.
Check this out for more about printing on vinyl banner displays.