It’s that time of year. No, not January white sale season. It's static discharge season. As the air gets drier, problems start to arise in some sign shops because of the unique properties of plastic films and static electricity. It’s common knowledge that his can cause problems for installers of window tint film. What is less well known is the fact that static electricity generated by backlit film can interfere with large format printers. This interference can cause problems that are hard to diagnose. Fortunately, it’s also easy to prevent. 

What Causes Static Electricity

Before we jump to the solution, it might be helpful to learn a little bit about what causes this phenomenon. All plastics can generate static electricity. But some types of films used in digital signage applications are more likely to produce static charges. These films can generate static electricity as the film is removed from the release liner, or as the film is unwound and fed through a vinyl cutter or printer. There’s a great article about static and polymers on the knowledge base. Here are some salient excerpts.  

“Static electricity is a surface phenomenon and occurs as soon as two or more surfaces come into contact with each other and are separated again. This causes some kind of splitting, i.e. a transfer of negative electrons from one surface to another. The higher the pressure or the speed of separation, the higher the charge. This charge can only flow away once contact is made with an otherwise charged surface (voltage difference). This can be metal, water, but also charged (ionized) air.
Most plastics (including polyethylene) are known for their poor conductivity. They have a high so-called surface resistance. The higher the resistance, the more energy is needed for an electron to get through. If the electron doesn’t have enough energy, it stays put and will only move when it finds a way out that offers less resistance. There are materials with a much better conductivity. Copper is a good example. Such materials are used in electrical wires to create a good electrical current."

Copper’s conductivity is an important part of the solution. You can read more about the phenomenon in’s excellent knowledge base article.

So, as polymer films like window tint and backlit film unwind and are fed through a cutter or printer, they generate static charges. In tinting, static electricity mainly attracts dust and hair that can contaminate an installation. In printing, the effect is more subtle, but just as disruptive.

Magenta Channel Loss

Large format digital printing comprises four process colors: cyan, magenta, yellow, and black. These colors are made from dyes and pigments that are ground and suspended in various ink solutions. Pigments have unique traits that can affect performance.  Some of these traits relate to static charges. Ink clogs are sometimes caused by the electrical charges generated by pigment particles drawing them together so closely that they clog the print head.

Magenta pigment is more susceptible to this phenomenon. So running a plastic film that generates static charges right under your piezoelectric print head can trigger this behavior in the magenta particles and cause clogging. The result is a sudden dropout of the magenta channel in an otherwise perfectly functioning printer. The sudden loss of one channel and seemingly random nature of the issue can make it hard to diagnose and may lead to expensive remedies that don’t address the core problem.

Seasonal Problem

Static electricity and the problems it causes are not a constant threat. It doesn’t happen everywhere all the time. It’s worse in more arid conditions. So climates where the relative humidity is always low, like the American southwest, will have more problems than humid climates like New Orleans or Seattle. In temperate areas, it becomes a seasonal problem because humidity drops in winter. So printers in temperate climates will see this issue more often in the drier winter months than in spring and summer. It can also occur with other media like printable vinyl and scrim banner rolls. It’s not limited to backlit film.

The AKZ Kit Solution

Fortunately, there are simple solutions. One is the Graphtec AKZ anti-static kit.  This kit reduces static fields for vinyl cutters and window tint film, and works the same way on large format printers. As noted above, copper is much more conductive than polymer films. So placing a copper wire above the film where it unwinds off the roll is a great way to prevent the film from generating a static field as it passes under the print head. This prevents the charges from pulling the magenta pigment particles together, clogging the Magenta channel.

The kit includes two strong magnets used to anchor the wire. Just string a thin copper (or other conductive material) wire between the magnets and place it against the back of the printer, just above the media, as seen below (FIG 1).

FIG 1: Deploy the copper wire just above the backlit film using the AKZ anti-static kit.

If you’re using backlit film, we highly recommend you purchase an AKZ kit and deploy a copper wire across the back of your printer. The problem can also arise printing on vinyl in winter. Likewise, if you’re working in an arid environment and experiencing loss of the magenta channel, try this simple solution before assuming there’s a more serious problem in the ink delivery system. Stringing a wire across the back of your printer can save you a lot of head scratching and down time.