Choosing the Right Window Film

Point of purchase graphics and displays continue to provide a major revenue generating opportunity for sign makers. It is a great time to take a fresh look at window graphics. While they are not a new application, the availability of new and improved inks, media, printing hardware and software has raised their achievable quality to a new level.

With today’s digital inkjet printing technologies, sign makers can easily produce one-of-a-kind display graphics to meet regional marketing requirements, as graphic modifications are significantly more cost effective than with traditional offset printing.

On the other hand, the continuous improvement of the digital imaging marketplace and all of its new technologies has made it more challenging for sign makers to select the right media for window graphics. With that in mind, the following are tips for specifying and creating eye catching window graphics that can be easily mounted and displayed by end users.

Media Options

Today’s digitally printable media offerings cover a wide range of materials, textures and adhesion options from many manufacturers, all of which can dramatically affect the appearance of window graphics. Window applications can be produced using clear films, textiles, repositionable polypropylene and perforated films, among others. It is important to understand the differences before choosing the best option for the intended job.

Clear Films

Clear films have become increasingly popular for several P.O.P. applications, including not only window graphics, but also backlit graphics, color overlays and screen positives, because they enable strong black printing densities. When applied to windows, they require a two sided, pressure sensitive, optically clear adhesive.

There are many clear films on the market today for solvent based, eco solvent, aqueous, latex and UV-cure inkjet printers. Polyester films are the best option, as they deliver the smoothest base uniformity and highest resolution for printed graphics. With the environment in mind, an increasing number of recyclable polyester films have become available.

It is important to note that some inkjet printers cannot detect clear films with their optical sensing mechanisms. In cases where a printer cannot recognize a transparent film, media manufacturers offer films with edge stripes or a paper interleaf. Both of these options add enough opacity to the film to be recognized as it is fed through the printer. For printers that use edge media sensing, clear films with stripes are the best option. For printers that do not have edge media sensing or the ability to ‘see’ clear films, an interleaf can provide a way around. For media sensing, or printer operators who simply prefer it, clear films without edge stripes can be used. For sign makers who do not wish to use edge stripes or interleaves with their printing systems, many substrate manufacturers offer clear films with a slight degree of opacity.

Perforated Films

Perforated window films are available for both outside and inside surface mounted graphics, many of which are compatible with solvent, eco solvent and latex inkjet printing systems. Perforated films are a great option for window graphics because they do not completely block out light or someone’s vision.

When selecting perforated window films, one of the keys is to look for the ideal solid-to-hole ratio. A 50/50 perforation ratio is ideal for vehicle graphics because it doesn’t compromise a person’s vision as the vehicle is moving. For retail and P.O.P. applications, a 60/40 perforation ratio is ideal. A 60/40 perforation ratio allows people inside a building to see through to what is happening outside, while people outside the building will only see a solid, vivid image.

Clear liquid laminates are compatible with perforated window films and will provide excellent surface protection. When applying them, the temperature of the film surface should be above 4˚C (40˚F).

Some perforated films are now specifically designed to be printed on the adhesive side. To accomplish this, they combine an adhesive with an ink receptive coating. The advantage of this innovative design is it eliminates the need to laminate by allowing window graphics to be mounted inside a store window, so as to be visible outdoors but without risk of damage from the elements or vandalism. Inside mounted films also make it easier to mount graphics on floors above ground level – removing the need to hire a lift truck and a professional installer. This is a great advantage for city advertising where buildings are typically multiple floors.

These materials require no additional adhesives or mounting tapes and, again, a 60/40 perforation ratio is ideal. To prevent any debris from settling on the printed side of these tacky window films, it is important to clean both the printer and the printing area prior to use, as well as place a clean silicone liner on the floor under the printer. Sign makers should unwind a few ‘wraps’ of the material to feed into the printer and then keep it draped on the unwinding roll, without the use of a take up reel.

Inside surface mounted window graphics should be applied to a clean, dry glass surface at a temperature of 4˚C (40˚F) or higher. As the graphic is held up toward the glass, only the top edge should be tacked down at first. Then the rest of the application surface can be touched as the film is gently tacked, working downward and outward, using a soft squeegee or roller or by hand.

When installing a perforated film window graphic, the film should first be peeled and folded back about one inch of the liner. Once the film is aligned along the window, the top edge should be tacked down. Then the remaining liner can be gently peeled away and the graphic applied evenly by hand, roller or squeegee. The graphic can be repositioned later if desired.

Repositionable Polypropylene

Repositionable polypropylene films with low tack adhesion are already popular for custom posters, short-term residential graphics and some retail displays, but they are now being increasingly used for both short and long term promotional window graphics, as well. PP is sufficiently durable for multiple uses and, unlike vinyl, will not shrink with heat nor suffer any edge curling.

polypropylene is a competitively priced option for maximizing the production of lower cost indoor and outdoor signage. Many substrate manufacturers offer it with a universal coating, allowing it to be printed across all platforms. By enhancing production flexibility, this allows sign shops to reduce their inventories of multiple substrates.

Once a polypropylene window graphic is unrolled, it should be allowed to flatten at a minimum air and surface temperature of 50˚ F, after which it can simply be peeled back from its liner and applied in the desired location. The graphic should be squeegeed with minimal pressure while the liner is removed, smoothing out any wrinkles and bubbles as the film is applied to the glass.

PP window graphics can be reapplied after removing them slowly, lifting at a 90˚ angle. They can also be applied to other smooth, flat, clean surfaces besides glass.

Textiles for Windows

Textiles can yield high image density on window displays, as well as excellent color gamut and a soft appearance. These traits have made them a popular choice for the printing of window graphics and displays, among other P.O.P. applications.

When choosing textile offerings, sign makers should select media constructed of 100 percent polyester woven fabric because polyester adds durability and dimensional stability. Many printable substrate manufacturers offer repositionable textiles with a low tack, non-permanent, pressure sensitive adhesive and a paper liner for easy mounting. For sign makers who choose this option, it is very important to look for materials that can print a full-bleed, and that will not shrink with the application of heat and are designed to prevent edge curling. By allowing the material to be reapplied and repositioned countless times, the low tack adhesive makes it ideal for both window and wall decal applications.

A New Generation

As seen in these and other examples, recent advances in technology have opened the door to a new generation of printable media options for highly appealing window graphics. Today’s sign makers can more easily produce high end images with a softer appearance, using more environmentally friendly materials than before.