In Window Films Under certain lighting conditions and viewing angles, the appearance of various colored
bands on the film surface that appear to “float” over the surface as the viewer changes his point of view or
an “oil on water” appearance on the surface. Please refer to Figure 1.
The coloration is not from dyes or other color substances rather it is due to the multilayer structure of
window films. Rainbow shows as varied colors and is the result from the interference of light waves
reflected from different surfaces within the film, and changes with the angle of view. In the case of window
films, the first layer of window film is the Anti-scratch layer (layer 1), applied to our UVIR (layer 2) is the
reason to cause the rainbow effect. While the first layer –Anti-scratch layer is optically clear, it has a
slightly different refractive index than the second layer – UVIR film as shown in Figure 2. Therefore when
the light from the interior space, some of the light transmits through to the exterior of the window and
some of the light is reflected off the first layer and back into the interior space (λ1). Moreover light is
reflected off the second layer – UVIR film and back again through the first layer (λ2). Variations in the
reflected light waves across the surfaces of the film produce the Rainbow effect.
Types of interior light sources can have a dramatic effect on the “rainbow appearance. Fluorescent lights,
compact fluorescent bulbs, and especially new energy-efficient “T8” lamps appear the generate the worst
There are a few things that can be done to reduce or eliminate this effect and following summary remarks,
followed by suggestions to mitigate the problem:
1. “Rainbow” can be seen on most window films if looked at closely under certain lighting conditions, even
2. It is impossible to avoid rainbow effects completely with most films because it is a physical effect not
completely controllable by manufacturing processes.
3. iridescence can be amplified under certain viewing conditions, such as with darker external backgrounds
like nighttime and with sloped glass
SOLUTIONS TO REDUCE THE RAINBOW EFFECTS:
1. Reducing the contrast between internal and external background color (Figure 3) – the rainbow effect is
2. To use a full spectrum light source like incandescent lighting or full spectrum LED lighting. Rainbow effect
is not a sign of product failure or deterioration.