Advantages of Using Light Guide Film for Backlighting Membrane Switches

Light Guide Film is designed to evenly distribute light from top or side firing LEDs, providing bright, uniformed illumination. It also reduces the amount of LEDs needed, saving power consumption. More on light guide film technology below. The design and utilization of light guide film (LGF) technology has become one of the most common methods of interface backlighting. CSI Keyboards uses proprietary techniques to design the light guide film so it is optimized for light redirection and reflection giving the customer the brightest possible backlighting solution. Light guide film dots are also designed and implemented which allow for the optimization of light distribution to obtain maximum brightness and uniformity. Common problems that many of our competitors face are light leakage and hot spots. CSI’s backlighting designs prevent any light leakage and hot spots from occurring, and also result in much brighter light guide film and interface.

The design typically consists of 1-4 side-firing LEDs as the light source. Hot pressing optical patterns or micro lens on the surface of the PC film to refract lights guided by the PC film. It can be easily assembled with dome switch or molded in keypad. 

The Features and Advantages of Light Guide Film are as follows:

Slim & Sleek Design

1. PC/PU/TPU film with optical pattern design (.125 – .30 mm thick)

2. Surface light source

3. High uniformed brightness


1. 50% cheaper than EL panels

2. 40% cheaper than using standalone LEDs

Energy Consumption

1. 6 LEDs light: 90mA. (LED: 15mA/pcs)

2 . LEDs + LGF: 40mA. (LED: 20mA/pcs)


1. LED light source offers 50,000 hours of life.

2. PC film is extremely durable and can function in bothhigh or low temperatures.

Use the Light Guide Film (LGF) for Keypads or LCD backlighting allows for backlighting only where needed. The CSI solution allows for uniform distribution of light regardless of the distance from LEDs. It also allows for segmentation of areas to avoid light leakage between areas or colors.

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