LGF backlight membrane switch:

LGF is the abbreviation of Light Guide Film. Under the LGF will have the LEDs. 

The light from the LEDs can be guide to top overlay by LGF very evenly. 

By LGF can reduce the LEDs on the circuit. Sometimes the LGF can be substituted by LGP(light guide panel). 

LGF is very think, but LGP is much thicker.

Main Advantages:

Ultra-thin (.125 - .30 mm thick) for LGF;

Thickness 1.0 mm for LGP;

Very cost effective (tooling and parts);

Uses up to 70% fewer LED's than traditional backlighting;

Less LED's = Less Power Consumption;

Less LED's = Less Heat;

Extremely flexible design;

Replaces expensive EL Foils and Fiber-Optic sheets;