Transflective LCD displays are commonly used for displays intended for use in direct sunlight such as handheld GPS units. In low light (indoors) transflective (transflective = transmissive + reflective) displays use backlighting. In bright light (sunlight) they reflect light off a mirrored surface behind the display to boost backlighting making the display more legible and reducing power consumption. Only the area of the display exposed to sunlight increases its light output making the difference in brightness between the shaded and lit areas far less than would be the case for a transmissive display.
Transflective screens are a more expensive option for GPS manufacturers and they also lack some of the sharpness and resolution of transmissive displays can produce but, if you can’t see a transmissive display clearly in sunlight itís a moot point.
Transflective LCD Display Resources
Transreflective LCD monitors for sunlight – Irontech Industrial Displays