How does an aluminum mirror work in a reflective LCD?

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Diagram comparing three liquid crystal phases: nematic with parallel rods aligned vertically, smectic A with rods arranged in horizontal layers, and smectic C with rods in tilted layers. — liquid crystal display Liquid crystal arrangements
In nematic arrangements the crystals are randomly positioned with all their long axes pointing in essentially the same direction, given by a vector known as the director. In smectic arrangements the crystals are further constrained to parallel planes; in smectic A the director is perpendicular to these planes, while in smectic C the director is at some other angle to the planes.

In a reflective liquid crystal display, an aluminum mirror serves as a substitute for a power-consuming backlight. Its function is to capture ambient light and reflect it back toward the viewer.1

When the liquid crystal layer is switched to a bright or transmissive state, the mirror directs incoming light through the display's optical layers, allowing the device to be viewed without internal illumination. This design is highly efficient for mobile electronics, as it significantly reduces battery consumption by utilizing external light sources.1

In some configurations, such as transflective displays, the mirror is designed to be partially reflective and partially transmissive. This allows the device to function as a reflective display in high-ambient-light conditions while still permitting the use of a backlight when light levels are low.1