Why LCDs Have Two Polarized Layers

Mar 7, 2022

Liquid-crystal displays (LCDs) contain many different layers. They feature a pixel layer, for instance, that contains the liquid pixels. They also feature a backlighting layer that’s responsible for illuminating the liquid pixels. LCDs, however, also feature two polarized layers. What are these polarized layers exactly, and why do LCDs have them?

The Basics of Polarized Layers

Also known simply as polarizers, polarized layers are thin sheets of a crystalline material. They are designed to control the passage of light. LCDs have two polarized layers. Depending on their orientation, they can either allow or prohibit light to pass through them.

Polarized layers live up to their namesake by polarizing light. You can find them in all types of LCDs. While other display devices typically don’t have them, polarized layers are an important part of LCDs. Most LCDs feature two separate polarized layers, which work together with the other layers to display visible images.

How Polarized Layers Work in LCDs

LCDs are constructed of several layers. A typical LCD has a backlighting layer, followerd by a polarized layer, a glass layer, a pixel layer, another glass layer and then another polarized layer.

The two polarized layers are typically polarized in the same way. As a result, light created from the backlighting can travel through them. As long as both polarized layers have the same polarity, light can travel through them. LCDs, though, are designed to change the polarity of these layers so that light can’t pass through them.

When an LCD applies a voltage to its pixel layer, the polarity will change. Some light may still pass through the polarized layers in certain areas, but other areas will remain dark. LCDs leverage polarized layers to control the passage of light. They feature two polarized layers that, depending on their orientation, can either allow or prohibit light from passing through them.

Different LCD Technologies

While they all share a similar design, LCDs are available in different technologies. Some of the most popular LCD technologies include twisted nematic (TN), in-plane switching (IPS) and vertical alignment (VA).

There are nuances between the various LCD technologies. Some of them are more energy efficient than others, for instance, and some of them produce brighter colors. Regardless, they all feature polarized layers. Polarized layers are responsible for controlling the passage of light. The light produced by an LCD’s backlighting layer must travel through the polarized layers.

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