Light-filtering layers play an important role in liquid-crystal displays (LCDs). Known as polarizers, they work in conjunction in with a backlighting system to illuminate the liquid pixels. All LCDs have liquid pixels. Since they aren’t made of an electroluminescent material, the liquid pixels must be externally illuminated, which is where the backlighting system comes into play. It will produce light that passes through a set of polarizers before reaching the LCD’s liquid pixels.

#1) Filters Light Based on Polarizers

They are known as “polarizers” because they are designed to filter light based on polarization. Only light of a specific polarization will pass through them. Polarizers will block all other light, meaning it won’t reach the LCD’s liquid pixel. Polarizers work by allowing light to pass if it’s aligned in a particular direction while simultaneously blocking light that’s aligned in a different direction.

#2) LCDs Have 2 Polarizers

Most LCDs don’t have a single polarizer. Instead, they have two polarizers. One of the polarizers is located at the front of the LCD, whereas the other polarizer is located at the back of the LCD. The polarizer at the back of the LCD is used to direct the backlighting’s light toward the liquid pixel layer near the front of the LCD.

#3) There Are Different Types of Polarizers

Not all polarizers are the same. There are several different types of polarizers. Linear polarizers are the most common. They allow for the passage of light of a specific polarization. Circular polarizers, conversely, are designed to allow light of all polarizations to pass through them — but only if the light has a specific polarization direction. Circular polarizers typically aren’t used in LCDs. LCDs are most commonly associated with linear polarizers.

#4) Positive vs Negative

Whether an LCD is in positive or negative mode is typically dependent upon its polarizers LCDs have a positive mode, and they have a negative mode. The former is characterized by the use of black letters on an unlit background. Negative mode, in comparison, is characterized by the use of letters in the same color as the backlighting light on a black background. An LCD’s polarizers will typically determine whether it’s in positive or negative mode.

#5) Reduce Glare

While polarizers are used primarily to filter light based on polarization, some of them are able to reduce glare as well. LCDs aren’t immune to glare. When exposed to light from a fixture, lamp or any other external source, they may succumb to glare. Fortunately, some LCDS are designed with polarizers that feature an antireflective (AR) coating.