What are the differences in how TN, VA, and IPS panels work?


I know the advantages and disadvantages of each from a consumer perspective, but I’m really interested in the specific engineering differences.

In: Technology

So first, LCD panels use two polarizers. A polarizer only allows light of a certain polarity to pass through it. If you put two polarizer plates on top of one another, and align them the same way, they will let light pass through. If you rotate one plate 90 degrees, they will block almost all of the light.

In TN and IPS panels, the liquid crystal likes to rest in a twisted state. Light goes through one polarizer and becomes polarized. The twist in the crystal rotates the polarity of the light 90 degrees, and then the light hits the second polarizer.

When power is applied, it causes the crystal to deform. In a TN panel, the crystals tend to just point forwards. In an IPS panel, the crystals untwist. In either case, the more power is applied to a liquid crystal, the less it rotates the polarity of the light. This is how liquid crystals control how bright every pixel is.

This is a good diagram of a TN panel. You can see how power is applied front to back:


This is a diagram of an IPS panel. You can see how the power is now applied on the same plane:


I don’t actually understand how vertical alignment crystals are arranged, I’m still trying to figure that out.