Overview
 
     Home
     Discovery of LCs
     LCs Introduction
     History of LCDs
     TFT basics
 
   LCD Modes
 
     ASV
     BiNem
     Cholesteric
     ECB
     SSFLC
     Guest-Host
     IPS
     LCoS
     MVA
     PDLC
     Pi-Cell
     PVA
     STN
     TN
     Transflective
 
  Acknowledgements

  LC Related Links

 
  About Author
 

[Multi-domain Vertical Alignment (MVA) mode]

In the basic VA mode, the molecules can tilt towards to any directions because of the lacking of in-place easy axis, therefore the umbilics defects appear, which is not desired in the display application because it not only produces transmission fluctuation but also slow down the response time.

In order to control obtain a symmetric viewing angle, the pixel is divided into domains, where the LC molecules will have pre-determined tilt directions. The multi-domain are obtained by introducing protrusions on both substrates. This is the Multi-Domain VA mode (MVA).

In the off state, the LC molecules are perpendicularly aligned, hence no transmission after crossed polarizers, this is the black state. In the on state, the LC molecules tilt in a direction controlled by the protrusions, a phase retardation is present to the incoming light, and transmission is not zero after the exist polarizer; at high field, the LC molecules in the mid-layer are all parallel to the substrate surface, a higher transmission is obtained.

Figure 1. Operating principle of Multi-domain Vertical alignment LCD

The MVA was first introduced by Fujitsu, and now adopted by a few manufactures. It can give very good viewing angles because of the symmetric LC domains. The MVA mode eliminates the need for a rubbing process, which makes manufacturing simpler and the MVA-TFTs more stable.

Figure 2. Viewing angle comparison between Mono-domain VA and Multi-domain VA.

Later improvement to the original MVA mode is to replace the protrusions on one substrates with patterned ITO slits. This improvement not only reduce manufacture steps, but also increase the contrast ratio since the residual birefringence around the protrusions on one substrate is removed. A brief comparison of performance between original MVA and improved MVA mode is listed in the following table.

Figure 3. Director and pixel configuration comparison between original MVA and improved version.

Figure 4. Performance comparison between original MVA and improved version.


Further Readings and References:

A. Takeda, S. Kataoka, T. Sasaki, H. Chida, H. Tsuda, K. Ohmuro, T. Sasabayashi, Y. Koike, and K. Okamoto, ^A super-high image quality
multi-domain vertical alignment LCD by new rubbing-less technology, ̄ SID Dig., pp. 1077C1100 (1998).

Y. Tanaka, Y. Taniguchi, T. Sasaki, A. Takeda, Y. Koibe, and K. Okamoto, ^A new design to improve performance and simplify the manufacturing process of high-quality MVA TFT-LCD panels, ̄ in SID Dig., pp. 206C209 (1999).

Y. Koike and K. Okamoto, ^Super high quality MVA-TFT liquid crystal displays, ̄ Fujitsu Sci. Tech. J., vol. 35, pp. 221C228 (1999).

 

Last update: April, 2006
Questions? Contact author.