X-bit labs

X-bit’s Guide: Contemporary LCD Monitor Parameters and Characteristics (page 19)

Category: Other

by Oleg Artamonov

[ 10/26/2004 | 02:58 PM ]

TN+Film Matrices

TN matrices are the oldest type of the LCD matrix, tracing its origin to the times of passive matrices. They have acquired the word Film into their name early – this additional film improves the viewing angles. Nowadays all matrices of this type have this film, so it is not necessary to mention it – speaking about modern matrices we can use terms “TN” and “TN+Film” interchangeably.

TN matrices never had the very best parameters. Their poor color reproduction was their main drawback – it was so specific that you had to get used to it even in office applications, not to mention processing photographs. That’s why some people claimed an imminent replacement of the TN technology with other matrix types, first IPS, then MVA, but reality proved different.

The name of the technology – Twisted Nematic – comes from the way of organizing liquid crystals in the panel: when voltage is applied, the crystals curl up into a helix whose axis is perpendicular to the panel’s surface. Regrettably, the shape of the helix is somewhat irregular (the borderline crystals are not exactly parallel to the surface, but are rather at a small angle to it), and the optical properties of the helix vary greatly depending on the line of sight – along its axis or at an angle. The first drawback prevents TN matrices from having a good contrast ratio, while the second drawback – from having wide viewing angles.

The TN technology got a second wind on the arrivals of matrices with a response time of 16 milliseconds. They were the only matrices at that time that you could specify such a low response time for, making a solid foundation for the marketing departments to build upon – they all started touting “unbelievably rapid matrices”. It’s always better to emphasize one parameter in an advertising campaign – one that the user intuitively understands (or thinks that understands) – and write it in bold big letters on the product’s package. Craig Barrett once put this idea down in a very laconic form, talking about the successful sales of Intel’s processors: “They buy the megahertz”. The clock rate was an intuitively comprehensible parameter for people who bought central processors. They thought it determined the processor’s speed, and it took AMD a lot of time and effort just to shake this common notion. Analogously, the response time became (or was made by the marketing departments of the manufacturing and selling companies) a parameter determining the quality of the matrix for the end customers.

Besides that, the TN technology is the cheapest of the available LCD matrix production technologies, so monitors with TN matrices could be sold at a lower price than their competitors. This killer combination – low price and the intuitive parameter – had a devastating effect on all other matrix types. Drawing the parallel with central processors further – imagine Intel starting to sell its many-gigahertz processors at much lower prices than the competitive products from AMD. AMD wouldn’t stand this competition long, I guess.