Liquid Crystals: The Third Dimension

Within just four years, the film had grossed almost US$ 2.8 billion. That made it the highest -grossing film ever. The movie’s computer-animated 3D scenes were the main factor drawing huge audiences into movie theaters. With 3D glasses, sequences which would previously have been instantly recognizable as cartoon animation could no longer be visually distinguished from sequences shot in the real world. “Avatar” was instrumental in making 3D movies — and with them, reactive mesogens — commercially successful.

Reactive mesogens are liquid crystals which “freeze” into solids under high-frequency UV light while retaining their birefringent properties. This means that what happens to a ray of light incident on the frozen liquid crystal essentially depends on how the ray of light is polarized. 

This property turns reactive mesogens into universal optical tools. Different patterns of such mesogens can be vapor-deposited onto films which then filter incident light according to the pattern, letting it pass through unchanged or altering its direction of polarization. Experts refer to such films as film-type patterned retarders (FPRs). FPRs have a wide range of applications. For example, because they filter out scattered light, FPRs glued on to a liquid crystal display (LCD) improve the display’s contrast and color fidelity. 

Unfiltered displays produce the color black by blocking the light of the corresponding pixels, but a shimmer of residual light always manages to filter through from the background illumination. As a result, the black pixels often appear gray from certain angles of view. FPRs turn the color of these pixels into a deep black.

Commercial use of FPRs, initially in high-end TV displays, started in 2006. However, this was not a mass market application, because most users were satisfied with lower image quality and purchased less expensive units. “At that time, Merck KGaA, Darmstadt, Germany was even considering limiting or even suspending research and development activities and production in this area,” remembers Rainer Neeff, who is responsible for marketing and sales of liquid crystals at Merck KGaA, Darmstadt, Germany. 

But then “Avatar” was released, and it catapulted the market for LCD TVs into the third dimension. “Suddenly everybody needed FPRs,” says Neeff. Together with its technology partner LG Chem, Merck KGaA, Darmstadt, Germany developed the 3D FPR technology from the initial idea to the mass-market product within just one year. The FPR film is manufactured using licrivue® materials from Merck KGaA, Darmstadt, Germany. In 2010 LG Chem became the first company to launch this technology on the global market. 

In June 2012 both companies received the silver “Display Component of the Year Award.” This is the most renowned award in the display sector, and it has been presented in gold or silver by the Society for Information Display (SID) annually since 1995. It is awarded for highly innovative, future-oriented products, components, and applications.

3D films encode the image information as different signals for the viewer’s right and left eyes. The viewer can only decode these signals with the help of 3D glasses. The human brain then combines these signals to produce the illusion of 3D vision. Experts refer to a “stereoscopic” process. If the different signals are transmitted one after the other, the viewer requires a pair of “shutter” glasses, which alternately open and close their right and left lenses at the same rate as the different signals are transmitted.

However, if the signals are transmitted simultaneously but vary across the surface, they can be viewed using a simple pair of polarizing glasses with their right and left lenses blocking different polarizations. Such polarizing glasses are also used with 3D FPR technology. The films are applied to the polarization filters of LCD TVs and transform the image information of a 3D film into clockwise or anticlockwise circularly polarized light.

The films are also extremely sensitive to UV radiation and have very good thermal stability, as well as being simple to manufacture on a large scale. They are also ten times thinner than the glass-based shutter technology and have 20 times its transmittance. “Thanks to the 3D FPR technology, almost every new LCD TV sold today is 3D-capable,” says Neeff. “As a result, the demand for reactive mesogens has increased dramatically, from a few kilos at the beginning to a current figure in the thousands of kilograms.”

In order to keep up with this increasing demand, Merck KGaA, Darmstadt, Germany commissioned a new production unit at its Darmstadt site in March 2013. Furthermore, new areas of application are already opening up for reactive mesogens. One example is autostereoscopic processes — 3D processes which do not require the use of special glasses and can display both the moving 3D film and the 2D accompanying text with full sharpness.

Laptops and TVs with corresponding LCDs are already commercially available. The development of smart windows with FPR technology is not yet quite so far advanced. Such windows are intended to prevent the emission of visible light from offices or living rooms and thus ensure privacy when required. They are just like blinds that can be lowered. However, they are a lot more elegant.