Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Self-aligning liquid crystal technique could simplify manufacture of display devices

25.09.2006
A new technique for creating vertical alignment among liquid crystal molecules could allow development of less costly flexible displays and lead to a better understanding of the factors that govern operation of the popular liquid crystal display systems.

Liquid crystals are a key component of the displays used in most laptop computers and the increasingly-popular flat panel televisions. Controlled by a network of transistors, the liquid crystals change their optical characteristics in response to electrical signals to create the text and images we see.

Manufacture of the panels is complex, requiring multiple steps that can introduce defects. Among the steps is the application of a polymer film – the so-called alignment layer – to the two pieces of glass between which the liquid crystals operate. The film, which must be rubbed after being coated on the glass, anchors the crystals with a fixed alignment. The process of rubbing to create the necessary alignment can damage some of the transistors and introduce dust, producing defects that can reduce the manufacturing yield of the panels.

By adding side chains to the polymer molecules, researchers at the Georgia Institute of Technology have found a way to eliminate the polymer rubbing step. Instead, they use the in-situ photopolymerization of alkyl acrylate monomers in the presence of nematic liquid crystals to provide a cellular matrix of liquid crystalline droplets in which the chemical structure of the encapsulating polymer controls the liquid crystal alignment.

"Small changes in the chemical nature of the polymer will change the alignment of the molecules at surfaces," said Mohan Srinivasarao, a professor in Georgia Tech's School of Polymer, Textile and Fiber Engineering. "It turns out that this can be done over a fairly large area, and it is reproducible. This would be an alternative way to create the alignment that is needed in these devices."

Srinivasarao described the self-aligning of liquid crystals on September 14th at the 232nd national meeting of the American Chemical Society in San Francisco. His presentation was part of the session "Organic Thin Films for Photonic Applications."

Beyond the potential for simplifying the manufacture of liquid crystal devices, the self-aligning technique could also be used in new types of diffraction gratings.

Srinivasarao and collaborators Jung Ok Park and Jian Zhou have used the technique and a nematic material with negative dielectric anisotropy to fabricate highly flexible liquid crystal devices that have high contrast and fast response times – without using an alignment layer. Control is obtained by variation of the alkyl side chains and through copolymerization of two dissimilar monofunctional acrylates.

Beyond simplifying the fabrication process and potentially increasing device yield, the technique also offers other advantages. Because devices are based on vertical alignment of the liquid crystals, their "off" state can be made completely dark. In addition, the liquid crystals provide strong binding between the two substrate surfaces, making the resulting display less sensitive to mechanical deformations and pressure – ideal for flexible displays that lack the structure provided by glass plates.

Though the technique developed at Georgia Tech offers advantages over existing systems, Srinivasarao doesn't expect a change in the way the current generation of laptop screens and televisions are made. That's because existing manufacturing processes are mature and changing them probably can't be justified economically.

But beyond applications to future flexible displays, what the researchers learn from their approach could apply to the next generation of display devices based on liquid crystals.

"When we make this polymer, the molecules automatically generate the alignment," Srinivasarao said. "We are interested now in figuring out what is responsible for making that happen. We want to link the chemical nature of these polymeric materials to how the liquid crystal molecules behave at the surface."

Current displays use polyimides for an alignment layer because these materials are heat resistant and can be used over a broad range of temperatures for extended periods of time. The alkyl acrylates that Srinivasarao and his colleagues are using lack that same robustness, so material improvements would be needed before they could be used to manufacture flexible displays.

"If we can show similar results – switching times faster than 30 milliseconds and high contrast ratios – with more robust polymeric materials, then we could say that this approach would be viable," he said.

John Toon | EurekAlert!
Further information:
http://www.gatech.edu

More articles from Materials Sciences:

nachricht A new tool for discovering nanoporous materials
23.05.2017 | Ecole Polytechnique Fédérale de Lausanne

nachricht Did you know that packaging is becoming intelligent through flash systems?
23.05.2017 | Heraeus Noblelight GmbH

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

Im Focus: Bacteria harness the lotus effect to protect themselves

Biofilms: Researchers find the causes of water-repelling properties

Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

Innovation 4.0: Shaping a humane fourth industrial revolution

17.05.2017 | Event News

 
Latest News

Scientists propose synestia, a new type of planetary object

23.05.2017 | Physics and Astronomy

Zap! Graphene is bad news for bacteria

23.05.2017 | Life Sciences

Medical gamma-ray camera is now palm-sized

23.05.2017 | Medical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>