Blue-phase liquid crystal displays could triple television and computer screen resolution

via OSA Publishing

An international team of researchers has developed a new blue-phase liquid crystal that could enable televisions, computer screens and other displays that pack more pixels into the same space while also reducing the power needed to run the device. The new liquid crystal is optimized for field-sequential color liquid crystal displays (LCDs), a promising technology for next-generation displays.

“Today’s Apple Retina displays have a resolution density of about 500 pixels per inch,” said Shin-Tson Wu, who led the research team at the University of Central Florida’s College of Optics and Photonics (CREOL). “With our new technology, a resolution density of 1500 pixels per inch could be achieved on the same sized screen. This is especially attractive for virtual reality headsets or augmented reality technology, which must achieve high resolution in a small screen to look sharp when placed close to our eyes.”

Although the first blue-phase LCD prototype was demonstrated by Samsung in 2008, the technology still hasn’t moved into production because of problems with high operation voltage and slow capacitor charging time. To tackle these problems, Wu’s research team worked with collaborators from liquid crystal manufacturer JNC Petrochemical Corporation in Japan and display manufacturer AU Optronics Corporation in Taiwan.

In the journal Optical Materials Express, from The Optical Society (OSA), the researchers report how combining the new liquid crystal with a special performance-enhancing electrode structure can achieve light transmittance of 74 percent with an operation voltage of 15 volts per pixel – operational levels that could finally make field-sequential color displays practical for product development.

“Field-sequential color displays can be used to achieve the smaller pixels needed to increase resolution density,” said Yuge Huang, first author of the paper. “This is important because the resolution density of today’s technology is almost at its limit.”

How it works
Today’s LCD screens contain a thin layer of nematic liquid crystal through which the incoming white LED backlight is modulated. Thin-film transistors deliver the required voltage that controls light transmission in each pixel. The LCD subpixels contain red, green and blue filters that are used in combination to produce different colors to the human eye. The color white is created by combining all three colors.

Blue-phase liquid crystal can be switched, or controlled, about 10 times faster than the nematic type. This sub-millisecond response time allows each LED color (red, green and blue) to be sent through the liquid crystal at different times and eliminates the need for color filters. The LED colors are switched so quickly that our eyes can integrate red, green and blue to form white.

“With color filters, the red, green and blue light are all generated at the same time,” said Wu. “However, with blue-phase liquid crystal we can use one subpixel to make all three colors, but at different times. This converts space into time, a space-saving configuration of two-thirds, which triples the resolution density.”

The blue-phase liquid crystal also triples the optical efficiency because the light doesn’t have to pass through color filters, which limit transmittance to about 30 percent. Another big advantage is that the displayed color is more vivid because it comes directly from red, green and blue LEDs, which eliminates the color crosstalk that occurs with conventional color filters.

Wu’s team worked with JNC to reduce the blue-phase liquid crystal’s dielectric constant to a minimally acceptable range to reduce the transistor charging time and get submillisecond optical response time. However, each pixel still needed slightly higher voltage than a single transistor could provide. To overcome this problem, the researchers implemented a protruded electrode structure that lets the electric field penetrate the liquid crystal more deeply. This lowered the voltage needed to drive each pixel while maintaining a high light transmittance.

“We achieved an operational voltage low enough to allow each pixel to be driven by a single transistor while also achieving a response time of less than 1 millisecond,” said Haiwei Chen, a doctoral student in Wu’s lab. “This delicate balance between operational voltage and response time is key for enabling field sequential color displays.”

Making a prototype
“Now that we have shown that combining the blue-phase liquid crystal with the protruded electron structure is feasible, the next step is for industry to combine them into a working prototype,” said Wu. “Our partner AU Optronics has extensive experience in manufacturing the protruded electrode structure and is in a good position to produce this prototype.”

Wu predicts that a working prototype could be available in the next year. Since AU Optronics already has a prototype that uses the protruded electrodes, it will only be a matter of working with JNC to get the new material into that prototype.

Learn more: Novel Liquid Crystal Could Triple Sharpness of Today’s Televisions

 

 

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Is the end in sight for reading glasses?

via University of Leeds

via University of Leeds

A University of Leeds researcher is developing a new eye lens, made from the same material found in smartphone and TV screens, which could restore long-sightedness in older people.

As people age, their lenses lose flexibility and elasticity. This leads to a condition known as presbyopia, common in people over 45 years old, and can require optical aids, such as reading glasses.

Devesh Mistry, a postgraduate research student in the School of Physics and Astronomy, is now working with liquid crystal to create a truly adjustable artificial lens.

He said: “As we get older, the lens in our eye stiffens, when the muscles in the eye contract they can no longer shape the lens to bring close objects into focus.”

“Using liquid crystals, which we probably know better as the material used in the screens of TVs and smartphones, lenses would adjust and focus automatically, depending on the eye muscles’ movement.”

Using these liquid crystal-based materials, Devesh’s research is developing synthetic replacements for the diseased lens in the eye – a new generation of lenses and intra-ocular lens implants to rejuvenate sight.

Devesh is currently researching and developing the lens in the lab and aims to have a prototype ready by the end of his doctorate in 2018.

Within a decade, the research could see the new lens being implanted into eyes in a quick and straightforward surgical procedure under local anaesthetic.

Eye surgeons would make an incision in the cornea and use ultrasound to break down the old lens. The liquid crystal lens would then be inserted, restoring clear vision.

The lens could also have application in tackling cataracts – the clouding of natural lenses – which affect many people in later life and which can seriously affect vision. A common treatment is to remove and replace the natural lens.

“Liquid crystals are a very under-rated phase of matter,” Devesh told The Times, “Everybody’s happy with solids, liquids and gases and the phases of matter, but liquid crystals lie between crystalline solids and liquids. They have an ordered structure like a crystal, but they can also flow like a liquid and respond to stimuli.”

Read more: Is the end in sight for reading glasses?

 

 

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Windows That Act Like an LCD Screen

A dye-doped PNLC cell in the transparent and opaque states, placed on a printed sheet of paper. In the transparent state, the clear background image can be seen because of the high transmittance of this cell. In the opaque state, black color is provided and the background image is completely blocked, because the incident light is simultaneously scattered and absorbed.

A dye-doped PNLC cell in the transparent and opaque states, placed on a printed sheet of paper. In the transparent state, the clear background image can be seen because of the high transmittance of this cell. In the opaque state, black color is provided and the background image is completely blocked, because the incident light is simultaneously scattered and absorbed.

A newly developed light shutter may pave the way for see-through displays and smart windows

The secret desire of urban daydreamers staring out their office windows at the sad brick walls of the building opposite them may soon be answered thanks to transparent light shutters developed by a group of researchers at Pusan National University in South Korea.

A novel liquid crystal technology allows displays to flip between transparent and opaque states — hypothetically letting you switch your view in less than a millisecond from urban decay to the Chesapeake Bay. Their work appears this week in the journal AIP Advances, from AIP Publishing.

The idea of transparent displays has been around for a few years, but actually creating them from conventional organic light-emitting diodes has proven difficult.

“The transparent part is continuously open to the background,” said Tae-Hoon Yoon, the group’s primary investigator. “As a result, they exhibit poor visibility.”

Light shutters, which use liquid crystals that can be switched between transparent and opaque states by scattering or absorbing the incident light, are one proposed solution to these obstacles, but they come with their own set of problems.

While they do increase the visibility of the displays, light shutters based on scattering can’t provide black color, and light shutters based on absorption can’t completely block the background. They aren’t particularly energy-efficient either, requiring a continuous flow of power in order to maintain their transparent ‘window’ state when not in use. As a final nail in the coffin, they suffer from a frustrating response time to power on and off.

Tae-Hoon Yoon’s group’s new design remedies all of these problems by using scattering and absorption simultaneously. To do this, Yoon’s group fabricated polymer-networked liquid crystals cells doped with dichroic dyes.

In their design, the polymer network structure scatters incident, or oncoming light, which is then absorbed by the dichroic dyes. The light shutters use a parallel pattern of electrodes located above and below the vertically aligned liquid crystals.

When an electric field is applied through the electrodes, the axes of the dye molecules are aligned with that of oncoming light, allowing them to absorb and scatter it. This effectively negates the light coming at the screen from its backside, rendering the display opaque – and the screen’s images fully visible.

“The incident light is absorbed, but we can still see through the background with reduced light intensity,” Yoon said.

In its resting state, this setup lets light pass through, so power need only be applied when you want to switch from transparent window view to opaque monitor view. And because the display’s on-off switch is an electric field, it has a response time of less than one millisecond – far faster than that of contemporary light shutters, which rely on the slow relaxation of liquid crystals for their off-switch.

Read more: Windows That Act Like an LCD Screen

 

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Let There Be Light: Chemists Develop Magnetically Responsive Liquid Crystals

Top: Scheme showing magnetic control over light transmittance in the novel liquid crystals. B is the alternating magnetic field. The polarized light is seen in yellow. The gray rods represent the polarizers. The magnetic field controls the orientation of the nanorods (seen in orange), which in turn affects the polarization of the light and, then, the amount of light that can pass through the polarizers. Bottom: Images show how a polarization-modulated pattern changes darkness/brightness by rotating the direction of the cross polarizers. The circles and background contain magnetic nanorods aligned at different orientations. Research by the Yin Lab at UC Riverside shows that by combining magnetic alignment and lithography processes, it is possible to create patterns of different polarizations in a thin composite film and control over the transmittance of light in particular areas. IMAGE CREDIT: YIN LAB, UC RIVERSIDE.

The discovery has applications in signage, posters, writing tablets, billboards and anti-counterfeit technology

Chemists at the University of California, Riverside have constructed liquid crystals with optical properties that can be instantly and reversibly controlled by an external magnetic field. The research paves the way for novel display applications relying on the instantaneous and contactless nature of magnetic manipulation—such as signage, posters, writing tablets, and billboards.

Commercially available liquid crystals, used in modern electronic displays, are composed of rod-like or plate-like molecules. When an electric field is applied, the molecules rotate and align themselves along the field direction, resulting in a rapid tuning of transmitted light.

“The liquid crystals we developed are essentially a liquid dispersion, a simple aqueous dispersion of magnetic nanorods,” said Yadong Yin, an associate professor ofchemistry, who led the research project. “We use magnetic nanorods in place of the commercial nonmagnetic rod-like molecules. Optically these magnetic rods work in a similar way to commercial rod-like molecules, with the added advantage of being able to respond rapidly to external magnetic fields.”

Yin explained that upon the application of a magnetic field, the nanorods spontaneously rotate and realign themselves parallel to the field direction, and influence the transmittance of polarized light.

“Prior attempts had been limited to materials with very limited magnetic responses,” Yin said. “We utilized our expertise in colloidal nanostructure synthesis to produce magnetite nanorods that can form liquid crystals and respond strongly to even very weak magnetic fields – even a fridge magnet can operate our liquid crystals.”

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Liquid crystal as lubricant – virtually no friction

The Stifteverband Science Prize for scientific excellence in Germany was awarded to: Dr. Holger Kretzschmann (Nematel), Werner Stehr and Susanne Beyer-Faiß (Dr. Tillwich GmbH), Dr. Andreas Kailer and Dr. Tobias Amann (Fraunhofer IWM). Credit: Dirk Mahler/Fraunhofer

Thanks to a new lubricant, small gears can run with virtually no friction. Made from liquid crystalline fluid, these lubricants drastically reduce friction and wear.

Lubricants are used in motors, axels, ventilators and manufacturing machines. Although lubricants are widely used, there have been almost no fundamental innovations for this product in the last twenty years.

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