Innovative Glass and Polymer Components Impress at Display Week
Among the oldest of flat-panel components, substrates and optical films in novel formats continue to improve display performance.
by Ken Werner
AS soon as you walked into the exhibition area at Display Week 2018, you were confronted with an impressive flexible display substrate, the one used in LG Display’s flexible 77-in. display (Fig. 1). In addition to having 8 million pixels and a bending radius of approximately 80 mm, the panel had a transparency of 40 percent. The transparency is obtained by placing a transparent, inactive area adjacent to each subpixel’s emitting area.
Fig. 1: LGD’s 77-in. flexible OLED screen with 8 million pixels and 40 percent transmittance greeted attendees at the Display Week exhibition. Photo: Ken Werner
This was just Display Week’s first example of innovative substrates and optical films used to produce improved and/or novel display characteristics. Flexible displays are increasing their market penetration, so substrates and optical-stack components that bend were very much in evidence at the show. But it is still true that most displays don’t bend, and there was no shortage of improved ways to use glass in displays.
Materials on the Floor
BenQ Materials featured its high-durability functional films, including a wide-viewing-angle polarizer that maintains color fidelity off angle (Fig. 2).
Fig. 2: BenQ Material’s wide-viewing-angle polarizer (right) maintains color fidelity at large viewing angles. Photo: Ken Werner
The company’s True Black Functional Film reduces ambient reflection and internal light leakage, while reducing screen luminescence by only 10 percent, according to BenQ Brand Management Director WeiYin Tsou. A demonstration comparing displays with and without the film was impressive (Fig. 3).
Fig. 3: BenQ Material’s True Black Functional Film (bottom) reduces ambient reflections and internal light leakage, as compared to the top image without the film. Photo: Ken Werner
BenQ’s UHDEP – Ultra-High Definition Enhancement Polarizer – is designed to improve the off-angle color of 4K vertically aligned (VA) displays, such as Samsung’s. With UHD, most LCD panels use only four VA domains instead of eight, said Chairman and CEO Z.C. Chen, which is why the film is needed. Other products currently available are a very flexible polarizer and a flexible hard coat that is foldable and stretchable.
The company was also showing a flexible smart-window film based on polymer-network liquid crystal (PNLC) – a reverse-mode polymer-dispersed liquid-crystal (PDLC) that is clear when the power is off, a desirable characteristic for automotive smart windows after a power-disrupting accident.
Polyimide Progress
Polyimides (PIs) are thermally stable and have good chemical resistance and excellent mechanical properties, including high flex strength. They would make excellent display substrates except for their orange/yellow color.
In its booth, the Korean company Kolon Industries was featuring a colorless PI (CPI) that was scheduled to be ready for mass production near the time of this publication, according to Principal Researcher Sang-Kyun Kim. (Kolon’s CPI received a 2018 Display Industry Component of the Year award from SID.) The material will be available in widths up to 1.55 meters, and its mechanical properties will allow it to directly replace glass, said Kim. Kolon’s competitors are not yet ready for volume production, he claimed, and their mechanical properties are not yet as good.
Kolon will also sell a CPI varnish and a CPI hard-coat (HC) sheet. In the booth, the company showed a folding test of an OLED display with CPI HC film as a cover window (Fig. 4).
Fig. 4: Kolon’s colorless polyimide hard-coat film served as a flexible cover glass for an OLED display. Photo: Ken Werner
Merck showed the latest generation of its licrivision-brand guest-host liquid-crystal exterior smart windows. The material was remarkably haze free in its transparent mode and more opaque than previously in its opaque mode. The licrystal product has demonstrated an equivalent of 10 years’ life in accelerated life testing, said Merck/EMD’s Bob Miller.
Corning’s Iris Glass for glass light-guide plates (LGPs) is now, for the first time, being used in commercially available monitors as well as TVs. Corning says Iris Glass allows product makers to reduce thickness, increase brightness, and design products with thinner bezels. Shown in the booth was a Dell 27 Ultrathin monitor with a thickness of 5.5 mm (at the thinnest point). Resolution was 2,560 × 1,440. A Lenovo 24-in. ThinkVision monitor had a thickness less than 4.0 mm. An upcoming issue of Information Display will include an article that further discusses this technology.
Pilkington, the UK specialty glass company that has been a subsidiary of Nippon Sheet Glass since 2006, was featuring an AR glass that does not introduce a color tint.
Schott Glass was showing its CONTURAN-brand chemically toughened, low reflectivity, and neutral-color cover glass at Display Week. In other words, this is Schott’s competition for Corning’s Gorilla Glass.
For augmented reality (AR) applications, Schott was aggressively promoting its RealView family of glasses (Fig. 5). RealView glass is intended for lenses in eyeglasses or goggles that will transfer AR imagery laterally to a position in front of the user’s eye, where an optical structure will direct the image to the eye.
Fig. 5: Schott’s RealView glass, intended for AR displays, is smooth and flat and has a high index of refraction. Photo: Matt Brennesholtz
These waveguides must be planar, and they require a high refractive index for a wide field of view (FOV). The thickness must be precisely controlled, and flatness must be plus or minus one micron – 10 times the flatness required in semiconductor processing, Augmented Reality VP Rudiger Sprengard told Information Display. (Look for an article on this technology as well in an upcoming issue of this magazine.) Schott refers to this as Waveprint technology, and it is currently used in motorcycle glasses for AR. The company is also developing its technology for automotive AR, where it would enable a much smaller light box than is possible with conventional approaches, according to Sprengard. At the consumer level, AR technology must be miniaturized, and waveguide technology is a likely candidate, he said.
Schott Business Development Manager Brian Sjogren told my colleague Matt Brennesholtz that the glass is specially manufactured from melt to coating. This control of the entire manufacturing chain, said Sprengard, is the company’s competitive advantage. Schott has been working on the technology for two years. The product has been developed and is ready for customers.
In its large booth, Asahi Glass Company (AGC) showed its XCV glass, which is AGC’s answer to Corning’s Iris Glass. AGC’s wrinkle is that the glass contains a prism structure. Asahi also showed its curved glass in Continental’s multicurved automotive cockpit display, versions of which were shown in Continental’s giant suite at CES in Las Vegas earlier this year.
Also on display were windows with active lighting or displays behind them. The first approach gave a convincing impression of moving foliage on the other side of a translucent window. AGC calls these Glaterrace Windows. Applications are basements, hospitals, offices, and closed spaces such as elevators. The second approach set large displays several inches behind windows. The spacing and the lake scene in the middle distance created a convincing sense of a lake really being outside the window.
AGC also demonstrated a glass speaker. The general idea here is the same as LGD’s Crystal Sound, but AGC has worked for very high-quality sound and an executive-suite look. AGC says it has realized the ideal of the “glass diaphragm” by suppressing the resonance of the glass.
Finally, it seemed that every Chinese display exhibitor was showing a flexible OLED. BOE, Tianma, Visionox, and others all had flexible OLED demos (Fig. 6). One or two even claimed they were products. Whether or not that’s true now, it will be.
Fig. 6: The pages of Visionox’s flexible display eBook were each 5.99 inches on the diagonal with a resolution of 1,080 × 2,160 and a thickness of 0.4 mm. Only the top pages seemed to be displays, but it still made for an effective demo. Photo: Ken Werner
It is easy to think of substrates and optical films as the relatively uninteresting components that simply support the high-tech processes that make displays work. That is not at all the case, as the exhibits at Display Week made clear. •
Ken Werner is the principal of Nutmeg Consultants, specializing in the display industry, manufacturing, technology, and applications, including mobile devices, automotive, and television. He consults for attorneys, investment analysts, and companies re-positioning themselves within the display industry or using displays in their products. He is the 2017 recipient of the Society for Information Display’s Lewis and Beatrice Winner Award. You can reach him at kwerner@nutmegconsultants.com.