Substrate - Page 4

Corning recently announced the new second-gen Lotus XT high-performance glass suitable for OLED displays. The company has been supplying glass substrate and cover glass for OLED displays for years now. Now Corning was kind enough to participate in a Q&A session here on OLED-Info to better explain how they see the OLED market and what the future holds for Corning and OLEDs.

We talked to two Corning executives. John Bayne is Corning's High Performance Displays VP and General Manager, while Harrison Smookler is the commercial director and program manager of Willow Glass Substrates (flexible glass).

Tianma selected Corning's Lotus XT Glass for its line of LTPS panels. Tianma is currently producing LCDs but will hopefully start AMOLED production in 2014.

Tianma says they chose Lotus XG Glass because of the advanced properties of the glass. The company’s LTPS line is located in Xiamen, China, and has a capacity of 30,000 TFT modules, and more than 30,000 color-filter modules per month. It is the first Gen 5.5 LTPS line in China.

In February 2013 LG Chem unveiled their flexible OLED lighting panels, with plans to start producing them in July 2013 (they now aim to do so in September 2013, a slight delay). Those panels use a thin-glass substrate and a metal protective layer with LG Chem's Face-Seal encapsulation.

Today LG Chem announced that they developed new plastic-based (transparent polyimide) OLED lighting panels (shown in the photos above and below). These panels are more bendable (see photo above) than the current metal/glass ones, and LG Chem refers to them as "Plastic Film type Truly-Flexible OLED Panels". The company aims to mass produce these new panels in H1 2015. The new panels are even lighter than the current ones (which are only 0.33 mm thick and weigh under 8 grams).

Corning announced their new, second-generation Lotus XT glass for high performance displays (LCDs and OLEDs). The Lotus XT offers better dimensional stability and can withstand higher temperatures compared to the previous version.

The new glass features better total-pitch variation (the distance features move during panel processing). All this means that using the new glass shall increase production yields and result in more precise manufacturing. The new glass can be used as substrate for LTPS and Oxide-TFT backplanes.

Indium-Tin-Oxide (ITO) is currently used in OLED panels for the transparent cathode (or anode in top-emission OLEDs). ITO is useful because it is conductive and transparent, but its supply is limited (even though companies are now harvesting ITO from recycled electronics devices) and it's also brittle (so it's not suitable for flexible panels) and so companies are looking for alternatives.

Some products that use Cambrios Ag-Wires

One possible alternative are silver wires (or ag-wire). This technology is pioneered by Cambrios - a company established in 2002 with an aim to commercialize Ag-Wire based products. Cambrios ClearOhm is a Ag-Wire coating material used to create transparent conductive layers. ClearOhm can be deposited on thin films using a roll-to-roll (R2R) process, and is compatible with plastic substrates. It's also possible to use a sheet process on glass or plastic. Cambrios has filed over 175 patents for this technology and they claim they hold basic ag-wire patents. My friend Sri Peruvemba recently joined the company to become its chief marketing officer and he was kind enough to discuss their technology with me and help me with this article.

In January 2010, the DOE awarded $1.6 million to PPG Industries to develop "Low-Cost Integrated Substrate for OLED Lighting". This program is now finished and PPG has been recognized by the DOE for significant achievements in advancing OLED lighting technology. PPG was the only company honored in the OLED lighting area during the DOE 2013 SSL R&D workshop.

The team at PPG demonstrated a float glass-based integrated substrate with scalable light-extraction technologies and transparent conductive films for OLED lighting applications. This substrate may lead towards significant cost and performance advantages when compared to conventional indium tin oxide (ITO)-coated display-grade glass substrates.

ITRI announced it has developed a full roll-to-roll process on 100um flexible glass substrates - they say they're the first in the world to do so. ITRI has been collaborating with Corning on this technology, and they are using Corning's flexible Willow glass, unveiled at SID 2012.

ITRI and Corning developed specially designed R2R machines that produce touch panel modules on Corning Willow Glass, a flexible display-grade glass substrate. ITRI are now looking for companies that sell this technology - which can be used for OLED display and lighting panels, solar panels and more applications.

Kyoto University professor Hiroyuki Yano developed a new technology that produces transparent paper (cellulose nanofibers). This new material may be used as a substrate for transparent OLED panels, OPVs and other applications.

Cellulose nanofibers are very strong (eight times stronger than steel, in fact) but also very light. By adding resin to the nanofibers, they become transparent. Yano's transparent sheets are only 100 micrometer thick and feature a light transmittance of 87.8%.

Corning's major announcement at SID was the new Willow glass product. This is an ultra-slim (50 um and 100 um) flexible glass that can support backplanes and color filters in both LCD and OLED panels. Willow glass can withstand temperatures up to 500 degrees Celsius, and can be used in roll-to-roll production processes.

Corning says that in the near future Willow glass can be used to produce rigid OLEDs panels in processes that need flexible glass (such as roll-to-roll), and in the long term it may also lead to actual flexible panels based on glass. Glass have several advantages over plastics, mainly that it's a better barrier and it can result in better displays in terms of resolution, backplane speeds, etc. However the major disadvantage is that it can be shattered, unlike plastic-based displays.

Sony has developed a 9.9" 960x540 (111ppi) flexible OLED panel, using an Oxide-TFT (IGZO) backplane and a WOLED-CF architecture (RGBW). The thickness of this panel is only 110 um. To make this panel, Sony used two glass substrates (for the backplane and the color filters) during the production process, which were later removed. This allows Sony to use their regular OLED manufacturing process. We're not sure what kind of material is used as the final substrate.

The small-molecule OLED materials were deposited using vapor deposition. Unfortunately the company didn't demonstrate this panel at SID.