HP flexible, unbreakable TFT display demonstrated

Friday, Dec 12th 2008 by Chris Davies

HP and Arizona State University have demonstrated what they’re calling the first prototype of “affordable, flexible electronic displays”. Constructed using the self-aligned imprint lithography (SAIL) technology invented by HP Labs, the display also uses E Ink’s Vizplex bi-stable electrophoretic imaging film that requires no power to maintain an image; the end result is a low-power, low-manufacturing-cost display suitable for color text and graphics.

Rather than being produced in sheets, in a batch process, SAIL allows the different layers to be combined in a roll-to-roll process. That continuous build reduces manufacturing complexity and material usage (up to 90-percent less materials by volume, in fact) and thus cost. It’s also being called “unbreakable”, with the patterning information imprinted in such a way that distortion does not impact perfect alignment.

HP envisage the new display technology to be used in laptops, smartphones and other electronic devices. Not only will form factors be able to change, thanks to the flexible screen, but the could be cheaper, too.

Press Release:

HP and Arizona State University Demo Flexible, Unbreakable Displays

Summary - HP and the Flexible Display Center (FDC) at Arizona State University (ASU) today announced the first prototype of affordable, flexible electronic displays.

Flexible displays are paper-like computer displays made almost entirely of plastic. This technology enables displays to become easily portable and consumes less power than today’s computer displays. Popular applications for the technology could include electronic paper and signage.

The production feat is a milestone in the industry’s efforts to create a mass market for high-resolution flexible displays. Plus, from an environmental standpoint, the displays leapfrog conventional display processes by using up to 90 percent less materials by volume.

Mass production of such displays can enable production of notebook computers, smart phones and other electronic devices at much lower costs since the display is one of the more costly components.

The unbreakable displays were created by the FDC and HP using self-aligned imprint lithography (SAIL) technology invented in HP Labs, HP’s central research arm. SAIL is considered “self aligned” because the patterning information is imprinted on the substrate in such a way that perfect alignment is maintained regardless of process-induced distortion.

SAIL technology enables the fabrication of thin film transistor arrays on a flexible plastic material in a low-cost, roll-to-roll manufacturing process. This allows for more cost-effective continuous production, rather than batch sheet-to-sheet production.

“The display HP has created with the FDC proves the technology and demonstrates the remarkable innovation we’re bringing to the rapidly growing display market,” said Carl Taussig, director, Information Surfaces, HP Labs. “In addition to providing a lower-cost process, SAIL technology represents a more sustainable, environmentally sensitive approach to producing electronic displays.”

Production of flexible displays

The first practical demonstration of the flexible displays was achieved through collaborative efforts between the FDC and HP as well as other FDC partners including DuPont Teijin Films and E Ink. To create this display, the FDC produces stacks of semiconductor materials and metals on flexible Teonex® Polyethylene Naphthalate (PEN) substrates from DuPont Teijin Films.

HP then patterns the substrates using the SAIL process and subsequently integrates E Ink’s Vizplex™ imaging film to produce an actively addressed flexible display on plastic. E Ink’s Vizplex bi-stable electrophoretic imaging film enables images to persist without applied voltage, thereby greatly reducing power consumption for viewing text.

“Producing a photolithography-free, flexible active-matrix display is an excellent example of the Flexible Display Center’s world-class development and manufacturing infrastructure,” said Shawn O’Rourke, director, Engineering, Flexible Display Center at Arizona State University. “It demonstrates how multiple industry partners can collaborate on innovative solutions, including roll-to-roll compatible technology that addresses the rapidly growing market for flexible electronics.”

“Flexible electronic displays are playing an increasingly important role in the global high-tech industry, serving as the crucial enabling technology for a new generation of portable devices, including e-readers and similar products designed to combine mobility with compelling user interfaces,” said Vinita Jakhanwal, principal analyst, Small and Medium Displays, iSuppli. “We expect the flexible display market to grow from $80 million in 2007 to $2.8 billion by 2013. The Flexible Display Center at Arizona State University is a key participant in helping to develop the technology and manufacturing ecosystem to support this market.”

HP SAIL technology is one example of the technologies available for licensing from the HP Intellectual Property Licensing Group.

Further information about DuPont Teijin Films is available at www.dupontteijinfilms.com.

About ASU Flexible Display Center

The FDC is a government–industry–academia partnership that’s advancing full-color flexible display technology and fostering development of a manufacturing ecosystem to support the rapidly growing market for flexible electronic displays. FDC partners include many of the world’s leading providers of advanced display technology, materials and process equipment. The FDC is unique among the U.S. Army’s University centers, having been formed through a 10-year cooperative agreement with Arizona State University in 2004. This adaptable agreement has enabled the FDC to create and implement a proven collaborative partnership model with more than 20 engaged industry members, and to successfully deploy world-class wafer-scale R&D and GEN-II display-scale pilot production lines for rapid flexible display technology development and manufacturing supply chain commercialization. More information about FDC is available at http://flexdisplay.asu.edu/.

About HP

HP, the world’s largest technology company, simplifies the technology experience for consumers and businesses with a portfolio that spans printing, personal computing, software, services and IT infrastructure. More information about HP (NYSE: HPQ) is available at http://www.hp.com/.

Source

Printable Thin-Film Transistor for Flexible Electronics

United States Patent Application	20080173865
Kind Code	A1
Fink; Richard Lee ; et al.	July 24, 2008

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Abstract

Fabrication of thin-film transistor devices on polymer substrate films that is low-temperature and fully compatible with polymer substrate materials. The process produces micron-sized gate length structures that can be fabricated using inkjet and other standard printing techniques. The process is based on microcrack technology developed for surface conduction emitter configurations for field emission devices.

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Inventors:	Fink; Richard Lee; (Austin, TX) ; Yaniv; Zvi; (Austin, TX)
Assignee Name and Adress:	NANO-PROPRIETARY, INC. Austin TX Claims 1. A thin film transistor (TFT) comprising:a substrate;a source electrode on the substrate;a drain electrode on the substrate positioned a distance from the source electrode;a layer of metal oxide deposited on the substrate between the source and drain electrodes, wherein the layer of metal oxide is reduced to metal to form a microcrack in the layer between the source and drain electrodes, wherein the microcrack separates a first portion of the metal layer contacting the source electrode from a second portion of the metal layer contacting the drain electrode;an active semiconductor material deposited so that it bridges the microcrack, contacting both the first and second portions of the metal layer;a gate dielectric material deposited over the active semiconductor material; anda gate electrode deposited on the gate dielectric material and not contacting the metal layer or the active semiconductor material. 9. A method of manufacturing a TFT comprising:inkjet printing conductive ink on a substrate to form source and drain electrodes spaced apart from each other;inkjet printing a PdO layer on the substrate between the source and drain electrodes;reducing the PdO layer to Pd metal resulting in formation of a microcrack in the Pd metal layer;inkjet printing an active semiconductor on the reduced PdO layer across the microcrack;inkjet printing a gate dielectric over the active semiconductor; andinkjet printing a gate electrode over the gate dielectric.

Advantages of this approach are:

[0041]1. Low cost: All-printing technologies are used to form feedlines and TFT components. Inkjet printing and other printing approaches may he used. Printing is an additive approach and not subtractive, thus in general, the materials cost will be less. In addition, the capital investment for printing equipment is much lower than CVD or vapor deposition equipment needed for a-Si TFT technology or high-performance pentacene transistors.

[0042]2. Low temperature; The fabrication processes are below 200.degree. C.

[0043]3. Compatible with flexible substrates: The fabrication processes are completely compatible with PEN substrates.

[0044]4. Scalable to large area: Ink-jet printers are used now to print billboard signage. 100'' diagonal will be no problem. The fact that Canon, is using this microcrack approach for their SED 36'' diagonal (and larger) displays also demonstrates that arrays of submicron channel TFTs can be fabricated over large areas reliably.

[0045]5. Performance specifications for emissive technologies: The driving currents from this TFT structure are sufficient to drive OLEDs.

Source

Suspension-deposited carbon-nanotube networks for flexible active-matrix displays

Axel Schindler
Stefan Spiessberger
Steffen Hergert
Norbert Fruehauf
James P. Novak
Zvi Yaniv

University of Stuttgart

Abstract — The unique properties of carbon nanotubes (CNTs) promise innovative solutions for a variety of display applications. The CNTs can be deposited from suspension. These simple and low-cost techniques will replace time-consuming and costly vacuum processes and can be applied to large-area glass and flexible substrates. Single-walled carbon nanotubes (SWNTs) have been used as conducting and transparent layers, replacing the brittle ITO, and as the semiconducting layer in thin-film transistors (TFTs). There is no need for alignment because a CNT network is used instead of single CNTs. Both processes can be applied to glass and to flexible plastic substrates. The transparent and conductive nanotube layers can be produced with a sheet resistance of 400 Ω/ at 80% transmittance. Such layers have been used to produce directly addressed liquid-crystal displays and organic light-emitting diodes (OLEDs). The CNT-TFTs reach on/off ratios of more than 105 and effective charge-carrier mobilities of 1 cm2/V-sec and above.


FIGURE 6 — A 5 × 6-mm2 OLED with a CNT-network anode at 5-V driving
voltage under illumination of a fluorescent tube.

FIGURE 3 — Fully processed CNT-network TFTs on a 50 × 50 mm2 PES

Information Display 5/08 93

Source