Flexible-Display Development for Army Applications

The U.S. Army has long recognized the significant role display technology plays in Army systems and has supported the development of the current flat-panel technologies. Flexible-display technology will provide an advantage over glass-based displays for Army applications; therefore, the U.S. Army is supporting research and development designed to speed commercialization of flexible displays.

by David Morton and Eric Forsythe

THE DEVELOPMENT of new display technology in the United States historically has had significant support from the U.S. Government through many funding organizations, including both defense- and non-defense-related organizations. One of the most recent examples of this is the Flexible Display Center (FDC) at Arizona State University (ASU), which was founded by the Army to advance flexible-display integration technology and manufacturing research. Figure 1 highlights the total flat-panel research funding profile over a 20-year time horizon.

In the mid-1990s, the research and development (R&D) funding for flat-panel-display research peaked at $160 million/year when the government was funding a number of display-technology-development initiatives. Early investments in plasma displays, active-matrix liquid-crystal displays (AMLCDs), projection displays, and head-mounted displays (HMDs) were one factor that led to the significant commercial success of these technologies, where now these displays have become commodities for commercial- and DoD-platform applications. For the DoD, the investments in technology development have transitioned to an acquisition and adopting, or commercial-off-the-shelf (COTS), model. For display technology in this model, commercial displays are obtained by system integrators who then adapt the technology for military applications. Accordingly, funding for display research has declined, but since 2000, what remains has been focused exclusively on the development of flexible displays.

The U.S. Army is improving and modernizing capabilities through several programs that address the U.S. Army's mission. The Future Combat Systems (FCS) program is the largest of these programs and requires the ability to perform essential command, communication, control functions for combat vehicles and dismounted soldiers. These applications will require compact, thin-profile displays to convey information from a network-centric battlespace to the individual. Unfortunately, key features of the flat-panel displays being produced for today's civilian electronics make them unsuitable for emerging military applications. Conventional displays tend to consume too much power and, critically, they are made out of glass. This last feature means that they require expensive and bulky "ruggedization" before they can be incorporated into military systems, adding significant size and weight. For the dismounted soldier, the high-power requirements of current displays compel the soldier to bear the additional weight of batteries during operations.

The promise of significant reduction in size, weight, and power is why intrinsically rugged flexible-substrate-based displays are so intrigu-ing to the military. Flexible displays for U.S. Army applications fall into two categories: replacement of existing technology equipment that is being fielded or is under development and new and novel applications that cannot be addressed by glass-based technology.


David Morton is the Display Technology Manager for the Army Research Laboratory and is the Cooperative Agreements Manager for the Army's Flexible Display Center, the United States Display Consortium, and the Center for Advanced Microelectronics Manufacturing at SUNY Binghamton. He can be reached at the Army Research Laboratory, AMSRD-ARL-SE, 2800 Powder Mill Rd., Adelphi, MD 20783; e-mail: dmorton@arl.army.mil. Eric Forsythe is the Team Leader for Display Technologies at the Army Research Laboratory and is an Associate Program Manager for the Army's Flexible Display Center.

 

Replacement of Existing Technology

There must be a strong justification to replace existing technology. For flexible displays in U.S. Army systems, the rational is based on reduced power, improved reliability, and reduced display volume and weight. Power is addressed by developing flexible displays based on technologies that offer an advantage compared to LCDs or plasma displays. The technologies we currently are developing into demonstrators include electro-phoretic, cholesteric liquid crystal (chLC), and organic light-emitting-diode (OLED) displays. The electrophoretic and chLC bistable reflective technologies1 are essentially zero power for low refresh rates, while OLEDs currently are a factor of 2–3 more efficient than comparable LCDs. These technologies are being commercialized on glass substrates and, as an interim step, may be integrated into U.S. Army systems to address the power issue. We have chosen to develop these technologies for U.S. Army systems because they are being commercialized on glass and because of their compatibility with flexible substrates.

Displays with flexible, rugged substrates have several implications for U.S. Army applications. When replacing the glass-based display in an existing system with a flexible display, two things happen. The first is that the power drops by at least one-half. This means a soldier can carry fewer batteries and be lighter or keep the same battery load and need twice the endurance. For fixed displays (displays on larger equipment or in vehicles), it means less power draw on the system, which can lead to reduced sizing of the power source. The other factor is that the display is much less likely to break during the mission. This means a reduction in the number of units carried, which for soldier-based applications reduces the weight carried.

In fixed applications, the ruggedness means a significant reduction in the weight and volume of the mounting of the display. A 17-in. display may weigh 30 lbs. in a military vehicle with 15 lbs. of metal-mounting hardware, and it may be more than 2-in. thick with a 24-in.-diagonal case size. If that can be replaced with a rugged display on a plastic or foil substrate, the weight may be reduced to 5 lbs. with 2 lbs. of mounting hardware and a 19-in.-diagonal size with a thickness of 1 in. This represents a significant advantage in designing a vehicle where space, power, and weight are at a premium.

If the breakage rate for both soldier and fixed applications is significantly reduced, the Army does not have to stock as many units in the repair depots, and the repair and replacement of non-repairable units is reduced, which translates to significant cost reductions over the system lifetime.

New Applications for the Soldier

Similar to the early development of other flat-panel-display technologies, flexible-display applications for the Army will likely evolve several ways as the technology matures. Figure 3 illustrates the anticipated technology evolution for Army flexible-display applications. A direct substitution of flat glass displays with flat flexible displays is the first envisioned application to improve system reliability and performance. As the technology matures, the system applications will evolve from small handheld applications (3–4-in. diagonals) to larger notebook-sized displays (6–12-in. diagonals) to displays for vehicles (17–21-in. diagonals). Simultaneously, having a display that can flex, be rolled up, and/or folded will enable new ways to convey information to soldiers to improve and enhance their capabilities. Likewise, flexible-display applications will evolve from conformal displays worn on the body to fully rollable displays with the same size evolution. A simple example is a body-worn card display that fits into a "cargo" pocket that serves as an electronic roll-up maps/communications device for mission planning and execution. Figure 4 illustrates one envisioned application where the conformal display is mounted to the sleeve of a soldier for rapid access to information. Here, the display size is approximately the same as those of handheld electronics (3–4-in. diagonal). As flexible-display technology matures, potential applications include displays conformally laminated to equipment, vehicles, and walls. Finally, the long-term goals for the application are large flexible displays that could replace a projection system by making the screen the entire display so it could be rolled up in a tube and transported, hung on a tent wall, or laid on the ground for mission planning.

 

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Fig. 1: U.S. funding profile for display research [(PTCOE: Phosphor Technology Center of Excellence); (AICM: Advanced Information Component Manufacturing); (TRP: Technology Research Program); (MT AMLCD: ManTech Active Matrix Liquid Crystal); (DARPA HMD: DARPA Helmet Mounted Displays); (USDC: U.S. Display Consortium); (DARPA HDS: High Definition Displays); (FDC: Flexible Display Center)].

 

The DoD technology benefits of enhanced ruggedness and reduced space, weight, and power have a direct correlation with the needs of the commercial marketplace. In some instances, the performance required may be higher than the commercial counterpart. For portable applications, power, weight, and readability are critical performance parameters for DoD and commercial applications. In fixed locations such as office and desk spaces, the volume of the displays and, indirectly, the improved ruggedness will offer unique new commercial applications. In vehicle applications, readability, volume, and related ruggedness, as well as power, are significant performance parameters. The future promises novel form factors, such as lightweight large-format displays that could be folded or rolled up for storage or transportation.

The U.S. Army recognizes the advantages that flexible displays will provide to both the commercial and military markets. As a first adopter of new display technology, the U.S. Army is trying to speed the commercialization of this technology through the Flexible Display Center (FDC) at Arizona State University (ASU). What follows is an overview of the program at the FDC.

Flexible Display Center

In 2004, the U.S. Army Deputy Assistant Secretary for Research and Technology established the Army's Flexible Display Center (FDC) at Arizona State University in partnership with the State of Arizona. The Center was formed through a cooperative agreement with the Army Research Laboratory, Sensor and Electron Devices Directorate, managed in conjunction with the Army Natick Soldier RDE Center. The initial 5-year phase of this 10-year program represents a $44 million investment by the Army and a comparable matching commitment by Arizona State University. It also includes significant participation by a growing list of industrial partners who pay an annual membership fee, make internal investments in support of development projects at the Center and work directly with the Center and its partners to collectively advance flexible-display and associated manufacturing technology. The industrial participation is governed by a unique partnership agreement that spells out the co-investment requirements, membership benefits, and intellectual-property rights of the participating organizations.

 

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Fig. 2: Towed Artillery Digitization (TAD) program with the TAD gunner glass display. Photographs courtesy of General Dynamics, Canada.

 

The mission of the FDC, which is headquartered in the first display research-and-development facility in the world to be dedicated to work on flexible displays, is to speed the commercialization of full-color flexible-display technology. The principal technical goal of the FDC is to develop the materials, processes, and manufacturing technology for high-performance, conformal, and flexible displays that are ultra-rugged, light-weight, reduced volume, low power, and low cost. The FDC demonstrates the achievement of these technology goals by providing integrated full-color flexible-display panels to Army and FDC partners for integration into prototypes and technology demonstrators. In turn, these prototypes and demonstrators show the capabilities of emerging flexible-display technology to Army and commercial users.

To achieve its mission, the FDC has established a dynamic university/industry/government collaborative partnership summarized in Fig. 5. This strategic partnership currently includes 16 industrial members including EV Group, Universal Display Corp. (UDC), the United States Display Consortium (USDC), E Ink, Kent Displays, DuPont-Teijin Films, Honeywell, Hewlett Packard, Surface Science Integration, Ito America, Litrex, Abbie Gregg, Inc. (AGI), Etched In Time, Inc., General Dynamics, Raytheon, and L-3 Communications. These partners leverage the FDC's world-class flexible-display infrastructure focused on pilot-line manufacturing to advance their technology and products. The Center also collaborates with seven different universities and a not-for-profit lab through a variety of research-focused projects. In turn, the FDC leverages the extensive capabilities, IP, and knowledge of the industrial partners.

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Fig. 3: Concepts for flat displays that benefit from the inherent ruggedness of flexible displays. (a) Hand-held PDA (3–4-in. diagonal); (b) Compact, Lightweight Commanders Assistant (6–10-in. diagonal); (c) large displays in vehicles (17–21-in. diagonal).

 

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Fig. 4: Illustration for future flexible displays that incorporate the capability of conforming and rolling displays. (a) Conformal displays worn on the sleeve and flexible roll-out displays; (b) conformal displays in vehicles and mounted on sides of vehicles; (c) large paper-like electronic maps; and (d) command-and-control pull-down electronic walls.

 

The FDC is headquartered in a state-of-the-art display R&D to manufacturing facility located within a university-owned industrial research park. Operated by a staff of professional engineers and technicians, the facility includes ~30,000 square ft. of class-10 clean room that houses both a development-scale production line and a GEN 2 pilot display-scale manufacturing line that will process flexible displays on 370 ´ 470 mm substrates. The Center also contains the research laboratories of a number of ASU faculty and their graduate students, who conduct affiliated longer-range research projects supported by a variety of traditional outside research funding sources.

Activities at the Flexible Display Center focus on the issues associated with the fabrication of active-matrix thin-film-transistor (TFT) arrays on flexible substrates, such as thin stainless steel or transparent specialty polyester. This challenging piece of large-area microelectronics is the critical subsystem required to control an array of electro-optical devices to create a digital display. To complete the display, one of three electro-optic technologies being developed by members of the Center is integrated with these TFT panels. Ultra-low-power reflective displays can be made using electrophoretic ink from Massachusetts Institute of Technology spin-out company E Ink, or cholesteric liquid-crystal films provided by Kent State University spin-out Kent Displays, Inc., in Ohio. Alternatively, vibrant full-color and full-motion-video organic electroluminescent displays can be built using materials developed by Universal Display Corp. These technologies were chosen because of their compatibility with flexible substrates, their power advantages, and their relative maturity.

The Army's investment in the FDC is highly leveraged through a close partnership with military-system integrators to develop technology-demonstration devices to showcase the new capabilities. Member companies General Dynamics, Honeywell International, L3 Communications, and Raytheon have all contributed to the identification of demonstrator projects whose success will help meet the technical requirements of their roadmaps for future system offerings. The display requirements for these demonstrator projects help define the detailed objectives of the Center's development programs.

The Soldier Flex PDA shown in Fig. 6 is the first demonstrator candidate for transition to Program Executive Office (PEO) Soldier from the FDC. It features a rugged, low-power reflective E Ink frontplane and low-temperature amorphous-silicon (a-Si) TFT backplane and weighs only 13 ounces. This application was demonstrated as part of the Army Future Force Warrior ATD program at the CERDEC C4ISR "On the Move" exercise at Fort Dix in July 2007. The FDC developed the display and, with "customer" funding and management support from Natick Soldier RDEC, a rugged and compact networked personal digital assistant was developed for use by individual infantry rifleman squad members.

 

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Fig. 5: The Army's Flexible Display Center at Arizona State University partnership as of August 2007.

 

 

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Fig. 6: From the Flexible Display Center, the transition is being made to the Army Program, Future Force Warrior.

 

The demonstration of innovative flexible-display technology is how the Flexible Display Center shows that it is achieving its central mission. Integral to that mission is the simultaneous development of reliable fabrication techniques that are sufficiently mature to stimulate their adoption by the existing display-manufacturing infrastructure. Because this approach necessarily involves the use of new materials and the adoption of unconventional manufacturing processes, it is crucial to engage industrial partners from these parts of the supply chain as early as possible. For such companies, the Center provides a unique integrated manufacturing pilot-line development environment in which they can create and test new products for the emerging field of flexible displays and microelectronics. For example, Center member DuPont-Teijin Films is developing a novel high-temperature polyetylene naphthalate (PEN) film; the Center's pilot line provides a testbed through which film characteristics can be improved and tailored for flexible or printed electronics.

Similarly, Center member Honeywell Electronic Materials has developed a new solution-based hybrid organic-inorganic dielectric material that has been qualified on the FDC developmental pilot line; they recently announced commercialization of this material for the flat-panel-display industry. In the critical area of manufacturing equipment, Center member EV Group (EVG) has developed a unique and versatile tool for the coating of ultra-high uniformity micrometer-thick films (0.5–15 μm) of conventional photo-resists and unconventional materials (e.g., adhesives, solution-based dielectrics) onto large-area substrates at a high materials utilization efficiency (>90%). The Center served as the beta-test site for this tool and, as a direct result, EVG has recently received an order for a number of these new machines from a commercial display manufacturer. A modification to an Azores stepper sponsored by the U.S. Display Consortium (USDC) that enables compensation for the distortion in plastic substrates caused by transistor-array fabrication processes has stimulated commercial interest in the modification of tools in existing display-fabrication facilities.

While these manufacturing technology successes in materials and toolsets have been the most public demonstrations of the power of the innovation capacity of the FDC partnership, a series of internal FDC milestones have been driving and enabling these advances. For example, the FDC has successfully developed a 180°C a-Si:H process that produces the highest-performance low-temperature TFTs in a high-resolution array at reasonable Pilot Line yields. Novel manufacturing protocols and processes have been developed to enable direct fabrication of these transistor arrays on flexible substrates. These active-matrix arrays in turn serve as the backplanes for ~4-in.-diagonal QVGA electrophoretic-ink technology demonstrators on DuPont-Teijin Films plastic substrates and on stainless-steel foils, including the display modules for the Soldier Flex PDA described above.

The Army's Flexible Display Center at Arizona State University represents a pioneering new approach to developing technologies to meet Army needs through the stimulation of commercial manufacturing capability. After less than 4 years of operation, integrated systems incorporating innovative displays developed by the Center have already been demonstrated, and the Center is on track to achieve initial technology insertion by the end of the decade.

For additional information, contact David Morton (dmorton@arl.army.mil); Eric Forsythe (eforsythe@arl.army.mil); FDC – Greg Raupp (raupp@asu.edu), http://flexdisplay.asu.edu/); Soldier Flex PDA – Henry Girolamo, henry.girolamo@us.army.mil.

References

1The reflective-display technologies being developed can be viewed utilizing night-vision goggles that use only ambient illumination, reducing the night-vision signature of the soldier. Programs are under way with ARL Human Research and Engineering Directorates (HRED) and Natick Human Factors Engineers to investigate more effective uses of this new capability. •