A plethora of opportunities are set to open up in the field of plastic electronics with the recent advancements and commercialization of completely flexible paper-like displays. These foldable displays are, in essence, based on the electronic ink circuit and transistor arrays printed onto plastic substrates�particularly polyethylene teraphthalate (PET) and polyethylene naphthalate (PEN). While the technology has found its way in portable electronics including ultra-compact e-readable devices, a substantial scope yet exists in areas including diagnostic devices in medicine, novel packaging and outdoor advertising signs, including readily updatable flexible and foldable electronic posters, billboards, and retail shelf displays. Products featuring revolutionary electronic ink possess a paper-like high contrast appearance, ultra-low power consumption and a thin, light form. The distinct advantages of using polymers in electronic display devices include the faster, cost efficient processes under less controlled conditions and an increased scope for roll-to-roll fabrication analogous to the continuous printing presses. However, several studies suggest that use of plastics in electronics and semiconductor industry will hardly pose a threat to silicon since both have their unique benefits for different applications. As far as speed of processing and miniaturization is concerned, silicon scores well above plastics; however, plastics race ahead with regards to flexibility, compactness in end devices, ease of processing and low power usage. Due to these factors, polymers including PET (offering curing advantages) and PEN (offering thermal and dimensional stability) are set to take off in coming years within the substrates market with the increase in demand for ultra compact, large, flexible, paper-like and energy efficient displays.
一些公司已经开发和商业化flexible displays for numerous applications. E Ink Corporation, is a renowned player in electronic paper display (EPD) technologies. The electronic paper display revolves around the concept of millions of tiny microcapsules, about the diameter of a human hair. At a time, each microcapsule contains positively charged white particles and negatively charged black particles suspended in a clear fluid. When a negative electric field is applied, the white particles move to the top of the microcapsule where they become visible to the user. This makes the surface appear white at that spot. At the same time, an opposite electric field pulls the black particles to the bottom of the microcapsules where they are hidden. By reversing this process, the black particles appear at the top of the capsule, which now makes the surface appear dark at that spot. To form an E Ink electronic display, the ink is printed onto a sheet of plastic film that is laminated to a layer of circuits or thin film transistors. The circuitry forms a pattern of pixels that can then be controlled by a display driver. These microcapsules are suspended in a liquid "carrier medium" allowing them to be printed using existing screen printing processes onto virtually any surface, including glass, plastic, fabric and even paper. E Ink�s proprietary Vizplex comprise of first producing microencapsulated electronic ink and has it coated onto an ITO-coated plastic substrate in a fast, efficient roll-to-roll process. The resulting ink film is combined with a thin adhesive and a plastic release sheet to form the Vizplex imaging film. The film is then converted into individual sheets and packaged for shipment to the TFT display manufacturer. The imaging film is designed for high performance and to be the most visually attractive active matrix electronic paper display. Amazon�s Kindle eBook employs this imaging Film, coupled with wireless technologies. This provides users the flexibility of selecting and downloading books, blogs and articles through Amazon's Whispernet.
Plastic Logic has already kick started production of its large, flexible electronic-paper display in Dresden, Germany. The displays will be used in its yet-to-be-launched electronic reader-The Plastic Logic reader, which is set to hit markets in January. It uses display technology from E Ink and backplane technologies that employ polymer electronics developed by firm�s founders at Cambridge University. This 8.5 inch x 11 inch reader from Plastic Logic will run neck-to-neck with already launched 6-inched Kindle and the Sony Reader from electronic giant, Sony. However, Philips Electronics spin out, Polymer Vision�s Readius�the very first commercial rollable display product is expected to be the closest of all in the race. All the devices employ E Ink�s electrophoretic display technology. Processing techniques for different players may differ. While the Polymer Vision's rollable displays depend on the lithography techniques conventionally used in the semiconductor industry, Plastic Logic uses a relatively simpler process for printing electronic circuits on plastic substrates, which can be combined with LCDs, organic light emitting diodes, or electrophoretic 'electronic ink' to make the final device.
In North America, the FlexTech Alliance, an organization devoted to developing the electronic display and the flexible, printed electronics supply chain, awarded a year long contract to Texas-based Raytheon Company to produce display demonstration units for military application field trials. Ultra low power, lightweight displays are of considerable interest for military applications where size, weight and power can greatly impact soldiers� effectiveness in the field. Raytheon is believed to modify an E Ink color research prototype to meet stringent military operational requirements, especially for dismounted soldier applications including power, communication range and robustness.
Coming to Europe, DuPont Teijin Films, the world's leading differentiated producer of PET and PEN polyester films, had recently joined Systems-in-Foil program of Holst Centre, a research initiative of the Flemish and Dutch research centers IMEC and TNO. By getting a major substrate vendor on board, Holst Centre gathers the entire ecosystem of industrial players around its Systems-in-Foil program line. One of the two program lines at Holst Centre (The Netherlands) focuses on processes and technologies for Systems-in-Foil, such as large-area printing, electrodes and barriers etc. Dupont Teijin Films joined the leading industrial players including Philips, Solvay, Akzo Nobel and Agfa in the program on Flexible Organic Lighting and Signage by bringing in its know-how on foil production. The aim of this Holst Centre program is to design and optimize OLED device concepts and processes that are compatible with roll-to-roll fabrication for lighting and signage applications. By bringing together equipment and materials suppliers with system integrators and device manufacturers around a well-defined roadmap, interactions originate that would not be possible in a scenario where each party sticks to in-house R&D.
另一个球员在创新的显示技术,SiPix Imaging, Inc., employs its patented Microcup� structure for manufacturing its SiPix e-Paper. The SiPix Microcup is manufactured using a high-speed roll-to-roll� embossing process. A continuous sheet of PET plastic, coated with a transparent conductor such as ITO, is fed through a coater which evenly distributes a proprietary resin across the surface. A microembosser then molds the three-dimensional structure of the Microcup� onto the resin. At this point, the Microcups� are filled with the desired materials and hermetically capped with a sealing layer. A removable layer then is applied to protect the Microcup� film until it may be attached to the backplane. This SiPix Microcup� is then applied to make flexible, low-power electronic paper module. Unlike existing display technologies, SiPix e-paper has image memory - the display content remains after the power has been removed. Due to this benefit, extremely low-power portable devices may be created. Because of the Microcup� architecture, SiPix e-Paper is known to be environmentally robust and highly resistant to impact and pressure. SiPix e-paper is created by inserting electrically-charged white particles and dielectric fluid within the Microcup� during roll-to-roll� manufacturing. Once the e-paper is laminated to a patterned conductor with adhesive, the e-paper display may be driven. When an electric current is applied, the charged particles migrate through the dielectric fluid. If the white particles are at the visible surface, that area of the display reflects a white color to the viewer. Otherwise, the display will reflect the alternate color, which presently is either black, red, green blue, or gold. Grayscale may be produced by modulating the electric field across the Microcup� film. Both monochrome and area color displays may be produced with SiPix e-Paper. The material has a viewing angle that is approximately 180�.
The foldable, flexible, energy-efficient displays have already found applications in compact electronic books, mobile phone, PDAs and the like. Research and development efforts in this field suggest the new applications of these paper-like displays on the horizon may be in foldable and updatable outdoor advertising, large-yet-compact military demonstration units for field trials, medical devices for diagnosis, chemical sensors and many more.
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