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Bendable backlight illuminates more
Printing replaces sputtering for a highly flexible, electroluminescent element
by David Bak, Editor-in-Chief, Global Design News -- Design News, January 20, 2002
Osaka, Japan — Changing the production method applied to one layer of a conventional electroluminescent (EL) "sandwich" lights up new applications. Flexibility, for example, permits new dome switch possibilities. Multiple layers allow one screen, two colors.
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A more flexible electroluminescent element allows center dome lighting. |
EL construction features a sandwich comprising the following: PET film, a transparent electrode made of an ink containing Indium Tin Oxide (ITO), a luminous layer with fluorescent materials, back electrode of carbon, and insulating layer. Applying ac current to the two electrodes heats the luminous layer, causing the fluorescent material to emit light.
Until now, manufacturers have used standard sputtering techniques to produce the transparent electrodes for LCDs, touch panels, and similar devices. Sputtering, however, results in a rigid, oxidized thin film, susceptible to cracking and diminished performance if bent. Consequently, applications have been limited to relatively flat surfaces.
High-precision ITO print technology, recently developed by Matsushita Electronic Components Co., offers an alternative production technique to conventional sputtering. The ITO, dispersed on a resin base, results in a more flexible transparent electrode that can be bent and can withstand repeated movements.
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Printing, rather than sputtering, allows a flexible EL element with better options for placement of electrical contacts. |
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Two transparent electrode layers permit multiple colors, and therefore images, from one element. |
The ability to bend has resulted in Panasonic's bi-stable "EL Dome" switch. Instead of using adhesive to attach an electroluminescent strip around the dome's flat perimeter, the new design incorporates the electroluminescent sandwich into the dome directly, to illuminate the center of the switch as well as its perimeter.
A second benefit of the printing process is better process control. Printing enables the manufacturer to coat the transparent electrode layer, yet leave areas for electrical contact. Sputtering, by contrast, covers the entire layer. Masking is possible, but the process is too labor-intensive and therefore expensive.
Better process control permits an EL element featuring two transparent electrodes. To ensure high transparency, Matsushita produces the top electrode by sputtering. However, the sputtering technique can be applied only to films. For the middle electrode to be formed on an object already printed several times, only ITO printing technology can be applied. Introduced by Panasonic as "Miracle EL," the new configuration gives consumer electronics product designers the option of placing two colors in one package. Color selection depends on which electrode combination is activated.
| Additional Details | ||
| Contact K. Takamitsu, Panasonic; Tel: +81 6 6908 7304; Fax: +81 6 6906 1619; E-mail: PAN50232@pas.mei.co.jp ; or Enter 502. | ||
