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Inkjet tech enables big-screen OLED TVs

Posted: 02 Jun 2009 ?? ?Print Version ?Bookmark and Share

Keywords:OLED? inkjet? display?

Seiko Epson Corp. has developed an inkjet technology that enables the uniform deposition of organic material in the production of large-screen OLED TVs. The new technology represents a major step toward the realization of 37-inch and larger full-HD OLED TVs by resolving the uneven layering that had previously been an issue with the inkjet method.

OLED TVs are the odds-on favorite to supplant current technologies as the next generation display. Offering outstanding viewing characteristics, including high contrast, wide viewing angle and fast response time, OLED TVs are also lightweight, ultrathin and have low power requirements. A major roadblock preventing mass production of large-screen OLED TVs has been the lack of a technology capable of reliably forming uniform organic layers on large substrates. Vacuum thermal evaporation (VTE), currently the most widely used method of depositing organic materials, is surrounded by technical hurdles that have prevented it from solving the layer uniformity issue and making the jump to mass production of large panels. An inkjet process that deposits organic material in liquid form has long been viewed as the ideal alternative.

Epson has recently developed the long-awaited solution in the form of an OLED display fabrication process that leverages the company's proprietary Micro Piezo inkjet technology to achieve markedly greater accuracy in organic material deposition than the conventional technology. The process has been used in trial production to fabricate a highly uniform prototype panel. Extremely uniform layers (volume error "Large-screen OLED TVs are the future of displays, and Epson is committed to contributing to the transition to volume production through research and development projects involving inkjet fabrication technologies," stated Satoru Miyashita, general manager of Epson's OLED Development Center.

Details about this technology will be presented at SID 2009, the Society for Information Display's international symposium, seminar and exhibition.

Inkjet advantage
A process for forming uniform, thin-film layers of organic material on glass substrates is essential for fabricating OLED TVs. VTE is currently the most widely used method for forming thin films on glass substrates. This method, performed in a vacuum chamber, requires that a shadow mask be placed in close proximity to the substrate to define the pattern of material deposited on the substrate. VTE, however, has several drawbacks when it comes to fabricating large-screen OLED TVs. On large panels it can be difficult to maintain a uniform deposition rate, primarily due to displacement of the shadow mask when it is exposed to the high temperatures used in this process.

An inkjet printing process is theoretically the better solution for larger display sizes because it enables thin-film layers to be formed via the deposition of liquid organic materials. Employing the same drop-on-demand approach as an inkjet printer, Epson's process accurately deposits organic materials in the precise locations and amounts required. Since inkjet systems use materials extremely efficiently, manufacturers can cut production costs. Used as an OLED TV fabrication system, inkjet technology, which does not require masks and thus involves fewer process steps than VTE, is widely expected to increase production throughput.

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