有机发光二极管(OLED)显示器具有色彩更丰富、既轻且薄的优点，而且可以制造成可挠曲、可穿戴或甚至是卷起来的显示器。然而，OLED的一大缺点就是价格较高。如今，加州一家新创公司宣称已经找到能以较低价格制造出 OLED 的解决方法了。
在日前于加州旧山金举行的印刷电子展(Printed Electronics 2013)上，总部设于美国加州Menlo Park的Kateeva Inc.发表一项能够以喷墨打印方式制造出OLED显示器的技术── Yeildjet 。
“Yieldjet 是专为大规模生产 OLED 而从头打造的首款印制平台，”Kateeva 公司总裁兼共同创办人Conor Madigan表示，“我们已经为喷墨印制OLED的技术解决了从研发到生产过程中的所有关键问题。”
Kateeva公司的Yieldjet平台能够透过喷墨印刷技术印制出OLED显示器
Source：KateevanBtesmc
目前， OLED 必须在真空室中用光罩沉积有机材料的方式制造出来，但这种方式十分浪费材料，而且也会对良率产生不利影响，例如光罩改变时会产生杂散颗粒。
“高达90%的沉积材料都被浪费掉了，”Madigan说 ，“而即使是一微米大小的颗粒都可能破坏一个画素。”
而这种喷墨打印方式只在需要时才沈积材料，可使原材料更具经济效益。根据Kateeva表示， Yieldjet 平台所产生的杂散颗粒也较少，并能在产生的颗料造成问题以前先行撷取出来，因而能使良率提高10倍以上。
三星的智能手表原型采用可挠式OLED显示器
Source：SamsungnBtesmc
本文授权编译自EE Times，版权所有，谢绝转载
本文下一页：OLED制造商关切的另一项重点
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OLED制造商关切的另一项重点是显示器的使用寿命，可能会因为空气中的氧和湿气带来负面影响。因此，传统上，必须在真空室进行沈积，才能让材料隔离氧气和与湿气。然而，喷墨打印机却不能在真空中进行打印，使其他喷墨打印机制造商只得在空气中进行操作，导致精密的有机薄膜在制造过程中被暴露于氧气和湿气中，严重影响 OLED 的使用寿命。
“在空气中进行印制本身就会降低设备的质量，”Madigan说。
为了解决这个问题，Kateeva在 OLED 制造过程中先将印制机隔离在氮气环境中，从而使透过 Yieldjet 平台制造的 OLED 显示器寿命可望提高两倍。
Kateeva公司声称已经解决的第三个关键问题是印刷的均匀度。只要曾经使用过喷墨打印机的人都知道喷墨堵塞时可能造成打印影像不连续的条带效应(banding effect)，这也会对于 OLED 面板的制造良率造成严重的影响。然而，Kateeva宣称经由喷墨压印绘图的学习经验，他们已经解决了这个问题。
Madigan介绍道：“我们借用了绘图艺术产业用的算法(用于改善喷墨打印机喷嘴产生画面不均匀的问题)，并将这种算法应用在 OLED 的制造过程中，直接监控在我们印制系统中的所有喷嘴，使我们可随时清楚掌握每一滴从喷嘴中流出的量。”
Yieldjet 是一款八代尺寸的印制机台，可印制达2,500 x 2,200mm(98 x86 吋)的 OLED显示器面板，以及用于可挠式显示器的小型面板。Kateeva公司声称，目前Yieldjet平台已经用于几家客户了，预计采用Yieldjet 制造的OLED显示器将在2014年后出现。
本文授权编译自EE Times，版权所有，谢绝转载
编译：Susan Hong
参考英文原文：Ink-Jet Printing for OLED Displays Debuts; Ink-jet printing is less costly，by R. Colin Johnson
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Ink-Jet Printing for OLED Displays Debuts
Ink-jet printing is less costly
R. Colin Johnson
PORTLAND, Ore. — Organic light emitting diode (OLED) displays have richer colors, are thinner and lighter, and can be fabricated for curved, bendable, wearable, or even roll-up displays. While OLEDs come at a high price, a California startup claims to have a less expensive solution to manufacturing.
Menlo Park, Calif.-based Kateeva Inc. unveiled Yeildjet, technology to manufacture OLED displays using ink-jet printing, at Printed Electronics 2013, Nov. 20-21 in San Jose, Calif.
"Our Yieldjet is the first printing platform built from the ground up for mass production of OLEDs," Conor Madigan, co-founder and president of Kateeva, told EE Times. "We've addressed all the key issues in moving ink-jet printing of OLEDs from R&D to production."
Kateeva's Yieldjet tool manufactures OLED displays using ink-jet printer techniques.
(Source: Kateeva)
Today, OLEDs are manufactured in a vacuum chamber using shadow masks to deposit the organic materials, which is wasteful of materials and adversely affects yields as stray particles are generated when masks are changed.
"Up to 90 percent of the deposited material is wasted," says Madigan. "And even a one-micron-sized particle can destroy a pixel."
Ink-jet printing, on the other hand, deposits material only where needed, thus being more economical of raw materials. Yieldjet also produces fewer stray particles, thus boosting yields by as much as 10 times, according to Kateeva, by producing fewer particles to begin with, and capturing any particles that are produced before they cause a problem.
Samsung concept smartwatch using a flexible OLED display.
(Source: Samsung)
The second major concern of OLED manufacturers is the lifetime of the displays, which are adversely affected by the oxygen and moisture in air. Traditionally, a vacuum chamber is used for deposition, thus isolating the materials from oxygen and moisture. Ink-jet printers, on the other hand, cannot print in a vacuum, leading other ink-jet printer makers to operate in air, thus exposing the delicate organic films to oxygen and moisture during manufacturing -- adversely affecting the lifetime of OLEDs.
"Printing in air inherently lowers device quality," says Madigan.
To solve that problem, Kateeva isolates its printer in a nitrogen environment during manufacturing, which it claims up to doubles the lifetime of OLED displays manufactured by its Yieldjet.
The third key problem Kateeva claims to have solved is print uniformity. Anybody who has used an ink-jet printer is familiar with the banding problem when jets get clogged -- a problem what would be disastrous for yields when manufacturing OLED panels. However, Kateeva claims to have solved this problem by borrowing from the lessons learned on graphics ink-jet printing presses.
"We've adopted the algorithms used in the graphics arts industry to average out the non-uniformity they get from nozzles, and adapt them to OLED manufacturing," says Madigan. "We also directly monitor all of the nozzles that are printing in our system so that we have accurate information about the volume of each drop coming out of each nozzle at all times. Then we layer on top of that algorithms that make us much more tolerant of variations."
Yieldjet is a Gen-8-sized printer, handling OLED panels up to 2,500 by 2,200 millimeters (98 by 86 inches) with smaller models available for flexible displays. Kateeva claims to already have customers for its Yieldjet, and that displays manufactured using them will begin appearing in 2014.
责编：Quentin
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