OLED (Organic Light Emitting Diodes) is a flat light emitting technology, made by placing a series of organic thin films (usually carbon based) between two conductors. When an electrical current is applied, light is emitted. OLEDs can be used to make displays and lighting, with possible applications that span TV sets, computer screens, mobile phones, decorative lighting and more. Since OLEDs emit light they do not require a backlight and so they are thinner than LCD displays, and are also more efficient, simpler to make and boast a better color contrast.
While OLED displays excel in color-contrast and efficiency compared to LCDs, they’ve also proven relatively hard to produce on a large scale. Current evaporation-based production techniques involve a lot of wasted material and risk of defects. OLEDs are also extremely sensitive to moisture and oxygen and therefore must be protected with a high performance encapsulating layer. All of these issues hinder OLEDs’ market takeover, but much work is put into resolving them.
OLED ink-jet printing
Current OLED producing methods rely on evaporation processes, in which the organic materials are deposited onto a glass sheet through a thin metal stencil, also known as a "shadow mask”. This process is problematic, as a significant amount of the material is wasted because it disperses all over the mask, in addition to inherent mask changes which expose the sheet to dust and compromise yields (OLEDs are by nature sensitive to contamination).
Inkjet OLED printing has the desirable ability to allow precision deposits without the use of a mask. It also produces less stray particles, thus boosting yields. These significant advantages make this technology interesting to many companies and virtually all OLED makers have active ink-jet printing development projects.
Inkjet methods form films by discharging the required amount of organic material onto large glass substrates in regular atmospheric conditions. This could be done, for example, by placing OLED pixels on glass or plastic using a portable platform and nozzles. Such methods have the potential to increase yields and lower prices, thus enabling OLED technology to take its deserving place in the market.
Unfortunately, OLED inkjet printing is not yet common, as printing OLED displays is a relatively challenging task for many reasons. A number of layers need to be deposited in pixels (the size of the pixels themselves is defined by the overall resolution the display will have). Being able to place the right number of drops of the active materials into the pixels is a challenge, in addition to developing a process in which the ink dries to deliver flat films of materials in the pixel.
Despite major progress, it is maintained that soluble OLED materials (required for inkjet printing) are less effective than evaporable ones. Ink-Jet printing is also not able to reach the same high densities of evaporation OLED production, which limits its applications for large-area production (TV panels) and not small mobile, VR and wearable OLEDs.
Ink Jet printing is still not used in any commercial OLED display production. But progress in past years have been rapid and some believe that initial OLED TV production using ink jet printing may begin in 1-2 years.
The latest OLED ink jet news:
TCL and Juhua Printing demonstrated a 31" FHD inkjet-printed rollable hybrid QD-OLED TV prototype. The display uses an IGZO (Oxide-TFT) backplane and TCL says that it has an aperture ratio of over 50%, brightness of 200 nits and a 90% DCI-P3 color gamut.
TCL's hybrid display technology (which TCL calls H-QLED) uses a blue OLED emitter coupled with red and green QD emitters. All three emitter materials are combined and printed using ink-jet printing technology.
Japan-based glass developer Asahi Glass (AGC) is developing new ultra-thin (9 mm) glass signage dispaly, called infoverre, that include OLED displays embedded within the glass which can be used in place where other display monitor installation was impossible - such as hanging ads in trains and buses and door pocket interior panels.
JOLED, which recently started sampling inkjet-printed OLED display panels in its 5.5-Gen production line, is providing the OLED panels to AGC. AGC uses JOLED's 21.6" 4K rigid OLEDs - two panels for each display as the signage is double sided.
DSCC updated their display industry forecasts, saying that as LCD prices continue to fall it revises the capacity forecast downward by 6% as Display makers are delaying and cancelling LCD investments. DSCC's OLED capacity forecast is also reduced by 4% - and is now growing at a CAGR of 19% from 2016 to 2025 (the main reason is the cancellation of Visionox V2 phase 2 and LGD's E6 Phase 3)..
DSCC says that OLED TV roadmap is still not clear as Chinese makers are not ready to commit to OLED TV production. DSCC does see next-generation TV capacity coming online in the future - which could be inkjet-printed OLEDs, OVJP, MicroLEDs and other potential technologies. But the next-generation display market is certainly not clear yet and DSCC sees an extended forecast during which demand will outpace supply (especially as average TV size continues to grow).
Meyer Burger announced that it is selling its PixDro inkjet printing business to Germany-based Suss MicroTec SE. The agreed price is $5 million, and the transaction is expected to be completed by the end of February 2020. Meyer Burger reveals that PixDro currently has annual sales of around $8 million. This transaction continues Meyer burger's strategic focus on its solar (PV) business.
PixDro develops and manufactures inkjet printing equipment for for the electronics and semiconductor industries. PixDro started out as a startup in Isarel, and was later integrated into the Netherlands-based OTB-Group, which was later renamed Roth & Rau AG, which was then acquired by Meyer Burger. The company continues its journey and will now be part of Suss MicroTec.
The monitor weighs only 1 Kg and is marketed as a "portable" ultra-slim monitor. Features include HDR support, 0.1 ms response time, 10-bit color (99% DCI-P3), USB-C input and micro HDMI.
Yesterday BOE held its Innovation Partner Conference (IPC) at the Beijing APEC Center and the company unveiled a 55" 8K (160 PPI) OLED TV prototype produced by inkjet printing. The panel achieves a maximum brightness of 400 nits and a color gamut of 95% DCI-P3.
BOE inkjet-printed 55" 4K OLED TV (2018)
This is BOE's 2nd inkjet printing OLED TV prototype, the first one being a 55" 4K panel presented at BOE's 2018 IPC. These displays were both produced at BOE's R&D production line in Hefei that uses Kateeva's inkjet deposition equipment.
JOLED announced that it has started sampling inkjet-printed OLED display panels in its 5.5-Gen (1300x1500 mm) production line in Nomi, Ishikawa Prefecture, Japan. Mass production is planned for 2020.
JOLED will market these medium-sized (10-32 inch) panels for use in applications such as high-end monitors, medical monitors and the automotive market. The Nomi site will have a monthly production of 20,000 substrates.
Researchers from Korea's Yonsei University has developed a 3D printing technique that can be used to deposit transparent OLED displays on any shape. The new technique 3D prints both the support structure and the 3D screen electronics.
The method is based in Digital Light Processing (DLP) system that prints the transparent plastic frames, and then uses an electrohydrodynamic jet (e-jet) printer to create the OLED layers as seen in the image above.
Tokyo Electron (TEL) announced a new OLED R&D inkjet printing system, the Elius 500 Pro that is capable of printing on 2-Gen substrates (370x470 mm).
The Elius 500 is able to accommodate 12 kinds of inks and can produce red, blue and green sub pixels at the same time. The maximum display density is 200 PPI.
AU Optronics has been developing OLED ink-jet technologies for many years, according to reports, and has setup a 3.5-Gen pilot ink-jet OLED printing line. Today AUO announced that the company is going to showcase its first ink-jet printed OLED panel at Touch Taiwan 2019.
AUO will demonstrate a 17.3" 4K (225 PPI) OLED display that was produced using an ink-jet printing process. AUO says that the display features a 120Hz refresh rate, a wide color gamut and high brightness (that AUO did not yet specify). AUO will also showcase 5.6" foldable OLEDs that can be folded inwards or outwards for customized design according to client requirements. The display's folding radius is 4 mm and it can be folded over 200,000 times. AUO will also demonstrate a 12.1" LTPS Micro-LED prototype, which seems to be the same one shown in 2018.