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:
China-based BOE Display demonstrated many OLED displays at SID 2019, including new flexible, foldable, rollable and automotive AMOLED displays. Here's a video showing the company's complete SID lineup:
Digitimes reports that AU Optronics has setup a 3.5-Gen test ink-jet OLED printing line, and the company now intends to start building a 6-Gen production line. AUO will start constructing the line before the end of 2019.
AUO's Chairman confirmed that the latest advances in printing materials and equipment are starting to make OLED printing viable for commercial use. AUO has not yet decided the schedule for volume production.
JOLED announced that it has raised 25.5 billion Yen (around $228 million USD) from INCJ, Sony and Nissha. JOLED also announced that it has started to build post-processing module production lines at its Mobara, Chiba prefecture, plant. Nissha will also collaborate with JOLED in the area of OLED touch sensors.
JOLED's printed OLED displays will be produced at the company's Nomi plant. JOLED currently uses a pilot 4.5-Gen line at Nomi, but the company has already announced plans for a new mass production 5.5-Gen line in Nomi by 2020.
In early 2018 ASUS announced the Asus ProArt PQ22UC- a 21.6" 4K (204 PPI) ultra-portable OLED monitor, and now the company finally started shipping the new device - starting in the UK where the price is set at for £4,529 (!) which would make the US price at around $5,000.
The OLED display in ASUS' monitor produced using an ink-jet printing process by JOLED - which would make this the world's first ink-jet printed OLED product. JOLED's production capacity is not large, the company is still using a pilot-scale line, but it's likely that Asus is not expecting to sell many units of this high-end OLED monitor with that price tag...
TCL unveiled that the company is developing a new hybrid display technology that uses a blue OLED emitter coupled with red and green QD emitters. All three emitter materials will be combined and printed using ink-jet printing technology. TCL calls this technology H-QLED and this could prove to be the technology of choice for TCL's future high-end emissive TV displays.
It seems as TCL believes that commercial-level red and green QD emitters will be achievable in the future, but blue QD emission will be more difficult to develop, and hence it will rely on OLED emitters. TCL did not disclose more details - but this R&D effort is being performed at the company's Juhua Printing platform.
Guangdong Juhua Printing Display Technology was established in 2016 by CSOT and Tianma with an aim to develop OLED ink-jet printing technologies and enable companies in China to collaborate on this technology.
While TCL-owned CSOT already announced that it is collaborating with Kateeva (and others), it was not clear whether Juhua Printing Display was also using Kateeva's printers, but we now have confirmation that indeed the China-based consortium is based on Kateeva's printers. This is obviously a major win for Kateeva, who is also working with BOE and Samsung, among others.
At the OLED Korea conference, both Merck and Sumitomo detailed their latest OLED inkjet material performance.
Tianma demonstrated new display technologies at Embedded World in Germany, including two new OLED prototypes. First up is a 10.3" 91 PPI transparent AMOLED panel that features a transparency of up to 50% and high brightness (not disclosed).
The second display is a 4.92" 403 PPI AMOLED that was produced using an ink-jet printing process. Tianma's technology was jointly developed with Guangdong Juhua Printing and Display Technology (which was established in 2016 by CSoT and TianMa).
Earlier this month JOLED unveiled new display prototypes at FineTech Japan. Today we have received this interesting new video from JOLED that shows the displays in action:
In the video you can see all of JOLED's new prototypes. First up is the Automotive demo - JOLED demonstrated two panels, a 12.3" 1920x720 (167 PPI) panel and a 12.2" 1920x1280 (180 PPI) panel. Both are printed on LTPS backplanes (as do the rest of the company's small and medium sized panels). JOLED's latest investors, Denso and Toyoto Tsusho, are both helping the company with its entry into the automotive display market.
Samsung progresses with its inkjet printing OLED technology, to apply it to next-generation monitors and laptops
According to ETNews, Samsung Display has made significant progress with its OLED ink-jet printing process technology, and the company now aims to apply this technology to produce medium-sized panels for OLED laptops and OLED monitors. Samsung may also use this process to produce smaller tablet displays.
It seems that Samsung is aiming to settle on three main next-generation OLED technologies - evaporation (FMM) OLEDs for small-sized display, ink-jet OLED deposition for medium-sized panels and hybrid QD-OLEDs for large-area OLED TV panels. It's other display technologies are QD-LEDs for TVs and Micro-LEDs for next-generation small and large area displays.