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:
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.
DSCC analysts say that OLED stack materials will grow from $1.04 billion in 2018 to over $2 billion in 2022 - a CAGR of 17%.
DSCC says that up until now it greatly underestimated Novaled's revenues, and it now says that Novaled generated revenues of $97 million in 2017 and $122 million in 2018. Novaled is the third largest OLED material company by revenue - following Universal Display and Merck. The three companies combined will hold a market share of 56% in 2023.
China-based display maker CSoT demonstrated several new OLED display prototypes and technologies at SID 2019, and this great new video shows these displays in action.
First up is a 31" 4K (3840 x 2160, 144 PPI) AMOLED that was produced using an ink-jet printing process on an IGZO substrate. The peak brightness is 200 nits and the refresh rate is 120 Hz. This seems to be the same panel announced in March 2018 by Joshua Printing Display Technology (established by CSoT and Tianma in 2016). The display has some noticable defects.
IHS says that ink-jet printing of OLED displays is finally ready to enter mass production in 2020. Production will begin at a rate of around 105,000 yearly substrates (209,000 sqm) in 2020, but will grow 12-fold within 4 years to reach 1.3 million yearly substrates in 2024 (or 7.3 million sqm).
The first producer to begin mass production using ink-jet printing will be JOLED who will enter mass production in 2020 (it already produces panels but at very low volume). OLED makers in China will quickly follow JOLED with mass production investments starting in 2020 or 2021.
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.