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 are used to make displays and lighting panels. OLEDs today are widely used in TVs, smartphones, tablets, laptops and wearables.
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.
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.
For many years, companies all over the world invested heavily in inkjet printing processes for OLED displays, but the process is not yet common, as printing OLED displays is a relatively challenging task, and soluble OLED materials 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.
Printed OLED panels on the market
One area in which inkjet printing is common in the OLED production process is the encapsulation layer deposition. Almost all OLEDs that adopt TFE encapsulation use inkjet printing to deposit the organic elements.
LG 32EP950 OLED monitor (31" 4K printed OLED panel by JOLED)
For actual OLED emitter layers deposition, currently the only company that commercially uses ink-jet printing is Japan's JOLED, who in 2021 started printing OLED display panels in its 5.5-Gen production line in Nomi, Ishikawa Prefecture, Japan.
The latest OLED ink jet news:
A report from Japan updates that JOLED , the OLED inkjet printing pioneer established in 2014, has filed for bankruptcy. The company has been struggling financially for a long time, and will now close down its two production lines and lay off 280 employees (out of 380), as it could not raise funds and has liabilities of around $257 million.
According to the report, display maker Japan Display will take over JOLED technology and remaining operations.
Inkjet printing developer Notion Systems is building a new company headquarters in Schwetzingen, Germany, with a new production plant. The company recently held a groundbreaking ceremony of the new building which will have 3,600 m² of floor space.
Notion Systems is growing at a rate of 20% per year, and these new premises are needed to cope with its increasing number of orders. The company estimates that 18% of its revenue in coming years will be generated from the display industry, for which the company offers machines for inkjet printing of OLEDs, QDs, and more.
Industrial inkjet printing developer Notion Systems announced that is has been selected by the Institute of Chemistry, Chinese Academy of Sciences (ICASS) for organic material R&D. Notion Systems worked together with its partner YixinTech as its system went through a long comparison against other inkjet printers in the market.
ICCAS is a multi-disciplinary research institute dedicated to basic research in broad fields of chemical sciences. One of its major research areas is organic materials for display applications.
According to reports, Kateeva started to ship quantum dots inkjet printing equipment to Samsung Display, for the production of QD-OLED panels. It appears as if Samsung is interested in producing 8K QD-OLEDs, and its current inkjet printing supplier, Semes, is not ready with printers that support 8K QD deposition.
Kateeva announced that it has designed a new system, called the YIELDjet Jarvis, that supports 8.5-Gen substrates and can indeed enable 8K TV deposition. Kateeva says that the Jarvis system has the ability to print using solvent-based RGB inks or nanoparticle inks with its proprietary ink recirculation system to ensure uniform particle distribution.
DSCC says that spending on equipment for the production of large area OLED panels (used in TVs and monitors) have decreased from $3 billion in 2019 to $2.05 billion in 2020, $1.47 billion in 2021 and will drop further to $1.42 billion in 2022.
DSCC estimates that in 2023, the spending on such equipment will be zero. But OLED producers will resume buying large OLED equipment in 2024. Spending in 2024 will amount $2.01 billion, and in 2025 - $1.51 billion.
JOLED (Japan OLED) was established in August 2014 by Japan Display, Sony and Panasonic with an aim to become an OLED medium display producer. Following years of R&D and initial production, the company initiated mass production of its OLEDIO panels in 2021 at its new 5.5-Gen production line in Nomi, Ishikawa Prefecture, Japan.
JOLED's panels appeared on the market, but only for high-end applications such as LG's professional monitor range. According to a new report from Korea, the company did not manage to find a new investor and is now on the verge of bankruptcy.
TCL's CSoT demonstrated a new prototype AMOLED display - a 17" IGZO foldable panel, that was produced using inkjet printing. The company says this kind of panel can be used in tablets, monitors and laptops.
CSoT is progressing with its inkjet printing technology, and aims to start production in 2023. Last year the company demonstrated a 65" 8K inkjet-printed OLED TV panel, in addition to a 14" rollable panel.
Korea-based OLED equipment maker AP Systems (APS) announced that it developed a new system to deposit optically transparent resin (OCR) using an inkjet printing process.
Current OLED production uses an adhesive tape (OCA) to connect the cover glass to the display. But OCA is time-consuming and relatively expensive. OCR, on the other hand, is deposited directly on the panel and is more cost effective. We recently reported that Samsung Display aims to adopt OCR technology in its foldable OLEDs to reduce costs, and is testing inkjet systems made by STI.
In January 2022 it was reported that Samsung has decided to change course, and rely on Kateeva's inkjet printers in its 2nd QD-OLED production line, as the Semes printers do not perform as well as Samsung hoped.
Notion Systems GmbH, a leading manufacturer of inkjet printing systems for functional materials, has received several orders for its newly developed n.jet EHD platform. The EHD (Electrohydrodynamic) technology is a promising technology to reduce structure sizes to less than one micron and enables the use of higher viscosity inks. It supports printing of small structures in microelectronics, semiconductor and next generation display manufacturing. Notion will ship the first four n.jet EHD systems to undisclosed customers in Europe in the third quarter of 2022.
The overall benefits of inkjet printing in the display industry are:
- Printing of smaller features sizes compared with conventional inkjet printing
- Elimination and replacement of various process steps
- Material savings, as printing is done digitally and without masks
- Replacement of expensive process steps
Several presentations and discussions with industry representatives during Display Week 2022 in San Jose USA revealed that inkjet printing technology for OLED/QLED displays will play an important role in future production. Since standard inkjet printing has a limitation at 400 dpi, EHD technology is the way to go. This was one of the main reasons why Notion entered into a cooperation with EHD printhead manufacturer Scrona in Switzerland last year, says Antonio Schmidt - SVP Sales & Marketing of Notions Systems