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:
A couple of days ago, LG Electronics announced its first OLED monitor, the 31.5-inch 4K UltraFine OLED Pro, model 32EP950. Today JOLED announced that LG's monitor uses the company's printed OLED panels.
JOLED (Japan OLED) was established in August 2014 by Japan Display, Sony and Panasonic to produce OLED displays using inkjet printing technology. In December 2017 JOLED started commercial low-volume production of its 21.6" 4K OLED panels, at the company's pilot 4.5-Gen line.
In October 2020 TCL's CSoT demonstrated some new rollable OLED technologies, and today at CES the company published this nice video you see below that again demonstrates new rollable OLEDs:
TCL first shows a rollable smartphone, that uses a 7.8-inch AMOLED that rolls into a 6.7-inch one. The display features a bending radius of 3 mm and CSoT says it can withstand up to 100,000 sliding cycles.
TCL has been involved with OLED inkjet printing technologies for many years, and the company''s chairman and founder Li Dongsheng yesterday posted that the company will reveal its first printed OLED products next week. Li also uploaded the following video that showcases the company's inkjet printing technology:
This is somewhat surprising as it may be too early for TCL to actually launch inkjet printed OLEDs. TCL has been a long time believer in inkjet printing for OLED displays, and the company has established Juhua Printing in 2016 (together with Tianma and other collaborators) as an "open-innovation platform" to develop ink-jet printing of OLED panels. Last year TCL invested $187 million USD in Japan's inkjet printing developer and producer JOLED, and has also signed an agreement to jointly develop OLED TV printing technologies.
Notion Systems, MBraun and the Fraunhofer IAP develop a novel display industrial production process based on inkjet printing
Notion Systems, MBraun and the Fraunhofer Institute for Applied Polymer Research (Fraunhofer IAP) are co-developing new inkjet production technologies, aimed for the display market - specifically for OLED, QD and microdisplays.
The three partners are combining their respective competencies to present themselves together as a partnership supplier off all-in-one solutions. The Fraunhofer IAP is developing custom-made processes for display manufacturing with tailor-made inks. To achieve an industrial-scale best-in-class process solution, the parties are looking into all major pre-and post-processing steps, the substrate and the production equipment such as the inkjet print head.
Japan-based inkjet printed OLED JOLED announced a partnership with Germany-based AERQ to integrate medium-sized OLED displays in aircraft cabins.
AERQ, interestingly, is a joint venture between LG Electronics and Lufthansa Technik, founded in 2019. AERQ aims to introduce innovative technologies to the aviation industry, and the company provides a digital ecosystem for aircraft cabins that consists of an open IT platform, inseat system, and Cabin Digital Signage. AERQ has already been showing large-area OLED display for aerospace applications (using panels by LG Display).
This is a sponsored post by Notion Systems
Najing Technology Corporation Ltd., the leading Chinese manufacturer of quantum dot materials uses the Notion n.jet display systems for QD displays and light emitting diodes development and pilot production.
The n.jet display series prints functional layers in various steps of display production and for various display technologies. This includes rigid, flexible, OLED, QLED and LCD displays. In addition to its unparalleled precision, the platform complies with highest demands on process environment and process stability.
According to reports from China, TCL says its CSOT OLED inkjet printing project is going well, and the company expects to start mass production at its 8.5-Gen Guangzhou T8 (owned by Huaxing Optoelectronics) production line in 2024.
Earlier this year the Guanghzhou development commission issued a report that says CSOT's investment in this R&D and production project will amount to 46 billion yuan ($6.8 billion USD), and the construction of the actual production line will be in 2021-2023.
Notion Systems and M.Braun announced a strategic partnership in OLED processing equipment. The two companies will combine their best-in-class OLED production technology to improve the production process offers and enhance market access in Asia.
M.Braun is a developer of glove boxes, inert gas purification and automation solutions while Notion Systems is a leading developer of industrial inkjet-printing systems for functional materials, and both companies already enjoy the growing demand of OLED manufacturing in Asia.
In December 2019 BOE 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.
At SID Displayweek 2020, the company demonstrated this display and gave more details regarding its production process and display structure.
Samsung Display has developed a 18.2" 2560x1440 202 PPI inkjet-printed OLED display, that features the highest current efficiency of any inkjet-printed OLED, with the brightness at 350 cd/m2 (full white).
Samsung Display says that the high brightness was achieved by tuning the top-emission device structure with high performance soluble materials. The high pixel resolution was achieved by modulating the jetting waveform for ejecting ink drops and improving the drop placement accuracy by selecting the right ink formulations in terms of viscosities and surface energies.