PPI

During Display Week 2023, the institute demonstrated its latest displays, including the world's highest-density OLED microdisplays, reaching a PPI of 10,000 with a pixel size of only 2.5 um.

Fraunhofer's 10,000 PPI display was e a 0.18" 1440x1080 (monochrome) panel, produced on 300 mm wafers, using a 28 nm backplane process. The Fraunhofer also showcases ultra low-power microdisplays, and more technologies.

Universal Display announced that it will detail advances in its latest PHOLED materials at Display Week 2023. The company's latest red, green, and blue PHOLED materials offer a narrow emission spectrum, which increases the efficiency of OLED devices, in addition to enhancing the color gamut.

UDC also unveil a new OVJP system printed on a 200mm x 500mm Corning Astra Glass substrate. UDC will also showcase the first-ever fully printed seven-layer (HIL/HTL/EBL/EML/HBL/ETL/EIL), 80 PPI, green commercial-level PHOLED device fabricated by its R&D OVJP system that has comparable device performance with vacuum thermal evaporation (VTE). 

The Fraunhofer FEP research institute announced that it has developed the world's highest-density OLED microdisplays, reaching a PPI of 10,000 with a pixel size of only 2.5 um. The Fraunhofer will demonstrate a 0.18" 1440x1080 (monochrome) OLED microdisplay next week at Display Week 2023.

The new microdisplays were produced on 300 mm wafers, using a 28 nm backplane process. The Fraunhofer explains that most OLED microdisplays to date are produced on 200 mm wafers, using CMOS processes ranging from 90-250 nm. The institutes new technologies enables the the performance increase in OLED display processing. 

Visionox is introducing a new OLED production technology, called Visionox Intelligent Pixelization (or ViP for short) that enables higher-density display production, at over 1,700 PPI.

The idea behind ViP is to replace the fine metal mask (FMM) method with photolithography-based pixel patterning. The process offers several advantages, mainly the increase of aperture ratio to almost 70% (Visionox says the currently reach 69%). FMM methods usually achieve up to 30%, which means that brightness, efficiency and lifetime can all be increased.

In 2021 The Korean government launched a new project that aims to develop technologies for the production of OLED microdisplays for AR applications. The project is led by AP Systems (APS Holdings), and aims to produce a direct emission OLED microdisplay with a resolution of 4,000 PPI by 2024. Earlier this year APS developed FMM masks that reached 1,000 PPI.

APS now announced that it has produced a 3,000 PPI direct-emission OLED microdisplay, based on its FMM technology. This is very impressive progress.

LG Display has demonstrated a 12" 100 PPI full-color stretchable MicroLED display. The display can stretch up to 20% (to create a 14" display).

The display is said to be "close to commercialization" - as it is highly flexible, durable, and reliable. LGD says that it is the world's first full-color high-resolution stretchable display that was ever produced. But we do know that companies have demonstrated stretchable OLED displays in the past, for example Samsung with its 13" stretchable display shown in 2021.

Yang Joon-Young, a VP at LG Display, says that recent improvement in OLED technologies will cause an industry shift from LCoS devices to OLED microdisplays in AR systems. LCoS will find a market in low-cost AR headsets, but most AR solutions will be based on OLEDs.

Next-generation VR systems, which will require higher pixel densities, will also switch from LCD and mobile AMOLED displays to OLED microdisplays that will offer pixel densities of over 3000 PPI.

In 2021 The Korean government launched a new project that aims to develop technologies for the production of OLED microdisplays for AR applications. The project is led by AP Systems (APS Holdings), and aims to produce a direct emission OLED microdisplay with a resolution of 4,000 PPI by 2024.

According to reports from Korea, APS Materials has managed to develop a 1,000 PPI FMM mask, and is now building a new R&D line that will be used to produce direct emission OLED microdisplays using FMM technology. The new APS production line will include OLED deposition and encapsulation.

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

Japan Display (JDI) announced that it has developed a new OLED deposition technology, which they refer to as eLEAP, that is cost effective and can be used to create OLEDs that are brighter, more efficient, and longer lasting compared to OLEDs produced using mask evaporation (FMM). eLEAP also enables OLED freeform deposition. JDI regards its new technology as a " historic breakthrough in display technology".

eLEAP is based on a lithographic method, and does not require any masks. The main advantage seems to be that OLED displays produced by eLEAP technology can achieve an aperture ratio of 60%, compared with FMM OLEDs which achieve a ratio of about 28%. This means that the OLED displays can be driven at lower currents - which extends the lifetime, improves the efficiency and also enables higher-peak brightness when needed.