This report consists of a detailed analysis of 94 patents filed by Samsung Display in relation to QNED, which were released by the second week of October 2020. In the first half of last year, QNED was analyzed as 41 patents, and there was a difference of about 6 months in the additional patents, but surprisingly technological progress was confirmed.
The backplane of QNED is 7T2C TFT, and it was found that the oscillator for aligning the nano-rod LED and the transistor for repair are arranged together. The QNED circuit was configured similar to the TFT structure used in OLED for mobile devices. Since QNED is also a current driven device, it seems that precise control is required. Large OLED uses 3T1C structure.
Among the additionally confirmed contents, the most remarkable one is the built-in alignment transistor (oscillator). Nano-rod LEDs are dropped onto the panel in ink state and aligned by dielectrophoretic force by the electric field applied to the panel. At this time, the number of nano-rod LEDs and the pixel yield are determined according to the alignment waveform. Oscillator technology has never been used in displays.
A concern among experts regarding QNED is yield. Since about 10 to 20 nano-rod LEDs that are supposed to be arranged in a pixel are all electrically connected, a short circuit may occur in the pixel due to self-defect or misalignment of the nano-rod LED. In order to solve this problem, Samsung Display has placed a series/parallel hybrid connection wiring structure and a repair transistor. The backplane manufacturing technology is much more complex than the previously expected structure, but it has been confirmed that it has a built-in technology that can secure a yield directly related to business feasibility.
This report contains patents related to solvents for nano-rod LED inks. Viscosity control is a key technology for the conditions necessary to disperse the nano-rod LED and for good alignment after spraying. Samsung Display was using a breakthrough technology that could change the viscosity of the solvent in the process.
In addition, the configuration of the inkjet equipment was described in detail. The inkjet printer system consisted of a unit that injects nano-rod LED ink, a module that checks the position and amount of the injected ink, and a unit that senses the number of aligned nano-rod LEDs. The inkjet printer was equipped with a technology capable of correcting the ink viscosity and quantity, inkjet head position by analyzing the results evaluated in each process and feeding back to the inkjet unit.
Samsung Display started filing for QNED patents in 2016. The technology development period is only 4 years, but the level of technology confirmed as a patent filed until 2019 is expected to have no problem with investment in mass production equipment in 2021.
If you are a display expert, you can see that the quality of QNED technology is close to mass production as analyzed in this report.