17.5: Luminance Instability of OLED panels at Various Situations

To decrease tack time during Demura process, images are captured directly after turning on panels or changing patterns and then used to generate compensation data which determines the Demura results. However, the panel's luminance stability in those situations have not been paid enough attention. Seven panels from five different OLED panel producers were tested at various situations which are from turning off to turning on the panel, changing patterns from different gray levels of the same color or from the same gray level but with different colors. Even after the panels were turned on for a while, their luminance is still instable, therefore luminance's stability was also tested. We found that when turning on panels or changing patterns from different colors, the luminance will go up or down 1–5% of the mean of the relatively stable luminance and need 4–30 seconds to get stable. However, when changing patterns among different gray levels but with the same color, there almost no luminance's sudden change at high gray level (above 160) while the luminance goes up or down 0–3% and need half time to get stable at low gray level (32). The results provide a choice to avoid the sudden change of panels' luminance when changing patterns during Demura process while not increasing the tack time so much and also a possible reason that why the Demura results are not good enough. We also found that the luminance instability could be 0–4% at high gray level (RGB192) and 0.3–4.9% at low gray level (RGB32) which should be paid enough attention since the compensation data based on only one image could not be accurate enough if the panels' luminance is not stable.