Yesterday we posted that TDK started to mass produce transparent PMOLEDs, and now we have some technical updates. It turns out that TDK is not using transparent cathodes and anodes: only the anode is transparent, while the cathode is still made of metal. What they did is reduce the line width of the cathode so only a part of the pixel is covered. TDK calls this panel structure "thin-line electrode structure".
This is how they achieved 40% transmittance. This also explains why viewing this display from the back side is impossible (it is not clear - although parts are showing). TDK claims this is good because users will not want other people to view their phone display from the other side.
TDK used a white OLED with color filters to bring this to market as soon as possible, even though this uses the brightness of the panel (current brightness is 150 cd/m2).
Finally, TDK is producing these panels at TDK Micro Devices fab in Kitaibaraki City, Ibaraki Prefecture, Japan. TDK has two production lines for these panels. These were hit in the earthquake. One of the lines was restarted on April 8th and the second on May 9th.