Sony Corp explained about the small-size OLED panels that are used for the electronic view finder (EVF) of its digital camera and its head mounted display (HMD) at SID 2012, which runs from June 3 to 8, 2012, in Boston, the US.
A 0.5-inch 1,024 x 768-pixel panel is used for the company's "Α" series of lens interchangeable digital cameras, and a 0.7-inch 1,280 x 720-pixel panel (resolution: 2,098ppi) is mounted in its "HMZ-T1" HMD.
This time, Sony showed the two panels, both of which realize color display by combining white OLED materials and red, green and blue (RGB) color filters. The high resolution was achieved by forming driver elements on a silicon (Si) substrate. The resolutions of the 0.5- and 0.7-inch panels are 2,560ppi and 2,098ppi, respectively, and their pixel pitches are 9.9μm and 12.0μm.
The OLED elements of the panels are formed by using low-molecular light-emitting materials and a vapor deposition technology. And white light is created by stacking RGB fluorescent materials. Though red and green phosphorescent materials have already been commercialized, Sony did not use them in consideration of product life, reliability, cost, etc.
Sony optimized the thicknesses of the electron transport layer (ETL), emission layer (EML) and hole-injection layer (HIL)/hole transport layer (HTL) for improving the light-emitting materials' quantum efficiency and stabilizing the balance of their carriers. For example, in the case of the blue light-emitting element, the ETL, EML and HIL/HTL are 140nm, 30nm and 40nm, respectively, realizing a high quantum efficiency and a long product life at the same time, the company said.
In regard to the technology for realizing a high resolution with a Si substrate, Sony will make an announcement June 8, 2012 (local time, thesis number: 70.4L).