Sharp: Mobile Displays with IGZO, UV2A
Sharp FYQ1’11 consolidated financial results presentation, page 5:
- LCD Color TVs: 156.0 → 154.3, -1.1%
- LCDs: 261.0 → 188.0, -28.0%
- Mobile Phones: 133.6 → 92.5, -30.8%
Revenues, in billions of yen, declined year over year in all three display sectors for Sharp. Due to deteriorating ASPs, revenues dropped despite LCD Color TV shipments increasing 22.3% Y/Y to 3.29 million units.
In the Consolidated Financial Release, page 4:
Meanwhile, in mobile LCDs, we will accelerate conversion of production lines at the Kameyama Plant and a shift to growth areas, including LCDs for smartphones and tablet terminals. At the same time, we will work to commercialize mobile LCDs using oxide semiconductor, InGaZnO (IGZO), developed in collaboration with Semiconductor Energy Laboratory Co., Ltd. This will allow us to create high value-added LCDs for next-generation mobile devices, featuring high definition, thin profile and low power consumption, which will contribute to enhancing the competitiveness of our LCD business.
SEL and Sharp jointly announced their Continuous Grain Silicon (CGS) technology back in 1998. CGS sported higher electron mobility: 600x amorphous silicon (a-Si) and 3x low temperature poly-silicon (LTPS). One of the benefits of high electron mobility is the possibility of integrating circuitry on the glass substrate itself and reducing the number of physical external connections, reducing the overall size of TFT LCDs. Another advantage is the ability to integrate more pixels. The 3.5-inch IPS LCD Retina Display in the iPhone 4 is based on LTPS and sports a class-leading pixel format of 960×640.
IGZO is related to CGS in that improving electron mobility is the goal. IGZO offers 10-30x electron mobility compared to a-Si but has the potential for cost reduction compared to LTPS. On April 21, 2011 Sharp made an oxide semiconductor announcement:
In collaboration with Semiconductor Energy Laboratory Co., Ltd., Sharp has developed and will commercialize a thin-film transistor using a new material, InGaZnO, a world’s first. High energy performance LCD panels will be made possible by downsizing the transistor and by increasing the light transmittance for each pixel. In addition, Sharp’s unique UV2A technology will achieve high display quality small- and medium- size LCD panels.
Smaller TFTs lead to improved light transmittance: more light passes through using the same backlight or at the same brightness level, backlight energy consumption is reduced. The smaller TFTs that IGZO allows can also be used for higher pixel density TFT LCDs.
Sharp’s UV2A technology precisely aligns liquid crystals to reduce light leakage resulting in improved contrast. One disadvantage of LCDs compared to OLEDs is the black level: LCDs generally show a dark grey whereas blacks on OLEDs are pure. Combine IGZO and UV2A and the possibility is high for a spectacular mobile LCD to be manufactured before the end of the year.