LTPS is a cutting edge manufacturing process for making TFT LCDs. Delivering excellent image quality and electron response time, LTPS features the technology of laser annealing, which achieves crystallization of polysilicon film under a temperature of 400˚C and provides faster electron response and low-power consumption, as illustrated below :
Increased electron mobility also enables integration of circuitry on the substrate as well as reducing the TFT dimension. In addition, LTPS allows integration of driver circuits onto the glass substrate. Since both the number of external connections and the bezel size of the substrate can be minimized, the overall system durability is enhanced. And since the TFT of the LTPS LCD is smaller than that of a-Si, the aperture ratio and screen brightness can be increased significantly.
Since the mass production of low temperature poly-Si TFT LCDs began in 1996, the production technology has improved in response to customers' requirements for small and medium sized LCD products which integrate various types of circuits, such as DC/DC converter, level shifter, and DAC.
Chimei Innolux, dedicated to building a strong foundation of LTPS technology, is currently one of the leaders in this field providing superior high-end mobile displays to top-tier customers globally.
A high-resolution LCD means that the number of pixels-per-unit area in an LCD is high. This is usually represented by PPI (pixels-per-inch). Higher PPI means higher resolution. High-resolution LCDs, usually made with LTPS, show clearer images and finer details.
LCDs made with LTPS have smaller TFT & storage capacitors compared with those made with a-Si. The larger transmission area at each pixel of an LTPS LCD can brighten a display while saving more power. When demand for PPI increases, it would be impossible to produce such a display with a-Si because less light could pass through. In such cases, LTPS becomes the best choice for high-resolution LCDs.
To realize a narrow border in high-resolution LCDs, the LTPS technology holds the advantage in pixel and SOP design over those of a-Si TFT LCD.
a-Si Gate On Glass technology, Its driver capability (mobility) is lower, so there is a need to enlarge its TFT device size and thus it becomes very challenging for a-Si TFT to achieve narrow borders in high PPI products.
On the other hand, the LTPS (SOP) technology has a TFT mobility around 100 times that of a-Si TFT. In this case, smaller TFT device size and advanced circuit design (SOP) enable the reduction in panel border for high PPI products.