From the first generation of AppleWatch to the fifth generation, the OLED panel of Apple Watch uses the common LTPS low-temperature polysilicon as the back substrate material. In OLED panel, in order to improve the resolution of the panel, the conventional method is to increase the electron mobility of TFT and make the capacitance smaller. At the same time, because organic light emitting diodes have multiple transistors per pixel, the capacitance size must be smaller.
Smaller capacitance will inevitably delay the channel resistance signal, and the most effective method is to improve the electron mobility through LTPS to achieve the effect of saving electricity. However, LTPS still has a big problem. It is difficult to be applied to large-size substrates, and LTPS does not optimize the high-performance state of small and medium-sized organic light-emitting diode panels, that is, we often say that the high refresh rate screens of mobile phones and notebooks will all be under LTPS, which will bring higher power consumption.
This means that if Apple wants to use a more energy-efficient screen with a higher refresh rate on the iPhone, iPad or even MacBook, it must find a suitable substitute.
At this time, LTPO appeared. The full name of LTPO is low temperature polycrystalline oxide, that is, low temperature polycrystalline oxide. Like LTPS, the electron mobility of oxides is about 100 times that of traditional amorphous silicon, which can combine the advantages of LTPS and IGZO at the same time to achieve higher charge mobility at lower production cost and provide stability and scalability.
According to the patent document of LTPO process, LTPO needs to build an oxide layer on the basis of LTPS. Last year, one of the most important issues was that manufacturers needed to ensure that the characteristics of transistors in the original LTPS interlayer dielectric were not affected when the oxide layer was laid. As Apple began to cooperate with LTPO to mass-produce OLED screens and put them on AppleWatch, which has the largest share of smart watches, it proved that Apple has taken a big step forward in mass production of LTPO.
So we also saw the excellent endurance parameters of AppleWatchSeries5 at the new product launch conference. Under the same brightness, it saves more than 65,438+05% power consumption for the OLED panel, and depends on the officially customized hardware. The minimum refresh rate of 1hz and the maximum refresh rate of 60Hz provide an effective guarantee for the constant bright display and 18-hour battery life of the AppleWatchSeries5.