iPad’s IPS Display

Maybe I’m completely out of it but there seems to be a consensus that AU Optronics (AUO) is a supplier to Apple’s iPad. Since when did AUO have capabilities to manufacture an IPS-based TFT LCD? And Vinita Jakhanwal, principal analyst for iSuppli, thinks Innolux is part of the game too. I say hogwash.

There are very few LCD companies capable of manufacturing IPS TFT LCD panels and even fewer able to supply the volume required by Apple. There is IPS Alpha, NEC and Hitachi in Japan. IPS Alpha focuses on mid-sized LCD panels geared for TV applications. NEC focuses on high-end IPS panels for monitor applications. Hitachi is more-or-less an IPS R&D and IP company. And then there is LG Display (LGD) based in South Korea. In my opinion, LGD is the only LCD manufacturer that has IPS R&D and volume manufacturing capabilities for the iPad. But I could be wrong.

While searching for more information on iPad’s IPS supplier I came up with an interesting article titled FAQ on the Apple iPad’s IPS display written by John Breeden II. There are some glaring mistakes in the article.

Most LCD screens today use TFT, which is a thin film transistor liquid crystal display. However, having tested both TFT and IPS, I can tell you that IPS offers far supperior image quality and color matching.

I don’t know where to start because it seems Breeden II doesn’t know the first thing about LCDs. First, IPS is a wide-viewing angle LCD technology. IPS re-arranges the liquid crystals so that it twists parallel to the panel, improving the viewing angles compared to a typical TN LCD panel. Second, TFT “is a special kind of field-effect transistor made by depositing thin films of a semiconductor active layer as well as the dielectric layer and metallic contacts over a supporting substrate,” (Source: Wikipedia) and is a technology used by all LCDs, which can be found in notebook PCs, smartphones, LCD TVs and LCD monitors. There can be no TFT versus IPS since any IPS LCD panel will need to make use of TFT technology.

… there are drawbacks to IPS, which make me wonder why Apple would put in the iPad. The first is that TFT displays require only one transistor, which twists the crystal to create an image. With IPS, you need two transistors for every single pixel, one for each end. Right there you are doubling the power consumption of your monitor.

This is entirely incorrect. All TFT LCDs require the use of two transistors. The difference between an IPS and a non-IPS TFT LCD is the location. On an IPS both transistors are located on a single side. The doubling of power consumption is simply ridiculous.

Because more of the surface area of the screen is “covered” by images, it also means you need a much more powerful backlight to shine through.

I think Breeden II might be referring to aperture ratio here. One of the challenges for all TFT LCDs is improving the aperture ratio. This is done by reducing the area taken up by the TFT, which blocks light. As far as I know IPS TFT LCDs do not have aperture ratios that are significantly lower than other technologies. The goal is for images to cover the entire LCD by minimizing the TFT. And when that happens you actually need a less powerful backlight.

… if you are actually using the device, my estimate would be less than three hours of power, and that’s being generous.

I don’t think I would stray too far from what Steve Jobs stated during the iPad introduction. Jobs stated that the battery power to be 10 hours for watching video. I would peg the iPad’s video playback at around 7-8 hours since most companies including Apple tend to share battery life that is slightly inflated. In a conversation with Walt Mossberg after the iPad launch Jobs states that for music the iPad can last about 140 hours. Watch the video here.