You’ll spend most of your time looking at the display more than anything else but what are smartphone display panels made of?
As with any technology, smartphone display panels are a mega business on their own. Japanese component and notebook giant Toshiba has had to brush aside rumours that Apple was planning to invest in a new production line built by Toshiba Mobile Display, such is the demand of high-quality, high-resolution display panels.
But when you start looking at the specs of smartphone displays, it can get very confusing very quickly. You might think you’re just looking at a bunch of pixels but how those pixels are created can affect everything from the price of your phone to how long the battery lasts.
The type of display your smartphone has is typically described by an alphabet soup – LTPS, AMOLED, SLCD, Super AMOLED and TFT LCD all represent different technologies used in the production of display panels. Knowing what each type does, its benefits and drawbacks will help you understand just how good (or not) your phone is.
LTPS – Low-temperature polycrystalline silicon
If you see these written as a display type, forget it – LTPS is a description of a manufacturing process, not a display technology. Low-temperature polycrystalline silicon can be used to make different types of screens – AMOLED as well as standard LCDs. It’s a way of creating tiny silicon crystals that go into making the pixels of a display. The “low temperature” part is important because it means this process can create screens using low temperatures, allowing low-cost substances such as plastics to be used as the backing material on which the display panel is infused or created. As a result, it also means you can create more flexible display panels.
AMOLED – Active-matrix organic light-emitting diode
Okay, this is a type of screen technology. OLEDs or organic light-emitting diodes have been around for a while now and they have one significant benefit: to produce black, you simply turn an OLED off. To produce a light colour, they have to produce light. So they have huge potential for power savings in mobile devices.
The “Active matrix” describes how each OLED is addressed or controlled. The alternative is a passive matrix display where rows or columns of OLEDs are addressed rather than individual pixels. As a result, AMOLED displays are not only brighter, use less power, they’re also faster.
The problem is that AMOLED panels are in high demand, with that demand exceeding supply.
The other issue with AMOLEDs is that because of the fabrication process, they can be difficult to see if viewed in direct sunlight. AMOLED panels are typically three layers, the AMOLEDs, the touch-panel sensor layer made of glass and then the top glass protective surface with air in between each layer. The diffusion of light through all three layers causes the AMOLED light to be diffused and difficult to see.
AMOLED panels are used in a number of phones including Google’s Nexus One and early versions of the HTC Desire.
Super AMOLED
So Korean giant Samsung decided to come up with a different method that combined the top glass layer and the touch-panel glass layer into one.
This promotional video gives you a brief overview of Samsung’s Super AMOLED technology.
By reducing the number of layers and removing one air gap, light dispersal is reduced, making these AMOLED displays easier to see in bright light.
Samsung uses the Super AMOLED panel in its Galaxy S phone and is expected to use it inside the upcoming Nexus S.
SLCD – Super liquid-crystal display
LCD has been the mainstay for display panels from PDAs to notebooks to TVs over the last 15 years or so. What makes Super LCD so super is said to be improved light bleeding so that blacks actually look a bit more like black than they typically used to, giving better overall contrast. In comparisions with AMOLED, some reviews suggest that SLCD gives warmer colours than AMOLED. However, battery life appears to be worse with SLCD displays.
SLCD shouldn’t be confused with S-LCD, which is the name for the Samsung/Sony joint venture for manufacturing LCD panels.
Smartphone maker HTC began using SLCD panels in its Desire smartphones in August 2010 due to shortages in AMOLED panels from Samsung. If you have an early Desire, it’ll more likely have an AMOLED panel whereas those manufactured after August 2010 will have an SLCD panel instead.
IPS – In-plane switching
Apart from poor contrast ratios, the other issue with LCD panels is poor viewing angles. The further you move of the centre axis of an LCD panel, the worse the image becomes until you begin to see the reflected negative of that display. In-plane switching is a more expensive solution to the viewing angle problem by changing the direction in which the liquid crystal molecules move. So instead of the normal right-angle or perpendicular switching, IPS panels switch molecules in the same plane as the panel. It means light transmitted through the molecules can be seen at (almost) any angle.
IPS technology is most often used in LCD monitors – and usually at prices three times the going rate. It’s the technology behind Apple’s Retina display in the iPhone 4.
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