In the battle of flat-screen displays, both liquid crystal displays (LCDs) and plasma displays have their strengths and weaknesses. LCDs are lightweight and often cost less than plasmas. Conversely, plasmas have a wider viewing angle and show crisper images of fast-moving objects. But now a Samsung prototype that uses a new kind of liquid crystal material illustrates how LCDs are overcoming their weaknesses.
At the recent Society for Information Display conference in Los Angeles, Samsung showed off a 15-inch display made with blue-phase liquid crystals, a type of liquid crystal that researchers have known about for years but that no one had ever demonstrated in a working display. Due to the optical properties of blue-phase liquid crystals, the new display has a much wider viewing angle than traditional LCDs do, and it can refresh images on a screen four times faster than early LCDs can, significantly reducing blur. Moreover, the new display can be made in fewer processing steps than today’s LCDs require, which means that blue-phase displays have the potential to be less expensive.
Scott Birnbaum, vice president of LCD business at Samsung, says that the company has no plans to commercialize its blue-phase display yet, but it’s easy to see the device’s potential. The benefits of the new liquid crystal are particularly apparent when watching a video with a lot of action, or one that’s in 3-D, Birnbaum says. There’s a lot of information there, and he thinks that “it makes a difference to have ultrafast switching.”
Today’s LCDs don’t provide a wide viewing angle because of the way that light reflects off them. When a person looks at an LCD straight on, the image is clear, but as she moves to the side of the display, the image fades because light isn’t efficiently deflected at greater angles. Blue-phase liquid crystals, on the other hand, are made of crystals with a highly helical structure that reflects a larger percentage of light over a wider angle.
The other drawback with some LCDs is that a fast-moving object like a baseball has a ghostly tail that marks its trajectory. Birnbaum explains that this is because each frame of motion–and there are typically 60 frames per second–is held on an LCD screen until the next one is displayed. This differs from traditional cathode-ray-tube and plasma displays, in which frames flash on the screen at a rate of 60 frames per second, allowing viewers’ brains to fill in the gaps. Newer LCDs can operate at 120 hertz, and a technology that produces extra images for these extra frames works well to reduce some blur. But due to the way that blue-phase crystals are structured, they are capable of changing orientations at twice the frequency, switching at 240 hertz, and producing a crisper picture.
Another advantage that blue phase has over traditional LCDs is that it’s easier to manufacture. Today’s LCDs require a two-step alignment process to ensure that the image is uniform across the display. First, an alignment layer is put down that acts as a mold for the liquid crystals to sit in. Second, the crystals need to be physically rubbed so that they fit into grooves in the mold and become aligned. The helical structure of blue-phase liquid crystals means that these crystals naturally self-align.
While Samsung didn’t invent blue phase, the company has taken it farther than anyone else, says Philip Bos, a professor of chemical physics at Kent State University and assistant director of the Liquid Crystal Institute. Traditionally, he says, blue-phase liquid crystals have not been used in electronics because they haven’t been able to withstand a great temperature range. In 2005, researchers at Cambridge University, in the U.K., developed a high-temperature-range blue-phase material by altering its structure. While Samsung isn’t forthcoming with the details, Bos suspects that researchers at the company did something similar and added a polymer to the liquid crystals to make them stable enough to use in a display.