Liquid crystal display (LCD) screens are omnipresent in our technologically saturated lives. Having largely displaced the older CRT screens, LCDs make up a large portion of the digital imaging we see all around us. They are present in everything from our ubiquitous smartphones and computer screens to digital billboards, wristwatches and vehicle and aircraft instrumentation. How do flat panel LCD screens work? One can often find videos and articles documenting eager teardowns of new devices, but few delve beyond the hardware and into the materials and design behind the screen itself. For this series of blog posts, we will be review some aspects of display technology , why they work, and how they are assembled. To illustrate my points, I’ve disassembled a legacy Sony Ericsson® S500i phone and subjected it to optical microscopy with a at various levels of magnification. Figure 1 shows the S500i displaying a solid-white screen at 400 times magnification.
Figure 1 shows the red, green, and blue subpixels that are in the screens on our devices (a “pixel” usually refers to the set of colored subpixels). My S500i was old enough that one could make out the different subpixels with the naked by peering closely; these days individual pixels are too small to see by visual inspection. One might be curious about why screens have red, green, blue and blue pixels? Most people are probably familiar with the color wheel that uses red, yellow and blue (RYB) as primary colors, taken as common knowledge and still used by many painters and artists. One the other hand, lighting, display, and online graphics industries use red-green-blue (RGB), as it produces a larger range of colors than RYB. In color theory parlance, this set of colors is called the gamut. RGB is specifically designed to capitalize on the three types of color receptors (cones) in our eyes, which detect red, green and blue light. The most effective way to cause our eyes to see colors is to trigger those cones directly with their specific wavelengths.
Figure 1: Powered LCD screen of a Sony Ericsson S500i at 200x magnification.