The Beginner’s Guide to Liquid Crystal Displays

source: shutterstock

source: shutterstock

Liquid crystal displays are a ubiquitous component to modern life, appearing on everything from mobile phones to refrigerators. It has been a long journey from the monochrome character displays of the last century to the multimillion color screens available today, but the future of LCD technology has never been brighter.

Twisted-Nematic LCD Devices and the Dawn of an Industry

Although researchers have been exploring the possibilities of liquid crystals since the late 19th century, the modern LCD industry reached its fundamental breakthrough in 1970 when a Swiss company filed a patent for the first twisted nematic LCD

In a twisted nematic (TN) device, liquid crystal molecules are arranged in columns whose ends are oriented perpendicular to one another, imparting a helix or twisted structure. By altering the degree of twist with an electrical current, each column can switch from blocking light to allowing it to pass through, forming the foundational basis for a pixel and thus for larger displays. Sandwiching this layer of liquid crystal between glass and other components allows a self-contained display module to be created.

TN technology has proven remarkably resilient, and remains the most common schema for LCD devices even today. The technique was taken a step further when Swiss researchers filed another patent for super-twisted nematic displays, which increased the twist from 90 degrees to 180 degrees and more, allowing manufacturers to further enhance the display properties and response times for LCD screens.

Passive and Active Matrix LCD

The earliest LCD screens were built using a passive matrix in which each individual pixel held its on/off state passively, only changing that state when a controlling current was applied. These displays were reliable but slow to update, making them unsuitable for use outside the realm of relatively static displays such as wristwatches and calculators. These old LCDs still see regular use in products like P-tec’s character modules that don’t require a more dynamic screen.

Technological advances soon allowed manufacturers to begin building active matrix displays in which individual pixel clusters could be continually and directly controlled to provide near real-time updates. This revolution led directly to the LCD computer monitors and television screens that have become the modern standard for displays.

Advances in LCD Construction

As the industry advanced, it began to focus on building ever-smaller displays that would eventually allow the smartphone revolution to take place. Two construction techniques were instrumental for this pursuit: thin-film-transistors (TFT) and the chip-on-glass (CoG) process.

Prior to the maturation of TFT technology, LCD pixels had to be controlled by bulky and expensive circuitry, which drastically limited the thinness of its screens. TFT technology allowed manufacturers to replace bulky circuit boards and wiring with a microscopically thin coating of a conductive or semi-conductive material applied to a substrate such as glass. This new technique was smaller and more responsive than legacy efforts and brought the industry into the modern age. The most advanced LCD modules offered by P-tec largely continue to revolve around TFT constructions.

The chip-on-glass technique offered a further refinement in this area as it focused on attaching the LCD driver directly to the surface of the glass. Older techniques had required a back-mounted driver that could account for 50 percent or more of the thickness of a display. As the technique has matured, it continues to allow manufacturers to create thinner displays. This technique is set to be a vital component as the industry enters a new area of paper-thin, ultra-flexible screens that are expected to revolutionize the sector within the next decade.

Liquid Crystal Display Lighting Technology

Early LCD screens were either reflective or transmissive. Reflective displays, like those found in calculators, relied solely on ambient light to illuminate the screens surface, while transmissive displays included a backlight array to light the screen from behind, allowing it to be seen even in low-light conditions.

A hybrid technology known as transflective (transmissive/reflective) allowed a user to toggle the LCD screen between the two states. This was familiar to most consumers in the form of wristwatches in the ‘90s that allowed the screen to be lit up with the push of a button so the time could be read in the dark.

Looking Ahead

As the future becomes present for the LCD industry, TFT and CoG techniques have allowed liquid crystal devices to exit the realm of static displays an enter a new era of fully interactive touch-screen technologies that allow users to control a device entirely through the screen’s surface. The miniaturization and increasingly precise drivers and controllers behind this process get better every year, and they will continue to drive innovations in P-tec’s product designs as LCD screens are integrated into products covering every facet of a consumer’s lifestyle.