Whether it’s a human machine interface (HMI), television, calculator or any other liquid crystal display (LCD) device, all LCDs use backlights. LCDs themselves do not produce light. This is in stark contrast to cathode ray tube (CRT) displays, which do produce light. And because of this, they require a separate component to illuminate the panel and ultimately create a visible image. Of course, there are several different types of backlighting technologies, some of which we’re going to explore in this blog post.
LED
One of the most common backlighting technologies is light-emitting diode (LED). There are actually two different types of LED backlights: colored and white. Colored LED backlights are typically used in small and inexpensive LCDs, whereas LED is the preferred choice for bigger, more premium LCDs.
CCFL
Another type of backlighting technology is cold cathode fluorescent lamp (CCFL). CCFL backlights produce illumination via two methods: electron discharge and fluorescence. When compared to traditional fluorescent lamps, CCFLs are smaller and have a longer lifespan; thus, making them an attractive choice for backlighting. However, CCFLs come with several caveats, including high power consumption and heat production. Nonetheless, many display manufacturers still use CCFL backlighting in their respective products.
HCFL
On the other side of the fence is hot cathode fluorescent lamp (HCFL) backlighting. It follows in the footsteps of CCFL by using electron discharge to produce light. The difference, however, is that HCFL is hot, whereas CCFL is cold. In a typical HCFL backlighting configuration, the cathode electrode is heated to a precise temperature; thus, allowing it to emit electrons and produce light. Hot cathodes have a higher power density than cold cathodes, making them more vibrant. However, they also have a shorter lifespan.
EEFL
External electrode fluorescent lamps (EEFL) are typically used for backlighting in large LCDs. As the name suggests, the electrodes of an EEFL are placed on the outside of the tube. This typically results in a longer lifespan while minimizing the risk of damage and failure.
So, which backlighting option is the best? Well, each one has its strengths and weaknesses. With that said, however, LED has become the industry’s most popular choice, and for good reason. LED backlights are energy efficient, long lasting and produce little-to-no heat. For these reasons and others, most LCD manufacturers choose LED backlighting for their products.
