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What Is a Cold Cathode Light?

Cold cathode lights are small-diameter, tubular lights that resemble conventional fluorescent lights. However, unlike conventional fluorescent lights, cold cathode lights don't use thermionic emission -- a process in which a negatively charged electrode, or cathode, is heated to create a discharge of electrically charged particles, or ions -- so they have several advantages.

How Cold Cathode Lights Work
- Cold cathode lights work by passing an electrical current through a gas or vapor at very low pressure. A high voltage is applied across the electrodes, creating a strong electrical field that causes the atoms of the gas the separate into positively charged ions and negatively charged ions. The positively charged ions bombard the cathode, which is coated with a substance, such as a rare earth metal, which encourages the emission of negatively charged particles called electrons. The electrons accelerate away from the cathode, due to the high voltage, and collide with ordinary gas atoms, causing them to gain energy, or become "excited." When the atoms lose this energy, they give off photons of visible light, known as glow discharge.
Efficiency
- The fact that cold cathode lights use much higher voltage than conventional fluorescent lights means that cold cathode lights are between 10 and 30 percent more efficient; they convert around 20 percent of the applied electrical energy into useful light. Cold cathode lights may use as little as 7.5 watts of electricity per foot and have the longest lifespan of any light fixture, at around 50,000 hours.
Other Advantages
- Cold cathode lights are not completely cold, but their operating temperature, around 392 degrees Fahrenheit, is significantly lower than that of standard, hot cathode fluorescent lights, at around 1,652 degrees Fahrenheit. Nevertheless, cold cathode lights burn up to five times brighter than their hot cathode counterparts. Power is supplied instantly to the cathode tube, which illuminates to its full brightness immediately and remains that way until the power is switched off. Furthermore, unlike regular incandescent lights, the lifespan of cold cathode lights is not shortened by repeatedly switching them off and on.
Applications
- Cold cathode lights are used for backlighting liquid crystal display screens in a wide range of electronic equipment, including flat-screen televisions, computers and digital cameras. These applications employ very thin cold cathode lights, with a diameter of around 0.16 inches, which create large amounts of light. Cold cathode lights are also used in instrument panels in automobiles, light boxes, publicity signage and emergency exit lighting.

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