The first LEDs were infrared (invisible).
In 1961 Bob Biard and Gary Pittman were working together on a project for Texas Instruments to develop gallium arsenide (GaAs) diodes. Using an infrared microscope, they found that these diodes emitted significant light in the infrared region.
Bob Biard and Gary Pittman received the patent for the infrared LED, and Texas Instruments marketed the first commercial LED product.
Based on their findings, T.I. immediately began a project to manufacture these diodes and announced the first commercial product, the SNX-100, in October, 1962. Infrared LEDs continue to be used today as transmitters in fiber optic data communication systems.
Semiconductors were a fertile field for investigation.
The work of Pittman and Biard followed intense interest in the properties of semi-conductor alloys at numerous other American industrial research labs in the 1950s. In 1955, for example, Rubin Braunstein, a physicist at RCA Laboratories in Princeton, NJ (now the David Sarnoff Research Center), was the first to report on experiments in which he observed light emission from GaAs and other semiconductor alloys.
Visible spectrum LEDs that could be used for watch displays were developed by Nick Holonyak Jr at G.E. in 1962.
Time Displays ~