The march towards mass production of the high brightness blue LED
30 June 2023
Rewind the clock 30 years to 1993, red, orange, and yellow-green LEDs were readily mass produced and available in the market. However, although blue LEDs utilizing different substrate materials were available in the market, production quantities were very limited. In fact, these blue LEDs were not as bright as the red and yellow-green LEDs. Therefore, because of the brightness difference between these 3 colors, balance could not be achieved between the three primary colors (red, blue, yellow) necessary to reproduce any color, including white. Various manufacturers and research institutes had been working to develop practical blue LEDs. If you are familiar with the period around the early 1990, you may remember that all LED Departure Boards installed at train stations, for example, were displayed either monochrome (red or orange or yellow-green) or tri-color. Due to the lack of practical blue LEDs, white or full colored displays were not possible. Fast forward 30 years, as the three primary colors of red, green, and blue with balanced brightness are available, more and more departure signs are being displayed in full color.
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