Blue Leds

[kujawski]

When did blue leds actually become available?
red ,orange, green and yellow, had been around for years,

why did it take so long to produce a blue?

[heathfield]

A product worth billions of dollars annually. Invented in 1971 by Jacques Pankove at RCA Labs, blue LEDs had a poor light output. The present high intensity blue LED was developed in 1993 by Prof Shiju Nakamura while working for Nichia Corporation in Japan. They made millions from them, but only awarded the inventor �200. He later sued, was awarded $189 million by a court, but settled with the company for $8.1 million.
The difficulty was in determining a suitable chemical mix, and then in getting the mix to adhere to a substrate in a manufacturing process.