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neiich45 · Joined: 16 Dec 2011 Posts: 60 Location: England

to further improve the external light efficiency ηe can take the following measures: ① transparent material with high refractive index (n = 1.55 is not ideal epoxy resin) covering the chip surface; ② the chips processed into hemispherical crystal surface; ③ with eg for large compound semiconductor crystal substrate to reduce light absorption. some people have used n = 2.4 ~ 2.6 in the low melting point glass [component as-s (se)-br (i)] and for sealing of thermoplastic large cap, can infrared gaas, gaa, gaalas the led 4 to 6 times more efficient . marker boards
the mid-70s, the introduction of elements of in and n, the led produces green (λp = 555nm), yellow (λp = 590nm) and orange (λp = 610nm), luminous efficiency is also increased to 1 lumen / watt. to the early 80s, there's gaalas led light source, so red led light efficiency of 10 lumens / watt. early 90s, red light, yellow light gaali and hair green and blue gai successful development of two new materials to make led light effect has been greatly improved. in 2000, the former is made of led in red, orange area (λp = 615nm) of the luminous efficiency of 100 lm / w, which made the green zone。led signs outdoor
but others already have substantial production capacity of the industry disagree, some japanese led industry believes that nichia chemical's strategy to make the japanese blue and white led in the competition, gradually europe, america and other countries to seize the initiative led industry, when japanese led industry as a whole will cause serious injury. so many firms will do everything possible to carry out the development of blue led production. at present, except at the chemical and sumitomo 。led signage