LED color temperature (SMD 1206 - 0805)

[MesharyHD]

Hello eev community...

Today I have solved my frustration with white smd led, I have wasted more than 200$ just to reach my goal.
I have always wondered how can some companies reach this color on screen,take a look at what I’m talking about ....

nokia 8850


ipad mini




Professional grade LED determined by x,y values which this graph can explain it
https://upload.wikimedia.org/wikipedia/commons/thumb/b/ba/PlanckianLocus.png/1200px-PlanckianLocus.png

However I have tried most of what Digi-Key, Arrow, and masterelectronics has to offer, and I found that the best chip was from lighton it can reach about 8000k white with a far hint of light purplish blue (it has slightly far pink hue which is disadvantage to me)
Here is the chips codes:
1206 LIGHTON (LTW-150TK)
0805 LIGHTON (LTW-170Tk)

I have contacted 2 Chinese vendors from AliExpress and they have provided me with good chips that can reach from 12000k up to 17000k

Here is the chips links:

-1206
http://s.aliexpress.com/eaINBrmE

-3806 (this is side mounted led same size as the 1206)
http://s.aliexpress.com/VvQZnmq2

-0805
http://s.aliexpress.com/eMRFveuM


At last i have successfully moded my Casio watch light using 0805 SMD LED, last 2 in the attachment ....

[floobydust]

The colour may be the LCD polarizer too?

Specialty colour temperature LEDs I have found only from Kingbright and I find they all due to different recipes of the phosphor.

They have one that matches your search, like an ionized mercury vapor rectifier, I'd have to dig it up to see what the part is called.
I tried to take pictures of five specialty blue LED's (3528) from Kingbright but the picture looks terrible.

[Buriedcode]

Yeah... actual colour temperature and spectrum should be measured from the LED itself, not when shone through a transflective LCD, which includes either a bluish or greenish semi transparent layer, as well as two polarizing layers that behave differently at different wavelengths.

It looks like you just wanted a "blue" backlight - which btw reduces the contrast on those older FSTN phone displays, that are designed to have the maximum contrast in the middle of the spectrum (= why they almost always had green backlights). FSTN is better than standard STN, but still won't have a flat response - it will change the colour of your backlight.

A Casio watch will be a simple TN-type LCD (not STN or film corrected STN) and as such will have quite good contrast, but will attenuate both ends of the spectrum, probably the red end a bit more leading to a blu-ish hue with a 5000k white backlight.

I mean, great you've found what you wanted, just that I think you may have been blaming LED specs when in fact you were judging said LED's through several "filters".

[MesharyHD]

It looks like you just wanted a "blue" backlight - which btw reduces the contrast on those older FSTN phone displays, that are designed to have the maximum contrast in the middle of the spectrum (= why they almost always had green backlights). FSTN is better than standard STN, but still won't have a flat response - it will change the colour of your backlight.

I have tried blue LED and I did not like it at all,the 5000k white led looks flat and it will kill the watch for me

[MesharyHD]

The colour may be the LCD polarizer too?

I did not Change the color polarizer it’s stock monochrome

[Buriedcode]

I think what he meant was - all polarizers affect the colour.  Some give it a blue hue, some a greenish hue, and this may not be apparent until you start using different colour backlights, and is a side effect of TN (twisted network) displays.  The only LCD that doesn't suffer this kind of colour skewing are TFT's, and that is because they are active and not multiplexed.