Why do eink displays need both black & white particles?

brecklundin · 05-08-2009, 08:49 PM

Just pondering the whole contrast problem and was wondering if anyone knows why there really needs to be black and white particles? Could not the same effect be achieved with black particles over a pure white substrate/back-plane?

I have to believe that was one of the first designed with eink but don't know. I also wonder if something like that does not work well due to depth perception problems, you know since the white back layer would be, relatively speaking, a fair distance from the black particles.

Just curious is all.

emellaich · 05-08-2009, 10:46 PM

Not sure I understand your substrate example. let's say that "----" is the top barrier, "b' is a black particle, and "wwww" is the white substrate. Then in order to show black we have:

----------------------------
bbbbbbbbbbbbbbbbbbbbbbbbb

wwwwwwwwwwwwwwwwww

Then in order to turn off the black we let the black fall down and we have:

-----------------------------------

bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
wwwwwwwwwwwwwwwwwwwwwww

which still looks black. The second case would only look white if the black particles could fall down below the white particles. For example, if there are holes in the wwwwww layer big enough for the b's to fall through. In this case we wouldn't have a solid white.

So is this what you meant? Or is it something else? If this is the approach, it doesn't appear that a white substrate would work that well. By making both the white and black out of individual particles they can flow past each other, and yet form a 'solid' surface when their respective shade is at the top.

brecklundin · 05-08-2009, 10:57 PM

not quite since from my understanding the white & black particles are in the same cell and controlled via charge. As described here:

http://www.eink.com/technology/howitworks.html

My question is, why not simply place the layer of cells with just black particles over a background layer of pure white. Then as the particles are directed around the cell, the pure white would show through.

Of course I am pretty sure, after thinking about it, it would never be possible to have a cell show only white since every cell has black with nowhere to go when the need is for just white.

EDIT: Oh, geeze, that is what you wrote...sorry about that, I was trying to read, eat & type all in the dark and all at the same time while watching Outer Limits on Hulu...hehehehe...YES, you are right...thanks!!!

djgreedo · 05-09-2009, 03:09 AM

Maybe they could have the particles black on one side and white on the other, then use a charge to 'flip' them over.

One way or another the contrast has to improve on the next generation of models.

pdurrant · 05-09-2009, 03:17 AM

That's been tried too. (& may still be being worked on AFAIK).

Quote:

Originally Posted by djgreedo

Maybe they could have the particles black on one side and white on the other, then use a charge to 'flip' them over.

One way or another the contrast has to improve on the next generation of models.

kacir · 05-09-2009, 03:26 AM

Quote:

Originally Posted by brecklundin

Could not the same effect be achieved with black particles over a pure white substrate/back-plane?

That would not work.
But there was a version that used white particles in black liquid.

CleverClothe · 05-09-2009, 12:10 PM

Quote:

Originally Posted by djgreedo

Maybe they could have the particles black on one side and white on the other, then use a charge to 'flip' them over.

One way or another the contrast has to improve on the next generation of models.

That would cause problems with making anything other than black or white.

brecklundin · 05-09-2009, 12:34 PM

sure gives an appreation of the tech in eink displays, but also illustrates the some of the inherent short comings as they currently exist. There is an interesting thread about the MIT project to develop eink/epaper displays which overcome the current limitations imposed by this design:

http://www.mobileread.com/forums/showthread.php?t=46414

Interesting stuff.

05-08-2009, 08:49 PM	#1
brecklundin Banned Posts: 1,906 Karma: 15348 Join Date: Jun 2007 Device: mine	Why do eink displays need both black & white particles? Just pondering the whole contrast problem and was wondering if anyone knows why there really needs to be black and white particles? Could not the same effect be achieved with black particles over a pure white substrate/back-plane? I have to believe that was one of the first designed with eink but don't know. I also wonder if something like that does not work well due to depth perception problems, you know since the white back layer would be, relatively speaking, a fair distance from the black particles. Just curious is all.

05-08-2009, 10:57 PM	#3
brecklundin Banned Posts: 1,906 Karma: 15348 Join Date: Jun 2007 Device: mine	not quite since from my understanding the white & black particles are in the same cell and controlled via charge. As described here: http://www.eink.com/technology/howitworks.html My question is, why not simply place the layer of cells with just black particles over a background layer of pure white. Then as the particles are directed around the cell, the pure white would show through. Of course I am pretty sure, after thinking about it, it would never be possible to have a cell show only white since every cell has black with nowhere to go when the need is for just white. EDIT: Oh, geeze, that is what you wrote...sorry about that, I was trying to read, eat & type all in the dark and all at the same time while watching Outer Limits on Hulu...hehehehe...YES, you are right...thanks!!! Last edited by brecklundin; 05-08-2009 at 10:59 PM.

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05-08-2009, 10:46 PM	#2
emellaich Wizard Posts: 1,017 Karma: 3630887 Join Date: Oct 2007 Device: Palm=> Ebookman=> IPaq=> Axim=> Cybook=> Kindle 2=>IPAD 1 & Kindle 3SO	Not sure I understand your substrate example. let's say that "----" is the top barrier, "b' is a black particle, and "wwww" is the white substrate. Then in order to show black we have: ---------------------------- bbbbbbbbbbbbbbbbbbbbbbbbb wwwwwwwwwwwwwwwwww Then in order to turn off the black we let the black fall down and we have: ----------------------------------- bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb wwwwwwwwwwwwwwwwwwwwwww which still looks black. The second case would only look white if the black particles could fall down below the white particles. For example, if there are holes in the wwwwww layer big enough for the b's to fall through. In this case we wouldn't have a solid white. So is this what you meant? Or is it something else? If this is the approach, it doesn't appear that a white substrate would work that well. By making both the white and black out of individual particles they can flow past each other, and yet form a 'solid' surface when their respective shade is at the top.

05-09-2009, 03:09 AM	#4
djgreedo Addict Posts: 285 Karma: 640696 Join Date: Feb 2009 Location: Perth, Australia Device: Kindle Touch 3G, HP Touchpad (Android), Samsung Omnia 7	Maybe they could have the particles black on one side and white on the other, then use a charge to 'flip' them over. One way or another the contrast has to improve on the next generation of models.

05-09-2009, 12:34 PM	#8
brecklundin Banned Posts: 1,906 Karma: 15348 Join Date: Jun 2007 Device: mine	sure gives an appreation of the tech in eink displays, but also illustrates the some of the inherent short comings as they currently exist. There is an interesting thread about the MIT project to develop eink/epaper displays which overcome the current limitations imposed by this design: http://www.mobileread.com/forums/showthread.php?t=46414 Interesting stuff.


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