I wonder if we’ll ever see significant improvements in e-ink contrast, which is still very poor. There hasn’t been much progress over the last decade. I’d love to have laser-printer-level e-ink.
For sure, my biggest question is if there are even any theoretical ideas about how to achieve it.
Color is currently dark and so faded-looking, and even the "whites" are so muddy gray, because of the color filter technology. You can improve the number of intermediate color levels and improve the refresh rate, but the contrast and darkness is just an inherent limitation of putting color filters on top of what is otherwise just a regular monochrome e-ink display.
Achieving true CMYK color would require each capsule to contain not just two pigments (white and black) but five (white, black, cyan, magenta, yellow). Two pigments we can do because there exist two electric charges -- the white pigment is charged positive and the black is negative.
But is there any kind of theoretical technology that could toggle five sets of pigments between the top and bottom of each capsule? And indeed, do so in "subcapsules" at a small enough scale to enable perceptual color mixing, the way subcapsules do for levels of gray now?
The only thing I could imagine is if instead of using pigments inside of capsules, we used actual microscopic physical cubes, since their 6 sides would allow for 5 colors. But how you could assemble and electromagnetically control microscopic cubes 180° along two axes of movement that were suspended in some way... I can't even imagine.
There are multi-pigment color e-ink displays that don't use a filter array. E-Ink's ACeP range uses four pigments (CMY+white). The white pigments are reflective, the others are transparent, and you basically sort of sort/stack them with different drive voltages, combining different pigments above white while leaving others below the white layer.
I think OP is dissatisfied even with greyscale e-ink panels, though.
