Colour eink has been possible since the resolution got good. You need four pixels in a block for each pixel.
It's not viable without a bright front light because:
1) If the dye filter was perfect each colour subpixel PHYSICALLY and MATHEMATICALLY only has 1/3rd of the light.
2) Real dyes are not perfect. You lose about 4/5th of the reflected ambient light.
3) The best layout isn't R G B, but
G B
R G
or similar blocks. So you need 600 DPI, or else a 300 dpi screen is only 150 DPI. A linear RGB layout would give 100 x 300 dpi or else an underlying 900 x 300 DPI is needed.
4) Why is colour printing not dim? Because it uses C Y M K subtractive mode. So does colour photographic film, though it started using R G B. The Lumière Autochrome was the first commercially successful colour process in 1907. It used a layer of random coloured (R G B) dots in front of the emulsion. The images were dim as have been demonstrated coloured eink. Colour photography did exist from the late Victorian era once they had plates sensitive in the red. It was very specialist.
A lot of the power on LCD is the backlight. You have losses in the LCD, the glass conductive areas, the two polarisers and the dye filters. Early ones used R G B stripes, but now the
G B
R G
or similar layout is often used. The OLED /AMLED is almost always the square block rather than stripes.
Mirasol is the only static low power colour technology that I've seen. Qualcomm wants too much in royalties, and often they double dip, they like a percentage of the total product ex-factory price. There was a reader using it with two brands, one in China and one in Korea, connected with bookshops. You see them at a very high price on eBay occasionally. It was a flop. I don't really know if the problem is cost or quality. The quality is very poor compared to LCD, though it can just about do video.
I've been hearing every year for about 12 years that colour eink is about to be released. Well it was and almost no-one is using it as the front light is less efficient than LCD backlight or OLED. It's nearly useless with ordinary indoor ambient light.
The fact is that ereaders are a niche. Most ebooks are read on phones and tablets. The eink is ideal for the dedicated reader of novels. Colour isn't needed. The cost is already high compared contract phones or a $60 tablet. Anything that dramatically cuts battery life (x5 brighter front light, i.e. about 125% setting based on 25% needed for poor ambient light levels) or increases cost can't compete with LCD tablets.
Quote:
Originally Posted by Marinolino
Wacom has disclosed to Good e-Reader at Connected Ink 2019 about the new technology and it will be in a series of products in late 2020 and target the digital note taking or e-note sector.
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Not for the ereader market. Sony don't make ereaders now. Their Electronic paper (10" & 14" approx) are for annotation of PDFs. Expensive corporate products that can't even do ebooks. PDFs are not ebooks.
Such products work better with a Wacom digitiser than using only touch (you need resistive anyway as Capacitive & IR are only good for a touch GUI, too low resolution for handwriting or sketching).
No mention of ereaders by Wacom. The ereader bit is pure speculation by Good eReader.