Digital BW, The Print

> From: Phil Rose <pjrose@...>


> 
> In the case of inkjet pigments, the organic dye molecules are not
> truly dissolved but rather caused to become aggregated (combined) into
> small, *solid* particles--i.e., tiny crystals each containing
> thousands of molecules. These dye particles can be kept in a stable
> liquid suspension (i.e. kept from clumping together) by forming a thin
> layer of a protective polymeric resin (or other stabilizers) on the
> surface of each particle.

This is how it has been explained to me also.  The polyacrylic resin
encapsulate in Epson K3 ink prevents the pigment particles from
agglomerating.  One also needs a high glycol content in the carrier to act
as a dispersant apparently.


>Dye molecules within these tiny crystals can
> absorb light (i.e., be colored) in a similar way as the dye in true
> solution. But not exactly the same.
> 
> Why bother with the extra work? It's because the dye molecules inside
> those pigment particles can be considerably more stabile against light
> and chemical degradation by virtue of being in a "solid state"
> environment--rather than in solution-state (i.e., rather than being
> "molecularly disperse"). The downside of using dye in the solid state
> may be that the pigment dye is less "efficient"--i.e., has lower
> optical absorption (optical density) than comparable amount of dye in
> true solution (i.e., the so-called "dye ink").

Now if one could add a substance, and I am speculating here, to the mix that
binds the pigment dye particles together when they dry or upon reaction with
an inkjet coating then you might potentially get the best of both worlds:
very high density in liquid form and agglomeration on and binding to the
substrate at printing.  One can see how the interaction of substrate,
coating and ink is important and why they need to be developed together.
Think of those two part glues that only bond when mixed together.

> 
> Both kinds of dye can (conceptually at least) be combined within one
> ink; a relatively small amount of free (dissolved) dye component might
> serve to boost the color density (although possibly at the cost of
> some loss in overall fade-resistance).

Or added to the acrylic encapsulate. K3?

In the end though the proof is in the pudding...