Digital BW, The Print

Ernst,

Oops, I forgot one variable in my list.  It's a biggie, too. The manufacturers can also add anti-oxidants. In fact anti-oxidant technology was first deployed to solve the early PE cracking issue in RC prints. In the early days, field failures tipped the RC paper manufacturers off to a problem that was caused by the switch to TiO2 whiteners.  When exposed to light TiO2 can generate free radicals that leads to peroxide formation and subsequent embrittlement/cracking of the PE layers (as well as severe silver tarnish in silver gelatin RC B&W prints. Anti-oxidants greatly reduced these problems, and I believe anti oxidants were once again enlisted to help control the ozone attack of the dyes in microporous inkjet papers (recall, the Epson 1270 era "orange fade" problem).

Your spectral plot database is growing!  Very cool.

kind regards,
Mark

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Ernst Dinkla <edinkla@...> wrote:
>
> Op 13-1-2011 16:17, Mark schreef:
> 
> > I believe there are several factors that influence OBA burnout and
> > media white point stability. Here are some of the key variables.
> >
> > 1) concentration of OBAs, ie.  how much does the initial media color
> > depend on the incorporated OBAs. If very little, then total burnout
> > produces only slight effect. If a lot, then total burnout produces
> > large effect.
> >
> > 2). Location of OBAs. When located in top microporous coatings, the
> > OBAs are extremely sensitive to oxidation (just like other dyes). The
> > oxidation can be photochemically induced, but even more so due to
> > ozone induced oxidation. The OBA's are more protected when located in
> > subbing layers and paper core.  Many RC papers, for example, have
> > subbing layers below the top ink receptor layer and above the PE/TiO2
> > layer where the manufacturer can include some OBAs.
> >
> > 3). Molecular structure of the OBA and interaction with the layer(s)
> > in which they are embedded. For example, swellable polymers will
> > indeed protect them more from oxidation, which in part explains why
> > OBAs in traditional darkroom type photo papers have not gotten as bad
> > a reputation (although some problems have been experienced in the
> > field with traditional photo papers as well).
> >
> > 4) As a corrollary to item 3), the pore size of the micro/nano porous
> > silcates used in the inkjet paper probably plays a role as it can
> > also affect the oxygen penetration rates to the OBAs as well as the
> > final physical shape of the OBA molecular chain structure due to
> > electronic charge influences from the silicates distorting the bonds
> > in the dye molecule.
> >
> > 5) Inclusion of additional tinting pigments in the paper
> > size/coatings to achieve cooler media white point thus lessening the
> > need for higher OBA concentrations.  Typically you will see lower L*
> > values for papers that add some cool-white hue with tinting
> > additives, and UV-cut spectral data should still show blue wavelength
> > region effects due to the added colorant.
> >
> > There's undoubtedly other variables as well, but these are some key
> > variables that affect OBA fading impact on media white point
> > stability.
> >
> > cheers, Mark http://www.aardenburg-imaging.com
> 
> Mark, thank you.
> 
> Printed it out  to remind me of all the variables, some I knew, the
> other ones about the silicates structure escaped me. For example the HP
> Advanced Photo Paper Glossy scored well on keeping its white but has a
> micro poreus layer suitable for both dye and pigment inks so I guess
> with no additional swellable coating at the top. HP
> 
> 
> -- 
> Met vriendelijke groeten,   Ernst
> 
> Try: http://tech.groups.yahoo.com/group/Wide_Inkjet_Printers/
> 
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