Some of the latest developments in the area of high performance pigments for inks have been in packaging inks, specifically in the screen printing area.
“In the high performance pigment area, we have focused recently on products for packaging inks and screen inks in particular,” said Christopher Bridge, regional manager Americas, business line imaging and inks, Ciba Specialty Chemicals.
Ciba has recently launched Ciba Cromophtal Magenta ST, which is the first real process magenta with outstanding fastness, according to Mr. Bridge. “This recognizes the fact that more and more packaging inks are being printed as process color, and a high performance offer is needed for some end applications. We also have launched, for packaging inks, Ciba Cromophtal Yellow 2RT, a high performance isoindoline yellow. Our Cromophtal high performance types should be used following normal good dispersion practice.”
High performance pigments are used in a variety of ink applications from screen printing and ink jet inks to UV inks.
“Clariant has been and will continue to pioneer high performance organic pigments for a variety of industries,” said David Dugan, marketing manager, BU ink pigments, Clariant. “One such development, initially intended for the industrial coatings market but also having utility for screen inks and other opaque ink systems, is our new thiazine indigo red pigment, Novoperm THI Red 4g 70 VP2543. This pigment exhibits a clean opaque scarlet shade that has excellent heat and chemical resistance as well as excellent lightfastness.”
Other shades are being developed in this new chemistry and Clariant has plans to bring these products to the market in the future.
Ink jet printing is highly demanding and puts many requirements on the inks it uses. Among those requirements are high fastness, good dispersion and good flow. Ciba offers a product for wide format ink jet that meets these needs.
“Current work is to expand in particular our offers for wide format ink jet applications, where there is a demanding combination of requirements for very high fastness, excellent dispersion, with good flow and ink stability,” said Mr. Bridge. “We have broadened our range of preparations to include a high performance yellow (developed) specially for wide format solvent-based ink jet called Ciba Microlith Yellow 4G-K. This product is recommended in other applications such as in PVC inks for wallcovering, flooring, etc. We are also working on the further broadening of our offers in the whole ink jet area. “The Microlith-K ink jet products are used in vinyl-based inks, which can be formulated to give good adhesion to many substrates, from plasticized and rigid PVC, metal foils, to polymer coated regenerated cellulose film,” said Mr. Bridge. “The high performance pigments are generally formulated for wide application, though they are mainly targeted at liquid packaging inks, screen inks and metal decorating inks.”
“With Microlith-K it is important to follow our guidelines to obtain the best dispersion and flocculation stability, which of course is particularly important to ink jet inks,” noted Mr. Bridge.
Some of these pigments offer special effect characteristics such as pearlescent pigments that achieve a variety of optical effects. This is especially important for inks used in packaging.
Engelhard’s Lumina colors are mica-based effect pigments that feature increased chromaticity at the reflection angle and higher color purity and clarity than traditional interference colors.
“The result is cleaner shades, more saturated colors and stronger flip-flop effects in coatings and inks,” said Stephane Rochard, marketing manager, automotive and powder coatings, Engelhard Corporation.
The colors include turquoise as well as gold, red, green, aqua-blue and red-blue.
Engelhard’s Mearlite industrial-grade pearlescent pigments impart a range of optical effects from a soft, satin luster to a sharp, metallic brilliance in coatings and inks. These effects are due to plate-like crystals of bismuth oxychloride that have a silver-white transparent appearance.
“When using these pigments with paint and inks, one should avoid mixing them with opaque pigments and colorants because special effect pigments are transparent,” said Mr. Rochard.
Specific particle-size distributions are recommended with inks, he added.
High performance pigment suppliers are also moving into the growing area of UV inks. Ciba is currently involved in work to optimize the use of pigment/photoinitiator combinations for UV inks. “As the leading supplier of photoinitiators and pigments, we are uniquely placed to be able to support the development of these types of ink,” said Mr. Bridge.
Another recent development in the high performance area is Clariant’s Hostaperm violet P-RL, a carbazole violet that exhibits superior viscosity characteristics in alcohol solvent ink systems as well as UV flexo. “Violet P-RL possesses almost Newtonian flow characteristics with virtually no thixotropic tendencies, even at high pigment loadings,” said Mr. Dugan.