C&EN: COVER STORY - FIT TO PRINT

BASF and other ink and pigment producers anticipate, for example, a gradual shift from sheet-fed to digital printing methods, such as ink-jet printing, in a variety of end-use markets, even textiles.

There are two ink-jet processes: continuous, where ink under pressure forms a stream of droplets that are then directed into place, and drop-on-demand, in which the ink is released as needed. Drop-on-demand technologies can regulate ink pressure through electrical and mechanical means, such as piezoelectric print heads, or by temperature, where heat generates vapor bubbles to force ink droplets through the nozzles.

"The entire prepress area has been digitized and computerized for just about all printing processes," Flint's Raksis explains. Digital printing then allows printers to customize each print--for example, in color or with unique information--at relatively low cost and rapid turnaround for small jobs. Other printing technologies have substantial start-up costs--making plates or cylinders for each image--and the overall economics depends on spreading that cost over thousands of copies.

"In general, digital printing has not penetrated industrial printing markets since it is relatively slow and expensive, but improved technology is on the way, and this segment will grow substantially in the next five to 10 years," Raksis says. An exception is in the printing of large-area signs, posters, and banners, where digital printing is already replacing traditional methods.

"Ink-jet printing historically has been geared primarily toward the desktop printer," agrees Mark Carrier, vice president for Avecia's ink-jet printing materials business. Personal or office printing is a relatively small-volume business, but "over the years, the technology's improved considerably in speed, image quality, and cost, such that now it is migrating off the desktop into the realms of the large traditional printing industry."

Avecia created its business in 1985, when ink-jet printing was in its infancy. Along with Avecia, other ink producers, including Sun and Flint, have created divisions devoted to the rapidly growing digital printing market.

"Sun has been rapidly expanding its technology to service this market over the past five to six years," Lewis says. "Such inks have to print at the speeds and temperatures required by these processes, besides being both color stable and resistant to flocculation. The dispersion of pigment into the ink vehicles has to be absolutely ideal; otherwise, blocking of the print head will occur."

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INK-JET PRINTING started with dyes, which differ from pigments in that they are dissolved, rather than dispersed, in the carrying vehicle. "The reason is obvious--you have to push the liquid through very fine nozzles--but dyes have certain advantages and disadvantages compared with pigments," Clariant's Sieber explains. "One major disadvantage is the stability, particularly light and weather fastness, so for long-lasting prints, particularly for outdoor applications, you'd better use pigments."

Improved dispersions are making pigment use possible in ink-jet applications, Sieber and others point out, through more finely ground pigment particles and narrow particle-size distributions. Additives that stabilize the dispersions are an additional approach to reconfiguring inks, including energy-cured inks, to suit ink-jet printers. Yet another is making functionalized pigments, with added chemical groups to make them more soluble or reliable in ink-jet inks.

"The challenge is getting the ink to work with the print heads--it's a hand-in-glove relationship--and then that ink has also got to work on the substrate," Avecia's Carrier says. "So it's getting a balance between ink, print head, and substrate."

A major goal in ink-jet printing is to achieve photoquality prints, and it's created a new demand for higher performance inks and pigments, producers say.

"While printing speed is the most important parameter for industrial applications, image quality is the primary concern in the photographic area," says Christine Halik, head of marketing for photographic, reproduction, and digital printing in Ciba's coating effects segment. Ciba is focusing on tailor-made pigments for ink-jet applications, dyes with improved resistance properties, and polymers for photoglossy ink-jet media or substrates.

Image quality is highly dependent not only on the inks but also on the paper or substrate. A plus for pigment and ink producers is that ink-jet photo prints use relatively large quantities of materials.

"Once ink-jet printing has the durability and the costs closer to what you would pay for silver halide snapshots, it should be able to penetrate a big portion of the photographic market," Carrier says. "It's still very early in the growth curve of digital photography taking off with ink-jet printing, but when it does, it should be a very big business.

"A main thrust of Avecia's business is developing dyes, with a target of 'silver halide-parity,'" he adds.

Equipment manufacturers have begun building photocapabilities into most printers, offering systems for the professional photo market, and developing self-service or retail kiosk and minilab capabilities. The idea is to go from computer to print, simplifying the process and increasing flexibility and customization.

For example, Hewlett-Packard and Kodak created a joint venture two years ago called Phogenix Imaging that launched its first product, the DFX digital photofinishing system for retailers, in February. The $39,900 minilab uses HP's thermal ink-jet technology and Kodak paper and software for image editing, enhancement, and sizing, and to control the work flow.

Potential one-hour services include custom print packages, special-sized prints up to 12 inches by 18 inches, posters, calendars, greeting cards, and CD-ROMs. Phogenix says the DFX system produces "high-quality, low-cost prints that meet or exceed today's retail photofinishing standards."

Partnerships, such as that between Kodak and HP, are common and extend throughout the pigment, ink, printing equipment, printing, and end-user business chain. In addition, many ink and pigment producers bring together internal organic and inorganic color expertise and formulation experience, as well as dispersant, additive, and polymer capabilities from across their companies.

The pigment and ink development process is extremely R&D intensive, producers say. "In all printing applications, it is very important to work closely with the customer, since their needs are often very specialized and we want to make sure our products meet their expectations," Raksis says.

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TEXTILES

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FLEXIBILITY Fabric patterns can be changed quickly and cleanly using ink-jet printing. CIBA PHOTO

Ink-jet technology is finding use in textile printing, where it offers flexibility, customization, short runs, and affordability, for example, when sampling patterns. Ink and pigment producers are responding with products that work both in the print heads and on different fiber substrates.

"Customers are interested in printing in one step, using inks that combine a pigment and binder, so that no fabric preparation is needed," explains Mickael Mheidle, head of new business applications for Ciba Specialty Chemicals' textile effects segment. For this market, the company produces water-based inks that are entirely picked up by the fabrics, leaving no waste products and requiring no cleanup between runs.

Ciba also is developing a range of inks to work with a new textile printer being developed with Reggiani Macchine Spa and ink-jet technology firm Aprion Digital. The system, which they hope will print between 150 and 200 m² per hour at 600 dots per inch, is being tested by key customers.

Last year, DuPont launched an integrated system that combines its Artistri Ink, which uses traditional textile colorants, and Artistri color control and management software, for color matching and reproduction, with an ink-jet printer made by VUTEk. DuPont says the system, which can print 30–60 m² per hour at 720 dpi for wide-width (3 meters) home furnishing applications, reduces cycle times from the many weeks needed with traditional textile printing to a few days.