Toner is a liquid or dry powder-like mixture that acts as the “ink” for electrophotographic equipment, including digital presses. Digital printers don’t say they have toner in their veins but they do rely on this substance the same way offset printers do ink. Toners for production printing, both black & white and color, are significant contributors to their manufacturing quality and cost.

Unlike offset printers who buy ink from ink companies, however, digital printers typically purchase toner from their machine vendors as opposed to independent toner manufacturers. This scenario is not absolute, however, and there are legitimate “third party,” toner manufacturers that sell direct or to dealers, as well as scam telemarketers and counterfeiters plying this multi-billion dollar revenue stream. (Ironically, well-known ink manufacturers sometimes make the toners for the original equipment vendors but it’s not publicized.)

Therefore, since toner represents both a significant part of the supplies income stream to hardware vendors as well as a potential quality and cost differentiator in the market for them and their printer customers, these companies invest heavily in research and development. And, although some gurus opine that toner capabilities are maximized today and all future development will be in inkjet, experts from Xerox, Hewlett-Packard, Canon, and Océ would say, in the current vernacular, they would be wrong.

Chemical Breakthroughs
Chemical toners for color printing are the most significant breakthrough in toner development in recent years. Canon, HP, Konica/Minolta, and Xerox among others have all brought different varieties to market for certain machines in their lines. According to a white paper from Xerox, conventional toner is manufactured by mixing plastic, pigment, and additives and then pulverizing the resulting block of composite plastic to a fine powder. Then, this powder is processed to remove oversized chunks and ultra fine particles. The process results in non-uniform angular particles with a somewhat wide size and shape distribution.

In any one of the chemical processes, the result is smaller, uniform particles. Canon (also OEM for HP) uses Suspension Polymerization, while Xerox and Konica/Minolta use Emulsion/Aggregation to “grow” toner particles as opposed to pulverizing a solid.

According to its website, Canon’s product, called S Toner, is made through a polymerization technology. Using this technology, monomer is meticulously blended with wax and color materials, and then dispersed into polymer particles. The result is very fine, homogeneous spheres that consist of wax inner layers and polymer outer layers.

Konica’s chemical toner and Xerox’s EA toner use the chemical process called emulsion aggregation to grow uniform particle sizes from even smaller (sub-micron size) toner components. Emulsion refers to the synthetic chemical process to form latex toner resin and aggregation means to bring the toner ingredient’s particles together to form the desired particle size and spherical shape.

Both of these chemical processes permit oil-less fusing systems in the printers, which, the vendors claim, provide sharper image quality, improved fine lines and text, plus higher reliability and lower service costs. While each company argues the superiority of its particular
product, they do agree about oil-less fusing systems and the enormous potential for chemical toners because of the small particle sizes possible. For example, EA toner particles can be as small as Xerox’s 5 microns and Canon’s 7.5 microns. In this area, the industry is just getting started.

“EA was about 10 years in development,” says John Laing, vice president Supplies Delivery Unit at Xerox. “In this case we had to develop a manufacturing process. That takes time and materials design work. And, the hardware to put it into had to be developed as well.” To date, the DocuColor 2240, 1632, and 3535 launched with EA toner. Other DocuColor models planned for the future will employ EA technology. “We intend to use EA everywhere but we probably will find that sometimes conventional will be better. It depends on the hardware,” Laing says.

Laing notes that sometimes system issues, especially in digital color reproduction, do come down to toner. He points out that in monochrome printing if halftones produced move from gray to light gray, you can certainly see it but it’s not as dramatic as in color. There, you actually get a change of color, not just a shade. “Consistency month after month is a system issue,” Laing says, “We need more consistent materials. That’s the challenge of color and toner is a sizable component.”

Basically, development issues are the reason the top of the line DocuColor iGen3 doesn’t use EA technology. Xerox notes that EA and iGen3 were being developed concurrently and were both in the “invention” stage when a toner technology needed to be selected for iGen3. The company’s white paper states, “The iGen3 toner formulation is one of the most complex Xerox has ever developed and although it is conventional toner, the particle size and distribution are optimized and the color gamut is benchmark in the industry.” Laing adds, “ I worked with toner for 20 plus years and have seen many advances and changes and I’m impressed with the set for the iGen. It has innovations that we’re very proud of, especially the color space and uniform gloss.”

Canon’s Carmine Pugliese, director, Sales Adminis-tration, Aftermarket Products Division, notes that his company’s S Toner that gets rid of both oil and developer is now available in certain models. However, like Xerox, Canon is using its special conventional Finer Brighter toner for its top CLC models. “It has good reproduction of the originals,” Pugliese points out.

Liquid Variation
But toner science doesn’t stop with dry conventional and chemical products. There are such things as liquid toners and the former digital press pioneer, Indigo, NV made the most of these. Its patented ElectroInk was one of Indigo’s unique selling points when it launched its E-Print 1000 in 1993 and new owner HP continues to develop it. The company says that this technology delivers offset-quality digital printing by electrically controlling the location of print particles as small as one micron. A look at this technology also shows that its name is based on more than marketing hype.

Jim Bearss, chief technology officer, HP, Indigo Division, explains that with dry toner, pigment is encapsulated in binder systems and either ground or grown into particles 5 microns in size or above. “There is no solvent process,” Bearss says. “ The pigment is pre-encapsulated in the binder and the process melts it and pushes it onto paper. It’s like a Velcro effect. With liquid toner, discrete particles are suspended in a fluid so they can be smaller in size. You add dispensing agents, binders and pigments are still together. Then you create a chemical charge on the surface of the particles and use electric fields to move them around.

“Now, the unique beast, ElectroInk, is partially solvinated. That is, the pigment is in a binder, and the binder is almost in a gel state. It’s not fully dissolved. It’s a particulated gel with chemically unique properties in the way it moves in an electrical field. It’s a hybrid, and it does behave more like offset ink than dry or traditional liquid toner.”

Bearss explains that instead of using a heat and pressure method for printing as do dry toners, ElectroInk goes through a process using thermal, chemical, and mechanical energy that form a kind film that’s transferred to the substrate—“a pigmented polyethylene film.”

Since the early days, however, permanent Electro-Ink adhesion has been problematic and at first only solved by using specially “sapphire coated” substrates. In recent years, however, several sheets that need no special coating have become available for HP Indigo presses but that’s just a few.

Bearss agrees that this chemical bonding remains a challenge. “We’ve made strides to create the right chemistries on the surface for improved adhesion,” he says. “We’re in good shape now. Remember, there is no plain paper. It’s always designed for an application. For example, offset papers are engineered and designed for this process. Now we are getting more interest from the paper mills in working on the surface chemistries. We’re getting good cooperation from the mills. Our goal is to have substrates that have the performance, price, and ready availability as do offset sheets. There are no technical barriers to doing this.”

The Black Side
Nor do there seem to be technical barriers to improvement in the black toner powder that’s been developing for over 60 years. Canon’s Carmine Pugliese says, “For color, the goal is to also drop the costs on toner. Dealers have to make a profit and color production prices have to drop further. For black toner, the trend is to make smaller sizes. The size of toner is critical to digital images. You get better gray scale, better yields, and better coverage.”

In addition to ongoing R&D, Walter Young, Océ’s Program Manager for VarioStream, notes that his company offers a number of toner selections to clients in order to meet their needs for quality and economy. Introduced at Xplor 2002, VarioStream is an entirely new line from Océ aimed at both the IT and commercial printing markets. Part of the flexibility of the machines is that they can be set to run datacenter transactional work like bills at 300 dpi and on demand projects like short run books at 600 dpi. Available toners are a component of this flexible scenario.

“We have four different kinds of toner for the VarioStream,” Young says. There’s standard black, which is the most economical for transactional printing. Most of our customers use this. We also offer a premium black, which has a finer particle size and is appropriate for technical manuals or projects with illustrations, halftones, and fine lines. It is simple to switch between the two levels using our quick-change developer station and you don’t have to worry about cleaning the machine or running out the previous toner. That way you can balance cost and quality.

“In addition, we have custom tone toner, which is monochrome toner for highlight or spot color or a special order to match a corporate color. Again, you use the quick-change developer station and don’t have to worry about running it out. And finally, the MICR toner for financial printing.” (For those who are curious, MICR toner has certain iron content so that check readers can measure the magnetic properties of the characters.)

Young says that Océ has also recently added transponders to its toner bottles that allow a VarioStream system to check to make sure that the toner appropriate for the job has been loaded. If everything doesn’t match, the machine won’t run.

For the Future
Manufacturers continue to not only focus on developing better ways to deliver pigment particles but also on peripherals that will increase productivity and hold down costs. Xerox’s Laing could be speaking for all digital press vendors when he says, “There are plenty of opportunities and applications for toner—especially chemical toner. Things could be put inside, that is different ingredients—something to carry a pigment. People will start to think of applications. Think of it in the broader sense of solutions. People are writing invention proposals week in and week out.”

[时间：2003-09-15  作者：Bisenet  来源：Bisenet]