If Letterhead Smears, Check Ink

Our preprinted letterhead shells are smearing when run through a laser printer for variable-data applications. What could be causing the problem?

Answer: In some cases, the temperature of high-speed office printer/copiers can exceed 400° F. Therefore, preprinted letterhead must use a heat-resistant type lithographic ink that can withstand these high temperatures and extreme pressures. If the ink is not formulated correctly, it will re-soften and adhere to the fuser rollers of the laser printer or drum of a copier.

To avoid these issues, a laser- safe ink should contain: 1) a high percentage of harder drying vegetable oils, 2) a hard binding resin component, 3) a lower percentage of petroleum oil than typical inks, 4) a heat-resistant or synthetic wax, and 5) a solid drier combination to allow full film hardness. Examples of hard- drying vegetable oils include Oticica and Tung oil, combined with fast-drying linseed oil.

One common misconception: an ink needs to be wax-free to be laser-safe. Not so! Though early waxes had low melting points that would cause inks to smudge under heat and pressure, most modern lithographic inks are formulated with heat-resistant, synthetic, high melting point waxes allowing for excellent slip under tremendous pressure.

Another misconception is that a fully oxidizing ink must be used with no petroleum oils. Most oil-based inks will be laser safe more than 99% of the time if allowed to cure for at least 72 hours. Only in rare cases will the ink be slow to cure, usually when non-evaporative wetting agents (such as glycerin) are used in the fountain solution or when the substrate is highly acidic. A small percentage of petroleum oil in the ink actually accelerates the setting speed and allows the oils on the surface to oxidize faster.

Rubber-based or acrylic inks should never be used to print materials that will be used later in a copier or laser printer. Rubber-base inks are formulated for uncoated stocks, contain no vegetable oils, and will never skin. They are designed for quick absorption, actually becoming part of the paper. The synthetic, rubber-like material never becomes heat-resistant, although occasionally it can sink far enough below the surface of the substrate to prevent contact with the laser. Even though the ink is below the surface, under certain conditions it could come off on the copier rollers.

Acrylic inks are similar to oil-based products, as they dry better on coated materials and sit up very well on uncoated stocks, but do not cure like oil-based inks. Because they sit up, acrylic inks will normally be picked up quickly by fuser rollers.

Adding driers or oxidizing varnish can accelerate the curing time of oil-based inks, which means you can use the printed materials in a copier in as little as 36 to 48 hours. The longer you can wait between printing and using the materials in a laser printer or copier, the more “laser- safe” you will be.

Whatever happened to RFID product-tracking tags?

Answer: Early visions of Radio Frequency Identification (RFID) tags imagined them in widespread use in the supply chain, tracking pallets of goods, or even individual merchandise items. The RFID tags were seen to be better than popular barcode markings, since their radio waves of product and inventory information can be read by receivers even if the RFID tag was not in the direct line of sight of the scanner—an attribute that made them seem quite superior to barcodes.

Mandates by Wal-Mart and the Department of Defense to begin widespread use of RFID in inventory control were expected to create a huge market. If massive adoption and mass-production brought tags down in price, a new market was expected to open up for commercial printers.

Then reality set in. Adoption has been slower than anticipated because of costly infrastructure, implementation and operation. RFID tags have trouble making their signals heard through liquids, like shampoo, and moisture-heavy foods, like frozen fish. So most solutions have focused on locating assets inside the confines of a plant, or identifying cartons and pallets.

A recent development may yet benefit printers, this time in paper inventory control. Israeli firm Yedioth Information Technologies is partnering with RFID hardware provider PowerID for a with a new tag technology that can be read from the center of a paper core. Called “PaperVue,” the RFID software and hardware offering is designed to track paper reels as they leave mills and are distributed to web operations.

PaperVue leverages a battery-assisted passive RFID tag called PowerR, designed by PowerID to overcome the challenges associated with tagging reels of paper. PowerID modified the antenna of its standard logistics RFID tag to compensate for the tendency of paper to block radio frequency signals. Paper contains approximate 10% humidity within each reel, so the signals have trouble getting from a core to the reader.

The tags—which are designed to be attached to the surface of the cardboard core on which paper is wound—also can withstand the physical forces and pressures of the winding machine, as well as emit their unique ID numbers through the multiple layers of paper later wound around the core.

GAM sister publication Modern Materials Handling magazine, helped with this perspective on RFID.