|There are other coatings that have particular impact on various roll applications. These are known as "active" coatings. The most common is known as “thermal.”
Direct thermal is a specialty form of ribbonless technology. It utilizes a heat-sensitive coating that, when brought in contact with a thermal printhead generates a deep black or in some cases a color image.
Thermal printers and papers come in a variety of heat sensitivities designed for specific applications.
- Few moving parts in the printer minimizes trouble issues.
- No variation of image from beginning to end of roll.
- Maintenance cost and cost of replacement printheads low. o Maintenance time minimized. o Will perform in any climate or atmosphere conditions as long as paper is enclosed.
- Base paper more expensive than bond, about the same as inkjet coated.
- Susceptible to image fading without proper handling and storage.
- Does not have the “feel” of “plain”, bond, or inkjet papers.
- Image and coatings susceptible to damage by sunlight, solvents, plasticizers, body fluids, carbonless papers, friction, and even other thermal papers.
How to store thermal papers safely
Avoid direct sunlight. Most papers tend to yellow in direct sunlight. Thermal especially so. The printed image also tends to fade when exposed to direct sunlight for extended periods. Thermal paper images also tend to fade when left exposed to conventional fluorescent light for extended periods. To keep the image intact, file as soon as reasonably possible.
Avoid hot or humid environments for long-term storage. Although thermal can be used in hot and/or humid environments, it is best to store imaged papers at temperatures lower than 80° F and a relative humidity lower than 65%.
Thermal rolls may be stored for the short term at higher temperatures, it is best that for long-term storage the same criteria are used.
Thermal coatings begin to activate (develop color and image) in printers between 140° F and 210° F and reach full color density at between 160° F and 240° F. Blanket activation has occurred under extended atmospheric conditions of high temperature or humidity. If thermal papers are to be used continuously, e.g. for more than 24 hours, at temperatures exceeding 105° F, be sure to pay attention to ambient temperature and humidity as well.
Avoid contact with plasticizers such as PVC. PVC contains plasticizers such as phthalate to increase flexibility. However, prolonged contact with PVC reduces the image forming ability of the coating and causes printed images to fade.
Phthalates are also found in adhesive cellophane tapes, causing image fade. If you need to stick thermal paper to something and you are not using MAXStick, use double-sided tape on the back of the thermal sheet.
Some thermal papers have wax-type coatings which may contain plasticizers as well. Do not store conventional thermal papers together.
Avoid contact with solvents or solvent-type adhesives. If you operate in an environment where solvents, especially organic, or solvent-based adhesives such as acetone, alcohols, ethanol, methyl acetate, turpentine, ketones, esters, etc. are used, be careful in handling thermal media. These substances can cause color formation and damage to image.
Body fluids such as sweat can cause the printed image to fade.
Friction, scratching, or pressure from fingernails, paper clips, hard plastic or metal objects can cause images to develop obstructing the printed image.
Images that face one another can transfer images. Store thermal sheets and tapes with the images away from one another.
Direct contact with carbon and carbonless papers. Either can cause thermal images to fade or reduce printability of the roll.