Direct Thermal Imaging is a common process used in many Stamped Epoxy Floors College Station applications. This process does not use ink; instead the paper is coated with a special material that turns dark when heated. The image is made when heat pulses applied by a direct thermal print head are delivered to the coated surface.
Because the only consumable part of the print system is the special paper or film, commercial direct thermal imaging printers can be made lighter and smaller than inkjet type printers. Additionally these systems can be refilled very rapidly and require very little maintenance. This makes direct thermal imaging ideal for point of sale systems that print receipts and self service systems such as gas station pumps, kiosks information systems and ATMs. Direct thermal imaging is also used in many hand held devices used in inventory tracking and they are also used in many medical monitoring devices. The applications for direct thermal imaging are expanding as technology enables smaller and more portable equipment.
Up until recently, paper and film converting companies had to rely on a select few suppliers with specialty equipment to obtain the coated material. However, now there are liquid formulations available that can be coated onto paper or film using common coating technologies. This is good news for the converter because they can use their existing coating equipment with no modifications. Using their own equipment should result in significant cost benefits, however one must insure that quality of product is not sacrificed.
The following are some of the more common coating methods that are used by converting companies.
Gravure Coating: An engraved roller picks up the coating liquid and then deposits it onto the substrate
Reverse Roll Coating: A precise layer of material is applied to an application roller by a metered roller. The material thickness is controlled by the gap between these two rollers. The material is then “wiped off” the application roller by the substrate.
Knife Coating: Coating is applied onto a substrate which then passes between a knife and a support roller. The knife then doctors the excess material away. The gap between the knife and roller determines the coating thickness.
Mayer Rod Coating: The Mayer rod is a stainless steel rod that is wound tightly with stainless steel wire of varying diameter. The rod is used to doctor off the excess coating solution and control the coating weight. The coating thickness is controlled by the diameter of the wire wound around the rod.
Air Knife Coating: Excess material is deposited onto the substrate before it passes under a powerful jet stream of air that “blows off” the excess material.
Slot Die Coating: The coating squeezed through a narrow slot onto the substrate. The slot width and the substrate speed along with the flow rate of the coating solution through the slot head determine the coating thickness.
The final coated product must be able to consistently enable quality printing in a number of different applications. Some of the characteristics to consider are:
Image density: The denser image results in more opaque printing. Less density results in “grayer” or lighter black making it more difficult to read.
Image clarity: The sharpness or clarity relates to the resolution. A sharper image is easier to read and allows higher resolution which is critical in bar code and QR code printing.