Title: 
The thermal paper is impregnated with a solid-state mixture of a dye and a suitable matrix.

Word Count:
408

Summary:
Thermal paper is paper that is impregnated with a chemical that changes color when exposed to heat. It is used in thermal printers and particularly in cheap, lightweight devices such as adding machines, cash registers, and credit card terminals.


Keywords:
Thermal Paper


Article Body:
Thermal paper is paper that is impregnated with a chemical that changes color when exposed to heat. It is used in thermal printers and particularly in cheap, lightweight devices such as adding machines, cash registers, and credit card terminals.

A thermal printer comprises these key components:

<ul>
<li>Thermal head — generates heat; prints on paper</li>
<li>Platen — a rubber roller that feeds paper</li>
<li>Spring — applies pressure to the thermal head, causing it to contact the thermo-sensitive paper</li>
<li>Controller boards — for controlling the mechanism</li>
</ul>

In order to print, one inserts thermo-sensitive paper between the thermal head and the platen. The printer sends an electrical current to the heating resistor of the thermal head, which in turn generates heat in a prescribed pattern. The heat activates the thermo-sensitive coloring layer of the thermo-sensitive paper, which manifests a pattern of color change in response. Such a printing mechanism is known as a thermal system or direct system.

The paper is impregnated with a solid-state mixture of a dye and a suitable matrix; a combination of a fluoran leuco dye and an octadecylphosphonic acid is an example. When the matrix is heated above its melting point, the dye reacts with the acid, shifts to its colored form, and the changed form is then conserved in metastable state when the matrix solidifies back quickly enough. See thermochromism.

Because of the high print speeds, the label printers have become very sophisticated, with powerful processors and large memory capacities, to allow them to produce the label images to be printed at the same speed as the print mechanism. To achieve this speed, almost all thermal label printers use special internal description languages to allow the label to be laid out inside the printers' memory prior to printing.

Each manufacturer has their own language and some are very complex and difficult to work with. For example to print a barcode on a label, the controlling computer would send a series of codes to the printer, requesting a particular barcode type and specifying its size and location on the label, along with the data to be printed as a barcode. The printer will then use pre-defined algorithms to construct the barcode, keeping very strictly to the resolution allowed by the printhead, to create the best possible barcode on that particular type of printer. Barcodes have very strict rules for accurate printing, to ensure readability in a wide range of circumstances.


