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Origins - not known, basic idea quite old. Recent manifestation 1970s.
Makers - Label - Avery, Epson, Sato, Wasp - Decorative - Roland
Types:
| Direct thermal - heat causes chemical reaction in paper, usually melting wax and releasing acid. |  |
| Thermal transfer - heat melts wax or resin with a colourant and transfers them from backing film to paper. | |
| Dye Sublimation - heat melts material so violently it diffuses into the paper - ideally as a gas (hence the name) but often just in liquid phase. | |
Merits
| Problems
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Thermal Printer Market - overshadowed by Inkjets and Lasers but widely used: 
| Label Printers. | |
| Point of Sale. | |
| Decorative Printers. | |
| Photography. |
Thermal Printer Basics -
Printhead is usually a ceramic bar containing hundreds or even thousands of resistor heating elements. Heat from the resistors:
melts a wax coat on the paper allowing a chemical reaction - direct thermal print
transfers coloured wax from a backing ribbon - thermal transfer and dye sub.
Fax machines. Labelling. Industrial processes. Photography
Direct Print - thermochromic materials coated onto paper as a size.
Chromisms - thermo, photo, electro, magneto
Leuco Dyes - flouran is yellowish until acidified and octadecylphosphonic acid wax.
Two Colour Print - one reaction at a low temperature, another at a higher.
Themo Autochrome - three colours with an intermediate UV fix.
Eraseable Print - one pass creates print, another pass erases it.
Simple Mechanism - nothing but paper, roller and printhead.
Improvements - thermochromic printing now one of the cheapest methods.
Development - reversible and Touch-It papers.
Printheads - thick film resistors coated onto or embedded in ceramic.
Problems - print quality usually low, odd paper, only moderately fast.
Paper stability - paper tends to yellow.
Printhead wear - tends to cause pixel dropouts. Take care not to scratch.
Environment & Health - doesn't seem to be an environmental hazard.
Cost - has fallen so tends to be quite low.
Thermal Transfer - melts a coloured wax or resin on a thin backing foil. Used for the most boring products like barcodes and in complete contrast - for decorative materials.
Barcodes -
Wax - strong print but degraded by damp and some chemicals.
Resin - particularly suited to plastic labels, designed to sink in.
Colour - usually black but other colours possible.
Decorative Materials - signwriting, product labelling, badge making - even T-shirts.
Pagewidth transfer - three or four panels of wax the same size as the paper.
Raster Scanning - thin selectable ribbons.
Colour - at low resolution, basically a gamut of 3 or 8 colours.
Thermal Transfer & Environment. Foil and most of the wax or resin are waste?.
Dye Sublimation - true dye sub vapourises ink but most just melt it and it diffuses into the paper. Because the temperature can be varied so can the amount of material transfered, giving a grey scale.
Film transfer - looks like wax transfer.
Inkjet - some inkjet type mechanisms using dye-sub - also see Xerox Phaser
Price - an issue with all thermal mechanisms and particularly with thermal transfer and dye sub.
Fast & Photographic Printers - wax and dye-sub give good economics because of high page cover.
Data Protection - thermal transfer leaves a negative of its data on the foil.
Solid Ink - Xerox Phaser.
Printer Design -
Most common mechanism is direct thermal - faxes for instance
Thermal transfer requires ribbon and paper stock - more expensive but lasting
Thermal Printers & Environment - wasteful of consumables but simple print mechanism.
Laser Cutters and Engravers
Sinclair Printers