Thermal printing
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Thermal printing (or direct thermal printing) is a digital printing process which produces a printed image by passing paper with a thermochromic coating, commonly known as thermal paper, over a print head consisting of tiny electrically heated elements. The coating turns black in the areas where it is heated, producing an image.[2]
Most thermal printers are monochrome (black and white) although some two-color designs exist.
Thermal-transfer printing is a different method, using plain paper with a heat-sensitive ribbon instead of heat-sensitive paper, but using similar print heads.
Design
A thermal printer typically contains at least these components:
- Thermal head: Produces heat to create an image on the paper
- Platen: A rubber roller which moves the paper
- Spring: Applies pressure to hold the paper and printhead together
Thermal paper is impregnated with a solid-state mixture of a dye and a suitable matrix, for example, a fluoran leuco dye and an octadecylphosphonic acid. 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, a process known as thermochromism.
This process is usually monochrome, but some two-color designs exist, which can print both black and an additional color (often red) by applying heat at two different temperatures.[3]
In order to print, the thermal paper is inserted between the thermal head and the platen and pressed against the head. The printer sends an
Thermal print heads can have a resolution of up to 1,200 dots per inch (dpi). The heating elements are usually arranged as a line of small closely spaced dots.[4]
Early formulations of the thermo-sensitive coating used in thermal paper were sensitive to incidental heat, abrasion, friction (which can cause heat, thus darkening the paper), light (which can fade printed images), and water. Later thermal coating formulations are far more stable; in practice, thermally printed text should remain legible for at least 50 days.[citation needed]
Applications
Thermal printers print more quietly and usually faster than impact
Commercial use
Commercial applications of thermal printers include filling station pumps, information kiosks, point of sale systems, voucher printers in slot machines, print on demand labels for shipping and products, and for recording live rhythm strips on hospital cardiac monitors.
Record-keeping in microcomputers
Many popular microcomputer systems from the late 1970s and early 1980s had first-party and aftermarket thermal printers available for them, such as the
Fax machines
Through the 1990s, many
printing technology largely supplanted thermal printing technology in fax machines, allowing printing on plain paper.Seafloor Exploration
Thermal printers are commonly used in seafloor exploration and
Other uses
Flight progress strips used in air traffic control (ACARS) typically use thermal printing technology.
In many hospitals in the
The Game Boy Printer, released in 1998, was a small thermal printer used to print out certain elements from some Game Boy games.
Health concerns
Reports began surfacing of studies in the 2000s finding the oestrogen-related chemical bisphenol A ("BPA") mixed in with thermal (and some other) papers. While the health concerns are very uncertain[citation needed], various health and science oriented political pressure organizations, such as the Environmental Working Group, have pressed for these versions to be pulled from market.[5]
See also
- Barcode printer
- Dye-sublimation printer
- Label printer
- Label printer applicator
- LightScribe
- Line matrix printer
- Line printer
- Thermographic printing
References
- ^ "Receipt Paper: Why It Fades and How to Restore It?". Panda Paper Roll. 2018-12-10.
- ^ "Definition of THERMAL PRINTER". www.merriam-webster.com.
- ISBN 978-1-4822-7736-4.
- ^ "Thermal Print Head | Toshiba Hokuto Electronics Corporation". www.hokuto.co.jp.
- ^ "Concerned About BPA: Check Your Receipts". Science News. Retrieved 2021-04-19.