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Thermal printer

Thermal printer

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A thermal printer produces a printed image by selectively heating coated thermochromic paper, or thermal paper
Thermal paper
Thermal paper is a special fine paper that is coated with a chemical that changes color when exposed to heat. It is used in thermal printers and particularly in inexpensive or lightweight devices such as adding machines, cash registers, and credit card terminals.The surface of the paper is coated...

 as it is commonly known, when the paper passes over the thermal print head
Computer printer
In computing, a printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a...

. The coating turns black
Black
Black is the color of objects that do not emit or reflect light in any part of the visible spectrum; they absorb all such frequencies of light...

 in the areas where it is heated, producing an image. Two-color direct thermal printers can print both black and an additional color
Color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...

 (often red
Red
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–740 nm. Longer wavelengths than this are called infrared , and cannot be seen by the naked eye...

) by applying heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

 at two different temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

s.

Thermal transfer printing
Thermal transfer printer
A thermal transfer printer is a printer which prints on paper by melting a coating of ribbon so that it stays glued to the material on which the print is applied. It contrasts with direct thermal printing where no ribbon is present in the process...

 is a related method that uses a heat-sensitive ribbon instead of heat-sensitive paper.

Essential mechanisms


A thermal printer comprises these key components:
  • Thermal head — generates heat; prints on paper
  • Platen — a rubber roller that feeds paper
  • Spring — applies pressure to the thermal head, causing it to contact the thermo-sensitive paper
  • Controller boards — for controlling the mechanism


In order to print, thermo-sensitive paper is inserted between the thermal head and the platen. The printer sends an electrical current to the heating elements of the thermal head, which generate heat. The heat activates the thermo-sensitive coloring layer of the thermo-sensitive paper, which changes color where heated. Such a printing mechanism is known as a thermal system or direct system. The heating elements are usually arranged as a matrix of small closely spaced dots
Dot matrix
A dot matrix is a 2-dimensional array of LED used to represent characters, symbols and images.Typically the dot matrix is used in older computer printers and many digital display devices. In printers, the dots are usually the darkened areas of the paper...

—thermal printers are actually dot-matrix printers, though they are not so called.

The paper is impregnated with a solid-state mixture of a dye and a suitable matrix; a combination of a fluoran
Fluoran
Fluoran is a triarylmethane dye. It is the structural core of a variety of other dyes....

 leuco dye
Leuco dye
A leuco dye is a dye whose molecules can acquire two forms, one of which is colorless.For example, the spiro form of an oxazine is a colorless leuco dye; the conjugated system of the oxazine and another aromatic part of the molecule is separated by an sp3-hybridized "spiro" carbon...

 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
Thermochromism
Thermochromism is the ability of substance to change color due to a change in temperature. A mood ring is an excellent example of this, but it has many other uses such as baby bottles and kettles. Thermochromism is one of several types of chromism.The two basic approaches are based on liquid...

.

Controller boards are embedded with firmware to manage the thermal printer mechanisms.
The Firmware
Firmware
In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...

 can manage multiple bar code types, graphics and logos. They enable the user to choose between different resident fonts (also including Asian fonts) and character sizes.

Controller boards can drive various sensors such as paper low, paper out, door open, top of form etc., and they are available with a variety of interfaces, such as RS-232
RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...

, parallel
Parallel port
A parallel port is a type of interface found on computers for connecting various peripherals. In computing, a parallel port is a parallel communication physical interface. It is also known as a printer port or Centronics port...

, USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....

 and wireless
Wireless LAN
A wireless local area network links two or more devices using some wireless distribution method , and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network...

. For point of sale
Point of sale
Point of sale or checkout is the location where a transaction occurs...

 application some boards can also control the cash drawer
Cash drawer
A cash drawer is generally a compartment underneath a cash register in which the cash from transactions is kept. The drawer typically contains a removable till. The till is usually divided into compartments used to store each denomination of bank notes and coins separately to make counting easier...

.

Applications


Thermal printers print more quietly and usually faster than impact dot matrix printer
Dot matrix printer
A dot matrix printer or impact matrix printer is a type of computer printer with a print head that runs back and forth, or in an up and down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like the print mechanism on a typewriter...

s. They are also smaller, lighter and consume less power, making them ideal for portable and retail applications. Cost of thermal paper, their only consumable, was somewhat less than US$0.10 per sheet . By comparison, one study of the per page cost of color inkjet printers found cost of third-party ink cartridge and paper to be about $0.05 per page (some low-capacity cartridges are more expensive to use). Roll-based printers can be rapidly refilled. Commercial applications of thermal printers include filling station
Filling station
A filling station, also known as a fueling station, garage, gasbar , gas station , petrol bunk , petrol pump , petrol garage, petrol kiosk , petrol station "'servo"' in Australia or service station, is a facility which sells fuel and lubricants...

 pumps, information kiosk
Kiosk
Kiosk is a small, separated garden pavilion open on some or all sides. Kiosks were common in Persia, India, Pakistan, and in the Ottoman Empire from the 13th century onward...

s, point of sale
Point of sale
Point of sale or checkout is the location where a transaction occurs...

 systems, voucher printers in slot machines, print on demand
Print on demand
Print on demand , sometimes called, in error, publish on demand, is a printing technology and business process in which new copies of a book are not printed until an order has been received...

 labels for shipping and products, and for recording live rhythm strips on hospital cardiac monitors.

Through the 1990s many fax
Fax
Fax , sometimes called telecopying, is the telephonic transmission of scanned printed material , normally to a telephone number connected to a printer or other output device...

 machines used thermal printing technology. Toward the beginning of the 21st century, however, thermal wax transfer
Thermal transfer printer
A thermal transfer printer is a printer which prints on paper by melting a coating of ribbon so that it stays glued to the material on which the print is applied. It contrasts with direct thermal printing where no ribbon is present in the process...

, laser
Laser printer
A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and multifunction printers , laser printers employ a xerographic printing process, but differ from analog photocopiers in that the image is produced...

, and inkjet
Inkjet printer
An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...

 printing technology largely supplanted thermal printing technology in fax machines, allowing printing on plain paper.

The Game Boy Printer
Game Boy Printer
The Game Boy Printer, known in Japan as the , is a thermal printer accessory released by Nintendo in 1998. Nintendo ceased manufacture in 2003. The Game Boy Printer is compatible with the Game Boy, Game Boy Pocket, Game Boy Color and Game Boy Advance systems and is designed to be used in...

, made in 1998
1998 in video gaming
-Events:*Academy of Interactive Arts & Sciences hosts 1st Annual Interactive Achievement Awards; inducts Shigeru Miyamoto of Nintendo to the AIAS Hall of Fame*British Academy of Film and Television Arts hosts the 1st annual BAFTA Interactive Entertainment Awards...

, was a small thermal printer used to print out certain elements from some Game Boy
Game Boy
The , is an 8-bit handheld video game device developed and manufactured by Nintendo. It was released in Japan on , in North America in , and in Europe on...

 games.

Early formulations of the thermo-sensitive coating used in thermal paper were sensitive to incidental heat, abrasion
Abrasion (mechanical)
Abrasion is the process of scuffing, scratching, wearing down, marring, or rubbing away. It can be intentionally imposed in a controlled process using an abrasive...

, friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

 (which can cause heat, thus darkening the paper), light (which can fade printed images), and water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

. Later thermal coating formulations are far more stable; theoretically, thermally printed text should remain legible at least 50 years.

Hospitals commonly record fetal ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...

 scan images on thermal paper. This can cause problems if the parents wish to preserve the image by laminating it, as the heat of most laminators will darken the entire page—this can be tested for beforehand on an unimportant thermal print. An option is to make and laminate a permanent ink duplicate of the image.

Health concerns


Reports began surfacing of studies in the 2000s finding the oestrogen-related chemical Bisphenol A
Bisphenol A
Bisphenol A is an organic compound with two phenol functional groups. It is used to make polycarbonate plastic and epoxy resins, along with other applications....

 ("BPA") mixed in with thermal (and some other) papers. While the health concerns are very uncertain, various health and science oriented political pressure organizations such as the Environmental Working Group
Environmental Working Group
The Environmental Working Group is an American environmental organization that specializes in research and advocacy in the areas of toxic chemicals, agricultural subsidies, public lands, and corporate accountability...

 have pressed for these versions to be pulled from market.

See also

  • Barcode printer
    Barcode printer
    A barcode printer is a computer peripheral for printing barcode labels or tags that can be attached to physical objects. Barcode printers are commonly used to label cartons before shipment, or to label retail items with UPCs or EANs....

  • Thermal transfer printer
    Thermal transfer printer
    A thermal transfer printer is a printer which prints on paper by melting a coating of ribbon so that it stays glued to the material on which the print is applied. It contrasts with direct thermal printing where no ribbon is present in the process...

  • Computer printer
    Computer printer
    In computing, a printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a...

  • Daisy wheel printer
    Daisy wheel printer
    Daisy wheel printers use an impact printing technology invented in 1969 by David S. Lee at Diablo Data Systems. It uses interchangeable pre-formed type elements, each with typically 96 glyphs, to generate high-quality output comparable to premium typewriters such as the IBM Selectric, but two to...

  • Dot matrix printer
    Dot matrix printer
    A dot matrix printer or impact matrix printer is a type of computer printer with a print head that runs back and forth, or in an up and down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like the print mechanism on a typewriter...

  • Dye-sublimation printer
    Dye-sublimation printer
    A dye-sublimation printer is a computer printer which employs a printing process that uses heat to transfer dye onto medium materials such as a plastic card, paper, or fabric. The sublimation name is applied because the dye transitions between the solid and gas states without going through a...

  • Line matrix printer
    Line matrix printer
    A line matrix printer is a computer printer that is a compromise between a line printer and a dot matrix printer. Basically, it prints a page-wide line of dots. It builds up a line of text by printing lines of dots.-Applications:...

  • Line printer
    Line printer
    The line printer is a form of high speed impact printer in which one line of type is printed at a time. They are mostly associated with the early days of computing, but the technology is still in use...

  • Inkjet printer
    Inkjet printer
    An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...

  • Label printer
    Label printer
    A label printer is a computer printer that prints on self-adhesive label material and/or card-stock . Label printers with built-in keyboards and displays, for stand-alone use , are often called label makers...

  • Label printer applicator
    Label printer applicator
    thumb|right|Label printer applicator applying a label to adjacent panels of a [[corrugated box]].thumb|right|Label printer applicatorLabel printer applicators are basic robots that automatically print and apply pressure sensitive labels to various products...

  • Laser printer
    Laser printer
    A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and multifunction printers , laser printers employ a xerographic printing process, but differ from analog photocopiers in that the image is produced...

  • Thermographic printing
    Thermographic printing
    Thermographic printing refers to two types of printing, both of which rely on heat to create the letters or images on a sheet of paper.The simplest type is where the paper has been coated with a material that changes colour on heating. This is called thermal printing and was used in older model...