Thermal paper is a special fine paper
Special fine paper
Special fine paper is a classification of paper used for copying and digital printing.- Copy paper :Copy paper is used for copying and laser printers. The basis weight is 70-90 g/m² and ISO brightness 80-96%. It is made of 90–100% virgin chemical pulp or 100% deinked pulp with total pigment content...
that is coated with a chemical that changes color when exposed to heat. It is used in thermal printer
A thermal printer produces a printed image by selectively heating coated thermochromic paper, or thermal paper as it is commonly known, when the paper passes over the thermal print head. The coating turns black in the areas where it is heated, producing an image...
s and particularly in inexpensive or lightweight devices such as adding machine
An adding machine was a class of mechanical calculator, usually specialized for bookkeeping calculations.In the United States, the earliest adding machines were usually built to read in dollars and cents. Adding machines were ubiquitous office equipment until they were phased out in favor of...
s, cash register
A cash register or till is a mechanical or electronic device for calculating and recording sales transactions, and an attached cash drawer for storing cash...
s, and credit card terminal
Credit card terminal
A Credit card terminal is a device that can do transactions with a debit card or a credit card.Several types of credit card terminals are available to merchants. Most have the same basic purpose and functions. They allow a merchant to swipe or key in required credit card information and transmit...
The surface of the paper is coated with a solid-state mixture of a dye and a suitable matrix; a combination of a fluoran
Fluoran is a triarylmethane dye. It is the structural core of a variety of other dyes....
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...
, octadecylphosphonic acids as 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.
Typically the coating will turn black when heated. But coatings that turn blue or red are sometimes used. While an open heat source such as a flame can discolor the paper, a fingernail swiped quickly across the paper will also generate enough heat from friction to produce a mark on such paper.
Most direct thermal papers require a protective topcoating to:
- reduce fading of the thermal image caused by exposure to UV light, water, oils, grease, lard, fats, plasticizers, and similar causes
- provide improved printhead wear
- reduce or eliminate residue from the thermal coating on the thermal printheads
- provide better anchorage of flexographic printing inks applied to the thermal paper
- focus the heat from the thermal printhead on the active coating.
HistoryThe earliest direct thermal papers were developed by NCR Corporation
NCR Corporation is an American technology company specializing in kiosk products for the retail, financial, travel, healthcare, food service, entertainment, gaming and public sector industries. Its main products are self-service kiosks, point-of-sale terminals, automated teller machines, check...
(using dye chemistry) and 3M (using metallic salts). The NCR technology became the market leader over time, although the image would fade rather rapidly compared with the much more expensive, but durable 3M
3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
invented the thermal print head in 1965, and the Silent 700
The Silent 700 was a line of portable computer terminals manufactured by Texas Instruments in the 1970s and 1980s. Silent 700s printed with a dot-matrix heating element onto a roll of heat-sensitive paper. Some models were equipped with an integrated acoustic coupler and modem that could receive...
, a computer terminal with a thermal printer, was put on market in 1969. The Silent 700 was the first thermal print system that printed on thermal paper. During the 1970s, Hewlett Packard integrated thermal paper printers into the design of its HP9800 series desktop computers, and integrated into the top of 2600-series CRT terminals as well as in plotters.
In the 1970s and early 1980s, Japanese producers (such as Ricoh
or Ricoh, is a Japanese company that was established in 1936 on February 6th, as , a company in the RIKEN zaibatsu. Its headquarters is located in Ricoh Building in Chūō, Tokyo....
, Jujo, and Kanzaki) using similar dye-based chemistry formed partnerships with 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....
manufacturers (such as TEC, Sato, and others) and entered the emerging global bar code industry, primarily in supermarkets. U.S. producers such as Appleton (NCR's licensee), Nashua Corporation
The Nashua Corporation is an American company headquartered in Nashua, New Hampshire that makes labels, specialty papers, and imaging products and services. On September 15, 2009, it was bought by Cenveo, Inc. As of early 2010, it had four factories in several states.It was formed in 1848 to make...
, Graphic Controls, and others fought to gain market share. Leading pressure-sensitive label producers such as Avery Dennison
Avery Dennison Corporation is a global manufacturer and distributor of pressure sensitive adhesive materials , office products, and various paper products....
became major consumers of direct thermal paper for label applications.
In the late 1980s and early 1990s, thermal transfer
In regards to printing a thermal transfer is when a specialized printer melts wax within its print-heads and uses it to print a design or text onto paper...
, laser printing
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...
Xerography is a dry photocopying technique invented by Chester Carlson in 1938, for which he was awarded on October 6, 1942. Carlson originally called his invention electrophotography...
, and, to a lesser extent, ink jet printing
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...
began to take away industrial and warehouse barcode applications due to better durability. Direct thermal made a strong comeback with point of sale receipts (gasoline pumps, cash registers, rental car receipts, etc.).
In 2006, NCR Corporation's Systemedia division introduced two-sided thermal printing technology, called "2ST"http://www.ncr.com/products-and-services/supplies/two-sided-thermal-printing
Health and environmental concernsSome thermal papers are coated with 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), a chemical considered to be an endocrine disruptor
Endocrine disruptors are chemicals that interfere with endocrine in animals, including humans. These disruptions can cause cancerous tumors, birth defects, and other developmental disorders...
. This material can contaminate recycled paper . BPA can transfer readily to skin in small amounts:
- Texas Instruments-Computers & Software and Industrial Controls
- Silent 700 Electronic Data Terminals, 1976(PDFPortable Document FormatPortable Document Format is an open standard for document exchange. This file format, created by Adobe Systems in 1993, is used for representing documents in a manner independent of application software, hardware, and operating systems....