How is thermal paper manufactured?
Have you ever been curious about the type of paper that is used in devices such as cash registers, credit card terminals when you are getting your bill generated? These lightweight devices and other machines such as thermal printers, adding machines etc. make use of a special variety of fine paper known as thermal paper. It is so called as it is coated with a chemical that changes color when exposed to heat. When a fingernail is swiped quickly across the paper, a mark is produced due to the heat generated from friction. Appvion Inc, USA one of the principal suppliers of thermal papers partners with thermal paper distributors to make these papers available at different corners of the world.
Thermal papers are engineered to provide rich, legible images at all print speeds for excellent readability. They have a wide ranging use from point-of-sale (POS) receipts and coupons to transit and parking tickets; entertainment and gaming tickets; luggage tags; medical charts; and labels for RFID, warehousing, inventory tracking, pharmacy and retail. Let us now try to understand the process of manufacturing these papers:
The surface of the paper is coated with a solid-state mixture of a dye and a suitable matrix. The coating includes four different types of chemicals:
- Leuco Dyes – Leuco dyes can switch between two chemical forms, one of which is colorless. The dyes used in thermal paper are usually triaryl methane phthalide dyes or fluoran dyes or Crystal Violet lactone. These dyes have a colorless leuco form when crystalline or when in a pH neutral environment, but become colored upon melting or when exposed to an acidic environment.
- Developers – Developers are basically organic acids which are also melted along with leuco dyes in order to provide more color. Examples of such developers include phenols, sulfonyl ureas and Zinc salts of substituted salicylic acids.
- Sensitizers – Sensitizers are also added to the paper surface to optimize the colorization temperature and to facilitate mixing of developers and leuco dyes upon melting. Sensitizers are commonly simple ether molecules.
- Stabilizers – Stabilizers are added in order to stabilize the layer or glass formed by the leuco dye, developer and sensitizer and prevent the dyes to return to their original colorless, crystalline forms when stored in hot or humid conditions.
Leading thermal paper distributors are making highest quality thermal paper available to a number of industries including converting and label industry.