Apply a layer of "heat-sensitive paint" (heat-sensitive discoloration layer) on high-quality base paper.
Although there are more than a dozen chemicals used in this color-changing layer, there are at least the following compounds: leuco dyes are various, and fluorescent compounds are the most commonly used; The chromogenic agent accounts for less than 20%, and bisphenol and p-hydroxybenzoic acid are commonly used; Sensitizer accounts for less than 10%, which contains benzenesulfonamide compounds; The filler accounts for less than 50%, and calcium carbonate (granules) is commonly used; The binder accounts for less than 10%, such as polyvinyl acetate; Stabilizers such as dibenzoyl terephthalate; Lubricant, etc. Thermal paper will change color when heated.
Extended data:
Thermal paper: used as the communication carrier of words and graphics on fax machines, that is, as fax paper; Used as recording materials in medical and metering systems, such as ECG paper, heat sensitive instrument recording paper, etc. Printing paper for Internet terminals; In commercial activities, it is used to make trademarks, identification codes (POS), etc., in which the amount of fax paper accounts for the largest proportion.
The principle of making thermal paper is to coat a common paper base with fine powder, which is composed of leuco dye phenol or other acidic substances and separated by a film. Under the heating condition, the film melts and the powder is mixed to form a color reaction. The color handwriting on thermal paper is unstable and easy to fade, which makes it difficult to identify the contents of the document.
Commonly used lottery tickets are made of heat-sensitive paper.
Ordinary thermal paper is not suitable for long-term storage, and good thermal paper can be stored for 30 years or even longer.
When the heat-sensitive paper is placed above 70℃, the heat-sensitive coating begins to change color. The reason for its discoloration should also be discussed from the composition.
There are two kinds of heat-sensitive components in the coating of heat-sensitive paper: one is leuco dye or leuco dye; The other is a color developer. This kind of thermal paper is also called two-component chemical thermal paper.
Commonly used as leuco dyes are crystal violet lactone (CVL), fluorane system, leuco benzoyl methylene blue (BLMB) or spiropyran system of triphenylmethane phthalein system.
Commonly used dispersants are: polyvinyl alcohol L-3266, polyvinyl alcohol GL-05 and polyvinyl alcohol KL-03 (manufactured by Japan Synthetic Chemical Corporation).
Commonly used topcoat and primer additives are: gohsefimer Z-200, polyvinyl alcohol T-350 and polyvinyl alcohol N-300.
Commonly used color developers are: p-hydroxybenzoic acid and its esters (PHBB, PHB), salicylic acid, 2,4-dihydroxy benzoic acid or aromatic sulfone.
When heat-sensitive paper is heated, leuco dye reacts with developer to produce color, so when heat-sensitive paper is used to receive signals and print on fax machine or directly on heat-sensitive printer, images and texts will be displayed. Because there are many kinds of leuco dyes, the colors of handwriting are different, such as blue, purple and black.
Baidu encyclopedia-thermal paper