1. Thermal paper concept
Thermal paper is a processed paper whose manufacturing principle is to coat a layer of “thermal paint” (thermal 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, which have a wide variety, and fluorescent compounds are the most commonly used; color developing agents account for about 20% or less, and commonly used two Phenol, p-hydroxybenzoic acid; sensitizers account for less than 10%, including benzenesulfonic acid amide compounds; fillers account for less than 50%, commonly used calcium carbonate (particles); adhesives account for less than 10%, Such as polyvinyl acetate; stabilizers, such as dibenzoyl terephthalate; lubricants, etc. Therefore, the process is difficult and the technical requirements are high.
Thermal paper, also known as thermal recording paper, thermal copy paper, thermal fax paper, is called thermal carbon paper in Taiwan, and was first developed by 3M (Minesota Mining Ink Character) in the United States in 1951.
The leuco dye two-component thermal paper is a processed paper coated with a special coating. Information paper with heat-sensitive recording effect composed of a color-sensitive coating.
2. Thermal paper usage
The main uses of thermal paper are as follows: fax machines, communications, medical care, recording and measurement systems such as electrocardiographs, thermal instruments, computer networking terminal printing, trademarks, signatures (POS), etc. Among them, the use of fax machines most. With the rapid development of information technology, ticket printer technology and barcode technology have been widely used, thermal paper has grown rapidly in the field of barcode recording information and ticket printing due to its unique properties, the superiority of rapid image generation and convenient barcode labels.
3. Classification of thermal paper
In terms of function, thermal paper can be divided into ordinary thermal paper and three-proof thermal paper. Three-proof thermal paper is coated with a protective layer on the heat-sensitive chromophoric layer to give the three-proof thermal paper better waterproof, oil-proof and anti-friction properties. It is mainly used in the high-end market.
In terms of structure, thermal paper is mainly divided into two categories. One is physical thermal paper that uses heat to physically color pigments to achieve the recording effect. Sublimation type, etc., of which the representative is melting transparent thermal paper, which is widely used in medical ECG and EEG, etc., and is used in printing paper for Internet terminals; in commercial activities, it is used to make trademarks, Signature (POS), etc., among which the consumption of fax paper accounts for the largest proportion. The other type is the chemical thermal paper that uses the chemical reaction under the action of heat to achieve the purpose of color development. It is the product with the largest amount on the market at present. Sensitive paper and leuco dye two-component thermal paper.
4. The principle of color development of thermal paper
The principle of color development of molten transparent thermal paper is to coat a layer of opaque wax as the surface layer on the black base paper. After the action of the hot pen, the opaque waxy material is melted and transparent, and the color of the bottom layer of the base paper is revealed. image.
The color development principle of metal compound color thermal paper is based on the mixing of heavy metal salts of fatty acids and reducing agents. The fatty acid salts are melted and reacted with reducing agents by heating and heating, so that the heavy metals are reduced to free color.
The color development principle of leuco dye-type thermal paper is based on the mixing of a leuco dye containing an internal alicyclic ring with a color developer. Under the action of heat, the color developer and the leuco dye are heated and melted to react and develop color.
Commonly used lottery tickets are thermal paper. Ordinary thermal paper is not suitable for long-term storage, but good thermal paper can be stored for 30 years or more. When the thermal paper is placed in an environment above 70°C, the thermal coating begins to change color. The reason for its discoloration also starts from its composition.
There are two main thermal components in thermal paper coating: one is leuco dye or leuco dye; the other is color developer. This type of thermal paper is also called two-component chemical type thermal recording paper.
Commonly used as leuco dyes are: crystal violet lactone (CVL) of trityl phthalide system, fluoran system, colorless benzoylmethylene blue (BLMB) or spiropyran system.
Commonly used dispersants are: polyvinyl alcohol L-3266, polyvinyl alcohol GL-05, polyvinyl alcohol KL-03 (produced by Japan Synthetic Chemical).
Commonly used top coat and bottom coat additives are: gohsefimer Z-200, polyvinyl alcohol T-350, polyvinyl alcohol N-300.
Commonly used as color-developing agents are: para-hydroxybenzoic acid and its esters (PHBB, PHB), salicylic acid, 2,4-dihydroxybenzoic acid or aromatic sulfones and other substances.
When the thermal paper is heated, the colorless dye and the developer react chemically to produce color, so when the thermal paper is used to receive signals on a fax machine or print directly with a thermal printer, the graphics and text are displayed. Since there are many varieties of leuco dyes, the color of the handwriting displayed is different, including blue, purple, black and so on. Guanhua Paper-top 10 cash register paper manufacturer & supplier.
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