What do you know about thermal paper?
1. Concept of thermal paper
Thermosensitive paper, also known as thermosensitive recording paper, thermosensitive copying
paper and thermosensitive fax paper, was first developed by American 3M (Minesota mining inkcharacter) Company in 1951. Colorless dye two-component thermal paper is a processing paper coated with a special coating. It is a kind of information paper with thermal recording effect of thermal coloring composed of paper, etc. as a carrier and recessive colorless dye, developer, sensitizer, adhesive, etc. as a thermal coloring coating.
2. Use of thermal paper
Thermal paper is mainly used in the following aspects: fax machine, communication, medical treatment, recording system such as electrocardiograph, thermal instrument, computer networking terminal printing, trademark, sign code (POS), etc., of which fax machine is most used. With the rapid development of information technology, bill printer technology and bar code technology have been widely used. Due to its unique performance, the advantages of fast image generation and convenient bar code label, thermal paper has been rapidly growing in the field of bar code recording information and bill printing.
3. Classification of thermal paper
Functionally, thermal paper can be divided into ordinary thermal paper and three anti thermal paper. The three proofing thermal paper is to apply a protective layer on the thermal color layer to give the three proofing thermal paper better waterproof, oil and friction resistance. It is mainly used in the high-end market.
Structurally, thermal paper is mainly divided into two categories. One category is physical thermal paper that uses heat to physically color the colored pigment to achieve the recording effect. This type of thermal paper is also divided into melt transparent type, melt transfer type and heat sublimation type. The representative is melt transparent thermal paper, which is widely used in medical electrocardiography and EEG; The other type is chemical thermal paper that uses chemical reaction under the action of heat to achieve the purpose of coloring. It is the largest product in the market at present. This type of thermal paper is divided into two-component metal compound coloring thermal paper and colorless dye two-component thermal paper.
4. Color development principle of thermal paper
The color development principle of molten transparent thermosensitive paper is that a layer of opaque wax is coated on the black base paper as the surface layer, and the opaque wax like material is melted and transparent through the action of a thermal pen, and the color of the bottom layer of the base paper is exposed to form an image. The color development principle of metal compound chromogenic thermosensitive paper is based on the common mixing of heavy metal salt of fatty acid and reducing agent, and the fatty acid salt melts and reacts with reducing agent by heating, so that the heavy metal is reduced to free color. The color development principle of colorless dye type thermal paper is based on the mixing of colorless dye containing inner aliphatic ring and color developing agent. Under the action of heat, the color developing agent and colorless dye will react with each other and melt to produce color.
5. How long can thermal paper printing be stored?
The main factors affecting the quality of thermal printing paper are thermal coating or protective layer. If the coating of the thermal paper is not uniform, it will lead to the deep color in some places and the light color in some places, and the printing quality will be significantly reduced. If the chemical formula of the thermal coating is unreasonable, the storage time of the thermal printing paper will be very short. Good printing paper can be stored (under the condition of normal temperature and avoiding direct sunlight) for 5 years after printing, and now there is a long-term thermal paper that can be stored for 10 years.
In addition, the protective coating is also critical to the storage time after printing. It can absorb part of the light that causes the chemical reaction of the thermal coating, slow down the deterioration of the printing paper, and protect the thermal element of the printer from damage. However, if the protective coating is not uniform, the protection of the thermal coating will be greatly reduced, and even the fine particles of the protective coating will fall off during printing, Rubbing the thermal element of the printer causes damage to the print thermal element.