Developers in thermal paper
Developers used in thermal papers are expected to have the following characteristics:
- High thermal sensitivity.
- A sharp melting point within the appropriate temperature range.
- Good compatibility with leuco dyes and high stability of reaction products.
- Low solubility to water.
- No sublimation.
There are some factors that have the opposite effect between the above characteristics, so it is very rare to have a developer that fully meets the above characteristics.
For example, for the purpose of high-speed recording, a developer with low melting point and low solubility heat is required. However, a developer with this characteristic is prone to produce shadow and leads to the deterioration of picture stability. In order to solve this problem, we often try to use low molecular weight developer, but it is easy to cause the sublimation of developer and leads to the phenomenon of migration in the coating. This opposition creates technical difficulties. The effect of color developing agent on the color characteristic curve, whiteness, heat resistance and preservation of paper is very important.
Our main developer products: Bisphenol S and D-8
4,4’-dlhydroxydiphenylsulfone (Bisphenol S, CAS 80-09-1), white powder, melting point 247-248 ºC. BPS is used as developer for high-performance thermal paper such as label, ticket, tag, and register paper for which storage stability, burning resistance, light resistance, water resistance, and oil resistance are required.
4-Hydroxy-4′-isopropoxydiphenylsulfone (D-8,CAS 95235-30-6), white powder, melting point 128-130 ºC. D-8 is a color developer widely used in industry at present. Its advantage is that the thermal paper produced has high whiteness and high sensitivity, and the image preservation performance is excellent.