In Understanding thermal paper sensitivity you must first understand that there are different areas of sensitivity exchange.
Static Sensitivity
One is static sensitivity, which is where the thermal layer begins to react and the paper begins to blacken. A low static sensitivity means that the paper has a high sensitivity to heat and requires a higher temperature to begin to blacken the paper.
A high static sensitivity, conversely means that the thermal layer has a lower sensitivity to heat and will begin to react, or blacken the paper at lower levels of heat.
Static sensitivity is important to understand in that it will help you determine in what environments the paper can be used or stored.
For example if the paper is to be used or stored in hot environments, such as parking receipts will often be placed on the dashboard of your car, or stored in a non climate controlled warehouse a low static sensitivity paper must be used so as not to react or blacken prematurely.
Dynamic Sensitivity
The other variable is dynamic sensitivity, which is the amount of energy that is needed to be applied by the thermal head for the paper to begin to react and images to appear.
This is important because it determines the speed at which the paper can be printed on in order to give you the maximum image.
So the dynamic sensitivity is important in helping you to determine which printer can be used for your thermal paper in order to receive the most qualified image.
The greater the dynamic sensitivity of the paper, the faster your printer is able to function, as faster printers use less energy, and therefore require a higher dynamic sensitivity paper to react more rapidly.
Choosing Your Printer
Increasing the speed however, reduces the impulse time and so the head must be designed to cool quicker between pulses.
In using more conventional printers a lower density sensitivity paper must be used in order to assure the quality of the impression, particularly when using small case text or horizontal graphs.