热敏纸是由遇热显色的一种化学物质涂布在表面的纸张。它主要用于热敏打印机上，特别是在一些轻便简易的设备上，如添加机，收款机，和信用卡终端设备。

纸张的表面涂布物质为固态混合物与染料并排列为一个合适的矩阵-是无色萤光黄母体和十八烷基膦酸的组合。当加热温度达到矩阵熔点时，染料与酸反应，形成显色，显色后会在矩阵回归原态前以一个相对稳定的状态保存下来。

通常情况下，涂层加热时会变成黑色。但有时也会使用蓝色或红色的涂层。

通常高档热敏纸会有一个保护活性涂层的保护层叫顶涂，作用如下：

*减少因接触紫外线，水，油，油脂，猪油，油脂，增塑剂，和类似的原因造成热图像的衰落

*减少打印头磨损

*减少或消除从热敏打印头的热涂层的残余物

*提供更好的柔性版印刷油墨更好地适用于热敏纸

*集聚热敏打印头的热量于活性涂层上

热敏纸主要用于热敏打印设备，如POS打印机，收款机，和信用卡终端。热敏纸卷涂有一种化学物质，接触到加热的打印头时就会显色。所以，热敏纸并不需要墨水来产生图像。

常见的克重：48gsm，55gsm，58gsm，60gsm，80gsm

以下是英文原文定义：

Thermal paper is paper that is impregnated with a chemical that changes color when exposed to heat. It is used in thermal printers and particularly in cheap, lightweight devices such as adding machines, cash registers, and credit card terminals.

The surface of the paper is impregnated with a solid-state mixture of a dye and a suitable matrix; a combination of a fluoran leuco dye, octadecylphosphonic acids as an example. When the matrix is heated above its melting point, the dye reacts with the acid, shifts to its colored form, and the changed form is then conserved in metastable state when the matrix solidifies back quickly enough.

Typically the coating will turn black when heated. But coatings that turn blue or red are sometimes used.

Most direct thermal papers require a protective topcoating to:

* reduce fading of the thermal image caused by exposure to UV light, water, oils, grease, lard, fats, plasticizers, and similar causes

* provide improved printhead wear

* reduce or eliminate residue from the thermal coating on the thermal printheads

* provide better anchorage of flexographic printing inks applied to the thermal paper

* focus the heat from the thermal printhead on the active coating.