First of all, we will introduce a two-color thermal paper. The two-color thermal paper means the paper that can produce two different colors after thermal development. It consists of two thermal layers. The upper layer is a thermal layer of the low melting point, and the bottom layer is a thermal layer of the high melting point. When heating, the upper layer develops first and produces a color. With the increase of temperature, a thermal layer of high melting point produces the second colors. This color is mixed of the two colors that produced by the thermal layer of low melting point and the thermal layer of the high melting point. For example, the upper layer is red and the lower layer is only green. Then the second color is black. In the above way, although we can produce two colors, we can not produce bright colors. For this reason, spot thermal layer of two-color thermal paper with clearance layer has been developed. The bottom is the thermal layer of the high melting point. There is a clearance layer between two layers. The melting point of the material contained in the clearance layer is close to the melting point of the underlying material. And when the melted material is mixed with the upper layer, the color of the upper development image can be faded and even become colorless, making the color of the underlying development more bright. So that there will be obvious differences between two color images.

Next, let me introduce you the colored thermal paper rolls of Third Session National Special Paper Technology Exchange Meeting and Special Paper Committee. 83 Fuji Ma Zhen film company has successfully developed the colored thermal paper, that is, the printing paper which can produce all the color by the effect of overheating. They sealed the chromogenic agent into the microcapsule and then coated it on the surface of the paper to make it colored thermal paper. Once the thermal interaction acts on the surface of the paper, the capsule breaks down and produces three colors depending on the heat, that is yellow, purple and crimson.

The final introduction is about the transfer of thermal paper rolls. Transfer thermal paper is a set of overlapped paper. A special ink is coated behind the original paper (such as the capacitor paper or polyester film of the thickness of 6 - 101xm) and then pack a white paper (the surface should be very smooth with high adsorbability). And when the hot head contacts the paper surface, the ink is melt and transferred to white paper. This thermal recording method facilitates the use of plain paper directly on facsimile without using thermal paper.