You will become an expert on thermal paper as long as you finish reading this article

THERMAL PRINTING
Thermal paper is a recording media to be printed with heat from the thermal printer. The image is produced by heat, without printing ink, when the selected area of the thermal paper passes over the thermal print head.

The image is created through the direct transfer of heat (thermal energy) to the thermal paper: thermal paper has a coating, which changes color to black when exposed to heat. No ink ribbon, toner, or ink cartridge is required to record information on the thermal paper. Thermal printing is done with small, compact thermal printers that do not need much maintenance. Thermal paper is widely used in many applications, such as labels, tickets, POS receipts, and medical charts, because of its high reliability and convenience.

THERMAL PAPER STRUCTURE

The thermal paper consists of a base paper and a few special coating layers. The precoat and thermal layers are coated on the surface side (the recording side).

• Base paper

The first layer of the thermal paper is base paper specially developed for thermal paper technology. A thermal layer coats the base paper.

• Precoat layer

The precoat layer improves heat insulation, smoothness, uniformity, and anchoring of the thermal layer.

• Thermal layer

The purpose of this layer is to produce images with a thermal reaction. In practice, the paper turns black in the heated areas due to this layer with chemicals like dye, developer, and sensitizer.

TOP COATED THERMAL PAPER STRUCTURE

A topcoat layer is applied to the thermal layer when high durability of the thermal printing image is needed. Also, the backside layer can be coated to improve both the printability and the reverse side protection against the adhesive.

• Topcoat layer

The topcoat layer protects the thermal layer from water, oil, solvent, humidity, scratches, etc.

• Backcoat layer

The backcoat layer is applied for de-curling, antistatic electricity treatment, and back-barrier against adhesive.

THERMAL PAPER FEATURES

The main function of thermal paper is "thermal printing." This is why, in addition to normal paper properties like grammage, thickness, or strength, the thermal printing quality and image stability are important. Furthermore, pre-printability by conventional printing methods like Flexo or Offset is also required for thermal paper.

General paper parameter

• Basic properties: grammage, thickness, moisture

• Strength properties: tensile and tearing strength, elongation

• Surface properties: brightness, opacity, whiteness, smoothness/roughness, surface strength

• Absorption properties: water, oil, printing ink

Thermal paper parameter

• Image stability refers to how many years the thermal print will be readable when stored under incorrect conditions.

•Density is an optical density value measured from the thermally printed image.

• Static sensitivity shows at which temperature the thermal image starts to formulate. Low static sensitivity means that the thermal image starts to formulate at high temperatures. High static sensitivity, in turn, means that thermal imaging starts at low temperatures. If the thermal paper is used at high-temperature conditions, the static sensitivity is a very significant feature.

•Dynamic sensitivity shows how fast and with what energy level the thermal paper can be printed. Basically, higher dynamic sensitivity equals better quality.