Thermal paper is kind of a special refined paper that encompasses a coating of a special material that changes color upon exposure to heat. This special feature eliminates the need to use traditional ink. Special heat-sensitive chemical materials are applied to the paper base during the manufacturing process of thermal papers. However, the types of chemicals used vary from manufacturer to manufacturer. Thermal papers are mainly used for the printing of labels, tickets, POS thermal receipt papers, medical charts, etc.
Thermal Paper Technology
In technical language, thermal paper is referred to as a recording media that gets printed by virtue of heat provided from the thermal printer.
It is basically heat that imparts the image on thermal papers when they pass over the thermal print head, without the use of printing ink. The direct transfer of heat (thermal energy) is responsible for the creation of an image on thermal papers. The use of thermal papers eliminates the risk of the ink ribbon, toner, or ink cartridges. Small, compact thermal printers are used for the purpose of thermal printing. These are very easy to maintain and thus, have high reliability and convenience.
What is the Structure of Thermal Paper?
A thermal paper comprises a base paper and a few special coating layers. The paper is coated with a precoat layer and a thermal layer on the recording side.
The base paper is the first layer of the thermal paper which is actually developed for the thermal paper technology. It is then coated by a thermal layer to serve the purpose!
This is the layer that refines heat insulation, smoothness, uniformity, and anchoring of the thermal layer.
The thermal layer is designed to create images on thermal papers with a thermal reaction. Practically, this layer, along with chemicals like date, developer, and sensitizer, is the reason that the paper turns black in the heated areas.
The thermal coat is comprised of several chemical compounds which include leuco dyes, developers, and sensitizers.
Components of Thermal Coat
Leucos dyes provide the black color that is present over the printed thermal paper. In the initial stage of the coating, the dye is in the form of the fine powder obtained from the grounding of colorless crystals. When the thermal print heads impart heat on the thermal paper, the due crystals are melted as per the head projection and the melted matter then gets mixed with an organic acid (Known as Developer and is also present in the thermal coating) to produce an opaque color.
Bisphenol-A (BPA) or Bisphenol-S (BPS) are some commonly used developers.
As for the sensitizers, these are incorporated to adjust the temperature required to activate the coating and form an image. Besides, the sensitizers also facilitate the mixing of dyes and developers.
Top Coated Thermal Paper Structure
Applied over the thermal layer is the topcoat layer which is applied to make the thermally printed image highly durable. Besides, even the layer on the backside can be coated to increase the printability and the backside protection against the adhesive.
Salient Features of Thermal Papers
Thermal papers have major applications in Thermal Printing, and that is why, properties like grammage, thickness or strength, thermal printing quality, and image stability are equally considerable for thermal papers like that of normal papers.
Which General Properties need Consideration?
The general properties that need to be considered are classified as follow:
- Basic properties like grammage, thickness, and moisture
- Properties regarding Strength like tensile and tearing strength, and elongation
- Surface properties i.e. opacity, brightness, smoothness/roughness, whiteness, and surface strength
- Absorption properties like water, oil, and printing ink
Which Thermal Properties need Consideration?
- Image Stability: It determines the duration for which a thermal print remains readable when it is stored in correct conditions.
- Density: It is the value of optical density that is measured from the thermally printed image.
- Dynamic Sensitivity: It determines the speed and energy level at which the thermal paper can be printed. The greater the dynamic sensitivity, the better the quality.
- Static Sensitivity: It determines the temperature at which the thermal image begins to formulate. Higher temperatures are required for the formulation of an image when the static sensitivity is low whereas if it is high, thermal images can be formed at low temperatures.
Advantages of Thermal Papers
Thermal papers and thermal printing have gained huge popularity over time. Not only these are beneficial but are also pretty cost-effective. Listed below are some mind-blowing advantages of thermal papers:
Accuracy and Quality
Printing gazillions of paper receipts, shipping labels, tickets, etc. is a routine part of business companies. These are major written evidence and that is why these should be legible and readable. The surface of thermal papers bear smooth and even coating and upon passing through the heated printer head, there is a chemical reaction on the coating cells of the surface due to which a high definition image is formed. Since the process does not involve the use of ink, there are no smears and smudges due to which the image or words get difficult to read.
The conventional printers operate at a slower pace as these involve the use of ribbons to transfer ink to the paper. The images are produced faster via thermal printing rather than regular printing. It is just a matter of milliseconds to print an image and the drying also happens instantly. The more the printing speed, the faster the printing rate of receipts and thus, a considerable amount of time can be saved.
Low Maintenance Costs
Using thermal printers lets you get rid of the hassle of maintenance expenses. You don’t need to replace those expensive ink or toners over regular intervals. Besides, the printer has few working parts which are quite swift and do not require frequent complicated repairs.
Reduced Printing Costs
The thermal paper rolls have a very low price compared to other forms of paper and printing modes. As the conventional printing modes do not only cost paper but also ink and cartridges. Thermal printing is an efficient means for businesses and industries to save both their time and money.
Durable and Time-Saving
Since thermal printers have very few parts, they are more reliable and durable than ink printers. There are no jamming glitches, moreover, these are resistant to climate, soils, UV rays, and other sources of damage.
With so many advantages, there’s no wonder people are biding goodbye to conventional printing and rapidly switching to thermal printing.