The Generation and Improvement of Carbon Deposit in Thermal Printing Process

■ Background

As thermal printing is widely used in retail, gaming, finance, clothing, logistics, medical and other fields, in order to meet a variety of applications, the formulation and coating of thermal media are different, sometimes due to the unreasonable coating of thermal media Or thermal print heads and printers are not properly designed and used, resulting in thermal media melt that cannot be well absorbed, resulting in carbon deposits (ie Sludge), which adhere to the heating element of the print head, thereby affecting the printing quality and even destroying the thermal mass. sensitive print head.

■ Carbon deposition mechanism

After the thermal paper is heated and colored, if the absorption is not good, when the thermal paper leaves the high-temperature heating element, the melt cools and solidifies. carbon. The schematic diagram of carbon deposition is shown in Figure 1.

■ Phenomenon of carbon deposition

During the printing process of thermal printers, black or white carbon deposits will be generated on the print head.

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Feasibility Study Report

The sensitive paper is in poor contact and white streaks or lines are printed. The carbon deposition phenomenon is shown in Figure 2 and the bad proof is shown in Figure 3.

Printing after carbon deposition Normal printing Figure 3 Schematic diagram of poor carbon deposition printing sample

■ Influencing factors

In descending order of impact, they are:

Thermal media characteristics, thermal print head structure, printer structure, printing energy, pressure, ambient temperature and humidity, etc.

■ Improvement of carbon deposition problem

We can adjust the cross-sectional structure of the thermal print head to make it easier to discharge carbon deposits, thereby reducing the accumulation of carbon deposits. However, the main source of carbon deposition is still the characteristics of heat-sensitive media. In order to compare the differences between different media, we have carried out a comparative test of carbon deposition on various paper samples at home and abroad. The experimental results of three representative papers are shown in Table 2.

Table 1 Comparison of carbon deposition with 3 different paper grades

From the comparison results in Table 2, under the same inca test conditions, different thermal media produce obvious differences in carbon deposition:

Therefore, the carbon deposition has a great relationship with the thermal paper primer, the organic and inorganic composition ratio of the thermal layer and the coating process. From the test results of the three kinds of paper, it can be seen that the difference between different thermal papers is very large, indicating that there is also a lot of room for improvement. Improving the structure of the thermal print head and adjusting the printing conditions can reduce the phenomenon of carbon deposition, but it cannot completely eliminate the carbon deposition from the root cause, so it is necessary to improve the thermal paper.