Problem and improvement of sticking paper in thermal printing process

■ Background

As thermal paper is widely used in retail, gaming, finance, clothing, logistics, medical and other fields, in order to meet a variety of applications, formulations and coatings are also different, such as to improve the coating of colorants and thermal base paper The cloth effect is added with sizing agents, etc., and problems such as sticking paper (Sticking) are introduced.

■ Mechanism of sticking paper

Under certain conditions such as low temperature or high humidity of thermal printers, the heat storage of the thermal body of the printing head is insufficient or the cooling speed is too fast, the thermal paper and the printing head are stuck, or the printing is compressed and noise is sticking (Sticking) Phenomenon. See Figure 1 for the color reaction of thermal paper and Figure 2 for the schematic diagram of TPH printing.

■ The phenomenon of sticking paper

When the thermal printer is printing normally, the paper feeds evenly, and the printing patterns are evenly distributed. When the paper sticks, the paper feeds faster and slower, and the printing patterns are also different in shades and noises, as shown in Figure 3.

■ Influencing factors

According to the degree of influence from large to small, they are: thermal medium characteristics, ambient temperature and humidity, printer structure and proofs,

Thermal print head construction, printing speed, pressure, etc.

■ Improvement of sticky paper problem

We can adjust the cross-sectional structure of the thermal print head to make the paper and the print head easier to peel off, thereby reducing noise. However, the main source of sticky paper is still the characteristics of thermal media. In order to compare the differences between different media,

We conducted comparative tests of carbon deposition on various paper samples at home and abroad, and the experimental results of three representative papers are shown in Table 2.

The thermal layer and top coating of thermal paper have a great influence on STICKING PHENOMENON, mainly because of the temperature resistance of organic components contained in the top coating, and the improper use of inorganic components such as lubricants in the thermal layer will cause STICKING.

Summarize

From the test results of the three kinds of paper, it can be seen that there are great differences between different thermal papers, indicating that there is also a lot of room for improvement.

The improvement of the characteristics of the thermal print head itself and the improvement of the printer's setting conditions can reduce the phenomenon of sticking paper, but the degree of improvement is limited, and the sticking paper cannot be completely eliminated from the root cause, so it is necessary to improve the thermal paper.

Major domestic printer manufacturers have found more and more feedback problems of carbon deposition and sticky paper, which are becoming more and more serious, seriously affecting normal printing and even destroying the print head. International Korean customers, Japanese customers, Bank of Malaysia, Bank of Thailand, etc. have also begun to complain about carbon deposits and sticky paper issues, and the improvement of paper quality is imminent.