Thermal transfer temperature measurement method
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The drying parameters of the thermal transfer printing of the gel ink ink layer are different from any other screen printing. With thermal transfer printing, the ink layers must be in a gelled state rather than thoroughly dried in order for the next step to be better transferred to the final substrate. In general, the temperature conditions for printing using plastic transfer inks are 100-120°C to get the ink layer properly gelled.
If the ink ink layer is not sufficiently gelled, it will remain tacky. This may cause the transfer papers that complete the transfer printing to stick together when piled together. If the temperature during the transfer printing process is insufficient, the plasticizer in the ink layer will not be properly absorbed by the PVC resin in the ink, and it may also cause the ink layer to become sticky.
Conversely, too high temperatures can lead to unsatisfactory results. That is, high temperatures can cause excessive absorption of the plasticizer by the ink layer and, upon transfer to the silk fabric, reduce the ability of the ink to re-soften and adhere to the silk fabric. The best way to gel plastic ink on transfer paper is to slowly heat the ink layer. Trying to complete the transfer job quickly will be counterproductive. For example, a printer tries to use the flash unit as an in-line heater to gel the ink layer on the transfer paper. As a result, the transfer paper that has been completed in a pile is scrapped. The transfer of the ink layer to the correct gel state, preferably using a glow dryer, allows the ink layer to reach a gelled state over a longer period of time. It is recommended that drying be achieved in the dryer for 45-60 seconds rather than rapid drying at 5-7 seconds at high temperatures.
Measurement of Temperature When the transfer paper is in the dryer, you can use temperature bars or expensive ring detectors to measure the temperature at that time. From the use of experience, the temperature-sensitive temperature bar is better and easier to use. The ring detector can give more accurate measurements, but it needs to block the entry of the product when it enters the dry crucible. In addition, you can also use a non-contact thermometer, but the temperature it reads only shows the dryer temperature at that time, and it cannot show how high the temperature rises when the transfer paper passes through the dryer.
In order to measure the output of the radiant dryer, the temperature bar gives an approximate temperature value. This "approximate value" is also sufficient for this type of measurement because there is no way to give an absolutely accurate temperature value.
Of course, the most authoritative test to prove whether heat transfer is fully dried is practice. When you transfer a printed transfer paper image to silk fabric, as long as it can perform the transfer task fairly well, it shows that Drying is sufficient. To further verify whether the drying parameters meet the requirements, rinse the silk fabric after transfer. If it can be washed, it will further prove the correctness of drying.
The storage of transfer paper to control the temperature of the storage environment is another issue of considerable concern, especially for multi-color printed images. Because the transfer paper is susceptible to changes in temperature and humidity, any large change in either of these two factors will have a significant effect on the color registration of the transfer paper.
To reduce the adverse effects of temperature and humidity on transfer paper, you must do preventive work. First of all, the best method is to store it in a house with controlled temperature and humidity. The temperature is controlled at 24-30°C and the humidity is 30%. Under this condition, the expansion and contraction of the transfer paper can be minimized. Second, you can store the transfer paper in a paint bag. In order to properly monitor and maintain properly controlled storage conditions, it is best to buy a better thermometer and hygrometer.
The transfer process assumes that you have correctly controlled the drying temperature to obtain a properly gelatinized transfer ink layer. Now the task is to transfer the transfer paper image to the silk fabric. If you are using tools for image transfer, note the following:
1. Many printers often make such mistakes that they always think that the transfer is easier than direct screen printing. They always want to "I just need to "bake" the image onto the silk fabric. What's the problem?" Actually, if you can't control the transfer process properly, defective products or waste products will appear in large numbers. Therefore, to properly handle the transfer process, you must not be sloppy.
2. Three basic parameters need to be remembered in order to obtain better viscosity and print durability. These parameters are temperature, time, and pressure. Any abnormality in any of these three parameters will lead to a decrease in the quality of the finished product.
3. To be able to achieve plastic transfer, the temperature is mostly 188-190°C. At this temperature, the printing ink on the transfer paper re-softens, and can be transferred and consolidated on the silk fabric. If this temperature is not reached at the time of transfer, the result is either that the bonding is not good or that the ink is not easily separated from the transfer paper.
4. So how do you know if the temperature meets the requirements under certain pressure? The best measurement method is to use a contact thermometer. In order to measure the temperature of the transfer, the thermometer should be in direct contact with the heated and pressurized rollers.
5. The contact thermometer is a good temperature measurement tool because it is directly in contact with the heating body and can obtain accurate temperature values. This tool not only gives the current temperature, but also recognizes the temperature change during the transfer process. Non-contact thermometers are also sometimes used to measure temperature, but it is not as accurate as contact thermometers. In short, no matter which kind of temperature measurement tool is used, if the temperature is abnormal, be sure to tell the transfer person immediately.
Conclusion Although we have discussed some of the control variables in thermal transfer printing, there are more variables in actual production. You must remember that unlike the direct printing after the drying of the printing, the direct printing is to achieve a complete drying, and in the thermal transfer it is necessary to reach a certain degree of the gelatinized ink before it is transferred to the final printed product. Can maintain a stable image. Although temperature and humidity are not all parameters that need to be controlled during thermal transfer, using a temperature control and monitoring process can help you achieve this goal. I believe that as long as continuous practice, you will be able to better complete the task of thermal transfer