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technological innovation

Hot stamping on the release layer


With the continuous development and maturity of China's printing technology and technology, the bronzing process has been more and more widely used in various printed materials. The traditional bronzing process has been quite mature and will not be described in this article. What I want to share with you today is an innovative technology in the bronzing process – bronzing on the release layer. The so-called bronzing on the release layer is to first print the release agent with a relatively low surface tension on the printing material, and then bronze it on the surface after drying. Its main purpose is to replace the use of scratch ink in the printing of traditional prize-winning bills. Since the anodized aluminum pattern is bronzing on the smooth release layer surface, the bronzing pattern is easily scratched, thereby showing the following prize information. However, it is well known that the lower the surface tension of the material, the greater the difficulty of bronzing. This is because the electrochemical aluminum is not easy to adhere to the material with low surface tension. The lower the surface tension, the more easily the gilded graphic is falsified. The author also took a lot of detours in the early stages of trying this new process. I will write down my experience and share it with everyone.

In order to solve the problem of unsatisfactory bronzing on the release layer with low surface tension, my team and I made the following attempts and finally achieved better results.

1, the choice of electrochemical aluminum

Aluminized aluminum is the first point I think of, because there are many manufacturers of electro-aluminum on the market, and the performance of anodized aluminum is also different. Many models of anodized aluminum can adapt to low surface energy bronzing. I and my team experimented with many kinds of electrochemical aluminum foils, and finally found an electrochemical aluminum foil that can adapt to lower surface tension bronzing. However, from the test results, although the bronzing effect is somewhat improved, it is still not ideal. Moreover, it is impossible to select such a higher-priced electrochemical aluminum foil for the sake of cost in the actual production process.

2, the temperature and speed of bronzing

The combination of temperature and speed of bronzing also affects the effect of bronzing. In this respect, we have also made many attempts. Because of the low surface tension bronzing, we have adopted a method of appropriately increasing the temperature and reducing the speed. It’s coming. The temperature is low or the speed is fast, it is not hot at all; the temperature is raised to 210 degrees Celsius, the speed is reduced to 30 meters / minute or less, the bronzing effect is barely arguable in the past, but the anodized aluminum is easily deformed by heat, and this is the case. The speed is too low to meet the needs of actual production.

3, the pressure of bronzing

So what about the hot pressing pressure to solve this problem? After increasing the pressure of bronzing, the effect is still not ideal. If the pressure is increased, it will still be hot and unreal. It seems that the fundamental reason is not here.

4, the application of primer ink

After the above failed attempts, I feel that I still have to solve the problem from the root cause. In fact, everyone knows here: the fundamental reason for the unsatisfactory bronzing on the release layer is that the surface tension of the material after printing the release agent is very low and cannot be combined with the electrochemical aluminum. So how can we improve the surface tension of the material while ensuring the release effect, so that the electrochemical aluminum can be very hot in the specified position of the bill? The answer is a printed undercoat. The undercoating ink is generally a colorless, transparent ink that acts in the opposite direction to the release agent. The release agent reduces the surface tension of the material and the effect of the primer is to increase the surface tension of the material.

The specific process is such that the prize information is first printed at the designated position of the printing material, and then the release agent is printed at the position of the prize information and dried by UV drying to form a release layer, and then the primer ink is printed on the release layer. UV drying, because the primer ink has good adhesion ability, it can be printed on the release layer. Here, a small skill is that the area of the primer layer is larger than the area of the release layer (generally, it is about 0.2mm around) The color rise can be). This is to allow the undercoat to completely cover the release layer to ensure that the bronzing image is completely applied to the undercoat. Finally, the enamel positioning hot stamping technique is used to bronze the undercoat layer. In this way, the anodized aluminum is burned on the undercoat layer with a high surface tension. Therefore, the effect of bronzing is quite satisfactory. The entire process requires one-time processing.

After the finished product, the bronzing graphic is also easily scratched. In fact, the undercoat layer is scraped off the release layer together with the bronzing graphic. Since the primer ink and the release agent are both colorless and transparent, there is no need to worry about covering the prize information below. At the same time, in general, the bronzing graphic is larger than the bonus information graphic, so in fact, as long as the middle part of the bronzing graphic can be smoothly scraped, there will be no problem.