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How to solve the problem that the film product is not bonded?
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In order to improve the surface gloss effect and mechanical resistance of printed products, the film is a frequently used surface treatment method for printed products, which is suitable for the packaging of various products, and can achieve the role of protecting and beautifying the goods and increasing the added value of the products.
In the film coating process, the most prone to quality problems is that the film of the film-covered product does not adhere well to the printed product and is easily detached. This will directly affect the use effect and the service life of the film-covered product. In order to solve this problem, it is necessary to comprehensively consider printing ink, printing process, and lamination process.
Printing ink
The lamination process is relatively simple, and the adhesive is used to bond the printed product to the film. The porous structure on the surface of the non-image area of the printed product is conducive to the penetration and diffusion of the adhesive. Therefore, the ink in the graphic area of the printed matter is the main reason that affects the binding of the printed product and the film.
The effect of the ink on the coating effect is mainly the effect of the surface properties of the ink after drying on the adhesive. When the ink is dry, the main component of the surface layer is the ink diluting agent, and also contains some other substances, for example, the silty particles in the white ink component will float on the surface layer of the ink due to insufficient binding force with the linking material, and then be dried; The aluminum hydroxide in the oil component is too light due to its light weight, and it also floats on the surface of the ink; the film-forming resin of the bright paste component can improve the film forming effect of the ink and is also on the surface of the ink.
When the film is covered, the white ink pigment particles on the surface of the ink will hinder the adhesive and affect the further penetration of the adhesive on the surface of the ink layer; the aluminum hydroxide in Willy oil is easy to form a barrier layer and hinder the adhesion of the adhesive. The interaction between the agent and the ink layer results in blistering or false bonding; the bright paste has an advantageous effect on the film coating, and the composition and the adhesive (the main component is a conjugated multi-bond terpene resin) have similar properties and affinity effects. it is good. Therefore, when adding an ink diluting agent, it is necessary to comprehensively consider the film coating effect of the product.
In addition, the particle size of the ink will also affect the coating effect. If the particle size is too large, it will affect the bonding effect between the film and the surface of the printed product, and it is likely to cause blistering and thus the adhesion is not true. In particular, gold and silver inks, because the metal pigment particles will be separated out after the ink is dried, hindering the mutual combination of the ink layer and the adhesive, the products printed using gold and silver ink are not suitable for film coating.
printing art
Pre-laminated prints need to be printed. As mentioned above, the surface properties of the dried ink will affect the film coating effect. However, under the premise of using suitable ink, the printing web, ink layer thickness, drying effect and the like will also cause the film adhesion to be impractical.
If the printing format is too large (or printing in the field), the contact area between the surface of the paper and the adhesive will be reduced, and the adhesive effect between the surface of the printing product and the adhesive will be reduced, and the quality and service life of the coated product will be greatly reduced. . Therefore, it is necessary to avoid laminating large-format or printed products printed on the ground.
If the printed ink layer is too thick, the hindrance to the adhesive will increase, and it will directly cause delamination, and thus it cannot be bonded. Comparing the characteristics of the ink layer obtained by various printing processes, the thickness of the ink layer of the offset printing ink is the lowest, which is 1 to 2 μm. Therefore, it is preferable to select the offset printing for offset printing, and to pay attention to controlling the overprinting effect and printing of the color printing. The final ink layer thickness.
Also, undried inks can cause the film to expand and elongate, resulting in blistering of the film product and thus poor adhesion. The key to solve this problem is to ensure that the ink is completely dry before the film is coated. It can be accelerated by means of auxiliary drying, but the use of the ink adjuvant should be minimized because the excessive use of the drying oil will increase the smoothness and fineness of the surface of the ink layer. , thereby increasing the adhesion of the film product is not true. At the same time, we must also pay attention to reduce the use of dusting and the impact of the workshop environment on the film of the printed product, because the dust on the surface of the printed product and the dust impurities adhering to the surface of the printed matter in the workshop will act with the adhesive, resulting in The "false adhesion" phenomenon makes it easier for the printed product and film to separate.
Film coating process
The film-coated product is finally completed by a laminating process, and the film quality depends on the implementation effect of the film-coating process. The coating process parameters mainly include the drying effect (ie, the coating film process), the composite temperature, the composite pressure, the coating condition of the adhesive, and the coating speed. Here, the author analyzes the drying effect of the adhesive, the effect of the binding force of the adhesive, and the effect of the coating pressure.
1. Drying effect of adhesive
The drying effect of the adhesive and the drying condition of the ink on the surface of the printing ink have similar effects on the quality of the coating film. If the solvent is not completely dried, the film will expand and stretch, causing blistering, which will result in false bonding.
2. Adhesive binding effect
The adhesive effect of the adhesive is mainly considered in two aspects. One is the application of adhesives, which requires that the adhesive on the surface of the film is uniform and effective, and the thickness of the adhesive must be controlled according to the surface characteristics and structure of the printed product: if the thickness is too thin, the adhesive will be reduced. Force; too thick, it will affect the drying speed. The second is composite temperature, which affects the molecular energy and molecular force of the adhesive. When the molecular force is too small, the adhesion of the film product is too small. In addition, if the composite temperature is too high, the structure of the film will be damaged. Generally, the composite temperature is controlled at 70 to 90°C.
3. Effect of film pressure
The effect of film pressure is affected by two factors: composite pressure and film speed. The composite pressure will promote the penetration and diffusion of the adhesive, and its size should be considered in conjunction with the coating material and other processes; the coating speed is also a multiple-influencing parameter, and its size will affect the coating thickness of the adhesive and the drying speed. Combine with other factors to adjust at the same time.
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