In-mold label materials are divided into two categories: paper and plastic film. The former will deform when exposed to water or moisture, reducing the use value, but its advantage is that there is no static electricity interference, which reduces the loss of label absorption when blowing the bottle. In addition, it is not the same material as the plastic bottle, which is not convenient for recycling. At present, plastic film-type in-mold label materials are generally used at home and abroad.
The in-mold label material structure consists of a printing surface, an intermediate layer and an adhesive layer. The function of the printing surface is to receive ink to form color graphics; the intermediate layer supports the printing surface, giving the material sufficient stiffness and transparency, and will not deform on the printing press and under the action of high temperature to ensure accurate overprinting. The adhesive layer will melt under the action of high temperature, so that the label material and the plastic container are integrated, ensuring that the label and the plastic bottle are firmly adhered to each other.
Printing of in-mold labels
Different printing manufacturers can choose different printing processes according to their own equipment conditions. Offset printing, flexo printing, letterpress printing and gravure printing can all print in-mold labels, and offset printing and flexo printing are currently the most common.
1. Offset printing
The advantages of offset printing in fine-dot printing are very prominent, but the line, solid printing effect and printing saturation are not comparable to other printing methods. Offset printing cannot achieve inline printing processing like flexo printing, so offline (Offline) die-cutting, cold stamping, glazing and other processes must be carried out after printing. However, offset printing is suitable for the printing of small batch labels, with short cycle times and strong flexibility.
2. Gravure
Solid printing and printing color saturation are better than offset printing, not suitable for printing small dots and rich layers of trademarks. But chromatic aberration control is more convenient. On a gravure press, the in-mold label material has a longer paper path than other printing methods, so there is a greater chance of static electricity. Gravure plate-making has high cost and long cycle time, so it is suitable for long-form in-mold label printing.
3. Embossing
Embossing is suitable for printing solid and line trademarks. The effect of printing small dots is not ideal. The color difference control of the same batch of products is also easier, but ink streaks will appear. From a cost perspective, it is cheaper than both gravure and flexo.
4. Flexo
The outstanding advantage of flexographic printing is that the printing and post-processing processes can be completed in one go. The front end is the feeding end, and the back end is the final printing and processing product, which realizes the in-line production of printing and post-processing. Now, with the improvement of flexographic plate-making technology, the quality of dot printing has been greatly improved. The use of flexo printing for in-mold labels has been recognized by some manufacturers, but printing with environmentally friendly water-based inks is not mature. At present, experienced manufacturers It is the use of UV ink with good fluidity, and it has become the trend of in-mold label printing.
Post time: Oct-14-2022