Resolving the Difficulties of the Quality of In-Mold Label Printing Process

The good performance of in-mold labeling makes it a packaging method with great potential for development. Different printing manufacturers can use different printing processes and post-printing processes to produce in-mold labels according to their own equipment conditions. This article will give a brief introduction to different in-mold label printing processes, post-printing processes, different production process flow problems and solutions to production difficulties.

First, the printing mode of the in-mold label

In-mold labels can be printed using a variety of printing methods.

1. The printing quality of offset printing in small outlets is better than other printing methods. For short-run business, the production cost of offset printing is lower than other printing methods. In the line, the actual printing effect and the saturation of the color are less than other printing methods. Offset printing on the color difference is more difficult than other printing methods.

2. The gravure printing method is better than the offset printing in field printing effect and color saturation. It is inferior to other printing methods in the fine dot printing quality and image level richness. It is better than offset printing and letterpress printing in the control of color difference. Since the gravure printing path is longer than other printing methods, static electricity is more easily generated than other printing methods. Intaglio printing plates have a long production time and cost, so medium and short-run in-mold label printing businesses are not suitable for gravure printing.

3, letterpress printing in the printing of small dot quality is worse than other printing methods, the printing plate of the printing force is lower than the gravure and flexographic version, in the control of printing color difference than offset printing, but the effect is not as good as gravure printing and flexographic printing , And it is easy to have ink bars, plate making costs and cycles lower than gravure printing and flexo printing.

4. The flexographic printing method is the mainstream packaging and printing method in Europe and America. With the CDI platemaking technology, the flexographic printing method can obtain better dot printing quality and saturated printing colors. The flexographic printing mode can not be compared with other printing methods. The advantages of multi-process combination printing, at present, due to the domestic related flexible printing plate and knife mold and other related facilities is not so convenient, so it can not reach the ideal printing effect.

5. The screen printing method is not as good as printing the in-mold label directly on the bottle body.

Second, the in-mold label printing process is the key to the use of ink

Although various printing methods can use different types of inks to print in-mold labels, the good adhesion of the UV ink to the surface of the in-mold label material and its drying characteristics are undoubtedly the best choice for various printing processes. The ink balance of the UV offset printing process is the key to high-quality printing of labels and high yields. The key to using UV inks in other printing processes is the selection of UV inks with both high color intensity and good leveling performance. Therefore, in the large-area printing thick real-time, in the appropriate color ink on the appropriate and appropriate amount of antistatic agent knot printing process will be a certain degree of elimination of static electricity.

Third, the in-mold labels glazing

In order to reduce the failure of in-mold labeling, if using the vacuum adsorption in-mold labeling method, the anti-static agent and the smoothness of the varnish should be properly added to the varnish, and the varnish should not be used when using the electrostatic adsorption in-mold labeling method. Add antistatic agent. If hot stamping is required after printing the in-mold labels, hot UV varnish should be used. If additives are added to the varnish, each batch of varnish should be tested beforehand to avoid the occurrence of scrapping of the entire batch of products.

IV. Die cutting of in-mold labels

For roll-shaped printing semi-finished products, if a die-cutting method is adopted after cutting, the pin-position movement phenomenon often occurs when the sheet is cut off. The movement of the needle position directly affects the efficiency of the entire production process and the final yield. To solve the problem of pin position movement when cutting Zhang Zhang: maintain tension stability, eliminate cumulative error of Zhang Zhang in time; Method 2: Make trapezoidal needle bit line at the time of plate making, and then select and classify different needle bit lines.

(I) In-mold labels Off-line die-cutting Die-cutting can be performed using a numerically-controlled automatic die-piercing machine, a semi-automatic trademark die-cutting machine, or a semi-automatic die-cutting machine.

1, using CNC automatic; die machine cutting should pay attention to:

(1) For the semi-finished products with different needle positions, the starting position and end position of the label and the die cutting distance should be promptly corrected;

(2) The same stack of semi-finished products will not produce too much slippage and avoid the uneven edges and asymmetries in the finished product;

(3) The number of stacked semi-finished products can not be too much, so as to avoid the trademark distortion and the phenomenon of the size and asymmetry of the finished product;

(4) The local protective rubber should use elastic and flexible materials to protect the die cutter.

2, use semi-automatic trademark; mold machine should pay attention to:

(1) Do not use to die-cut larger gauge labels;

(2) Avoid punching of the entire stack of marks to prevent the appearance of large or small marks or asymmetry of the mark when punching.

(3) The relative position of trademarks and die cutters should be observed to avoid the appearance of large and small marks and asymmetry of trademarks;

3, use semi-automatic die cutting machine to die cutting need to pay attention to:

(1) The full-page pressure needs to be adjusted;

(2) Monitoring whether the positioning block has slippage at any time;

(2) Linkage die cutting of in-mold labels: In-mold label manufacturers are prone to disorderly marking when using a flexographic printing press to perform in-line die-cutting. The occurrence of disordered labels is mainly caused by the static nature of the labels and the non-smooth transfer of labels. Therefore, when disorder occurs, the collection and arrangement of finished products should pay attention to checking whether there is a phenomenon of inversion or back-marking.

Five, in-mold label bronzing process

The bronzing above the in-mold label material can be performed by first hot oiling, or by different hot stamping techniques after oiling. Bronzing can use cold and hot scalding.

The main factors affecting the effect of hot foil stamping are: anodized aluminum, hot stamping temperature, hot stamping pressure, and hot stamping speed.

First, based on the material characteristics of the in-mold label and the adaptability of the aluminum foil, the bronzing temperature and the bronzing pressure are determined according to the size of the bronzing plate and the bronzing speed. The pressure is adjusted first, and then the bronzing temperature is determined.

Cold-foil gold is mainly used for flexographic printing. The use of cold-foil gold to obtain good visual effects requires a relatively high process technology. It is recommended for general manufacturers to use the process of printing after the first cold-hot printing, and use a thicker layer of ink to cover the edge of the cold hot stamping. glitch.

VI. Elimination of static electricity

The in-mold label material has a good electrical insulation, and the static electricity generated by the friction during printing is hardly eliminated by its own conduction.

The main effects of static electricity on in-mold labels are:

1, easy to absorb the dust in the air, resulting in printing dirty spots, pinholes, graphic burr phenomenon, thus affecting the appearance of the label;

2. The in-mold label with static electricity has strong adsorptivity, which makes it easier to increase the difficulty of printing and die-cutting, and the phenomenon of label re-elongation occurs.

The main measures to eliminate static electricity in the mold label:

1, try not to use corona processor when printing;

2. Adding antistatic agent to Varnish and Large Solid Ink;

3, install static elimination device;

4, the work shop humidity control at about 60%;

The above is a brief introduction to the general printing process of in-mold labels. The above mentioned introduction relates to the UV offset printing process, the flexographic printing process, the printability of UV inks, the bronzing process on non-absorbing materials, and the cold gilding (cold transfer) technology. , CNC automatic; China mold has not been widely used in the country, but the use of these emerging process technology, expand the combination of in-mold label production process, enhance the trademark's anti-counterfeiting performance, is the development direction of in-mold label production process.

(Author/Li Xiaodong)