In-mold label security and printing technology

In Mould Label (IML) is a special label that uses a hot melt solid adhesive to bond with the surface of a plastic bottle when it is made into a bottle body, and is integrated with the bottle body in the mold. The most important feature of using plastic bottles with in-mold labels is that the label and bottle body are on the same surface, and there is no label. The color pattern is printed directly on the surface of the bottle body.

First, the characteristics of the in-mold label

1. Aesthetics The traditional labels are in the form of heat-shrinkable labels, direct screen printed labels, and self-adhesive labels. The direct screen printing label directly prints the pattern and the text on the container packaging through the screen printing method. The overall effect is good, and the pattern and the text have the texture, but it is difficult to reflect the delicate pattern and the fineness by the limitation of the screen printing. Text, when printing more colors, the use of direct screen printing is more expensive. Heat shrink film is used as a label, and its cost is lower than adhesive label and direct screen printed label, but the heat shrinkable label is easily damaged, the overall image is not very good, and it is not conducive to environmental protection; self-adhesive label can be perfect Reflects the requirements of the exquisite label, but its cost is more expensive than the heat shrinkable film label.

The close integration between the in-mold label and the bottle body has the overall effect of direct screen printing, and it can perfectly embody fine patterns and small texts like stickers. Since the in-mold label is combined with the bottle body, it is less likely to be damaged or detached than the self-adhesive label and the heat shrinkable label, and the label can be kept intact and beautiful for a long time.

2. Anti-counterfeiting The use of in-mold labels requires special molds. This mold has a higher production cost and functions as a cost anti-counterfeit. At the same time, the in-mold label printing process is more difficult than traditional labels, and thus serves the purpose of anti-counterfeiting.

3. There are more varieties of environmental-friendly in-mold label materials. Common plastic containers have matching in-mold label materials with the same composition. At the same time, the labels are combined with the container, so that the recycling rate of the bottles is higher.

4, limitations Traditional labels are glued to the surface of the container by adhesive, the in-mold label tightly binds the label and the container together. The sales situation of the product is not as good as expected. If a self-adhesive label is used, only some labels will be wasted, and a new batch of labels can be reprinted on the unused bottle, and if the bottle body is not satisfied, Only the bottle body can be changed and the label can continue to be used. In this case, if an in-mold label is used, it is likely to cause a large amount of waste of the bottle body and the label. Containers made by blow molding process If the use of in-mold labels is required, the curvature of the container must be taken into account. If the curvature of the container is too large, such as a round bottle, during the in-mold labeling process, if the exhaust is difficult, the in-mold label should not be used. In addition, the volume of the blow-molded containers is too large, and it is not particularly suitable to use in-mold labels.

Second, the label printing technology

The in-mold label is to embed the printed label into the container during the blow molding or injection molding process so that the label and the container are integrated. The basic process of in-mold labeling in the blowing process: the pre-printed in-mold labels (pre-labels and back labels) are stacked in a single sheet format and placed in the two label boxes of the in-mold labeling machine. . With the opening of the bottle mold, the robot picks up the front label and the back label, the label printing surface faces inwards, the solid adhesive surface faces outwards and is placed on both sides of the mold. The vacuum hole on the mold firmly holds the label. In the mold. When the raw material of the plastic bottle is heated and hangs down in a hose-like form, the labelled mold quickly closes and the air is blown into the hose so that it closely contacts the mold wall. This is the blow molding process. At this time, the temperature in the entire mold is still relatively high, and the label-shaped solid adhesive close to the preform of the bottle body starts to melt and is combined with the plastic bottle body. When the mold is opened again, the plastic bottle body is molded and the label is integrated with the bottle body.

1, in-mold label material selection

The film materials used for in-mold labeling are classified into two major categories: paper and film. Ordinary synthetic paper has poor surface smoothness, low strength, no elastic deformation, and is not suitable for high-grade color printing, and is generally suitable for applications of large-area barrels. The unique multi-layer co-extruded face material of film material has a smooth surface suitable for a variety of printing methods, and the process of label processing will not cause overprinting or inaccurate die cutting due to deformation, among which materials such as Primax, FasClear, etc. can be stretched and contracted. The plastic bottle body can be deformed along with the deformation of the bottle body, and the wrinkling of the label will not appear on the surface of the bottle body. The surface of the film material does not absorb ink, so the label printed by the film material has a bright color, a strong three-dimensional effect, and the color effect is obviously better than the paper material, and is suitable for high-end color printing and generally suitable for various kinds of delicate products. PE, PP or a combination of PE and PP.

2. Printing and processing of in-mold labels

Design the surface of the container as an INL tag. The shape of the logo is determined by the contour of the container to be filmed, and the thickness of the label is between 60 and 100 μm.

1For paper feeding and tension control, 152mm paper core tube should be used as the label material, and the paper core tube with large diameter can ensure that the material near the paper core is small in bending and deformation, and the label deformation after processing is small. In addition, the machine is required to be equipped with an automatic material tension control device, which can ensure accurate label overprinting.

2 Corona treatment, when the surface tension is greater than 40 dyne, can satisfy the ink wetting without corona treatment. However, when the surface tension is less than 40 dyne, corona must be applied to satisfy the firmness of the ink after printing. The negative effect of random corona treatment is to generate a large amount of static electricity on the surface, making it difficult to peel off the label when applied. Therefore, minimizing random corona and reducing the occurrence of static electricity.

3 Printing, the surface material of the in-mold label material is synthetic paper. Can use offset printing, convex / flexographic printing, gravure and screen printing and other printing methods to achieve. In these several printing methods, they can be subdivided according to the quantity and requirements. Offset printing has the advantages of flexible production and rich printing layers, suitable for printing small batches and many varieties. The in-mold labels with high printing quality requirements are printed with convex/flexible UV inks, which makes the printing colors more brilliant, fast drying, and high efficiency of one-piece molding. It is suitable for medium and large batch production. The gravure printing ink layer is thick and has the best scratch resistance, and the printing speed is also the fastest. It is particularly suitable for long-lived printing of large quantities, and screen printing is suitable for making transparent labels that require the use of a background color or a printing field.

a. First, determine the printing surface and the adhesive surface. Use the method to identify the dyne value of the material, or use solvent to wipe the surface of the film.

b. According to the proportion of film shrinkage and deformation, the direction of the label's labeling should be parallel to the machine direction to ensure the minimum deformation of the label. Correctly control the tension of the material, avoid the distortion of the oversized material and cause the machine direction label to bend.

c. Select the appropriate ink and varnish to ensure the scratch resistance of the label. Offset printing is suitable for quick-drying and non-skinning inks, such as POP and TSP inks. UV ink printing can achieve the best printing quality. The amount of fountain solution is reduced by 10% to 15% compared with the general situation (the printing Plate does not dry out). Excessive dampening solution can cause spurious drying and ink emulsification in printing. The pH of fountain solution should be controlled between 6 and 6.5.

The use of UV inks for embossing and flexo printing allows instant drying and bright ink.

d. The more commonly used film type in-mold label material is softer and requires stacking when labeling, and it is prone to generate static electricity. In order to print the labels can be stacked neatly, labeling can be successfully peeled, requiring the printing press, die cutting, waste discharge, label cutting, label stacking and other workstations must also install static eliminator to ensure that the finished product label No static electricity. Static electricity is related to temperature and humidity. The ideal temperature in the printing room is 21°C±2°C and the relative humidity is about 50%.

4 Hot Stamping, In-Mold Labeling Materials The foil stamping process can be performed using an electro-aluminum stamping foil of a general-purpose film material.

5 glazing. The in-mold label material must be glazing after printing to protect the ink and achieve a smooth surface of the label. Use a high-quality, scratch-resistant special coating that does not cause shrinkage to avoid bending after bending. Flat, smooth surface labels do not stick and easily separate when stacked. Varnish can be selected to match the ink water or oily IR Varnish and UV Varnish.

6 die-cutting, because there is no bottom paper, die-cutting in-mold labels is not the same as the traditional non-lithic label die-cutting. According to the customer's specific circumstances, die-cutting can be done online or after cutting. No matter which kind of die cutting is used, special hardened steel die-cutting tools must be used. On-line die-cutting die-cutting rollers are specially manufactured by the supplier and die-cut after dicing using a wine mark die-cutting machine.

7 The packaging of finished product labels. Due to the inconsistent surface ink layer of the finished product label, there will be inconsistencies in the thickness when binding. If the binding is unreasonable, label bending may occur. It is recommended to use rigid carton packaging, or plywood binding at both ends. Use shrinkage. Membrane packaging to ensure the flatness of the label and prevent damage to the edge of the label.

8 Labeling, placing labels on robots with special operating devices via special handling equipment. The tag is placed by the robot and the tag is fused with the plastic to form a seamless whole.

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