Thermal shrink film label printing and application analysis

This article describes the characteristics of the heat shrinkable film label, its printing process and future application prospects.

In recent years, the global label market has grown rapidly, with an average annual growth of 5% -7%. The global label market output reached US$62 billion in 2005. From the point of view of increase in label usage, the global label usage will increase by 6 in 2006. .2%. Therefore, we can estimate that the global label market output now exceeds 33 billion square meters, and the label production in Europe has exceeded 10 billion square meters, and per capita consumption has exceeded 15 square meters. The United States increases by 5% each year, Japan increases by 3% to 5% each year, and China, Latin America, and Eastern Europe have the fastest growth rate by 15% to 20%.

Heat shrink packaging is a kind of packaging method widely used in commodity packaging, which can be used to package various types of products, with features such as transparent assembly, sealing, moisture-proof, etc., with simple process and equipment, low packaging cost and various packaging methods. Greatly loved by businesses and consumers. Heat shrink labels are part of the label market and are used in heat-shrinkable packaging. They are in rapid growth and their market share continues to expand. It is expected that the annual growth rate can be maintained at about 15%, far exceeding the annual growth rate of about 5% in the general label market, with huge development potential and becoming the biggest highlight of the label industry.

The heat-shrinkable label has strong adaptability. It can be used to decorate and decorate wooden paper metal glass, ceramics and other packaging containers. The main application areas are food and beverages, health products, daily chemical products, and chemical products.

First, the heat shrink film label and its characteristics

Heat shrink film label is a type of film label printed on plastic film or plastic tube using special ink. During the labeling process, the shrinking label will quickly shrink along the outer wheel of the container when heated, and cling to the surface of the container.

1. The advantages of heat-shrinkable label packaging.

(1) Shrink-wrapped packaging can be used to pack special-shaped products that are difficult to pack, such as vegetables, meat, poultry, aquatic products, toys, gadgets, and small electronic products.

(2) The heat shrinkable film has a high transparency, so the label has a bright color and a good gloss.

(3) The shrink film is tightly adhered to the product after shrinking, the package is compact and the appearance of the product is displayed, and the packaged product is beautiful.

(4) The heat shrinkable film can provide a full 360 degree decoration of the packaging container. Product information such as product descriptions can be printed on the label so that consumers can understand the product's performance without opening the package.

(5) The shrink film has good abrasion resistance and high strength to ensure that it bears the weight of the contents. Printing belongs to the film printing (in the film sleeve, the text), can play a role in the protection of the imprint, and the label wear resistance is better.

(6) The heat shrinkable packaging has a good seal, moisture, anti-fouling, anti-rust effect, can extend the shelf life of food, easy to store. Convenient for stacking in the open air. Save storage space.

(7) Heat shrink packaging process and equipment are relatively simple. Good heat sealability, no adhesive is required for labeling.

(8) Shrink-wrapped packaging can also use in-situ shrink packaging methods to package bulky products such as racing boats and cars. Shrinking film itself has better softness; neutrality and toughness; it can prevent vibration during transportation and Damage to products due to impact, transportation can no longer use other packaging materials, low packaging costs, lower costs than adhesive labels.

(9) Now that the shape of the packaging container is unique, there is an increasing number of individual designs. The heat shrinkable film label can clearly show the outline of the outer surface of the packaging container.

(10) The residual amount of solvent is low, and the residual amount of solvent will be maintained at about 5 mg/m2, which is far lower than other printing methods.

(1 1) Heat shrinkable film as a label to save forest resources, reduce costs, hygiene, and ease of use.

2. The disadvantage of heat shrinkable film labels.

(1) It is necessary to consider that the shrinkage rate of the graphic image is the same as the shrinkage rate of the shrink film, and can be accurately reproduced.

(2) The ink used in the thermal shrink film label printing must also have a certain shrinkage rate in order to accurately reproduce the graphic.

(3) Since the heat shrinkable film label must be shrinked during the printing process, and the barcode can be read only with accurate reproduction, it must undergo strict design and print quality control. If the pattern shrinks and deforms, it will cause the barcode quality to be unqualified or unreadable.

(4) The printability of most heat-shrinkable films is not very good and requires prepress prepress. $Page break $

Second, the thermal shrink film label printing process

1. Prepress processing.

As a heat shrinkable film label. In the printing process. Contraction deformation is inevitable. Sometimes it is even more serious, and the shrinkage in different directions and positions may be different. Therefore, how to design the graphic and barcode distortion before the printing is to make the shrink label different from other prints. Below is a brief analysis of how to deal with it.

(1) Prepress treatment of heat shrinkable film.

Theoretically speaking, to obtain good printability on plastic films, the surface tension of the film should be higher than the surface tension of the ink, and the surface should have a certain roughness to form the adsorption force.

Polyolefins such as PP and PE films in plastic films are non-polar polymer materials. Chemical stability. Surface tension is less than the tension of the ink. Poor adhesion to ink. Although some films have surface tensions that are comparable or even higher than the ink tension, they have a smooth surface and a small pore-free surface with low adsorption force. At the same time, various film anti-aging agents and other anti-aging agents added to synthetic resins also affect the film surface tension. The surface properties of the film degrade its printability. Therefore, there are some printability problems in most shrink films currently used. Therefore, in order to improve the printability of the film surface, the surface of the film with poor printing performance must be pretreated to increase the surface tension and the surface adsorption force. Common methods include corona treatment plasma treatment chemical treatment coating treatment method and the like.

(2) The determination of the label image size.

First, according to the thickness of the shrink film, the horizontal and vertical shrinkage rate of the film and the allowable shrinkage in all directions after the package, the deformation error allowed after the text shrinkage deformation, etc., to determine the size of the text on the shrink label to ensure the shrinkage after deformation The text can be accurately restored.

(3) The flat design of heat shrink labels.

The graphic design of the shrink label needs to consider the appearance of the container. Designers in the pre-press department need to correct the deformation of certain parts of the label, and do not put the key image on the place with high shrinkage as much as possible. In addition, it is also possible to work with container manufacturers to make the density of the containers suitable. Whether it is in the smaller size or in the larger size, it can provide the correct shrinkage.

Another factor to consider is where the bar code is placed. For shaped containers, there must be a regular section in order to use the bar code, the bar code is generally vertical printing. In case of image distortion. Impact scan. Completely irregular shaped containers cannot use barcodes.

(4) The identification and placement of barcodes on heat shrink labels.

1 size choice. On the heat shrink label. The size of the bar code must first consider the shrinkage of the material. When the label is used, the shrinkage is generally 2% to 3%. Therefore, the magnification factor of the barcode should not be lower than 0.85. Otherwise the shrinking bar code size will be less than 0.8 times the original size. EpBfJ will be very difficult. It may also affect reading.

2 color and location selection. The selection of the bar code color and position on the heat shrink label follows the bar code and the empty color should be consistent with the bar code color matching principle. The choice of bar code position also follows the general principle. First, it should be selected on the right side of the main display of the product packaging. Followed by the plane with the main display surface. Finally, it should be on the back of the main display. The surface curvature of the bar code symbol on a curved article must not exceed 30 degrees.

2. printing art.

Currently. The printing of heat shrink film labels is mainly gravure printing. Use solvent-based inks. Because the gravure plate has high precision. The print quality of gravure printing on the film is the best among all printing. Ink thickness is strong and three-dimensional. Graphic and rich layers. And printing plate printing rate is large. Suitable for long live. The label's output is often relatively large. Therefore gravure is more appropriate. But gravure printing plates are complicated. Long period. higher cost. Easy to pollute. Followed by flexible layout printing. With the development of flexo plate making and printing technology. Clear and clear printing. Thick and high gloss with gravure. And flexo more use of water-based ink. Good for the environment. Therefore, the environmental protection requirements increase. Flexo printing will have even greater applications. In addition. Offset and digital printing also have a certain range of applications. To meet the specific needs of customers. The process of printing the heat shrinkable film label is as follows: unwinding a print, testing a slit, slitting a center stitch, cross-cutting a heat shrink, and a finished product.

The following is a brief analysis of the issues that should be noted in printing.

(1) Selection of ink. According to the performance of heat shrink film label materials, special printing inks are used. There are four major types of inks used for heat shrink label printing: solvent ink, water-based ink, cationic UV ink and radical UV ink. From the current application situation, solvent-based inks still dominate, followed by water-based inks and free radical UV inks. Solvent-based gravure inks are best suited for long live printing, making solvent-based inks the best choice for shrink label markets today. However, with the development of the shrink label market, the improvement of environmental protection requirements and the increase of small batches and short-lived products have increased. The demand for water-based inks and free-radical UV inks continues to grow. The cationic uV ink due to higher prices. And when printing is too much trouble. There is less application in the shrink film field.

In addition, because the film itself has no adsorption. Contraction label EpBfJf~g requires ink with strong adhesion and flexibility. There must also be considerable heat resistance. Can not produce back sticking." Pigment in the ink is not easy to discolor or fade at high temperatures. Therefore, when choosing, we should consider the ink friction coefficient COF, shrinkage, adhesion, chemical residue and migration and other performance indicators.

1COF (Friction Coefficient): For shrink label printing inks. COF is an important indicator. It determines the slippage efficiency of the label on the surface of the container.

2 Shrinkage: The shrinkage of the ink is critical for shrink film label printing. It must match the shrinkage of the shrink film. When printing shrinkage film with high shrinkage. The required ink shrinkage is also high. About 60% to 70%; shrink shrinkage film printing shrinkage. Ink shrinkage is low. About 10% to 20%. Water-based inks, solvent-based inks and cationic uV inks all have a shrinkage of more than 40%, providing greater flexibility.

Among them, cationic UV inks have higher shrinkage and flexibility. The shrinkage of free radical type uV inks and EB inks is usually less than 20%, and the flexibility is slightly inferior. Therefore, when the ink shrinkage rate is selected, it should be treated specifically.

3 Adhesion: As the shrink film itself is poorly adsorbed, the adhesion of the ink is required to be good. The solvent-based ink and the cationic uV ink have good adhesion to the film material and have a wide range of adaptability. Water-based inks and free-radical-type uV inks have poor adhesion due to the limitations of the chemicals used, but they have greatly improved in recent years.

4 Residues and migration of chemical substances: Residues of chemical substances will affect the environmental protection of the packaged products. Therefore, the inks are required to be dried quickly to avoid migration of residual chemical substances onto the surface of the printed products. Water-based inks are environmentally friendly inks with less chemical residue and cheaper prices than uV inks. The residual migration of chemical components in solvent-based inks is relatively high. The radical type uV ink cures rapidly, but the chemical substances in the ink may migrate to the surface of the substrate. Cationic UV inks cure instantaneously with less chemical migration, but they are more expensive than free radical UV inks. Therefore, with the ever-increasing environmental protection requirements, more environmentally-friendly inks will surely be used more widely.

(2) Control of tension during printing. Because the film material is easy to pull