In the flexo printing process, the application of the sticker tape has always been a concern for everyone. Mr. Wu Lianqi from Desa Tape Shanghai Co., Ltd. introduced us to the selection and use of adhesive tape.

With the development of China's national economy, especially the development of food, daily chemicals, detergents, medicine, cosmetics, household appliances, small household appliances, logistics and other industries, the label industry has experienced a rapid growth with an annual growth rate maintained at 15%. 20% has become the fastest growing sub-sector in the printing industry.

Flexographic printing is a technique that uses flexographic media to transfer ink through anilox rollers to achieve printing. Compared with traditional printing technologies such as offset printing, gravure printing and letterpress printing, flexographic printing has the advantages of less equipment investment, shorter plate-making cycle, faster printing speed, strong adaptability to substrates, and the use of environment-friendly inks. At present, in the field of packaging and printing in Europe and the United States, the popularity of flexographic printing is high, and it can even reach 90% in the United States. In recent years, with the advancement of technology and awareness of environmental protection, the proportion of flexographic printing in China's printing industry has continuously increased, and it has gradually become a printing technology favored by the industry. From the perspective of the development trend of printing technology in the global label market, flexo printing is also one of the fastest growing label printing technologies in the past.

Unlike other printing technologies, flexo printing requires the plate to be affixed to a platen roller or sleeve, which requires the use of a sticker tape. The function of the sticker tape is mainly to fix the position of the printing plate, to ensure that the printing plate does not fall off during the printing process, does not shift, and buffers part of the pressure on the plate material to enhance the printing effect. Attaching the plate to the platen roller or cylinder is a very important part of the printing process, so it is very important to choose the appropriate plate adhesive tape. The adhesive tape in flexo printing is mainly a double-sided pressure-sensitive adhesive tape, which can be classified into foamed and non-foamed tapes according to different substrates. The substrate of non-foamed tapes includes films or cloth bases. The application of these tapes in label printing is less. Therefore, this article mainly introduces the selection of foam tapes, and it also meets the needs of customers during the use process. Questions are explored.

Sticker foam tape introduction

A good foam tape not only serves as a fixed plate, but also improves the printing quality. Take tesa softprint series as an example, the typical foam tape consists of glue, foam, stable film and release paper. The glue is applied on both sides of the tape, and is affixed to the plate material and the plate roller, respectively, to function as a fixed plate material. Foam is an important part of the sticker tape. Through the density of the foam substrate, fine control of the printing pressure can be achieved to enhance the printing effect. There are three aspects affecting the properties of the foam: the cell structure of the foam, the compression recovery rate of the foam, and the hardness of the foam. Compared with irregular cells, uniform circles and evenly distributed cells provide excellent and stable solid and dot printing effects.

A good foam compression recovery rate can ensure stable printing quality and extend the life of the tape. The density of the foam determines the softness of the foam. Different foam hardness can produce different dot and field printing effects, which is an important factor in the choice of tape. The stabilizing film in the tape can prevent stretching of the foam during pasting and repositioning of the sticker, and at the same time provides a uniform force area during the printing process. The role of the release paper is to prevent the tape from sticking to each other. Release papers with rugged surfaces can also help eliminate air bubbles during the paste process.

Patch foam tape selection

How to choose a suitable sticker tape can be considered from the following aspects:

1. In the case of foamed tape, the thickness generally refers to the thickness at the time of printing, and the thickness when not pressed is generally slightly thicker. The thickness of the sticker tape will affect the repeat length of the printing, and will also affect the printing quality to a certain extent. In general, the thicker the tape, the more space the printing effect can be adjusted. However, flexographic printing presses have their own tape thickness requirements. For label flexographic printing, 0.38mm thick sticker tape is the mainstay. It should be noted that the thickness of the sticker tape needs to be taken into account when calculating the flex print gap.

2. The main function of the sticker tape is to firmly fix the printing plate on the plate roller or sleeve. The manufacturer of the sticker tape usually uses the peel strength of the tape on the surface of the printing plate or sleeve as the universality of the adhesive tape. index. The higher the peel strength of the tape, the stronger its stickiness and the stronger the adhesive. However, in the process of pasting, repositioning, printing and unloading, the stickiness of the adhesive tape and the plate surface is not the same. The ideal glue is to keep the consistency in the whole process, but in practical applications, due to the use of pressure-sensitive glue, the viscosity of tape products of some manufacturers gradually increases at the later stage of printing, resulting in difficulty in unloading plates, and a good tape product will have one in printing. Little change in stickiness. One side of the adhesive plate adhesive plate and the adhesive roller side of the adhesive plate are often different in the design of the adhesive viscosity, generally the high viscosity is for a reliable plate and to avoid warping, and the low viscosity is to facilitate the repositioning and unloading or unloading of the plate material. Adhesive tape is easy and does not leave adhesive residue. The specific choice depends on the printing company's operating habits and requirements.

3. Printing patterns are usually divided into dots and fields, and different printing effects can be achieved mainly by selecting different soft hardness sticker tapes. In the case of foam tapes, ultra-soft tapes can achieve the finest dot printing, or make up for the impact of gear hopping on the printing (ink bars); soft tapes satisfy fine dot printing; neutral tapes satisfy comprehensive printing; Hard tape meets good field effect.

4. The current development trend of label printing is that it has many varieties, a small amount of print, and a short cycle. Therefore, the quality and stability of the tape are also becoming more and more important. The quality of the tape when selecting the tape is good and the operation is good. Performance is also an aspect that needs to be considered.

Application should pay attention to the problem

The effect of a sticker depends on each procedure in the sticker process. The correct use of sticker tape can improve the printing quality.

1. The temperature has a great influence on the use of sticker tape. All operations should be performed at room temperature to avoid affecting the viscosity due to temperature.

2. Before affixing, the surface of the plate and roller should be kept clean. Dust, rust, ink and other dirt will destroy the adhesive force of the tape, resulting in poor adhesion and warpage phenomenon. Plates and plate rollers should be cleaned with high alcohol concentrations because other chemical solvents may damage the plate or sleeve.

3. When pasting, the area of ​​the sticker tape should be larger than the area of ​​the plate, so the edge of the tape should be larger than the edge of the plate, which can greatly reduce the risk of warpage.

4. When attaching a plate, the interface of the plate and the interface of the tape should be avoided. If the interface of the plate is facing the interface of the tape, the printing plate at the interface may easily be stuck, the edge may be awkward, and the plate may come off.

5. Do not directly press the tape directly with the adhesive tape. Take double-sided adhesive tape to remove one side of the paper. Do not open the release paper immediately. After a part of the tape is fixed, gradually release the release paper. Adhere the tape to the plate cylinder in accordance with the position of the plate. In the sticking process, because the pressure of the hand on the tape is not uniform, if the hand tape is used to roll the tape, it is easy to form small bubbles, and it is also possible to damage fine dots. The softer rubber roller can be used to evenly paste the tape. The method of rolling is compacting from the middle to both sides in a "human" shape, so that the air in the middle of the tape can be squeezed out. There is currently a roller with a needle in the market, which is also very effective for the elimination of bubbles.

6. After the plate is attached, in order to prevent the ink and solvent from contacting the tape and the adhesive on the edge of the plate at the time of printing and cleaning, a circle of edge-sealing tape may be affixed around the plate to avoid warpage phenomenon. The thickness of the edge tape is preferably thin.

7. During unloading, it is recommended that the plate be slowly and smoothly removed at an angle of less than 90° (the angle of the tangent between the removed plate and the surface of the drum) so that the plate can be prevented from wrinkling or cracking. The slower the unloading, the weaker the adhesive force to the tape material, and vice versa, the faster the adhesive force. When unloading the tape, the method is the same as that for removing the plate material.

Flexography is a fine printing process where many variables need to be controlled. With the increasing requirements of manufacturers on the quality of label printing, the process control of each printing process becomes more and more important. I hope that the simple discussion on adhesive tape in this paper can help you.