Metal packaging screen printing features and requirements

Metal packaging screen printing features and requirements

In recent years, with the development of China's economy, the market is increasingly demanding packaging. Screen printing processes have become increasingly popular for metal packaging. Especially for metal packaging barrel products, screen printing has become an important way to improve the quality of industrial products, and has been widely used in China.
Screen printing of metal packaging is a kind of special packaging printing. It is a screen printing method based on hard materials unique to metal packaging products. The printing materials mainly include tinplate (tinned steel sheet) and chrome-plated steel sheet. Galvanized steel sheets, cold-rolled carbon steel sheets, hot-rolled carbon steel sheets, etc., and special packaging materials such as aluminum sheets and stainless steel sheets.
Metal packaging screen printing is an integral part of the metal packaging production process, and is a signage of the contents of the package, containing certain advertising ingredients. Therefore, in order to arouse consumers' desire to purchase and increase the sales value of goods, as a promotion means, novel binding design and fine printing should be carried out, so that the metal packaging screen printing is more important.
First, the performance characteristics of screen printing metal packaging
1. Physical properties and characteristics of screen printed metal materials.
Metal packaging materials generally have good heat transfer, electrical conductivity, high mechanical strength, and are ideal materials for metal packaging. Because of its good ductility, it is easy to cut, punch, bend, stretch and other processes. More importantly, metal packaging materials can withstand a variety of watches to meet the decorative functions of various packaging.
2. Technical requirements for screen printing on metal materials.
1 Straightness: The metal sheet shall not be warped.
2 Surface roughness: The surface of the metal sheet should be free from surface abrasion such as mechanical scratches, scratches, unevenness, and rough stripes.
3 Cleanliness: The printed surface of metal packaging should be clean and free from oil, dust, water and other unclean phenomena.
3. Printing adaptability requirements.
1 Metal packaging materials, good processability and diversity of design
Metal packaging materials have good mechanical properties and processing and forming properties. Metal packaging containers can realize novel and unique design, and manufacture various packaging containers such as shaped barrels, cans, boxes, etc., to achieve the purpose of beautifying goods and improving the competitiveness of goods. .
2 bright colors, rich layers, good visual effects
Metal packaging, such as tinplate, because of its tin-plated surface, has a flashing color effect, and then printed by the background color, printed graphics are more vivid. For Wuxi steel plates or other metal materials, after surface treatment and coating, special flash effects can be reproduced after screen printing.
3 Conducive to the realization of the use value and artistic unity of goods
The good performance of metal packaging materials and the good wear resistance and durability of screen printing inks not only create conditions for achieving unique design and fine screen printing, but also make the packaging more beautiful after being decorated with metal packaging surfaces. Moreover, the value of the metal package itself can be greatly improved and the durability and maintainability of the product can be improved, and the use value of the product and the artistic unity can be better reflected.
4 Important means of reducing costs
By means of screen printing, the production process of certain metal packaging products (such as steel drums) is changed or simplified, and the production cost is reduced.
For the above reasons, screen printing of metal packaging has been rapidly developed in recent years.
Second, the design characteristics and requirements of metal packaging screen printing
1. Design features of metal packaging screen printing
Packaging is a concentrated expression of product features, but also a compelling face of the product. A high-quality packaging can not only reflect the face of science and technology of the times, but also reflect the modern aesthetics and the high technical value of the products. Therefore, improving the functional design, design and decorative design of packaging, and choosing the appropriate technology are the goals pursued by the packaging industry today.
At present, the use of screen printing methods to make metal packaging graphics has become an important means, because screen printing has a unique performance, a variety of types of ink, ever-changing colors, are free to choose. Therefore, to improve the design and process level to create a new metal packaging screen printing. The specific practices are as follows:
(1) Modeling ratio: The proportion of graphic design of metal packaging products is closely related to the structure, overall shape and layout of the products. With the development of the times and the changes in aesthetics, the proportion of packaging and modeling is also constant. Variety.
(2) Layout design: The design of each function of the metal packaging surface should be reasonable and provide consumers with maximum convenience. The design of the pattern is profound, representing both the nature of the product and the production unit. Pattern design should pay attention to the following factors: 1 should have long-term use, should not be changed frequently; 2 concise and eye-catching, can make a deep impression; 3 has a unique and novel style; 4 reflects the characteristics and nature of the product .
2, metal packaging screen printing design requirements
The most important thing for any job is the initial basic work. The design of screen printing as the main process, in addition to following the principles of economic and practical, should also pay attention to the combination of science and craft. In the case of ensuring accurate content and reasonable layout, the decorative pattern is appropriately added, and the characteristics of screen printing are organically linked with the aesthetics and the optical color of the material, which becomes an important design concept for making the packaging appearance by screen printing. .
(1) Since the screen brush is not easy to express the effect of fine lines, there should be space left or overlap at the adjacent or junction of the two colors. The width of the line and the size of the writing should exceed the maximum resolution of the plate. Mm or more.
1 When designing the color block printing, the outer ink frame size should be as large as possible to ensure the inner frame size and shape are accurate, so as to ensure that the inner frame is not touched when the net is closed.
2 When there is no space required in adjacent color zones, separate design, two rows, which are two different shapes of color zones, no gap is required in the middle.
3 The intersection of two color blocks is not easy to print. This situation can be compensated by the overlapping design method, and the outer frame of the color frame is added. This should also be designed separately for secondary lighting. The size of the surrounding area of ​​the color block area is slightly larger than the required size of the drawing. That is to say, when the two colors are adjacent, the light color area design is larger and the first color is printed. On the light color, prevent gaps in the middle.
(2) If you encounter more appearance requirements, whether it is multi-level overprinting or multiple color block printing, it will make the layout look messy, although it is colorful, it loses its elegant and solemn feeling. According to the principle of density and darkness of the dot, the adjacent parts of the complex area are printed with the same color in different sizes, or different shapes, or dots of different densities, and the change is made in the same. Because of one design, one row of printing, and one printing, the problem of multiple positioning and multiple printing is reduced, and the effect is improved. It can not only play the role of the division of color blocks, but also make the color of the layout conform to the aesthetic style of the times, and skillfully combine the functional beauty with the artistic beauty. Packaging and printing are well matched, comfortable and strong. Fully demonstrate the value of the product.
(3) Emphasize the decorative effect. For those printed surfaces with simple contents and large space, properly matched with different shapes of color blocks, plus the decorative decorations of the lines, will make the monotonous and boring few simple contents lively and vivid.
(4) Select the appropriate font. Text design, Chinese, Chinese Pinyin, English, and numbers are common languages ​​for packaging patterns. The design of texts not only needs to meet the needs of content functions, but also must have good craftsmanship and aesthetics. Most Chinese characters use Song, imitation, and scorpion. Chinese Pinyin and English use normal body, long line body, flat line body, etc. Numbers are the most common symbols. The ratio of height to width directly affects the recognition effect. Height: width is generally (5:3)~(3:2). Commonly used Song characters, because of the shape of the square, the pen front is obvious, the horizontal and vertical are not thick, the body is printed on the metal packaging when it is below 4.2mm, it will appear thin, and the printed title will also appear light and bleached; the imitation of the Chinese characters is the same horizontal and vertical thickness, the shuttle angle is distinct, The font is clear, the small print or the title is very good. When the font is more than 4.8mm, the black-faced characters are used. The fonts are dignified and generous, and the strokes are thick and thick. The printed on the packaging is sturdy and eye-catching. When the larger title or vacancy is larger, you can use the square Song or the deformed scorpion, which is open, discouraged and has a strong sense of calligraphy.
In short, the selection of words must conform to the characteristics of screen printing, and it should be stable, thin, easy to read and easy to distinguish after printing.
(5) Use standard symbols. Some products are nominally expressed in English letters or symbols, such as Kg, mm, L, Ω, φ, etc. For the sake of accuracy, we try to map directly with standard symbols. Generally, the commonly used Chinese characters are not handwritten, but the words on the letter board are placed into a positive piece as required, pasted onto the drawing, and then turned into a yin and yang negative film to ensure the consistency of the full-board font.
(6) Take each drawing seriously and, on the premise of respecting the user's wishes, actively negotiate with the user about the re-creation of the art, apply the mature techniques and unified image to different products, and establish their own style.
(7) Take seriously the weak links in the overprint. The level of craftsmanship is the technical basis for ensuring and expressing the level of design, as well as the protection of the beauty of the product and the enhancement of form beauty. Therefore, screen printing should also prevent rough and damage, and damage the appearance. It is often found that the same negative film, different manufacturers print different products. There are technical differences, as well as differences in color matching and material selection, and more differences in process quality.
(8) Perform drawing, engraving or mapping according to the design sketch provided by the user, and then make the plate making. Since the microcomputer has been used to design the system, the microcomputer design is adopted, and the light drawing version is a relatively advanced technology, and the size of the design is also relatively accurate. If there is no advanced equipment, drawings, maps, engravings, etc. can also be used for less demanding products.
Third, the quality characteristics and requirements of metal packaging screen printing
Metal packaging screen printing, from the process point of view, the printed patterns, lines must be clear, the ink layer is full, which is related to the selection of mesh mesh, stretch tension, printing pressure, printing speed, ink viscosity, etc. Print data.
1, carefully choose the wire mesh
According to the printed characters and lines, the screen is generally 300-350 mesh. When a screen of 350 mesh or more is used, although a good printing effect can be obtained, since the ink layer is too thin, the lithographic corrosion resistance is not strong in the subsequent process. The selected wire mesh is tensioned under 8 tensions, and the glued mesh frame is placed on the tensioned wire mesh surface to be stretched downwards. The purpose is to stretch several small nets at the same time to save the wire mesh. The frame can also be discharged at any angle, avoiding right angle stretch nets and reducing the chance of sawing during printing.
2, stretch net
When printing general graphics, manual stretch nets can be used, which saves money and saves labor. For printing complex or detailed graphics, the tension of the mesh first affects the printing accuracy, and the tension is too small, and the consequences are almost unclear. Therefore a mechanical or pneumatic stretcher must be used. When the net is stretched, the tension of the net should be gradually increased, and the required tension cannot be pulled at one time. The screen should be evenly leveled. When the tension is reached, it should be left for a few minutes while sticking to the net and then bonded. It is best to let the stretched net sit for 3~4 days, put it on the tabletop or other places that are not easy to touch, and use it after the tension is even.
3, wire mesh degreasing treatment
Drain the screen with running water, apply it to both sides of the screen with detergent or detergent, and scrub with a brush to achieve the purpose of finger removal and roughen the screen. The alkaline detergent on the net must be washed under running water, otherwise it will affect the quality of the plate.
4, dry
The washed wire mesh is placed in a ventilated dust-free place or dried in an oven, and the drying degree should not be too high, so as not to affect the deformation of the wire mesh.
5, plate making
Screen printing requires clear patterns and characters. The ink layer is full, which requires a high quality screen. First, two cases should be excluded: the first one is that the photosensitive film is too thin, the printed patterns and lines are not only unclear, but also have jagged, sprinkled, and rounded edges; the second is that the photosensitive film is too thick, although printing When a lot of pressure is added, the ink layer is still very thin, the line is severely broken, and it cannot withstand the corrosion of the medicine. Therefore, the thickness of the photosensitive film on the 350 mesh screen is preferably two or two. Among them, the scraping speed and the inclination of the bucket are also the main factors affecting the film thickness. The speed of scraping can not be fast, and the scraper can be moved slowly, which can eliminate the bubbles in the glue and obtain a uniform photosensitive layer. The angle between the back of the bucket and the screen is 25°, and the force of both hands should be even when the glue is scraped.
It is worth mentioning that the printing precision of the photosensitive adhesive plate is not as high as that of the capillary film, but the film durability of the film is not as good as that of the photosensitive adhesive. Therefore, immediately after the application of the photoresist, a polyester film is attached to the non-printing surface, and the scraper is pressed twice to remove the air bubbles to prevent the pinhole from appearing; then it is placed in an oven and dried at a low temperature, and the temperature is controlled at 40 ° C. Inside; after drying, remove the screen and remove the polyester film, then dry for 1~2 minutes to expose. This method of "changing" the film with a photosensitive adhesive can improve the precision of screen printing.
6, exposure
Most use sun exposure. Expose for 30~45 seconds according to the content of photosensitizer. The film should be repaired before exposure to remove dust and stains. If the screen is facing up, the frame opening is downward, and a piece of black paper or blue carbon paper should be sandwiched between the pad and the screen to prevent light from being refracted, resulting in unclear pattern or difficulty in development.
7, development
At the end of the exposure, it should be put into development immediately. Soak the screen with warm water at 30 °C for 1-2 minutes, and spray the tap water until the unexposed film is swollen until the pattern is clear.
8, dry
Use a sponge to remove excess water, allow it to dry naturally in a ventilated sun or dry in an oven at 40 °C.
9, revision and network closure
The film is proofed with the film, and the mesh outside the pattern is sealed and dried to deliver the printing process.
10, printing
Self-drying anti-corrosion ink is used to keep the distance between the screen and the metal packaging surface 3~4 mm; the scraper is required to be sharp, straight and without gap, and the ink is scraped from front to back. The squeegee is inclined at an angle of 45°, parallel, and it is not advisable to scrape the ink too quickly. Try printing for about 10 times. If the amount of ink leakage is normal and the pattern is clear, you can print in batches. In order to reduce the workload of the patch, it is best to check the print quality every 10 prints in order to correct it in time. Often due to the dry environment, the dust is serious, white spots and lines appear on the printing plate, mainly caused by particles of dust stuck on the net and in the ink. Apply a proper amount of thinner to remove the dirt. After printing, the screen should be cleaned in time. Generally, a propionic acid cleaning solution is preferred, and when it is irritated to the skin, the ink adhered to the net is easily washed. The cleaned screen should be packed in time and placed properly for reuse.
11, overhaul of the print
The printed printed matter cannot be directly corroded. After the ink is completely dried, the defective parts in the printing are carefully and step by step; the place to be filled is repaired with the plate-making glue, and the characters are unclear and modified with a stylus; Investigate, check, and investigate, and minimize the lack of printing quality before you can transfer to the next process.
12. Reasonable ink selection
Layered multi-color overprinting, you must print the next color when the previous color is too dry. Once the last color is printed, do not smear the background. In order to ensure the yield and reduce the difficulty of repairing, the ink type and diluent are screened.
When the surface of the metal packaging surface is light, the color of the resin ink can be added by using the UV white ink to ensure uniform color. After printing, it is cured by ultraviolet light. The color ink particles will be firmly embedded by the curing of the UV ink, and the surface will not stick, and the color can be printed immediately. The next color ink can be made of a thermosetting metal ink, which is cured by post-pressing. Not only can the ideal bond strength and hardness be obtained, but also an unexpected pearly shiny base color can be obtained. Generally, the solvent is not rubbed off, and the repair is convenient.
13, pre-press printing plan, color sequence
Use a non-stick coated paper to test the print, check whether the graphic is lacking, whether the scraper blade is straight, whether the mesh distance is suitable, whether the ink color is uniform, and test printing 2~3 times. After the net is evenly printed, the printing is officially printed. The continuous graphic can be printed with a large scraper at the time of printing. For the separate graphic, it can be partially printed with small scrapers of various specifications. After all printing, lift the net. A small area is easy to obtain a flat surface. The printed words are full and there will be no difference in depth.
14, the cleaning of the screen is very important
Residual ink in the image, especially the frame used for repeated recycling, will cause the barrier hole, and the degree of reproduction of the graphic is affected, that is, the printing defect. The screen can be wiped clean in the following ways.
(1) Wipe the net with an ink cleaner to remove the ink, but the taste is large.
(2) Wipe the net with banana water, the taste is small, and the amount of cotton yarn is large.
(3) Wipe the net with cotton yarn and alcohol. The ink leaves the mesh surface in a state of stripping, and then wiped with an ink cleaning agent. This method is convenient and efficient.
In short, from the design of the film production, from the preparation of the screen to the screen printing, from ink selection to printing, the best process conditions are selected as much as possible in each link. (Yang Wenliang)