Gravure printing method for decorative texture
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
The screen printed decorative texture is characterized by natural, disordered, gravure decorative textures, which are formed by plate making. Firstly, according to the design requirements, the textures such as frosting, wrinkles, ice flowers, refraction, coral, etc. are made on the gravure plate cylinder in the form of mesh or lines. When printing, use the scraper to scrape the excess ink of the plate and transfer the ink in the cell. Go to the substrate. Therefore, the gravure decorative texture depends on the plate making and the matching with the ink. The plate making process is very important, it directly affects the printing effect. For example, when making a frosted printing plate, the mesh can be made into a circular shape, a regular hexagon, a diamond shape, a square shape, a triangle shape, etc., and the printed effects are different, and Factors such as the number of network lines, the depth of the cell, and the width of the mesh wall also have an impact on the final printing effect. If the number of thick lines and large cells are made, no matter how to adjust the printing process and change the ink, it is impossible to print high-quality fine sanding, wrinkles, ice and other textures. That is to say, the gravure decorative texture is artificial and orderly, which also determines the gravure printing method has good reproducibility and anti-counterfeiting function. When making plates, you can make coarse sanding, fine sanding, wrinkles, ice flowers, refraction and other textures on the same plate cylinder as needed. You can get all the effects in one printing, without having to print multiple times like screen printing. The textures can be seamlessly combined to solve the overprinting problems that exist in screen printing. However, the development of UV gravure decorative inks is very difficult, mainly due to the following aspects.
(1) The gravure printing speed is very fast, generally above 100m/min, and the printing ink layer is also thick, so it is very difficult to completely cure the ink. Relatively speaking, the screen printing speed is only 10 ~ 30m / min, the curing is more thorough.
(2) UV gravure has the problem of dirty ink. In the gravure process, when the ink is transferred to the plate cylinder, the excess ink must be scraped off with a squeegee to ensure that there is enough ink in the cell, and there is no ink in the blank, otherwise it will appear dirty. Version". In general, solvent-based gravure inks have very low viscosity and are very easy to scrape, while UV gravure inks have much higher viscosity and are difficult to scrape because of the high viscosity of reactive diluents in UV inks. A sufficient amount of high viscosity semi-polymer must be added to ensure good adhesion fastness and faster cure speed. This is one of the reasons why UV gravure inks have so far been rarely used in production.
(3) After the UV gravure decorative ink is transferred to the substrate, it must remain in its original state before curing, and it cannot be leveled, otherwise it will not get a good print, but it increases the difficulty of scraping the ink.
Nowadays, UV gravure decorative inks have achieved good printing results. Although there are many varieties, unlike UV printing inks, UV gravure decorative inks do not have any points such as matte, wrinkles, ice, and refraction. There are only a variety of decorative textures on the printing plate cylinder, and there is only a difference in texture between them. If the printed matter is mainly frosted, it is necessary to use ink with high hiding rate; if the printed matter is mainly based on refraction, ink with high transparency and high refractive index should be used; if the printed matter is mainly wrinkles or ice, it must be used for both. Ink variety. In other words, which ink type to use depends on the subject matter of the print.
Gravure printing decorative textures are sheetfed gravure presses and rotary gravure presses. Due to the reasons mentioned above, high-quality UV gravure inks are difficult to come out. Therefore, most of the imported and domestic rotary gravure printing machines do not have UV curing devices. If UV gravure decorative inks are to be printed, UV curing devices must be installed. The UV curing device consists of a medium pressure mercury lamp, a mirror and a protective cover. The working pressure of the medium pressure mercury lamp is 1.33×104 Pa, and the ratio of the 365 nm and 366.5 nm lines in the emission spectrum is high. Most photoinitiating systems have strong absorption in the line region, which is extremely effective for UV ink curing. important. In addition, the medium-pressure mercury lamp used has a power density of 80 to 240 W/cm, and the actual light-emitting area of the lamp tube is slightly larger than the maximum width of the solidified region. If 80W/cm lamp is used, at least 3 should be installed; if the lamp with power density greater than 120W/cm is selected, at least 2 should be installed. In actual use, the greater the power density of the lamp, the stronger the penetration of UV light, and the better the curing effect. Two 120W/cm lamps and three 80W/cm tubes have the same total power density, but the former has better curing effect than the latter.
Pay attention to the following points when installing a UV curing unit:
(1) Install an aluminum mirror.
(2) Pay attention to the protection of UV light and discharge the ozone outside.
(3) The UV lamp must be cooled.
(4) Pay attention to explosion protection.