Computer and other high-tech applications in screen printing

Nowadays, high technologies such as computers have been widely used in the printing field, which has promoted the development of the printing industry. Screen printing is no exception. In addition to pre-press and post-press processing, as well as other printing methods, computer and other high technologies are fully utilized. In printing, new technologies and methods are constantly being absorbed and utilized to improve printing quality and printing speed. Broaden the business area.

The digital plate-making of silk screens, screen-printing and pre-printing, has undergone several stages of manual platemaking, photoengraving, laser photocopying and computer direct plate making. The first two are analog plate making, so that the original image can be optimally reproduced. The latter two are digital plates, which require not only a good reproduction of the manuscript but also the ability to create new images. The application of digital plate making provides screen printing with excellent conditions for improving the printing quality and printing sophisticated products. In digital platemaking, there are mainly indirect plate making of the output film (film), and a computer-to-plate system that does not directly output the film on the surface of the plate.

Indirect digital platemaking, which is the digital plate-making method of outputting the film output by the output device after the computer interprets the original electronic information. Based on the material of the film, it can be divided into two types: silver salt film plate-making and silver salt-free film plate-making. The silver salt film is plated using the same silver salt film as the photolithography, and the output film also needs the process of developing, fixing, washing, drying and the like in the dark room to obtain a printable film, which is then attached to the silk. Online printing, washing, made screen printing plate. The representative method of this method is laser photosetting, which belongs to the earliest and most widely used digital platemaking method. The resolution of the Phototype Dispenser has reached more than 2400dpi, which makes the quality of the platemaking has been greatly improved in the resolution, sharpness, speed and other aspects of the image. However, because the silver salt film is also exported, and the chemicals are used for development, there is a certain amount of pollution to the environment.

The non-silver salt film output method has been developed in recent years using micro-piezoelectric technology to make ink droplets eject small droplets of ink, and directly sprayed on the surface of polyester film coated with ink layers, using a "physical imaging method" of digital plate making. The film used does not contain silver salts and does not require any treatment in the darkroom to achieve "what you see is what you get." The output is the result. It is called "a true green environmental protection material". It can achieve 100% transfer, which can effectively avoid plate-making problems such as under-exposure, over-exposure, under-development, and over-development. Compared with the process of plate-making of the output silver salt film, there are few processes, and the input of the entire system is only equivalent to 1/5-1/10 of the output of the same-format laser photo-discharging system. This plate-making device has a resolution of 720 X 1440 dpi and a droplet size of 5-6 PL (equivalent to 1/4-1/5 of the diameter of the hair filament). The resolution of the image is 133 lines/inch, which can fully meet the requirements of color screen printing plate production.

Computer Direct Imaging Plate (CTP), the traditional color screen printing color separation screen production, can not be separated from the photographic film, especially in the ultra-large screen printing, must use film imposition, enlarge the film or cast screen printing plate. No matter what kind of method, it must be based on the premise of producing high-precision, high-line count films. Not only is it expensive, but it is difficult to guarantee the quality of the stitching. Enlarging film and casting screens are restricted by objective factors such as image distance and lens surface, causing many troubles for actual production, and the quality of screen printing is difficult to control. In the case of screen printing, the projection exposure of the sensitized emulsion screen is a new technique that has been gradually applied in recent years.

With the successful application of computer-to-plate technology in other fields of printing, it has also had a profound impact on screen printing. At the end of the 20th century, with the continuous maturation of digital processing technology, computer non-film-making (CTS, also known as digital direct plate-making) came into being. Direct digital imaging uses existing precision computer technology to control the wax injection system and scan the screen version with a modulated scan head. First, the computer performs grid layout and rasterization processing, and then rasterizes the layout information. Through laser, inkjet, and wax injection, various imaging technologies directly copy the dot matrix to silver, polyester, and silk screens. On the material. Direct digital imaging as a high-tech application in screen printing is a revolution in screen printing plate technology. Computer Direct Imaging Plate Making is the technique that the screen printing plate does not need to be coated with photoresist, that is, a coating is directly applied by a computer, and an image is formed on the template and then screened and developed to obtain a screen plate. The printing plate dot angle, the thickness of the sprayed material, the density, the exposure time, etc. are all set by the computer. The image is scanned and imaged according to the original image, and the plate is directly scanned and then the unreacted chemical material is washed away with water to make a printing plate. This method of plate-making directly on the stencil is the future direction of screen printing.

In addition, there is also a method of direct image plate-making which uses a computer to perform laser scanning and etching directly on a special metal alloy film. The pattern making method has the characteristics of non-deformation, alignment, and high printing accuracy. , Its application makes screen printing can only print the low line number products become history. Compared with projection platemaking, direct digital imaging platemaking has many advantages. It is more advanced in technology, and can be used to make printing plates in one step. It does not use silver salt film at all, thus avoiding the environmental pollution caused by chemical washing. Computer-aided design data can be transmitted directly to the template without intermediate photographic steps, making the image sharper and easier to control. The use of computer direct plate making has the characteristics of simple plate making, rapidity, prevention of pollution, and improvement of plate making and printing quality. It is the latest plate making method for photosensitive screen printing plates. Its appearance and application brings traditional screen printing plate making process The fundamental changes signify that the screen-making technology has entered a new phase of digitization.

This kind of new technology that directly forms a printable plate by computer processing can only process black-and-white format files due to the limitations of technology and equipment. Compared with the computer laser image-scheduling technology of the same period, its application range is relatively narrow. However, with the development and maturity of computers and laser imaging systems, by 1995, color CTP technology could directly perform digital imaging on aluminum plates, films, screens, and other materials, further promoting the use of CTP plate-making technology for screen printing. The use of CTP plate making technology greatly simplifies the entire process flow. Now it is possible to obtain screen printing products only through graphic typesetting, direct plate making, and printing. Compared with the traditional printing process, phototaking output films (including film development, fixing, cleaning and drying) are omitted. Etc., etc., and printing and other processes have the advantages of rapidity, accuracy, stability, repeatability, simplicity, quality control, and no need for film, which are incomparable with other traditional platemaking systems.

Due to the obvious advantages of CTP plate making technology, it has attracted the attention of the screen printing industry and produced a variety of CTP plate making systems. Among these platemaking systems, representative is the JetScreen Wax Direct Plate Making System of Luscher, Switzerland, which has carried out a comprehensive reform of the screen plate making technology and formed a blockade function as a mask directly on the photosensitive resist by means of inkjet printing. Waxed black ink image layer. After the full-plate exposure, the wax black ink image and the unsensitized photosensitive layer were removed by hot water washing to produce a high-quality image with a web size of 3m X 8m, a resolution of 75 lines/inch and a repeatability of 0.02mm. Reusing screen printers, the images were printed directly on the screens coated with sensitized adhesives to form a complete set of color screen printing color separation stencil making systems. The system does not need to send out the film in the screen making process, and does not need vacuum adsorption printing. In addition, it can eliminate sand holes formed by scratches or dust on the glass, and can completely avoid the moire caused by mesh and yarn hitting the net, and its print resolution can reach 630dpi. Screen resolution accuracy (repetition accuracy) 0.02mm. The JetScreen platemaking system has enabled color screen printing screen printing technology to enter a new era, enabling the difficult-to-achieve large-format screen printing design problems to be solved.

In recent years, the combination of screen printing technology, the rapid development of the combination of printing, a printing machine can be combined with any of several different methods of printing, which makes the original to be printed on a number of machines can be processed products, printing once It can be done. Practice has proved that the combination printing can be as expected as people can not only play a complementary role, but also create new printing effects and expand the scope of printing. As the screen printing can make up for some deficiencies in other printing and improve the printing quality, it can also add decoration and artistic effects to other printed matter, so that the printed material has unique features, and thus has a broad application prospect in the combination printing.

At present, screen printing is mainly combined with flexographic printing and is applied to the following situations:

â–² To enhance the attractiveness of the product, using air-through effect design, the use of very strong colors or luminous ink, etc.

â–² Some labels used in harsh environments, such as battery labels, paint labels, etc.

â–² Emphasize product branding and labeling products, such as drug labeling and injections;

â–² Some components need to be warned by law, including the blind,

â–² To obtain metal effects such as gold and silver,

▲Simple and elegant decoration effects, such as the use of screen printing to print a large area of ​​the field and anti-white characters, and no longer print fine text;

â–² Appears embossed and frosted effects on cigarette packs or cosmetic packaging;

â–² Printing scratch prizes, all kinds of lottery and other securities;

â–²Using optical variable and temperature-variable screen inks to improve the security features of valuable tickets and high-grade trademarks.

In the future, with the continuous development of science and technology, especially the popularization and application of digital printing in the printing field, combined printing will be combined with digital printing. For example, digital printing has long since entered into relatively few prints. The short-run printing market has become an ideal technology for printing personalized prints, and the full application of computer technology in combination printing will greatly expand the printing market.

All in all, under the current rapid development of science and technology, screen printing, like other printing methods, will continue to absorb high-tech applications, more fully demonstrate its own characteristics, and complement the advantages of other printing technologies to make its own market prospects. growing.

Source: Screen Printing Industry