T-shirt printing prepress process (2)
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Third, digital direct plate making technology
The application technology of digital to plate-making technology (CTP) in screen printing is mainly three types:
1. Inkjet (wax) CTP plate making. The technology uses a computer-controlled lithographic inkjet or wax-jet printer to print images onto screen pre-forms that have been pre-coated with photoresist. This ink image replaces the role of the plate-making film, and is exposed to light and developed into a printing screen. Both the United States and Switzerland have produced inkjet (wax) CTP platesetters. In 1992, Gerber produced a C T P platemaking system for T-shirt printing and plate making: Screen Jet (maximum plate-making area 65cmx95cm), which has been sold in the world for hundreds.
2. Glue CTP plate making. Different from inkjet CTP, it is sprayed on the screen plate with a photosensitive polymer glue. The image is exactly the opposite of inkjet. After curing, it becomes a printing screen.
3. Laser CTP plate making. That is, an optical system is controlled by a computer to scan a prefabricated photosensitive screen with a modulated laser beam, and the laser beam scanning point is exposed and cured, and after being washed, it becomes a printing screen.
Compared with the current plate making technology, the advantages of CTP technology are quite obvious. The process of making a plate-making negative film has been canceled, which is convenient and quick, and the quality is also improved. The transmission and storage of data is more reliable and simple, and its market prospect is very broad.
Fourth, the screen production
1. Screen making materials, tools
The screen is composed of a mesh frame, a wire mesh and a photosensitive adhesive; the materials used are nail mesh nails, adhesive mesh adhesives, sealing mesh tapes, etc.; the tools for making the mesh version mainly include: stretcher, stretcher, nail gun , gluing machine, gluing scraper, dryer, printing machine, water spray gun, etc.
T-shirt printing generally needs to save a certain number of pattern screens and has a long shelf life. Generally, a net frame is generally adopted from the economic point of view. The material of the wooden frame is preferably fir, and the wood nail gun with too hard texture is difficult to nail the nail, and the wood with too loose texture is easily deformed and loosened.
The use of a nail gun has the advantage of being faster and more convenient than using a glue mesh, but the screen stability is poor. If you can combine the two best.
Since T-shirt printing mostly uses water-based paint, polyester mesh should be used because nylon mesh is easy to expand and relax when exposed to water.
2. Stretching net
The T-shirt screen version of the stretcher process is the same as the normal screen version. However, it should be noted that the screens selected for different prints should be suitable. For example, if there is a water-based printing material and a foaming printing material or a gold-silver paste printing material in a set of screen printing, the water-slurry should adopt a 120-mesh wire mesh, and the foaming pulp and gold-silver pulp should adopt a mesh of 80-100 mesh. Screening is recommended for a 140 mesh screen. For printing containing chemical fiber or purified fiber fabric, if using water-based printing, 140-160 mesh screen should be used, and ink should be used for more than 240 mesh.
3. Photosensitive plate making
Water-based printing materials use water-based photosensitive adhesives, thermosetting inks and solvent-based photosensitive gels are available, and solvent-based photosensitive gels are preferred because film removal is relatively easy.
Applying the photosensitive adhesive on the screen should pay attention to the uniformity of the adhesive layer. Generally, the printing adhesive layer is thicker than the scratch-coated adhesive layer. The thickness of the photoresist film varies greatly depending on the print, fabric and graphics.
(1) Adding a net version of the film to the book. If the film is thick, there are many materials that are missing, and it is easy to make the dot paste.
(2) Whether the chemical fiber fabric uses ink or water-based pulp or heat-fixed ink, the screen film of the screen should be used to prevent the paste, and the printed products will be softer due to the printed book. However, if the printed oxford fabric (400 dens or more, used for school bags, etc.), the film can be thicker.
(3) The screen layer of the glue printing and foaming printing must be thick. Especially when printing glue on dark fabrics and rough fabrics, the screen adhesive layer should be about 3 times (0.3mm or more) of the thickness of the screened layer, so that the printed glue will have a strong hiding power. The print is smooth.
The production and process requirements of the T-shirt printing screen are basically the same as those of the conventional screen printing. However, since the glue printing uses a mesh of about 80 mesh and is a thick film, pay attention to the exposure time to avoid the exposure time. The edges of the image appear jagged.
The prepress process not only determines the good or bad T-shirt production, but also determines its success or failure. In business, a well-designed T-shirt is not very fine-printed, and it can still be sold, because consumers know that printing technology is rare; but if a T-shirt is not well designed If you print it fine, the quality of the fabric is good, and no one will buy it. Because buying T-shirts is a culture, and the value of T-shirts is more than the value of T-shirts. Therefore, the design of the T-shirt pattern plays an important role in the value of the T-shirt. Of course, this is not to say that print quality is not important. T-shirts with high printing quality, even those who do not understand printing technology, will distinguish the level of their resistance by feeling. We summed up a sentence in practice: the pattern decides whether to sell it; the printing decides whether it sells well (price).
In addition, in terms of exposure, our company's time requirements for exposure are not very accurate, but if you use the test plate to test, you will find that the control of the printing time may have little effect on the thick lines, but for Fine lines and screened dots have a great influence. To produce a high-quality screen printing plate, you must carefully determine the exposure time. It is the same set of four-color screen negative film. Due to the different dot density of different colors, the exposure time should be different. The low-profile screen exposure time should be slightly shorter. The high-profile screen exposure time should be slightly longer to avoid the high-gloss dot being washed away. .
In addition to computer production, the prepress process can be said to be difficult to master. The important thing is to be serious and keep improving.