Application and technology of full-water four-color ink
In recent years, textile printing using the principle of four-color separation has gradually attracted attention. The color patterns of tourist textile crafts and cultural shirts currently popular in the market are all four-color printing.
The MD-994 full-water four-color ink produced by Shanghai Meide Fine Chemical Co., Ltd. does not require additional equipment investment for existing flat screen printing machine manufacturers. As long as the company ’s products and technical guidance are used, the printed products can be mass-produced, and The operation procedure and production speed are the same as usual paint printing.
MD-994 full water-based four-color dot ink, bright color, easy operation, and cheap price (only five to one-seventh of imported four-color ink). For such an excellent product, it is necessary to use it well, that is, to produce a four-color screen printing work that is more than 98% similar to the original, there must be an excellent four-color screen printing process, which will improve the four-color screen of the electronic color separation version The printing effect is very helpful. So, how to do four-color dot printing?
Screen material selection
Wire mesh: choose a monofilament polyester yellow wire mesh of around 200-350 mesh. Because when the white silk screen is exposed, the light will be refracted and the highlight level of the pattern will be lost. The elongation of the wire mesh must be low. In order to avoid moiré, it is best to choose the mesh of the wire mesh to be 5-6 times the number of dots of the electric segment.
Photosensitive glue: Use high solid content, good resolving power, and good adhesion to the double-cured diazo photosensitive resin with good adhesion to the wire mesh. This ensures that the highlight dots are not lost during exposure, and a high-resolution, high-resolution screen can be generated.
Screen making
Electronic filming: hand over the manuscript to be printed to the unit holding the computer screen printing color separation and plate-making system for image scanning, layout design and production, until the output of electronic filming. It is best to choose 35-80 lines / inch for the frequency modulation dots of the electro-division film, and the photosensitive drug film is on the front of the film. The number of dots and lines of the electronic sub-film should be selected according to the size of the printed product and the distance between the visual inspection and the printed matter. General advertising production pays attention to the effect of far-sightedness (more than 1 meter above the visual inspection distance). It is better to select 35-40 lines / inch for the dots and 200-300 mesh for the wire mesh. Such as textile printing, handicraft printing, the number of dot lines should be higher, generally choose 55, 60, 65, 70, 80, 100 lines.
Stretching the net: Use the diagonal stretch method. The dots of various colors are generally used: 90 degrees for the yellow version, 75 degrees for the blue version, 15 degrees for the red version and 45 degrees for the black version. If the screen mesh number exceeds 5-6 times the number of dots of the electric segmentation screen, a straight stretch method can also be used, which can prevent the headache-like moire often encountered in the four-color screen printing. The most important rule of stretch screen is: the screen tension of the four printing screen frames should be the same. If the tension is different, it will cause the screen to stretch different lengths during the printing process, resulting in inaccurate overprinting.
Photosensitive adhesive coating: first wash the four screen frames with washing powder or cleaning liquid. After drying, choose a sizing device with a sharp blade. The width is preferably close to the inside of the printing plate, and the force should be even. First coat the scraping surface once, then turn the screen upside down, then coat the scraping ink once, and apply the same method to the printing surface twice. The film thickness is preferably 20 microns. The sizing should not be too thick, otherwise the dots will spread easily. After coating, the screen should be placed horizontally and dried, and the drying should not exceed 30 degrees Celsius, and then blown with a fan. The working darkroom environment should be clean and dust-free.
Exposure: In order to keep the negative film close to the glass during the exposure, it is best to choose a vacuum exposure box. The float glass used in the exposure box can reduce the refraction, otherwise it will affect the clarity and resolution of the screen. It is best to use a revision box when attaching negatives. First, align the four negative film lines with 100%. The side of the revision box is pre-ordered against the backing. It should be consistent with the official table printing backing. Use transparent double-sided tape to fix it And screen, and then put it on the photosensitive table to expose. In this way, when the official printing, the registration is much easier.
Rinse and develop: Wet both sides of the screen with tap water. After softening for 1-2 minutes, rinse the printing surface with a small high-pressure water gun. The pressure should not be too large during the processing until the screen reproduces the negative. Then rinse both sides of the screen with tap water until there is no softened photoresist residue. Dry the screen, repair the pinholes, and expose again to increase the durability of the screen.
Printing machine: Flat screen printing machine is the most important piece of hardware to improve the printing effect. For four-color screen printing, a flat screen printing machine with higher alignment accuracy should be selected. The printing platen must be flat.
Scraper: In order to obtain high-quality printed products, a scraper with a hardness of 70 degrees should be used. The surface of the printing squeegee should be smoothed with a squeegee, and the edges have a linear profile, and the effective squeegee angle is about 70 degrees. The pressure of the printing blade should be adjusted to be consistent.
Paste: MD-994 four-color dot ink is used, the new product has good thixotropy, PH value is 7-8, and it is equipped with additives to adjust: raw pulp diluent, standard color deepening agent, retarder, basic original Pulp, primer pulp.
Printing: The sequence is yellow, blue, red and black. The black version is printed first when the registration is started, and then one by one. After the four-color screen is correctly aligned, it can be printed.
Manual printing and machine printing: For large-scale manual printing, you should choose four hand touch strengths to cooperate with more tacit operators, and try printing first. The printing platen must be flat. Pay special attention to the screen distance (that is, the distance between the screen and the platen) should be controlled between 2-3mm. It is particularly emphasized that the printing speed of the doctor blade also affects the printing effect, so the speed must be determined according to the fineness of the four-color screen printing pattern and the background color, moisture absorption and surface structure characteristics of the printing material. Compared with the original color manuscript, all aspects of the commissioning are correct and then officially printed.
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