Best printing moire elimination method

2022-08-08
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In the printing industry, how to eliminate moire in halftone reproduction is a very important topic, because it has a great impact on the printing quality. In the color halftone printing, the silk interferes with the high temperature, which makes the appearance of Moire more complicated. In the printing process, there are two kinds of Moire: overprint moire and silk moire

in color reproduction, predecessors told that the included angle between two strong colors must be greater than 22 and a half degrees, and less than 22 and a half degrees, moire will appear

I. production of moire pattern

in multicolor eye tone reproduction, due to improper technical treatment, two kinds of moire pattern will appear: overprint moire pattern and silk moire pattern

II. Method to eliminate moire:

1. Correctly select the match between the number of lines added to the original and the number of silk meshes: the smaller the mesh/thread ratio, the more serious the moire will occur. Generally, it is required to be above 3.5 ∶ L. At present, the ratio of mesh/thread is more than 4.5:1 in the world. Within this range, there is a slight moire, which is within the allowable range of printing. Generally, 5:1 or more is selected for color halftone printing. This proportion is generally stretched or printed version will not appear moire

expert Michel Kaiser of France: he has made many experiments on the generation and elimination of moire in halftone silk printing. In the case of eye/line mismatch, he adopted the oblique stretching method to eliminate the generation of moire. He cited two examples:

the above methods are very effective, but the disadvantage is that they consume a lot of cloth

2. Master the template making technology correctly:

pay attention to the surface tension of the template during stretching. If the tension is not good, the wire will be deformed, showing wavy shape or poor internal square, which will cause local moire. It must be stretched according to the specification requirements. Two sets of plates (four plates in each set) must be stretched at one time, and all of them must meet the printing size requirements

positive tension (zero tension) is adopted. The wire diameter is parallel to the frame, which can save cloth and make minor positioning correction. Oblique stretching, the warp and weft threads of the cloth and the frame edge form an angle of 4-8 degrees, and the mesh number and tension of the four plates should be consistent. The disadvantage is Fabry, and the advantage is that it can ensure that the silk threads are completely parallel and square. In order to save cloth, the positive tension can be used, and the oblique printing plate can be 4-8 degrees. During exposure, the negative film can be placed obliquely on the film plate to fix the printing plate, or the positioning of the table plate should be rotated by an angle during printing

mastering the correct exposure time and the current technology, more than 40% of the new houses use plastic doors and windows; More than 80% of the newly-built houses in Qingdao and Dalian use light crosslinked diazo photosensitive adhesive light source for plastic windows. The technical indicators of the paper tensile testing machine match ultraviolet light, with a wavelength of 365 to 420um. Exposure is equal to illuminance times time (h=ext). The number of cloth mesh and color have influence on the exposure time. The higher the mesh number, the thinner the film and the shorter the exposure time; Low mesh plate film thickness exposure time to be long; The exposure time of white silk should be short, and that of substitute silk should be long

3. Select the ink and substrate:

the ink shall be the connecting material ink compatible with the substrate material. Ink with fine pigment particle size. Generally, the pigment particle size of the ink is one-third of the inner hole diameter of the cloth mesh. Otherwise, it will be blocked. Substrate to choose a smooth surface texture and ink compatible substrate. The texture shall be double-sided coated paper

4. Correct selection of adding angle:

it is very important to select adding angle, so as to prevent the generation of moire, organize the beautiful patterns of picture and text points and reproduce the color of powerful pictures and text. The normally set plus angles are 0, 15, 45, 75 and 4. Another method is to use the angle of oblique stretching or oblique printing because the number/number of items is not enough. Ensure that there is no silk moire between the negative and the silk, and that there is no overprint moire after overprinting of various color plates. It is better to set the single intersection angle of 45 degrees as the main color angle, 75 degrees and 15 degrees as the strong color angle, and 0 degrees (90 degrees) as the weak color angle. The color angle of type I or type II samples shall be adopted for yellow

5. Selection of point shape:

select different point shapes according to the intensity of the middle tone and dark tone image levels of the original. Diamond dots and circular dots are often used in images with rich levels of middle tones. Those with rich levels of dark tones mostly use square dots. Those with few levels of dark tones can use circular dots, while those with general popularity often use diamond dots

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