Spot color screen printing technology of the hotte

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Textile spot color plus printing technology (Part 1)

this paper introduces the characteristics of spot color plus printing technology and its differences from four-color printing technology, and describes in detail the requirements of spot color plus printing on the original, the color separation technology of spot color plus printing, the ink used and the requirements for equipment. It is pointed out that spot color plus printing technology has attracted more and more attention in the industry with its advantages of high quality, high efficiency and high profit

key words: spot color; Textiles; Add printing

spot color plus printing and CMYK four-color printing

). Spot color plus printing is currently mainly used in the field of textile printing. Why should we develop spot color plus printing technology? What are the differences and technical advantages between spot color plus printing and CMYK four-color printing

)) 1. The most fundamental difference between four-color printing and spot color plus printing is the transparency of ink. Four color printing technology requires that the higher the transparency of the ink, the better (see Figure 1 A, B, c). In Figure 1a, the transparency of the ink is 100%. No matter which color is printed first, its composite color (overlapping part) is emerald green (100% C + 100% y). If the transparency of the ink is only 50%, print yellow first (yellow is covered by 50% green), then its composite color is blue; If cyan is printed first, its composite color is yellow (see Figure 1b, c). This is the color deviation often heard in four-color printing

the spot color plus printing technology requires that the lower the transparency of the ink, the better, that is, the higher the hiding power of the ink, the better, preferably 100% hiding power. Its printing effect is shown in Figure 1D, e. Why does spot color plus printing technology require that the higher the hiding power of ink, the better? Because the spot color plus printing technology is developed for the printing of color textile fabrics. Obviously, when printing on colored textile fabrics, the higher the hiding power of the ink, the better. It's like printing white patterns on black textile fabrics. If the hiding power of white ink is not enough, it may take three or four times to meet the whiteness requirements. If the hiding power of white ink reaches 100%, one time is enough

then, what will happen to four-color printing on color substrate due to the above unique nanostructure and excellent performance? Because the four-color ink is highly transparent, the printing effect of the substrate is of course a mess after the background color of the substrate is penetrated. The only way is to print a layer of white background first, and then a layer of CMYK four colors. However, if textile fabrics are printed in this way, there will be two major problems: first, the ink is thick and the hand feel is poor; The second is like sticking a plaster. Therefore, it is not advisable to print on colored textile fabrics, but to use spot color plus printing technology

)) 2. Compared with CMYK four-color printing, spot color plus printing technology has the following characteristics:

A. color images can be printed on the substrate of any color (including white)

b. the printing color of the image can be adjusted arbitrarily. For example, for a spot color plus pattern orange, we can not only adjust the color depth of orange, but also replace it with red, rose, golden yellow, etc., without affecting other colors

c. the brightness of color is much better than that of four-color printing. In four-color printing, it is difficult to solve the problem of gray scale in colors, especially green, purple, orange, etc., which are always bright and not bright enough. This is because there are several difficult problems in four-color printing: it is difficult for the color separation three primary color ink to achieve a 35% weight reduction of the whole vehicle compared with that in 2015; Three primary color ink is difficult to achieve 100% purity and 100% transparency. Spot color plus printing not only does not have these problems, but also has richer colors. Metal ink (gold, silver, etc.), fluorescent ink, color changing ink, etc. can be used, so that the pattern of spot color plus printing is far more beautiful and strange than four-color printing

d. the printing color of spot color plus printing is usually more than four colors

it can be seen that spot color plus printing technology is a new technology specially developed for clothing and T-shirt printing, which is also applied to other textile products and other substrate printing. Spot color plus printing technology is developed on the basis of four-color printing

requirements of spot color plus printing on the original and revision

). The design of spot color plus printing pattern gives designers greater and more free design space than traditional spot color printing pattern. Whether painting: Chinese painting, oil painting, watercolor painting, photographic works, computer 3D images or physical scanning can be used as the originals of printing patterns

however, spot color plus printing requires far more clarity (i.e. image resolution) than traditional printing. The remote manuscript of traditional printing can be color paper manuscript with general definition, or monochrome paper manuscript with color block line color marked by text, and copies, faxes and drafts can be used. As long as the color block and simple transition color pattern outline the excellent block, add solid color (black) in the contour line or set the gradient direction and density, the computer can add uniform color in a few seconds. Color patches and simple transition color patterns generally use vector graphics software, which has no resolution requirements for far draft and does not set resolution in drawing. Most of the originals with spot color and printing are paintings, photographic works, computer 3D images, etc., and their color gradients are irregular. Therefore, it is impossible to draw and separate such originals with vector graphics software, and bitmap graphics software must be used to draw and separate their far drafts. The scanning resolution determines the clarity of the image. If the resolution set when scanning the original is very low, the quality of the image is certainly not good

in actual production, many customers bring low-quality originals, a T-shirt, a floppy disk, a low-quality print, or a small color print. What should I do? There is only one way: draw! Redraw! Or draw with bitmap drawing software, or draw on paper by hand. Whether you use bitmap drawing software to draw on a computer or manually draw on paper, painters are required to have a high level of professional painting, which is not what ordinary computer draftsmen can do

the requirements of spot color plus printing on the manuscript are: the painting manuscript should be 1:1 as far as possible, and the color printing manuscript should have high printing quality and large size; The resolution of computer design manuscript is 200-300dpi

spot color plus printing color separation technology

)) spot color plus printing color separation technology is much more complex than color block graphic color separation and four-color color separation. Color block graphic color separation can be used not only by computer, but also by hand drawing; For general four-color color separation, as long as the color mode of the image is set to CMYK mode in any set of bitmap drawing software, the color separation can be completed (there are four color channels in CMYK mode, namely cyan, magenta, black and yellow, which can be made by adding films respectively). But spot color plus printing technology is far from so simple

it is impossible to use hand-painted manuscript for color separation of spot color and printing, and only computer digital technology can be used. There are two main methods of spot color and color separation using computer Digitization: one is to directly use bitmap drawing software (the most commonly used is Photoshop software) for color separation, and the other is to use professional printing spot color separation software for automatic color separation

a. direct use of Photoshop software for color separation, also known as computer manual, such as color separation with cutter, dryer, printing device, etc. This is the only way without printing spot color separation software

if you design the pattern yourself, you can use the "layers" of Photoshop software to directly set different color layers for design. After the design is finalized, each color layer can be added to each spot color separator

)) if it is a contribution or a design using a color manuscript, first open the image file in Photoshop, and then select the command of "color range" in "select" in the menu to open the color dialog box, as shown in Figure 2. Use the dropper to select the corresponding color. After "OK", store the selected color in the channel, that is, complete the color separation of the spot color

)) directly using Photoshop software for color separation requires not only rich experience in color separation printing, but also time-consuming and laborious

b. use printing spot color separation software for color separation

generally, printing software is used as a Photoshop plug-in. Open the color separation software, and open the black background image in turn according to its prompt. After the white background image (as shown in Figure 3), the color separation will be automatically completed. Finally, make appropriate adjustments to each channel

)), it should be noted here that no matter how good the color separation software is, the spot color separation cannot be 100% consistent with the original, because the color of the original is always between the colors, and using a limited number of spot colors to represent the colorful original can only achieve a similar effect

at present, the clothing printing spot color software that can be seen in China mainly includes the American version (fast films, spot process, weifeishi color separation software) and Guangzhou wantongda version. Domestic agents are mainly Guangzhou Lixin company, Shanghai Shalian and Tongli company, which provide corresponding technical guidance. Suzhou Chenggong company also provides guidance on FM dot color separation and addition technology

)), in addition to the above two methods, a new spot color separation method developed internationally in recent years - spot color tone increased by 72% over the same period last year In addition, frequency plus color separation

traditional addition technology is amplitude modulation point, which is a milestone in the development of human printing technology. The characteristic of AM points is to use the size change of points to reflect the gray image, and the points are arranged linearly. The characteristic of frequency modulation points is to use the density change of points to reflect the gray-scale image. The size of points is the same, and they are randomly arranged according to the density value of the image, which is irregular (see Figure 4). According to its simulation principle, FM dot printing is closer to the gray original image than am dot printing

)), while in actual printing engineering, FM dot printing has the following advantages over am dot printing:

))) A. moire phenomenon that cannot be overcome by am dot is removed

)) B. plate making is easier, and the produced version is closer to film. We know that the highlight part (density less than 15%) and the dark part (density more than 85%) of the AM points appear as tiny black or transparent points, which are inevitably lost in plate making and printing. What we can do is to minimize this loss as much as possible. Moreover, in practice, taking care of the highlight part (increasing the exposure value) will lose the dark part points, and taking care of the dark part (reducing the exposure value) will lose the highlight part points. Because all points of FM are of the same size, as long as the exposure value of a point is determined, all points can be exposed without loss

)) C. the ink layer of printing is thinner than that of amplitude modulation point printing, which not only saves ink, but also makes the textile feel soft

)) d. amplitude modulated dot printing can not only add frequency modulation after dividing the original color image into gray-scale images, but also convert the original color image into index color mode, and then separate colors. The latter method has such an advantage that multiple colors can be specified to form a new FM image. Of course, there will be a difference with the original color image

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