High-fidelity screening printing technology features and market prospects

In image printing, screening technology plays a decisive role in the quality of prints. In order to improve the quality of printed matter, screening technology has always been the subject of research in the printing industry. The research content includes dot shape, size, screen angle, and combination. Today, high-fidelity screening technology has become a new step in color image printing. New technology.

Development and Defects of Screening Technology
1. Characteristics of AM screening

At present, AM technology is widely used in the printing and platemaking industry. It adopts halftone screening to achieve continuous adjustment of image effects. After many years of application, it has proved to have more advantages. However, it has defects such as loss of details, grid conflicts, and moiré, rose spots, and visual impingement. In particular, moire, because the meshes of the four color plates of the amplitude modulation screen are regularly arranged according to their respective angles, when they are overlapped, it is easy to produce obvious periodic interference fringes, so-called moire, which seriously affects the image. The printing effect, but it cannot be eradicated, will increase with the increase of the printing plate. Therefore, when the print quality is demanding, it is difficult to achieve high-resolution printing. Therefore, at present, the most basic criterion for measuring the quality of screening technology is whether it can effectively prevent moiré. In order to make the image achieve the best color reproduction effect, although the best dot combination angle is explored in the production practice to avoid the collision of the four-color screen angle (moirage) phenomenon, it cannot be completely avoided. Practice has shown that it is difficult to reduce the effect of moiré when using four-color inks.

2. FM screening features

Due to the defects in the AM screening technology, especially the defects such as moire, rose spots, and gradation jumping (ie, jumping before and after the seam starts), the printing quality is affected, and it is difficult to develop to four-color printing. This makes the application of AM screening technology affected. For the defects of AM screening, FM screening (random screening) technology is researched. This screening technology uses dot density to represent the image hierarchy, and dot distribution is random. In FM screening, due to the elimination of the small squares, there is no frequency interference, so no moiré and rose spots are formed, effectively preventing moire. Because of the invariable size of the ink spot, this method only changes the frequency of dots. Compared with AM screening, printed color prints are more detailed and significantly better than products using AM screening technology under the same printing conditions.

Compared with AM screening, FM screening can improve the output quality, and high-resolution images can also be obtained with a low-resolution photo-composer: no moiré and mottled spots are produced; the print has high definition, and the copying effect is good and stable. Good performance; not limited by the screen angle; effectively avoid the wrong network; is not sensitive to overprint errors that occur in the process of printing plates; dark tone is not easy to paste and so on. However, FM screening changes the distance between the center of the network according to the brightness and darkness of the input pixels. Although it avoids the defects of the AM screening technology, it also has deficiencies, which are mainly affected by the network expansion (perimeter perimeter perimeter). With the increase, the number of point enlargement increases, it is difficult to reproduce the dark tone level of the image, and the high-light level (skin color, etc.) tends to be rough; in addition, the requirements for all materials (films, plates) are high, and the resistance to printing is low.

Such as; 1 due to the same size of the site and have a sense of grain, especially in the high light part and about 25% more pronounced tone; 2 the whole production process latitude than the amplitude modulation screening decreases, so the need for more detailed process control than the amplitude modulation screening And monitoring technology; 3 Because increasing the ink film thickness has no significant effect on the size of FM dots as in the case of AM screening, images with poor color separation are difficult to improve quality on the press with ink adjustment: 4 Minimum micro-dots Too small, so that many printers can not be reproduced correctly; 5 Due to the small network, there are still some difficulties in proofing, copying, printing, etc.; 6 The imaging on the plate is relatively difficult, not stable; as long as the traditional plate-making process Any change will affect the tuning of final FM screening and reduce its screening reliability. In addition, the prints made with random dots have a difficulty in duplicating the images because the ink dots are too small.

3. Hybrid Screening Features

In order to make full use of the advantages of AM and FM screening, AM/FM hybrid screening technology is now introduced. Hybrid screening in the highlight area and shadow area is the same as FM screening. The level change of the screen is represented by the density of fine meshes with the same size. The positions of the dots are randomly distributed and processed so that the dots do not overlap each other nor are they too spaced. In order to adapt to printing, another calculation method has been added, that is, using a plurality of small dots to form a larger printing dot. In the midtone region, the position of the dot is random, and the size of the dot can also be changed like an AM screen. Therefore, the outlets in the middle part have both the distribution characteristics of FM outlets and the tone performance of AM outlets.

Hybrid screening has the following features: 1 Highlights and dark areas Due to the special treatment of the dot positions, the particles are reduced in relative FM. The combination of small dots was calculated and processed. The midtone region was prevented from jumping in the AM due to the randomness of the position of the dots in the midtone region. Because of the number of intermediate dots It is fixed and can calculate the dot density per unit area, thus defining the density of the intermediate tone dot point.As for the printing process, it can adopt the conventional precision production process and equipment to realize the printing quality of the high-line dot spot and the production efficiency at the same time. Not affected.

Hybrid screening technology came into being with the advent of the CTP era. For example, the AGFA and the screen will be added to the network, are two kinds of high-precision printing for the introduction of hybrid screening technology for CTP. As the core of digital CTP technology proofing, it also introduced its own hybrid screening proofing technology that is imitation real net technology. This hybrid screening technology can not only express colors, but also can fully reveal the flaws in the CTP process flow. Therefore, hybrid screening will be the best choice for future image replication and digital process inspections. Practice has shown that the application of this new technology with thermal CTP imaging technology can produce clearer, more replicable dot quality.