Web-free printing is closely followed by dot printing

Dots play a very important role in the printing of images, but in some special printing, dots cannot be used.

Regular image dot printing

The depth of the image is composed of the density of the imaging material particles per unit area and is called continuous tone. Continually adjusting the shades of the image is a stepless change, but in regular image printing, the shades of color and shade are represented by dots. There is always a limit to the number of stages of screening, and the level change of the image cannot be infinitely changed like continuous tone adjustment. Therefore, the screening image is called a halftone image.

In the screening technology, there are amplitude modulation and frequency modulation screening for the nodes that represent the color image hierarchy. The characteristic of amplitude modulation and screening is that the distance between the points in the screening network (ie, the frequency of the network points) is fixed and changes only the amplitude of the eldest son of the network points. However, there are some defects in this technology, such as loss of details, gradation hopping, and grid conflicts. Screening will produce moire, rose spots, visual impact, impact on the quality of printing, and it is difficult to develop to four-color printing. FM screening can well avoid the defects of AM screening technology. FM screening is the use of dot density to represent the level of the image, and dot distribution is random, it is also called a random dot.

Whether it is AM or FM, the level of images you want to display is inseparable from the network. However, not all image printing must be printed with dots. Some special printing, such as banknotes, stamps, and other anti-counterfeiting printing, oil paintings, prints, and other artistic printing, all use non-network printing.

Web-free printing applications

1. Banknote printing

Due to the wide range of dot printing applications and relatively small technical content, it is easier to imitate. In order to improve the anti-counterfeit effect, banknotes are basically printed without dots and printed in a variety of ways such as letterpress printing and gravure printing. The portraits and the main scene images in the banknotes were not printed using dot printing. In gravure printing, it uses fine mesh lines of different density, different directions and different colors to express the image effect, and it cleverly links with the surrounding security patterns to form a complete pattern.

The gravure inked area is concave, and under strong pressure during printing, the printing plate is in direct contact with the paper surface so that the ink in the concave pattern is transferred to the paper, and the ink is in a three-dimensional state on the paper. It is characterized by fine print lines, distinct layers, and a touch of concave and convex on the hand. It was initially printed in monochrome and has now been developed as a multicolor gravure.

2. Oil Painting

On rice paper, the use of dot-printing failed to fully reflect the unique artistic charm of the work, but the use of dot-less printing of Chinese paintings, oil paintings, prints, and other works of art can fully reproduce the continuous artistic tone of the original manuscript. At present, there are no three types of dot-net printing: the printing of Mu Luo printing, the watermark printing of woodcuts, and the printing of silk screens.

a. Milon printing

The use of glass for plate printing, it is also known as glass printing, the process flow is:

(1) Grind glass. The smooth surface of the 10mm thick glass is ground; (2) The bottom layer is coated. The ground glass is washed, dried, coated with a mixture of sodium silicate and protein solution as a bottom layer; (3) coated with photosensitive resin. After the mixed liquid of sodium silicate and protein liquid to be coated is dried, a layer of dichromate and gelatin photosensitive liquid is coated on the dried bottom layer, and then dried and baked at 40-60 degrees Celsius. When dry, light sensitive adhesive will produce fine wrinkles; (4) Plate making. After the photosensitive adhesive coating is dried, the negative film with continuous adjustment and the photosensitive film are closely exposed and developed. The unexposed photoresist was washed away during development and a water-absorbing layer was formed during printing. Photoresist in the light-receiving part, due to different levels, the sensitivity of the photosensitive film is also different, the thickness of the ink-absorbing layer is also different; (5) printing on the machine. After the plate is finished, it can be printed on a dedicated platform with a stencil printing machine. The structure is round and flat, and the roller is used for ink. Application soap ink should have good fluidity and low viscosity.

Because the Feiluo plate is negatively printed on the negative plate, the larger the amount of hardened layer on the plate image is, the larger the wrinkles are, the more the amount of adhered ink is, and the darker the tone is when printed. The brighter it is. Although Minami printing is currently accepted as a dotless printing method in the world, it is difficult to reproduce fine images due to insufficient level of detail, and only rough prints such as certificates can be made.

b. Woodcut watermark

Also known as the woodblock watermark, it is an engraving printing method that originated in the Tang and Song dynasties and prevailed in the Ming Dynasty. It uses lines and retreats to copy manuscripts with shades of intensity. It is mainly used to reproduce ink and ink paintings, color ink paintings, and enamel paintings and other handicrafts. The printed products can maintain the original style to achieve spurious effects. Woodcut watermarking platemaking and printing processes are completely done by hand. After getting the manuscript, first determine how many plates are to be divided according to the complexity of the colors, the levels of shades, the artist's style and artistic characteristics, and the size of the screen. During the trace, the transparent and impervious film paper is first smeared on the original, and then the picture is faithfully copied onto the film paper. The original has several tones and is divided into several sets of color plates. It is necessary not only to have a high level of painting skills, but also to have a profound knowledge of Chinese painting. Even how to print must be decided. The carved wood version is overprinted in sequence according to the original shade. The method is to emboss the wood plate, that is, the picture part, first brush the ink, then spread the rice paper on it, and then hold the brush and brush it on the rice paper. How many pieces of woodblock were printed on this rice paper, and the final product was made.

c. Screen printing

Screen printing technology can also be used for Chinese-style paintings, oil paintings, advertising paintings and other non-network printing, and the speed, quality and other effects are also ideal, there are the following advantages: (1) low cost, strong adaptability. Not only can directly print paper, fabrics and other soft materials, almost all of the water, oil, synthetic resin and other liquid or powder ink, pigment, etc., and the ink deployment method is simple. (2) The ink layer is thick, strong in three-dimensional, and rich in texture. Silk screen printing is the thickest and the ink layer can be adjusted. (3) Strong light resistance, good color rendering, bright color. (4) Since the screen printing has the feature of missed printing, the texture and color of silk screen printing are far more than offset printing even if the same color printing product with very light color printing is used. The use of screen printing can make the image appear to be raised and can achieve the original effect. Therefore, it can be said that it is the main direction for the development of non-network printing in the future.

In summary, works of art such as traditional Chinese paintings, oil paintings, and prints are printed. Because replicas of AM or FM technology have outlets, the effect of simulation printing cannot be achieved. However, due to lack of space and limited space, there is no network printing. The disadvantages of mass printing and so on are gradually being eliminated. At the moment, although the watermark can achieve real effects, the production cycle is long, the amount of printing is small, and the cost is high. The processes of tracing, adjusting, printing, and brush printing are mostly manual operations and are rather complicated. Although technical personnel such as operations are experts, they are also very Difficult to ensure that each tone is consistent, easy to appear color cast, at the same time there are problems such as overprinting, deformation, and so on, it is also unable to bear a high quality, a large number of printing. As the screen printing is mechanized, the number of manual operations is relatively small. In recent years, computers have also been widely used to analyze originals, scan originals in layers, and output layered negatives, and then printed through the screen printing and layered printing. The artefacts that make it more accurate, more subtle and more reproducible, so it can be said that in the future the main direction of the development of Chinese paintings, oil paintings and other artworks.

Source: Graphic Arts