Section 1 Classification and Characteristics of Gravure Platemaking Technology
The gravure printing has high ink glossiness, strong coloring power, good color reproducibility, good transfer printing and superimposition performance, high printing density, large contrast, balanced distribution of halftone dots, and superior printing plate resistance, especially in color Packaging printing is a promising printing method.
However, due to the complexity and variability of the gravure platemaking, especially the traditional photogravure, proofing and modification are not convenient, which hinders the development of the gravure printing technology. In recent years, there have been dot gravure, electronic color screen gravure, and electronic engraving gravure (mechanical, laser, electron beam engraving, etc.), can be offset and gravure conversion, can directly use the color separation pictures, Electronic dichroic gravure dots and other pictures are taken to obtain the gravure printing plate roller, and the plate-making pictures can be verified by the plain printing and proofing to make necessary corrections. This opened up a bright future for gravure plates.
According to the characteristics of commercial packaging products, gravure color reproduction should be reproduced with the hope of color, so that the original color, physical color and the desired color of the three coordinated and achieve the desired effect of replication, the method should be the reduction of technology and It is hoped that the combination of color re-creation will make the reproduction quality better than the original color and faithful to the actual color.
(1) First, on the basis of manuscripts, do a good job in the standardization and data color management of the process technology of the gravure platemaking process, so as to accurately transfer colors, control errors in the reproduction of colors, and ensure the reproduction of manuscripts. In terms of image scanning color separation, one is to make a friend balance curve parameter set to ensure the gray, complex color reproduction in the manuscript; secondly, to do a standard color correction amount based on the gray balance, to ensure the accurate reproduction of the original color This is a very important basic work. Color copying is a restoration technique, no matter what process, regardless of the quality of the original, no matter how large the adjusted color gamut, the extent of adjustment, the accurate color reproduction is the fundamental of the copying technology, which is the commonality of replication technology.
(2) The color of the original is reproduced after the color separation is set by the standard correction amount parameter based on the gray balance. Then further adjustments were made to the flaws in the original color and to the requirements put forward by the customer. Such adjustments belonged to the category of recreating in the reproduction technology. Regardless of the quality of the original, it should be based on the true color of the original physical object and be adjusted and processed according to the desired color. This kind of re-creation adjustment and processing, on the one hand, should be fully faithful to the original color of the product and highlight the attributes of the product; on the other hand, it must meet the various requirements of customers, emphasize the commercial effect of color, and highlight the saturation of color, that is, Color exaggeration and rendering, even exaggerated to some degree too much, giving people a strong sense of color, so that people look at the bag, you can generate a desire to buy, this is the characteristics of the gravure plate reproduction of this type of product, is also currently The key to improving the quality of packaging products.
To sum up, only under the guidance of the correct copying theory can we do a good job in scanning color separation and color correction of images, and we can get a multiplier effect.
A modern gravure plate making method
The modern gravure platemaking process methods mainly include:
1. Dot gravure
Gravure dot screens are used for photographic screening or electronic screening to produce positive (or negative) images of the screens. They are directly printed on the photopolymer material plate cylinder or the copper roller coated with photoresist. The former only It needs to be washed and developed. The latter is then eroded (or electrolyzed) to make a gravure plate. It is also called direct etching. The plate making procedure is simple, the data is stable and easy to operate.
The gravure plate made by this method has the same depth of the cell site, but its depth can be uniformly changed (15 to 35 Î¼m). The dot size varies with the image level, and the ratio of the line wall to the dot can vary from 1:3 to 1:6 (up to a maximum of 13, but not tolerated) with the original coordination contrast requirement. Although it can only express a dot scale of 56% to 73% (up to 79%), due to its thick printing ink layer and high contrast, as well as the expansion of printing tone levels, its tone reproduction is still better than offset printing. . And the picture is flat, uniform and soft, suitable for decoration and printing of building materials and trademarks.
The dot screen gravure screen images can be screened with color separation screens, and electronic color screen printing is more advantageous. The majority of electronic color separation machines in modern times have a gravure dot system, which has white cross-line dots, honeycomb hexagonal dots, and other odd-shaped dots. The electronic color separation of the image can be flexibly adjusted and the data can be accurately recorded. Intaglio dot images can be directly recorded. And can use flat printing proofing to verify, the picture can be amended again, plastic gravure data can be converted, is a modern common gravure plate making process.
2. Electronic engraving gravure
In recent years, a variety of performance gravure electronic engraving machines have been launched one after another. You can use the desktop system to separate color or electronic color continuous adjustment picture, or add screen yin and yang pictures to scan originals, and scan the head through the engraving machine. Covering the outlets, the image scanning signal drives the electronic machinery (diamond cutter) as a synchronous engraving dot version (such as Helio K200, 201, 202, 203, etc.). In addition, the image output signal of the color separation system is directly input to an electronic engraving machine and an intaglio printing cylinder is engraved.
The color separation screening chart used by the electronic engraving machine can use the offset proofing or digital proofing to check the color separation version to achieve accurate gum gravure conversion. The electronic engraving machines all have different dot systems and multiple sets of engraving levels, and can be freely adjusted to produce fine-grained images suitable for different gravure printing requirements.
The intaglio dots of the electronic engraving change at the same time as the size of the dot and the depth of the cell site. The hierarchical resolution is very fine, and the image coordination level and contrast can be well reproduced, which is more suitable for the gravure printing of fine color images.
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