Introduction to flexographic and flexographic CTP basics
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CTP is a turning point in the development of prepress technology. In the printing aspect has played a pivotal role, CTP technology has developed rapidly, and has been applied in the fields of commerce, newspaper, packaging and printing. Today, flexo CTP has been applied to printing in various fields such as packaging, wallpaper, beverage boxes, etc., and the quality is widely recognized.
Flexographic printing is one of the most common printing methods currently available, as traditional printing methods have their own characteristics. As a relatively new printing industry in China, flexographic printing has achieved considerable growth in recent years. The water-based ink used in flexo printing is an environmentally friendly printing method that does not have as much contamination as gravure. Relatively speaking, the cost of flexo printing is relatively low, and the printing volume is large. It is suitable for the printing of sheet and web materials of different materials, and is most suitable for packaging printing and various labels and large-area substrates.
First, the characteristics of flexographic printing
Compared to traditional offset, gravure and embossing, flexographic printing has the following characteristics:
1. High production efficiency. Flexographic printing uses a roll material, which not only enables double-sided printing of the printing material, but also completes the work of light, bronzing, die cutting, waste discharge, winding, etc. on the line;
2. A wide range of substrates, such as paper, plastic film, aluminum foil, self-adhesive paper, etc.;
3. The quality of the printed matter is good, the printing precision can reach the number of printing lines of offset printing, and is especially suitable for the requirements of packaging and printing;
4. The use of new water-based inks and solvent-based inks, fully in line with green printing requirements, can also meet the requirements of food packaging;
5. Shorten the production cycle, save materials and manpower, reduce production costs and improve efficiency.
Second, the traditional flexo process
Computer document or blue pattern → according to the printed Fingerprint, adjust the corresponding dot expansion compensation curve → Phototype machine output negative image film → plate machine back exposure of the traditional plate → the front side of the plate and the film vacuum close the film Face main exposure → After removing the film, put the plate into the plate washer, use solution washing → plate drying and UVA, UVC and other post-treatment → check the size and modify the edge → complete the traditional flexible plate making.
Third, CTP flexo plate making process
Computer document → digital proofing or blue pattern → backlighting machine on the back of the digital plate → the digital plate in the front of the flexographic CTP main exposure → into the traditional washing machine, with solution washing → plate drying and UVA , UVC and other post-processing → inspection completed digital flexible plate production.
Fourth, the flexo process interpretation
In the flexographic printing process, there are often some terms that are different from traditional signboards. We explain the following.
Plate cutting: select the appropriate layout size according to the size of the negative image;
Backside exposure of the plate: The thickness of the substrate is formed to ensure that the relief depth is as high as required. Activate the plate to save the main exposure time;
Front exposure: first remove the surface protection film of the printing plate, closely adhere the film surface of the negative film to the photosensitive film surface of the printing plate, cover the vacuum film to form a negative pressure, and then expose the printing plate to make the light portion The photosensitive material is cross-linked and hardened to determine the slope of the image and the size of the dots;
Development: using tetrachloroethylene or an environmentally friendly solution to dissolve the photosensitive material in the unexposed area to form a relief; drying: the developed printing plate needs to be dried under hot air to volatilize the solvent inside the plate, and the material shrinks and returns to The thickness of the raw material as it is;
De-sticking post-treatment: removing the viscosity of the resin by UVC on the printing plate for a period of time, increasing the smoothness and hardness of the surface of the printing plate;
Post-exposure: Perform a comprehensive and uniform exposure on the dried plate to completely crosslink the resin without hardening inside the plate, so as not to be deformed by the influence of ink or solvent, and improve the printing durability of the plate;
Loading the plate to the drum: After the required size is cut, the plate is loaded onto the drum according to the prompt of the computer, and the vacuum adsorbing plate is inside the drum while the plate is being loaded;
Laser imaging exposure: The digital signal transmitted from the desktop system controls the laser in the flexographic CTP through a computer. The drum rotates and the laser head moves along the axial direction of the drum for exposure.
Five, the characteristics of flexographic CTP
At present, the familiar flexographic plate-making equipment is a system using argon ion (Yag) laser imaging (Esko and Dupon equipment), which uses a digital signal to direct the YAG laser to produce infrared rays, which are coated with a black synthetic film. On the photopolymer plate, the black film is ablated by a laser to form a negative image, and then the same processing steps as exposure, rinsing, drying, and post-exposure are carried out to form a flexographic plate. The other is a system that uses laser diode imaging, with both fiber optic transmission and laser tube arrays (Kodak's equipment). The two plates are basically the same.
The flexographic plate-making plate is composed of a resin film base, a photosensitive resin layer, a black laser absorbing layer on the photosensitive layer, and a protective sheet. The photosensitive resin layer is the same as the ordinary flexographic plate, and the black laser absorbing layer can be laser ablated. When it is exposed, the underlying photosensitive resin layer is exposed, and the ablated laser absorbing layer functions as a film, so that no film is required, and no vacuum is required for printing. If you use CTP flexible media, it also has the following advantages:
1. Reproduces from 1% to 99% of the dots during printing;
2. Effectively control the expansion of outlets at small outlets.
3. Stable reproduction of intermediate level outlets.
4. The details of the highlights and shadows are preserved, and the flat and gradient meshes are very smooth.
5. The same needs for UV printing machine and plate printing machine, the existing equipment investment will not be wasted.
6. Effectively shorten the plate making cycle;
7. Digital flexo always touches the printing material at the center point when printing. The traditional flexo is that the edge of the dot touches the printing material first, so it is easy to cause the hollow dot. Digital flexo does not have this problem.
8. Compared with traditional flexo plate making, the lines are clearer and the thickness changes are easier to control.
Six, special technology of flexographic CTP
Hybrid flexo screening technology uses FM screening technology to add screens in the highlights of the image (10% to 15%), while using the traditional AM plus in the mid-tone and dark-tone (15% or more) Network technology screening. The size of the FM screening dot is about 50 microns. After the mesh is added by Hybrid technology, the dot with a diameter of only 50 micrometers will have a relatively large wear at the tip of the plate, so it will be lower than the average height of the large dot. Reduce the expansion of outlets.
In the 1%-10% highlight and 90%-99% dark-adjustment areas, the special screening technology uses fixed-size dots to achieve the replication of the tone changes by changing the density of the dots; and in the 10%-90% The midtones are reproduced by changing the dot size as in the case of amplitude modulation, called MaxTone. Originally, this technology was tailored for flexo printing, and the technology can now be used in any printing process. Kodak introduced MaxTone screening technology, which allows users to define a micron-sized minimum mesh point size, and allows the screening engine to remove the mesh points in a random manner, while ensuring that each dot is larger than the specified dot. Maintaining the integrity of the entire tone, so that the highlights can be very well reproduced, this is the HyperFlex technology, currently MaxTone is the Prinergy package workflow options.
In addition, in the processing of pre-printing trapping, some improvements can be made when using the CTP plate making method. The trapping is mainly designed to compensate for the registration error of the printing press, but the trapping also brings another bad result, that is, the original design will be changed in a small part. For example, if there is a 0.15mm overprint at the intersection of the magenta block and the blue block, the adjacent lines of the two color blocks will produce purple lines close to 0.15mm width, which is not for customers with higher requirements. accept. In the CTP process, we can use the advantages of the CTP plate to support the base with a large slope and clear edges of the printed lines, and adjust the thickness of the set of color plates. The CTP version of the registration line is commonly used from the traditional version. The 0.1mm is improved to 0.05~0.07mm, and the overprint in the workpiece can be adjusted to about 0.07~0.1mm.
With the digitalization of the prepress field and the improvement of flexographic CTP technology, the development of mechanical roller precision and laser technology, the sleeve technology has gradually matured in the field of flexographic plate making. The sleeve technology is essentially an extension of CTP technology in flexographic printing. If the plate is made on a sleeve, a flexographic plate can be made on the press. And this method can achieve accurate positioning of the laser beam, achieve good overprinting and continuous seamless printing, thereby effectively saving time and a large amount of cartridge paper.
Seven, flexo CTP market
With the improvement of printing technology and printing environmental awareness, flexographic printing has been accepted by more and more people, and the flexible version of CTP technology has become a hot topic. In countries with developed printing industries such as Europe and America, flexographic printing It has developed rapidly, and packaging printing has changed from gravure and offset printing to the current flexographic printing. At present, about 70% of packaging materials use flexographic printing. With the continuous application of new technologies, flexographic printing Printing has made great progress, and the quality of the products is directly offset by offset printing and gravure printing, and has a strong market competitiveness.
At present, the domestic flexo CTP version is mainly used for printing high-end prints. According to statistics, there are more than 40 companies engaged in flexographic printing in China, but only 10 companies have installed flexographic CTP plate making equipment. Many domestic enterprises are quite satisfied with the quality of CTP plate making. From the comparison of more than 1,000 sets of flexographic CTPs in the world, we have a certain gap with the world advanced level. However, we also see that the flexographic CTP has not only started in China, but is also in the development of a fast high starting point. The annual consumption of flexographic plates in China is around 20-40,000 square meters, with the development of flexo printing. With the increase in plate making, the existing flexo CTP can no longer meet the requirements for use. We believe that with the joint efforts of industry colleagues, Flexo CTP will be well developed in China.
Kodak ThermoFlex is a core laser-to-plate making device on the market. It is a typical offset printing CTP technology that extends in the flexo printing industry and has a good reputation in the flexographic printing industry. Kodak's products are targeted at the mid- to high-end flexo market and are used in the production of high-fidelity packaging, film, folding cartons, multi-layer paper bags and fine corrugated boxes. Recently, a large-format, full-featured flexo CTP of Thermo Flex Wide II has been installed in Shenzhen Luolanxin Laser Technology Co., Ltd., which can output large-format flexo and output sleeve flexo, and is in good working condition. .
Current flexographic platemaking technology is moving in a simpler, faster direction. With the technological advancement of flexible plates and flexible inks, the printing quality of flexographic plates can fully meet different requirements. The proportion of flexographic printing in the entire printing market will also increase. We look forward to the direct plate making and tradition of flexographic plates. The CTP can produce benign competition to a certain extent, form a mutually inclusive situation in the domestic market, and ultimately provide customers with all-round printing services with lower prices and better quality.