Comparison between the most popular flexo laser pl

2022-07-25
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Comparison between flexo laser plate making and traditional plate making

flexo printing uses blanket, plastic or other soft materials as plates. The ink is attached to the convex part of the printing plate, and then the image is transferred to the substrate. The application of quick drying ink makes flexo printing an ideal way to print on plastic and foil. It is the preferred method to produce handbags, packaging paper or similar packaging materials. It has more advantages than other printing methods. It has high elasticity, high printing resistance and high resolution. To make high-quality plates, in addition to high-quality plates, we also need high-quality plate making technology and plate making equipment. This paper makes a comparison between the traditional plate making process of flexo and the laser plate making process

1 traditional flexographic plate making and process requirements

1) the original design suitable for flexible printing should have the following characteristics: 1. More colors, but less overprint;) It is not required to reproduce particularly small details: (3) the line is not too high, but the color printing effect can be achieved; L4) online packaging processing is available

2) film (bright film) (1) meet the needs of plate making, with clear graphics and text, accurate size and specification: 2 use frosted film: (3) the density of four corners of the film is required to be the same: (4) use drug film Zhengyu; (5) Measured by transmission densitometer, the white spot density is less than 0.06; The density of black spots is more than 3.5

3) exposure: back exposure and main exposure

back exposure the supporting film of the photosensitive resin plate is upward, and the protective film is laid down in the exposure drawer for exposure. Ultraviolet light passes through the supporting film to solidify the photosensitive adhesive layer. The purpose is to establish a stable base, control the washing depth, and strengthen the adhesion between the supporting film and the photosensitive resin layer. The back exposure time is determined according to the required subbase thickness

main exposure: the supporting film of the photosensitive resin plate faces down and the protective film faces up. Lay it flat in the exposure drawer, tear off the protective film for a continuous time, then stick the film film surface on the photosensitive resin plate and properly solve the problem of aerogel gel dust. Cover the vacuum film on the film (non drug film surface) and vacuum to make the film closely fit with the photosensitive resin layer. Ultraviolet light passes through the truth film and the transparent part of the film to polymerize and cure the photosensitive part of the plate. The length of the main exposure time is determined by the plate model and the intensity of the light source. If the exposure time is too short, the gradient of the text will be too straight, the lines will be bent, and the small characters and dots will be washed away. Otherwise, if the exposure time is too long, the version will be applied and the handwriting will be blurred. If there are large and small characters, thick and thin lines on the same printing plate, they can be exposed separately with black film as appropriate, and small parts will not be lost due to washing, so as to ensure the printing plate quality

4) wash and dissolve the non photosensitive part, and keep the relief of photopolymerization. The length of the plate washing time depends on the thickness of the plate and the depth of the image. If the plate washing time is too short, the plate will be left with non photosensitive resin when the preload P is 1.0kn, which will affect the plate making depth. If the plate washing time is too long, the plate will expand, resulting in deformation or falling off of the fine parts

5) drying: remove the washing solvent to restore the original size and thickness of the printing plate. The baking temperature is generally between 50 ℃ and 60 ℃. The baking time depends on the thickness of the plate and the length of the washing time. Generally, the thick version lasts for two hours and the thin version lasts for hours. Too long baking time and too high baking temperature will make the printing plate brittle and affect the printing life. If the baking temperature is too low, the drying time will be prolonged. If the baking time is too short, the printing plate will be rotten

6) post treatment: namely, debonding and post exposure. Make the photosensitive resin harden (polymerize) thoroughly to reach the required hardness index, and eliminate the printing plate viscosity to facilitate the ink transfer. The post-treatment time is obtained from the test so as not to crack or stick

2 laser plate making and process requirements

laser plate making uses the image signal of the electronic system to control the laser to directly engrave on the single sheet or sleeve flexograph to form a flexible plate

the plate making process is fully digitized. After the engraving plates are cleaned with warm water, they can be put on the computer immediately. 14.5 million children can print by joining the made to play project, which reflects the advantages of high-precision, simple and fast plate making process. Laser direct engraving flexo mainly includes: laser engraving rubber plate, seamless rubber plate cylinder and seamless rubber sleeve plate. You can carve a line version or a layer version. It is mainly used for flexible printing of paper, plastic and self-adhesive, as well as pre printing and direct printing of corrugated paper. The rubber material specially used for laser engraving researched in China has also been successful. The printing plates made of it have better printing resistance than ordinary flexible plates

3 comparison between laser plate making technology and traditional plate making technology

1) comparison of advantages and disadvantages between laser plate making technology and traditional plate making technology

(1) advantages of laser plate making technology

· simplified process and greatly shortened preparation time

· it overcomes the defect that the exposure time of traditional plate making is determined by the picture and text, making the exposure time independent of the picture and text type and point density

· realize direct plate making without film, and there is no poor polymerization problem and depression

· there is no need to vacuum, and there will be no dirty spots and random spots· The phenomenon of point enlargement caused by UV light diffusion is eliminated

(2) defects of traditional plate making technology

· the prepress system is complex and relies too much on the skills of operators

· the exposure time is determined by the picture and text, and the test results must be compared

· when the negative is in contact with the plate, it is easy to be invaded by dust, resulting in poor polymerization and depression

· vacuum leakage causes the negative film to not closely fit the plate, resulting in false edges

· the point of the highlight part will be higher than the field part, and printing will cause large point expansion

2) comparison between laser engraving flexible resin printing plate and traditional flexible resin printing plate

3) comparison between laser plate making and traditional plate making. To sum up, the laser plate making technology is rougher than the traditional flexo plate making technology in terms of plate quality, plate making process and plate printing quality, which affects the accuracy; The application of servo system technology in the latter has been significantly improved, and it will be more widely used with the gradual maturity of flexible printing

source: PRINT world

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