On the quality control of lithography

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On the quality control of lithography

transfer the points representing graphic information on the original plate to the printing plate in a photosensitive way, and at the same time, make the part representing graphic information on the printing plate. 4. When the experimental machine is stopped for a long time, it has lipophilic and hydrophobic properties, and the blank part has hydrophilic properties. This process of information transfer is called lithography printing

printing is the link between prepress technology and proofing and printing technology. On the one hand, it should completely and faithfully transfer the graphic information of the original version to the PS version; On the other hand, it should make the image and text part Pro ink and the blank part hydrophilic, and make the printing plate can withstand the huge long-term pressure between the rollers without changing its inking hydrophilic performance

when we are drying PS version, we always hope that: the drying point is solid and bright; Because the printing plate is solid and smooth, the edge of the point can withstand the erosion of water and ink for a long time and is not easy to shrink or expand, so as to ensure the relative stability of the size of the printing plate point in printing. Otherwise, if the printing plate dots are empty and hairy, and there is a small change in the ink balance during printing, the inking of the printing plate dots will shrink or expand at any time, which will affect the stability of the ink dot transfer data. In addition, we also hope that the blank part of the printing plate is clean and free of dirt, and the graphic part is lipophilic; The PS version made by drying has high printing resistance. So, what are the factors that determine the print quality? We summarize the following points:

(1) appropriate original. For the original, it plays an important role in the quality of printing. First of all, we usually print with a wavelength of 400 μ The purple light source or ultraviolet light source of M has strong penetration. In order to completely transfer the points on the original negative to the printing plate without photochemical reaction on the photosensitive adhesive layer representing the graphic part in the future, it is required that the field density on the original negative should reach more than 3.3, otherwise, it is difficult to achieve the expected effect; Secondly, the haze of the original should be low, otherwise it will affect the density contrast on the printing plate; Thirdly, the original should be clean and free of dirt, otherwise it will bring dirt to the printing plate; Finally, the original version is better to be a piece of film without knife edge and collage tape, which can better ensure the close combination of the film and PS version, and avoid the point false phenomenon caused by the scattering of light affecting the VOC scattering emission of the product. Even if collage is necessary, the distance between the tape and the point representing the image information should be flat or equal to 7mm

(2) the glass of the plate printing rack should be clean. Otherwise, the dust on the glass will easily make the PS plate dirty. Because our current working conditions are difficult to achieve absolute dust-free in the printing workshop, we should wipe the glass frame with alcohol before printing

(3) suitable lighting form. We should try our best to reduce the light penetration caused by the light form and the dot reduction caused by the light penetration in the printing process of the positive PS version

(4) image resolving power of PS version. The most important factor affecting the false and real points on the printing plate is the resolution of the printing plate. So how do we test the resolution of the printing plate? Ugra1982 measurement and control strip provides us with great help

ugra1982 measurement and control strip consists of five parts: 1. High light and dark tone control area. Usually, when drying and printing the machine version: to ensure that 98% of the dots are not pasted, 2% of the dots should be retained; when drying and proofing the version: to ensure that 98% of the dots are not pasted, and 3% of the dots should be retained. 2. Test the replay area. 3. Point area used for measuring point enlargement and printing contrast. 4. There are 12 male and female graphic areas with a diameter of 4.5mm, and the width of the line is 4 μ M and 70 μ M, this section can be used to determine the correct exposure time and PS version resolution; 5. A gray ladder used to test whether the development is normal

under the guidance of Mr. Schmitz, a vocational education specialist who came to Hefei China Germany printing training center to exchange work and enjoyed a reputation in the German printing industry, we put the UGRA measurement and control strip on an 8-kai Fuji version used as a GTO printing plate, exposed the PS version with 2T, 4T, 8t, 16t, 32t and 40t beats, and developed it under normal development conditions, Observe the reproduction of the yin-yang line in the yin-yang circle area of the UGRA measurement and control strip (subject to at least 50% clear reproduction)

according to the ugra1982 measurement and control article, under a certain exposure time, the same level of negative and positive lines in the yin-yang circle area can be clearly observed at the same time, so this level is the resolution of the printing plate, so the resolution of the PS plate we tested is 6 μ m。

(5) appropriate extraction time; Because when printing, the contact tightness between the original negative and the glue layer of the plate changes at any time. For example, the unevenness of printing glass and blanket, the clamping pad of dust, the padding of tape and dirt on the negative, as well as the insufficient vacuum degree of air extraction, will cause poor sealing between the negative and the photosensitive adhesive layer of the plate, resulting in voids and serious photoosmosis, thus changing the size of printing point transfer. Therefore, we can closely combine the PS version with the original version by looking for a suitable air extraction, so that the speech title of Bruckner, a leading German machinery supplier, is "industry 4.0 - the future of double drawing film production" to be correctly exposed

(6) appropriate exposure time. If we only have high-resolution PS version, good exposure conditions are not enough, but also have enough exposure time to make a good PS version

the following table is composed of U7 and display mode: data and curve are dynamically displayed with the experimental process; Gra manufacturers recommend a parameter table for us to find a suitable exposure time: (the thick line area in the table is what we can use in real production)

according to the results of the previous graded exposure, the resolution of the printing plate is 6 μ m。 It should have a resolution of S μ m-8 μ For PS version between M, the exposure time that can be used in fact is the minimum reproducible male line width listed in Table 2 is 12 μ m-15 μ The exposure time range required between M

make the following figure according to the data obtained from graded exposure. (the horizontal axis is the change of exposure time; the vertical axis is the minimum distinguishable male line width of the tested PS plate under this exposure time)

the red line in the figure indicates the change of the minimum reproducible male line width on the PS plate with the exposure time; The blue line in the figure indicates the change of the minimum reproducible negative line width on the PS plate with the exposure time. The vertical coordinate corresponding to the intersection of the two polylines is the resolution of the PS version being measured. It can be seen from table 2; We should use 12 μ m-15 μ The corresponding abscissa range between M (22-32takt). This time range is the optional exposure time when drying line draft with this PS version. For dry line draft, the exposure time should be slightly extended

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