FM network points: irregular distribution performance image shading level (below)
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FM dot printing suitability
The generation of dots from the film to the substrate is converted through many processes, and the changes in each conversion directly affect the color reproduction of the image, which is the existence of any screening technology. However, FM screening, due to different structure, fine dot, change rule and traditional screening are also different, the control conditions may be more strict, according to the actual conditions, assuming 1200dpi recording accuracy, that is, the ink point is 20μm To explore the requirements of the printing suitability of FM outlets.
1. Image density of the output film
Usually, the laser spot of the FM screen is often a jagged dot on the edge. The finer the dots, the less the halogen silver particles are deposited on the film, and the lower the density. According to the standardization requirements of the printing plate, the density must be greater than 2.30. At the same time, there are no more than two bright spots with a diameter of 6μm inside the dot, otherwise it does not meet the requirements.
Therefore, it is preferable that the film output from the laser recording apparatus use a special hard film that matches the apparatus. The outlets required to be output are strong, dense, and the film is transparent and clean. Because the dots are small, it is not allowed to use the etching method to eliminate spots or correct the dots during film processing, and to avoid repeated copies. Therefore, in addition to the strict conditions of the film rinsing conditions, standard operation, it is best to have a suitable environmental treatment environment suitable for FM screening and dustproof cleaning environment.
2. Printing requirements
The basis of the printing dot is the sand surface on the surface of the printed spot. The finer the sand, the more the number of sand meshes supporting the mesh, the stronger the adsorption force, and the smoother the edge of the dot, so for a frequency modulation dot of only 20μm, In order to maintain the desired print durability without being worn, try to use a plate with fine grain size and high resolution. According to international standards, the ideal average grain thickness is 2.5μm and the depth is 3μm. Assuming each sand is considered as a cone, there are 64 sand support for each 20μm frequency modulation point, and the total contact area is about 817μm. ×μm. However, the average thickness of the PS plate in China is more than 5μm. It is obvious that there is only 16 sand support in one FM point, and the total contact area is 490μm×μm. The number of supported sand particles or the total contact area is relatively small, so the adsorption The strength is weakened, which is one of the reasons for the dot-off. At the same time, the particles are coarse, and the amount of the photosensitive resin applied is more, and the thicker the film layer, the dot tends to increase due to the light osmosis effect. Of course, it is not as fine as possible, otherwise it will affect the hydrophilicity of the printing plate. From this point of view, the printing plate of the FM frequency point is preferably at a certain particle size, increasing the particle side area or changing the plate property to obtain the best. Hydrophilic.
The key to the printing operation is to ensure that the dots are not lost or deformed. Therefore, the printing plate is required to be in close contact with the film, and the point source is exposed to reduce the deformation of the dots caused by the light seepage effect, and the developer concentration, temperature and printing plate are strictly controlled. Environmental conditions, any dust or stain on the glass of the printer can affect the quality of the printing plate.
c, blanket. The blanket is an intermediate carrier in the offset printing, which acts as an ink transfer. Therefore, the blanket not only has good ink adhesion and water resistance, but also has a good ability to transfer ink. In FM dot printing, especially the smoothness and flatness of the blanket should be emphasized to maintain the integrity and clarity of the dots. It is best to use a printed dot to increase the smaller air cushion blanket.
4. Suitability of printing operations
The correct transfer of dots during printing is one of the key elements for evaluating print quality. However, the concept of controlling percentage and tone in traditional screen printing is no longer applicable. FM dot printing can only check whether the idea is complete without loss. The increase in outlets is inevitable.
We know that if the pressure is too large in the printing, or if the amount of grinding is too large, the idea will definitely increase. According to the theoretical rule of the surrounding area of the dot, the dot gain is calculated by the circumference of all printed dots. The FM dot is small and almost isolated. The sum of the dots is much larger than the traditional dot, but all the dots are normal. The situation increase value is uniform. At the same time, due to the high precision of the FM dot recording, the fine points and the repeatable tone are almost unlimited. Therefore, the image is still soft in level and high in definition, but it is not said that the pressure or the amount of ink can be increased by this. Because the FM network is isolated, and the distribution is uneven, the force of each part of the unit area is not uniform, especially the highlights are few and thin, the points on the unit area are the most stressed, the wear is serious, and the risk of the loss is the largest. . Therefore, the use of rigid pads is more suitable for FM dot printing.
In addition, since all the surrounding ink dots on the printing are surrounded by the dampening liquid, it is easily wetted by the chemical liquid, and the water consumption is too large or the pH value is inappropriate, which may cause the dot to be lost. Therefore, the key to printing is to master the printing pressure and ink balance.
At the same time, the printing quality control strip used in the original printing is not suitable for FM dot printing, and it is necessary to develop a new tool for measuring and controlling the printing quality.
FM network points are good for printing
In summary, FM dot printing is performed throughout the printing process, and all aspects of operations must be standardized, and environmental conditions are extremely high, especially in the plate making stage. However, in the printing operation, it is obviously much easier than the traditional dot printing.
a. Not sensitive to the exact requirements of overprinting. Because the frequency modulation points on each color plate are irregularly distributed, even if the distribution of dots of different colors in the same part is different, a slight error can not reflect the significant change of color, and it is easy to obtain gray balance, so it can save the cost of adjusting the overprinting error. A lot of time.
b. The key in printing is to pay attention to the fact that the FM network can't be lost. Even if the network point is increased, it is uniform and will not affect the too much change of the value adjustment. At the same time, you don't have to worry about white spots and moiré.
c. Because the FM network is fine, the dark tone is not easy to produce a paste, so the ink balance is not too sensitive.
d. Since the frequency modulation dots are randomly distributed and isolated, it is not easy to cause the paper to be pulled during printing, and the back surface increase phenomenon is also greatly reduced, so the printing ink viscosity can be slightly larger.
According to the test, the frequency modulation network printing using a laser spot of 1200 dpi as an ink point can not only improve the printing quality, but also reduce the labor level of the operator, and is a new technology worthy of promotion.