2.19.2019
Editor of plate making process
Label printing covers several main printing methods, in the plate-making stage. According to the nature of different products, different printing methods are chosen, and different printing methods, plate-making processes are also different. In this paper, the flexible plate making process as an example is briefly introduced.
The process flow of flexographic plate making is as follows: original, film, exposure, flushing, drying and post-processing.
1. Manuscript. Manuscript design suitable for flexible printing should have the following characteristics: more colors, but less overlap; no need to reproduce particularly small details; less wire, but can achieve color printing effect; online packaging processing can be done.
2. Film (negative film). It meets the requirements of plate making, with clear pictures and text, accurate size and specifications; with ground film, the four corners of the film are required to have the same density; with film orthography; measured by transmission densitometer, the white density is less than 0.06; and the black density is more than 3.5.
3. Exposure includes back exposure and main exposure.
Label Printing
Back exposure. The supporting film of the photosensitive resin plate is laid up and the protective film is laid down flat in the exposure drawer for exposure. Ultraviolet ray solidifies the photosensitive adhesive layer through the supporting film, so as to establish a solid base, control the depth of plate washing, and strengthen the bonding force between the supporting film and the photosensitive resin layer. Back exposure time is determined according to the required base thickness.
(2) Main exposure. Also known as positive exposure, photosensitive resin plate support film facing down, protective film facing up. Lay it flat in the exposure drawer. Tear off the protective film once in a row, then paste the film on the photosensitive resin plate. Cover the vacuum film flat on the film (non-drug film surface), vacuum, so that the film and the photosensitive resin layer adhere closely. Ultraviolet radiation penetrates through the vacuum film and the transparent part of the film, so that the photosensitive part of the plate can be polymerized and cured. The length of main exposure time is determined by plate type and light source strength. Short exposure time will lead to too straight slope, curved lines, small words, small dots washed out, and conversely, too long exposure time will cover the plate, the handwriting is blurred. If there are big and small woods, thick and thin lines on the same plate, and exposed separately with black film, as the case may be, the small parts will not be lost due to washing, so as to ensure the quality of the plate. The main operating points of the main exposure are shown in Table 1.
4. Rinse. The non-photosensitive part is washed and dissolved, and the relief of photopolymerization is retained. The length of plate washing depends on the thickness of plate and the depth of print. If the time of plate washing is too short, there will be no light-sensitive resin left on the plate, which will affect the depth of plate making. If the plate washing time is too long, the plate will expand, resulting in deformation or shedding of fine parts.
5. Drying. Remove the solvent to make the plate return to its original size and thickness. The baking temperature ranges from 50 to 60 degrees Celsius. The baking time is determined by the thickness of the plate and the length of the washing time. Generally, the thick plate lasts two hours and the thin plate lasts one hour. If the baking time is too long and the baking temperature is too high, the plate will become brittle and the printing life will be affected. Too low baking temperature will prolong the drying time, too short baking time, printing will appear rotten plate phenomenon.
6. Post-processing. That is, debonding and post exposure. Make the photosensitive resin harden thoroughly (polymerization) to meet the required hardness index, and eliminate the plate stickiness, in order to facilitate ink transmission. The post-processing time is obtained from the test in order not to crack or stick.
The process flow of flexographic plate making is as follows: original, film, exposure, flushing, drying and post-processing.
1. Manuscript. Manuscript design suitable for flexible printing should have the following characteristics: more colors, but less overlap; no need to reproduce particularly small details; less wire, but can achieve color printing effect; online packaging processing can be done.
2. Film (negative film). It meets the requirements of plate making, with clear pictures and text, accurate size and specifications; with ground film, the four corners of the film are required to have the same density; with film orthography; measured by transmission densitometer, the white density is less than 0.06; and the black density is more than 3.5.
3. Exposure includes back exposure and main exposure.
Label Printing
Back exposure. The supporting film of the photosensitive resin plate is laid up and the protective film is laid down flat in the exposure drawer for exposure. Ultraviolet ray solidifies the photosensitive adhesive layer through the supporting film, so as to establish a solid base, control the depth of plate washing, and strengthen the bonding force between the supporting film and the photosensitive resin layer. Back exposure time is determined according to the required base thickness.
(2) Main exposure. Also known as positive exposure, photosensitive resin plate support film facing down, protective film facing up. Lay it flat in the exposure drawer. Tear off the protective film once in a row, then paste the film on the photosensitive resin plate. Cover the vacuum film flat on the film (non-drug film surface), vacuum, so that the film and the photosensitive resin layer adhere closely. Ultraviolet radiation penetrates through the vacuum film and the transparent part of the film, so that the photosensitive part of the plate can be polymerized and cured. The length of main exposure time is determined by plate type and light source strength. Short exposure time will lead to too straight slope, curved lines, small words, small dots washed out, and conversely, too long exposure time will cover the plate, the handwriting is blurred. If there are big and small woods, thick and thin lines on the same plate, and exposed separately with black film, as the case may be, the small parts will not be lost due to washing, so as to ensure the quality of the plate. The main operating points of the main exposure are shown in Table 1.
4. Rinse. The non-photosensitive part is washed and dissolved, and the relief of photopolymerization is retained. The length of plate washing depends on the thickness of plate and the depth of print. If the time of plate washing is too short, there will be no light-sensitive resin left on the plate, which will affect the depth of plate making. If the plate washing time is too long, the plate will expand, resulting in deformation or shedding of fine parts.
5. Drying. Remove the solvent to make the plate return to its original size and thickness. The baking temperature ranges from 50 to 60 degrees Celsius. The baking time is determined by the thickness of the plate and the length of the washing time. Generally, the thick plate lasts two hours and the thin plate lasts one hour. If the baking time is too long and the baking temperature is too high, the plate will become brittle and the printing life will be affected. Too low baking temperature will prolong the drying time, too short baking time, printing will appear rotten plate phenomenon.
6. Post-processing. That is, debonding and post exposure. Make the photosensitive resin harden thoroughly (polymerization) to meet the required hardness index, and eliminate the plate stickiness, in order to facilitate ink transmission. The post-processing time is obtained from the test in order not to crack or stick.
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