The water-soluble solid photosensitive resin plate occupies an increasingly larger share in the letterpress printing because of its short plate making cycle, easy operation, high resistance to printing force, high resolution, and good ink transfer performance. It is precisely because of these advantages and the fact that the one-time input of plate-making equipment has few funds, the plate-making system has expanded from the original professional plate-making factory to the printing house and individual operators. However, most users do not have professional plate-making operations training, and some even use homemade products. equipment. The author summarizes the issues arising from improper operation found in the production and sales process over the years as summarized below.
The printing plate has low resistance to printing during the printing process, the printing plate loses the word, and the cracked version
1. If the problem of the plate itself is ruled out, it may be caused by printing. The resin version is a polymer material, so the prepared version is wear-resistant and not pressure-resistant compared to the metal plate; when looking for pressure on the upper plate, from small to large, a sudden increase in pressure will produce a cracked plate; If the operation is not proper, the shear force is too large to be cracked and the word is dropped. Therefore, the pressure must be adjusted during printing.
2. The occurrence of this phenomenon may also be caused by the lack of a good grasp of the drying process in the plate making. Insufficiently dried plates appear to have no problem, but due to the hardness of the plates, they cannot withstand normal friction during the printing process and are quickly worn out. This makes the graphics and lines become "fat" and resistant to printing. The force is greatly reduced; insufficient drying also degrades the adhesive properties between the resin layer and the substrate, resulting in word drop during normal printing; when insufficient drying occurs, water molecules remain in the resin, making the resin layer crunchy and slightly stressful. It will crack version. Therefore, the general requirements of plate-making drying temperature 70 ~ 80 °C, time 30 minutes or more, when the large field layout, to lengthen the drying time.
In the process of plate-making, there are word drop, line bend and word paste.
1. Caused by short exposure time. Since the photosensitive layer of the resin plate material has a thickness of 0.85 mm or more, when the exposure time is insufficient, the bottom of the photosensitive layer cannot be sufficiently cross-linked and cured, and if the light scattering treatment is not performed, a trapezoidal shape with a large bottom and a small bottom will be formed. Small trapezoids are prone to word dropouts and line bends; or due to plate material or water temperature, etc., they cause washouts to take a long time, resulting in missing characters and line bends.
2. Caused by the film's "thin, thick, transparent" and positive and negative issues. The exposure to the film is a process that induces a chemical reaction in the photosensitive layer. Therefore, the transparent part of the film must be absolutely transparent, the density is less than 0.05, and the part of the light blocking density is 3 or more. When the light-transmitting portion is high in fog, it will cause underexposure and drop characters, line bends, and when the density of the light-blocking portion is low, the heavy portion cannot be developed, and the light portion will not appear between the lines.
When the negative film is reversed, the non-positive negative image plate-making is not the film surface of the negative film is tightly attached to the photosensitive layer of the plate material, but the medicine film is wrongly faced up, and there is a colorless layer between the two photosensitive layers. Transparent polyester polyester film, when exposed, the light passes through the film immediately after scattering through the polyester film layer, resulting in the same word and line thicker paste.
3. Caused by the light source. The photosensitive region of the general resin plate is in the wavelength range of 300-400nm. The wavelength emitted by the light source selected by the user for the exposure should be mainly in this region. After the exposure of the light source with incorrect spectral characteristics, the lines appear “shoulder†and the plate is stuck. .
In addition, the development with more floating water for drying can also result in word dropouts and line bends; vacuuming at the time of exposure is not true, and it is impossible to make the film and the photosensitive layer in close contact with each other to produce a full or partial paste.
Source: "Printing Technology"
The printing plate has low resistance to printing during the printing process, the printing plate loses the word, and the cracked version
1. If the problem of the plate itself is ruled out, it may be caused by printing. The resin version is a polymer material, so the prepared version is wear-resistant and not pressure-resistant compared to the metal plate; when looking for pressure on the upper plate, from small to large, a sudden increase in pressure will produce a cracked plate; If the operation is not proper, the shear force is too large to be cracked and the word is dropped. Therefore, the pressure must be adjusted during printing.
2. The occurrence of this phenomenon may also be caused by the lack of a good grasp of the drying process in the plate making. Insufficiently dried plates appear to have no problem, but due to the hardness of the plates, they cannot withstand normal friction during the printing process and are quickly worn out. This makes the graphics and lines become "fat" and resistant to printing. The force is greatly reduced; insufficient drying also degrades the adhesive properties between the resin layer and the substrate, resulting in word drop during normal printing; when insufficient drying occurs, water molecules remain in the resin, making the resin layer crunchy and slightly stressful. It will crack version. Therefore, the general requirements of plate-making drying temperature 70 ~ 80 °C, time 30 minutes or more, when the large field layout, to lengthen the drying time.
In the process of plate-making, there are word drop, line bend and word paste.
1. Caused by short exposure time. Since the photosensitive layer of the resin plate material has a thickness of 0.85 mm or more, when the exposure time is insufficient, the bottom of the photosensitive layer cannot be sufficiently cross-linked and cured, and if the light scattering treatment is not performed, a trapezoidal shape with a large bottom and a small bottom will be formed. Small trapezoids are prone to word dropouts and line bends; or due to plate material or water temperature, etc., they cause washouts to take a long time, resulting in missing characters and line bends.
2. Caused by the film's "thin, thick, transparent" and positive and negative issues. The exposure to the film is a process that induces a chemical reaction in the photosensitive layer. Therefore, the transparent part of the film must be absolutely transparent, the density is less than 0.05, and the part of the light blocking density is 3 or more. When the light-transmitting portion is high in fog, it will cause underexposure and drop characters, line bends, and when the density of the light-blocking portion is low, the heavy portion cannot be developed, and the light portion will not appear between the lines.
When the negative film is reversed, the non-positive negative image plate-making is not the film surface of the negative film is tightly attached to the photosensitive layer of the plate material, but the medicine film is wrongly faced up, and there is a colorless layer between the two photosensitive layers. Transparent polyester polyester film, when exposed, the light passes through the film immediately after scattering through the polyester film layer, resulting in the same word and line thicker paste.
3. Caused by the light source. The photosensitive region of the general resin plate is in the wavelength range of 300-400nm. The wavelength emitted by the light source selected by the user for the exposure should be mainly in this region. After the exposure of the light source with incorrect spectral characteristics, the lines appear “shoulder†and the plate is stuck. .
In addition, the development with more floating water for drying can also result in word dropouts and line bends; vacuuming at the time of exposure is not true, and it is impossible to make the film and the photosensitive layer in close contact with each other to produce a full or partial paste.
Source: "Printing Technology"
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