Fourth, post-processing
After the positive PS version is exposed and developed, it is also subjected to processing such as removing dirt, repairing, baking, developing black ink, and gluing, collectively referred to as the Ps version of post-processing.
1. Dirty and repair
1) In addition to dirty. In addition to the dirty, it uses the dirty liquid to remove the excess lines, adhesive paper, marks left on the original edge, dust and dirt, etc. on the plate.
In addition to dirty liquid, also known as trimming fluid, should have the following properties: on the plate surface stains, dirty marks have a strong solubility; have a certain degree of emulsification, so that the dissolved lipophilic substances are no longer dirty plates; The plate can be wetted relatively quickly and it cannot be spread freely on the plate to prevent dirt from spreading to parts of the text that do not need to be removed. In order to make dirty liquids have these properties, the components of the dirty liquid should include ink solvents, photosensitive layer solvents, wetting agents, thickeners, pigments, and the like.
The ink solvent is used to dissolve the developed black ink and ink attached to the surface of the image to be removed, exposing the underlying photosensitive layer. Commonly used ink solvents are benzene, toluene, xylene and so on.
The photosensitive layer solvent is used to dissolve the photosensitive layer, and a solvent having a small volatility and a fast dissolving speed is selected so that the dissolved photosensitive layer can be quickly detached from the surface of the plate, and the resolubilized surface will not be regenerated. Commonly used photosensitive layer solvents include methyl ethyl ketone, butanone, cyclohexanone, butyronitrile, valerolactone, diethylene glycol, dimethylformamide, ethylene glycol monomethyl ether, and ethylene glycol ether alone.
The wetting agent is used to reduce the surface tension of the dirty liquid, so that it can be rapidly dispersed to various parts of the plate surface that need to be removed, and the dirt removal efficiency is improved. If a wetting agent with both emulsifying and emulsifying capabilities is used, it can also prevent the photosensitive layer from dissolving after it has been dissolved and the effect is better. Common wetting agents include Tween-60, sodium dodecylbenzene sulphonate, and the like.
The thickening agent is used to increase the viscosity of the dirty liquid and make it a thick fluid. When it is used, it will not flow freely, and damage the graphic part of the printing plate. Commonly used thickeners are silica powders having a particle diameter of 2 to 4 μm. It is a kind of porous granular material with strong adsorption capacity. The smaller the particles, the stronger the adsorption ability and the thickening effect.
The function of the pigment added to the dirty liquid is to observe the effect of removing the dirty, and the color is obviously different from the color of the photosensitive layer to facilitate the identification. Commonly used pigments are alcohol-soluble red and blue pigments.
Different PS plates, the sensitivity of the solvent solubility is not the same, the preparation of dirty liquid (or choose to remove the dirty fluid), must be based on the PS version of the photosensitive layer to select the various components of the dirty fluid (or choose to remove dirty Liquid type).
Here are two recipes for removing dirty fluids for reference.
Formula 1:
Xylene 70 g
Valerolactone 10 g
Tween-60 0.3 g
Silica powder 0.5 g
Basic Brilliant Blue BO Micro Formula 2:
Methyl ethyl ketone 1～1.5 g
Diethylene glycol 2~6 g
Silica powder 1～3 g
In addition to the long-term contact with the air, the dirty liquid will degenerate. In addition to the reduced dirt capacity, deteriorating dirt can not be used. In addition to the dirty liquid contains more volatile substances, should be stored in a closed container.
When using dirty liquid in addition to dirty, the operation must be careful, in addition to the dirty droplets in the graphics, the graphic immediately dissolved, you need to re-print. Care should be taken when removing the small stains on the adjacent parts of the picture and text. You can use the grindstone bar, pumice bar or scraper to remove the photosensitive layer at the stain and then apply the dirty liquid to the stain to wipe off dirt.
2) Repair. The developed PS plate sometimes requires additional graphics, and sometimes it is found that the image is missing due to various reasons and can be repaired. There are two commonly used patching methods. One method is to supplement the text, that is, to apply a photo-sensitive liquid on the surface of the board again, supplementing the photo with the supplementary text, and using the repair liquid to fill the pen.
The formulation of a repair solution is listed below for reference.
M-cresol formaldehyde resin
After the positive PS version is exposed and developed, it is also subjected to processing such as removing dirt, repairing, baking, developing black ink, and gluing, collectively referred to as the Ps version of post-processing.
1. Dirty and repair
1) In addition to dirty. In addition to the dirty, it uses the dirty liquid to remove the excess lines, adhesive paper, marks left on the original edge, dust and dirt, etc. on the plate.
In addition to dirty liquid, also known as trimming fluid, should have the following properties: on the plate surface stains, dirty marks have a strong solubility; have a certain degree of emulsification, so that the dissolved lipophilic substances are no longer dirty plates; The plate can be wetted relatively quickly and it cannot be spread freely on the plate to prevent dirt from spreading to parts of the text that do not need to be removed. In order to make dirty liquids have these properties, the components of the dirty liquid should include ink solvents, photosensitive layer solvents, wetting agents, thickeners, pigments, and the like.
The ink solvent is used to dissolve the developed black ink and ink attached to the surface of the image to be removed, exposing the underlying photosensitive layer. Commonly used ink solvents are benzene, toluene, xylene and so on.
The photosensitive layer solvent is used to dissolve the photosensitive layer, and a solvent having a small volatility and a fast dissolving speed is selected so that the dissolved photosensitive layer can be quickly detached from the surface of the plate, and the resolubilized surface will not be regenerated. Commonly used photosensitive layer solvents include methyl ethyl ketone, butanone, cyclohexanone, butyronitrile, valerolactone, diethylene glycol, dimethylformamide, ethylene glycol monomethyl ether, and ethylene glycol ether alone.
The wetting agent is used to reduce the surface tension of the dirty liquid, so that it can be rapidly dispersed to various parts of the plate surface that need to be removed, and the dirt removal efficiency is improved. If a wetting agent with both emulsifying and emulsifying capabilities is used, it can also prevent the photosensitive layer from dissolving after it has been dissolved and the effect is better. Common wetting agents include Tween-60, sodium dodecylbenzene sulphonate, and the like.
The thickening agent is used to increase the viscosity of the dirty liquid and make it a thick fluid. When it is used, it will not flow freely, and damage the graphic part of the printing plate. Commonly used thickeners are silica powders having a particle diameter of 2 to 4 μm. It is a kind of porous granular material with strong adsorption capacity. The smaller the particles, the stronger the adsorption ability and the thickening effect.
The function of the pigment added to the dirty liquid is to observe the effect of removing the dirty, and the color is obviously different from the color of the photosensitive layer to facilitate the identification. Commonly used pigments are alcohol-soluble red and blue pigments.
Different PS plates, the sensitivity of the solvent solubility is not the same, the preparation of dirty liquid (or choose to remove the dirty fluid), must be based on the PS version of the photosensitive layer to select the various components of the dirty fluid (or choose to remove dirty Liquid type).
Here are two recipes for removing dirty fluids for reference.
Formula 1:
Xylene 70 g
Valerolactone 10 g
Tween-60 0.3 g
Silica powder 0.5 g
Basic Brilliant Blue BO Micro Formula 2:
Methyl ethyl ketone 1～1.5 g
Diethylene glycol 2~6 g
Silica powder 1～3 g
In addition to the long-term contact with the air, the dirty liquid will degenerate. In addition to the reduced dirt capacity, deteriorating dirt can not be used. In addition to the dirty liquid contains more volatile substances, should be stored in a closed container.
When using dirty liquid in addition to dirty, the operation must be careful, in addition to the dirty droplets in the graphics, the graphic immediately dissolved, you need to re-print. Care should be taken when removing the small stains on the adjacent parts of the picture and text. You can use the grindstone bar, pumice bar or scraper to remove the photosensitive layer at the stain and then apply the dirty liquid to the stain to wipe off dirt.
2) Repair. The developed PS plate sometimes requires additional graphics, and sometimes it is found that the image is missing due to various reasons and can be repaired. There are two commonly used patching methods. One method is to supplement the text, that is, to apply a photo-sensitive liquid on the surface of the board again, supplementing the photo with the supplementary text, and using the repair liquid to fill the pen.
The formulation of a repair solution is listed below for reference.
M-cresol formaldehyde resin
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