The plate-making process of the positive figure PS plate (4)

3. Post-processing

After exposure and development, the positive-type PS plate is also subjected to processing such as removing dirt, repairing, baking, coating and developing black ink, gluing, etc., which are collectively called post-processing of the Ps plate.

1. Decontamination and repair
1) Remove dirt. Decontamination is to use the decontamination liquid to remove excess rule lines, adhesive paper, traces left by the edges of the original plate, dust and dirt.

Degreasing fluid, also called trimming fluid, should have the following properties: it has a strong solubility for stains and dirt on the plate surface; it has a certain emulsifying ability so that the dissolved lipophilic substances will no longer stain the plate; It can quickly wet the printing plate but can not be arbitrarily spread on the printing plate, so as to prevent the spreading liquid from spreading to the part of the picture and text that does not need to be removed. In order to make the decontamination fluid possess these properties, the components of the decontamination fluid should include ink solvent, photosensitive layer solvent, wetting agent, thickener, pigment, etc.

The ink solvent is used to dissolve the developing black ink and ink adhering to the surface of the graphic to be removed, exposing the photosensitive layer below. Commonly used ink solvents include benzene, toluene and xylene.

The photosensitive layer solvent is used to dissolve the photosensitive layer. A solvent with low volatility and fast dissolution rate should be selected so that the dissolved photosensitive layer can quickly fall off from the plate surface, so as not to stain the plate surface again. Commonly used photosensitive layer solvents include methyl ethyl ketone, methyl ethyl ketone, cyclohexanone, butyrolactone, valerolactone, diethylene glycol, dimethyl formamide, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, etc.

The wetting agent is used to reduce the surface tension of the decontamination fluid, so that it can be quickly dispersed to various parts of the plate surface that needs to be decontaminated, and improve the efficiency of decontamination. If a wetting agent with washing and emulsifying ability is selected, it can also prevent the photosensitive layer from dissolving the plate surface after being dissolved, and the effect is better. Commonly used wetting agents include Tween-60, sodium dodecylbenzene sulfonate, etc.

The thickener is used to increase the viscosity of the decontamination fluid and make it into a thick fluid, which will not cause random flow during use and damage the graphic part of the printing plate. Commonly used thickeners are those with a particle diameter of 2 to 4 μm (Silica powder). It is a porous granular material with strong adsorption capacity. The smaller the particles, the stronger the adsorption capacity and the greater the thickening effect.

The function of the pigment added to the decontamination liquid is to observe the effect of decontamination, and the color is obviously different from the color of the photosensitive layer for identification. Commonly used pigments are alcohol-soluble red and blue pigments.

Different PS plates have different sensitivities to the solubility of solvents. When preparing a decontamination solution (or use the decontamination solution), the individual components of the decontamination solution must be selected according to the solubility of the PS plate photosensitive layer Type of fluid).

The formulas of the two decontamination fluids are listed below for reference.

Recipe 1:
Xylene 70 g
Valerolactone 10 g
Tween-60 0.3 g
Silica powder 0.5 g
Basic brilliant blue BO trace

Recipe 2:
Methyl ethyl ketone 1 ～ 1.5 g
Diethylene glycol 2 ~ 6 g
Silica powder 1 ～ 3 g

The long-term contact with air will deteriorate the decontamination fluid, and the decontamination capacity is reduced. The decontaminated decontamination fluid cannot be used. The decontamination fluid contains more volatile substances and should be stored in a closed container.

When using the decontamination fluid to decontaminate, the operation should be careful, the decontamination droplets are on the graphics, and the graphics are dissolved immediately, and you need to reprint the plate. Care should be taken when removing the small stains on the adjacent parts of the picture and text. You can use a grindstone, pumice stick or scraper to remove the photosensitive layer of the stain first, then apply the stain removal solution to the stain and wipe it off.

2) Repair. The developed PS version sometimes needs to be supplemented with graphics, and sometimes it is found that the image is less scratched due to various reasons and can be repaired. There are two commonly used repair methods. One method is to supplement the graphic, that is, apply the photosensitive liquid on the plate again to supplement the graphic that needs to be supplemented. The other method is to use the repair liquid to supplement the pen.

The formulation of a repair fluid is listed below for reference.

M-cresol formaldehyde resin (viscosity greater than 0.4 Pa · S) 7g
Ethylene glycol monoacetic acid 15ml
Basic Blue BO Trace
The repair method of the make-up pen is to first scrub the parts to be repaired with the developer solution (dilute alkaline solution), then wipe off the developer solution with a wet towel, and then use 2% of the remaining developer wave The solution is neutralized, then washed with water and dried with hot air; after the plate is completely dried, use a brush to repair the defect of the pen with a repair solution; finally, dry the printing plate with hot air again to make the solvent in the repair solution ( Ethylene glycol monoacetic acid) quickly volatilizes, m-cresol formaldehyde resin is dried to form a film, and is firmly attached to the plate surface. The repair solution can sometimes be replaced with wax gram, but wax gram has a dissolving effect on the photosensitive layer of the PS plate. When making up the pen, it is necessary to stick a plate-making adhesive tape around the graphic to protect the graphic.

When using the repair liquid or wax to fill the printing plate, the fine parts of the graphics and text are very difficult to repair, even if it is barely filled, it is difficult to be the same as the original graphics or text, or make the supplement The graphics and text have the same durability as the original graphics. In this case, the method of supplementary sun is more appropriate.

After all, repair is a remedy to ensure the quality of the printing plate. It is impossible to achieve perfect results. The fundamental way to improve the quality of the printing plate is to improve the quality of the original version as much as possible and reduce or eliminate the graphic defects of the printing plate.

2. Baked version

The PS plate's print resistance is generally between 50,000 and 100,000 prints. If you need to print more than 100,000 prints, you must increase the print plate's print resistance. One of the methods is to bake the PS plate after development, decontamination and repair. Version processing.

The method of baking plate treatment is to apply a protective liquid to the surface of the plate after development, decontamination and repair, and then put it into a plate baking machine, and bake 5 to 8 mini at a constant temperature of 23O to 250 ℃ to take out the printing plate , After completely cooled, use developer to develop again; Finally, remove the remaining protective solution on the plate and dry it with hot air.

During the baking process, the resin in the photosensitive layer of the PS plate is cross-linked by heating to form a network-like macromolecule, the photosensitive group disappears, the photosensitive layer changes from green to reddish brown, and the photosensitive layer of the image part is photosensitive from the original The performance becomes non-photosensitive, so the abrasion resistance, corrosion resistance and solvent resistance of the printing plate are improved. Experiments have shown that after printing 200,000 to 300,000 prints, the PS plate that has been processed by roasting is used to observe the dots on the plate surface with a magnifying glass, and no obvious changes are observed. The processed PS version, after 24 hours, the photosensitive layer of the printing plate is still intact; soaked with organic solvents such as ethanol, butanol, cyclohexanone, ethylene glycol monomethyl ether, ethyl acetate, kerosene, gasoline and other organic solvents PS version, after 24 hours, there is no obvious change in the outlets on the printing plate.

However, in the baking process of the PS plate, part of the oxide film formed by anodizing on the surface of the aluminum plate will lose water, causing some of the pores treated by the sealing process to reopen, and the strong adsorption of the plate surface is restored. There will be a dirty fault. Before baking the plate, the plate surface is coated with a protective liquid to protect the micropores after the sealing treatment, just to prevent the dehydration phenomenon of the oxide film during the baking process. Commonly used substances for the preparation of protective liquids are Pingpingjia-20, Pingpingjia-OP-10, Pingpingjia-0, borate compounds, sodium dodecylbenzene phosphate, detergents, etc.

Pingpingjia is a non-ionic surfactant, the main component is polyoxyalkylene fatty alcohol ether, the molecular formula is: , Where R represents or . Pingping has good film-forming properties and good hydrophilic and oleophobic capacity, is easy to disperse, and is very stable to alkalis, acids and alcohols.

Potassium tetraborate, sodium tetraborate, ammonium tetraborate, etc. are commonly used borate compounds in the preparation of protective solutions. The protective solution prepared with these compounds and Pingping Plus together, after drying to form a film and attaching to the plate surface, there will be no cracks and crystalline structure, and the coverage is good and stable.

Sodium dodecyl benzene sulfonate has good wettability and dispersibility. It will not decompose and degrade under 250 ℃. It is added to the protective liquid to improve the spreading performance of the protective liquid, making it easy to apply on the plate Evenly. Instead of sodium dodecylbenzenesulfonate, other cationic or nonionic surfactants with good wettability and dispersibility can be used.

There are many formulas of protective liquids, one of which is listed below for reference.

Pingping plus one OP-10 40 ～ 60 g
Ammonium tetraborate 10 g
Sodium dodecylbenzenesulfonate 10 ml,
Water 1000 ～ 1500ml.

Since the substances in the protective solution are soluble in water, the preparation method of the protective solution is very simple. Just put the substances into the water according to the above formula, stir or properly heat them, and then use them after dissolving. When applying the protective liquid to the plate surface, wipe it gently with absorbent cotton to avoid the fiber falling off and affect the baking plate. The amount of the protective liquid is not easy to be too much, otherwise there will be water-like marks, which makes it difficult to apply ink. Baking is a processing method that causes the photosensitive layer to be baked and condensed on the surface of the lead plate under the action of heat, thereby improving the mechanical and physical and chemical properties of the image. After the roasting process, the photosensitive layer is firmly attached to the plate surface, and the dirt on the printing plate can no longer be removed with a decontamination solution. Therefore, the printing plate must be thoroughly decontaminated before baking.

The baking version should be carried out in a special closed baking box, and the temperature change is required Within 2 ° C, the temperature of the entire roaster should be uniform.

The temperature and time of the baking plate are related to the aluminum plate base, the photosensitive material used, and the structure of the plate baking machine used, and are generally determined according to the change of the curing point and color of the photosensitive layer. For example, m-cresol formaldehyde resin is a hot-melt resin at room temperature. When it is heated to 180 ° C, it starts to cure. When baked at 230 ° C for 5 min, all resins are cured to a good degree and the color From green to red brown, if the baking temperature is increased or the baking time is increased, the color of the resin will change from red brown to black brown, indicating that the photosensitive layer has undergone carbonization and deterioration and can no longer be used. Therefore, for the use of m-cresol Formaldehyde resin as the photosensitive material of the PS version, at a temperature of 230 ℃, a baking time of 5 minutes is suitable. If the baking temperature is too high and the baking time is too long, the mechanical properties of the aluminum base will decrease and the texture will deteriorate. In order to ensure the quality of the baking version, the standard baking temperature and time must be determined according to the type of PS version and baking conditions.

The printing plate taken out of the baking machine must be cooled naturally, and must not be forcedly cooled by cold water spraying. During the forced cooling process, the printing plate will be greatly deformed due to the rapid temperature change. The cooled printing plate also needs to use developer to remove the protective liquid on the plate surface. If the protective liquid remains on the plate surface, it will cause the emulsification of the ink during printing.

Red Wine Canvas Tote Bags are covered with printed canvas to the surface with a layer of transparent PVC film, making the canvas fabric which is strong and wear-resistant even stronger. And fabric is easy to do, as long as the dirty wipe with a wet cloth can be.
Cotton Bag is one of the most popular environmetally-frindly bags. It is made from the natural cotton and most of the cotton bag doesn't make dyeing, so it is eco-friendly from the raw material. It is biodegradable and doesn't do any pollution to the environment. Besides, it is more durable than Non Woven Bags and more easily to clean.

Red Wine Canvas Tote Bags

Canvas Tote Bags,Wine Freezer Tote Bags,Wine Canvas Tote Bags,Red Wine Canvas Tote Bags

Wenzhou Shandao Electronic Commerce Co., Ltd. , https://www.reusablebaglife.com