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Plate base oxide quality index
Plate base oxide layer quality index control range: 1.50 ~ 3.50g/m2, within the same version of the deviation ≤ 0.20g/m2, the same batch within the deviation ≤ 0.20g/m2.
A good quality oxide layer has high hardness and wear resistance, and the hardness can even be compared with high-quality steel. In this way, the anodized plate is printed 400,000 to 700,000 times and the shape of the sand remains intact. The oxide layer with good quality has strong corrosion resistance, and the aluminum plate covered with this oxide layer is soaked in ordinary fountain solution for 15 days without any traces of corrosion; it is kept in a ventilated and dry room for 6 months. The layout is still intact. For the hydrochloric acid, sulfuric acid, nitric acid and other solutions, this oxide layer also has a certain resistance to corrosion.
In general, the wear resistance and corrosion resistance of the PS plate oxide layer increase with its thickness, but at the same time the brittleness of the oxide layer also increases with the thickness. If the oxide layer on the plate is too thick, it will cause cracking of the oxide layer due to bending deformation after being mounted on the roller. To achieve the inherent quality of the oxide layer, the following process conditions must be specified in production.
1. Oxidation temperature
During the anodization of the aluminum plate, the reaction to form an oxide layer is an exothermic reaction. Therefore, raising the temperature of the oxidizing solution will accelerate the formation of an oxide layer and accelerate the dissolution of the oxide layer. In this way, the thickness of the oxide layer decreases as the temperature of the oxidizing solution increases, and wear resistance and hardness also decrease. Production practice shows that anodizing in the production line, the oxidation temperature is lower than 16 °C, the obtained oxide layer is thick, easy to embrittlement; if the temperature exceeds 26 °C, the oxide layer is thin, sparse oxide layer is thick, easy to brittle If the temperature exceeds 26°C, the oxide layer is thin, loose, and not abrasion-resistant, so it is generally appropriate to control the temperature at 17 to 25°C.
2. Sulfuric acid concentration
In the case of anodization using a DC power source, the dissolution rate of the oxide layer will increase as the sulfuric acid concentration increases. Therefore, the use of low-concentration sulfuric acid oxidation solution is conducive to the growth of the oxide layer, the oxidation layer obtained in the dilute oxidation solution is hard and wear-resistant, the porosity is low, but the lower the concentration of sulfuric acid, the better, generally considered, 16% ~ 17% of the concentration is more appropriate, but offset printing also requires the plate has the appropriate flexibility and toughness, therefore, should be considered to increase the concentration to 17% to 19%, and the temperature slightly higher, this time, hardness and The wear resistance is slightly reduced, but the elasticity and toughness of the oxide layer are appropriately increased.
3. Current density and voltage
Experiments have shown that the thickness of the resulting oxide layer is directly proportional to the anode current density and the anodization time. The current density increases, the growth rate of the oxide layer is accelerated, the oxide layer is thickened, and the abrasion resistance and corrosion resistance are also increased. However, an excessively high current density may cause the surface of the aluminum plate to overheat and cause the local temperature of the oxidation liquid to rise. Cause uneven aluminum oxide layer thickness. The production practice shows that the allowable current density of the anodizing on the production line is 2.5 to 3.5 A/dm2, so that the oxidation film obtained after oxidation has high hardness, and has strong wear resistance and corrosion resistance.
After the anodic oxidation begins, a barrier layer is rapidly formed on the surface of the aluminum plate to reduce the current. At this time, the voltage must be gradually increased to a stable value. It can be seen that the voltage has great influence on the performance of the oxide layer. The voltage is too low, the oxidation process cannot proceed smoothly, the voltage is relatively high, the formed oxidation barrier has a large aperture, and it may even break through the aluminum plate. The anodizing voltage on the general production line is 11 to 14V.
Sensitive layer quality index
Sensitive layer quality index control range: 1.60 ~ 2.50g/m2, within the same version of the deviation ≤ 0.15g/m2, the same batch within the deviation ≤ 0.20g/m2. The thickness of the photosensitive layer of the PS plate must be strictly controlled, the coating is too thin, the ink and printing resistance of the printing plate graphic part will be reduced, and the printing performance is poor; the coating is too thick, the photosensitive speed is slow, the printing plate has a long time, and the resolution is also Will fall, 2% of the small outlets are easy to lose, and the development time is longer, resulting in the waste of photoresist and developer, also has a certain impact on the plate making efficiency.
In the production of photosensitivity to achieve the above three standard indicators, can refer to the method of view quality indicators.
Sensitivity index
The photographic performance index is: resolution ≤ 10.0 μm; dot reproduction capability is 2% to 98% with complete dots; plate base color density is ≤ 0.03.
From the photosensitive adhesive point of view, the design of photosensitive adhesive formulations should consider the exposure latitude to be greater, the developer laxity should also be large, and make the photosensitive adhesive and developer matching, in the coating as long as the fine grain of the base, The coating machine has high precision, the coating room environment meets the process requirements, and the coating operation is carefully performed. The produced PS plate is detected by the FOGRA signal bar, and the two steps of the whitening can be achieved. The 10 μm line is neat, the line is continuous, and the negative line is clear. There is no problem if you stick to death and belong to the high-quality version. To achieve the requirements of the layout base color density ≤ 0.03, the production of exposure to ensure that the exposure of the photosensitive adhesive, the development tolerance should be large, the drying time in the lower limit of the exposure time, the blank part does not have a background color, the version of the base sand surface without bottom ash.
Ink properties and hydrophilic properties
With a dedicated PS version of the imaging performance test strip (the gray ladder density level difference of 0.15), according to the manufacturer's recommended conditions, at a voltage of 220V, using 3KW iodine lamp, lamp distance of 1m, normal exposure, development, and use of absorbent gauze The ink was raised on the plate, and the ink was visually observed after rinsing with fresh water. The parts with exposure ash scale density below 0.35 and 0.35 were not inked, and the parts with density above 0.8 and 0.8 were all inked, which was regarded as passing ink performance and hydrophilicity.
Source: Printing Technology
Plate base oxide layer quality index control range: 1.50 ~ 3.50g/m2, within the same version of the deviation ≤ 0.20g/m2, the same batch within the deviation ≤ 0.20g/m2.
A good quality oxide layer has high hardness and wear resistance, and the hardness can even be compared with high-quality steel. In this way, the anodized plate is printed 400,000 to 700,000 times and the shape of the sand remains intact. The oxide layer with good quality has strong corrosion resistance, and the aluminum plate covered with this oxide layer is soaked in ordinary fountain solution for 15 days without any traces of corrosion; it is kept in a ventilated and dry room for 6 months. The layout is still intact. For the hydrochloric acid, sulfuric acid, nitric acid and other solutions, this oxide layer also has a certain resistance to corrosion.
In general, the wear resistance and corrosion resistance of the PS plate oxide layer increase with its thickness, but at the same time the brittleness of the oxide layer also increases with the thickness. If the oxide layer on the plate is too thick, it will cause cracking of the oxide layer due to bending deformation after being mounted on the roller. To achieve the inherent quality of the oxide layer, the following process conditions must be specified in production.
1. Oxidation temperature
During the anodization of the aluminum plate, the reaction to form an oxide layer is an exothermic reaction. Therefore, raising the temperature of the oxidizing solution will accelerate the formation of an oxide layer and accelerate the dissolution of the oxide layer. In this way, the thickness of the oxide layer decreases as the temperature of the oxidizing solution increases, and wear resistance and hardness also decrease. Production practice shows that anodizing in the production line, the oxidation temperature is lower than 16 °C, the obtained oxide layer is thick, easy to embrittlement; if the temperature exceeds 26 °C, the oxide layer is thin, sparse oxide layer is thick, easy to brittle If the temperature exceeds 26°C, the oxide layer is thin, loose, and not abrasion-resistant, so it is generally appropriate to control the temperature at 17 to 25°C.
2. Sulfuric acid concentration
In the case of anodization using a DC power source, the dissolution rate of the oxide layer will increase as the sulfuric acid concentration increases. Therefore, the use of low-concentration sulfuric acid oxidation solution is conducive to the growth of the oxide layer, the oxidation layer obtained in the dilute oxidation solution is hard and wear-resistant, the porosity is low, but the lower the concentration of sulfuric acid, the better, generally considered, 16% ~ 17% of the concentration is more appropriate, but offset printing also requires the plate has the appropriate flexibility and toughness, therefore, should be considered to increase the concentration to 17% to 19%, and the temperature slightly higher, this time, hardness and The wear resistance is slightly reduced, but the elasticity and toughness of the oxide layer are appropriately increased.
3. Current density and voltage
Experiments have shown that the thickness of the resulting oxide layer is directly proportional to the anode current density and the anodization time. The current density increases, the growth rate of the oxide layer is accelerated, the oxide layer is thickened, and the abrasion resistance and corrosion resistance are also increased. However, an excessively high current density may cause the surface of the aluminum plate to overheat and cause the local temperature of the oxidation liquid to rise. Cause uneven aluminum oxide layer thickness. The production practice shows that the allowable current density of the anodizing on the production line is 2.5 to 3.5 A/dm2, so that the oxidation film obtained after oxidation has high hardness, and has strong wear resistance and corrosion resistance.
After the anodic oxidation begins, a barrier layer is rapidly formed on the surface of the aluminum plate to reduce the current. At this time, the voltage must be gradually increased to a stable value. It can be seen that the voltage has great influence on the performance of the oxide layer. The voltage is too low, the oxidation process cannot proceed smoothly, the voltage is relatively high, the formed oxidation barrier has a large aperture, and it may even break through the aluminum plate. The anodizing voltage on the general production line is 11 to 14V.
Sensitive layer quality index
Sensitive layer quality index control range: 1.60 ~ 2.50g/m2, within the same version of the deviation ≤ 0.15g/m2, the same batch within the deviation ≤ 0.20g/m2. The thickness of the photosensitive layer of the PS plate must be strictly controlled, the coating is too thin, the ink and printing resistance of the printing plate graphic part will be reduced, and the printing performance is poor; the coating is too thick, the photosensitive speed is slow, the printing plate has a long time, and the resolution is also Will fall, 2% of the small outlets are easy to lose, and the development time is longer, resulting in the waste of photoresist and developer, also has a certain impact on the plate making efficiency.
In the production of photosensitivity to achieve the above three standard indicators, can refer to the method of view quality indicators.
Sensitivity index
The photographic performance index is: resolution ≤ 10.0 μm; dot reproduction capability is 2% to 98% with complete dots; plate base color density is ≤ 0.03.
From the photosensitive adhesive point of view, the design of photosensitive adhesive formulations should consider the exposure latitude to be greater, the developer laxity should also be large, and make the photosensitive adhesive and developer matching, in the coating as long as the fine grain of the base, The coating machine has high precision, the coating room environment meets the process requirements, and the coating operation is carefully performed. The produced PS plate is detected by the FOGRA signal bar, and the two steps of the whitening can be achieved. The 10 μm line is neat, the line is continuous, and the negative line is clear. There is no problem if you stick to death and belong to the high-quality version. To achieve the requirements of the layout base color density ≤ 0.03, the production of exposure to ensure that the exposure of the photosensitive adhesive, the development tolerance should be large, the drying time in the lower limit of the exposure time, the blank part does not have a background color, the version of the base sand surface without bottom ash.
Ink properties and hydrophilic properties
With a dedicated PS version of the imaging performance test strip (the gray ladder density level difference of 0.15), according to the manufacturer's recommended conditions, at a voltage of 220V, using 3KW iodine lamp, lamp distance of 1m, normal exposure, development, and use of absorbent gauze The ink was raised on the plate, and the ink was visually observed after rinsing with fresh water. The parts with exposure ash scale density below 0.35 and 0.35 were not inked, and the parts with density above 0.8 and 0.8 were all inked, which was regarded as passing ink performance and hydrophilicity.
Source: Printing Technology
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