3. The exposure is in the normal plate making process. Exposure is the most important factor affecting network changes and layout depth. We know that the exposure of the printing plate = illumination x printing time. As the commonly used positive version of the PS version belongs to the photolysis type. Therefore, when the exposure exceeds the critical light amount, that is, overexposure, the dots will be reduced, fine strokes and small dots will be difficult to reproduce, and when the amount of exposure is less than the critical light amount, that is, when the exposure is insufficient. The outlets will expand accordingly. Make the layout dirty and affect the depth of the layout. Therefore, during the printing process, the exposure amount is controlled. The continuous scale or Bruner test strip should be used for monitoring. The function is to check the exposure after development. The general proofing version is controlled at grade 3-4 (density is 0.4-0.55) and the printing plate is controlled at grade 4.5-5.5 (density 0.625-0.775). When printing a positive plate, if a pair of 0.5% dots and 99.5% hollow dots are sunned in pairs, such a printing plate can be considered qualified.
4. Development of the developed PS plate consists in removing the photosensitive layer of the blank portion to maintain the hydrophilicity of the surface of the PS plate. It is an important part of the PS plate making process. It is not only restricted by the properties of the photosensitizer and the original state, but also influenced by the development conditions such as the concentration of the developer, the temperature, the degree of fatigue, and the development time.
(1) The concentration of developer affects the concentration of the developer. Generally refers to the content of the developer base. Insufficient developer concentration will not only increase the development time but also cause incomplete development. Cause the layout of the face; excessive concentration, the development time is accelerated, the entire process is difficult to control, easy to cause excessive development, network points are reduced or damaged, dissolve unsensitized photosensitive layer, reduce the printing plate's sensory and resistance to force. Therefore, in order to accurately control the concentration, the plate can be developed after 30-60s, observe whether the hollow point of the Bruner test strip 98%-99% is clear and whether the 1%-2% small black point is firm, if The idea of ​​clear and sturdy indicates that the concentration is appropriate.
(2) The effect of temperature is relatively stable under other conditions of development. The higher the development temperature, the faster the development speed and vice versa. The general development temperature should be controlled at about 20 °C. The automatic developing machine should be controlled at 25°C, and when it exceeds 30°C, the dots will dissolve. In the photosensitive layer, the binding force between the photosensitive material and the film forming material is weakened, the alkali resistance is decreased, the area percentage of the screen area is reduced, and the reproduction of the printing plate is damaged.
(3) Fatigue degree of the developer The fatigue of the developer means that the developing ability of the developer drops. Such as the use of hand-developed development, due to the exposure of the developer to the air, the absorption of water and CO2, accelerated developer degeneration, affecting the development performance. Another cause of the fatigue of the developing solution is that the photodegradable substance is dissolved therein, and the developing ability is significantly reduced. Therefore, the currently used alkaline developer should minimize contact with air in the process of storage and use, reduce the impact of moisture and CO2 on it, and regularly replace and quantitatively make up the medicine.
(4) Influence of developing time Because the developing time is affected by the exposure of the printing plate, the performance of the photosensitive agent, the developing method, the state of the developer, etc. Therefore, to control the degree of development, the above-mentioned variable factors should be grasped and stabilized first, and then The gray scale is tested to determine the development conditions and the correct development time. The general development time is about 1 minute.
4. After the baking plate has been baked, the photosensitive base in the photosensitive layer disappears, and the phenolic resin undergoes thermal cross-linking reaction by heat, which turns from linear molecules to large-scale network molecules. At this time, the solvent resistance, corrosion resistance, and abrasion resistance of the printing plate and the adsorption of the photosensitive layer to the plate surface are greatly improved. However, during baking, in addition to the change in the photosensitive portion of the graphic part, the micropores of the anodized aluminum substrate surface that was closed by the plugging treatment may cause the flow of water to be increased due to the loss of water, causing the plate to be dirty. Therefore, before baking, it is necessary to evenly apply a layer of protective agent to the plate with absorbent cotton to protect the blank from dirt. The general coating amount is one pair of open coating 20ml-30ml. Baking plate temperature control at 230 °C -250 °C. The time is 5-8 minutes. It must be noted that the special roasting machine used in the roasting plate must have a constant temperature control device with a temperature difference of ±2°C. The baking temperature is too high or the time is too long can cause carbonization of the photosensitive layer, aluminum plate deformation and mechanical strength. Reducing affects the printing plate's resistance to printing force and the life of the plate base; the temperature is too low or the time is too short, and the thermal curing degree of the photosensitive layer is not enough, which will also affect the printing resistance. After baking, it must be cooled naturally, and it should not be cooled by water to avoid deformation of the plate base. After cooling, the protective agent is washed off with a waste developer, neutralized with 3% phosphoric acid, and washed with water, dried, and temporarily coated with gum arabic for protection.
The production and drying of the PS plate play a decisive role in improving the printing plate's resistance to printing. When the printing process is operated in accordance with data, standardization and standardization, the production and drying of printing plates are particularly important. therefore. We only carefully deal with the above issues, eliminate the external and human factors in the production and printing process, strongly promote data, standardization, and standardization of drying, ensure maximum plate quality, and improve the printing plate resistance to printing. Put it into practice.
4. Development of the developed PS plate consists in removing the photosensitive layer of the blank portion to maintain the hydrophilicity of the surface of the PS plate. It is an important part of the PS plate making process. It is not only restricted by the properties of the photosensitizer and the original state, but also influenced by the development conditions such as the concentration of the developer, the temperature, the degree of fatigue, and the development time.
(1) The concentration of developer affects the concentration of the developer. Generally refers to the content of the developer base. Insufficient developer concentration will not only increase the development time but also cause incomplete development. Cause the layout of the face; excessive concentration, the development time is accelerated, the entire process is difficult to control, easy to cause excessive development, network points are reduced or damaged, dissolve unsensitized photosensitive layer, reduce the printing plate's sensory and resistance to force. Therefore, in order to accurately control the concentration, the plate can be developed after 30-60s, observe whether the hollow point of the Bruner test strip 98%-99% is clear and whether the 1%-2% small black point is firm, if The idea of ​​clear and sturdy indicates that the concentration is appropriate.
(2) The effect of temperature is relatively stable under other conditions of development. The higher the development temperature, the faster the development speed and vice versa. The general development temperature should be controlled at about 20 °C. The automatic developing machine should be controlled at 25°C, and when it exceeds 30°C, the dots will dissolve. In the photosensitive layer, the binding force between the photosensitive material and the film forming material is weakened, the alkali resistance is decreased, the area percentage of the screen area is reduced, and the reproduction of the printing plate is damaged.
(3) Fatigue degree of the developer The fatigue of the developer means that the developing ability of the developer drops. Such as the use of hand-developed development, due to the exposure of the developer to the air, the absorption of water and CO2, accelerated developer degeneration, affecting the development performance. Another cause of the fatigue of the developing solution is that the photodegradable substance is dissolved therein, and the developing ability is significantly reduced. Therefore, the currently used alkaline developer should minimize contact with air in the process of storage and use, reduce the impact of moisture and CO2 on it, and regularly replace and quantitatively make up the medicine.
(4) Influence of developing time Because the developing time is affected by the exposure of the printing plate, the performance of the photosensitive agent, the developing method, the state of the developer, etc. Therefore, to control the degree of development, the above-mentioned variable factors should be grasped and stabilized first, and then The gray scale is tested to determine the development conditions and the correct development time. The general development time is about 1 minute.
4. After the baking plate has been baked, the photosensitive base in the photosensitive layer disappears, and the phenolic resin undergoes thermal cross-linking reaction by heat, which turns from linear molecules to large-scale network molecules. At this time, the solvent resistance, corrosion resistance, and abrasion resistance of the printing plate and the adsorption of the photosensitive layer to the plate surface are greatly improved. However, during baking, in addition to the change in the photosensitive portion of the graphic part, the micropores of the anodized aluminum substrate surface that was closed by the plugging treatment may cause the flow of water to be increased due to the loss of water, causing the plate to be dirty. Therefore, before baking, it is necessary to evenly apply a layer of protective agent to the plate with absorbent cotton to protect the blank from dirt. The general coating amount is one pair of open coating 20ml-30ml. Baking plate temperature control at 230 °C -250 °C. The time is 5-8 minutes. It must be noted that the special roasting machine used in the roasting plate must have a constant temperature control device with a temperature difference of ±2°C. The baking temperature is too high or the time is too long can cause carbonization of the photosensitive layer, aluminum plate deformation and mechanical strength. Reducing affects the printing plate's resistance to printing force and the life of the plate base; the temperature is too low or the time is too short, and the thermal curing degree of the photosensitive layer is not enough, which will also affect the printing resistance. After baking, it must be cooled naturally, and it should not be cooled by water to avoid deformation of the plate base. After cooling, the protective agent is washed off with a waste developer, neutralized with 3% phosphoric acid, and washed with water, dried, and temporarily coated with gum arabic for protection.
The production and drying of the PS plate play a decisive role in improving the printing plate's resistance to printing. When the printing process is operated in accordance with data, standardization and standardization, the production and drying of printing plates are particularly important. therefore. We only carefully deal with the above issues, eliminate the external and human factors in the production and printing process, strongly promote data, standardization, and standardization of drying, ensure maximum plate quality, and improve the printing plate resistance to printing. Put it into practice.
Sanjin Plastic Industry Co., Ltd. , http://www.sdmakeuppackaging.com