Intaglio printing inks are relatively thin. In storage, the solids in them are always subject to sinking due to gravity. Therefore, the mixing of the ink in the packaging should not be neglected before use. The ink that is poured from the unstirred ink layer may have low viscosity, poor color density and hiding power. The viscosity of the ink removed from the unstirred lower layer may be greater, and the ratio of the pigment to the film forming material may be higher. As a result, the adhesion will be poor, so before use, use a clean stick or a metal rod to whisk it evenly. Generally, it is necessary to agitate the ink for at least 3 to 5 minutes. If the ink is stored longer, more agitation is required.
Second, in the use of ink, it is necessary to pay attention to the sealing of the ink tank and prevent the mixing of impurities. Since these inks are volatile and involve scraper and dot problems, it is necessary to prevent dry agglomerates and to prevent volatilization during storage. The above problem should be completely removed to dry the ink particles and debris, in order to maintain the original state of the ink.
In general, the printing problem is nothing more than three reasons: the first is the ink problem; the second is the condition of the printing press and the printing object; and the third is the skill of the operator. All three reasons can be the main factor in the success or failure of a print job. Therefore, when the problem occurs, it is necessary to conduct a more detailed analysis of the three, to clarify the cause of the failure, and to take countermeasures. The following lists common faults and their countermeasures.
1. Phenomenon phenomenon: Small prints or patterns cannot be printed. In severe cases, a layer of ink can be seen.
Reason: The ink is too dry, which causes the ink to settle in the pocket; the speed is slow, and the printing plate is not good.
Treatment method: In the ink can be adjusted into the appropriate solvent boiling point 120 ~ 150 °C slow dry; appropriate increase speed; re-plate.
2. Bite the color phenomenon: In overprinting, the second color ink sticks off the first color pattern ink.
Reason: Ink drying is not good (slow); the second color of the machine is too much pressure; speed is faster; on the thinner material discomfort; bad cold and hot air; adhesion is not good.
Treatment method: For the first color, add a quick-drying solvent; increase the amount of hot air; reduce the pressure on the second color or make it less viscous than the first color;
3. Viscous dirty phenomenon: The printed products stick to each other and the blot stains back.
Reason: Slow dry ink; speed too fast; poor ventilation.
Treatment method: add quick-drying solvent; slow down; increase hair blow.
4. Adhesion is poor Phenomenon: The printing product is rubbed and faded (printed plastic, aluminum).
Cause: The ink is not correct, the amount of resin in the ink is too small; the plastic is not handled well; the film is brittle and hard.
Treatment method: Change the ink of the film, use the resin diluent when adjusting the ink; reprocess the plastic surface. Regarding adhesion, this is a difficult problem to solve. It is generally related to the adaptability of the ink to the film. That is, the resin, solvent, and pigment system used in the ink should have greater softness on the surface of the film and also be related to the adaptability of the film to the ink. That is to say, the film surface has a greater affinity for the ink. For the ink, the polyamide resin and some other resins have a good affinity for the film. However, due to the different nature of the pigments, the effects are not uniform. . The treatment of the film surface is to overcome its smooth, non-polar defects in order to increase the adsorption of the ink. Long processing time, many times, good adhesion, good printing effect with the treatment. The stronger the voltage, the better the impact effect. The voltage is at least 9000 volts, preferably 12,000 to 15,000 volts. The surface energy can be treated to more than 38 dynes/cm2, or some wax can be added to plastic during blow molding.
5. Pinholes Phenomenon: Tiny holes appear on the prints, especially in the larger area of ​​the pattern.
Reasons: First, when it is printed, the ink becomes a very thin transparent layer, and it can see the Internet lines of the printing roller. The printed products are pinholes (blisters) of the same size and evenly spread over the prints. This is called a mechanical pinhole. The second is the result of ink leveling and poor wettability of the substrate. Impressive pinholes on chemical products are called chemical pinholes.
Treatment method: The mechanical pinhole can be increased by properly increasing the viscosity of the ink or drying the ink slowly. For chemical pinholes, adjust the ink pair and do not remove the ink too short to ensure the adhesion and leveling of the ink. Therefore, it can be corrected by adding polyamide resin oil or other moisturizing substance adjustment at the same time when diluting.
6. Fainting and halo phenomenon: pattern imprinting is not true, and the ink layer is thin and thin, and it is called faint, and it is bilateral from the edge of the printing product, called halo circle.
Causes: The pressure of the plate is not uniform, or the blanket is uncomfortable; there is also the lack of ink concentration or the lack of ink caused by the deficiency. The plate cylinder is under too much pressure and the viscosity of the ink is insufficient, allowing the ink in the pockets to flare out before embossing. Static electricity causes halos.
Treatment method: Adjust the pressure, adjust the ink concentration and viscosity, and increase the dry speed.
7. Scratches: There is a color in the non-patterned part of the print.
The reason: The total cause is scraper problems, among which there are ink scraper problems such as:
(1) There are impurities in the ink and the particles are rough.
(2) The viscosity of the ink is too high.
(3) The ink has a strong adhesion to the plate roller.
(4) The ink dries too quickly or too slowly.
Also caused by the plate cylinder:
(1) Poor roller processing.
(2) Pattern lines are too deep.
(3) The chrome plating material is poor.
Also due to scraper:
(1) The blade is not straight and damaged.
(2) Inappropriate pressure.
(3) Discomfort between blade and roller angle.
Treatment method: It is the cause of the ink, before filtering, adjusting to the proper viscosity, adjusting the dryness and adhesion; it is the reason of the roller, use the smooth roller, correct the pattern, and even the chrome plating; if it is the reason of the scraper, then use the straight sharp Scraper, adjust the knife's angle and pressure.
8. Inaccurate hue Cause: The ink does not meet the requirements of the product, and the color is thin.
Approach.
(1) The desired color tone can be adjusted according to the ink subtractive principle.
(2) Intensity of hiding power is increased by 1% to 2% of white ink in the color ink.
9. Albino Phenomenon: Printing into white film, if there is cloudiness.
the reason:
(1) Solvent whitening, more common in flexible letterpress. When the surrounding environment is wet with high humidity, due to the latent heat of solvent evaporation, the temperature of the traces is reduced, and thus some of the solvents are cooled down, but some of the water is mixed into the film to cause whitening.
(2) The resin is whitened. Since the solvent in the ink is out of balance, the true solvent is volatilized first. The increase of the thinner causes precipitation of the resin in the ink and causes whitening.
Approach:
(1) Reduce the environmental humidity.
(2) Strengthen heat drying.
(3) Raise the boiling point of the true solvent and slow it down.
(4) Change to slow-drying diluent.
10. Poor ink phenomenon:
(1) The ink does not fall out of the bucket, and it becomes frozen in winter.
(2) The ink is thicker and thixotropic.
(3) Do not flow into gel after dilution.
the reason:
(1) The resin freeze-dried in the ink is poor.
(2) The amount of pigment in the ink is large, the wettability is poor, and the nature is uncomfortable.
(3) Excessive dilution, moisture in the diluent.
(4) The diluent is not used properly.
Approach:
(1) Place the room above 20°C one day ahead of time or warm up.
(2) Stir first to restore ink.
(3) Ink plus thinner, special thinner produced by ink factory.
(4) Use less ink and keep it right, and apply ink to thin materials at the same time.
(5) Do not adjust the ink too thin.
Second, in the use of ink, it is necessary to pay attention to the sealing of the ink tank and prevent the mixing of impurities. Since these inks are volatile and involve scraper and dot problems, it is necessary to prevent dry agglomerates and to prevent volatilization during storage. The above problem should be completely removed to dry the ink particles and debris, in order to maintain the original state of the ink.
In general, the printing problem is nothing more than three reasons: the first is the ink problem; the second is the condition of the printing press and the printing object; and the third is the skill of the operator. All three reasons can be the main factor in the success or failure of a print job. Therefore, when the problem occurs, it is necessary to conduct a more detailed analysis of the three, to clarify the cause of the failure, and to take countermeasures. The following lists common faults and their countermeasures.
1. Phenomenon phenomenon: Small prints or patterns cannot be printed. In severe cases, a layer of ink can be seen.
Reason: The ink is too dry, which causes the ink to settle in the pocket; the speed is slow, and the printing plate is not good.
Treatment method: In the ink can be adjusted into the appropriate solvent boiling point 120 ~ 150 °C slow dry; appropriate increase speed; re-plate.
2. Bite the color phenomenon: In overprinting, the second color ink sticks off the first color pattern ink.
Reason: Ink drying is not good (slow); the second color of the machine is too much pressure; speed is faster; on the thinner material discomfort; bad cold and hot air; adhesion is not good.
Treatment method: For the first color, add a quick-drying solvent; increase the amount of hot air; reduce the pressure on the second color or make it less viscous than the first color;
3. Viscous dirty phenomenon: The printed products stick to each other and the blot stains back.
Reason: Slow dry ink; speed too fast; poor ventilation.
Treatment method: add quick-drying solvent; slow down; increase hair blow.
4. Adhesion is poor Phenomenon: The printing product is rubbed and faded (printed plastic, aluminum).
Cause: The ink is not correct, the amount of resin in the ink is too small; the plastic is not handled well; the film is brittle and hard.
Treatment method: Change the ink of the film, use the resin diluent when adjusting the ink; reprocess the plastic surface. Regarding adhesion, this is a difficult problem to solve. It is generally related to the adaptability of the ink to the film. That is, the resin, solvent, and pigment system used in the ink should have greater softness on the surface of the film and also be related to the adaptability of the film to the ink. That is to say, the film surface has a greater affinity for the ink. For the ink, the polyamide resin and some other resins have a good affinity for the film. However, due to the different nature of the pigments, the effects are not uniform. . The treatment of the film surface is to overcome its smooth, non-polar defects in order to increase the adsorption of the ink. Long processing time, many times, good adhesion, good printing effect with the treatment. The stronger the voltage, the better the impact effect. The voltage is at least 9000 volts, preferably 12,000 to 15,000 volts. The surface energy can be treated to more than 38 dynes/cm2, or some wax can be added to plastic during blow molding.
5. Pinholes Phenomenon: Tiny holes appear on the prints, especially in the larger area of ​​the pattern.
Reasons: First, when it is printed, the ink becomes a very thin transparent layer, and it can see the Internet lines of the printing roller. The printed products are pinholes (blisters) of the same size and evenly spread over the prints. This is called a mechanical pinhole. The second is the result of ink leveling and poor wettability of the substrate. Impressive pinholes on chemical products are called chemical pinholes.
Treatment method: The mechanical pinhole can be increased by properly increasing the viscosity of the ink or drying the ink slowly. For chemical pinholes, adjust the ink pair and do not remove the ink too short to ensure the adhesion and leveling of the ink. Therefore, it can be corrected by adding polyamide resin oil or other moisturizing substance adjustment at the same time when diluting.
6. Fainting and halo phenomenon: pattern imprinting is not true, and the ink layer is thin and thin, and it is called faint, and it is bilateral from the edge of the printing product, called halo circle.
Causes: The pressure of the plate is not uniform, or the blanket is uncomfortable; there is also the lack of ink concentration or the lack of ink caused by the deficiency. The plate cylinder is under too much pressure and the viscosity of the ink is insufficient, allowing the ink in the pockets to flare out before embossing. Static electricity causes halos.
Treatment method: Adjust the pressure, adjust the ink concentration and viscosity, and increase the dry speed.
7. Scratches: There is a color in the non-patterned part of the print.
The reason: The total cause is scraper problems, among which there are ink scraper problems such as:
(1) There are impurities in the ink and the particles are rough.
(2) The viscosity of the ink is too high.
(3) The ink has a strong adhesion to the plate roller.
(4) The ink dries too quickly or too slowly.
Also caused by the plate cylinder:
(1) Poor roller processing.
(2) Pattern lines are too deep.
(3) The chrome plating material is poor.
Also due to scraper:
(1) The blade is not straight and damaged.
(2) Inappropriate pressure.
(3) Discomfort between blade and roller angle.
Treatment method: It is the cause of the ink, before filtering, adjusting to the proper viscosity, adjusting the dryness and adhesion; it is the reason of the roller, use the smooth roller, correct the pattern, and even the chrome plating; if it is the reason of the scraper, then use the straight sharp Scraper, adjust the knife's angle and pressure.
8. Inaccurate hue Cause: The ink does not meet the requirements of the product, and the color is thin.
Approach.
(1) The desired color tone can be adjusted according to the ink subtractive principle.
(2) Intensity of hiding power is increased by 1% to 2% of white ink in the color ink.
9. Albino Phenomenon: Printing into white film, if there is cloudiness.
the reason:
(1) Solvent whitening, more common in flexible letterpress. When the surrounding environment is wet with high humidity, due to the latent heat of solvent evaporation, the temperature of the traces is reduced, and thus some of the solvents are cooled down, but some of the water is mixed into the film to cause whitening.
(2) The resin is whitened. Since the solvent in the ink is out of balance, the true solvent is volatilized first. The increase of the thinner causes precipitation of the resin in the ink and causes whitening.
Approach:
(1) Reduce the environmental humidity.
(2) Strengthen heat drying.
(3) Raise the boiling point of the true solvent and slow it down.
(4) Change to slow-drying diluent.
10. Poor ink phenomenon:
(1) The ink does not fall out of the bucket, and it becomes frozen in winter.
(2) The ink is thicker and thixotropic.
(3) Do not flow into gel after dilution.
the reason:
(1) The resin freeze-dried in the ink is poor.
(2) The amount of pigment in the ink is large, the wettability is poor, and the nature is uncomfortable.
(3) Excessive dilution, moisture in the diluent.
(4) The diluent is not used properly.
Approach:
(1) Place the room above 20°C one day ahead of time or warm up.
(2) Stir first to restore ink.
(3) Ink plus thinner, special thinner produced by ink factory.
(4) Use less ink and keep it right, and apply ink to thin materials at the same time.
(5) Do not adjust the ink too thin.
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