There are many reasons for the failure of glass screen printing, involving screen printing screen printing, screen printing, screen printing ink, screen printing equipment, screen printing materials, and operating techniques. There are single reasons for the occurrence of screen printing faults, but more are the result of cross-effects of various causes. This is where the operator pays special attention to determining the cause of the fault and taking appropriate countermeasures.
First, paste version
The paste version, also known as plugging, refers to the phenomenon that the hole of the screen printing plate can not transfer ink to the printing Material during printing. The appearance of this phenomenon will affect the printing quality, even if it is severe, it will not be able to print normally.
The cause of the stencil phenomenon in the screen printing process is intricate. The reasons for plagiarism can be analyzed from the following aspects.
1 The reason for the substrate. The glass surface has not been treated cleanly, and there are also watermarks, paper prints, mimeographs, fingerprints, dust particles, and other contaminants. Thus resulting in paste version.
2 The reason for workshop temperature, humidity and ink properties. Screen printing workshops require maintaining a certain temperature of about 20 degrees and a relative humidity of about 50%. If the temperature is high and the relative humidity is low, the volatile solvents in the ink will evaporate quickly, and the viscosity of the ink on the network will become high, thus blocking the Mesh hole. Another point that should be noted is that if the downtime is too long, it will produce a paste version phenomenon, the longer the paste version becomes more serious. Second, if the ambient temperature is low, the ink flowability is also poor, it is easy to produce paste.
3 reasons for screen printing plate. The prepared screen plate can be used after being rinsed with water and dried before use. If the printed version is left over for a long time, it will not adhere to the dust more or less during the preservation process. If it is not cleaned during printing, it will cause a paste plate.
4 reasons for printing pressure. Excessive embossing force during the printing process will cause the blade to bend. The blade and the screen plate and the substrate are not in line contact, but are in surface contact, so that each time the ink is scraped, the ink can be scraped and left behind. Residual ink, after a certain period of time will cause conjunctiva caused paste plate.
5 screen printing plate and the substrate gap due to improper reasons. The gap between the screen printing plate and the substrate should not be too small. When the gap is too small, the screen plate cannot be detached from the substrate in time after the squeegee is printed. When the screen plate is raised, a certain ink is stuck on the bottom of the plate, which is also easy. Create a paste board.
6 ink reasons. When the pigments in the screen printing ink and other solid particles are large, it is easy to block the mesh.
In addition, the mesh size and through-hole area of ​​the selected mesh are smaller than those of the ink, so that it is one of the reasons why the coarse-grained ink does not easily pass through the mesh. For stencils caused by larger particles of the ink, the ink can be solved from the time the ink is manufactured. The main method is to strictly control the fineness of the ink.
In the printing process, the increase in ink viscosity caused by paste version, the main reason is that the screen printing ink solvent evaporation, resulting in increased ink viscosity, and closure of the network phenomenon. If the area for printing graphics is large, the ink on the screen printing plate will consume more, and the stencil printing will be less. If the picture area is small, the ink consumption on the screen printing plate is small, it is easy to cause paste printing. The countermeasure is to use a small amount of ink refilling principle. Poor flow of ink will cause the ink to produce a paste when not passed through the screen. This can be solved by lowering the viscosity of the ink and improving the fluidity of the ink without affecting the print quality.
After a paste failure occurs, an appropriate solvent scrub can be used depending on the nature of the ink on the plate. The method of scrubbing starts from the printing surface and gently wipes from the center to the periphery. Check the plate after wiping, if any defects should be promptly repaired, and re-start printing after repair. It should be noted that the plate is thinned each time it is scrubbed, and if it is wiped out, it causes a major defect in the plate.
Second, the ink is not firmly fixed on the substrate
1. When printing on glass, it is very important that the glass is subjected to strict degreasing and pre-treatment inspection before printing. When the surface of the glass adheres to substances such as greases, binders, and dust, poor adhesion between the ink and the glass can result.
2 Insufficient adhesion of the ink itself causes the ink film to be hardened, and it is better to replace other inks for printing. Improper use of diluting solvent can also cause the ink film to be stuck. When selecting the diluting solvent, the properties of the ink must be taken into consideration to avoid the occurrence of ink sticking to the substrate.
Third, the ink film edge defects
In glass screen printing products, a problem that often occurs is saw-like burrs (including incomplete or broken lines) at the edges of the printed ink film. There are many reasons for glitches, but the main reason is the quality of screen printing.
1 The sensitivity of the photosensitive adhesive is not high, resulting in the fine lines of the mountain is now red or incomplete.
2 The exposure time is insufficient or the exposure time is too long, the development is not sufficient, and the edge of the screen printing graphic is not neat, and appears jagged. For a good screen printing plate, the edges of the graphic should be smooth and neat.
3 When the surface of the screen printing plate is coated unevenly, there is still a gap between the screen plate and the substrate during printing. Due to the ink penetrating into the space, burrs are formed on the edge of the printing ink.
4 During the printing process, due to the swelling of the printing film after contact with the solvent, and the degree of swelling in the latitude and longitude is different, the surface of the printing film is uneven. During the printing, a gap appears between the screen printing plate and the surface of the printing material, and the ink is suspended and infiltrated. Ink film will appear burrs.
In order to prevent the appearance of jagged haircuts, the solution can be considered from the following aspects:
1 Use high mesh screen plate making;
2 Select high-sensitivity photosensitive materials for plate making; use bridging type and good photosensitivity.
3 Make a thick screen printing plate to reduce the expansion deformation;
4 It is also possible to use a diagonal stretch net to stretch the net, the best angle being 22.5.
5 fine line printing, can also be used indirect plate making method, because indirect plate making glitch may be smaller:
6 In the process of plate making and printing, try to control the temperature expansion factor and use a photosensitive material with a small expansion coefficient:
7 Improve the quality of plate making, ensure that the surface of the screen plate is smooth, and the edges of the screen lines must be neat;
8 Spray the screen printing plate with a water jet gun to improve the development effect;
9 The distance between the screen plate and the substrate, the angle of the squeegee, and the printing pressure should be appropriate.
Fourth, ink uneven
Ink film thickness is uneven due to a variety of reasons. In terms of ink, the ink is poorly formulated, or the normally formulated ink is mixed with ink. When printing, the ink expands and softens due to the effect of the solvent. Mesh hole is blocked, play the role of the plate, so that the ink can not pass.
In order to prevent such failures, the formulated ink (especially the old ink) should be screen-filtered before use. When you reuse a used plate, you must completely remove the old ink that has adhered to the plate. When the plates are stored after printing, they must be fully washed (including scrapers).
If this is done as described above, accidents with ink unevenness will not happen.
If the tip of the ink return plate is damaged, a trace will appear along the direction of movement of the squeegee. When printing glass, there will be obvious ink inconsistencies. Therefore, it is necessary to protect the front end of the squeegee so as not to cause damage. If it is damaged, it must be grinded with a grinder.
The unevenness of the printing table also affects the uniform ink. The convex ink layer is thin, and the recessed ink layer is thick. This phenomenon is also called ink inhomogeneity. In addition, if the back surface of the substrate or the printing table adheres with dust, the above failure may occur.
V. Pinhole
The phenomenon of pinholes is the biggest headache for workers engaged in glass screen printing. The reasons for the occurrence of pinholes are also varied, many of which are currently unexplained, and some are still problems of quality management. Pinholes are one of the most important inspection items in the inspection of printed products.
1 Dust and foreign objects attached to the plate. At the time of plate making, there are some sols mixed into the water wash image. In addition, when the emulsion is applied, dust may be mixed in, and pinholes may be formed on the screen. These tests can be found and repaired promptly if they are checked. If dust and foreign matter adhere to the screen, blocking the screen openings can also cause pinholes. Before the formal printing, carefully check the screen and eliminate the dirt on the plate.
2 substrate surface cleaning. Before printing, the glass plate should be pre-treated to make its surface clean and printed immediately. If the glass is processed, it will not be printed immediately and it will be recontaminated. After pre-treatment, dirt such as grease can be removed, and dust attached to the surface can also be removed.
Pay particular attention to the fingerprints of your hands that will adhere to the printed surface when you move the cloud glass by hand, forming pinholes when printing.
Six, bubbles
Substrate will appear bubbles on the ink after printing. The main reasons for bubbles are as follows:
1 The substrate is poorly processed before printing. Substrate attached to the surface of dust and oil traces and other substances.
2 bubbles in the ink. In order to adjust the ink, adding solvents and additives to stir, the ink will be mixed with some bubbles, if placed regardless of the low viscosity of the ink will naturally deaeration, high viscosity inks and some can not be natural deaeration. Some of these bubbles are naturally eliminated in the printing process due to the transfer of ink, while others become larger and larger. In order to remove these bubbles, defoamers should be used. The amount of defoamer added in the ink is generally about 0.1 to 1%. If j exceeds the specified amount, it will have a foaming effect.
After the ink is transferred, even if it is foamed, as long as the wettability of the substrate and the ink flowability are good, the bubbles on the surface of the printing ink film will be gradually eliminated, and the ink forms a flat printing ink film. If ink bubbles are not eliminated, the ink film will form a ring-shaped uneven film surface. Bubbles in general inks can also be degassed by the action of the screen when passing through the screen.
3 If the printing speed is too fast or the printing speed is uneven, bubbles may also be generated. The printing speed should be properly reduced to maintain the uniformity of the printing speed.
If none of the above measures can eliminate air bubbles in prints, consider using other types of ink.
Seven, net marks
Screen marks sometimes appear on the surface of the ink film. The main cause of the screen marks is the poor fluidity of the ink. During the screen printing process, when the printing plate is lifted, the ink transferred to the printing material fills the screen traces with its own flow, making the surface of the ink film smooth. If the ink has poor fluidity, when the screen printing plate is lifted, the ink flow is relatively small, and the screen marks cannot be filled, and a smooth and smooth ink film cannot be obtained. To prevent the appearance of screen marks on prints, the following method can be used.
1 Use leveling ink for printing.
2 Consider printing with slow drying inks. Increase the ink flow time to gradually level and cure the ink.
9 Try to use finer, monofilament mesh when making plates.
Eight, the printing position is not accurate
It is related to the screen size, the repeatability of the printing press, and the glass size.
Nine, the size of the finished ink film
After screen printing, the print size sometimes increases. The main reason for the increase in printing size is the relatively low viscosity of the ink and excessive fluidity; the size of the screen printing plate is also the cause of the increase in the printing size.
In order to avoid the ink flowability caused by the overflow of the ink after printing, causing the print size becomes larger, consider increasing the viscosity of the ink to reduce the ink's fluidity. In the production of screen printing plate inch, we must strictly guarantee the quality of the screen plate to ensure the screen plate tension.
Ten, the back of the dirty
Dirty back refers to the phenomenon that the ink on the lower glass sticks to the back of the upper glass when the glass is stacked. Printed glass can be isolated using release liners, spacers, and blown paper.
Eleven, printing ink leak
Part of the ink leaked from the printing plate is called ink leakage failure. The reason for this is: some of the squeegee has been damaged; the pressure of the squeegee is large; the gap between the plate and the substrate is too large; the plate frame is deformed, and the printing pressure is insufficient. : Inhomogeneous ink; fine mesh; too fast printing speed.
If the printing material and the ink are mixed with dust and printed without processing, the printing plate will be damaged due to the pressure of the squeegee; when the plate is underexposed, pinholes, etc., will cause the printing ink to leak. At this time, adhesive tapes, etc. can be used for emergency handling from the back of the plate.
If this operation is not very fast, the ink on the layout will be dried, and the whole of the plate will have to be wiped with solvent. Wipe plates are also the cause of delamination of the plate, so it is best avoided. The ink leakage of the printing plate often occurs in the ink staying part, so it is better to strengthen this part in the plate making.
Twelve, image distortion
The printing pressure applied to the plate by the squeegee during printing can make the line contact between the plate and the object to be printed. It should not exceed. If the printing pressure is too high, the printing plate contacts with the printing material and the screen may expand and contract, causing the printing image to be deformed. Screen printing is the smallest type of printing in various printing methods. If we forget this, we cannot print good prints.
If you cannot print without increasing the pressure, reduce the gap between the plate and the surface of the substrate so that the pressure on the blade can be reduced.
XIII.
Ink-wetting refers to the dot-like blotting of the graphics and dark-sounding parts of the substrate, which impairs the printing effect. Glass screen printing is easy and this phenomenon occurs. The reasons are as follows: printing speed and ink drying are too slow; ink layer is too thin; ink thixotropic; electrostatic effects; Dot blots. .
The improved methods are: improving the fluidity of the ink; using a quick-drying flux; printing with a high-viscosity ink as much as possible: increasing the wet film thickness of the ink, using an ink made of a pigment with a small oil absorption amount as much as possible: minimizing the influence of static electricity .
XIV. Flying ink.
Flying ink is the phenomenon of ink drawing. The causes are: the ink is unevenly grinded; the squeegee is slow from the printing when printing; the blank space around the printed image is too small; static electricity is generated, and the angle of the ink from the stencil is too small.
15. Electrostatic fault
Electrostatic current is generally very small, the potential difference is very large, and there may be a phenomenon of attraction, repulsion, conduction, and discharge.
1 adverse effects on screen printing. In the screen during printing, the rubber portion and the screen are charged by the pressure scraping of the blade rubber. If the screen itself is charged, it will affect the normal inking and produce blockage failures; it will be absorbed by the screen at the moment when the substrate is output.
a. The glass is easily charged when the heater wire is printed.
b. Static electricity makes it easy to absorb ink particles on the glass surface, making the glass surface unclean.
c. The human body's electric shock due to static electricity is caused by contact with a charged object, or by electrostatic discharges that generate spark discharges when grounded. Although the electric current generated by electric shock is small, no danger will occur, but electric shocks often occur, which will have an adverse effect on the operator's psychology.
2 method to prevent static electricity. The methods for preventing static electricity generation include: adjusting the ambient temperature and increasing the air humidity; the appropriate temperature is generally about 20° C. and the relative humidity is about 60%; static electricity can be transferred in the wet air; the net pitch is reduced, and the printing speed is reduced.
First, paste version
The paste version, also known as plugging, refers to the phenomenon that the hole of the screen printing plate can not transfer ink to the printing Material during printing. The appearance of this phenomenon will affect the printing quality, even if it is severe, it will not be able to print normally.
The cause of the stencil phenomenon in the screen printing process is intricate. The reasons for plagiarism can be analyzed from the following aspects.
1 The reason for the substrate. The glass surface has not been treated cleanly, and there are also watermarks, paper prints, mimeographs, fingerprints, dust particles, and other contaminants. Thus resulting in paste version.
2 The reason for workshop temperature, humidity and ink properties. Screen printing workshops require maintaining a certain temperature of about 20 degrees and a relative humidity of about 50%. If the temperature is high and the relative humidity is low, the volatile solvents in the ink will evaporate quickly, and the viscosity of the ink on the network will become high, thus blocking the Mesh hole. Another point that should be noted is that if the downtime is too long, it will produce a paste version phenomenon, the longer the paste version becomes more serious. Second, if the ambient temperature is low, the ink flowability is also poor, it is easy to produce paste.
3 reasons for screen printing plate. The prepared screen plate can be used after being rinsed with water and dried before use. If the printed version is left over for a long time, it will not adhere to the dust more or less during the preservation process. If it is not cleaned during printing, it will cause a paste plate.
4 reasons for printing pressure. Excessive embossing force during the printing process will cause the blade to bend. The blade and the screen plate and the substrate are not in line contact, but are in surface contact, so that each time the ink is scraped, the ink can be scraped and left behind. Residual ink, after a certain period of time will cause conjunctiva caused paste plate.
5 screen printing plate and the substrate gap due to improper reasons. The gap between the screen printing plate and the substrate should not be too small. When the gap is too small, the screen plate cannot be detached from the substrate in time after the squeegee is printed. When the screen plate is raised, a certain ink is stuck on the bottom of the plate, which is also easy. Create a paste board.
6 ink reasons. When the pigments in the screen printing ink and other solid particles are large, it is easy to block the mesh.
In addition, the mesh size and through-hole area of ​​the selected mesh are smaller than those of the ink, so that it is one of the reasons why the coarse-grained ink does not easily pass through the mesh. For stencils caused by larger particles of the ink, the ink can be solved from the time the ink is manufactured. The main method is to strictly control the fineness of the ink.
In the printing process, the increase in ink viscosity caused by paste version, the main reason is that the screen printing ink solvent evaporation, resulting in increased ink viscosity, and closure of the network phenomenon. If the area for printing graphics is large, the ink on the screen printing plate will consume more, and the stencil printing will be less. If the picture area is small, the ink consumption on the screen printing plate is small, it is easy to cause paste printing. The countermeasure is to use a small amount of ink refilling principle. Poor flow of ink will cause the ink to produce a paste when not passed through the screen. This can be solved by lowering the viscosity of the ink and improving the fluidity of the ink without affecting the print quality.
After a paste failure occurs, an appropriate solvent scrub can be used depending on the nature of the ink on the plate. The method of scrubbing starts from the printing surface and gently wipes from the center to the periphery. Check the plate after wiping, if any defects should be promptly repaired, and re-start printing after repair. It should be noted that the plate is thinned each time it is scrubbed, and if it is wiped out, it causes a major defect in the plate.
Second, the ink is not firmly fixed on the substrate
1. When printing on glass, it is very important that the glass is subjected to strict degreasing and pre-treatment inspection before printing. When the surface of the glass adheres to substances such as greases, binders, and dust, poor adhesion between the ink and the glass can result.
2 Insufficient adhesion of the ink itself causes the ink film to be hardened, and it is better to replace other inks for printing. Improper use of diluting solvent can also cause the ink film to be stuck. When selecting the diluting solvent, the properties of the ink must be taken into consideration to avoid the occurrence of ink sticking to the substrate.
Third, the ink film edge defects
In glass screen printing products, a problem that often occurs is saw-like burrs (including incomplete or broken lines) at the edges of the printed ink film. There are many reasons for glitches, but the main reason is the quality of screen printing.
1 The sensitivity of the photosensitive adhesive is not high, resulting in the fine lines of the mountain is now red or incomplete.
2 The exposure time is insufficient or the exposure time is too long, the development is not sufficient, and the edge of the screen printing graphic is not neat, and appears jagged. For a good screen printing plate, the edges of the graphic should be smooth and neat.
3 When the surface of the screen printing plate is coated unevenly, there is still a gap between the screen plate and the substrate during printing. Due to the ink penetrating into the space, burrs are formed on the edge of the printing ink.
4 During the printing process, due to the swelling of the printing film after contact with the solvent, and the degree of swelling in the latitude and longitude is different, the surface of the printing film is uneven. During the printing, a gap appears between the screen printing plate and the surface of the printing material, and the ink is suspended and infiltrated. Ink film will appear burrs.
In order to prevent the appearance of jagged haircuts, the solution can be considered from the following aspects:
1 Use high mesh screen plate making;
2 Select high-sensitivity photosensitive materials for plate making; use bridging type and good photosensitivity.
3 Make a thick screen printing plate to reduce the expansion deformation;
4 It is also possible to use a diagonal stretch net to stretch the net, the best angle being 22.5.
5 fine line printing, can also be used indirect plate making method, because indirect plate making glitch may be smaller:
6 In the process of plate making and printing, try to control the temperature expansion factor and use a photosensitive material with a small expansion coefficient:
7 Improve the quality of plate making, ensure that the surface of the screen plate is smooth, and the edges of the screen lines must be neat;
8 Spray the screen printing plate with a water jet gun to improve the development effect;
9 The distance between the screen plate and the substrate, the angle of the squeegee, and the printing pressure should be appropriate.
Fourth, ink uneven
Ink film thickness is uneven due to a variety of reasons. In terms of ink, the ink is poorly formulated, or the normally formulated ink is mixed with ink. When printing, the ink expands and softens due to the effect of the solvent. Mesh hole is blocked, play the role of the plate, so that the ink can not pass.
In order to prevent such failures, the formulated ink (especially the old ink) should be screen-filtered before use. When you reuse a used plate, you must completely remove the old ink that has adhered to the plate. When the plates are stored after printing, they must be fully washed (including scrapers).
If this is done as described above, accidents with ink unevenness will not happen.
If the tip of the ink return plate is damaged, a trace will appear along the direction of movement of the squeegee. When printing glass, there will be obvious ink inconsistencies. Therefore, it is necessary to protect the front end of the squeegee so as not to cause damage. If it is damaged, it must be grinded with a grinder.
The unevenness of the printing table also affects the uniform ink. The convex ink layer is thin, and the recessed ink layer is thick. This phenomenon is also called ink inhomogeneity. In addition, if the back surface of the substrate or the printing table adheres with dust, the above failure may occur.
V. Pinhole
The phenomenon of pinholes is the biggest headache for workers engaged in glass screen printing. The reasons for the occurrence of pinholes are also varied, many of which are currently unexplained, and some are still problems of quality management. Pinholes are one of the most important inspection items in the inspection of printed products.
1 Dust and foreign objects attached to the plate. At the time of plate making, there are some sols mixed into the water wash image. In addition, when the emulsion is applied, dust may be mixed in, and pinholes may be formed on the screen. These tests can be found and repaired promptly if they are checked. If dust and foreign matter adhere to the screen, blocking the screen openings can also cause pinholes. Before the formal printing, carefully check the screen and eliminate the dirt on the plate.
2 substrate surface cleaning. Before printing, the glass plate should be pre-treated to make its surface clean and printed immediately. If the glass is processed, it will not be printed immediately and it will be recontaminated. After pre-treatment, dirt such as grease can be removed, and dust attached to the surface can also be removed.
Pay particular attention to the fingerprints of your hands that will adhere to the printed surface when you move the cloud glass by hand, forming pinholes when printing.
Six, bubbles
Substrate will appear bubbles on the ink after printing. The main reasons for bubbles are as follows:
1 The substrate is poorly processed before printing. Substrate attached to the surface of dust and oil traces and other substances.
2 bubbles in the ink. In order to adjust the ink, adding solvents and additives to stir, the ink will be mixed with some bubbles, if placed regardless of the low viscosity of the ink will naturally deaeration, high viscosity inks and some can not be natural deaeration. Some of these bubbles are naturally eliminated in the printing process due to the transfer of ink, while others become larger and larger. In order to remove these bubbles, defoamers should be used. The amount of defoamer added in the ink is generally about 0.1 to 1%. If j exceeds the specified amount, it will have a foaming effect.
After the ink is transferred, even if it is foamed, as long as the wettability of the substrate and the ink flowability are good, the bubbles on the surface of the printing ink film will be gradually eliminated, and the ink forms a flat printing ink film. If ink bubbles are not eliminated, the ink film will form a ring-shaped uneven film surface. Bubbles in general inks can also be degassed by the action of the screen when passing through the screen.
3 If the printing speed is too fast or the printing speed is uneven, bubbles may also be generated. The printing speed should be properly reduced to maintain the uniformity of the printing speed.
If none of the above measures can eliminate air bubbles in prints, consider using other types of ink.
Seven, net marks
Screen marks sometimes appear on the surface of the ink film. The main cause of the screen marks is the poor fluidity of the ink. During the screen printing process, when the printing plate is lifted, the ink transferred to the printing material fills the screen traces with its own flow, making the surface of the ink film smooth. If the ink has poor fluidity, when the screen printing plate is lifted, the ink flow is relatively small, and the screen marks cannot be filled, and a smooth and smooth ink film cannot be obtained. To prevent the appearance of screen marks on prints, the following method can be used.
1 Use leveling ink for printing.
2 Consider printing with slow drying inks. Increase the ink flow time to gradually level and cure the ink.
9 Try to use finer, monofilament mesh when making plates.
Eight, the printing position is not accurate
It is related to the screen size, the repeatability of the printing press, and the glass size.
Nine, the size of the finished ink film
After screen printing, the print size sometimes increases. The main reason for the increase in printing size is the relatively low viscosity of the ink and excessive fluidity; the size of the screen printing plate is also the cause of the increase in the printing size.
In order to avoid the ink flowability caused by the overflow of the ink after printing, causing the print size becomes larger, consider increasing the viscosity of the ink to reduce the ink's fluidity. In the production of screen printing plate inch, we must strictly guarantee the quality of the screen plate to ensure the screen plate tension.
Ten, the back of the dirty
Dirty back refers to the phenomenon that the ink on the lower glass sticks to the back of the upper glass when the glass is stacked. Printed glass can be isolated using release liners, spacers, and blown paper.
Eleven, printing ink leak
Part of the ink leaked from the printing plate is called ink leakage failure. The reason for this is: some of the squeegee has been damaged; the pressure of the squeegee is large; the gap between the plate and the substrate is too large; the plate frame is deformed, and the printing pressure is insufficient. : Inhomogeneous ink; fine mesh; too fast printing speed.
If the printing material and the ink are mixed with dust and printed without processing, the printing plate will be damaged due to the pressure of the squeegee; when the plate is underexposed, pinholes, etc., will cause the printing ink to leak. At this time, adhesive tapes, etc. can be used for emergency handling from the back of the plate.
If this operation is not very fast, the ink on the layout will be dried, and the whole of the plate will have to be wiped with solvent. Wipe plates are also the cause of delamination of the plate, so it is best avoided. The ink leakage of the printing plate often occurs in the ink staying part, so it is better to strengthen this part in the plate making.
Twelve, image distortion
The printing pressure applied to the plate by the squeegee during printing can make the line contact between the plate and the object to be printed. It should not exceed. If the printing pressure is too high, the printing plate contacts with the printing material and the screen may expand and contract, causing the printing image to be deformed. Screen printing is the smallest type of printing in various printing methods. If we forget this, we cannot print good prints.
If you cannot print without increasing the pressure, reduce the gap between the plate and the surface of the substrate so that the pressure on the blade can be reduced.
XIII.
Ink-wetting refers to the dot-like blotting of the graphics and dark-sounding parts of the substrate, which impairs the printing effect. Glass screen printing is easy and this phenomenon occurs. The reasons are as follows: printing speed and ink drying are too slow; ink layer is too thin; ink thixotropic; electrostatic effects; Dot blots. .
The improved methods are: improving the fluidity of the ink; using a quick-drying flux; printing with a high-viscosity ink as much as possible: increasing the wet film thickness of the ink, using an ink made of a pigment with a small oil absorption amount as much as possible: minimizing the influence of static electricity .
XIV. Flying ink.
Flying ink is the phenomenon of ink drawing. The causes are: the ink is unevenly grinded; the squeegee is slow from the printing when printing; the blank space around the printed image is too small; static electricity is generated, and the angle of the ink from the stencil is too small.
15. Electrostatic fault
Electrostatic current is generally very small, the potential difference is very large, and there may be a phenomenon of attraction, repulsion, conduction, and discharge.
1 adverse effects on screen printing. In the screen during printing, the rubber portion and the screen are charged by the pressure scraping of the blade rubber. If the screen itself is charged, it will affect the normal inking and produce blockage failures; it will be absorbed by the screen at the moment when the substrate is output.
a. The glass is easily charged when the heater wire is printed.
b. Static electricity makes it easy to absorb ink particles on the glass surface, making the glass surface unclean.
c. The human body's electric shock due to static electricity is caused by contact with a charged object, or by electrostatic discharges that generate spark discharges when grounded. Although the electric current generated by electric shock is small, no danger will occur, but electric shocks often occur, which will have an adverse effect on the operator's psychology.
2 method to prevent static electricity. The methods for preventing static electricity generation include: adjusting the ambient temperature and increasing the air humidity; the appropriate temperature is generally about 20° C. and the relative humidity is about 60%; static electricity can be transferred in the wet air; the net pitch is reduced, and the printing speed is reduced.
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