2 printing process
In the first step, ink is added to the etched recessed area of ​​the printing plate, which marks the beginning of the printing cycle. Some pad printers use open inked holes, while others use closed ink holes (such ink holes prevent solvents from escaping in the ink holes). The viscosity of the ink at this time must be sufficiently low so that the ink can spread flatly on the surface of the transfer printing plate and can enter the recessed etching image area.
In the second step, the ink on the convex portion (blank portion) of the printing plate is scraped with a squeegee to allow the ink to enter only the etched concave image area. Due to the high volatilization rate of the solvent, this will cause the ink on the surface of the image depression to be more viscous than the underlying ink (as shown in Figure 2).
In the third step, the print head applies pressure evenly to the rolling intaglio while extruding the air on the gravure. At this time, since the viscosity of the surface layer ink in the depressed region of the image is large, the ink can be moved away from the etching depression region and adhered to the print head.
In the fourth step, the solvent in the ink on the surface of the print head evaporates when the print head is removed from the pad, which makes the ink on the surface of the pad more viscous.
In the fifth step, when the surface of the print head comes into contact with the surface of the substrate, the viscosity of the ink on the surface of the print head is large, so that the ink leaves the print head and adheres to the surface of the substrate. At this point, the print head is designed to be curved and flexible, despite the fact that the print head may exert very great pressure, so that the image can be brought into contact with the substrate in a curved manner rather than a flat manner. In fact, a well-designed print head does not form a 0° contact with the substrate. This prevents air from remaining between the print head and the substrate. If air remains in the image, it can cause incomplete image transfer. .
In the sixth step, the head moves away from the surface of the substrate and returns to its original state. If the change factors involved in these six steps are properly controlled, the print head will leave the substrate cleanly, and a complete pad printing cycle will be completed. The pad head will be ready for the next pad printing cycle.
From the above six steps, it can be seen that one of the distinctive features inherent in pad printing inks is the ability of the inks to become sticky, and the pigment particle size and the proportion of pigments are very different from other types of inks. Many pad printing etched images have a depth of 25 μm, or even less. In this case, the pigment particles contained in the pad ink must be smaller than most screen printing inks. In addition, since the thickness of the ink film for pad printing is about 20% of the screen printing, the pigment concentration in the pad ink must be sufficiently high in order to obtain a sufficient hiding power.
Since pad printing inks have a very high viscosity change requirement, the solvent used in pad printing inks can be vaporized at a much faster rate than conventional screen printing inks. Otherwise, it is difficult to obtain a desired printing effect.
In the first step, ink is added to the etched recessed area of ​​the printing plate, which marks the beginning of the printing cycle. Some pad printers use open inked holes, while others use closed ink holes (such ink holes prevent solvents from escaping in the ink holes). The viscosity of the ink at this time must be sufficiently low so that the ink can spread flatly on the surface of the transfer printing plate and can enter the recessed etching image area.
In the second step, the ink on the convex portion (blank portion) of the printing plate is scraped with a squeegee to allow the ink to enter only the etched concave image area. Due to the high volatilization rate of the solvent, this will cause the ink on the surface of the image depression to be more viscous than the underlying ink (as shown in Figure 2).
In the third step, the print head applies pressure evenly to the rolling intaglio while extruding the air on the gravure. At this time, since the viscosity of the surface layer ink in the depressed region of the image is large, the ink can be moved away from the etching depression region and adhered to the print head.
In the fourth step, the solvent in the ink on the surface of the print head evaporates when the print head is removed from the pad, which makes the ink on the surface of the pad more viscous.
In the fifth step, when the surface of the print head comes into contact with the surface of the substrate, the viscosity of the ink on the surface of the print head is large, so that the ink leaves the print head and adheres to the surface of the substrate. At this point, the print head is designed to be curved and flexible, despite the fact that the print head may exert very great pressure, so that the image can be brought into contact with the substrate in a curved manner rather than a flat manner. In fact, a well-designed print head does not form a 0° contact with the substrate. This prevents air from remaining between the print head and the substrate. If air remains in the image, it can cause incomplete image transfer. .
In the sixth step, the head moves away from the surface of the substrate and returns to its original state. If the change factors involved in these six steps are properly controlled, the print head will leave the substrate cleanly, and a complete pad printing cycle will be completed. The pad head will be ready for the next pad printing cycle.
From the above six steps, it can be seen that one of the distinctive features inherent in pad printing inks is the ability of the inks to become sticky, and the pigment particle size and the proportion of pigments are very different from other types of inks. Many pad printing etched images have a depth of 25 μm, or even less. In this case, the pigment particles contained in the pad ink must be smaller than most screen printing inks. In addition, since the thickness of the ink film for pad printing is about 20% of the screen printing, the pigment concentration in the pad ink must be sufficiently high in order to obtain a sufficient hiding power.
Since pad printing inks have a very high viscosity change requirement, the solvent used in pad printing inks can be vaporized at a much faster rate than conventional screen printing inks. Otherwise, it is difficult to obtain a desired printing effect.
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