In the exposure process of network version in packaging and printing industry, the light curing reaction produced by emulsion is similar to the curing reaction of UV ink or other inks on printed matter. Effect of light source on exposure time of screen printing plate.
Screen latex is sensitive to the wavelength of the mixed spectrum of UV light, blue and purple light. Because the scraper repeatedly scrapes back and forth on the screen during printing, the exposure emulsion should completely cover the screen fiber after hardening.Effect of light source on exposure time of screen printing plate.
1. Exposure source.
The spectral characteristics and intensity of the light source are the decisive factors affecting the exposure. Screen emulsion is sensitive to UV in the wavelength range of 365nm-420nm. To cure the emulsion completely, it needs a certain energy light source to make it react chemically.
Generally speaking, incandescent lamps and floodlights emit limited light with a wavelength of 365nm-420nm, so they are not the best exposure light source choice. Metal halogen lamps, mercury lamps and some fluorescent lamps have photochemical light sources, but the proportion of UV light and blue violet light emitted by them is different. Effect of light source on exposure time of screen printing plate.
Except for special cases, all network emulsions can use the above three light sources as exposure sources. Because the proportion of UV light and blue violet light emitted by them is slightly different, the exposure time is also slightly different, and the images on the final screen are also somewhat different.Effect of light source on exposure time of screen printing plate.
The intensity of the light source refers to the energy of the light source reaching the network version emulsion. It is not the brightness of the light source seen by human eyes, but UV light is invisible light. The length of use of the exposure light source, the power of the exposure device and the distance from the light source to the screen are the three main factors affecting the light source intensity. During work, the light source intensity should be checked regularly, because the lamp tube will attenuate during use, resulting in the weakening of the light source intensity.Effect of light source on exposure time of screen printing plate.
2. Distance from light source to screen.
In the process of plate making, once the distance between the light source and the screen plate changes, the optimal exposure time must be recalculated, which is a square proportional relationship. For example, if the distance is doubled, the current exposure time is four times the original exposure time. On the contrary, when the distance is reduced by half, the exposure time is reduced to a quarter of the original.Effect of light source on exposure time of screen printing plate.