The photopolymer is an ordinary polyvinyl alcohol PVA with an embedded photoreceptor. The following example illustrates the cross-linking of a pure photopolymer.
+UV light source
The kind of photosensitive adhesive is mainly used for the use of printing materials to require additional mixing with non-photosensitive polymer.
The above photoresist is fully sensitized. If you put it under ultraviolet light, you can complete its changes. This change is what has been mentioned earlier - light chain. The cross-linking or photopolymerization in the photo-sensitive adhesive causes the photo-resist to harden and solidify. In order to obtain the durability of the screen printing plate, it is necessary to specify the thickness of the photoresist, the number of screen meshes, the exposure time, and the solvent resistance.
The above diagram shows the diazo absorption ultraviolet light used in the plate-making photosensitive adhesive. The highest absorption point occurs at a wavelength of about 371 nanometers.
The clear photopolymer for use in plate-making photopolymers has desirable UV absorbance and has a wavelength of about 340 nm.
Ultraviolet lamps emit light waves at various wavelengths along the ultraviolet spectrum. The most important thing for screen printing personnel is to understand the different stages of sensitivity and reaction time of each photosensitizer. It is also important to know the aging of the UV lamp. The light radiation becomes weak and the exposure time should be adjusted accordingly. The plate printer equipped with a light meter can correct the fluctuation of ultraviolet light by automatically adjusting the exposure time. This can also lead to a balanced energy consumption during subsequent exposures.
Photosensitive adhesive performance of the three major families:
Finally, the characteristics of the three major families of Diazo, Dual Cure, and Pure Photopolymer were introduced. Although manufacturers produce different photosensitive adhesives, a comparison of the characteristics of the three types of photosensitive adhesives can be obtained.
(1) Diazo photosensitive adhesives are heat-sensitive, must be mixed, and have a short storage time. The solid content of the photosensitive adhesive is higher than that of the diazo photosensitive adhesive, which is more expensive. However, this type of photoresist can use standard exposure time, which is conducive to the correct reproduction of the image and is resistant to all screen printing inks.
(3) The pure photopolymer photosensitive adhesive usually has a relatively high solid content according to its composition, and has a short exposure time and a long storage time. Its price is more expensive than that of both nitrogen sensitive and dual photosensitizers. However, the photosensitive adhesive is different from the two photosensitive adhesives described above. It is non-thermosensitive and does not need to be mixed.
As mentioned earlier, today's highly developed screen printing technology has not changed its foundation, and although the development of the chemical industry has produced many kinds of photoresist, the basic principle of photoresist is still the same.
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