When you say multi-layer colored plastic characters, it should be double-layer or three-layer plastic characters.
The practice of double-layer plastic-absorbing characters: first, absorb a layer of bottom plate, then absorb a layer of characters on it, then write the manuscript of the upper words with kraft paper, and fix the upper words on the bottom layer with plexiglass glue. Then make a hole in the back of the ground floor, and then hollow it out with a small edge machine, so that light can penetrate in. The same is true for the third floor.
There is also a plane multi-layer color plastic suction, which is to suck a layer of white panel first and then stick a layer of transparent film.
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