Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Screen other than for cathode-ray tube
Patent
1985-03-19
1986-09-09
Kittle, John E.
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Screen other than for cathode-ray tube
101129, 430280, 430308, 430309, 430312, 430313, 430328, 430331, G03C 500
Patent
active
046109412
ABSTRACT:
A process is described for improving the quality of images which have been formed by screen printing a liquid photo curable photopolymer. Images formed by screen printing, especially heavy coatings such as solder masks on printed wiring boards, inherently have indistinct boundaries, and may have feathered edges and photopolymer smears. These indistinct boundaries are removed and the resolution improved by a process which utilizes the oxygen inhibition effect characteristic of selected photopolymers. Thus, a screen printed image can be 0.001 inches thick at the center of a line, tapering off to 0.0001 inch thick smears, and these smears may be eliminated by irradiating the entire image with a moderate amount light energy, which cures the thick image portion and leaves a liquid boundary layer on the order of 0.0001 inch thick due to the oxygen effect. When washed with a mild solvent the liquid layer is removed, including the smears, leaving the thick image portion undisturbed. In a preferred embodiment a phototransparency is interposed over and out of contact with the images and then irradiated with non-collimated UV light so as to harden the thicker image sections while indistinct boundary areas are shielded by opaque phototransparency areas. Light undercutting due to the use of non-collimated light does not polymerize the smears because of the oxygen-inhibition effect and the thinness of the smears, and thus only the undersirable smears will be inhibited and left in the liquid state for removal to improve the resolution.
REFERENCES:
patent: 4260675 (1981-04-01), Sullivan
patent: 4324815 (1982-04-01), Mitani et al.
patent: 4436806 (1984-03-01), Rendulic et al.
patent: 4528261 (1985-07-01), Hauser
patent: 4548895 (1985-10-01), Irving et al.
Brown Laurence R.
Kittle John E.
Ryan Patrick J.
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