GB1251751A - - Google Patents

Abstract

1,251,751. Photo-copying. W. R. GRACE & CO. Jan.16, 1969, No.2650/69. Headings G2A and G2H. Photo-copying apparatus comprises an actinic light source, a vacuum table 38 to which a liquid photo-curable composition is supplied by a dispenser 48 and levelled by a doctor blade 117, Fig. 10, and a transparent film holder 94 positionable over the levelled liquid composition with a transparency held thereby in contact with or spaced from the upper liquid surface by a spacer. Sequence of operations. A support layer and a framing mould are placed on the vacuum table 38 and vacuum applied through a duct 112. A carriage 40 is traversed to the right (as seen in Fig. 10), and on contacting a switch 56, a tube 44 and the dispenser 48 pivot about the axis of the dispenser to uncover slots through which warmed photo-curable composition is dispensed. The composition is continuously agitated prior to supply to prevent the entrapment of air. When the carriage 40 contacts a switch 58, dispensing is terminated and the members 44, 48 returned to the position shown. The carriage 40 is then traversed to the left (i.e. back to the position shown in Fig. 10) whereby the doctor blade 117 levels the composition on the vacuum table 38 and then a stream of heated air from a chamber 98 removes surface bubbles. Movement of the carriage past the switch 56 turns off the air stream. Excess composition is scraped off into a trough 118 which is later shielded from the actinic light so that the composition therein can be reused. If desired, a spacer may be positioned on the filled mould. The frame 94, to which a transparency adheres by suction is lowered. A bar 18 for generating ions to prevent static electricity accumulating on the transparency is provided. The exposure is made and the vacuum to the table 38 shut off to remove the support and photo-cured composition from the apparatus.