| 摘要 |
A transfer coating comprises pine rosin, camphor, ethylcellulose, paraffin wax, rubber and an azo dye, or the rosin may be replaced by gum damar, gum elami, or gum copal. The dye may be red or a combination of red and brown to form a transfer layer that is transparent to part of the spectrum but opaque to another part, or a pigment, e.g. carbon-black, may be used to form a transfer layer that is opaque to all wavelengths.ALSO:A sheet material for making negative transparencies comprises a transparent carrier foil, an intermediate layer and a transfer layer. The intermediate layer holds the other layers together, but prevents adhesion when the transfer layer is activated, and may be a continuous layer of frangible solid material. The transfer layer comprises a solvent-activable adhesion composition that is normally non-tacky and includes colouring material that is at least partly opaque to at least part of the light spectrum. The carrier foil may be of terephthalate polyester, polystyrene, polycarbonate or cellulose ester. The intermediate layer may be of dextrin, glycerol and sodium lauryl sulphate, or the dextrin may be replaced by gelatin, gum arabic or soap. The transfer layer may be of pine rosin, camphor, ethylcellulose, paraffin wax, rubber and an azo dye, or the rosin may be replaced by gum damar, gum elami, gum copal, polyvinyl ethers or esters, polyisobutylene or acrylic resins. The dye may be red or a combination of red and brown to form a transfer layer that is transparent to part of the spectrum but opaque to another part, or a pigment, e.g. carbon-black, may be used to form a transfer layer that is opaque to all wavelengths. The transparency is made by securing the sheet to a rigid support, with the transfer layer exposed, exposing it to the vapour of a solvent, e.g. toluene, that will activate the adhesive, pressing on to it a type forme, and then lifting the forme off. The forme carries with it portions of the transfer layer corresponding with the type, and so forms a negative transparency that can be used to prepare a printing plate by a photographic method. |
