| 摘要 |
1,109,468. Preparing surfaces for printing. E. I. DU PONT DE NEMOURS & CO. 1 March, 1966 [2 March, 1965], No. 8982/66. Heading B6C. [Also in Division B5] The ink-receptive properties of a biaxially oriented, heat set film consisting essentially of a synthetic polymer, a cellulose derivative or regenerated cellulose, the film containing an inorganic filler, particularly a film for use in drawing offices, are improved by exposing the film to a uniform electric discharge preferably having an energy level below 15 electron volts and thereafter immediately heating the film to at least 90‹ C., particularly a temperature between 90‹ and 200‹ C. The heat treatment should follow the electrical discharge treatment prior to other operations on the film such as winding it on a roll and then unwinding it. The film may consist of polyethylene terephthalate or of polypropylene. The film may contain 2À5 to 10% by weight of the filler which may consist of hard inorganic particles of, for example, natural or synthetic silica of 4 to 6 micron size used to impart opacity and/or to provide a toothing surface for pencil receptivity. While conventional electrical discharge treatments impart ink-receptivity to films, the inked markings tend to feather or spread. The subsequent heat treatment of the present process prevents this and enables ink markings having a sharp definition to be obtained. The potential difference between the spaced electrodes used in the electrical discharge treatment may be of the order of 1000 volts to 100,000 volts or over, preferably 3000 volts to 4800 volts. Frequencies in the range of 3000 to 10,000 cycles supplied as a sine wave are preferred. The current supplied to the electrodes is preferably 0À3 RMS to 3À5 RMS amperes. Power to the electrodes may range from 10 to 100 watts per lineal inch of electrode length. The exposure time is preferably not less than 4 x 10<SP>-4</SP> second. |
