| 摘要 |
PURPOSE:To obtain a film positive plate for forming copy preventing paper by constituting the coarse part of a checkers-like pattern of lines consisting of 60 lines-10%, constituting the fine part of dots of 150 lines-10% and constituting a latent image of a part of the coarse part and the fine part. CONSTITUTION:A latent image pattern positive film 2 is superposed to the upper surface of a checkers-like positive film 1, a fine negative film 3 of 60 lines-90% consisting of the lines inclined by 45 deg. is superposed to the positive film 2, and an unexposed film 4 is superposed to the negative film 3 to form a film group consisting of four-layer structure. The 1st exposure is applied from the lower part of the film group by a light source 5. After the 1st exposure, the latent image pattern positive film 2 is replaced by a latent image pattern negative film 2', the fine negative film 3 is replaced by a dot negative film 3' consisting of 150 lines-90% and then the 2nd exposure is applied. After the 2nd exposure, the positive film 1 is replaced by a checker-like negative film 1', the net point negative film 2' is replaced by the fine negative film 3 and the 3rd exposure is applied. After the 3rd exposure, the negative film 2' is replaced by the positive film 2, the fine negative film 3 is replaced by the dot negative film 3' and then the 4th exposure is applied. |
