Abstract: A process for preparing a confidential postcard contains dehydrating a starting paper material containing 25 to 45% by weight of fibers of a thermoplastic resin and 55 to 75% by weight of fibers of a natural plant to thereby form a paper layer, heating, during or after drying, the paper layer at a temperature not lower than a softening point of the thermoplastic resin fibers to thereby obtain a paper sheet in which the fibers of the thermoplastic resin retain fiber shape and are entangled with the fibers of the natural plant, inscribing a statement to be kept confidential on the paper sheet, superposing the paper sheet to conceal the statement and attaching provisionally the superposed paper sheet by heating under pressure at a temperature not lower than a softening point of the thermoplastic resin fibers to obtain the confidential postcard. The confidential postcard is capable of being peeled off with the statement on the paper sheet being left intact.
December 6, 1990
Date of Patent:
December 24, 1991
Japan Pulp and Paper Co. Ltd., Miki Tokushu Paper Mfg. Co., Ltd., ECS-88 Co., Ltd.