To solve problems in the knurling process applied to sheets for layering at least two sheets of sanitary paper such as facial tissue or toilet paper, etc. to be held in the layered state, wherein the quality of the product and the production efficiency are reduced because the sheets are easily broken or holes are easily bored if the knurling pressure is strengthened for increasing the joint strength and because the sheets are easily peeled if the pressure is weakened, and wherein the outside appearance may be impaired because of the knurling.
The sheets of the sanitary paper product are knurled for layering at least two sheets of the sanitary product to be held in the layered state. The joint area of the sheets by the knurling is composed of aggregation of linear joint parts which are separated and independent from one another in the longitudinal direction of the knurling, and the linear joint parts are left-right symmetrical or asymmetrical to the center line in the longitudinal direction of the knurling.
YASUI KENYA
MITSUZUKA TAKAYOSHI
FURUYA TOSHIYUKI
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