| 摘要 |
PROBLEM TO BE SOLVED: To provide a packaging bag made of a thin thermoplastic synthetic resin material which can be easily processed and can prevent an appearance from being degraded by keeping joint force between both halves of a gusset at heat-fused portions between the gusset and front and rear walls of a bag body. SOLUTION: A single rectangular film of a thermoplastic synthetic resin is two-folded and also folded in an acute angle at a position slightly toward an end from a lengthwise center to form a gusset 2. Both left and right side rims of front and rear walls 1a, 1b are heat-fused to have end rims of both halves 2b, 2b of the gusset interposed at an upper part to provide four-face heat-fused parts 7b, 7b. Only side rims of the front and rear walls 1a, 1b are heat-fused below the four-face heat-fused parts 7b, 7b to provide two-face heat- fused parts 7a, 7a. Upper ends of the two-face heat-fused parts 7a, 7a, that is, regions connected with the four-face heat-fused parts 7b, 7b are formed into wide heat-fused parts 7c, 7c directing toward a widthwise center of the front and rear walls 1a, 1b from the four-face heat-fused parts 7b, 7b.
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