In a tetrahedral shape packaging container shown in a conventional technique, in comparison with a flat bag assembly, the tetrahedral shape packaging container having a minimum sheet area and a maximum content volume is obtained, the tetrahedral shape packaging container is used as a milk carton for drinking and a packaging container for storing a morsel size relish etc.
In a former milk carton, an inner face of the milk carton is formed by a laminated hard paper and it is possible to drink milk almost by inserting a straw into an upper opened small hole, however it is impossible to drink by unsealing a part of the milk carton using figure.
In a later packaging container for storing the morsel size relish being sold by a kiosk (register trademark) etc., by tearing apart and unsealing a part of the packaging container formed by a thin synthetic resin sheet, the relish is taken out from an inner portion and it is possible to eat the relish.
The conventional tetrahedral shape packaging container has a feature in which a content volume is the maximum in comparison with that of the flat bag, and further since the packaging container being composed of a truss structure the packaging container has a large strength, and also the packaging container may be crushed hardly against an outside force.
Accordingly, the tetrahedral shape packaging container is suitable to become a packaging container for food etc., which will be damaged by crushing during an overlap custody and during a transportation and further will be failed remarkably a quality of a stored article.
An inventor of the present invention has proposed a tetrahedral shape packaging container in WO 2007/119780 A1. WO 2007/119780 A1 discloses the packaging container having a tetrahedral-shaped bag assembly formed by closing two opposing sides of a pair of film or sheet portions facing each other by using a left side face seam formed between first and second corners of the left side face seam, and a right side face seam formed between first and second corners of the right side face seam, by closing one side of the other two sides of the pair of film or sheet portions facing each other by using a lower side face seam or a lower side face folded portion between the first corner of the left side face seam and the first corner of the right side face seam.
The above tetrahedral shape packaging container is formed closing the other side of the other two sides of the pair of film or sheet portions by an upper side face seam that is substantially orthogonal to the lower side face seam as a result of bringing together and joining the second corner of the left side face seam and the second corner of the right side face seam, and the left side face seam and the right side face seam being constructed as to be respective torn off when used as respective unsealed portions for tearing open the packaging container.
The above tetrahedral shape packaging container composed of a thin sheet is unsealed easily by finger, and in an unsealed state by tearing apart, the packaging container is formed with a dish shape and the packaging container is capable to use as a container (a vessel) as leaving it is.
Since the above tetrahedral shape packaging container can form the dish shape when the packaging container is unsealed as leaving it is, the user can eat a contents without a use of a dinnerware (a tableware) etc. Since it is unnecessary to wash the dinnerware etc, it can save a time and also since it can economize a detergent and a quantity of water, thereby it can correspond easily to an environment.
Further, it is unnecessary to use a foamed polystyrene tray used in the flat bag, and an environment destroy caused by the tray employment and a cost needed for a disposal of a waste matter, in particular it can restrain a discharge of a carbonic acid gas by burning and further it may safety be said that it will be a remarkable technique to improve a transit performance of the packaging container.