Stock material or miscellaneous articles – Hollow or container type article – Nonself-supporting tubular film or bag
Reexamination Certificate
2000-06-21
2003-07-22
Nolan, Sandra M. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Nonself-supporting tubular film or bag
C428S035400, C428S035500, C428S035700, C428S036700, C428S346000, C428S483000
Reexamination Certificate
active
06596355
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to packaging materials particularly usable in a high temperature atmosphere or environment such as in a state heated by a microwave oven (electronic oven) and also relates to packaging bags or containers formed of such packaging materials capable of automatically reducing inner pressure of the packaging bags and containers and preventing them from being broken or burst when they are heated by the microwave oven or like in contents filling-up condition.
Usually, frozen food and chilled food are frozen in a state contained and hermetically sealed in a packaging bag manufactured by a packaging material of plastic and a container having a cover member, covering a body (tray) of the container, which is formed of such packaging material. Further, it is to be noted that such packaging bags and containers may be called hereinlater totally as packaging bag or like for the sake of convenience. Such foods packaged are then conveyed and stored in the frozen state, and when used, the frozen food or chilled food is heated and cooked by means of microwave oven through a heating process. However, at a time when such packaged food is heated in the microwave oven, there is a fear of increasing an inner pressure of the sealed bag or package due to the expansion of inner air or steam generated from the contained food, breaking or bursting the bag or package with a large bursting voice and splashing the contained food, being dangerous and providing an inconvenient problem.
Incidentally, in a box lunch, daily dish, frozen food, chilled food and like, which are called as “box lunch” totally, herein, piece of dried bonito, fish flour, pepper, green laver, powdered cheese, mayonnaise, or like, which will be totally called as seasoning, is usually appended or added when the box lunch is sold in convenience stores, supermarkets or like. Such lunch box is heated and cooked by the microwave oven, for example, when eaten, and in such time, when the seasonings which are packaged in small packaging bags or like are heated together with the box lunch, there is a fear of swelling or expanding an air, steam or like in the small packaging bags, increasing an inner pressure of the bag and then breaking or bursting the bags with large bursting noise, the seasonings being splashed or scattered.
In order to obviate such problem, in the prior art, only the box lunch is heated by the microwave oven, for example, after taking out the small bag, pack or package, or the small bag is pierced before the heating to prevent the increasing an inner pressure of the packaging bag. However, it is inconvenient to previously take out the small bag or package from the box lunch or to pierce the same, also providing a troublesome problem and being inconvenient.
In order to obviate such inconveniences or problems, in the prior art, Japanese Patent Laid-open Publication No. HEI 9-40030 discloses a packaging container in which perforations as through holes for degassing or venting an inner gas in a plastic container are formed along a peeling (releasing) agent applied along a seal surface of the container due to the increasing of the inner pressure at the time of heating the container. Furthermore, Japanese Patent Laid-open Publication No. HEI 9-272180 discloses a package container in which such perforations as those in the above publication are formed on the seal surface along the peeling (releasing) agent applied between a heat-resistant thermoplastic resin layer and a sealant film. Such perforations are formed (occur) through the peeling of the sealed portion which has been sealed through the peeling agent layer by the increasing of the inner pressure in the container due to the heating in the microwave oven, for example. That is, through the peeling or releasing of the peeling agent layer of the sealed layer portion, the strength of the sealed portion is weakened, and as a result, the sealed portion is peeled along the released portion, and accordingly, the perforations (through holes) are formed to the container.
Furthermore, another prior art discloses a use of unwoven cloth as packaging material for preventing the package made of the unwoven cloth material from being burst such as disclosed in Japanese Patent Laid-open Publication No. HEI 9-249267, or further prior art discloses a formation of an unsealed portion for suppressing an increasing of an inner pressure of the container such as disclosed in Japanese Patent Laid-open Publication No. HEI 11-178713. Further, for example, Japanese Patent Laid-open Publication No. HEI 5-49462 discloses previous formation of small holes. All such prior art references teach the technique for previously forming the degassing holes to prevent the packages, bags or packs from being burst without providing a sealed condition of the package or container.
However, since the peeling (releasing) agent layers mentioned above are formed essentially to be easily peelable, there is a fear that such peeling agent layers are easily peeled by a pressure or impact applied in a usual transporting or storing time. Moreover, in the case of sealing the container or packaging bag by coating the peeling agent to the inner surface thereof, there is a fear of the peeling agent being contacted to the inner content by being easily bled from the sealed portion, thus being inconvenient. Because of such reasons, in the conventional art, it is necessary to take care of suitably forming the pattern shape of the peeling agent layer or to form the same so as not to be bled from the sealed portion. Therefore, there are provided some complicated matters in manufacturing processes or like.
Further, in the structure of forming the degassing holes, since the package or container is not in a sealed state, there is a fear that the inner content of the container or the seasonings in the small pack or package may be deteriorated through the contact to oxygen, steam or like during the transporting, selling or like process, which provides a significant problem.
SUMMARY OF THE INVENTION
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a packaging material particularly suitable for a packaging bag or a container usable in an atmosphere heated by, for example, a microwave oven and also provide a packaging bag or container formed of such packaging material, which is capable of being easily treated to be manufactured, being not peelable during usual transporting or storing time by any pressure or impact applied thereto and being heated safely in the microwave oven or like with an inner content being packaged therein.
This and other object can be achieved according to the present invention by providing, in a first aspect, a packaging material comprising:
a heat resistant base layer;
a sealant layer; and
a resin layer disposed at least a portion between the heat resistant base layer and the sealant layer,
the resin layer being composed of a resin material having a predetermined strength in a non-heated state of less than a room temperature and the strength is lowered in a heated state.
Further, according to a second aspect of the present invention, there is provided a packaging bag formed of a packaging material having a predetermined portion to be sealed, the packaging material comprising a sealant layer facing inside when a packaging bag is formed, a heat-resistant base layer and a resin layer disposed at least a portion between the heat-resistant base layer and the sealant layer, the resin layer being composed of a resin material having a predetermined strength in a non-heated state of less than a room temperature and the strength is lowered in a heated state, wherein the resin layer is formed so that the sealed portion has at least a portion which transverses from an inside portion towards an outside portion of the packaging bag.
Furthermore, according to a third aspect of the present invention, there is also provided a container having a container body and a container lid to be applie
Mita Kozo
Shigeta Kazunori
Takahagi Atsuko
Tsuchiya Hirotaka
Dai Nippon Printing Co. Ltd.
Ladas & Parry
Nolan Sandra M.
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