Package easy-to-open for photosensitive material

Details Package easy-to-open for photosensitive material Package easy-to-open for photosensitive material

2000-01-07

2001-07-31

Thibodeau, Paul (Department: 1773)

Stock material or miscellaneous articles

Hollow or container type article

Nonself-supporting tubular film or bag

C428S035700, C428S516000, C428S523000, C428S910000

Reexamination Certificate

active

06268029

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
This invention relates to a package easy-to-open for photosensitive material, particularly, an easy-to-open packaged photosensitive material. More particularly, it relates to a package easy-to-open for photosensitive material having excellent hermetic sealing properties, easy-to-tear performance, that is easy-to-open performance, excellent physical strength, such as impact strength or Gelbo test strength, high heat-sealing amenability, especially high chronological heat-sealing strength, and optimum light-shielding properties.
BACKGROUND OF THE INVENTION
With respect to photosensitive materials which lose the qualitative values by exposing them to light, known packaging bags can shield light completely. In such cases, the package is required to have not only complete light-shielding properties, but also freeness from ill effects on photographic performance, various physical strength (bursting strength, tear strength, impact puncture strength, Gelbo test strength, tensile strength, and the like), and have excellent heat sealing properties (heat-sealing strength, sealing properties against foreign matter, hot sealing strength or chronological heat sealing strength, and the like), anti-static properties, amenability to recycling, amenability to incineration, and the like. The following techniques, for example, have so far been disclosed for meeting these characteristics.
A film for packaging a photosensitive material having at least one layer of a light-shielding film comprised of a polyethylene based polymer and not less than 1 wt % of a light-shielding material, with not less than 50 wt % of the total polyethylene based polymer being linear low-density polyethylene (JP Patent Kokoku JP-B-2-2700). A packaging material for a photosensitive material comprised of a layered material made up of a substrate and a polyethylene based polymer layer formed on at least one surface of the substrate, in which the polyethylene based polymer layer is formed of not less than 50 wt % of linear low density polyethylene substantially free of a light shielding material and in which the layered material has a light-shielding layer sufficient for light shielding (JP Patent Kokoku JP-B-2-2701). An easy-to-open packaging material for a photosensitive material comprised of an inner light-shielding heat-sealable film layer containing a lubricant, a light-shielding material and not less than 50 wt % of the high-pressure low-density polyethylene resin, an aluminum foil layer layered on the light-shielding heat-sealable film layer, with a peeling strength of 400 g/15 mm width or more and having an anchor coating layer towards the light-shielding heat-sealable film layer, and a heat-resistant flexible sheet layer layered on the aluminum foil layer and having heat resistant properties of not less than 5° C. with respect to the light-shielding heat-sealable film layer (JP Utility Model Kokoku JP-B-2-19226).
SUMMARY OF THE DISCLOSURE
In the course of the present invention, the following problems have been found.
Of these, the technique disclosed in JP Patent Kokoku JP-B-2-2700 is not optimum in easy-to-open performance, although it is superior in tear strength, Gelbo test strength, impact puncture strength or have excellent heat sealing properties, while being superior in tight sealing performance or in complete light-shielding performance required of the photosensitive material. The technique disclosed in JP Patent Kokoku JP-B-2-2701 is again not optimum in easy-to-open performance, even although it is superior in tear strength or bending strength. On the other hand, with the technique disclosed in JP Utility Model Kokoku JP-B-2-19226, it is difficult to maintain optimum tight sealing and light-shielding properties in, for example, the physical distribution processes, if the packaging material is processed into a roll or formed into a package of the sheet-like photosensitive material weighing not less than 500 g, since the material is low in tear strength or impact puncture strength and is deteriorated in heat sealing strength with lapse of time.
For assuring optimum tight sealing properties and optimum light-shielding performance required of a packaging material, it is crucial to increase the tear strength, Gelbo test strength or impact puncture strength. However, the easy-to-open performance is similarly crucial for product designing. Thus it has been desired to satisfy the two contradictory properties, namely the high physical strength and high easy-to-open characteristics. The above techniques were not sufficient in this respect. It is therefore an object of the present invention to provide a package easy-to-open for photosensitive material such as an easy-to-open packaged photosensitive material wherein the package used therein satisfies two contradictory characteristics, namely the high physical strength, optimum tight sealing properties and optimum light-shielding properties, and easy-to-open characteristics, and which exhibits amenability to disposal and recycling without adversely affecting the quality, such as photographic performance of the photosensitive material.
Still further objects will become apparent in the entire disclosure.
The present invention provides a package easy-to-open for photosensitive material made by employing and processing thereto a layered film comprised of a biaxially stretched plastic film layer having high physical strength, such as tensile strength, Gelbo test strength or impact puncture strength, and a heat-sealable layer containing pre-set components, at least one of the above layers being a light-shielding layer and at least one layer other than the biaxially stretched plastic film being molecular-oriented in the flowing direction for assuring the easy-to-open performance.
Stretching means mechanically extending a material, such as a plastic film, at a temperature lower than the melting point, for orienting the molecules in a direction parallel to the stretching direction. By this processing, the tensile strength in the stretching direction is significantly improved to increase toughness. Therefore, if the material is stretched in mutually perpendicular directions (bi-axial stretching), the resulting material is increased in physical strength, such as tensile strength, Gelbo test strength or impact puncture strength in either directions, thus assuring complete hermetic sealing properties of the packaged photosensitive material employing the packaging material and the package therefrom. By additionally providing a light-shielding layer, complete light-shielding properties are also assured.
If a plastic film, for example, is molecular-oriented only in one direction, the physical properties of the film in a direction perpendicular to the direction of molecular orientation are lowered, such that the film is liable to be torn in the direction of molecular orientation. Therefore, if there are provided a biaxially stretched plastic film layer, having high physical strength, such as tensile strength, a thermoplastic resin film layer containing pre-set components and a light-shielding layer, it becomes possible to produce a packaged photosensitive material which is improved in impact-proofness during transport, is not lowered in heat-sealing strength during transport and which exhibits superior tight sealing and complete light shielding performance. In addition, by layering a thermoplastic resin film layer that is ready to be torn off in the molecular-oriented direction, the packaged photosensitive material further exhibits unidirectional tear-off characteristics, that is easy-to-open characteristics.
Thus, the present invention provides a package easy-to-open for photosensitive material such as an easy-to-open packaged photosensitive material made by employing and processing thereto a layered film exhibiting complete light-shielding characteristics, at least including a biaxially stretched plastic film layer and a thermoplastic resin film layer containing at least 5 wt % of an ethylene copolymer resin and/or a thermoplastic elastomer, at least

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