U.S. patent application number 10/580831 was filed with the patent office on 2007-05-17 for packaging container for microwave oven.
Invention is credited to Keizou Kanzaki.
Application Number | 20070110856 10/580831 |
Document ID | / |
Family ID | 34635631 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070110856 |
Kind Code |
A1 |
Kanzaki; Keizou |
May 17, 2007 |
Packaging container for microwave oven
Abstract
A packaging container for a microwave oven. Completion of
heating of the container contents and automatic opening of the
container can be easily recognized. This can be achieved without
requiring a special member and complex steps, but by processing
wrapping materials constructing the packaging container. Also
provided is a packaging container for a microwave oven, where
danger, including spilling of the contents of the container and
burning by touching an opening section occurring in heating by a
microwave oven, can be avoided. Further provided is a packaging
container for a microwave oven, sealed by heat-sealing plastic
films and having a steam vent seal section having a weakened
section. The steam vent seal section has mark emerging means, and
when the steam vent seal section is separated and opened, the means
shows different surface- and back face-wrapping materials
constituting the steam vent seal section, enabling recognition of
opening.
Inventors: |
Kanzaki; Keizou; (Kanagawa,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
34635631 |
Appl. No.: |
10/580831 |
Filed: |
November 19, 2004 |
PCT Filed: |
November 19, 2004 |
PCT NO: |
PCT/JP04/17278 |
371 Date: |
May 26, 2006 |
Current U.S.
Class: |
426/107 |
Current CPC
Class: |
B65D 81/3461 20130101;
B65D 75/008 20130101; B65D 2205/00 20130101; B65D 77/225 20130101;
B65D 2581/3436 20130101 |
Class at
Publication: |
426/107 |
International
Class: |
B65D 81/34 20060101
B65D081/34 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2003 |
JP |
2003-399237 |
Oct 1, 2004 |
JP |
2004-290168 |
Claims
1. A packaging container for a microwave oven hermetically sealed
by heat-sealing with a plastic film, the packaging container
comprising a vapor release seal part having a weakened part,
characterized in that the vapor release seal part is provided with
a mark developing means with which exfoliation opening of the vapor
release seal part can be recognized by a difference between surface
and back packaging materials constituting the vapor release seal
part.
2. A packaging container for a microwave oven according to claim 1,
characterized in that the mark developing means is constituted by
providing a vapor release seal part of one plastic film
constituting the packaging container with a printing layer having a
pattern having void parts and by providing a vapor release seal
part of the other plastic film constituting the packaging container
with a printing layer having patterns corresponding to the void
parts.
3. A packaging container for a microwave oven according to claim 1,
characterized in that the mark developing means is constituted by
coloring a vapor release seal part of one plastic film constituting
the packaging container a first color and by coloring a vapor
release seal part of the other plastic film constituting the
packaging container a second color different from the first
color.
4. (canceled)
5. (canceled)
6. A packaging container for a microwave oven according to claim 1,
characterized in that the vapor release seal part is formed
continuously along a peripheral edge seal part of the packing
container.
7. A packaging container for a microwave oven according to claim 1,
characterized in that the vapor release seal part is formed
separately from the peripheral edge seal part of the packing
container.
8. A packaging container for a microwave oven according to claim 1,
characterized in that the vapor release seal part is provided with
a through-hole, a semi through-hole, or a slit to thereby form a
weakened part.
9. A packaging container for a microwave oven according to claim 1,
characterized in that a cutout is formed in the packing container
inwardly into the container and a periphery edge of the cutout is
heat-sealed to thereby form the vapor release seal part having a
weakened part.
10. A packaging container for a microwave oven according to claim
1, characterized in that a pouring port forming means is arranged
near the vapor release seal part.
11. A packaging container for a microwave oven according to claim
1, characterized in that the packaging container comprises a
packaging pouch hermetically sealed by heat-sealing with a plastic
film.
12. A packaging container for a microwave oven according to claim
11, characterized in that the packaging pouch comprises a standing
pouch.
13. A packaging container for a microwave oven according to claim
11, characterized in that the packaging pouch comprises a packaging
pouch having a branched section.
14. A packaging container for a microwave oven according to claim
1, characterized in that the packaging container is hermetically
sealed by heat-sealing of a container main body having a flange
part with a lid composed of a plastic film.
15. A packaging container for a microwave oven according to claim
14, characterized in that the vapor release seal part is formed by
causing a heat-seal part between the flange part of the packaging
container and the lid to project toward an inside of the container.
Description
TECHNICAL FIELD
[0001] The present invention relates to a packaging container for a
microwave oven such as a packaging pouch, a cup, or a tray filled
with contents such as a retort food containing a liquid substance,
a solid substance, or a mixture of them. The packaging container of
the present invention is capable of automatically releasing water
vapor or the like to be generated inside the packaging container,
preventing the rupture and deformation of the packaging container,
scattering of the content, and allowing one to easily recognize the
fact that the packaging container is opened under heating in a
microwave oven.
BACKGROUND ART
[0002] Heating of a packing container such as a packaging pouch, a
cup, or a tray hermetically filled with a retort food, a frozen
food, or the like in a microwave oven increases the pressure inside
the pouch and a container due to water vapor or the like to be
generated from contents under heating. The packaging container may
tear, and the content may scatter, to thereby make the inside of
the microwave oven dirty or harm a human body by burning or the
like.
[0003] Thus, before heat-cooking such a packaging container in a
microwave oven, methods of preventing tearing of the packaging
container are employed. That is, the packaging container is partly
opened in advance or the packaging container itself is pierced, to
thereby discharge out water vapor or the like to be generated
inside the packaging container.
[0004] However, such methods involve much time and effort for a
general consumer. Further, when these methods are applied, the
methods have disadvantages in that a flavor of the contents cooked
by heating is lost because the water vapor generated by microwave
heating is immediately discharged out of the packaging container
and a heat steaming effect of the water vapor on the content is
reduced.
[0005] To overcome such disadvantages, there have been proposed
various packaging containers each provided with an automatic
opening mechanism with which an increase in the inner pressure of
the packaging container under heating in a microwave oven is
automatically relieved (see, for example, Patent Documents 1 to
4).
[0006] In each of those packaging containers, the opening of the
packaging container by heating in a microwave oven can be judged on
the basis of the sound of water vapor to be released on and after
opening and clouding of the inside of the microwave oven due to the
water vapor. However, this method of judging the opening is hard to
recognize and may cause one to ignore the opening of a packaging
container.
[0007] To overcome such disadvantages, there has been proposed a
container, a food pouch, and the like, each of which is
specifically designed to be heated in a microwave oven and is
coupled with a separate alarm seedling (see Patent Document 5).
However, each of those containers requires a step of using a
high-cost, separate alarm whistle and coupling the alarm whistle.
Accordingly, there arises, for example, a problem in that the
production process of each of the containers becomes complicated,
which results in an increase in cost.
[0008] Meanwhile, there has been also proposed an ordinary
packaging pouch not heated in a microwave oven, a heat seal part of
which is provided with a hidden printing layer so that a letter or
symbol appears upon opening of the pouch to prevent, for example,
mixing of a toxic substance or the like (see, for example, Patent
Document 6). However, in such a packaging pouch, it becomes
difficult to recognize a letter or symbol appearing upon opening
unless an area of a portion to be provided with the hidden printing
layer is equal to or larger than a certain value. Therefore, it has
not been possible to apply this technique to a vapor release seal
part opening automatically upon heating of a packaging container
for a microwave oven such as a packaging pouch, a cup, or a
tray.
Patent Document 1: JP 10-59433 A
Patent Document 2: JP 10-95471 A
Patent Document 3: JP 10-101154 A
Patent Document 4: JP 2002-249176 A
Patent Document 5: JP 06-245861 A
Patent Document 6: Japanese Utility Model Application Laid-open No.
62-90334 A
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0009] Therefore, an object of the present invention is to provide
a packaging container for a microwave oven such as a packaging
pouch, a cup, or a tray constituted by a packaging material which
itself is processed with no need for a special member or a
complicated step so that one can easily recognize that heat-cooking
of contents in the packaging container has been completed and the
packaging container has automatically opened. Another object of the
present invention is to provide a packaging container for a
microwave oven capable of avoiding a risk of spilling contents in
the packaging container or a risk of contact with an opening to
cause a heat injury upon heating in a microwave oven.
Means for Solving the Problems
[0010] The inventors of the present invention have made extensive
studies. As a result, they have found that the above-mentioned
problems can be solved by providing, by means of printing
processing or the like, a vapor release seal part having a weakened
part of each of surface and back packaging materials constituting a
packaging container for a microwave oven such as a packaging pouch,
a cup, or a tray with a mark developing means with which
exfoliation opening of the vapor release seal part can be
recognized by a difference between the surface and back packaging
materials. Thus, the inventors have completed the present
invention.
[0011] That is, the present invention employs the following
constitutions 1 to 15.
[0012] 1. A packaging container for a microwave oven hermetically
sealed by heat-sealing with a plastic film, the packaging container
including a vapor release seal part having a weakened part,
characterized in that the vapor release seal part is provided with
a mark developing means with which exfoliation opening of the vapor
release seal part can be recognized by a difference between surface
and back packaging materials constituting the vapor release seal
part.
[0013] 2. A packaging container for a microwave oven according to
the above item 1, characterized in that the mark developing means
is constituted by providing a vapor release seal part of one
plastic film constituting the packaging container with a printing
layer having a pattern having a void part and by providing a vapor
release seal part of the other plastic film constituting the
packaging container with a printing layer having a pattern
corresponding to the void part.
[0014] 3. A packaging container for a microwave oven according to
the above item 1, characterized in that the mark developing means
is constituted by coloring a vapor release seal part of one plastic
film constituting the packaging container a first color and by
coloring a vapor release seal part of the other plastic film
constituting the packaging container a second color different from
the first color.
[0015] 4. A packaging container for a microwave oven according to
the above item 1, characterized by the mark developing means
comprising a peeling surface of which opacifies or whitens in
association with peeling due to cohesion failure of the vapor
release seal parts of the plastic films constituting the packaging
container.
[0016] 5. A packaging container for a microwave oven according to
the above item 4, characterized in that the mark developing means
is constituted by providing a color printing layer for an upper
layer of the vapor release seal part of at least one plastic film
constituting the packaging container on a side of an external
surface of the container.
[0017] 6. A packaging container for a microwave oven according to
any one of the above items 1 to 5, characterized in that the vapor
release seal part is formed continuously along the peripheral edge
seal part of the packing container.
[0018] 7. A packaging container for a microwave oven according to
any one of the above items 1 to 5, characterized in that the vapor
release seal part is formed separately from the peripheral edge
seal part of the packing container.
[0019] 8. A packaging container for a microwave oven according to
any one of the above items 1 to 7, characterized in that the vapor
release seal part is provided with a through-hole, a semi
through-hole, or a slit to thereby form a weakened part.
[0020] 9. A packaging container for a microwave oven according to
any one of the above items 1 to 5, characterized in that a notch is
formed inwardly into the container and a periphery edge of the
notch is heat sealed to thereby form the vapor release seal part
having the weakened part.
[0021] 10. A packaging container for a microwave oven according to
any one of the above items 1 to 9, characterized in that a pouring
port forming means is arranged near the vapor release seal
part.
[0022] 11. A packaging container for a microwave oven according to
any one of the above items 1 to 10, characterized in that the
packaging container includes a packaging pouch hermetically
heat-sealed with a plastic film.
[0023] 12. A packaging container for a microwave oven according to
the above item 11, characterized in that the packaging pouch
includes a standing pouch.
[0024] 13. A packaging container for a microwave oven according to
the above item 11 or 12, characterized in that the packaging pouch
includes a packaging pouch having a branched section.
[0025] 14. A packaging container for a microwave oven according to
any one of the above items 1 to 5, characterized in that the
packaging container is hermetically sealed by heat-sealing of a
container main body having a flange part with a lid composed of a
plastic film.
[0026] 15. A packaging container for a microwave oven according to
the above item 14, characterized in that the vapor release seal
part is formed by causing a heat seal part between the flange part
of the packaging container and the lid to project toward an inside
of the container.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] [FIG. 1] A view showing an example of the application of the
present invention to a packaging pouch for a microwave oven.
[0028] [FIG. 2] Views each explaining a mark developing means to be
provided for a vapor release seal part of the packaging pouch of
FIG. 1.
[0029] [FIGS. 3] Views each explaining a mark developing upon
exfoliation opening of the vapor release seal part of the packaging
pouch of FIG. 1.
[0030] [FIG. 4] A view showing another example of the application
of the present invention to a packaging pouch for a microwave
oven.
[0031] [FIG. 5] A view showing another example of the application
of the present invention to a packaging pouch for a microwave
oven.
[0032] [FIG. 6] A view showing another example of the application
of the present invention to a packaging pouch for a microwave
oven.
[0033] [FIG. 7] A view showing another example of the application
of the present invention to a packaging pouch for a microwave
oven.
[0034] [FIG. 8] A view showing another example of the application
of the present invention to a packaging pouch for a microwave
oven.
[0035] [FIG. 9] A view showing an example of the application of the
present invention to a tray-shaped container for a microwave
oven.
[0036] [FIGS. 10] A plan view of the container of FIG. 9.
[0037] [FIGS. 11] Schematic views each showing the section of the
vapor release seal part of the container of FIG. 9.
DESCRIPTION OF SYMBOLS
[0038] 1, 21, 31, 41, 51, 61 packaging pouch for a microwave oven
[0039] 2, 112 peripheral edge seal part [0040] 3, 43, 53, 113 vapor
release seal part [0041] 4, 44, 54 weakened part [0042] 5 notch
[0043] 6 perforation [0044] 7 bottom folding part [0045] 11 void
part [0046] 12,14 solid pattern part [0047] 13 pattern [0048] 52
branched section [0049] 56 part (opposing part) [0050] 57 opening
preventive mean [0051] 58 branched section base part [0052] 100
packaging container for a microwave oven [0053] 101 container main
body [0054] 102 flange part [0055] 103 lid [0056] 115 opening
part
MODE FOR CARRYING OUT THE INVENTION
[0057] Plastic films forming a packaging container such as a
packaging pouch, a cup, and a tray for a microwave oven in the
present invention employ a plastic material having heat sealing
property and generally used for production of a packaging
container. Examples of such a plastic material include: monolayer
films or sheets each formed of a thermoplastic resin having a heat
sealing property; and multilayer films, sheets, or the like each
prepared by laminating a thermoplastic resin having heat sealing
property and other thermoplastic resin(s) or the like.
[0058] Examples of such a plastic material having a heat sealing
property include: a known olefin resin such as a low density
polyethylene, a linear low density polyethylene, a medium density
polyethylene, a high density polyethylene, a polypropylene, a
propylene-ethylene copolymer, an ethylene-vinyl acetate copolymer,
an olefin-based resin subjected to graft modification with an
ethylene-based unsaturated carboxylic acid or an anhydride thereof;
a polyamide resin or copolyamide resin having a relatively low
melting point or relatively low softening point; a polyester resin
or copolyester resin; and a polycarbonate resin.
[0059] Examples of other plastic material(s) to be laminated with
the plastic materials having heat sealing property include a
thermoplastic resin or various barrier films each having heat
sealing property or having no heat sealing property.
[0060] Examples of such thermoplastic resin can include:
polyolefins such as crystalline polypropylene, a crystalline
propylene-ethylene copolymer, crystalline polybutene-1, crystalline
poly4-methylpentene-1, low-density polyethylene, medium-density
polyethylene, high-density polyethylene, an ethylene-vinyl acetate
copolymer (EVA), a saponified product of an EVA, an ethylene-ethyl
acrylate copolymer (EEA), and an ion-crosslinked olefin copolymer
(ionomer); aromatic vinyl copolymers such as polystyrene and a
styrene-butadiene copolymer; vinyl halide polymers such as
polyvinyl chloride and a vinylidene chloride resin; a polyacrylic
resin; nitrile polymers such as an acrylonitrile-styrene copolymer
and an acrylonitrile-styrene-butadiene copolymer; polyesters such
as polyethylene terephthalate and polytetramethylene terephthalate;
various polycarbonates; a fluorine-based resin; and polyacetals
such as polyoxymethylene. Those thermoplastic resins can be used
independently, or with being blended with two or more kinds of
them. Furthermore, those thermoplastic resins may be used to be
blended with various additives.
[0061] In addition, examples of various barrier films can include:
a silica-deposited polyester film; an alumina-deposited polyester
film, a silica-deposited nylon film, an alumina-deposited nylon
film, an alumina-deposited polypropylene film, a carbon
film-deposited polyester film, and a carbon film-deposited nylon
film; a co-deposited film obtained by simultaneously
vapor-depositing alumina and silica onto a base film such as a
polyester film or a nylon film; a film obtained by co-extruding
nylon 6/metha-xylylene diamine nylon 6 and a film obtained by
co-extruding a polypropylene/ethylene-vinyl alcohol copolymer; an
organic resin-coated film such as a polyvinyl alcohol-coated
polypropylene film, a polyvinyl alcohol-coated polyester film, a
polyvinyl alcohol-coated nylon film, a polyacrylic acid-based
resin-coated polyester film, a polyacrylic acid-based resin-coated
nylon film, a polyacrylic acid-based resin-coated polypropylene
film, a polyglycolic acid resin-coated polyester film, a
polyglycolic acid resin-coated nylon film, and a polyglycolic acid
resin-coated polypropylene film; and a film obtained by coating a
hybrid coating material consisting of an organic resin material and
an inorganic material on a base film such as a polyester film, a
nylon film, a polypropylene film, and the like. Those barrier films
can be used independently, or with being combined with two or more
kinds of barrier films.
[0062] In the present invention, a packaging container for a
microwave oven such as a packaging pouch, a cup, or a tray is
produced by forming or molding an unoriented, uniaxially oriented,
or biaxially oriented film or sheet constituted by any one of the
above plastic materials into a pouch and the like according to an
ordinary method. When a packaging pouch is produced by means of a
laminated film composed of a thermoplastic resin having
heat-sealing property and a thermoplastic resin having no
heat-sealing property, heat-sealing is performed in a state where
thermoplastic resin layers each having a heat-sealing property are
arranged so that each of them serves as an inner surface. An
adhesive resin layer can be interposed between adjacent layers
constituting the laminated film as required.
[0063] Next, the packaging container for a microwave oven of the
present invention will be described in detail on the basis of the
drawings in conjunction with an example of the application of the
present invention to a packaging pouch. However, the following
specific examples do not limit the present invention.
[0064] FIGS. 1 to 3 are views of the present invention, each
showing an example of a packaging pouch for a microwave oven
provided with a vapor release seal part having a weakened part.
FIG. 1 is a front view of the packaging pouch, and FIG. 2 are
enlarged schematic views each explaining the mark developing means
to be provided for the vapor release seal part of the packaging
pouch. In addition, FIG. 3 are enlarged schematic views each
explaining a mark developing owing to the exfoliation opening of
the vapor release seal part upon heating of the packaging pouch in
a microwave oven.
[0065] The packaging pouch 1 for a microwave oven was produced by
subjecting a peripheral edge seal part 2 of a packaging material
(plastic film) constituting the surface and back of the pouch to
heat-sealing and by providing a corner part of the pouch with a
vapor release seal part 3 having a weakened part 4. Notches 5 are
formed in the upper part of the pouch to facilitate an opening of
the pouch after the completion of cooking by means of a microwave
oven.
[0066] In the packaging pouch, the weakened part 4 is formed by
providing the vapor release seal part 3 with a single through-hole.
The weakened part can also be formed by providing a semi
through-hole or a slit instead of the through-hole. The vapor
release seal part 3 may be provided with multiple through-holes,
semi through-holes, or slits.
[0067] As shown in FIG. 2(A), a pattern 12 having a void part 11 is
solid-printed on the vapor release seal part 3 of the packaging
material of one of the surface and the back constituting the
packaging pouch 1. Meanwhile, as shown in FIG. 2(B), a pattern 13
corresponding to the void part 11 of FIG. 2(A) is printed on the
vapor release seal part 3 of the other packaging material. The
pattern 13 is preferably formed to be larger than the void part 11
so that alignment upon heat-sealing of the packaging pouch may be
easily performed.
[0068] The vapor release seal part 3 is formed by superimposing the
void part 11 of each of the surface and back packaging materials
constituting the packaging pouch 1 and the pattern 13 corresponding
to the part on each other, and by subjecting the resultant to
heat-sealing. As a result, as shown in FIG. 2(C), the vapor release
seal part 3 is provided with a pattern 14, the entire surface of
which is uniformly solid-printed. The weakened part 4 is formed in
the vapor release seal part 3 by providing a through-hole
simultaneously with or after the heat-sealing.
[0069] When contents such as curry or stew is added and
hermetically sealed in the packaging pouch 1 and the packaging
pouch 1 is heated in a microwave oven, an inner pressure of the
packaging pouch 1 increases owing to water vapor or the like
generated from the content, and then the packaging pouch 1 expands
from its center point P toward its peripheral edge part. As a
result, stress concentrates on a part B of the vapor release seal
part 3 closest to the center point P, whereby the breakage and
opening of the vapor release seal part 3 starts.
[0070] The vapor release seal part 3 peels and regresses owing to
the stress concentration. When the peeling reaches the weakened
part 4, the packaging pouch 1 partially opens so that water vapor
or the like is discharged to the outside. Accordingly, the rupture
of the packaging pouch 1 can be prevented.
[0071] As shown in FIGS. 3(A) and 3(B), the solid-printed pattern
12 having the void part 11 printed on the vapor release seal part
of each packaging material constituting the packaging pouch 1 and
the pattern 13 corresponding to the void part 11 develop in the
vapor release seal part 3 that has peeled and opened. As a result,
one can easily recognize automatical opening of the packaging pouch
1 and completion of the heat-cooking of the contents. The pattern
to be formed in the vapor release seal part can be arbitrarily
selected. In addition, the pattern can be provided for not only the
vapor release seal part but also a part adjacent to the vapor
release seal part.
[0072] In the above example, the mark developing means was
constituted by printing a pattern on the vapor release seal part of
each packaging material constituting the packaging pouch. The mark
developing means can also be constituted by coloring the vapor
release seal part of one packaging material constituting the
packaging pouch a first color and by coloring the vapor release
seal part of the other packaging material a second color different
from the first color.
[0073] For example, when printing is performed so that the surface
of the vapor release seal part of the packaging pouch has a red
color and the back of the part has a blue color, the vapor release
seal part is colored to be purple after heat-sealing. When the
packaging pouch is heated in a microwave oven so that the vapor
release seal part peels and opens, the color of the surface changes
to red and the color of the back changes to blue. Therefore, one
can easily recognize that the heat-cooking of the content has been
completed and the pouch has automatically opened.
[0074] In the above example, the corner part of the packaging pouch
1 was provided with the vapor release seal part 3 of a circular
shape in such a manner that the vapor release seal part 3 would be
separated from the peripheral edge seal part 2. The position where
the vapor release seal part 3 is placed, the number of the vapor
release seal parts 3, the shape and dimensions of each of the vapor
release seal parts 3, and the like can be arbitrarily selected. The
shape, dimensions, and the like of the weakened part 4 to be formed
in the vapor release seal part 3 can also be appropriately
selected. In addition, any one of the methods such as machine work
(for example, punching) and laser processing can be arbitrarily
selected as a method of forming the weakened part 4.
[0075] FIGS. 4 to 6 are views each showing another example of the
application of the present invention to a packaging pouch for a
microwave oven.
[0076] A packaging pouch 21 of FIG. 4 shows an example of the
application of the present invention to a standing pouch. In this
example, the shape of the vapor release seal part 3 to be formed in
a corner part of the packaging pouch 21 is substantially a
triangle, and the bottom of the packaging pouch 21 is provided with
a bottom folding part 7. The other constitutions of the packaging
pouch are the same as those of the packaging pouch 1 of FIG. 1.
[0077] Of course, the shape of the vapor release seal part 3 can be
appropriately changed to an oblong, a quadrangle, a trapezoid, or
the like instead of the triangle.
[0078] FIG. 5 is a view showing another example of the application
of the present invention to a standing pouch.
[0079] In this packaging pouch 31, the shape of the vapor release
seal part 3 is substantially a quadrangle, and the vapor release
part 3 is connected to the peripheral edge seal part of a corner
part. In addition, a perforation 6 is formed to facilitate the
opening of the pouch. The other constitutions of the packaging
pouch are the same as those of the packaging pouch 21 of FIG.
4.
[0080] FIG. 6 is a view showing another example of the packaging
pouch for a microwave oven of the present invention.
[0081] In a packaging pouch 41, a cutout 44 serving as a weakened
part and directed toward the inside of the pouch is arranged near a
corner part of the packaging pouch 41. A vapor release seal part 43
having a weakened part is formed by subjecting the peripheral edge
part of the cutout 44 to heat-sealing. A part distinguished from
the pouch main body of the packaging pouch 41 by the cutout 44 is
provided with an opening facilitating means 6 such as a perforation
or laser processing. The peripheral edge seal part 2 is provided
with the notches 5. A pouring port (not shown) can be formed in the
packaging pouch 41 by opening the pouch 41 along the opening
facilitating means 6 from the notch 5 after the completion of
heating in a microwave oven.
[0082] FIG. 7 is a perspective view showing another example of the
application of the present invention to a packaging pouch for a
microwave oven.
[0083] A foldable branched section 52 that can be lodged to one
surface of a packaging pouch main body is formed in this packaging
pouch 51. In addition, an upper edge part of the branched section
52 is provided with a cutout 54 directed toward the inside of the
pouch. The peripheral edge part of the cutout 54 is subjected to
heat-sealing so as to have a width equal to or narrower than that
of the peripheral edge seal part 2, whereby a vapor release seal
part 53 having a weakened part is formed. In addition, each of the
water vapor release seal part 53 of the packaging pouch 51 and a
part 55 adjacent to the part 53 is provided with the mark
developing means based on printed patterns as in the case of the
packaging pouch 1 shown in each of FIGS. 1 to 3.
[0084] In addition, in the packaging pouch 51 provided with the
branched section 52, opening preventive means 57 based on
heat-sealing are arranged at four sites in the branched section 52
of the packaging pouch main body and a part (opposing part) 56
opposed to the branched section 52 in order to prevent the break of
the packaging pouch and the leakage of a content due to the peeling
of the heat-seal of the pouch at a base part 58 of the branched
section 52.
[0085] FIG. 8 is a perspective view showing another example of the
application of the present invention to a packaging pouch for a
microwave oven.
[0086] This packaging pouch 61 is produced by removing the outside
of the opening preventive means 57 provided for the branched
section 52 in the packaging pouch 51 of FIG. 7 along the outer
periphery of the means 57. The other constitutions of the packaging
pouch 61 are the same as those of the packaging pouch 51 of FIG.
7.
[0087] In the examples of FIGS. 1 to 8, description has been given
of an example of the application of the present invention to a
packaging pouch for a microwave oven. Of course, the present
invention is applicable to any packaging container for a microwave
oven except a packaging pouch such as a cup, a tray, or a box.
[0088] Any one of such containers is provided with a flange part. A
vapor release seal part having a weakened part is formed in the
flange part. The mark developing means of the present invention can
be provided for the vapor release seal part or the vicinity of the
part.
[0089] FIGS. 9 to 11 are views showing an example of the
application of the present invention to a tray-shaped container for
a microwave oven. FIG. 9 is a perspective view of the container,
and FIG. 10 is a plan view of the container. In addition, FIG. 11
are schematic views each showing the section of a vapor release
seal part of the container. FIG. 11(A) is a view showing a state
before the peeling of the vapor release seal part, and FIG. 11(B)
is a view showing a state after the peeling of the vapor release
seal part.
[0090] The packaging container 100 for a microwave oven is
hermetically sealed by subjecting a flange part 102 of a container
main body 101 made of polypropylene to heat-sealing with a lid 103.
A vapor release seal part 113 is formed in one corner portion of
the container by causing a peripheral edge heat seal part 112 to
project in a U-shape fashion toward the inside of the container. In
addition, an opening part 115 for opening the lid 103 after the
container has been subjected to heat-cooking in a microwave oven is
formed in a corner portion opposed to the vapor release seal part
113 by causing the peripheral edge seal part 112 to project in a
V-shape fashion toward the outside of the container.
[0091] As shown in FIG. 11, the lid 103 of the packaging container
100 is constituted by polyethylene terephthalate (PET) 121 having a
thickness of 12 .mu.m, a printing layer 122, an adhesive layer 123,
nylon 124 having a thickness of 15 .mu.m, the adhesive layer 123,
and an easy-peel layer 125 having a thickness of 50 .mu.m and
composed of an unoriented polypropylene-based resin (CPP) in the
stated order from the outside. In addition, the lid 103 is
subjected to heat-sealing with the flange part 102 of the container
main body at the easy-peel layer 125.
[0092] When the container is heated in a microwave oven, the inner
pressure of the container increases owing to water vapor or the
like generated from contents in the container. The cohesion failure
of CPP constituting the easy-peel layer 125 of a heat seal part
starts from the tip part of the vapor release seal part 113
projecting in a U-shape fashion, so the vapor release seal part 113
starts to peel. When the inner pressure of the container
additionally increases so that the peeling at the tip part of the
vapor release seal part 113 reaches the outer edge of the heat seal
part, the heat seal part opens as shown in FIG. 11(B).
[0093] In association with the peeling of the heat seal part in the
vapor release seal part 113, irregularities are formed on a CPP
peeling surface that has undergone cohesion failure to roughen the
surface. In addition, the CPP peeling surface that has been
transparent becomes white and opaque owing to a phenomenon such as
stress whitening, so a white opacified layer 126 is formed on the
surface of the easy-peel layer 125. As a result, such a state that
the lower layer of the printing layer 122 of the lid 103 is
white-coated is established. Accordingly, the peeled part can be
easily recognized because the color of the printing of the peeled
part appears to be different from the color of a peripheral part.
The white opacified layer 126 formed by the peeling of the heat
seal part can be recognized even when the printing layer 122 of the
lid 103 is omitted; provided that the printing layer 122 is
preferably arranged to enable the white opacified layer 126 to be
recognized with improved definition.
[0094] The layer constitution of the lid 103 is not limited to that
described above, and can be appropriately changed. For example,
another layer constitution of the lid 103 is composed of the nylon
121 having a thickness of 15 .mu.m, the printing layer 122, the
adhesive layer 123, an ethylene-vinyl alcohol copolymer 124 having
a thickness of 12 .mu.m, the adhesive layer 123, and the easy-peel
layer 125 having a thickness of 50 .mu.m and composed of a
polyolefin-based resin in the stated order from the outside. Of
course, the number of layers constituting the lid 103 may be
increased or decreased. The printing layer can be provided for not
only the vapor release seal part 113 but also a part adjacent to
the vapor release part 113 or the entire surface of the lid 103. An
adhesive to be interposed between adjacent layers constituting the
lid 103 is not particularly limited, and an ordinary adhesive such
as a polyurethane-based adhesive or an acid-modified
polyolefin-based adhesive can be used.
[0095] The flange part 102 of the container main body can be
subjected to printing or coloring as desired. The shape and
dimensions of the container main body are arbitrary, and the
container may be, for example, a cylindrical cup, a rectangular
parallelopiped tray, or a box.
[0096] The seal strength of each of the peripheral edge seal part
and vapor release seal part of the packaging container for a
microwave oven of the present invention can be 2.3 kg/15 mm width
or more.
[0097] A conventional packaging container automatically opening
upon heating in a microwave oven involved a significant reduction
in seal strength of an opening part upon heating, and could not
achieve a seal strength of 2.3 kg/15 mm width or more needed for a
packaging container for a retort food. A material, the seal
strength of which reduces upon heating, is used in neither the
peripheral edge seal part of the packaging container for a
microwave oven of the present invention, nor the vapor release seal
part of the container. In addition, the above seal strength can be
maintained because no seal part is subjected to a processing
treatment that results in a reduction in seal strength upon
heating.
[0098] As a result, the packaging container does not burst from its
vapor release seal part or its peripheral edge seal part when the
packaging container is subjected to a retort treatment after the
packaging container has been filled with contents. In addition, the
breakage of the packaging container at the time of the transport or
storage of the packaging container can be prevented.
[0099] In addition, even in the case of heating in a microwave
oven, the vapor release seal part of the packaging container
maintains its seal strength for a certain time period, and the
inner pressure of the packaging container is kept high by water
vapor. Therefore, a heat steaming effect on the content in the
packaging container is obtained. As a result, significant effects,
that is, an improvement in taste of the contents and a reduction in
time required for the cooking of the contents, are exerted.
* * * * *