ZIPPER TAPE AND PACKING BAG WITH ZIPPER TAPE

TECHNICAL FIELD

The present invention relates to a zipper tape and a packaging bag provided with the zipper tape.

BACKGROUND ART

There has typically been known a packaging bag with a zipper tape (hereinafter, occasionally abbreviated as a packaging bag) provided by bonding the zipper tape to an inner surface of the bag body. When such a packaging bag is filled with powdery substances and liquids as contents, the contents may leak toward a top seal beyond the zipper tape during transportation. Accordingly, a zipper tape with a separating structure provided between the zipper tape and the contents and a packaging bag with the zipper tape have been known for preventing leakage of the contents (see, for instance, Patent Literatures 1 to 3).

The separating structure provided in the zipper tape is exemplified by a cut portion, a part of which can be easily cut, and a seal that is easily peelable from an inner surface of a bag body. In opening the packaging bag, the cut portion is cut or peeled to take out the contents.

Patent Literature 1 discloses a packaging bag including a wide seal base provided to a belt-like base of a male member near the contents. The seal base includes a linear cut portion. The packaging bag is sealed by the linear cut portion being bonded to an end of a belt-like base of a female member. The linear cut portion is cut by a force in opening the zipper tape, thereby opening the packaging bag.

Patent Literature 2 (e.g., FIG. 10) discloses that a thin and linear cut portion is provided in a belt-like base of a male member near the contents and the cut portion is cut to open a packaging bag.

Patent Literature 3 discloses that a connecting portion is provided as a cut portion by connecting ends of non-opening-side-flanges of a male member and a female member of a joint to each other and the connecting portion is cut to open the packaging bag. Patent Literature 3 also discloses that a protrusion having a triangular cross section is formed on each of the ends of the male member and the female member, thereby allowing a stress to concentrate on the cut portion.

CITATION LIST
Patent Literature(s)

Patent Literature 1 JP-A-2008-24324

Patent Literature 2 International Publication No. WO2004/050487

Patent Literature 3 JP-A-2006-51987

SUMMARY OF THE INVENTION
Problems to be Solved by the Invention

In Patent Literatures 1 and 2, since the cut portion is linearly formed, when sealing the belt-like bases or the seal base of the male and the female members to the inner surface of the bag body, it is difficult to position the seal base and the cut portion at a right place. Accordingly, the cut portion may be directly bonded to the inner surface of the bag body, or the belt-like base and the seal base may be bonded to each other. In such a case, cuttability of the cut portion may be impaired.

In such a structure as disclosed in Patent Literature 3, unless at least one of the protrusions is fixed to a bag body film, a sufficient force cannot be applied on the cut portion to open the bag. Accordingly, it may be difficult to cut the cut portion.

An object of the invention is to provide an easily openable and favorably sealable zipper tape and a packaging bag with the zipper tape.

Means for Solving the Problems

According to an aspect of the invention, a zipper tape includes: a pair of a male member and a female member including: an engagement portion that is engageable and disengageable and defines a containing space inside a bag body; and belt-like bases that are continuously connected to the engagement portion and are bondable to an inner surface of the bag body, in which a first one of the belt-like bases includes: a thick portion that is formed thicker than the first one of the belt-like bases at an end near the containing space; a cut portion that is continuously connected to the end of the thick portion near the containing space and is formed thinner than the first one of the belt-like bases; and a seal base that is continuously connected to an end of the cut portion near the containing space, formed thicker than the first one of the belt-like bases, and attached to the inner surface of the bag body to which a second one of the belt-like bases is attached, in which the thick portion is attached to the inner surface of the bag body to which the second one of the belt-like bases is attached by a strength lower than a strength for the seal base to be attached to the inner surface of the bag body, and the cut portion is provided in a form of a belt spaced away from the inner surface of the bag body, the cut portion isolating the containing space from the outside and having a strength lower than the strength for the seal base to be attached to the inner surface of the bag body.

In the above aspect of the invention, it is preferable that the thick portion and the seal base are formed substantially in the same thickness.

In the above aspect of the invention, it is preferable that the thick portion is formed narrower toward the inner surface of the bag body.

In the above aspect of the invention, it is preferable that a surface of the thick portion and a surface of the seal base which face each other across the cut portion are substantially parallel to each other and are substantially orthogonal to the inner surface of the bag body to which the thick portion and the seal base are attached.

According to another aspect of the invention, a packaging bag with a zipper tape includes: a bag body having an opening portion for defining a containing space; and the zipper tape according to any one of claims 1 to 4, the zipper tape being provided on an inner surface of the bag body.

According to the invention, even if external pressure or internal pressure of the bag is applied on the bag body with the zipper tape attached and containing the contents in the containing space, since a substantially hermetically sealed area is formed by the thick portion, the cut portion, the seal base and the inner surface of the bag body, the substantially hermetically sealed area works as a pressure buffer area. Accordingly, even if the cut portion is configured to be easily cut in opening, the cut portion can be prevented from being stretched by external pressure or internal pressure of the bag to impair sealability for separating the containing space from the outside, particularly water-tightness. Consequently, both a favorable openability and a sufficient sealability can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view showing a packaging bag with a zipper tape according to a first exemplary embodiment of the invention.

FIG. 2 is a cross section taken along the line II-II in FIG. 1 for showing engagement of a male member and a female member.

FIG. 3 is an enlarged cross section of a seal base of the zipper tape in FIG. 2.

FIG. 4 is a cross section showing disengagement of the male member and the female member in FIG. 2.

FIG. 5 is a cross section showing when a cut portion is cut to open the bag in FIG. 2.

FIG. 6 is a cross section showing how contents are sealed in the packaging bag with the zipper tape.

FIG. 7 is a perspective view showing seal bars used for sealing the contents.

FIG. 8 is a partially cut perspective view showing how the contents are sealed with the seal bars.

FIG. 9 is an enlarged perspective view showing an enlarged zipper tape in a packaging bag with a zipper tape according to a second exemplary embodiment.

FIG. 10 is a cross section showing engagement of a male member and a female member of a packaging bag with a zipper tape according to a third exemplary embodiment.

FIG. 11 is a cross section showing engagement of a male member and a female member of a packaging bag with a zipper tape according to a fourth exemplary embodiment.

FIG. 12 is a cross section showing engagement of a male member and a female member of a packaging bag with a zipper tape according to a fifth exemplary embodiment.

DESCRIPTION OF EMBODIMENT(S)
First Exemplary Embodiment

A packaging bag with a zipper tape according to a first exemplary embodiment of the invention (hereinafter, occasionally referred to simply as “a packaging bag”) will be described with reference to drawings.

The packaging bag of the invention is suitably filled with liquids as contents. However, the packaging bag may be filled with powders, solids or gel. Although a thick portion, a cut portion and a seal base are exemplarily provided to a female member, the thick portion, the cut portion and the seal base may be provided to a male member.

Arrangement of Packaging Bag with Zipper Tape

As shown in FIGS. 1 and 2, a packaging bag 1 of this exemplary embodiment includes a bag body 10 provided by laying base films 11 (packing material) one on the other and forming side seal bases 12 and a top seal base 13 on the periphery of the base films. A zipper tape 20 includes a pair of a male member 21 and a female member 22 including an engagement portion 23. The male member 21 includes a male belt-like portion 211. The female member 22 includes a female belt-like portion 221. The male belt-like portion 211 and the female belt-like portion 221 are continuously connected to the engagement portion 23. The zipper tape 20 is attached to an inner surface 10A of an opening portion 14 of the bag body 10. The zipper tape 20 is sealed to the bag body 10 in a belt extending from one of the side seal bases 12 to the other of the side seal bases 12. The engagement portion 23 of the zipper tape 20 defines a containing space 15 in the packaging bag 1.

In FIGS. 1 to 3, after the contents (not shown) are put through a bottom of the bag body 10, the bottom side of the bag body 10 is sealed, whereby the packaging bag 1 is hermetically sealed.

In use, a user cuts the opening portion 14 to open the packaging bag 1, and reseals the packaging bag with the zipper tape 20.

As shown in the cross section in FIG. 2, the zipper tape 20 includes the male member 21 provided on one side and the female member 22 provided to the other side to engage with the male member 21, the male and female members 21 and 22 each formed of a thermoplastic resin and having a belt-like shape.

The male member 21 includes: the male belt-like base 211 sealed to the bag body 10; a head 212 shaped substantially in an arrowhead in cross section; and a connecting portion 213 for connecting the male belt-like base 211 and the head 212. The male belt-like base 211, the head 212 and the connecting portion 213 are integrally formed.

Similarly to the male member 21, the female member 22 includes: the female belt-like base 221 sealed to the bag body 10; and a first hook 222 and a second hook 223 that each have an arcuate cross section and are connected to the female belt-like base 221. The first hook 222 and the second hook 223 face each other and are in a form of a groove detachably engageable with the head 212 of the male member 21.

The male belt-like base 211 of the male member 21 includes: a base facing surface 221A that is sealed to the inner surface 10A in a manner to substantially face the inner surface 10A; and an engagement-portion formation surface 221B near the engagement portion 23 opposite to the base facing surface 221A. The female belt-like base 221 of the female member 22 includes: a base facing surface 221A that is sealed to the inner surface 10A in a manner to substantially face the inner surface 10A; and an engagement-portion formation surface 221B near the engagement portion 23 opposite to the base facing surface 221A.

The engagement portion 23 of the zipper tape 20 is provided by the head 212 of the male member 21 and the first and second hooks 222, 223 of the female member 22. By engagement or disengagement of the engagement portion 23, the packaging bag 1 is sealed or opened.

As shown in FIGS. 2 and 3, the female belt-like base 221 integrally formed with the female member 22 includes a thick portion 31, which is thicker than the female belt-like base 221, at an end 224 of the bag body 10 near a containing space 15.

To an end of the thick portion 31 near the containing space 15, a belt-like cut portion 32, which is formed thinner than the thick portion 31 and isolates the containing space 15 from the outside, is connected.

To an end of the cut portion 32 near the containing space 15, a seal base 33, which is formed thicker than the female belt-like base 221 and is sealed to the inner surface 10A, is connected.

The thick portion 31 is formed thicker than the female belt-like base 221 and projects from the engagement-portion formation surface 221B while being formed in a belt from one side seal base 12 to the other side seal base 12. The thick portion 31 is formed substantially in the same thickness as that of the seal base 33.

A thickness of the thick portion 31 is preferably in a range of 250 μm to 550 μm, more preferably in a range of 350 μm to 450 μm. When the thickness of the thick portion 31 is less than 250 μm, a stress in opening the packaging bag 1 is difficult to concentrate on the cut portion 32. On the other hand, when the thickness of the thick portion 31 is more than 550 μm, it is difficult to form the side seal base 12.

The thick portion 31 is formed narrower toward the inner surface 10A of the bag body 10, the inner surface 10A facing the engagement-portion formation surface 221B. In other words, the thick portion 31 is formed in a cross-sectionally trapezoidal shape, in which a width of the thick portion 31 becomes narrower toward its projecting end.

The thick portion 31 is sealed to the inner surface 10A through an end surface 311 facing the inner surface 10A. Under such a sealed situation, an end surface 312 of the thick portion 31, to which the cut portion 32 is connected, is formed substantially orthogonal to the inner surface 10A. Seal strength of the thick portion 31 to the inner surface 10A is lower than that of the seal base 33 to the inner surface 10A. The seal strength of the thick portion 31 is adjusted by configuring the thick portion 31 to have a seal area smaller than a seal area of the seal base 33 (a seal area of an adhesion portion 331A later described) through a partial seal portion 311A that is sealed in a dashed line in a longitudinal direction (a horizontal direction in FIG. 1) of the cut portion 32.

The thick portion 31 is formed at a distance of 0.5 mm or more between an outside edge of the end surface 311 and an end of the male belt-like base 211 near the containing space 15. This is because, if the distance is less than 0.5 mm, when the thick portion 31 is sealed to the inner surface 10A, the thick portion 31 and the male belt-like base 211 may adhere to each other, so that a favorable opening feeling may not be obtained or the bag cannot be opened depending on the case. The thick portion 31 in a cross-sectionally trapezoidal shape is formed to have an inclined surface 313 such that the outer edge of the end surface 311 is spaced away from the male belt-like base 211. Accordingly, the thick portion 31 is prevented from adhering to the male belt-like base 211 in sealing.

The cut portion 32 is formed in a belt extending from one of the side seal bases 12 to the other of the side seal bases 12 and in a direction orthogonal to the end surface 312 of the thick portion 31 (a vertical direction in FIG. 3). The cut portion 32 is formed to have a seal strength lower than that of the seal base 33 to the inner surface 10A. In other words, the cut portion 32 is formed so as to be cut before the seal base 33 is peeled from the inner surface 10A of the bag body 10. Specifically, a thickness of the cut portion 32 is preferably in a range of 10 μm to 80 μm, more preferably in a range of 30 μm to 60 μm. When the thickness of the cut portion 32 is less than 10 μm, the cut portion 32 may be cut by external pressure when the packaging bag 1 is dropped. On the other hand, when the thickness of the cut portion 32 is more than 80 μm, it may be difficult to cut the cut portion 32 by hand. It should be noted that the strength of the cut portion 32 may not be adjusted simply by setting the thickness of the entire cut portion 32 in the above range. For instance, thin portions may be formed in the cut portion 32 at every predetermined distance between one of the side seal bases 12 and the other of the side seal bases 12.

A width of the cut portion 32, i.e., a dimension in a direction substantially orthogonal to a longitudinal direction of the zipper tape 20 (i.e., the vertical direction in FIG. 3), is preferably in a range of 0.3 mm to 1.5 mm, more preferably in a range of 0.8 mm to 1.2 mm. If the width of the cut portion 32 is less than 0.3 mm, when the zipper tape 20 is sealed to the bag body 10, it may be difficult to position the cut portion 32 so as not to contact with the male belt-like base 211 of the male member 21 and the inner surface 10A. On the other hand, when the width of the cut portion 32 is more than 1.5 mm, the cut portion 32 may be stretched in cutting to become difficult to cut.

The seal base 33 is formed in a belt having a cross-sectionally rectangular shape extending from one of the side seal bases 12 to the other of the side seal bases 12.

A seal surface 331 of the seal base 33 which is sealed to the inner surface 10A is formed substantially flush with the end surface 311 of the thick portion 31 which is sealed to the inner surface 10A (see FIG. 6). The seal surface 331 includes the adhesion portion 331A that is bonded to the inner surface 10A in a comb-shape pattern. As shown in FIG. 1, the adhesion portion 331A includes: a linear seal surface 331A1 that is linearly sealed along the longitudinal direction (the horizontal direction in FIG. 1) of the cut portion 32; and a plurality of end seal surfaces 331A2 that are continuously formed with the linear seal surface 331A1, to which an end surface 333 of the seal base 33 is sealed in a dashed line. The linear seal surface 331A1 prevents leakage of the contents and the plurality of end seal surfaces 331A2 allow the stress to concentrate on the cut portion 32.

The end surface 333 of the seal base 33, to which the cut portion 32 is connected, is formed substantially parallel to the end surface 312 of the thick portion 31 facing the seal base 33 and substantially orthogonal to the inner surface 10A of the bag body 10.

The male member 21 of the zipper tape 20 of the exemplary embodiment can be integrally formed by co-extrusion, where the head 212 and the connecting portion 213 are continuously formed with the male belt-like base 211. Similarly, the female member 22 can be integrally formed by co-extrusion, where the first hook 222 and the second hook 223 are continuously formed with the female belt-like base 221. When the zipper tape 20 is formed by such co-extrusion, the zipper tape 20 can be manufactured in a simplified process at low costs, and can be stably manufactured in a continuous manner.

The male member 21 and the female member 22 of the zipper tape 20 may be formed of polyethylene and polypropylene and are preferably formed of extension-resistant polypropylene. Specifically, thermoplastic resins such as homo-polypropylene, block-polypropylene, random polypropylene (RPP), propylene-ethylene-butene-1 random terpolymer and polyolefin-based special flexible resins, and a mixture thereof are usable.

When random polypropylene (RPP) is used as the resin forming zipper tape 20, a melt flow rate (MFR) of RPP is preferably from 0.5 to 20 g/10 min, particularly preferably from 1 to 15 g/10 min.

When the MFR of random polypropylene is less than 0.5 g/10 min, co-extrusion moldability of the engagement portion 23, which is formed continuously and integrally with the male belt-like base 211 and the female belt-like base 221, may be deteriorated. On the other hand, the MFR exceeding 20 g/10 min may cause ends of the first and second hooks 222 and 223 of the female member 22 to be likely closed or may cause the connecting portion 213 of the male member 21 to be likely tilted down, which may make it difficult to extrude the zipper tape 20 into a predetermined reopenable/resealable shape.

By sealing the zipper tape 20 to the base film 11 of the bag body 10 and forming the base film 11 into a bag, the packaging bag 1 as shown in FIG. 1 can be obtained.

While the base film 11 (packaging material) for forming the bag body 10 is preferably a layered film in which a sealant layer 111 is layered onto a base layer 112, the base film 11 may be a layered film in which a layered film layer (not shown) including layers of a gas barrier layer, a light-shielding layer and a strength-reinforcing layer is provided as a middle layer between the base layer 112 and the sealant layer 111, depending on a required performance.

Examples of the material for the base layer 112 are preferably a biaxially-oriented polypropylene film (OPP film), a biaxially-oriented polyester film such as biaxially-oriented polyethylene terephthalate film (PET film) and biaxially-oriented polyethylene naphthalate film and a biaxially-oriented polyamide film such as nylon 6, nylon 66 and MXD6 (poly-meta-xylylene adipamide). Depending on needs, various engineering plastic films are also usable. One of the above may be used alone, or a combination of two or more of the above may be layered in use.

When the middle layer is a gas barrier layer, examples of the usable material for the middle layer are a film of saponified ethylene-vinyl acetate copolymer (EVOH) or polyacrylonitrile (PAN), aluminum foil, a deposited layer of silica, alumina or aluminum and a coating layer of PVDC.

When a deposited layer of silica, alumina or aluminum or a coating layer of PVDC is used, such a layer may be deposited or coated on the inner surface 10A of the bag body 10 of the base layer 112. Alternatively, such a layer may be preliminarily deposited or coated on another biaxially-oriented nylon film (ONy film), biaxially-oriented polyethylene terephthalate film (PET film) or biaxially-oriented polypropylene film (OPP film), and the film may be layered on the middle layer.

Among the above, aluminum foil and a deposited layer of aluminum, which are opaque, can also serve as a light-shielding layer.

The layering of the base layer 112 and the film of the intermediate layer can be conducted by a known dry lamination method or extrusion lamination method (sandwich lamination method).

For the sealant layer 111 (the innermost layer), polypropylene (CPP) and the like are usable.

In order to layer the sealant layer 111, the above resins may be formed into film and layered by a dry lamination method or extrusion lamination method. Alternatively, the above resins may be layered thereon by extrusion coating.

The packaging bag 1 according to this exemplary embodiment can be easily manufactured with use of, for instance, a bag-making machine for three-sided sealing and attaching a zipper tape.

Sealing conditions (temperature, pressure, etc.) in the manufacturing can be properly determined in accordance with types of the resins for forming the zipper tape 20 and the base film 11 for forming the bag body 10.

Opening Operation of Packaging Bag with Zipper Tape

Next, description will be made with reference to FIGS. 2, 4 and 5 on how the packaging bag 1 according to this exemplary embodiment is opened.

FIG. 2 shows engagement of the male member 21 and the female member 22 of the zipper tape 20. In this engagement, at a lower side of the engagement portion 23 (i.e., near the containing space 15) in FIG. 2, the adhesion portion 331A of the seal base 33 is sealed to the inner surface 10A of the bag body 10. This arrangement can maintain air-tightness and water-tightness of the bag, and liquid contents can be kept from infiltrating into a gap in the engagement portion 23 of the zipper tape 20, for instance, during transportation.

Next, when the contents are to be taken out from the packaging bag 1, as shown in FIG. 4, the opening portion 14 is cut to open the zipper tape 20, thereby disengaging the engagement of the engagement portion 23. By further opening an upper side (a side opposite to the containing space 15) of the bag body 10, the thick portion 31 is peeled from the inner surface 10A of the bag body 10 by such an opening force, as shown in FIG. 5. By the opening force to further open the upper side of the bag body 10, stretching force acts on the cut portion 32. At this time, since the end surface 333 of the seal base 33 near the cut portion 32 is kept orthogonal to the inner surface 10A of the bag body 10 by the end seal surfaces 331A2 of the adhesion portion 331A, the end surface 333 of the seal base 33 does not become loose from the inner surface 10A, so that the stretching force efficiently acts on the cut portion 32. The cut portion 32 is cut by the stretching force, so that the thick portion 31 is separated from the seal base 33. Thus, the contents can be taken out from the inside of the packaging bag 1.

Manufacturing Instrument of Packaging Bag with Zipper Tape

Next, a manufacturing instrument of the packaging bag with the zipper tape according to the first exemplary embodiment will be described with reference to FIGS. 6 to 8.

The manufacturing instrument used for manufacturing the packaging bag 1 includes a bag-making section. FIG. 6 shows how the contents are sealed in a substantial part of the bag-making section.

In FIG. 6, the bag-making section includes: a tape adhesion section (not shown) that positions the zipper tape 20 fed from a tape feeder (not shown) between a pair of the base films 11 fed from a packaging material feeder (not shown) and heat-seals the zipper tape 20 to both of the base films 11; and a seal section that seals and weld-cuts the delivered base films 11 at a predetermined distance in a delivering direction of the base films 11, i.e., at a distance corresponding to a dimension in a width direction of the packaging bag 1, thereby forming the packaging bag 1.

The seal section includes a pair of seal bars 60 that are disposed to face each other with interposing the packaging bag 1 that is filled with contents P while the zipper tape 20 is fastened.

The seal bars 60 are mutually approachable and separable. When the seal bars 60 are separated from each other, the packaging bag 1 containing the contents P is held at a predetermined position. At this time, when the seal bars 60 approach each other, one of the seal bars 60 presses the seal base 33 via the base film 11, thereby forming the adhesion portion 331A on the seal base 33.

As shown in FIG. 7, the one of the seal bars 60 is provided with pressing protrusions 60A in the same continuous comb-shape as that of the adhesion portion 331A. As shown in FIG. 8, the adhesion portion 331A of the seal base 33 is formed to have a predetermined width in the width direction of the bag body 10 and a comb-shape dented at a predetermined distance in the longitudinal direction of the bag body 10. The adhesion portion 331A is sealed with the seal bars 60 in such a manner that ends of the pressing protrusions 60A reach the thick portion 31 across the cut portion 32.

In this exemplary embodiment, when the zipper tape 20 near the containing space 15 is sealed, the adhesion portion 331A is formable by using the seal bars 60 provided with the pressing protrusions 60A having the same shape as the adhesion portion 331A. Thus, it is possible to manufacture the packaging bag 1 in which the thick portion 31 is easily peelable and the cut portion 32 is easily cuttable by the force applied for opening the zipper tape 20.

Advantages of First Exemplary Embodiment

With the above-described packaging bag 1, the following advantages can be attained.

Specifically, in the first exemplary embodiment, the thick portion 31 is formed thick at the end 224 of the female belt-like base 221 near the containing space 15. To the thick portion 31 near the containing space 15, the cut portion 32 thinner than the female belt-like base 221 is provided. To the cut portion 32 near the containing space 15, the seal base 33, which is thicker than the female belt-like base 221 and is sealed to the inner surface 10A of the bag body 10 to which the male belt-like base 211 is attached, is provided. The thick portion 31 is attached to the inner surface 10A to which the male belt-like base 211 is attached by the seal strength lower than that of the seal base 33. The cut portion 32 is formed to have strength lower than the seal strength of the seal base 33 and to be spaced away from the inner surface 10A of the bag body 10 and separate the containing space 15 from the outside in a form of a belt.

With this arrangement, an area surrounded by the thick portion 31, the cut portion 32, the seal base 33 and the inner surface 10A of the bag body 10 becomes substantially hermetically sealed. Accordingly, even if external pressure or internal pressure of the bag is applied on the bag body 10 to which the zipper tape 20 is attached and which contains the contents P in the containing space 15, the substantially hermetically sealed area works as a buffer area of the pressure applied on a surface of the cut portion 32 near the containing space 15. With this arrangement, even if the cut portion 32 is set to have a predetermined strength enough to be easily cut in opening, the cut portion 32 is prevented from being stretched by external pressure or internal pressure of the bag to be broken on next impact, or the cut portion 32 is prevented from occasionally having pinholes to damage sealability for separating the containing space 15 from the outside, particularly water-tightness. Consequently, according to this exemplary embodiment, it is avoidable to damage openability by forming the cut portion 32 thick for improving sealability, thereby providing both a favorable openability and a sufficient sealability.

Moreover, in the first exemplary embodiment, the thick portion 31 and the seal base 33 are formed substantially in the same thickness.

With this arrangement, when the seal bars 60 heat-weld the thick portion 31 and the seal base 33, the seal bars 60 come into contact with the thick portion 31 and the seal base 33 substantially at the same time, whereby a predetermined pressure is applied on the end surface 311 of the thick portion 31 and the seal surface 331 of the seal base 33, so that the end surface 311 and the seal surface 331 can be bonded under a predetermined heat-welding condition.

In other words, if one of the end surface 311 and the seal surface 331 is formed thicker than the other, the seal bars 60 need to be pressed harder in order to seal the other, so that the cut portion 32 may be damaged by heat. If the thick portion 31 is formed thinner and is not appropriately sealed on the bag body 10, the cut portion 32 may be stretched to damage sealability when external pressure is applied on the bag body 10. On the other hand, if the thick portion 31 is formed thicker, the seal strength is increased to require a large force for peeling the thick portion 31 from the bag body 10 in opening, so that an opening feeling may be impaired. If the seal bars 60 are formed corresponding to different thicknesses for solving such disadvantages, a shape of the seal bars 60 becomes complicated to increase instrument costs and positioning of the seal bars 60 in sealing also becomes complicated, so that the manufacturing efficiency of the packaging bag 1 may not be improved.

For solving such disadvantages, according to the above arrangement of this exemplary embodiment, an arrangement in which the thick portion 31 is sealable by the seal strength lower than that of the seal base 33 is provided by a simple arrangement in which the thick portion 31 and the seal base 33 are formed substantially in the same thickness.

Moreover, in the first exemplary embodiment, the thick portion 31 is formed in a cross-sectionally trapezoidal shape, in which a width of the thick portion 31 becomes narrower toward the inner surface 10A of the bag body 10.

With this arrangement, in sheet-sealing, a seal depth is easily adjustable, which makes it possible to set the seal conditions in a broad range.

For instance, when the thick portion 31 is formed in a cross-sectionally inverse trapezoidal shape in which the width of the thick portion 31 becomes wider toward the end surface 311 and the inclined surface 313 is inversely inclined, it is difficult to stably mold the thick portion 31 to hinder improvement in productivity. Particularly, in a cross-sectionally inverse trapezoidal shape in which the end surface 312 of the thick portion 31 approaches the seal base 33 toward the end surface 311, resins flowed out in sealing may be bonded to the cut portion 32 or the seal base 33, so that an opening feeling may be impaired.

In view of the above, according to the above arrangement of this exemplary embodiment, an arrangement to provide a favorable opening feeling can easily be manufactured by co-extrusion.

The cut portion 32 is formed in a belt extending in a direction orthogonal to the end surface 312 of the thick portion 31 (in the vertical direction in FIG. 3).

Accordingly, even when external pressure is applied on the bag body 10, the external pressure is substantially evenly applied on the entire cut portion 32, so that the cut portion 32 can be kept from being stretched by partially receiving a high pressure, and decrease in water-tightness caused by generation of pinholes can be prevented.

Further, the surfaces of the thick portion 31 and the seal base 33 to be sealed on the inner surface 10A of the bag body 10 are formed substantially flush with each other. The seal base 33 is designed to have a higher seal strength higher than the thick portion 31.

Examples of methods to achieve the above arrangement include: sealing the thick portion 31 and the seal base 33 from an outer surface of the bag body 10 using comb-shaped heat seal bars 60; forming the thick portion 31 using a non-compatible resin with the resin used in the sealant layer 111 of the bag body 10; and setting a melting point of the resin used for the thick portion 31 higher than a melting point of the resin used for the seal base 33. By using these methods, such design that the seal base 33 is sealed by the seal strength higher than that of the thick portion 31 is reliably obtained, thereby easily providing an arrangement with a favorable openability and a sufficient water-tightness.

Second Exemplary Embodiment

Next, a second exemplary embodiment of the invention will be described with reference to the drawings.

FIG. 9 is an enlarged perspective view showing a vicinity of a seal base of a zipper tape of a packaging bag according to the second exemplary embodiment of the invention. It should be noted that, in the second exemplary embodiment, description of an arrangement that is the same as or similar to the arrangement of the first exemplary embodiment is omitted or simplified.

A thick portion 41 of the second exemplary embodiment is provided by forming the thick portion 31 of the first exemplary embodiment into a cross-sectionally rectangular shape. The thick portion 41 includes two ribs 411 having a cross-sectionally triangular shape along a longitudinal direction of the cut portion 32 on a surface of the thick portion 41 facing the inner surface 10A of the bag body 10 to which the male belt-like base 211 is attached. The ribs 411 are preferably formed to have a predetermined height. Specifically, when the height is less than 5 μm, the rib is sealed up to an end surface of a base thereof, which means that formation of the ribs 411 is not necessary. When the height is more than 300 μm, it is difficult to form the side seal bases 12 in the packaging bag 1.

A thickness of the thick portion 41, which is defined as a dimension from a bottom surface continuous to the female belt-like base 221 to a tip end of the rib 411, is formed substantially the same as that of the seal base 33.

In the second exemplary embodiment, the seal base 33 is bonded to the bag body 10 with an arrangement in which the linear seal surface 331A1 and the end seal surface 331A2 of the adhesion portion 331A in the first exemplary embodiment are separated.

According to the second exemplary embodiment, since the ribs 411 to be bonded to the bag body 10 are provided, the seal strength is reduced because of decrease in seal area on the bag body 10, so that a large force is not required in opening and a favorable opening feeling can be provided. Particularly, even when the thick portion 41 needs to be bonded to the bag body 10 all along the longitudinal direction of the cut portion 32 in order to more reliably prevent the cut portion 32 from being damaged by external pressure, the thick portion 41 can easily be bonded to the bag body 10 by a seal strength lower than that of the seal base 33 and a favorable opening can be provided.

Moreover, even by the method of bonding the linear seal surface 331A1 and the end seal surface 331A2 in the separate arrangement in the second exemplary embodiment, similarly to the first exemplary embodiment, the stress appropriately concentrates on the cut portion 32 in opening, whereby the cut portion 32 can be cut and a favorable opening feeling can be provided,

In the second exemplary embodiment, the ribs 411 are not limited to two ribs, but may be provided by a single rib or plural ribs. A shape of each of the ribs 411 is not only linear, but may be wavy or in a dashed line. The adhesion portion 331A of the seal base 33 may be bonded by any bonding method such as one in a comb-shape pattern of the first exemplary embodiment.

Third Exemplary Embodiment

Next, a third exemplary embodiment of the invention will be described with reference to the drawings.

FIG. 10 is a cross-sectional view showing engagement of a male member and a female member of a zipper tape in a packaging bag according to a third exemplary embodiment of the invention. Also in the third exemplary embodiment, description of an arrangement that is the same as or similar to the arrangement of the above exemplary embodiments is omitted or simplified.

According to the third exemplary embodiment, a cut portion 42 is provided by forming the cut portion 32 of the second exemplary embodiment in a plane on which the cut portion 42 intersects with the inner surface 10A of the bag body 10 facing the thick portion 41 and the seal base 33. In case external pressure is applied, in order to prevent pressure concentration, it is preferable to provide a curved surface 421 formed in a cross-sectionally arc at an acute connecting point between the cut portion 42 and the seal base 33.

Also with this arrangement, similar to the second exemplary embodiment, a favorable opening feeling can be provided in opening and a favorable sealability can be obtained without causing such damage as the cut portion 42 is stretched even when external pressure is applied.

In the third exemplary embodiment, a direction in which the plane of the cut portion 42 is inclined is not limited to the above arrangement, but may be an inverse direction. The cut portion 42 may be curved.

Fourth Exemplary Embodiment

Next, a fourth exemplary embodiment of the invention will be described with reference to the drawings.

FIG. 11 is a cross-sectional view showing engagement of a male member and a female member of a zipper tape in a packaging bag according to a fourth exemplary embodiment of the invention. Also in the fourth exemplary embodiment, description of an arrangement that is the same as or similar to the arrangement of the above exemplary embodiments is omitted or simplified.

According to the fourth exemplary embodiment, a cut portion 52 is provided by forming the cut portion 42 of the second exemplary embodiment thicker toward the thick portion 41.

With this arrangement, a position where the cut portion 52 is cut is a connecting point (the thinnest point) between the cut portion 52 and the seal base 33, so that the products can be cut at the same cut position and the opening feeling can be kept constant.

Fifth Exemplary Embodiment

Next, a fifth exemplary embodiment of the invention will be described with reference to the drawings.

FIG. 12 is a cross-sectional view showing engagement of a male member and a female member of a zipper tape in a packaging bag according to a fifth exemplary embodiment of the invention. Also in the fifth exemplary embodiment, description of an arrangement that is the same as or similar to the arrangement of the above exemplary embodiments is omitted or simplified.

In the fifth exemplary embodiment, the female belt-like base 221 of the female member 22 in the first exemplary embodiment includes an adhesion base 24 at an end near the opening portion 14. The female belt-like base 221 of the female member 22 is bonded to the inner surface 10A of the bag body 10 near the male member 21 with the engagement-portion formation surface 211B via the adhesion base 24. An opening tape 40 is attached between the adhesion base 24 and the male belt-like base 211 of the male member 21.

The base facing surface 221A opposite to the engagement-portion formation surface 211B is spaced away from the inner surface 10A of the bag body 10 at a predetermined distance. In other words, the female belt-like base 221 of the female member 22 is not sealed to the inner surface 10A of the bag body 10.

With this arrangement, the base facing surface 221A is spaced away from the inner surface 10A of the bag body 10 at a predetermined distance. Accordingly, the containing space 15 is enlarged, i.e., a so-called dead space is decreased, so that the packaging bag 1 can contain larger amount of contents. Moreover, the internal pressure of the packaging bag 1 is less likely to be applied on the cut portion 32, so that damage (e.g., the stretch) to the cut portion 32 can be prevented even when an external force (e.g., impact on the bag body 10 when dropped) is applied.

Modification

The scope of the invention is not limited to the above-described embodiments but also includes modifications and improvements as long as an object of the invention can be achieved.

The pair of seal bars 60 that are positioned to face each other with the packaging bag 1 interposed therebetween are used for heat-welding the thick portion 31, 41 and the seal base 33, but an arrangement of the seal bars 60 is not limited to this. For instance, only a single seal bar may be provided on one side of the packaging bag 1, or plural seal bars may be provided on one side of the packaging bag 1.

The adhesion method for the thick portion 31, 41 and the seal base 33 is not limited to the heat-welding method. Various methods such as an adhesion method using an adhesive or the like are applicable.

Other specific arrangements and shapes for carrying out the invention may be altered as long as an object of the invention is achieved.

EXAMPLES

The invention will further be described below with reference to examples and a comparative example. It should be noted that the invention is not limited to the contents of the examples and the like.

Example 1

With use of random polypropylene having MFR of 7 and a melting point of 140 degrees C., the zipper tape shaped as shown in FIG. 2 was manufactured under the following conditions.

Arrangement of Zipper Tape

Thickness of Thick Portion: 300 μm

Thickness of Cut Portion: 50 μm

Width of Cut Portion: 0.5 mm

Thickness of Seal Base: 400 μm

Arrangement of Bag Body

The base film forming the bag body, which was a film provided by dry-laminating the biaxially-oriented polyester film (thickness: 12 μm), the biaxially-oriented nylon film (thickness: 15 μm) and a cast polypropylene film (60 μm), was used for manufacturing a bag shown in FIG. 1.

As shown in FIG. 8, the seal base was sealed at a 1-mm width in the width direction of the bag (the direction orthogonal to the longitudinal direction of the zipper tape) and was sealed by the comb-shaped seal bar having a 1-mm width and 10-mm intervals in the longitudinal direction of the zipper tape in such a manner that ends of the comb reached the thick portion 31 across the cut portion 32.

An inner size of the bag from the seal of the seal base to the bottom of the containing space was set to be a width of 180 mm and a depth of 200 mm.

Example 2

A packaging bag was manufactured in the same manner as that in Example 1 except that the dimensions of the portions of the zipper tape in Example 1 were replaced by the following.

Thickness of Thick Portion: 500 μm

Thickness of Cut Portion: 50 μm

Width of Cut Portion: 0.5 mm

Thickness of Seal Base: 400 μm

Example 3

A packaging bag was manufactured in the same manner as that in Example 1 except that the dimensions of the portions of the zipper tape in Example 1 were replaced by the following.

Thickness of Thick Portion: 400 μm

Thickness of Cut Portion: 50 μm

Width of Cut Portion: 0.5 mm

Thickness of Seal Base: 400 μm

Comparative 1

With use of random polypropylene having MFR of 7 and a melting point of 140 degrees C., in the same shape as that of the zipper tape disclosed in JP-A-2008-24324 (FIG. 4), a zipper tape was manufactured under the following conditions.

JP-A-2008-24324 (FIG. 4) discloses:

Thickness of Male Belt-like Base (reference numeral 321 in FIG. 4) of Male Member and Female Belt-like Base (reference numeral 331 in FIG. 4) of Female Member: 150 μm

Seal Base (reference numeral 36): 150 μm

Thickness of Cut Portion (Linear Portion: reference numeral 35): 40 μm

Width of Cut Portion: 0.1 mm

The base film, which was a film provided by dry-laminating a biaxially-oriented polyester film (12 μm), a biaxially-oriented nylon film (15 μm) and a cast polypropylene film (60 μm), was used for manufacturing the bag shown in FIG. 2, similarly to Example 1.

Similarly to Example 1, as shown in FIG. 8, the seal base was sealed at a 1-mm width in the width direction of the bag and was sealed by the comb-shaped seal bar having a 1-mm width and 10-mm intervals in the longitudinal direction in such a manner that ends of the comb reached the belt-like base across the cut portion.

An inner size of the bag from the seal of the seal base to the bottom of the containing space was set to be a width of 180 mm and a depth of 200 mm.

Evaluation

The packaging bags manufactured in Examples 1 to 3 and Comparative 1 were evaluated according to the following method. The evaluation results are shown in Table 1.

Evaluation Method

(1) The cut portion was opened by hand.

A: easily openable

B: resistant to be opened, but openable

C: difficult to be opened

(2) Water of 400 ml was filled in the manufactured bag and the bag was sealed. The bag was dropped by N10 from a height of 1.2 m. It was checked whether the cut portion was cut. This procedure was carried out on 50 bags in total.

A: No cut

B: Cut in one or two bags

C: Cut in three bags or more

(3) Total Evaluation

A: A for all of the items

B: one of B and the others of A

C: one or more of C

TABLE 1

Opening
Dropped-Bag
Total

Feeling
Breakage Resistance
Evaluation

Example 1
A
B
B

Example 2
B
A
B

Example 3
A
A
A

Comparative 1
C
B
C

INDUSTRIAL APPLICABILITY

The invention is applicable as a packaging bag for packaging various articles such as foods, pharmaceutical and medical products, cosmetics and groceries.

EXPLANATION OF CODES

- 1: packaging bag with a zipper tape
- 10: bag body
- 10A: inner surface
- 14: opening portion
- 15: containing space
- 20: zipper tape
- 21: male member
- 211: male belt-like base
- 22: female member
- 221: female belt-like base
- 23: engagement portion
- 31, 41: thick portion
- 32,42,52: cut portion
- 33: seal base

ZIPPER TAPE AND PACKING BAG WITH ZIPPER TAPE

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