Packaging bag

The packaging bag is a packaging bag made of a laminate formed in a bag shape, the laminate being composed of a paper substrate, a foamed sheet made of polyolefin resin laminated on an inner side relative to the paper substrate, and a sealant layer laminated on an inner side relative to the foamed sheet, which are laminated with the sealant layer facing inward. In the packaging bag, a thickness of the foamed sheet is in a range of 0.8 mm to 5.0 mm, an expansion ratio of the foamed sheet is in a range of 15 to 50 times, and a bending stiffness of the paper substrate in an MD direction is in a range of 150 mN to 700 mN.

TECHNICAL FIELD

The present invention relates to packaging bags.

BACKGROUND ART

Packaging bags having a cushioning function for protecting the contents from impact or the like are known in the logistics industry. As an example, PTL 1 discloses an envelope formed of kraft paper folded in half with the fold taken as the bottom of the envelope and both sides respectively adhered, and a plastic air bubble wrap sheet bonded to the inside of the envelop.

SUMMARY OF THE INVENTION

Technical Problem

In this technical field, in order to appropriately protect the contents from impact or the like, packaging bags made of a substrate such as kraft paper and a cushioning material have been provided. However, packaging bags made of general kraft paper and a plastic air bubble wrap sheet laminated thereon, when dropped with fragile contents such as a CD case, may fail to protect the contents from impact. Further, when a plastic air bubble wrap sheet is used as a cushioning material, the contents may have indentations made by the bubbles of the plastic air bubble wrap sheet. Accordingly, there is a demand for packaging bags that appropriately protect the contents from impact or the like without the bubbles causing indentations.

An object of the present invention is to provide packaging bags that attempt to better protect the contents.

Solution to Problem

A packaging bag according to one aspect of the present invention is a packaging bag made of a laminate formed in a bag shape, the laminate being composed of a paper substrate, a foamed sheet made of polyolefin resin laminated on an inner side relative to the paper substrate, and a sealant layer laminated on an inner side relative to the foamed sheet, which are laminated with the sealant layer facing inward, wherein a thickness of the foamed sheet is in a range of 0.8 mm to 5.0 mm, an expansion ratio of the foamed sheet is in a range of 15 to 50 times, and a bending stiffness of the paper substrate in an MD direction is in a range of 150 mN to 700 mN.

In this packaging bag, the foamed sheet has the thickness in the range of 0.8 mm to 5.0 mm and the expansion ratio in the range of 15 to 50 times, and the paper substrate laminated on the outer side relative to the foamed sheet has the bending stiffness in the range of 150 mN to 700 mN. With this configuration in which the paper substrate having the bending stiffness of 150 mN or more is laminated on the foamed sheet having a cushioning function and a predetermined thickness, the paper substrate is not easily collapsed when dropped in the MD direction, for example, to thereby reduce drop impact transferred to the contents. Besides, the impact which is not absorbed by the paper substrate will be absorbed by the foamed sheet having the above predetermined thickness and expansion ratio. In the conventional art in which a plastic air bubble wrap sheet is simply attached to general kraft paper as a cushioning material, the strength may be low as a packaging bag, which causes drop impact to be transferred to the contents. In the above-mentioned packaging bag, however, the contents can be appropriately protected. In addition, according to the configuration of the above packaging bag, a plastic air bubble wrap sheet is not provided on the inner surface. Accordingly, the contents do not have indentation made by the bubbles or the like. Moreover, when the paper substrate has the bending stiffness of more than 700 mN, processing of the laminate into a packaging bag will be laborious. Therefore, the paper substrate preferably has the bending stiffness of 700 mN or less. Further, the term “bending stiffness” as used herein refers to stiffness of the material expressed by a load applied when a sample, which has been cut with a predetermined width and length and formed in a loop shape, is pressed to collapse. The bending stiffness can be measured by using a measurement machine available on the market, for example, a loop stiffness tester.

In the above packaging bag, the expansion ratio of the foamed resin sheet may be in the range of 30 to 40 times. Further, the bending stiffness of the paper substrate in the MD direction may be in the range of 200 mN to 600 mN. With this configuration, drop impact is less likely to be transferred to the contents so that the contents can be more appropriately protected.

In the above packaging bag, the sealed section in which the sealant layers facing each other are sealed may be provided in at least part of the periphery of the packaging bag, and the impact absorption section may be formed of the laminate on the outer edge of the sealed section. In this case, since the impact absorption section is provided on the outer edge of the sealed section sealed section, drop impact is mitigated by the impact absorption section, which first comes into contact with the ground when the packaging bag is dropped with the sealed section downward. Accordingly, the contents can be attempted to be better protected.

Furthermore, in the above packaging bag, the impact absorption section may be the unsealed section formed on the outer edge of the sealed section, or the wavy section which is the outer edge of the sealed section formed in a wavy shape. In the unsealed section, since the sealant layers facing each other are not sealed to each other, high flexibility can be obtained compared with the sealed section fixed by sealing. Accordingly, impact can be better absorbed. Further, in the wavy section, which is formed of continuous projecting pieces and recessed pieces, the projecting pieces of the wavy section have high flexibility compared with a general sealed section which is linearly formed. Accordingly, impact can be appropriately absorbed.

The above packaging bag may include a main body formed in a bag shape with an opening; and a sealing section that seals the opening of the main body. In this case, perforations may be formed in the sealing section. The sealing section may have a tab which is formed by cutting the sealing section. The tab may extend from a center to an end of the sealing section in a width direction. The tab may be formed at a position spaced from the adhesion region to the main body side by 3 to 20 mm. The perforations may be formed continuously from the tab in the sealing section. A tear tape may be attached continuously from the tab in the sealing section. With this configuration, the packaging bag can be easily opened from the tab.

Further, either one of the main body and the sealing section may have an adhesion region that adheres the main body and the sealing section, and the adhesion region may be formed of a double-sided tape or an adhesive which does not permit re-attachment between the main body and the sealing section. With this configuration, the sealing section is prohibited from being re-attached when the packaging bag was tampered with.

In the above packaging bag, the thickness of the adhesion region may be 50 μm or more, and the adhesive that constitutes the adhesion region may be a synthetic rubber-based thermoplastic adhesive having viscosity at 140° C. of 50000 mPa·s or more. In this case, the adhesion region may have high adhesiveness in normal temperature. Further, since the adhesive contained in the adhesion region is a synthetic rubber-based thermoplastic adhesive (or a pressure sensitive adhesive), the adhesive tends to have high hardness. In the packaging bag using such an adhesive, the adhesive itself is less likely to be broken when the sealing section is opened. As a consequence, in opening of the packaging bag, at least part of either the main body or the sealing section to which the adhesive is adhered, instead of the adhesive, is delaminated and broken. Accordingly, in opening of the sealing section, evidence of opening is created on the packaging bag so that tampering can be prevented. In the above packaging bag, the adhesive may be a styrene-isoprene based thermoplastic adhesive. In this case, evidence of opening can be more reliably created on the packaging bag. The thickness of the adhesion region may be 100 μm or more.

The packaging bag may be formed in a pillow shape. With this configuration, a decrease in the volume ratio of the capacity to the outer volume of the packaging bag can be prevented. Further, the packaging bag may include a plurality of storage spaces. With this configuration, the contents stored in the respective storage spaces do not overlap each other.

Advantageous Effects of Invention

According to a packaging bag of the present invention, the contents can be attempted to be better protected.

DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

With reference to the drawings, representative embodiments of the present invention will be described in detail. For the purpose of convenience, substantially the same elements are denoted by the same reference numbers, and the redundant description thereof may be omitted. In the following description, the thicknesses of the layers constituting a laminate are described based on the thicknesses after lamination. Further, it is to understood that these embodiments are intended to be representative of the present invention and that the present invention is not necessarily limited to the following embodiments.

First Embodiment

FIG. 1is a schematic cross-sectional view that illustrates a structure of a laminate10constituting a packaging bag according to the present embodiment. The laminate10includes a paper substrate8which includes a paper layer3, a foamed sheet7laminated on an inner surface of the paper substrate8, and a sealant layer9laminated on an inner surface of the foamed sheet7. The paper substrate8includes the paper layer3, which constitutes an outer surface of the packaging bag1, and an adhesive layer5laminated on the paper layer3. In the present embodiment, the adhesive layer5is made of polyethylene, for example. The paper substrate8has an MD direction (machine direction), which is a flow direction of the material according to production processes. The paper layer3and the adhesive layer5, which constitute the paper substrate8, have the MD direction in the same direction. A bending stiffness of the paper substrate8in the MD direction is in the range of 150 mN to 700 mN, and preferably in the range of 200 mN to 600 mN. Further, a thickness of the adhesive layer5is in the range of 5 to 40 μm, and a grammage of the entire paper substrate8including the paper layer3is in the range of 50 g/m2to 120 g/m2, and more preferably in the range of 60 g/m2to 100 g/m2. Further, a thickness of the paper substrate8is in the range of 50 to 250 μm. In addition, a peeling strength of the adhesive layer5may be higher than that of the paper layer3of the paper substrate8. In this case, delamination fracture of the adhesive layer5is less likely to occur than tearing of the paper layer3.

The material of the foamed sheet7is a polyolefin resin having cushioning characteristics, which may be, for example, polyethylene (PE) or polypropylene (PP). A thickness of the foamed sheet7is in the range of 0.8 mm to 5.0 mm, and preferably in the range of 0.8 to 2.5 mm in view of the volume ratio of the capacity to the outer volume and ease of production. An expansion ratio of the foamed sheet7is in the range of approximately 15 to 50 times, and preferably in the range of approximately 30 to 40 times. The expansion ratio is expressed as the density of resin before foaming/the density of resin after foaming. A peeling strength of the foamed sheet7may be higher than that of the paper layer3of the paper substrate8. In this case, delamination fracture of the foamed sheet7is less likely to occur than the paper layer3.

The sealant layer9is a layer having a portion to be thermally sealed when the laminate10is formed into a bag shape. A material for the sealant layer9may be, for example, linear low density polyethylene (LLDPE), high density polyethylene (HDPE), or the like. A thickness of the sealant layer9is, for example, in the range of 8 to 40 μm. The sealant layer9is an inner surface of the packaging bag1and a layer in contact with the contents. In the present embodiment, it is contemplated that the contents are slid into the packaging bag1which is pre-formed in a bag shape. Accordingly, in view of slipperiness of the contents, the sealant layer9is preferably made of HDPE, which is slippery.

Although the thicknesses of the respective layers in the laminate10are not specifically limited, the thickness of the laminate10can be reduced over the conventional one so that the volume ratio of the capacity to the outer volume of the packaging bag1can be improved.

The laminate10is produced, for example, by a method described below. First, the adhesive layer5is laminated on one surface of the sheet-shaped paper layer3by extruder processing such as extrusion lamination to thereby form the paper substrate8. Further, the sheet-shaped sealant layer9is laminated on the foamed sheet7by thermal lamination. Then, the paper substrate8is laminated on the laminate of the foamed sheet7and the sealant layer9by thermal lamination. Thus, the laminate10having the paper layer3, the adhesive layer5, the foamed sheet7, and the sealant layer9, which are laminated in sequence is formed. The production method is not specifically limited, and the laminate10can also be formed by extruder processing to laminate the paper substrate8formed by extruder processing on the laminate of the foamed sheet7and the sealant layer9formed by thermal lamination. The laminate10can be formed into a bag after it is cut into a predetermined width by slit processing.

FIGS. 2A and 2Bare plan views of the packaging bag1formed of the laminate10. As shown inFIGS. 2A and 2B, the packaging bag1, which has a substantially rectangular shape in plan view, includes a main body20formed in a bag shape with an opening21, and a sealing section30for sealing the opening21. The sealing section30is a cover (also referred to as a head or flap) that seals the packaging bag1, and is integrally formed with the main body20. In the following description, a direction in which the opening21extends is defined as a width direction, and a direction perpendicular to the width direction is defined as an opening direction.FIG. 3is a cross-sectional view taken along the width direction of the packaging bag1, andFIG. 4is a cross-sectional view taken along the opening direction of the packaging bag1. In the illustrated example, a side of the packaging bag1which is opposite to the opening21is folded to form a folded section22. Further, sealed sections23are formed on both sides of the packaging bag1in the width direction. In the sealed section23, the sealant layers9facing each other are thermally sealed along the opening direction. Thus, the folded section22and the sealed sections23are formed to thereby define an inner space S in the packaging bag1(seeFIGS. 3 and 4).

As shown inFIG. 4, the sealing section30is formed by the paper substrate8extending from the laminate10to the outside of the opening21. Although the sealing section may also be formed by the laminate10, the sealing section, when formed by only the paper substrate8, can be reduced in thickness. The sealing section30can be folded over to cover the opening21. The sealing section30has an adhesion region31which extends in the width direction. The adhesion region31may be made of a double-sided tape or an adhesive that is prevented from being re-attached to the main body20. With this configuration, the sealing section30is prevented from being re-attached when the packaging bag1has been tampered with. Examples of an adhesive prevented from being re-attached include a hot melt adhesive.

The above packaging bag1is produced, for example, by a method described below. First, the elongated laminate10is formed by laminating the elongated laminate of the foamed sheet7and the sealant layer9fed out from a roll on the elongated paper substrate8fed out from a roll. In the present embodiment, the foamed sheet7and the sealant layer9are not laminated in the sealing section30. Accordingly, the laminate of the foamed sheet7and the sealant layer9are laminated, leaving a predetermined area unlaminated from one end edge of the paper substrate8in the direction perpendicular to the longitudinal direction. Then, the laminate10is folded in the direction perpendicular to the longitudinal direction. Here, the sealant layer9of the laminate10faces inward. Then, in the laminate10thus folded, a portion of the sealant layer9corresponding to the sealed section23is thermally sealed in the direction perpendicular to the longitudinal direction (opening direction of the packaging bag). Thus, bag-shaped portions are continuously formed in the laminate10. Subsequently, the bag-shaped portions continuously formed are separated at positions of the thermal seal, to thereby obtain the packaging bag1. The adhesion region31may be formed in the sealing section30in any of the above steps. This production method is not specifically limited. For example, the sealant layer9may be thermally sealed after the laminate10is cut.

In the present embodiment, the MD direction of the paper substrate8, the foamed sheet7, and the sealant layer9corresponds to the width direction of the packaging bag1, and the adhesion region31extends in the MD direction. Further, for ease of opening along the adhesion region31, perforations33are formed in the sealing section30. The perforations33are formed at positions spaced from the adhesion region31to the main body20side by a distance of 3 to 20 mm when the sealing section30is unsealed. Accordingly, by cutting the sealing section30along the perforations33, the packaging bag1can be easily opened.

As described above, in the packaging bag1according to the present embodiment, the foamed sheet7has the thickness in the range of 0.8 mm to 5.0 mm and the expansion ratio in the range of 15 to 50 times, and the paper substrate8disposed on the outer side relative to the foamed sheet7has the bending stiffness in the range of 150 mN to 700 mN. Accordingly, due to the synergy of the paper substrate8having the bending stiffness of 150 mN or more and the foamed sheet7laminated on the paper substrate8, the paper substrate8is not easily collapsed, for example, when dropped in the MD direction and the drop impact is less likely to be transferred to the contents. Besides, the impact which is not absorbed by the paper substrate8will be absorbed by the foamed sheet7having the thickness of 0.8 mm to 5.0 mm and the expansion ratio of 15 to 50 times.

In the conventional art in which a plastic air bubble wrap sheet is attached to a general kraft paper as a cushioning material, for example, when a plastic air bubble wrap sheet is simply attached to the substrate having the bending stiffness of approximately 140 to 160 mN, the strength may be low as a packaging bag, which causes drop impact to be transferred to the contents. However, in the packaging bag1of the present embodiment, which uses the above configuration, the contents can be appropriately protected and do not have indentation made by the bubbles or the like.

Referring now toFIGS. 5A, 5B, 6A, and 6B, a first modified example and a second modified example of the packaging bag according to the first embodiment will be described.FIGS. 5A and 5Bare plan views of a packaging bag1aof the first modified example formed of the laminate10. With reference toFIGS. 5A and 5B, the packaging bag1a, as with the packaging bag1, includes a main body20formed in a bag shape with an opening21, and a sealing section30for sealing the opening21. In the packaging bag1a, sealed sections23are formed on both sides in the width direction. Further, an impact absorption section is formed on the outer edge of the sealed section23, extending from one end to the other end in the opening direction. The impact absorption section mitigates drop impact or the like on both end edges in the width direction of the packaging bag1a. The impact absorption section in the present embodiment is formed of, for example, a wavy section24a. That is, the outer edge of the sealed section23is formed in a wavy shape which extends outward in the width direction at a regular interval along the opening direction. The size of the wavy form is not specifically limited. For example, the height and pitch of the wave shapes in the wavy section24aare 2 mm and 8 mm, respectively. The wavy section24ais softer than the sealed section23, and can efficiently absorb impact.

The packaging bag1ahaving the above wavy section24acan be formed, for example, by cutting the thermally heated portion into the wavy shape in production process of the above packaging bag1to thereby form a predetermined impact absorption section.

Further,FIGS. 6A and 6Bare plan views of a packaging bag1bof the second modified example formed of the laminate10. With reference toFIGS. 6A and 6B, the packaging bag1b, as with the packaging bag1, includes a main body20formed in a bag shape with an opening21, and a sealing section30for sealing the opening21. In the packaging bag1b, sealed sections23bare formed on both sides in the width direction. The impact absorption section in this modified example is provided by an unsealed section24b. In the unsealed section24b, the sealant layers9facing each other are not sealed at the outer edge, and the laminates10face each other (see the unsealed section24dinFIG. 25). That is, the sealed section23bis disposed slightly inward from the outer edge of the packaging bag1b. Therefore, the unsealed section24bhas flexibility compared with the sealed section23of the packaging bag1to thereby efficiently absorb impact. As an example, the length in the width direction of the sealed section23bis 10 mm, and the length in the width direction of the unsealed section24bis 5 mm.

The packaging bag1bis formed by the same method as that of the packaging bag1aof the modified example. According to the above production method, the packaging bags1aare continuously formed, the sealed section23bof one packaging bag1band the sealed section23bof the subsequent packaging bag1bare adjacent to each other with their unsealed sections24binterposed therebetween. That is, an unsealed portion between the sealed sections23bis cut to thereby form the impact absorption section (unsealed section24b).

According to the packaging bag1aand1b, since the impact absorption section formed of the wavy section24aor the unsealed section24bis provided on the outer edge of the sealed section23, drop impact is mitigated by the impact absorption section, which first comes into contact with the ground when the packaging bags1aand1bare dropped with the sealed section23downward. Further, in the packaging bags1aand1b, since the paper substrate8has the bending stiffness in the range of 150 mN to 700 mN and the foamed sheet7has the predetermined thickness and the expansion ratio as described above, the impact which is not absorbed by the impact absorption section formed of the wavy section24aor the unsealed section24bis prevented from being easily transferred to the contents by virtue of the paper substrate8and the foamed sheet7. Therefore, accordingly to the packaging bags1aand1bof this modified example, the contents in the packaging bag can be more reliably protected.

Further, in the wavy section24aof the packaging bag1aaccording to the modified example, which is formed by continuous projecting pieces and recessed pieces, the projecting pieces have high flexibility compared with a general sealed section23. Further, the unsealed section24bof the packaging bag1baccording to the modified example, which has an unsealed portion in the sealant layers9facing each other on the outer edge of the packaging bag1b, is configured to have high flexibility compared with a typical sealed section23. Therefore, these impact absorption sections can effectively absorb impact.

Second Embodiment

A packaging bag101according to the present embodiment differs from the packaging bag1of the first embodiment in that the laminate10is formed in a pillow shape. The following provides a description mainly of the differences from the first embodiment. The elements and components that are the same as those of the first embodiment are referred to by the same reference numbers, and detailed description thereof will be omitted.

As shown inFIGS. 7 and 8, the packaging bag101is a bag body formed of the laminate10in a pillow shape with the sealant layer9facing inward (the paper layer3facing outward). The packaging bag1is in a substantially rectangular shape in plan view. The term “pillow shape” as used herein refers to a shape in which a pair of opposing two sides are folded over, and the ends of these folded over portions are sealed to each other. In the illustrated example, both end sides102of the packaging bag101in the width direction are folded over, and the ends of these folded over portions form a sealed section103. In the sealed section103, both ends are thermally sealed to each other in the longitudinal direction at a center of the packaging bag101in the width direction. The present embodiment shows the packaging bag101in a sealed state. Both ends of the packaging bag101in the longitudinal direction are sealed sections105and106, which are each thermally sealed. Thus, an inner space S is formed in the packaging bag101.

At the sealed sections103in the laminate10, the sealant layers9are thermally sealed to each other in the state of being laminated facing each other (seeFIG. 8). This packaging form is performed by a pillow packaging machine, which uses the laminate10in a roll shape to wrap the contents in a continuous manner. In this case, the laminate10is formed into a package with the contents placed on the sealant layer9. Accordingly, in view of slipperiness of the contents, the sealant layer9is preferably made of LLDPE, which is less slippery than HDPE. Further, in this production method, the longitudinal direction of the sealed section103corresponds to the MD direction of the laminate10.

The sealed section105has a notch (start point of cutting)107(seeFIG. 7). In the present embodiment, the notch107is formed on one end of the sealed section105in the width direction. As a result, since the opening direction by the notch107corresponds to the MD direction of the laminate10, the packaging bag101can be easily opened. Further, the contents contained in the inner space S are prevented from being damaged when the packaging bag1is opened. In the illustrated example, the notch107is shown as a Y notch formed in Y-shape. However, the notch17is not limited to the Y notch, and may be an I notch or the like.

In the packaging bag101formed as a pillow shape as described above, the same effects as those of the packaging bag1of the first embodiment can be achieved. In addition, a decrease in the volume ratio of the capacity to the outer volume of the packaging bag101can be prevented.

Referring now toFIG. 9, a modified example of the packaging bag according to a second embodiment will be described.FIG. 9is a plan view of a packaging bag according to the second embodiment of the present invention. As shown inFIG. 9, a packaging bag101ais a bag body formed of the laminate10in a pillow shape with the sealant layer9facing inward as with the packaging bag101. The packaging bag101ais in a substantially rectangular shape in plan view. In the illustrated example, an impact absorption section is formed on the outer edge of the sealed section105aand106ain the width direction. The impact absorption section of the present embodiment is formed of an unsealed section108as with the second modified example of the first embodiment. That is, in the unsealed section108, the sealant layers9of the laminates10facing each other are not thermally sealed.

In this packaging bag101a, the same effects as those of the packaging bag101can be achieved. In addition, as with the modified example of the first embodiment, drop impact is mitigated by the impact absorption section (unsealed section108), which first comes into contact with the ground when the packaging bag101ais dropped with the sealed sections105aand106adownward, to thereby appropriately protect the contents. Moreover, instead of the unsealed section108, the impact absorption section having a configuration such as the wavy section24acan also be provided in the packaging bag101.

Third Embodiment

A packaging bag201according to the present embodiment is the same as the first embodiment in that it is formed of the laminate10, but differs from the packaging bag1of the first embodiment in that it has a plurality of inner spaces. The following provides a description mainly of the differences from the first embodiment. The elements and components that are the same as those of the first embodiment are referred to by the same reference numbers, and detailed description thereof will be omitted.

As shown inFIG. 10, the packaging bag201includes a main body220formed in a bag shape with an opening221, and a sealing section30for sealing the opening221. The packaging bag201has a substantially rectangular shape in plan view. In the packaging bag201, a side opposite to the opening221is folded to form a folded section22. Further, sealed sections23are formed on both sides of the packaging bag201in the width direction. A sealed section223is formed at the center in the width direction of the main body220so as to extend in the opening direction. In the sealed section223, the sealant layers9facing each other are thermally sealed as with the sealed section23. Accordingly, inner spaces S1and S2are formed as two storage spaces in the main body of the packaging bag201. Since the inner space S1and the inner space S2are separated by the sealed section223, the contents in the inner space S1and the contents in the inner space S2do not overlap each other. Further, the packaging bag201has the same effects as those of the packaging bag1of the first embodiment.

In the packaging bag of the present embodiment, as shown inFIG. 11, the wavy section24awhich is the impact absorption section can be provided on the end of the packaging bag201aas with the modified example of the first embodiment. Accordingly, drop impact can be mitigated by the wavy section24aabsorbing an impact to the packaging bag201ato thereby appropriately protect the contents. Further, the unsealed section24bmay be provided as the impact absorption section instead of the wavy section24a.

Fourth Embodiment

A packaging bag301according to the present embodiment is the same as the first embodiment in that it is formed of the laminate10, but differs from the packaging bag1of the first embodiment in that it has a tab in the sealing section. The following provides a description mainly of the differences from the first embodiment. The elements and components that are the same as those of the first embodiment are referred to by the same reference numbers, and detailed description thereof will be omitted.

As shown inFIG. 12, the packaging bag301includes a main body20and a sealing section330, and has a substantially rectangular shape in plan view. Two tabs335, which are formed by cutting the sealing section330, are provided at the center in the width direction of the sealing section330. The tab335has two cutting lines335awhich are spaced in the opening direction and extend in the width direction and a cutting line335bwhich connects the ends of the cutting line335a. The tab335is formed to extend from the center to the end in the width direction of the sealing section330. The direction in which the tab335extends corresponds to the MD direction of the laminate10. The tab335is provided at a position spaced from the adhesion region31to the proximal end side of the sealing section330by 3 to 20 mm. A user can easily open the packaging bag301sealed by the adhesion region31by pulling the tab335of the packaging bag301in the width direction. Further, the packaging bag301has the same effects as those of the packaging bag1of the first embodiment.

In the packaging bag of the present embodiment, as shown inFIG. 13, the wavy section24awhich is the impact absorption section can be provided on the end of the packaging bag301aas with the modified example of the first embodiment. Accordingly, drop impact can be mitigated by the wavy section24aabsorbing an impact to the packaging bag301ato thereby appropriately protect the contents. Further, the unsealed section24bmay be provided as the impact absorption section instead of the wavy section24a.

Fifth Embodiment

A packaging bag401according to the present embodiment differs from the packaging bag301of the fourth embodiment in that it has perforations in the sealing section. The following provides a description mainly of the differences from the fourth embodiment. The elements and components that are the same as those of the first embodiment are referred to by the same reference numbers, and detailed description thereof will be omitted.

As shown inFIG. 14, the packaging bag401includes a main body20and a sealing section430, and has a substantially rectangular shape in plan view. Two tabs435are provided at the center in the width direction of the sealing section430. The tab435has two cutting lines435awhich are spaced in the opening direction and extend in the width direction and a cutting line435bwhich connects the ends of the cutting line435a. The tab has perforations which extend from the cutting line435ato the end in the width direction of the sealing section430. That is, the sealing section430has perforations436which are continuous from the cutting line435aof the tab435. The direction in which the tab435and the perforations436extend corresponds to the MD direction of the laminate10. The tab435and the perforations436are provided at a position spaced from the adhesion region31to the proximal end side of the sealing section430by 3 to 20 mm. A user can easily open the packaging bag401sealed by the adhesion region31by pulling the tab435of the packaging bag401in the width direction. Further, the packaging bag401has the same effects as those of the packaging bag1of the first embodiment.

In the packaging bag of the present embodiment, as shown inFIG. 15, the wavy section24awhich is the impact absorption section can be provided on the end of the packaging bag401aas with the modified example of the first embodiment. Accordingly, drop impact can be mitigated by the wavy section24aabsorbing an impact to the packaging bag401ato thereby appropriately protect the contents. Further, the unsealed section24bmay be provided as the impact absorption section instead of the wavy section24a.

Sixth Embodiment

A packaging bag501according to the present embodiment is the same as the fifth embodiment in that it is formed of the laminate10, but differs from the packaging bag401of the fifth embodiment in the shape of the tab and the perforations. The following provides a description mainly of the differences from the fifth embodiment. The elements and components that are the same as those of the first embodiment are referred by the same reference numbers, and detailed description thereof will be omitted.

As shown inFIG. 16, the packaging bag501includes a main body20and a sealing section530, and has a substantially rectangular shape in plan view. In the sealing section530, the perforations536are provided by two lines of perforations formed in the width direction. The direction in which the perforations536extend corresponds to the MD direction of the laminate10. Further, the perforations536are provided at a position spaced from the adhesion region31to the proximal end side of the sealing section530by 3 to 20 mm. Tabs535are continuously formed on both ends of the perforations536. The tab535has two cutting lines535awhich are spaced in the opening direction and extend in the width direction. These cutting lines535aare formed to be continuous from the end in the width direction of the sealing section530to the perforations536. A user can easily open the packaging bag501sealed by the adhesion region31by pulling the tab535of the packaging bag501in the width direction. Further, the packaging bag501has the same effects as those of the packaging bag1of the first embodiment.

In the packaging bag of the present embodiment, as shown inFIG. 17, the wavy section24awhich is the impact absorption section can be provided on the end of the packaging bag501aas with the modified example of the first embodiment. Accordingly, drop impact can be mitigated by the wavy section24aabsorbing an impact to the packaging bag501ato thereby appropriately protect the contents. Further, the unsealed section24bmay be provided as the impact absorption section instead of the wavy section24a.

Seventh Embodiment

A packaging bag601according to the present embodiment is the same as the sixth embodiment in that it is formed of the laminate10, but differs from the packaging bag501of the sixth embodiment in that it has a tear tape. The following provides a description mainly of the differences from the sixth embodiment. The elements and components that are the same as those of the first embodiment are referred to by the same reference numbers, and detailed description thereof will be omitted.

As shown inFIG. 18, the packaging bag601includes a main body20and a sealing section630, and has a substantially rectangular shape in plan view. The sealing section630has perforations536and tabs535as with the sixth embodiment. On the inner side surface of the sealing section630, a tear tape638which extends in the width direction is formed at a position where the perforations536and the tabs535are provided. The tear tape638is continuously formed from one end to the other end in the width direction of the sealing section630. A user can easily open the packaging bag601sealed by the adhesion region31by pulling the tab535of the packaging bag601in the width direction. Further, the packaging bag601has the same effects as those of the packaging bag1of the first embodiment.

In the packaging bag of the present embodiment, as shown inFIG. 19, the wavy section24awhich is the impact absorption section can be provided on the end of the packaging bag601aas with the modified example of the first embodiment. Accordingly, drop impact can be mitigated by the wavy section24aabsorbing an impact to the packaging bag601ato thereby appropriately protect the contents. Further, the unsealed section24bmay be provided as the impact absorption section instead of the wavy section24a.

While the embodiments of the present invention were described in detail with reference to the drawings, specific configurations are not limited to these embodiments. For example, in the aforementioned example, the sealed section23was formed on one end edge in the MD direction of the foamed sheet in the laminate10so as to extend in the direction perpendicular to the MD direction. However, in this case, the direction perpendicular to the MD direction should be construed as including not only being exactly at a right angle but also an angle with a margin of approximately ±10 degrees.

Further, configurations of the aforementioned embodiments may be partially combined or replaced. For example, a tear tape may be formed along the perforations436in the sealing section430of the fifth embodiment as with the tear tape638in the sealing section630of the seventh embodiment.

Further, the impact absorption section of the above embodiment may be formed in the unsealed section or in the wavy section. In addition, the impact absorption section is only required to be formed of the laminate which forms the packaging bag. For example, the impact absorption section may be provided by the outer edge of the sealed section formed in a comb shape. Further, the impact absorption section may be formed on part of or the entire peripheral edge of the packaging bag as with other embodiments.

Further, for the adhesion region31that adheres the main body20and the sealing section30, a general hot melt adhesive or the like can be used. However, the adhesion region31may contain a synthetic rubber-based thermoplastic adhesive such as a styrene-isoprene based thermoplastic adhesive (pressure sensitive adhesive). This adhesive may contain additives such as a filler, thickener, heat resistant resin and pigment. Further, the adhesive may have viscosity (melt viscosity) at 140° C. of 15000 mPa·s or more. In this case, since the adhesive in the adhesion region31has high adhesiveness at normal temperature, the paper layer3that constitutes the surface of the main body20can successfully exhibit delamination fracture in opening of the sealing section30. The viscosity of the adhesive may be, for example, 50000 mPa·s or more, or alternatively 68000 mPa·s or more at 140° C. Further, the viscosity of the adhesive may be, for example, 270000 mPa·s or more at 120° C., 30000 mPa·s or more at 160° C., and 16500 mPa·s or more at 180° C. The sealing strength of the adhesion region31may be, for example, in the range of 6 N to 15 N. The sealing strength may be measured in accordance with JIS Z 1707:1997, for example, by using a tensile and compression test machine (Tensilon RTF-1250, manufactured by A & D Co., Ltd.).

When the thickness of the adhesion region31is more than 50 μm and the viscosity of the adhesive at 140° C. is 50000 mPa·s or more as described above, the adhesion region31can exhibit high adhesiveness at normal temperature. Further, since the adhesive contained in the adhesion region31is a synthetic rubber-based thermoplastic adhesive, the adhesion region31tends to have high hardness. In the packaging bag1or the like using the adhesion region31, since the adhesion region31is less likely to be broken in opening of the sealing section30, part of at least either the paper layer3of the main body20or the adhesive layer5of the sealing section30to which the adhesion region31is adhered, instead of the adhesion region31, is delaminated and broken in opening of the packaging bag1or the like. Accordingly, after the sealing section was opened, evidence of opening is created on the packaging bag so that tampering can be prevented. Further, the evidence of opening corresponds to a portion of the main body20and the sealing section30which is delaminated and broken by the adhesion region31.

The term tampering as used herein refers to, for example, opening of the packaging bag and alteration or removal of the contents by a third party other than the addressee during delivery. If no evidence of opening is created when the packaging bag was opened by a third party, it is difficult for the addressee to determine whether the contents were tampered with. However, by using the packaging bag having the aforementioned adhesion region, the addressee can easily determine whether it was tampered with or not depending on the presence or absence of evidence of opening. Therefore, by using such a packaging bag, tampering such as removal of the contents can be prevented. In addition, the packaging bag1does not need to be provided with an opening assistance function such as perforations to ensure the sealing section30can be opened without requiring particular force.

Further, when a natural rubber-based adhesive is uses as an adhesive, the natural rubber-based adhesive and the paper layer3of the main body20tend to be easily peeled from each other. Accordingly, even if the natural rubber-based adhesive has high viscosity (adhesiveness), the paper layer3fails to exhibit delamination fracture. As a consequence, the packaging bag may be resealed without leaving evidence of opening. Therefore, it is preferred to use a synthetic rubber-based thermoplastic adhesive as an adhesive.

Further, the adhesive used may be a styrene-isoprene based thermoplastic adhesive. In this case, evidence of opening can be more reliably created on the packaging bag1. The thickness of the adhesion region31may be 100 μm or more. In this case, since the amount of an adhesive per unit area increases in the adhesion region31, evidence of opening is more reliably created in the packaging bag1.

Further, the surface of the main body20adhering to the adhesion region31may be the paper layer3in the paper substrate8, or alternatively, the surface of the sealing section30adhering to the adhesion region31may be the adhesive layer5in the paper substrate8. In this case, in opening of the sealing section30, at least part of the paper layer3that constitutes the surface of the main body20and adheres to the adhesion region31, instead of the adhesion region31, is delaminated and broken to thereby create evidence of opening. The adhesion region31may be provided in either the main body20or the sealing section30. Further, the length of the adhesion region31in the opening direction is provided to leave a margin of, for example, approximately in the range of 2 mm to 10 mm from the inside of the opening width. The thickness of the sealing section30is, for example, more than 50 μm. In this case, a sufficient amount of an adhesive can be provided per unit area in the sealing section30, and the paper layer3that constitutes the surface of the main body20can successfully exhibit delamination fracture in opening of the sealing section30. The thickness of the sealing section30may be 100 μm or more and 200 μm or less.

EXAMPLES

The above embodiments will be further described with reference to the examples and comparative examples as below. However, the sizes and the like of the packaging bag are merely examples, and the above embodiments are not limited to what is described in the examples. The packaging bags according to Examples 1 to 11 below have the shape of the packaging bag1of the first embodiment. Table 1 shows Examples 1 to 11 and Comparative Examples 1 to 6.

First, on a paper substrate having a paper layer and an adhesive layer made of PE with 15 μm thickness, a sealant layer made of a foamed PE sheet with 1.5 mm thickness and HDPE with 15 μm thickness was thermally laminated to thereby obtain a laminate. Subsequently, both sides of the laminate in the opening direction were thermally sealed with the sealant layer facing inward so that the packaging bag of Example 1 was obtained with a long side (side in the width direction) of 255 mm and a short side (side in the opening direction) of 195 mm. The grammage of the paper substrate was 75 g/m2, and the bending stiffness of the paper substrate in the MD direction was 241 mN. Further, the expansion ratio of the foamed PE sheet was 30 times. The bending stiffness was measured by a loop stiffness tester (e.g., manufactured by Toyo Seiki Co., Ltd.). The measurement was performed using a sample, which was a loop of a strip made of a paper substrate having 15 mm width and 160 mm length. The number of samples was five.

In Example 2, the thickness of the foamed PE sheet was different from Example 1. That is, the packaging bag of Example 2 was formed of a laminate composed of a paper substrate having a bending stiffness of 241 mN, a foamed PE sheet having a thickness of 1.0 mm and an expansion ratio of 30 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

In Example 3, the thickness of the foamed PE sheet was different from Example 1. That is, the packaging bag of Example 3 was formed of a laminate composed of a paper substrate having a bending stiffness of 241 mN, a foamed PE sheet having a thickness of 3.0 mm and an expansion ratio of 30 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

In Example 4, the thickness of the foamed PE sheet was different from Example 1. That is, the packaging bag of Example 4 was formed of a laminate composed of a paper substrate having a bending stiffness of 241 mN, a foamed PE sheet having a thickness of 4.0 mm and an expansion ratio of 30 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

In Example 5, the expansion ratio of the foamed PE sheet was different from Example 1. That is, the packaging bag of Example 5 was formed of a laminate composed of a paper substrate having a bending stiffness of 241 mN, a foamed PE sheet having a thickness of 1.5 mm and an expansion ratio of 20 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

In Example 6, the expansion ratio of the foamed PE sheet was different from Example 1. That is, the packaging bag of Example 6 was formed of a laminate composed of a paper substrate having a bending stiffness of 241 mN, a foamed PE sheet having a thickness of 1.5 mm and an expansion ratio of 40 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

In Example 7, the expansion ratio of the foamed PE sheet was different from Example 1. That is, the packaging bag of Example 7 was formed of a laminate composed of a paper substrate having a bending stiffness of 241 mN, a foamed PE sheet having a thickness of 1.5 mm and an expansion ratio of 50 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

In Example 8, the configuration of the sealant layer was different from Example 1. That is, the packaging bag of Example 8 was formed of a laminate composed of a paper substrate having a bending stiffness of 241 mN, a foamed PE sheet having a thickness of 1.5 mm and an expansion ratio of 30 times, and an LLDPE sheet having a thickness of 30 μm, laminated in the same manner as Example 1.

In Example 9, the grammage and bending stiffness of the paper substrate was different from Example 1. That is, the packaging bag of Example 9 was formed of a laminate composed of a paper substrate having a grammage of 60 g/m2and a bending stiffness of 159 mN, a foamed PE sheet having a thickness of 1.5 mm and an expansion ratio of 30 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

In Example 10, the grammage and bending stiffness of the paper substrate was different from Example 1. That is, the packaging bag of Example 10 was formed of a laminate composed of a paper substrate having a grammage of 84 g/m2and a bending stiffness of 393 mN, a foamed PE sheet having a thickness of 1.5 mm and an expansion ratio of 30 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

In Example 11, the grammage and bending stiffness of the paper substrate was different from Example 1. That is, the packaging bag of Example 11 was formed of a laminate composed of a paper substrate having a grammage of 100 g/m2and a bending stiffness of 531 mN, a foamed PE sheet having a thickness of 1.5 mm and an expansion ratio of 30 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

Comparative Example 1

In the packaging bag of Comparative Example 1, an air bubble cushioning material made of PE with 2.5 mm thickness was disposed inside a packaging bag made of kraft paper. The air bubble cushioning material and kraft paper were bonded to each other by an adhesive. The kraft paper had a grammage of 80 g/m2and a bending stiffness of 166 mN. In this packaging bag, a sealed section was provided on one of the long sides, and an adhesive tape was adhered to the sealed section.

Comparative Example 2

In Comparative Example 2, the thickness of the foamed PE sheet was different from Example 1. That is, the packaging bag of Comparative Example 2 was formed of a laminate composed of a paper substrate having a bending stiffness of 241 mN, a foamed PE sheet having a thickness of 5.5 mm and an expansion ratio of 30 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

Comparative Example 3

In Comparative Example 3, the thickness of the foamed PE sheet was different from Example 1. That is, the packaging bag of Comparative Example 2 was formed of a laminate composed of a paper substrate having a bending stiffness of 241 mN, a foamed PE sheet having a thickness of 0.5 mm and an expansion ratio of 30 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

Comparative Example 4

In Comparative Example 4, the grammage and bending stiffness of the paper substrate was different from Example 1. That is, the packaging bag of Comparative Example 4 was formed of a laminate composed of a paper substrate having a grammage of 50 g/m2and a bending stiffness of 93 mN, a foamed PE sheet having a thickness of 1.5 mm and an expansion ratio of 30 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

Comparative Example 5

In Comparative Example 5, the configuration of the sealant layer was different from Comparative Example 4. That is, the packaging bag of Comparative Example 5 was formed of a laminate composed of a paper substrate having a grammage of 50 g/m2and a bending stiffness of 93 mN, a foamed PE sheet having a thickness of 1.5 mm and an expansion ratio of 30 times, and an LLDPE sheet having a thickness of 30 μm, laminated in the same manner as Example 1.

Comparative Example 6

In Comparative Example 6, the grammage and bending stiffness of the paper substrate was different from Example 1. That is, the packaging bag of Comparative Example 6 was formed of a laminate composed of a paper substrate having a grammage of 120 g/m2and a bending stiffness of 961 mN, a foamed PE sheet having the thickness of 1.5 mm and an expansion ratio of 30 times, and an HDPE sheet having a thickness of 15 μm, laminated in the same manner as Example 1.

For Examples 1 to 11 and Comparative Examples 1 to 6, the puncture strength, impact resistance and processability were tested to evaluate the basic performance practically required as a packaging bag.

The evaluation of puncture strength was performed on the basis of the puncture strength (compliant with JIS Z 1707) of the laminate that forms the packaging bag. The evaluation was made as follows: A. The puncture strength was 6.5 N or more, which was rated as being most preferred; B. The puncture strength was in the range of 4.5N or more and less than 6.5 N, which was rated as having no practical problem; and C. The puncture strength was less than 4.5N, which was rated as having a practical problem. The number of samples was 5.

An impact resistance test was a test to check whether a packaging bag and the contents inside are not damaged when a certain impact is applied to the packaging bag containing the contents. The test was performed by dropping a sample containing the contents from a position of 70 cm height. The contents were a compact disk (CD) stored in a plastic case. The test was performed 7 times per sample with different impact locations. The impact locations were front and rear surfaces of the packaging bag, a side of the packaging bag on the sealing section side, a side of the packaging bag opposite to the sealing section, one of the sides in the width direction of the packaging bag, a corner between the other of the sides in the width direction and the side on the sealing section side, and a corner between the other of the sides in the width direction and the side opposite to the sealing section. The number of samples was 50. The evaluation was made as follows: A. The breakage ratio of the plastic case was less than 40%, which was rated as being preferred; B. The breakage ratio was in the range of 40% or more and less than 70%, which was rated as having no practical problem; and C. The breakage ratio was more than 70%, which was rated as having a practical problem.

The evaluation of processability was performed based on whether the laminate can be easily folded, and can be appropriately processed by a laminating machine, bag forming machine, or the like in the production process. That is, the evaluation was a flexibility evaluation, and rated as follows: A. Bending was easy according to the flexibility evaluation; B. No practical problem found; and C. A practical problem found.

Table 2 shows the results of these evaluation.

As the results of evaluation, a practical problem was not found in Examples 1 to 11. On the other hand, Comparative Example 1 was evaluated as C in the impact resistance test. The reason for this seems to be that the entire external material that constitutes the packaging bag of Comparative Example 1 has low strength since the bag is configured of the paper substrate having a relatively low bending stiffness and a highly soft air bubble cushioning material attached to the paper substrate. In this case, impact tends to be transferred to the contents particularly when the packaging bag is dropped with the side or corner facing downward. In Comparative Example 2, which uses a foamed sheet having a large thickness as 5.5 mm, the processability was evaluated as C. In Comparative Example 3, which uses a foamed sheet having a small thickness as 0.5 mm, the impact resistance and puncture strength were both evaluated as C. In Comparative Examples 4 and 5, which use a paper substrate having small bending stiffness, the impact resistance and puncture strength were evaluated as C. In Comparative Example 6, the impact resistance and puncture strength were evaluated as A, while the processability was evaluated as C due to the bending stiffness of the paper substrate being too large. Based on the above evaluations, it was found that the contents were appropriately protected by the packaging bag according to the present embodiment.

Next, the examples will be described for an anti-tamper function with the adhesive included in the adhesion region31having the viscosity of a predetermined amount or more. Similarly to the above examples, the sizes and the like of the packaging bag are merely examples, and the above embodiments are not limited to what is described in the examples. Further, the packaging bags according to Example 21 and Comparative Examples 21 to 23 described below have the shape of the packaging bag1of the first embodiment (seeFIGS. 1 to 4).

First, a paper substrate formed of a paper layer and an adhesive layer made of polyethylene provided on the paper layer. As the paper layer, Taio Atlas manufactured by Daio Paper Corporation (grammage: 75 g/m2) was used. Further, as the adhesive layer, a polyethylene layer having 30 μm thickness was used. Then, a foam layer and a sealant layer was laminated by polyethylene sandwich lamination. As the foam layer, Minafoam (registered trademark) manufactured by Sakai Chemical Industry Co., Ltd. having approximately 1.0 mm thickness was used. Further, as the sealant layer, a polyethylene layer having 30 μm thickness was used. Then, the paper substrate, the foam layer, and the sealant layer were laminated by thermal lamination to thereby obtain a laminate. Then, this laminate was folded with the sealant layer facing inward. At this time, the laminate was folded to have a long side (side in the width direction) of 255 mm length and a short side (side in the opening direction) of 195 mm length. Both sides in the width direction of the folded laminate were thermally sealed to thereby obtain the packaging bag of Example 21 having the main body with an opening and the sealing section. Further, the sealing section of the packaging bag had only the paper substrate.

Then, on the adhesive layer of the substrate that constitutes the sealing section, an adhesive was applied in the width direction to thereby form an adhesive layer having 10 mm width, 250 mm length, and 100 μm thickness. As the adhesive, a styrene-isoprene based thermoplastic adhesive (TN-571Z, manufactured by MORESCO corporation), which is a synthetic rubber-based thermoplastic adhesive, was used. Then, the sealing section was folded over, and the adhesive layer was adhered to the main body to thereby seal the packaging bag. In Example 21, the adhesive had viscosity of 68000 mPa·s at 140° C.

Comparative Example 21

The packaging bag which was sealed in the same manner as Example 21 except that an adhesive layer having 50 μm thickness was prepared.

Comparative Example 22

The packaging bag which was sealed in the same manner as Example 21 except that a styrene-isoprene based thermoplastic adhesive (TN-553Z, manufactured by MORESCO corporation) was used as the adhesive was prepared. In Comparative Example 22, the adhesive had viscosity of 15000 mPa·s at 140° C.

Comparative Example 23

The packaging bag which was sealed in the same manner as Example 21 except that a natural rubber based thermoplastic adhesive (HIRODINE 5132, manufactured by Yasuhara Chemical Co., Ltd.) was used as the adhesive was prepared. In Comparative Example 23, the adhesive had viscosity of 21000 mPa·s at 160° C.

(Test for Evidence of Opening)

After the packaging bags of Example 21 and Comparative Examples 21 to 23 were left at normal temperature for more than 1 hour, the sealing sections were opened. Opening of the sealing section was measured by using a tensile and compression test machine (Tensilon RTF-1250, manufactured by A & D Co., Ltd.). Specifically, while the main body is fixed, an end of the tab of the sealing section was held and pulled in the direction of elevation angle of 45 degrees at a tensile rate of 200 mm/min. After the packaging bag was opened, whether evidence of opening was created or not in the packaging bag was visually observed. When evidence of opening was recognized by visual observation, it was rated as A. When evidence of opening was not recognized by visual observation, it was rated as C. Table 3 shows the test results of Example 21 and Comparative Examples 21 to 23.

For Example 21 and Comparative Examples 21 to 23, evaluation was performed whether the packaging bag can be resealed or not after the evaluation of evidence of opening. In this evaluation, no adhesive was added to the packaging bag. When resealing was not possible, it was rated as A. When resealing was possible, it was rated as C. Table 3 shows the test results of Example 21 and Comparative Examples 21 to 23.

For Example 21 and Comparative Examples 21 to 23, the sealing strength of the adhesion region was measured by using a tensile and compression test machine (Tensilon RTF-1250, manufactured by A & D Co., Ltd.) in accordance with JIS Z 1707:1997. The strength when the main body and the sealing section was peeled from each other with the tensile rate of 200 mm/min was determined as the sealing strength.

As shown in Table 3, in Example 21, evidence of opening was recognized and resealing was not possible. On the other hand, in Comparative Example 21, evidence of opening was not recognized, while resealing was not possible. Therefore, in Comparative Example 21, resealing was possible without creating evidence of opening by, for example, applying an additional adhesive on the adhesive layer after the packaging bag was opened. As described above, the thickness of the adhesive layer of Comparative Example 21 was smaller than the thickness of the adhesive layer of Example 21. Therefore, in order to create evidence of opening in the packaging bag, it seems that the amount of adhesive applied needs to be adjusted.

In Comparative Example 22, evidence of opening was not recognized and resealing was possible. As described above, the viscosity of the adhesive of Comparative Examples was smaller than the viscosity of the adhesive of Example 1. Therefore, in order to create evidence of opening in the packaging bag, it seems that the viscosity of the adhesive needs to be adjusted.

In Comparative Example 23, evidence of opening was not recognized and resealing was possible. As described above, the adhesive of Comparative Example 3 was a natural rubber based thermoplastic adhesive, while the adhesive of Example 21 was a synthetic rubber-based thermoplastic adhesive. Therefore, in order to create evidence of opening in the packaging bag, it seems that a synthetic rubber-based thermoplastic adhesive needs to be used as an adhesive.

For the packaging bag having an anti-tamper function with the adhesive included in the adhesion region31having the viscosity of a predetermined amount or more, the supplementary notes are provided as below.

A packaging bag made of a laminate formed in a bag shape, the laminate being composed of a substrate, and a foamed resin sheet laminated on the substrate, the packaging bag comprising: a bag-shaped main body having an opening; a sealing section for sealing the opening of the main body; and an adhesive layer provided on one of the main body and the sealing section so as to adhere the main body and the sealing section to each other, wherein a thickness of the adhesive layer is more than 50 μm, and the adhesive is a synthetic rubber-based thermoplastic adhesive having a viscosity of 50000 mPa·s or more at 140° C.

The packaging bag according to the supplementary note 1, wherein the adhesive is a styrene-isoprene based thermoplastic adhesive.

The packaging bag according to the supplementary note 1 or 2, wherein the thickness of the adhesive layer is 100 μm or more.

The packaging bag according to any one of the supplementary notes 1 to 3, wherein a surface of the main body which adheres to the adhesive layer is a paper layer in the substrate, and a surface of the sealing section which adheres to the adhesive layer is a resin film in the substrate.

The packaging bag according to any one of the supplementary notes 1 to 3, wherein a surface of the main body which adheres to the adhesive layer is a paper layer in the substrate, and a surface of the sealing section which adheres to the adhesive layer is the resin foamed sheet.

The packaging bag according to any one of the supplementary notes 1 to 5, wherein the sealing section is integrally formed with the main body, and extends outside the main body relative to the opening.

According to the packaging bag of the supplementary note 1, the thickness of the adhesive layer is more than 50 μm, and the viscosity of the adhesive at 140° C. is 50000 mPa·s or more. Accordingly, the adhesive layer has high adhesiveness at normal temperature. Further, since the adhesive contained in the adhesive layer is a synthetic rubber-based thermoplastic adhesive, the adhesive layer tends to have high hardness. In the packaging bag having such an adhesive layer, the adhesive layer is less likely to be broken in opening of the sealing section. As a consequence, in opening of the packaging bag, at least part of either the main body or the sealing section to which the adhesive layer is adhered, instead of the adhesive layer, is delaminated and broken. Accordingly, in opening of the sealing section, evidence of opening is created on the packaging bag so that tampering can be prevented.

According to the packaging bag of the supplementary note 2, evidence of opening can be more reliably created on the packaging bag. According to the packaging bag of the supplementary note 3, since the amount of an adhesive per unit area increases in the adhesion layer, evidence of opening is more reliably created in the packaging bag. According to the packaging bag of the supplementary note 4, in opening of the sealing section, at least part of the paper layer that constitutes the surface of the main body and adheres to the adhesion layer, instead of the adhesion layer, is delaminated and broken. According to the packaging bag of the supplementary note 5, in opening of the sealing section, at least part of the paper layer that constitutes the surface of the main body and adheres to the adhesion layer, instead of the adhesion layer, is delaminated and broken to thereby create evidence of opening.

Alteration of the Present Invention

Next, with reference toFIGS. 20 to 25, examples in which the aforementioned impact absorption section is applied to the packaging bag formed of another laminate will be described.

First Embodiment of Alteration

FIGS. 20A and 20Bare schematic cross-sectional views that illustrates a structure of a laminate10aconstituting a packaging bag701according to the present embodiment. As shown inFIG. 20A, the laminate10aincludes a paper substrate8which includes a paper layer3, and a sealant layer9laminated on an inner surface of the paper substrate8. The paper substrate8includes the paper layer3, which constitutes an outer surface of the packaging bag1, and an adhesive layer5laminated on the paper layer3. In the present embodiment, the adhesive layer5is made of polyethylene. The paper substrate8has an MD direction, which is a flow direction of the material due to the production processes. The paper layer3and the adhesive layer5, which constitute the paper substrate8, have the MD direction in the same direction. A bending stiffness of the paper substrate8in the MD direction is in the range of 150 mN to 700 mN, and preferably in the range of 200 mN to 600 mN. Further, a thickness of the adhesive layer5is in the range of 5 to 40 μm, and a grammage of the entire paper substrate8including the paper layer3is in the range of 50 g/m2to 120 g/m2. Further, a thickness of the paper substrate8is in the range of 50 to 250 μm, for example.

The sealant layer9is a layer having a portion to be thermally sealed when the laminate10ais formed into a bag shape. A material for the sealant layer9may be, for example, linear low density polyethylene (LLDPE), high density polyethylene (HDPE), or the like. Further, as shown inFIG. 20B, a foamed film9amay be used as the sealant layer9. The foamed film9a, which is a laminate made up of a foamed resin layer4having interconnected pores and a polyolefin layer6, is formed by using a foaming agent. When the foamed film9ais used, it is laminated with the foamed resin layer4being in contact with the paper substrate8. A thickness of the sealant layer9is, for example, in the range of 100 to 200 μm. The sealant layer9(when the foamed film9ais used, the polyolefin layer6) is an inner surface of the packaging bag1and a layer in contact with the contents.

Although the thicknesses of the respective layers in the laminates10aand10bare not specifically limited, the thickness of the laminates10aand10bcan be reduced over the conventional ones so that the volume ratio of the capacity to the outer volume of the packaging bag701can be improved.

The laminate10aand the like is produced, for example, by a method described below. First, the adhesive layer5is laminated on one surface of the sheet-shaped paper layer3by lamination processing to thereby form the paper substrate8. Subsequently, the sheet-shaped sealant layer9is laminated by lamination processing on the adhesive layer5which has been laminated on the paper layer3. Thus, the laminate10ahaving the paper layer3, the adhesive layer5, and the sealant layer9, which are laminated in sequence, is formed. For example, extrusion lamination, dry lamination, or the like can be used as the lamination processing. The production method is not specifically limited, and the laminate10acan also be formed by extrusion lamination of the sealant layer9onto the paper substrate8formed by thermal lamination. The laminate10aor the like can be formed into a bag after it is cut into a predetermined width by slit processing.

FIGS. 21A and 21Bare plan views of the packaging bag701formed of the laminate10a. As shown inFIGS. 21A and 21B, the packaging bag701includes a main body20cformed in a bag shape with an opening21, and a sealing section30for sealing the opening21. The packaging bag701has a substantially rectangular shape in plan view. In the following description, a direction in which the opening21extends is defined as a width direction, and a direction perpendicular to the width direction is defined as an opening direction.FIG. 22is a cross-sectional view taken along the width direction of the packaging bag701, andFIG. 23is a cross-sectional view taken along the opening direction of the packaging bag701. In the illustrated example, a side of the packaging bag701which is opposite to the opening21is folded to form a folded section22. Further, sealed sections23care formed on both sides in the width direction of the packaging bag701. In the sealed section23c, the sealant layers9facing each other are thermally sealed along the opening direction. Thus, the folded section22and the sealed sections23care formed to thereby define an inner space S in the packaging bag701(seeFIGS. 22 and 23).

An impact absorption section is formed on the outer edge of the sealed section23c, extending from one end to the other end in the opening direction. The impact absorption section mitigates drop impact or the like on both end edges in the width direction of the packaging bag701. The impact absorption section in the present embodiment is formed of a wavy section24c. That is, the outer edge of the sealed section23cis formed in a wavy shape which extends outward in the width direction at a regular interval along the opening direction. The size of the wavy form is not specifically limited. For example, the height and pitch of the wave shapes in the wavy section24care 2 mm and 8 mm, respectively. The wavy section24cis softer than the sealed section23c, and can efficiently absorb impact.

As shown inFIG. 23, the sealing section30is formed by the paper substrate8extending out of the laminate10ato the outside of the opening21. The sealing section30may be formed of the laminate10a. The sealing section30can be folded over to cover the opening21. The sealing section30has an adhesion region31which extends in the width direction. The adhesion region31may be made of a double-sided tape or an adhesive that is prohibited from being re-attached to the main body20. With this configuration, the sealing section30is prohibited from being re-attached when the packaging bag701was tampered with. Examples of an adhesive prohibited from being re-attached include a hot melt adhesive.

The packaging bag701is produced, for example, by a method described below. First, the elongated laminate10ais formed by laminating the elongated sealant layer9fed out from a roll on the elongated paper substrate8fed out from a roll. In the present embodiment, the sealant layer9are not laminated in the sealing section30. Accordingly, the sealant layer9is laminated while leaving a predetermined area unlaminated from one end edge of the paper substrate8in the direction perpendicular to the longitudinal direction. Further, when the sealing section30is formed of the laminate10a, the sealant layer9is laminated on the entire surface of the paper substrate8. Then, the laminate10ais folded in the direction perpendicular to the longitudinal direction. Here, the sealant layer9of the laminate10afaces inward. Then, in the laminate10athus folded, a portion of the sealant layer9corresponding to the sealed section23cis thermally sealed in the direction perpendicular to the longitudinal direction (opening direction of the packaging bag). Thus, bag-shaped portions are continuously formed in the laminate10a. Subsequently, the bag-shaped portions continuously formed are separated to thereby obtain the packaging bag701. Since the impact absorption section is formed of the wavy section24cin the packaging bag701, the impact absorption section is formed, for example, by cutting the thermally heated portion into the wavy shape. The adhesion region may be formed in the sealing section30in any of the above steps. The production method is not specifically limited. For example, the sealant layer9may be thermally sealed after the laminate10ais cut.

In the present embodiment, the MD direction of the paper substrate8and the sealant layer9corresponds to the width direction of the packaging bag701, and the adhesion region31extends in the MD direction. Further, for ease of opening along the adhesion region31, perforations33are formed in the sealing section30. The perforations33are formed at positions spaced from the adhesion region31to the main body20side by a distance of 3 to 20 mm. Accordingly, by cutting the sealing section30along the perforations33, the packaging bag701can be easily opened.

According to the packaging bag701, since the wavy section24cis provided on the outer edge of the sealed section23c, drop impact is mitigated by the wavy section24c, which first comes into contact with the ground when the packaging bag701is dropped with the sealed section23cdownward. Moreover, the sealant layer9has a thickness in the range of 100 μm to 200 μm, and the paper substrate8laminated on the outer side relative to the sealant layer9has a bending stiffness in the range of 150 mN to 700 mN. With this configuration in which the paper substrate having the bending stiffness of 150 mN or more is laminated on the sealant layer9having a predetermined thickness, the paper substrate8is not easily collapsed. Accordingly, the impact which is not absorbed by the wavy section24is prevented from being easily transferred to the contents. Thus, in the packaging bag701of the present embodiment, the contents can be appropriately protected and do not have indentation made by the bubbles or the like. In addition, when the laminate10ais provided as a roll, the replacement frequency of the roll can be reduced since the packaging bag701is formed of the relatively thin laminate10a.

Second Embodiment of Alteration

A packaging bag801according to the present embodiment differs from the packaging bag701of the first embodiment in that it has an impact absorption section of a different shape. The following provides a description mainly of the differences from the packaging bag701of the first embodiment. The elements and components that are the same as those of the first embodiment are referred to by the same reference numbers, and detailed description thereof will be omitted.

As shown inFIGS. 24A, 24B, and 25, the packaging bag801includes a main body20dformed in a bag shape with an opening21, and a sealing section30for sealing the opening21. The packaging bag801has a substantially rectangular shape in plan view. In the packaging bag801, a side opposite to the opening21is folded to form a folded section22. Further, sealed sections23dare formed on both sides of the packaging bag801in the width direction. An impact absorption section is formed on the outer edge of the sealed section23d, extending from one end to the other end in the opening direction. The impact absorption section in this embodiment is provided by an unsealed section24d. In the unsealed section24d, the sealant layers9facing each other are not thermally sealed, and the laminates10aface each other. Accordingly, the unsealed section24dis softer than the sealed section23d, and can efficiently absorb impact. As an example, the length in the width direction of the sealed section23dis 10 mm, and the length in the width direction of the unsealed section24dis 5 mm.

The packaging bag801can be produced by the same method as the packaging bag701. According to the above production method, since the packaging bags801are continuously formed, the sealed section23dof one packaging bag801and the sealed section23dof the subsequent packaging bag801are adjacent to each other with their unsealed sections24dinterposed therebetween. That is, an unsealed portion between the sealed sections23dis cut to thereby form the impact absorption section (unsealed section24d). In addition, the packaging bag may have the same configuration as that of the modified example of the third embodiment or the like by using the laminates10aand10bdescribed above.

EXAMPLES

The packaging bag of the above alteration will be further described with reference to the examples and comparative examples as below. However, the sizes and the like of the packaging bag are merely examples, and the above embodiments are not limited to what is described in the examples. Further, the packaging bags according to Examples 31, 33 to 41 below have the shape of the packaging bag701of the first embodiment of the alteration. Further, the packaging bags according to Example 32 have the shape of the packaging bag801of the second embodiment of the alteration. Table 4 shows Examples 31 to 41 and Comparative Examples 31 to 37.

First, on a paper substrate having a paper layer and an adhesive layer made of PE with 30 μm thickness, a sealant layer made of LLDPE with 150 μm thickness was laminated to thereby obtain a laminate. As the lamination processing, dry lamination was used. Subsequently, both sides of the laminate in the opening direction were thermally sealed with the sealant layer facing inward to thereby obtain the packaging bag of Example 31. The packaging bag had a long side (side in the width direction) of 255 mm length and a short side (side in the opening direction) of 195 mm length, and the sealed section had a wavy section as an impact absorption section. The height and pitch of the wave shapes in the wavy section are 2 mm and 8 mm, respectively. The grammage of the paper substrate was 75 g/m2, and the bending stiffness of the paper substrate was 237 mN. The bending stiffness was measured by a loop stiffness tester (manufactured by Toyo Seiki Co., Ltd.). The measurement was performed using a sample, which was a loop of a strip made of a paper substrate having 15 mm width and 160 mm length. The number of samples was five.

Example 32 was different from Example 31 in the shape of the impact absorption section. That is, the packaging bag of Example 32 was formed of a laminate composed of a paper substrate having a bending stiffness of 237 mN and the sealant layer made of LLDPE with 150 μm thickness, which were laminated in sequence, and included an unsealed section as an impact absorption section on the outer edge of the sealed section. The width of the sealed section was 10 mm, and the width of the unsealed section was 5 mm.

In Example 33, the grammage and bending stiffness of the paper substrate were different from Example 31. That is, the packaging bag of Example 33 was formed of a laminate composed of a paper substrate having a bending stiffness of 159 mN and a sealant layer made of LLDPE with a 150 μm thickness, which were laminated in sequence, and included a wavy section as an impact absorption section. The height and pitch of the wave shapes in the wavy section are 2 mm and 8 mm, respectively.

In Example 34, the grammage and bending stiffness of the paper substrate were different from Example 31. That is, the packaging bag of Example 34 was formed of a laminate composed of a paper substrate having a bending stiffness of 214 mN and a sealant layer made of LLDPE with 150 μm thickness, which were laminated in sequence, and included a wavy section as an impact absorption section. The height and pitch of the wave shapes in the wavy section are 2 mm and 8 mm, respectively.

In Example 35, the grammage and bending stiffness of the paper substrate were different from Example 31. That is, the packaging bag of Example 35 was formed of a laminate composed of a paper substrate having a bending stiffness of 393 mN and a sealant layer made of LLDPE with 150 μm thickness, which were laminated in sequence, and included a wavy section as an impact absorption section. The height and pitch of the wave shapes in the wavy section are 2 mm and 8 mm, respectively.

In Example 36, the grammage and bending stiffness of the paper substrate were different from Example 31. That is, the packaging bag of Example 36 was formed of a laminate composed of a paper substrate having a bending stiffness of 531 mN and a sealant layer made of LLDPE with 150 μm thickness, which were laminated in sequence, and included a wavy section as an impact absorption section. The height and pitch of the wave shapes in the wavy section are 2 mm and 8 mm, respectively.

In Example 37, the thickness of the sealant layer was different from Example 31. That is, the packaging bag of Example 37 was formed of a laminate composed of a paper substrate having a bending stiffness of 237 mN and a sealant layer made of LLDPE with 110 μm thickness, which were laminated in sequence, and included a wavy section as an impact absorption section. The height and pitch of the wave shapes in the wavy section are 2 mm and 8 mm, respectively.

In Example 38, the thickness of the sealant layer was different from Example 31. That is, the packaging bag of Example 38 was formed of a laminate composed of a paper substrate having a bending stiffness of 237 mN and a sealant layer made of LLDPE with 180 μm thickness, which were laminated in sequence, and included a wavy section as an impact absorption section. The height and pitch of the wave shapes in the wavy section are 2 mm and 8 mm, respectively.

In Example 39, the configuration of the sealant layer was different from Example 31. That is, the packaging bag of Example 39 was formed of a laminate composed of a paper substrate having a bending stiffness of 237 mN and a foamed sealant layer having a thickness of 150 μm, which were laminated by extrusion lamination, and included a wavy section as an impact absorption section. The height and pitch of the wave shapes in the wavy section are 2 mm and 8 mm, respectively. The foamed sealant layer was formed of a foamed film composed of a foam layer with 100 μm thickness made of polyolefin-based resin and a sealant layer with 50 μm thickness.

In Example 40, the configuration of the sealant layer was different from Example 31. That is, the packaging bag of Example 40 was formed of a laminate composed of a paper substrate having a bending stiffness of 237 mN and a foamed sealant layer with 150 μm thickness, which were laminated in sequence, and included a wavy section as an impact absorption section. The height and pitch of the wave shapes in the wavy section are 2 mm and 8 mm, respectively. The foamed sealant layer was formed of a foamed film composed of a foam layer with 75 μm thickness made of polyolefin-based resin and a polyethylene layer with 75 μm thickness.

In Example 41, the configuration of the sealant layer was different from Example 31. That is, the packaging bag of Example 41 was formed of a laminate composed of a paper substrate having a bending stiffness of 237 mN and a foamed sealant layer with 180 μm thickness, which were laminated in sequence, and included a wavy section as an impact absorption section. The height and pitch of the wave shapes in the wavy section are 2 mm and 8 mm, respectively. The foamed sealant layer was formed of a foamed film composed of a foam layer with 110 μm thickness made of polyolefin-based resin and a polyethylene layer with 70 μm thickness.

Comparative Example 31

In the packaging bag of Comparative Example 31, an air bubble cushioning material made of PE was disposed inside a packaging bag was made of kraft paper. The air bubble cushioning material and kraft paper were bonded to each other by an adhesive. The kraft paper had a grammage of 80 g/m2and a bending stiffness of 166 mN. In this packaging bag, a sealed section was provided on one of the long sides, and an adhesive tape was adhered to the sealed section. Further, in the packaging bag of Comparative Example 31, an impact absorption section was not provided.

Comparative Example 32

Comparative Example 32 was different from Example 31 in that it did not include a sealant layer. That is, the packaging bag of Comparative Example 32 was formed by folding over a paper substrate having a bending stiffness of 237 mN, and adhering both ends in the width direction. Further, in the packaging bag of Comparative Example 32, an impact absorption section was not provided.

Comparative Example 33

In Comparative Example 33, the thickness of the sealant layer was different from Example 31. That is, the packaging bag of Comparative Example 33 was formed of a laminate composed of a paper substrate having a bending stiffness of 237 mN and a sealant layer made of LLDPE with 80 μm thickness, which were laminated in sequence. Further, in the packaging bag of Comparative Example 33, an impact absorption section was not provided.

Comparative Example 34

In Comparative Example 34, the thickness of the sealant layer was different from Example 31. That is, the packaging bag of Comparative Example 34 was formed of a laminate composed of a paper substrate having a bending stiffness of 237 mN and a sealant layer made of LLDPE with 250 μm thickness, which were laminated in sequence. Further, in the packaging bag of Comparative Example 34, an impact absorption section was not provided.

Comparative Example 35

In Comparative Example 35, the grammage and bending stiffness of the paper substrate were different from Example 31. That is, the packaging bag of Comparative Example 35 was formed of a laminate composed of the paper substrate having a grammage of 50 g/m2and a bending stiffness of 93 mN and the LLDPE sheet having the thickness of 150 μm, which were laminated in sequence. Further, in the packaging bag of Comparative Example 35, an impact absorption section was not provided.

Comparative Example 36

In Comparative Example 36, the grammage and bending stiffness of the paper substrate were different from Example 31. That is, the packaging bag of Comparative Example 36 was formed of the laminate composed of the paper substrate having the grammage of 120 g/m2and the bending stiffness of 961 mN and the LLDPE sheet having the thickness of 150 μm, which were laminated in sequence. Further, in the packaging bag of Comparative Example 36, an impact absorption section was not provided.

Comparative Example 37

Comparative Example 37 was different from Example 31 in that it did not include an impact absorption section. That is, the packaging bag of Comparative Example 37 was formed of a laminate composed of a paper substrate having a bending stiffness of 237 mN and a sealant layer made of LLDPE with 150 μm thickness, which were laminated in sequence.

For Examples 31 to 41 and Comparative Examples 31 to 37, the impact resistance and strength were tested to evaluate the basic performance practically required as a packaging bag.

An impact resistance test and a strength test were tests to check whether a packaging bag and the contents inside are not damaged when a certain impact is applied to the packaging bag containing the contents. The test was performed by dropping a sample containing the contents from a position of 70 cm height. The contents were a compact disk (CD) stored in a plastic case. The test was performed 7 times per sample with different impact locations. The impact locations were front and rear surfaces of the packaging bag, a side of the packaging bag on the sealing section side, a side of the packaging bag opposite to the sealing section, one of the sides in the width direction of the packaging bag, a corner between the other of the sides in the width direction and the side on the sealing section side, and a corner between the other of the sides in the width direction and the side opposite to the sealing section. The number of samples was 50. In the impact resistance test, when the number of plastic cases broken was not more than 30 out of 50 samples, it was evaluated as not having a practical problem. In the strength test, when the number of packaging bags broken was not more than 30 out of 50 samples, it was evaluated as not having a practical problem. Table 5 shows the results of these tests.

As the results of evaluation, a practical problem was not found in Examples 31 to 41. On the other hand, Comparative Examples 31, 32, 35, and 37 were evaluated as having a practical problem in the impact resistance test. In particular, in Comparative Examples 31 and 32 which have low strength as the entire external material that constitutes the packaging bag, breakage was found in 40 samples or more out of 50 samples. Further, Comparative Example 32 was evaluated as having a practical problem in the strength test as well. Comparative Examples 34 and 36 were evaluated as having no practical problem in both the impact resistance test and strength test. However, Comparative Example 34 was evaluated as having decreased processability due to the sealant layer being too thick. Further, Comparative Example 36 was evaluated as having decreased processability due to the bending stiffness being too high.

Moreover, for Examples 31, 39 to 41, and Comparative Example 31, a vibration test was performed as another evaluation method. A vibration test is a test to check whether a packaging bag and the contents inside are not damaged by vibration when the packaging bag containing the contents is transported. The test was performed under the condition that samples (Examples 31, 39 to 41, and Comparative Example 31) were horizontally stacked in a cardboard box with a weight of 2.5 kg placed on the samples. Further, the test was performed under the conditions of land transportation of 2000 km or more by using a transport vehicle (compliant to JIS Z 0200). The number of samples was 3. The contents were a plastic CD case, a plastic CD case wrapped with 20 μm OPP film, and a magazine, which were packaged together. The vibration test was evaluated based on the area of the abrasion marks created on the contents. The area of the abrasion marks which is less than 20% of the total area was rated as level 1, 20% or more and less than 40% was rated as level 2, 40% or more and less than 60% was rated as level 3, 60% or more and less than 80% was rated as a level 4, and 80% or more and less than 100% was rated as a level 5. The levels 1 and 2 were regarded as high quality.

As a result, while Comparative Example 31 was rated as level 4, Examples 31, and 39 to 41 were evaluated as high quality (level 1 or 2). It was confirmed that Examples 39 to 41, which use a foamed film as a sealant layer, had high vibration resistance.

For the packaging bags701and801formed of the above laminates10aand10b, the supplementary notes are provided as below.

A packaging bag made of a laminate formed in a bag shape, the laminate being composed of a paper substrate, and a sealant layer laminated on an inner side relative to the paper substrate, which are laminated with the sealant layer facing inward, wherein a sealed section in which the sealant layers facing each other are sealed is provided in at least part of the periphery of the packaging bag, an impact absorption section is formed of the laminate on the outer edge of the sealed section, a bending stiffness of the paper substrate in an MD direction is in a range of 150 mN to 700 mN, and a thickness of the sealant layer is in a range of 100 μm to 200 μm.

The packaging bag according to the supplementary note 1, wherein the bending stiffness of the paper substrate in the MD direction is in a range of 200 mN to 600 mN.

The packaging bag according to the supplementary note 1 or 2, wherein the impact absorption section is an unsealed section formed on the outer edge of the sealed section, or a wavy section which is the outer edge of the sealed section formed in a wavy shape.

A method for producing the packaging bag according to any one of the supplementary notes 11 to 13, the method including: laminating an elongated sealant layer fed out from a roll on an elongated paper substrate fed out from a roll; folding a laminate composed of the paper substrate and the sealant layer in a direction perpendicular to the longitudinal direction with the sealant layer facing inward, and then sealing parts of the sealant layers facing each other to form a bag, wherein, in the step of laminating the sealant layer on the paper substrate, the sealant layer is laminated while leaving a predetermined area unlaminated from one end edge of the paper substrate in the direction perpendicular to the longitudinal direction.

In the packaging bag according to the supplementary note 11, since the impact absorption section is provided on the outer edge of the sealed section, drop impact is mitigated by the impact absorption section, which first comes into contact with the ground when the packaging bag is dropped with the sealed section downward. Moreover, the sealant layer has the thickness in the range of 100 μm to 200 μm, and the paper substrate laminated on the outer side relative to the sealant layer has the bending stiffness in the range of 150 mN to 700 mN. With this configuration in which the paper substrate having the bending stiffness of 150 mN or more is laminated on the sealant layer having a predetermined thickness, the paper substrate is not easily collapsed. Accordingly, the impact which is not absorbed by the impact absorption section is prevented from being easily transferred to the contents. In the conventional art in which a plastic air bubble wrap sheet is simply attached to general kraft paper as a cushioning material, the strength may be low as a packaging bag, which causes drop impact to be transferred to the contents. In the above-mentioned packaging bag, however, the contents can be appropriately protected. In addition, according to the configuration of the above packaging bag, a plastic air bubble wrap sheet is not provided on the inner surface. Accordingly, the contents do not have indentation made by the bubbles or the like. In addition, when the laminate is provided as a roll, the replacement frequency of the roll can be reduced since the packaging bag is formed of the relatively thin laminate. Moreover, when the paper substrate has the bending stiffness of more than 700 mN or the sealant layer has the thickness of more than 200 μm, processing of the laminate into a packaging bag will be laborious. Therefore, the paper substrate preferably has the bending stiffness of 700 mN or less and the sealant layer preferably has the thickness of 200 μm or less. Further, the term “bending stiffness” as used herein refers to stiffness of the material expressed by a load applied when a sample, which has been cut with a predetermined width and length and formed in a loop shape, is pressed to collapse. The bending stiffness can be measured by using a measurement machine available in the market, for example, a loop stiffness tester. In the packaging bag of the supplementary note 13, the sealant layers facing each other are not sealed in the unsealed section. Therefore, the unsealed section has higher flexibility than the sealed section. Further, in the wavy section, which is formed by continuous projecting pieces and recessed pieces, the projecting pieces have high flexibility compared with the sealed section. Thus, the impact absorption section having high flexibility compared with the sealed section can effectively absorb an impact. Further, according to the production method of the supplementary note 14, the thickness of the cushioning material can be reduced to thereby increase the length of the cushioning material per roll. This allows for reduction of the replacement frequency of the roll, leading to improvement in production efficiency.

INDUSTRIAL APPLICABILITY

The present invention is applicable to packaging bags that are able to appropriately protect the contents.

REFERENCE SIGNS LIST