EASY-OPEN PACKAGING BODY

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Bypass Continuation of International Application No. PCT/JP2023/046007 filed Dec. 21, 2023, claiming priority based on Japanese Patent Application No. 2023-000621 filed Jan. 5, 2023, and JP 2023-193953 filed Nov. 14, 2023, the contents of all of which are incorporated herein by reference in their respective entireties.

TECHNICAL FIELD

The disclosure relates to an easy-open packaging body composed of a container including a flange portion, and a lid member that can be attached to the flange portion by heat sealing, and more specifically, to an easy-open packaging body with which the sealing position can be easily controlled, and the lid member can be attached by heat sealing with easy openability and sealability.

BACKGROUND

Resin containers in which a flexible lid member is heat-sealed to a flange portion are widely used as simple containers for food and beverages. In such resin containers, it is necessary to achieve the conflicting performances of high sealability and easy openability by means of heat sealing.

As a container addressing this requirement, for example, JP-A-2005-119692 discloses a multilayer container in which a flange portion is disposed around the periphery of an opening, at least one layer including the inner layer of the container is formed in a manner allowing peeling, two annular cuts are provided on the upper surface of the flange portion, and a portion lower than the upper surface of the flange portion is formed in connection with the outer one of the two annular cuts.

In JP-A-2005-119692, since a portion lower than the upper surface of the flange portion is formed, even if a seal ring is positioned on the outer lower portion, the lid member will not be heat-sealed at the outer portion of the flange portion due to the cut including the lower portion, or even if sealed, the sealing will be weak, thereby not impairing openability.

Japanese Patent No. 5878683 discloses an easy-open container including a container body including a flange portion at a periphery of an opening and formed from a layered body including at least a surface layer and an underlying layer, and a lid member including at least a seal layer capable of adhering to the surface layer, in which the surface layer of the flange portion and the seal layer of the lid member are annularly heat-sealed, and the lid member is made openable by cohesive failure occurring in at least one of the seal portion of the lid member and the container body, and a mound-shaped resin accumulation portion composed of the constituent resins of the surface layer and the underlying layer of the container body and the seal layer of the lid member is formed on the inner peripheral side of the seal portion on the flange portion, along the entire periphery of the opening, so as to satisfy the conditions represented by Equation (F1).

Japanese Patent No. 5878683 discloses that the lid member is opened by cohesive failure of the surface layer of the container body due to heat sealing of the lid member to the flange portion, thereby exhibiting excellent openability, and that high sealability is ensured by the formation of a resin accumulation composed of the constituent resins of the surface layer and the underlying layer of the container body and the seal layer of the lid member.

Further, in order to achieve both sealability and easy openability in containers with a flange, it has also been proposed to control the seal strength between the lid member and the flange portion. For example, JP-A-2013-100138 discloses a container in which the flange portion includes a flat portion where a seal portion is formed and an extended portion extending from the outer peripheral edge of the flat portion, in which the container body includes at least two layers including a seal layer and a base material layer; the seal layer has a thin portion or a missing portion on at least one of the outer peripheral side and the inner peripheral side of the flat portion, and has an easy-to-separate member on the other side; and in the flat portion, the thickness of the side having the thin portion or the missing portion is 20% to 98% relative to the thickness at the center.

JP-A-2013-100138 discloses that, by forming the flange portion that becomes thinner toward the inner edge, it is possible to eliminate the need for position control of the seal portion when sealing the lid member to the container body, thereby easily achieving both easy openability and sealability.

SUMMARY

However, in JP-A-2005-119692, opening is started by pulling up the lid member, thereby causing stress concentration at the layer end portion between the inner layer and the adjacent layer of the container body, which poses a risk of unintentional opening during distribution or the like. Therefore, it is desirable to enable more reliable initiation of interlayer peeling at the time of opening. Further, since two annular cuts are provided on the upper surface of the flange portion, there is a concern that in containers with thin walls, a gas barrier layer or the like may be exposed, which makes it difficult to apply such barrier layers.

In addition, in Japanese Patent No. 5878683 described above, high sealability is achieved by forming a resin accumulation; however, since the lid member is peeled off by causing cohesive failure of the surface layer of the container during opening, a greater force is required compared to interlayer peeling, and thus the openability is still not fully satisfactory.

In addition, in the container described in JP-A-2013-100138, a tight seal that cannot be peeled off is formed between the lid member and the inclined surface of the flange portion. However, when severe sealing conditions occur, a resin accumulation containing the seal layer is formed on the inner edge side. If there is a large circumferential variation in the thickness of the flange, the areas with greater thickness are subjected to harsher sealing conditions. As a result, when the internal pressure increases and the lid is deformed into a dome shape, unintended interlayer peeling may start from the inner edge side of a thin sealing portion formed near the resin accumulation containing the seal layer, thus leading to a decrease in seal strength (burst strength). In addition, the burst strength significantly varies depending on the sealing temperature, and as a result product-to-product variation may result, which may complicate product management.

In addition, when the upper surface of the flange portion is formed as an inclined surface simultaneously with the formation of the flange portion, the mold processing becomes more complicated compared to the case where the upper surface of the flange portion is formed as a flat surface. As a result, the cost of mold production may be increased, which is also unsatisfactory in terms of economic efficiency.

An object of the disclosure is to provide an easy-open packaging body that has excellent sealability through heat sealing, and can be easily opened with a smaller opening force using a resin accumulation resulting from heat sealing.

Another object of the disclosure is to provide an easy-open packaging body with excellent sealability and easy openability that is applicable also to a thin container.

Still another object of the disclosure is to provide an easy-open packaging body capable of facilitating product management by reducing variations in burst strength even under the same sealing condition, or sealing conditions that are different in the circumferential direction.

An easy-open packaging body according to the disclosure includes: a container; and a lid member, the container including a flange portion at a periphery of an opening, and a surface seal layer formed at least on a top surface of the flange portion, the surface seal layer being joinable to the lid member and easy to peel off from a base material of the container, the lid member being configured to seal the container by joining to the surface seal layer of the flange portion, wherein in the flange portion, a side wall portion extending in a container axial direction is formed on an outer side of an outer peripheral edge of a joining position with the lid member, and the surface seal layer includes a resin accumulation protruding outward from the outer peripheral edge of the joining position, and a surface seal layer having a small thickness serving as an opening start portion on a lower or inner side of the resin accumulation.

Preferably, in the easy-open packaging body according to the disclosure,

• • (1) the side wall portion is a perpendicular surface extending in the container axial direction or an inclined surface with an outer diameter increasing toward a lower side in the container axial direction;
  • (2) on the side wall portion, a surface seal layer decreasing in thickness toward a lower side in the container axial direction is formed;
  • (3) the opening start portion is located near an interface between the surface seal layer and the base material of the container at the outer peripheral edge of the joining position;
  • (4) in an open operation, cohesive failure of the surface seal layer having a small thickness occurs from the opening start portion, and then interlayer peeling of the base material of the container and the surface seal layer proceeds, whereby the easy-open packaging body is opened;
  • (5) in the flange portion, an outer step portion located on the outer side of the outer peripheral edge of the joining position with the lid member and on a lower side of a position of the joining position in the container axial direction is formed, and the side wall portion is formed between the outer peripheral edge of the joining position and an inner peripheral edge of the outer step portion;
  • (6) the side wall portion is formed as an annular skirt portion extending downward in the container axial direction from the outer peripheral edge of the flange portion;
  • (7) an outer inclined surface with an outer diameter increasing toward a lower side in the container axial direction is formed at an upper portion of the annular skirt portion;
  • (8) in the flange portion, an inner step portion is formed on an inner side of an inner peripheral edge of the joining position and on a lower side of a position of the joining position in the container axial direction, and on the inner step portion, a surface seal layer having a thickness smaller than a thickness of the surface seal layer of the flange portion before joined to the lid member is formed, or no surface seal layer is formed;
  • (9) between the resin accumulation and the lid member, a resin accumulation resulting from a seal layer of the lid member is formed;
  • (10) a first joining portion and a second joining portion that are joinable to the lid member, and a coupling portion are provided in the joining position of the flange portion, the first joining portion has a protruding shape protruding upward from the flange portion, the coupling portion is coupled with the first joining portion and/or the second joining portion, and a top surface of the first joining portion is located on an upper side relative to a top surface of the second joining portion in the container axial direction;
  • (11) a height difference between the top surface of the first joining portion and the top surface of the second joining portion is 0.01 mm to 0.20 mm;
  • (12) the top surface of the flange portion has a step shape including the first joining portion, the coupling portion and the second joining portion;
  • (13) the coupling portion has a recess shape or an uneven shape;
  • (14) a width of a protrusion of the uneven shape in a container radial direction is smaller than a width of the first joining portion in the container radial direction; and
  • (15) the container includes a layered body in which the surface seal layer is formed on the base material layer.

The easy-open packaging body of the disclosure includes the resin accumulation protruding outward from the outer peripheral edge of the joining position of the lid member and the flange portion, and the thin surface seal layer serving as the opening start portion disposed on the lower or inner side of the resin accumulation. As a result, at the start of opening, the resin accumulations of the lid member and the container integrally move up with the lid member, and the thin surface seal layer adjacent to the interface with the base material layer that serves as the opening start portion can be easily fractured, thus easily causing interlayer peeling between the surface seal layer and the base material layer. In this manner, it can be opened without requiring a large opening force.

In addition, since a step portion or an inclined portion including a surface seal layer as thin as possible or no surface seal layer is provided on the outer circumference side of the joining position, it can be easily fractured and can provide excellent openability.

Further, since the lid member is firmly heat-sealed at the joining position, excellent sealability is ensured, and unintended opening is also prevented.

In addition, the first joining portion that is located on the outer peripheral edge side, and the second joining portion that is located on the inner peripheral edge side and is lower in height than the first joining portion in the container axial direction are formed at the joining position of the flange portion serving as the sealing position with the lid member, such that during the heat sealing, the pressure of the seal head is easily exerted on the first joining portion, while the pressure is less exerted on second joining portion. As a result, the resin accumulation composed of the container surface seal layer is easily formed on the outer side of the first joining portion in the radial direction, which is bonded to the resin accumulation composed of the lid member seal layer, thus improving easy openability. On the other hand, at the second joining portion, the resin accumulation composed of the container surface seal layer is less formed on the inner side of the second joining portion in the radial direction, that is, formation of the initiation point of the cohesive failure can be suppressed, and thus unintentional peeling from the inner side due to internal pressure increase can be effectively prevented.

In addition, in this aspect, since the resin accumulation composed of the container surface seal layer on the inner side of the second joining portion in the radial direction can be easily controlled as described above, it is possible to reduce variations in the strength (burst strength) that causes interlayer peeling from the inner side due to an increase in internal pressure, and to control the burst strength in accordance with the sealing temperature. Thus, it is possible to provide containers with stable quality, thereby facilitating product management.

Further, since the top surface of the joining portion is flat, the pressure received at the joining portion from the seal head during the heat sealing can be received by the entirety of the top surface of the joining portion, and the influence on the base material making up the container can be suppressed to prevent deformation of the base material. In addition, since the mold (locator) used for forming the first joining portion, the second joining portion and the coupling portion can be processed using a tool for forming a flat shape, the processing is easy and economical.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a perspective view illustrating an example of a container used in the disclosure, and FIG. 1B is a diagram for describing a cross-sectional structure of the portion X in FIG. 1A.

FIG. 2 is a partially enlarged cross-sectional view illustrating an enlarged view of a flange portion of the container illustrated in FIG. 1A.

FIG. 3A is a partially enlarged cross-sectional view illustrating an enlarged view of the flange portion with a lid member heat-sealed to the container illustrated in FIG. 1A, and FIG. 3B is a diagram for describing a cross-sectional structure of the portion Y in FIG. 3A.

FIG. 4 is a partially enlarged cross-sectional view illustrating an enlarged view of the flange portion in a state where opening is started by pulling up the lid member from the state illustrated in FIG. 3A.

FIG. 5 is a top view of an example of the container used in the disclosure.

FIG. 6 is a partially enlarged cross-sectional view illustrating an enlarged view of the flange portion in another example of the container used in the disclosure.

FIG. 7 is a partially enlarged cross-sectional view illustrating a state where the lid member is set to heat-seal the container flange portion illustrated in FIG. 6.

FIG. 8 is a partially enlarged cross-sectional view illustrating a state where heat sealing has been performed from the set state illustrated in FIG. 7.

FIG. 9 is a partially enlarged cross-sectional view illustrating an enlarged view of another example of the flange portion of the container used in the disclosure.

FIG. 10 is a partially enlarged cross-sectional view illustrating an enlarged view of the flange portion with the lid member heat-sealed to the container illustrated in FIG. 9.

FIG. 11 is a partially enlarged cross-sectional view illustrating an enlarged view of another example of the flange portion of the container used in the disclosure.

FIG. 12 is a partially enlarged cross-sectional view illustrating an enlarged view of the flange portion with the lid member heat-sealed to the container illustrated in FIG. 11.

FIGS. 13A and 13B are top views illustrating a part of an example of the container used in the disclosure, FIG. 13A illustrates an aspect in which a protrusion for air venting of a locator is formed, and FIG. 13B illustrates an aspect in which a steam vent portion for releasing the internal pressure is formed.

FIG. 14 is a diagram for describing a method for measuring the opening force.

DESCRIPTION OF EMBODIMENTS

FIG. 1A is a perspective view of an example of the container used in the disclosure, FIG. 1B illustrates a layer structure, FIG. 2 is a cross-sectional view illustrating an enlarged view of the flange portion of the container illustrated in FIG. 1A, and FIG. 3A is a cross-sectional view illustrating an enlarged view of the flange portion with a lid member heat-sealed to the container illustrated in FIG. 2.

In general, the container, the entirety of which is indicated by 1, includes a bottom portion 2, a barrel portion 3, a flange portion 4 extending outward from the upper end of the barrel portion 3 in the container radial direction, and an annular skirt portion 5 extending downward from the outer peripheral edge of the flange portion 4. As is clear from FIG. 2, the container 1 is integrally molded from a layered body composed of a base material layer 6 and a surface seal layer 7 such that the surface seal layer 7 is the top surface located to face the lid member (not illustrated) at the flange portion 4.

Note that, the base material layer 6 and the surface seal layer 7 are formed of resin that is easy to peel off, thus allowing easy peeling between the base material layer 6 and the surface seal layer 7 when the lid member is opened, thus improving the openability.

As is clear from FIG. 2, at the top surface of the flange portion 4, an annular joining portion 41, which is the joining position (heat seal position) of the lid member, is formed at the center portion, and an outer step portion 42 is formed on the outer side of the annular joining portion 41. In addition, in the specific example illustrated in FIG. 2, an inner step portion 45 is formed with an inclined portion 46 therebetween on the inner side of the annular joining portion 41.

The outer step portion 42 is lower than the axial height of the top surface of the annular joining portion 41 by L1, and a side wall portion 43 serving as a step is formed between it and the annular joining portion 41. In the side wall portion 43, a surface seal layer 7b thinner than a surface seal layer 7a of the annular joining portion 41 is formed. A groove 44 is formed at the boundary of the side wall portion 43 and the outer step portion 42. Similarly, also in the outer step portion 42, a surface seal layer 7c with a thickness smaller than that of the surface seal layer 7a of the annular joining portion 41 is formed.

As illustrated in FIG. 3A, the container is sealed by heat-sealing a lid member 10 to the annular joining portion 41 of the flange portion 4 of the container 1. As is clear from FIG. 3B, the lid member 10 is composed of a base material layer 10a, and a heat seal layer 10b composed of a heat-sealable resin that can be heat-sealed to the surface seal layer 7 of the container 1.

As illustrated in FIG. 3A, when the lid member 10 is pressed and heated at the annular joining portion 41 of the container 1 by a publicly known method using a heat-sealing head and the like, the surface seal layer 7 of the container 1 and the heat seal layer 10b of the lid member 10 are melted and joined at the annular joining portion 41. During the heat sealing, the heat seal layer 10b of the lid member 10 and the surface seal layer 7 of the container 1 are melted, and protruded from an outer peripheral end 41a of the annular joining portion (heat sealing portion) 41 to form a lid member side resin accumulation 11 and a container side resin accumulation 8. In general, during the heat sealing, heating is performed from the lid member side, and therefore the heat seal layer 10b of the lid member 10 melts more than the surface seal layer 7 of the container 1. As a result, the lid member side resin accumulation 11 is larger than the container side resin accumulation 8, and the lid member side resin accumulation 11 and the container side resin accumulation 8 are integrated with each other such that the lid member side resin accumulation 11 covers the upper portion of the container side resin accumulation 8, with the lower portion of the container side resin accumulation 8 being continuous from a thin heat seal layer of the side wall portion 43.

In this manner, when the lid member 10 is pulled up for opening, as illustrated in FIG. 4, the lid member 10 can be pulled up while reinforcing the lid member 10 because the lid member side resin accumulation 11 with a large volume is present at the point of action of an opening force P, and moreover the container side resin accumulation 8 also easily moves up together with the lid member side resin accumulation 11 because the lid member side resin accumulation 11 and the container side resin accumulation 8 are integrated with each other. In this manner, the thin surface seal layer 7b located at the lower portion of the container side resin accumulation 8, or the surface seal layer 7a of the outer peripheral end of the joining portion thinned by heat sealing that is located on the inner side of the container side resin accumulation 8 is easily fractured (cohesive failure). Since the surface seal layer 7b or the surface seal layer 7a is located near the interface with the base material layer 6, the interlayer peeling of the surface seal layer 7 and the base material layer 6 can easily proceed, thereby making it possible to easily perform an initial opening operation with a small opening force.

In addition, opening can be easily achieved as long as the lid member side resin accumulation 11 and the container side resin accumulation 8 protruding from the outer peripheral end 41a of the annular joining portion (heat sealing portion) 41 are integrated with each other, and the lower portion of the container side resin accumulation 8 is continuous from the thin surface seal layer of the side wall portion 43. However, as illustrated in FIG. 5, it is preferable to provide a protruding portion 48 whose shape of the annular joining portion as viewed from the container top surface is a shape in which the outer step portion protrudes outward in the container radial direction (so-called beak-like shape), because the stress exerted during the opening is further concentrated, and the fracture of the surface seal layer 7d of the inner step portion 45 described later easily occurs. Alternatively, the protruding shape of the annular joining portion may be a U-shape, an L-shape, or a wave-like shape formed of a series of these shapes, for example.

In addition, in the specific example illustrated in the drawing, as described above, the inner step portion 45 is formed inside the annular joining portion 41 with the inclined portion 46 therebetween. The surface seal layer 7d of the inner step portion 45 is thinner than the surface seal layer 7a of the annular joining portion 41, or more preferably not formed. In the case where a groove (notch) 47 is formed in the outer peripheral side edge portion (the lower end of the inclined portion 46) of the inner step portion 45, the surface seal layer 7 is not formed inside the groove 47, or it is formed as thin as possible.

Note that, preferably, a lid member side resin accumulation 11′ and a container side resin accumulation 8′ are not formed at an inner peripheral end 41b of the annular joining portion 41. Specifically, the reason for this is that if there is an integration of such resin accumulations when the internal pressure of the container increases, they are pulled up along with the lift of the lid member, and the surface seal layer 7a under the resin accumulation at the inner peripheral end 41b is fractured, thus resulting in a risk of opening from the inside. As such, it is preferable that at the outer peripheral end 41a, the container side resin accumulation 8 and the lid member side resin accumulation 11 are integrated, and whereas at the inner peripheral end 41b, the resin accumulation is not formed or only the lid member side resin accumulation 11 is present.

A simplest method of integrally forming the container side resin accumulation 8 and the lid member side resin accumulation 11 at the outer peripheral end 41a is, for example, forming the annular joining portion of the container prior to heat sealing that has a high height on the outer circumference side and a low height on the inner peripheral side. In this manner, when the lid member 10 is heat-sealed with a flat seal head, the highest outer circumference side is preferentially melted, and the container side resin accumulation 8 and the lid member side resin accumulation 11 are integrally formed at the outer peripheral end 41a, while only the lid member side resin accumulation 11 is formed at the inner peripheral end 41b. In addition, in the case where the annular joining portion prior to heat sealing has a flat shape with the same height on the outer circumference side and the inner peripheral side, the same effect can be achieved by using a seal head with a tapered shape. Further, even when a flat seal head is used in the case where the annular joining portion prior to heat sealing has a flat shape with the same height on the outer circumference side and the inner peripheral side, the same effect can be achieved by adopting a cantilevered structure for the flange support of the container, thereby making it difficult for pressure to be applied to the inner peripheral side.

FIGS. 6 to 8 are diagrams illustrating another aspect of the easy-open packaging body of the disclosure. FIG. 6 is a partially enlarged cross-sectional view illustrating an enlarged view of the flange portion of an example of the container to be used, FIG. 7 is a partially enlarged cross-sectional view illustrating a state where the lid member is set to the container flange portion illustrated in FIG. 6 for heat sealing, and FIG. 8 is a partially enlarged cross-sectional view illustrating a state where heat sealing has been performed from the set state illustrated in FIG. 7.

Also in this aspect, in general, the container includes the bottom portion (not illustrated), the barrel portion 3, the flange portion 4 extending outward from the upper end of the barrel portion 3 in the container radial direction, and the annular skirt portion 5 extending downward from the outer peripheral edge of the flange portion 4. In addition, also in this aspect, the container 1 is integrally molded from a layered body composed of the base material layer 6 and the surface seal layer 7 such that the surface seal layer 7 is the top surface located to face the lid member (not illustrated) at the flange portion 4.

As is clear from FIG. 6, in this aspect, the flange portion 4 forms an outer protruding portion 51 protruding upward on the outer circumference side, and includes an outer inclined surface 52 with the outer diameter that increases toward the lower side at the boundary portion of the outer peripheral end of the outer protruding portion 51 and the upper portion of the annular skirt portion 5. In addition, also on the inner peripheral side relative to the center portion, an inner protruding portion 53 protruding upward is formed from the center portion with an inner inclined surface 54 therebetween.

As is clear from FIGS. 6 and 7, the surface seal layer 7 formed on the surface of the flange portion 4 has substantially the same thickness as the thickness of the surface seal layer 7 of the layered body used in the range of the outer protruding portion 51 of the container to the joining position (an installation position of a heat-sealing head 60) 41 at the center portion, but its thickness decreases as it extends inward in the range of a distance L2 from the inner peripheral end 41b of the joining position 41 to the lower end of the inner inclined surface 54 of the inner protruding portion 53. In addition, at the boundary portion between the outer peripheral end of the outer protruding portion 51 and the upper portion of the annular skirt portion 5, the surface seal layer 7b with a very small thickness is formed (or the surface seal layer is not formed) also at the outer inclined surface 52. Further, also at the inner inclined surface 54, the surface seal layer 7d with a very small thickness is formed (or the surface seal layer is not formed).

As illustrated in FIG. 8, when the lid member 10 is pressed and heated at the joining position (heat sealing portion) 41 of the container 1 by a publicly known method using a heat-sealing head and the like, the surface seal layer 7 of the container 1 and the heat seal layer 10b of the lid member 10 are melted and joined at the joining position 41. Also in this aspect, during the heat sealing, the heat seal layer 10b of the lid member 10 and the surface seal layer 7 of the container 1 are melted and protruded from the outer protruding portion 51 in the direction of the outer inclined surface 52 to form the lid member side resin accumulation 11 and the container side resin accumulation 8, and the lid member side resin accumulation 11 and the container side resin accumulation 8 are integrated with each other such that the lid member side resin accumulation 11 covers the upper portion of the container side resin accumulation 8, with the lower portion of the container side resin accumulation 8 being continuous from a thin heat seal layer of the outer inclined surface 52.

In this manner, as in the case illustrated in FIG. 4, when the lid member 10 is pulled up for opening, the lid member 10 can be pulled up while reinforcing the lid member 10 because the lid member side resin accumulation 11 with a large volume is present at the point of action of the opening force, and moreover the container side resin accumulation 8 also easily moves up together with the lid member side resin accumulation 11 because the lid member side resin accumulation 11 and the container side resin accumulation 8 are integrated with each other. In this manner, the thin surface seal layer 7b of the outer inclined surface 52 that is present at the lower portion of the container side resin accumulation 8 is easily fractured (cohesive failure), and then the interlayer peeling of the base material layer 6 and the surface seal layer 7 can proceed, thereby making it possible to easily perform an initial opening operation with a small opening force. Further, when the peeling between the base material layer 6 and the surface seal layer 7 has proceeded and the inner peripheral end 41b of the heat sealing portion 41 has been reached, the surface seal layer 7 smoothly separates from the base material layer 6 because the thickness of the surface seal layer 7c gradually decreases and the surface seal layer 7d only has a very small thickness or no surface seal layer is present at the inner inclined surface 54, thus making it possible to remove the lid member 10 from the container.

In the disclosure, preferably, the step (L1) of the outer step portion illustrated in FIG. 2 is, but not limited to, within a range of 0.1 mm to 0.5 mm, more preferably within a range of 0.25 mm to 0.5 mm. When the value is within the above-mentioned ranges, the contact of the resin accumulation with the outer step portion can be effectively prevented. In addition, in the second aspect, the distance L2 from the inner peripheral end 41b of the joining position 41 to the inner inclined surface 54 is preferably 0.5 mm to 5.0 mm, with which the surface heat seal layer can be finally smoothly separated from the container after the interlayer peeling of the surface seal layer and the base material layer.

FIG. 9 is a diagram illustrating another aspect of the flange portion in the container used in the easy-open packaging body of the disclosure.

As is clear from FIG. 9, at the top surface of the flange portion 4, the annular joining portion 41, which is heat-sealed and joined to the lid member, is formed at the center portion, and the inner step portion 45 is formed on the inner side of the annular joining portion 41. In addition, in the specific example illustrated in FIG. 9, the outer step portion 42 is formed on the outer side of the annular joining portion 41.

In the specific example illustrated in FIG. 9, the annular joining portion 41 is composed of a first joining portion 141a located on the outer side of the container radial direction and a second joining portion 141b located on the inner side of the container radial direction. The top surface of the second joining portion 141b is located lower than the top surface of the first joining portion 141a by a distance L3 in the container axial direction, and a width (D2) of the second joining portion 141b in the container radial direction is greater than a width (D1) of the first joining portion 141a in the container radial direction. In addition, between the first joining portion 141a and the second joining portion 141b, a step (side wall portion) is formed by a height difference (L3) between them to form a coupling portion 141c.

In addition, as described above, in the case where the container is composed of a layered body in which the base material layer 6 and the surface seal layer 7 are easy to peel off, a surface seal layer 7′ of the side wall portion 43 between the first joining portion 141a and the outer step portion 42 and a side wall portion 49 between the second joining portion 141b and the inner step portion 45 are formed with a smaller thickness compared to the surface seal layer 7 in other portions. In addition, the groove (notch) 44 is formed at the lower end of the side wall portion 43, and the groove (notch) 47 is formed at the lower end of the side wall portion 49 or the outer peripheral side of the inner step portion.

FIG. 10 is a partially enlarged cross-sectional view illustrating a sealed state of a packaging body in which the lid member 10 is joined to the container illustrated in FIG. 9.

As illustrated in FIG. 10, the container is sealed when the lid member 10 is heat-sealed and joined to the annular joining portion 41 of the flange portion 4 of the container 1. Specifically, the lid member 10 and the flange portion 4 of the container 1 are not joined at the inner step portion 45 formed on the inner side of the annular joining portion 41 and the outer step portion 42 formed on the outer side of the annular joining portion 41. As is clear from FIG. 10, the lid member 10 is composed of the base material layer 10a, and the heat seal layer 10b composed of a heat-sealable resin that can be heat-sealed to the surface seal layer 7 of the container 1.

As illustrated in FIG. 10, when the lid member 10 is pressed and heated at the annular joining portion 41 of the container 1 by a publicly known method using a heat-sealing head and the like, a large amount of the pressure from the heat-sealing head (not illustrated) is exerted on the top surface of the first joining portion 141a, while the pressure is less exerted on the second joining portion 141b. As a result, at the first joining portion 141a, the surface seal layer 7 of the container 1 and the heat seal layer 10b of the lid member 10 are melted and joined to a greater extent than at the second joining portion 141b, and the resin accumulation 8 composed of the surface seal layer 7 is formed at an outer peripheral end 51 of the first joining portion 141a. In general, during the heat sealing, heating is performed from the lid member side and as a result, a larger amount of the heat seal layer 10b of the lid member 10 is melted, thus forming a resin accumulation 11a composed of a lid member heat seal layer larger than the resin accumulation 8 composed of the container surface seal layer.

On the other hand, unlike the inner step portion 45, the second joining portion 141b is heat-sealed and joined to the lid member 10, but almost no resin accumulation composed of the container surface seal layer 7 of the second joining portion 141b is formed because the pressure of the seal head is less exerted and the radial width is greater than that of the first joining portion, and, the top surface is flat. In addition, since the lid member 10 is directly pressed by the seal head, a resin accumulation 11b composed of the lid member heat seal layer is formed as with the outer peripheral end of the first joining portion 141a, while a resin accumulation 11b composed of the lid member heat seal layer is hardly in contact with the side wall portion 49.

During opening, the resin accumulation 8 composed of the container surface seal layer 7 formed at the outer peripheral end 51 of the first joining portion 141a is peeled off from the interface between the container surface seal layer 7 and the base material layer 6 together with the resin accumulation 11a composed of the lid member heat seal layer, and thus opening proceeds. As described above, the surface seal layer 7′ of the side wall portion 43 between the first joining portion 141a and the outer step portion 42 is formed with a small thickness, and the resin accumulation 8 composed of the container surface seal layer 7 is in contact with the thin surface seal layer 7′ on the lower or inner side of the resin accumulation 8. Therefore, when the lid member is pulled up during opening, the cohesive failure of the surface seal layer 7 can be easily caused from the lower or inner side of the resin accumulation 8 composed of the container surface seal layer 7 integrated with the resin accumulation 11a composed of the lid member heat seal layer. Since this cohesive failure occurs near the interface between the surface seal layer 7 and the base material layer 6, the subsequent interlayer peeling between the surface seal layer 7 and the base material layer 6 easily proceeds, thus making it possible to easily remove the lid member from the container.

In addition, when the internal pressure of the container increases, the upward movement of the lid member 10 with the inner peripheral end 50 of the second joining portion as the initiation point is suppressed by the presence of the resin accumulation 11b composed of the lid member heat seal layer in the vicinity of an inner peripheral end 50 of the second joining portion, and, since the resin accumulation composed of the container surface seal layer 7 is not formed, the resin accumulation 11b composed of the lid member heat seal layer is prevented from being peeled off together with the surface seal layer 7. Thus, unintentional opening due to an internal pressure increase is effectively prevented, and excellent sealability (pressure resistance) is achieved.

FIG. 11 is a diagram illustrating still another aspect of the flange portion in the container used in the easy-open packaging body of the disclosure.

FIG. 11 is a partially enlarged cross-sectional view illustrating an enlarged view of the flange portion of the container, and FIG. 12 is a partially enlarged cross-sectional view illustrating an enlarged view of with the flange portion with the lid member heat-sealed to the container illustrated in FIG. 11.

In the aspect illustrated in FIGS. 11 and 12, the basic shape is the same as the above-described container except that the coupling portion 141c includes an uneven shape composed of a recess 141c1 and a protrusion 141c2, each of which has a flat top surface.

In this aspect, the first joining portion 141a and the protrusion 141c2 in the coupling portion 141c have the same height in the container axial direction. Regarding the second joining portion 141b and the recess 141c1 in the coupling portion 141c, the recess 141c1 in the coupling portion 141c may have a height different from that of the second joining portion 141b in the container axial direction (for example, the height of the recess 141c1 in the container axial direction is smaller), but preferably, it is formed lower than the first joining portion 141a by L3. In this manner, since the pressure from the seal head can be received by the first joining portion 141a and the protrusion 141c2, as in the aspect illustrated in FIGS. 9 and 10, the resin accumulation 8 composed of the container surface seal layer 7 can be formed near the outer peripheral end 51 of first joining portion at the first joining portion 141a, and the pressure from the seal head is less exerted on the second joining portion 141b, thus suppressing the formation of the resin accumulation composed of the container surface seal layer 7 near the inner peripheral end 50 of the second joining portion 141b. In addition, since the protrusion 141c2 is located at the same height as the first joining portion 141a, joining with the lid member can be reliably achieved.

In addition, as described above, in the case where the first joining portion 141a and the protrusion 141c2 in the coupling portion 141c have the same height in the container axial direction, a width (D3) of the protrusion 141c2 in the container radial direction is smaller than the width (D1) of the first joining portion 141a, and thus the crushing amount of the container surface seal layer 7 at the first joining portion 141a can be increased. In this manner, the resin accumulation 8 composed of the container surface seal layer 7 in the vicinity of the outer peripheral end 51 of the first joining portion 141a can be reliably formed, thus improving openability.

On the other hand, if the width (D3) of the protrusion 141c2 is excessively small, the protrusion is crushed during the heat sealing, and the pressure of the seal head easily exerted on the second joining portion 141a. Therefore, it is preferable that the width (D3) of the protrusion 141c2 is greater than the width (D2) of the second joining portion 141b and a width (D4) of the recess 141c1.

Also in this aspect, since the pressure of the seal head is less exerted on the second joining portion 141b, and the resin accumulation composed of the container surface seal layer 7 is less formed in the vicinity of the inner peripheral end 50 of the second joining portion, unintentional opening due to an internal pressure increase is effectively prevented. Note that, at the second joining portion 141b, a resin accumulation 9 composed of the container surface seal layer 7 is formed near an inner peripheral end 55 of the protrusion 141c2, but since it is formed on the outer circumference side of the inner peripheral end of the joining portion of the container surface seal layer 7 and the lid member seal layer 10b, the sealability during internal pressure increase is not affected, but rather the resin accumulation 9 with a wedge-shape disposed in the lid member seal layer 10b can improve the sealability of the lid member 10 at the second joining portion 141b.

In the disclosure, the height difference (L3) between the first joining portion and the second joining portion illustrated in FIGS. 9 and 11 is preferably in the range of 0.01 mm to 0.20 mm. This ensures the sealability resulting from reliable joining of the annular joining portion, and makes it possible to form the resin accumulation composed of the container surface seal layer 7 near the outer peripheral end of the first joining portion, and form no or only an extremely small resin accumulation composed of the container surface seal layer 7 near the inner peripheral end of the second joining portion. As a result, formation of the resin accumulation composed of the container surface seal layer 7 can be controlled, and easy openability and reduction in non-uniformity in burst strength due to the sealing temperature can be achieved.

In addition, in the aspect illustrated in FIG. 9, the width (D1) of the first joining portion in the container radial direction and the width (D2) of the second joining portion in the container radial direction are preferably set in the range of D1:D2=1:2 to 5:1. In this manner, the above-described effects can be efficiently achieved.

In addition, the width (D1) of the first joining portion in the container radial direction and the width (D3) of the protrusion of the coupling portion in the container radial direction in the aspect illustrated in FIG. 11 need only to be D1≥D3 as described above, but preferably in the range of D1:D3=5:1 to 1:1.

Further, the width (D2) of the second joining portion in the container radial direction in the aspect illustrated in FIG. 11 is preferably in the range of 10% to 70%, more preferably in the range of 10% to 25%, of the width of the annular joining portion in the container radial direction. In this manner, formation of the resin accumulation composed of the container surface seal layer 7 at the inner peripheral end of the second joining portion can be suppressed, and non-uniformity of burst strength can be suppressed.

Further, the width (D4) of the recess of the coupling portion in the container radial direction is preferably in the range of 10% to 50%, more preferably in the range of 10% to 20%, of the width of the annular joining portion in the container radial direction. In this manner, the molten resin from the coupling portion protrusion and the first joining portion can be received within the recess.

In the disclosure, the thickness of the surface seal layer of the annular joining portion can be set as necessary in accordance with the type of resin making up the surface seal layer, the width of the annular joining portion and the like, but is preferably in the range of 10 μm to 80 μm. In addition, in the case where the thickness of the surface seal layer of the annular joining portion is within the above-mentioned range, the step of the inner step portion is preferably in the range of 0.1 mm to 0.5 mm, more preferably in the range of 0.25 mm to 0.5 mm. In addition, the step of the outer step portion is preferably in the range of 0.1 mm to 0.5 mm, more preferably in the range of 0.25 mm to 0.5 mm.

In the container used in the disclosure, by forming a stress concentrating portion protruding outward from the container as viewed from the top surface of the container in a part of the annular joining portion, opening with a small force can be achieved. Specifically, FIG. 13A is a diagram illustrating the top surface of the container flange portion in the aspect illustrated in FIG. 9, and the shape of the annular joining portion 41 includes a protruding portion 56 protruding in a V-shape extending outward in the container radial direction, which is preferable because the thin surface seal layer 7 at the groove (notch) 47 on the inner peripheral side is easily fractured due to stress concentration after the interlayer peeling of the base material layer 6 and the surface seal layer 7 during opening. Alternatively, the protruding shape of the annular protruding portion may be a U-shape, an L-shape, or a wave-like shape formed of a series of these shapes, for example.

In addition, in the specific example illustrated in FIG. 13A, a protrusion 57 for air venting of the metal mold (locator) for molding the annular joining portion is formed on the outer side of the protruding portion 56. In this manner, retention of air in the recess of the locator corresponding to the first joining portion can be suppressed, and the annular joining portion that matches the shape of the metal mold can be molded with good dimensional stability, for example.

In addition, in the container of the disclosure, a steam vent portion for releasing the internal pressure when the internal pressure increases due to microwave heating or the like can be formed in a part of the annular joining portion. Specifically, as illustrated in FIG. 13B, as viewed from the top surface of the container, a plurality of steam vent portions 58 protruding inward of the container is formed, and when the internal pressure increases due to microwave heating, the stress concentrates at the steam vent portions protruding inward, and interlayer peeling is started preferentially at other portions, thus efficiently releasing the internal pressure. Note that, the top surface of the annular joining portion is flat at the location of the steam vent portions 58, and therefore in the aspect illustrated in FIG. 9, the second joining portion is not formed (FIG. 13B), whereas in the aspect illustrated in FIG. 11, the second joining portion and the recess of the coupling portion are not formed.

The disclosure is not limited to the specific examples illustrated in FIGS. 1A to 13B, and can be variously modified.

For example, while the outer step portion is formed on the outer side of the annular joining portion in the specific examples illustrated in FIGS. 1A to 5 and FIGS. 9 to 12, the outer step portion may not be formed, and the outer peripheral end of the flange portion and the outer peripheral end of the annular joining portion may coincide with each other. Similarly, as long as the heat seal layer can be completely separated from the container via the notch and the like, the inner step portion may not be formed.

In addition, the side wall portion extending outward in the container axial direction from the outer peripheral edge of the joining position is substantially perpendicular in the specific example illustrated in the drawing, but it may be an inclined surface with the outer diameter that increases toward the lower side in the container axial direction.

Preferably, the flange portion includes the annular skirt portion 5 extending downward from the outer peripheral end of the flange portion in view of improving the mechanical strength and the like of the flange portion, but the annular skirt portion may not be formed depending on the thickness of the flange portion and the like.

Further, while the container is integrally molded from the layered body including the base material layer and the surface seal layer, and the surface seal layer is formed also at the container inner surface in the specific example illustrated in the drawing, the surface seal layer may be formed only at the flange portion.

Preferably, the container of the disclosure has a cup shape, but this is not limitative, and the container may have a tray shape as long as the flange portion is provided. In addition, while FIGS. 1A, 5 and 13A and 13B illustrate a round container shape, containers with square shapes, containers with other polygonal shapes, and containers with ellipse shapes may also be adopted.

The lid member that can be used with the container of the disclosure may be a molded lid member in the form of a drop-in lid, as well as a flexible sheet-shaped lid member.

In addition, the base material layer of the container and the surface seal layer are preferably peeled off from each other through interlayer peeling as described above, cohesive peeling or interface peeling may also be adopted as long as they are easy to peel off. In addition, the surface seal layer and the base material layer on the lid member side may be easy to peel off.

As the peeling strength suitable for satisfying both the sealability and easy openability, it is preferable that the opening force (peeling strength), which is measured by attaching a push-pull gauge to the gripping portion of the lid member and pulling it upward at an angle of 45 degrees with respect to the lid member as illustrated in FIG. 14, falls within a range of 3.0 N to 30.0 N, more preferably within a range of 5.0 N to 25.0 N.

As a combination of resins capable of exhibiting such peeling strength, two or more thermoplastic resins that have heat sealability and are incompatible with each other can be appropriately combined.

The base material layer of the container may be made of an olefin resin, a polyester resin, or other known thermoplastic resins that have been used for forming resin containers in the related art. For example, in the case where the base material layer is composed of a propylene-based polymer, and sealability can be ensured while maintaining easy openability by forming the surface seal layer with a blend of an ethylene-based polymer and a propylene-based polymer, and the peeling strength can be adjusted by appropriately changing the blending ratio of the blend.

Examples of the above-described propylene-based polymer include, in addition to homopolypropylene, block or random copolymers of propylene with ethylene or other α-olefins, such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Examples of the above-described ethylene-based polymer include ethylene homopolymers such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and medium- or high-density polyethylene (MDPE, HDPE), or copolymers of ethylene with other α-olefins such as 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, or 1-octene, or with vinyl-based monomers such as (meth)acrylic acid, (meth)acrylic acid ethyl ester, (meth)acrylic acid methyl ester, vinyl acetate, or styrene, as well as ionomers.

As the blend, in addition to combinations of the above-mentioned olefin-based polymers, combinations of olefin-based polymers with thermoplastic polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and copolymers modified with isophthalate, or with other resins such as polycarbonate resin and polyacrylonitrile resin, can also be used.

When using a blend of a propylene-based polymer and an ethylene-based polymer, in order for the flange member made of the blend to exhibit favorable peelability from the container body made of a propylene-based polymer, it is preferable to use a blend in which the propylene-based polymer and the ethylene-based polymer are blended at a weight ratio in the range of 5:5 to 9.5:0.5.

In addition, in order to favorably form the resin accumulation from the surface seal layer, it is preferable to adjust the fusing point and the melt flow rate (MFR) as necessary such that the resin making up the surface seal layer can exhibit fluidity in accordance with the heat sealing condition.

While the container may be provided by integrally molding the two-layer layered body composed of the base material layer and surface seal layer, the container may also have a multilayer structure including a gas barrier intermediate layer between the base material layers. In addition, as described above, the surface seal layer may be formed only at the flange portion of the container.

The manufacturing method of the container of the disclosure is not limited as long as the flange portion satisfies the above-described configurations, but it is preferable to integrally mold the layered body by thermoforming such as vacuum forming or plug-assist pressure forming. According to this method, it is possible to easily form protrusions and recesses corresponding to the annular joining portion, the outer step portion, and the inner step portion on the top surface of the flange portion during molding by using a locator (flange presser).

EXAMPLES

Experimental Example 1

Using a two-layer sheet composed of a 1 mm thick polypropylene (PP) layer and a high-density polyethylene (HDPE) layer as the surface layer, a cup-shaped container having a skirt flange configuration with an opening diameter of 84 mm and a flange width of 5 mm was fabricated by plug-assist vacuum pressure forming. An annular joining portion having three different shapes as shown in Table 1 below was formed on the flange portion. The HDPE used had a MFR of 5 g/10 min at 190° C., and the thickness of the layer was 20 μm.

With respect to the three types of annular joining portions shown in Table 1, the type having a tapered shape had a taper angle of 5°, and the height difference between the highest and lowest positions of the tapered portion was 0.11 mm. The annular joining portion having the shape shown in FIG. 9 had L3=0.11 mm, D1=0.5 mm, and D2=0.8 mm. The annular joining portion having the shape shown in FIG. 11 had L3=0.90 mm, D1=0.55 mm, D4=0.20 mm, D3=0.30 mm, and D2=0.25 mm.

A lid member (100 μm) composed of a seal layer made of linear low-density polyethylene (LLDPE) was heat-sealed to the container at the sealing temperatures shown in Table 1, with a sealing time of 2.3 seconds and a sealing pressure of 100 kgf/cup, and the burst strength was measured. The burst strength under each sealing condition was measured, and the variation in burst strength was evaluated. The results are shown in Table 1.

As is apparent from Table 1, in the case where an annular joining portion having a tapered shape was formed, the burst strength was 21 kPa to 40 kPa (range 19). In the case where an annular joining portion having the shape shown in FIG. 9 was formed, the burst strength was 32 kPa to 48 kPa (range 16). In the case where an annular joining portion having the shape shown in FIG. 11 was formed, the burst strength was 36 kPa to 44 kPa (range 8). Although all were 20 kPa or higher, which is required for retort containers under the Food Sanitation Act, those having the annular joining portion formed in the shape shown in FIG. 9 or FIG. 11 exhibited relatively small variation in burst strength depending on the sealing conditions, resulting in superior performance in terms of product management.

Experimental Example 2

For the containers obtained in Experimental Example 1, the opening force (peeling strength) was measured by attaching a push-pull gauge to the gripping portion of the lid, and pulling it upward at an angle of 45 degrees with respect to the lid, as shown in FIG. 14. The results are shown in Table 1.

As is apparent from Table 1, in the case where an annular joining portion having a tapered shape was formed, the opening force was 8.0 N to 11.8 N, in the case where an annular joining portion having the shape shown in FIG. 9 was formed, the opening force was 6.2 N to 7.6 N, and in the case where an annular joining portion having the shape shown in FIG. 11 was formed, the opening force was 5.9 N to 8.5 N. Thus, it can be understood that the container of the disclosure also exhibits excellent easy openability. In this case, when no resin accumulation was present, or even when a resin accumulation was present but no thin surface seal layer serving as an opening start portion was provided on the lower or inner side, it was difficult to achieve opening.

Experimental Example 3

A cup-shaped container having the same shape as in Experimental Example 1 was produced by plug-assist vacuum pressure forming using a two-layer sheet composed of a 1 mm thick PP layer and an HDPE layer as the surface layer, and annular joining portions having three types of shapes as shown in Table 2 below were formed at the flange portion. The HDPE had an MFR of 7 g/10 min at 190° C., and the thickness of the layer was 30 μm. A lid member of the same type as in Experimental Example 1 was heat-sealed to this container at the sealing temperatures shown in Table 2, with a sealing time of 2.3 seconds and a sealing pressure of 100 kgf/cup, and the burst strength was measured. The burst strength under each sealing condition was measured, and the variation in burst strength was evaluated. The results are shown in Table 2.

As is apparent from Table 2, in the case where an annular joining portion having a tapered shape was formed, the burst strength was 26 kPa to 73 kPa (range 47), in the case where an annular joining portion having the shape shown in FIG. 9 was formed, the burst strength was 36 kPa to 49 kPa (range 13), and in the case where an annular joining portion having the shape shown in FIG. 11 was formed, the burst strength was 49 kPa to 60 kPa (range 11). Although all were 20 kPa or higher, which is required for retort containers under the Food Sanitation Act, those having the annular joining portion formed in the shape shown in FIG. 9 or FIG. 11 exhibited relatively small variation in burst strength depending on the sealing conditions, resulting in superior performance in terms of product management.

Experimental Example 4

For the containers obtained in Experimental Example 3, the opening force (peeling strength) was measured by attaching a push-pull gauge to the gripping portion of the lid, and pulling it upward at an angle of 45 degrees with respect to the lid, as shown in FIG. 14. The results are shown in Table 2.

As is apparent from Table 2, in the case where an annular joining portion having a tapered shape was formed, the opening force was 9.1 N to 12.5 N, in the case where an annular joining portion having the shape shown in FIG. 9 was formed, the opening force was 8.7 N to 11.9 N, and in the case where an annular joining portion having the shape shown in FIG. 11 was formed, the opening force was 8.9 N to 9.1 N. Thus, it can be understood that the container of the disclosure also exhibits excellent easy openability. In this case, when no resin accumulation was present, or even when a resin accumulation was present but no thin surface seal layer serving as an opening start portion was provided on the lower or inner side, it was difficult to achieve opening.

INDUSTRIAL APPLICABILITY

The easy-open packaging body of the disclosure can be applied even to thin containers, and can be easily opened with a smaller opening force while having excellent sealability through heat sealing, and therefore, can be suitably used as a packaging body for food and beverages.

Moreover, it exhibits excellent pressure resistance when the internal pressure increases in the sealed state, and is suitably usable as a container for filling and sealing contents that require thermal sterilization, such as retort sterilization. Further, since variation in burst strength does not occur due to the sealing conditions, it is possible to provide containers with stable quality, thereby facilitating product management.

While preferred embodiments of the disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. The scope of the disclosure, therefore, is to be determined solely by the following claims.