paper container

Abstract

This ensures the heat-sealing properties of the lid material when it is heat-sealed to the flange portion of a paper container. [Solution] A paper container (1) manufactured as a package has an opening surrounded by the upper edge (3U) of a side portion (3) folded up from the periphery of a bottom portion (2), a flange portion (4) extending outward from the upper edge (3U) relative to the upper edge (3U), and a lid material covering the opening is heat-sealed to the flange portion (4). The package has a curled portion (4C) in which the outer periphery of the flange portion (4) is rolled up, and a flat top surface (4U) that extends continuously between the upper edge (3U) and the curled portion (4C), and a flat portion (4F) provided on the inside of the curled portion (4C) and on the outside of the upper edge (3U) of the flange portion (4), wherein the curled portion (4C) is provided at the same vertical position (P) as the top surface (4U) or below the top surface (4U).

Description

Technical Field

[0001] The present invention relates to a paper container.

Background Art

[0002] There is known a paper container having an opening surrounded by an upper edge of a side surface portion folded upward from a peripheral edge of a bottom surface portion, and a flange portion extending outwardly of the opening. In addition, there is known a package in which a lid material covering an opening of a paper container is heat-sealed (also referred to as "top seal") on the flange portion. As a method of heat-sealing the lid material to the flange portion, a part of the lid material covering the opening and located above the flange portion is heated while being pressed from above to below by a flat hot plate, and the flange portion is supported from below by a bucket.

[0003] The paper container used in the process of manufacturing the package as described above can be said to be a semi-finished product for manufacturing the package. On the contrary, the package manufactured using the paper container and the lid material can be said to be a finished product manufactured using the semi-finished product. As one of the paper containers, a paper container having a curling portion (also referred to as "edge curling portion" or "curl portion") in which an outer peripheral edge portion of the flange portion is involved has been proposed. For example, a paper container has been proposed in which at least a part of the curling portion protrudes above a flat plane portion in the flange portion (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, in paper containers where the curled portion of the flange protrudes above the flat portion, the flange portion has two regions: a flat region where the flat portion extends and a convex region that protrudes above the flat portion. When a lid material is heat-sealed to a flange portion with these two regions, the pressing force and heat are not applied uniformly to the lid material, which may lead to the problem of not being able to stably heat-seal the lid material (ensuring heat sealing performance). Therefore, when a lid material is heat-sealed to the flange portion of a paper container, there is room for improvement in ensuring the heat-sealing properties of the lid material.

[0006] This invention was conceived in view of the above-mentioned problems, and one of its objectives is to ensure the heat-sealing properties of the lid material when it is heat-sealed to the flange portion of a paper container. However, other objectives of this invention include achieving effects and benefits that cannot be obtained with conventional technology, derived from the various configurations shown in the "Modes for Carrying Out the Invention" described later. [Means for solving the problem]

[0007] The paper container disclosed herein has the following configurations (1) to (5). (1) A semi-finished paper container manufactured as packaging, having an opening surrounded by the upper edge of a side portion folded upward from the periphery of the bottom portion, a flange portion extending outward from the upper edge on the side opposite to the opening relative to the upper edge, and a lid material covering the opening heat-sealed upward from the flange portion, The flange portion includes a curled portion in which the outer peripheral edge is rolled in, The flange portion has a flat upper surface that extends continuously between the upper edge and the curling portion, and a flat portion provided on the inside of the curling portion and on the outside of the upper edge, The curling portion is provided at the same vertical position as the upper surface or below the upper surface. A paper container characterized by the following features.

[0008] (2) The curling portion has a base portion extending downward from the outer peripheral edge of the flat portion, and an outer winding portion that is wound around the portion adjacent to the outside of the base portion. A paper container as described in (1), characterized by the features described above. (3) The curling portion has a base portion that extends horizontally outward from the outer peripheral edge of the flat portion, and an inner curling portion that is wound up including the portion adjacent to the lower side of the base portion. A paper container as described in (1), characterized by the features described above.

[0009] (4) The planar portion has a lower surface provided parallel to the upper surface. A paper container as described in any one of (1) to (3), characterized by the above. (5) An auxiliary layer is provided on the upper surface to assist in the heat sealing of the lid material. A paper container as described in any one of (1) to (4), characterized by the above. [Effects of the Invention]

[0010] According to this invention, when a lid material is heat-sealed to the flange portion of a paper container, the heat-sealing properties of the lid material can be ensured. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view (exploded perspective view of the packaging) showing the paper container and lid material. [Figure 2] This is a diagram illustrating an example of a flange portion in a paper container, and is a partially enlarged cross-sectional view showing the flange portion and its surrounding area in detail. [Figure 3] This drawing illustrates another example of a flange portion in a paper container, and is a partially enlarged cross-sectional view showing the flange portion and its surrounding area in detail. [Figure 4] This is a schematic cross-sectional view illustrating a method for manufacturing packaging from paper containers. [Figure 5]It is a schematic cross-sectional view for explaining a mode of manufacturing a package from a paper container of a comparative example. (a) shows the paper container placed on a bucket, (b) shows an initial mode in the process of pressing a lid material against the paper container, and (c) shows a final mode in the process of pressing the lid material against the paper container.

Mode for Carrying Out the Invention

[0012] Hereinafter, a mode of implementing a paper container will be described. The paper container of the present embodiment is a paper container having an open opening and is a semi-finished product for manufacturing a package. When this opening is covered with a lid material, it is the completion of a package in which the paper container is sealed (sealed) by the lid material. That is, the package is a finished product manufactured using a semi-finished paper container and a lid material.

[0013] Note that the paper container is formed from a paper base material (so-called blank sheet). For example, the paper container may be formed by molding (forming) the paper base material with a mold, or the paper base material may be formed by bending. Also, the paper container may be formed from a single paper base material, or a plurality of paper base materials may be combined and formed. As the paper base material, a paper base material made of only paper may be used, or a paper base material in which a functional layer is laminated on the paper material may be used. Examples of the functional layer laminated on the paper material include a heat-sealing layer in which a heat-sealing agent is applied to the paper material, a layer of wax brazed on the paper material, and a layer of film laminated on the paper material. A paper material laminated with a heat-sealing layer, a layer of wax, or a layer of a film having thermoplasticity, for example, can be welded by applying heat, and can also be said to be an auxiliary layer that assists heat sealing, contributing to an improvement in the weldability of the lid material to the paper container. Also, a paper material laminated with a layer of film can improve various functions due to the barrier properties, water resistance, heat resistance, etc. of the film.

[0014] In the present embodiment, the description is based on the posture in which the paper container is placed on a horizontal plane, and the directions used in the description are defined as follows. Regarding the vertical direction, the direction in which gravity acts is downward (denoted as "D" in the drawing), and the opposite direction of downward is upward (denoted as "U" in the drawing). The horizontal direction is along the four directions of forward (denoted as "F" in the drawing), backward (denoted as "B" in the drawing), leftward (denoted as "L" in the drawing), and rightward (denoted as "R" in the drawing). Further, the side facing the opening (accommodation space) of the paper container is the inner side, and the opposite side of the inner side is the outer side. In addition, the outer peripheral edge is also referred to as the "outer peripheral edge".

[0015] Note that the expressions "along", "along with", and "extending along" as used in this embodiment do not refer only to the direction parallel to the reference direction or plane, but also include a direction slightly inclined with respect to the reference direction or plane (for example, a direction inclined by 5[°] or 10[°]). Also, the expression "upward" as used in this embodiment does not refer only to the form facing upward parallel to the vertical direction, but also includes a form of a direction slightly inclined with respect to the upward parallel to the vertical direction.

[0016] [I. One Embodiment] In the following one embodiment, the configuration regarding the paper container is described in item [1], and the actions and effects due to the configuration of item [1] are described in item [2]. [1. Configuration] In this item [1], the basic configuration of the paper container according to one embodiment is described in sub-item [1-1], and the paper container of the comparative configuration that causes problems to be solved by the paper container according to one embodiment is mentioned in sub-item [1-2]. Then, the main part configuration of the paper container according to one embodiment is explained in sub-item [1-3]. In the following one embodiment, a paper container formed from a paper base material with a functional layer laminated on the paper material is exemplified.

[0017] [1-1. Basic Configuration] As shown in FIG. 1, the paper container 1 is provided with a bottom surface portion 2 extending along the horizontal direction, and side surface portions 3 folded up from the peripheral edge of the bottom surface portion 2, and an upward opening 9 is surrounded by the upper end edge 3U of the side surface portions 3. A flange portion 4 is provided to extend outside the opening 9 (on the side opposite to the opening 9 with respect to the upper end edge 3U of the side surface portions 3) of this paper container 1.

[0018] Figure 1 illustrates a paper container 1 in which a rectangular bottom portion 2 and an opening 9 are provided, and four side portions 3 are erected facing in the front, back, left, and right directions. In other words, the bottom portion 2, the side portions 3, and the opening 9 define a truncated square pyramidal storage space S (which can also be called the "internal space S" when the opening 9 is closed). However, the storage space S of the paper container 1 is not limited to a truncated square pyramid shape, but may be any shape such as a truncated cone shape, a truncated polygonal shape (except for the truncated square pyramid shape), or a rectangular parallelepiped shape. In this case, the paper container 1 is provided with a bottom surface 2, side surfaces 3, and an opening 9 of a shape and size corresponding to the shape of the storage space S.

[0019] The flange portion 4 is provided with a curled portion 4C in which the outer peripheral edge (outer peripheral edge) of the flange portion 4 is rolled in, and a flat portion 4F provided inside the curled portion 4C and outside the upper end edge 3U of the side portion 3. The curling portion 4C is also called the "edge wrapping portion," "curl portion," or "curling ring portion," and is formed by wrapping a part of the paper substrate that corresponds to the flange portion 4 into the paper container 1. This curling portion 4C extends around the entire circumference on the outside of the flange portion 4 and has a hollow structure that encircles the outer edge of the flange portion 4.

[0020] The curled section 4C described above is formed by wrapping a portion of the paper substrate around it, and therefore performs various functions such as reinforcement, moisture absorption suppression, and improved feedability. The reinforcing function is the function of reinforcing the outer edge of the flange portion 4, and can also be described as the function of maintaining the shape of the paper container 1 (in other words, ensuring its shape consistency). The moisture absorption suppression function is the function of suppressing moisture absorption from the edge surface of the paper substrate, and can also be described as the function of suppressing deformation and deterioration caused by the paper container 1 becoming soggy. The feedability improvement function is the function of ensuring gaps between stacked paper containers 1 to make it easier to remove the paper containers 1 one by one, and can also be described as the function of suppressing malfunctions in devices (feeders, automatic supply devices) that automatically supply multiple paper containers 1 sequentially.

[0021] The flat section 4F extends continuously and flatly between the upper edge 3U of the side section 3 and the curled section 4C. More specifically, as shown in Figure 2, the upper surface 4U of the flat section 4F is a horizontal (flat) surface that extends continuously between the upper edge 3U of the side section 3 and the curled section 4C. The lower surface 4D of the flat section 4F is provided parallel to the upper surface 4U. In other words, both the upper surface 4U and the lower surface 4D of the flat section 4F are provided horizontally.

[0022] In this embodiment, the upper surface 4U has laminated functional layers (auxiliary layers, not shown) that assist in heat sealing, such as a heat seal layer coated with a heat sealant, a wax layer applied to the paper material, and a film layer laminated to the paper material. In addition, functional layers are laminated on the inward-facing surface of the side section 3 (see Figure 1) and the upward-facing surface of the bottom section 2 (see Figure 1) (the inward-facing surface in the paper container 1).

[0023] As shown in Figure 1, when the opening 9 of the aforementioned paper container 1 is covered with a lid material 8, it becomes a package 11. The lid material 8 is made of a sheet material that melts when heat is applied. Examples of sheet materials used for the lid material 8 include thermoplastic films and weldable laminated paper.

[0024] In the packaging 11, the lid material 8 is heat-sealed (also called "top sealing") over the flange portion 4. The lid material 8 is sized to span both the opening 9 and the flange portion 4 in a plan view, and is pressed against the flange portion 4 from above while heat is applied. In this way, the lid material 8 is heat-sealed to the flange portion 4 from above. As described above, the top-sealed packaging 11 has the opening 9 of the paper container 1 sealed with a lid 8. This packaging 11 is completed when the contents are placed in the storage space S of the paper container 1 and the lid 8 is heat-sealed. Alternatively, a so-called MAP (Modified Atmosphere Packaging) packaging 11 may be used, in which the air in the storage space S is replaced with an inert gas after the contents are placed in the storage space S of the paper container 1.

[0025] [1-2. Comparative Configuration] Incidentally, as previously stated in "Problems the Invention Aims to Solve," depending on the configuration of the flange portion in the paper container, there is a risk that the lid material may not be able to be stably heat-sealed. The following describes an embodiment of manufacturing a package 110 from a paper container 10 with a comparative configuration that does not allow for stable heat sealing of the lid material 80, with reference to Figures 5(a) to 5(c). In order to heat seal the lid material 80 to the paper container 10, only the flat portion 40F of the flange portion 40 is placed on the bucket 50 in order to seal the lid material 80 without crushing the curling portion 40C.

[0026] As shown in Figure 5(a), the paper container 10 has a flange portion 40 that extends from the upper edge 30U of the side portion 30, with a part 41C of the curled portion 40C protruding above the flat portion 40F. The flange portion 40 contains a mixture of two types of regions R1 and R2 as described below. • Flat region R1: The region extending from the flat section 40F. • Convex region R2: Region that protrudes above the flat portion 40F.

[0027] Then, as shown in Figure 5(b), a flat heating plate 60 is lowered from above the flange portion 40 to press the cover material 80 against the flange portion 40. This causes the convex region R2 on the flange portion 40 to be pushed down via the cover material 80. This downward pressure causes the inside of the flat portion 40F to lift from the bucket 50, causing the flat region R1 to face slightly outward, and also causes the upper edge 30U of the side portion 30 to be lifted upward, resulting in a bend (malfunction).

[0028] Then, as shown in Figure 5(c), when the flat heating plate 60 is lowered further, a flat area R1 is sandwiched between the bucket 50 and the heating plate 60. This sandwiching may cause damage (malfunction) to the flange portion 40, such as tearing or ripping at the joint 49 between the flat portion 40F and the curled portion 40C. Such damage to the flange portion 40 may also cause a malfunction in which the lid material 80 cannot be properly heat-sealed to the paper container 10.

[0029] Furthermore, the flat region R1 on the upper surface 40U of the flange portion 40 changes from a slightly outward orientation as shown in Figure 5(b) to an upward orientation as shown in Figure 5(c) while the lid material 80 is heat-sealed. As a result, there is a risk that the pressing force and heat from the heating plate 60 will be applied unevenly to the flange portion 40. Specifically, there is a risk that the pressing force and heat from the heating plate 60 will not be sufficiently applied to the outer region of the flat region R1, while the pressing force and heat from the heating plate 60 will be excessively applied to the convex region R2 and the inner region of the flat region R1.

[0030] In areas where sufficient pressing force or heat is not applied, the lid material 80 may not be adequately heat-sealed, potentially leading to leakage of the contents sealed in the packaging 110. In areas where excessive pressing force or heat is applied, the lid material 80 may become difficult to remove, potentially reducing the ease of opening the packaging 110. As a result of the uneven application of pressing force and heat, there is a risk of failure to ensure the heat-sealing properties of the lid material 80 to the paper container 10.

[0031] [1-3.Main part configuration] Therefore, as shown in Figure 2, the paper container 1 of this embodiment is provided with a curled portion 4C at a vertical position that does not protrude upward from the upper surface 4U of the flat portion 4F. That is, the curled portion 4C is provided at the same vertical position P as the upper surface 4U of the flat portion 4F, or below the upper surface 4U. In this way, the flange portion 4 provided with the curled portion 4C does not have a region that protrudes upward from the flat portion 4F, and only a flat region exists on the upper surface 4U of the flat portion 4F to which the lid material 8 (see Figure 1) is heat-sealed.

[0032] The curled portion 4C illustrated in Figure 2 is provided with a base portion 4A extending downward from the outer peripheral edge of the flat portion 4F, and an outer winding portion 4B that is wound around the base portion 4A, including the portion adjacent to the outside of the base portion 4A. In other words, the curled portion 4C illustrated here has a form in which the outer winding portion 4B is wound outward from the base portion 4A. Figure 2 illustrates a curled portion 4C in which the outer winding portion 4B is wound counterclockwise from the base portion 4A.

[0033] The outward-curling portion 4C described above is formed by rolling up the portion that extends downward from the outer edge of the flat portion 4F. As the outward-curling portion 4C is formed in this way, the portion that is rolled up from below the flat portion 4F is the outer-curling portion 4B. Therefore, the base portion 4A and the outer-curling portion 4B are formed when the portion of the curling portion 4C that was located below the flat portion 4F is rolled up to a position where it does not protrude upward from the flat portion 4F. In other words, in the molding process of the curling portion 4C, there are no portions that are formed as the base portion 4A and the outer-curling portion 4B above the flat portion 4F.

[0034] Instead of the outward-curling section 4C described above, an inward-curling section 4C' may be used, as shown in Figure 3. The inwardly curled portion 4C' is provided with a base portion 4A' that extends horizontally outward from the outer peripheral edge of the flat portion 4F, and an inwardly curled portion 4B' that is wound around the base portion 4A', including the adjacent portion below it. In other words, the curled portion 4C' illustrated here has a form in which the inwardly curled portion 4B' is wound inward from the base portion 4A'. Figure 3 illustrates a curled portion 4C' in which the inwardly curled portion 4B' is wound clockwise from the base portion 4A'.

[0035] The inwardly curled portion 4C' described above is formed by curling the portion that extends upward from the outer edge of the flat portion 4F. As the inwardly curled portion 4C' is formed in this way, the portion that is curled from above the flat portion 4F is the inwardly curled portion 4B'. Therefore, in the formation process of the curled portion 4C', the portion that was located above the flat portion 4F is rolled down to a position where it does not protrude upward from the flat portion 4F, and the base portion 4A' and the inwardly curled portion 4B' are formed. In other words, in the formation process of the curled portion 4C', the portions that are formed as the base portion 4A and the inwardly curled portion 4B' are located above the flat portion 4F. In conventional paper containers, it is more common to use an inwardly curled section rather than an outwardly curled section.

[0036] [2. Action and Effects] Because the paper container 1 of this embodiment has the above-described configuration, the following actions and effects can be obtained. (1) In the paper container 1 of this embodiment, the flange portion 4 is provided with a curling portion 4C at the same vertical position P as the upper surface 4U of the flat portion 4F or below this upper surface 4U. That is, only a flat area exists on the upper surface 4U of the flat portion 4F to which the lid material 8 is heat-sealed.

[0037] The following describes how to manufacture a package 11 from a paper container 1 having the flange portion 4 provided as described above, with reference to Figure 4. As shown in Figure 4, the paper container 1 has a flange portion 4 in which the curled portion 4C does not protrude above the flat portion 4F, as described above. Only the upper surface 4U of the flat portion 4F extends to the area in which the lid material 8 is heat-sealed. In order to heat-seal the lid material 8 to the paper container 1, only the flat portion 4F of the flange portion 4 is placed on the bucket 5 so as not to crush the curled portion 4C.

[0038] A flat heating plate 6 is lowered from above the flange portion 4 onto the paper container 1 described above, pressing the lid material 8 against the flange portion 4. As a result, the lid material 8 is heat-sealed simultaneously over the entire area extending from the upper surface 4U of the flat portion 4F of the flange portion 4. Therefore, bending (defects) such as the flat section 4F lifting up from the bucket 5 or the upper edge 3U of the side section 3 being lifted upwards is suppressed. In addition, damage (defects) to the flange section 4, such as tearing or ripping at the joint between the flat section 4F and the curled section 4C, can also be suppressed. By suppressing such bending and damage to the flange section 4, the heat sealing performance of the lid material 8 to the paper container 1 is improved.

[0039] Furthermore, since the lid material 8 is heat-sealed without any change in the orientation of the upper surface 4U facing upward on the flat section 4F, the pressing force and heat from the heating plate 6 are uniformly applied to the upper surface 4U of the flat section 4F. Therefore, it is possible to suppress the occurrence of areas where the lid material 8 is not sufficiently heat-sealed or areas where the lid material 8 is excessively heat-sealed. By suppressing the occurrence of areas where the lid material 8 is not sufficiently heat-sealed, leakage of the contents sealed in the packaging 11 is prevented. By suppressing the occurrence of areas where the lid material 8 is excessively heat-sealed, the lid material 8 can be easily peeled off the paper container 1, ensuring the ease of opening the packaging 11. Therefore, when the lid material 8 is heat-sealed to the flange portion 4 of the paper container 1, the lid material 8 can be heat-sealed stably, and the heat-sealing properties of the lid material 8 can be ensured.

[0040] (2) The outward-curling portion 4C is provided with a base portion 4A that extends downward from the outer peripheral edge of the flat portion 4F, and an outward-curling portion 4B that is wrapped around the portion adjacent to the outside of the base portion 4A. Since this curling portion 4C is provided by wrapping around the portion that extends downward from the outer peripheral edge of the flat portion 4F, it is easy to mold (manufacture) it without it protruding upward from the upper surface 4U of the flat portion 4F. Even if the outer curled portion 4B unwinds in the outward curled portion 4C, it unwinds downwards, so the unwound portion is structurally less likely to protrude upward from the upper surface 4U of the flat portion 4F. This also contributes to ensuring the heat sealing properties of the lid material 8.

[0041] (3) On the other hand, the inwardly curled portion 4C' is provided with a base portion 4A' that extends horizontally outward from the outer peripheral edge of the flat portion 4F, and an inwardly curled portion 4B' that is curled in, including the portion adjacent to the lower side of the base portion 4A'. Since inwardly curled portions are commonly used in conventional paper containers, the inwardly curled portion 4C' of this embodiment can be formed using conventional methods and molds for forming the curled portion of paper containers. This contributes to reducing the manufacturing cost of the paper container 1.

[0042] (4) The flat portion 4F of the flange portion 4 has an upper surface 4U and a lower surface 4D that are parallel to each other, and these upper surface 4U and lower surface 4D are horizontally positioned. Therefore, when the lid material 8 is heat-sealed not only by uniformly pressing it against the upper surface 4U of the flat portion 4F, but also by sandwiching the flat portion 4F and the lid material 8 from the lower surface 4D, pressing force and heat can be applied more uniformly to the lid material 8 that is heat-sealed against the upper surface 4U of the flange portion 4. Thus, the heat-sealing performance of the lid material 8 can be improved. (5) In addition, a functional layer (auxiliary layer) that assists in heat sealing is laminated on the top surface 4U. As a result, the heat sealing performance of the lid material 80 to the top surface 4U is improved.

[0043] [II. Variant Examples] The embodiments described above are merely illustrative, and there is no intention to exclude various modifications or applications of techniques not explicitly stated in these embodiments. Each configuration of these embodiments can be modified in various ways without departing from their spirit. Furthermore, they can be selected and combined as needed. For example, the functional layer laminated on the upper surface of the flat portion of the flange may be omitted. Also, the flat portion of the flange only needs to have a flat upper surface, and the direction in which the lower surface of the flat portion extends is arbitrary. Furthermore, the orientation of the paper container during the manufacturing process of the packaging is not limited to the orientation in which the paper container is placed on a horizontal surface with the opening facing upwards; it may be any orientation. If the packaging is manufactured with the opening facing downwards, then upwards should be read as downwards. Also, the orientation of the paper container during molding is arbitrary. [Explanation of Symbols]

[0044] 1. Paper container 2 Bottom part 3 Side part 3U upper edge 4. Flange section 4F flat area 4U top 4A,4A′ base 4B Outer winding part 4B′ Inner winding part 4C, 4C' Curling Club 4D bottom side 5 buckets 6 hot plate 8 Lid material 9 aperture 11 Packaging P Vertical position S Containment space

Claims

1. A semi-finished paper container manufactured as packaging, having an opening surrounded by the upper edge of a side portion folded upward from the periphery of the bottom portion, a flange portion extending outward from the upper edge on the side opposite to the opening relative to the upper edge, and a lid material covering the opening heat-sealed upward from the flange portion, The flange portion includes a curled portion in which the outer peripheral edge is rolled in, The flange portion has a flat upper surface that extends continuously between the upper edge and the curling portion, and a flat portion provided on the inside of the curling portion and on the outside of the upper edge, The curling portion is provided at the same vertical position as the upper surface or below the upper surface. A paper container characterized by the following features.

2. The curling portion has a base portion extending downward from the outer peripheral edge of the flat portion, and an outer winding portion that is wound around the portion adjacent to the outside of the base portion. The paper container according to feature 1.

3. The curling portion has a base portion that extends horizontally outward from the outer peripheral edge of the flat portion, and an inner curling portion that is wound up including the portion adjacent to the lower side of the base portion. The paper container according to feature 1.

4. The planar portion has a lower surface provided parallel to the upper surface. The paper container according to feature 1.

5. An auxiliary layer is provided on the upper surface to assist in the heat sealing of the lid material. A paper container according to any one of claims 1 to 4.

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