JP7497699B2 - Tray-shaped container - Google Patents

Description

The present invention relates to a tray-shaped container.

Conventionally, plastic tray-shaped containers have been used. Such plastic tray-shaped containers are capable of storing food without requiring any special processing on the inner surface.
In recent years, in response to the trend toward eliminating or reducing plastic, there has been a shift from plastic tray-type containers to paper tray-type containers.
When food is placed in a paper tray-like container, oil dripping from the food will soak into the paper, so it has been proposed to laminate the paper with a resin such as polyethylene or polypropylene beforehand, or to laminate and adhere a resin film layer to the inner surface of the tray-like container (see, for example, Patent Documents 1 to 3). However, paper tray-like containers such as those described above have the problem that when a food-containing container is placed in a microwave oven, the outer surface becomes too hot, making it impossible to hold the container by hand.
In order to solve such problems, it has been considered to use cut paper as a base material for the paper layer to insulate the heat from the inner surface of the tray-shaped container (see, for example, Patent Document 4).

Japanese Patent Application Laid-Open No. 10-114327 JP 2013-545675 A JP 2015-528762 A JP 2000-153830 A

However, when cut balls are used as the base material for the paper layer, there is a problem that the shape of the tray-shaped container becomes distorted, resulting in reduced airtightness when the top is sealed.
Therefore, an object of the present invention is to provide a tray-shaped container that can achieve both thermal insulation and airtightness.

After extensive investigation, the inventors have found that in a tray-like container having an open top, a paper layer based on cardboard having front and back liners and a core, and a resin film layer laminated and bonded to the inner surface of the opening side of the paper layer, the tray-like container having a bottom, a side standing up from the bottom, and a flange surface arranged around the periphery of the opening and on the same plane, the above-mentioned problem can be solved by setting the thickness of the cardboard, the number of corrugations per 300 mm of the cardboard, the basis weight of the front and back liners, and the basis weight of the core within specific ranges.
That is, the present invention relates to the following <1> to <8>.
<1> A tray-like container having an open top and a paper layer based on cardboard, and a resin film layer laminated and bonded to the inner surface of the paper layer on the opening side, wherein the tray-like container has a bottom, a side surface erected from the bottom, and a flange surface disposed around the opening edge, the flange surfaces being on the same plane, the cardboard having front and back liners and a core disposed between the front and back liners, the cardboard having a thickness of 0.3 mm to 0.7 mm, the cardboard having 100 to 190 corrugations per 300 mm, the front and back liners having a basis weight of 40 g/ ^m2 to 190 g/ ^m2 , and the core having a basis weight of 40 g/ ^m2 to 190 g/ ^m2 .
<2> A tray-shaped container described in <1>, in which the length-weighted average fiber length of the pulp constituting the front and back liners is 0.60 mm or more and 2.00 mm or less, and the proportion of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the front and back liners is 5% or more and 25% or less.
<3> The tray-shaped container according to <1> or <2>, wherein the length-weighted average fiber length of the pulp constituting the core is 0.60 mm or more and 2.00 mm or less, and the proportion of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the core is 5% or more and 25% or less.
<4> The tray-shaped container according to any one of <1> to <3>, wherein the side includes a main side surface extending from the bottom surface and directly connected to the flange surface, and the taper angle of the main side surface is 3.5° or more and 18° or less.
<5> The tray-shaped container according to any one of <1> to <4>, wherein the depth of the tray-shaped container is 16 mm or more and 90 mm or less.
<6> The tray-shaped container according to any one of <1> to <5>, wherein the paper layer is bonded by the resin film layer.
<7> The tray-shaped container according to any one of <1> to <6>, wherein the paper layers at the four corners of the flange surface are separated and the paper layers at the four corners are joined by the resin film layer.
<8> The tray-shaped container according to any one of <1> to <7>, wherein the side surface further includes a sub-side surface that is erected from the bottom surface and is not directly connected to the periphery of the opening.

The present invention provides a tray-shaped container that is both insulating and airtight.

FIG. 1 is a perspective view of a tray-shaped container according to a first embodiment of the present invention. FIG. 2 is a plan view showing the tray-shaped container of FIG. FIG. 3 is a cross-sectional view showing the AA section of FIG. FIG. 4 is a plan view of a blank sheet for the container body of FIG. FIG. 5 is a perspective view of a tray-shaped container according to a second embodiment of the present invention. FIG. 6 is a plan view showing the tray-shaped container of FIG. FIG. 7 is a plan view of a blank sheet for the container body of FIG. FIG. 8A is an explanatory diagram of a modified example of a tray-shaped container. FIG. 8B is an explanatory diagram of a modified example of the tray-shaped container. FIG. 8C is an explanatory diagram of a modified example of the tray-shaped container. FIG. 8D is an explanatory diagram of a modified example of the tray-shaped container. FIG. 9A is an explanatory diagram showing cardboard as a base material for the paper layer in the tray-shaped container of FIG. 1. FIG. 9B is an explanatory diagram showing a double-sided corrugated board, which is a modified example of the corrugated board of FIG. 9A. FIG. 9C is an explanatory diagram showing a triple-sided corrugated board, which is a modified example of the corrugated board of FIG. 9A. FIG. 10 is a perspective view of a mold (a molding die) for manufacturing the tray-shaped container of FIG. FIG. 11 is an explanatory diagram of a method for manufacturing the tray-shaped container of FIG.

The present invention will be described in detail below.
In this specification, the definitions that are considered to be preferable may be adopted arbitrarily, and it can be said that the combination of preferable definitions is more preferable.
In addition, in this specification, the lower limit and upper limit described in stages for the preferred numerical range (for example, the range of the content, etc.) can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to obtain "10 to 60". In addition, in the numerical range described in this specification, the upper limit or lower limit of the numerical range may be replaced with a value shown in the examples.
In addition, in this specification, the "thickness of the corrugated board" means "the distance from the surface of the front liner to the surface of the back liner". In other words, the thickness of the corrugated board includes the thickness of the front and back liners. If the corrugated board is a multi-layered (multi-layered) corrugated board, the "thickness of the corrugated board" means "the distance from the surface of the topmost front liner to the surface of the backmost back liner in the multi-layered (multi-layered) board". In other words, the total thickness of the multi-layered (multi-layered) corrugated board needs to be within a specified range.
In addition, in this specification, "the number of corrugated crests per 300 mm of the corrugated board" means "the number of crests present per 300 mm in the wave traveling direction of the core of the corrugated board sheet."
In addition, when the corrugated board is a multi-layered (multi-layered) corrugated board, the "number of corrugations per 300 mm of the corrugated board" means the "number of corrugations present per 300 mm in the wave traveling direction of the core of the corrugated board sheet of at least one layer in the multi-layered (multi-layered) corrugated board." In other words, it is sufficient that the number of corrugations per 300 mm in at least one layer in the multi-layered (multi-layered) corrugated board is within a predetermined range.
In addition, when the cardboard is a multi-layered (multi-layered) cardboard, the "basis weight of the front and back liners" means "at least the basis weight of the front liner of the outermost layer and the basis weight of the back liner of the innermost layer in the multi-layered (multi-layered) cardboard." In other words, it is sufficient that at least the basis weight of the front liner of the outermost layer and the basis weight of the back liner of the innermost layer in the multi-layered (multi-layered) cardboard are within a specified range.
In addition, when the corrugated board is a multi-layered corrugated board, the "basis weight of the core" means the "basis weight of the core of at least one layer in the multi-layered (multi-layered) structure." In other words, it is sufficient that the basis weight of the core of at least one layer in the multi-layered (multi-layered) corrugated board is within a predetermined range.
In addition, the term "taper angle" in this specification refers to the inclination angle of the main side surface with respect to the normal line (see "taper angle A" in Figure 3). When there are multiple main side surfaces, there will be multiple taper angles for one tray-shaped container, and the average value of these multiple taper angles will be the taper angle.
Furthermore, in this specification, the "depth of the tray-shaped container" means the minimum distance from the periphery (portion) of the opening to the bottom surface (see "depth B" in Figure 3).

[Tray-shaped container]
The tray-shaped container of the present invention is a tray-shaped container with an open top, a paper layer based on cardboard, and a resin film layer laminated and bonded to the inner surface of the open side of the paper layer, the tray-shaped container has a bottom, a side surface erected from the bottom, and a flange surface disposed on the periphery of the opening, the flange surfaces being on the same plane, the cardboard has front and back liners and a core disposed between the front and back liners, the cardboard has a thickness of 0.3 mm to 0.7 mm, the number of corrugations per 300 mm of the cardboard is 100 to 190, the front and back liners have a basis weight of 40 g/m ² to 190 g/m ² , and the core has a basis weight of 40 g/m ² to 190 g/m ^2. The tray-shaped container is capable of achieving both heat insulation and airtightness.

The tray-shaped container of the present invention further has a flange surface disposed around the periphery of the opening, which allows a top seal to be applied to the opening of the tray-shaped container after food is placed in the tray-shaped container.

The tray-shaped container of the present invention has flange surfaces that are on the same plane, i.e., the flange surfaces have no overlapping portions, so that when food is placed into the tray-shaped container and then the opening of the tray-shaped container is top-sealed, the airtightness (sealing) of the tray-shaped container can be ensured, thereby maintaining the freshness of the food placed in the tray-shaped container.
More specifically, the paper layers at the four corners of the flange surface are usually separated, but if there are overlapping parts at the four corners of the flange surface, air will enter and exit through the overlapping parts even if a top seal is applied.By not having overlapping parts at the four corners of the flange surface, it is possible to better ensure the airtightness (sealing ability) of the tray-shaped container by top sealing the opening of the tray-shaped container after placing food in the tray-shaped container.

The thickness of the cardboard, which is the base material of the paper layer in the tray-shaped container of the present invention, is not particularly limited as long as it is 0.3 mm or more and 0.7 mm or less, but it is preferably 0.35 mm or more, more preferably 0.4 mm or more, even more preferably 0.45 mm or more, and preferably 0.65 mm or less, more preferably 0.6 mm or less, and even more preferably 0.55 mm or less.
By setting the thickness of the cardboard as the base material of the paper layer in the tray-shaped container of the present invention to 0.3 mm or more, the heat insulating properties can be improved. Also, by setting the thickness of the cardboard as the base material of the paper layer in the tray-shaped container of the present invention to 0.7 mm or less, the airtightness can be improved.

The number of corrugations per 300 mm of the cardboard which is the base material of the paper layer in the tray-shaped container of the present invention is not particularly limited, so long as it is 100 or more and 190 or less, but it is preferably 110 or more, more preferably 120 or more, even more preferably 130 or more, and preferably 180 or less, more preferably 175 or less, and even more preferably 1170 or less.
Airtightness can be improved by making the number of corrugations per 300 mm of the corrugated board, which is the base material of the paper layer in the tray-shaped container of the present invention, 100 or more. Also, heat insulation can be improved by making the number of corrugations per 300 mm of the corrugated board, which is the base material of the paper layer in the tray-shaped container of the present invention, 190 or less.

The basis weight of the front and back liners in the tray-shaped container of the present invention is not particularly limited as long as it is 40 g/ ^m2 or more and 190 g/ ^m2 or less, but it is preferably 50 g/ ^m2 or more, more preferably 60 g/ ^m2 or more, even more preferably 70 g/ ^m2 or ^more , and preferably 180 g/m2 or less, more preferably 170 g/ ^m2 or less, and even more preferably 160 g/ ^m2 or less.
By making the basis weight of the front and back liners in the tray-shaped container of the present invention 40 g/ ^m2 or more, the heat insulation properties can be improved. Also, by making the basis weight of the front and back liners in the tray-shaped container of the present invention 190 g/ ^m2 or less, the airtightness can be improved.
The basis weight of the front and back liners is measured by the method described in the examples below.

The basis weight of the core in the tray-shaped container of the present invention is not particularly limited as long as it is 40 g/ ^m2 or more and 190 g/ ^m2 or less, but it is preferably 50 g/ ^m2 or more, more preferably 60 g/ ^m2 or more, even more preferably 70 g/ ^m2 or ^more , and preferably 180 g/m2 or less, more preferably 170 g/ ^m2 or less, and even more preferably 160 g/ ^m2 or less.
In the tray-shaped container of the present invention, the core has a basis weight of 40 g/ ^m2 or more, thereby improving heat insulation. In addition, in the tray-shaped container of the present invention, the core has a basis weight of 190 g/ ^m2 or less, thereby improving airtightness.
The basis weight of the core is measured by the method described in the examples below.

The length-weighted average fiber length of the pulp constituting the front and back liners in the tray-shaped container of the present invention is not particularly limited, but is preferably 0.60 mm or more, more preferably 0.70 mm or more, even more preferably 0.80 mm or more, and is preferably 2.00 mm or less, more preferably 1.90 mm or less, and even more preferably 1.80 mm or less.
When the length-weighted average fiber length of the pulp constituting the front and back liners in the tray-shaped container of the present invention is 0.60 mm or more, the fibers are more likely to be entangled, the strength of the paper is improved, and the occurrence of distortion when formed into a tray-shaped container is prevented, thereby improving airtightness. Also, when the length-weighted average fiber length of the pulp constituting the front and back liners in the tray-shaped container of the present invention is 2.00 mm or less, the number of short fibers is increased, the number of gaps between the fibers is reduced, the distance between the gaps between the fibers is shortened, and heat is less likely to pass through, thereby improving heat insulation.
Furthermore, when the length-weighted average fiber length of the pulp constituting the front and back liners in the tray-shaped container of the present invention is 0.60 mm or more and 2.00 mm or less, appropriate strength as paper can be ensured and folding becomes easier, thereby preventing distortion of the tray when the tray sheet is formed into a tray-shaped container.
The length-weighted average fiber length of the pulp constituting the front and back liners is measured by the method described in the examples below.

The proportion of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the front and back liners of the tray-shaped container of the present invention is not particularly limited, but is preferably 5% or more, more preferably 7% or more, even more preferably 9% or more, particularly preferably 10% or more, most preferably 13% or more, and is preferably 25% or less, more preferably 23.5% or less, even more preferably 22% or less, particularly preferably 19% or less, and most preferably 17% or less.
When the ratio of the number of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the front and back liners of the tray-shaped container of the present invention is 5% or more, the number of short fibers is increased, the number of gaps between the fibers is reduced, the distance between the gaps between the fibers is shortened, and heat is less likely to pass through, thereby improving heat insulation. Also, when the ratio of the number of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the front and back liners of the tray-shaped container of the present invention is 25% or less, the entanglement of the fibers is increased (interfiber bonding is increased), the strength of the paper is improved, and distortion when formed into a tray-shaped container is prevented, thereby improving airtightness.
The percentage of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the front and back liners is measured by the method described in the examples below.

The length-weighted average fiber length of the pulp constituting the core in the tray-shaped container of the present invention is not particularly limited, but is preferably 0.60 mm or more, more preferably 0.70 mm or more, even more preferably 0.80 mm or more, and is preferably 2.00 mm or less, more preferably 1.90 mm or less, and even more preferably 1.80 mm or less.
When the length-weighted average fiber length of the pulp constituting the core of the tray-shaped container of the present invention is 0.60 mm or more, the fibers are more likely to be entangled, the strength of the paper is improved, and the occurrence of distortion when formed into a tray-shaped container can be prevented, thereby improving airtightness. When the length-weighted average fiber length of the pulp constituting the core of the tray-shaped container of the present invention is 2.00 mm or less, the number of short fibers is increased, the number of gaps between the fibers is reduced, the distance between the gaps between the fibers is shortened, and heat is less likely to pass through, thereby improving heat insulation.
The length-weighted average fiber length of the pulp constituting the core is measured by the method described in the examples below.

The proportion of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the core of the tray-shaped container of the present invention is not particularly limited, but is preferably 5% or more, more preferably 7% or more, even more preferably 9% or more, and is preferably 25% or less, more preferably 23.5% or less, and even more preferably 22% or less.
When the ratio of the number of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the core of the tray-shaped container of the present invention is 5% or more, the number of short fibers is increased, the number of gaps between the fibers is reduced, the distance between the gaps between the fibers is shortened, and heat is less likely to pass through, thereby improving heat insulation. Also, when the ratio of the number of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the core of the tray-shaped container of the present invention is 25% or less, the entanglement of the fibers is increased (interfiber bonding is increased), the strength of the paper is improved, and distortion when formed into a tray-shaped container is prevented, thereby improving airtightness.
The proportion of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the core is measured by the method described in the examples below.

The taper angle of the main side surface in the tray-shaped container of the present invention is not particularly limited, but is preferably 3.5° or more, more preferably 4° or more, even more preferably 4.5° or more, even more preferably 5° or more, and is preferably 18° or less, more preferably 17° or less, even more preferably 16° or less, and even more preferably 15° or less.
When the taper angle of the main side surface of the tray-shaped container of the present invention is 3.5° or more, it becomes easy to laminate and adhere the resin film layer to the inner surface of the opening side of the paper layer, and the resin film layer can be prevented from breaking. Also, when the taper angle of the main side surface of the tray-shaped container of the present invention is 18° or less, the resin film layer can be prevented from breaking even when an impact is applied.

The depth of the tray-shaped container of the present invention is not particularly limited, but is preferably 16 mm or more, more preferably 17 mm or more, even more preferably 18 mm or more, even more preferably 20 mm or more, and is preferably 90 mm or less, more preferably 87 mm or less, even more preferably 84 mm or less, and even more preferably 80 mm or less.
When the depth of the tray-shaped container of the present invention is 16 mm or more, the strength of the container is improved, distortion when the tray-shaped container is subjected to an impact can be prevented, and the usefulness as a container can be improved by increasing the food filling capacity, etc. When the depth of the tray-shaped container of the present invention is 90 mm or less, breakage of the resin film layer can be prevented when the resin film layer is laminated and bonded to the inner surface of the opening side of the paper layer, and the stability as a tray-shaped container can be improved.

In the tray-shaped container of the present invention, the paper layers are preferably joined together with a resin film layer. When the paper layers are joined together with a resin film layer, the tray-shaped container can be produced without using an adhesive.
In addition, in the tray-shaped container of the present invention, the paper layers at the four corners of the flange surface are usually separated, but it is preferable that the paper layers at the four corners are joined by a resin film layer.

The tray-shaped container of the present invention preferably further includes a sub-side surface that is erected from the bottom surface and is not directly connected to the periphery of the opening. By including a sub-side surface that is erected from the bottom surface and is not directly connected to the periphery of the opening, the resin film layer can be evenly and reliably laminated and bonded to the inner surface of the opening side of the paper layer by eliminating corners that are prone to distortion and holes in the resin film layer, and the ease of eating food stored in the tray-shaped container can be improved when the tray-shaped container is used as a lunch container (bowl).

Furthermore, the tray-shaped container of the present invention may or may not have an overlapping portion other than the flange surface, so long as the flange surface does not have an overlapping portion. If there is an overlapping portion other than the flange surface, the strength of the tray-shaped container is improved. On the other hand, if there is no overlapping portion other than the flange surface, more reliable adhesion between the paper layer and the resin film layer can be achieved.

A tray-shaped container 100 according to a first embodiment will be described below with reference to FIGS.
In the first embodiment, a tray-shaped container is placed on a horizontal surface. The tray-shaped container 100 according to the first embodiment is symmetrical in the front-rear and left-right directions (indicated by "FBLR" in the drawings).
The vertical direction in which gravity acts is referred to as the downward direction (indicated by "D" in the figure), and the opposite direction of the downward direction is referred to as the upward direction (indicated by "U" in the figure). Furthermore, the space side in which the items are stored in the storage space of the container body is referred to as the inside, and the side opposite the inside is referred to as the outside.

Figure 1 is a perspective view of a tray-shaped container according to a first embodiment of the present invention, Figure 2 is a plan view of the tray-shaped container of Figure 1, Figure 3 is a cross-sectional view showing the A-A cross section of Figure 2, and Figure 4 is a plan view of a blank sheet for the container body of Figure 1.

As shown in Fig. 1, the tray-shaped container 100 is a bowl-shaped or rice bowl-shaped paper tray-shaped container. An example of the tray-shaped container 100 is a food packaging container that contains food. However, the tray-shaped container 100 can contain various items other than food.
The tray-shaped container 100 comprises a paper layer 100A forming the container body, and a resin film layer 12 laminated and bonded to the inner surface of the paper layer 100A on the opening 110A side.

The tray-shaped container 100 is a package having an octagonal opening 110A on the upper surface (top surface) and an internal storage space.
The tray-shaped container 100 has an octagonal (polygonal) bottom surface 20, side surfaces 30 standing upright from the bottom surface 20, and a flange surface 40 disposed on the opening periphery 13. The side surfaces 30 have a main side surface 31 standing upright from the bottom surface 20 and directly connected to the opening periphery 13, a first minor side surface 32A standing upright from the bottom surface 20 and not directly connected to the opening periphery 13, and a second minor side surface 32B directly connected to the opening periphery 13 and not standing upright from the bottom surface 20. Folds 14 extend between each side of the bottom surface 20 and the side surfaces 30.
The flange surfaces are flush with each other and have no overlapping portions (overlapped pieces) on the flange surfaces 40. The paper layers 100A are joined by the resin film layer 12, and no adhesive or the like is used to join the paper layers 100A together.

The tray-shaped container 100 is formed into a truncated pyramid shape by folding eight sides 30 at creases 14.

As shown in Figures 1 to 3, when the side surfaces 30 are folded and formed into a truncated pyramid shape, the side edges 34, 35 of adjacent side surfaces 30 extending from the bottom surface 20 toward the opening 110A butt against each other to form corners of the truncated pyramid shape. The tray-shaped container 100 is formed into an octagonal truncated pyramid shape having eight corners where the side edges 34, 35 of the eight side surfaces 30 butt against each other. Note that the "corner" referred to here refers to the corner portion of the side surface 30 connecting the upper and lower bases of the truncated pyramid, and does not include the corner portion between the side surface 30 and the bottom surface 20.

A gap 36 is provided at the corner where the side edges 34, 35 are butted against each other.
The gap 36 is formed by separating the side edges 34, 35 from each other, and extends linearly between the bottom surface 20 and the opening 110A.
The gap portion 36 is a portion at the corner that connects the inner side (inside the storage space) and outer side (outside the storage space) of the container body formed by the paper layer 100A, and serves as a passage (flow passage) for air to pass from the inner side to the outer side of the paper layer (container body) 100A during vacuum suction in the manufacturing process of the tray-shaped container 100 described below.
The dimension by which the side edges 34, 35 are separated from each other at the gap 36 is set taking into consideration both the breathability during suction and the moldability of the container body.

The gap 36 in the first embodiment is set to a dimension longer than the dimension of a straight line connecting the bottom surface 20 and the opening 110A. The "straight line" here means a straight line connecting from a corner of the bottom surface 20 to the upper ends of the side edges 34, 35 of the side surface 30 (the intersections of the opening periphery 13 and the side edges 34, 35).
The gap 36 includes a bent portion 37 formed by bending the gap 36 at an intermediate position 100M between the bottom surface 20 and the opening 110A. In the first embodiment, the gap 36 is bent into an L-shape at the bent portion 37. A detailed configuration of the gap 36 will be described later.

In addition, the tray-shaped container 100 has a flange surface 40 that extends from the opening periphery 13 on the upper side (the opening 110A side) of each side surface 30 to the side opposite the opening 110A. The flange surface 40 is a brim-shaped portion that is provided along the outer periphery of the opening 110A. The side edges of the flange surfaces 40 extending from adjacent side surfaces 30 are also butted against each other and are spaced apart to form a gap 36. In other words, the gap 36 extends to the flange surface 40.

The detailed configuration of the tray-shaped container 100 according to the first embodiment will be described.
The minor side 32 is formed by a first minor side 32A and a second minor side 32B connected to each other via a fold 38. The fold 38 is a broken line extending parallel to the edge of the bottom surface 20 along the surface of the minor side 32 at an intermediate position 100M. In the minor side 32, the first minor side 32A is folded toward the inside of the tray-shaped container 100 via the fold 38 relative to the second minor side 32B.

The first minor side surface 32A has a trapezoidal shape that narrows from the bottom surface 20 toward the intermediate position 100M. The second minor side surface 32B has a trapezoidal shape that widens from the fold 38 corresponding to the upper base of the first minor side surface 32A toward the opening 110A.
That is, the minor side surface 32 is an hourglass-shaped surface portion that is narrowed at a middle position 100M when viewed from the side, and both side edges 34 thereof are bent in an L-shape at the middle position 100M.

The main side surface 31 has a side edge 35 bent into a shape that matches the side edge 34 of the sub-side surface 32, and is a hexagonal side surface 30 having a portion that becomes wider from the bottom surface 20 toward the intermediate position 100M.
Specifically, the side edge 35 of the main side surface 31 is bent along the side edge 34 of the adjacent sub-side surface 32 to form an L-shaped shape. Therefore, a L-shaped gap 36 is formed between the side edge 34 of the sub-side surface 32 and the side edge 35 of the main side surface 31, and this gap 36 is bent into an L-shape at a bend 37 at an intermediate position 100M.

In addition, in the tray-shaped container 100 of this first embodiment, multiple notches are intermittently formed along the folds 14 extending between each side of the bottom surface 20 and the side surfaces 30 (main side surfaces 31 and sub-side surfaces 32).
Additionally, a plurality of cuts are intermittently formed on the minor side 32 along a fold 38 extending between the first minor side 32A and the second minor side 32B.

The multiple cuts formed along the folds 14, 38 form gaps (slits penetrating the container body in the thickness direction) that extend intermittently in a line at the folds 14, 38, and serve as a passageway for air to pass from the inner surface to the outer surface of the container body during suction, as described below.
The dimensions of the cuts along the extension direction of the folds 14, 38 and the number of cuts are set taking into consideration both the breathability during suction and the moldability of the container body.

In addition, if the four minor sides 32 of the tray-shaped container 100 shown in Figures 1 to 3 are regarded as "corner surfaces forming the corners of a quadrangular pyramid," the tray-shaped container 100 can also be viewed as a quadrangular pyramid-shaped container having four main sides (main sides 31) and four corner surfaces (minor sides 32) provided between these sides.
In this way, when the tray-shaped container 100 is considered to have a quadrangular pyramid shape, it can be said that the container has gaps 36 bent in a dogleg shape along both side edges of the corners (sub-side surfaces 32) that form the corners of the quadrangular pyramid shape. The first sub-side surface 32A of the sub-side surface 32 can also be said to form a surface that is chamfered on the bottom surface 20 side of the corners that form the corners of the quadrangular pyramid shape.

As shown in FIG. 4, the blank sheet 100A' used to form the paper layer (container body) 100A has an octagonal bottom sheet piece 20' and side sheet pieces 30' extending from each side of the bottom sheet piece 20'. In the explanation of FIG. 4, the direction in which the side sheet piece 30' extends from each side of the bottom sheet piece 20' is referred to as the "extension direction", the side of the side sheet piece 30' that faces the bottom sheet piece 20' along the extension direction is referred to as the "inside" of the extension direction, and the opposite side is referred to as the "outside" of the extension direction.

A fold line 14' is provided between the bottom sheet piece 20' and the side sheet piece 30' along the edge of the bottom sheet piece 20'.
In each side sheet piece 30', a parallel fold line 13' is provided along the edge of the bottom sheet piece 20' at the outer edge in the extension direction, and a flange surface sheet piece 40' extends from the fold line 13' toward the outside in the extension direction.

Of each side sheet piece 30', the secondary side sheet piece 32' comprises a first secondary side sheet piece 32A' which has a trapezoidal shape whose width narrows from the edge of the bottom sheet piece 20' toward the outside in the extension direction, and a second secondary side sheet piece 32B' which is connected to the first secondary side sheet piece 32A' and has a trapezoidal shape whose width widens toward the outside in the extension direction toward the opening 110A.
The side edge 34' of the minor side sheet piece 32' is bent in an L-shape.

Of the side sheet pieces 30', the main side sheet piece 31' has a hexagonal shape with a portion that widens from the side of the bottom sheet piece 20' toward the outside in the extension direction. The side edge 35' of the main side sheet piece 31' has a dogleg shape that fits the side edge 34' of the adjacent secondary side sheet piece 32'.

Since the tray-shaped container 100 according to the first embodiment has the configuration described above, it can achieve the following actions and effects (1) to (6).
(1) Since the gap 36 is set to a dimension longer than the dimension of a straight line connecting the bottom surface 20 and the opening 110A, the cross-sectional area of the air flow passage (the dimension of the gap 36 when viewed from the front) can be secured in the gap at the corner. Therefore, the air between the paper layer (container body) 100A and the resin film layer 12 is reliably sucked in, and the resin film layer 12 can be reliably laminated and bonded to the inner surface of the paper layer (container body) 100A.
In addition, since air is more easily sucked in uniformly through the linear gaps 36, the suction load is distributed and the resin film layer 12 is less likely to be damaged. From this point of view, the resin film layer 12 can be reliably laminated and bonded to the inner surface of the paper layer (container body) 100A.
It is therefore possible to provide a tray-shaped container 100 in which the resin film layer 12 is appropriately laminated and bonded to the inner surface of the paper layer (container body) 100A.

(2) Since the gap 36 is bent at the bend 37, the dimension of the gap through which air can pass can be increased with a simple configuration compared to a straight gap.
(3) The gaps 36 are bent in a L-shape along the side edges 35, 34 of the main side surface 31 and the sub-side surface 32, respectively, and the structure for ensuring the length of the dimensions of these pair of gaps 36 is simple.

Furthermore, the sub-side surface 32 is formed by the trapezoidal first sub-side surface 32A and the second sub-side surface 32B, and the number of planar portions is increased at the corners of the container body 100A, making the container body 100A less likely to bend and making it easier to ensure the strength of the container body 100A. By increasing the number of planar portions at the corners of the container body 100A, the shape of the inner surface of the storage space of the container body 100A becomes closer to a spherical shape, improving the heat circulation efficiency when the tray-shaped container 100 is heated and cooked in a microwave oven.

(4) Since multiple notches are formed along the folds 14 between each side of the bottom surface 20 and the side surfaces 30, a linear gap is provided in addition to the gap portion 36, making it easier to pull the resin film sheet described below toward the bottom surface 20, and the resin film layer 12 can be formed more reliably.
(5) Since a plurality of cuts are formed along the fold 38 between the first minor side surface 32A and the second minor side surface 32B on the minor side surface 32, linear gaps can be further increased in addition to the gap portion 36. This makes it easier to draw in a resin film sheet (described later) on the minor side surface 32 side, and allows the resin film layer 12 to be formed more reliably.

(6) The flange surfaces 40 extend from each side surface 30, and the side edges of adjacent flange surfaces 40 are butted together, which reduces the likelihood of partial overlap between the flange surfaces 40 and the resulting step. This makes it easier to mold the upper surface of the flange surface 40 into a flat shape, and therefore the resin film layer 12 can be reliably formed on the upper surface of the flange surface 40 as well.

Next, a tray-shaped container 200 according to a second embodiment will be described with reference to FIGS.
Fig. 5 is a perspective view of a tray-shaped container according to a second embodiment of the present invention, Fig. 6 is a plan view showing the tray-shaped container of Fig. 5, and Fig. 7 is a plan view of a blank sheet for the container body of Fig. 5. The tray-shaped container 200 of Figs. 5 to 7 is different from the tray-shaped container 100 of Figs. 1 to 4 mainly in the side surfaces 50 (41, 42, 43) adjacent to each other at the corners of the container, and the gaps 46 and bent portions 47 provided at the corners, but the other configurations are the same. In the following description, descriptions that overlap with Figs. 1 to 4 will be omitted. The tray-shaped container 200 has less strength than the tray-shaped container 100.

As shown in Figures 5 and 6, the tray-shaped container 200 has a rectangular opening 110B and an octagonal bottom surface 21, and eight side surfaces 50 extending from each side of the bottom surface 21 are folded to form a truncated pyramid shape.
The side surfaces 50 of this tray-shaped container 200 include three types: a first main side surface 41 , a second main side surface 42 , and a sub-side surface 43 .

The first main side surface 41 and the second main side surface 42 butt against each other at their respective side edges 44, 45 in a region from the opening 110B to the intermediate position 200M. Each of the first main side surface 41 and the second main side surface 42 is formed in a hexagonal shape whose width increases from the bottom surface 21 toward the opening 110B, and the opening periphery 13 forms one side of the opening 110B.
The sub-side surface 43 is disposed between the first main side surface 41 and the second main side surface 42, and is formed in a triangular shape extending from the bottom surface 21 to the intermediate position 200M.

The gap 46 of the tray-shaped container 200 is formed by a side edge 45 of the first major side surface 41 , a side edge 44 of the second major side surface 42 , and a side edge 48 of the minor side surface 43 .
Specifically, the gap 46 is linear along the side edges 44, 45 from the opening 110B to the intermediate position 200M, and branches out from the bent portion 47 at the intermediate position 200M toward the bottom surface 21 into two gaps: a gap along the side edge 44 of the second main side surface 42 and one side edge 48 of the sub-side surface 43, and a gap along the side edge 45 of the first main side surface 41 and the other side edge 48 of the sub-side surface 43.

In addition, in the tray-shaped container 200 shown in Figures 5 and 6, the secondary side surface 43 can be said to form a surface portion that is chamfered on the bottom surface 21 side of the four corners of the quadrangular pyramid shape. Also, the gap portion 46 can be said to be a "Y-shaped gap" that branches along the surface portion that is chamfered on the bottom surface 21 side of the four corners of the quadrangular pyramid shape.

As shown in Figure 7, in the blank sheet 200B' used to form the paper layer (container body) 200B, the side sheet pieces 50' extending from each side of the octagonal bottom sheet piece 21' include a first main side sheet piece 41', a second main side sheet piece 42', and a secondary side sheet piece 43'.
Each of the first main side sheet piece 41' and the second main side sheet piece 42' has a hexagonal shape whose width increases from one side of the bottom sheet piece 21' toward the outside in the extension direction. Each of the first main side sheet piece 41' and the second main side sheet piece 42' has a side edge 45', 44' bent into a dogleg shape.

The minor side sheet piece 43' has a triangular shape extending outward in the extension direction from one side of the bottom sheet piece 21'. More specifically, the minor side sheet piece 43' has an isosceles triangle shape with both side edges 48' having the same length.
The dimension (height of the triangle) along the extension direction of the secondary side sheet piece 43' is set smaller than the dimensions along the extension direction of the first main side sheet piece 41' and the second main side sheet piece 42', so that the gap portion 46 in the paper layer (container body) 200B formed using the blank sheet 200B' branches into two at the intermediate position 200M.

Since the tray-shaped container 200 according to the second embodiment has the configuration described above, it can achieve the following actions and effects.
Since the gap 46 is branched into two, it is possible to ensure a longer gap dimension through which air can pass compared to a straight gap, which makes it easier to ensure the suction properties of the resin film sheet described below, and ensures the formation of the resin film layer 12. In addition, the suction load is easily distributed, which makes it harder for the resin film sheet described below to tear, and ensures the formation of the resin film layer 12.
Therefore, the tray-shaped container 200 can be manufactured appropriately.
Furthermore, triangular sub-side surfaces 43 are formed on the bottom surface 21 side at the corners of the container body 200B, and the number of planar portions at the corners of the container body 200B increases, making the container body 200B less likely to bend and making it easier to ensure the strength of the container body 200B. Since the number of planar portions at the corners of the container body 200B increases, the shape of the inner surface of the storage space of the container body 200B becomes closer to a spherical shape, improving the heat circulation efficiency when the tray-shaped container 200 is heated and cooked in a microwave oven.
In addition, the same configuration as the first embodiment provides the same effects as the first embodiment.

The above-described embodiments are merely examples, and are not intended to exclude the application of various modifications or techniques not explicitly stated in these embodiments. Each configuration of the present embodiment can be modified in various ways without departing from the spirit of the invention. In addition, the configurations can be selected as necessary, and can be combined as appropriate.

For example, the gap is not limited to a bent shape at a bend portion, and may be a curved gap.
The shape of the tray-shaped container is not limited to the bowl-shaped or bowl-shaped (deep dish-shaped) described above, and may be any polygonal truncated pyramid shape, not limited to the octagonal truncated pyramid shape (FIG. 1) or the quadrangular truncated pyramid shape (FIG. 5). Also, the shape may be any shape, not limited to each pyramid.
The notches provided at the folds of the tray-shaped container may be omitted.

In addition, as shown in FIGS. 8A to 8D, holding pieces 180, 185, 190, and 195 may be provided extending from one edge of the side surface.
FIG. 8A shows an M-shaped restraining piece 180 extending from the side edge 35 of the main side surface 31 toward the sub-side surface 32 of the tray-shaped container 100 .
FIG. 8B shows triangular restraining pieces 185 extending from both side edges 48 of the minor side surface 43 of the tray-shaped container 200 toward the first major side surface 41 and the second major side surface 42 .
FIG. 8C shows a tray-shaped container 200 that has a trapezoidal restraining piece 190 extending from the side edge 45 of the first major side surface 41 toward the second major side surface 42 in addition to the restraining piece 185 of FIG. 8B.
FIG. 8D shows triangular restraining pieces 195 extending from both side edges 48 of the minor side surface 43 of the tray-shaped container 200 toward the first major side surface 41 and the second major side surface 42 .
The restraining pieces 180, 185, 190, and 195 can improve the connection strength between adjacent side portions.

<Paper layer>
As shown in Fig. 9A, the cardboard constituting the paper layer is cardboard 91A having a front liner 92A, a back liner 92B, and a core 93 disposed between the front liner 92A and the back liner 92B. The front liner 92A, the back liner 92B, and the core 93 are bonded together using a known adhesive or the like to form, for example, a single-layer (single-ply) cardboard as shown in Fig. 9A.

The cardboard constituting the paper layer is usually a cardboard of a single layer (one layer) configuration as shown in Fig. 9A, but may be a cardboard of a multi-layer configuration (double-sided cardboard 91B (Fig. 9B), quadruple-sided cardboard 91C (Fig. 9C)). From the viewpoint of ease of folding, the cardboard constituting the paper layer is preferably a cardboard of a single layer (one layer) configuration as shown in Fig. 9A.
By using cardboard with a single layer (one layer) structure, when folding the cardboard to form a tray-shaped container, it is possible to prevent the corrugations of each layer from getting in the way and making it difficult to fold at the desired points, compared to when using cardboard with a multi-layer structure (multi-layer structure).
Here, when the cardboard constituting the paper layer is a multi-layered (multi-layered) cardboard such as double-sided cardboard (Figure 9B) or quadruple-sided cardboard (Figure 9C), each layer in the multi-layered (multi-layered) structure has a front and back liner and a core arranged between the front and back liners, the total thickness of each layer is 0.3 mm to 0.7 mm, the number of corrugations per 300 mm of each layer is 100 to 190, the basis weight of the front and back liners in each layer is 40 g/ ^m2 to 190 g/ ^m2 , and the basis weight of the core in each layer is 40 g/ ^m2 to 190 g/ ^m2 .
In addition, in both the double-sided cardboard 91B in Figure 9B and the triple-double-sided cardboard 91C in Figure 9C, the liners 92A, 92B at the boundary between layers in the multi-layered (multi-layered) structure are a single liner that serves as both the front liner 92A and the back liner 92B, but this is not limited to this, and the front liner 92A and the back liner 92B may be provided separately, and the front liner 92A and the back liner 92B may be bonded together with an adhesive or the like.

The thickness of the front and back liners (thickness of each liner) is not particularly limited, but is preferably 50 μm or more, more preferably 80 μm or more, even more preferably 100 μm or more, and is preferably 400 μm or less, more preferably 300 μm or less, and even more preferably 250 μm or less.

The thickness of the core is not particularly limited, but is preferably 50 μm or more, more preferably 80 μm or more, even more preferably 100 μm or more, and is preferably 400 μm or less, more preferably 300 μm or less, even more preferably 250 μm or less.

The front and back liners and the core are made of base paper. The base paper constituting the front and back liners and the core is not particularly limited as long as it is a commonly used paper, and is preferably paper whose main component is plant-derived pulp, and more preferably paper whose main component is wood pulp.
Specific examples include kraft paper, fine paper, (white) paperboard, base paper for paper containers, base paper for milk cartons, base paper for cups, coated paper, one-sided glossy paper, etc. These may be used alone or in combination of two or more kinds.
Examples of the kraft paper include bleached kraft paper, unbleached kraft paper, and one-sided glazed bleached kraft paper. These may be used alone or in combination of two or more kinds.
The front and back liners may be any of the following types of liners: C5, C6, K5, K6 and K7.

In addition, there is almost no change in the physical properties, such as the basis weight, of the base paper when it is formed into a tray-shaped container. Therefore, the basis weight of the base paper that constitutes the front and back liners and the core before it is formed into a tray-shaped container is approximately the same as the basis weight of the front and back liners and the core after it is formed into a tray-shaped container, and the preferred ranges are the same for each.

The density of the base paper constituting the front and back liners and the core is not particularly limited, but from the viewpoint of molding processability, it is preferably 0.60 g/ ^cm3 or more, more preferably 0.65 g/ ^cm3 or more, even more preferably 0.70 g/ ^cm3 or more, and preferably 0.90 g/ ^cm3 or less, more preferably 0.85 g/ ^cm3 or less, and even more preferably 0.80 g/ ^cm3 or less.

As described above, the raw material pulp for the base paper constituting the front and back liners and the core is preferably wood pulp, more preferably kraft pulp.
Kraft pulp is classified into hardwood kraft pulp (LKP) and softwood kraft pulp (NKP) based on the difference in raw materials.
In addition, depending on the treatment state, bleached kraft pulp (BKP), unbleached kraft pulp (UKP) and oxygen bleached kraft pulp (OKP) can be mentioned, and from the viewpoint of strength, bleached kraft pulp (BKP) is preferred.

Among these, the raw material pulp is preferably hardwood kraft pulp (LKP) or softwood kraft pulp (NKP), and more preferably a combination of hardwood kraft pulp (LKP) and softwood kraft pulp (NKP). The mass ratio (LKP/NKP) when hardwood kraft pulp (LKP) and softwood kraft pulp (NKP) are used in combination is not particularly limited as long as it is a ratio used in general paper, and is preferably 1/99 to 99/1, more preferably 20/80 to 99/1, even more preferably 30/70 to 99/1, even more preferably 50/50 to 99/1, and particularly preferably 70/30 to 95/5.
Furthermore, as the hardwood kraft pulp (LKP), hardwood bleached kraft pulp (LBKP) is preferred, and as the softwood kraft pulp (NKP), softwood bleached kraft pulp (NBKP) is preferred.

The length-weighted average fiber length of the pulp constituting the front and back liners and the core is not particularly limited, but from the viewpoint of obtaining the paper strength as the base paper, it is preferably 0.60 mm or more, more preferably 0.70 mm or more, even more preferably 0.80 mm or more, and is preferably 2.00 mm or less, more preferably 1.90 mm or less, even more preferably 1.80 mm or less.
The length-weighted average fiber length of the fibers constituting the front and back liners and the core is calculated by disintegrating the base paper using the method described in the Examples, and measuring the fiber length of the obtained pulp slurry with a fiber length measuring device (manufactured by Valmet, model FS-5, equipped with a UHD base unit).
The length-weighted average fiber length is calculated from the fiber lengths of selected fibers having a length of 0.2 mm or more and 7.6 mm or less.

The proportion of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the front and back liners and the core is not particularly limited, but is preferably 5% or more, more preferably 7% or more, even more preferably 9% or more, and is preferably 25% or less, more preferably 23.5% or less, and even more preferably 22% or less.
The number of fine fibers with a fiber length of 0.2 mm or less in the pulp fiber constituting the paper base material is calculated by disintegrating the base paper using the method described in the Examples, and measuring the fiber length of the resulting pulp slurry with a fiber length measuring device (manufactured by Valmet, model FS-5, with UHD base unit). Fibers with a fiber length of 0.2 mm or less and a fiber width of 75 μm or less are defined as fine fibers, and the ratio of the number of fine fibers to the number of measured pulp fibers is calculated.

In order to bring the length-weighted average fiber length and the proportion of fine fibers of the pulp constituting the front and back liners and the core into the above-mentioned ranges, appropriate adjustments can be made by selecting the raw pulp, whether or not to filter the pulp in the chemical and mechanical treatments of the pulp, the concentration and beating load of the beating treatment, etc.
Furthermore, for the purpose of increasing the proportion of fine fibers, powdered pulp obtained by mechanically pulp fiber crushing may be added.
Furthermore, when manufacturing the base paper for the front and back liners and the core, adding a retention aid which is a cationic polymer during the papermaking process increases the proportion of fine fibers that remain in the base paper during papermaking, so the proportion of fine fibers can be increased by adding a cationic polymer during the papermaking process.

The disintegration freeness (freeness) of the raw pulp of the base paper constituting the front and back liners and the core, measured in accordance with JIS P8121-2:2012, is preferably 750 mL or less, more preferably 700 mL or less, and even more preferably 650 mL or less. The lower limit is preferably 300 mL or more, more preferably 400 mL or more, and even more preferably 500 mL or more. Here, disintegration freeness refers to the Canadian standard freeness (CSF) of the pulp obtained by disintegrating the paper after papermaking in accordance with JIS P8220-1:2012, measured in accordance with JIS P8121-2:2012. The method of beating the pulp to adjust the disintegration freeness can be a known method.

Examples of the internal sizing agent include rosin-based, alkyl ketene dimer-based, alkenyl succinic anhydride-based, styrene-acrylic, higher fatty acid-based, petroleum resin-based, etc. These may be used alone or in combination of two or more.
The content of the internal sizing agent is preferably 3 parts by mass or less per 100 parts by mass of the raw pulp of the base paper constituting the front and back liners and the core.

In addition to the internal sizing agent, other known internal additives may be added to the base paper constituting the front and back liners and the core. Examples of internal additives include aluminum sulfate, paper strength agents, polymer flocculants, fillers, retention aids, pH adjusters, drainage improvers, water resistance agents, softeners, antistatic agents, defoamers, slime control agents, dyes and pigments, etc. These may be used alone or in combination of two or more.
Examples of the filler include titanium dioxide, kaolin, talc, calcium carbonate, etc. These may be used alone or in combination of two or more kinds.

In making the base paper constituting the front and back liners and the core, a known wet papermaking machine can be appropriately selected and used.
Examples of the paper machine include a Fourdrinier paper machine, a gap former type paper machine, a cylinder paper machine, a short wire paper machine, a twin wire paper machine, etc. These may be used alone or in combination of two or more kinds.
The front and back liners and the medium formed by the papermaking machine are preferably transported, for example, on a felt and dried in a dryer. A multi-stage cylinder dryer may be used as a pre-dryer before drying in the dryer.

<Resin film layer>
The resin film layer in the tray-shaped container of the present invention is a layer in which the inner surface of the paper layer (container body) is covered (interior) with a resin film sheet. The resin film layer is a functional layer that not only maintains the folded state of each side of the paper layer (container body), but also provides functions such as water resistance and heat resistance to the inner surface of the paper layer (container body).
The resin film sheet used in the resin film layer is made of a sheet material with properties according to the function to be imparted. For example, a plastic sheet with extensibility that takes into account the extension of the resin film sheet when it is attached to the paper layer (container body), water resistance, heat resistance, heat fusion, etc. is used for the resin film sheet.

The resin film layer in the tray-shaped container of the present invention is preferably a resin laminate having extensibility and barrier properties, from the viewpoint of having a role of protecting the surface of the paper layer (container body) from the stored items such as food. The resin laminate includes a barrier layer in the middle layer, and since the layer in contact with the inner surface of the paper layer (container body) needs to be heat-sealed to the paper layer (container body), it is more preferable that the resin laminate has a layer made of a thermoplastic resin.

The barrier layer is not limited to resin and may be metal foil or the like. From the viewpoint of allowing the printed surface of the paper layer to be visible and enhancing the design, however, it is preferable that the barrier layer be made of resin, and more preferably of transparent resin.
The resin constituting the barrier layer is preferably at least one selected from the group consisting of polyamide resins, polyvinyl alcohol, ethylene-vinyl alcohol copolymers (EVOH), and polyvinylidene chloride resins, and more preferably at least one selected from the group consisting of polyamide resins, polyvinyl alcohol, and ethylene-vinyl alcohol copolymers.
The polyamide resin constituting the barrier layer is preferably an aromatic polyamide, more preferably polyamide MXD6.
Examples of resins constituting the layer in contact with the inner surface of the paper layer (container body) of the resin laminate include polyolefin resins such as ethylene vinyl acetate (EVA), polyethylene (PE), and polypropylene (PP), aliphatic polyamide resins such as nylon 6, and polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc. These may be used alone or in combination of two or more.
Examples of layers facing the inside of the storage space include ethylene vinyl acetate (EVA) and polypropylene (PP) resins, specifically homopolypropylene, random polypropylene copolymers, and block polypropylene copolymers, and it is particularly preferable to use random polypropylene copolymers.

Examples of polyamide resins constituting the layer in contact with the inner surface of the paper layer (container body) of the resin laminate include aliphatic polyamide polymers such as nylon 6, nylon 66, nylon 69, nylon 610, nylon 612, nylon 11, nylon 12, etc.; aliphatic polyamide copolymers such as nylon 6-66 (a copolymer of nylon 6 and nylon 66, hereinafter the same), nylon 6-10, nylon 6-12, nylon 6-69, nylon 6-610, nylon 66-69, etc. These may be used alone or in combination of two or more kinds.
Among these, aliphatic polyamide copolymers are preferred, and nylon 6-66, nylon 6-10, or nylon 6-12 is more preferred.

Examples of polyester resins constituting the layer in contact with the inner surface of the paper layer (container body) of the resin laminate include poly(ethylene terephthalate), poly(butylene terephthalate), poly(ethylene terephthalate/isophthalate), and poly(ethylene glycol/cyclohexane dimethanol/terephthalate). Furthermore, these polymers may contain, as copolymerization components, diols or isophthals such as ethylene glycol, butylene glycol, cyclohexane dimethanol, neopentyl glycol, and pentanediol; dicarboxylic acids such as benzophenone dicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenylmethane dicarboxylic acid, propylene bis(phenyl carboxylic acid), diphenyl oxide dicarboxylic acid, oxalic acid, maleic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and diethylsuccinic acid.

Examples of polyolefin resins constituting the layer in contact with the inner surface of the paper layer (container body) of the resin laminate include polyethylene resins such as linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene; polypropylene resins such as polypropylene; propylene-ethylene copolymers; ethylene-vinyl acetate copolymers; ionomer resins; ethylene-(meth)acrylic acid copolymers; ethylene-(meth)acrylic acid-unsaturated carboxylic acid ester copolymers; etc. These may be used alone or in combination of two or more.
Among these, polyethylene resins are preferred, and linear low-density polyethylene is more preferred.

The resin film sheet used for the resin film layer may have the above-mentioned configuration, or may have a multi-layer configuration in which various types are combined.
From the viewpoint of reducing the environmental load, it is also preferable to use a biodegradable resin such as polylactic acid (PLA), polyglycolic acid (PGA), or polybutylene succinate (PBS) as the resin film sheet used for the resin film layer.
The resin film sheets used in the resin film layers may be laminated by a dry lamination method, but are preferably films formed by a co-extrusion method in which the resin film sheets are simultaneously melt-extruded. The resin film sheets A to C used in the examples described later are films formed by a co-extrusion method.

The film thickness of the resin film layer is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more, and is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 200 μm or less.
By setting the film thickness of the resin film layer to 300 μm or less, the mass of the paper layer can be made greater than the mass of the resin film layer, and the tray-shaped container can be used as a target for applying a paper mark.
Commercially available resin laminates (laminate films) suitable for use in the resin film layer include a PE (polyethylene)/PE (polyethylene)/EVA (ethylene vinyl acetate) three-layer film (product name: Skin Pack, thickness 150 μm) manufactured by Enshu Kasei Co., Ltd., a PP (polypropylene)/EVOH (ethylene-vinyl alcohol copolymer)/special adhesive layer (undisclosed) three-layer film (product name: Diamiron F680, thickness 200 μm) manufactured by Mitsubishi Chemical Corporation, and a PP (polypropylene)/EVOH (ethylene-vinyl alcohol copolymer)/PP (polypropylene) three-layer film (trade name: Diamiron F001, film thickness 40 μm), PP (polypropylene) / PVOH (polyvinyl alcohol) / PP three-layer film (trade name: ECO-B, film thickness 20 μm) manufactured by Futamura Chemical Industry Co., Ltd., NY6 (nylon 6) / EVOH (ethylene-vinyl alcohol copolymer) / NY6 three-layer film (trade name: Heptax HP, film thickness 17 μm) manufactured by Gunze Ltd., NY6 / MXD6 (polyamide MXD6) / NY6 three-layer film (trade name: Embron M, film thickness 15 μm) manufactured by Unitika Ltd., etc. These may be used alone or in combination of two or more kinds.

<Method of manufacturing tray-shaped container>
First, the structure of a molding die 160 used in manufacturing the tray-shaped container 100 using the blank sheet 100A' of FIG. 4 will be described with reference to FIGS.
FIG. 10 is a perspective view of a mold 160 used to manufacture the tray-shaped container 100 using the blank sheet 100A'.
The molding die 160 is a metal mold (cavity, female die) for forming the blank sheet 100A' into a pyramidal paper layer (container body) 100A and for laminating and bonding (pressing) the resin film layer 12 to the inner surface of the paper layer (container body) 100A by vacuum suction.

The molding die 160 has a recess 72 recessed into the upper surface side of a base portion 161. The base portion 161 is a base portion that supports the recess 72. The recess 72 is formed in a shape corresponding to the paper layer (container body) 100A (see FIGS. 1 to 3) to be molded, and forms a recess into which the blank sheet 100A' is pressed.
In order to perform suction processing, a plurality of air holes (indicated by reference numeral 78 in FIG. 11 described later) are provided on the inner surface of the recess 72, which communicates between the inside and outside of the recess 72. These air holes are spaced apart from one another and scattered.

The recess 72 has a plurality of surface portions 65 on its inner surface that correspond to the surface shape of the paper layer (container body) 100A (see Figures 1 to 3) when the paper layer (container body) 100A (see Figures 1 to 3) is placed on it.
The multiple surface portions 65 specifically include one first surface portion 60 corresponding to the bottom surface 20 (see Figures 1 to 3) of the paper layer (container body) 100A (see Figures 1 to 3) when the paper layer (container body) 100A (see Figures 1 to 3) is placed in the recess 72, and eight second surface portions 71 corresponding to the side surfaces 30 (see Figures 1 to 3) of the paper layer (container body) 100A.

The molding die 160 has a flange surface portion 53 extending from the upper edge of the recess 72 toward the outside of the recess 72. The flange surface portion 53 can be divided into eight portions along the outer periphery of the recess 72 corresponding to the eight second surface portions 71, respectively.
Furthermore, a stepped portion 90 is provided so as to protrude along the outer periphery of each flange surface portion 53. The stepped portion 90 forms a step that rises outward relative to the surface portion of each flange surface portion 53.

A groove portion 70 is provided on the inner surface of the recess 72, extending along a linear region corresponding to a linearly extending gap in the paper layer (container body) 100A (see Figures 1 to 3) when the paper layer (container body) 100A is placed in the recess 72.
The grooves 70 are provided in communication with at least two of the scattered air holes, and form air passages that extend linearly on the inner surface of the recess 72 during suction processing.
The grooves 70 in this embodiment extend linearly along the boundaries between the multiple surface portions 65 on the inner surface of the recess 72. The boundaries between the multiple surface portions 65 are recessed facing the locations where each edge of the bottom surface 20 contacts the side surface 30 in the paper layer (container body) 100A (see FIGS. 1 to 3 ) and where adjacent side surfaces 30 butt against each other.
The groove portion 70 illustrated here includes a side groove portion 75 extending along the boundary between the second surface portions 71 among the boundaries between the multiple surface portions 65, a bottom groove portion 76 extending along the boundary between the first surface portion 60 and the second surface portion 71, an upper groove portion 73 extending along the boundary between the flange surface portions 53, and a middle groove portion 77 extending along a linear region corresponding to the fold 38.

The side groove portion 75 is provided between the side edges of the second surface portion 71 that correspond to the side surface 30 (see FIGS. 1 to 3) when the paper layer (container body) 100A (see FIGS. 1 to 3) is placed in the recess 72. The bottom groove portion 76 faces between the bottom surface 20 and the side surface 30 of the container body 100A (see FIGS. 1 to 3) when the container body 100A (see FIGS. 1 to 3) is placed in the recess 72.
The upper groove portion 73 faces the gap between the side edges of the flange surface 40 of the paper layer (container body) 100A (see Figures 1 to 3) when the paper layer (container body) 100A is placed in the recess 72.
The middle groove portion 77 faces between the first minor side surface 32A and the second minor side surface 32B of the minor side surface 32 when the paper layer (container body) 100A (see Figures 1 to 3) is placed in the recess 72.

The mold used to manufacture a tray-shaped container 200 using the blank sheet 200B' in Figure 7 has a recess formed in a shape corresponding to the paper layer (container body) 200B (see Figures 5 and 6) to be molded, and differs from the mold 160 in Figure 10 in that it has a groove portion corresponding to the container body, but the other configurations are the same.
The inner surface of the mold recess used to manufacture the tray-shaped container 200 is provided with grooves, such as a side groove portion facing the point where the first main side surface 41, the second main side surface 42 and the sub-side surface 43 are butted together when the paper layer (container body) 200B is placed on it, a bottom groove portion facing the area between the bottom surface 21 and the side surface 50, and an upper groove portion facing the gap between the side edges of the flange surfaces 40.

Next, with reference to FIG. 11, a manufacturing apparatus 150 for manufacturing the tray-shaped container 100 using the molding die 160 will be described.
The manufacturing apparatus 150 includes a first preparation section 201 that folds and arranges a blank sheet 100A' of a paper layer (container body) 100A along the recess 72 of the molding die 160, a second preparation section 202 that arranges a resin film sheet 12A' above the blank sheet 100A' folded in the first preparation section 201, a press section 203 that heats and presses the resin film sheet 12A' arranged in the second preparation section 202 toward the blank sheet 100A' arranged in the first preparation section 201, and a suction section 204 that presses the resin film sheet 12A' pressed in the press section 203 against the blank sheet 100A' arranged in the first preparation section 201, and a suction section 204 that presses the resin film sheet 12A' pressed in the press section 203 against the blank sheet 100A' by vacuum suction.

The suction section 204 is equipped with a suction device (not shown) that draws in air through the air hole 78 .
The pressing section 203 is equipped with a heating device (not shown) for heating and softening the resin film sheet 12A', and a protruding portion 80 for pressing the resin film sheet 12A'. The protruding portion 80 is a metal mold (plug, male mold) having a protruding shape corresponding to the recessed portion 72, and is biased downward by a biasing device (not shown). The protruding shape of the protruding portion 80 is set to a smaller dimension than the recessed portion 72.

The method for manufacturing the tray-shaped container 100 by the above-mentioned manufacturing apparatus 150 includes the following steps S1 to S4.
Step S1: A first preparation step of folding and arranging a blank sheet 100A' of a paper layer (container body) 100A along the recess 72 of the forming mold 160. Step S2: A second preparation step of arranging a resin film sheet 12A' above the blank sheet 100A' folded in the first preparation step. Step S3: A pressing step of pressing the resin film sheet 12A' arranged in the second preparation step toward the blank sheet 100A' arranged in the first preparation step while heating it. Step S4: A suction step of pressing the resin film sheet 12A' pressed in the pressing step to the blank sheet 100A' by vacuum suction.

In the above manufacturing device 150, when the resin film sheet 12A' arranged in the second preparation section 202 is heated and pressed toward the blank sheet 100A' arranged in the first preparation section 201, the blank sheet 100A' pressed into the recess 72 has its side surface 30 folded against the bottom surface 20 to form a paper layer (container body) 100A.

In this state, when air is sucked in through the air hole 78 by the suction section 204, the air between the paper layer (container body) 100A and the resin film sheet 12A' is sucked outward through the gap 36 in the paper layer (container body) 100A and the cuts in the folds 14 and 38. This creates a vacuum between the paper layer (container body) 100A and the resin film sheet 12A', and the resin film sheet 12A' is tightly attached to the bottom surface 20, side surface 30, and flange surface 40, forming (vacuum forming) a tray-shaped container 100 in which the resin film layer 12 is laminated and bonded to the inner surface of the paper layer (container body) 100A.

In the tray-shaped container 100 molded as described above, when food or other objects are stored in the storage space of the tray-shaped container 100, the storage space of the paper layer (container body) 100A is replaced with gas, and the opening 110A is closed with a sealing material (film sheet) attached to the flange surface 40.

The molding die 160 is not limited to a structure in which the grooves extend along all the boundaries of the multiple surface portions, but may have a structure in which the grooves extend along some of the boundaries of the multiple surface portions. For example, the upper groove 73 of the flange surface portion 53 may be omitted.
The manufacturing apparatus 150 is not limited to performing only vacuum forming in the above-mentioned suction step (suction means 204), but may also perform vacuum/pressure forming using both vacuum suction and compressed air.

Furthermore, since the molding die 160 has the above-mentioned configuration, it is possible to obtain the following actions and effects (1) to (6).
(1) The grooves 70 are provided in the recesses 72 of the mold 160, communicating with at least two air holes 78, and extend along linear regions corresponding to the linearly extending gaps 36 in the paper layer (container body) 100A, allowing the resin film sheet on the upper surface side of the paper layer (container body) 100A to be sucked in a linear fashion. This distributes the suction load, ensuring uniform adsorption of the resin film sheet.
(2) The mold 160 is used to manufacture a tray-shaped container 100 having a top surface (top surface) with an opening 110A, a plurality of side surfaces 30 folded at creases 14 along each side of a polygonal bottom surface 20, and a paper layer (container body) 100A formed into a truncated pyramid shape with side edges 34, 35 of adjacent side surfaces 30 butted together to form corners, and a resin film layer 12 formed by pressing a resin film sheet laminated on the inner surface of the paper layer (container body) 100A. The mold 160 is suitable for the truncated pyramid-shaped tray-shaped container 100 configured as described above, since it can suck the resin film sheet linearly and uniformly along a linear region corresponding to the linearly extending gap portion 36 in the paper layer (container body) 100A.

(3) The grooves 70 extend linearly along the boundaries between the multiple surface portions 65 that correspond to the surface shape of the paper layer (container body) 100A, so that the paper layer (container body) 100A can be sucked uniformly linearly along the contact points between each edge of the bottom surface 20 and the side surface 30 and along the contact points between adjacent side surfaces 30. This distributes the suction load and ensures uniform adsorption of the resin film sheet.
(4) The side grooves 75 allow the resin film sheet on the upper surface side of the paper layer (container body) 100A to be sucked evenly along the gaps 36 at the joints between the side surfaces 30. This makes the adhesiveness of the resin film sheet more reliable.
Furthermore, since the side grooves 75 function as clearances for the side edges 34, 35 at the butting points of the side surfaces 30, a gap can be reliably secured between the side edges 34, 35 of the side surfaces 30 at the butting points. Also, the side surfaces 30 are less likely to be arranged overlapping each other, ensuring the formability of the paper layer (container body) 100A.

(5) The bottom groove portion 76 allows suction along the boundary between the bottom surface 20 and the side surface 30 of the paper layer (container body) 100A, so that the resin film sheet can be reliably drawn into the bottom side of the recess 72.
(6) The upper groove portion 73 ensures a clearance at the point where the flange surfaces 40 are butted together, making it difficult for the flange surfaces 40 to be positioned overlapping each other, thereby ensuring the formability of the paper layer (container body) 100A.
In addition, the stepped portion 90 provided in a protruding manner along the outer periphery of the flange surface portion 53 makes it easier to peel the resin film sheet from the molding die 160 after the tray-shaped container 100 has been molded.

The features of the present invention are explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below.

[Preparation of cardboard as the base material for the paper layer]
<Production Example 1>
To 70 parts by mass of bleached softwood bleached kraft pulp (NBKP), 30 parts by mass of a powdered pulp hardwood bleached kraft pulp (LBKP) dry sheet mechanically pulverized with a cutter mill (HORAI Corporation, HA8 2542 30E, screen 0.24 mm) was added, and the mixture was beaten at a low concentration (slurry concentration at the time of beating: 2% by mass) until the Canadian Standard Freeness (CSF) reached 600 mL, thereby preparing Pulp 1.
To 100 parts by mass of the prepared pulp 1 (converted into solids content), 0.2 parts by mass of a synthetic sizing agent (SPS400, manufactured by Arakawa Chemical Industries, Ltd.), 1.0 part by mass of aluminum sulfate (aluminum sulfate) (converted into solids content), 0.2 parts by mass of polyacrylamide (product name: Polystron 1222, manufactured by Arakawa Chemical Industries, Ltd.) as a paper strength agent, and 0.025 parts by mass of nonionic acrylamide (Percoll 47, manufactured by Allied Colloids) as a polymer flocculant were added to prepare a base paper stock.
Furthermore, the prepared stock was made into base paper A-1 using a twin-wire paper machine so that the overall paper had a basis weight of 80 g/m ² , a thickness of 110 μm and a density of 0.73 g/cm ³ .

<Production Example 2>
Base paper A- ² was produced in the same manner as base paper A-1, except that in Production Example 1, instead of making the entire paper to have a basis weight of 80 g/m ² , a thickness of 110 μm, and a density of 0.73 g/cm 3, the entire paper was made to have a basis weight of 160 g/m ² , a thickness of 210 μm, and a density of 0.76 g/cm ³ .

<Production Example 3>
Base paper ^A-3 was produced in the same manner as base paper A-1, except that in Production Example 1, instead of making the entire paper to have a basis weight of 80 g/m ² , a thickness of 110 μm, and a density of 0.73 g/cm 3, the entire paper was made to have a basis weight of 200 g/m ² , a thickness of 270 μm, and a density of 0.74 g/cm ³ .

<Production Example 4>
Base paper A- ⁴ was produced in the same manner as base paper A-1, except that in Production Example 1, instead of making the entire paper to have a basis weight of 80 g/m ² , a thickness of 110 μm, and a density of 0.73 g/cm 3, the entire paper was made to have a basis weight of 300 g/m ² , a thickness of 380 μm, and a density of 0.79 g/cm ³ .

<Production Example 5>
Base paper B was produced in the same manner as base paper A-1, except that 25 parts by mass of powdered pulp was added to 75 parts by mass of softwood bleached kraft pulp (NBKP) instead of adding 30 parts by mass of powdered pulp to 70 parts by mass of softwood bleached kraft pulp (NBKP).

<Production Example 6>
Base paper C was produced in the same manner as base paper A-1, except that 20 parts by mass of powdered pulp was added to 80 parts by mass of bleached softwood kraft pulp (NBKP) instead of adding 30 parts by mass of powdered pulp to 70 parts by mass of bleached softwood kraft pulp (NBKP).

<Production Example 7>
Base paper D was produced in the same manner as base paper A-1, except that 15 parts by mass of powdered pulp was added to 85 parts by mass of softwood bleached kraft pulp (NBKP) instead of adding 30 parts by mass of powdered pulp to 70 parts by mass of softwood bleached kraft pulp (NBKP).

<Production Example 8>
Base paper E was produced in the same manner as base paper A-1, except that 5 parts by mass of powdered pulp was added to 95 parts by mass of softwood bleached kraft pulp (NBKP) instead of adding 30 parts by mass of powdered pulp to 70 parts by mass of softwood bleached kraft pulp (NBKP).

[Preparation of resin film sheet constituting resin film layer]
The following three types of resin film sheets were prepared.
(1) Resin film sheet α: Company name: Enshu Kasei Co., Ltd., Product number: Skin Pack, Layer structure: PE (polyethylene) / PE (polyethylene) / EVA (ethylene vinyl acetate) (/paper layer), Thickness: 150 μm
(2) Resin film sheet β: Company name: Mitsubishi Chemical Corporation, Product number: Diamiron F680, Layer structure: PP (polypropylene) / EVOH (ethylene-vinyl alcohol copolymer) / Special adhesive layer (undisclosed) (/paper layer), Thickness: 200 μm
(3) Resin film sheet γ: Company name: Mitsubishi Chemical Corporation, Product number: Diamiron F001, Layer structure: PP (polypropylene) / EVOH (ethylene-vinyl alcohol copolymer) / PP (polypropylene) (/paper layer), Thickness: 40 μm

[Production of tray-shaped containers]
Example 1
From the base paper A-1 prepared in Production Example 1, a corrugator was used to prepare front and back liners and a core (150 corrugations). The prepared front and back liners and core were bonded together using an adhesive (cornstarch for corrugated board paste manufactured by Oji Cornstarch Co., Ltd.) to prepare a corrugated board having a single-layer structure as shown in Fig. 9, with the ratio of the basis weight of the front liner to the basis weight of the back liner to the basis weight of the core being 1:1:1 (front liner: back liner: core) (the basis weight of the front liner, the basis weight of the back liner, and the basis weight of the core were all 80 g/ ^m2 ).
A blank sheet made from the prepared cardboard was sucked from above with a vacuum, the sucked blank sheet was inserted into a mold, and the blank sheet was pressed into the mold by sucking air through the air hole, and folded into a box shape (length of one side of the flange surface 40: about 16.5 cm) as shown in FIG. 5 to obtain a paper layer (container body). Next, using a film laminating machine (company name: manufactured by Wakisaka Engineering Co., Ltd., product number: FVT-400), the heater setting temperature for both the upper and lower heaters was set to 450° C., and a resin film sheet α was heated for 10 seconds, and then the resin film layer was laminated and bonded to the inner surface of the opening side of the paper layer (container body) by vacuum and compressed air adsorption, thereby obtaining a tray-shaped container 1. The taper angle of the main side of the tray-shaped container 1 was 10°, and the depth of the tray-shaped container was 55 mm.

[Physical property measurement and evaluation]
<Measurement of the basis weight of the front and back liners and the core>
The basis weights of the front and back liners and the core were measured in accordance with JIS P8124:2011. However, when a resin film layer was laminated and bonded to the inner surface of the opening side of the paper layer (container body), the paper layer was peeled off from the resin film layer, taking care not to let the paper adhere to the resin film layer, and then the basis weights of the front and back liners and the core of the peeled paper layer were measured. The measurement results are shown in Table 1.

<Measurement of thickness of front and back liners and core>
The thicknesses of the front and back liners and the core were measured in accordance with JIS P 8118:2014. However, when a resin film layer was laminated and bonded to the inner surface of the opening side of the paper layer (container body), the paper layer was peeled off from the resin film layer, taking care not to let the paper adhere to the resin film layer, and then the thicknesses of the front and back liners and the core of the peeled paper layer were measured. The measurement results are shown in Table 1.

<Measurement of density of front and back liners and core>
The densities of the front and back liners and the core were measured in accordance with JIS P 8118:2014. However, when a resin film layer was laminated and bonded to the inner surface of the opening side of the paper layer (container body), the paper layer was peeled off from the resin film layer, taking care not to let the paper adhere to the resin film layer, and then the densities of the front and back liners and the core in the peeled paper layer were measured. The measurement results are shown in Table 1.

<Cardboard thickness measurement>
The thickness of the cardboard was measured in accordance with JIS P 8118:2014. However, when a resin film layer was laminated and bonded to the inner surface of the opening side of the paper layer (container body), the paper layer was peeled off from the resin film layer while being careful not to let the paper adhere to the resin film layer, and then the thickness of the cardboard at the peeled paper layer was measured. The measurement results are shown in Table 1.

<Measurement of the length-weighted average fiber length of the pulp constituting the front and back liners and the core>
Samples of 40 cm square were cut out from the front and back liners and the center core, and were immersed in ion-exchanged water adjusted to a concentration of 2%, and then left to soak for 24 hours.
After soaking for 24 hours, the pulp was defibrated into fibers using a standard defibrator (Kumagaya Riki Kogyo Co., Ltd.) until no undefibrated fibers remained. When the pulp had a resin film layer, the slurry (dispersion of pulp fibers) after defibration from which the resin film layer had been removed was sampled, and the "length-weighted average fiber length" was measured using a fiber length measuring device (Valmet, Model FS-5, with UHD base unit).
The "length-weighted average fiber length" is a length-weighted average fiber length calculated by selecting fibers having a length of 0.2 mm or more and a length of 7.6 mm or less.
The measurement results are shown in Table 1.

<Measurement of the proportion of fine fibers with a fiber length of 0.2 mm or less in the pulp constituting the front and back liners and the core>
Samples of 40 cm square were cut out from the front and back liners and the center core, and were immersed in ion-exchanged water adjusted to a concentration of 2%, and then left to soak for 24 hours.
After soaking for 24 hours, the pulp was disintegrated into fibers using a standard disintegrator (manufactured by Kumagai Riki Kogyo Co., Ltd.) until no undisintegrated fibers remained. When a resin film layer was present, the slurry (dispersion of pulp fibers) after disintegration from which the resin film layer had been removed was sampled, and the "amount of fine fibers" was measured using a fiber length measuring device (manufactured by Valmet, model FS-5, with UHD base unit).
The "amount of fine fibers" is the percentage of the number of fine fibers having a fiber width of 75 μm or less and a length of 0.2 mm or less in the defibrated pulp fibers.
The measurement results are shown in Table 1.

<Thermal insulation>
300 mL of water was placed in the prepared tray-shaped container 1 and heated at 500 W for 300 seconds using a microwave oven (company name: SHARP Corporation, product number: RE-T2).
Immediately after removing the tray-shaped container 1 from the microwave oven, the temperature of the center of the bottom surface of the outside of the tray-shaped container 1 (within 1 cm from the center) was measured using a non-contact thermometer (manufacturer: BOSCH Professional, product number: GIS500) and evaluated according to the following criteria. The evaluation results are shown in Table 1.
<<Evaluation criteria>>
5: The measurement temperature was 40° C. or lower.
4: The measurement temperature was greater than 40°C and less than 50°C.
3: The measurement temperature was greater than 50°C and equal to or less than 60°C.
2: The measurement temperature was greater than 60°C and less than 70°C.
1: The measurement temperature was above 70°C.

<Airtightness>
300 mL of water was poured into the prepared tray-shaped container 1. Next, a film having heat sealing properties was top-sealed to the tray-shaped container 1 under conditions of 150°C x 10 seconds. Next, the top-sealed tray-shaped container 1 was checked for gas leakage from inside the tray using a leak tester (manufacturer: Takachiho Seiki Co., Ltd., product number: PLT-3000) at an inspection pressure of -7500 mmH ₂ O, and evaluated according to the following criteria. The evaluation results are shown in Table 1.
<<Evaluation criteria>>
5: In the leak tester test, the pressure was 20 MPa or more and less than 30 MPa, and no gas leakage was observed.
4: Gas leakage occurred at more than 15 MPa and less than 20 MPa in the leak tester test.
3: Gas leakage occurred at more than 10 MPa and 15 MPa or less in the leak tester test.
2: Gas leakage occurred at more than 5 MPa and 10 MPa or less in the leak tester test.
1: Gas leakage occurred at 5 MPa or less in the leak tester test.

<Examples 2 to 16 and Comparative Examples 1 to 6>
A tray-shaped container was obtained in the same manner as in Example 1, except that the manufacturing conditions described in Table 1 were changed (tray shape, thickness of cardboard, base paper type of front and back liners, basis weight of front and back liners, thickness of front and back liners, density of front and back liners, length-weighted average fiber length of pulp constituting front and back liners, ratio of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the front and back liners ("fine fiber amount" in Table 1), base paper type of core, basis weight of core, thickness of core, density of core, number of corrugations per 300 mm of cardboard, length-weighted average fiber length of pulp constituting core, ratio of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting core ("fine fiber amount" in Table 1), type of resin film). The evaluation results are shown in Table 1.
However, in Comparative Example 6, instead of using a cardboard having a front liner, a back liner and a core, the paper was made from base paper A-4 (whole paper basis weight 300 g/m ² , thickness 380 μm, density 0.79 g/cm ³ ) as is.

The results in Table 1 show that the tray-shaped containers of Examples 1 to 16 are capable of achieving both heat insulation and airtightness.
Furthermore, in the tray-shaped containers of Examples 6 to 9, the length-weighted average fiber length of the pulp constituting the front and back liners is 1.00 mm or more and 1.70 mm or less, and the proportion of fine fibers with a fiber length of 0.2 mm or less in the pulp constituting the front and back liners is 10% or more and 19% or less, thereby improving the insulation and airtightness.
In addition, in the tray-shaped containers of Examples 7 and 8, the length-weighted average fiber length of the pulp constituting the front and back liners is 1.10 mm or more and 1.50 mm or less, and the proportion of fine fibers with a fiber length of 0.2 mm or less in the pulp constituting the front and back liners is 13% or more and 17% or less, which further improves the insulation and airtightness.
Furthermore, in the tray-shaped containers of Examples 10 to 13, the length-weighted average fiber length of the pulp constituting the core is 1.00 mm or more and 1.70 mm or less, and the proportion of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the core is 10% or more and 19% or less, thereby improving the insulation properties and airtightness.
In addition, in the tray-shaped containers of Examples 11 and 12, the length-weighted average fiber length of the pulp constituting the core is 1.10 mm or more and 1.50 mm or less, and the proportion of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the core is 13% or more and 17% or less, thereby further improving the insulation properties and airtightness.
Moreover, in the tray-shaped containers of Comparative Examples 1 to 3, the basis weights of the front and back liners and the core are outside the specified range, and therefore it is clear that the airtightness is not good.
Moreover, in the tray-shaped containers of Comparative Examples 4 and 5, the number of steps in the core is outside the specified range, and therefore it is clear that the heat insulation is not good.
Furthermore, in the tray-shaped container of Comparative Example 6, the paper-made base paper A-4 was used as is, rather than being made into a cardboard having a front liner, a back liner and a core, so it is clear that the insulation properties and airtightness are not good.

According to the present invention, a tray-shaped container capable of achieving both heat insulation and airtightness can be obtained.
The tray-shaped container of the present invention can be used as a container for food, medicines, medical supplies, electronic components, daily necessities, etc., but is preferably suitable for storing fresh foods such as vegetables, meat, fresh fish, and other fresh foods, as well as processed foods made from these foods, since the items can be stored in a sealed manner.
When the tray-shaped container of the present invention is used as a food container, food can be placed in the tray-shaped container, the inside of the tray-shaped container can be replaced with an inert gas, and the top can be sealed with a film, and the tray-shaped container can be displayed in convenience stores, supermarkets, etc.
Furthermore, the tray-like container of the present invention is suitable for storing, transporting, and displaying food for long periods of time.

12 Resin film layer 12A' Resin film sheet 13 Opening periphery 13' Fold line 14 Fold 14' Fold line 20 Bottom surface 20' Bottom sheet piece 21 Bottom surface 21' Bottom sheet piece 30 Side surface 30' Side sheet piece 31 Main side surface 31' Main side sheet piece 32 Minor side surface 32' Minor side sheet piece 32A First minor side surface 32A' First minor side surface sheet piece 32B Second minor side surface 32B' Second minor side surface sheet piece 34 Side edge 34' Side edge 35 Side edge 35' Side edge 36 Gap portion 37 Bend portion 38 Fold 38' Fold line 40 Flange surface 40' Flange surface sheet piece 41 First major side surface 41' First major side surface sheet piece 42 Second major side surface 42' Second major side surface sheet piece 43 Minor side surface 43' Minor side surface sheet piece 44 Side edge 44' Side edge 45 Side edge 45' Side edge 46 Gap portion 47 Bend portion 48 Side edge 48' Side edge 50 Side surface 50' Side sheet piece 53 Flange surface portion 60 First surface portion 65 Surface portion 70 Groove portion 71 Second surface portion 72 Recess portion 73 Upper groove portion 75 Side groove portion 76 Bottom groove portion 77 Center groove portion 78 Air hole 80 Convex portion 90 Step portion 91A Corrugated cardboard 91B Double-sided corrugated cardboard 91C Triple-sided corrugated cardboard 92A Front liner 92B Back liner 93 Core 100 Tray-shaped container 100A Paper layer (container body)
100A' Blank sheet 100M Intermediate position 110A Opening 110B Opening 150 Manufacturing device 160 Mold 161 Base portion 180 Holding piece 185 Holding piece 190 Holding piece 195 Holding piece 200 Tray-shaped container 200B Paper layer (container body)
200B' Blank sheet 200M Intermediate position 201 First preparation section 202 Second preparation section 203 Press section 204 Suction section (suction means)
A Taper angle B Depth D Down U Up

Claims (7)

A tray-shaped container having an open top and a paper layer made of corrugated cardboard as a base material and a resin film layer laminated and bonded to the inner surface of the paper layer on the open side,
The tray-shaped container has a bottom surface, a side surface extending from the bottom surface, and a flange surface disposed on an opening periphery,
The flange surfaces are coplanar;
The cardboard has a front and back liner and a core disposed between the front and back liners,
The thickness of the cardboard is 0.3 mm or more and 0.7 mm or less,
The number of corrugations per 300 mm of the cardboard is 100 or more and 190 or less,
The basis weight of the front and back liners is 40 g/m ² or more and 190 g/m ² or less,
The core has a basis weight of 40 g/ ^m2 or more and 190 g/ ^m2 or less ,
The length-weighted average fiber length of the pulp constituting the front and back liners is 0.60 mm or more and 2.00 mm or less,
A tray-shaped container , in which the proportion of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the front and back liners is 5% or more and 25% or less . A tray-shaped container having an open top and a paper layer made of corrugated cardboard as a base material and a resin film layer laminated and bonded to the inner surface of the paper layer on the open side,
The tray-shaped container has a bottom surface, a side surface extending from the bottom surface, and a flange surface disposed on an opening periphery,
The flange surfaces are coplanar;
The cardboard has a front and back liner and a core disposed between the front and back liners,
The thickness of the cardboard is 0.3 mm or more and 0.7 mm or less,
The number of corrugations per 300 mm of the cardboard is 100 or more and 190 or less,
The basis weight of the front and back liners is 40 g/m ² More than 190g/m ² is as follows:
The core has a basis weight of 40 g/m ² More than 190g/m ² is as follows:
The length-weighted average fiber length of the pulp constituting the core is 0.60 mm or more and 2.00 mm or less,
A tray-shaped container, wherein the percentage of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the core is 5% or more and 25% or less. 3. The tray-shaped container according to claim 1 or 2 , wherein the side includes a main side surface extending upright from the bottom surface and directly connected to the flange surface, and the taper angle of the main side surface is 3.5° or more and 18° or less. 4. The tray-shaped container according to claim 1 , wherein the depth of the tray-shaped container is 16 mm or more and 90 mm or less. The tray-shaped container according to any one of claims 1 to 4 , wherein the paper layer is bonded by the resin film layer. 6. The tray-shaped container according to claim 1 , wherein the paper layers at the four corners of the flange surface are separated, and the paper layers at the four corners are joined by the resin film layer. The tray-shaped container according to any one of claims 1 to 6 , wherein the side surface further includes a sub-side surface that stands upright from the bottom surface and is not directly connected to the periphery of the opening.