Tray

Abstract

To provide a tray which achieves both easy separability and floating prevention property of a resin film.SOLUTION: A tray (100) includes a paper blank (10), and a resin film (20). The blank has a recess (11), and a flange part (12). The flange part annularly overhangs from the upper end of the recess in plan view. The resin film covers the inner wall surface of the recess, and the upper surface of the flange part continuous to the inner wall surface. Arithmetic average roughness on the surface of paper is 0.2 μm or more and 3 μm or less. A first shrinkage rate as a heat shrinkage rate of the resin film in a first direction and a second shrinkage rate as a heat shrinkage rate of the resin film in a second direction perpendicular to the first direction are 2% or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tray. [Background technology]

[0002] JP2021-517097A (Patent Document 1) describes a tray. The tray described in Patent Document 1 has a paper container and a liner. The container has a recess formed of a side wall and a bottom wall, and a flange that protrudes in a ring shape in a plan view from the upper end of the recess. The liner is attached to the container so as to cover the inner wall surface of the recess (side wall, bottom wall) and the upper surface of the flange that is continuous with the inner wall surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2021-517097 Summary of the Invention [Problem to be solved by the invention]

[0004] When attempting to reuse the material used in the tray, it is necessary that the liner can be easily separated from the container. On the other hand, if the liner is easily peeled off from the container, the liner may float (partially peel off) from the container during transportation of the tray, etc. The tray described in Patent Document 1 does not achieve both the easy separation of the liner from the container and the prevention of the liner from floating off the container.

[0005] The present invention has been made in consideration of the above-mentioned problems of the conventional technology. More specifically, the present invention provides a tray that achieves both easy separation of a resin film and prevention of floating. [Means for solving the problem]

[0006] The tray of the present invention comprises a paper blank and a resin film. The blank has a recess and a flange portion. The flange portion protrudes in an annular shape from the upper end of the recess in a plan view. The resin film covers the inner wall surface of the recess and the upper surface of the flange portion connected to the inner wall surface. The arithmetic mean roughness of the paper surface is 0.2 μm or more and 3 μm or less. A first expansion / contraction rate, which is the thermal expansion / contraction rate of the resin film in a first direction, and a second expansion / contraction rate, which is the thermal expansion / contraction rate of the resin film in a second direction perpendicular to the first direction, are 2 percent or less. Effect of the Invention

[0007] According to the tray of the present invention, it is possible to achieve both easy separation of the resin film and prevention of floating. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is an exploded perspective view of the tray 100. [Diagram 2] FIG. 2 is a plan view of the tray 100. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 2 is a plan view of the blank 10 after assembly. [Diagram 5] FIG. 2 is a plan view of the blank 10 before assembly. [Figure 6] 2 is a schematic cross-sectional view of a resin film 20. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The details of the embodiment of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference characters, and overlapping descriptions will not be repeated. The tray according to the embodiment is referred to as a tray 100.

[0010] (Configuration of tray 100) The configuration of the tray 100 will be described below.

[0011] Fig. 1 is an exploded perspective view of a tray 100. Fig. 2 is a plan view of the tray 100. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. As shown in Figs. 1 to 3, the tray 100 has a blank 10 and a resin film 20.

[0012] The blank 10 has a recess 11 and a flange portion 12. The recess 11 is closed at its lower end and open at its upper end. The flange portion 12 is continuous with the upper end of the recess 11. The flange portion 12 protrudes in an annular shape from the upper end of the recess 11 in a plan view. More specifically, the flange portion 12 protrudes in a rectangular annular shape from the upper end of the recess 11 in a plan view.

[0013] The resin film 20 covers the inner wall surface of the recess 11 and the upper surface of the flange portion 12 that is continuous with the inner wall surface. The resin film 20 is softened by heating and placed so as to cover the inner wall surface of the recess 11 and the upper surface of the flange portion 12, and the blank 10 is sucked from the outer wall surface side, so that the resin film 20 is adhered closely to the blank 10.

[0014] Fig. 4 is a plan view of the blank 10 after assembly. As shown in Fig. 4, the recess 11 is composed of a side wall 11a and a bottom wall 11b. The bottom wall 11b is continuous with the lower end of the side wall 11a. The bottom wall 11b closes the lower end of the recess 11. The flange portion 12 is continuous with the upper end of the side wall 11a.

[0015] Fig. 5 is a plan view of the blank 10 before assembly. As shown in Fig. 5, the blank 10 has, for example, a bottom panel 13 and a plurality of side panels 14. In the example shown in Fig. 5, the number of side panels 14 is four. The bottom panel 13 is rectangular (square) in plan view. The direction parallel to the sides constituting the bottom panel 13 is the width direction, and the direction perpendicular to the width direction is the length direction.

[0016] The side panel 14 has one end and the other end in the second direction. One end of the side panel 14 is connected to a side that forms the outer periphery of the bottom panel 13. The side panel 14 has a first portion 14a and a second portion 14b in the second direction. The first portion 14a is located on the one end side of the side panel 14, and the second portion 14b is located on the other end side of the side panel 14. The first portion 14a and the second portion 14b are connected to each other.

[0017] The width of the first portion 14a in the width direction increases with increasing distance from the side that forms the outer periphery of the bottom panel 13 along the length direction. That is, the first portion 14a is trapezoidal in plan view. The width of the second portion 14b in the width direction increases with increasing distance from the first portion 14a along the length direction. That is, the second portion 14b is trapezoidal in plan view. When the blank 10 is assembled, the bottom panel 13 forms the bottom wall 11b, the first portions 14a of the side panels 14 form the side walls 11a, and the second portions 14b of the side panels 14 form the flange portions 12. The blank 10 is assembled by sandwiching the blank 10 before assembly between male and female molds that conform to the shape of the blank 10 after assembly.

[0018] The blank 10 is made of paper. The paper constituting the blank 10 has a surface 10a and a surface 10b (see FIG. 3). Surface 10b is the opposite surface to surface 10a. Surfaces 10a and 10b are end surfaces in the thickness direction of the paper constituting the blank 10. Surface 10a forms, for example, the inner wall surface of the recess 11 and the upper surface of the flange portion 12. At least one of surfaces 10a and 10b is coated with clay.

[0019] The arithmetic mean roughness (Ra) of the surface of the paper constituting the blank 10 is 0.2 μm or more and 3 μm or less. The arithmetic mean roughness of the surface of the paper constituting the blank 10 is preferably less than 1 μm. The arithmetic mean roughness of the surface of the paper constituting the blank 10 is measured on the surface 10a. The arithmetic mean roughness of the surface of the paper constituting the blank 10 is measured using a one-shot 3D shape measuring instrument VR-500 manufactured by Keyence, with reference to the method specified in JIS B 0601.

[0020] The basis weight of the paper constituting the blank 10 is 100 g / m 2 More than 500g / m 2 The basis weight of the paper constituting the blank 10 is preferably 190 g / m 2 More than 400g / m 2 It is more preferable that the number of layers of the paper constituting the blank 10 is 5 or more. It is preferable that the paper constituting the blank 10 contains a starch type as an interlayer strength agent.

[0021] Fig. 6 is a schematic cross-sectional view of the resin film 20. As shown in Fig. 6, the resin film 20 has a surface 20a and a surface 20b. The surface 20b is the surface opposite to the surface 20a. The surfaces 20a and 20b are end surfaces in the thickness direction of the resin film 20. The surface 20a is the surface that faces the blank 10 when the resin film 20 is attached to the blank 10.

[0022] The resin film 20 has an adhesive layer 21, a base layer 22, and a barrier layer 23. The adhesive layer 21 and the base layer 22 form a surface 20a and a surface 20b, respectively. The barrier layer 23 is disposed between the adhesive layer 21 and the base layer 22. An adhesive layer 24 is interposed between the adhesive layer 21 and the barrier layer 23 and between the base layer 22 and the barrier layer 23. The material of the adhesive layer 21 is, for example, any one of polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin, and polyethylene terephthalate. The material of the base layer 22 is, for example, any one of polyethylene, polypropylene, and polyethylene terephthalate. The material of the barrier layer 23 is, for example, any one of ethylene-vinyl alcohol copolymer resin and barrier nylon resin.

[0023] In a plan view, the resin film 20 has a first direction and a second direction. The second direction is a direction perpendicular to the first direction. The first direction is, for example, the MD direction of the resin film 20. The MD direction is a direction in which the resin film 20 is stretched during production. From another perspective, the second direction is, for example, the TD direction of the resin film 20.

[0024] The thermal expansion rate of the resin film 20 in the first direction and the thermal expansion rate of the resin film 20 in the second direction are defined as the first expansion rate and the second expansion rate, respectively. The thermal expansion rate of the resin film 20 is measured by the following method with reference to the method specified in JIS K 7133. First, the resin film 20 is heated at 90°C for 1 hour on a bisque plate placed in an oven. Second, the thermal expansion rate of the resin film 20 is calculated based on the formula 100 x (L-L0) / L0. Here, L is the dimension of the resin film 20 after the heating, and L0 is the dimension of the resin film 20 before the heating.

[0025] The first and second stretch rates are 2 percent or less. The first stretch rate is preferably different from the second stretch rate. The absolute value of the difference between the first and second stretch rates is preferably 1 percent or less. The first stretch rate is preferably greater than the second stretch rate. When the first stretch rate is greater than the second stretch rate, the first and second directions are preferably, for example, the MD direction and the TD direction, respectively. Note that when the first stretch rate is greater than the second stretch rate, the first and second directions may be the TD direction and the MD direction, respectively.

[0026] A first rate of change is a rate of mass change before and after peeling of a portion of the resin film 20 that covered the inner wall surface of the bottom portion (bottom wall 11b) of the recess 11 when the resin film 20 is peeled off from the blank 10. A second rate of change is a rate of mass change before and after peeling of a portion of the resin film 20 that covered the upper surface of the flange portion 12 when the resin film 20 is peeled off from the blank 10. Before heating in the microwave, the first rate of change and the second rate of change are preferably 0.1 percent or more and 1 percent or less.

[0027] The first rate of change and the second rate of change are measured by the following method. First, before being attached to the blank 10, the mass of the resin film 20 having the same dimensions as the test piece described later is measured in advance. Second, the resin film 20 is peeled off from the blank 10, and a test piece is cut out from the part that covered the inner wall surface of the bottom wall 11b and the part that covered the upper surface of the flange portion 12. Third, the mass of the test piece is measured, and the first rate of change and the second rate of change are calculated based on the formula 100×(g−g0) / g0. Here, g0 is the mass of the resin film 20 having the same size as the test piece measured in advance, and g is the mass of the test piece.

[0028] After heating in the microwave, the first rate of change and the second rate of change are preferably 0.1 percent or more and 1 percent or less. Heating in the microwave is performed by putting 200 g of water in the recess 11, covering the recess 11 with a lid material made of polyethylene terephthalate having an easy-peel material, and attaching the lid material to the flange portion 12 using the easy-peel material with a resin film 20 interposed therebetween. The microwave heating is performed at 600 W for 2 minutes.

[0029] (Effects of Tray 100) The effects of the tray 100 will be described below.

[0030] When the arithmetic mean roughness of the surface (surface 10a) of the paper constituting the blank 10 is increased, an anchoring effect is produced, which improves the adhesion between the blank 10 and the resin film 20. That is, by increasing the arithmetic mean roughness of the surface 10a, the resin film 20 is prevented from floating away from the blank 10. On the other hand, when the arithmetic mean roughness of the surface 10a is too large, the adhesion between the blank 10 and the resin film 20 is too high, which may cause difficulty in separating the resin film 20 from the blank 10.

[0031] The larger the thermal expansion rate of the resin film 20, the easier it is to peel off the resin film 20 from the blank 10, and therefore the easier it is to separate the resin film 20 from the blank 10. On the other hand, if the thermal expansion rate of the resin film 20 is too large, the resin film 20 will easily peel off from the blank 10, and there is a risk that the resin film 20 will float off the blank 10.

[0032] In the tray 100, the arithmetic mean roughness of the surface 10a is 0.2 μm or more and 3 μm or less, and the first and second expansion rates are 2 percent or less, so that the adhesion between the resin film 20 and the blank 10 is within an appropriate range. Therefore, the tray 100 makes it possible to achieve both easy separation of the resin film 20 and prevention of lifting.

[0033] (Example) In order to confirm the effect of the tray 100, Sample 1 to Sample 32 were prepared. In Sample 1 to Sample 32, the arithmetic mean roughness, the first expansion rate, and the second expansion rate on the surface 10a were changed. Details of Sample 1 to Sample 32 are shown in Tables 1 and 2. In Sample 1 to Sample 32, the first direction is the MD direction, and the second direction is the TD direction.

[0034] [Table 1]

[0035] [Table 2]

[0036] Samples 1 to 32 were evaluated for ease of separation and for resistance to floating. They were rated on a 5-point scale from 5 points to 1 point. A score of 5 indicates the highest ease of separation, and a score of 1 indicates the lowest ease of separation. The ease of separation was evaluated before and after heating in the microwave.

[0037] The anti-floating property was evaluated based on the degree of floating during molding and the degree of floating during transportation. The degree of floating during molding was rated as 5 points if no floating was observed, 4 points if almost no floating was observed, 3 points if some floating was observed at the corners of the tray but did not affect practical use, 2 points if some floating was observed at the edges of the tray but did not affect practical use, and 1 point if significant floating was observed at the edges of the tray and did not affect practical use. The degree of floating during transportation was rated as 3 points if no floating was observed, 2 points if some floating was observed but did not affect practical use, and 1 point if floating was observed that caused practical problems.

[0038] The degree of floating during transportation was evaluated after a vibration test was conducted with reference to JIS Z 0200. In order to simulate the conditions during transportation, 200 g of water was poured into the recess 11, and then the recess 11 was covered with a lid material made of polyethylene terephthalate having an easy-peel material, and the lid material was attached to the flange portion 12 using the easy-peel material with a resin film 20 interposed therebetween.

[0039] Condition 1 is that the arithmetic mean roughness on the surface 10a is 0.2 μm or more and 3 μm or more. Condition 2 is that the first and second stretch rates are 2 percent or less. As shown in Tables 1 and 2, both Condition 1 and Condition 2 were satisfied in Samples 1 to 28. Either Condition 1 or Condition 2 was not satisfied in Samples 29 to 32. In the samples that satisfied Condition 1, the evaluation of the ease of separation was good, with a score of 2 or more. In the samples that satisfied Condition 2, the degree of floating during molding and the degree of floating during transportation were 2 or more, and the evaluation of the float prevention was good. From these comparisons, it was experimentally clarified that the ease of separation and float prevention of the resin film 20 were compatible when both Condition 1 and Condition 2 were satisfied.

[0040] Condition 3 is that the arithmetic mean roughness of surface 10a is less than 1 μm. In samples that further satisfy condition 3, the ease of separation was evaluated as 4 points or more even after heating in a microwave. In samples that satisfy condition 1 but do not satisfy condition 3, the ease of separation was evaluated as 1 point after heating in a microwave. From this comparison, it was experimentally revealed that the ease of separation is maintained even after heating in a microwave by further satisfying condition 3.

[0041] Condition 4 is that the absolute value of the difference between the first and second stretch rates is 1 percent or less. In samples in which condition 4 was further satisfied, the degree of molding lift was 4 points or more. On the other hand, in samples that satisfied condition 2 but did not satisfy condition 4, the degree of molding lift was evaluated as 3 points or less. From this comparison, it was experimentally revealed that the lifting of resin film 20 is further suppressed by further satisfying condition 4.

[0042] Samples 1 and 2, Sample 4 and 19, Sample 6 and 20, Sample 11 and 21, and Sample 14 and 23 have the same configuration, except that the first expansion rate (heat expansion rate in the MD direction) is larger than the second expansion rate (heat expansion rate in the TD direction). In these paired samples, when the first expansion rate is larger than the second expansion rate, the ease of separation is equal to or greater than that when the second expansion rate is larger than the first expansion rate. From this comparison, it was experimentally clarified that the ease of separation is further improved by the first direction and the second direction corresponding to the MD direction and the TD direction, respectively, and by the first expansion rate being larger than the second expansion rate.

[0043] (Additional Note) The above embodiment includes the following configurations.

[0044] <Appendix 1> Paper blanks and A resin film, The blank has a recess and a flange portion, The flange portion protrudes in an annular shape in a plan view from an upper end of the recess, the resin film covers an inner wall surface of the recess and an upper surface of the flange portion connected to the inner wall surface, The arithmetic mean roughness of the surface of the paper is 0.2 μm or more and 3 μm or less, A tray, wherein a first expansion rate, which is a thermal expansion rate of the resin film in a first direction, and a second expansion rate, which is a thermal expansion rate of the resin film in a second direction perpendicular to the first direction, are 2 percent or less.

[0045] <Appendix 2> 2. The tray of claim 1, wherein the arithmetic mean roughness is less than 1 μm.

[0046] <Appendix 3> 3. The tray of claim 1 or 2, wherein the first stretch rate is different from the second stretch rate.

[0047] <Appendix 4> 4. The tray of any one of claims 1 to 3, wherein an absolute value of the difference between the first and second stretch rates is 1 percent or less.

[0048] <Appendix 5> The first stretch rate is greater than the second stretch rate, The tray according to any one of claims 1 to 4, wherein the first direction and the second direction are the MD direction and the TD direction of the resin film, respectively.

[0049] <Appendix 6> The basis weight of the paper is 100 g / m 2 More than 500g / m 2 6. The tray of claim 1, wherein:

[0050] <Appendix 7> The basis weight of the paper is 190 g / m 2 More than 400g / m 2 7. The tray of claim 1, wherein:

[0051] <Appendix 8> the paper has a first surface and a second surface opposite the first surface; 8. The tray of any one of claims 1 to 7, wherein at least one of the first surface and the second surface is coated with a clay coating.

[0052] <Appendix 9> The resin film has a third surface facing the blank and a fourth surface opposite the third surface, 9. The tray of any one of claims 1 to 8, wherein the resin film has an adhesive layer forming the third surface, a base layer forming the fourth surface, and a barrier layer between the adhesive layer and the base layer.

[0053] <Appendix 10> The adhesive layer is made of any one of polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin, and polyethylene terephthalate. The base layer is made of any one of polyethylene, polypropylene, and polyethylene terephthalate. The tray according to claim 9, wherein the barrier layer is made of an ethylene-vinyl alcohol copolymer resin and a barrier nylon resin.

[0054] <Appendix 11> A tray as described in any one of Appendix 1 to Appendix 10, wherein when the resin film is peeled off from the blank, the mass change rate of the portion of the resin film covering the inner wall surface at the bottom of the recess and the portion of the resin film covering the top surface before and after peeling is 0.1 percent or more and 1 percent or less.

[0055] Although the embodiment of the present invention has been described above, the above embodiment can be modified in various ways. The scope of the present invention is not limited to the above embodiment. The scope of the present invention is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0056] 10 blank, 10a, 10b surface, 11 recess, 11a side wall, 11b bottom wall, 12 flange portion, 13 bottom panel, 14 side panel, 14a first portion, 14b second portion, 20 resin film, 20a, 20b surface, 21 adhesive layer, 22 base layer, 23 barrier layer, 24 adhesive layer, 100 tray.

Claims

1. Paper blanks and A resin film, The blank has a recess and a flange portion, The flange portion protrudes in an annular shape in a plan view from an upper end of the recess, the resin film covers an inner wall surface of the recess and an upper surface of the flange portion connected to the inner wall surface, The arithmetic mean roughness of the surface of the paper is 0.2 μm or more and 3 μm or less, A tray, wherein a first expansion / contraction rate, which is the thermal expansion / contraction rate of the resin film in a first direction, and a second expansion / contraction rate, which is the thermal expansion / contraction rate of the resin film in a second direction perpendicular to the first direction, are 2 percent or less.

2. 2. The tray of claim 1, wherein the arithmetic mean roughness is less than 1 μm.

3. The tray of claim 1 , wherein the first rate of expansion is different from the second rate of expansion.

4. 4. The tray of claim 3, wherein an absolute value of a difference between the first and second stretch rates is 1 percent or less.

5. The first stretch rate is greater than the second stretch rate, The tray according to claim 3 , wherein the first direction and the second direction are the MD direction and the TD direction of the resin film, respectively.

6. The basis weight of the paper is 100 g / m ２ More than 500g / m ２ 2. The tray of claim 1, wherein:

7. The basis weight of the paper is 190 g / m ２ More than 400g / m ２ 2. The tray of claim 1, wherein:

8. the paper has a first surface and a second surface opposite the first surface; 2. The tray of claim 1, wherein at least one of the first surface and the second surface is coated with a clay coating.

9. The resin film has a third surface facing the blank and a fourth surface opposite the third surface, 2. The tray of claim 1, wherein the resin film has an adhesive layer on the third surface, a base layer on the fourth surface, and a barrier layer between the adhesive layer and the base layer.

10. The adhesive layer is made of any one of polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin, and polyethylene terephthalate. The base layer is made of any one of polyethylene, polypropylene, and polyethylene terephthalate.

10. The tray according to claim 9, wherein the barrier layer is made of an ethylene-vinyl alcohol copolymer resin and a barrier nylon resin.

11. A tray as described in any one of claims 1 to 10, wherein when the resin film is peeled off from the blank, the mass change rate of the portion of the resin film covering the inner wall surface at the bottom of the recess and the portion of the resin film covering the top surface before and after peeling is 0.1 percent or more and 1 percent or less.

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