Laminated film, packaging bag, lid, food packaging container, and packaged food

Abstract

To provide a laminated sheet excellent in durability.SOLUTION: The laminated sheet 10 includes a paper base material 3 and a heat seal layer 1, and the elongation when the tensile stress in the MD of the laminated sheet 10 becomes maximum and the elongation when the tensile stress in the TD of the laminated sheet 10 becomes maximum are both 8% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminated sheet, a packaging bag, a lid, a food packaging container, and a packaged food. [Background technology]

[0002] In addition to changes in household structure and lifestyles due to the recent trend toward nuclear families, advances in distribution, freezing, and refrigeration technologies have led to an increase in demand for cooked or processed chilled and frozen foods sold at convenience stores, supermarkets, etc. At the same time, demand for packaging containers for chilled and frozen foods is also increasing.

[0003] Meanwhile, as efforts to reduce plastic waste continue, there is growing demand for food packaging containers that use paper as a base material, a renewable resource with a low environmental impact. There is also a demand for packaging containers made of paper that use paper as a base material for packaging containers that hold chilled and frozen foods.

[0004] For example, Patent Document 1 discloses a food packaging material in which two gas barrier layers using ethylene-modified polyvinyl alcohol resin are laminated on a paper substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-184138 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a laminate sheet having excellent durability. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a laminated sheet including a paper substrate and a heat seal layer, The laminate sheet is provided such that the elongation when the tensile stress in MD of the laminate sheet is at its maximum and the elongation when the tensile stress in TD of the laminate sheet is at its maximum are both 8% or more.

[0008] According to another aspect of the present invention, there is provided a laminate sheet according to the above aspect, wherein the puncture strength from the heat seal layer side and the puncture strength from the side opposite to the heat seal layer are both 7.5 N or more.

[0009] According to yet another aspect of the present invention, there is provided a laminate sheet according to any one of the above aspects, wherein the tensile strength in MD is 80 N / 15 mm or more and the tensile strength in TD is 35 N / 15 mm or more.

[0010] According to yet another aspect of the present invention, there is provided a laminate sheet according to any one of the above aspects, further comprising a support layer between the heat seal layer and the paper substrate.

[0011] According to yet another aspect of the present invention, there is provided the laminate sheet according to the above aspect, wherein the support layer contains polyamide.

[0012] According to yet another aspect of the present invention, there is provided a laminate sheet according to any one of the above aspects, further comprising a gas barrier layer between the paper substrate and the heat seal layer.

[0013] According to yet another aspect of the present invention, there is provided a laminate sheet according to any of the above aspects, further comprising a support layer facing the heat seal layer with the paper substrate sandwiched therebetween.

[0014] According to yet another aspect of the present invention, there is provided a laminate sheet according to any one of the above aspects, further comprising a print layer facing the heat seal layer with the paper substrate sandwiched therebetween.

[0015] According to yet another aspect of the present invention, there is provided a laminate sheet according to any of the above aspects, further comprising a water-resistant functional layer facing the heat seal layer with the paper substrate sandwiched therebetween.

[0016] According to yet another aspect of the present invention, there is provided a laminate sheet according to any of the above aspects, in which, when the layers other than the paper base material contained in the laminate sheet are classified into layers made of plastic and other layers, the mass of the paper base material is greater than the total mass of the layers made of plastic and the total mass of the other layers.

[0017] According to yet another aspect of the present invention, there is provided a laminate sheet according to any of the above aspects, wherein the tensile strength of the paper substrate in MD is 70 N / 15 mm or more, the tensile strength of the paper substrate in TD is 35 N / 15 mm or more, and the tensile breaking elongation of the paper substrate in MD and the tensile breaking elongation of the paper substrate in TD are both 7% or more.

[0018] According to yet another aspect of the present invention, there is provided a laminate sheet according to any of the above aspects, wherein the paper substrate is stretched paper.

[0019] According to yet another aspect of the present invention, there is provided a laminate sheet according to any of the above aspects, wherein the heat seal layer comprises a polyolefin.

[0020] According to yet another aspect of the present invention, there is provided a laminate sheet according to any one of the above aspects, wherein the heat seal layer is formed by coating a heat seal varnish which is a water-based emulsion.

[0021] According to yet another aspect of the present invention, there is provided a laminate sheet according to the above aspect, wherein the glass transition temperature of the solid content of the heat seal varnish is in the range of -40°C or higher and -10°C or lower, and the melting point of the solid content of the heat seal varnish is in the range of 40°C or higher and 100°C or lower.

[0022] According to yet another aspect of the present invention, there is provided a packaging bag made of the laminate sheet according to any one of the above aspects.

[0023] According to yet another aspect of the present invention, there is provided a lid made of the laminate sheet according to any one of the above aspects.

[0024] According to yet another aspect of the present invention, there is provided a food packaging container comprising a container body having an opening and a lid body relating to the above-mentioned side that covers the opening, wherein the heat seal layer is disposed between the paper base material and the internal space of the food packaging container.

[0025] According to yet another aspect of the present invention, there is provided a food packaging container according to the above aspect, wherein the container body has a flange around the opening, and the lid body is heat-sealed to the flange via the heat-seal layer.

[0026] According to yet another aspect of the present invention, there is provided a food packaging container according to any of the above aspects, wherein the internal space of the food packaging container is filled with a mixed gas containing oxygen gas, nitrogen gas, and carbon dioxide gas.

[0027] According to yet another aspect of the present invention, there is provided a food packaging container according to any one of the above aspects, wherein the food packaging container is a packaging container for chilled food or a packaging container for frozen food.

[0028] According to yet another aspect of the present invention, there is provided a packaged food product comprising the food packaging container according to any one of the above aspects and food contained in the food packaging container. [Effects of the Invention]

[0029] According to the present invention, a laminated sheet having excellent durability is provided. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a partial cross-sectional view schematically showing an example of a laminate sheet according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a partial cross-sectional view schematically showing an example of a laminate sheet according to a modified example. [Figure 3] FIG. 10 is a cross-sectional view schematically showing a food packaging container according to a fourth embodiment of the present invention. [Figure 4] Graph showing the relationship between load and elongation. [Figure 5] Graph showing the relationship between load and elongation. [Figure 6] Graph showing the relationship between load and elongation. [Figure 7] Graph showing the relationship between puncture strength and needle movement. [Figure 8] Graph showing puncture strength. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are more specific embodiments of any of the above aspects. The following items can be incorporated into each of the above aspects, either singly or in combination.

[0032] Furthermore, the embodiments shown below are merely examples of configurations for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not limited by the materials, shapes, structures, etc. of the components described below. Various modifications can be made to the technical idea of ​​the present invention within the technical scope defined by the claims.

[0033] In the drawings, elements having the same or similar functions are denoted by the same reference numerals, and redundant explanations will be omitted. Furthermore, the drawings are schematic, and the relationship between dimensions in one direction and dimensions in another direction, and the relationship between the dimensions of one member and the dimensions of another member, etc. may differ from the actual relationship.

[0034] [First embodiment] FIG. 1 is a partial cross-sectional view schematically showing an example of a laminate sheet according to a first embodiment of the present invention.

[0035] In one example, the laminated sheet 10 shown in FIG. 1 is used as a lid in a food packaging container that includes a container body with an opening and a lid that covers the opening. That is, in this example, the laminated sheet 10 is a lid material that is used either as the lid itself or a portion cut out from the laminated sheet 10 is used as the lid. As will be described later, packaged foods that include a lid made of the laminated sheet 10 are less likely to suffer damage to the lid during transportation. In this disclosure, "during transportation" refers to the time when the packaged food is being transported. Packaged foods will be described later.

[0036] In another example, the laminate sheet 10 is used as a food packaging bag. The packaging bag may be a known bag such as a palm-shaped bag, a three-sided bag, a two-sided bag, a standing pouch, or a gusset bag. Packaged foods that are provided with a packaging bag made of the laminate sheet 10 as a food packaging bag are also less likely to be damaged during transportation. As such, the laminate sheet 10 has excellent durability.

[0037] The laminate sheet 10 includes a heat seal layer 1 and a paper substrate 3. Because this laminate sheet 10 does not include a gas barrier layer, which will be described later, it is suitable for applications that do not require high gas barrier properties. Furthermore, because this laminate sheet 10 does not include a support layer, which will be described later, it is suitable as a flexible packaging material. Each layer included in the laminate sheet 10 will be described below. Of the two main surfaces of the laminate sheet 10, the main surface on the heat seal layer 1 side will be referred to as the bottom surface, and the main surface opposite the heat seal layer 1 will be referred to as the top surface.

[0038] (Paper base material) The laminate sheet 10 includes a paper base material 3. The mass of the paper base material 3 is preferably greater than the mass of any other layer included in the laminate sheet 10. The mass of the paper base material 3 in the mass of the laminate sheet 10 is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. In one example, this proportion is 98% or less. The larger this proportion, the smaller the environmental impact of the laminate sheet 10.

[0039] When the layers other than the paper base material 3 contained in the laminate sheet 10 are classified into layers made of plastic and other layers, it is preferable that the mass of the paper base material 3 is larger than the total mass of the layers made of plastic and the total mass of the other layers. In this case, in Japan, the laminate sheet 10 can be treated as paper under the Containers and Packaging Recycling Act.

[0040] The above classification follows the "Container and Packaging Recycling Law Explanatory Materials." In other words, "plastic" is a material that contains polymers as an essential component and is shaped and manufactured using fluidity during processing. Paints and adhesives are not included in plastics because they are unrelated to the concept of "shaping." Therefore, in the example shown in Figure 1, the heat seal layer 1 is a "layer made of plastic." In the example shown in Figure 2, the support layer 2 is a "layer made of plastic," and the printing layer 4 formed from ink, the functional layer 5 formed by coating, and the adhesive layer (not shown) made of adhesive are "other layers." The laminated sheet shown in Figure 2 will be discussed later.

[0041] As the paper substrate 3, it is preferable to use paper having the following tensile properties (i) to (iv). (i) The tensile strength in MD is 70N / 15mm or more. (ii) The tensile force at TD is 35 N / 15 mm or more. (iii) The tensile elongation at break in the MD is 7% or more. (iv) The tensile elongation at break in the TD is 7% or more.

[0042] In this specification, MD is an abbreviation for machine direction, and TD is an abbreviation for transverse direction. In the paper substrate 3, most of the paper fibers are oriented in the MD. In the laminated sheet, the MD of the paper substrate is aligned with the MD of the laminated sheet.

[0043] The tensile strength of the paper base material 3 in the MD is more preferably 80N / 15mm or more. The tensile strength of the paper base material 3 in the MD is, for example, 120N / 15mm or less. The tensile strength of the paper base material 3 in the TD is more preferably 40N / 15mm or more. The tensile strength of the paper base material 3 in the TD is, for example, 60N / 15mm or less.

[0044] The tensile breaking elongation in MD of the paper base material 3 is more preferably 10% or more. The tensile breaking elongation in MD of the paper base material 3 is, for example, 20% or less. The tensile breaking elongation in TD of the paper base material 3 is more preferably 10% or more. The tensile breaking elongation in TD of the paper base material 3 is, for example, 20% or less.

[0045] Here, the tensile strength and tensile elongation at break are measured using the measurement methods specified in JIS Z1707:2019 "General Rules for Food Packaging Plastic Films." In these measurements, the test specimen width is 15 mm, the length is 100 mm, the gauge length is 50 mm, and the test speed is 300 mm / min. The tensile strength is the maximum force (N) when the test specimen is pulled until it breaks, converted into the force equivalent to a 15 mm width of the test specimen (N / 15 mm).

[0046] It should be noted that JIS Z1707:2019 describes a measurement method specified for plastic films, but in this specification, this measurement method is applied to the paper base material 3 and the laminate sheet.

[0047] An example of a paper substrate 3 having the above tensile properties (i) to (iv) is Clupak paper. Clupak paper not only has excellent tensile elongation at break, but also high tensile strength. Therefore, Clupak paper has high puncture strength. Tensile strength will be described later.

[0048] It is preferable to use stretched paper as the paper substrate 3. Stretched paper is paper with excellent elongation and fine wrinkles on its surface. Stretched paper is, for example, stretched kraft paper. Stretched kraft paper is kraft paper that has excellent impact resistance and stretchability due to minute shrinkage of the paper on a paper machine, as described in JIS P0001:1998. Stretched kraft paper is, for example, Kraft Paper Type 5 No. 1 or No. 2 described in JIS P3401:2000. Kraft Paper Type 5 No. 1 is kraft stretched paper that has been given MD (machine direction) stretchability by minute shrinkage of the paper on a paper machine. Kraft Paper Type 5 No. 2 is kraft stretched paper that has been given TD (transverse direction) stretchability by minute shrinkage of the paper on a paper machine. The stretched kraft paper may be made of unbleached kraft pulp or bleached kraft pulp.

[0049] Thus, the stretched paper may be stretched paper in which stretchability is imparted in the MD (machine direction) by creasing the paper in the MD, or stretched paper in which stretchability is imparted in the TD (transverse direction) by creasing the paper in the TD. Clupak paper is known as an example of the former stretched paper. Clupak paper is included in the category of kraft stretched paper. Fracto paper is known as an example of the latter stretched paper. Fracto paper is included in the category of kraft stretched paper. Alternatively, the stretched paper may be stretched paper in which stretchability is imparted in both the MD and TD by creasing the paper in both the MD and TD.

[0050] A paper substrate 3 or stretched paper having the tensile properties (i) to (iv) above can have excellent puncture strength. The puncture strength here is preferably 6.0 N or more, more preferably 7.0 N or more, and even more preferably 8.0 N or more. The puncture strength here is, for example, 10.0 N or less. The method for measuring puncture strength will be described later.

[0051] The thickness of the paper substrate 3 is preferably in the range of 50 μm to 200 μm, and more preferably in the range of 50 μm to 150 μm.

[0052] The basis weight of the paper substrate 3, i.e., the mass per area, is 50 g / m 2 More than 100g / m 2 It is preferable that the thickness is within the range of 60 g / m 2 More than 90g / m 2 It is more preferable that it is within the following range:

[0053] When the laminate sheet 10 is used as a lid, increasing the basis weight or thickness of the paper substrate 3 results in a hard lid and reduced ease of opening. Reducing the basis weight or thickness of the paper substrate 3 reduces the strength of the lid, making it more likely to tear when opened. Furthermore, when the laminate sheet includes a support layer, a lid made of such a laminate sheet has high strength, but if the support layer is too thick, it places a heavy burden on the environment. Furthermore, increasing the strength of the lid by thickening the paper substrate 3 may result in the lid being too rigid, which may reduce ease of opening. Thus, there is a trade-off between the strength of the lid, reduced environmental impact, and ease of opening. To achieve reduced environmental impact, high strength, and high ease of opening, it is preferable that the thickness or basis weight of the paper substrate 3 be within the above-mentioned range. The support layer will be described later.

[0054] Increasing the basis weight of the paper base material 3 also increases the proportion of the mass of the paper base material 3 in the mass of the laminated sheet 10. However, increasing the basis weight of the paper base material 3 increases the amount of carbon dioxide emissions associated with the manufacture of the paper base material 3 and the disposal of the laminated sheet 10.

[0055] (heat seal layer) The heat seal layer 1 enables, for example, heat sealing of a lid 21 to a container body 22 of a food packaging container 20 shown in FIG. 3 (described later), thereby sealing the container. The heat seal layer 1 may be made of, for example, a film made of ethylene-vinyl acetate (EVA), an ionomer resin, or other polyolefins. The heat seal layer 1 preferably contains a polyolefin. Examples of polyolefins include linear low density polyethylene (LLDPE), very low density linear polyethylene (VLDPE), or polypropylene.

[0056] The heat seal layer 1 shown in FIG. 1 is a sealant layer (also called an easy-peel sealant) with an easy-peel function. Easy-peel properties refer to excellent removability and ease of opening. The sealant layer is, for example, a laminate having an easy-peel layer with easy-open properties and a support layer. The main surface of the sealant layer facing the paper substrate 3 may be corona-treated. Methods for bonding such a heat seal layer 1 by lamination or the like include dry lamination using a solvent-based adhesive, non-solvent lamination using a solventless adhesive, and sand lamination using a molten resin as an adhesive. Furthermore, extrusion lamination can also be used when the heat seal layer is extruded with a molten resin.

[0057] The heat seal layer 1 does not have to be an easy-peel sealant. Another example of the heat seal layer 1 is a coating of heat seal varnish. Various coating methods, such as gravure coating, die coating, blade coating, knife coating, and bar coating, can be used to apply the heat seal varnish. When heat seal varnish is used, adhesives can be omitted, thereby reducing the environmental impact. Furthermore, in this case, the thickness of the heat seal layer 1 can be reduced compared to when the heat seal layer 1 is formed by lamination. In this case, the proportion of the mass of the paper substrate 3 in the mass of the laminate sheet 10 can be increased.

[0058] The heat seal varnish is preferably an aqueous emulsion. The glass transition temperature of the solid content of the heat seal varnish is preferably in the range of -40°C to -10°C. The melting point of the solid content of the heat seal varnish is preferably in the range of 40°C to 100°C. The glass transition temperature refers to a value measured using a DSC (differential scanning calorimeter) in accordance with JIS K7271:2012. When the solid content of the heat seal varnish has a glass transition temperature and a melting point within the above-mentioned temperature ranges, the heat seal layer 1 formed from such a heat seal varnish can exhibit excellent heat sealing performance even in packaging containers for chilled or frozen foods.

[0059] The thickness of the heat seal layer 1 is not particularly limited. The thickness of the heat seal layer 1 is preferably 60 μm or less, more preferably 35 μm or less, and even more preferably 30 μm or less. The thickness of the heat seal layer 1 is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 1.5 μm or more. The thickness of the heat seal layer 1 is preferably in the range of 0.5 μm to 60 μm, and more preferably 1 μm to 30 μm.

[0060] The peelability of the heat seal layer 1 can be adjusted depending on, for example, the peel mechanism of the heat seal layer 1 or the heat seal strength of the heat seal layer 1. The peel mechanism is, for example, interfacial peeling, cohesive failure, or interlayer peeling.

[0061] (Laminated sheet) The laminate sheet has an elongation of 8% or more when the tensile stress in MD is at its maximum. This elongation is preferably 10% or more. This elongation is, for example, 15% or less.

[0062] The laminate sheet also has an elongation of 8% or more when the tensile stress in the TD reaches a maximum, and this elongation is preferably 10% or more, and is, for example, 20% or less.

[0063] The "elongation at maximum tensile stress" is the elongation at the maximum force when the test piece is pulled until it breaks. This elongation can be obtained by the same method as the above-mentioned method for measuring the tensile elongation at break.

[0064] The laminate sheet preferably has a tensile strength in MD of 80 N / 15 mm or more and a tensile strength in TD of 35 N / 15 mm or more. The tensile strength in MD of the laminate sheet is more preferably 90 N / 15 mm or more. The tensile strength in MD of the laminate sheet is, for example, 140 N / 15 mm or less. The tensile strength in TD of the laminate sheet is more preferably 40 N / 15 mm or more. The tensile strength in TD of the laminate sheet is, for example, 110 N / 15 mm or less. The "tensile strength" of the laminate sheet is also obtained by the same method as the method for measuring the tensile strength of the paper base material 3.

[0065] The puncture strength from the upper surface side of the laminated sheet is preferably 7.5 N or more, and more preferably 10 N or more. This puncture strength is, for example, 20 N or less.

[0066] The puncture strength of the laminate sheet from the lower surface side is preferably 7.5 N or more, and more preferably 10 N or more. This puncture strength is, for example, 20 N or less.

[0067] Here, the "puncture strength" of the laminate sheet or lid is a value measured according to the method specified in JIS Z1707:2019 "General Rules for Food Packaging Plastic Films." The puncture strength is measured when a needle is pierced from the side of the heat seal layer 1, and when the needle is pierced from the side opposite the heat seal layer 1. Specifically, a needle with a diameter of 1 mm and a semicircular tip is pierced from the top or bottom side of the laminate sheet or lid at a speed of 50 mm / min, and the maximum force required for the needle to penetrate is measured. This measurement is performed multiple times, and the arithmetic average of the maximum forces is taken as the puncture strength.

[0068] Although the laminated sheet 10 described above contains paper, it is possible to achieve excellent durability. Furthermore, a lid made of the laminated sheet 10 described above is less likely to peel off the paper. Paper peeling will be described later.

[0069] [Variations] The laminate sheet can be modified in various ways. For example, the laminate sheet may further include one or more of a printed layer, a water-resistant functional layer, and a support layer. A modified laminate sheet further including a printed layer, a water-resistant functional layer, and a support layer will be described below with reference to FIG. 2. The matters described with reference to FIG. 1 can be applied singly or in combination to the laminate sheet according to the modified example described herein.

[0070] FIG. 2 is a partial cross-sectional view schematically showing a laminated sheet according to one modified example. The laminate sheet 11 shown in Fig. 2 includes, in this order, a heat seal layer 1, a support layer 2, a paper substrate 3, a printed layer 4, and a water-resistant functional layer (water-resistant layer) 5. The laminate sheet 11 is similar to the laminate sheet 10 described with reference to Fig. 1 except that it further includes, in this order from the paper substrate 3 side, a printed layer 4 and a water-resistant functional layer 5 on the side of the paper substrate 3 opposite to the side having the heat seal layer 1, and further includes a support layer 2 between the paper substrate 3 and the heat seal layer 1.

[0071] (Printing layer) The printed layer 4 is a layer formed to prepare the laminate sheet 11, packaging bag, or lid for practical use as a commercial product. The printed layer 4 is a layer formed of ink containing additives such as various pigments, extender pigments, plasticizers, desiccants, and stabilizers added to a conventionally used ink binder resin, such as urethane, acrylic, nitrocellulose, rubber, or vinyl chloride, and displays patterns such as letters and pictures. The printed layer 4 can be formed by known printing methods such as offset printing, gravure printing, and silkscreen printing, or known coating methods such as roll coating, knife-edge coating, and gravure coating.

[0072] The thickness of the printed layer 4 is not particularly limited, and may be, for example, in the range of 0.1 μm to 5 μm, or in the range of 0.2 μm to 1 μm. In addition, the printed layer 4 may be omitted.

[0073] (Water-resistant functional layer) The water-resistant functional layer (water-resistant layer) 5 is a layer that, in packaged foods described below, prevents liquids outside the container, such as water due to condensation or oil, from penetrating the lid and prevents these liquids from reaching layers such as the printed layer 4 and the paper base material 3. By preventing liquids outside the container from reaching layers such as the printed layer 4 and the paper base material 3, the functional layer 5 prevents, for example, deterioration, destruction, or a decrease in adhesion of these layers.

[0074] According to one example, the functional layer 5 is formed on the printing layer 4 to control the water absorbency of the partial laminate sheet, which is the portion of the laminate sheet 10 from the functional layer 5 to the paper substrate 3. The functional layer 5 controls the water absorbency of the laminate sheet by the Cobb method described below to 20 g / m 2 It is preferable that the material has the following water resistance.

[0075] Here, the water absorbency is the water absorbency obtained by the method specified in JIS P8140:1998 "Paper and paperboard - Water absorbency test method - Cobb method" when the measurement surface is the surface of the functional layer 5 and the contact time between the test piece and water is 300 seconds. This water absorbency is 20 g / m as described above. 2 Preferably, it is 10 g / m or less. 2 More preferably, it is 5 g / m or less. 2 The lower limit of the water absorbency is ideally 0 g / m 2 According to one example, this water absorption is 1 g / m 2 That's all.

[0076] The functional layer 5 is preferably an overprint varnish layer (hereinafter referred to as "OP varnish layer").

[0077] According to one example, the functional layer 5 contains a water-resistant resin. Any resin capable of achieving the above-mentioned water absorbency can be used without limitation as the water-resistant resin. Examples of water-resistant resins that can be used include polyolefin-based resins such as polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, and vinyl chloride-vinyl acetate copolymers, silicone-based resins, acrylic resins, epoxy-based resins, polyester-based resins, cellulose-based resins, and urethane-based resins. The functional layer 5 can be obtained, for example, by applying a paint containing the water-resistant resin to the paper substrate 3 on which the printing layer 4 has been formed, using a known method. In addition to the water-resistant resin, the paint may further contain additives such as pigments, dyes, curing agents, leveling agents, antiblocking agents, and lubricants, as well as solvents.

[0078] The functional layer 5 preferably has high abrasion resistance and scratch resistance so as to maintain sufficient water resistance. From this perspective, the thickness of the functional layer 5 and the amount of paint applied, which is its material, are preferably greater than the thickness and amount of paint applied of a typical OP varnish layer. Here, the "amount applied" refers to the solid mass per area.

[0079] For example, in the laminated sheet 11 shown in FIG. 2, the coating amount of the paint for forming the functional layer 5 is 0.2 g / m 2 It is preferable to coat the coating amount so that it is 2.0 g / m or more. 2 It is more preferable to apply the coating material so that the coating amount is 10 g / m or more. 2 The functional layer 5 is coated so as to have the following thickness. The thickness of the functional layer 5 is preferably 0.2 μm or more, and more preferably 2.0 μm or more. The thickness of the functional layer 5 is, for example, 10 μm or less. The functional layer 5 may be provided on the printing layer 4 by lamination. The functional layer 5 may also be omitted.

[0080] (Support layer) The support layer 2 improves the strength of the laminated sheet 11 . Examples of the support layer 2 include unstretched or biaxially stretched films such as ethylene-vinyl alcohol copolymer film, nylon film, PET (polyethylene terephthalate) film, PAN (polyacrylonitrile) film, PBT (polybutylene terephthalate) film, and PMP (polymethylpentene), but are not limited to these and may also include films made of polyvinyl alcohol resin, olefin resin, unsaturated polyester resin, etc.

[0081] The support layer 2 preferably contains at least one of polybutylene terephthalate and polyamide, and more preferably contains polyamide. For example, the support layer 2 is a layer made of polybutylene terephthalate or a layer made of polyamide.

[0082] In a support layer 2 containing polyamide, hydrogen bonds are formed between adjacent polyamide molecules at the amide bond positions. This gives the molecules that make up the support layer 2 containing polyamide a high cohesion. Therefore, the support layer 2 containing polyamide is resistant to tearing even when pierced with a needle, and is therefore stretchable. Therefore, the support layer 2 containing polyamide has particularly high puncture strength.

[0083] The polyamide, for example, contains an aliphatic backbone. The polyamide is, for example, nylon, such as nylon 6, nylon 66, nylon 612, nylon 11, nylon 12, and nylon 46. In one example, the polyamide is nylon 6 or nylon 66. Nylon does not contain a structure with low elasticity, such as a benzene ring, and therefore is difficult to tear even when pierced with a needle, and is therefore particularly stretchable.

[0084] The support layer 2 may further contain additives such as a curing agent, a filler, an antiblocking agent, an antistatic agent, etc. Materials that are cured by irradiation with active energy rays such as ultraviolet rays and electron beams may also be used as the material for the support layer 2.

[0085] The support layer 2 is preferably a stretched film. When a stretched film is used, it is preferable to use a biaxially stretched film. This is because biaxial stretching reduces the variation in physical properties such as breaking strength in the in-plane direction of the film compared to uniaxial stretching. The biaxially stretched film may be a simultaneous biaxially stretched film or a sequentially biaxially stretched film. It is preferable that the support layer 2 has anisotropy. Sequential biaxial stretching can achieve higher anisotropy than simultaneous biaxial stretching, so it is preferable to use a sequentially biaxially stretched film as the support layer 2.

[0086] The thickness of the support layer 2 is preferably 20 μm or less, more preferably 17 μm or less, and even more preferably 16 μm or less. The thickness of the support layer 2 is preferably 4 μm or more, more preferably 10 μm or more, and even more preferably 12 μm or more. The thickness of the support layer 2 is preferably in the range of 4 μm to 20 μm, and more preferably 10 μm to 16 μm.

[0087] Increasing the thickness of the support layer 2 makes it easier to increase the durability of the laminate sheet 11, but makes it difficult to increase the proportion of the mass of the paper base material 3 in the mass of the laminate sheet 11. In addition, in this case, the environmental load is likely to increase.

[0088] If the support layer 2 is too thin, the support layer 2 is prone to breakage. In this case, when a packaged food provided with a lid made of a laminated sheet 11 including such a support layer 2 is opened, the lid may break and part of the lid may remain in the container body.

[0089] The breaking strength of the support layer 2 is preferably greater than the heat seal strength between the lid and the container body. Here, "the breaking strength of the support layer 2 is greater than the heat seal strength between the lid and the container body" means that the breaking strength of the support layer is greater than the heat seal strength between the lid and the container body in the MD of the lid, and that the breaking strength of the support layer is greater than the heat seal strength between the lid and the container body in the TD of the lid.

[0090] The breaking strength of the support layer 2 is obtained by the measurement method specified in JIS Z1707:2019 "General rules for plastic films for food packaging." The breaking strength is the value obtained by converting the maximum force at which the test piece breaks into a force equivalent to a 15 mm width of the test piece (N / 15 mm).

[0091] If the breaking strength of the support layer 2 is greater than the heat seal strength between the lid and the container body, peeling of the paper is unlikely to occur when the lid is peeled off from the container body. Here, "peeling of the paper" refers to the cohesive failure of the paper base material when the lid is peeled off from the container body, causing part of the lid to remain on the container body. Peeling of the paper can make it difficult to remove the contents from the container body.

[0092] The heat seal strength is adjusted depending on the use and purpose of the packaging container. For example, the heat seal strength may be reduced to make the container easier to open. Increasing the breaking strength of the support layer 2 increases the effect of reinforcing the laminated sheet 11 to prevent paper peeling. However, thickening the support layer 2 to increase the breaking strength increases the carbon dioxide emissions and costs associated with the production of the support layer 2 and the disposal of the laminated sheet 11.

[0093] The support layer 2 can be formed by laminating it to the paper substrate 3 via an adhesive. Examples of such lamination methods include dry lamination, which uses a solvent-based adhesive, non-solvent lamination, which uses a solventless adhesive, and sand lamination, which uses a molten resin as an adhesive. The support layer 2 can also be formed directly on the paper substrate 3 by extruding the composition that makes up the layer in a molten state, such as by extrusion lamination. In this case, an adhesive layer may also be formed on the paper substrate 3, if necessary. The support layer 2 may also be omitted.

[0094] (adhesive layer) As noted above, laminate sheet 11 may further include one or more adhesive layers. The adhesive layer is made of an adhesive resin or adhesive agent that can provide the required adhesive strength depending on the material of the layer to be bonded thereto.

[0095] As the adhesive resin, for example, one or more resins selected from polyethylenes such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, and copolymers of ethylene with an α-olefin polymerized using a metallocene catalyst; ethylene-unsaturated carboxylic acid copolymers such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, and ethylene-maleic acid copolymer; and ionomer resins can be used.

[0096] The adhesive is, for example, an adhesive composition obtained by mixing a first composition containing a base agent and a solvent with a second composition containing a curing agent and a solvent. The adhesive layer obtained from this adhesive contains a cured product produced by reaction between the base agent and the curing agent in the adhesive composition.

[0097] Examples of the base agent include polyols. Examples of the curing agent include isocyanate compounds. Examples of the adhesive include two-component ether-based reactive adhesives and two-component ester-based reactive adhesives.

[0098] The cured product of the ether-based two-component reactive adhesive is, for example, polyether polyurethane, which is produced by reacting a polyether polyol as a base agent with an isocyanate compound as a curing agent.

[0099] Examples of the cured product of the ester-based two-component reactive adhesive include polyester polyurethane and polyester. Polyester polyurethane is produced by reacting a polyester polyol as a base resin with an isocyanate compound as a curing agent.

[0100] In the two-component reactive adhesive, an acrylic polyol may be used as the main component. Furthermore, the adhesive composition may not contain a solvent as long as it melts or has a low viscosity when heated. Various coating methods, such as gravure coating, die coating, blade coating, knife coating, and bar coating, can be used as the coating method.

[0101] In the laminate sheet shown in Figure 2, the heat seal layer 1 is more stretchable than the support layer 2, which is more stretchable than the paper base material 3. Therefore, in the laminate sheet shown in Figure 2, the heat seal layer 1, support layer 2, and paper base material 3 are arranged from the bottom side of the laminate sheet in the order of highest elongation properties. With this arrangement, paper peeling is less likely to occur. The laminated sheet 11 shown in FIG. 2 has been described above.

[0102] In the laminate sheet 11, the support layer 2 may face the heat seal layer 1 with the paper substrate 3 sandwiched therebetween. For example, the laminate sheet 11 may include the support layer 2, the printing layer 4, the paper substrate 3, and the heat seal layer 1 in this order. In this case, in order to achieve high adhesion, the heat seal layer 1 is preferably the above-mentioned easy-peel sealant. In this case, the functional layer 5 may be omitted.

[0103] As described below, the laminate sheet may further include a gas barrier layer.

[0104] (gas barrier layer) The gas barrier layer is interposed, for example, between the printing layer 4 and the heat seal layer 1. The gas barrier layer has gas barrier properties such as oxygen barrier property and water vapor barrier property. In packaged foods described below, the gas barrier layer prevents gases such as oxygen, water vapor, and aroma components from outside the container from penetrating into the container. As a result, the gas barrier layer prevents deterioration of the food contents in packaged foods. Furthermore, the gas barrier layer prevents odor components and the like from the contents from diffusing to the outside of the container in packaged foods. In one example, the gas barrier layer has an oxygen transmission rate of 0.1 cc / m 2 in an atmosphere at a temperature of 30°C and a relative humidity of 70%. 2 / day / atm or more 100cc / m 2 / day / atm or less.

[0105] The gas barrier layer is, for example, a metal layer, an inorganic oxide layer, a resin-containing layer, or a combination of two or more thereof. When microwave heating using a microwave oven is expected, the gas barrier layer is preferably an inorganic oxide layer, a resin-containing layer, or a combination thereof.

[0106] The gas barrier layer may be formed by coating, by melt molding, or by vapor deposition of an inorganic oxide, or may be a metal foil such as aluminum foil, or may be vapor deposited with a metal such as aluminum.

[0107] Examples of inorganic oxides that can be used include silicon oxide, boron oxide, and metal oxides such as aluminum oxide, magnesium oxide, calcium oxide, potassium oxide, tin oxide, sodium oxide, titanium oxide, lead oxide, zirconium oxide, and yttrium oxide.

[0108] The resin-containing layer can be formed, for example, by coating. In this case, a coating liquid containing a resin such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, polyvinylidene chloride, polyacrylonitrile, or epoxy resin can be used. Additives such as organic or inorganic particles, layered compounds, and curing agents may also be added to the coating liquid.

[0109] When the resin-containing layer is formed by melt molding, the material may be, for example, the above-mentioned resin or a mixture of the above-mentioned resin and an additive. For melt molding, for example, an extrusion molding technique such as a T-die or inflation molding can be used.

[0110] The thickness of the gas barrier layer is, for example, in the range of 0.01 μm to 30 μm, and, for another example, in the range of 0.1 μm to 12 μm.

[0111] For example, the laminate sheet 11 has a gas barrier layer between the paper substrate 3 and the heat seal layer 1. In this case, the laminate sheet 11 may include the gas barrier layer and the support layer 2 as a barrier film in which the gas barrier layer is provided on the support layer 2. In this case, the barrier film may be formed by bonding a resin-containing layer formed by melt molding to the support layer 2. Alternatively, the laminate sheet 11 may have a laminate including two support layers 2 and a gas barrier layer provided between these support layers 2 as the support layer 2 and the gas barrier layer.

[0112] A laminate sheet including a gas barrier layer not only has gas barrier properties but also is less likely to experience a decrease in gas barrier properties, particularly oxygen barrier properties, as will be explained below.

[0113] Food packaging containers are often required to have excellent oxygen barrier properties that prevent oxygen from entering from the outside in order to prevent oxidation of the food contained therein. In such food packaging containers, the lids are also required to have oxygen barrier properties.

[0114] To impart gas barrier properties against oxygen and the like to a paper-based lid, for example, a metal foil or a metal-deposited film made of a metal such as aluminum is often provided as a gas barrier layer on the paper base. However, food packaging containers whose lids contain a metal layer have problems such as the inability to inspect for metal foreign matter using a metal detector after filling the contents, the inability to incinerate the lid as paper and the inability to reuse it as waste paper due to the metal content, and the inability to use the lid as a packaging container for chilled foods and the like that are expected to be cooked in a microwave oven.

[0115] As mentioned above, some gas barrier layers do not include a metal layer. Such gas barrier layers often include resins such as polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyamides such as nylon MXD6, and polyacrylonitrile. A metal-layer-free lid can avoid the above problems.

[0116] The optimum temperature range for distribution and storage of chilled foods is set for each food product, but it is generally within the range of 0°C to 10°C. After production, packaged foods, which are made by placing chilled foods in food packaging containers, are delivered to consumers through various distribution channels. During this process, the packaged foods are kept at room temperature, for example, from the time a consumer purchases the packaged food at a store until they store it in their home refrigerator, and from the time a consumer takes the packaged food out of the refrigerator until they begin cooking it.

[0117] The present inventors have found that packaged foods, in which chilled foods are housed in food packaging containers whose lids include a paper base material and a gas barrier layer, particularly packaged foods in which the gas barrier layer is made of a resin-containing layer, experience a significant decrease in the gas barrier properties, particularly the oxygen barrier properties, of the lids during the first few hours of exposure from a refrigerated state to a room temperature environment. This decrease is particularly noticeable when the paper base material accounts for a large proportion of the lid mass.

[0118] The inventors have discovered that the above problem is caused by condensation on the surface of the lid. That is, when a packaged product that has been stored in a refrigerated environment is exposed to a room-temperature environment, condensation forms on the outer surface of the lid, and the moisture reaches the gas barrier layer, damaging it. As a result, the oxygen barrier property of the lid is reduced.

[0119] According to one example, the laminate sheet including the gas barrier layer also includes a water-resistant functional layer 5. In this case, in a packaged food using this laminate sheet as a lid, moisture generated on the outer surface of the lid due to condensation is unlikely to reach the gas barrier layer. Therefore, in a packaged food using this laminate sheet as a lid, damage to the gas barrier layer due to condensation on the outer surface of the lid is unlikely to occur, and deterioration of the oxygen barrier property is unlikely to occur.

[0120] The inventors have further discovered that, in particular, packaged foods in which chilled food is housed in a food packaging container, when the lid contains a paper base material, the paper is likely to peel off when the lid is peeled off from the container body. The laminated sheet described above has an elongation within the above-mentioned range when the tensile stress is at its maximum, so the paper is less likely to peel off.

[0121] The problems described above when the contents are chilled food may also occur when the contents are frozen food. The configuration described here can achieve the same effects as those described above when the contents are chilled food, even when the contents are frozen food.

[0122] [Second embodiment] The lid body according to the second embodiment of the present invention is a lid body obtained from the laminated sheet according to the first embodiment or the modified example described above. An example of the lid body according to the second embodiment is the lid body 21 described later with reference to Fig. 3. The lid body according to this embodiment is less likely to be damaged during transportation.

[0123] [Third embodiment] The packaging bag according to the third embodiment of the present invention is obtained from the laminated sheet according to the first embodiment or the modified example. The packaging bag according to this embodiment is less likely to be damaged during transportation.

[0124] [Fourth embodiment] Fig. 3 is a cross-sectional view showing a food packaging container according to a fourth embodiment of the present invention. The food packaging container 20 shown in Fig. 2 comprises a container body 22 having an opening, and a lid 21 that covers the opening.

[0125] The container body 22 is, for example, a cylindrical shape with a bottom. Here, the container body 22 includes a bottom, a body (or a side wall), and a flange 22a. The flange 22a widens outward at the position of the upper opening of the body.

[0126] The container body 22 contains, for example, an olefin-based resin such as polypropylene. The container body 22 may further contain a component such as an ethylene-vinyl alcohol copolymer to enhance its gas barrier properties. The container body 22 may also further contain additives, for example, additives for improving processability, designability, and chemical durability.

[0127] The container body 22 may have a single-layer structure or a multi-layer structure. This multi-layer structure may be a two-layer structure or may include three or more layers. In the latter case, the multi-layer structure may include a gas barrier layer, for example, a layer containing a component such as the above-mentioned ethylene-vinyl alcohol copolymer, as an intermediate layer.

[0128] The container body 22 can also be made of paper. When the contents include a liquid, the container body 22 can have a multilayer structure including a paper base material and a layer of resin or the like provided on the surface facing the contents to prevent the liquid from seeping into the paper base material. Examples of materials that can be used for the container body 22 containing a paper base material include paper sheets, paper powder, pulp, and recycled paper. The container body 22 can be formed using general-purpose techniques, such as folding and pasting sheets including paper sheets, as is done in the manufacture of paper cartons, press molding of sheets using a mold, and pulp molding. Using paper for the container body 22 can reduce carbon dioxide emissions associated with the manufacture and disposal of the entire food packaging container 20, thereby reducing the environmental impact.

[0129] The lid 21 is one of the laminate sheets 10 and 11, or is cut out from the laminate sheet 10. After the contents are placed in the container body 22, the lid 21 is heat-sealed to the flange 22a via the heat-seal layer 1. In this heat-sealing, the sealing temperature, sealing pressure, and sealing time can be set as appropriate.

[0130] The lid 21 typically has a tab (not shown) on a part of its outer edge, and the user opens the food packaging container 20 by pulling this tab. The relationship between the opening direction of the lid 21 and the fiber direction of the paper base material 3 is not particularly limited, but it is preferable that the opening direction of the lid 21 is approximately parallel to the MD of the paper base material 3 (i.e., the MD of the laminated sheet). The opening direction of the lid 21 may change from the start to the end of the opening operation depending on the shape of the lid 21 and the position of the tab. In such cases, the "opening direction of the lid 21" refers to the opening direction at any point during the opening operation of the lid 21. In this way, when the lid 21 is positioned so that the opening direction of the lid 21 is approximately parallel to the MD (i.e., the fiber direction) of the paper base material 3, the tensile force in the MD of the paper base material 3 is greater than the tensile force in the TD, making it less likely for the paper base material 3 to peel off when opened. For example, if the lid body 21 is substantially rectangular and has tabs at the corners of the lid body 21, the lid body 21 is opened substantially in the diagonal direction of the lid body 21 at the start of the opening operation, and peeling continues in substantially the same direction, and in the latter half of the opening operation, the lid body 21 is opened along the longitudinal direction of the lid body 21. For this reason, in the case of such a lid body 21, it is preferable that the diagonal direction of the lid body 21 is substantially parallel to the MD of the paper base material 3 (i.e., the MD of the laminate sheet), or that the longitudinal direction of the lid body 21 is substantially parallel to the MD of the paper base material 3 (i.e., the MD of the laminate sheet).

[0131] [Fifth embodiment] The packaged food product according to the fifth embodiment of the present invention is obtained by packaging food in the food packaging container according to the fourth embodiment described above. The food packaged is not particularly limited, but is preferably a chilled food or a frozen food. Chilled foods and frozen foods are, for example, cooked or processed foods. Chilled foods and frozen foods are, for example, grilled fish, boiled fish, or prepared dishes.

[0132] As described above, in this packaged food, the heat seal strength between the lid 21 and the container body 22 is preferably smaller than the breaking strength of the support layer 2 included in the lid 21. Here, the heat seal strength is a value obtained by the method specified in JIS Z0238:1998 "Test methods for heat-sealed flexible packaging bags and semi-rigid containers."

[0133] In producing this packaged food, the gas inside the container body 22 may be replaced by a known method before heat-sealing the lid 21 to the container body 22, for example, after the contents have been placed inside the container body 22 and before heat-sealing the lid 21 to the container body 22. For example, the container body 22 may be filled with an inert gas. By appropriately changing the gas composition inside the container, it is possible to suppress bacterial growth and extend the shelf life, to prevent oxidation and thereby maintain the flavor, color, etc. of the food, and to prevent vitamin loss. The replacement gas is selected appropriately depending on the type of food contained therein. A mixed gas of oxygen gas, nitrogen gas, and carbon dioxide gas is preferably used as the replacement gas.

[0134] Packaged foods are packed into boxes prior to transportation. In packaging, the packaged foods are often laid out at the bottom of the box, and then one or more other packaged foods are stacked on top of each packaged food. Therefore, during transportation, collisions between stacked packaged foods occur due to vehicle vibrations and the like. In such cases, the lid may be damaged. Furthermore, the present inventors have found that when sharp foods such as fish bones are contained as contents, or when the contents are hard at low temperatures, particularly freezing temperatures, the above-mentioned vibrations can cause the contents to collide with the lid, resulting in damage to the lid.

[0135] The laminate sheet has an elongation of 8% or more when the tensile stress in the TD and the tensile stress in the MD are both maximum. Packaged foods equipped with lids or packaging bags made of such a laminate sheet are less likely to break during transportation, particularly when the contents are hit. Therefore, the contents of the packaged foods are less likely to deteriorate due to breakage of the lid or packaging bag during transportation. [Example]

[0136] The following describes tests carried out in connection with the present invention.

[0137] <1> Laminated sheet manufacturing (Example 1) The laminated sheet 10 shown in FIG. 1 was produced by the following method. First, as the paper substrate 3, a paper sheet having a basis weight of 70 g / m 2 The stretched paper was prepared as follows. Unbleached kraft Clupak paper (Taioh Atlas (registered trademark) Clupak paper (manufactured by Daio Paper Co., Ltd.)) was used as the stretched paper. A printing layer 4 and a functional layer 5 were sequentially formed on this paper substrate 3 using a gravure multicolor printing machine. The printing layer 4 was formed using a normal printing ink. The coating amount of the printing ink was 1.0 g / m 2 The functional layer 5 was formed using an OP varnish whose main components were a nitrocellulose resin and polyethylene granular wax. The amount of OP varnish applied was 0.6 g / m 2 It was decided.

[0138] Next, the heat seal layer 1 was attached by dry lamination to the laminate consisting of the paper substrate 3, the printing layer 4, and the functional layer 5. The heat seal layer 1 included a support layer and an easy-peel layer, and had a mass per area of ​​27.6 g / m 2 The film used was 30 μm thick and had easy-peel properties, with the surface opposite the easy-peel layer having been corona-treated. For dry lamination, a dry laminating agent was first applied to three sides of the paper substrate using a gravure coater to form an adhesive layer. A two-component reactive adhesive containing an ester-based polyol and an isocyanate-based curing agent was used as the dry laminating agent. The amount of dry laminating agent applied was 3.0 g / m. 2 Next, the laminate and the heat seal layer 1 were attached together with the adhesive layer sandwiched between them so that the corona-treated surface of the heat seal layer 1 faced the paper substrate 3.

[0139] Thereafter, the obtained laminate was aged for 2 days at 40° C. In this manner, the laminate sheet 10 shown in FIG.

[0140] (Example 2) A laminate sheet identical to the laminate sheet 11 shown in FIG. 2, except that a support layer 2 and a gas barrier layer were further provided between the heat seal layer 1 and the paper substrate 3, was produced by the following method. First, a laminate consisting of a paper substrate 3, a printed layer 4, and a functional layer 5 was prepared in the same manner as in Example 1.

[0141] Next, a first laminate including a support layer 2 and a gas barrier layer was attached to this laminate by dry lamination. The first laminate was a laminate of a biaxially oriented polyethylene terephthalate film and a layer made of an inorganic oxide. The first laminate had a thickness of 12 μm and a mass per area of ​​16.4 g / m. 2 In addition, both sides of the first laminate were subjected to a corona treatment. For dry lamination, a dry laminating agent was first applied to the gas barrier layer side of the first laminate using a gravure coater to form an adhesive layer. A two-component reactive adhesive containing an ester-based polyol and an isocyanate-based curing agent was used as the dry laminating agent. The amount of dry laminating agent applied was 3.0 g / m 2 Next, the laminate consisting of the paper base material 3, the printed layer 4, and the functional layer 5 was bonded to the first laminate with this adhesive layer sandwiched between them, so that the gas barrier layer faced the side of the paper base material 3 on which the printed layer 4 was not provided.

[0142] Thereafter, the heat seal layer 1 was attached to the laminate including the support layer 2, the gas barrier layer, the paper substrate 3, the print layer 4 and the functional layer 5 in the same manner as in Example 1.

[0143] Thereafter, the obtained laminate was aged for 2 days at 40° C. In this manner, a laminate sheet according to Example 2 was obtained.

[0144] (Example 3) A laminate sheet was produced in the same manner as in Example 2, except for the following points: In this example, instead of using the first laminate, a support layer 2 having a thickness of 15 μm and a mass per area of ​​20.9 g / m 2 The biaxially oriented polybutylene terephthalate film was used, and the film was corona-treated on both sides. The gas barrier layer was omitted.

[0145] (Example 4) A laminate sheet was produced in the same manner as in Example 2, except for the following points: In this example, instead of using the first laminate, a support layer 2 having a thickness of 15 μm and a mass per area of ​​17.4 g / m 2 The film used was a simultaneous biaxially oriented nylon film with corona treatment on both sides. The gas barrier layer was omitted.

[0146] (Example 5) A laminate sheet was produced in the same manner as in Example 2, except for the following points: In this example, instead of using the first laminate, a support layer 2 having a thickness of 15 μm and a mass per area of ​​17.4 g / m 2 The film used was a sequentially biaxially oriented nylon film with corona treatment on both sides. The gas barrier layer was omitted.

[0147] (Example 6) A laminate sheet was produced in the same manner as in Example 2, except for the following points: In this example, instead of using the first laminate, a support layer 2 having a thickness of 15 μm and a mass per area of ​​17.4 g / m 2 The film used was a sequentially biaxially oriented nylon film with corona treatment on both sides. The gas barrier layer was omitted.

[0148] (Example 7) A laminate sheet was produced in the same manner as in Example 2, except for the following points. In this example, instead of using the first laminate, a second laminate was used, which consisted of two support layers containing nylon and a gas barrier layer containing an ethylene-vinyl alcohol copolymer interposed between these two layers. In the second laminate, the thickness of each layer was 5 μm. The mass per area of ​​this laminate was 17.4 g / m. 2 It was.

[0149] (Example 8) A laminate sheet was produced using the same method as in Example 2, with the following exceptions. In this example, instead of providing a first laminate between the paper substrate 3 and the heat-seal layer 1, the first laminate was provided on the opposite side of the paper substrate 3 on which the heat-seal layer 1 was provided. Specifically, a printed layer 4 was first formed on the side of the first laminate to be bonded to the paper substrate 3, and the paper substrate 3 and the side of the first laminate on which the printed layer 4 was formed were bonded using an adhesive. The paper substrate 3 and the first laminate were bonded together so that a biaxially oriented polyethylene terephthalate film was interposed between the layer made of inorganic oxide and the paper substrate 3. Next, using the same method as in Example 1, a heat-seal layer 1 was bonded to the side of the laminate consisting of the printed layer 4, the first laminate, and the paper substrate 3 facing the paper substrate 3. The resulting laminate was then aged at 40°C for two days. In this manner, a laminate sheet according to Example 8 was obtained.

[0150] (Example 9) A laminate sheet was produced in the same manner as in Example 8, except for the following points: In this example, instead of using the first laminate, a support layer identical to the support layer used in Example 3 was used, and the gas barrier layer was omitted.

[0151] (Example 10) A laminate sheet was produced in the same manner as in Example 8, except for the following points: In this example, instead of using the first laminate, a support layer identical to the support layer used in Example 4 was used, and the gas barrier layer was omitted.

[0152] (Example 11) A laminate sheet was produced in the same manner as in Example 8, except for the following points: In this example, instead of using the first laminate, a support layer identical to the support layer used in Example 5 was used, and the gas barrier layer was omitted.

[0153] (Example 12) A laminate sheet was produced in the same manner as in Example 8, except for the following points: In this example, instead of using the first laminate, a support layer identical to the support layer used in Example 6 was used, and the gas barrier layer was omitted.

[0154] (Example 13) A laminate sheet was produced in the same manner as in Example 8, except for the following points: In this example, instead of using the first laminate, a laminate identical to the second laminate used in Example 7 was used.

[0155] (Example 14) A laminated sheet was produced in the same manner as in Example 2, except for the following points. In this example, the heat seal layer was formed by applying a heat seal varnish to the support layer 2 and drying the coating, instead of laminating a film including a support layer and an easy-peel layer to a paper substrate 3 via a dry laminating agent. The heat seal varnish used was an aqueous emulsion containing ethylene-vinyl acetate copolymer as the main component and water and isopropanol as the solvent or dispersion medium. The solid content of this heat seal varnish had a glass transition temperature of -27°C and a melting point of 50°C or higher and 90°C or lower. The heat seal varnish was printed by gravure printing to a dry mass per area of ​​3 g / m. 2 The coating was applied so that the

[0156] (Example 15) A laminate sheet was produced in the same manner as in Example 3, except for the following points. In this example, the heat seal layer was formed by applying heat seal varnish to the support layer 2 and drying the coating, instead of laminating a film including a support layer and an easy-peel layer to the paper substrate 3 via a dry laminating agent. The heat seal layer was formed in the same manner as in Example 14.

[0157] (Example 16) A laminate sheet was produced in the same manner as in Example 4, except for the following points. In this example, the heat seal layer was formed by applying heat seal varnish to the support layer 2 and drying the coating, instead of laminating a film including a support layer and an easy-peel layer to the paper substrate 3 via a dry laminating agent. The heat seal layer was formed in the same manner as in Example 14.

[0158] (Example 17) A laminate sheet was produced in the same manner as in Example 5, except for the following points. In this example, the heat seal layer was formed by applying heat seal varnish to the support layer 2 and drying the coating, instead of laminating a film including a support layer and an easy-peel layer to the paper substrate 3 via a dry laminating agent. The heat seal layer was formed in the same manner as in Example 14.

[0159] (Example 18) A laminate sheet was produced in the same manner as in Example 6, except for the following points. In this example, the heat seal layer was formed by applying heat seal varnish to the support layer 2 and drying the coating, instead of laminating a film including a support layer and an easy-peel layer to the paper substrate 3 via a dry laminating agent. The heat seal layer was formed in the same manner as in Example 14.

[0160] (Example 19) A laminate sheet was produced in the same manner as in Example 7, except for the following points. In this example, the heat seal layer was formed by applying heat seal varnish to the support layer 2 and drying the coating, instead of laminating a film including a support layer and an easy-peel layer to the paper substrate 3 via a dry laminating agent. The heat seal layer was formed in the same manner as in Example 14.

[0161] (Comparative Example 1) A laminated sheet was produced in the same manner as in Example 2, except for the following points: In this example, the paper substrate had a thickness of 50 μm and a basis weight of 52.3 g / m2 The single-sided coated paper used had a basis weight of 37.3 g / m 2 The coating solution was applied to a surface of a large paper with a mass of 15 g / m 2 The coating solution contains polyvinyl alcohol (PVA) and styrene butadiene rubber (SBR) as main components, and further contains silica and layered silicate.

[0162] (Comparative Example 2) A laminate sheet was produced in the same manner as in Example 3, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0163] (Comparative Example 3) A laminate sheet was produced in the same manner as in Example 4, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0164] Comparative Example 4 A laminate sheet was produced in the same manner as in Example 5, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0165] (Comparative Example 5) A laminate sheet was produced in the same manner as in Example 6, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0166] (Comparative Example 6) A laminate sheet was produced in the same manner as in Example 7, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0167] (Comparative Example 7) A laminated sheet was produced in the same manner as in Example 2, except for the following points: In this example, a paper substrate having a basis weight of 73.3 g / m 2 Single-sided coated paper was used.

[0168] (Comparative Example 8) A laminate sheet 10 was produced in the same manner as in Example 1, except for the following points. That is, in this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate. Also, the heat seal layer was formed by applying a heat seal varnish to the paper substrate and drying the coating, instead of laminating a film including a support layer and an easy-peel layer to the paper substrate via a dry laminating agent. The heat seal varnish used was the same as that used in Example 14. The heat seal varnish was printed by gravure printing to a dry mass per area of ​​3 g / m. 2 The coating was performed so that the thickness was 100 μm. Aging was also omitted.

[0169] Comparative Example 9 A laminate sheet was produced in the same manner as in Example 14, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0170] (Comparative Example 10) A laminate sheet was produced in the same manner as in Example 15, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0171] (Comparative Example 11) A laminate sheet was produced in the same manner as in Example 16, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0172] (Comparative Example 12) A laminate sheet was produced in the same manner as in Example 17, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0173] (Comparative Example 13) A laminate sheet was produced in the same manner as in Example 18, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0174] (Comparative Example 14) A laminate sheet was produced in the same manner as in Example 19, except for the following points: In this example, the same single-sided coated paper as used in Comparative Example 1 was used as the paper substrate.

[0175] (Reference example 1) As the paper base material for Reference Example 1, the same paper base material as that used in Comparative Example 1 was prepared.

[0176] (Reference example 2) As the paper substrate for Reference Example 2, the same paper substrate as that used in Example 1 was prepared.

[0177] (Reference example 3) As the paper substrate according to Reference Example 3, parchment paper was prepared.

[0178] (Reference example 4) As a laminate according to Reference Example 4, the same laminate as the first laminate used in Example 2 was prepared.

[0179] (Reference example 5) As the support layer in Reference Example 5, the same support layer as that used in Example 3 was prepared.

[0180] (Reference example 6) As the support layer according to Reference Example 6, the same support layer as that used in Example 4 was prepared.

[0181] (Reference example 7) As the support layer of Reference Example 7, the same support layer as that used in Example 6 was prepared.

[0182] (Reference example 8) As the support layer of Reference Example 8, the same support layer as that used in Example 5 was prepared.

[0183] <2> evaluation (Tensile force, tensile strength and elongation at maximum tensile stress) For the laminate sheets of Examples 1 to 19 and Comparative Examples 1 to 14, the tensile force, tensile strength, and elongation at maximum tensile stress were measured using the methods described above. These measurements were performed in the MD and TD directions of the laminate sheets. A Tensilon universal testing machine was used for these measurements. The relationship between load and elongation for the laminate sheets of Example 2 and Comparative Example 1 is shown in Figures 4 and 5. The tensile strength is the maximum force applied when a test piece is pulled until it breaks, as specified in JIS Z 1707:2019. Each of the tensile force, tensile strength, and elongation was obtained by arithmetically averaging the values ​​obtained from three measurements.

[0184] Fig. 4 is a graph showing the relationship between load and elongation in MD for the laminate sheets according to Example 2 and Comparative Example 1. Fig. 5 is a graph showing the relationship between load and elongation in TD for the laminate sheets according to Example 2 and Comparative Example 1. As shown in Figs. 4 and 5, the laminate sheet according to Example 2 had larger elongation at maximum tensile force and maximum tensile stress than the laminate sheet according to Comparative Example 1.

[0185] The elongation of the paper substrates of Reference Examples 1 to 3 was also measured using the same method as described above. The results are shown in Figure 6. Figure 6 is a graph showing the relationship between load and elongation for the paper substrates of Reference Examples 1 to 3. As shown in Figure 6, the paper substrate of Reference Example 2 was particularly excellent in terms of maximum load in MD. The paper substrate of Reference Example 2 also had excellent elongation in TD.

[0186] (Measurement of puncture strength) The puncture strengths of the laminate sheets according to Examples 1 to 19 and Comparative Examples 1 to 14, the paper substrates according to Reference Examples 1 and 2, the laminate according to Reference Example 4, and the support layers according to Reference Examples 5 to 8 were measured by the method described above. Here, for laminate sheet 10, the puncture strength was measured when a needle was pierced from the top side of the laminate sheet, and when a needle was pierced from the bottom side of the laminate sheet. Each puncture strength was obtained by arithmetically averaging the values ​​obtained from five measurements.

[0187] Fig. 7 is a graph showing the relationship between puncture strength and needle movement when measuring the puncture strength of the paper substrates of Reference Examples 1 and 2, and the laminate of Reference Example 4. As shown in Fig. 7, the paper substrate of Reference Example 2 has a higher puncture strength than the paper substrate of Reference Example 1. The support layer of Reference Example 4 also has a high puncture strength. Fig. 8 is a graph showing the puncture strength of the laminate of Reference Example 4 and the support layers of Reference Examples 5 to 8. As shown in Fig. 8, the support layer of Reference Example 7 had particularly excellent puncture strength.

[0188] (Transportation Test) Lids were cut from the laminate sheets of Examples 1 to 19 and Comparative Examples 1 to 14. These lids were used to produce packaged foods, each containing food in a food packaging container 20 as shown in FIG. 3 . 36 packaged foods were produced for each laminate sheet. The container body 22 used here was a tray-shaped resin sheet containing polypropylene as the main component. The container body 22 had a substantially rectangular opening with a long side dimension of 130 mm and a short side dimension of 80 mm, a height of 30 mm, and a flange width of 10 mm. The bottom of the container body 22 was rectangular with a long side dimension of 125 mm and a short side dimension of 75 mm. The food was 100 g of a commercially available frozen processed food, sautéed pork with green peppers.

[0189] The lid 21 was heat-sealed to the flange 22a as follows. First, a jig was prepared, which had a recess and a 5 mm-high support portion on the edge of the recess's opening that conformed to the shape of the flange 22a. Next, the container body 22 was fitted into the recess of the jig so that the flange 22a and the support portion were in contact. Next, the lid body 21 was placed on the container body 22, and the lid body 21 and the flange 22a were heat-sealed. During heat-sealing, the lid body 21, which had a substantially rectangular shape, was positioned so that its longitudinal direction was substantially parallel to the MD of the paper base material 3 (i.e., the MD of the laminated sheet). Heat-sealing was performed using a 4 mm-wide seal bar manufactured to conform to the shape of the flange 22a, applying a temperature of 190°C and a pressure of 0.2 MPa for 1 second.

[0190] The packaged foods were then packed into cardboard boxes. Six packaged foods were first placed at the bottom of the box, and then five packaged foods were stacked on top of each other. The packed foods were then stored at -20°C for two hours.

[0191] The frozen food was then loaded onto a vehicle and transported approximately 650 km. The packaged food was then opened to check whether the lid had been torn. If the lid had been torn, it was determined whether the torn lid had been caused by the food colliding with itself or by the food colliding with the lid.

[0192] Specifically, if the cross section of the broken lid was not soaked with oil from the food, the lid was determined to have broken due to the collision of the packaged food with itself.Furthermore, if the cross section was soaked with oil from the food, the lid was determined to have broken due to the food colliding with the lid.

[0193] Many of the lid tears that did not result in the penetration of oil from food were located in the area that came into contact with the edge of the bottom of the packaged food stacked on top of the lid. Therefore, it was determined that the lid tears were caused by the edge piercing the lid due to vibrations during transportation.

[0194] (Openability test) Using the laminate sheets according to Examples 1 to 19 and Comparative Examples 1 to 14, packaging containers identical to the food packaging containers described in the "Transportation Test" section above were prepared.

[0195] Next, for each food packaging container 20, the lid 21 was peeled off by hand from a corner of the container body 22, and the openability was evaluated based on the following criteria. A: Cohesive failure occurred in the heat seal layer, and no paper peeling occurred. B: Although the paper peeled off, part of the lid material remained on the container body only at the seal or around it, and this did not affect removal of the contents. C: Paper peeling occurred, and the lid material remained on the container body in areas other than the seal area and its surroundings. For example, the double lid or the lid itself was torn.

[0196] The results of the above measurements and tests are summarized in Tables 1 to 7 below.

[0197] [Table 1]

[0198] [Table 2]

[0199] [Table 3]

[0200] [Table 4]

[0201] [Table 5]

[0202] [Table 6]

[0203] [Table 7]

[0204] In the table, "Ny," "PBT," and "PET" represent nylon, polybutylene terephthalate, and polyethylene terephthalate, respectively. Additionally, "Top" represents the puncture strength when a needle is pierced from the top side of the laminated sheet, and "Bottom" represents the puncture strength when a needle is pierced from the bottom side of the laminated sheet. In the column labeled "Transportation Test," "X" represents the number of packaged foods whose lids were torn due to collisions between the packaged foods, and "Y" represents the number of packaged foods whose lids were torn due to collisions between the packaged foods. In the columns labeled "X" and "Y," "A" indicates that no packaged foods had torn lids, "B" indicates that one to three packaged foods had torn lids, and "C" indicates that four or more packaged foods had torn lids.

[0205] In Tables 6 and 7, "mass" refers to mass per area. The classification of "paper," "plastic," and "other" follows the "Container and Packaging Recycling Law Explanation Material."

[0206] As shown in Tables 1 to 3, in the transportation test, no lid breakage occurred in the packaged foods equipped with lids made of the laminated sheets of Examples 1 to 19. Therefore, the lids made of these laminated sheets were excellent in durability. In contrast, lid breakage occurred in the packaged foods equipped with lids made of the laminated sheets of Comparative Examples 1 to 14.

[0207] The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the invention. Furthermore, the embodiments may be implemented in appropriate combinations, in which case the combined effects can be obtained. Furthermore, the above-described embodiments include various inventions, and various inventions can be extracted by combining selected elements from the disclosed elements. For example, if the problem can be solved and the desired effect can be obtained even if some elements are deleted from all elements shown in the embodiments, the configuration from which these elements are deleted can be extracted as an invention. [Explanation of symbols]

[0208] 1...heat seal layer, 2...support layer, 3...paper base material, 4...printed layer, 5...functional layer, 10...laminated sheet, 11...laminated sheet, 20...food packaging container, 21...lid body, 22...container body, 22a...flange.

Claims

1. A laminated sheet including a paper substrate and a heat seal layer, A laminate sheet in which the elongation when the tensile stress of the laminate sheet in the MD and the elongation when the tensile stress of the laminate sheet in the TD are both 8% or more.

2. 2. The laminate sheet according to claim 1, wherein the puncture strength from the heat seal layer side and the puncture strength from the opposite side to the heat seal layer are both 7.5 N or more.

3. 2. The laminate sheet according to claim 1, wherein the tensile strength in the MD is 80 N / 15 mm or more and the tensile strength in the TD is 35 N / 15 mm or more.

4. The laminate sheet according to claim 1 , further comprising a support layer between the heat seal layer and the paper substrate.

5. 5. The laminate sheet of claim 4, wherein the support layer comprises a polyamide.

6. The laminate sheet according to claim 4 , further comprising a gas barrier layer between the paper substrate and the heat seal layer.

7. 2. The laminated sheet according to claim 1, further comprising a support layer facing the heat seal layer with the paper substrate sandwiched therebetween.

8. The laminated sheet according to claim 1 , further comprising a printing layer facing the heat seal layer with the paper substrate sandwiched therebetween.

9. The laminated sheet according to claim 1 , further comprising a water-resistant functional layer facing the heat seal layer with the paper substrate sandwiched therebetween.

10. 2. The laminate sheet according to claim 1, wherein when the layers other than the paper substrate included in the laminate sheet are classified into layers made of plastic and other layers, the mass of the paper substrate is greater than the total mass of the layers made of plastic and the total mass of the other layers.

11. 2. The laminated sheet according to claim 1, wherein the tensile strength of the paper substrate in the MD is 70 N / 15 mm or more, the tensile strength of the paper substrate in the TD is 35 N / 15 mm or more, and the tensile breaking elongation of the paper substrate in the MD and the tensile breaking elongation of the paper substrate in the TD are both 7% or more.

12. 2. The laminated sheet of claim 1, wherein the paper substrate is stretched paper.

13. The laminate sheet of claim 1 , wherein the heat seal layer comprises a polyolefin.

14. 2. The laminated sheet according to claim 1, wherein the heat seal layer is formed by coating a heat seal varnish which is a water-based emulsion.

15. The laminate sheet according to claim 14, wherein the glass transition temperature of the solid content of the heat seal varnish is in the range of -40°C or higher and -10°C or lower, and the melting point of the solid content of the heat seal varnish is in the range of 40°C or higher and 100°C or lower.

16. A packaging bag made of the laminate sheet according to any one of claims 1 to 15.

17. A lid body made of the laminated sheet according to any one of claims 1 to 15.

18. A food packaging container comprising a container body having an opening and a lid body as described in claim 17 that covers the opening, wherein the heat seal layer is disposed between the paper base material and the internal space of the food packaging container.

19. A packaged food product comprising the food packaging container according to claim 18 and food contained in the food packaging container.

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