Lamination sheet for lid body, lid body, food packaging container and packaged food

Abstract

To provide a lid body which is used for a food packaging container and is resistant to damage during transportation of a packaged food.SOLUTION: A lamination sheet 10 for a lid body of the present invention is used for a lid body of a food packaging container having a container body provided with an opening and the lid body for covering the opening, and includes a paper base material 3, a support layer 2, and a heat seal layer 1 in this order, a piercing strength from a side opposite to the heat seal layer 1 is 7N or more, and the piercing strength from the heat seal layer 1 side is 9N or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, the demand for pre-cooked or pre-processed chilled and frozen foods sold at convenience stores, supermarkets, etc. is growing, supported by advances in distribution, freezing and refrigeration technologies, in addition to changes in household structure and lifestyles due to the trend towards nuclear families. At the same time, the demand for packaging containers for chilled and frozen foods is also growing.

[0003] Meanwhile, as efforts to reduce plastic waste progress, there is an increasing demand for food packaging containers that use paper as a base material, which is a renewable resource with a low environmental impact. There is also a demand for paper packaging containers 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 an ethylene-modified polyvinyl alcohol resin are laminated on a paper base material.

[0005] Moreover, Patent Document 2 discloses a container including a sheet material formed by laminating a film layer and a paper layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-184138 A [Patent Document 2] Patent Publication No. 2022-188755 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a lid body that is used for a food packaging container and is resistant to damage during transportation of the packaged food. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided a laminate sheet for a lid used in a lid of a food packaging container having a container body with an opening and a lid covering the opening, the laminate sheet for a lid including, in this order, a paper base material, a support layer, and a heat seal layer, and having a puncture strength of 7N or more from the side opposite the heat seal layer and a puncture strength of 9N or more from the heat seal layer side.

[0009] According to another aspect of the present invention, there is provided a laminate sheet for a lid body relating to the above aspect, wherein the breaking strength A1 of the support layer in a first direction is greater than the breaking strength A2 of the support layer in a second direction perpendicular to the first direction, and the difference between the breaking strength A1 and the breaking strength A2 is 1 N or more.

[0010] According to yet another aspect of the present invention, there is provided a laminate sheet for a lid body relating to any of the above aspects, wherein the breaking strength A1 of the support layer in a first direction is 41 N or more, and the breaking strength A2 of the support layer in a second direction perpendicular to the first direction is 40 N or more.

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

[0012] According to yet another aspect of the present invention, there is provided the laminate sheet for a lid according to the above aspect, wherein the polyamide is nylon.

[0013] According to yet another aspect of the present invention, there is provided the laminate sheet for a lid according to any one of the above aspects, wherein the thickness of the support layer is 17 μm or less.

[0014] According to yet another aspect of the present invention, there is provided a lid laminate sheet according to any of the above aspects, wherein the mass of the paper base material is greater than the mass of any other layer included in the lid laminate sheet.

[0015] According to yet another aspect of the present invention, there is provided a laminate sheet for a lid body relating to the above aspect, in which, when layers other than the paper base material contained in the laminate sheet for a lid body 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.

[0016] According to yet another aspect of the present invention, there is provided the laminate sheet for a lid according to any one of the above aspects, wherein the thickness of the paper base material is 70 μm or less.

[0017] According to yet another aspect of the present invention, there is provided the laminate sheet for a lid according to any one of the above aspects, wherein the heat seal layer is a sealant having easy peelability.

[0018] According to yet another aspect of the present invention, there is provided the laminate sheet for a lid according to any one of the above aspects, wherein the heat seal layer has a thickness of 35 μm or less.

[0019] According to yet another aspect of the present invention, there is provided a laminate sheet for a lid body relating to any of the above aspects, further comprising a printed layer facing the support layer with the paper base material sandwiched therebetween, the paper base material being a coated paper having a coating layer on one side, and the printed layer being provided on the coating layer.

[0020] According to yet another aspect of the present invention, there is provided a lid comprising the lid-forming laminate sheet according to any one of the above aspects.

[0021] 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 covering the opening, wherein the support layer is disposed between the paper base material and the internal space of the food packaging container.

[0022] 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.

[0023] According to yet another aspect of the present invention, there is provided a food packaging container relating to any of the above aspects, wherein the internal space of the food packaging container is filled with a mixed gas including oxygen gas, nitrogen gas, and carbon dioxide gas.

[0024] 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 food packaging container is a chilled food packaging container or a frozen food packaging container.

[0025] According to yet another aspect of the present invention, there is provided a packaged food comprising a food packaging container according to any one of the above aspects and food contained in the food packaging container. Effect of the Invention

[0026] According to the present invention, there is provided a lid that is used for a food packaging container and is resistant to damage during transportation of the packaged food. [Brief description of the drawings]

[0027] [Figure 1] 1 is a partial cross-sectional view illustrating an example of a lid laminate sheet according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a cross-sectional view showing a food packaging container according to a third embodiment of the present invention. [Diagram 3] FIG. 4 is a cross-sectional view of the lid laminate sheet showing a state in which a needle is pressed against the lid laminate sheet from the paper base material side. [Figure 4] FIG. 4 is a cross-sectional view of the lid laminate sheet showing a state in which a needle is pressed against the lid laminate sheet from the heat seal layer side. [Diagram 5] 13 is a graph showing the relationship between the load and the amount of movement when measuring the puncture strength. [Figure 6] Graph showing tensile strength. [Figure 7] Graph showing tensile elongation. [Figure 8] Graph showing tensile modulus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The embodiment described below is a more specific embodiment of any of the above aspects. Elements having the same or similar functions are given the same reference numerals, and duplicated descriptions will be omitted.

[0029] [First embodiment] FIG. 1 is a cross-sectional view that illustrates an example of a lid laminate sheet according to a first embodiment of the present invention.

[0030] The lid laminate sheet 10 shown in Fig. 1 is used as a lid in a food packaging container having a container body with an opening and a lid that covers the opening. That is, the lid laminate sheet 10 is a lid material that is used as a lid by itself or a portion cut out from the lid laminate sheet 10 is used as a lid. As described below, packaged foods equipped with a lid made of the lid laminate sheet 10 are less likely to suffer damage to the lid during transportation. In this disclosure, "during transportation" means when the packaged food is transported. The packaged food will be described later.

[0031] The lid laminate sheet 10 includes a heat seal layer 1, a support layer 2, a paper substrate 3, a print layer 4, and a functional layer (water-resistant layer) 5 having water resistance, in this order. This lid laminate sheet 10 does not include a gas barrier layer, which will be described later, and is therefore suitable for applications that do not require high gas barrier properties. Each layer included in the lid laminate sheet 10 will be described below. Of the two main surfaces of the lid laminate sheet 10, the main surface on the heat seal layer 1 side is called the lower surface, and the main surface opposite the heat seal layer 1 is called the upper surface.

[0032] (Paper base material) The lid 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 lid laminate sheet 10. The mass ratio of the paper base material 3 to the mass of the lid laminate sheet 10 is preferably 40% or more, more preferably 45% or more, even more preferably 48% or more, even more preferably 50% or more, and even more preferably more than 50%. In one example, this ratio is 80% or less, in another example, 70% or less, and in yet another example, 65% or less. If the above ratio is high, the environmental impact of the lid laminate sheet 10 is small.

[0033] When the layers other than the paper base material 3 contained in the lid 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 lid laminate sheet 10 can be treated as paper under the Container and Packaging Recycling Law.

[0034] Here, the above classification follows the "Explanatory Materials for the Container and Packaging Recycling Law." 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 support layer 2 and the heat seal layer 1 attached to it are "layers made of plastic." Also, in the example shown in Figure 1, 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."

[0035] The thickness of the paper base material 3 is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less. The thickness of the paper base material 3 is preferably 35 μm or more, more preferably 40 μm or more, and even more preferably 45 μm or more.

[0036] The thickness of the paper base material 3 is preferably in the range of 35 to 90 μm, more preferably in the range of 40 to 80 μm, and even more preferably in the range of 45 to 70 μm.

[0037] The basis weight of the paper base material 3, i.e., the mass per area, is 35 to 90 g / m 2 and preferably in the range of 40 to 80 g / m 2 More preferably, the range is from 45 to 70 g / m 2 It is more preferable that the ratio is in the range of 1:1.

[0038] When the basis weight or thickness of the paper base material 3 is increased, the lid becomes hard and the opening property is reduced. When the basis weight or thickness of the paper base material 3 is decreased, the strength of the lid decreases and the lid becomes easily torn when opened. Although the lid including the support layer 2 has high strength, if the support layer 2 is too thick, the environmental load increases. In addition, when the strength of the lid is increased by thickening the paper base material 3, the rigidity of the lid is too high, and the opening property may be reduced. Thus, there is a trade-off between the strength of the lid, the reduction of the environmental load, and the opening property. In order to achieve the reduction of the environmental load, high strength, and high opening property, it is preferable that the thickness or basis weight of the paper base material 3 is within the above-mentioned range.

[0039] In addition, when the basis weight of the paper base material 3 is increased, the proportion of the mass of the paper base material 3 in the mass of the lid laminate sheet 10 also increases. However, when the basis weight of the paper base material 3 is increased, the amount of carbon dioxide emissions associated with the manufacture of the paper base material 3 and the disposal of the lid laminate sheet 10 increases.

[0040] There are no particular limitations on the paper base material 3 as long as it is made mainly of plant-derived pulp. Examples of the paper base material 3 include coated papers such as fine paper, medium quality paper, and lightly coated paper, one-sided glossy paper, and bleached and unbleached kraft paper (acid paper or neutral paper).

[0041] The paper base material 3 is preferably a coated paper having a coating layer on at least one side. That is, the paper base material 3 is preferably a single-sided coated paper or a double-sided coated paper. The surface of the coated paper having the coating layer is superior in smoothness to the surface of a paper not having a coating layer.

[0042] When the paper substrate 3 is a coated paper having a coating layer on one side, the printing layer 4 can be provided, for example, on the coating layer. In this case, it is easy to display a high-quality image on the printing layer 4. Furthermore, by providing the coating layer, the base surface of the functional layer 5 becomes smooth, and the water resistance of the functional layer 5 is also improved.

[0043] When the paper base material 3 is a coated paper having a coating layer on one side, the support layer 2 may be bonded to the paper base material 3 so as to face the coating layer. In this way, when the paper base material 3 and the support layer 2 are bonded together via an adhesive, for example, the smoothness of the coating layer makes it easier to form a uniform adhesive layer containing the adhesive, improving the adhesion of the support layer 2 to the paper base material 3 and reducing the amount of adhesive used.

[0044] When coated paper having coating layers on both sides is used as the paper base material 3, it becomes easy to display a high-quality image on the printed layer 4, and it is possible to improve the water resistance of the functional layer 5. In addition, it becomes easy to realize excellent adhesion between the paper base material 3 and the support layer 2.

[0045] The coating layer contains a resin. Examples of the resin contained in the coating layer include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymers polymerized using a metallocene catalyst (single-site catalyst), polypropylene, ethylene-vinyl acetate copolymers, ionomer resins, ethylene-ethyl acrylate copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, ethylene-propylene copolymers, methylpentene polymers, acid-modified polyolefin resins obtained by modifying polyolefin resins such as polyethylene and polypropylene with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, and fumaric acid, polyethylene terephthalate resins, polybutylene terephthalate resins, nylon resins, and thermoplastic resins such as styrene-butadiene rubber. Two or more of these resins may be used in combination, or two or more may be copolymerized. The coating layer may further contain additives, such as fillers such as clay, kaolin, calcium carbonate, talc, mica, and titanium oxide.

[0046] The thickness of the coating layer is preferably in the range of 0.5 to 50 μm, and more preferably in the range of 1 to 15 μm.

[0047] (Support layer) The support layer 2 improves the strength of the lid laminate sheet 10 . 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.

[0048] In the support layer 2 containing polyamide, hydrogen bonds are formed between adjacent polyamide molecules at the position of the amide bond. As a result, the molecules constituting the support layer 2 containing polyamide have high cohesive strength. Therefore, the support layer 2 containing polyamide is not easily broken even when pierced with a needle, and can therefore be stretched. Therefore, the support layer 2 containing polyamide has a particularly high puncture strength. The puncture strength will be described later.

[0049] In addition, polybutylene terephthalate has excellent molecular elasticity due to the longer carbon chains contained in the unit structure compared to, for example, polyethylene terephthalate, and therefore the support layer 2 containing polybutylene terephthalate can achieve a higher tensile elongation than a layer containing polyethylene terephthalate, and therefore has a particularly high puncture strength.

[0050] 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. According to 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 break even when pierced with a needle, and is therefore particularly easy to stretch.

[0051] When the support layer 2 contains at least one of polybutylene terephthalate and polyamide, the birefringence of the support layer 2 is preferably 0 or more, more preferably 0.002 or more, and even more preferably 0.0025 or more. In the above case, the birefringence of the support layer 2 is preferably 0.045 or less, more preferably 0.03 or less, and even more preferably 0.025 or less.

[0052] When the support layer 2 contains at least one of polybutylene terephthalate and polyamide, if the birefringence is within the above-mentioned range, a lid laminate sheet 10 having particularly high puncture strength can be obtained. Therefore, packaged foods equipped with lids made of the lid laminate sheet 10 containing such a support layer 2 are particularly unlikely to break during transportation.

[0053] The birefringence is the absolute value of the difference between the refractive index in MD and the refractive index in TD of the support layer 2. The birefringence is measured using a phase difference measuring device KOBRA (manufactured by Oji Scientific Instruments Co., Ltd.).

[0054] The support layer 2 may further contain additives such as a curing agent, a filler, an antiblocking agent, and an antistatic agent. In addition, 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.

[0055] When the support layer 2 contains at least one of polybutylene terephthalate and polyamide, the proportion of the total mass of polybutylene terephthalate and polyamide in the mass of the support layer 2 is preferably 50 mass% or more, and more preferably 70 mass% or more. When the thickness of the support layer 2 is constant, increasing this proportion increases the puncture strength of the lid body.

[0056] The support layer 2 is preferably a stretched film. In the case of a stretched film, it is preferable to use a biaxially stretched film. This is because the variation in various physical properties such as breaking strength in the in-plane direction of the film is smaller by biaxial stretching than by uniaxial stretching. The biaxially stretched film may be a simultaneous biaxially stretched film or a sequential biaxially stretched film. As described later, it is preferable that the support layer 2 has anisotropy. In sequential biaxial stretching, higher anisotropy can be achieved compared to simultaneous biaxial stretching, so it is preferable to use a sequential biaxially stretched film as the support layer 2.

[0057] The support layer 2 is preferably anisotropic. In one example, the breaking strength A1 of the support layer 2 in the first direction is greater than the breaking strength A2 of the support layer 2 in the second direction perpendicular to the first direction, and the difference between the breaking strength A1 and the breaking strength A2 is preferably 1N or more. In another example, the tensile elongation B2 of the support layer 2 in the second direction is greater than the tensile elongation B1 of the support layer 2 in the first direction, and the difference between the tensile elongation B2 and the tensile elongation B1 is preferably 10% or more. In yet another example, the tensile modulus C2 of the support layer 2 in the second direction is greater than the tensile modulus C1 of the support layer 2 in the first direction, and the difference between the tensile modulus C2 and the tensile modulus C1 is preferably 0.1 GPa or more.

[0058] The difference between the breaking strength A1 and the breaking strength A2 is more preferably 2 N or more, and even more preferably 4 N or more. The difference between the breaking strength A1 and the breaking strength A2 is preferably 40 N or less, more preferably 30 N or less, and even more preferably 25 N or less.

[0059] The difference between the tensile elongation B2 and the tensile elongation B1 is preferably 15% or more, and more preferably 20% or more. The difference between the tensile elongation B2 and the tensile elongation B1 is preferably 50% or less, more preferably 45% or less, and even more preferably 40% or less.

[0060] The difference between the tensile modulus C2 and the tensile modulus C1 is preferably 0.2 GPa or more, more preferably 0.3 GPa or more. The difference between the tensile modulus C2 and the tensile modulus C1 is preferably 2.2 GPa or less, more preferably 2.0 GPa or less, and even more preferably 1.8 GPa or less.

[0061] When at least one of the difference between the breaking strength A1 and the breaking strength A2, the difference between the tensile elongation B2 and the tensile elongation B1, and the difference between the tensile modulus C2 and the tensile modulus C1 is large, a lid laminate sheet 10 having particularly high puncture strength is obtained. Therefore, packaged foods equipped with a lid made of the lid laminate sheet 10 including the support layer 2 having the above-mentioned anisotropy are particularly unlikely to break during transportation.

[0062] The first direction is, for example, TD (Transverse Direction). The second direction is, for example, MD (Machine Direction). The support layer 2 having the above anisotropy can be easily obtained, for example, by stretching a film-formed resin in MD and then stretching it in TD. In addition, the difference between the breaking strength A1 and the breaking strength A2, the difference between the tensile elongation B2 and the tensile elongation B1, and the difference between the tensile modulus C2 and the tensile modulus C1 can be adjusted by adjusting the stretching ratio.

[0063] The method for measuring the breaking strength of the support layer 2 will be described later. The tensile elongation and tensile modulus of elasticity of the support layer 2 are obtained by the measurement method specified in JIS K7127:1999. Here, the test speed is 300 mm / min, the width of the test piece is 15 mm, and the length of the test piece is 150 mm.

[0064] The breaking strength A1 is preferably 41N or more, more preferably 45N or more, and even more preferably 50N or more. The breaking strength A1 is preferably 100N or less, more preferably 90N or less, and even more preferably 85N or less. The breaking strength A2 is preferably 40N or more, more preferably 45N or more, and even more preferably 50N or more. The breaking strength A2 is preferably 100N or less, more preferably 90N or less, and even more preferably 85N or less. When at least one of the breaking strengths A1 and A2 is within the above range, the lid is particularly unlikely to break during transportation.

[0065] 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 to 20 μm, and more preferably in the range of 10 to 16 μm.

[0066] By making the support layer 2 thicker, it becomes easier to increase the puncture strength of the lid body, but it becomes difficult to increase the proportion of the mass of the paper base material 3 in the mass of the lid body laminate sheet 10. In addition, in this case, the environmental load is likely to increase.

[0067] If the support layer 2 is too thin, the support layer 2 is easily broken. In this case, when a packaged food provided with a lid made of the lid laminate sheet 10 including such a support layer 2 is opened, the lid may break and part of the lid may remain in the container body.

[0068] 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 being 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 MD, and is greater than the heat seal strength between the lid and the container body in TD.

[0069] The breaking strength of the support layer 2 is a tensile force obtained by the measurement method specified in JIS Z1707:2019 "General Rules for Food Packaging Plastic Films." Note that this tensile force (N / 15mm) is the maximum force at which the test piece breaks, converted into a force (N / 15mm) equivalent to a test piece width of 15mm.

[0070] When the breaking strength of the support layer 2 is greater than the heat seal strength between the lid and the container body, paper peeling is unlikely to occur when the lid is peeled off from the container body. For example, when the breaking strength of the support layer 2 is greater than 20 N / 15 mm, the occurrence of paper peeling can be suppressed up to a heat seal strength of about 20 N / 15 mm. Here, "paper peeling" refers to the occurrence of 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. If paper peeling occurs, it may become difficult to remove the contents contained in the container body.

[0071] The heat seal strength is adjusted according to the use and purpose of the packaging container. For example, the heat seal strength may be reduced to provide easy opening. Therefore, the breaking strength of the support layer 2 does not need to exceed 20N / 15mm, but if the breaking strength of the support layer 2 is 20N / 15mm or more, it is easy to select the heat seal layer 1 according to the use of the lid. The breaking strength of the support layer 2 is not particularly limited, but is preferably in the range of 10 to 100N / 15mm, and more preferably in the range of 25 to 85N / 15mm. If the breaking strength is increased, the effect of reinforcing the lid laminate sheet 10 to suppress paper peeling is increased. However, if the support layer 2 is made thicker to increase the breaking strength, the carbon dioxide emissions and costs associated with the manufacture of the support layer 2 and the disposal of the lid laminate sheet 10 will increase.

[0072] The support layer 2 can be formed by laminating it on the paper substrate 3 via an adhesive, and examples of such lamination methods include the dry lamination method using a solvent-based adhesive, the non-solvent lamination method using a solventless adhesive, and the sand lamination method using a molten resin as the adhesive. In addition, the support layer 2 can be formed directly on the paper substrate 3 by extruding the composition that constitutes it in a molten state, such as by extrusion lamination. In this case, an adhesive layer may also be formed on the paper substrate 3 as necessary.

[0073] (Printing layer) The printed layer 4 is a layer formed for putting the lid laminate sheet 10 or the lid into practical use as a commercial product. The printed layer 4 is a layer formed of ink in which additives such as various pigments, extender pigments, plasticizers, desiccants, and stabilizers are added to conventionally used ink binder resins such as urethane, acrylic, nitrocellulose, rubber, and vinyl chloride, and displays patterns such as letters and designs. The printed layer 4 can be formed by known printing methods such as offset printing, gravure printing, and silk screen printing, or known coating methods such as roll coating, knife edge coating, and gravure coating.

[0074] The thickness of the printed layer 4 is not particularly limited, and may be, for example, in the range of 0.1 to 5 μm, or in the range of 0.2 to 1 μm.

[0075] (Water-resistant functional layer) The water-resistant functional layer (water-resistant layer) 5 is a layer that, in a packaged food described below, prevents liquids outside the container, such as moisture due to condensation or oil, from penetrating into the lid and prevents the 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 deterioration in adhesion of these layers.

[0076] 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 lid laminate sheet 10 from the functional layer 5 to the paper base material 3. The functional layer 5 controls the water absorbency of the lid laminate sheet by the Cobb method described below to 20 g / m 2 It is preferable that the material has the following water resistance.

[0077] The water absorbency here is the water absorbency obtained in the method specified in JIS P8140:1998 "Paper and paperboard - Water absorbency test method - Cobb method" when the surface of the functional layer 5 is used as the measurement surface and the contact time between the test piece and water is 300 seconds. This water absorbency is 20 g / m 2It is preferable that the thickness is less than 10 g / m 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.

[0078] The functional layer 5 is preferably an overprint varnish layer (hereinafter referred to as "OP varnish layer").

[0079] According to one example, the functional layer 5 contains a water-resistant resin. As the water-resistant resin, any resin capable of realizing the above-mentioned water absorbency can be used without limitation. As the water-resistant resin, for example, polyolefin-based resins such as polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, and vinyl chloride-vinyl acetate copolymers, silicone-based resins, acrylic-based resins, epoxy-based resins, polyester-based resins, cellulose-based resins, or urethane-based resins can be used. The functional layer 5 can be obtained, for example, by applying a paint containing a water-resistant resin to the paper substrate 3 on which the printing layer 4 is formed, by a known method. In addition to the water-resistant resin, the paint can further contain additives such as pigments, dyes, hardeners, leveling agents, antiblocking agents, and lubricants, and solvents.

[0080] The functional layer 5 preferably has high abrasion resistance and scratch resistance so as to maintain sufficient water resistance. From this viewpoint, the thickness of the functional layer 5 and the coating amount of the paint which is its material are preferably larger than the thickness of a normal OP varnish layer and the coating amount of a normal OP varnish. Here, the "coating amount" refers to the solid mass per area.

[0081] For example, in the lid laminate sheet 10 shown in FIG. 1, the coating amount of the paint for forming the functional layer 5 is 0.2 g / m 2 It is preferable to coat the film so that the coating amount is 2.0 g / m or more. 2It is more preferable to coat the coating material so that the coating amount is, for example, 10 g / m or more. 2 The functional layer 5 is coated so as to have a thickness as described below. 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 be omitted.

[0082] (Heat seal layer) The heat seal layer 1 may be any layer that enables heat sealing of the lid 21 to the container body 22 of the food packaging container 20 shown in Fig. 2 described later, thereby sealing the container. For example, a film made of ethylene-vinyl acetate (EVA), ionomer resin, or other polyolefins is used as the heat seal layer 1. The heat seal layer 1 is preferably a layer that contains at least any one of linear low density polyethylene (LLDPE), very low density linear polyethylene (VLDPE), or polypropylene.

[0083] A sealant layer having an easy peel function (simple peeling function) can also be used as the heat seal layer 1. Easy peel property indicates excellent re-peelability and easy opening. Means for bonding the heat seal layer 1 by lamination or the like include the dry lamination method using a solvent-based adhesive, the non-solvent lamination method using a solvent-free adhesive, and the sand lamination method using a molten resin as an adhesive. In addition, when the heat seal layer is extruded with molten resin, the extrusion lamination method can also be used.

[0084] The heat seal layer 1 is provided on the support layer 2 by, for example, lamination. The heat seal layer 1 can also be formed by applying heat seal varnish. As a coating means, various coating methods such as gravure coating, die coating, blade coating, knife coating, and bar coating can be used. When using heat seal varnish, the thickness of the heat seal layer 1 can be made smaller than when the heat seal layer 1 is formed by lamination. In this case, the proportion of the mass of the paper base material 3 in the mass of the lid laminate sheet 10 can be made larger.

[0085] 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 to 60 μm, and more preferably in the range of 1 to 30 μm.

[0086] (Adhesive layer) The lid laminate sheet 10 may further include one or more adhesive layers. For example, the lid laminate sheet 10 may include an adhesive layer between the heat seal layer 1 and the support layer 2 to bond them. Alternatively, the lid laminate sheet 10 may include an adhesive layer between the support layer 2 and the paper base material 3 to bond them. Alternatively, the lid laminate sheet 10 may include an adhesive layer between the heat seal layer 1 and the support layer 2 to bond them, and may include another adhesive layer between the support layer 2 and the paper base material 3 to bond them. When the heat seal layer 1 is made of heat seal varnish, the adhesive layer between the heat seal layer 1 and the support layer 2 may be omitted.

[0087] The adhesive layer is made of an adhesive resin or adhesive that can provide the required adhesive strength depending on the material of the layer to be bonded thereto.

[0088] The adhesive resin may be 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 and 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.

[0089] 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 the reaction of the base agent and the curing agent in the adhesive composition.

[0090] An example of the base agent is polyol. An example of the curing agent is isocyanate compound. An example of the adhesive is an ether-based two-liquid reactive adhesive or an ester-based two-liquid reactive adhesive.

[0091] The cured product of the ether-based two-liquid 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.

[0092] Examples of the cured product of the ester-based two-component reactive adhesive include polyester polyurethane and polyester. The polyester polyurethane is produced by reacting a polyester polyol as a base material with an isocyanate compound as a curing agent.

[0093] In the two-liquid reactive adhesive, an acrylic polyol may be used as the main agent. In addition, the adhesive composition may not contain a solvent as long as it melts or has a low viscosity when heated. As a coating method, various coating methods such as gravure coating, die coating, blade coating, knife coating, and bar coating can be used.

[0094] The lid laminate sheet 10 has a mass per area of ​​50 to 160 g / m 2 and preferably in the range of 60 to 140 g / m 2 More preferably, the range is 90 to 130 g / m 2 It is more preferable that the value is within the range of 100%. If the value is reduced, the strength of the lid decreases. If the value is increased, the lid becomes hard and the ease of opening decreases. Furthermore, if the value is increased, the cost increases and the amount of carbon dioxide emitted during production and exhaust increases.

[0095] As described above, this lid laminate sheet 10 is used as a lid material for food packaging containers and includes a paper base material 3. When a paper base material is used, it is difficult to achieve high puncture strength, but by combining the above structure and materials, a lid with excellent puncture strength can be realized. Packaged foods equipped with such a lid are less likely to suffer lid damage during transportation.

[0096] The puncture strength from the upper surface side of the lid laminate sheet 10 is 7 N or more. The puncture strength from the upper surface side of the lid laminate sheet 10 is preferably 7.5 N or more, and more preferably 8 N or more. This puncture strength is preferably 20 N or less, more preferably 16 N or less, and even more preferably 12 N or less.

[0097] The puncture strength from the underside of the lid laminate sheet 10 is 9 N or more. The puncture strength from the underside of the lid laminate sheet 10 is preferably 10 N or more, more preferably 11 N or more, and even more preferably 12 N or more. This puncture strength is preferably 25 N or less, more preferably 20 N or less, and even more preferably 16 N or less.

[0098] Here, the "puncture strength" of the lid laminate sheet or lid is a value obtained by piercing the lid laminate sheet or lid from the top or bottom side in the method specified in JIS Z1707:2019 "General Rules for Food Packaging Plastic Films". Specifically, a needle with a diameter of 1 mm and a semicircular tip is pierced from the top or bottom side of the lid laminate sheet or lid at a speed of 50 mm / min, and the maximum force until the needle penetrates is measured. This measurement is performed multiple times, and the arithmetic average of the maximum forces is obtained as the puncture strength.

[0099] [Variations] The lid laminate sheet can be modified in various ways. For example, as described below, the lid laminate sheet may further include a gas barrier layer. The items described with reference to FIG. 1 can be applied to the lid laminate sheet according to the modified example described here, either alone or in combination.

[0100] (Gas barrier layer) The gas barrier layer is interposed 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 a packaged food 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 content in the packaged food. In addition, the gas barrier layer prevents odor components and the like of the contents from diffusing to the outside of the container in the packaged food. According to one example, the gas barrier layer has an oxygen transmission rate of 0.1 to 100 cc / m in an atmosphere at a temperature of 30°C and a relative humidity of 70%. 2 / day / atm.

[0101] 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 assumed, the gas barrier layer is preferably an inorganic oxide layer, a resin-containing layer, or a combination thereof.

[0102] The gas barrier layer may be formed by coating, 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.

[0103] As the inorganic oxide, for example, silicon oxide, boron oxide, or 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 can be used.

[0104] 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, and epoxy resin can be used. Additives such as organic or inorganic particles, layered compounds, and curing agents may be added to the coating liquid.

[0105] 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 additives. For melt molding, for example, extrusion molding techniques such as T-die and inflation molding can be used.

[0106] The thickness of the gas barrier layer is in one example in the range of 0.01 to 30 μm, and in another example in the range of 0.1 to 12 μm.

[0107] The lid laminate sheet 10 may include the gas barrier layer and the paper base material 3 as a barrier paper in which the gas barrier layer is provided on the paper base material 3. Alternatively, the lid laminate sheet 10 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.

[0108] The laminated sheet for a lid including a gas barrier layer has gas barrier properties and is also less susceptible to deterioration of the gas barrier properties, particularly the oxygen barrier properties. This will be described below.

[0109] In order to suppress oxidation of the food contained in the food packaging container, it is sometimes desired that the food packaging container has excellent oxygen barrier properties to prevent oxygen from entering from the outside. In such food packaging containers, the lids thereof are also required to have oxygen barrier properties.

[0110] 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 in which the lid contains a metal layer have problems such as the inability to check for the presence of metal foreign matter using a metal detector after filling the contents, the inability to incinerate the paper as paper because it contains metal, and the inability to reuse the paper as waste paper, and the inability to use the lid as a packaging container for refrigerated foods that are expected to be cooked in a microwave oven.

[0111] 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 lid without a metal layer can avoid the above problems.

[0112] The optimum temperature range for distribution and storage of chilled foods is set for each food, but it is generally within the range of 0 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 in a room temperature environment, for example, from the time a consumer purchases the packaged food at a store until the time they store it in their home refrigerator, and from the time a consumer takes the packaged food out of the refrigerator until the time they start cooking it.

[0113] The present inventors have found that a packaged food in which a chilled food is housed in a food packaging container with a lid comprising a paper base material and a gas barrier layer, particularly a packaged food in which the gas barrier layer is made of a resin-containing layer, experiences a significant decrease in the gas barrier properties, particularly the oxygen barrier properties, of the lid during the first few hours of exposure from a refrigerated state to a room temperature environment. This is particularly noticeable when the mass of the paper base material accounts for a large proportion of the mass of the lid.

[0114] The inventors have found that the above problem is caused by condensation on the surface of the lid. That is, when a packaged product that has been in a refrigerated environment is exposed to a room temperature environment, condensation occurs on the outer surface of the lid, and the moisture reaches the gas barrier layer, damaging the gas barrier layer. As a result, the oxygen barrier property of the lid is reduced.

[0115] The laminated sheet for lids containing the gas barrier layer also contains a functional layer 5 having water resistance, according to one example. In this case, in a packaged food using this laminated sheet for lids as a lid material, 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 laminated sheet for lids as a lid material, damage to the gas barrier layer caused by condensation on the outer surface of the lid is unlikely to occur, and the oxygen barrier property is unlikely to decrease.

[0116] The inventors have further found that, in particular, in a packaged food in which chilled food is contained 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. As described above, by making the breaking strength of the support layer 2 greater than the heat seal strength between the lid and the container body, it is possible to make the paper less likely to peel off.

[0117] 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.

[0118] [Second embodiment] The lid according to the second embodiment of the present invention is a lid obtained from the lid laminate sheet according to the first embodiment or the modified example. An example of the lid according to the second embodiment is the lid 21 described later with reference to FIG. 2. As described in relation to the lid laminate sheet 10, the lid according to this embodiment has excellent puncture strength. Therefore, this lid is less likely to be damaged during transportation.

[0119] [Third embodiment] Fig. 2 is a cross-sectional view showing a food packaging container according to a third embodiment of the present invention. The food packaging container 20 shown in Fig. 2 includes a container body 22 having an opening, and a lid 21 that covers the opening.

[0120] 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 expands outward at the position of the upper opening of the body.

[0121] The container body 22 includes, for example, an olefin resin such as polypropylene. The container body 22 may further include a component such as an ethylene-vinyl alcohol copolymer in order to enhance its gas barrier properties. The container body 22 may further include an additive, for example, an additive for improving processability, designability, and chemical durability.

[0122] 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.

[0123] The container body 22 may be made of paper. When the contents include a liquid, the container body 22 may have a multi-layer structure including a paper base material and a layer of resin or the like provided on the surface of the container body 22 facing the contents to prevent the liquid from seeping into the paper base material. The container body 22 may be made of paper leaves, paper powder, pulp, or recycled paper. The container body 22 may be formed by folding or pasting a sheet including paper leaves, as in the manufacture of paper packs, press molding of a sheet using a mold, or other general-purpose techniques such as pulp molding. By using paper for the container body 22, it is possible to reduce the amount of carbon dioxide emissions associated with the manufacture and disposal of the food packaging container 20 as a whole, and therefore the burden on the environment is reduced.

[0124] The lid body 21 is the lid body laminate sheet 10 or is cut out from it. After the contents are placed in the container body 22, the lid body 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 appropriately set.

[0125] [Fourth embodiment] The packaged food according to the fourth embodiment of the present invention is obtained by packaging food in the food packaging container according to the third embodiment described above. The food to be packaged is not particularly limited, but is preferably a chilled food or a frozen food. The chilled food and frozen food are, for example, cooked or processed foods. The chilled food and frozen food are, for example, grilled fish, boiled fish, or side dishes.

[0126] In this packaged food, as described above, 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. This heat seal strength is preferably in the range of 5N / 15mm to 60N / 15mm, more preferably in the range of 10N / 15mm to 50N / 15mm. The difference between the breaking strength of the support layer 2 and the heat seal strength between the lid 21 and the container body 22 is preferably in the range of 5 to 60N / 15mm, more preferably in the range of 10 to 40N / 15mm. Here, the heat seal strength is a value obtained by a method specified in JIS Z0238:1998 "Test method for heat-sealed flexible packaging bags and semi-rigid containers".

[0127] In the manufacture of this packaged food, before the lid 21 is heat-sealed to the container body 22, for example, after the contents are placed in the container body 22 and before the lid 21 is heat-sealed to the container body 22, the gas in the container body 22 may be replaced by a known method. For example, the container body 22 may be filled with an inert gas. By appropriately changing the gas composition in the container, it is possible to suppress the growth of bacteria and extend the quality retention period, to prevent oxidation and thereby to maintain the flavor, color, etc. of the food for a long time, and to prevent the loss of vitamins. The replacement gas is appropriately selected depending on the type of food that is the content. As the replacement gas, a mixed gas of oxygen gas, nitrogen gas, and carbon dioxide gas is preferably used.

[0128] The lid included in this packaged food has excellent puncture resistance, so that the packaged food is less likely to develop defects such as pinholes or holes in the lid during transportation, and therefore the contents are less likely to deteriorate as a result.

[0129] Prepackaged foods are packed in boxes prior to transportation. In packaging, the packaged foods are often laid out on the bottom of a box, and then one or more other packaged foods are stacked on top of each packaged food. For this reason, during transportation, the stacked packaged foods collide with each other due to vibrations of the vehicle body, etc. In this case, the lid may be damaged. The present inventors have also found that when sharp foods such as fish bones are contained as contents, or when the contents are hard at low temperatures, particularly at freezing temperatures, the above-mentioned vibrations may cause the contents to collide with the lid, resulting in damage to the lid.

[0130] The puncture strength from the upper surface side and the puncture strength from the lower surface side of the above-mentioned lid laminate sheet 10 are within the above-mentioned ranges. Therefore, a packaged food provided with a lid 21 made of such a lid laminate sheet 10 is unlikely to suffer damage to the lid during transportation as described above.

[0131] The above-mentioned lid 21 is particularly unlikely to be damaged by the collision of the contents. This is because the above-mentioned lid laminate sheet 10 has excellent puncture strength from the underside, as described below.

[0132] FIG. 3 is a cross-sectional view of the lid laminate sheet 10 showing a state where a needle is pressed against the lid laminate sheet 10 from the paper base material 3 side. Although the functional layer 5 and the printed layer 4 are omitted in FIG. 3 and FIG. 4, the effect of these layers on the puncture strength is small. Since the paper base material 3 has the property of being difficult to stretch and difficult to deform under stress, as shown in FIG. 3, stress is likely to be concentrated in the area of ​​the paper base material 3 where the needle comes into contact. As a result, when a needle is pressed against the lid laminate sheet 10 from the paper base material 3 side, the puncture strength is smaller than when the needle is pressed against the support layer alone.

[0133] 4 is a cross-sectional view of the lid laminate sheet 10 showing a state in which a needle is pressed against the lid laminate sheet 10 from the heat seal layer 1 side. The heat seal layer 1 has a property of being easily stretched and easily deformed by stress. Therefore, the above-mentioned problems caused by the property of the paper base material 3 do not occur when a needle is pressed against the lid laminate sheet 10 from the heat seal layer 1 side, and the heat seal layer 1 disperses the stress. Therefore, the puncture strength from the heat seal layer 1 side is greater than the puncture strength from the paper base material 3 side.

[0134] Furthermore, the lid laminate sheet 10 including the support layer 2 having the above-mentioned anisotropy, i.e., the support layer 2 having the breaking strength A1 greater than the breaking strength A2 and the difference between the breaking strengths A1 and A2 within the above-mentioned range, has particularly excellent puncture strength. Therefore, a packaged food including a lid 21 made of such a lid laminate sheet 10 is particularly unlikely to break as described above. The fact that the lid laminate sheet 10 including such a support layer 2 has excellent puncture strength will be described below.

[0135] In the above-mentioned support layer 2, the proportion of molecules oriented in the first direction is greater than the proportion of molecules oriented in the second direction. When a needle is pressed against this support layer 2, the molecules located near the needle are oriented radially from the tip of the needle.

[0136] At this time, the molecules in the area adjacent to the needle in the second direction change their orientation from the first direction to the second direction. This change in orientation makes the support layer 2 more likely to stretch in the second direction, and therefore less likely to break in the first direction.

[0137] In addition, the molecules in the region away from the needle and the molecules in the region adjacent to the needle in the first direction in the vicinity of the needle are unlikely to change orientation before and after the needle is pressed. That is, even when the needle is pressed, the molecules in these regions remain oriented in the first direction. In these regions, molecular aggregation is maintained between two molecules adjacent in the second direction during the needle pressing process. Due to such aggregation, the support layer 2 is unlikely to deform excessively in the second direction and can have an appropriate hardness.

[0138] The above-mentioned lid laminate sheet 10 has the above-mentioned characteristics. Therefore, even if the pressure applied by the needle is increased, the stress can be dispersed and the sheet can continue to stretch while maintaining an appropriate hardness. Therefore, the lid laminate sheet 10 including the support layer 2 having the above-mentioned anisotropy has high puncture strength. EXAMPLES

[0139] Tests carried out in relation to the present invention are described below.

[0140] <1> Manufacturing of laminated sheets for lids (Example 1) The lid laminate sheet 10 shown in FIG. 1 was produced by the following method. First, the paper base material 3 has a thickness of 50 μm and a basis weight of 52.3 g / m 2 The single-sided coated paper had a basis weight of 37.3 g / m 2 The coating layer solution is applied to a surface of the paper with a mass of 15 g / m 2 The paper was obtained by coating so that the coating solution contained polyvinyl alcohol (PVA) and styrene butadiene rubber (SBR) as main components, and further contained silica and layered silicate. A printing layer 4 and a functional layer 5 were successively formed on the coating layer of this paper base material 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 2The functional layer 5 was formed using an OP varnish mainly composed of nitrocellulose resin and polyethylene granular wax. The amount of the OP varnish applied was 0.5 g / m 2 It was decided.

[0141] Next, the support layer 2 was attached by dry lamination to the laminate consisting of the paper base material 3, the printing layer 4, and the functional layer 5. The support layer 2 had a thickness of 15 μm and a mass per area of ​​17.4 g / m 2 A sequentially biaxially oriented nylon film was used, which had a breaking strength of 55 N / 15 mm in MD and 60 N / 15 mm in TD, and was corona-treated on both sides. For dry lamination, a dry laminating agent was first applied to one side of the support layer 2 using a gravure coater to form an adhesive layer. A two-part reactive adhesive containing an ester polyol and an isocyanate 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 support layer 2 were bonded together with the adhesive layer sandwiched between them, so that the support layer 2 faced the surface of the paper base material 3 on which no coating layer was provided. The method for measuring the breaking strength of the support layer 2 will be described later.

[0142] Thereafter, the heat seal layer 1 was attached by dry lamination to the laminate including the support layer 2, the paper base material 3, the printing layer 4, and the functional layer 5. The heat seal layer 1 includes a support layer and an easy peel layer, and has a mass per area of ​​27.6 g / m 2 The film used was easy-peelable, with a thickness of 30 μm and a corona treatment applied to the side opposite the easy-peel layer. For dry lamination, a dry laminating agent was first applied to the two sides of the support layer using a gravure coater to form an adhesive layer. A two-part reactive adhesive containing an ester polyol and an isocyanate curing agent was used as the dry laminating agent. The amount of dry laminating agent applied was 3.0 g / m 2Next, the above laminate and the heat seal layer 1 were attached to each other with the adhesive layer sandwiched therebetween so that the corona-treated surface of the heat seal layer 1 faced the support layer 2.

[0143] Thereafter, this was aged for 2 days at 40° C. In this manner, a lid laminate sheet 10 shown in FIG.

[0144] (Example 2) A lid laminate sheet 10 was produced in the same manner as in Example 1, except for the following points. In this example, instead of using the above-mentioned sequentially biaxially oriented nylon film as the support layer 2, a 15 μm thick, 17.4 g / m mass per area laminate sheet was used. 2 The film used was a sequentially biaxially oriented nylon film having a breaking strength of 46 N / 15 mm in MD and 65 N / 15 mm in TD, and having been corona-treated on both sides.

[0145] (Example 3) A lid laminate sheet 10 was produced in the same manner as in Example 1, except for the following points. That is, instead of using a sequentially biaxially oriented nylon film as the support layer 2, a sequentially biaxially oriented nylon film having a thickness of 15 μm and a mass per area of ​​17.4 g / m was used. 2 A simultaneous biaxially oriented nylon film with corona treatment on both sides was used.

[0146] (Example 4) A lid laminate sheet 10 was produced in the same manner as in Example 1, except for the following points. In this example, instead of using a sequentially biaxially oriented nylon film as the support layer 2, a sequentially biaxially oriented nylon film having a thickness of 15 μm and a mass per area of ​​20.9 g / m was used. 2 A simultaneous biaxially stretched polybutylene terephthalate film having both sides subjected to corona treatment was used.

[0147] (Comparative Example) Instead of using a sequentially biaxially oriented nylon film as the support layer, a film with a thickness of 12 μm and a mass per area of ​​16.4 g / m 2A lid laminate sheet was produced in the same manner as in Example 1, except that a biaxially oriented polyethylene terephthalate film of was used.

[0148] <2> evaluation (Measurement of breaking strength) The breaking strength of the support layers used in Examples 1 to 4 and the Comparative Example was measured by the method described above.

[0149] Here, three test pieces whose length direction is parallel to MD and three test pieces whose length direction is parallel to TD were cut out from each support layer. Each test piece was in the shape of a strip with a width of 15 mm and a length of 100 mm.

[0150] The gauge length was 50 mm, and the test speed was 1000 mm / min. The breaking strength was measured using a Tensilon universal testing machine.

[0151] The breaking strength in MD was obtained by arithmetically averaging the measurements obtained using specimens whose length direction was parallel to MD, and the breaking strength in TD was obtained by arithmetically averaging the measurements obtained using specimens whose length direction was parallel to TD.

[0152] (Measurement of puncture strength) The puncture strength of the lid laminate sheets according to Examples 1 to 4 and Comparative Example, and the support layers used in Examples 1 to 4 and Comparative Example, were measured by the above-mentioned method. Here, for the lid laminate sheet 10, the puncture strength when a needle was pierced into the lid laminate sheet from the upper surface side and the puncture strength when a needle was pierced into the lid laminate sheet from the lower surface side were measured. Each puncture strength was obtained by arithmetically averaging the values ​​obtained from nine measurements.

[0153] Fig. 5 is a graph showing the relationship between the load and the needle movement when the puncture strength was measured for the support layers used in Examples 1 to 3 and the Comparative Example. As shown in Fig. 5, the support layers according to Examples 1 to 3 were less likely to break when punctured with a needle than the support layer according to the Comparative Example. Therefore, they were more likely to stretch. Among the support layers according to Examples 1 to 3, the support layers according to Examples 1 and 2 were particularly more likely to stretch.

[0154] (Tensile strength, tensile elongation and tensile modulus) The tensile strength, tensile elongation, and tensile modulus of elasticity of the support layers used in Examples 1 to 4 and Comparative Example were measured. The results are shown in Figures 6 to 8. The tensile elongation and tensile modulus of elasticity were measured by the method described above. The tensile strength was also measured by the same method as the method for measuring the tensile elongation and tensile modulus of elasticity.

[0155] Fig. 6 is a graph showing the tensile strength of the support layers used in Examples 1 to 4 and the Comparative Example. As shown in Fig. 6, the support layers according to Examples 1 and 2 had a higher tensile strength in TD than the support layer according to Example 3. This is because in the support layers according to Examples 1 and 2, the proportion of molecules oriented in TD is greater than the proportion of molecules oriented in MD, and therefore cohesive forces are more likely to occur between adjacent molecules in MD.

[0156] Fig. 7 is a graph showing the tensile elongation of the support layers used in Examples 1 to 4 and the Comparative Example. As shown in Fig. 7, in the support layers according to Examples 1 and 2, the tensile elongation in MD was greater than the tensile elongation in TD. In the support layers according to Examples 1 and 2, the proportion of molecules oriented in TD was greater than the proportion of molecules oriented in MD. Therefore, when the support layers are pulled in MD, in the support layers according to Examples 1 and 2, the molecules oriented in TD change their orientation direction from TD to MD. Due to such an orientation change, the support layers according to Examples 1 and 2 are easily stretched in MD.

[0157] FIG. 8 is a graph showing the tensile modulus of the support layer used in Examples 1 to 4 and Comparative Example. As shown in FIG. 8, in the support layers according to Examples 1 and 2, the tensile modulus in MD was greater than the tensile modulus in TD. As described above, in the support layers according to Examples 1 and 2, the proportion of molecules oriented in TD is greater than the proportion of molecules oriented in MD. Therefore, when the support layer is pulled in MD, the support layers according to Examples 1 and 2 are less likely to deform due to molecular aggregation between two molecules adjacent in MD. Therefore, the support layers according to Examples 1 and 2 have a high tensile modulus in MD. In addition, the support layer according to Comparative Example had a high tensile modulus, but had a smaller puncture strength than the support layers according to Examples 1 to 4.

[0158] (Birefringence) The birefringence of the support layers used in Examples 1 to 4 and the Comparative Example was measured by the method described above.

[0159] (Transportation Test) Lids were cut out from the lid laminate sheets according to Examples 1 to 4 and Comparative Example. These lids were used to produce packaged foods in which food was contained in the food packaging container 20 shown in FIG. 2. For each lid laminate sheet, 36 packaged foods were produced. Here, the container body 22 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 surface 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, chinjaorusu.

[0160] The lid 21 was heat sealed to the flange 22a as follows. First, a jig was prepared having a recess and a support part of 5 mm in height that conforms to the shape of the flange 22a at the edge of the opening of the recess. Next, the container body 22 was fitted into the recess of the jig so that the flange 22a and the support part were in contact with each other. Next, the lid body 21 was placed on the container body 22, and the lid body 21 and the flange 22a were heat-sealed. The heat sealing was performed by applying a temperature of 190°C and a pressure of 0.2 MPa for 1 second using a seal bar with a width of 4 mm that was made to conform to the shape of the flange 22a.

[0161] The packaged foods were then packed into cardboard boxes. Six packaged foods were first laid out on the bottom of the box, and then five packaged foods were stacked on top of each packaged food. The packaged foods were then stored at -20°C for two hours.

[0162] Next, while still frozen, the packaged foods were loaded onto a vehicle and transported over a distance of approximately 650 km. The packaged foods were then opened to check whether the lids had been torn. If the lids had been torn, it was determined whether the torn lids had been caused by the food colliding with itself or by the food colliding with the lid.

[0163] Specifically, if the cut surface of the broken lid was not soaked with oil from the food, the court determined that the breakage was caused by the packaged food colliding with itself, and if the cut surface was soaked with oil from the food, the court determined that the breakage was caused by the food colliding with the lid.

[0164] Most of the tears in the lids, which did not involve soaking in oil from food, were located in the area that was in contact with the edge of the bottom of the packaged food stacked on top of the lids. For this reason, it was determined that the tears in the lids were caused by the edge of the package piercing the lid due to vibrations during transportation.

[0165] The physical properties of the support layer contained in the above-mentioned laminated sheet for a lid are shown in the following Table 1. The results of the above-mentioned measurements and tests are summarized in the following Table 2.

[0166] [Table 1]

[0167] [Table 2]

[0168] In Tables 1 and 2, "Ny," "PBT," and "PET" represent nylon, polybutylene terephthalate, and polyethylene terephthalate, respectively. In Table 2, "mass" is the mass per area. In Table 2, the classification of "paper," "plastic," and "other" in the column labeled "mass" follows the "Explanatory Materials for the Containers and Packaging Recycling Law."

[0169] In the column in Table 2 entitled "Puncture strength of lid body," "top surface" represents the puncture strength when a needle is pierced from the top side of the lid body laminate sheet, and "bottom surface" represents the puncture strength when a needle is pierced from the bottom side of the lid body laminate sheet.

[0170] In the column titled "Transportation Test" in Table 2, "X" indicates the number of packaged foods whose lids were broken due to collisions between the packaged foods, and "Y" indicates the number of packaged foods whose lids were broken due to collisions between the packaged foods and the lids. In the column titled "X" or "Y," "A" indicates that no packaged foods had broken lids, "B" indicates that the number of packaged foods whose lids were broken was 1 to 3, and "C" indicates that the number of packaged foods whose lids were broken was 4 or more.

[0171] As shown in Table 2, in the transportation test, the number of packaged foods with lids made of the lid laminate sheet according to Examples 1 to 4 in which the lids were torn was 3 or less. None of the packaged foods with lids made of the lid laminate sheet according to Examples 1 and 2 in which the lids were torn was packaged foods. In contrast, the number of packaged foods with lids made of the lid laminate sheet according to the comparative example in which the lids were torn was 4 or more.

[0172] As shown in Table 1, the support layer according to the comparative example had a higher birefringence than the support layers according to Examples 1 to 4. The support layer according to the comparative example contains polyethylene terephthalate, which contains a benzene ring. Cyclic hydrocarbons such as benzene rings have a higher orientation than chain hydrocarbons. In addition, in a layer having a ring structure containing π electrons such as a benzene ring, the difference in MD and TD in optical properties such as refractive index is large due to the coordination direction of the ring. Therefore, it is considered that the support layer according to the comparative example has a higher birefringence than the support layers according to Examples 1 to 3 which do not contain a benzene ring.

[0173] In addition, polybutylene terephthalate has a longer carbon chain in its unit structure than polyethylene terephthalate, and therefore has a lower orientation of benzene rings than polyethylene terephthalate, which is why the support layer of Example 4 containing polybutylene terephthalate is thought to have a smaller birefringence than the support layer of Comparative Example containing polyethylene terephthalate.

[0174] The present invention is not limited to the above-mentioned embodiment, and can be modified in various ways without departing from the gist of the present invention. The embodiments may be combined as appropriate, and in that case, the combined effect can be obtained. Furthermore, the above-mentioned embodiment includes various inventions, and various inventions can be extracted by combinations selected from the multiple components disclosed. For example, if the problem can be solved and the effect can be obtained even if some components are deleted from all the components shown in the embodiment, the configuration from which the components are deleted can be extracted as an invention. [Explanation of symbols]

[0175] Reference Signs List 1...heat seal layer, 2...support layer, 3...paper base material, 4...printed layer, 5...functional layer, 10...laminated sheet for lid, 20...food packaging container, 21...lid, 22...container body, 22a...flange, 30...needle.

Claims

1. A laminated sheet for a lid used for a lid of a food packaging container having a container body with an opening and a lid covering the opening, the laminated sheet for a lid including, in this order, a paper base material, a support layer, and a heat seal layer, the puncture strength from the side opposite the heat seal layer being 7N or more and the puncture strength from the heat seal layer side being 9N or more.

2. The laminated sheet for a lid body as described in claim 1, wherein the breaking strength A1 of the support layer in a first direction is greater than the breaking strength A2 of the support layer in a second direction perpendicular to the first direction, and the difference between the breaking strength A1 and the breaking strength A2 is 1 N or more.

3. 2. The laminated sheet for a lid according to claim 1, wherein the breaking strength A1 of the support layer in a first direction is 41 N or more, and the breaking strength A2 of the support layer in a second direction perpendicular to the first direction is 40 N or more.

4. The lid laminate sheet according to claim 1 , wherein the support layer contains polyamide.

5. 5. The lid laminate sheet according to claim 4, wherein the polyamide is nylon.

6. 2. The lid laminate sheet according to claim 1, wherein the thickness of the support layer is 20 [mu]m or less.

7. The lid laminate sheet according to claim 1 , wherein the mass of the paper base material is greater than the mass of any other layer included in the lid laminate sheet.

8. The laminate sheet for a lid body according to claim 7, wherein when layers other than the paper base material contained in the laminate sheet for a lid body 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.

9. 2. The lid laminate sheet according to claim 1, wherein the paper base material has a thickness of 90 μm or less.

10. 2. The lid laminate sheet according to claim 1, wherein the heat seal layer is a sealant having easy peelability.

11. 2. The lid laminate sheet according to claim 1, wherein the heat seal layer has a thickness of 60 [mu]m or less.

12. The laminated sheet for a lid body as described in claim 1, further comprising a printed layer facing the support layer with the paper base material sandwiched therebetween, the paper base material being a coated paper having a coating layer on one side, and the printed layer being provided on the coating layer.

13. A lid comprising the laminate sheet for a lid according to any one of claims 1 to 12.

14. A food packaging container comprising a container body having an opening and a lid body as described in claim 13 that covers the opening, wherein the support layer is disposed between the paper base material and the internal space of the food packaging container.

15. 15. The food packaging container according to claim 14, 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.

16. 15. The food packaging container according to claim 14, wherein the internal space of the food packaging container is filled with a mixed gas containing oxygen gas, nitrogen gas, and carbon dioxide gas.

17. The food packaging container according to claim 14, wherein the food packaging container is a chilled food packaging container or a frozen food packaging container.

18. A packaged food comprising the food packaging container according to claim 14 and food contained in the food packaging container.

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