Cover material

Abstract

The present invention provides a lid material that can reduce or suppress the occurrence of blistering during moisture absorption and heat sealing, and that has good heat resistance. [Solution] In one aspect of the present invention, as shown in Figure 1(a), the lid material of the present invention is a lid material having at least an overprint varnish layer 102, a printed layer 104, a paper layer 106, and a sealant layer 108 in this order, The overprint varnish layer 102 contains hydrocarbon wax.

Description

[Technical Field]

[0001] This invention relates to a lid material. [Background technology]

[0002] In recent years, various studies have been conducted on lid materials that use paper as a base material.

[0003] For example, Patent Document 1 discloses a lid material characterized by being a laminate having a biaxially oriented plastic film with a water-retaining layer on at least one side of the paper and a vapor-deposited inorganic oxide film on the other side, an adhesion adjusting layer, and a hot-melt layer.

[0004] Patent Document 2 discloses a heat-sealable lid material made of a laminated sheet containing a paper layer supplied with a water-retaining agent, with the innermost layer being a hot-melt layer, characterized in that a light-shielding ink layer is laminated on at least the inner surface side of the paper layer, and the light transmittance of the lid material in the wavelength range of 200 to 800 nm is 15% or less.

[0005] Patent Document 3 discloses a lid material for paper cups, characterized by being laminated in the order of a paper layer, an adhesive layer, a biaxially oriented plastic film layer, and a hot melt layer.

[0006] Patent Document 4 discloses a lid material that is heat-sealed to a cup-shaped container having at least a resin layer formed on its surface, and the lid material is made of a composite sheet having paper as an intermediate layer and resin layers or aluminum foil layers on both sides of the front and back surfaces of the paper, characterized in that the air permeability of the paper is 10 seconds or less according to the "JIS P8117 Gurley Testing Machine Method". [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2000-118546 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-006295 [Patent Document 3] Japanese Patent Application Laid-Open No. 09-066586 [Patent Document 4] Japanese Patent Application Laid-Open No. 2004-196381 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] In the present invention, there is provided a lid material capable of reducing or suppressing the generation of blisters during moisture absorption and heat sealing and having good heat resistance. [Means for Solving the Problems]

[0009] As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have completed the present invention. That is, the present invention is as follows: <Aspect 1> A lid material having at least an overprint varnish layer, a printing layer, a paper layer, and a sealant layer in this order, where the overprint varnish layer contains a hydrocarbon wax, Lid material. <Aspect 2> The lid material according to Aspect 1, having at least the overprint varnish layer, the printing layer, the paper layer, an intermediate layer, and the sealant layer in this order. <Aspect 3> The lid material according to Aspect 2, wherein the intermediate layer is a metal foil layer. <Aspect 4> The lid material according to Aspect 2, wherein the intermediate layer is a layer composed of a polyester resin. <Aspect 5> The lid material according to any one of Aspects 1 to 4, wherein the content of the hydrocarbon wax is 5 to 80% by mass based on the mass of the solid content of the overprint varnish layer. <Aspect 6> When dried in a vacuum oven at 60°C for 4 hours and seasoned for 60 minutes in an environment of 23°C and 50% RH (relative humidity), the moisture absorption amount based on the mass before seasoning after drying is 2.2 g / m 2 Less than, the lid material according to any one of Aspects 1 to 5. <Aspect 7> The lid material according to any one of aspects 1 to 6, wherein the laminate of the overprint varnish layer, the printing layer, and the paper layer has an air permeability of 150,000 seconds or less when measured from the paper layer side toward the overprint varnish layer side using the Wang Ken test machine method of JIS P8117:2019. <Aspect 8> A container having a flange portion and a housing portion, and A lid material according to any one of embodiments 1 to 7, which is heat-sealed at the flange portion of the container, thereby sealing the container. A container with a lid. <Aspect 9> The lidded container according to aspect 8, further comprising contents contained in the storage section. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a lid material that can reduce or suppress the occurrence of blistering during moisture absorption and heat sealing, and that has good heat resistance. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1(a) is a side cross-sectional view of a lid material according to one embodiment of the present invention. Figure 1(b) is a side cross-sectional view of a lid material according to another embodiment of the present invention, having an intermediate layer. [Figure 2] Figure 2(a) is a top view of the lidded container of the present invention. Figure 2(b) is a side cross-sectional view of the lidded container of the present invention. [Modes for carrying out the invention]

[0012] 《Lid material》 The lid material of the present invention is A lid material having at least an overprint varnish layer, a printed layer, a paper layer, and a sealant layer in this order, The aforementioned overprint varnish layer contains hydrocarbon wax.

[0013] The inventors have found that the above configuration can reduce or suppress moisture absorption and blister formation during heat sealing. While we do not wish to be bound by theory, this is thought to be because the hydrophobic hydrocarbon wax impregnates the paper layer at least partially, thereby suppressing moisture absorption by the paper layer without significantly impairing air permeability.

[0014] To address the problem of curling observed in general-purpose paper lid materials, various methods have been proposed, such as providing a water-retaining layer on top of the paper base material or using a paper layer supplied with a water-retaining agent.

[0015] However, when humectants or water-retaining agents are applied to a paper substrate, curling can be suppressed during the manufacturing of the lid material, but curling can still occur when the manufactured lid material is placed in an environment with fluctuating humidity. More specifically, for example, a lid material manufactured by applying a mixture of water and methanol to the back surface of a paper substrate can suppress the occurrence of convex curling under high humidity conditions, but concave curling can occur under low humidity conditions.

[0016] In response to this, a lid material has been proposed in which, for example, a resin layer or aluminum foil layer is provided on both sides of a paper substrate. Since such a paper substrate allows for relatively little moisture to enter or leave, it is possible to suppress the occurrence of curling caused by changes in humidity.

[0017] However, in the case of lid materials that have a resin layer or aluminum foil layer on both sides of a paper base material, when the lid material is heat-sealed to a container or the like, the heat applied causes the moisture contained in the paper base material to vaporize, generating high-temperature water vapor inside the paper base material of the lid material. This water vapor has nowhere to escape except from the edges of the paper base material of the lid material, which can cause a problem where partial delamination occurs inside the lid material, for example, at the adhesive surface between the paper base material and the resin layer or aluminum foil layer (this phenomenon is also called "blistering" or "bubbling").

[0018] On the other hand, using a paper substrate with low air permeability (i.e., a paper substrate that is easily permeable) can suppress the occurrence of the aforementioned blisters, but the exchange of moisture becomes relatively more intense. As a result, the lid material may absorb moisture, and curling may not be suppressed. In addition, using a paper substrate with low air permeability may result in poor printability.

[0019] Thus, it has been difficult to achieve both suppressing moisture absorption and suppressing blister formation during heat sealing in lid materials. However, with the lid material having the above configuration of the present invention, moisture absorption by the paper layer can be suppressed without significantly impairing air permeability, and this suppression of moisture absorption is expected to suppress curling of the lid material due to changes in humidity.

[0020] Furthermore, the lid material of the present invention can have heat resistance, particularly sufficient heat resistance to smoothly heat-seal the lid material to the container. In particular, even when the overprint varnish layer is located on the outermost surface opposite the sealant layer, the lid material can be heat-sealed to the container via the sealant layer without the overprint varnish layer adhering to the sealing plate, similar to conventional overprint varnish layers.

[0021] On the other hand, when a known water vapor barrier coating, such as a water-based acrylic resin-based water- and oil-resistant varnish, is placed on the outermost surface opposite the sealant layer instead of the conventional overprint varnish layer, good moisture absorption is obtained, but sufficient heat resistance is not, and when attempting to heat-seal the lid material to the container via the sealant layer, the overprint varnish layer sometimes adheres to the sealing plate.

[0022] In other words, the lid material of the present invention having the above-described overprint varnish layer suppresses moisture absorption to the same extent as or better than when a water vapor barrier layer is used, suppresses blistering during heat sealing, and, like conventional overprint varnish layers, has heat resistance that prevents it from sticking to the sealing plate when heat-sealed.

[0023] The lid material of the present invention may further have an intermediate layer between the paper layer and the sealant layer. That is, the lid material of the present invention may have at least the overprint varnish layer, the printing layer, the paper layer, the intermediate layer, and the sealant layer in this order.

[0024] When the lid material of the present invention is dried in a vacuum oven at 60°C for 4 hours and seasoned for 60 minutes in an environment of 23°C and 50% RH (relative humidity), the moisture absorption amount based on the mass before seasoning after drying is 2.2 g / m 2 It can be less. More specifically, the moisture absorption amount under these conditions is 2.2 g / m 2 Less than, 2.1 g / m 2 Hereinafter, 2.0 g / m 2 Hereinafter, 1.9 g / m 2 Hereinafter, 1.8 g / m 2 Hereinafter, 1.7 g / m 2 Hereinafter, 1.6 g / m 2 Hereinafter, 1.5 g / m 2 Hereinafter, 1.4 g / m 2 Hereinafter, 1.3 g / m 2 Hereinafter, 1.2 g / m 2 Hereinafter, 1.1 g / m 2 Hereinafter, or 1.0 g / m 2 It can be less than or equal to. Also, the lower limit value of the moisture absorption amount under these conditions is not particularly limited. For example, 0.0 g / m 2 Or more, 0. @ g / m 2 Exceeding, 0.1 g / m 2 Or more, 0.2 g / m 2 Or more, 0.3 g / m 2 Or more, 0.4 g / m 2 Or more, 0.5 g / m 2 Or more, 0.6 g / m 2 Or more, 0.7 g / m 2 Or more, 0.8 g / m 2 Or more, 0.9 g / m 2 Or more, or 1.0 g / m 2 It can be more than or equal to.

[0025] The above moisture absorption amount can be obtained by the following method. The lid material is in a substantially round shape with a diameter of 101 mm (area of 0. @ m 2After cutting out the material, it is dried in a vacuum oven at 60°C for 4 hours, and the mass after drying is set as the baseline (0 (zero)). Next, the dried lid material is seasoned in an environment of 23°C and 50% RH (relative humidity), and the change in mass is measured. Then, the amount of moisture absorbed after 60 minutes can be calculated based on the following formula. Moisture absorption amount (g / m 2 ) = Mass after moisture absorption (g / m³) 2 )- Mass after drying in a vacuum oven (g / m³) 2 )

[0026] In the present invention, the laminate of the overprint varnish layer, the printed layer, and the paper layer described above can have an air permeability of 150,000 seconds or less when measured from the paper layer side toward the overprint varnish layer side using the Wang Ken testing machine method of JIS P8117:2019. More specifically, this air permeability value may be, for example, 150,000 seconds or less, 100,000 seconds or less, 90,000 seconds or less, 80,000 seconds or less, 70,000 seconds or less, 60,000 seconds or less, 50,000 seconds or less, 40,000 seconds or less, 30,000 seconds or less, or 20,000 seconds or less. Furthermore, the lower limit of this air permeability is not particularly limited and may be, for example, 500 seconds or more, 1,000 seconds or more, 2,000 seconds or more, 3,000 seconds or more, 4,000 seconds or more, 5,000 seconds or more, 6,000 seconds or more, 7,000 seconds or more, 8,000 seconds or more, 9,000 seconds or more, 10,000 seconds or more, 20,000 seconds or more, 30,000 seconds or more, or 40,000 seconds or more. Note that the value of the air permeability of this laminate is obtained by measuring from the back side of the paper layer toward the front side (overprint varnish layer side).

[0027] The thickness of the lid material of the present invention is not particularly limited and may be, for example, 40 μm or more and 200 μm or less. This thickness may be, for example, 40 μm or more, 50 μm or more, 60 μm or more, 70 μm or more, 80 μm or more, 90 μm or more, 100 μm or more, or 150 μm or more, and may also be 200 μm or less, 180 μm or less, 150 μm or less, 120 μm or less, or 100 μm or less.

[0028] In one aspect of the present invention, as shown in Figure 1(a), the lid material of the present invention is a lid material having at least an overprint varnish layer 102, a printed layer 104, a paper layer 106, and a sealant layer 108 in this order, The overprint varnish layer 102 contains hydrocarbon wax.

[0029] In another aspect of the present invention, as shown in Figure 1(b), the lid material of the present invention may have at least an overprint varnish layer 102, a printed layer 104, a paper layer 106, an intermediate layer 109, and a sealant layer 108 in this order.

[0030] Although not shown in Figure 1, the lid material of the present invention may have a tab for pinching and pulling up when opening.

[0031] The layer structure of the lid material of the present invention will be described below.

[0032] <Overprint varnish layer> The overprint varnish layer is a layer laminated on top of the printed layer. In particular, the overprint varnish layer of the present invention contains a hydrocarbon wax. The overprint varnish layer may be located on the outermost surface opposite the sealant layer.

[0033] An overprint varnish layer can be obtained by printing an overprint varnish layer composition onto a printed layer.

[0034] (Hydrogen-based wax) Hydrocarbon waxes are contained in the overprint varnish layer.

[0035] Hydrocarbon waxes refer to organic substances that primarily consist of a long-chain alkyl group skeleton, are solid at room temperature, and become liquid when heated. These skeletons may also contain acid groups, ester groups, hydroxyl groups, etc.

[0036] Specific examples of hydrocarbon waxes include one or more selected from the group consisting of natural waxes such as paraffin wax, microcrystalline wax, beeswax, montan wax, ozokerite, ceresin, carnauba wax, candelilla wax, beeswax, wood wax, and rice wax, as well as synthetic waxes. Commercially available hydrocarbon waxes can be used. In addition, oxidized waxes produced by chemical reactions such as oxidation, saponification, esterification, maleation, and acid anhydride formation using these as raw materials, as well as blended waxes obtained by incorporating these into resins, and emulsion waxes obtained by dispersing these waxes in water, can also be used as hydrocarbon waxes in the present invention.

[0037] Furthermore, it is preferable that 80% or more by mass of the hydrocarbon wax has a linear structure without branching, and more preferably 90% or more has a linear structure without branching. Also, as hydrocarbon materials exhibiting similar properties, such as being solid at room temperature and having a melting point of 30°C to 80°C, waxy olefins having double bonds in their molecules are also included in hydrocarbon waxes, and mixtures thereof can be cited. Among the hydrocarbon waxes described above, paraffin wax and microcrystalline wax are preferred, with paraffin wax being the most preferred. Because of their excellent crystallinity, they can particularly promote the formation of wax aggregate structures in the overprint varnish layer composition of the present invention.

[0038] The hydrocarbon wax content may be 5% by mass or more and 80% by mass or less relative to the mass of the solid content of the overprint varnish layer. This content may be 5% by mass or more, 10% by mass or more, 15% by mass or more, 18% by mass or more, or 20% by mass or more, and may also be 80% by mass or less, 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, 50% by mass or less, 47% by mass or less, 45% by mass or less, 40% by mass or less, 38% by mass or less, or 35% by mass or less. In particular, when the hydrocarbon wax content is 20% by mass or more relative to the mass of the overprint varnish layer, the hygroscopicity of the lid material can be suppressed in particular.

[0039] <Printing layer> The lid material of the present invention has a printed layer. The printed layer can be used to apply patterns, textual information, etc., and can also be used as a functional layer for purposes such as light shielding and ultraviolet protection.

[0040] In the present invention, the thickness of the printed layer is not particularly limited and may be, for example, 0.1 μm or more, 0.5 μm or more, 1.0 μm or more, 2.0 μm or more, 3.0 μm or more, 4.0 μm or more, 5.0 μm or more, 6.0 μm or more, 7.0 μm or more, 8.0 μm or more, 9.0 μm or more, or 10 μm or more, or 10 μm or less, or 10 μm or less, or 8.0 μm or less, 5.0 μm or less, 3.0 μm or less, or 1.0 μm or less.

[0041] In the present invention, the ink layer of the printing layer is not particularly limited and may include, for example, an ink selected from the group consisting of water-based ink, oil-based ink, curable ink, and two or more combinations thereof.

[0042] In the present invention, the printing method is not particularly limited and may be, for example, gravure printing or flexographic printing.

[0043] <Paper layer> The lid material of the present invention has a paper layer.

[0044] In the present invention, the paper layer is not particularly limited and may be, for example, art paper, coated paper, pure white paper, or fine paper.

[0045] Furthermore, in this invention, the basis weight of the paper layer is not particularly limited, for example, 30 g / m². 2 More than 200g / m 2 The following is acceptable. This basis weight is 30 g / m². 2 More than 40g / m 2 More than 50g / m 2 More than 60g / m 2 or more, or 70g / m² 2 The above is sufficient, and also 200g / m 2 Below 150g / m 2 Below 120g / m2 Below 100g / m 2 Below 90g / m 2 The following, or 80 / m 2 The following is acceptable:

[0046] <Sealant layer> The lid material of the present invention has a sealant layer. The sealant layer is a layer for heat-sealing the container to be sealed by the lid material and the lid material itself.

[0047] The material of the sealant layer is not particularly limited and may be appropriately selected depending on the material of the container to be sealed, for example. The material of the sealant layer may be, for example, a polyolefin resin or an ethylene vinyl acetate copolymer resin (EVA). These resins can be provided, for example, in the form of stretched or unstretched films, molten resins for extrusion lamination, or coatings for hot melt.

[0048] Furthermore, the polyolefin resin is not particularly limited, and for example, polyethylene resins and polypropylene resins can be used.

[0049] In the present invention, the sealant layer may be an interfacial peel-type sealant layer made by mixing resins of different compositions, an agglomeration peel-type sealant layer made by forming multiple layers of sealant layers in which the film peels off with cohesive failure when opened, or an interlayer peel-type sealant layer made by forming multiple layers in which at least one layer is a layer that fuses to the container (seal layer) and the other layer is a layer adjacent to the seal layer (release layer), and when opened, it peels off between the seal layer and the release layer, or any other easy-peel sealant layer that provides easy peelability.

[0050] In the present invention, the thickness of the sealant layer is not particularly limited and may be, for example, 1.0 μm or more, 5.0 μm or more, or 10 μm or more, or 100 μm or less, 80 μm or less, 50 μm or less, or 20 μm or less.

[0051] <Middle class> The lid material of the present invention may have an intermediate layer. The intermediate layer may be located between the paper layer and the sealant layer. The presence of the intermediate layer can, for example, enhance the physical strength and / or barrier properties of the lid material.

[0052] As the intermediate layer, an intermediate resin layer and / or a barrier layer can be used.

[0053] (Intermediate resin layer) The intermediate resin layer may be composed of a thermoplastic resin with excellent impact resistance, abrasion resistance, etc., such as a vinyl resin, polyester resin, polyamide resin, or polypropylene resin. The intermediate resin layer may be a single layer or a laminate.

[0054] Examples of vinyl resins include polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polychlorotrifluoroethylene, polytetrafluoroethylene, and polyacrylonitrile (PAN).

[0055] Examples of polyester resins include polyethylene terephthalate (PET) and polybutylene terephthalate.

[0056] Examples of polyamide resins include nylon (registered trademark) 6, nylon MXD6, and other types of nylon.

[0057] As for the polypropylene resin, the resins mentioned below can be used for the inorganic particle-containing layer.

[0058] From the viewpoint of the mechanical strength of the lid material, the thickness of the intermediate resin layer is preferably 7 μm or more, or 10 μm or more. From the viewpoint of the flexibility of the intermediate resin layer, this thickness is preferably 55 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less. In other words, the intermediate resin layer may be a soft intermediate resin layer.

[0059] The resins constituting the intermediate resin layer may be a blend of two or more types, not just one, and additives to impart functionality may be included as needed.

[0060] Furthermore, it is preferable that the intermediate resin layer be made from a pre-formed film. The film that becomes the intermediate resin layer can be any film formed from the above-mentioned resin, and may be unstretched, uniaxially or biaxially stretched, or otherwise. Among these, a biaxially stretched film is preferred.

[0061] (Barrier layer) As the barrier layer, a material can be used that can suppress the permeation of moisture, organic gases, and inorganic gases from the overprint varnish layer to the sealant layer, and / or protect the contents on the sealant layer side. Examples of such barrier layers include metal foil layers, inorganic vapor-deposited films, organic coating films, and barrier resin layers. In particular, when the contents are microwaveable food, an inorganic vapor-deposited film, an organic coating film, or a barrier resin layer can be used as the barrier layer.

[0062] As the metal foil layer, for example, a single metal foil layer such as copper foil or aluminum foil, or an alloy foil layer such as stainless steel foil can be used.

[0063] Examples of inorganic vapor-deposited films that can be used include aluminum vapor-deposited films, silica vapor-deposited films, alumina vapor-deposited films, or silica-alumina binary vapor-deposited films. In particular, such inorganic vapor-deposited films may be those that are commercially available in a vapor-deposited state on a film, such as "vapor-deposited PET."

[0064] As the organic coating film, for example, a polyvinylidene chloride coating film, a polychlorotrifluoroethylene coating film, or a polyvinylidene fluoride coating film can be used.

[0065] As the barrier resin layer, for example, ethylene-vinyl alcohol copolymer (EVOH), cyclic olefin polymer (COP), or cyclic olefin copolymer (COC) can be used.

[0066] When using an inorganic vapor-deposited film or an organic coating film as the barrier layer, the thickness of the barrier layer is preferably 100 nm or more, 200 nm or more, 300 nm or more, 500 nm or more, 700 nm or more, or 1 μm or more from the viewpoint of ensuring strength and barrier properties, and is preferably 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less from the viewpoint of reducing the overall thickness of the lid material.

[0067] When a metal foil layer or a barrier resin layer is used as the barrier layer, the thickness of the barrier layer is preferably 5 μm or more, or 7 μm or more, from the viewpoint of ensuring strength and barrier properties. Furthermore, a thickness of 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less is preferable from the viewpoint of reducing the overall thickness of the lid material.

[0068] <Other layers> Other optional layers include, for example, adhesive layers. Examples of adhesive layers that can be used include dry laminating adhesives, sand laminating adhesives, and hot melt adhesives.

[0069] Container with lid As shown in Figures 2(a) and (b), the lidded container 300 of the present invention is A container 200 having a flange portion 202 and a housing portion 204, and The lid material 100 is heat-sealed at the flange portion 202 of the container 200, thereby sealing the container 200. It holds.

[0070] The lid material described above may have a tab 110 for pinching and pulling up when opening.

[0071] The lidded container of the present invention may be a lidded container that further contains contents contained in the storage compartment of the lidded container described above.

[0072] <container> The container is a container having a flange portion and a housing portion. The resin constituting the surface of the container that is heat-sealed to the lid material may be selected according to the resin constituting the sealant layer. This resin is not particularly limited and is composed of, for example, a polyolefin resin.

[0073] The container is not particularly limited as long as the lid can be heat-sealed. Examples of containers that can be used include paper containers coated with polyolefin resin, or containers made of polyolefin resin.

[0074] (Flange section) The flange portion is the peripheral edge of the container's housing section and may be a flange-shaped portion. The shape of the outer circumference of the flange portion can be selected according to the shape of the lid material.

[0075] (Detention area) The storage section is the part in which the contents are stored. The shape of this section can be, for example, a roughly rounded square truncated pyramidal shape, a roughly rounded cone truncated pyramidal shape, a polygonal truncated pyramidal shape, a rectangular prism, a cube, etc.

[0076] <Contents> The contents are the contents contained in the storage compartment. Examples of such contents include microwaveable foods that can be stored at room temperature, such as soup, instant noodles, and cooked rice; microwaveable foods such as chilled foods and frozen foods; and non-heated foods such as snacks and gummy candies. [Examples]

[0077] The present invention will be specifically described by examples and comparative examples, but the present invention is not limited thereto.

[0078] 《Preparation of the lid material》 <Example 1> Art paper as a paper layer (basis weight 79.1 g / m²)2 A nitrocellulose-based gravure ink (nitrocellulose-based ink) is used to print on the surface to obtain a printed layer, and an overprint varnish layer is applied on top of the printed layer at a rate of 1.5 g / m². 2 The layers were then laminated. Next, the side of the paper layer opposite the printed layer and an aluminum foil layer (AL, 6.5 μm thick) as an intermediate layer were sand-laminated via polyethylene (PE, 15 μm thick) as an adhesive layer. Then, an ethylene-acrylic acid copolymer (EAA, 18 μm thick) was back-laminated as an adhesive layer, and finally, an ethylene vinyl acetate copolymer (EVA, 15 μm thick) was back-laminated as a sealant layer to produce the laminate for the lid material of Example 1.

[0079] The composition used for the overprint varnish layer was a varnish (OL-based varnish) containing 10% to 20% by mass of synthetic resin, 5 to 10% by mass of paraffin wax, 1 to 3% by mass of silica, 1 to 3% by mass of an auxiliary agent, 5 to 10% by mass of methyl ethyl ketone, and 50 to 60% by mass of methylcyclohexane. <Example 2> Art paper as a paper layer (basis weight 79.1 g / m²) 2 A nitrocellulose-based gravure ink (nitrocellulose-based ink) is used to print on the surface to obtain a printed layer, and an overprint varnish layer is applied on top of the printed layer at a rate of 1.5 g / m². 2 The layers were then laminated. Next, the side of the paper layer opposite the printed layer and a polyethylene terephthalate film (PET, 12 μm thick) as an intermediate layer were dry-laminated via a two-component dry laminating adhesive (DryLami) as an adhesive layer. Then, an ethylene-methacrylic acid copolymer (EMAA, 18 μm thick) was back-laminated as an adhesive layer, and a sealant layer was back-laminated thereon to produce the laminate for the lid material of Example 2. The same overprint varnish layer and sealant layer as in Example 1 were used.

[0080] <Comparative Examples 1-4> Laminated lid materials for Comparative Examples 1 to 4 were fabricated in the same manner as in Example 1, except that each component was modified as shown in Table 1.

[0081] <Comparative Examples 5-7> Laminated lid materials for Comparative Examples 5-7 were fabricated in the same manner as in Example 2, except that each component was modified as shown in Table 1.

[0082] Other materials shown in Table 1 are as follows: Nitrocellulose varnish: Nitrocellulose varnish Water vapor barrier A: Water-based acrylic resin-based water- and oil-resistant varnish Water vapor barrier B: Water-based polyester coating agent

[0083] "evaluation" <Air permeability> The air permeability was measured for a laminate obtained by printing a paper layer, an ink layer, and an overprint varnish layer in that order. More specifically, the measurement was taken from the back side of the paper layer (i.e., the paper layer side) towards the front side of the paper layer (i.e., the overprint varnish layer side). The Wang Research Testing Machine method was used for the measurement.

[0084] <Moisture absorption capacity> Each sample was processed into a lid shape (approximately circular shape with a diameter of 101 mm; area 0.00824 m²). 2 The material was dried in a vacuum oven (60°C, 4 hours). Subsequently, the mass change was measured while seasoning was carried out in an environment of 23°C and 50% RH (relative humidity). The mass immediately after drying in the vacuum oven was used as the baseline (0). For the following formulas, the mass after 60 minutes of moisture absorption was calculated as the amount of moisture absorbed. Moisture absorption amount (g / m 2 ) = Mass after moisture absorption (g / m³) 2 )- Mass after drying in a vacuum oven (g / m³) 2 )

[0085] <Blister pack> Each sample, processed into a lid shape, was seasoned for one day at 20°C and 50% RH (relative humidity). The seasoned samples were then heat-sealed into containers (temperature: 150-160°C, pressure: 180 kgf, time: 1.3 seconds). The presence or absence of blistering was visually checked.

[0086] Regarding the occurrence of blisters, the absence of blisters was rated as "none," and the occurrence of blisters was rated as "present."

[0087] <Heat resistance> The heat resistance of a laminate obtained by printing an ink layer and an overprint varnish layer in that order onto a paper layer was evaluated. Specifically, the laminate was cut to a width of 25 mm. Next, the cut laminate was placed on an aluminum base with the overprint varnish layer facing upwards, and a 12 g weight was placed in a position where it would not come into contact with the sealing plate. This laminate was pressed with an aluminum sealing plate at a temperature of 100°C for 1 second. After releasing the press, it was visually checked whether the laminate was adhered to the sealing plate or not. The evaluation criteria were as follows. A: It peeled off the seal plate within seconds of releasing the press. B: Even after releasing the press, it remained stuck to the seal plate for a while.

[0088] Table 1 shows the configuration and evaluation results of the example.

[0089] [Table 1]

[0090] From Table 1, it can be seen that the lid material of the example, in which the overprint varnish layer contains hydrocarbon wax, can reduce or suppress moisture absorption and blister formation during heat sealing. [Explanation of Symbols]

[0091] 100 Lid material 102 Overprint varnish layer 104 Printing layer 106 Paper layer 108 Sealant layer 109 Middle Class 110 tabs 200 containers 202 Flange section 202a Flange seal section 204 Storage Unit 250 Contents

Claims

1. A lid material having at least an overprint varnish layer, a printed layer, a paper layer, and a sealant layer in this order, The overprint varnish layer contains hydrocarbon wax. Lid material.

2. The lid material according to claim 1, comprising at least the overprint varnish layer, the printing layer, the paper layer, the intermediate layer, and the sealant layer in this order.

3. The lid material according to claim 2, wherein the intermediate layer is a metal foil layer.

4. The lid material according to claim 2, wherein the intermediate layer is a layer made of polyester resin.

5. The lid material according to claim 1 or 2, wherein the hydrocarbon wax content is 5 to 80% by mass relative to the mass of the solid content of the overprint varnish layer.

6. When dried in a vacuum oven at 60°C for 4 hours and then seasoned for 60 minutes in an environment of 23°C and 50% RH (relative humidity), the moisture absorption after drying, based on the mass before seasoning, was 2.2 g / m². ２ A lid material according to claim 1 or 2, which is less than [amount missing].

7. The lid material according to claim 1 or 2, wherein the laminate of the overprint varnish layer, the printing layer, and the paper layer has an air permeability of 150,000 seconds or less when measured from the paper layer side toward the overprint varnish layer side using the Wang Ren testing machine method of JIS P8117:2019.

8. A container having a flange portion and a housing portion, and The lid material according to claim 1 or 2, which is heat-sealed at the flange portion of the container, thereby sealing the container. A container with a lid.

9. The container with a lid according to claim 8, further comprising contents contained in the aforementioned storage section.

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