Laminates and packaging materials

Abstract

To provide a laminate capable of comparatively inexpensively producing a packaging material usable for a food product and difficult to adhere specifically for a solid content having adhesiveness, and also to provide a packaging material using the same.SOLUTION: A laminate includes a transparent substrate layer 1, a printed layer 2, an adhesion layer 3 and a sealant layer 7 in this order. The sealant layer 7 is an embossed film with irregularities applied to an entire thickness thereof. A contact area at a sealant surface of the laminate to the content is 50% or less of the total area.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate and a packaging material using the same, and more particularly to a laminate that can be used to produce a packaging material to which solid, sticky contents are less likely to adhere. [Background technology]

[0002] Various packaging materials, such as packaging bags, are widely produced using laminates of synthetic resin films. Packaging materials are required to have various properties, one of which is that the contents do not easily adhere to them and can be easily removed.

[0003] The liquid-repellent sealant film described in Patent Document 1 is a sealant film that can sufficiently prevent adhesion of contents, even when the contents contain a large amount of surfactant, such as liquid detergent, etc. This sealant film is characterized by including a thermal adhesive resin layer containing a fluorine-based additive in its layer structure, and the fluorine-based additive bleeds out onto the surface of the sealant film.

[0004] The liquid-repellent sealant film described in Patent Document 1 is effective for contents such as liquid detergent, but cannot be used as a packaging material for food, which cannot contain additives. Another problem is that fluorine-based additives that bleed out onto the surface can impair heat sealing properties.

[0005] The liquid-repellent sealant film described in Patent Document 2 has properties that prevent adhesion of contents such as yogurt, as well as gas barrier properties, and furthermore, allows printed images to be clearly visible from the inner surface.

[0006] The liquid-repellent sealant film described in Patent Document 2 is a liquid-repellent sealant film formed by laminating a gas barrier substrate, a printing ink coating, a sealant layer, and an anti-adhesion layer in this order, and is characterized in that it includes a metal foil or a metal vapor deposition layer as the gas barrier substrate, and that the anti-adhesion layer contains fine particles with an average secondary particle diameter of 100 nm to 100 μm.

[0007] The liquid-repellent sealant film described in Patent Document 2 can be used for food products, but it was developed as a lid for yogurt with a printed image showing the results of a prize draw, and unfortunately can only be used for very limited, specialized purposes. Furthermore, there is an inherent risk of fine particles falling off and contaminating the contents.

[0008] The packaging material described in Patent Document 3 is intended to prevent adhesion of liquid contents, thereby enabling quicker removal and preventing contents from remaining, and to solve conventional problems such as the use of additives and the dropping off of fine particles. This packaging material has on its inner surface ridges or grooves that extend in a zigzag pattern parallel to the opening.

[0009] The packaging material described in Patent Document 3 has zigzag convex or concave stripes on the inner surface, which requires a special processing method, resulting in high processing costs and a fairly expensive product. Furthermore, since the purpose is to allow highly viscous liquid contents to flow easily, it cannot be expected to be effective for solid, sticky contents. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2018-178005 [Patent Document 2] Japanese Patent Application Publication No. 2019-31015 [Patent Document 3] Patent No. 6690292 Summary of the Invention [Problem to be solved by the invention]

[0011] The problem to be solved by the present invention is to provide a laminate that can be used for food, and that can be used to relatively inexpensively produce packaging material to which solid, sticky contents in particular do not easily adhere, as well as a packaging material using the same. [Means for solving the problem]

[0012] As a means for solving the above-mentioned problems, the invention described in claim 1 is a laminate having a transparent substrate layer, a printing layer, an adhesive layer, and a sealant layer in this order, wherein the sealant layer is an embossed film having an uneven surface across its entire thickness, The difference in height of the unevenness is 70 μm or more and 183 μm or less, The contact area of ​​the sealant surface of the laminate with the contents is 50% or less of the total area and no anti-adhesion layer is provided on the sealant layer. The laminate is characterized by the above.

[0013] The laminate of the present invention uses an embossed film with unevenness across its entire thickness as the sealant layer, which is the surface that comes into contact with the contents, and therefore the sealant layer has unevenness on its surface, which reduces the contact area with the contents and makes it easier to remove solid, sticky contents.

[0014] The invention described in claim 2 is a laminate having a transparent substrate layer, a printing layer, an adhesive layer, a gas barrier layer, another adhesive layer, and a sealant layer in this order, wherein the sealant layer is an embossed film having an uneven surface across its entire thickness, The difference in height of the unevenness is 70 μm or more and 183 μm or less, The contact area of ​​the sealant surface of the laminate with the contents is 50% or less of the total area and no anti-adhesion layer is provided on the sealant layer. The laminate is characterized by the above.

[0015] The invention described in claim 3 is the laminate described in claim 1 or 2, characterized in that the adhesive layer in contact with the sealant layer is a melt-extruded adhesive resin layer.

[0016] Furthermore, the invention described in claim 4 is a laminate described in any one of claims 1 to 3, characterized in that the embossed shape of the embossed film is a pattern of continuous unit shapes such as diamonds, squares, hexagons, circles, etc.

[0017] The invention described in claim 5 is a packaging material obtained by placing the sealant layers of the laminate described in any one of claims 1 to 4 opposite each other and heat-sealing the periphery. [Effects of the Invention]

[0018] The laminate of the present invention uses an embossed film with unevenness across its entire thickness as the sealant layer, so that the contact area of ​​the sealant surface of the laminate with the contents is 50% or less of the total area. As a result, packaging materials using this laminate have the effect of reducing adhesion to solid contents with sticky surfaces, making them easier to remove from the bag.

[0019] When a gas barrier layer is included in the layer structure as in the invention described in claim 2, the preservation of the contents is further improved.

[0020] When a melt-extruded adhesive resin layer is used as the adhesive layer in contact with the sealant layer, as in the invention described in claim 3, the unevenness of the sealant layer surface after the adhesive treatment is more easily maintained than in dry lamination, and the loss of the unevenness can be minimized.

[0021] As in the invention described in claim 4, when the embossed shape of the embossed film is a pattern of continuous unit shapes such as diamonds, squares, hexagons, circles, etc., a commercially available embossed film can be used. In this case, there is no need to spend money on creating a new custom-made embossing roll, which contributes to reducing the total cost. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a cross-sectional view showing a layer structure in one embodiment of the laminate according to the present invention. [Figure 2] FIG. 2 is a cross-sectional explanatory view showing how the contact area with the contents is reduced when the laminate according to the present invention is used as a packaging material. [Figure 3] FIG. 3 is a plan view showing an example of an embossed film used as a sealant layer in the laminate according to the present invention. [Figure 4] FIG. 4 is a cross-sectional schematic diagram showing the AA′ cross section of the embossed film of FIG. [Figure 5] FIG. 5 is a plan view showing another example of an embossed film used as a sealant layer in the laminate according to the present invention. [Figure 6] FIG. 6 is a plan view showing another example of an embossed film used as a sealant layer in the laminate according to the present invention. [Figure 7] FIG. 7 is a plan view showing another example of an embossed film used as a sealant layer in the laminate according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] The laminate of the present invention and a packaging material using the same will be described in detail below with reference to the drawings. Fig. 1 is a cross-sectional schematic diagram showing the layer structure of one embodiment of the laminate of the present invention. Fig. 2 is a cross-sectional explanatory diagram showing how the contact area with the contents is reduced when the laminate of the present invention is used as a packaging material.

[0024] The laminate 10 of the present invention is a laminate having a transparent substrate layer 1, a printing layer 2, an adhesive layer 5, and a sealant layer 7 in this order, wherein the sealant layer 7 is an embossed film having an uneven surface throughout its entire thickness, and the contact area of ​​the sealant surface of the laminate with the contents 30 is 50% or less of the total area.

[0025] 1 and 2, an adhesive layer 3 and a gas barrier layer 4 are inserted between a printed layer 2 and an adhesive layer 5, and the adhesive layer 5 is a melt-extruded adhesive resin layer 6. The gas barrier layer 4 prevents the permeation of water vapor and oxygen, and although it is not essential, it is expected to have the effect of improving the shelf life of the contents.

[0026] A transparent synthetic resin film suitable for printing is used as the transparent substrate layer 1. Specifically, a polyethylene terephthalate resin (PET) film having a thickness of 9 to 25 μm, an oriented polypropylene resin (OPP) film having a thickness of 15 to 50 μm, an oriented nylon (ONY) film having a thickness of 15 to 25 μm, etc. are preferably used.

[0027] The printing layer 2 is printed on the back side of the transparent substrate layer 1, so it is reverse printing and is printed with a left-right reversed image. The ink used for printing is selected appropriately depending on the material of the transparent substrate layer 1 and the printing method. There are no particular restrictions on the printing method, and in addition to general gravure printing, printing methods such as flexographic printing, offset printing, and screen printing can also be used.

[0028] 1, a gas barrier layer 4 is used, and the printed layer 2 and the gas barrier layer 4 are bonded together by an adhesive layer 3. Although the gas barrier layer 4 is not essential, it has the effect of further improving the shelf life of the contents by inhibiting the permeation of oxygen and water vapor.

[0029] Examples of gas barrier layer 4 that can be used include gas barrier films such as polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl alcohol copolymer film, gas barrier nylon film, and gas barrier polyethylene terephthalate (PET) film; metal vapor deposition films in which a metal such as aluminum is vapor-deposited on a PET film; inorganic oxide vapor deposition films in which an inorganic oxide such as aluminum oxide or silicon oxide is vapor-deposited on a PET film; gas barrier coating layers such as polyvinylidene chloride coating, a coating containing a water-soluble resin and an inorganic layered compound, or a resin layer formed by reacting a metal alkoxide or its hydrolyzate with an isocyanate compound; and metal foils such as aluminum foil.

[0030] In this case, a dry lamination adhesive can be used as the adhesive layer 3. An embossed film with unevenness across its entire thickness is used as the sealant layer 7. The embossed film is produced by either heating a flat film to soften it and pressing it against an embossing roll with embossed surfaces to form embosses, or by pressing a molten thermoplastic resin against an embossing roll to impart embossments.

[0031] Generally, embossing rolls are expensive and time-consuming to produce, so using commercially available embossing films is often advantageous in terms of total cost and manufacturing lead time. Embossing film materials can be made from any material typically used for the sealant layer of packaging materials. Examples of suitable materials include ethylene-based resins such as low-density polyethylene (LDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, and ethylene-methacrylic acid copolymer; blends of polyethylene and polybutene; and polypropylene-based resins such as homopolypropylene (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer.

[0032] 1, in addition to the usual dry lamination method, methods for bonding the sealant layer 7, which has been given an uneven texture across its entire thickness, to the gas barrier layer 4 include a method using a melt-extruded adhesive resin layer 6. In general, in lamination bonding operations, heat and pressure are applied, so it is unavoidable to some extent that the unevenness of the embossed film will be reduced.

[0033] Even with the dry lamination method, it is possible to reduce the reduction in unevenness by applying a larger amount of adhesive than usual, but there is a limit to how much can be done because there is a possibility of odor problems due to residual solvent. In this respect, using a melt-extruded adhesive resin layer 6 as the adhesive layer 5 is more advantageous than a dry lamination adhesive in terms of preventing the reduction in unevenness of the embossed film.

[0034] The melt-extruded adhesive resin layer 6 can be made of the most common low-density polyethylene resin (LDPE) or linear low-density polyethylene resin (LLDPE), as well as medium-density polyethylene resin (MDPE), high-density polyethylene resin (HDPE), polypropylene resin (PP), etc.

[0035] When a melt-extruded adhesive resin layer 6 is used as the adhesive layer 5, an anchor coat (A Applying agent C is effective in increasing adhesive strength (lamination strength). Lamination strength must be at least 100g / 15mm, and ideally 500g / 15mm.

[0036] When the laminate 10 does not include a gas barrier layer, the back surface of the printed layer 2 and the embossed film 7, which is a sealant layer, are directly laminated together via the adhesive layer 5. The adhesive layer in this case is similar to that in the case where a gas barrier layer is present.

[0037] 2 is a cross-sectional explanatory view showing how the contact area with the contents 30 is reduced when the laminate 10 according to the present invention is used as a packaging material 20. By using an embossed film as the sealant layer, unevenness remains on the sealant layer surface, which is the inner surface of the packaging material 20, and as a result, the contact area with the contents 30 is reduced to less than 100%.

[0038] As shown schematically in FIG. 2, the content 30 and the sealant layer 7 come into contact mainly at the convex portions 8, but not at the concave portions 9, so the contact area is reduced from 100%.

[0039] It has been found that if the contact area of ​​the sealant surface of the laminate 10 with the contents 30 is 50% or less of the total area, the adhesion between the packaging material 20 and the contents 30 is reduced, making it easier to remove various contents.

[0040] Fig. 3 is a plan view showing an example of an embossed film 7 used as a sealant layer in the laminate according to the present invention. Fig. 4 is a cross-sectional view showing the AA' cross section of the embossed film of Fig. 3. In this example, diamonds are arranged in an orderly fashion to form a pattern. The colored parts in Fig. 3 are convex parts 8, and the uncolored parts are concave parts 9.

[0041] The embossed film shown in Figure 3 is a commercially available embossed film called Hishikinume, with a material thickness of 50 μm and a total thickness including the embossing of 166 μm. Note that the thickness of the film is exaggerated in Figure 4.

[0042] Figure 5 is a schematic plan view of another example of an embossed film 7 used as a sealant layer in a laminate according to the present invention. This example is a commercially available embossed film called "Diamond," which has a neatly arranged pattern of vertically elongated diamonds. Similarly, the thickness of the material is 50 μm, and the total thickness including the embossing is 120 μm.

[0043] Figure 6 is a schematic plan view of another example of an embossed film 7 used as a sealant layer in a laminate according to the present invention. This example is a commercially available embossed film called "Kikko" (hexagonal shell) with a neatly arranged pattern of horizontally elongated hexagons. In this example, the material thickness is also 50 μm, and the total thickness including the embossing is 233 μm.

[0044] The embossed film used in the laminate of the present invention is not limited to these, and may be, for example, one in which circular protrusions 8 are arranged in an orderly polka dot pattern, as in the example shown in FIG.

[0045] When the sealant layers of the laminate 10 are placed opposite each other and the edges are heat-sealed to form a packaging bag, the unevenness of the sealant layer 7 tends to reduce the seal strength compared to when the sealant layer is normally flat. To address this, it is necessary to improve the sealing conditions to prevent a reduction in seal strength.

[0046] The required seal strength is 300 g / 15 mm or more, preferably 1000 g / 15 mm or more.

[0047] The laminate 10 according to the present invention can be used not only for general packaging bags obtained by placing the sealant layers 7 opposite each other and heat-sealing the periphery, but also for various other packaging materials by taking advantage of its releasability. The laminate and packaging material according to the present invention will be described in more detail below with reference to examples. [Example]

[0048] Example 1 A 12 μm-thick polyethylene terephthalate (PET) resin film was used as the transparent substrate layer, with a printed layer facing in the reverse direction on the backside. This printed surface was then bonded to a 7 μm-thick aluminum foil by extrusion lamination using polyethylene resin to form an intermediate laminate. The polyethylene resin thickness was 15 μm.

[0049] Next, an embossed film (linear low-density polyethylene resin, thickness 50 μm, diamond pattern) with a pre-formed embossing as shown in Figure 3 was used as a sealant layer, and was bonded to the aluminum foil surface of the intermediate laminate using a polyethylene resin extrusion laminate equivalent to a thickness of 20 μm to obtain a laminate.

[0050] <Example 2> A laminate was produced in the same manner as in Example 1, except that an embossed film (linear low-density polyethylene resin, thickness 50 μm, diamond) with a pre-formed embossment as shown in FIG. 5 was used as the sealant film.

[0051] Example 3 A laminate was produced in the same manner as in Example 1, except that an embossed film (linear low-density polyethylene resin, thickness 50 μm, hexagonal pattern) with a pre-formed embossment as shown in Figure 6 was used as the sealant film.

[0052] When adhesive food was placed on the sealant surface of the laminates of Examples 1 to 3 and the adhesiveness was evaluated, all of the food was easily peeled off by hand. Furthermore, when two laminates were placed facing each other and the edges were sealed to create a packaging bag, there was no problem with sealing suitability. [Explanation of symbols]

[0053] 1...Transparent base material layer 2...printing layer 3...Adhesive layer 4. Gas barrier layer 5...adhesive layer 6. Melt-extruded adhesive resin layer 7. Sealant layer (embossed film) 8. Convex part 9. Recess 10. Laminate 20...Packaging material 30...Contents

Claims

1. A laminate having a transparent substrate layer, a printing layer, an adhesive layer, and a sealant layer in this order, wherein the sealant layer is an embossed film having an uneven surface across its entire thickness, the difference in height between the uneven surfaces being 70 μm or more and 183 μm or less, the contact area of ​​the sealant surface of the laminate with the contents being 50% or less of the total area, and no anti-adhesion layer being present on the sealant layer.

2. A laminate having a transparent substrate layer, a printing layer, an adhesive layer, a gas barrier layer, another adhesive layer, and a sealant layer in this order, wherein the sealant layer is an embossed film having irregularities across its entire thickness, the difference in height between the irregularities is 70 μm or more and 183 μm or less, the contact area of ​​the sealant surface of the laminate with the contents is 50% or less of the total area, and no anti-adhesion layer is provided on the sealant layer.

3. 3. The laminate according to claim 1, wherein the adhesive layer in contact with the sealant layer is a melt-extruded adhesive resin layer.

4. 4. The laminate according to claim 1, wherein the embossed shape of the embossed film is a pattern of continuous unit shapes such as diamonds, squares, hexagons, and circles.

5. A packaging material obtained by placing the sealant layers of the laminate according to any one of claims 1 to 4 opposite each other and heat-sealing the periphery.

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