Composite films, lids, and lidded containers containing contents

Abstract

In order to provide a composite film, a cover material formed from the composite film, and a covered container containing contents, a cover material with an opening can be formed in a partial peeling portion before complete opening. When peeling is performed to form the opening, abnormalities such as cracking or hole residue can be suppressed to achieve reliable peel strength. As the composite film forming the cover material, the easy-peel resin layer and the polyester film disposed on both sides thereof adopt a specific configuration. Specifically, in the composite film (1) that sequentially includes a first polyester film layer (8a), an easy-peel resin layer (10), and a second polyester film layer (8b), no corona treatment is performed on either side of the first polyester film layer (8a), corona treatment is performed on at least the side of the second polyester film layer (8b) that is in contact with the easy-peel resin layer (10), and the composition and structure of the easy-peel resin layer are set within a specific range.

Description

Technical Field

[0001] This invention relates to a composite film, a capping material, and a capped container containing contents. Specifically, it relates to a composite film for forming the capping material, the capping material formed from the composite film, and a capped container containing contents. Here, the capping material may have openings for liquid drainage formed in a partially peeled portion before complete opening by removing the entire material. Prior Technology

[0002] Previously, packaging for instant foods such as fried noodles, which are prepared by pouring hot water into a covered container and then pouring it out, and for boiled foods such as vegetables and eggs, which are prepared by draining the water, used a lid material with a partial peel-off section. This peel-off section is used to create an opening before the container is fully opened.

[0003] As such a cover material, Patent Document 1 proposes, for example, a laminate composed of a paper layer / polyester layer (PET layer) / easily peelable resin layer / adhesive layer / intermediate layer / sealing layer, and a laminate composed of a paper layer / adhesive layer / easily peelable resin layer / PET layer / intermediate layer / sealing layer.

[0004] For example, Patent Document 2 proposes a cover material in which a paper layer / polyester layer / easily peelable resin layer / polyester layer / barrier layer / sealing layer are sequentially stacked from the outer surface side. The polyester layer configured through the easily peelable resin layer is stacked with the easily peelable resin layer through a surface that has undergone roughening treatment, and can be peeled off using the interface between the other polyester layer and the easily peelable resin layer as the peeling surface. Moreover, the aforementioned paper layer is hardened by applying varnish. In Patent Document 2, a polyester layer (PET layer) with a peelable surface is formed at the interface between the polyester layer and the easy-peelable resin layer. The preferred surface wetting tension is 3.5×10⁻² N / m (35 dyn / cm) to 6.0×10⁻² N / m (60 dyn / cm). If the surface wetting tension is less than 3.5×10⁻² N / m, the adhesion will be too low, and unintentional peeling will easily occur. If it exceeds 6.0×10⁻² N / m, the adhesion will be too high, and peeling between the polyester layer and the easy-peelable resin layer 10 will become difficult.

[0005] These covers are made by peeling off the interface between a polyester layer (like a PET layer) and an easy-to-peel resin layer, thereby creating openings for pouring out or draining hot water. [Previous Technical Documents] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2007-320580 [Patent Document 2] International Publication No. 2012 / 073274 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] In the past, when forming openings in lids for pouring or draining hot water, depending on the material used, the lids could crack or exhibit unsightly appearances due to cloudiness on the peeled surface during the process of creating the openings. In other words, the peel strength of the lid material used for pouring or draining hot water can significantly impact the final product. For example, excessively strong peel strength may cause the lid to crack, while insufficient peel strength may prevent proper opening formation, potentially resulting in residual holes or hole detachment.

[0009] The present invention was developed in view of the above background, and its purpose is to provide a composite film, a capping material formed from the composite film, and a capped container containing contents, wherein an opening can be formed in a partial peeling portion before the container is fully opened, and when peeling is performed to form the opening, abnormalities such as cracking or hole residue can be suppressed to achieve reliable peeling strength. [Technical means to solve the problem]

[0010] The inventors of this invention have diligently explored solutions to the aforementioned problems. They discovered that when the easily peelable resin layer and the polyester films disposed on both sides of the composite film forming the cover material are configured in a specific way, the aforementioned problems can be solved, thus leading to the completion of this invention. In other words, this invention is as described below.

[0011] "Style 1" A composite film comprises, in sequence, a first polyester film layer, an easy-to-peel resin layer, and a second polyester film layer. The aforementioned first polyester film layer and the aforementioned second polyester film layer are bonded together by the aforementioned easy-peel resin layer. No corona treatment was applied to either side of the aforementioned first polyester film layer. Corona treatment is applied to at least one surface of the second polyester film layer that is in contact with the aforementioned easily peelable resin layer. The aforementioned easily peelable resin layer is composed of a mixture of polyethylene and cyclic olefin copolymers. The proportion of the aforementioned cyclic olefin copolymer is 1 to 10% by mass relative to the total amount of the aforementioned polyethylene and the aforementioned cyclic olefin copolymer. Furthermore, the interface between the aforementioned first polyester film layer and the aforementioned easily peelable resin layer can be used as the peeling surface for peeling. "State 2" The composite film as described in Sample 1 has a heat-sealing layer on the side of the first polyester film layer opposite to the easy-peel resin layer, or on the side of the second polyester film layer opposite to the easy-peel resin layer. Appearance 3 The composite film as described in sample 1 or 2, wherein the polar component of the surface free energy of the surface of the first polyester film layer in contact with the aforementioned easily peelable resin layer is less than 9.0 mN / m. Appearance 4 The composite film described in any of the states 1 to 3, wherein the polar component of the surface free energy of the aforementioned peeled surface of the first polyester film layer after peeling is less than 2.0 mN / m. Appearance 5 A cover material is formed from a composite film as described in any one of the states 1 to 4. Appearance 6 The cover material as described in sample 5 has the following features: A first half-cut is formed from the side of the aforementioned first polyester film layer to the depth reaching the aforementioned easily peelable resin layer. The second and third half-cuts, formed from the second polyester film layer side in the thickness direction through the aforementioned easily peelable resin layer and at a depth at least reaching the interface between the aforementioned easily peelable resin layer and the aforementioned first polyester film layer, and Tabs are used for partial dissection of the peripheral portion. The aforementioned first half-cut and the aforementioned partial dissection tabs define the outer edge of the partially dissected portion. The aforementioned second half-cut marks define the outer edge of the liquid flow hole. The aforementioned third half-cut is a protrusion used to define the partial dissection. Furthermore, the aforementioned liquid flow hole is disposed within the aforementioned partial stripping section. Therefore, when the aforementioned partial peeling tab is grasped to peel off the aforementioned partial peeling portion, the peeling occurs at the interface between the aforementioned first polyester film layer and the aforementioned easy-peel resin layer in areas other than the aforementioned liquid flow hole, and at the aforementioned liquid flow hole, the peeling does not occur at the interface between the aforementioned first polyester film layer and the aforementioned easy-peel resin layer, thereby removing the aforementioned second polyester film layer along with the aforementioned first polyester film layer, thereby forming the aforementioned liquid flow hole. "State 7" A lidded container for containing contents, comprising: The container body has a storage section and a flange section. The contents contained in the aforementioned container body, and As described in sample 5 or 6, the cover material The aforementioned cover material has a heat-sealing layer on the side of the first polyester film layer opposite to the aforementioned easy-peel resin layer, or on the side of the second polyester film layer opposite to the aforementioned easy-peel resin layer. The aforementioned cover material is heat-sealed to the aforementioned flange portion through the aforementioned heat-sealing layer. [Effects of the Invention]

[0012] The composite film according to the present invention enables a cap material in which an opening can be formed in a partially peeled portion before complete opening, allowing for reliable peeling to form the opening. That is, during peeling to form the opening, defects such as cap material breakage and cloudy peeled surfaces can be suppressed. Simple Explanation of the Diagram

[0013] [Figure 1] is a cross-sectional view of a composite film and cover material according to an embodiment of the present invention. [Figure 2] is a top view of the cover material of one embodiment of the present invention. [Figures 3(a)~(c)] are explanatory diagrams of an example of the use of the cover material in one embodiment of the present invention. Implementation

[0014] Composite Thin Films

[0015] The composite film of the present invention comprises at least, sequentially, a first polyester film layer, an easy-peel resin layer, and a second polyester film layer, wherein the first polyester film layer and the second polyester film layer are adhered to each other by the easy-peel resin layer. Furthermore, the surfaces of the first and second polyester film layers, and the easy-peel resin layer, have specific configurations.

[0016] Specifically, in the composite film of the present invention, neither side of the first polyester film layer is subjected to corona treatment, and at least the side of the second polyester film layer in contact with the peelable resin layer is subjected to corona treatment. The peelable resin layer is composed of a mixture of polyethylene and cyclic olefin copolymers, and the proportion of the cyclic olefin copolymer relative to the total mass of polyethylene and cyclic olefin copolymers is 1 to 10 by mass.

[0017] The composite film of the present invention employs a specific configuration in which an easy-peel resin layer and first and second polyester film layers disposed on both sides thereof are made such that the interface between the first polyester film layer and the easy-peel resin layer is capable of interlayer peeling.

[0018] The easy-peel resin layer, by changing the mixing ratio of polyethylene and cyclic olefin copolymer, can suppress the peel strength of the interface between the first polyester film layer and the easy-peel resin layer.

[0019] Generally, when the content of cyclic olefin copolymer is high, the peel strength decreases. If the content exceeds a certain level, the interlayer strength becomes too weak, resulting in unintentional peeling and making it difficult to maintain the stacking. On the other hand, when the content of cyclic olefin copolymer is low, the peel strength at the interface between the first polyester film layer and the easy-peel resin layer increases, making it difficult to peel.

[0020] In the composite film of the present invention, the proportion of the easily peelable resin layer to the total mass of polyethylene and cyclic olefin copolymer is as low as 1 to 10% by mass, indicating a relatively low content of cyclic olefin copolymer. Generally, in such cases, the peel strength increases, and peeling tends to become more difficult. However, in the present invention, no corona treatment is performed on either side of the first polyester film layer, while corona treatment is performed on at least the side of the second polyester film layer that contacts the easily peelable resin layer, thereby ensuring reliable peeling at the interface between the first polyester film layer and the easily peelable resin layer.

[0021] Generally speaking, corona treatment increases the polarity of the polymer film surface, thereby improving its adhesion to adjacent layers. Therefore, in the case of peeling at the interface between the first polyester film layer and the easy-peel resin layer as in this invention, corona treatment is performed on the side of the first polyester film layer opposite to the easy-peel resin layer to improve its adhesion to other layers, while the side of the first polyester film layer opposite to the easy-peel resin layer is not corona treated to promote peeling at the interface between the first polyester film layer and the easy-peel resin layer.

[0022] However, the inventors of this case discovered that by not performing corona treatment on either side of the first polyester film layer, even when the content of cyclic olefin copolymer in the peelable resin is relatively low, peeling at the interface between the first polyester film layer and the peelable resin layer can still be reliably performed.

[0023] Although not bound by theory, this is because even if corona treatment is applied only to the side of the first polyester film layer opposite to the easy-peel resin layer, the side of the first polyester film layer opposite to the easy-peel resin layer will also be affected by the corona treatment.

[0024] In the process of forming openings in cover materials for pouring out or draining hot water, variations in peel strength can significantly impact the final product. For example, excessively high peel strength can cause the cover material to crack, while insufficient peel strength can prevent proper opening formation, potentially leading to defects such as residual or detached openings. Therefore, controlling the desired peel strength is crucial in the formation of opening cover materials.

[0025] Moreover, generally speaking, when forming a laminate, a corona treatment is performed to ensure the adhesion between layers. The inventors of this case have found that the slight deviation from the expected peel strength is due to the effect of the corona treatment on the non-peel side.

[0026] Furthermore, the corona treatment varies depending on the treatment equipment, treatment conditions, and batches. Therefore, even when the same resin is selected, different peel strengths can still occur, leading to a situation that is difficult to control.

[0027] Therefore, as in this invention, if a polyester film that has not undergone corona treatment on either side is used, there will be no difference in peel strength, and the corona treatment process can be reduced, which is also beneficial to production costs.

[0028] The structure of the composite film of the present invention will be described below with reference to the figures. Figure 1 is a cross-sectional view of a composite film according to an embodiment of the present invention.

[0029] The composite film 1 shown in Figure 1 is a laminate formed by sequentially stacking a paper layer 7, a first polyester film layer 8a, an easy-to-peel resin layer 10, a second polyester film layer 8b, a barrier layer 11, and a heat-sealing layer 12 from the outer surface side.

[0030] In one embodiment of the composite film 1, the interface between the first polyester film layer 8a adjacent to the paper layer 7 and the easily peelable resin layer 10 is peelable, and this interface forms a peelable surface 13 during peeling. That is, in one embodiment of the composite film 1, with the peelable surface 13 as the boundary, the paper layer 7 and the first polyester film layer 8a adjacent to the paper layer 7 constitute the outer layer 9, and the easily peelable resin layer 10, the second polyester film layer 8b, the barrier layer 11, and the heat-sealing layer 12 constitute the inner layer 14. Furthermore, the outer layer 9 and the inner layer 14 are laminated together so that peeling can be performed using their interface as the peelable surface 13.

[0031] The composite film of the present invention can be provided with a first polyester film layer, an easy-peel resin layer and a second polyester film layer in sequence, wherein the first polyester film layer and the second polyester film layer are bonded to each other by the easy-peel resin layer, and may arbitrarily include other layers.

[0032] In one embodiment of the composite film 1 shown in Figure 1, the outermost layer 9 is provided with a paper layer 7, and the innermost layer 14 is provided with a barrier layer 11 and a heat-sealing layer 12.

[0033] The thickness of each layer constituting the composite film of the present invention can be suitably determined according to the intended use of the composite film. Hereinafter, each layer will be described.

[0034] <First Polyester Film Layer> The first polyester film layer is an essential constituent layer in the composite film of the present invention. The first polyester film layer is adjacent to the easy-peel resin layer and is deposited on the second polyester film layer through the easy-peel resin layer.

[0035] (Material) The polyester resin used as the material for the first polyester film layer is not particularly limited. For example, it can be a general resin such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polybutylene naphthalate (PBN), polycyclohexanedimethyl terephthalate (PCT), or polycarbonate (PC).

[0036] The polyester resin used as the material for the first polyester film layer can be a single type or a combination of two or more types. In the first polyester film layer, resins other than polyester resin or additives may be added in small amounts, for example, in amounts of 20% by mass or less, 10% by mass or less, 5% by mass or less, or 3% by mass or less.

[0037] The polyester resin used as the material for the first polyester film layer and the polyester resin used as the material for the second polyester film layer (described later) can be the same or different. When the polyester resin used to form the first polyester film layer and the polyester resin used to form the second polyester film layer are the same, it is easier to adjust its adhesion to the easy-to-peel resin layer based on the presence or absence of corona treatment.

[0038] The polyester resin used as the material for the first polyester film layer is preferably polyethylene terephthalate (PET) because it is cheaper than other polyester films and is a common material used in food packaging materials.

[0039] The first polyester film layer in the composite film of the present invention is formed from a pre-formed film using polyester resin as the material. The polyester film may be unstretched or subjected to uniaxial or biaxial stretching. From the viewpoint of heat resistance and low shrinkage, a biaxially stretched film is preferred.

[0040] (thickness) There is no particular limitation on the thickness of the first polyester film layer. For example, it can be 5μm or more, 8μm or more, 10μm or more, 12μm or more, or 15μm or more, and it can be less than 30μm, less than 25μm, or less than 20μm. If it is 5μm or more, it can give the film the rigidity to withstand use as a packaging material, and therefore is preferred.

[0041] (Corona treatment) In the composite film of the present invention, no corona treatment is performed on either side of the first polyester film layer. That is, in the composite film of the present invention, the first polyester film layer is not subjected to corona treatment on the surface in contact with the adjacent easily peelable resin layer having a specific composition and structure, or on its opposite outer surface. Moreover, the surface of the first polyester film layer in contact with the easily peelable resin layer is the interface surface that forms the peel surface in the composite film of the present invention.

[0042] In one embodiment of the composite film 1 shown in Figure 1, the first polyester film layer 8a is not corona treated on either the surface adjacent to the paper layer 7 or the surface in contact with the easily peelable resin layer 10. Furthermore, in the composite film 1, the interface between the first polyester film layer 8a and the easily peelable resin layer 10 forms the peel surface 13.

[0043] (The polar component of the surface free energy of the surface in contact with the easily peelable resin layer) The polar component of the surface free energy of the surface in contact with the easy-to-peel resin layer of the first polyester film layer may be 9.0 mN / m or less. Here, the value of the polar component of the surface free energy is the value before the first polyester film layer is deposited on the easy-to-peel resin layer.

[0044] The polar component of the surface free energy of the surface of the first polyester film layer in contact with the easily peelable resin layer may be 8.5 mN / m or less, 8.0 mN / m or less, 7.5 mN / m or less, 7.25 mN / m or less, 7.0 mN / m or less, 6.75 mN / m or less, or 6.5 mN / m or less. This value may also be 2.0 mN / m or more, 3.0 mN / m or more, 4.0 mN / m or more, 5.0 mN / m or more, or 6.0 mN / m or more.

[0045] If the polarity of the surface free energy of the surface of the first polyester film layer in contact with the easy-peel resin layer before the first polyester film layer is deposited on top of the easy-peel resin layer is within the above range, when a cover material is formed that can peel off a portion of the peeling portion to form an opening before it is fully opened, a peel strength that can be reliably peeled off can be achieved.

[0046] Regarding the present invention, the polar component of the surface free energy of the surface of the first polyester film layer in contact with the easy-to-peel resin layer before the first polyester film layer is deposited on the easy-to-peel resin layer is determined using a dual-titration portable contact angle and surface free energy analysis device MSA (KRUSS Corporation). The contact angle between water and diiodomethane is measured, and the polar component of the surface free energy is analyzed according to the OWRK method (Owens, Wendt, Rebbel, Kaelble method).

[0047] (Polar component of the surface free energy of the peeled surface) The composite film of the present invention uses the interface between the first polyester film layer and the easily peelable resin layer as the peeling surface for peeling. The polar component of the surface free energy of the peeling surface of the first polyester film layer after peeling can be less than 2.0 mN / m.

[0048] The polar component of the surface free energy of the peel surface of the first polyester film layer after peeling can be less than 1.8 mN / m, less than 1.6 mN / m, or less than 1.5 mN / m. Alternatively, this value can be greater than 0.5 mN / m, greater than 1.0 mN / m, or greater than 1.25 mN / m.

[0049] If the polarity of the surface free energy of the peel surface of the first polyester film layer after peeling is within the above range, when a cover material is formed that can peel off a portion of the peel portion to form an opening before it is fully opened, a peel strength that can be reliably peeled off can be achieved.

[0050] Regarding the present invention, the polarity of the surface free energy of the peeled surface of the first polyester film layer after peeling can be measured as follows: (1) Peeling is performed at the interface between the first polyester film layer and the easy-to-peel resin layer. (2) Using a toluene-soaked wiping cloth, move it in one direction without applying force on the peel surface of the first polyester film layer to perform toluene-based wiping, and perform this wiping 10 times. (3) After wiping with toluene, in order to allow the toluene to dry, use a new wiping cloth and move it in one direction without applying force to perform dry wiping 10 times. (4) After dry wiping, the contact angle between water and diiodomethane was measured using a dual titration portable contact angle and surface free energy analysis device MSA (KRUSS Corporation), and the polar components of the surface free energy were analyzed according to the OWRK method (Owens, Wendt, Rebbel, Kaelble method).

[0051] <Second Polyester Film Layer> The second polyester film layer is an essential constituent layer in the composite film of the present invention. The second polyester film layer is adjacent to the easy-peel resin layer and is deposited on the first polyester film layer through the easy-peel resin layer.

[0052] (Material) The polyester resin used as the material for the second polyester film layer is the same as the polyester resin used as the material for the first polyester film layer.

[0053] (thickness) The thickness of the second polyester film layer is the same as the thickness of the first polyester film layer.

[0054] (Corona treatment) In the composite film of the present invention, corona treatment is performed on at least the surface of the second polyester film layer that is in contact with the easily peelable resin layer. It is sufficient to perform corona treatment on only the surface in contact with the easily peelable resin layer; corona treatment can also be performed on both surfaces.

[0055] <Easy-to-peel resin layer> The easily peelable resin layer is an essential constituent layer in the composite film of the present invention. It is located between the first polyester film layer and the second polyester film layer and adheres them to each other.

[0056] The easy-peel resin layer is composed of a mixture of polyethylene and cyclic olefin copolymers, which are mixed in a predetermined ratio. The mixture constituting the easy-peel resin layer only needs to contain polyethylene and cyclic olefin copolymers as essential components; other resins and additives may be included without compromising the effectiveness of the invention.

[0057] (Polyethylene) Examples of polyethylenes constituting the easily peelable resin layer of the present invention include: low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0058] Based on the considerations that it is easy to process, inexpensive, has a stable supply, and is a resin commonly used in food packaging, low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE) is preferred.

[0059] Low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE) refers to polyethylene containing branches, having more than 80 mol%, 90 mol%, 95 mol%, or 98 mol% of methylene repeating units, or substantially all repeating units being methylene, and having a density of less than 0.930 g / cm³.

[0060] When the polyethylene constituting the easily peelable resin layer of the present invention is low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE), its density may be less than 0.925 g / cm³, or less than 0.923 g / cm³, or more than 0.870 g / cm³, more than 0.875 g / cm³, more than 0.880 g / cm³, more than 0.900 g / cm³, more than 0.910 g / cm³, or more than 0.915 g / cm³.

[0061] Low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE) can have long-chain or short-chain branched structures. The short-chain branched structure can be derived from α-olefins with 4 to 18, 4 to 10, or 4 to 8 carbon atoms, such as 1-butene, 1-hexene, 4-methylpentene-1, 1-octene, etc.

[0062] The thermal properties of the polyethylene constituting the easily peelable resin layer of the present invention are not particularly limited. For example, its melt flow rate, when measured according to JIS K6922-1 and -2 and JIS K7210-1 at a temperature of 190°C and a load of 21.18N, is preferably 0.1g / 10min or more, 0.5g / 10min or more, 1.0g / 10min or more, 2.0g / 10min or more, 3.0g / 10min or more, or 5.0g / 10min or more, 100g / 10min or less, 50g / 10min or less, 30g / 10min or less, 20g / 10min or less, or 10g / 10min or less.

[0063] (Cyclic olefin copolymer) Cyclic olefin copolymers are polymers that use cyclic olefins as monomers and have saturated cyclic olefin structures in the main chain or side chains of the polymer.

[0064] The cyclic olefin copolymer constituting the peelable resin layer of the present invention is preferably a copolymer using at least one cyclic olefin and at least one ethylene compound other than a cyclic olefin as monomers.

[0065] The cyclic olefin copolymer may also be: a cyclic olefin random copolymer (COC) based on addition polymerization using at least one cyclic olefin and at least one ethylene compound other than the cyclic olefin as monomers; or a cyclic olefin ring-opening polymer or its hydride (COP) based on ring-opening polymerization using at least one compound having a double bond in the condensation ring backbone and at least one unsaturated compound other than the compound as monomers.

[0066] When the cyclic olefin copolymer constituting the easily peelable resin layer of the present invention is a random copolymer (COC) of cyclic olefins based on addition polymerization, the cyclic olefin as a monomer is not particularly limited. Examples include: monocyclic cyclic olefins such as cyclobutene, 3-methylcyclobutene, 3,4-diisopropenylcyclobutene, cyclopentene, 1-methylcyclopentene, 3-methylcyclopentene, cyclohexene, cyclooctene, 1-methylcyclooctene, 5-methylcyclooctene, cyclooctatetraene, and cyclododecene; polycyclic cyclic olefins such as tetracyclododecene and norcamphene; and derivatives thereof.

[0067] Furthermore, ethylene compounds other than cyclic olefins, which are comonomers of cyclic olefin random copolymers (COC), are not particularly limited. Examples include: α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene; monocyclic dienes such as cyclopentadiene, 1,3-cyclohexadiene, and 1,4-cyclohexadiene; polycyclic dienes with noronene rings (having two unsaturated bonds); and straight-chain or branched dienes such as butadiene and isoprene.

[0068] When the cyclic olefin copolymer constituting the easily peelable resin layer of the present invention is based on a ring-opening polymer of a cyclic olefin or its hydride (COP), the monomer is a compound having a double bond in the condensation ring backbone, as long as it can be polymerized by a metathesis polymerization catalyst, without particular limitation. Examples include compounds having a norunbenene backbone such as tetracyclododecene, norcamphene, or derivatives thereof.

[0069] Furthermore, as a comonomer of cyclic olefin ring-opening polymers, any unsaturated compound other than compounds having double bonds in the condensed ring backbone is acceptable, as long as it can be polymerized by a displacement polymerization catalyst; there are no particular limitations. Examples include: cyclic olefins, cyclic dienes, monomers having carbon-carbon double bonds in the main chain, and their derivatives, which are monomers of the aforementioned cyclic olefin random copolymers (COCs).

[0070] Cycloolefin ring-opening polymers have carbon-carbon double bonds (C=C) in the main chain. Furthermore, hydrogenation can be performed to obtain hydrides (COP) that transform the double bonds in the main chain into carbon-carbon single bonds (CC). From the perspective of heat resistance, weather resistance, etc., it can be a polymer in which at least the carbon-carbon double bonds in the main chain are hydrogenated.

[0071] (composition) The composition of polyethylene and cyclic olefin copolymers, which are essential components in the mixture constituting the easily peelable resin layer, is such that the proportion of cyclic olefin copolymers is 1 to 10 by mass relative to the total mass of polyethylene and cyclic olefin copolymers.

[0072] The proportion of cyclic olefin copolymer relative to the total mass of polyethylene and cyclic olefin copolymer can be 2% or more by mass, 3% or more by mass, 4% or more by mass, 5% or more by mass, 6% or more by mass, 7% or more by mass, 8% or more by mass, or 9% or more by mass, or can be less than 10% by mass, less than 9% by mass, less than 8% by mass, less than 7% by mass, less than 6% by mass, less than 5% by mass, less than 4% by mass, less than 3% by mass, or less than 2% by mass.

[0073] (thickness) Regarding the thickness of the easily peelable resin layer, in order to obtain stable peelability with the first polyester film layer and stable adhesion with the second polyester film layer, it is preferably 10 μm or more, 12 μm or more, 14 μm or more, 16 μm or more, 18 μm or more, 20 μm or more, 22 μm or more, or 24 μm or more, and preferably 30 μm or less, 28 μm or less, 26 μm or less, 24 μm or less, 22 μm or less, or 20 μm or less.

[0074] <Other Layers> The composite film of the present invention may arbitrarily include other layers besides the first polyester film layer, the easy-to-peel resin layer, and the second polyester film layer.

[0075] Other layers may be configured on: the side of the first polyester film layer opposite to the easy-peel resin layer, or the side of the second polyester film layer opposite to the easy-peel resin layer.

[0076] Preferably, a heat-sealing layer is disposed on the outermost surface of the first or second polyester film layer on the side opposite to the easy-peel resin layer, particularly on the outermost surface of the second polyester film layer on the side opposite to the easy-peel resin layer. By having a heat-sealing layer on the outermost surface, when using the composite film of the present invention to form packaging or the like, the composite films can be heat-sealed together or with other materials.

[0077] Preferably, a substrate layer is disposed on the outermost surface of the first or second polyester film layer on the side opposite to the easy-peel resin layer, particularly on the outermost surface of the first polyester film layer on the side opposite to the easy-peel resin layer. Since the substrate layer becomes the surface layer of the composite film, it serves as the outer layer of the packaging or similar product when the composite film of the present invention is used to form a package or similar product. When a heat-sealing layer is provided in the innermost layer, it can serve as a protective layer during heat sealing to form the packaging or similar product. Furthermore, printing for indicating the contents of the packaging or similar product can also be performed on the substrate layer.

[0078] Other layers are not particularly limited. Besides the substrate layer and heat-sealing layer, examples include: barrier layers for imparting barrier properties, reinforcing layers for reinforcing strength, and adhesive layers for bonding layers together. Although not shown in Figure 1, in the composite film 1 of one embodiment of the present invention shown in Figure 1, the first polyester film layer 8a and the paper layer 7 are bonded together by an adhesive layer, and the second polyester film layer 8b and the barrier layer 11 are bonded together by an adhesive layer. Furthermore, the first polyester film layer 8a, the easy-peel resin layer 10, and the second polyester film layer 8b are directly bonded together by sandwich lamination. Also, the barrier layer 11 and the heat-sealing layer 12 are directly bonded together by extrusion lamination.

[0079] In the composite film 1 of one embodiment of the present invention shown in FIG1, as other layers, a paper layer 7 is disposed on the outermost surface of the first polyester film layer 8a opposite to the easy-to-peel resin layer 10, and a barrier layer 11 and a heat-sealing layer 12 are disposed on the second polyester film layer 8b opposite to the easy-to-peel resin layer 10.

[0080] (Substrate layer) In the composite film of the present invention, the substrate layer, which is any of the constituent layers, can be a single layer or a multilayer laminate.

[0081] When the substrate layer is a single layer, it can be a resin layer composed of resin, especially a printable resin that serves as a protective layer. When the substrate layer is a resin layer, commonly used resins can be used as its material, such as polyesters like polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); polyolefins like polyethylene (PE), polypropylene (PP), and polystyrene (PS); polyamides like nylon-6 and nylon-66; and polycarbonate (PC).

[0082] Furthermore, the aforementioned resin is not only a single type, but can also be a mixture of two or more types, and can be combined with additives to impart functionality, etc., as necessary.

[0083] When the substrate layer is a resin layer, a pre-formed resin film can be used. The resin film used as the substrate layer can be any film formed from the aforementioned resins, and can be unstretched or subjected to uniaxial or biaxial stretching. A biaxially stretched film is preferred.

[0084] The substrate layer can also be a layer made of materials other than resin, such as a paper layer. Examples of paper layers include: woodfree paper, coated paper, and art paper. When the paper layer is the outermost layer of the composite film, gravure printing, flexographic printing, and other printing techniques can be performed on the paper layer.

[0085] Alternatively, an inorganic vapor-deposited film can be formed by vapor-depositing metals such as aluminum or inorganic materials such as silicon oxide or aluminum oxide onto the substrate layer. Or, a barrier coating such as a polyvinylidene chloride coating or a polyvinylidene fluoride coating can be applied. Furthermore, when the substrate layer is composed of a resin film, a roughening treatment can be performed to roughen its surface.

[0086] When the substrate layer is a laminate with two or more layers, multiple layers can be provided, which are composed of resin as in the single-layer case, or layers using materials other than resin can be provided.

[0087] (Heat-sealing layer) In the composite film of the present invention, the heat-sealing layer, which is an arbitrary constituent layer, is a layer used for heat sealing when the composite film of the present invention is used to form a package or the like. Therefore, the heat-sealing layer is configured to be the innermost layer of the composite film.

[0088] As for the material constituting the heat-sealing layer, any material that is heat-sealable and can impart sufficient sealing strength to the packaging formed by the composite film of the present invention is acceptable, and there are no particular limitations. Known materials can be used, such as: low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), polypropylene (PP), ethylene-propylene copolymer (EP), ethylene-acrylate copolymer (EAA), ethylene-methacrylate copolymer (EMAA), ionomer resin, ethylene-vinyl acetate copolymer (EVA), etc.

[0089] For example, in the case of forming packaging bags for filling contents, the heat-sealing layer becomes the layer that forms the space for filling the contents. Therefore, when it is necessary to impart resistance to the contents, it is preferable to use, for example, low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE).

[0090] The heat seal layer can be formed using a pre-formed film of the aforementioned materials, or by melting and extruding the material used to form the heat seal layer and then allowing it to cool and solidify.

[0091] Furthermore, the resin that constitutes the heat-sealing layer is not only one type, but can also be a mixture of two or more types, and additives such as those used to impart functionality can be added as needed.

[0092] Furthermore, the heat-sealing layer can be a single layer or a multi-layer structure.

[0093] Furthermore, the heat-sealing layer can have easy-peelability (easy-openability) to facilitate opening the joint during use. If the heat-sealing layer has easy-peelability, for example, when the cap material is formed from the composite film of the present invention and the cap material is heat-fused to the container body to form a package, it makes it easy to open and remove the contents.

[0094] (Barrier layer) Barrier layers are layers used to impart barrier properties to composite films.

[0095] Examples of barrier layers include resin layers composed of ethylene-vinyl alcohol copolymer (EVOH), nylon (NY), polyvinylidene chloride (PVDC), or polyacrylonitrile (PAN), which can function as barriers to gases such as oxygen and water vapor.

[0096] Furthermore, the aforementioned resin is not only a single type, but can also be a mixture of two or more types, and can be combined with additives to impart functionality, etc., as necessary.

[0097] For example, it can be an inorganic vapor-deposited film layer, a metal foil layer, or an organic coating.

[0098] Inorganic vapor-deposited films that serve as barrier layers include, for example, silicon dioxide vapor-deposited films, aluminum vapor-deposited films, alumina vapor-deposited films, and silicon dioxide and alumina vapor-deposited films.

[0099] Metal foils used as barrier layers include, for example, aluminum foil, copper foil, titanium foil, and alloy foils such as aluminum alloy foil and stainless steel foil.

[0100] Organic coatings used as barrier layers can be barrier coatings such as polyvinylidene chloride coatings and polyvinylidene fluoride coatings.

[0101] When an inorganic vapor-deposited film layer or an organic coating layer is present as a 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, based on the viewpoint of ensuring strength and barrier properties. Furthermore, based on the viewpoint of improving operability when using composite films as packaging materials, the thickness is preferably 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less.

[0102] When a metal foil is present as a barrier layer, from the viewpoint of ensuring strength and barrier properties, the thickness of the barrier layer is preferably 5μm or more, 7μm or more, 10μm or more, or 15μm or more. From the viewpoint of improving operability when using composite films as packaging materials, the thickness is preferably 100μm or less, 80μm or less, 60μm or less, 55μm or less, 50μm or less, 45μm or less, 40μm or less, or 35μm or less.

[0103] (Reinforcement layer) A reinforcing layer is a layer used to strengthen the composite film. Materials used as reinforcing layers include, for example, coated paper, art paper, synthetic paper, and non-woven fabric. When the reinforcing layer, such as paper, is present on the outermost surface of the composite film, printing techniques such as gravure printing or flexographic printing can be applied to its surface.

[0104] (Adhesive layer) An adhesive layer is a layer located between layers and used to bond the layers together. Examples of adhesive layers include layers composed of ethylene-acrylate copolymers (EAA), ethylene-methacrylate copolymers (EMAA), and ionomers.

[0105] The adhesive layer can also be a layer composed of adhesives. For example, it can be a dry laminate adhesive, a hot melt adhesive, a water-soluble adhesive, an emulsion adhesive, a solvent-free laminate adhesive, and a thermoplastic resin used for extrusion lamination, etc.

[0106] Manufacturing Methods of Composite Thin Films The manufacturing method of the composite film of the present invention is not particularly limited and can employ known methods. Examples include: dry lamination, hot melt lamination, extrusion lamination, and sandwich lamination.

[0107] Applications of Composite Films The uses of the composite film of the present invention are not particularly limited. For example, it can be used as a packaging material to form packaging bags, lids, etc.

[0108] <Packaging Bags> The composite film of the present invention can be used as a packaging material to form packaging bags. When the composite film of the present invention has a heat-sealing layer, by heat-sealing the heat-sealing layers together, three-side sealed bags, four-side sealed bags, gusseted bags with reinforced edges, pillow bags, etc., can be formed.

[0109] <Cover Material> The composite film of the present invention can be formed into a capping material. For example, it can be used as a capping material for sealing the upper opening of a container body.

[0110] (half-cut mark) The cover material made from the composite film of the present invention may have a half-cut. The half-cut can be suitably provided according to the application of the composite film.

[0111] For example, when the composite film of the present invention is used as a cover material, the cover material has the interface between the first polyester film layer and the easy-peel resin layer as the peel surface, and an opening can be formed in the peel portion before opening. The cover material may have: a first half-cut from the first polyester film layer side to a depth reaching the easy-peel resin layer; a second half-cut and a third half-cut from the second polyester film layer side, penetrating the easy-peel resin layer in the thickness direction and reaching at least the interface between the easy-peel resin layer and the first polyester film layer. Here, the second and third half-cuts may also be formed to a depth reaching the first polyester film layer.

[0112] This type of cover material has an opening tab and a partial peeling tab at its periphery. The first half-cut and the partial peeling tab define the outer edge of the partially peeled portion, the second half-cut defines the outer edge of the liquid flow hole, and the third half-cut defines the partial peeling tab. Moreover, the liquid flow hole is located within the partially peeled portion.

[0113] Specifically, at least one second half-cut and a third half-cut are provided near the partial dissection protrusion, and a first half-cut is provided on both sides of the partial dissection protrusion to connect the periphery in a manner that covers the area where the second half-cut is formed.

[0114] Based on this configuration, when the partial peeling tab is grasped and the partial peeling portion is peeled off, the peeling occurs at the interface between the first polyester film layer and the easy-peel resin layer in areas other than the liquid flow hole, while at the liquid flow hole, the peeling does not occur at the interface between the first polyester film layer and the easy-peel resin layer, so that the second polyester film is removed along with the first polyester film layer, thereby forming the liquid flow hole.

[0115] The half-cut marks of the cover material of the present invention formed from the composite film of the present invention will be explained using Figures 1 to 3. Figure 1 is a cross-sectional view of the composite film of an embodiment of the present invention. Figure 2 is a top view of the cover material of an embodiment of the present invention. Figure 3 is an explanatory diagram of an example of the use of the cover material of an embodiment of the present invention.

[0116] Figure 1 shows a cross-sectional view of the composite film 1 according to one embodiment of the present invention, and Figure 2 also shows a cross-sectional view of the cover material 1. The structure of each layer of the composite film 1 is as described above.

[0117] The cover material 1 shown in Figure 2 is composed of a composite film 1, which is punched into the necessary cover shape. In one embodiment of the cover material 1, a portion of the approximately circular periphery extends outward to form an opening tab 2, and a portion of the periphery on the opposite side of the opening tab 2 also extends outward to form a partial peeling tab 3.

[0118] The cover material 1 series includes: a first half-cut 5 as a partial peeling half-cut, a second half-cut 4 as an opening half-cut, and a third half-cut 6 as a tab forming half-cut.

[0119] In the cover material 1, the second half-cut 4, which serves as a half-cut for opening, is annular in shape, and there are two of the second half-cut 4 on the cover material 1.

[0120] In the cap material of the present invention formed from the composite film of the present invention, the partial peeling tab is provided on the outer edge of the outer layer (partial peeling portion) covering the area where the second half-cut, which serves as the opening half-cut, is formed, to facilitate peeling off. The opening tab is provided to facilitate pulling the cap material open when the entire cap material is peeled off from the container body of the sealed object; it is sufficient that it is provided on the outer edge of the outer layer covering the area where the second half-cut, which serves as the opening half-cut, is formed.

[0121] In the composite film 1 of one embodiment of the present invention shown in FIG. 1, and the cover material 1 of one embodiment of the present invention shown in FIG. 2, the first half-cut 5, which is a partial peeling half-cut, is formed in the thickness direction through the outer layer 9, i.e., the paper layer 7 and the first polyester film layer 8a, to a depth reaching the peeling surface 13. The second half-cut 4, which is an opening half-cut, and the third half-cut 6, which is a tab forming half-cut, are formed in the thickness direction through the inner layer 14, i.e., the heat-sealing layer 12, the barrier layer 11, the second polyester film layer 8b, and the easy-peel resin layer 10, to a depth reaching the peeling surface 13, i.e., the interface between the easy-peel resin layer and the first polyester film layer.

[0122] In the cover material 1 made of the composite film 1, the first half-cut 5 and the partial peeling tab 3 define the outer edge of the partially peeled portion. The second half-cut 4 defines the outer edge of the liquid flow hole, which is disposed within the partially peeled portion. The third half-cut 6 defines the partial peeling tab 3. Thus, when the partially peeled portion is peeled off by grasping the partial peeling tab 3, the liquid flow hole can be formed at the interface between the first polyester film layer 8a and the easy-to-peel resin layer 10, except for the liquid flow hole.

[0123] Specifically, in the composite film 1 and the cover material 1 described above, the second half-cut 4, which serves as a half-cut for opening, is annular in shape. When the outer surface layer 9 of the area forming the second half-cut 4 is peeled from the inner surface layer 14 by the peeling surface 13 using the first half-cut 5, which serves as a partial peeling half-cut, the inner part of the annular shape of the second half-cut 4 is removed along with it while it is attached to the outer surface layer 9, thereby forming an opening.

[0124] Next, an example of the use of the cover material 1 of the present invention will be described with reference to FIG3.

[0125] As shown in Figure 3(a), the lid material 1 is typically used to seal the container body 16. Figure 3(a) shows a lidded container containing contents, formed by heat-sealing the lid material 17 onto the flange portion 16 of the container body 16 containing contents (not shown). In the lidded container containing contents shown in Figure 3(a), the lid material 1 is placed on the container body 16 such that the heat-sealing layer 12 located on the outermost surface of the inner layer 14 faces the container body 16, and the heat-sealing layer 12 is heat-sealed onto the flange portion 17 protruding from the periphery of the opening of the container body 16.

[0126] Figure 3(b) shows the opening formed before the lidded container containing the contents of Figure 3(a) is fully opened. As shown in Figure 3(b), the partial peeling tab 3 is grasped and pulled upwards, and the outer layer 9 (partially peeled portion) covering the area forming the second half-cut 4, which serves as the opening half-cut, is separated from the outer layer 9 of other areas through the third half-cut 6, which serves as the tab forming half-cut, and peeled off and removed from the inner layer 14. During the peeling of the outer layer 9, the inner part of the annular shape of the second half-cut 4 of the inner layer 14 is removed along with it while it is attached to the outer layer 14, thereby forming the opening 15.

[0127] After the opening 15 is formed, the container body 16 is tilted toward the opening 15 so that liquids such as water inside the container body 16 can be discharged through the opening 15. By setting the size of the opening 15 to be smaller than the size of the contents, the leakage of the contents can be prevented.

[0128] Figure 3(c) shows the container being fully opened after the outer layer 9 is peeled off to form the opening 15, and the lid material 1 is removed from the lidded container. As shown in Figure 3(c), the lid material 1 is peeled off from the flange 17 of the container body 16 by pulling the opening tab 2 upward, so that the opening of the container body 16 is fully open and the contents can be taken out.

[0129] When the contents are instant fried noodles, etc., firstly, in the state shown in Figure 3(a), pull the opening tab 2 upwards to partially open the opening of the container body 16, and remove the ingredient packets, sauces, etc. from inside the container. Then, pour in hot water and reseal the container. After a certain period of time, an opening 15 is formed as shown in Figure 3(b). Pour out the hot water through the opening 15, and then, as shown in Figure 3(c), fully open the opening of the container body 16 and add the ingredients, sauces, etc.

[0130] In the cap material of the present invention formed from the composite film of the present invention, the shape of the second half-cut as the opening half-cut is simply annular and is not particularly limited. In addition to a circle, it can also be suitably set as an ellipse, a rounded rectangle, an egg shape, a triangle, a square, a pentagon or more polygons, etc. To avoid jamming when the inner part of the annular shape of the opening half-cut is removed while it is attached to the outer layer, it is preferable to have a circle, an ellipse, a rounded rectangle, an egg shape, etc. without corners. Furthermore, the second half-cut can be singular or plural, and it is preferable to form a plurality of them in order to facilitate the drainage of liquid at a size that prevents the contents from flowing out.

[0131] As the first half-cut of a partial stripping half-cut, it is usually formed as a continuous line, but it can also be formed as a perforation or a discontinuous line.

[0132] As the third half-cut for forming the tab, when the partially peeling tab is grasped and pulled upward, in order to allow the tension to act on the interface between the outer layer and the inner layer, it can be formed from the inner side across the base of the partially peeling tab at the same depth as the second half-cut for opening.

[0133] A lidded container containing contents comprises: a container body, contents, and a lid material formed from the composite film of the present invention. (Container body) The container body used to form a lidded container for containing contents has a storage section and a flange section.

[0134] The material of the container body is not particularly limited, as long as it allows the heat-sealing layer of the cap material formed by the composite film of this invention to be heat-sealed. Examples include: paper containers with resin coatings on the surface, or resin containers, etc.

[0135] {Storage Department} The storage section is the part used to store contents. There are no particular restrictions on the shape of this section; for example, it can be roughly shaped like a frustum of a cone, a polygonal frustum of a cone, a cuboid, or a cube.

[0136] {Flange} The flange is the part around the upper opening of the main body of the container. Its shape is not particularly limited; for example, it can be flange-shaped. Furthermore, the shape of the outer perimeter of the flange can be appropriately chosen according to the shape of the lid material.

[0137] When the container body is made of paper, the flange may have a coating based on polyethylene resin.

[0138] (Contents) The contents are those held in the storage section. There are no particular limitations on the contents; for example, heated foods such as instant noodles, refrigerated foods, and frozen foods, or non-heated foods such as snacks, gummies, and beverages can be included. [Example]

[0139] The present invention is specifically illustrated by means of examples and comparative examples, but the present invention is not limited to these.

[0140] <Materials> In the embodiments and comparative examples, the materials used as the constituent layers are the following materials.

[0141] (1) Paper layer Paper (basis weight: 80g / m²)

[0142] (2) First polyester film layer PET film 1 (Company A, thickness: 12μm) PET film 2 (Company B, thickness: 12μm) PET film 3 (Company C, thickness: 8μm) PET film 4 (Company D, thickness: 12μm)

[0143] (3) Easy-to-peel resin layer A mixture is prepared using the following polyethylene and cyclic olefin copolymers, wherein the proportion of the cyclic olefin copolymer relative to the total amount of polyethylene and cyclic olefin copolymers is less than 10% by mass. Polyethylene: (Low-density polyethylene (LDPE)) cyclic olefin copolymers

[0144] (4) Second polyester film layer PET film 3 (Company C, thickness: 8μm)

[0145] (5) Aluminum layer Aluminum foil (thickness: 6.5μm)

[0146] (6) Heat seal layer Easy-to-peel polyolefin resins

[0147] Examples 1-3 and Comparative Examples 1-4 <Fabrication of Composite Films> Using the materials shown in Table 1, a composite film consisting of (paper layer / / first polyester film layer / easy-to-peel resin layer / second polyester film layer / / aluminum layer / heat-sealing layer) is manufactured according to the method shown below. The parts that are dry-laminated are indicated by " / / ".

[0148] In Examples 1-3, the polyester film used to form the first polyester film layer was one on neither side subjected to corona treatment. In Comparative Examples 1-3 and Comparative Example 4, the polyester film used to form the first polyester film layer was one on only one side subjected to corona treatment, with the corona-treated side as the paper layer side and the untreated side as the easy-to-peel resin layer side, thus forming a composite film.

[0149] Regarding the polyester film that becomes the second polyester film layer, both the examples and comparative examples used films that had undergone corona treatment on both sides.

[0150] 1. A paper layer and a polyester film, which forms the first polyester film layer, are dry-laminated to create a laminate (paper layer / / first polyester film layer). A two-component curing dry-laminated adhesive is used as the dry-laminated adhesive, with a coating amount of 2.5 g / m².

[0151] 2. An aluminum foil, which will become the aluminum layer, and a polyester film, which will become the second polyester film layer, are dry-laminated together to form a laminate (second polyester film layer / / aluminum layer). A two-component curing dry-laminated adhesive is used as the dry-laminated adhesive, with a coating amount of 2.5 g / m².

[0152] 3. A component forming an easy-to-peel resin layer is sandwiched between the prepared (paper layer / / first polyester film layer) laminate and the (second polyester film layer / / aluminum layer) laminate to form a laminate of (paper layer / / first polyester film layer / easy-to-peel resin layer / second polyester film layer / / aluminum layer). The thickness of the easy-to-peel resin layer is 20 μm.

[0153] 4. On the aluminum layer, an easy-to-peel polyolefin resin, which serves as a heat-sealing layer, is extruded and laminated to a thickness of 20 μm, thereby producing a composite film composed of (paper layer / / first polyester film layer / easy-to-peel resin layer / second polyester film layer / / aluminum layer / heat-sealing layer).

[0154] <Making of Covering Materials> The prepared composite film is punched and partially cut to produce the cover material shown in Figure 2.

[0155] <Making Lid Containers> Using a heated heat-sealing rod, the prepared lid material is heat-sealed onto a polystyrene cup (flange width: 6mm, opening inner diameter: 157mm) under the conditions of a heat-sealing width of 5mm, a temperature of 130℃, a pressure of 0.3Mpa, and a time of 0.3 seconds to make a lidded container.

[0156] "evaluate"

[0157] (The opening after hot water is injected forms the test site) Regarding the lidded containers produced in Examples 1-3 and Comparative Examples 1-4, after opening by grasping the opening tab and pulling it upwards by about 1 / 3, hot water at 98°C was poured in, and the tab was bent to reseal the container. After resealing for 3 minutes, the partial peeling tab was grasped and pulled upwards to separate the partially peeled portion from the outer layer of other areas and peel it from the inner layer to form an opening. Whether the paper layer breaks or the peeled surface becomes cloudy during peeling was visually confirmed. The evaluation criteria are as follows. 〇: Some of the paper layer from the peeling section did not remain on the inner layer, and no whitening occurred on the peeling surface of the inner layer. ×: Some of the paper layer remaining in the peeling section is on the inner layer, or the peeling surface of the inner layer becomes cloudy.

[0158] (Analysis of the polar components of the surface free energy of the surface in contact with the easily peelable resin layer of the first polyester film layer) Regarding the polyester films used as the first polyester film layers in Examples 1-3 and Comparative Examples 1-4, the polar component of the surface free energy of the surface without corona treatment was analyzed. The measuring apparatus was a dual-titer portable contact angle and surface free energy analysis apparatus (MSA, KRUSS Corporation), which measured the contact angles of water and diiodomethane, and analyzed the polar component of the surface free energy using the OWRK method (Owens, Wendt, Rebbel, Kaelble method).

[0159] (Analysis of the polar components of the surface free energy of the peeling surface) The caps produced in Examples 1-3 and Comparative Examples 1-4 were peeled off at the interface between the first polyester film layer and the easy-peel resin layer. A toluene-based wiping was performed by moving a toluene-moistened cloth in one direction without applying force on the peeling surface of the first polyester film layer. Each cap was wiped 10 times, with a new cloth used for each cap.

[0160] After 10 toluene-based wiping cycles, a dry wipe was performed to allow the toluene to dry. The dry wipe was performed 10 times on each cover using a new wiping cloth, moving it gently in one direction. For each cover after the dry wipe, the polar component of the surface free energy was analyzed, as described above.

[0161]

[0162] 1: Composite film 2: Kaifeng uses protruding pieces 3: Partial peeling tabs 4: Second half cut 5: First half cut 6: Third half cut 7: Paper layer 8a: First polyester film layer 8b: Second polyester film layer 9: Outer layer 10: Easy-to-peel resin layer 11: Barrier layer 12: Heat seal layer 13: Peeling surface 14: Inner layer 15: Opening 16: Container body 17: Flange portion

Claims

1. A composite film comprising, sequentially, a first polyester film layer, an easy-peel resin layer, and a second polyester film layer, wherein the first polyester film layer and the second polyester film layer are adhered to each other by the easy-peel resin layer, neither side of the first polyester film layer is subjected to corona treatment, and at least the side of the second polyester film layer in contact with the easy-peel resin layer is subjected to corona treatment, wherein the easy-peel resin layer is composed of a mixture of polyethylene and a cyclic olefin copolymer, wherein the proportion of the cyclic olefin copolymer is 1 to 10% by mass relative to the total amount of the polyethylene and the cyclic olefin copolymer, and the film can be peeled off using the interface between the first polyester film layer and the easy-peel resin layer as the peel surface, wherein the polar component of the surface free energy of the side of the first polyester film layer in contact with the easy-peel resin layer is 9.0 mN / m or less, and the polar component of the surface free energy of the peel surface of the first polyester film layer after peeling is 2.0 mN / m or less.

2. The composite film as described in claim 1, wherein, A heat-sealing layer is provided on the side of the first polyester film layer opposite to the aforementioned easy-to-peel resin layer, or on the side of the second polyester film layer opposite to the aforementioned easy-to-peel resin layer.

3. A cover material formed from a composite film as described in claim 1 or 2.

4. The cover material as described in claim 3, comprising: a first half-cut extending from the first polyester film layer to the depth of the easily peelable resin layer; a second half-cut and a third half-cut extending from the second polyester film layer to the thickness direction through the easily peelable resin layer and to a depth at least reaching the interface between the easily peelable resin layer and the first polyester film layer; and a partial peeling tab at the periphery, wherein the first half-cut and the partial peeling tab define the outer edge of the partially peeled portion; the second half-cut defines the outer edge of a liquid flow hole; the third half-cut defines the partial peeling tab; and the liquid flow hole is disposed within the partially peeled portion. In this way, when the aforementioned partial peeling tab is grasped to peel off the aforementioned partial peeling portion, the peeling occurs at the interface between the aforementioned first polyester film layer and the aforementioned easy-peel resin layer in areas other than the aforementioned liquid flow hole, and at the aforementioned liquid flow hole, the peeling does not occur at the interface between the aforementioned first polyester film layer and the aforementioned easy-peel resin layer, thereby removing the aforementioned second polyester film layer along with the aforementioned first polyester film layer, thereby forming the aforementioned liquid flow hole.

5. A lidded container containing contents, comprising: a container body having a receiving portion and a flange portion, contents contained in the container body, and a lid material as described in claim 3 or 4, wherein the lid material has a heat-sealing layer on the side of the first polyester film layer opposite to the easily peelable resin layer, or on the side of the second polyester film layer opposite to the easily peelable resin layer, and the lid material is heat-sealed to the flange portion through the heat-sealing layer.

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