JP2024054573A - Transparent multi-layer film and packaging - Google Patents

Abstract

[Problem] To provide a transparent multilayer film capable of forming an easy-peel lid material and a base material containing polyethylene terephthalate for producing a package by heat-sealing the lid material, the lid material having transparency in the package, capable of suppressing the occurrence of stringiness when the package is opened, and providing a good peeling feel of the lid material. [Solution] A transparent multilayer film 1 having at least an easy-peel layer 11, the easy-peel layer 11 containing a hot melt adhesive and an incompatible component that is incompatible with the hot melt adhesive, and the haze of the transparent multilayer film 1 measured in accordance with JIS K 7136:2000 is 20% or less. [Selected Figure] Figure 1

Description

The present invention relates to a transparent multilayer film and a packaging body.

For example, known food packaging materials include a packaging material in which a tray is sealed with a lid material (a packaging material with a tray), and a packaging material in which a deep-drawn base material is sealed with a lid material (a deep-drawn packaging material). The tray, base material, and lid material can all be made of resin.

Among food packages, those with transparent lids are in high demand because the packaged food can be seen through the lid from outside the package.
On the other hand, the film constituting the lid material is required to have easy peelability from the tray or base material, barrier properties to suppress oxygen permeation, pinhole resistance, and the like.
Therefore, a transparent multi-layer film is usually used as the film constituting the lid material.

In recent years, efforts to realize a recycling-oriented society have led to a demand for the reuse (recycling) of resources, and among various resins, polyethylene terephthalate (PET) in particular has the most advanced recycling technology. In the field of food packaging, there is also a desire to reuse resins, and packaging using a tray or base material containing polyethylene terephthalate and a lid material made of a multilayer film is being considered (see Patent Document 1).

JP 2011-026408 A

When a package obtained by heat-sealing an easy-peel lid material and an object to be sealed (e.g., a base material, a tray, etc.) with the lid material is opened by peeling the lid material, a peeling at the interface between the lid material and the object to be sealed, called interfacial peeling, may occur. In addition, a part of the layer of the lid material on the heat-sealed side may remain on the object to be sealed, called interlayer peeling, may occur. When interlayer peeling occurs, a resin thread-like material is easily generated between the peeled surfaces, called "stringing." When stringing occurs, there is a problem that a part of the thread-like material, a thread-like piece, may be mixed into the contents such as the packaged food. On the other hand, when interfacial peeling occurs, there is a problem that a crackling sound is generated during peeling, making the peeling feel worse. When the composition of the lid material is adjusted to suppress the occurrence of stringing or to improve the peeling feel of the lid material, there is a problem that the transparency of the lid material is easily reduced.

The present invention aims to provide a transparent multilayer film that can be used to form a lid material for producing a package by heat sealing an easy-peel lid material and a base material containing polyethylene terephthalate, in which the lid material has transparency within the package, the occurrence of stringiness is suppressed when the package is opened, and the lid material has a good peeling feel.

In order to solve the above problems, the present invention employs the following configuration.
[1] A transparent multilayer film having at least an easy peel layer, the easy peel layer containing a hot melt adhesive and an incompatible component that is incompatible with the hot melt adhesive, and the haze of the transparent multilayer film measured in accordance with JIS K 7136:2000 is 20% or less.
[2] The transparent multilayer film according to [1], wherein the ratio of the content of the incompatible component to the content of the hot melt adhesive in the easy peel layer is 2 to 45 mass %.
[3] The transparent multilayer film according to [1] or [2], wherein the incompatible component is a (meth)acrylic acid ester-styrene copolymer.
[4] The transparent multilayer film according to [3], wherein the ratio of the amount of structural units derived from a (meth)acrylic acid ester to the total amount of structural units in the (meth)acrylic acid ester-styrene copolymer is 10 to 90 mol %, and the ratio of the amount of structural units derived from styrene is 90 to 10 mol %.

[5] The transparent multilayer film according to [4], wherein the (meth)acrylic acid ester-styrene copolymer is a methacrylic acid ester-styrene copolymer.
[6] The transparent multilayer film according to [1] or [2], further comprising a flexible layer.
[7] The transparent multilayer film according to [1] or [2], further comprising an intermediate layer.
[8] The transparent multilayer film according to [1] or [2], further comprising an oxygen barrier layer.

[9] The transparent multilayer film according to [1] or [2], further comprising a flexible layer, an intermediate layer, and an oxygen barrier layer, the flexible layer and the intermediate layer being disposed between the easy peel layer and the oxygen barrier layer.
[10] The transparent multilayer film according to [6], wherein the flexible layer is disposed adjacent to the easy-peel layer.
[11] The transparent multilayer film according to [1] or [2], wherein the easy peel layer has a surface resistivity of 1×10 ⁵ to 1×10 ¹⁴ Ω/□, as measured in accordance with JIS C 2139-3-1:2018.
[12] The transparent multilayer film according to [9], further comprising an outer layer containing a propylene-based polymer, a polyamide or a polyester on the side of the oxygen barrier layer opposite to the intermediate layer.

[13] The transparent multilayer film according to [7], wherein the intermediate layer contains polyamide.
[14] The transparent multilayer film according to [13], wherein the polyamide is a biomass-derived polyamide.
[15] The transparent multilayer film according to [6], wherein the flexible layer contains one or more materials selected from the group consisting of polyethylene, modified polyethylene, and ionomer.
[16] The transparent multilayer film according to [15], wherein the polyethylene is a biomass-derived polyethylene.
[17] A packaging body comprising the transparent multilayer film according to [1] or [2].

According to the present invention, a transparent multilayer film capable of forming a lid material for producing a package by heat sealing an easy-peel lid material and a base material containing polyethylene terephthalate is provided, in which the lid material has transparency in the package, the occurrence of stringiness is suppressed when the package is opened, and the lid material has a good peeling feel.

1 is a cross-sectional view illustrating a schematic example of a transparent multilayer film according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a schematic diagram of another example of a transparent multilayer film according to one embodiment of the present invention. FIG. 1 is a cross-sectional view showing a schematic example of a packaging body according to an embodiment of the present invention.

<<Transparent multi-layer film>>
A transparent multilayer film according to one embodiment of the present invention is a transparent multilayer film having at least an easy peel layer, the easy peel layer containing a hot melt adhesive and an incompatible component that is incompatible with the hot melt adhesive, and the haze of the transparent multilayer film measured in accordance with JIS K 7136:2000 is 20% or less.
The transparent multilayer film of this embodiment has transparency throughout its entirety.

The transparent multilayer film of the present embodiment is suitable for use as a component of a package, and is particularly suitable for use as a lid material for a deep-draw package.
A deep-drawn package is a package constructed by joining a resin base material, in which a recess for forming a storage section is formed by deep-draw molding, and a lid material by heat sealing or the like.

The transparent multilayer film of this embodiment has an easy-peel layer containing a hot melt adhesive and the incompatible component, and therefore the haze is 20% or less, making it possible to form a transparent lid material in a package. Therefore, the contents can be clearly seen from the outside of the package obtained using the transparent multilayer film. Furthermore, a package is produced by heat-sealing the lid material and the base material containing polyethylene terephthalate, and when the package is opened by peeling off the lid material, the occurrence of stringiness can be suppressed and the lid material can be peeled off with a good feel.

When a package obtained by heat-sealing an easy-peel lid material and an object to be sealed (e.g., a base material, a tray, etc.) with the lid material is opened by peeling the lid material, either interfacial peeling or interlayer peeling may occur. In interfacial peeling, peeling occurs at the interface between the lid material and the object to be sealed. In interlayer peeling, a part of the layer on the heat-sealed side of the lid material remains on the object to be sealed, and peeling occurs. Usually, when interlayer peeling occurs, a so-called "stringing" in which a resin thread-like material is generated between the peeled surfaces is likely to occur. When interfacial peeling occurs, a crackling sound is likely to occur during peeling, and the peeling feeling is likely to be deteriorated. It is speculated that this deterioration in the peeling feeling is due to the high orientation of the resin component in the easy-peel layer during the production of the lid material. And, when the composition of the lid material is adjusted to suppress the occurrence of stringing or to improve the peeling feeling of the lid material, the transparency of the lid material is likely to decrease.
In contrast, the transparent multilayer film of the present embodiment has the above-mentioned configuration and can solve all of these problems.

In this embodiment, the "substrate" refers to the object to which the lid material is heat sealed when manufacturing the package, and specific examples include the base material, trays, etc.

The transparent multilayer film of this embodiment can be used to manufacture packages other than deep drawn packages, so long as the package is manufactured by heat sealing. In other words, the use of the transparent multilayer film of this embodiment is not limited to deep drawn packages. For example, a package (package with a tray) can be manufactured by using the transparent multilayer film of this embodiment as a lid material and heat sealing this lid material and a tray.

The haze of the transparent multilayer film measured in accordance with JIS K 7136: 2000 is 20% or less, preferably 18% or less, and may be, for example, any one of 15% or less, 12% or less, and 9% or less. When the haze of the transparent multilayer film is equal to or less than the upper limit, the lid material in the package has transparency, and the contents can be more clearly seen from the outside of the package obtained using the transparent multilayer film.
The lower limit of the haze of the transparent multilayer film is not particularly limited. For example, a transparent multilayer film having a haze of 1% or more can be more easily produced.
In one embodiment, the haze of the transparent multilayer film may be any of 1 to 20%, 1 to 18%, 1 to 15%, 1 to 12%, and 1 to 9%, although these are just examples of the haze of the transparent multilayer film.

In this specification, unless otherwise specified, the haze of a transparent multilayer film means the haze measured from the outside of the easy-peel layer side of the transparent multilayer film in accordance with JIS K 7136:2000.

The haze of the transparent multilayer film can be adjusted by adjusting the type or content of the components contained in any of the layers constituting the transparent multilayer film. For example, the haze of the transparent multilayer film can be easily adjusted by adjusting the type of incompatible component or the content of the incompatible component in the easy-peel layer. Furthermore, when the easy-peel layer contains an anti-fogging agent described below, the haze of the transparent multilayer film can be more easily adjusted by adjusting the type of incompatible component and anti-fogging agent, or the total content of the incompatible component and anti-fogging agent in the easy-peel layer. The incompatible component and anti-fogging agent will be described in detail later.

In the transparent multilayer film of this embodiment, when a test piece of the easy peel layer having a width of 25.4 mm and a thickness of 6 μm and a polyethylene terephthalate film having a thickness of 200 μm (hereinafter sometimes abbreviated as "test PET film") are heat-sealed at a sealing temperature of 140° C. for 2 seconds, the hot tack strength at 0.22 seconds after the heat sealing is defined as H _140. The H ₁₄₀ may be, for example, 0.7 N/25.4 mm or more, but is preferably 1 N/25.4 mm or more, and may be, for example, any one of 2 N/25.4 mm or more, 2.5 N/25.4 mm or more, and 3.5 N/25.4 mm or more. When the H ₁₄₀ is 1 N/25.4 mm or more, peeling of the lid material from the base material is highly suppressed when a deep-draw package is produced by heat-sealing a long lid material (the transparent multilayer film) and a long base material containing polyethylene terephthalate.

Hot tack strength is the peel strength of the sealed area immediately after heat sealing when the resin component of the sealed area is in a molten state, and can be measured using a commercially available hot tack strength measuring device. The method for measuring hot tack strength will be explained in detail later.

When a deep-drawn package is manufactured using the long transparent multilayer film as a lid material and a long base material, for example, a long base material (connected body of base materials) in which recesses for forming storage sections are arranged in the longitudinal direction and a long lid material are used, and while applying a tension of a specific value or more to the long lid material and further filling the area in which the storage section is formed with an inert gas and the packaged object, the long lid material and the long base material are heat-sealed sequentially in their longitudinal direction. After all heat sealing is completed, the long lid material and the base material are cut for each storage section formed, thereby obtaining the desired deep-drawn package. In this manufacturing method, the cutting of the long lid material and the base material is not performed immediately after the completion of each heat sealing (in other words, after the formation of each storage section), so that tension continues to be applied to the heat-sealed long lid material until all heat sealing is completed (in other words, until the cutting of the long lid material and the base material is started). Furthermore, during this time, the internal pressure of the storage section is high because it is filled with an inert gas. Furthermore, it is usually difficult to increase the seal strength when a base material containing polyethylene terephthalate and an easy-peel lid material are heat-sealed. Therefore, when a conventional long lid material is used, the heat-sealed long lid material is easily peeled off from the base material due to the influence of these tensions, internal pressure, and the constituent material of the lid material, and the area of the part where the seal is maintained between the lid material and the base material becomes small, or in the worst case, a gap is generated between the lid material and the base material. In particular, the lid material is easily peeled off from the base material in the region of the peripheral part of the long base material that will eventually become a corner part. In contrast, when a long lid material made of the transparent multilayer film of this embodiment having H ₁₄₀ of 1 N/25.4 mm or more is used, such peeling of the lid material from the base material during the manufacturing process of the package is highly suppressed.
Thus, the transparent multilayer film of this embodiment having an H ₁₄₀ of 1 N/25.4 mm or more provides particularly remarkable effects when used in the production of deep-draw packaging products.

The transparent multilayer film of the present embodiment, which has a H ₁₄₀ of 1 N/25.4 mm or more, has excellent adhesion to polyethylene terephthalate films, including the above-mentioned test PET film. Therefore, when such a transparent multilayer film is used as a long lid material constituting a deep-draw package and this lid material is heat-sealed with a long base material containing polyethylene terephthalate to produce a deep-draw package, peeling of the lid material from the base material can be suppressed.
In this specification, unless otherwise specified, "peeling of the lid material from the base material" means "peeling of the lid material from the base material when producing a deep-draw packaging body".

The upper limit of H ₁₄₀ is not particularly limited.
For example, transparent multilayer films with H ₁₄₀ of 7N/25.4mm or less are easier to manufacture.

H ₁₄₀ can be appropriately adjusted within a range set by any combination of the above-mentioned lower limit value and upper limit value. For example, in one embodiment, H ₁₄₀ may be, for example, any of 0.7 to 7 N/25.4 mm, 1 to 7 N/25.4 mm, 2 to 7 N/25.4 mm, 2.5 to 7 N/25.4 mm, and 3.5 to 7 N/25.4 mm. However, these are only examples of H ₁₄₀ .

In the transparent multilayer film of the present embodiment, when a test piece of the easy peel layer having a width of 25.4 mm and a thickness of 6 μm is heat-sealed with the test PET film at a sealing temperature of 140° C. for 2 seconds, the seal strength S ₁₄₀ 24 hours after the heat sealing may be, for example, 1 N/ _25.4 mm or more, but is preferably 3 N/25.4 mm or more, and may be, for example, any one of 4 N/25.4 mm or more, 5 N/25.4 mm or more, 6 N/25.4 mm or more, and 7 N/25.4 mm or more. When S ₁₄₀ is 3 N/25.4 mm or more, peeling of the lid material from the base material is more highly suppressed when a deep-draw package is produced by heat-sealing a long lid material (the transparent multilayer film) and a long base material containing polyethylene terephthalate.

When the transparent multilayer film is used as a long lid material and a long base material (connected body of base material) is used to manufacture a deep-draw package, as described above, by the time all heat sealing is completed (in other words, cutting of the long lid material and base material is started), unlike the case of using a conventional lid material, peeling of the lid material from the base material is highly suppressed by having H ₁₄₀ of 1 N/25.4 mm or more. And, by having S ₁₄₀ of 3 N/25.4 mm or more, peeling of the lid material from the base material is more highly suppressed in this manner during the manufacturing process of the package, and further, even after a certain amount of time has passed since the manufacturing of the package and the structure of the package has stabilized, peeling of the lid material from the base material is highly suppressed while maintaining the easy-peel property of the package.

The upper limit of _S140 is not particularly limited.
For example, transparent multilayer films with S ₁₄₀ of 11 N/25.4 mm or less are easier to manufacture.

S ₁₄₀ can be appropriately adjusted within a range that is set by any combination of the above-mentioned lower limit value and upper limit value. For example, in one embodiment, S ₁₄₀ may be any of 1 to 11 N/25.4 mm, 3 to 11 N/25.4 mm, 4 to 11 N/25.4 mm, 5 to 11 N/25.4 mm, 6 to 11 N/25.4 mm, and 7 to 11 N/25.4 mm. However, these are just examples of S ₁₄₀ .

The test piece for measuring H ₁₄₀ and S ₁₄₀ was adjusted to a width of 25.4 mm and a thickness of 6 μm using the easy peel layer itself in the transparent multilayer film, or a test easy peel layer having the same composition as the easy peel layer in the transparent multilayer film and prepared separately.

H ₁₄₀ is the peel strength (N/25.4 mm) measured 0.22 seconds after a test piece of the easy peel layer and a test PET film are heat-sealed at a sealing temperature of 140° C., and can be measured by a known method.
At this time, the entire surface of one side of the test piece of the easy-peel layer is placed over one side of the test PET film, and in this state, they are heat-sealed.
H ₁₄₀ is the peel strength of the heat-sealed product between the test piece of the easy-peel layer and the test PET film, measured in a state where the sealed portion of the heat-sealed product is not yet solidified.

When measuring H ₁₄₀ , the seal pressure can be 0.473 Pa and the seal time can be 2 seconds when the test piece of the easy peel layer and the test PET film are heat sealed together.
The peel strength (H ₁₄₀ ) can be measured by peeling the test piece of the easy-peel layer from the test PET film after heat sealing. The pulling speed at this time can be 33.3 mm/s, and the angle (peel angle) between the test piece of the easy-peel layer and the test PET film during peeling can be 90°.

The test PET film has a thickness of 200 μm, and there is no particular limit to its size, so long as it is possible to heat seal the test piece with the easy-peel layer as described above and to peel off the test piece with the easy-peel layer.

S ₁₄₀ is the peel strength (N/25.4 mm) measured 24 hours after a test piece of the easy peel layer and a test PET film are heat-sealed at a sealing temperature of 140° C., and can be measured by a known method.
S ₁₄₀ can be measured in the same manner as S 140, except that the test piece of the easy peel layer and the test PET film are heat-sealed at a sealing temperature _{of 140° C., and the time from this heat-sealing to peeling the heat-sealed product is 24 hours instead of 0.22 seconds. S 140 is} preferably measured after leaving the heat-sealed product at room temperature for 24 hours.
S ₁₄₀ is the peel strength of the heat-sealed product measured in a state where the heat-sealed product between the test piece of the easy-peel layer and the test PET film is sufficiently solidified at the sealed portion.

In this specification, "room temperature" means a temperature that is neither particularly cold nor hot, i.e., a normal temperature, such as a temperature between 15 and 25°C.

The transparent multilayer film preferably satisfies both the above-mentioned conditions of H ₁₄₀ and S _140. For example, the transparent multilayer film preferably has H ₁₄₀ of 1 N/25.4 mm or more and S ₁₄₀ of 3 N/25.4 mm or more.

In the transparent multilayer film, H ₁₄₀ and S ₁₄₀ can be adjusted by adjusting the type and content of the components contained in the easy peel layer. For example, when the easy peel layer contains an anti-fogging agent described later, H 140 and _{S 140 can} be more easily adjusted by adjusting the type of anti-fogging agent or the content of the anti-fogging agent in the easy peel layer. The components contained in the easy peel layer, such as the anti-fogging agent, will be described in detail later.

The transparent multilayer film of this embodiment only needs to have at least the easy peel layer, and typically has the easy peel layer and one or more other layers, but the layers other than the easy peel layer are optional layers. The transparent multilayer film of this embodiment may or may not have these optional layers. The optional layers of the transparent multilayer film can be appropriately selected depending on the purpose.

For example, the transparent multilayer film may further include a flexible layer in addition to the easy-peel layer, which serves to cushion an impact applied to the transparent multilayer film and to stabilize the seal strength of a heat-sealed product (e.g., a package) obtained by heat-sealing the transparent multilayer film with another film or sheet.
The flexible layer can be made to function as a water vapor barrier layer for suppressing water vapor transmission through the transparent multilayer film by adjusting the type of constituent material of the flexible layer. The constituent material of the flexible layer will be described in detail later.

In the transparent multilayer film, it is preferable that the flexible layer is disposed adjacent to the easy-peel layer. In such a transparent multilayer film, the effect obtained by providing the flexible layer is enhanced.

For example, the transparent multilayer film may further include an oxygen barrier layer for suppressing oxygen transmission through the transparent multilayer film in addition to the easy peel layer. A transparent multilayer film including the oxygen barrier layer has excellent oxygen barrier properties. The constituent materials of the oxygen barrier layer will be described in detail later.

For example, the transparent multilayer film may further include an intermediate layer in addition to the easy peel layer. Examples of the intermediate layer include a layer that imparts moldability to the transparent multilayer film or that suppresses the occurrence of pinholes in the transparent multilayer film. In the transparent multilayer film, the intermediate layer is disposed so as not to be the outermost layer. The constituent material of the intermediate layer will be described in detail later.

For example, when the transparent multilayer film includes a flexible layer, an intermediate layer, and an oxygen barrier layer, the flexible layer and the intermediate layer may be disposed between the easy-peel layer and the oxygen barrier layer. In such a transparent multilayer film, the effects obtained by including each layer are well-balanced and enhanced.

For example, the transparent multilayer film may further include an outer layer in addition to the easy-peel layer, such as a layer for protecting other layers constituting the transparent multilayer film, or a layer for imparting new properties to the transparent multilayer film.
In the transparent multilayer film, the outer layer is preferably disposed as the outermost layer on the side opposite to the easy-peel layer.
When the transparent multilayer film comprises an oxygen barrier layer and an intermediate layer, it may also comprise an outer layer on the side of the oxygen barrier layer opposite to the intermediate layer side.
The materials from which the outer layer is made will be described in more detail below.

For example, the transparent multilayer film may further include an adhesive layer for adhering the two layers constituting the transparent multilayer film in addition to the easy peel layer. A transparent multilayer film having an adhesive layer has a more stable multilayer structure. The adhesive layer is arranged so as not to be the outermost layer in the transparent multilayer film. The constituent materials of the adhesive layer will be described in detail later.

The transparent multilayer film of this embodiment preferably comprises the easy peel layer, and further comprises one or more layers selected from the group consisting of the flexible layer, oxygen barrier layer, intermediate layer, outer layer, and adhesive layer, and may comprise all of the easy peel layer, flexible layer, oxygen barrier layer, intermediate layer, outer layer, and adhesive layer.

FIG. 1 is a cross-sectional view that illustrates an example of the transparent multilayer film of the present embodiment.
In addition, the figures used in the following explanation may show enlarged key parts for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as the actual ones.

The transparent multilayer film 1 shown here is constructed by laminating an easy-peel layer 11, a flexible layer 12, an intermediate layer 13, and an oxygen barrier layer 14.
In the transparent multilayer film 1, the easy-peel layer 11 is the outermost layer on one side, and the oxygen barrier layer 14 is the outermost layer on the other side.
The flexible layer 12 is disposed adjacent to the easy peel layer 11 .
The flexible layer 12 and intermediate layer 13 are disposed between the easy peel layer 11 and the oxygen barrier layer 14 .
Furthermore, the transparent multilayer film 1 includes an adhesive layer 19 between the flexible layer 12 and the intermediate layer 13 .
That is, the transparent multilayer film 1 is constructed by laminating an easy-peel layer 11, a flexible layer 12, an adhesive layer 19, an intermediate layer 13 and an oxygen barrier layer 14 in this order in the thickness direction.
The exposed surface of the easy-peel layer 11, i.e., the surface 11b opposite to the flexible layer 12, is one of the outermost surfaces 1b of the transparent multilayer film 1 and is the sealing surface when the transparent multilayer film 1 is heat-sealed.
The exposed surface of the oxygen barrier layer 14 , i.e., the surface 14 a opposite to the easy-peel layer 11 side, is the other outermost surface 1 a of the transparent multilayer film 1 .

In the transparent multilayer film 1, the easy peel layer 11 contains a hot melt adhesive and the incompatible component.
The haze of the transparent multilayer film 1, measured from the outside of the easy peel layer 11 side of the transparent multilayer film 1 in accordance with JIS K 7136:2000, is 20% or less.

FIG. 2 is a cross-sectional view that illustrates a schematic diagram of another example of the transparent multilayer film of the present embodiment.
In FIG. 2 and subsequent figures, the same components as those shown in the figures already described are given the same reference numerals as in the figures already described, and detailed description thereof will be omitted.

The transparent multilayer film 2 shown here further includes an outer layer 15 on the side of the oxygen barrier layer 14 opposite the intermediate layer 13 side, but is otherwise the same as the transparent multilayer film 1 shown in FIG.
That is, the transparent multilayer film 2 is constructed by laminating an easy-peel layer 11, a flexible layer 12, an adhesive layer 19, an intermediate layer 13, an oxygen barrier layer 14 and an outer layer 15 in this order in the thickness direction.
The exposed surface of the easy peel layer 11, i.e., the surface 11b opposite to the flexible layer 12, is one of the outermost surfaces 2b of the transparent multilayer film 2 and is the sealing surface when the transparent multilayer film 1 is heat sealed.
The exposed surface of the outer layer 15 , i.e., the surface 15 a opposite to the easy-peel layer 11 side, is the other outermost surface 2 a of the transparent multilayer film 2 .

Next, we will explain in more detail each layer that makes up the transparent multilayer film of this embodiment.

<Easy peel layer>
An easy peel layer (for example, easy peel layer 11 in transparent multilayer film 1 shown in Figure 1 and transparent multilayer film 2 shown in Figure 2) is one of the outermost layers in the transparent multilayer film, and is arranged on one of the outermost sides in the stacking direction of the layers that constitute the transparent multilayer film.
A package can be constructed by sealing the transparent multilayer film to another film or sheet via the easy-peel layer therein. The exposed surface of the easy-peel layer (the surface opposite to the flexible layer) is the seal surface for heat sealing to another film or sheet.
The easy peel layer is preferably transparent.
The easy peel layer is preferably a non-oriented layer.

The easy peel layer contains a hot melt adhesive and the incompatible component.
The hot melt adhesive is solid at room temperature, melts when heated, and solidifies when cooled between adherends to form a bond.
The hot melt adhesive may be any known adhesive.
The hot melt adhesive preferably does not contain a solvent component.

More specifically, examples of hot melt adhesives include terpene resins.
Examples of the terpene resin include hydrocarbon resins having structural units derived from isoprene (2-methyl-1,3-butadiene).
Preferred examples of terpene resins include tackifier resins (also known as tackifiers).

The easy peel layer may contain only one type of hot melt adhesive, or two or more types. If there are two or more types, the combination and ratio of the adhesives can be selected as desired depending on the purpose.

The incompatible component is incompatible with the hot melt adhesive and is a component that does not mix uniformly with (separates from) the hot melt adhesive at room temperature and pressure. The easy peel layer has good easy peel properties because it contains the hot melt adhesive and the incompatible component. Furthermore, it makes it possible to reduce the haze of the transparent multilayer film to 20% or less, and to produce a package by heat sealing a lid material made of the transparent multilayer film and a base material containing polyethylene terephthalate, and when the package is opened by peeling off the lid material, it is possible to suppress the occurrence of stringiness and to achieve a good peeling feel of the lid material.

The incompatible component may be a known component.
The incompatible component is preferably a (meth)acrylic acid ester-styrene copolymer.

In this specification, the term "(meth)acrylic acid" is intended to encompass both "acrylic acid" and "methacrylic acid." The same applies to terms similar to (meth)acrylic acid.

The (meth)acrylic ester which is a monomer of the (meth)acrylic ester-styrene copolymer is preferably an alkyl (meth)acrylic ester.
The alkyl group bonded to the ester bond (-C(=O)-O) in the alkyl (meth)acrylate is preferably an alkyl group having 1 to 3 carbon atoms.
Such preferred (meth)acrylic acid alkyl esters include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, and isopropyl methacrylate.

The (meth)acrylic acid ester may be either an acrylic acid ester or a methacrylic acid ester, but is preferably a methacrylic acid ester, and more preferably a methacrylic acid alkyl ester.
That is, the (meth)acrylic acid ester-styrene copolymer is preferably a methacrylic acid ester-styrene copolymer, and more preferably a methacrylic acid alkyl ester-styrene copolymer.

The ratio of the amount of structural units derived from the (meth)acrylic acid ester to the total amount of structural units in the (meth)acrylic acid ester-styrene copolymer (sometimes referred to herein as the "copolymerization ratio of the (meth)acrylic acid ester") is preferably 10 to 90 mol%, and may be, for example, any of 10 to 70 mol%, 10 to 45 mol%, and 10 to 25 mol%, any of 20 to 90 mol%, 30 to 90 mol%, and 50 to 90 mol%, or any of 20 to 70 mol% and 30 to 45 mol%. However, these are just examples of the ratio (copolymerization ratio of the (meth)acrylic acid ester).

The ratio of the amount of structural units derived from styrene to the total amount of structural units in the (meth)acrylic acid ester-styrene copolymer (sometimes referred to as the "copolymerization ratio of styrene" in this specification) is preferably 10 to 90 mol%, and may be, for example, any of 10 to 75 mol%, 10 to 55 mol%, and 10 to 35 mol%, or any of 25 to 90 mol%, 40 to 90 mol%, and 55 to 90 mol%, or any of 25 to 75 mol% and 40 to 55 mol%. However, these are just examples of the ratios (copolymerization ratios of styrene).

It is preferable that the (meth)acrylic acid ester-styrene copolymer has both the above-mentioned copolymerization ratio of the (meth)acrylic acid ester and the above-mentioned copolymerization ratio of the styrene. For example, it is preferable that the ratio of the amount of the structural units derived from the (meth)acrylic acid ester to the total amount of the structural units in the (meth)acrylic acid ester-styrene copolymer is 10 to 90 mol %, and the ratio of the amount of the structural units derived from the styrene to the total amount of the structural units in the (meth)acrylic acid ester-styrene copolymer is 90 to 10 mol %.

In the easy peel layer, the ratio of the content of the incompatible component to the content of the hot melt adhesive ([content of the incompatible component in the easy peel layer (parts by mass)]/[content of the hot melt adhesive in the easy peel layer (parts by mass)]×100) may be 2% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, and may be, for example, any one of 10% by mass or more and 15% by mass or more. The higher the ratio, the more remarkable the effect of using the incompatible component. For example, when a package is produced by heat-sealing a lid material composed of a transparent multilayer film and a base material containing polyethylene terephthalate, and the package is opened by peeling off the lid material, the higher the ratio, the more the occurrence of stringiness can be suppressed and the better the peeling feel of the lid material becomes.
The above ratio is usually the same as the ratio of the content (parts by mass) of the incompatible component to the content (parts by mass) of the hot melt adhesive in the composition for forming an easy peel layer described below ([content (parts by mass) of the incompatible component in the composition for forming an easy peel layer] / [content (parts by mass) of the hot melt adhesive in the composition for forming an easy peel layer] × 100).

In the easy peel layer, the ratio of the content of the incompatible component to the content of the hot melt adhesive may be either 45% by mass or less or 35% by mass or less, preferably 30% by mass or less, more preferably 27% by mass or less, and may be, for example, either 20% by mass or less or 15% by mass or less. The lower the ratio, the higher the transparency of the lid material made of the transparent multilayer film in the package tends to be.

In the easy peel layer, the ratio of the content of the incompatible component to the content of the hot melt adhesive can be appropriately adjusted within a range set by any combination of any of the lower limit values described above and any of the upper limit values described above. For example, in one embodiment, the ratio may be any of 2 to 45% by mass and 2 to 35% by mass, and is preferably 3 to 30% by mass, and may be any of 5 to 30% by mass, 10 to 30% by mass, and 15 to 30% by mass, or any of 3 to 27% by mass, 5 to 27% by mass, 10 to 27% by mass, and 15 to 27% by mass, or any of 3 to 20% by mass, 5 to 20% by mass, 10 to 20% by mass, and 15 to 20% by mass, or any of 3 to 15% by mass, 5 to 15% by mass, and 10 to 15% by mass. However, these are just examples of the ratios.

The easy-peel layer preferably contains a hot melt adhesive and the incompatible component, and further contains an anti-fogging agent that does not fall into any of the above categories. When the easy-peel layer contains an anti-fogging agent, the anti-fogging property of the lid material is enhanced when the package obtained using the transparent multilayer film is stored in a refrigerator.
The anti-fogging agent contained in the easy-peel layer is a component for suppressing fogging of the transparent multi-layer film, particularly fogging on the exposed surface of the easy-peel layer.

The anti-fogging agent contained in the easy peel layer may be a known agent. Examples of anti-fogging agents include polyglycerin fatty acid esters and diglycerin fatty acid esters.

The easy peel layer may contain only one type of anti-fogging agent, or two or more types. If there are two or more types, the combination and ratio of the anti-fogging agents can be selected as desired depending on the purpose.

When an anti-fogging agent is used, the ratio of the content of the anti-fogging agent in the easy peel layer to the total mass of the easy peel layer ([content of anti-fogging agent in easy peel layer (parts by mass)]/[total mass of easy peel layer (parts by mass)]×100) is preferably 0.2 mass% or more, more preferably 0.4 mass% or more, and may be, for example, any one of 1.5 mass% or more and 4 mass% or more. When the ratio is equal to or more than the lower limit, the effect of using the anti-fogging agent can be more significantly obtained.
The above ratio is usually the same as the ratio of the content (parts by mass) of the anti-fogging agent to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an easy peel layer described below ([content (parts by mass) of the anti-fogging agent in the composition for forming an easy peel layer] / [total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an easy peel layer] × 100).

When an anti-fog agent is used, the ratio of the content of the anti-fog agent in the easy peel layer to the total mass of the easy peel layer is preferably 11% by mass or less, more preferably 9% by mass or less, and may be, for example, 6% by mass or less. When the ratio is equal to or less than the upper limit, excessive use of the anti-fog agent is suppressed. For example, when the content of the anti-fog agent in the easy peel layer is high, the amount of the anti-fog agent that migrates to the surface (exposed surface) of the easy peel layer increases, and as a result, H ₁₄₀ and S ₁₄₀ tend to decrease, but when the ratio is equal to or less than the upper limit, the decrease in H ₁₄₀ and S ₁₄₀ can be suppressed. That is, by reducing the content of the anti-fog agent in the easy peel layer, H ₁₄₀ and S ₁₄₀ can be increased, and by increasing the content of the anti-fog agent in the easy peel layer, H ₁₄₀ and S ₁₄₀ can be decreased.

When an anti-fogging agent is used, the ratio of the content of the anti-fogging agent in the easy peel layer to the total mass of the easy peel layer can be appropriately adjusted within a range set by any combination of any of the above-mentioned lower limit values and any of the above-mentioned upper limit values. For example, in one embodiment, the ratio may be any of 0.2 to 11 mass%, 0.4 to 11 mass%, 1.5 to 11 mass%, and 4 to 11 mass%, or any of 0.2 to 9 mass%, 0.4 to 9 mass%, 1.5 to 9 mass%, and 4 to 9 mass%, or any of 0.2 to 6 mass%, 0.4 to 6 mass%, 1.5 to 6 mass%, and 4 to 6 mass%. However, these are just examples of the ratios.

The easy peel layer may contain other components that do not fall under any of the hot melt adhesive, the incompatible component, and the anti-fogging agent, as long as the effects of the present invention are not impaired.
Examples of the other components contained in the easy peel layer include an antiblocking agent, an antistatic agent, and the like.

In the easy peel layer, the ratio of the content of the other components to the total mass of the easy peel layer ([content of other components in easy peel layer (parts by mass)]/[total mass of easy peel layer (parts by mass)]×100) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, particularly preferably 1% by mass or less, and may even be 0% by mass. When the ratio is less than the upper limit, the effect obtained by the easy peel layer containing the hot melt adhesive and the incompatible component, or the hot melt adhesive, the incompatible component, and the antifogging agent is further enhanced.

In other words, in the easy peel layer, the ratio of the total content of the hot melt adhesive, the incompatible component, and the antifogging agent to the total mass of the easy peel layer (([content of hot melt adhesive in easy peel layer (parts by mass)] + [content of incompatible component in easy peel layer (parts by mass)] + [content of antifogging agent in easy peel layer (parts by mass)]) / [total mass of easy peel layer (parts by mass)] × 100) is preferably 90 mass% or more, more preferably 95 mass% or more, even more preferably 97 mass% or more, and particularly preferably 99 mass% or more. When the ratio is equal to or more than the lower limit, peeling of the lid material from the base material is more highly suppressed when a deep draw package is produced by heat sealing a long lid material (the transparent multilayer film) and a long base material containing polyethylene terephthalate.
On the other hand, the proportion is 100% by mass or less.
The above ratio is usually the same as the ratio of the total content (parts by mass) of the hot melt adhesive, the incompatible component, and the antifogging agent to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an easy peel layer described later (([content (parts by mass) of hot melt adhesive in composition for forming an easy peel layer] + [content (parts by mass) of incompatible components in composition for forming an easy peel layer] + [content (parts by mass) of antifogging agent in composition for forming an easy peel layer]) / [total content (parts by mass) of components that do not vaporize at room temperature in composition for forming an easy peel layer] × 100).

The surface resistivity of the easy peel layer measured in accordance with JIS C 2139-3-1:2018 (for example, in the transparent multilayer film 1 shown in FIG. 1 and the transparent multilayer film 2 shown in FIG. 2, the surface resistivity of the surface 11b of the easy peel layer 11 opposite the flexible layer 12) may be 7×10 ⁴ to 1.3×10 ¹⁴ Ω/□, but is preferably 1×10 ⁵ to 1×10 ¹⁴ Ω/□, and may be, for example, any of 1×10 ⁷ to 1×10 ¹⁴ Ω/□ and 1×10 ⁹ to 1×10 ¹⁴ Ω/□, or any of 1×10 ⁵ to 1×10 ¹³ Ω/□, 1×10 ⁵ to 1×10 ¹¹ Ω/□, and 1×10 ⁵ to 1×10 ¹⁰ Ω/□. The higher the surface resistivity of the easy-peel layer, the more likely it is that the lid material will be prevented from peeling off from the base material when a deep-draw package is produced by heat-sealing a long lid material made of the transparent multilayer film and a long base material containing polyethylene terephthalate.On the other hand, the lower the surface resistivity of the easy-peel layer, the more likely it is that the lid material will have high anti-fogging properties when a package obtained using the transparent multilayer film is stored in a refrigerator.

As explained above, when a deep-draw package is manufactured using the long transparent multilayer film as a lid material and a long base material, the heat-sealed long lid material is usually in a state where it is easily peeled off from the base material, and the area of the area where the seal is maintained between the lid material and the base material is reduced, or in the worst case, a gap is generated between the lid material and the base material. In particular, the lid material is easily peeled off from the base material in the area of the periphery of the long base material that will eventually become the corner. In contrast, the high surface resistivity of the easy-peel layer tends to suppress such peeling of the lid material from the base material during the manufacturing process of the package.
Thus, the transparent multilayer film of this embodiment, in which the surface resistivity of the easy-peel layer is high, provides particularly remarkable effects when used in the production of deep-draw packaging products.

The surface resistivity of the easy peel layer can be adjusted, for example, by adjusting the type and content of the components contained in the easy peel layer. For example, generally, reducing the content of the anti-fog agent in the easy peel layer can increase the surface resistivity of the easy peel layer, and increasing the content of the anti-fog agent in the easy peel layer can decrease the surface resistivity of the easy peel layer. This is because the anti-fog agent is generally a component that reduces the surface resistivity of the film. When the content of the anti-fog agent in the easy peel layer is high, the amount of the anti-fog agent that migrates to the surface (exposed surface) of the easy peel layer increases, and the surface resistivity of the easy peel layer decreases, whereas when the content of the anti-fog agent in the easy peel layer is low, the amount of the anti-fog agent that migrates to the surface (exposed surface) of the easy peel layer decreases, and the surface resistivity of the easy peel layer increases.

The easy peel layer may consist of one layer (single layer) or may consist of two or more layers. When the easy peel layer consists of multiple layers, these multiple layers may be the same or different, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

In this specification, not only in the case of easy-peel layers, "multiple layers may be the same or different from each other" means "all layers may be the same, all layers may be different, or only some layers may be the same", and further, "multiple layers are different from each other" means "at least one of the constituent materials and thickness of each layer is different from each other".

The ratio of the thickness of the easy peel layer to the thickness of the transparent multilayer film ([thickness of easy peel layer]/[thickness of transparent multilayer film]×100) is preferably 5 to 35%, and may be, for example, any of 10 to 35% and 15 to 35%, any of 5 to 30% and 5 to 25%, or any of 10 to 30% and 15 to 25%. When the ratio is equal to or more than the lower limit, the seal strength of the easy peel layer becomes higher within an appropriate range. When the ratio is equal to or less than the upper limit, excessive thickness of the easy peel layer can be avoided.
The easy peel layer may have a thickness of, for example, 2 to 11 μm.
Here, "the thickness of the easy peel layer" means the thickness of the entire easy peel layer. For example, the thickness of an easy peel layer consisting of multiple layers means the total thickness of all layers that make up the easy peel layer.

In this specification, as described below, the thickness ratios of not only the easy peel layer, but also the flexible layer, intermediate layer, oxygen barrier layer, outer layer and adhesive layer to the thickness of the transparent multilayer film are given, but the total thickness ratios of all these layers in the transparent multilayer film shall not exceed 100%.

In this specification, the "thickness of the transparent multilayer film" means the "total thickness of the transparent multilayer film", and for example, in the case of the transparent multilayer film 2 shown in Figure 2, it is the total thickness of the easy peel layer 11, the flexible layer 12, the intermediate layer 13, the oxygen barrier layer 14, the outer layer 15, and the adhesive layer 19.

<Flexible layer>
It is preferable that the flexible layer (for example, flexible layer 12 in transparent multilayer film 1 shown in FIG. 1 and transparent multilayer film 2 shown in FIG. 2) is arranged adjacent to the easy peel layer and laminated in contact with the easy peel layer.
The flexible layer is transparent.
The flexible layer is preferably a non-oriented layer.

The flexible layer is preferably a resin layer containing a resin.
The resin contained in the flexible layer is preferably a water vapor barrier resin having water vapor barrier properties.

Examples of the resin contained in the flexible layer include polyethylene (PE) such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene-catalyzed linear low density polyethylene (mLLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE); ethylene-α-olefin copolymer; polypropylene (also known as propylene homopolymer, homopolypropylene, sometimes referred to as "hPP" in this specification); propylene-ethylene random copolymer (also known as polypropylene random copolymer, sometimes referred to as "rPP" in this specification); propylene-ethylene block copolymer (also known as polypropylene block copolymer, sometimes referred to as "rPP" in this specification); Examples of such copolymers include ethylene-cyclic olefin copolymers obtained by copolymerizing a cyclic olefin such as cyclopentadiene or norbornene; ethylene-vinyl acetate copolymer (EVA); partially or completely saponified ethylene-vinyl acetate copolymers; ethylene-(meth)acrylic acid copolymers; esterified ethylene-(meth)acrylic acid copolymers; ionically crosslinked ethylene-(meth)acrylic acid copolymers; ethylene-(meth)acrylic acid-(meth)acrylic acid ester terpolymers; maleic anhydride graft-modified polyethylene (maleic anhydride graft-modified polyethylene); and maleic anhydride-polyethylene copolymers.
All of the resins listed here are also suitable as water vapor barrier resins.

In this specification,
Copolymers of ethylene and monomers other than propylene, such as ethylene-α-olefin copolymers, ethylene-vinyl acetate copolymers, partially or completely saponified products of ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers, esterified products of ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid-(meth)acrylic acid ester terpolymers, and maleic anhydride-polyethylene copolymers;
Graft polymers of ethylene and monomers other than propylene, such as maleic anhydride grafted polyethylene;
These are sometimes collectively referred to as "modified polyethylene."

The above-mentioned ionically crosslinked ethylene-(meth)acrylic acid copolymer means a resin in which an ethylene-(meth)acrylic acid copolymer has an ionically crosslinked structure due to salt formation between an acid portion in the ethylene-(meth)acrylic acid copolymer and a metal ion, and may be referred to as an "ionomer" in this specification.
Examples of the metal ion include sodium ions, zinc ions, etc. In this specification, an ionomer in which the metal ion is a sodium ion may be referred to as a "sodium-based ionomer," and an ionomer in which the metal ion is a zinc ion may be referred to as a "zinc-based ionomer."

The flexible layer may contain only one type of resin, or two or more types. If there are two or more types, the combination and ratio of the resins can be selected as desired depending on the purpose.

The flexible layer preferably contains one or more resins selected from the group consisting of polyethylene, modified polyethylene, and ionomers, and more preferably contains one or more resins selected from the group consisting of low-density polyethylene, ethylene-vinyl acetate copolymer, and ionomers. When the flexible layer contains such a resin, the flexibility of the flexible layer and the transparent multilayer film becomes higher.

The flexible layer may contain biomass-derived polyethylene as the resin, and in that case, it is preferable that the flexible layer contains biomass-derived low-density polyethylene. By using biomass-derived polyethylene in a transparent multilayer film, the amount of petroleum resources used can be reduced, and the amount of carbon dioxide emitted during the production and disposal of the transparent multilayer film can be reduced. In other words, such a transparent multilayer film has a remarkable effect in terms of reducing the environmental load. A transparent multilayer film in which the flexible layer contains biomass-derived polyethylene as the polyethylene is one preferred example.

The biomass-derived polyethylene may be, for example, polyethylene derived from plants such as carbon-neutral sugar cane.
Examples of the biomass-derived polyethylene include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene-catalyzed linear low-density polyethylene (metallocene LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

When the flexible layer contains the biomass-derived polyethylene, the polyethylene may be only biomass-derived polyethylene, or it may contain both biomass-derived polyethylene and non-biomass-derived polyethylene.

The flexible layer may contain other components in addition to the above resins, as long as the properties of the flexible layer are not impaired.
The other components contained in the flexible layer are non-resin components, and examples thereof include a crystallization nucleating agent.

The crystallization nucleating agent is a component for improving the transparency of the flexible layer by controlling crystal growth in the flexible layer.
The crystallization nucleating agent may be a known one, and examples of the crystallization nucleating agent include sorbitol-based crystallization nucleating agents.

The flexible layer may contain only one type of other component, or two or more types. If there are two or more types, the combination and ratio of these components can be selected as desired depending on the purpose.

In the flexible layer, the ratio of the content of the other components to the total mass of the flexible layer ([content of other components in the flexible layer (parts by mass)]/[total mass of the flexible layer (parts by mass)] x 100) is preferably 20% by mass or less, more preferably 10% by mass or less, and may be, for example, 5% by mass or less, 3% by mass or less, or 1% by mass or less, or may be 0% by mass. When the ratio is less than the upper limit, the effect obtained by the flexible layer containing the resin is enhanced.

In other words, in the flexible layer, the ratio of the content of the resin to the total mass of the flexible layer ([content of resin in flexible layer (parts by mass)]/[total mass of flexible layer (parts by mass)]×100) is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the flexibility of the flexible layer and the transparent multilayer film is increased. As a result, the seal strength is more stable in a deep-draw package obtained by heat-sealing a long lid material (the transparent multilayer film) and a long base material containing polyethylene terephthalate. And, when the resin is a water vapor barrier resin, when the ratio is equal to or more than the lower limit, the water vapor barrier property of the flexible layer and the transparent multilayer film is increased.
On the other hand, the proportion is 100% by mass or less.
The above ratio is usually the same as the ratio of the resin content (parts by mass) to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a flexible layer described below ([resin content (parts by mass) of the composition for forming a flexible layer] / [total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming a flexible layer] x 100).

When the flexible layer contains polyethylene, the ratio of the content of biomass-derived polyethylene to the total content of polyethylene in the flexible layer (the total content of non-biomass-derived polyethylene and biomass-derived polyethylene) ([content of biomass-derived polyethylene in the flexible layer (parts by mass)]/([content of biomass-derived polyethylene in the flexible layer (parts by mass)]+[content of non-biomass-derived polyethylene in the flexible layer (parts by mass)])×100) may be, for example, 10% by mass or more, 30% by mass or more, 50% by mass or more, 70% by mass or more, or 90% by mass or more, or it may be 100% by mass, i.e., all of the polyethylene contained in the flexible layer is biomass-derived polyethylene. The higher the ratio, the greater the effect of reducing the environmental load of the transparent multilayer film.

The flexible layer may be made up of one layer (single layer) or two or more layers. When the flexible layer is made up of multiple layers, these multiple layers may be the same or different, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

The ratio of the thickness of the flexible layer to the thickness of the transparent multilayer film ([thickness of flexible layer]/[thickness of transparent multilayer film] x 100) is preferably 15 to 45%, and may be, for example, any one of 20 to 45% and 25 to 45%, any one of 15 to 40% and 15 to 35%, or any one of 20 to 40% and 25 to 35%. When the ratio is equal to or greater than the lower limit, the flexibility of the flexible layer and the transparent multilayer film is increased. When the ratio is equal to or less than the upper limit, excessive thickness of the flexible layer is avoided.
The thickness of the compliant layer may be, for example, 5 to 14 μm.
Here, "thickness of the flexible layer" means the thickness of the entire flexible layer; for example, the thickness of a flexible layer consisting of multiple layers means the total thickness of all layers that make up the flexible layer.

<Middle class>
An intermediate layer (for example, intermediate layer 13 in transparent multilayer film 1 shown in FIG. 1 and transparent multilayer film 2 shown in FIG. 2) is disposed so as not to be the outermost layer in the transparent multilayer film.
The intermediate layer is transparent.
The intermediate layer is preferably a non-oriented layer.

The intermediate layer preferably contains a nitrogen-containing resin as a constituent material thereof.
The nitrogen-containing resin is a resin having a nitrogen atom as a constituent atom thereof, and is preferably a resin having a nitrogen atom in its main chain.
In particular, it is more preferable that the nitrogen-containing resin is a polyamide, i.e., that the intermediate layer contains a polyamide, in terms of the effect of imparting moldability to the transparent multilayer film and the effect of suppressing the occurrence of pinholes in the transparent multilayer film.

Examples of the polyamide include polyamides obtained by polymerizing or copolymerizing nylon salts obtained by reacting cyclic lactams (lactams having 3 or more ring members), amino acids, or diamines with dicarboxylic acids.

Examples of the cyclic lactam include ε-caprolactam, ω-enantholactam, ω-laurolactam, α-pyrrolidone, and α-piperidone.

Examples of the amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid.

Examples of the diamine that forms the nylon salt include aliphatic amines such as tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, and 2,4,4-trimethylhexamethylenediamine;
Alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, isophoronediamine, piperazine, bis(4-aminocyclohexyl)methane, and 2,2-bis-(4-aminocyclohexyl)propane;
Examples of the diamine include aromatic diamines such as metaxylylenediamine and paraxylylenediamine.

Examples of the dicarboxylic acid that forms the nylon salt include aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sepatic acid, undecanedioic acid, and dodecanedioic acid;
Alicyclic carboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid;
Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid.

More specifically, the polyamide may be, for example, 4-nylon, 6-nylon, 7-nylon, 11-nylon, 12-nylon, 46-nylon, 66-nylon, 69-nylon, 610-nylon, 611-nylon, 612-nylon, 6T-nylon, 6I nylon, copolymer of 6-nylon and 66-nylon (nylon 6/66), copolymer of 6-nylon and 610-nylon, copolymer of 6-nylon and 611-nylon, copolymer of 6-nylon and 12-nylon (nylon 6/12), copolymer of 6-nylon and 612 nylon. , copolymers of 6-nylon and 6T-nylon, copolymers of 6-nylon and 6I-nylon, copolymers of 6-nylon, 66-nylon and 610-nylon, copolymers of 6-nylon, 66-nylon and 12-nylon (nylon 6/66/12), copolymers of 6-nylon, 66-nylon and 612-nylon, copolymers of 66-nylon and 6T-nylon, copolymers of 66-nylon and 6I-nylon, copolymers of 6T-nylon and 6I-nylon, copolymers of 66-nylon, ... and copolymers of 66-nylon, 6T-nylon and 6I-nylon.

In terms of heat resistance, mechanical strength, and availability, the polyamide is preferably 6-nylon, 12-nylon, 66-nylon, nylon 6/66, nylon 6/12, or nylon 6/66/12.

The polyamide contained in the intermediate layer may be a biomass-derived polyamide. By using a biomass-derived polyamide in a transparent multilayer film, the amount of petroleum resources used can be reduced, and the amount of carbon dioxide emitted during the production and disposal of the transparent multilayer film can be reduced. In other words, such a transparent multilayer film has a significant effect in terms of reducing the environmental load. A transparent multilayer film in which the intermediate layer contains a biomass-derived polyamide as the polyamide is one preferred example.

The biomass-derived polyamide may be, for example, a carbon-neutral polyamide derived from a plant such as sugar cane.
Examples of the biomass-derived polyamide include those using biomass-derived monomers as part or all of the raw material monomers in nylon 6, nylon 11, nylon 12, nylon 66, nylon 6/66, nylon 6/12, nylon 6/66/12, etc. More specifically, one example of such a biomass-derived polyamide is vegetable 11-nylon, which is a condensation polymer of 11-aminoundecanoic acid obtained from castor oil, a vegetable oil.

When the intermediate layer contains the biomass-derived polyamide, the polyamide may be only biomass-derived polyamide, or may contain both biomass-derived polyamide and non-biomass-derived polyamide.

When the intermediate layer contains polyamide, the ratio of the content of biomass-derived polyamide to the total content of polyamide in the intermediate layer (the total content of non-biomass-derived polyamide and biomass-derived polyamide) ([content of biomass-derived polyamide in intermediate layer (parts by mass)]/([content of biomass-derived polyamide in intermediate layer (parts by mass)]+[content of non-biomass-derived polyamide in intermediate layer (parts by mass)])×100) may be, for example, 10% by mass or more, 30% by mass or more, 50% by mass or more, 70% by mass or more, or 90% by mass or more, or may be 100% by mass, i.e., all of the polyamide contained in the intermediate layer is biomass-derived polyamide. The higher the ratio, the greater the effect of reducing the environmental load in the transparent multilayer film.

The intermediate layer may contain only one type of nitrogen-containing resin, or two or more types. When two or more types are contained, the combination and ratio of the resins can be selected as desired according to the purpose.

The intermediate layer may contain other components in addition to the nitrogen-containing resin as long as the effect of the intermediate layer is not impaired.
Examples of the other components contained in the intermediate layer include an antioxidant.

The intermediate layer may contain only one type of other component, or two or more types. When there are two or more types, the combination and ratio of the components can be selected as desired depending on the purpose.

In the intermediate layer, the ratio of the content of the other components to the total mass of the intermediate layer ([content of other components in intermediate layer (parts by mass)]/[total mass of intermediate layer (parts by mass)]×100) is preferably 20% by mass or less, more preferably 10% by mass or less, and may be, for example, 5% by mass or less, 3% by mass or less, or 1% by mass or less, or may be 0% by mass. When the ratio is equal to or less than the upper limit, the effect obtained by the intermediate layer containing the nitrogen-containing resin is enhanced.

In other words, in the intermediate layer, the ratio of the content of the nitrogen-containing resin to the total mass of the intermediate layer ([content of nitrogen-containing resin in intermediate layer (parts by mass)]/[total mass of intermediate layer (parts by mass)]×100) is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the moldability of the transparent multilayer film and the effect of suppressing the occurrence of pinholes are further improved.
On the other hand, the proportion is 100% by mass or less.
The above ratio is usually the same as the ratio of the content (parts by mass) of the nitrogen-containing resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an intermediate layer described below ([content (parts by mass) of the nitrogen-containing resin in the composition for forming an intermediate layer] / [total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an intermediate layer] x 100).

The intermediate layer may be one layer (single layer) or may be two or more layers. When the intermediate layer is made up of multiple layers, these multiple layers may be the same or different, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

The ratio of the thickness of the intermediate layer to the thickness of the transparent multilayer film ([thickness of intermediate layer]/[thickness of transparent multilayer film]×100) is preferably 7 to 23%, and may be, for example, any one of 10 to 23% and 13 to 23%, any one of 7 to 20% and 7 to 17%, or any one of 10 to 20% and 13 to 17%. When the ratio is equal to or more than the lower limit, the moldability of the transparent multilayer film and the effect of suppressing the occurrence of pinholes are improved. When the ratio is equal to or less than the upper limit, excessive thickness of the intermediate layer is avoided.
The thickness of the intermediate layer may be, for example, from 2 to 7 μm.
Here, "the thickness of the intermediate layer" means the thickness of the entire intermediate layer. For example, the thickness of an intermediate layer consisting of multiple layers means the total thickness of all layers that make up the intermediate layer.

<Oxygen Barrier Layer>
The oxygen barrier layer (for example, the oxygen barrier layer 14 in the transparent multilayer film 1 shown in FIG. 1 and the transparent multilayer film 2 shown in FIG. 2) may or may not be the outermost layer of the transparent multilayer film.
The oxygen barrier layer is transparent.
The oxygen barrier layer is preferably a non-oriented layer.

The oxygen barrier layer is preferably a resin layer containing an oxygen barrier resin having oxygen barrier properties.

Examples of the oxygen barrier resin include ethylene-vinyl alcohol copolymer (also known as saponified ethylene-vinyl acetate copolymer, EVOH), polyamide, polyvinyl alcohol, polyacrylonitrile, etc.

In the ethylene-vinyl alcohol copolymer, the ratio of the amount of structural units derived from ethylene to the total amount of structural units in the ethylene-vinyl alcohol copolymer (sometimes referred to herein as the "copolymerization ratio of ethylene") is preferably 30 to 50 mol%, and may be, for example, either 30 to 40 mol% or 40 to 50 mol%. When the copolymerization ratio of ethylene is in such a range, the oxygen barrier property and other properties of the transparent multilayer film are improved in a well-balanced manner.

The oxygen barrier layer preferably contains an ethylene-vinyl alcohol copolymer as the oxygen barrier resin.

The oxygen barrier layer may contain only one type of oxygen barrier resin, or two or more types. When there are two or more types, the combination and ratio of the resins can be selected as desired depending on the purpose.

The oxygen barrier layer may contain other components in addition to the oxygen barrier resin as long as the oxygen barrier properties are not impaired.
Examples of the other components contained in the oxygen barrier layer include an antioxidant.

The oxygen barrier layer may contain only one type of other component, or two or more types. If there are two or more types, the combination and ratio of these components can be selected as desired depending on the purpose.

In the oxygen barrier layer, the ratio of the content of the other components to the total mass of the oxygen barrier layer ([content of other components of the oxygen barrier layer (parts by mass)]/[total mass of the oxygen barrier layer (parts by mass)]×100) is preferably 20% by mass or less, more preferably 10% by mass or less, and may be, for example, 5% by mass or less, 3% by mass or less, or 1% by mass or less, or may be 0% by mass. When the ratio is equal to or less than the upper limit, the effect obtained by the oxygen barrier layer containing the oxygen barrier resin is enhanced.

In other words, in the oxygen barrier layer, the ratio of the content of the oxygen barrier resin to the total mass of the oxygen barrier layer ([content of oxygen barrier resin in oxygen barrier layer (parts by mass)]/[total mass of oxygen barrier layer (parts by mass)]×100) is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the oxygen barrier property of the oxygen barrier layer and the transparent multilayer film is further improved.
On the other hand, the proportion is 100% by mass or less.
The above ratio is usually the same as the ratio of the content (parts by mass) of the oxygen barrier resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an oxygen barrier layer, which will be described later ([content (parts by mass) of the oxygen barrier resin in the composition for forming an oxygen barrier layer]/[total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an oxygen barrier layer]×100).

The oxygen barrier layer may consist of one layer (single layer) or may consist of two or more layers. When the oxygen barrier layer consists of multiple layers, these multiple layers may be the same or different, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

The ratio of the thickness of the oxygen barrier layer to the thickness of the transparent multilayer film ([thickness of oxygen barrier layer]/[thickness of transparent multilayer film]×100) is preferably 5 to 35%, and may be, for example, any one of 10 to 35% and 15 to 35%, any one of 5 to 30% and 5 to 25%, or any one of 10 to 30% and 15 to 25%. When the ratio is equal to or more than the lower limit, the oxygen barrier properties of the oxygen barrier layer and the transparent multilayer film are further improved. When the ratio is equal to or less than the upper limit, an excessive thickness of the oxygen barrier layer is avoided.
The oxygen barrier layer may have a thickness of, for example, 2 to 11 μm.
Here, "the thickness of the oxygen barrier layer" means the thickness of the entire oxygen barrier layer. For example, the thickness of an oxygen barrier layer consisting of multiple layers means the total thickness of all layers that make up the oxygen barrier layer.

The oxygen gas permeability of the oxygen barrier layer is preferably 100 cc/m ² ·atm·day or less in an atmosphere of, for example, 20° C. and 60% RH (relative humidity).
The oxygen gas permeation amount of the oxygen barrier layer can be measured, for example, in accordance with JIS K 7126-2.

<Outer layer>
The outer layer (for example, outer layer 15 in the transparent multilayer film 2 shown in FIG. 2) is an optional layer, and the transparent multilayer film of the present embodiment may or may not have an outer layer. However, by having an outer layer, the transparent multilayer film has advantageous effects such as protecting other layers and imparting new properties derived from the outer layer.

In a transparent multilayer film having an outer layer, an oxygen barrier layer, and an intermediate layer, the outer layer is disposed on the side of the oxygen barrier layer opposite to the intermediate layer.
In a transparent multilayer film having an outer layer, the outer layer is preferably the outermost layer of the other side, and is preferably disposed on the outermost side of the other side opposite the easy-peel layer side in the stacking direction of the layers constituting the transparent multilayer film. That is, the surface of the outer layer opposite the easy-peel layer side (for example, surface 15a of outer layer 15 opposite easy-peel layer 11 side in the transparent multilayer film 2 shown in Fig. 2) is preferably an exposed surface in the transparent multilayer film.
The outer layer is transparent.
The outer layer is preferably a non-oriented layer.

The outer layer is preferably a resin layer containing resin.

Examples of the resin that constitutes the outer layer include propylene-based polymers, nitrogen-containing resins, polyesters, etc.

The propylene-based polymer refers to a polymer (resin) having at least structural units derived from propylene, not limited to the outer layer, and may be a homopolypropylene (propylene homopolymer, hPP) having only structural units derived from propylene, or a propylene-based copolymer having structural units derived from propylene and structural units derived from a monomer other than propylene.

Examples of the propylene-based copolymer contained in the outer layer include propylene-ethylene copolymers such as propylene-ethylene random copolymer (rPP) and propylene-ethylene block copolymer (bPP).

The nitrogen-containing resin contained in the outer layer may be the same as the nitrogen-containing resins listed above as the constituent material of the intermediate layer.
For example, the polyamide of the nitrogen-containing resin contained in the outer layer may be the same as the polyamide contained in the intermediate layer described above.

The polyamide contained in the outer layer may be a biomass-derived polyamide. A transparent multilayer film in which the outer layer contains a biomass-derived polyamide has the same effect as a transparent multilayer film in which the intermediate layer contains a biomass-derived polyamide in terms of reducing the environmental load. In other words, a transparent multilayer film in which the outer layer contains a biomass-derived polyamide as the polyamide is a preferred example.

The embodiment in which the outer layer contains a biomass-derived polyamide is the same as the embodiment in which the intermediate layer contains a biomass-derived polyamide described above.
For example, when the outer layer contains a biomass-derived polyamide, the outer layer may contain only a biomass-derived polyamide as the polyamide, or may contain both a biomass-derived polyamide and a non-biomass-derived polyamide.
For example, when the outer layer contains polyamide, the ratio of the content of biomass-derived polyamide to the total content of polyamide in the outer layer (the total content of non-biomass-derived polyamide and biomass-derived polyamide) ([content of biomass-derived polyamide in outer layer (parts by mass)]/([content of biomass-derived polyamide in outer layer (parts by mass)]+[content of non-biomass-derived polyamide in outer layer (parts by mass)])×100) may be any one of 10% by mass or more, 30% by mass or more, 50% by mass or more, 70% by mass or more, and 90% by mass or more, or may be 100% by mass, i.e., all of the polyamide contained in the outer layer may be biomass-derived polyamide.

Examples of the polyester that is the constituent material of the outer layer include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), etc.

The polyester contained in the outer layer may be a biomass-derived polyester. A transparent multilayer film whose outer layer contains a biomass-derived polyester has the same effect as a transparent multilayer film whose outer layer contains a biomass-derived polyamide in terms of reducing the environmental load. In other words, a transparent multilayer film whose outer layer contains a biomass-derived polyester as the polyester is a preferred example.

Examples of the biomass-derived polyester include carbon-neutral polyester derived from plants such as sugar cane.
Examples of the biomass-derived polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and the like, in which biomass-derived monomers are used as some or all of the raw material monomers.

When the outer layer contains the biomass-derived polyester, the polyester may be only biomass-derived polyester, or may contain both biomass-derived polyester and non-biomass-derived polyester.

When the outer layer contains polyester, the ratio of the content of the biomass-derived polyester to the total content of polyester in the outer layer (the total content of non-biomass-derived polyester and biomass-derived polyester) ([content of biomass-derived polyester in the outer layer (parts by mass)]/([content of biomass-derived polyester in the outer layer (parts by mass)]+[content of non-biomass-derived polyester in the outer layer (parts by mass)])×100) may be, for example, 10% by mass or more, 30% by mass or more, 50% by mass or more, 70% by mass or more, or 90% by mass or more, or it may be 100% by mass, i.e., all of the polyester contained in the outer layer is biomass-derived polyester. The higher the ratio, the greater the effect of reducing the environmental load of the transparent multilayer film.

A preferred example is a transparent multilayer film in which the outer layer contains a biomass-derived polyamide or a biomass-derived polyester as the polyamide or polyester.

The outer layer may contain only one type of resin, or two or more types. If there are two or more types, the combination and ratio of the resins can be selected as desired depending on the purpose.

The outer layer preferably contains, as the resin, a propylene-based polymer, a nitrogen-containing resin, or a polyester, and more preferably contains a propylene-based polymer, a polyamide, or a polyester.
That is, it is more preferable that the transparent multilayer film further comprises an outer layer containing a propylene-based polymer, polyamide or polyester on the side opposite to the intermediate layer side of the oxygen barrier layer.

The outer layer may contain other components in addition to the above resins, provided that the properties of the outer layer are not impaired.
The other components contained in the outer layer are non-resin components.
Examples of the other components contained in the outer layer include an antioxidant.

The outer layer may contain only one type of other component, or two or more types. If there are two or more types, the combination and ratio of these components can be selected as desired depending on the purpose.

In the outer layer, the ratio of the content of the other components to the total mass of the outer layer ([content of other components in outer layer (parts by mass)]/[total mass of outer layer (parts by mass)]×100) is preferably 20% by mass or less, more preferably 10% by mass or less, and may be, for example, 5% by mass or less, 3% by mass or less, or 1% by mass or less, or may be 0% by mass. When the ratio is equal to or less than the upper limit, the effect obtained by the outer layer containing the resin is enhanced.

In other words, in the outer layer, the ratio of the resin content to the total mass of the outer layer ([resin content of outer layer (parts by mass)]/[total mass of outer layers (parts by mass)]×100) is preferably 80% by mass or more, more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the effect obtained by the transparent multilayer film having an outer layer is enhanced.
On the other hand, the proportion is 100% by mass or less.
The ratio is usually the same as the ratio of the content (parts by mass) of the resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an outer layer described below ([content (parts by mass) of the resin in the composition for forming an outer layer] / [total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an outer layer] × 100).

The outer layer may be one layer (single layer) or may be two or more layers. When the outer layer is made up of multiple layers, these multiple layers may be the same or different, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

The outer layer is preferably a biaxially oriented layer. A biaxially oriented outer layer is preferable because it allows the printing layer to be stably formed when a printing layer, which will be described later, is provided on the surface opposite the easy peel layer.

The ratio of the thickness of the outer layer to the thickness of the transparent multilayer film ([thickness of outer layer]/[thickness of transparent multilayer film]×100) is preferably 10 to 50%, and more preferably 15 to 45%. When the ratio is equal to or greater than the lower limit, the effect obtained by the transparent multilayer film having an outer layer is enhanced. When the ratio is equal to or less than the upper limit, excessive thickness of the outer layer is avoided.
The thickness of the outer layer may be, for example, 10 to 20 μm.
Here, the "thickness of the outer layer" means the thickness of the entire outer layer. For example, the thickness of an outer layer consisting of multiple layers means the total thickness of all layers that make up the outer layer.

<Adhesive Layer>
The adhesive layer is an optional layer, and the transparent multilayer film of the present embodiment may or may not have an adhesive layer, although the inclusion of an adhesive layer makes the multilayer structure of the transparent multilayer film more stable.
In a transparent multilayer film having an adhesive layer, the adhesive layer is arranged so as not to be the outermost layer, and adheres two adjacent layers to it. For example, in the transparent multilayer film 1 shown in Fig. 1 and the transparent multilayer film 2 shown in Fig. 2, the adhesive layer 19 adheres the adjacent flexible layer 12 and intermediate layer 13 to each other.
The adhesive layer has transparency.
The adhesive layer is preferably a non-oriented layer.

The adhesive layer is preferably a resin layer containing an adhesive resin.

The adhesive resin may be, for example, a polyolefin resin.
The polyolefin resin is a resin having structural units derived from an olefin, and may be a modified polyolefin such as an acid-modified polyolefin having an acidic group or an acid-modified polyolefin having an anhydride group in which the acidic group is modified.
Examples of polyolefin-based resins include ethylene-based copolymers, propylene-based copolymers, butene-based copolymers, modified products of these copolymers (in other words, modified copolymers), etc. The polyolefin-based resin is preferably a random copolymer, a graft copolymer, or a block copolymer, in terms of further improving adhesiveness.

The ethylene-based copolymer, not limited to the adhesive layer, has a structural unit derived from ethylene and a structural unit derived from another monomer which does not fall into either ethylene or propylene.
The ethylene copolymer includes, for example, an ethylene-butene copolymer.
Examples of the ethylene copolymer contained in the adhesive layer include these ethylene copolymers and modified products thereof (modified copolymers).

The propylene-based copolymer is as described above, and examples of the propylene-based copolymer contained in the adhesive layer include copolymers of propylene and vinyl group-containing monomers, modified products thereof (modified copolymers), and the like.
More specifically, examples of the propylene copolymer contained in the adhesive layer include linear low-density polypropylene grafted with maleic anhydride, and propylene-based thermoplastic elastomers.

Examples of the butene copolymer contained in the adhesive layer include copolymers of 1-butene and vinyl group-containing monomers, copolymers of 2-butene and vinyl group-containing monomers, and modified products of these copolymers (modified copolymers).

The adhesive layer may contain only one type of adhesive resin, or two or more types. If there are two or more types, the combination and ratio of the adhesive resins can be selected as desired depending on the purpose.

The adhesive layer may contain other components in addition to the adhesive resin as long as the adhesive layer's adhesiveness is not impaired.
Examples of the other components contained in the adhesive layer include an antioxidant.

The adhesive layer may contain only one type of other component, or two or more types. If there are two or more types, the combination and ratio of these components can be selected as desired depending on the purpose.

In the adhesive layer, the ratio of the content of the adhesive resin to the total mass of the adhesive layer ([content of adhesive resin in adhesive layer (parts by mass)]/[total mass of adhesive layer (parts by mass)]×100) is preferably 80% by mass or more, and more preferably 90% by mass or more. When the ratio is equal to or more than the lower limit, the adhesiveness of the adhesive layer is higher.
On the other hand, the proportion is 100% by mass or less.
The above ratio is usually the same as the ratio of the content (parts by mass) of the adhesive resin to the total content (parts by mass) of components that do not vaporize at room temperature in the composition for forming an adhesive layer described below ([content (parts by mass) of adhesive resin in composition for forming an adhesive layer] / [total content (parts by mass) of components that do not vaporize at room temperature in composition for forming an adhesive layer] x 100).

The adhesive layer may consist of one layer (single layer) or may consist of two or more layers. When the adhesive layer consists of multiple layers, these multiple layers may be the same or different from each other, and the combination of these multiple layers is not particularly limited as long as it does not impair the effects of the present invention.

The ratio of the thickness of the adhesive layer to the thickness of the transparent multilayer film ([thickness of adhesive layer]/[thickness of transparent multilayer film]×100) is preferably 5 to 25%, and more preferably 7 to 23%. When the ratio is equal to or greater than the lower limit, the adhesiveness of the adhesive layer is increased. When the ratio is equal to or less than the upper limit, excessive thickness of the adhesive layer is avoided.
The thickness of the adhesive layer may be, for example, from 1.5 to 7.5 μm.
Here, "thickness of adhesive layer" means the thickness of the entire adhesive layer; for example, the thickness of an adhesive layer consisting of multiple layers means the total thickness of all layers that make up the adhesive layer.

The thickness of the transparent multilayer film 1 is not particularly limited, but is preferably 20 to 70 μm, and more preferably 25 to 65 μm.

The transparent multilayer film of this embodiment is not limited to the above-mentioned aspects, and some of the configuration may be changed, deleted, or added without departing from the spirit of the present invention.

For example, the transparent multilayer film 1 shown in FIG. 1 comprises an easy peel layer 11, a flexible layer 12, an intermediate layer 13, an oxygen barrier layer 14, and an adhesive layer 19, and the transparent multilayer film 2 shown in FIG. 2 further comprises an outer layer 15 in addition to these, but the transparent multilayer film of this embodiment may further comprise other layers that do not fall into any of the above categories.
The other layer is not particularly limited and can be arbitrarily selected depending on the purpose.

For example, the transparent multilayer film 1 and the transparent multilayer film 2 may have another adhesive layer similar to the adhesive layer 19 between two other layers other than between the flexible layer 12 and the intermediate layer 13. An example of the other adhesive layer is one provided between the oxygen barrier layer 14 and the outer layer 15, which is one example of the other adhesive layer. The adhesive layer 19 and the other adhesive layer may be the same as or different from each other.

For example, the transparent multilayer film 2 shown in FIG. 2 may have a printed layer on a surface 15 a of the outer layer 15 opposite to the easy-peel layer 11 side.
When the transparent multilayer film 2 has the printed layer, it is preferable that the printed layer is provided on only a portion of the surface 15a of the outer layer 15 rather than on the entire surface 15a, so that the stored contents can be clearly seen from outside the packaging body obtained using the transparent multilayer film 2 through the transparent multilayer film 2 (e.g., a lid material).
The shape and thickness of the printed layer can be selected arbitrarily depending on the purpose and are not particularly limited.
The printing layer may be of a known type.

One example of a preferred transparent multilayer film of the present embodiment is one formed by laminating an easy-peel layer, a flexible layer, an adhesive layer, an intermediate layer, and an oxygen barrier layer in this order, in direct contact with each other in the thickness direction.
Another example of a preferred transparent multilayer film of the present embodiment is one formed by laminating an easy-peel layer, a flexible layer, an adhesive layer, an intermediate layer, an oxygen barrier layer, and an outer layer in this order and in direct contact with each other in the thickness direction.
Yet another example of a preferred transparent multilayer film of the present embodiment is one formed by laminating an easy-peel layer, a flexible layer, an adhesive layer, an intermediate layer, an oxygen barrier layer, an adhesive layer, and an outer layer in this order, in direct contact with each other in the thickness direction.

<<Method of manufacturing transparent multilayer film>>
The transparent multilayer film can be produced, for example, by a feed block method in which resins or resin compositions that are materials for forming each layer are melt-extruded using several extruders, a co-extrusion T-die method such as a multi-manifold method, or an air-cooled or water-cooled co-extrusion inflation method.

The transparent multilayer film can also be produced by coating the surface of another layer that constitutes the transparent multilayer film with a resin or resin composition that is a material for forming one of the layers, and drying it as necessary to form a laminated structure in the transparent multilayer film, and then further laminating other layers as necessary to obtain the desired arrangement.

The transparent multilayer film can also be produced by separately preparing two or more films for constituting any two or more of the layers, laminating the films together using an adhesive by any one of dry lamination, extrusion lamination, hot melt lamination and wet lamination, and further laminating other layers as necessary so as to form the desired arrangement. In this case, the adhesive used may be one capable of forming the adhesive layer.
For example, a transparent multilayer film having an outer layer may be produced by laminating a laminate film having an easy-peel layer and an outer layer or a laminate film having an outer layer by any of the methods described above. In this case, the outer layer before lamination may be biaxially stretched as necessary.

The transparent multilayer film can also be produced by laminating two or more films, which have been prepared separately in advance, by thermal lamination or the like without using an adhesive, and, if necessary, laminating other layers so as to achieve the desired arrangement. For example, unlike the above, a laminate film having an easy-peel layer and an outer layer or a laminate film having an outer layer may be laminated together without using an adhesive.

When producing the transparent multilayer film, two or more of the methods for forming any of the layers (in other words, films) in the transparent multilayer film described above may be combined.

The resin composition that is the material for forming any of the layers in the transparent multilayer film may be produced by adjusting the type and content of the components so that the layer to be formed contains the desired components in the desired content. For example, the content ratio of the components that do not vaporize at room temperature in the resin composition is usually the same as the content ratio of the components in the layer formed from this resin composition.

An example of a resin composition (sometimes referred to herein as an "easy peel layer forming composition") for forming an easy peel layer (e.g., easy peel layer 11 in transparent multilayer film 1 shown in FIG. 1 and transparent multilayer film 2 shown in FIG. 2) is a resin composition containing the hot melt adhesive, the incompatible component, and, if necessary, the antifogging agent and, if necessary, the other components.

Examples of resin compositions (sometimes referred to herein as "flexible layer-forming compositions") for forming flexible layers (e.g., flexible layer 12 in transparent multilayer film 1 shown in FIG. 1 and transparent multilayer film 2 shown in FIG. 2) include resin compositions containing the resin (e.g., water vapor barrier resin) and, if necessary, the other components.

Examples of resin compositions (sometimes referred to herein as "compositions for forming intermediate layers") for forming intermediate layers (e.g., intermediate layer 13 in transparent multilayer film 1 shown in FIG. 1 and transparent multilayer film 2 shown in FIG. 2) include resin compositions containing the nitrogen-containing resin and, if necessary, the other components.

Examples of resin compositions (sometimes referred to herein as "oxygen barrier layer forming compositions") for forming an oxygen barrier layer (for example, oxygen barrier layer 14 in transparent multilayer film 1 shown in FIG. 1 and transparent multilayer film 2 shown in FIG. 2) include resin compositions containing the oxygen barrier resin and, if necessary, the other components.

The resin composition (sometimes referred to herein as the "composition for forming the outer layer") for forming the outer layer (e.g., outer layer 15 in the transparent multilayer film 2 shown in FIG. 2) may be, for example, a resin composition containing the resin (e.g., the propylene-based polymer, the nitrogen-containing resin, or the polyester) and, if necessary, the other components.

Examples of resin compositions (sometimes referred to herein as "adhesive layer forming compositions") for forming adhesive layers (e.g., adhesive layer 19 in transparent multilayer film 1 shown in FIG. 1 and transparent multilayer film 2 shown in FIG. 2) include resin compositions containing the adhesive resin and, if necessary, the other components.

<<Packaging>>
A package according to one embodiment of the present invention includes the transparent multilayer film.
The transparent multilayer film can be sealed to a substrate such as another resin film, a resin sheet or a resin molded article (for example, a base material or a tray) via the easy-peel layer therein to form various packages.

A preferred example of the packaging body is a packaging body (deep-drawn packaging body) that includes a lid material and a base material, in which the lid material is made of the transparent multilayer film and the base material is a deep-drawn resin molded body, and the easy-peel layer in the lid material (the transparent multilayer film) is sealed to the base material.
A preferred example of the packaging body is a packaging body (packaging body with a tray) that includes a lid material and a tray, in which the lid material is made of the transparent multilayer film and the tray is made of resin, and the easy-peel layer in the lid material (the transparent multilayer film) is sealed to the tray.
A preferred example of the packaging body is a soft gas pack in which the transparent multilayer film is sealed to the same type of transparent multilayer film or to a different type of film or sheet by an easy-peel layer therein.

The substrate, which is the object to be sealed by the lid material, preferably contains polyethylene terephthalate, and may be a substrate made of polyethylene terephthalate. By using such a substrate, the reusability of the package is increased. Furthermore, when the H ₁₄₀ and S ₁₄₀ of the transparent multilayer film are sufficiently increased and a deep-draw package is manufactured as the package, peeling of the lid material (transparent multilayer film) from the base material (substrate) is highly suppressed, as described above.

In the substrate, the ratio of the polyethylene terephthalate content to the total mass of the substrate ([polyethylene terephthalate content of substrate (parts by mass)]/[total mass of substrate (parts by mass)]×100) is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, and may be, for example, any one of 95% by mass or more, 97% by mass or more, and 99% by mass or more. When the ratio is equal to or more than the lower limit, the effect obtained by using a substrate containing polyethylene terephthalate is further enhanced.
On the other hand, the proportion is 100% by mass or less.

FIG. 3 is a cross-sectional view illustrating an example of the packaging body of the present embodiment.
The packaging body 101 shown here comprises a cover material 8 and a base material 10 which are sealed together.
The lid material 8 is the transparent multilayer film according to one embodiment of the present invention described above. For example, the transparent multilayer film 1 shown in FIG.
The base material 10 is a molded body (deep-draw molded body) obtained by deep-drawing a resin film. That is, the packaging body 101 is a deep-draw packaging body.
In the cover material 8 in FIG. 3, the distinction between the layers of the transparent multi-layer film constituting it is omitted.

The base material 10 has a recess 100 formed therein.
One surface 10b of the base material 10 in the area excluding the recess 100 (sometimes referred to as the "second surface" in this specification) and one surface 8b of the cover material 8 (sometimes referred to as the "second surface" in this specification) are both sealing surfaces and face each other.
The package 101 is formed by sealing the lid material 8 and the base material 10. More specifically, the second surface 10b of the base material 10 except for the recess 100 and the second surface 8b of the lid material 8 are overlapped and sealed to each other in the area near their peripheral edges. As a result, in the area of the recess 100 of the base material 10, a storage section 101a is formed between the second surface 10b of the base material 10 and the second surface 8b of the lid material 8. The item 9 is stored in this storage section 101a.

When the lid material 8 is the transparent multilayer film 1 or the transparent multilayer film 2, one side (second side) 8b of the lid material 8 is the same as the side 11b of the easy-peel layer 11 in the transparent multilayer film 1 or the transparent multilayer film 2, which is opposite the flexible layer 12 side. The other side (sometimes referred to as the "first side" in this specification) 8a of the lid material 8 is the same as the side 14a of the oxygen barrier layer 14 in the transparent multilayer film 1, which is opposite the easy-peel layer 11 side, or the same as the side 15a of the outer layer 15 in the transparent multilayer film 2, which is opposite the easy-peel layer 11 side.

In FIG. 3, some gaps can be seen between the stored item 9 and the base material 10, and between the stored item 9 and the lid material 8 within the storage section 101a of the package 101, but the presence of these gaps is not essential for the package 101 when the stored item 9 is stored therein.

The thickness of the lid material 8 is the same as the thickness of the transparent multilayer film 1 or transparent multilayer film 2 described above.

The base material 10 may be a single-layer or multi-layer resin film molding that can be used in ordinary deep-draw packaging.
The base material 10 preferably contains polyethylene terephthalate, and may be a base material made of polyethylene terephthalate.
The thickness of the base material 10 at its flat portion is preferably 100 to 300 μm.

The items 9 to be stored can be selected arbitrarily depending on the purpose, but preferred items 9 to be stored include, for example, food, cosmetics, medicines, etc.

In the packaging body 101, the contents 9 in the storage section 101a can be clearly seen from outside the packaging body 101 through the lid material 8.

When the package 101 is opened by peeling off the lid material 8, the occurrence of so-called stringing, in which resin thread-like material is generated between the peeled surfaces, can be suppressed. In addition, the phenomenon in which a crackling sound is generated when peeling off the lid material 8, which makes the peeling feel worse, is suppressed, and the peeling feel of the lid material 8 is improved.

Up to this point, a deep-drawn package has been used as an example of a package having the transparent multilayer film, but the package having the transparent multilayer film is not limited to a deep-drawn package and may be another package.
However, in order to obtain the excellent effects of the transparent multilayer film more significantly, it is preferable that the package be a deep-draw package.

When opening the package 101, the cover material 8 is peeled off from the base material 10, and the easy-peel layer in the cover material 8 is easily peeled off from the base material 10.

<<Manufacturing method of packaging body>>
The package can be produced by heat-sealing the transparent multilayer film and an object to be sealed, so as to form a storage section for storing the object to be packaged, such as the above-mentioned resin molded body (e.g., base material, tray), other resin film, resin sheet, etc.

The base material can be produced, for example, by deep drawing a resin film using a known method.
The tray can be produced, for example, by forming a flat resin sheet into a desired shape by a known method.

When the transparent multilayer film and the object to be sealed are heat-sealed, the sealing temperature may be, for example, 120 to 150°C, the sealing time may be, for example, 0.5 to 3 seconds, and the sealing pressure may be, for example, 0.15 to 0.8 MPa (1.5 to 8 kgf/cm ² ).

The method for manufacturing a deep-drawn package using the long transparent multi-layer film as a lid material and a long base material is as described above. In this case, for example, a long base material (connected body of base materials) in which recesses for forming a storage section are arranged in the longitudinal direction and a long lid material are used, and the longitudinal directions of these are aligned, and the easy-peel layer of the lid material and one of the outermost layers of the base material are arranged opposite each other, and while applying a tension of a specific value or more to the lid material, and further filling the area forming the storage section with an inert gas and the packaged object, the lid material and the base material are heat-sealed sequentially in the longitudinal direction. After all heat sealing is completed, the long lid material and the base material are cut for each storage section formed, thereby obtaining the desired deep-drawn package. In the manufacturing process of such a package, by using the transparent multilayer film as the lid material, which is long and has sufficiently high H ₁₄₀ and S ₁₄₀ , peeling of the long lid material from the long base material is suppressed even when a long base material containing polyethylene terephthalate is used. Furthermore, peeling of the lid material from the base material is suppressed in the obtained package.
Thus, the transparent multilayer film of this embodiment provides particularly significant effects when used in the production of deep-draw packaging products.

On the other hand, when the long transparent multilayer film is used as a lid material and a tray is used to manufacture a package with a tray, the tray and the long lid material are heat-sealed sequentially for each tray, and the long lid material is cut for each tray immediately after heat sealing, so tension is not continuously applied to the heat-sealed lid material. The long lid material made of the transparent multilayer film of this embodiment can also be used to manufacture such a package with a tray, allowing for more stable manufacture of the package.

The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited to the examples shown below.

The resins used in each of the examples and comparative examples are as follows.
TA: Aromatic terpene resin ("Hirodine 7560" manufactured by Yasuhara Chemical Co., Ltd.)
IC(1): Methyl methacrylate-styrene copolymer (incompatible component, "MS-750" manufactured by Toyo Styrene Co., Ltd., copolymerization ratio of methyl methacrylate: 75 mol%, copolymerization ratio of styrene: 25 mol%)
IC(2): Methyl methacrylate-styrene copolymer (incompatible component, "MS-600" manufactured by Toyo Styrene Co., Ltd., copolymerization ratio of methyl methacrylate: 60 mol%, copolymerization ratio of styrene: 40 mol%)
IC(3): Methyl methacrylate-styrene copolymer (incompatible component, Toyo Styrene "MS-300", copolymerization ratio of methyl methacrylate 30 mol%, copolymerization ratio of styrene 70 mol%)
IC(4): Methyl methacrylate-styrene copolymer (incompatible component, Toyo Styrene "MS-200", copolymerization ratio of methyl methacrylate: 20 mol%, copolymerization ratio of styrene: 80 mol%)
IC(5): Methyl methacrylate-styrene copolymer (incompatible component, Toyo Styrene "MS-500", copolymerization ratio of methyl methacrylate: 50 mol%, copolymerization ratio of styrene: 50 mol%)
LDPE (1): Low-density polyethylene (UBE Polyethylene (registered trademark) F222NH, manufactured by Ube Maruzen Polyethylene Co., Ltd., density 0.922 g/cm ³ )
LDPE (2): Biomass-derived low-density polyethylene ("SEB853" manufactured by Braskem, density 0.923 g/cm ³ )
ION: Ionomer ("1652" manufactured by Mitsui Dow Polychemicals)
Ny6: 6-nylon ("1030B2" manufactured by Ube Industries, Ltd.)
EVOH: ethylene-vinyl alcohol copolymer ("EVAL (registered trademark) E173B" manufactured by Kuraray Co., Ltd., copolymerization ratio of ethylene: 44 mol%)
Modified PE: Maleic anhydride modified polyethylene (adhesive resin, "Admer (registered trademark) NF536" manufactured by Mitsui Chemicals, Inc.)
EVA: Ethylene-vinyl acetate copolymer ("P2505C" manufactured by Dow Polychemicals, Mitsui)
Ad: higher fatty acid ester compound (anti-fogging agent, "Elecut C-031L" manufactured by Takemoto Oil Co., Ltd.)
PET: Polyethylene terephthalate ("Novapex GM700Z" manufactured by Mitsubishi Chemical Corporation)

[Example 1]
<<Manufacturing of transparent multilayer films>>
<Production of composition for forming easy peel layer>
The TA (89 parts by mass), the IC(1) (10 parts by mass), and the Ad (1 part by mass) were mixed at room temperature to prepare a composition for forming an easy peel layer.

<Manufacturing transparent multi-layer film (covering material)>
The easy peel layer-forming composition, the LDPE (1), the modified PE, the Ny6, and the EVOH were co-extruded in this order to obtain a long transparent multilayer film (thickness 30 μm) having the configuration shown in FIG. 1 , in which an easy peel layer (thickness 6 μm), a soft layer (thickness 9 μm), an adhesive layer (thickness 4.5 μm), an intermediate layer (thickness 4.5 μm), and an oxygen barrier layer (thickness 6 μm) were laminated in this order in the thickness direction.
The easy peel layer, the flexible layer, the adhesive layer, the intermediate layer, and the oxygen barrier layer are all unoriented layers.
The obtained transparent multilayer film was hereafter used as a long lid material for producing packaging materials.

<<Evaluation of transparent multilayer films>>
<Measurement of _H140 >
Separately, a single easy-peel layer (thickness: 6 μm) was prepared by extrusion molding, which was the same as that in the transparent multilayer film, and a first test piece having a width of 25.4 mm was prepared from this.
Using a hot tack strength tester (Teller's "Model HT Hot Tack Heat Seal Tester"), the entire surface of one side of this first test piece was overlapped with one side of a polyethylene terephthalate film (the above-mentioned test PET film, thickness 200 μm), and heat-sealed under conditions of a sealing temperature of 140° C., a sealing pressure of 0.473 Pa, and a sealing time of 2 seconds, and 0.22 seconds later, the peel strength was measured at a pulling speed of 33.3 mm/s and an angle (peel angle) between the first test piece and the test PET film at the time of peeling of 90°, and the measured value was taken as H ₁₄₀ (N/25.4 mm). The results are shown in Table 1.

<Measurement of _S140 >
Furthermore, the first test piece was prepared separately, and this first test piece was heat-sealed to the polyethylene terephthalate film (test PET film) under the same conditions as in the measurement of H _140. After 24 hours, the peel strength was measured at a pulling speed of 33.3 mm/s and an angle (peel angle) between the first test piece and the test PET film at the time of peeling of 90°, and the measured value was adopted as S ₁₄₀ (N/25.4 mm). The results are shown in Table 1.

<Measurement of haze of transparent multilayer film>
The haze (%) of the transparent multilayer film obtained above was measured from the outside of the easy peel layer side in accordance with JIS K 7136: 2000. The results are shown in Table 1.

<Measurement of surface resistivity of easy peel layer>
Separately, a single-layer easy peel layer (thickness 6 μm) was prepared by extrusion molding, which was the same as that in the transparent multilayer film, and this was used as a second test piece. The surface resistivity (Ω/□) of this second test piece was measured in accordance with JIS C 2139-3-1:2018. The results are shown in Table 1.

<<Manufacturing of packaging bodies>>
Using the PET, a long laminated film (thickness 200 μm) was prepared, which was constructed by laminating a PET layer (thickness 50 μm), a PET layer (thickness 100 μm), and a PET layer (thickness 50 μm) in this order in the thickness direction.
The oxygen transmission rate of this laminated film was measured in accordance with JIS K 7126-2:2006 under conditions of a temperature of 23° C. and a relative humidity of 60%, and was found to be 10 cc/(m ² ·24 h ·atm).

Using a deep drawing molding machine ("R-535" manufactured by Multivac), the laminated film was deep drawn under conditions of a forming temperature of 100°C, a heating time of 3 seconds, and a forming time of 3 seconds to produce a long base material (connected base material) with continuous recesses (storage areas) formed in the longitudinal direction of the laminated film.

The long base material and the long lid material obtained above were aligned in the longitudinal direction, and the easy-peel layer of the lid material was placed facing one of the outermost layers of the base material. Cut lettuce (80 g) was placed in each recess of the base material, and the peripheral parts of the lid material and base material were heat-sealed sequentially under conditions of a sealing temperature of 130°C, a sealing pressure of 0.2 MPa, and a sealing time of 2 seconds, to produce a package. Next, after all heat sealing was completed, the long lid material and the molded body were cut in the obtained long package for each storage section formed, thereby obtaining a package (vacuum package, deep-draw package) in which the molded body of the laminated film was used as the base material (thickness 200 μm) and the transparent multilayer film (thickness 30 μm) was used as the lid material.

<<Evaluation of packaging>>
<Evaluation of peel resistance of packaging during manufacturing>
The ten packages (deep-drawn packages) obtained above immediately after production were visually observed to check for peeling between the lid material and the base material. The peel resistance of the packages during production was evaluated according to the following criteria. The results are shown in Table 1.
[Evaluation criteria]
A: No peeling was observed in any of the packages.
B: Slight peeling is observed in one or more packages.

<Evaluation of peel resistance of packaging when dropped>
In the above evaluation of the peel resistance of the packages during production, one package in which peeling between the lid material and the base material was not observed was selected, and this package was dropped from a height of 0.8 m onto the floor in accordance with JIS Z 0202:2017. The package after the drop was then visually observed to confirm the presence or absence of peeling between the lid material and the base material. The peel resistance of the package when dropped was evaluated according to the following criteria. The results are shown in Table 1.
[Evaluation criteria]
A: No peeling was observed.
B: Even a slight peeling is observed.

<Evaluation of anti-fogging properties of lid materials>
In the above evaluation of the peel resistance of the packages during production, one package in which peeling between the lid material and the base material was not observed was selected, and this package was left to stand and stored at 5° C. for 60 minutes.
The package after storage was then visually observed from the outside of the lid side to confirm the visibility of the contents, and the anti-fogging ability of the lid in the package was evaluated according to the following criteria. The results are shown in Table 1.
[Evaluation criteria]
A: No clouding is observed on the lid material, and the entire contents can be clearly seen.
B: There is slight cloudiness on the lid material, but the entire contents can be seen.
C: Severe clouding was observed on the lid material, making at least a portion of the contents invisible.

<Evaluation of transparency of lid material in packaging>
In the evaluation of the peel resistance of the packages during manufacture, one package in which peeling between the lid material and the base material was not observed was separately selected, and this package was visually observed from the outside of the lid material side at room temperature, and the transparency of the lid material in the package was evaluated according to the following criteria. The results are shown in Table 1.
[Evaluation criteria]
A: The lid material is colorless and transparent, and has high transparency.
B: The lid material is slightly cloudy but transparent.
C: The lid material is clouded to a degree that cannot be described as slight, and is opaque.

<Evaluation of peeling sensation of lid material>
The above-mentioned packages for which the transparency of the lid material in the package had been evaluated were used, and the peeling sensation when the lid material was peeled off and opened was evaluated according to the following criteria. The results are shown in Table 1.
[Evaluation criteria]
A: The lid material can be peeled off smoothly and the peeling feeling is excellent.
B: When peeling off the lid material, slight resistance was felt, but peeling was easy.
C: When the lid material was peeled off, a crackling sound was heard and resistance that could not be described as mild was felt, resulting in a poor peeling feel.

<Evaluation of the effect of suppressing stringiness when opening a package>
At the same time as the evaluation of the peelability of the lid material, the presence or absence of stringiness between the peelable surfaces was visually confirmed, and the stringiness suppression effect was evaluated according to the following criteria. The results are shown in Table 1.
[Evaluation criteria]
A: No stringiness at all.
B: Slight stringiness occurs, but does not interfere with practical use.
C: Stringiness is more than slight, and is a hindrance to practical use.

<<Production and evaluation of transparent multilayer films, and production and evaluation of packaging materials>>
[Example 2]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 88 parts by mass, and the amount of Ad used was changed from 1 part by mass to 2 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 3]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 87 parts by mass, and the amount of Ad used was changed from 1 part by mass to 3 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 4]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 85 parts by mass, and the amount of Ad used was changed from 1 part by mass to 5 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 5]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 83 parts by mass, and the amount of Ad used was changed from 1 part by mass to 7 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 6]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 89.5 parts by mass, and the amount of Ad used was changed from 1 part by mass to 0.5 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Example 7]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 89.7 parts by mass, and the amount of Ad used was changed from 1 part by mass to 0.3 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Example 8]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 80 parts by mass, and the amount of Ad used was changed from 1 part by mass to 10 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Example 9]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the LDPE (2) was used instead of the LDPE (1) to form a flexible layer, and these transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Example 10]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 92 parts by mass, and the amount of IC (1) used was changed from 10 parts by mass to 7 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Example 11]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 95 parts by mass, and the amount of IC (1) used was changed from 10 parts by mass to 4 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Example 12]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 84 parts by mass, and the amount of IC (1) used was changed from 10 parts by mass to 15 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Example 13]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 79 parts by mass, and the amount of IC (1) used was changed from 10 parts by mass to 20 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Example 14]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 74 parts by mass, and the amount of IC (1) used was changed from 10 parts by mass to 25 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Example 15]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the amount of TA used was changed from 89 parts by mass to 69 parts by mass, and the amount of IC (1) used was changed from 10 parts by mass to 30 parts by mass, during the preparation of the composition for forming an easy peel layer. These transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Example 16]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the EVA was used instead of the LDPE (1) to form the flexible layer, and these transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Example 17]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that the ION was used instead of the LDPE (1) to form a flexible layer, and these transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Example 18]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that IC(2) (10 parts by mass) was used instead of IC(1) (10 parts by mass) when preparing the composition for forming an easy peel layer, and these transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 4.
In Table 4, the single-layer flexible layers in Example 18 and Examples 19 to 21 described below are listed in the "First Flexible Layer" column to list them alongside the three-layer flexible layer (first flexible layer, second flexible layer, and third flexible layer) in Comparative Example 1.

[Example 19]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that IC(3) (10 parts by mass) was used instead of IC(1) (10 parts by mass) when preparing the composition for forming an easy peel layer, and these transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 4.

[Example 20]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that IC(4) (10 parts by mass) was used instead of IC(1) (10 parts by mass) when preparing the composition for forming an easy peel layer, and these transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 4.

[Example 21]
A transparent multilayer film and a package similar to those in Example 1 were produced in the same manner as in Example 1, except that IC(5) (10 parts by mass) was used instead of IC(1) (10 parts by mass) when preparing the composition for forming an easy peel layer, and these transparent multilayer films and packages were evaluated in the same manner as in Example 1. The results are shown in Table 4.

[Comparative Example 1]
<<Manufacturing of transparent multilayer films>>
<Production of composition for forming easy peel layer>
The TA (67 parts by mass), the IC(1) (32 parts by mass), and the Ad (1 part by mass) were mixed at room temperature to prepare a composition for forming an easy peel layer.

<Manufacturing transparent multi-layer film (covering material)>
The composition for forming an easy peel layer, the ION, the EVA, the LDPE (1), the modified PE, the Ny6, and the EVOH were co-extruded in this order to obtain a long transparent multilayer film (thickness 48 μm) having the configuration shown in FIG. 1 , in which an easy peel layer (thickness 6 μm), a first flexible layer (thickness 9 μm), a second flexible layer (thickness 9 μm), a third flexible layer (thickness 9 μm), an adhesive layer (thickness 4.5 μm), an intermediate layer (thickness 4.5 μm), and an oxygen barrier layer (thickness 6 μm) were laminated in this order in the thickness direction.
The easy-peel layer, the first flexible layer, the second flexible layer, the third flexible layer, the adhesive layer, the intermediate layer, and the oxygen barrier layer are all unoriented layers.
The obtained transparent multilayer film was hereafter used as a long lid material for producing packaging materials.

<<Evaluation of transparent multilayer films>>
The transparent multilayer film obtained above was evaluated in the same manner as in Example 1. The results are shown in Table 4.

<<Production and evaluation of packaging>>
Except for using the transparent multilayer film obtained above, a package was produced and evaluated in the same manner as in Example 1. The results are shown in Table 4.

As is clear from the above results, in Examples 1 to 21, in the deep-drawn packages obtained by heat-sealing an easy-peel lid material and a base material containing polyethylene terephthalate, the lid material had transparency, the occurrence of stringiness was suppressed when the package was opened, and the lid material had a good peeling feel.
In Examples 1 to 21, the easy peel layer contained a component incompatible with the hot melt adhesive, and the haze of the transparent multilayer film was 20% or less (7 to 20%).

In particular, in Examples 1 to 14 and 16 to 21, the transparency of the lid material in the package was high. In Examples 1 to 14 and 16 to 21, the haze of the transparent multilayer film was 17% or less (7 to 17%).

In the easy peel layer, the ratio of the content of the incompatible components to the content of the hot melt adhesive was 4.2 to 43.5 mass% in Examples 1 to 21 (43.5 mass% in Example 15), but was 4.2 to 33.8 mass% in Examples 1 to 14 and 16 to 21, and was 4.2 to 25.3 mass% in Examples 1 to 13 and 16 to 21 in particular.

The results of Examples 1 to 21 confirmed that the haze of the transparent multilayer film tends to increase when the ratio of the content of incompatible components to the content of hot melt adhesive in the easy peel layer increases.

The results of Examples 1 to 21 confirmed that when the ratio of the content of incompatible components to the content of hot melt adhesive in the easy peel layer is high, there is a tendency for the effect of suppressing stringiness when opening the package and the feel of peeling off the lid material to improve.

The anti-fogging properties of the lid materials during refrigerated storage of the packages (when the packages were stored stationary at 5°C for 60 minutes) were good in Examples 1 to 6 and 8 to 21, and were better in Examples 1 to 5 and 8 to 21. In Examples 1 to 6 and 8 to 21, H ₁₄₀ was 4.5 N/25.4 mm or less (0.8 to 4.5 N/25.4 mm), S ₁₄₀ was 7.9 N/25.4 mm or less (2.1 to 7.9 N/25.4 mm), and the surface resistivity of the easy peel layer was 7.6 x 10 ¹³ Ω/□ or less (8.9 x 10 ⁴ to 7.6 x 10 ¹³ Ω/□). In Examples 1 to 5 and 8 to 21, H ₁₄₀ was 4.1 N/25.4 mm or less (0.8 to 4.1 N/25.4 mm), S ₁₄₀ was 7.6 N/25.4 mm or less (2.1 to 7.6 N/25.4 mm), and the surface resistivity of the easy peel layer was 9.4×10 ¹² Ω/□ or less (8.9×10 ⁴ to 9.4×10 ¹² Ω/□).

In Examples 1 to 7 and 9 to 21, the peel resistance of the package during production and the peel resistance of the package after production (peel resistance when the package is dropped) were both high, and the transparent multilayer films of these Examples had particularly preferable properties for producing deep drawn packages. In Examples 1 to 7 and 9 to 21, H ₁₄₀ was 1.4 N/25.4 mm or more (1.4 to 5.2 N/25.4 mm), S ₁₄₀ was 3.1 N/25.4 mm or more (3.1 to 8.2 N/25.4 mm), and the surface resistivity of the easy peel layer was 6.2 x 10 ⁶ Ω/□ or more (6.2 x 10 ⁶ to 1.2 x 10 ¹⁴ Ω/□).

From the results of Examples 1 to 21, it was confirmed that as the content of the antifogging agent in the easy-peel layer decreases, H ₁₄₀ and S ₁₄₀ increase, and the surface resistivity of the easy-peel layer tends to increase. It was also confirmed that as the surface resistivity of the easy-peel layer increases (in other words, as the content of the antifogging agent in the easy-peel layer decreases), the antifogging property of the lid material in the package tends to deteriorate.

In contrast, the lid material in the deep drawn package was cloudy and opaque in Comparative Example 1. In Comparative Example 1, the haze of the transparent multilayer film was 21%.
Furthermore, in Comparative Example 1, the peel resistance of the package after production (peel resistance when the package is dropped) was low. In Comparative Example 1, S ₁₄₀ was 2.4 N/25.4 mm.
In the easy peel layer of Comparative Example 1, the ratio of the content of the incompatible component to the content of the hot melt adhesive was 47.8 mass %.

The present invention can be used to manufacture packaging, and is particularly suitable for use in the manufacture of deep-drawn packaging.

1, 2: transparent multilayer film 11: easy peel layer 11b: surface of easy peel layer opposite to the flexible layer (exposed surface)
12: Flexible layer 13: Intermediate layer 14: Oxygen barrier layer 15: Outer layer 8: Lid material 10: Base material 101: Package

Claims (17)

A transparent multilayer film having at least an easy peel layer,
The easy peel layer contains a hot melt adhesive and an incompatible component that is incompatible with the hot melt adhesive,
A transparent multilayer film, wherein the haze of the transparent multilayer film measured in accordance with JIS K 7136:2000 is 20% or less. The transparent multilayer film according to claim 1, wherein the ratio of the content of the incompatible component to the content of the hot melt adhesive in the easy peel layer is 2 to 45 mass %. The transparent multilayer film according to claim 1 or 2, wherein the incompatible component is a (meth)acrylic acid ester-styrene copolymer. The transparent multilayer film according to claim 3, wherein the ratio of the amount of structural units derived from (meth)acrylic acid ester to the total amount of structural units in the (meth)acrylic acid ester-styrene copolymer is 10 to 90 mol %, and the ratio of the amount of structural units derived from styrene is 90 to 10 mol %. The transparent multilayer film according to claim 4, wherein the (meth)acrylic acid ester-styrene copolymer is a methacrylic acid ester-styrene copolymer. The transparent multilayer film according to claim 1 or 2, further comprising a flexible layer. The transparent multilayer film according to claim 1 or 2, further comprising an intermediate layer. The transparent multilayer film according to claim 1 or 2, further comprising an oxygen barrier layer. The transparent multilayer film further comprises a flexible layer, an intermediate layer, and an oxygen barrier layer;
3. The transparent multilayer film of claim 1, wherein the flexible layer and the intermediate layer are disposed between the easy peel layer and the oxygen barrier layer. The transparent multilayer film of claim 6, wherein the flexible layer is disposed adjacent to the easy peel layer. 3. The transparent multilayer film according to claim 1, wherein the surface resistivity of the easy peel layer, measured in accordance with JIS C 2139-3-1:2018, is 1×10 ⁵ to 1×10 ¹⁴ Ω/□. The transparent multilayer film according to claim 9, further comprising an outer layer containing a propylene-based polymer, polyamide or polyester on the side of the oxygen barrier layer opposite the intermediate layer. The transparent multilayer film according to claim 7, wherein the intermediate layer contains polyamide. The transparent multilayer film according to claim 13, wherein the polyamide is a biomass-derived polyamide. The transparent multilayer film according to claim 6, wherein the flexible layer contains one or more selected from the group consisting of polyethylene, modified polyethylene, and ionomer. The transparent multilayer film according to claim 15, wherein the polyethylene is biomass-derived polyethylene. A package comprising the transparent multilayer film according to claim 1 or 2.

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