JP2021122967A - Laminate film, packaging material, and package - Google Patents

Abstract

To provide a laminate film that makes it possible to obtain excellent heat sealability, and excellent releasability from a to-be-packaged material.SOLUTION: A laminate film 100 has a substrate layer 120 and a release layer 110, which are layered in this order. A surface 11 of the laminate film 100 on the release layer 110 side has a surface free energy (Eb) of 25-45 mJ/m2. When a surface 12 of the laminate film 100 on the release layer 120 side and the surface 11 of the laminate film 100 on the release layer 110 side are heat-sealed at 140°C, the heat seal strength is 1.0 N/15 mm or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to laminated films, packaging materials, and packaging bodies.

Various packaging materials have been developed that are intended to package articles such as foods, pharmaceuticals, and electronic parts that have problems with aging and storage stability. These packaging materials are widely sealed by heat sealing for the purpose of improving the storage stability and protection of the object to be packaged. Further, as the performance required for the packaging material, peelability to the object to be packaged and the like are required.

For example, in Patent Document 1, the heat-sealing layer is specified in a packaging laminated film in which a base material layer and a heat-sealing layer are laminated in order to achieve both releasability to sliced cheese and heat-sealing property at a low temperature. It is disclosed that the saturated copolymer polyester and the release agent of the above are contained in a specific amount.

JP-A-2019-156441

Conventionally, various studies have been made on packaging materials. However, as a result of the examination by the present inventor, in the conventional packaging material as disclosed in Patent Document 1, by containing a specific amount of the saturated copolymer polyester and the release agent, the cheese is not denatured at a low temperature. It was found that there is room for improvement in terms of achieving both heat-sealability and releasability at high temperatures, focusing only on obtaining heat-sealability.

The present invention has been made in view of such circumstances. That is, one of the objects of the present invention is to provide a laminated film having good heat-sealing property and good peelability to an object to be packaged.

As a result of diligent studies, the present inventors have found that the following inventions can be made and the above problems can be achieved.

The present invention is as follows.
[1]
A laminated film in which (a) a base material layer and (b) a release layer are laminated in this order.
The surface free energy (Eb) of the surface of the laminated film (b) on the release layer side is 25 to 45 mJ / m ² .
The heat-sealing strength when the surface of the laminated film (a) on the base material layer side and the surface of the laminated film (b) on the release layer side are heat-sealed at 140 ° C. is 1.0 N / 15 mm or more. , Laminated film.
[2]
A laminated film in which (a) a base material layer and (b) a release layer are laminated in this order.
The surface free energy (Eb) of the surface of the laminated film (b) on the release layer side is 25 to 45 mJ / m ² .
(B) A laminated film having a heat-sealing strength of 0.5 N / 15 mm or more when the surfaces on the release layer side of the laminated film are heat-sealed at 140 ° C.
[3]
A laminated film in which (a) a base material layer and (b) a release layer are laminated in this order.
The laminated film according to [1] or 2, wherein the heat-sealing strength of the laminated film (a) when the surfaces on the base material layer side are heat-sealed at 140 ° C. is 9.0 N / 15 mm or more.
[4]
The laminated film according to any one of [1] to [3], wherein the haze value when four of the laminated films are laminated is 20% or less.
[5]
(B) The laminated film according to any one of [1] to [4], wherein the release layer contains an ethylene / α-olefin random copolymer.
[6]
(A) The laminated film according to any one of [1] to [5], wherein the substrate layer is a polyolefin film.
[7]
(B) The laminated film according to any one of [1] to [6], wherein the thickness of the release layer is 0.01 μm or more and 1.0 μm or less.
[8]
The ratio (Ea / Eb) of the surface free energy (Ea) of the surface of the laminated film (a) on the substrate layer side to the surface free energy (Eb) of the surface of the laminated film (b) on the release layer side. The laminated film according to any one of [1] to [7], wherein is 0.9 to 1.3.
[9]
The laminated film according to any one of [1] to [8], which is used for food packaging.
[10]
A packaging material using the laminated film according to any one of [1] to [9].
[11]
A packaging body in which an article is packaged using the packaging material according to [10].

According to the present invention, it is possible to provide a laminated film having good heat-sealing property and good peelability to an object to be packaged.

It is sectional drawing which shows typically the laminated film which concerns on this embodiment. It is a schematic diagram for showing the procedure of wrapping using the laminated film which concerns on this embodiment. It is a figure which shows the TEM image of the cross section of the laminated film of an Example.

Hereinafter, embodiments of the present invention will be described in detail.
In all drawings, similar components are designated by the same reference numerals, and description thereof will be omitted as appropriate. In order to avoid complication, when there are a plurality of the same components in the same drawing, only one of them is coded and all of them are not coded, and especially in FIGS. 2 and later, FIG. The same components as in may not be re-signed. All drawings are for illustration purposes only. The shape and dimensional ratio of each member in the drawing do not necessarily correspond to the actual article.

In the present specification, the notation "a to b" in the description of the numerical range means a or more and b or less unless otherwise specified.
In the notation of a group (atomic group) in the present specification, the notation that does not indicate whether it is substituted or unsubstituted includes both those having no substituent and those having a substituent. For example, the "alkyl group" includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group). The notation "(meth) acrylic" herein represents a concept that includes both acrylic and methacrylic. The same applies to similar notations such as "(meth) acrylate".

<Laminated film>
FIG. 1 is a cross-sectional view schematically showing a laminated film 100 according to the present embodiment.
As shown in FIG. 1, in the laminated film 100, the base material layer 120 and the release layer 110 are laminated in this order. In the laminated film 100, the surface 11 on the release layer 110 side is the packaged object side, and the surface 12 on the base material layer 120 side is the outside.
In the present embodiment, the releasability of the laminated film 100 means that the laminated film 100 has at least at least the object to be packaged even after the packaged object is packaged using the laminated film 100 and the packaging state is stabilized. It is intended to suppress the adhesion of a part of the film and to have good releasability (releasability).

[Heat seal strength]
The laminated film 100 of the present embodiment has a heat-sealing strength a when the surface 12 on the base material layer 120 side of the laminated film 100 and the surface 11 on the release layer 110 side of the laminated film 100 are heat-sealed at 140 ° C. It is 0.5 N / 15 mm or more, and preferably 1.0 N / 15 mm or more. On the other hand, the upper limit of the heat seal strength a is not particularly limited, but from the viewpoint of maintaining good peelability, 20 N / 15 mm or less is preferable, and 15 N / 15 mm or less is more preferable.
Good heat-sealing properties can be obtained on the surfaces 11 and 12 of the laminated film 100, in other words, the front surface and the back surface (inner side surface and outer surface) of the packaging material, so that the front surface and the back surface of the packaging material overlap each other. It can be performed. For example, when the bun is wrapped with the laminated film 100 so as to cover it from above and bound on the lower side of the bun, the front surface and the back surface of the laminated film 100 are randomly folded without distinction on the lower surface. Therefore, by heat-sealing the folded surface, the region where the front surface and the back surface of the laminated film 100 overlap can be brought into close contact with each other.

In the present embodiment, the laminated film 100 can achieve both heat sealability and peelability by combining the heat seal strength a and the surface free energy (Eb) described later and controlling both within a specific numerical range.

In the laminated film 100 of the present embodiment, the heat seal strength b when the surfaces 11 on the release layer 110 side of the laminated film 100 are heat-sealed at 140 ° C. is 0.3 N / 15 mm or more, and 0.5 N / 15 mm. The above is preferable. On the other hand, the upper limit of the heat seal strength b is not particularly limited, but from the viewpoint of maintaining good peelability, 20 N / 15 mm or less is preferable, and 15 N / 15 mm or less is more preferable.
Since good heat-sealing properties can be obtained between the surfaces 11 of the laminated film 100, in other words, between the back surfaces (inner surfaces) of the packaging material, it is possible to perform packaging such that the back surfaces of the packaging materials overlap, or to manufacture a packaging material. It is possible to expand the variety of packaging to manufacture bags of various shapes, and to handle a wide variety of packaging methods.
For example, when a bag-shaped packaging material is manufactured using the laminated film 100, the laminated film 100 is formed into a tubular shape so that the surface 11 on the release layer 110 side is on the inside, and both end portions are heat-sealed, and then the upper and lower surfaces are formed. One of the openings can be heat-sealed so that the surfaces 11 are stuck together to form a bag shape.

In the present embodiment, the laminated film 100 can achieve both heat sealability and peelability by combining the heat seal strength b and the surface free energy (Eb) described later and controlling both within a specific numerical range.

Further, in the laminated film 100 of the present embodiment, the heat sealing strength c when the surfaces 12 on the base material layer 120 side of the laminated film 100 are heat-sealed at 140 ° C. is preferably 5N / 15mm or more, and 10N / It is more preferably 15 mm or more. On the other hand, the upper limit of the heat seal strength c is not particularly limited, but from the viewpoint of maintaining good peelability, 20 N / 15 mm or less is preferable, and 15 N / 15 mm or less is more preferable.
Since good heat-sealing properties can be obtained between the surfaces 12 of the laminated film 100, in other words, the surfaces (outer surfaces) of the laminated film 100, the surfaces of the packaging materials can be overlapped with each other, or the packaging material can be manufactured. It is possible to expand the variety of packaging to manufacture bags of various shapes, and to handle a wide variety of packaging methods.
I can.

Since the laminated film 100 of the present embodiment has the above-mentioned good heat-sealing strengths a to c, it is possible to cope with various types of packaging by combining the heat-sealing properties of each surface.
Further, the heat seal strengths a to c of the laminated film 100 can be adjusted by controlling the selection and combination of the raw materials of the base material layer 120 and the release layer 110, which will be described later, and the thickness of each layer.

[Surface free energy]
In the present embodiment, the ratio (Ea) of the surface free energy (Ea) of the surface 12 on the base material layer 120 side of the laminated film 100 to the surface free energy (Eb) of the surface 11 on the release layer 110 side of the laminated film 100 (Ea). / Eb) is preferably 0.9 to 1.3, and more preferably 0.95 to 1.1.
Here, it is generally known that when the surface free energy is reduced, it becomes difficult for water to adhere to the surface, and the releasability for a material containing water increases.
The smaller the ratio (Ea / Eb), the smaller the difference in surface free energy between the surfaces 12 and 11.
When the laminated film 100 of the present embodiment contains a fatty acid amide, the fatty acid amide segregates on the surfaces 12 and 11 to the same extent, and the fatty acid amide is separated from the base material layer 120 and the release layer as a whole of the laminated film 100. It will be unevenly distributed through 110. As a result, in the laminated film 100 of the present embodiment, better releasability can be easily obtained. Although the details of the reason are not clear, it is presumed that when the affinity between the fatty acid amide and the packaged product is low, the releasability between the fatty acid amide and the packaged product is improved. Further, when the affinity between the fatty acid amide and the packaged object is high, the adhesion between the fatty acid amide and the release layer is small, so that the releasability between the fatty acid amide and the release layer is improved. Alternatively, it is presumed that the releasability due to agglomeration and exfoliation between the unevenly distributed fatty acid amides was improved.
In the present embodiment, the surface 12 on the base material layer 120 side of the laminated film 100 is the uncoated surface of the base material layer 120. The coated surface of the base material layer 120 is a surface on which the release layer 120 is laminated after being subjected to corona treatment in the manufacturing process of the release film 100 of the present embodiment, and the non-coated surface is defined as a non-coated surface. , Show the surface opposite to the coated surface.

In the present embodiment, the surface free energy of the substrate layer 120 side surface 12 of the laminated film 100 (Ea) is preferably 25~45mJ / ^{m 2,} and more preferably 30~40mJ / ^{m 2} ..
By setting the surface free energy (Ea) to the above lower limit value or more, it is possible to improve the heat sealability and the film forming property while maintaining the releasability. On the other hand, by setting the surface free energy (Ea) to the above upper limit value or less, the releasability can be improved.

In the present embodiment, the surface free energy of the release layer 110 side surface 11 of the laminated film 100 (Eb) is preferably 25~45mJ / ^{m 2,} and more preferably 30~40mJ / ^{m 2} ..
By setting the surface free energy (Eb) to the above lower limit value or more, it is possible to improve the heat sealability and the film forming property while maintaining the releasability. On the other hand, by setting the surface free energy (Eb) to the above upper limit value or less, the releasability can be improved.

The surface free energy can be calculated based on the contact angle measured using a contact angle meter, for example, "Drop Master DM701" manufactured by Kyowa Interface Science Co., Ltd. Details will be described later.

Further, the surface free energy can be controlled by subjecting the laminated film 100 to a surface treatment, adjusting the raw materials and the thickness of the base material layer 120 and the release layer 110, and the like.

[Haze]
The laminated film 100 of the present embodiment preferably has a haze value of 20% or less, more preferably 16% or less, and further preferably 13% or less when four laminated films 100 are laminated. ..
As a result, the visibility of the formed package can be improved. The haze value of the laminated film 100 can be adjusted by the draw ratio of the base material layer 120, the thickness of each layer, and the like.
The haze value can be measured according to JIS K-7136.

Hereinafter, each layer of the laminated film 100 will be described in detail.

[Base layer 120]
Various known thermoplastic resins can be used for the base material layer 120 constituting the present embodiment. Examples of the thermoplastic resin include polyolefins (polyethylene, polypropylene, poly4-methyl / 1-pentene, poly1-butene, etc.), polyesters (polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyamides (nylon-6). , Nylon-66, polymethoxylen adipamide, etc.), polyvinyl chloride, polyimide, ethylene / vinyl acetate copolymer or its saponified product, polyvinyl alcohol, polyacrylonitrile, polycarbonate, polystyrene, ionomer, or a mixture thereof. It is a film that becomes.
Among these thermoplastic resins, a film made of polyester, polyamide, or polyolefin is preferable, and a film made of polyolefin is preferable, from the viewpoint of improving the transparency of the packaging material.

The base material layer 120 may be a non-stretched film, a uniaxial or biaxially stretched film, or may be a single layer or a multilayer of two or more layers.

The base material layer 120 is more preferably a film made of unstretched polyethylene and polypropylene from the viewpoint of obtaining good releasability. As a result, the releasability is improved, and good heat sealability to the base material layer 120 and the releasable layer 110 can be obtained.

Further, the base material layer 120 preferably contains a fatty acid amide. As a result, the fatty acid amide is likely to segregate on the surface 11 of the laminated film 100, and is unevenly distributed in the laminated film 100 so as to pass through the release layer 110, so that the releasability can be further improved.

The surface (coated surface) of the base material layer 120 is subjected to, for example, corona treatment, plasma treatment, undercoat treatment, primer coating treatment, and frame treatment in order to improve the adhesiveness with the release layer 110 described later. Such surface activation treatment may be performed.

The thickness of the base material layer 120 is not particularly limited, but is preferably in the range of 10 to 200 μm, more preferably 12 to 100 μm, and further preferably 15 to 50 μm from the viewpoint of obtaining good packaging and releasability. ..

[Release layer 110]
The release layer 110 serves as a surface on the side to be packaged, and is used to prevent the object to be packaged from adhering to the laminated film 100 and reducing the releasability.

The material of the release layer 110 preferably contains an ethylene / α-olefin random copolymer. As a result, the releasability is improved, and good heat sealability to the base material layer 120 and the releasable layer 110 can be obtained.
As the above-mentioned α-olefin of the ethylene / α-olefin random copolymer, α-olefin having 3 or more carbon atoms is preferable, α-olefin having 3 to 10 carbon atoms is more preferable, and propylene, 1-butene, 1- More preferably, they are hexene, 4-methyl-1-pentene, 1-octene, and 1-decene.

The density of the ethylene / α-olefin random copolymer is preferably 850 to 950 kg / m ³ , and more preferably 860 to 900 g / m ³ . By setting the density of the ethylene / α-olefin random copolymer in such a numerical range, it becomes easy to obtain good releasability while obtaining adhesion to the base material layer 120.

The melting point (Tm) of the ethylene / α-olefin random copolymer is preferably 50 to 90 ° C, more preferably 55 to 85 ° C or lower, and further preferably 60 to 80 ° C.
By setting the melting point (Tm) to be equal to or higher than the above lower limit value, the melting point of the laminated film 100 can be made higher than the temperature at which the laminated film 100 is exposed in the manufacturing process including the packaging step, whereby the package to be packaged. Adhesion to objects is suppressed, and good releasability can be easily obtained.
On the other hand, by setting the melting point (Tm) to be equal to or lower than the above upper limit value, it is possible to maintain good mold releasability while improving handleability and productivity.

In the present embodiment, the ethylene / α-olefin random copolymer is usually in the range of 70 to 92 mol%, although the ethylene content is not particularly limited as long as the density and melting point (Tm) are in the above ranges. ..

In the present embodiment, the ethylene / α-olefin random copolymer has an MFR (load: 2160 g, temperature: 190 ° C.) of preferably 0.1 to 50 g / 10 minutes, more preferably 0.2 to 20 g. The range is / 10 minutes.

In the present embodiment, the durometer A hardness of the ethylene / α-olefin random copolymer is preferably in the range of 50 to 150, more preferably in the range of 65 to 100. By setting the durometer A hardness within the above numerical range, appropriate flexibility can be obtained, stress applied to the packaged object can be reduced, excessive adhesion to the packaged object can be suppressed, and good peelability can be obtained. It will be easier to obtain.

The ethylene / α-olefin random copolymer of the present embodiment can be produced by using various known production methods. Specific examples thereof include a method of randomly copolymerizing ethylene and α-olefin using a vanadium catalyst or a metallocene catalyst.

The thickness of the release layer 110 is preferably in the range of 0.01 to 1.0 μm or less, more preferably 0.02 to 0.09 μm, and further preferably 0.03 to 0.08 μm.
By setting the thickness of the release layer 110 to the above lower limit value or more, the adhesion to the base material layer 120 is improved while maintaining good releasability. On the other hand, by setting the thickness of the release layer 110 to be equal to or less than the above upper limit value, the releasability can be easily improved, the thickness of the entire laminated film 100 can be reduced, appropriate flexibility can be obtained, and the wrapping property is good. Can be done.

<Manufacturing method of laminated film>
The laminated film 100 can be manufactured by applying and drying a solution in which a material constituting the release layer 110 is dissolved on one side of a base material layer 120 obtained in advance to form the release layer 110.
The solvent used to prepare the solution of the ethylene / α-olefin random copolymer (A) is not particularly limited, but is not particularly limited, but is limited to aliphatic hydrocarbons such as n-decane, n-heptane, and n-hexane, toluene, xylene, and the like. Examples thereof include aromatic hydrocarbons such as, alicyclic hydrocarbons such as decalin and tetralin, organic solvents such as methyl ethyl ketone and methyl isobutyl ketone, and mixed solvents thereof.

As a method of applying a solution in which the material constituting the release layer 110 is dissolved in the base material layer 120, a method of applying the solution to the surface of the base material layer 120, a method of immersing the base material layer 120 in the solution, and a method of immersing the base material layer 120 in the solution. Various known methods such as a method of spraying the solution on the surface of the base material layer 120 can be adopted.

Examples of the above coating method include an air knife coater, a direct gravure coater, a gravure offset, an arc gravure coater, a gravure coater such as a gravure reverse and a jet nozzle method, a top feed reverse coater, a bottom feed reverse coater and a nozzle feed reverse. Examples thereof include a method using various known coating machines such as a reverse roll coater such as a coater, a five-roll coater, a lip coater, a bar coater, a bar reverse coater, and a die coater.

The coating temperature of the solution can be usually in the temperature range of normal temperature, for example, 10 to 40 ° C., preferably 15 to 30 ° C., but the material constituting the release layer 110 is difficult to dissolve in the solvent at room temperature. In some cases, the temperature may be lower than the boiling point, depending on the solvent used.

The applied solution is usually dried at a temperature of 60 to 120 ° C., preferably 80 to 100 ° C. for usually 1 to 30 seconds, preferably 2 to 10 seconds.

[Use]
The laminated film 100 can be widely applied to materials having a problem of releasability from the packaging material, and is particularly suitable for food packaging. Examples of foods include those containing a relatively large amount of water (free water) on the surface. Specifically, for example, castella, cakes, buns, sweet potatoes, sakura mochi, biscuits and cookies with a thin chocolate coating on the surface. , Shredded or frozen pizza dough with powdered cheese pieces attached. From the viewpoint of the water activity value of the food, for example, it may be preferably 0.5 or more, more preferably 0.7 or more, still more preferably 0.8 or more. The water activity value is a numerical value indicating the amount of free water contained in the food, and 1 is the maximum value. The higher the water activity value, the more free water that is not bound to salt, sugar, etc. in food.

The form of packaging may be individual packaging found in buns and the like. In addition, the packaging includes various aspects in which the laminated film 100 and the object to be packaged come into contact with each other at least. For example, the packaging includes a mode in which the laminated film 100 is used as an underlay of the object to be packaged, a mode in which only the side surface or the upper surface of the object to be packaged is covered with the laminated film 100, and the like.

<Packaging material, packaging body>
The packaging material using the laminated film 100 can be appropriately designed according to the packaging form. For example, the laminated film 100 is cut to a desired size, the object to be packaged is covered, and the laminated film 100 is heat-sealed and sealed. A bag is created using the laminated film 100, and the inside of the bag is formed. Examples include those that accommodate the items to be packaged. From the viewpoint of obtaining good releasability, the packaging material preferably has the released layer 110 of the laminated film 100 on the side to be packaged.

The package is an article packaged using the above-mentioned packaging material. When the package of the present embodiment is opened and the article is taken out, good releasability between the article and the packaging material can be obtained.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above can be adopted.

Next, the present invention will be described in detail by way of examples, but the content of the present invention is not limited to the examples.

<Example 1>
First, pellets of ethylene / α-olefin random copolymer A (density 885 kg / m ³ , melting point 66 ° C., MFR 18 (190 ° C.), A hardness 86) are mixed with a mixed solvent (toluene: hexane: MEK = 5: 5: 1). , Weight ratio) was weighed so that the solid content was 0.8 wt%, and the pellets were dissolved at 80 ° C. for 30 minutes to prepare a coating liquid.
Next, a non-stretched polypropylene film with corona treatment applied to the coated surface side (thickness 18 μm: tensile modulus (MD direction and TD direction) (measured according to JISK7161 (2014)) 665 MPa, tensile elongation (JISK7127 (JISK7127) Measured according to 1999)) MD direction: 255%, TD direction: 775%, containing erucic acid amide) is aged at 40 ° C. for 1 day, and the above coating liquid is dried and then applied. The film was coated with a bar coat so that the amount was 0.05 g / m ² , dried at 90 ° C. for 5 seconds to form a release layer, and an aging period was provided at 40 ° C. for 1 day to obtain a release film having a laminated structure. rice field.

<Example 2>
Instead of ethylene / α-olefin random copolymer A, ethylene / α-olefin random copolymer B (density 893 kg / m ³ , melting point 77 ° C., MFR 3.6 (190 ° C.), A hardness 92) was used. A release film was obtained in the same manner as in Example 1 except for the above.

<Example 3>
Instead of ethylene / α-olefin random copolymer A, ethylene / α-olefin random copolymer C (density 885 kg / m ³ , melting point 66 ° C., MFR 3.6 (190 ° C.), A hardness 86) was used. A release film was obtained in the same manner as in Example 1 except for the above.

<Comparative example 1>
A platinum catalyst (CAT-PL-50T) was added to 100 parts of a silicone release agent (X-62-1112, manufactured by Shin-Etsu Chemical Co., Ltd.) in a mixed solvent (toluene: hexane: MEK = 3: 5: 2, weight ratio). A coating liquid was prepared by weighing so that the solid content composed of 3 parts was 3 wt%. Next, the coating amount after drying the above coating liquid on the corona-treated surface of the unstretched polypropylene film (thickness 18 μm: CPP # 18 manufactured by DIC Corporation) as the base material layer is 0.2 g / m ^2. The film was coated with a bar coat and dried at 90 ° C. for 5 seconds to form a release layer (thickness 0.2 μm) to obtain a release film having a laminated structure.

The following measurements and evaluations were performed using each of the obtained release films. The results are shown in Table 1.

[measurement]
・ Heat seal strength (release layer / base material layer)
Two release films cut into strips having a width of 70 mm and a length of 70 mm were prepared as test pieces. Next, the two prepared test pieces were superposed so that the surface of the release layer, that is, the coated surface and the surface of the base material layer, that is, the non-coated surface face each other, and then a heat seal tester (Tester Sangyo Co., Ltd.) Heat sealing is performed using TP-701-B) under the conditions of an upper temperature (heat seal temperature) of 140 ° C., a lower temperature of 25 ° C., a seal width of 10 mm, a seal pressure of 0.2 MPa, and a seal time of 1 second. rice field.
Next, the heat-sealed film was taken out from the testing machine and cut into a width of 15 mm. Using a Tensilon universal tester (RTC-1225, manufactured by Orientec Co., Ltd.), this heat-sealed film with a width of 15 mm was subjected to the maximum value of peel strength under the conditions of a tensile speed of 300 mm / min and a temperature of 23 ° C. It was measured. Then, this maximum value was taken as the heat seal strength (unit: N / 15 mm). The heat seal strength was measured for three test pieces, and an average value was calculated.

・ Heat seal strength (release layer / release layer)
The heat seal strength (unit: N / 15 mm) was calculated in the same manner as the above heat seal strength (release layer / base material layer) except that the release layer and the release layer were overlapped so as to face each other.

・ Heat seal strength (base material layer / base material layer)
The heat seal strength (release layer / base material layer) is the same as the heat seal strength (release layer / base material layer) except that the surface of the base material layer and the surface of the base material layer, that is, the uncoated surfaces are overlapped so as to face each other. Unit: N / 15 mm) was calculated.

-Surface free energy First, using DM-701 manufactured by Kyowa Interface Science Co., Ltd., a droplet (about 2 μl) of a solvent (water, diiodomethane, 1-bromonaphthalene) is released from a syringe under a 50% RH environment at 23 ° C. It was placed on each surface of the film (the surface of the release layer, that is, the coated surface and the surface of the base material layer, that is, the uncoated surface), and the angle (θ) formed by the tangent line at the end of the droplet and each surface was measured. ..
Next, the surface free energy was calculated by the following Kitazaki-Hata theory.
It is assumed that the surface free energy consists of a dispersion component γd, a polar component γp, and a hydrogen bond component γh. At this time, the surface free energy γ is represented by the following equation (1).
γ = γd + γp + γh (1)
The relationship between the surface free energy γL of the liquid, the surface free energy γS of the solid, and the contact angle θ is expressed by the following equation (2).
γL (1 + cosθ) = 2 (γSdγLd) 1/2 + 2 (γSpγLp) 1/2 + 2 (γShγLh) 1/2 (2)
Here, γS can be obtained by measuring the contact angle θ of each of three types of liquids having known γL components and solving simultaneous equations relating to γSd, γSp, and γSh.

-The haze release film was folded in four and measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH5000) in accordance with the method described in JIS K7136.

-Tape peeling force Polyester adhesive tape (Nitto Denko Co., Ltd.) in which each release film is placed on a horizontal table with the release layer facing up and has an acrylic adhesive layer on the surface of the release layer, that is, the coated surface. Acrylic adhesive layer of product No. 31B) was attached, cut to a size of 200 mm x 50 mm, and a load was placed ^{on the polyester adhesive tape so that it was 20 g / cm 2 at 40 ° C.} Aged for 20 hours.
After aging, 180 ° peeling was performed at a tensile speed of 300 m / min with a tensile tester, and the value obtained by dividing the average peeling load in the region where the peeling was stable by the polyester adhesive tape width was determined as the tape peeling force [N / 50 mm]. ..

[evaluation]
-Evaluation of releasability (peeling property) A brown sugar bun (commercially available, manufactured by Yamazaki Bread Co., Ltd.) individually wrapped with a transparent film was prepared, and the wrapping film was peeled off so as not to damage the thin skin of the brown sugar bun. Next, heating was performed with an oven range NE-MS232 manufactured by Panasonic Corporation so that the surface temperature of the brown sugar bun was 50 ° C. The surface temperature was measured using a radiation thermometer TDH-330 manufactured by TRUSCO NAKAYAMA Co., Ltd.
Next, the brown sugar bun was packaged as shown in FIG. The heated brown sugar bun 10 obtained above is packaged so that the release layer 120 of the 180 mm square release film 100 prepared in advance is in contact with the brown sugar bun 10, and the release film 100 is placed on the lower surface of the brown sugar bun 100. Was bound (FIGS. 2 (a) and 2 (b)). Then, the brown sugar bun 10 was placed on a horizontal table so as to maintain the packaging form under its own weight, and stored in an environment of 25 ° C. for one day (FIG. 2 (c)).
After storage for 1 day, the release film is peeled off from the brown sugar bun, and if no thin skin remains on the release layer in contact with the curved surface of the brown sugar bun on the release film side, 〇, the thin skin remains, but the brown sugar bun When the thin skin residual rate exceeded 95%, it was evaluated as Δ, and when the thin skin remained, and the thin skin residual rate of brown sugar bun was 95% or less, it was evaluated as ×. The thin skin is a region excluding the back surface (lower surface) of the brown sugar bun, and is a surface layer covering the curved surface portion.

-TEM observation To protect the surface, a metal-coated sample is embedded in epoxy resin, stained with ruthenium tetroxide, and then a section with a thickness of about 100 nm is prepared with an ultramicrotome, and a transmission electron microscope (transmission electron microscope) is used. A cross-sectional observation image of the release film was obtained with H-7650) manufactured by Hitachi High-Technologies Corporation. The results are shown in FIG.
In FIG. 3, the region where the gray color is strong indicates the release layer (release layer), the region where the gray color is light indicates the base material layer, and the linear black color seen in the upper part of the release layer indicates the metal coat layer. Shown. From FIG. 3, it is presumed that the release layer has a two-layer structure with regions having different shades in the vertical direction.

100 Laminated film 110 Release layer 120 Base material layer

Claims (11)

A laminated film in which (a) a base material layer and (b) a release layer are laminated in this order.
The surface free energy (Eb) of the surface of the laminated film (b) on the release layer side is 25 to 45 mJ / m ² .
The heat-sealing strength when the surface of the laminated film (a) on the base material layer side and the surface of the laminated film (b) on the release layer side are heat-sealed at 140 ° C. is 1.0 N / 15 mm or more. , Laminated film. A laminated film in which (a) a base material layer and (b) a release layer are laminated in this order.
The surface free energy (Eb) of the surface of the laminated film (b) on the release layer side is 25 to 45 mJ / m ² .
(B) A laminated film having a heat-sealing strength of 0.5 N / 15 mm or more when the surfaces on the release layer side of the laminated film are heat-sealed at 140 ° C. A laminated film in which (a) a base material layer and (b) a release layer are laminated in this order.
The laminated film according to claim 1 or 2, wherein the heat-sealing strength of the laminated film (a) when the surfaces on the base material layer side are heat-sealed at 140 ° C. is 9.0 N / 15 mm or more. The laminated film according to any one of claims 1 to 3, wherein the haze value when four of the laminated films are laminated is 20% or less. (B) The laminated film according to any one of claims 1 to 4, wherein the release layer contains an ethylene / α-olefin random copolymer. (A) The laminated film according to any one of claims 1 to 5, wherein the base material layer is a polyolefin film. (B) The laminated film according to any one of claims 1 to 6, wherein the release layer has a thickness of 0.01 μm or more and 1.0 μm or less. The ratio (Ea / Eb) of the surface free energy (Ea) of the surface of the laminated film (a) on the substrate layer side to the surface free energy (Eb) of the surface of the laminated film (b) on the release layer side. The laminated film according to any one of claims 1 to 7, wherein the film is 0.9 to 1.3. The laminated film according to any one of claims 1 to 8, which is used for food packaging. A packaging material using the laminated film according to any one of claims 1 to 9. A packaging body in which an article is packaged using the packaging material according to claim 10.

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