JP2018176670A - Laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated film having an outer layer, a barrier layer, an intermediate layer and a sealant layer, in which cracking of the barrier layer due to ultrasonic sealing is suppressed and excellent in straight-line cutability. SOLUTION: The laminated film 10 has an outer layer 1, a barrier layer 2, an intermediate layer 3, and a sealant layer 4 in this order. The barrier layer 2 includes a metal foil layer, and the intermediate layer 3 is JIS K. The crystallinity calculated as the ratio of the heat of fusion obtained from the DSC curve drawn in accordance with 7121 to the heat of fusion of the perfect crystal is 28.0% or more, and in accordance with JIS K 7127. The laminated film 10 in which the ratio of the measured tensile elastic modulus in the TD direction to the tensile elastic modulus in the MD direction is 0.7 or more and 1.2 or less. [Selection diagram] Fig. 1

Description

  The present invention relates to a laminated film.

  Ultrasonic sealing is known as a method of sealing a laminated film to form a packaging bag for packaging food, seasonings, medicines, supplements and the like. The ultrasonic seal is a technique of causing two sealant films of the innermost layer of the laminated film to vibrate and causing friction heat generated thereby to fuse the two laminated films.

  The ultrasonic seal uses frictional heat, so the heat does not fuse around the seal portion. Unlike heat sealing in this respect, it is excellent in precise controllability of the sealing portion. Moreover, since vibration is applied at the time of sealing, it is possible to seal while avoiding the contents. Therefore, it is excellent in dirt sealability.

  The laminated film used for packaging bags, such as foodstuffs, is comprised by laminating | stacking the layer which has various functions. The laminated film typically has an outer layer, a barrier layer, and a sealant layer. The outer layer has, for example, a function of protecting the package and the contents from physical impact. The barrier layer has a function of, for example, suppressing the entry of gas (especially oxygen), moisture, and light from the outside, and protecting the contents. The sealant layers can be fused together and have the function of sealing the packaging bag.

  A metal foil is often used as the barrier layer in the laminated film for a package. When ultrasonically sealing a laminated film including a metal foil, in particular, an aluminum foil as a barrier layer, cracks or cracks may occur in the metal foil. When a crack is generated in the metal foil as the barrier layer, the cracked part appears dark and the appearance becomes poor. Furthermore, the contents caught in the seal part may leak to the outside when the foreign matter is sealed.

  Patent Document 1 pointed out that, in the prior art, a method for sufficiently preventing a crack of a metal foil as a barrier layer at the time of ultrasonic sealing was not performed, and then an outer layer, an aluminum foil layer (barrier layer In a three-layer tube laminate comprising an inner layer (a sealant layer) and an inner layer (a sealant layer), a technique is disclosed that suppresses the cracking of an aluminum foil layer at the time of ultrasonic sealing.

  In recent years, in the field of packaging bags for food and the like, there is a high demand for improving mechanical strength such as pressure resistance and piercing strength of packaging bags. Therefore, a laminated film having a four-layer structure is known in which an intermediate layer made of a crystalline resin is added to the three layers of the outer layer, the barrier layer, and the sealant layer. Non-Patent Document 1 is known as a reference on the crystallinity of a resin used as an intermediate layer.

JP, 2015-58649, A

THERMAL APPLICATIONS NOTE Polymer Heats of Fusion, Roger L. Blaine TA Instruments, 109 Lukens Drive, New Castle DE 19720, USA

  An object of the present invention is to provide a laminated film having an outer layer, a barrier layer, an intermediate layer, and a sealant layer, in which cracking of the barrier layer due to ultrasonic sealing is suppressed.

  The present invention is as follows.

[1] A laminated film having an outer layer, a barrier layer, an intermediate layer, and a sealant layer in this order,
The barrier layer comprises a metal foil layer,
The intermediate layer has a crystallinity of 28.0% or more, which is calculated as a ratio of the heat of fusion obtained from the DSC curve drawn according to JIS K 7121 to the heat of fusion of a perfect crystal, and The ratio of the tensile modulus in the TD direction to the tensile modulus in the MD direction measured according to JIS K 7127 is 0.7 or more and 1.2 or less.
Laminated film.
[2] The laminated film according to [1], wherein the heat of fusion measured by DSC according to JIS K 7121 for the intermediate layer is 65.0 mJ / mg or more.
[3] The laminated film according to [1] or [2], wherein the intermediate layer comprises a nylon film.
[4] The laminated film according to any one of [1] to [3], wherein the outer layer comprises an easily cut film.
[5] The laminated film according to [4], wherein the easily cut film is a uniaxially stretched polypropylene film.
[6] The laminated film according to any one of [1] to [5], wherein the layer thickness of the barrier layer is 10 μm or less.
[7] A method for producing a packaging bag, comprising ultrasonically sealing the sealant layers of the laminated film according to any one of [1] to [6].
[8] The method according to [7], wherein the total light transmittance of the ultrasonic sealing portion of the packaging bag is 0.50% or less as measured according to JIS K 7361-1.
[9] A packaging bag comprising the laminated film according to any one of [1] to [6] and including an ultrasonic seal portion.
[10] The packaging bag according to [9], having a total light transmittance of 0.50% or less measured in accordance with JIS K 7361-1 for the ultrasonic seal portion.

  The laminated film of the present invention is a laminated film having a configuration having an outer layer, a barrier layer, an intermediate layer, and a sealant layer, and cracking of the barrier layer due to ultrasonic sealing is suppressed. The laminated film of the present invention is excellent in easy-to-cut property according to the preferable mode. Therefore, the laminated film of the present invention is formed by using an ultrasonic seal, a packaging bag to be used by manual tearing, for example, a packaging bag for packaging food (eg, jelly etc.), seasonings, medicines, supplements, etc. To be suitable.

FIG. 1 is a schematic cross-sectional view showing the structure of the laminated film of the present invention. FIG. 2 is a schematic view for explaining the outline of a sample prepared to measure the total light transmittance in Examples and Comparative Examples. FIG. 3 is a photograph showing a state in which a crack is generated in the barrier layer by ultrasonic sealing in Comparative Example 5. FIG. 4 is a photograph showing the state of the sample after ultrasonic sealing obtained in Example 1.

The laminated film of the present invention is
A laminated film having an outer layer, a barrier layer, an intermediate layer, and a sealant layer in this order,
The barrier layer comprises a metal foil layer,
For the intermediate layer, the degree of crystallinity calculated as the ratio of the heat of fusion obtained from the DSC curve drawn according to JIS K 7121 to the heat of fusion of the fully crystallized product is 28.0% or more, and JIS The ratio of the tensile modulus in the TD direction to the tensile modulus in the MD direction measured according to K 7127 is 0.7 or more and 1.2 or less.

  Hereinafter, the laminated film of the present invention and a packaging bag made into a bag using the same will be described in detail by way of a preferred embodiment (hereinafter referred to as "the present embodiment") as an example.

<Laminated film>
The schematic sectional drawing which shows the structure of the laminated | multilayer film of this embodiment in FIG. 1 was shown.

  The laminated film of this embodiment is a laminated film 10 having an outer layer 1, a barrier layer 2, an intermediate layer 3 and a sealant layer 4 in this order as shown in FIG.

In the laminated film of the present embodiment, the barrier layer 2 includes a metal foil layer,
The crystallinity of the intermediate layer 3 calculated as a ratio of the heat of fusion obtained from the DSC curve drawn in accordance with JIS K 7121 to the heat of fusion of the fully crystallized product is 28.0% or more, The ratio of the tensile modulus in the TD direction to the tensile modulus in the MD direction measured according to JIS K 7127 is 0.7 or more and 1.2 or less.

Outer layer
The outer layer in the laminated film of this embodiment has impact resistance for protecting the package and contents from physical impact applied after the production of the packaging bag, and preferably has barrier properties and is excellent in tearability. It is appropriate to be composed of an easily cut film.

  The material of the film constituting the outer layer in the present embodiment may be, for example, polypropylene, polyethylene terephthalate, nylon or the like. Preferred is an easily cut film selected from uniaxially stretched polypropylene, biaxially stretched polyethylene terephthalate, and biaxially stretched nylon, and particularly preferred is a uniaxially stretched polypropylene film.

  The layer thickness of the outer layer is not particularly limited. The layer thickness of the outer layer may be, for example, 7 μm or more, 8 μm or more, 9 μm or more, or 10 μm or more in order to give sufficient strength and good cuttability to the obtained packaging bag. On the other hand, the upper limit of the layer thickness of the outer layer is from the viewpoint of improving the visibility of the contents when the packed package is displayed, and the excessive damping of the ultrasonic vibration when applying the ultrasonic wave to the seal at the time of bag making. Or less, 45 μm or less, 40 μm or less, 35 μm or less, or 30 μm or less.

  A commercial item may be used as the outer layer in the present embodiment. As a commercial item of a polypropylene film, the brand name "MCMD-NBT" by Futamura Chemical Co., Ltd., the brand name "ASS" by Tokyo Ink Co., Ltd., etc. can be mentioned, for example.

[Barrier layer]
The barrier layer in the laminated film of the present embodiment is a layer having a function of suppressing the penetration of gas (especially oxygen), moisture, and light from the outside, and protecting the contents.

  The barrier layer in the laminated film of the present embodiment includes a metal foil layer. The material which comprises metal foil in a barrier layer may be aluminum etc., for example.

The barrier layer may consist only of a metal foil layer, or may be a laminate of a metal foil layer and a layer made of another material. The material other than the metal foil constituting the barrier layer may be, for example, silica, polyvinylidene chloride, polyvinyl alcohol and the like.

  The layer thickness of the barrier layer may be, for example, 1 μm or more, 3 μm or more, or 5 μm or more, and may be, for example, 50 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less. In the laminated film of the present embodiment, even when the layer thickness of the barrier layer is reduced, cracking of the barrier layer due to ultrasonic sealing is highly suppressed. Therefore, the layer thickness of the barrier layer may be 10 μm or less, or 8 μm or less, particularly 7 μm or less.

[Intermediate]
The middle layer in the laminated film of the present embodiment gives stiffness to the whole laminated film, improves mechanical strength such as pressure resistance and piercing strength of the laminated film to increase the tear strength, and in the case of ultrasonic sealing. May have the function of suppressing the above-mentioned cracking of the barrier layer.

  The intermediate layer may be made of a material having crystallinity because it is required to stiffen the laminated film and to improve the mechanical strength of the laminated film. Specifically, it is a material having a crystallinity of 28.0% or more, which is calculated as the ratio of the heat of fusion obtained from the DSC curve drawn according to JIS K 7121 to the heat of fusion of a completely crystalline form. You may

The DSC curve is drawn according to JIS K 7121 from the DSC data obtained at the first temperature increase carried out under the following conditions.
Sample amount: Approximately 5 mg precisely weighed Measuring atmosphere: in nitrogen Measuring range: from room temperature to 260 ° C. Heating rate: 10 ° C./min

As the crystallinity of the intermediate layer, a value calculated by the following equation (1) is adopted from the heat of fusion obtained from the above-mentioned DSC curve and the heat of fusion of a completely crystalline substance.
Crystallinity [%] = (heat of fusion determined by DSC / heat of fusion of completely crystallized product) × 100 (1)

  As the heat of fusion of a completely crystalline material, a literature value may be adopted, for example, Non-Patent Document 1 (THERMAL APPLICATIONS NOTE Polymer Heats of Fusion, Roger L. Blaine TA Instruments, 109 Lukens Drive, New Castle DE 19720, USA) Values described in are preferred.

  The crystallinity of the material of the intermediate layer may be 28.2% or more, 28.4% or more, 28.6% or more, 28.8% or more, or 29.0% or more.

  From the same viewpoint as above, the heat of fusion determined by the above method for the material of the intermediate layer is 65.0 mJ / mg or more, 66.0 mJ / mg or more, 67.0 mJ / mg or more, or 68.0 mJ / mg or more And may be 72.0 mJ / mg or less, 71.0 mJ / mg or less, or 70.0 mJ / mg or less.

When the in-plane anisotropy of the intermediate layer is high, under ultrasonic sealing conditions, the material of the intermediate layer moves intensively in a specific direction, and the barrier layer is subjected to stress concentration in a specific part, thereby generating a crack. It will be easier to do. In order to avoid this, it is desirable that the intermediate layer be isotropic in the plane. From this viewpoint, the ratio of the tensile elastic modulus in the TD direction to the tensile elastic modulus in the MD direction measured in accordance with JIS K 7127 may be 0.7 or more and 1.2 or less for the intermediate layer. The measurement of tensile modulus may be performed under the following conditions.
Sample shape: 15 mm × 150 mm strip sample thickness: 15 μm
Tension speed: 300 mm / min

  Since the material of the intermediate layer preferably has the same tensile modulus in the MD and TD as described above, the ratio of the tensile modulus in the TD to the tensile modulus in the MD is More preferably, it may be 0.8 or more or 0.9 or more, 1.1 or less or 1.0 or less.

  The tensile modulus in the MD direction and the tensile modulus in the TD direction of the material of the intermediate layer are each independently 1.5 GPa or more, 1.6 GPa or more, 1.7 GPa or more, 1.8 GPa or more, 1.9 GPa or more, or It may be 2.0 GPa or more, 3.0 GPa or less, 2.9 GPa or less, 2.8 GPa or less, 2.7 GPa or less, 2.6 GPa or less, or 2.5 GPa or less.

  The middle layer may, for example, consist of nylon film. The nylon film may be selected, for example, from nylon 6, nylon 66, copolymers of nylon 6 and nylon 66, etc., and blends thereof.

  The middle layer may consist of a stretched film. The stretching method may be a simultaneous biaxial stretching method, a sequential biaxial stretching method, a tubular stretching method or the like.

  The thickness of the intermediate layer may be 8 μm or more, 9 μm or more, 10 μm or more, 11 μm or more, or 12 μm or more, and may be 30 μm or less, 25 μm or less, 20 μm or less, 19 μm or less, or 18 μm or less.

[Sealant layer]
The sealant layer in the laminated film of the present embodiment is suitably made of a material that can be melted and fused together by friction caused by vibration upon application of ultrasonic waves.

  The sealant layer may be of a relatively hard material. When the sealant layer is a hard layer, when ultrasonic wave sealing of the laminated film is performed, damping of vibration due to the ultrasonic wave is suppressed and good foreign matter sealability is obtained.

  Specific examples of the material forming the sealant layer include, for example, low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene (PP), ethylene -Vinyl acetate copolymer, ionomer resin, ethylene (meth) acrylic acid copolymer, ethylene (meth) acrylic acid alkyl ester copolymer, ethylene-propylene copolymer (EPM), polymethylpentene, polybutene, etc. Can be mentioned. Among these, LLDPE is preferred because it exhibits good ultrasonic sealability, particularly good foreign matter sealability by the application of ultrasonic waves.

  The sealant layer may be a single layer or multiple layers.

  The thickness of the sealant layer may be 15 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more from the viewpoint of forming a strong seal by melting. On the other hand, the thickness of the sealant layer is 100 μm or less, 80 μm or less, 70 μm from the viewpoint of suppressing the damping of the vibration by the ultrasonic wave and suppressing the cracking of the barrier layer due to the increase of the molten resin moving amount at the time of ultrasonic sealing. Or less or 60 μm or less.

[Optional component in each layer]
Each of the above layers may contain an appropriate additive as required. As an additive used here, a lubricant, an antioxidant, an antistatic agent, a coloring agent etc. can be mentioned, for example.

[printing]
It is assumed that the laminated film of the present embodiment is printed with a product name, a product logo, etc. for identification of the contents when it is made into a packaging bag, or for an appeal to consumers when displayed as a product. Ru. The printing can be applied to any surface of any layer of the laminated film. However, for printing protection, it is appropriate to avoid printing on the outside of the outer layer and on the inside of the sealant layer. Typically, printing is applied between the outer layer and the barrier layer, or between the barrier layer and the intermediate layer.

[Total thickness of laminated film]
The total thickness of the laminated film of the present embodiment is preferably 200 μm or less from the viewpoint of achieving good ultrasonic sealability. That is, by adjusting the total thickness of the laminated film to 150 μm or less, it is possible to suppress the attenuation of the vibration due to the ultrasonic wave and to suppress the cracking of the barrier layer due to the increase of the molten resin moving amount at the time of ultrasonic sealing. The total thickness of the laminated film may be 150 μm or less, 120 μm or less, or 100 μm or less. On the other hand, from the viewpoint of giving practical geometrical strength to the laminated film, the total thickness of the laminated film may be 35 μm or more, 50 μm or more, 60 μm or more, 70 μm or more, or 80 μm or more.

<Method of manufacturing laminated film>
The laminated film of the present embodiment can be manufactured by a known method other than laminating the above-described layers in a predetermined order. For example, it can be manufactured by a dry lamination method, a wet lamination method, an extrusion lamination method, etc., or a combination thereof. Of these, dry lamination is preferred. The dry lamination can be performed by a known method using a known adhesive for dry lamination, for example, a polyester-based adhesive, a polyether-based adhesive, a polyurethane-based adhesive and the like.

<Method of manufacturing packaging bag>
The laminated film of this embodiment may be formed into a package by a method including ultrasonic sealing of the sealant layers. In bag making, it is not necessary to ultrasonically seal all the seal parts, and a part of the seal may be sealed by another sealing method, for example, heat sealing.

  The laminated film of the present embodiment is excellent in ultrasonic sealability, and particularly excellent in foreign matter sealability by application of ultrasonic waves. Therefore, the laminated film of the present embodiment may be used for bag filling with a sealing process by ultrasonic waves, and in particular, may be used for bag filling with a foreign matter sealing process by ultrasonic waves.

  The bag making may be specifically performed by, for example, the following method.

  First, the laminated film of the present embodiment is made to face each other so that the sealant layers face each other, or is bent, two sides facing each other or one side facing the bent portion are heat sealed, and two sides facing each other are It is a closed cylindrical molded body. In this molded body, two closed sides constitute the bottom side and the top side of the package.

  Then, the molded product as described above is mounted on a commercially available bag making machine equipped with an ultrasonic sealing device, and the bag is made by ultrasonic sealing. Here, using the bag-making filling machine that performs bag-making while filling the contents as a bag-making machine, by performing bag-making filling in a mode in which the ultrasonic seal is a foreign matter seal, the laminated film of the present embodiment The benefits are expressed effectively.

  The ultrasonic seal is connected to the ultrasonic transducer directly or via a booster, sandwiches the above-mentioned formed body between the ultrasonically vibrating horn and the anvil which is a receiving jig, and applies the ultrasonic wave thereto It is done by doing.

  At this time, the efficiency of the ultrasonic seal can be improved by providing a rib or a concavo-convex pattern on at least one of the horn and the anvil, and concentrating energy locally on the seal surface. The uneven pattern may be a pattern having a large number of pyramidal recesses, a pattern having uneven stripes, and the like.

  The ultrasonic vibration may be longitudinal vibration or lateral vibration.

  The above-mentioned bag-making and filling with ultrasonic sealing may be performed using, for example, a filling and packaging machine "VH-100" manufactured by ORIHIRO.

  The laminated film of the present embodiment is one in which cracking of the barrier layer due to ultrasonic sealing is suppressed. Therefore, since the packaging bag obtained as mentioned above using the laminated film of this embodiment has very few cracks of the barrier layer of an ultrasonic sealing part, the light transmittance of this part is low. Specifically, the total light transmittance measured according to JIS K 7361-1 can be limited to 0.50% or less for the ultrasonic seal portion in the package. Further, the total light transmittance of the ultrasonic seal portion of the package may be 0.40% or less, 0.30% or less, 0.20% or less, or 0.10% or less.

<Packaging bag>
The present specification also relates to a packaging bag comprising the laminated film of the present embodiment described above and including an ultrasonic sealing portion. The packaging bag may be manufactured by the method described above. Therefore, the total light transmittance measured according to JIS K 7361-1 for the ultrasonic sealing portion of the packaging bag of the present embodiment is 0.50% or less, 0.40% or less, 0.30% or less , 0.20% or less, or 0.10% or less.

  The film used for each layer of the laminated | multilayer film in a following example and a comparative example is as follows, respectively.

<Outer layer>
Uniaxial PP: uniaxially stretched polypropylene film, manufactured by Tokyo Ink, product name "ANN", layer thickness 20 μm
PET: polyethylene terephthalate, manufactured by Toyobo Co., Ltd., product name "E-5102", layer thickness 12 μm

<Barrier layer>
AL: aluminum foil, manufactured by Toyo Aluminum Co., Ltd., product name “1N30”, layer thickness 7 μm or 20 μm

<Middle class>

<Sealant layer>
LLDPE: LLDPE single layer film, manufactured by Tamapoli, product name “SE625L”, layer thickness 50 μm

  The tensile modulus of elasticity of the intermediate layer was measured at a tensile speed of 300 mm / min, with a sample shape of 15 mm × 150 mm in strip shape in accordance with JIS K 7127.

  The DSC of the intermediate layer was a DSC curve drawn according to JIS K 7121. The DSC curve was created from a DSC measurement when the temperature was adjusted from room temperature to 260 ° C. at a heating rate of 10 ° C./min under a nitrogen stream with a precisely weighed sample of approximately 5 mg. The peak temperature of the endothermic peak and the heat of fusion were determined from this DSC curve. As a ratio of the heat of fusion to the heat of fusion of the complete crystal, the value calculated by the above equation (1) is taken as the degree of crystallization.

  As the heat of fusion of the fully crystallized form, the completely crystallized form of nylon described in THERMAL APPLICATIONS NOTE Polymer Heats of Fusion, Roger L. Blaine TA Instruments, 109 Lukens Drive, New Castle DE 19720, USA. A literature value (230 mJ / mg) was adopted.

Example 1
(1) Preparation of laminated film Using dry laminator and polyester based dry laminate adhesive, uniaxial PP as outer layer, AL (layer thickness 7 μm) as barrier layer, NY1 as intermediate layer, and SE625L as sealant layer Were laminated in this order to produce a laminated film.

(2) Measurement of total light transmittance Using a dry laminator, a uniaxial laminate PP as an outer layer, NY1 as an intermediate layer, and SE625L as a sealant layer were laminated in this order to prepare a transparent laminated film. This transparent laminated film and the above-mentioned laminated film are laminated so that sealant layers may be opposed to each other, and formed into a bag of 70 mm long × 100 mm wide by heat sealing, filled with water to produce a four-way bag did. Next, using a bag-filling machine “VH-100” manufactured by ORIHIRO, ultrasonically seal a portion of 15 mm long × 65 mm wide at the center of the water-filled 4-way bag, and measure the total light transmittance measurement sample Prepared. The shape of this sample is shown in FIG.

  The above-mentioned ultrasonic sealing was performed by a longitudinal vibration method using a flat horn and an anvil having a pattern in which a large number of pyramidal concave portions are arranged.

  The total light transmittance of the above sample was measured using a haze meter "HR-100" manufactured by Murakami Color Research Laboratory, with reference to JIS K 7361-1. The evaluation results are shown in Table 2.

  In the measurement of the total light transmittance, if no cracks occur in the aluminum foil which is the barrier layer, the measurement light can not pass through the barrier layer, and the total light transmittance becomes “0”. However, if the aluminum foil is cracked, the measurement light can pass through the cracked part, so a significant value is observed as the total light transmittance. The greater the degree of cracking, the higher the total light transmittance. Therefore, by examining the total light transmittance of the measurement sample, it is possible to estimate the degree of cracking of the aluminum foil due to the ultrasonic seal.

Examples 2 to 4 and Comparative Examples 1 to 5
A laminated film was produced in the same manner as in Example 1 except that the barrier layer and the interlayer described in Table 2 were used, respectively, and a total light transmittance measurement sample was prepared and evaluated using this. The outer layer and the sealant layer each used the same layer as in Example 1. Further, in Comparative Example 1, the intermediate layer was not used.

  The evaluation results are summarized in Table 2 and shown.

<Discussion>
In the measurement of the total light transmittance, if no cracks occur in the aluminum foil which is the barrier layer, the measurement light can not pass through the barrier layer, and the total light transmittance becomes “0”. However, if a crack occurs in the barrier layer, the measurement light can pass through the portion of the crack, so a significant value is observed as the total light transmittance. The greater the degree of cracking, the higher the total light transmittance. Therefore, by examining the total light transmittance of the measurement sample, it is possible to estimate the degree of cracking of the barrier layer due to the ultrasonic seal.

  The sample of Comparative Example 1 uses uniaxial PP film, aluminum foil, and LLDPE as the outer layer, the barrier layer, and the sealant layer, respectively, but does not use the intermediate layer. In Comparative Example 1, the value of the total light transmittance showed a relatively small value of 0.23%. However, the pressure resistance of the bag obtained from the laminated film of Comparative Example 1 was significantly inferior to that in the case of using the laminated film of another example having an intermediate layer, and the bag was easily broken.

  The samples of Comparative Examples 2 to 4 use, as the intermediate layer, nylon having a smaller degree of crystallinity than that of Examples 1 to 4. Since the laminated films of these comparative examples show relatively large values of the total light transmittance, it can be seen that the cracks in the barrier layer are large.

  In Example 4, the layer thickness of the barrier layer is large. The total light transmittance of the sample of this Example 4 is 0.00%, and it is considered that no crack is generated in the barrier layer by the ultrasonic seal.

Example 5 and Comparative Example 6
A laminated film is produced in the same manner as in Example 1 or Comparative Example 2 except that a PET film is used instead of the uniaxial PP film as the outer layer, and a total light transmittance measurement sample is prepared and evaluated using this. did. The same layers as in Example 1 or Comparative Example 2 were used as the barrier layer, the intermediate layer, and the sealant layer, respectively.

<Discussion>
The samples of Example 5 and Comparative Example 6 use PET for the outer layer. Compared with the laminated film of Comparative Example 6 in which a nylon film having a relatively small crystallinity of 26.8 is used as an intermediate layer, a nylon film having a crystallinity of a relatively large value of 29.6 is used in Example 5 It can be seen that the laminated film has a reduced total light transmittance, and thus, the cracking of the aluminum foil layer which is the barrier layer is suppressed. From this, it is inferred that the occurrence of the cracking of the barrier layer due to the ultrasonic sealing is due to the degree of crystallinity of the film used for the intermediate layer.

<About the mode of the crack of the barrier layer>
In the laminated film of the four-layer structure in the prior art, the samples of Comparative Examples 3 to 6 in which the layer thickness of the barrier layer is reduced have a high total light transmittance of 0.62% to 1.11%, and the barrier by ultrasonic sealing. It is considered that a considerable degree of cracking has occurred in the layer. Of the ultrasonic seal portion of Comparative Example 5, a photograph of a pyramid pattern in which a crack occurred is shown in FIG.

  It can be seen from FIG. 3 that the barrier layer is cracked at the apex of the pyramidal shape. This is because, in ultrasonic sealing, the resin in the region near the base of the pyramid-like concave portion where the gap between the horn and the anvil becomes smaller than the total thickness of the two laminated films to be bonded It is thought that the film was pushed in the direction of the top of the groove and pierced the barrier layer.

  On the other hand, in the samples of Examples 1 to 3 and 5, even when the layer thickness of the barrier layer is thin, the total light transmittance shows a small value of 0.05% to 0.53%. It can be seen that cracking of the barrier layer due to sonic sealing is suppressed. A photograph of the pyramid pattern of the ultrasonic seal portion of Example 1 is shown in FIG.

  The layer thickness of the barrier layer in the samples of Examples 1 to 3 and 5 is a value assumed to be particularly thin in the normal use mode of the laminated film of the present embodiment. Even in such a case, in the laminated film of the present embodiment, cracking of the barrier layer due to ultrasonic sealing is suppressed.

  The samples of Examples 1 to 4 are uniaxially stretched PP films in which the outer layer has an easy cut property. Therefore, a packaging bag made of a film having easy cutability as the outer layer has excellent easy cutability.

1 outer layer 2 barrier layer 3 middle layer 4 sealant layer 10 laminated film

Claims (10)

A laminated film having an outer layer, a barrier layer, an intermediate layer, and a sealant layer in this order,
The barrier layer comprises a metal foil layer,
The intermediate layer has a crystallinity of 28.0% or more, which is calculated as a ratio of the heat of fusion obtained from the DSC curve drawn according to JIS K 7121 to the heat of fusion of a perfect crystal, and The ratio of the tensile modulus in the TD direction to the tensile modulus in the MD direction measured according to JIS K 7127 is 0.7 or more and 1.2 or less.
Laminated film.   The laminated film according to claim 1, wherein the heat of fusion measured by DSC according to JIS K 7121 for the intermediate layer is 65.0 mJ / mg or more.   The laminated film according to claim 1, wherein the intermediate layer comprises a nylon film.   The laminated film according to any one of claims 1 to 3, wherein the outer layer comprises an easily cut film.   The laminated film according to claim 4, wherein the easily cut film is a uniaxially stretched polypropylene film.   The laminated film according to any one of claims 1 to 5, wherein the layer thickness of the barrier layer is 10 μm or less.   The manufacturing method of a packaging bag including ultrasonically sealing sealant layers of laminated | multilayer film as described in any one of Claims 1-6.   The method according to claim 7, wherein the total light transmittance of the ultrasonic sealing portion of the packaging bag is 0.50% or less measured in accordance with JIS K 7361-1.   A packaging bag comprising the laminated film according to any one of claims 1 to 6 and including an ultrasonic seal portion.   The packaging bag according to claim 9, wherein the total light transmittance of said ultrasonic seal portion measured according to JIS K 7361-1 is 0.50% or less.