JP7443834B2 - pouch - Google Patents

Description

The present invention relates to a pouch.

BACKGROUND ART Conventionally, standing pouches that can be heated in a microwave oven and that can accommodate contents such as retort foods and frozen foods have been widely used. Such pouches are configured to stand on their own in a microwave oven, and are equipped with a steam release mechanism that automatically releases steam generated from heating in the microwave to the outside of the pouch (for example, (See Patent Document 1).

Patent No. 4029590

Currently, there is a need to improve the appearance of pouches in order to increase purchase motivation. However, if the Young's modulus of the packaging material constituting the pouch is small, the dimensions of the packaging material may change when cooked in a microwave oven, and the appearance of the pouch may be impaired.

Furthermore, when a pouch is heated in a microwave oven, excessive pressure is applied, which may prevent steam from being released from the steam release mechanism, and parts other than the steam release mechanism may open.

The present invention has been made to solve the above problems. That is, the object is to provide a pouch that can improve the appearance after being heated in a microwave oven and can stably release steam during heating in a microwave oven.

The present invention includes the following inventions.
[1] A pouch containing a packaging material and having a storage space, the packaging material comprising a first biaxially stretched plastic film, a second biaxially stretched plastic film, and a sealant film in this order. , the sealant film mainly contains polypropylene,
There are only two biaxially stretched plastic films in the packaging material, and the packaging material includes a seal portion for sealing the pouch, and the seal portion is configured to peel off due to an increase in pressure in the accommodation space. The pouch is provided with a bleed seal portion, and the pouch is configured such that steam can be released by peeling off the steam bleed seal portion, and the packaging material is kept at 25°C for 1 minute, The Young's modulus in one direction when measured in a 100°C environment is 3000 MPa or more, and the seal strength of the seal portion is measured in a 100°C environment after being held for 1 minute in a 100°C environment. , 20.0N or less, a pouch.

[2] The pouch according to [1] above, wherein the product of the tensile elongation (%) and the thickness (μm) in the one direction of the sealant film is 30,000 or more and 50,000 or less.

[3] The pouch according to [1] or [2] above, wherein the product of tensile elongation (%) and thickness (μm) in the direction orthogonal to the one direction of the sealant film is 45,000 or more and 55,000 or less. .

[4] The pouch according to any one of [1] to [3] above, wherein the sealant film contains a propylene-ethylene block copolymer.

[5] The above [1] wherein the first biaxially oriented plastic film is a biaxially oriented polyethylene terephthalate film, and the second biaxially oriented plastic film is a biaxially oriented polyethylene terephthalate film or a biaxially oriented nylon film. ] to [4].

[6] The packaging material further includes a transparent vapor deposited layer provided between the first biaxially stretched plastic film and the second biaxially stretched plastic film, and the transparent vapor deposited layer is made of a metal oxide or an inorganic material. The pouch according to any one of [1] to [5] above, which contains an oxide.

[7] The pouch according to [6] above, wherein the packaging material further includes a transparent gas barrier coating film provided on the surface of the transparent vapor deposition layer.

[8] The packaging material further includes a light-shielding printed layer provided between the first biaxially stretched plastic film and the sealant film, and the total light transmittance of the packaging material is 25.0% or less. The pouch according to any one of [1] to [7] above.

[9] The pouch according to [8] above, wherein the L ^* value in the L ^* a ^* b ^* color system measured by the SCE method (specular reflection light elimination method) of the packaging material is 65.0 or more.

[10] The pouch according to any one of [1] to [9] above, wherein a content is accommodated in the accommodation space of the pouch.

According to the present invention, it is possible to provide a pouch that can improve the appearance after being heated in a microwave oven and can stably release steam during heating in a microwave oven.

FIG. 1 is a front view of a pouch according to an embodiment. FIG. 2 is a diagram for explaining the dimensions of each component of the pouch shown in FIG. 1. FIG. 3 is a cross-sectional view of the packaging material used in the pouch. FIG. 4 is a diagram when a test piece for measuring the Young's modulus of the packaging material is cut out from the front surface of the pouch. FIG. 5 is a diagram when a test piece for measuring the Young's modulus of the packaging material is cut out from the back side of the pouch. FIG. 6 is a diagram showing how Young's modulus is measured using a test piece. FIG. 7 is a diagram when a test piece for measuring the hot seal strength of packaging material is cut out from a pouch. FIG. 8 is a diagram showing how hot seal strength is measured using a test piece. FIG. 9 is a diagram illustrating hot seal strength (maximum tensile strength). FIG. 10 is a cross-sectional view of another packaging material used in pouches. FIG. 11 is a diagram when a test piece for measuring the total light transmittance of the packaging material is cut out from the front surface of the pouch. FIG. 12 is a diagram when a test piece for measuring the total light transmittance of the packaging material is cut out from the back surface of the pouch. FIG. 13 is a diagram when a test piece for measuring the L ^* value of the packaging material is cut out from the front surface of the pouch.

Hereinafter, a pouch according to an embodiment of the present invention will be described with reference to the drawings. As used herein, terms such as "film", "sheet", etc. are not distinguished from each other solely on the basis of differences in designation. Therefore, for example, the term "film" is used to include members also called sheets. FIG. 1 is a front view of the pouch according to the embodiment, FIG. 2 is a diagram for explaining the dimensions of each component of the pouch shown in FIG. 1, and FIG. 3 is a diagram of the packaging material used in the pouch. FIG. FIG. 4 shows a test piece for measuring the Young's modulus of packaging material cut out from the front surface of the pouch, and FIG. 5 shows a test piece for measuring Young's modulus of packaging material cut out from the front surface of the pouch. This is a diagram when cutting out from the back surface, and FIG. 6 is a diagram showing how Young's modulus is measured using a test piece. FIG. 7 is a diagram showing how a test piece for measuring the hot seal strength of packaging material is cut out from the pouch, and FIG. 8 is a diagram showing how the hot seal strength is measured using the test piece. , FIG. 9 is a diagram illustrating hot seal strength (maximum tensile strength). FIG. 10 is a cross-sectional view of another packaging material used for pouches, and FIG. 11 is a view when cutting out a test piece from the front surface of the pouch for measuring the total light transmittance of the packaging material. , FIG. 12 is a diagram when a test piece for measuring the total light transmittance of the packaging material is cut out from the front surface of the pouch, and FIG. 13 is a diagram showing a test piece for measuring the L ^* value of the packaging material. FIG. 6 is a diagram showing when a piece is cut out from the front surface of the pouch.

＜＜＜Pouch＞＞＞
The pouch 10 shown in FIG. 1 is a standing pouch and has a storage space 10A for storing contents. The contents include, but are not limited to, solids, liquids, or mixtures thereof. Examples of the contents include cooked foods such as curry, stew, and soup. The cooked food may be subjected to heat sterilization treatment such as boiling treatment or retort treatment. That is, a heat-sterilized food or a pressure-heat-sterilized food may be accommodated as the contents. "Retort processing" is a process in which the contents are filled into a pouch, the pouch is sealed, and then the pouch is heated under pressure using steam or heated hot water. The temperature of the retort treatment is, for example, 120° C. or higher. A pouch is a concept that includes not only a pouch that is not filled with contents but also a pouch that is filled with contents.

The pouch 10 shown in FIG. 1 has a front film 11, a back film 12, and a bottom film 13. The front film 11 and the back film 12 have rectangular outlines. In the state shown in FIG. 1, the bottom film 13 is folded in two.

The pouch 10 has an upper part 10B, a bottom part 10C opposite to the upper part 10B, and a first side part 10D and a second side part 10E extending between the upper part 10B and the bottom part 10C. The second side 10E is a side opposite to the first side 10D. Further, in this specification, the positions of "upper", "lower", "side", and "bottom" refer to the positions of the pouch in a free-standing state.

The ratio (H/W1) of the height H (see FIG. 2) of the pouch 10 to the width W1 (see FIG. 2) of the pouch 10 is preferably 0.6 or more and 2.0 or less. If H/W1 is 0.6 or more, more contents can be accommodated, and if H/W1 is 2.0 or less, the pouch 10 can stably stand on its own before opening. . The height H of the pouch 10 is the length from the lower edge 10G of the pouch 10 to the upper edge 10F of the pouch 10 in the Y direction DRY parallel to the direction in which the first side seal portion 16 (described later) extends. If the length of the pouch is not constant, the height of the pouch shall be the maximum value. The width W1 of the pouch 10 is the length from the side edge 10H of the pouch 10 on the first side portion 10D side to the side edge 10I of the second side portion 10E in the X direction DRX orthogonal to the Y direction DRY. When the pouch width W1 is not constant, the pouch width is set to the shortest value. The dimensions of the pouch and the dimensions of each component constituting the pouch in this embodiment are all values measured with the pouch in a substantially flat state without expanding the gusset folded portion of the pouch. The lower limit of H/W1 may be 0.70 or more, 0.75 or more, 0.80 or more, 0.85 or more, or 0.90 or more, and the upper limit of H/W1 is 1.90 or more. Hereinafter, it may be 1.80 or less, 1.70 or less, 1.60 or less, or 1.50 or less.

As shown in FIG. 1, the pouch 10 has a bottom gusset portion 14 folded in a gusset manner on the bottom portion 10C side. In addition, although the pouch 10 shown in FIG. 1 is a standing pouch, the pouch may be a planar pouch (flat pouch).

<Bottom gusset part>
The bottom gusset portion 14 includes a part of the front film 11 , a part of the back film 12 , and a bottom film 13 . The bottom film 13 is divided into a first portion and a second portion via a fold line 14A. A first pleat is formed by a portion of the front film 11 and a first portion of the bottom film 13, and a second pleat is formed by a portion of the back film 12 and a second portion of the bottom film 13. . Providing the bottom gusset portion 14 allows the pouch 10 to be self-supporting while being able to accommodate larger contents and increasing the capacity of the contents.

In the Y direction DRY, the ratio (W2/H) of the folding width W2 (see FIG. 2) of the bottom gusset portion 14 to the height H of the pouch 10 is preferably 0.1 or more and 0.5 or less. If the above W2/H is 0.1 or more, more contents can be accommodated. Moreover, when W2/H is 0.5 or less, when the pouch 10 is made to stand on its own, it is possible to stably make the pouch stand on its own. The folding width W2 of the bottom gusset portion 14 is the length from the lower edge 10G of the bottom portion 10C to the folding line 14A. When the folding width of the bottom gusset portion is not constant, the folding width of the bottom gusset portion is set to the shortest value. The lower limit of W2/H is more preferably 0.15 or more or 0.20 or more, and the upper limit of W2/H is 0.45 or less, 0.40 or less, 0.35 or less, or 0. More preferably, it is .30 or less. The folding width W2 of the bottom gusset portion 14 may be 20 mm or more and 50 mm or less. The lower limit of the folding width W2 of the bottom gusset portion 14 is more preferably 25 mm or more, 30 mm or more, 35 mm or more, or 40 mm or more.

As shown in FIG. 1, the pouch 10 includes a seal portion 15 for sealing the pouch 10. The seal portion 15 in the pouch 10 includes a first side seal portion 16 formed on the first side portion 10D, a second side seal portion 17 formed on the second side portion 10E, and a bottom portion 10C. The first bottom seal portion 18, the second bottom seal portion 19, and the bottom auxiliary seal portions 20 formed on the side edges 10H and 10I, respectively, are configured to peel off due to an increase in pressure in the accommodation space 10A of the pouch 10. The steam release seal portion 24 is provided with a steam release seal portion 24. In addition, although the upper part of the pouch 10 is open in FIG. 1, after filling the storage space 10A with the contents, it is heat-sealed to form an upper seal surrounded by the upper edge 10F and the two-dot chain line in FIG. An upper seal portion is formed in the region R, and the pouch 10 is sealed. When the upper seal part is formed, it is preferable that the width W5 (see FIG. 2) of the upper seal part is, for example, 2 mm or more and 15 mm or less. The lower limit of the width W5 of the upper seal portion is more preferably 3 mm or more, 4 mm or more, or 5 mm or more, and the upper limit is more preferably 14 mm or less, 13 mm or less, or 12 mm or less.

<First side seal portion and second side seal portion>
The first side seal portion 16 is a portion where the front film 11 and the back film 12 are joined to each other in the first side portion 10D, and is formed from the fold line 14A to the upper edge 10F. The second side seal portion 17 is a portion where the front film 11 and the back film 12 are joined to each other in the second side portion 10E, and is formed from the fold line 14A to the upper edge 10F of the pouch 10. There is. The front film 11 and the back film 12 are joined by heat sealing (thermal fusion) when forming the first side seal portion 16 and the second side seal portion 17.

It is preferable that the width W3 (see FIG. 2) of the first side seal part 16 and the second side seal part 17 is, for example, 2 mm or more and 15 mm or less, respectively. If the width W3 of the first side seal part 16 and the second side seal part 17 is each 2 mm or more, the first side seal part 16 and the second side seal part 17 can reliably seal, Moreover, if it is 15 mm or less, the accommodation space 10A can be secured more widely. In this specification, the "width" of each seal portion means the length in the direction perpendicular to the extending direction of the seal portion. Note that when the width of the seal portion is not constant, the width of the seal portion is the shortest value among the lengths in the direction perpendicular to the direction in which the seal portion extends. The lower limit of the width W3 is more preferably 4 mm or more or 6 mm or more, and the upper limit is more preferably 12 mm or less, 10 mm or less, or 8 mm or less.

<First bottom seal portion and second bottom seal portion>
The first bottom seal part 18 is a part where a part of the front film 11 and a part of the bottom film 13 are joined to each other, and the second bottom seal part 19 is a part where a part of the back film 12 and a part of the bottom film 13 are joined to each other. It is a part where parts of are joined together. The first bottom seal part 18 is formed by heat-sealing the front film 11 and the bottom film 13, and the second bottom seal part 19 is formed by heat-sealing the back film 12 and the bottom film 13. It is formed by

<Bottom auxiliary seal part>
The bottom auxiliary seal portion 20 is formed below the fold line 14A and includes the side edges 10H and 10I of the pouch 10. The bottom auxiliary seal portion 20 is a portion where the front film 11 and the back film 12 are joined to each other. The auxiliary bottom seal portion 20 is formed by heat-sealing the front film 11 and the back film 12 through a notch provided in the bottom film 13. Therefore, the pouch 10 can be stably made to stand on its own. Note that a through hole may be provided in the bottom film 13 instead of the notch.

As shown in FIG. 1, the first side seal part 16 and the second side seal part 17 are provided with opening initiation means 21 that can serve as a starting point for opening. The unsealing initiation means 21 may be provided in either the first side seal part 16 or the second side seal part 17.

<<Means for starting opening>>
The opening initiation means 21 can serve as a starting point when opening the pouch 10. The pouch 10 can be opened by grasping the first side seal part 16 or the second side seal part 17 above one of the opening initiation means 21 and pulling it toward you or pushing it toward the back. Examples of the unsealing initiation means 21 include a notch, a notch, and the like. The opening initiation means 21 shown in FIG. 1 is a notch.

A steam release mechanism 22 is provided on the first side 10D of the pouch 10 in order to release the steam inside the pouch 10 to the outside when the pressure inside the pouch 10 increases due to steam generated during heating by the microwave oven. ing.

<<Steam release mechanism>>
The steam release mechanism 22 shown in FIG. 1 includes a first unsealed part 23 that is not sealed and is isolated from the accommodation space 10A, and a first side seal that isolates the first unsealed part 23 from the accommodation space 10A. The steam release seal part 24 extends from the part 16 toward the housing space 10A.

<First unsealed part>
The first unsealed portion 23 has an opening 23A serving as a steam port that reaches the side edges of the front film 11 and the back film 12, and communicates with the outside via the opening 23A.

<Steam release seal part>
The steam release seal portion 24 is connected to the first side seal portion 16 . The steam release seal part 24 shown in FIG. 1 has one end connected to the upper part 16A of the first side seal part 16, and the other end connected to the lower part 16B. Thereby, the first unsealed portion 23 is isolated from the accommodation space 10A. The width W4 (see FIG. 2) of the steam release seal portion 24 is set to, for example, 2.5 mm or more and 6 mm or less. The lower limit of the width W4 of the steam release seal portion 24 is more preferably 3.0 mm or more, 3.5 mm or more, or 4.0 mm or more, and the upper limit is more preferably 5.5 mm or less. preferable.

The steam release seal portion 24 is peeled off when the pressure inside the pouch 10 reaches a predetermined pressure due to heating, and as a result, the accommodation space 10A and the first unsealed portion 23 communicate with each other. The steam in 10A is automatically released to the outside of the pouch 10 via the first unsealed portion 23. In addition, since the steam vent seal portion 24 protrudes toward the housing space 10A side from the first side seal portion 16, when the pressure inside the pouch 10 increases due to heating in a microwave oven, the steam vent seal portion Stress tends to concentrate on 24. Further, since peeling tends to progress from the steam release seal portion 24, it is possible to suppress the progress of peeling from the first side seal portion 16 and the like.

Note that the steam venting mechanism 22 is not limited to the above-mentioned example, as long as it is configured to be able to release steam by peeling off the steam venting seal portion 24.

Further, in the pouch 10, a second unsealed part 25 is formed in the second side sealed part 17, but this is because the first unsealed part 23 is It is provided to ensure that the openings 23A are formed at the side edges of the front film 11 and the back film 12. That is, the second unsealed portion 25 is provided to improve the manufacturing efficiency of the pouch 10. The second unsealed portion 25 reaches the side edges of the front film 11 and the back film 12 and opens. Note that the second unsealed portion 25 does not necessarily have to be provided.

<<Packaging materials>>
The front film 11 and the back film 12 are made of packaging material 30 shown in FIG. Moreover, the bottom film 13 may be comprised of the packaging material 30 shown in FIG. The packaging material 30 includes at least a first biaxially stretched plastic film 31, a second biaxially stretched plastic film 32, and a sealant film 33 in this order. The packaging material 30 does not include a metal foil layer. The packaging material 30 has only two biaxially oriented plastic films in the packaging material 30. The sealant film 33 is a layer that constitutes the inner surface of the pouch 10. The packaging material 30 shown in FIG. 3 includes, for example, a first biaxially stretched plastic film 31, a pattern printing layer 34, a first adhesive layer 35, a second biaxially stretched plastic film 32, and a second adhesive layer 36. and a sealant film 33 in this order. Note that the packaging material may further include a functional layer that exhibits a desired function between the first biaxially stretched plastic film 31 and the sealant film 33. Examples of the functional layer include a transparent vapor deposition layer and a transparent gas barrier coating film. The pouch 10 can be manufactured while continuously conveying the packaging material 30 wound up into a roll.

The packaging material 30 has a Young's modulus in one direction of 3000 MPa or more when measured in a 25° C. environment after being held for 1 minute in a 25° C. environment. The Young's modulus in one direction of the packaging material 30 is preferably 3100 MPa or more, more preferably 3200 MPa or more, and even more preferably 3300 MPa or more. The Young's modulus in one direction of the packaging material 30 is preferably 3400 MPa or less. Further, the Young's modulus of the packaging material 30 in a direction orthogonal to one direction is preferably 2,800 MPa or more, more preferably 2,900 MPa or more, and even more preferably 3,000 MPa or more. One direction of the packaging material 30 may be, for example, the X direction DRX (see FIG. 1) in the pouch 10, and a direction perpendicular to the one direction of the packaging material 30 may be, for example, the Y direction DRY in the pouch 10. Further, for example, the flow direction (MD) of the packaging material 30 may correspond to the X direction DRX of the pouch 10, and for example, the width direction (TD) of the packaging material 30 may correspond to the Y direction DRY of the pouch 10. Further, for example, one direction of the packaging material 30 may correspond to the machine direction (MD), and for example, a direction perpendicular to the one direction of the packaging material may correspond to the width direction (TD).

The Young's modulus of the packaging material 30 is measured in accordance with JIS K7127 except for the lengths of test pieces S1 and S2, which will be described later. First, from the front film 11 of the pouch 10, excluding the seal part 15, one side L1 (see FIG. 4) is 15 mm, and the other side L2 (see FIG. 4) extending in a direction perpendicular to the one side L1 is Five 100 mm rectangular test pieces S1 (see FIG. 4) are cut out. The test piece S1 is cut out so that the other side L2 is parallel to the X direction DRX (the direction perpendicular to the direction in which the first side seal portion 16 extends). Next, from the back film 12 of the pouch 10, one side L1 (see FIG. 5) is 15 mm and the other side L2 (see FIG. 5) extending in a direction perpendicular to the one side L1 is 100 mm, excluding the seal part 15. Five rectangular test pieces S2 (see FIG. 5) are cut out. The test piece S2 is cut out so that the other side L2 is parallel to the Y direction DRY (a direction parallel to the direction in which the first side seal portion 16 extends). Then, the Young's modulus of the test pieces S1 and S2 is measured using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.). Specifically, first, as shown in FIG. 6, both ends of the test piece S1 in the longitudinal direction are gripped using grippers 51 and 52. In addition, in FIG. 6, the layer structure of test pieces S1 and S2 is partially omitted. After holding the test piece S1 in an environment of a temperature of 25°C and a relative humidity of 50% for 1 minute, the initial distance between the grippers D1 (see Fig. 6) was set to 50 mm in an environment of a temperature of 25°C and a relative humidity of 50%. In this state, a tensile test is performed in which the test piece S1 is pulled in the longitudinal direction of the test piece S1 at a pulling speed of 300 mm/min, and the Young's modulus of the test piece S1 is measured. Note that the Young's modulus of the test piece S1 may be measured using the test piece S1 held in a 25° C. environment for 24 hours. The Young's modulus of the test piece S2 is also measured under the same measurement conditions as the test piece S1. Then, the Young's modulus of the five test pieces S1 is measured, and the average value is taken as the Young's modulus of the packaging material 30 in the X direction DRX. Further, the Young's modulus of the five test pieces S2 is measured, and the average value is taken as the Young's modulus of the packaging material 30 in the Y direction DRY.

The packaging material 30 has a seal strength (hot seal strength) of 20.0 N or less when measured in a 100° C. environment after being held in a 100° C. environment for 1 minute. The hot seal strength is preferably 18.0N or less, more preferably 16.0N or less. Furthermore, if the hot sealing strength is too low, the steam release seal portion 24 may peel off before the contents are sufficiently heated and pressurized, causing the pressure and temperature of the accommodation space 10A to drop. It will be done. Considering this point, the hot sealing strength of the seal portion 15 of the pouch 10 is preferably 4N or more, more preferably 5N or more. Note that the seal strength of the steam release seal portion 24 may change due to sterilization treatment such as retort treatment, but when the pouch 10 is subjected to retort treatment, unless otherwise specified, the “seal strength of the seal portion” means the seal strength of the seal portion of the pouch after being subjected to retort treatment.

In measuring the hot seal strength of the packaging material 30, first, one pouch is prepared. Regarding the pouch, including the first side seal part 16 or the second side seal part 17, one side L3 (see FIG. 7) with the front film 11 and the back film 12 joined is 15 mm, and one side L3 is 15 mm. Five rectangular test pieces S3 (see FIG. 7) with the other side L4 (see FIG. 7) extending in the orthogonal direction of 70 mm are cut out. For example, as shown in FIG. 7, three test pieces S3 including the first side seal part 16 and two test pieces S3 including the second side seal part 17 are cut out. The test piece S3 is cut out so that the other side L4 is parallel to the X direction DRX (direction perpendicular to the direction in which the first side seal part 16 extends) and does not include the steam release seal part 24. Hot seal strength is measured using this test piece S3. The hot seal strength is measured using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.) in accordance with JIS Z1707:1997 7.5. First, the two packaging materials 30 in the unsealed portion of the test piece S3 were each held by the gripping tools 53 and 54 (see FIG. 8) of the testing machine. Note that in FIG. 8, the layer structure of the test piece S3 is partially omitted. Then, the gripping tools 53 and 54 were each pulled at a speed of 300 mm/min in directions perpendicular to the surface direction of the seal portion of the test piece S3 in opposite directions, and the maximum value of the tensile stress was measured. Then, the average value of the maximum values is taken as the seal strength (see FIG. 9). The hot seal strength is measured by holding the test piece S3 in an environment of a temperature of 100° C. and a relative humidity of 5% for 1 minute, and then in an environment of a temperature of 100° C. and a relative humidity of 5%. The hot seal strength of the five test pieces S3 is measured, and the average value is taken as the hot seal strength of the pouch.

<Biaxially stretched plastic film>
A biaxially stretched plastic film is a plastic film that has been intentionally stretched in order to improve the mechanical strength of the plastic film. In the present invention, the biaxially stretched plastic film refers to a film that satisfies at least one of the following (a) or (b).
(a) Young's modulus is 1000 MPa or more in one direction and the direction orthogonal to the one direction (b) Tensile elongation is 200% or less in the one direction and the direction orthogonal to the one direction

The Young's modulus and tensile elongation of the biaxially stretched plastic film shall be measured in accordance with JIS K7127. Using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.), the test piece was held in an environment of 25°C and 50% relative humidity for 1 minute, and then tested at 25°C and 50% relative humidity. % Young's modulus and tensile elongation measurements are performed on the test piece. Measurement is performed using a rectangular test piece with one side of 15 mm and the other side extending in a direction perpendicular to one side of 150 mm, the initial distance between the gripping tools is 100 mm, and the tensile speed is 300 mm/min. Note that the length in the direction perpendicular to one side can be adjusted as long as the initial distance between the grippers can be measured as 100 mm.

(First biaxially stretched plastic film)
The first biaxially stretched plastic film 31 is a plastic film stretched in two predetermined directions. The first biaxially stretched plastic film 31 functions as a base film for giving the packaging material 30 a predetermined strength. The stretching direction of the first biaxially stretched plastic film 31 is not particularly limited. For example, the first biaxially stretched plastic film 31 may be stretched in the direction in which the side edge 10H extends and in the direction orthogonal to this direction. The stretching ratio of the first biaxially stretched plastic film 31 is, for example, 1.05 times or more.

The first biaxially stretched plastic film 31 preferably contains polyester as a main component. As used herein, "containing polyester as a main component" means that the biaxially oriented plastic film contains more than 50% by mass of polyester. Examples of polyester include polyethylene terephthalate (hereinafter also referred to as PET), polybutylene terephthalate (hereinafter also referred to as PBT), and the like. In addition, the polyester exceeding 50% by mass in the first biaxially stretched plastic film 31 may be composed of one type of polyester, or may be composed of two or more types of polyester. A biaxially stretched PET film can be used as the first biaxially stretched plastic film. The biaxially stretched PET film preferably contains 80% by mass or more of PET. Furthermore, the biaxially stretched PET film more preferably contains 90% by mass or more of PET, and even more preferably 95% or more.

The thickness of the first biaxially stretched plastic film 31 is preferably 8 μm or more, more preferably 9 μm or more, and still more preferably 12 μm or more. Moreover, the thickness of the first biaxially stretched plastic film 31 is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less. By setting the thickness of the first biaxially stretched plastic film 31 to 8 μm or more, the first biaxially stretched plastic film 31 has sufficient strength. Furthermore, by setting the thickness of the first biaxially stretched plastic film 31 to 30 μm or less, the first biaxially stretched plastic film 31 exhibits excellent moldability. Therefore, the process of manufacturing the pouch 10 by processing the packaging material 30 can be efficiently carried out.

(Second biaxially stretched plastic film)
The second biaxially stretched plastic film 32 is, for example, a base film stretched in two predetermined directions, similar to the first biaxially stretched plastic film 31. For example, the second biaxially stretched plastic film 32 may be stretched in the direction in which the side edge 10H extends and in a direction orthogonal to this direction. Like the first biaxially stretched plastic film 31, the second biaxially stretched plastic film 32 also functions as a base film for giving the packaging material 30 a predetermined strength. Similarly to the case of the first biaxially stretched plastic film 31, the stretching direction of the second biaxially stretched plastic film 32 is not particularly limited.

The second biaxially oriented plastic film 32 is preferably a biaxially oriented plastic film containing polyamide as a main component or a biaxially oriented plastic film containing polyester as a main component. As used herein, "containing polyamide as a main component" means that the second biaxially oriented plastic film contains more than 50% by mass of polyamide. As examples of polyamides, mention may be made of aliphatic polyamides or aromatic polyamides. Examples of aliphatic polyamides include nylons such as nylon-6, nylon-6,6, and copolymers of nylon 6 and nylon 6,6; examples of aromatic polyamides include polymethaxylene adipamide ( MXD6), etc. Since the second biaxially stretched plastic film 32 contains polyamide as a main component, the puncture strength of the packaging material 30 including the second biaxially stretched plastic film 32 can be increased. Examples of polyesters include the polyesters listed in the column of the first biaxially oriented plastic film. As the second biaxially oriented plastic film, a biaxially oriented nylon film or a biaxially oriented polyethylene terephthalate film can be used. The biaxially stretched nylon film preferably contains 80% by mass or more of polyamide. Further, the biaxially stretched nylon film preferably contains polyamide in an amount of 90% by mass or more, and even more preferably 95% or more.

The thickness of the second biaxially stretched plastic film 32 is preferably 12 μm or more, more preferably 15 μm or more. Moreover, the thickness of the second biaxially stretched plastic film 32 is preferably 30 μm or less, more preferably 25 μm or less, and still more preferably 20 μm or less.

The second biaxially oriented plastic film 32 may be configured to have tearability in the machine direction (MD). In the following description, a biaxially stretched plastic film having tearability in the machine direction (MD) is also referred to as a biaxially stretched straight cut film. By using a biaxially stretched straight-cut film, the packaging material 30 can be given tearability in the machine direction (MD). The tensile strength of the biaxially stretched straight cut film in the machine direction (MD) is greater than the tensile strength of the biaxially stretched straight cut film in the width direction (TD). The tensile strength of the biaxially stretched straight cut film in the machine direction (MD) is preferably 1.05 times or more, more preferably 1.10 times the tensile strength of the biaxially stretched straight cut film in the width direction (TD). It is at least twice as large, more preferably at least 1.20 times. Further, the tensile strength of the biaxially stretched straight cut film in the machine direction (MD) is, for example, 200 MPa or more and 300 MPa or less.

<Sealant film>
Next, the sealant film 33 will be explained. The sealant film 33 may be a single layer or a multilayer. Further, the sealant film 33 is preferably made of an unstretched film. Note that "unstretched" is a concept that includes not only a film that has not been stretched at all, but also a film that has been slightly stretched due to the tension applied during film formation.

The sealant film refers to a film that satisfies at least either (c) or (d) below.
(c) Young's modulus is less than 1000 MPa in one direction and the direction orthogonal to the one direction (d) Tensile elongation is 300% or more in the one direction and the direction orthogonal to the one direction

The Young's modulus and tensile elongation of the sealant film shall be measured in accordance with JIS K7127. Using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.), the test piece was held in an environment of 25°C and 50% relative humidity for 1 minute, and then tested at 25°C and 50% relative humidity. % Young's modulus and tensile elongation measurements are performed on the test piece. Measurement is performed using a rectangular test piece with one side of 15 mm and the other side extending in a direction perpendicular to one side of 150 mm, the initial distance between the gripping tools is 100 mm, and the tensile speed is 300 mm/min. Note that the length in the direction perpendicular to one side can be adjusted as long as the initial distance between the grippers can be measured as 100 mm.

The pouch 10 made of the packaging material 30 is subjected to sterilization treatment such as retort treatment at a high temperature. Therefore, the sealant film 33 used has heat resistance that can withstand processing at these high temperatures.

The melting point of the material constituting the sealant film 33 is preferably 150°C or higher, more preferably 160°C or higher. By increasing the melting point of the sealant film 33, the pouch 10 can be retorted at a high temperature, and therefore the time required for the retort treatment can be shortened. Note that the melting point of the material constituting the sealant film 33 is lower than the melting point of the resin constituting the first biaxially stretched plastic film 31 and the second biaxially stretched plastic film 32.

The sealant film 33 contains polypropylene as a main component. As used herein, "containing polypropylene as a main component" means that the sealant film contains more than 50% by mass of polypropylene. Specific examples of materials containing propylene as a main component include polypropylene such as propylene/ethylene block copolymer, propylene/ethylene random copolymer, homopolypropylene, or a mixture of polypropylene and polyethylene. I can do it. Here, "propylene/ethylene block copolymer" means a material having the structural formula shown in the following formula (1). Moreover, "propylene/ethylene random copolymer" means a material having the structural formula shown in the following formula (2). Moreover, "homopolypropylene" means a material having the structural formula shown in the following formula (3).

上記式（１）中、ｍ１、ｍ２、ｍ３は、１以上の整数を表す。

In the above formula (1), m1, m2, and m3 represent an integer of 1 or more.

上記式（２）中、ｍ、ｎは、１以上の整数を表す。

In the above formula (2), m and n represent an integer of 1 or more.

上記式（３）中、ｍは、１以上の整数を表す。

In the above formula (3), m represents an integer of 1 or more.

When a mixture of polypropylene and polyethylene is used as the material whose main component is propylene, the material may have a sea-island structure. Here, the "sea-island structure" refers to a structure in which polyethylene is discontinuously dispersed within a continuous region of polypropylene.

Preferably, the sealant film 33 is a single layer film containing a propylene-ethylene block copolymer. For example, the sealant film 33 is a single-layer unstretched film containing a propylene/ethylene block copolymer as a main component. By using the propylene/ethylene block copolymer, the impact resistance of the sealant film 33 can be increased, and thereby the pouch 10 can be prevented from being torn due to impact when dropped. Moreover, the puncture resistance of the packaging material 30 can be improved.

Furthermore, by using the propylene/ethylene block copolymer, the strength of the seal portion formed by the sealant film 33 at high temperatures, for example, 100°C, that is, the above-mentioned hot seal strength, is lower than that at low temperatures, for example, at room temperature. It is extremely small compared to the seal strength. Due to the low hot seal strength, when the pouch 10 is heated using a microwave oven, the steam release seal portion 24 is likely to peel off, and the steam in the accommodation space 10A is likely to escape to the outside of the pouch 10. Therefore, it is possible to prevent the internal pressure of the housing space 10A from becoming excessively high, and thereby it is possible to prevent damage to the packaging material 30 during heating.

The propylene/ethylene block copolymer includes, for example, a sea component made of polypropylene and an island component made of an ethylene/propylene copolymer rubber component. The sea component can contribute to increasing the blocking resistance, heat resistance, rigidity, seal strength, etc. of the propylene/ethylene block copolymer. Additionally, the island component can contribute to increasing the impact resistance of the propylene/ethylene block copolymer. Therefore, by adjusting the ratio of the sea component to the island component, the mechanical properties of the sealant film 33 containing the propylene/ethylene block copolymer can be adjusted.

In the propylene/ethylene block copolymer, the mass ratio of the sea component made of polypropylene is higher than the mass ratio of the island component made of the ethylene/propylene copolymer rubber component. For example, in a propylene/ethylene block copolymer, the mass ratio of the sea component made of polypropylene is at least 51% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more.

The content of the propylene/ethylene block copolymer in the sealant film 33 is, for example, 80% by mass or more, preferably 90% by mass or more.

A method for producing a propylene/ethylene block copolymer includes a method of polymerizing raw materials such as propylene and ethylene using a catalyst. As the catalyst, a Ziegler-Natta type catalyst, a metallocene catalyst, or the like can be used.

The thickness of the sealant film 33 is preferably 30 μm or more, more preferably 40 μm or more, still more preferably 50 μm or more, and most preferably 60 μm or more. Further, the thickness of the sealant film 33 is preferably 100 μm or less, more preferably 80 μm or less.

As the single-layer sealant film 33 containing a propylene/ethylene block copolymer, there is a type having a high tensile modulus, such as ZK207, which will be described later. By using this type of sealant film 33, it is possible to improve the tearability when the pouch 10 is opened by the consumer by tearing the pouch 10 along the machine direction (MD).

The tensile elongation (%) of the sealant film 33 in the machine direction (MD) measured in a 25°C environment after being held for 1 minute in a 25°C environment is preferably 1100 (%) or less, more preferably is 1000 (%) or less, and may be 900 (%) or less, or 800 (%) or less. Further, the product of the tensile elongation (%) of the sealant film 33 in the machine direction (MD) and the thickness (μm) of the sealant film 33 is preferably 30,000 or more and 50,000 or less. The lower limit of this product in the flow direction (MD) is more preferably 34,000 or more, 36,000 or more, or 38,000 or more.

The tensile elongation (%) of the sealant film 33 in the width direction (TD) measured in a 25°C environment after being held for 1 minute in a 25°C environment is preferably 1200 (%) or less, more preferably is 1100 (%) or less, and may be 1000 (%) or less, or 900 (%) or less. Further, the product of the tensile elongation (%) of the sealant film 33 in the width direction (TD) and the thickness (μm) of the sealant film 33 is preferably 45,000 or more and 55,000 or less. The lower limit of this product in the width direction (TD) is more preferably 47,000 or more, or 49,000 or more.

The tensile modulus (MPa) of the sealant film 33 in the machine direction (MD) measured in a 25°C environment after being held in a 25°C environment for 1 minute is preferably 500 MPa or more, more preferably 600 MPa or more. and may be 650 MPa or more, or 700 MPa or more. Further, the product of the tensile modulus (MPa) of the sealant film 33 in the machine direction (MD) and the thickness (μm) of the sealant film 33 is preferably 35,000 or more, more preferably 38,000 or more, and even more preferably 45,000. That's all. Since the sealant film 33 has a high tensile modulus, tearability when opening the pouch 10 can be improved.

The tensile modulus (MPa) of the sealant film 33 in the width direction (TD) measured at 25° C. after being held for 1 minute at 25° C. is preferably 450 MPa or more, more preferably 500 MPa or more. and may be 550 MPa or more, or 600 MPa or more. Further, the product of the tensile modulus (MPa) of the sealant film 33 in the width direction and the thickness (μm) of the sealant film 33 is preferably 28,000 or more, and more preferably 30,000 or more.

The tensile modulus of the sealant film 33 is measured using the same measuring method and the same measuring conditions as the tensile elongation of the sealant film 33.

<Picture printing layer>
The pattern printing layer 34 is a layer for imparting information about the contents and packaged products, or for imparting beauty to the pouch, and includes, for example, a coloring material and a binder resin. By forming the pattern printing layer 34, a pattern can be formed on the pouch 10. The term "picture" in this specification is not particularly limited, and broadly includes, for example, figures, characters, patterns, patterns, symbols, patterns, marks, and the like. As the ink for gravure printing, Finart manufactured by DIC Graphics Corporation can be used.

The pattern printing layer 34 may also contain any other additives. Examples of additives include lubricants, antiblocking agents, fillers, curing agents, pigment dispersants, antifoaming agents, leveling agents, waxes, silane coupling agents, preservatives, antioxidants, ultraviolet absorbers, and rust preventives. agent, plasticizer, flame retardant, color developer, etc. These additives are used especially for the purpose of improving printing suitability, printing effects, etc., and the type and amount used can be appropriately selected depending on the printing method, printing substrate, and printing conditions. The pattern printing layer 34 can be formed on the first biaxially stretched plastic film 31 by a printing method such as gravure printing.

(color material)
The coloring material is not particularly limited, and known pigments and dyes can be used, and are appropriately selected according to the desired color.

(binder resin)
Examples of the binder resin include linseed oil, cut oil, soybean oil, hydrocarbon oil, rosin, rosin ester, rosin modified resin, shellac, alkyd resin, phenolic resin, maleic resin, natural resin, hydrocarbon resin, Polyvinyl chloride resin, polyacetic acid resin, polystyrene resin, polyvinyl butyral resin, (meth)acrylic resin, polyamide resin, polyester resin, polyurethane resin, epoxy resin, urea resin, melamine resin, amino alkyd Examples include polymers of type resins, nitrocellulose, ethylcellulose, chlorinated rubber, cyclized rubber, (meth)acrylate compounds, and mixtures thereof.

<First adhesive layer>
The first adhesive layer 35 includes an adhesive for bonding the first biaxially stretched plastic film 31 and the second biaxially stretched plastic film 32 by a dry lamination method. The adhesive constituting the first adhesive layer 35 is produced from an adhesive composition prepared by mixing a first composition containing a base agent and a solvent and a second composition containing a curing agent and a solvent. Specifically, the adhesive includes a cured product produced by a reaction between the base agent and the solvent in the adhesive composition.

Examples of adhesives include polyurethane. Polyurethane is a cured product of a polyol and an isocyanate compound produced by the reaction of a polyol as a main ingredient and an isocyanate compound as a curing agent. Examples of polyurethane include polyether polyurethane, polyester polyurethane, and the like. Polyether polyurethane is a cured product produced by the reaction of a polyether polyol as a main ingredient and an isocyanate compound as a curing agent. Polyester polyurethane is a cured product produced by the reaction of a polyester polyol as a main ingredient and an isocyanate compound as a curing agent.

Isocyanate compounds include aromatic isocyanate compounds such as tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), etc. or adducts or multimers of the various isocyanate compounds mentioned above can be used.

The thickness of the first adhesive layer 35 is preferably 2 μm or more, more preferably 3 μm or more. Further, the thickness of the first adhesive layer 35 is preferably 6 μm or less, more preferably 5 μm or less.

<Second adhesive layer>
The second adhesive layer 36 includes an adhesive for bonding the second biaxially stretched plastic film 32 and the sealant film 33 together by dry lamination. An example of the adhesive for the second adhesive layer 36 is polyurethane, as in the case of the first adhesive layer 35. In addition to the configuration, materials, and characteristics described below, the configuration, materials, and characteristics of the second adhesive layer 36 may be similar to those of the first adhesive layer 35.

The thickness of the second adhesive layer 36 is preferably 2 μm or more, more preferably 3 μm or more. Further, the thickness of the second adhesive layer 36 is preferably 6 μm or less, more preferably 5 μm or less.

By the way, as the isocyanate compounds constituting the curing agent of the adhesive, there are aromatic isocyanate compounds and aliphatic isocyanate compounds, as described above. Among these, aromatic isocyanate compounds elute components that cannot be used in food applications in high-temperature environments such as heat sterilization. By the way, the second adhesive layer 36 is in contact with the sealant film 33. Therefore, when the second adhesive layer 36 contains an aromatic isocyanate compound, the components eluted from the aromatic isocyanate compound will not adhere to the contents accommodated in the accommodation space 10A in contact with the sealant film 33. There is. In consideration of such problems, preferably, the adhesive constituting the second adhesive layer 36 is a cured product produced by the reaction of a polyol as a main ingredient and an aliphatic isocyanate compound as a curing agent. Use. This can prevent components that cannot be used in food applications caused by the second adhesive layer 36 from adhering to the contents.

<Transparent vapor deposition layer>
The transparent vapor deposition layer is formed on the surface of the first biaxially stretched plastic film 31 or the second biaxially stretched plastic film 32.

The transparent vapor deposition layer functions as a layer having a gas barrier function of blocking the permeation of oxygen gas, water vapor, and the like. Note that two or more transparent vapor deposition layers may be provided. When there are two or more transparent vapor deposited layers, they may have the same composition or different compositions. Examples of methods for forming the transparent vapor deposition layer include physical vapor deposition methods (PVD methods) such as vacuum evaporation methods, sputtering methods, and ion plating methods, plasma chemical vapor deposition methods, and thermal vapor deposition methods. Examples include chemical vapor deposition methods (Chemical Vapor Deposition methods, CVD methods) such as chemical vapor deposition methods and photochemical vapor deposition methods. Specifically, a transparent vapor deposition layer can be formed on a film forming roller using a roller type vapor deposition film forming apparatus.

The transparent vapor deposition layer is made of a transparent inorganic material. Examples of inorganic materials include metal oxides and inorganic oxides. Metal oxides include aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), boron (B), titanium (Ti), and lead (Pb). , zirconium (Zr), yttrium (Y), and other metal oxides. Examples of inorganic oxides include silicon (Si) oxides. As the inorganic material constituting the transparent vapor deposition layer, aluminum oxide (aluminum oxide) or silicon oxide is preferable.

The thickness of the transparent vapor deposition layer is preferably 40 Å (4 nm) or more and 130 Å (13 nm) or less. The lower limit of the thickness of the transparent vapor deposition layer is more preferably 50 Å (5 nm) or more, 60 Å (6 nm) or more, or 70 Å (7 nm) or more, and the upper limit is more preferably 120 Å (12 nm) or less, 110 Å (11 nm). It is as follows.

<Transparent gas barrier coating film>
The transparent gas barrier coating film has transparency and is formed on the surface of the transparent vapor deposition layer. The transparent gas barrier coating film is a layer that functions as a layer that suppresses the permeation of oxygen gas, water vapor, and the like. The transparent gas barrier coating film has the general formula R ³ _n M(OR ⁴ ) _m (wherein R ³ and R ⁴ represent an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the valence of M.) and at least one alkoxide represented by the above-mentioned polyvinyl alcohol. system resin and/or ethylene/vinyl alcohol copolymer, and further polycondensed by a sol-gel method in the presence of a sol-gel method catalyst, acid, water, and an organic solvent. It will be done.

As the alkoxide represented by the above general formula R ³ _n M(OR ⁴ ) _m , at least one of a partial hydrolyzate of an alkoxide and a condensate of hydrolysis of an alkoxide can be used. In addition, the partial hydrolyzate of the alkoxide described above does not necessarily have to have all the alkoxy groups hydrolyzed, and may be one in which one or more alkoxy groups have been hydrolyzed, or a mixture thereof. As the condensate of alkoxide hydrolysis, a dimer or more of partially hydrolyzed alkoxide, specifically a dimer to hexamer, is used.

In the alkoxide represented by the above general formula R ³ _n M(OR ⁴ ) _m , silicon, zirconium, titanium, aluminum, and the like can be used as the metal atom represented by M. In this embodiment, preferable metals include silicon, titanium, and the like. Furthermore, in the present embodiment, the alkoxide can be used alone or in combination of two or more different metal atom alkoxides in the same solution.

Further, in the alkoxide represented by the general formula R ³ _n M (OR ⁴ ) _m , specific examples of the organic group represented by R ³ include, for example, a methyl group, an ethyl group, an n-propyl group, an i Examples include alkyl groups such as -propyl group, n-butyl group, i-butyl group, sec-butyl group, t-butyl group, n-hexyl group, n-octyl group, and others. Further, in the alkoxide represented by the general formula R ³ _n M (OR ⁴ ) _m , specific examples of the organic group represented by R ⁴ include, for example, a methyl group, an ethyl group, an n-propyl group, an i -propyl group, n-butyl group, sec-butyl group, and others. Note that these alkyl groups in the same molecule may be the same or different.

When preparing the above gas barrier composition, for example, a silane coupling agent or the like may be added. As the silane coupling agent, known organoalkoxysilanes containing organic reactive groups can be used. In this embodiment, organoalkoxysilane having an epoxy group is particularly preferably used, and specifically, for example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β -(3,4-epoxycyclohexyl)ethyltrimethoxysilane and the like can be used. The above silane coupling agents may be used alone or in combination of two or more.

The thickness of the transparent gas barrier coating film is preferably 100 nm or more and 500 nm or less. If the thickness of the transparent gas barrier coating film is 100 nm or more, stable gas barrier properties can be obtained, and if the thickness is 500 nm or less, a good coating film can be obtained. The lower limit of the thickness of the transparent gas barrier coating film is more preferably 125 nm or more, 150 nm or more, or 200 nm or more, and the upper limit is preferably 450 nm or less, 400 nm or less, or 300 nm or less.

Specific examples of the packaging material 30 include the following packaging materials. Note that "/" is used as a notation to indicate a boundary between layers when listing layers. Layers shall be written from the outside of the pouch to the inside. That is, the layer described on the rightmost side is the sealant film.
Biaxially oriented PET film/Picture printing layer/Adhesive layer/Biaxially oriented nylon film/Adhesive layer/Sealant film Biaxially oriented PET film/Picture printing layer/Adhesive layer/Biaxially oriented PET film/Adhesive layer/ Sealant film Biaxially stretched PET film / Pattern printing layer / Adhesive layer / Biaxially stretched straight cut nylon film / Adhesive layer / Sealant film Biaxially stretched PET film / Design printed layer / Adhesive layer / Biaxially stretched straight cut PET Film/Adhesive layer/Sealant film Biaxially oriented PET film/Transparent vapor deposited layer/Transparent gas barrier coating film/Design printing layer/Adhesive layer/Biaxially oriented nylon film/Adhesive layer/Sealant film Biaxially oriented PET film/ Transparent vapor deposition layer / Transparent gas barrier coating film / Pattern printing layer / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Sealant film Biaxially oriented PET film / Pattern printing layer / Adhesive layer / Transparent gas barrier coating film / Transparent vapor deposition layer/biaxially oriented PET film/adhesive layer/sealant film

<<Other packaging materials>>
It is also possible to use a packaging material 40 shown in FIG. 10 instead of the packaging material 30. The physical properties (for example, Young's modulus, hot seal strength, etc.) of the packaging material 40 are the same as the physical properties of the packaging material 30 unless otherwise specified, so a description thereof will be omitted here.

Like the packaging material 30, the packaging material 40 includes at least a first biaxially stretched plastic film 31, a second biaxially stretched plastic film 32, and a sealant film 33 in this order. 40 further includes a light-shielding printed layer 41 provided between the first biaxially stretched plastic film 31 and the sealant film 33. The packaging material 40 does not include a metal foil layer. The packaging material 40 has only two biaxially oriented plastic films in the packaging material 40. The packaging material 40 shown in FIG. 10 includes, for example, a first biaxially stretched plastic film 31, a transparent vapor deposition layer 42, a transparent gas barrier coating film 43, a pattern printing layer 34, a light shielding printing layer 41, and a first adhesive layer 35. , a second biaxially stretched plastic film 32, a second adhesive layer 36, and a sealant film 33 in this order. Note that the packaging material may further include another functional layer that exhibits a desired function between the first biaxially stretched plastic film 31 and the sealant film 33. Further, at least one of the transparent vapor deposition layer 42, the transparent gas barrier coating film 43, and the pattern printing layer 34 may not be provided.

In FIG. 10, members denoted by the same reference numerals as those in FIG. 3 are the same as those shown in FIG. 3, so their explanation will be omitted. Further, the transparent vapor deposited layer 42 is the same as the transparent vapor deposited layer explained in the section of the packaging material 30, and the transparent gas barrier coating film 43 is the same as the transparent gas barrier coating film explained in the section of the packaging material 30. , the explanation will be omitted.

The light-shielding printed layer 41 may be provided between the first biaxially stretched plastic film 31 and the sealant film 33. For example, the light-shielding printed layer 41 may be provided between the first biaxially stretched plastic film 31 and the second or between the second biaxially stretched plastic film 32 and the sealant film 33.

It is preferable that the light-shielding printed layer 41 is provided closer to the sealant film 33 than the pattern printed layer 34 is. Thereby, the pattern on the pattern printing layer 34 can be visually recognized from the outside of the pouch 10.

The total light transmittance of the packaging material 40 is preferably 25.0% or less. Thereby, a pouch having good light-shielding properties can be obtained. The total light transmittance is preferably 23.0% or less, 20.0% or less, 18.0% or less, or 16.0% or less, from the viewpoint of obtaining a pouch with better light blocking properties, From the viewpoint of obtaining a pouch with excellent light-shielding properties, the content is more preferably 10.0% or less, 5.0% or less, or 3.0% or less.

The total light transmittance can be measured in accordance with JIS K7361-1:1997 using a haze meter (product name "HM-150", manufactured by Murakami Color Research Institute Co., Ltd., measuring diameter 20 mmφ). Specifically, as shown in FIG. 11, first, from the front surface of the pouch, excluding the seal part, one side L5 is 50 mm, and the other side L6 extending in a direction perpendicular to one side L1 is 50 mm. Three square test pieces S4 are cut out, and as shown in FIG. 12, one side L5 is 50 mm and the other side L6 extending in a direction perpendicular to one side L1 is 50 mm from the back side of the pouch, not including the seal part. Cut out two square test pieces S4. Note that the test piece S4 may include a pattern printing layer. The test piece S4 is cut out so that the other side L6 is parallel to the X direction (the direction perpendicular to the direction in which the first side seal portion extends). Thereafter, the test piece S4 was placed in a haze meter so that the first biaxially stretched plastic film 31 was on the light source side without any curls or wrinkles, and the test piece was placed in an environment with a temperature of 25° C. and a relative humidity of 50%. After holding S4 for 1 minute, the total light transmittance of test piece S4 is measured in an environment of a temperature of 25° C. and a relative humidity of 50%. The total light transmittance of the five test pieces S4 is measured, and the average value is taken as the total light transmittance of the packaging material.

The appearance of the pouch is sometimes required to be bright white in order to give a clean and refreshing feeling or to highlight the pattern of the pattern printing layer. On the other hand, in order to lower the total light transmittance, it is preferable to provide a layer darker in color than the white layer (dark color layer) inside the white layer. However, when such a dark-colored layer is provided, even though there is a white layer on the outside of the dark-colored layer, when the pouch is viewed from the outside, it looks dull and white due to the color of the dark-colored layer. There is a risk that bright whiteness may not be obtained. Therefore, in order to obtain a pouch with vivid whiteness, the L ^* value in the L ^* a ^* b ^* color system measured by the SCE method (specular reflection light elimination method) of the packaging material 40 must be 65.0 or more. It is preferable that there be. The L ^* value essentially represents the whiteness, with the closer it approaches 100, the higher the whiteness, and the closer it approaches 0, the lower the whiteness. The reason why the SCE method is used for measurement is that the SCE method is a measurement method that is similar to the sense of seeing with the human eye. The above L ^* value is more preferably 68.0 or more or 70.0 or more from the viewpoint of obtaining a pouch with better whiteness, and 72.0 or more from the viewpoint of obtaining a pouch with more vivid whiteness. More preferably, it is 0 or more or 75.0 or more.

The L ^* value is based on JIS Z8781-4:2013 (color measurement - Part 4: CIE 1976L ^* a ^* b ^* color space) and is measured using a spectrophotometer (product name "SpectroEye", manufactured by X-Rite, It can be measured using a measuring diameter of 2 mmφ). Specifically, as shown in FIG. 13, first, from the front surface of the pouch, one side L7 is 5 mm and the other side extends in a direction perpendicular to one side L1, excluding the pattern printing layer and the seal part. Five square test pieces S5 with L8 of 5 mm are cut out. Although the test piece S5 has a square shape, it may have any shape as long as it is larger than the area of the measurement diameter of 2 mm. The test piece S5 may be cut out from the back side of the pouch. The test piece S5 is cut out so that the other side L8 is parallel to the X direction (the direction perpendicular to the direction in which the first side seal portion extends). Thereafter, the test piece S5 is placed on a white plate (material: paper, size: A4 size (210 mm x 297 mm), thickness: 0.3 mm) so that the first biaxially stretched plastic film 31 is on the top surface. Thereafter, after holding the test piece S5 in an environment of a temperature of 25°C and a relative humidity of 50% for 1 minute, the L ^* value of the test piece S5 was measured using the SCE method (specular reflection light (removal method). Furthermore, when measuring the L ^* value, the light source is D50 and the viewing angle is 2°. The L ^* value is measured for the five test pieces S5, and the average value is taken as the L ^* value of the packaging material.

<Light-shielding printing layer>
The light-shielding printed layer 41 is a layer for obtaining light-shielding properties. By forming the light-shielding print layer 41, it is possible to prevent the contents from being seen through, and it is also possible to suppress photodeterioration such as discoloration of the contents during long-term storage.

The thickness of the light-shielding printed layer 41 is preferably 2.0 μm or more and 6.0 μm or less. If this thickness is 2.0 μm or more, the total light transmittance of the packaging material 40 can easily be 25.0% or less. If the thickness of the light-shielding printed layer 41 is 6.0 μm or less, it is possible to suppress the thickening of the entire packaging material 40 and to improve production efficiency and processing suitability. The lower limit of the thickness of the light-shielding printed layer 41 is preferably 3.0 μm or more, 3.5 μm or more, or 4.0 μm or more, and the upper limit is preferably 5.5 μm or less and 5.0 μm or less. In this specification, the "thickness of the light-shielding printed layer" refers to cases where the light-shielding printed layer has a multilayer structure, such as a laminated structure of a white layer and a gray layer or a laminated structure of a white layer and a metal flake-containing layer, as described later. shall mean the total thickness of each layer constituting the light-shielding printing layer.

For example, the light-shielding printing layer 41 is formed on the first biaxially stretched plastic film 31 and the second biaxially stretched plastic film 32 by a known method such as a gravure printing method, an offset printing method, a letterpress printing method, a silk screen printing method, etc. It can be formed using a printing method.

It is preferable that the light-shielding printed layer 41 is provided on substantially the entire surface of the packaging material 40. Substantially the entire surface means 80% or more of the surface of the packaging material, preferably 90% or more, more preferably 95% or more, still more preferably 99% or more, and most preferably 100%.

The light-shielding printing layer 41 includes (1) a layer containing a white pigment (hereinafter, this layer may be referred to as a "white layer"), and a layer containing a white pigment and a black pigment (hereinafter, this layer may be referred to as a "gray layer"); or (2) a layer containing a white pigment and a layer containing metal flakes (hereinafter, this layer may be referred to as a "metal flake-containing layer"). It is preferable that it is a laminate comprising: Among these, the laminate described in (2) above is more preferable as the light-shielding printed layer 41 because a lower total light transmittance (for example, 10.0% or less) can be obtained.

(white layer)
The white layer may have a single layer structure, or may have a multilayer structure in which two or more white layers having the same composition or different compositions are laminated. The white layer is preferably located closer to the first biaxially stretched plastic film 31 (viewer side) than the gray layer or the metal flake-containing layer. When the packaging material 40 includes a metal flake-containing layer, the metal flake-containing layer has a high proportion of a diffusion component, but the proportion of a diffusion component is still lower than that of a white layer, so when looking directly at the reflection from the metal flake-containing layer, People feel dazzling, albeit slightly. That is, by locating the white layer closer to the first biaxially stretched plastic film 31 (viewer side) than the metal flake-containing layer, the specular reflection of the metal-containing flake layer is softened, and the design of the packaging material 40 is improved. It can be calming. Furthermore, although the white layer can improve the light-shielding properties of the packaging material 40, its contribution to the light-shielding properties is lower than that of the gray layer or the metal flake-containing layer.

The thickness of the white layer is preferably 0.5 μm or more and 5.0 μm or less. If the thickness of the white layer is 0.5 μm or more, the total light transmittance of the packaging material 40 can be easily reduced to 25.0% or less, and the white layer can easily soften the specular reflection of external light. It is easy to make the design calm. Moreover, if the thickness of the white layer is 5.0 μm or less, it is possible to suppress the thickening of the entire packaging material 40 and improve production efficiency and processing suitability. The lower limit of the thickness of the white layer is preferably 0.7 μm or more, 1.0 μm or more, or 1.5 μm or more, and the upper limit is 4.5 μm or less, 4.0 μm or less, or 3.5 μm or less. is preferred. The "thickness of the white layer" in this specification means the total thickness of each layer constituting the white layer when the white layer has a multilayer structure.

Examples of the white pigment contained in the white layer include titanium oxide, barium sulfate, magnesium oxide, calcium carbonate, zinc oxide, and white lead. Among these, titanium oxide is preferred because of its excellent hiding power.

Titanium oxide includes anatase type, rutile type and brookite type depending on the crystal structure. Among these, the rutile type and brookite type are preferred because of their low photocatalytic activity, and the rutile type is more preferred because of its versatility.

The white pigment preferably has an average primary particle diameter of 150 nm or more and 500 nm or less, from the viewpoint of strengthening diffusion and increasing hiding power. The lower limit of the average primary particle diameter of the white pigment is more preferably 250 nm or more, and the upper limit is more preferably 450 nm or less. In this specification, the average primary particle diameter of various pigments such as white pigments is measured using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM) at a magnification of 40,000 times to 200,000 times. The primary particle diameters of 20 white pigments are measured from the image of the cross section of the white layer, and the arithmetic mean value of the primary particle diameters of the 20 white pigments is determined.

It is preferable that the white layer contains a binder resin. Examples of the binder resin include polyolefin resins such as polyethylene resins and chlorinated polypropylene resins, poly(meth)acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, and vinyl chloride-vinyl acetate copolymers. , polystyrene resin, styrene-butadiene copolymer, vinylidene fluoride resin, polyvinyl alcohol resin, polyvinyl acetal resin, polyvinyl butyral resin, polybutadiene resin, polyester resin, polyamide resin, alkyd resin, epoxy resins, unsaturated polyester resins, thermosetting poly(meth)acrylic resins, melamine resins, urea resins, polyurethane resins, phenolic resins, xylene resins, maleic acid resins, nitrocellulose, ethylcellulose, acetyl Examples include cellulose resins such as butyl cellulose and ethyloxyethyl cellulose, rubber resins such as chlorinated rubber and cyclized rubber, petroleum resins, and natural resins such as rosin and casein. These may be used alone or in combination of two or more. Further, from the viewpoint of the global environment, it is preferable that the binder resin includes resin derived from plants such as trees, rice bran, and seeds.

The content of the white pigment is preferably 3% by mass or more and 50% by mass or less of the total solid content of the white layer. If the white pigment content is 3% by mass or more, the total light transmittance of the packaging material 40 can be easily reduced to 25.0% or less, and if the white pigment content is 50% by mass or less, the white layer Adhesion between the adjacent layer and the white layer is improved, and retort resistance can be easily improved. The lower limit of the white pigment content is more preferably 5% by mass or more or 7% by mass or more of the total solids of the white layer, and the upper limit of the white pigment content is 30% by mass of the total solids of the white layer. % or less or 20% by mass or less.

The white layer preferably contains inorganic particles having an average primary particle diameter of 1 nm or more and 100 nm or less. By including inorganic particles with such an average primary particle size in the white layer, the white pigment is prevented from sinking below the white layer, and the adhesion between the white layer and the white layer is improved. It can be done easily. The lower limit of the average primary particle diameter of the inorganic particles is more preferably 2 nm or more or 5 nm or more, and the upper limit is more preferably 50 nm or less or 30 nm or less.

The content of inorganic particles in the white layer is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 2 parts by mass or more and 15 parts by mass or less, based on 100 parts by mass of the white pigment. It is more preferably at least 10 parts by mass.

Examples of inorganic particles include silica, alumina, and zirconia. Among these, silica is preferred because of its excellent transparency. Further, since silica and alumina have excellent insulating properties, they are preferable in that they can improve microwave resistance.

In the white layer, if necessary, for example, fillers, stabilizers, plasticizers, antioxidants, light stabilizers such as ultraviolet absorbers, dispersants, thickeners, desiccants, lubricants, antistatic agents, Any additives such as crosslinking agents can be added.

(gray layer)
The gray layer may have a single layer structure, or may have a multilayer structure in which two or more gray layers having the same composition or different compositions are laminated. The gray layer can be formed from gray ink, and the gray ink may be made by, for example, mixing a white ink containing a white pigment and a black ink (black ink) containing a black pigment. good.

The thickness of the gray layer is preferably 0.5 μm or more and 5.0 μm or less. If the thickness of the gray layer is 0.5 μm or more, the total light transmittance of the packaging material 40 can be easily set to 25.0% or less. Moreover, if the thickness of the gray layer is 5.0 μm or less, it is possible to suppress the thickening of the entire packaging material 40 and improve production efficiency and processing suitability. The lower limit of the thickness of the gray layer is more preferably 0.7 μm or more, 1.0 μm or more, or 1.5 μm or more, and the upper limit is 4.5 μm or less, 4.0 μm or less, or 3.5 μm or less. It is more preferable. The "thickness of the gray layer" in this specification means the total thickness of each layer constituting the gray layer when the gray layer has a multilayer structure.

The white pigment contained in the gray layer is the same as the white pigment contained in the white layer, so a description thereof will be omitted here. Examples of the black pigment contained in the gray layer include carbon black, titanium black, and iron black. Among these, carbon black is more preferred because it is versatile and can easily provide a desired color.

The ratio of the black pigment content to the white pigment content in the gray layer ((black pigment content/white pigment content)×100) is preferably 0.1% or more and 10% or less. If this ratio is 0.1% or more, the total light transmittance of the packaging material 40 can be easily set to 25.0% or less. Moreover, if this ratio is 10% or less, it is possible to suppress the packaging material 40 from becoming grayish. The lower limit of this ratio is more preferably 0.5% or more, 1.0% or more, or 1.5% or more, and the upper limit of this ratio is 8.0% or less, 7.0% or less, or More preferably, it is 5.0% or less.

The content of the white pigment in the gray layer is preferably 18.0% by mass or more and 29.7% by mass or less of the total solid content of the gray layer. If the white pigment content is 18.0% by mass or more, it is possible to suppress the packaging material 40 from becoming grayish, and if it is 29.7% by mass or less, the light-shielding property can be improved. The lower limit of the white pigment content in the gray layer is more preferably 18.2% by mass or more, 18.4% by mass or more, or 19.0% by mass or more, and the upper limit is 29.4% by mass or less. , 29.1% by mass or less, or 28.8% by mass or less.

The content of the black pigment in the gray layer is preferably 0.2% by mass or more and 3.0% by mass or less based on the total solid content of the gray layer. If the content of the black pigment is 0.2% by mass or more, the total light transmittance can be easily reduced to 25.0% or less, and if the content is 3.0% by mass or less, the packaging material 40 will not have a grayish tinge. It can be suppressed. The lower limit of the black pigment content in the gray layer is more preferably 0.3% by mass or more, 0.4% by mass or more, or 0.6% by mass or more, and the upper limit is 2.4% by mass or less. , more preferably 2.0% by mass or less, or 1.5% by mass or less.

It is preferable that the gray layer contains a binder resin. Examples of the binder resin include those similar to the binder resins described in the section regarding the white layer.

In the gray layer, if necessary, for example, fillers, stabilizers, plasticizers, antioxidants, light stabilizers such as ultraviolet absorbers, dispersants, thickeners, desiccants, lubricants, antistatic agents, Any additives such as crosslinking agents can be added.

(Metal flake containing layer)
It is possible to reduce the total light transmittance of the packaging material to 25.0% or less with just the white layer, but in that case, the white layer needs to be extremely thick, which tends to cause odor due to residual solvent. Furthermore, the processing suitability of the packaging material is reduced. For this reason, a metal flake-containing layer is provided in addition to the white layer.

The metal flake-containing layer may have a multilayer structure in which a plurality of metal flake-containing layers having the same composition or different compositions are laminated. By laminating a plurality of metal flake-containing layers, the metal flakes are easily laminated in the thickness direction, and the total light transmittance can be reduced.

The thickness of the metal flake-containing layer is preferably 0.5 μm or more and 5.0 μm or less. If the thickness of the metal flake-containing layer is 0.5 μm or more, the total light transmittance of the packaging material 40 can be easily reduced to 25.0% or less. Moreover, if the thickness of the metal flake-containing layer is 5.0 μm or less, it is possible to suppress the thickening of the packaging material 40 as a whole and improve production efficiency and processing suitability. The lower limit of the thickness of the metal flake-containing layer is more preferably 0.7 μm or more, 1.0 μm or more, or 1.5 μm or more, and the upper limit is 4.5 μm or less, 4.0 μm or less, 3.5 μm or less, Or, it is more preferable that it is 3.0 μm or less. The "thickness of the metal flake-containing layer" as used herein means the total thickness of each layer constituting the metal flake-containing layer when the metal flake-containing layer has a multilayer structure.

When the thickness of the white layer is t1 and the thickness of the metal flake-containing layer is t2, t1/t2 is preferably 0.2 or more and 2.0 or less. When t1/t2 is 0.2 or more, specular reflection can be easily softened sufficiently by the white layer, and the design of the packaging material can be easily made calm. Moreover, when t1/t2 is 2.0 or less, light-shielding properties can be easily imparted by the metal flake-containing layer. The lower limit of t1/t2 is more preferably 0.3 or more, and the upper limit is more preferably 1.8 or less.

Examples of the material of the metal flakes include metals and alloys such as aluminum, gold, silver, brass, titanium, chromium, nickel, nickel-chromium, and stainless steel. Among these, aluminum and silver are preferred from the viewpoint of easily obtaining a color tone close to white, and aluminum is more preferred from the viewpoint of suppressing cost increases.

Metal flakes can be obtained, for example, by mixing the above metal or alloy powder with a solvent and spreading and/or pulverizing the powder using a media stirring mill, a ball mill, an attritor, or the like. Since the metal flakes obtained in this manner are made into flakes by stretching the metal powder, the surface of the metal flakes has undulations and depressions, which can improve diffusibility.

When producing metal flakes using the above method, the length, thickness, and aspect ratio of the metal flakes can be adjusted by adjusting the size of the bearing ball, the time and intensity of spreading and/or crushing, and the like. For example, by increasing the time for spreading and crushing, and by increasing the intensity of spreading and crushing, the average length and thickness become smaller.

The average length of the metal flakes is preferably 1 μm or more and 10 μm. If this average length is 1 μm or more, the diffusivity will be improved and the brightness will be improved. Moreover, if this average length is 10 μm or less, the density of metal flakes in the metal flake-containing layer can be increased. The lower limit of the average length of the metal flakes is more preferably 2 μm or more or 3 μm or more, and the upper limit is more preferably 7 μm or less or 5 μm or less. As mentioned above, by stacking relatively short metal flakes in the thickness direction within the metal flake-containing layer, multiple reflections occur at many locations within the plane of the metal flake-containing layer, reducing the total light transmittance. can be lowered.

The average length of the metal flakes is determined as the average value of the lengths of 20 arbitrary metal flakes observed from the plane direction of the packaging material using an optical microscope or an electron microscope. Note that the length of one metal flake means the maximum length of one metal flake in the planar direction.

Moreover, it is preferable that the average thickness of the metal flakes is 0.01 μm or more and 0.50 μm or less. By setting the average thickness of the metal flakes to 0.01 μm or more, the hiding power of each metal flake can be improved, and the total light transmittance can be easily made to be 25.0% or less. In addition, by setting the average thickness of the metal flakes to 0.50 μm or less, the metal flakes are more likely to be stacked in the thickness direction within the metal flake-containing layer, and multiple reflections can occur between the metal flakes. Light transmittance can be reduced. The lower limit of the average thickness of the metal flakes is more preferably 0.03 μm or more or 0.05 μm or more, and the upper limit is more preferably 0.30 μm or less or 0.15 μm or less.

The average thickness of the metal flakes is determined as the average value of the thicknesses of 20 arbitrary metal flakes obtained by observing the cross section of the packaging material using an optical microscope or an electron microscope. The thickness of one metal flake is determined by dividing the cross-sectional image of one metal flake into five regions of equal length in the length direction, and calculating the thickness of the central part of each region (t ₁ , t ₂ , t ₃ , t ₄ , t _{5 )} and the average of t ₁ to t ₅ .

The aspect ratio (average length/average thickness) of the metal flakes is preferably 25 or more and 100 or less. By setting the aspect ratio of the metal flakes to 25 or more, it becomes difficult for the metal flakes to tilt within the metal flake-containing layer, so that the metal flakes are easily stacked in the thickness direction within the metal flake-containing layer. As a result, multiple reflections can be caused between the metal flakes, and the total light transmittance can be reduced. Further, by setting the aspect ratio of the metal flakes to 100 or less, when the metal flakes are tilted, adjacent metal flakes are less likely to come into contact with each other, and microwave oven resistance can be improved. The lower limit of the aspect ratio of the metal flakes is more preferably 27 or more or 30 or more, and the upper limit is still more preferably 70 or less or 50 or less.

Preferably, the metal flakes are of the non-leafing type. With non-leafing type metal flakes, metal flakes are prevented from floating near the coating surface during the formation process of the metal flake-containing layer, so metal flakes are more likely to be stacked in the thickness direction within the metal flake-containing layer. As a result, multiple reflections can occur between the metal flakes, so the optical path length of light passing through the metal flake-containing layer becomes extremely long, and the total light transmittance can be reduced. This makes it possible to lower the total light transmittance compared to leafing type metal flakes.

Furthermore, with non-leafing type metal flakes, during the formation process of the metal flake-containing layer, the metal flakes are uniformly dispersed within the layer, so even if the metal flakes are tilted, the spacing between the metal flakes is narrow enough to cause sparks and overheating. Therefore, it is possible to suppress deterioration of the packaging material during use of the microwave oven.

In addition, when laminating a plurality of metal flake-containing layers, the metal flakes can be laminated as a whole of the plurality of silver layers even if leafing type metal flakes are used. However, in the case of the leafing type, much of the light is specularly reflected by the metal flakes arranged on the coating surface of the metal flake-containing layer that the light reaches first, making it difficult for the light to reach the next metal flake-containing layer. , hard to cause multiple reflections. Therefore, even when a plurality of metal flake-containing layers are laminated, non-leafing type metal flakes tend to reduce the total light transmittance. Additionally, non-leafing type metal flakes are useful in that they can easily reduce residual solvent.

Non-leafing type metal flakes are metal flakes that are not surface-treated with long-chain saturated fatty acids such as palmitic acid, stearic acid, and behenic acid; for example, metal flakes that are surface-treated with unsaturated fatty acids such as linoleic acid, Examples include metal flakes without surface treatment.

From the viewpoint of microwave oven resistance, the surface of the metal flakes is preferably coated with a resin. Resin-coated metal flakes can be produced, for example, by the methods described in JP-A-62-253668, JP-A-64-40566, JP-A-2003-213157, and JP-A-2012-241039. .

The content of metal flakes in the metal flake-containing layer is preferably 20% by mass or more and 60% by mass or less of the total solid content of the metal flake-containing layer. By setting the content of metal flakes to 20% by mass or more, the total light transmittance of the packaging material can easily be 25.0% or less. In addition, by setting the content of metal flakes to 60% by mass or less, it is possible to easily improve microwave resistance, and the adhesion between the layer adjacent to the metal flake-containing layer and the metal flake-containing layer is also improved, resulting in better resistance to microwave ovens. Good retortability can be easily achieved. The lower limit of the metal flake content is more preferably 30% by mass or more or 35% by mass or more, and the upper limit is still more preferably 55% by mass or less or 50% by mass or less.

Preferably, the metal flake-containing layer contains a binder resin. Examples of the binder resin for the metal flake-containing layer include those similar to those for the white layer. In addition, when the metal flake-containing layer has a multilayer structure, in order to suppress interface reflection, it is preferable that the binder resin of the plurality of metal flake-containing layers has a refractive index difference within 0.03, and preferably within 0.01. It is more preferable to do so.

The metal flake-containing layer may contain fillers, stabilizers, plasticizers, antioxidants, light stabilizers such as ultraviolet absorbers, dispersants, thickeners, desiccants, lubricants, antistatic agents, etc., as necessary. Any additives such as crosslinking agents and crosslinking agents can be added.

Specific examples of the packaging material 40 include the following packaging materials. Note that, similarly to the above, "/" is used as a notation to indicate the boundary between layers when listing layers. Layers shall be written from the outside of the pouch to the inside. That is, the layer described on the rightmost side is the sealant film.
Biaxially oriented PET film / Transparent vapor deposited layer / Transparent gas barrier coating film / Pattern printing layer / Shade printing layer / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Sealant film Biaxially oriented PET film / Transparent vapor deposited layer / Transparent gas barrier coating film / Light shielding printed layer / Adhesive layer / Biaxially oriented PET film / Adhesive layer / Sealant film Biaxially stretched PET film / Pattern printing layer / Light shielding printed layer / Adhesive layer / Transparent gas barrier coating film / Transparent vapor deposited layer / Biaxially oriented PET film / Adhesive layer / Sealant film Biaxially oriented PET film / Light shielding printing layer / Adhesive layer / Transparent gas barrier coating film / Transparent vapor deposited layer / Biaxially oriented PET film / Adhesive layer / Sealant film Biaxially stretched PET film / Pattern printing layer / Light-shielding printed layer / Adhesive layer / Biaxially stretched PET film / Adhesive layer / Sealant film Biaxially stretched PET film / Light-shielding printed layer / Adhesive layer / Biaxially stretched PET Film / Adhesive layer / Sealant film Biaxially oriented PET film / Pattern printing layer / Light shielding print layer / Adhesive layer / Biaxially stretched straight cut PET film / Adhesive layer / Sealant film Biaxially stretched PET film / Light shielding print layer / Adhesive layer/biaxially stretched straight cut PET film/adhesive layer/sealant film

According to this embodiment, the Young's modulus of the packaging material 30 in one direction (for example, machine direction (MD)) is 3000 MPa or more when measured in an environment of 25° C., so the Young's modulus in one direction is high. When the contents stored in the pouch are heated in a microwave oven, the water contained in the contents evaporates and steam is generated, increasing the internal pressure of the pouch and stretching the packaging material that makes up the pouch. However, if the Young's modulus of the packaging material is high, it is possible to suppress the packaging material from being stretched during heating. Thereby, it is possible to suppress changes in the dimensions of the packaging material 30 constituting the pouch 10 when heated using a microwave oven, so that the appearance of the pouch 10 after being heated in the microwave oven can be improved. Furthermore, when a standing pouch is produced using the packaging material 30, the pouch can be more self-supporting.

If the seal strength of the steam vent seal in a pouch that has been heated to a high temperature in a microwave oven reaches a moderately low value, the steam vent seal will easily peel off based on the force received from the pressure of the water vapor generated in the storage space. Become. That is, the steam release seal portion will peel off at a lower pressure. According to the present embodiment, the hot sealing strength of the pouch 10 when measured in an environment of 100° C. is 20.0 N or less, so the hot sealing strength is low. This makes it easier for steam to escape, allowing for stable steam release.

Normally, when trying to obtain light-shielding properties in a pouch, a packaging material containing a metal foil layer such as aluminum foil is used, but when such packaging material is used, there is a risk of sparks occurring when heated in a microwave oven. Therefore, metal foil layers cannot be used as packaging materials for pouches used in microwave ovens. On the other hand, in this embodiment, when a packaging material 40 having a light-shielding printed layer 41 and a total light transmittance of 25.0% or less is used as the packaging material as shown in FIG. 10, it is difficult to obtain light-shielding properties. At the same time, sparks can be suppressed when heating in a microwave oven. Thereby, it is possible to obtain a pouch that can be heated in a microwave oven and can suppress photodeterioration of the contents.

If the contents contained in the pouch have a high viscosity or a high oil content, the contents may become overheated when heated in a microwave oven, and there is a risk that holes may be formed in the packaging material constituting the pouch. On the other hand, when biaxially stretched polyethylene terephthalate films are used as the first biaxially stretched plastic film 31 and the second biaxially stretched plastic film 32 of the packaging materials 30 and 40, the heat resistance is excellent. Therefore, it is possible to prevent holes from forming in the packaging materials 30 and 40 when heated in a microwave oven.

EXAMPLES In order to explain the present invention in detail, Examples will be given and explained below, but the present invention is not limited to these descriptions.

<Example 1>
First, a biaxially stretched polyethylene terephthalate film (product name "E5100", manufactured by Toyobo Co., Ltd.) having a thickness of 12 μm was prepared as a first biaxially stretched plastic film. Subsequently, a pattern printing layer was formed on this film. The thickness of the pattern printing layer was 1.0 μm. Further, as a second biaxially stretched plastic film, a biaxially stretched nylon film (product name: "Bonyl QC", manufactured by Kojin Film & Chemicals Co., Ltd.) with a thickness of 15 μm was prepared. Further, as a sealant film, an unstretched polypropylene film (product name "ZK207", manufactured by Toray Film Kako Co., Ltd.) with a thickness of 70 μm was prepared. ZK207 contained the propylene/ethylene block copolymer described above.

ZK207 has low tensile elongation. Specifically, the tensile elongation of ZK207 in the machine direction (MD) is 790% when the thickness is 50 μm and 730% when the thickness is 60 μm. Further, the tensile elongation of ZK207 in the width direction (TD) is 1020% when the thickness is 50 μm, and 870% when the thickness is 60 μm. Therefore, the product of tensile elongation (%) and thickness (μm) of ZK207 in the machine direction is 39,500 when the thickness is 50 μm and 43,800 when the thickness is 60 μm. Further, the product of tensile elongation (%) and thickness (μm) of ZK207 in the width direction is 51,000 when the thickness is 50 μm, and 52,200 when the thickness is 60 μm.

Next, by a dry lamination method, the biaxially oriented polyethylene terephthalate film, the pattern printing layer, the first adhesive layer, the biaxially oriented nylon film, the second adhesive layer, and the unoriented polypropylene film are laminated in this order to form the packaging material. Created. As the first adhesive layer and the second adhesive layer, a two-component polyurethane adhesive (base resin: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used. Note that the main ingredient RU-40 is a polyester polyol. The thickness of the first adhesive layer and the second adhesive layer was 3.0 μm.

Then, using the three packaging materials produced above, the standing pouch shown in FIG. 1 was produced by filling with 200 ml of water. Specifically, first, the packaging material that will be the bottom is folded in half so that the unstretched polypropylene film that is the sealant film is on the outside, and the first and second parts that are connected to each other through the fold line are folded. The pouch was formed and folded in half, and when it was cut and made into a pouch, a circular shape with a diameter of 10 mm was punched out at a portion that would be near the lower end of both lateral edges of the bottom surface to form a through hole.

Then, the packaging material that will become the bottom film is placed in a predetermined position between the packaging material that will become the front film and the packaging material that will become the back film, and the packaging material will be heat-sealed under the following conditions. A first side seal, a second side seal, a first bottom seal, a second bottom seal, and a steam vent seal were formed. This resulted in a pouch with an open top. In addition, since there is no packaging material that will become the bottom film folded in half in the through-hole area, the packaging material that will become the front film and the packaging material that will become the back film will be directly fused to form the auxiliary bottom seal. A division was formed.
(Heat fusion conditions)
・Heat fusion device: Heat sealer TP-701-A (manufactured by Tester Sangyo Co., Ltd.)
・Heat fusion temperature: 220℃
・Heat fusion pressure: 0.1MPa
・Heat fusion time: 1 second

Thereafter, each pouch was filled with 200 ml of water through its opening, and then heat-sealed under the same heat-sealing conditions as described above to form an upper seal portion and seal the pouch. Thereafter, each pouch was subjected to retort treatment under the following conditions to produce a retort-treated pouch according to Example 1. In Example 1, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.
(Retort processing)
・Method: Spray type ・Retort temperature: 121℃
・Retort time: 30 minutes

In the manufactured pouch according to Example 1, the height H of the pouch was 160 mm, the width W1 of the pouch was 147 mm, the folding width W2 of the bottom gusset part was 46 mm, the first side seal part and the second side seal part. The width W3 of the steam release seal portion was 7.0 mm, the width W4 of the steam release seal portion was 5 mm, and the width W5 of the upper seal portion was 10.0 mm.

<Example 2>
In Example 2, instead of a 15 μm thick biaxially stretched nylon film (product name “Bonyl QC”, Kojin Film & Chemicals Co., Ltd.), a 12 μm thick biaxially stretched nylon film was used as the second biaxially stretched plastic film. A packaging material was produced in the same manner as in Example 1, except that an axially stretched polyethylene terephthalate film (product name "E5200", manufactured by Toyobo Co., Ltd.) was used. Then, a pouch according to Example 2 was produced in the same manner as in Example 1 using these three packaging materials. In Example 2, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

<Example 3>
In Example 3, a 60 μm thick unstretched polypropylene film (product name “ZK207”) was used as a sealant film instead of a 70 μm thick unstretched polypropylene film (product name “ZK207”, manufactured by Toray Film Kako Co., Ltd.). A packaging material was produced in the same manner as in Example 2, except that the material was used (Toray Film Processing Co., Ltd.). Then, a pouch according to Example 3 was produced in the same manner as in Example 1 using these three packaging materials. In Example 3, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

<Example 4>
First, a biaxially stretched polyethylene terephthalate film (product name "E5100", manufactured by Toyobo Co., Ltd.) having a thickness of 12 μm was prepared as a first biaxially stretched plastic film. Subsequently, one surface of this film was subjected to corona discharge treatment, and then a transparent vapor deposited layer of silicon oxide having a thickness of 10 nm was formed.

Next, the transparent vapor deposited layer was subjected to plasma treatment using a mixed gas of oxygen and argon, and then a coating solution containing ethyl silicate and polyvinyl alcohol as main components was applied using a gravure roll coater to form a film with a thickness of 300 nm after drying. A transparent gas barrier coating film was formed.

Thereafter, a pattern printing layer was formed on a part of the surface of the transparent gas barrier coating film. The thickness of the pattern printing layer was 1.0 μm. After forming the pattern printing layer, a 5 μm thick light-shielding printing layer was formed on the surface of the pattern printing layer. The light-shielding printing layer was composed of two white layers and one gray layer. Specifically, first, a white ink containing titanium oxide (product name "Rio Alpha (registered trademark) R631 white", manufactured by Toyo Ink Co., Ltd.) was applied to the surface of the pattern printing layer, and dried at 50 ° C. A white layer with a thickness of 1.0 μm was formed. Furthermore, a white ink containing titanium oxide (product name "NKFS series R69K", manufactured by Toyo Ink Co., Ltd.) is applied to the surface of this white layer and dried at 60°C to form a white layer with a thickness of 2.0 μm. did. Thereafter, a gray ink containing titanium oxide and carbon black was applied to the surface of this white layer and dried at 60° C. to form a gray layer with a thickness of 2.0 μm. The gray ink was created by adding 5% by mass of black ink containing carbon black and polyurethane resin to white ink (product name "NKFS series R69K", manufactured by Toyo Ink Co., Ltd.) containing titanium oxide and polyurethane resin. Created.

Further, as a second biaxially stretched plastic film, a biaxially stretched polyethylene terephthalate film (product name "E5100", manufactured by Toyobo Co., Ltd.) having a thickness of 12 μm was prepared. Further, as a sealant film, an unstretched polypropylene film (product name "ZK207", manufactured by Toray Film Kako Co., Ltd.) with a thickness of 70 μm was prepared.

Then, by a dry lamination method, a biaxially oriented polyethylene terephthalate film, a transparent vapor deposition layer, a transparent barrier coating film, a pattern printing layer, a light-shielding printing layer, a first adhesive layer, a biaxially oriented polyethylene terephthalate film, and a second adhesive layer were formed. , and an unstretched polypropylene film were sequentially laminated to produce a packaging material. As the first adhesive layer and the second adhesive layer, a two-component polyurethane adhesive (base resin: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used. The thickness of the first adhesive layer and the second adhesive layer was 3.0 μm.

Then, a pouch according to Example 4 was produced in the same manner as in Example 1 using these three packaging materials. In Example 4, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

<Example 5>
In Example 5, instead of the light-shielding printed layer consisting of a 1 μm thick white layer, a 2 μm thick white layer, and a 2 μm thick gray layer, the following 2 μm thick white layer and the following 2 μm thick white layer were used. A packaging material was produced in the same manner as in Example 4, except that a light-shielding printed layer consisting of an aluminum flake-containing layer was formed. Then, a pouch according to Example 5 was produced in the same manner as in Example 1 using these three packaging materials. In Example 5, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

The white layer according to Example 5 was formed by applying a white ink containing titanium oxide (product name "LG-FK690R White C", manufactured by Tokyo Ink Co., Ltd.) and drying it at 60°C. The aluminum flake-containing layer is formed by coating the surface of this white layer with an aluminum flake-containing ink containing non-leafing type aluminum flakes (product name ``LG-FK High Hidden Silver D'', manufactured by Tokyo Ink Co., Ltd.). Formed by drying at °C.

<Example 6>
First, a biaxially stretched polyethylene terephthalate film (product name "E5100", manufactured by Toyobo Co., Ltd.) having a thickness of 12 μm was prepared as a first biaxially stretched plastic film. Subsequently, a 1.0 μm thick pattern printing layer was formed on one side of this film in the same manner as in Example 4, and then a 5 μm thick light-shielding print was applied on the surface of the pattern printing layer in the same manner as in Example 4. formed a layer.

Further, as a second biaxially stretched plastic film, a biaxially stretched polyethylene terephthalate film (product name "E5100", manufactured by Toyobo Co., Ltd.) having a thickness of 12 μm was prepared. A transparent vapor deposited layer of silicon oxide having a thickness of 10 nm and a transparent gas barrier coating film having a thickness of 300 nm after drying were formed on one side of this film in the same manner as in Example 4.

Further, as a sealant film, an unstretched polypropylene film (product name "ZK207", manufactured by Toray Film Kako Co., Ltd.) with a thickness of 70 μm was prepared.

Thereafter, by a dry lamination method, a biaxially oriented polyethylene terephthalate film, a pattern printing layer, a light-shielding printing layer, a first adhesive layer, a barrier coating film, a transparent vapor deposition layer, a biaxially oriented polyethylene terephthalate film, a second adhesive layer, and an unstretched polypropylene film were laminated in order to produce a packaging material. As the first adhesive layer and the second adhesive layer, a two-component polyurethane adhesive (base resin: RU-40, curing agent: H-4) manufactured by Rock Paint Co., Ltd. was used. The thickness of the first adhesive layer and the second adhesive layer was 3.0 μm.

Then, a pouch according to Example 6 was produced in the same manner as in Example 1 using these three packaging materials. In Example 6, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

<Example 7>
In Example 7, instead of the light-shielding printed layer consisting of a 1 μm thick white layer, a 2 μm thick white layer, and a 2 μm thick gray layer, the same 2 μm thick white layer and 2 μm thick white layer as in Example 5 were used. A packaging material was produced in the same manner as in Example 6, except that a light-shielding print layer consisting of a layer containing aluminum flakes with a thickness of 2 μm was formed. Then, a pouch according to Example 6 was produced in the same manner as in Example 1 using these three packaging materials. In Example 7, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

<Example 8>
In Example 8, a packaging material was produced in the same manner as in Example 4, except that the transparent vapor deposition layer and the transparent barrier coating film were not provided. Then, a pouch according to Example 8 was produced in the same manner as in Example 1 using these three packaging materials. In Example 8, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

<Example 9>
In Example 9, a packaging material was produced in the same manner as in Example 5, except that the transparent vapor deposition layer and the transparent barrier coating film were not provided. Then, a pouch according to Example 9 was produced in the same manner as in Example 1 using these three packaging materials. In Example 9, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

<Example 10>
In Example 10, a packaging material was produced in the same manner as in Example 4, except that the light-shielding printing layer was composed of a laminated structure of a 1 μm thick white layer and a 1 μm thick white layer. Then, a pouch according to Example 10 was produced in the same manner as in Example 1 using these three packaging materials. In Example 10, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

<Example 11>
In Example 11, instead of the biaxially stretched polyethylene terephthalate film (product name "E5100", manufactured by Toyobo Co., Ltd.) as the second biaxially stretched plastic film, a biaxially stretched nylon film (product name: A packaging material was produced in the same manner as in Example 10, except that "Bonyl QC" (Kojin Film & Chemicals Co., Ltd.) was used. Then, a pouch according to Example 11 was produced in the same manner as in Example 1 using three of these packaging materials. In Example 11, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

<Comparative example 1>
In Comparative Example 1, a 60 μm thick unstretched polypropylene film (product name “ZK99S”) was used as a sealant film instead of a 70 μm thick unstretched polypropylene film (product name “ZK207”, manufactured by Toray Film Kako Co., Ltd.). A packaging material was produced in the same manner as in Example 1, except that the material was used (Toray Film Processing Co., Ltd.). Then, a pouch according to Comparative Example 1 was produced in the same manner as in Example 1 using these three packaging materials. In Comparative Example 1, the flow direction (MD) of the packaging material corresponds to the X direction DRX of the pouch, and the width direction (TD) of the packaging material corresponds to the Y direction DRY of the pouch.

<Young's modulus measurement>
The Young's modulus of the packaging materials constituting the retort-treated pouches of Examples 1 to 11 and Comparative Example 1 was measured. Note that the Young's modulus was measured in accordance with JIS K7127 except for the length of the test piece, which will be described later. As shown in FIG. 4, from the front surface of each pouch, excluding the seal part, a rectangular test piece S1 with one side L1 of 15 mm and the other side L2 extending in a direction perpendicular to one side L1 of 100 mm is shown. I cut out 5 pieces. The test piece S1 was cut out so that the other side L2 was parallel to the X direction (the direction perpendicular to the direction in which the first side seal portion extends). Subsequently, as shown in FIG. 5, a rectangular test piece S2 having one side L1 of 15 mm and the other side L2 extending in a direction orthogonal to one side L1 of 100 mm was prepared from the back side of each pouch, not including the seal part. I cut out 5 pieces. The test piece S2 was cut out so that the other side L2 was parallel to the Y direction (a direction parallel to the direction in which the first side seal portion extends). Then, using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.), the test piece S1 was held in an environment of a temperature of 25°C and a relative humidity of 50% for 1 minute, and then tested at a temperature of 25°C. A tensile test was conducted in an environment of 50% relative humidity such that the initial distance D1 between the grippers was 50 mm and the tensile speed was 300 mm/min, and the Young's modulus of the test piece S1 was measured. The Young's modulus of the five test pieces S1 was measured, and the average value was taken as the Young's modulus of the packaging material in the X direction. Similarly, Young's modulus of test piece S2 was measured. The Young's modulus of the five test pieces S2 was measured, and the average value was taken as the Young's modulus of the packaging material in the Y direction. Note that L1, L2, S1, S2, and D1 are as shown in FIGS. 4 to 6.

<Hot seal strength measurement>
The seal strength (hot seal strength) at 100° C. of the retort-treated pouches of Examples 1 to 11 and Comparative Example 1 was measured. First, one pouch after retort treatment according to Examples 1 to 11 and Comparative Example 1 was prepared. For each pouch, including the first side seal part or the second side seal part, one side L3 with the front film and the back film joined is 15 mm, and the other side L4 extends in a direction perpendicular to the one side L3. Five rectangular test pieces S3 each having a diameter of 70 mm were cut out. Specifically, three test pieces S3 were cut out so as to include the first side seal part, and two test pieces S3 were cut out so as to include the second side seal part. The test piece S3 was cut out so that the other side L4 was parallel to the X direction (the direction perpendicular to the direction in which the first side seal part extends) and did not include the steam release seal part. Hot seal strength was measured using this test piece S3. The hot seal strength was measured using a Tensilon universal material testing machine RTC-1310A (manufactured by A&D Co., Ltd.) in accordance with JIS Z1707:1997 7.5. First, the two packaging materials in the unsealed portion of the test piece S3 were each held by the gripping tool of the tensile testing machine. Further, the gripping tools were each pulled in opposite directions at a speed of 300 mm/min in a direction orthogonal to the surface direction of the seal portion of the test piece S3, and the maximum value of the tensile stress was measured. The average value of the maximum values was defined as the seal strength. The hot seal strength was measured under an environment of a temperature of 100° C. and a relative humidity of 5% after being held for 1 minute in an environment of a temperature of 100° C. and a relative humidity of 5%. The hot seal strength of five test pieces S3 was measured, and the average value was taken as the hot seal strength of the pouch. Note that L3, L4, and S3 are as shown in FIGS. 7 and 8.

<Dimension change>
The retort-treated pouches of Examples 1 to 11 and Comparative Example 1 were heated in a microwave oven, and dimensional changes in the pouches after heating were evaluated. Specifically, first, the pouch was placed in a self-supporting state in a microwave oven with an output of 600 W (model number "NE-MS264", manufactured by Panasonic Corporation) and heated for 3 minutes. Then, in the pouch after heating, all the water was drained from the pouch, and the folding width W2 was measured at the center of the pouch with the bottom film folded in half so that the pouch became flat. Then, it was evaluated how much the fold width W2 after heating was larger than the fold width W2 before heating.

<Appearance evaluation>
The appearance of the pouches after retort treatment according to Examples 1 to 11 and Comparative Example 1 was evaluated. Appearance evaluation was performed as follows. First, instead of the retort treatment described above, the pouch was subjected to retort treatment under the following conditions.
(Retort processing)
・Method: Spray type ・Retort temperature: 135℃
・Retort time: 40 minutes

Next, 10 pouches were prepared for each pouch after retort treatment, and it was visually confirmed whether wrinkles were generated in the pouches. This process was performed on 10 pouches, and among the 10 bags, the number of pouches with no wrinkles, the number of pouches with wrinkles but whose wrinkles were at a practically acceptable level, and the number of pouches with wrinkles at an NG level. The number of pouches was counted for each.

<Total light transmittance measurement>
The total light transmittance of the packaging materials constituting the pouches after retort processing according to Examples 4 to 11 was measured using a haze meter (product name "HM-150", Murakami Color Co., Ltd.) in accordance with JIS K7361-1:1997. Measurement was carried out using a measuring diameter 20 mm (manufactured by Gijutsu Kenkyusho). Specifically, as shown in FIG. 11, first, from the front surface of the pouch, excluding the seal part, one side L5 is 50 mm, and the other side L6 extending in a direction perpendicular to one side L5 is 50 mm. Three square test pieces S4 are cut out, and as shown in FIG. 12, one side L5 is 50 mm and the other side L6 extending in a direction perpendicular to one side L1 is 50 mm from the back side of the pouch, not including the seal part. Two square test pieces S4 were cut out. The test piece S4 was cut out so that the other side L6 was parallel to the X direction (the direction perpendicular to the direction in which the first side seal portion extends). After that, the test piece S4 was placed in a haze meter so that the biaxially stretched polyethylene terephthalate film as the first biaxially stretched plastic film was on the light source side without any curls or wrinkles, and the temperature was 25°C and the relative humidity was 50°C. After holding the test piece S4 in an environment with a temperature of 25° C. and a relative humidity of 50% for one minute, the total light transmittance of the test piece S4 was measured in an environment with a temperature of 25° C. and a relative humidity of 50%. The total light transmittance was measured for the five test pieces S4, and the average value was taken as the total light transmittance of the packaging material. Note that L5, L6, and S4 are as shown in FIGS. 11 and 12.

<L ^* value measurement>
The L ^* value of the packaging materials constituting the pouches after retort processing according to Examples 4 to 11 was determined based on JIS Z8781-4:2013 (colorimetry - Part 4: CIE 1976L ^* a ^* b ^* color space). , was measured using a spectrophotometer (product name "SpectroEye", manufactured by X-Rite). Specifically, as shown in FIG. 13, first, from the front surface of the pouch, one side L7 is 5 mm and the other side extending in a direction perpendicular to one side L7, excluding the pattern printing layer and the seal part. Five square test pieces S5 with L8 of 5 mm were cut out. The test piece S5 was cut out so that the other side L8 was parallel to the X direction (the direction perpendicular to the direction in which the first side seal portion extends). After that, test piece S5 was placed on a white plate (material: paper, size: A4 size (210 mm x 297 mm), thickness: 0.3 mm), and a biaxially stretched polyethylene terephthalate film as a first biaxially stretched plastic film was placed on the top surface. It was arranged so that Thereafter, after holding the test piece S5 in an environment of a temperature of 25°C and a relative humidity of 50% for 1 minute, the test piece S5 was The L ^* value was measured. In SpectroEye, the light source was D50 and the viewing angle was 2°. The L ^* value was measured for the five test pieces S5, and the average value was taken as the L ^* value of the packaging material. Note that L7, L8, and S5 are as shown in FIG. 13.

<Light blocking property>
In the pouches before retort processing according to Examples 4 to 9, 200 g of cream stew was added instead of water as the content, and the pouches were sealed under the same conditions as Example 1, and the contents were as described in the column of Example 1. After performing retort treatment under the following conditions, the cream stew was left to stand for 60 days under an environment of a temperature of 25° C. and a relative humidity of 50% and under a fluorescent lamp (D65 light source), and discoloration of the cream stew was visually confirmed. The evaluation criteria were as follows.
○: No discoloration of the cream stew was observed.
△: A slight discoloration of the cream stew was observed, but it was at a level that caused no problems with the product.
×: Clear discoloration of the cream stew was confirmed.

<Heat resistance>
In the pouches according to Examples 4 to 11, 150 g of meat sauce was added instead of water as the content, and the pouches were heated in a microwave oven. If wrinkles were not observed, it was evaluated whether wrinkles were observed. Specifically, first, 150 g of meat sauce was put into a pouch before retort treatment, the pouch was sealed under the same conditions as in Example 1, and retort treatment was performed under the conditions described in the column of Example 1. . Then, the pouch after the retort treatment was placed in a microwave oven with an output of 600 W (model number "NE-MS264", manufactured by Panasonic Corporation) in a self-standing state, and heated for 3 minutes. Then, in the pouch after heating, it was evaluated whether holes were observed in the packaging material, and if no holes were observed in the packaging material, whether wrinkles were observed. The evaluation criteria were as follows.
○: No holes or wrinkles were observed in the packaging material.
Δ: No holes were observed in the packaging material, but some wrinkles were observed at a level that caused no practical problems.
×: Holes were observed in the packaging material.

The compositions of the packaging materials are shown in Tables 1 to 3 below, and the evaluation results are shown in Tables 4 and 5.

The results are described below. As shown in Table 4, the pouches according to Examples 1 to 11 had smaller dimensional changes after heating in a microwave oven than the pouch according to Comparative Example 1. It can improve the appearance. In addition, considering that in the pouches according to Examples 1 to 11, the elongation of the folding width W2 due to heating in a microwave oven was suppressed, it is possible to suppress the folding width W2 from the height H in the packaging material constituting the storage space. Since it can be interpreted that the elongation of the removed portion can be suppressed, it can also be interpreted that the elongation of the packaging material when heated in a microwave oven can be similarly suppressed in the case of flat pouches.

In addition, since the packaging materials constituting the pouches according to Examples 1 to 11 have lower hot sealing strength than the packaging materials constituting the pouch according to Comparative Example 1, it is necessary to make it easier for steam to escape from the steam release seal portion. The steam can be removed stably.

Furthermore, in the pouches according to Examples 1 to 11, compared to the pouch according to Comparative Example 1, the occurrence of wrinkles in the pouches after retort treatment was suppressed.

As shown in Table 5, the pouches according to Examples 4 to 9 use packaging materials with a light-shielding printed layer and a total light transmittance of 25.0% or less. It was able to suppress photodeterioration of the contents better than the pouch.

In the pouches according to Examples 4 to 10, a packaging material comprising a biaxially oriented polyethylene terephthalate film as the first biaxially oriented plastic film and a biaxially oriented polyethylene terephthalate film as the second biaxially oriented plastic film was used. Therefore, from the pouch according to Example 11 using a packaging material comprising a biaxially oriented polyethylene terephthalate film as the first biaxially oriented plastic film and a biaxially oriented nylon film as the second biaxially oriented plastic film. It also had excellent heat resistance.

10...Pouch 10A...Accommodating space 11...Front film 12...Back film 13...Bottom film 15...Seal portion 24...Steam release seal portion 30, 40...Packaging material 31...First biaxially stretched plastic film 32... Second biaxially stretched plastic film 33...Sealant film 41...Light-shielding printing layer

Claims (9)

A pouch containing packaging material and having a storage space,
The packaging material comprises a first biaxially oriented plastic film, a second biaxially oriented plastic film, and a sealant film in this order,
The first biaxially oriented plastic film is a biaxially oriented polyethylene terephthalate film, the second biaxially oriented plastic film is a biaxially oriented polyethylene terephthalate film or a biaxially oriented nylon film,
The sealant film has polypropylene as a main component,
There are only two biaxially oriented plastic films in the packaging material,
comprising a sealing part for sealing the pouch,
The packaging material further includes a light-shielding printed layer provided between the first biaxially oriented plastic film and the sealant film,
The total light transmittance of the packaging material is 25.0% or less,
The L ^* value in the L ^* a ^* b ^* color system measured by the SCE method (specular reflection light elimination method) of the packaging material is 65.0 or more,
The seal portion includes a steam release seal portion configured to peel off due to an increase in pressure in the accommodation space,
The pouch is configured so that the steam can be released by peeling off the steam release seal part,
The packaging material has a Young's modulus in one direction of 3000 MPa or more when measured in a 25° C. environment after being held in a 25° C. environment for 1 minute,
A pouch, wherein the seal strength of the seal portion is 20.0 N or less when measured in an environment of 100° C. after being held in an environment of 100° C. for 1 minute. The pouch according to claim 1, wherein the product of tensile elongation (%) and thickness (μm) in the one direction of the sealant film is 30,000 or more and 50,000 or less. The pouch according to claim 1 or 2, wherein the product of tensile elongation (%) and thickness (μm) of the sealant film in a direction orthogonal to the one direction is 45,000 or more and 55,000 or less. The pouch according to any one of claims 1 to 3, wherein the sealant film contains a propylene-ethylene block copolymer. The packaging material further includes a transparent vapor deposition layer provided between the first biaxially oriented plastic film and the second biaxially oriented plastic film, and the transparent vapor deposition layer is made of a metal oxide or an inorganic oxide. The pouch according to any one of claims 1 to 4 , comprising: The pouch according to claim 5 , wherein the packaging material further comprises a transparent gas barrier coating film provided on the surface of the transparent vapor deposition layer. The pouch according to any one of claims 1 to 6 , wherein the light-shielding printed layer is a laminate including a layer containing a white pigment and a layer containing metal flakes. The pouch according to claim 7 , wherein the layer containing the white pigment is located closer to the first biaxially stretched plastic film than the layer containing the metal flakes. The pouch according to any one of claims 1 to 8 , wherein a content is accommodated in the accommodation space of the pouch.

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