Pouch for microwave oven

Abstract

To provide a pouch for a microwave oven which has excellent openability and an easy-to-open part that is not broken unintentionally when heated.SOLUTION: A pouch 100 for a microwave oven is formed into a bag shape by thermally bonding a laminated film, and is equipped with an automatic steam release mechanism 120 that automatically releases steam inside a storage part 101 when heated, the laminated film is formed by laminating in order from an outer layer at least a biaxially oriented film layer, a biaxially oriented film layer, and a sealant layer, the moisture content of the laminated film when a content is filled in the storage part 101 is 1.0% or less, the laminated film has an easy-to-open part 130 in an intermediate layer 220, the easy-to-open part is composed of an intermittent cut line 221 in which a processed part 222 being cut so as to completely penetrate the intermediate layer in a thickness direction is intermittently connected linearly.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pouch for use in a microwave oven, which is formed into a bag shape by thermally bonding overlapping laminated films and is equipped with an automatic steam release mechanism that automatically releases internal steam when heated. [Background technology]

[0002] Conventionally, packaged foods available on the market are prepared by placing cooked or semi-cooked food in a pouch formed by thermally bonding overlapping laminated films, and heating and cooking the food in a microwave oven when the food is to be eaten.

[0003] When such a pouch is heated in a microwave oven, the internal pressure of the pouch increases due to the steam generated by the food and the thermal expansion of the air inside, which may cause the pouch to tear or deform, or the food inside the pouch may be scattered if the pouch tears.

[0004] For this reason, in recent years, pouches for use in microwave ovens have generally been provided with an automatic steam release mechanism that automatically releases internal steam during heating. A known example of such a pouch equipped with an automatic steam release mechanism is a pouch in which a portion of a laminated film is heat-bonded to provide an annular steam release seal portion, and a steam release hole is provided in a steam release portion surrounded by the annular steam release seal portion (see, for example, Patent Documents 1 and 2).

[0005] In the pouch of Patent Document 1, when the internal pressure of the pouch increases as a result of heating in a microwave oven, part of the steam release seal begins to rupture, and the steam release seal retreats due to stress concentration caused by the increase in internal pressure of the pouch. When the peeling reaches the weakened part, water vapor and the like are released to the outside. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2002-249176 A [Patent Document 2] JP 2005-187079 A Summary of the Invention [Problem to be solved by the invention]

[0007] On the other hand, there are known pouches that have been processed so that users can open them by hand to remove the contents without using scissors, etc. One such processing is half-cut processing, which forms a linear easy-to-open portion in a film. However, when a pouch for use in a microwave oven is subjected to the half-cut processing as described above, there is a risk that the processed portion may break when the internal pressure of the pouch increases as a result of heating in a microwave oven.

[0008] SUMMARY OF THE PRESENT DISCLOSURE The present invention has been made to solve the above problems, and has an object to provide a pouch for use in a microwave oven which has excellent openability while preventing the easy-open portion from being unintentionally broken when heated. [Means for solving the problem]

[0009] The pouch for use in a microwave oven of the present invention is formed into a bag shape by thermally bonding a laminated film, and is equipped with an automatic steam release mechanism for automatically releasing steam from within a storage section when heated, The automatic steam release mechanism includes a steam release seal portion configured to start peeling when an internal pressure of the storage portion increases when the storage portion is heated, and a steam release portion surrounded by the steam release seal portion; The laminated film is formed by laminating, in order from the outer layer, at least a biaxially oriented film layer, a biaxially oriented film layer, and a sealant layer, The moisture content of the laminated film when the content is filled in the storage section is 1.0% or less, The laminated film has an easy-to-open portion in an intermediate layer thereof, The above problem is solved by the fact that the easy-to-open portion is composed of an interrupted cut line, which is a linear series of processed portions cut so as to completely penetrate the intermediate layer in the thickness direction.

[0010] In the microwave pouch of the present invention, the laminated film may be configured so that, from the outer layer, at least a biaxially oriented film layer, a polybutylene terephthalate layer, and a sealant layer are laminated, or, from the outer layer, at least a biaxially oriented film layer, a polyethylene terephthalate layer, and a sealant layer are laminated, and further, the laminated film may be configured so that, from the outer layer, at least a polyethylene terephthalate layer or a vapor-deposited polyethylene terephthalate layer, a polybutylene terephthalate layer, and a non-oriented polypropylene layer are laminated.

[0011] In the microwave pouch of the present invention, the ratio A / B of the length A of the processed portion to the shortest distance B between adjacent processed portions is preferably 2.0 to 4.8.

[0012] In the microwave pouch of the present invention, the breaking strength of the laminated film in a direction perpendicular to the stretch direction of the easy-open portion is preferably 55 N / 15 mm or more.

[0013] The pouch for use in a microwave oven of the present invention is formed into a bag shape by thermally bonding a laminated film, and is equipped with an automatic steam release mechanism for automatically releasing steam from within a storage section when heated, The automatic steam release mechanism includes a steam release seal portion configured to start peeling when an internal pressure of the storage portion increases when the storage portion is heated, and a steam release portion surrounded by the steam release seal portion; The laminated film is formed by laminating, in order from the outer layer, at least a biaxially oriented film layer, a biaxially oriented film layer, and a sealant layer, The moisture content of the laminated film when the content is filled in the storage section is 1.0% or less, The laminated film has an easy-to-open portion in an intermediate layer thereof, The easy-to-open portion is formed by a continuous cut line that extends continuously through the entire intermediate layer in a thickness direction, In a tensile test of the biaxially stretched film (ambient temperature 200°C, sample width 10 mm, chuck distance 20 mm, tensile speed 1 mm / min), the load per unit thickness of the sample at the point where the sample has elongated to 10 mm is 0.25 N / μm or less, thereby solving the above problem.

[0014] In the microwave pouch of the present invention, the laminated film may be configured so that, from the outer layer, at least a biaxially oriented film layer, a polybutylene terephthalate layer, and a sealant layer are laminated, or, from the outer layer, at least a biaxially oriented film layer, a polyethylene terephthalate layer, and a sealant layer are laminated, and further, the laminated film may be configured so that, from the outer layer, at least a polyethylene terephthalate layer or a vapor-deposited polyethylene terephthalate layer, a polybutylene terephthalate layer, and a non-oriented polypropylene layer are laminated. Effect of the Invention

[0015] According to the microwave pouch of the present invention, basically, the automatic steam release mechanism that automatically releases steam from within the storage section when heated ensures reliable steam release, and the laminated film constituting the microwave pouch has an easy-open section in the intermediate layer, which provides excellent openability. Moreover, the easy-open section is made up of an intermittent cut line in which processed sections cut so as to completely penetrate the intermediate layer in the thickness direction are connected intermittently in a line, so that there are unprocessed sections without cuts between the processed sections in the intermediate layer, i.e., there remains an area in the intermediate layer that connects one area and the other area sandwiching the easy-open section, and this, combined with the effect that the heat resistance is not easily impaired even when the internal pressure is high due to the moisture content of the laminated film being 1.0% or less, makes it possible to prevent the easy-open section from being unintentionally broken when heated due to the presence of the unprocessed section, even at high temperatures.

[0016] Furthermore, according to the microwave pouch of the present invention, by using a polybutylene terephthalate layer as the intermediate layer, unprocessed portions without cuts exist between processed portions that have been cut in the polybutylene terephthalate layer, i.e., an area remains in the polybutylene terephthalate layer that connects one area and the other area that sandwiches the easy-open portion, so that the property of polybutylene terephthalate that it stretches and is difficult to break at high temperatures is exerted, and the above-mentioned effect of preventing unintentional rupture of the easy-open portion when heated is reliably obtained.

[0017] According to the microwave pouch of the present invention, basically, the automatic steam venting mechanism that automatically releases steam from within the storage section when heated ensures reliable steam venting, and the laminated film that constitutes the microwave pouch has an easy-open section with continuously extending slits in the middle layer, which provides excellent openability. Moreover, since the biaxially oriented film that is the outer layer of the laminated film has a specific tensile strength, a predetermined elongation is ensured in the outer layer when heated, so that even if an easy-open section with continuously extending slits is formed in the middle layer, it is possible to prevent the easy-open section from breaking unintentionally when heated. [Brief description of the drawings]

[0018] [Figure 1] 1 is a plan view showing a microwave pouch according to one embodiment of the present invention; [Diagram 2] FIG. 2 is an explanatory cross-sectional view showing a schematic configuration of an interrupted cut line in a laminated film. [Diagram 3] 11A to 11C are explanatory diagrams showing examples of shapes of interrupted cut lines. [Figure 4] 4 is an explanatory diagram showing an enlarged view of the shape of the interrupted cut lines shown in FIG. 3(b) and FIG. 3(d). [Diagram 5] 2 is an enlarged view showing the configuration of the automatic steam release mechanism of the microwave pouch shown in FIG. 1. [Figure 6] FIG. 13 is a diagram for explaining the state of steam release from the pouch, and is a schematic diagram showing a cross section taken along a straight line connecting the center point of the pouch and the seal peeling start point. [Figure 7] 1A to 1C are explanatory diagrams showing examples of the shapes of interrupted cut lines in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The microwave pouch of the present invention is formed by heat-sealing stacked laminated films into a bag shape, and is equipped with an automatic steam vent mechanism that automatically releases steam inside the pouch to the outside when heated.

[0020] The microwave pouch of the present invention will now be described with reference to the drawings.

[0021] [First embodiment] FIG. 1 is a plan view showing a microwave pouch according to a first embodiment of the present invention. This microwave pouch (hereinafter simply referred to as "pouch") 100 has an outer shape, for example, rectangular when viewed in a plane, and is configured so that a peripheral seal portion 105, which is formed by thermally bonding a front side laminated film 110 (see Figure 6) and a back side laminated film 115 (see Figure 6), is formed so as to surround all four sides of a storage portion 101 located in the center of pouch 100.

[0022] As shown in FIG. 2, the laminated film has a layer structure in which a biaxially oriented film layer serving as an outer layer 210, a biaxially oriented film layer serving as an intermediate layer 220, and a sealant layer serving as an inner layer 230 are laminated in this order. Depending on the application, etc., the laminated film may have appropriate layers laminated therein other than the outer layer 210, the intermediate layer 220, and the inner layer 230. The biaxially stretched film layer of the outer layer 210 is preferably a polyethylene terephthalate layer (PET layer) or a vapor-deposited polyethylene terephthalate layer (vapor-deposited PET layer), and the biaxially stretched film layer of the intermediate layer 220 is preferably a polybutylene terephthalate layer (PBT layer) or a polyethylene terephthalate layer (PET layer). The sealant layer can be, for example, a non-oriented polypropylene layer (CPP layer). The vapor-deposited polyethylene terephthalate layer is a film containing a vapor-deposited film formed on a polyethylene terephthalate film by a vapor-deposited film of a metal oxide such as alumina or silicon oxide. The thickness of the outer layer 210 is, for example, not less than 10 μm and not more than 50 μm. The thickness of the intermediate layer 220 is, for example, not less than 10 μm and not more than 50 μm. The thickness of the inner layer 230 is, for example, not less than 20 μm and not more than 150 μm.

[0023] In the laminated film, the easy-open part 130 is formed in the PBT layer which is the intermediate layer 220. The easy-open part 130 is a substantially linear part extending in the pouch width direction of the intermediate layer 220, and is arranged so as to connect two notches 135 formed on both sides of the peripheral seal part 105 and cross the storage part 101. The easy-open part 130 may be formed only in the intermediate layer 220, or may be formed by cutting a part of the thickness direction of the inner layer 230 (sealant layer) together with the intermediate layer 220, for example, when a laminate of the intermediate layer 220 and the inner layer 230 (sealant layer) is processed to form the easy-open part 130. The easy-to-open portion 130 can be formed by, for example, half-cut processing. The easy-to-open portion 130 is not limited to being linear, but may be curved or bent.

[0024] The easy-to-open portion 130 is composed of intermittent cut lines 221 in which processed portions 222, which are cut so as to completely penetrate the intermediate layer 220 in the thickness direction, are connected intermittently (discontinuously) in one direction (the pouch width direction). Specifically, the intermittent cut lines 221 are formed by regularly alternatingly arranging processed portions 222, which are short slits that completely penetrate the intermediate layer 220 in the thickness direction, and non-processed portions 225, which do not penetrate at all in the thickness direction, in one direction (the pouch width direction). Moreover, the easy-to-open portion 130 may be configured with a plurality of interrupted cut lines 221 extending parallel to each other and adjacent to each other. The width of the interrupted cut line 221, i.e., the width in the direction perpendicular to the pouch width direction (pouch height direction), is the maximum width in the pouch height direction of the processed portion 222. The width of the non-processed portion 225 in the pouch height direction is at most the same as the width of the interrupted cut line 221.

[0025] The shape of the intermittent cut line 221, i.e., the shape and arrangement of the processed portion 222, may be any shape that can be guided so that the intermittent cut line 221 can be cut in a straight line when the pouch is opened, and a specific shape of the intermittent cut line 221 may be, for example, that shown in Figure 3. The intermittent cut line 221 shown in Figure 3(a) is a dashed line in which processed portions 222 consisting of short straight lines extending in the pouch width direction (left and right direction in Figure 3, indicated by arrow MD) are arranged at the same level in the pouch width direction, separated by non-processed portions 225. The interrupted cut lines 221 shown in Figure 3 (b) are in a V-shape and comprise an upper row of processed portions 222 consisting of short diagonal lines extending at an angle to the pouch width direction, arranged regularly and parallel to each other so that one end of each is positioned at the same level in the pouch width direction, via non-processed portions 225, and a lower row of similar configuration arranged symmetrically in the pouch width direction. The intermittent cut lines 221 shown in Figure 3(c) are slanted V-shaped lines in which the upper and lower rows are shifted in the pouch width direction in the V-shaped line of Figure 3(b), and each end of the processed portion 222 consisting of corresponding short diagonal lines is not at the same level in the pouch height direction (up and down direction in Figure 3). The intermittent cut line 221 shown in Figure 3 (d) has a Y-shape in which the short straight lines are regularly arranged at the same level and in the same direction in the pouch width direction, with Y-shaped processed portion 222 consisting of a short straight line extending in the pouch width direction and two short oblique lines continuing from this short straight line and extending on both sides at symmetrical angles with respect to the pouch width direction, and non-processed portion 225 between them. The interrupted cut line 221 shown in FIG. 3(e) has a separated Y shape configured such that a short oblique line on one side of the processed portion 222 in the Y shape of FIG. 3(d) extends discontinuously from the short straight line. The interrupted cut line 221 shown in Figure 3 (f) has a hook shape in which the broken line-like processed portion 222 is composed of a short straight line extending in the pouch width direction and a short diagonal line continuing from this short straight line at an angle in the pouch width direction and extending to only one side, and the short straight lines are regularly arranged at the same level and in the same direction in the pouch width direction, via non-processed portion 225.

[0026] The ratio A / B of the length A of the processed portion 222 constituting the interrupted cut line 221 to the shortest distance B (length of the non-processed portion 225) between the adjacent processed portions 222 is preferably 2.0 to 4.8. With such a configuration, the easy-open portion 130 can be reliably provided with an openability, while the length of the non-processed portion 225 is appropriately secured, so that the effect of preventing the easy-open portion 130 from being unintentionally broken when heated can be reliably obtained. If the ratio A / B is too large, the length of the non-processed portion 225 is not sufficiently secured relative to the length A of the processed portion 222, so that the easy-open portion 130 may not be sufficiently prevented from being unintentionally broken when heated. On the other hand, if the ratio A / B is too small, the length A of the processed portion 222 is not sufficiently secured for the easy-open portion 130 as a whole, so that the openability may be poor. In the interrupted cut line 221, it is preferable that the length A of each of the processed parts 222 is 0.8 to 2.5 mm and the shortest distance B between adjacent processed parts 222 is 0.3 to 0.8 mm, and it is particularly preferable that the length A of each of the processed parts 222 is 1.2 mm and the shortest distance B between adjacent processed parts 222 is 0.5 mm. By making the shortest distance B between adjacent processed parts 222 0.8 mm or less, it is possible to prevent the step of the cut edge from being visually noticeable in the appearance of the pouch 100 after it has been torn open. The length A of the processed portion 222 refers to the path length (the maximum path length without branches) of the short straight lines and short diagonal lines on one side that constitute the processed portion 222, in the case of an interrupted cut line 221 that has a branched Y shape, and refers to the path length of one independent processed portion 222, in the case of an interrupted cut line 221 that has any other shape without branches. The shortest distance B between adjacent processed parts 222 refers to the shortest distance between any point C of one processed part 222 and any point D of the other adjacent processed part 222. The path of the shortest distance B between adjacent processed parts 222 is not necessarily parallel to the pouch width direction, but may be oblique. Fig. 4(a) shows the length A and shortest distance B of the processed part 222 in the shape of the interrupted cut line 221 shown in Fig. 3(b), and Fig. 4(b) shows the length A and shortest distance B of the processed part 222 in the shape of the interrupted cut line shown in Fig. 3(d). From the viewpoint of ease of opening, the angle of the short oblique lines constituting the processed portion 222 in the interrupted cut lines 221 having the shapes shown in Figs. 3(b) to (f) with respect to the pouch width direction is preferably, for example, 15 to 30 degrees.

[0027] The laminate film has a moisture content of 1.0% or less when the contents are filled in the storage section 101. By using a laminate film with a moisture content of 1.0% or less when the contents are filled in the storage section 101, the heat resistance of the entire laminate film is maintained, and in combination with the presence of a steam release mechanism described below, the heat resistance is effectively prevented from being impaired even when the internal pressure is high. If the moisture content of the laminate film is greater than 1.0%, the laminate film will be subjected to internal pressure in a state where it has absorbed a lot of moisture, causing thermal damage, which may result in unintentional rupture of the easy-open portion. In the present invention, the state in which the content is filled in the storage section 101 means the state in which the product is commercially available, and specifically refers to the state at any timing after aseptic filling or hot pack filling of the content, filling the content and subjecting it to heat sterilization such as boiling or retort, etc. Among these, the timing immediately after heat sterilization is the state in which the moisture content of the film is highest. In order for the laminated film to achieve the above moisture content when filled with contents, it is preferable that each layer constituting the laminated film has a moisture content of 0.6% or less immediately after retort sterilization at 121°C for 30 minutes.

[0028] The moisture content of the laminated film can be calculated by measuring 0.1±0.005 g of the laminated film of pouch 100, heating it at 230°C immediately after the packaging bag in which the contents have been filled and sealed in the storage section 101 of pouch 100 is subjected to hot water retort sterilization at 121°C for 30 minutes, and measuring the moisture content using a trace moisture measuring device CA-200 manufactured by Mitsubishi Chemical Analytech Co., Ltd.

[0029] The breaking strength (TD breaking strength) in the direction perpendicular to the pouch width direction in which the easy-open part 130 of the laminated film stretches (i.e., in the pouch height direction) is preferably 55 N / 15 mm or more, more preferably 65 to 70 N / 15 mm. When the TD breaking strength is 55 N / 15 mm or more, breaking due to stress that the laminated film receives in the direction perpendicular to the easy-open part 130 during heating is suppressed, so that the effect of preventing unintentional breaking of the easy-open part 130 during heating can be reliably obtained. In addition, when the TD breaking strength is 70 N / 15 mm or less, the openability of the pouch 100 can be reliably obtained. The TD breaking strength is measured in accordance with JIS K 7127. Specifically, the measuring instrument used is a Tensilon universal material testing machine "RTI-1310" manufactured by A&D Corporation, the test piece is a rectangular film cut into a width of 15 mm and a length of 150 mm, the environmental temperature during the test is set to 23°C, the distance between a pair of chucks holding the test piece is set to 50 mm at the start of the measurement, and the tensile speed is set to 300 mm / min.

[0030] The biaxially stretched film constituting the intermediate layer 220 is preferably formed so that an orientation angle is obtained by biaxial stretching, and the orientation angle is preferably 20° or less, more preferably 10° or less. In such a biaxially stretched film, when the film width direction is set at an angle of 0°, parts are formed with different molecular orientation directions, i.e., molecular orientation angles, and generally, the molecular orientation angle of the central part of the film tends to be small and the molecular orientation angle of the outer extension part tends to be large. It is known that a laminated film using a biaxially stretched film with a large molecular orientation angle is impaired in tearability, so when such a biaxially stretched film is used as the intermediate layer 220, it is preferable to form the intermediate layer 220 so that the orientation angle is 0 to 20°.

[0031] Pouch 100 is provided with an automatic steam release mechanism 120 that automatically releases steam within storage section 101 to the outside when heated. As also shown in Figures 5 and 6, the automatic steam release mechanism 120 includes a steam release seal portion 121 that is configured so that the internal pressure of the storage portion 101 increases when heated, causing the front side laminate film 110 and the back side laminate film 115 to begin peeling off, a steam release portion 122 that is surrounded by the steam release seal portion 121, and a steam release portion 123 formed in the steam release portion 122.

[0032] The steam release seal portion 121 is formed, for example, in a ring shape by thermally bonding the front side laminate film 110 and the back side laminate film 115, and has a seal peeling initiation portion S at the part of the outer periphery closest to the center of the storage portion 101, where peeling begins due to steam generated inside the storage portion 101 when heated in a microwave oven. The formation of the vapor release seal 121 can be performed simultaneously with the formation of the peripheral seal 105 or separately.

[0033] The steam release portion 122 is formed, for example, as an unsealed portion where the front side laminate film 110 and the back side laminate film 115 are not thermally bonded together. The specific form of the steam release portion 122 is not limited to this, and the steam release portion may be formed, for example, as a weakly bonded portion that has been thermally bonded so that the seal strength is lower than that of the peripheral seal portion 105 and the steam release seal portion 121, or as a patterned adhesive portion that has been applied with a knurled seal or the like to the front side laminate film 110 and the back side laminate film 115.

[0034] The vapor release portion 123 is formed as a hole or a slit, and in this embodiment, for example, is formed as a through-hole having a circular opening shape. The vapor release portion 123 may be provided on only one of the front side lamination film 110 and the back side lamination film 115 , or may be provided on both the front side lamination film 110 and the back side lamination film 115 .

[0035] It is preferable that seal peeling start portion S of steam release seal portion 121 is located on or inside the circumference of imaginary circle R inscribed in the center of the inner end of peripheral seal portion 105 of the two short sides of pouch 100. With this configuration, water vapor within pouch 100 can be discharged from the weakened portion, and automatic opening by automatic steam release mechanism 120 can be performed more reliably. In pouch 100 of this embodiment, steam release seal portion 121 is provided so as to be continuous with peripheral seal portion 105 while satisfying the above conditions.

[0036] Thus, when pouch 100 is heated, pouch 100 expands from center point P toward peripheral seal portion 105 due to steam and the like generated from the contents, and stress concentration occurs radially as shown by imaginary circle R with a radius equal to the distance from center point P to the inner end of peripheral seal portion 105 on the short side in Fig. 1. This stress concentration causes peeling between front side laminate film 110 and back side laminate film 115 to start at seal peeling start portion S, which is the portion closest to center point P of pouch 100, in steam release seal portion 121. Then, as shown in Fig. 6, steam release seal portion 121 retreats due to stress concentration caused by an increase in the internal pressure of pouch 100, and when the peeling reaches steam release portion 122, pouch 100 is partially opened and steam and the like are discharged to the outside through steam release portion 123.

[0037] Second Embodiment The microwave pouch of the second embodiment has a similar configuration to the pouch 100 of the first embodiment, except that the outer layer has a specific tensile strength and the shape of the easy-open portion formed in the middle layer is different. The easy-open portion of the pouch according to the second embodiment is made of a continuous cut line that is a continuous incision that penetrates the entire intermediate layer in the thickness direction, and may be made of a plurality of continuous cut lines that extend closely in parallel. The continuous cut line does not have a non-processed portion that does not penetrate the intermediate layer in the thickness direction.

[0038] When a tensile test is performed on the biaxially stretched film which is the outer layer under conditions of an atmospheric temperature of 200°C, a sample width of 10 mm, a chuck distance of 20 mm, and a speed of 1 mm / min, the specific tensile strength (the load at which the sample elongates to 10 mm divided by the sample thickness) is 0.25 N / μm or less, and preferably in the range of 0.1 N / μm to 0.2 N / μm. A tensile test for calculating the tensile strength of the outer layer can be performed using an A&D Tensilon universal testing machine.

[0039] Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various design modifications can be made without departing from the present invention described in the claims. For example, the pouch of the present invention is not limited to the above-mentioned four-side sealed type, but can be applied to various types of pouches such as a standing pouch, flat pouch, three-side sealed type, pillow type, gusset type, etc. Furthermore, the shape of the pouch may be any shape other than the rectangular shape shown in the above embodiment, such as a trapezoid or an irregular shape with some unevenness.

[0040] Furthermore, the steam release seal portion does not need to be provided so as to be continuous with the peripheral seal portion, and may be provided independently inside the peripheral seal portion. The steam release seal portion may be formed in other shapes, such as a rectangular ring, and the dimensions of the steam release seal portion may be appropriately selected. Furthermore, when the steam release portion is formed as a hole, the opening shape of the hole does not have to be circular, but can be any shape, such as oval, triangular, rectangular, trapezoidal, rice ball shape, etc., and the dimensions can also be selected appropriately.

[0041] Examples performed to confirm the effects of the present invention will now be described.

[0042] [Example 1, Comparative Example 1] With reference to the configuration shown in Fig. 1, a four-side sealed type microwave pouch with an automatic steam release mechanism was produced, in which the easy-open portion shown in Table 1 was formed. The pouch had a width dimension (left-right dimension in Fig. 1) of 130 mm and a length (top-bottom dimension in Fig. 1) of 175 mm. This laminated film is a film laminated in this order with an outer layer made of a vapor-deposited PET layer having a thickness of 12 μm, an intermediate layer made of a PBT layer having a thickness of 15 μm, and an inner layer made of a polypropylene layer having a thickness of 70 μm, and has the TD breaking strength shown in Table 1. The easy-to-open parts are formed at the positions shown in Figure 1. Each easy-to-open part completely penetrates the middle layer in the thickness direction, and the cuts of the processed part do not reach the inner layer or the outer layer. In addition, the multiple rows of each cut line are formed close to each other and parallel to each other. The moisture content of the vapor-deposited PET outer layer is 0.4%, the moisture content of the PBT middle layer is 0.3%, and the moisture content of the polypropylene inner layer is 0.01%, giving a total moisture content of 0.9% for the laminated film.

[0043] [Examples 2 to 7, Comparative Examples 2 to 5] With reference to the configuration shown in Fig. 1, a four-side sealed type microwave pouch with an automatic steam release mechanism was produced, in which the easy-open portion shown in Table 1 was formed. The pouch had a width dimension (left-right dimension in Fig. 1) of 130 mm and a length (top-bottom dimension in Fig. 1) of 175 mm. This laminated film is a film laminated in this order with a 12 μm thick vapor-deposited PET layer or an outer layer consisting of a 12 μm thick PET layer (see Table 1), a 15 μm thick intermediate layer consisting of a 15 μm thick PBT layer, and an inner layer consisting of a 70 μm thick polypropylene layer, and has the TD breaking strength shown in Table 1. The easy-to-open parts are formed at the positions shown in Figure 1, and the processed parts of the easy-to-open parts all penetrate the middle layer in the thickness direction, and the cuts of the processed parts do not reach the inner layer or the outer layer. In addition, the multiple rows of each cut line are formed close to each other and parallel to each other. FIG. 7(a) shows an easy-open portion in which three parallel rows of V-shaped interrupted cut lines are formed, and FIG. 7(b) shows an easy-open portion in which three parallel rows of Y-shaped interrupted cut lines are formed. The moisture content of the outer layers, the vapor-deposited PET layer and the PET layer, is 0.4%, the moisture content of the middle PBT layer is 0.3%, and the moisture content of the inner polypropylene layer is 0.01%, giving a total moisture content of 0.9% for the laminated film.

[0044] As a heating test, the pouches according to Examples 1 to 7 and Comparative Examples 1 to 5 were heated with 180 g of curry as the content at a rated power of 500 W for a heating time of 3 minutes to check whether the easy-to-open part was broken or not, and after heating in the microwave oven, the pouches were opened by tearing along the easy-to-open part from the notch to check the openability. The results are shown in Table 1. In Table 1, the evaluation was performed as follows: "○" if no break was observed in the easy-open part when heated in the microwave; "×" if break was observed in the easy-open part when heated in the microwave; "○" if the package could be torn along the easy-open part when torn after microwave heating; and "×" if the package detached from the easy-open part when torn after microwave heating. In addition, when checking whether the steam release seal portion automatically opened (steamed through) when heated in a microwave oven, it was confirmed that the automatic steam release mechanism automatically opened properly in all of the pouches of Examples 1 to 7 and Comparative Examples 1 to 5.

[0045] [Table 1] [Explanation of symbols]

[0046] 100 ··· Microwave Pouches 101 ..... Storage section 105 Peripheral seal portion 110 Surface laminated film 115 Back side laminated film 120 Automatic steam release mechanism 121 Steam release seal 122 Steam release section 123 Steam release section 130 ··· Easy opening part 135 ··· Notch 210 ... outer layer 220 Middle Class 221 ··· Intermittent cut line 222... Processing section 225... Unprocessed part 230 Inner layer P: Center point of pouch R: Virtual circle S: Seal peeling start point

Claims

1. A microwave pouch formed into a bag shape by thermally bonding a laminated film, the pouch having an automatic steam release mechanism that automatically releases steam from within a storage section when heated, The automatic steam release mechanism includes a steam release seal portion configured to start peeling when an internal pressure of the storage portion increases when the storage portion is heated, and a steam release portion surrounded by the steam release seal portion; The laminated film is formed by laminating, in order from the outer layer, at least a biaxially oriented film layer, a biaxially oriented film layer, and a sealant layer, The moisture content of the laminated film when the content is filled in the storage portion is 1.0% or less, The laminated film has an easy-to-open portion in an intermediate layer thereof, a processing section for processing the intermediate layer by cutting the intermediate layer in a thickness direction so as to completely penetrate the intermediate layer;

2. 2. The pouch for use in a microwave oven according to claim 1, wherein the laminated film is formed by laminating, in order from the outer layer, at least a biaxially oriented film layer, a polybutylene terephthalate layer, and a sealant layer, or by laminating, in order from the outer layer, at least a biaxially oriented film layer, a polyethylene terephthalate layer, and a sealant layer.

3. 3. The pouch for use in a microwave oven according to claim 2, wherein the laminated film is formed by laminating, in order from the outer layer, at least a polyethylene terephthalate layer or a vapor-deposited polyethylene terephthalate layer, a polybutylene terephthalate layer, and a non-oriented polypropylene layer.

4. 2. The pouch for use in a microwave oven according to claim 1, wherein a ratio A / B of a length A of the processed portion to a shortest distance B between adjacent processed portions is 2.0 to 4.

8.

5. 2. The pouch for use in a microwave oven according to claim 1, wherein the breaking strength of said laminated film in a direction perpendicular to the stretching direction of said easy-open portion is 55 N / 15 mm or more.

6. A microwave pouch formed into a bag shape by thermally bonding a laminated film, the pouch having an automatic steam release mechanism that automatically releases steam from within a storage section when heated, The automatic steam release mechanism includes a steam release seal portion configured to start peeling when an internal pressure of the storage portion increases when the storage portion is heated, and a steam release portion surrounded by the steam release seal portion; The laminated film is formed by laminating, in order from the outer layer, at least a biaxially oriented film layer, a biaxially oriented film layer, and a sealant layer, The moisture content of the laminated film when the content is filled in the storage portion is 1.0% or less, The laminated film has an easy-to-open portion in an intermediate layer thereof, The easy-to-open portion is formed by a continuous cut line that extends continuously through the entire intermediate layer in a thickness direction, A microwave pouch characterized in that, in a tensile test of the biaxially stretched film (ambient temperature 200°C, sample width 10 mm, chuck distance 20 mm, tensile speed 1 mm / min), the load per unit thickness of the sample at the point where the sample has elongated to 10 mm is 0.25 N / μm or less.

7. 7. The pouch for use in a microwave oven according to claim 6, wherein the laminated film is formed by laminating, in order from the outer layer, at least a biaxially oriented film layer, a polybutylene terephthalate layer, and a sealant layer, or by laminating, in order from the outer layer, at least a biaxially oriented film layer, a polyethylene terephthalate layer, and a sealant layer.

8. 7. The pouch for use in a microwave oven according to claim 6, wherein the laminated film is formed by laminating, in order from the outer layer, at least a polyethylene terephthalate layer or a vapor-deposited polyethylene terephthalate layer, a polybutylene terephthalate layer, and a non-oriented polypropylene layer.

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