Bag and method for manufacturing the same

Abstract

To provide a bag or similar item that has a weak joint that reliably separates when heated in a microwave oven but does not separate during transport or storage. [Solution] A bag body 1 for containing microwave-safe food 22 is provided, comprising a main body 10 made of folded film 12 that forms a sealed internal space, the bag body comprising a strip-shaped joint portion 16 in which the films are overlapped and joined together to seal the internal space of the bag body, at least one of the strip-shaped joint portions includes a weak joint portion 24 in part which has a lower joining strength than the strip-shaped joint portion, the weak joint portion is formed by a linear joint portion 24 which is narrower than the strip-shaped joint portion and has a width of 0.2 mm to 0.7 mm, and has a substantially V-shape that converges toward the internal space.

Description

【Technical Field】 【0001】 The present invention relates to a bag body and a method for manufacturing the same, and more particularly to a bag body for accommodating a microwave oven-compatible food provided by heating in a microwave oven and a method for manufacturing the same. 【Background Art】 【0002】 In recent years, many microwave oven-compatible foods that are stored in a bag body and heated in the bag body in a microwave oven and then provided on the dining table have been sold. Such microwave oven-compatible foods include not only foods stored in a frozen state but also foods stored in a refrigerated state and foods stored at room temperature. 【0003】 Since these microwave oven-compatible foods contain moisture, when heated by a microwave oven, this moisture becomes water vapor and the pressure inside the bag body increases. As a result, problems such as the bag body bursting or the resin tray on which the food is placed being deformed may occur. 【0004】 In order to address such problems, a technique has been proposed in which a weak seal portion is provided in a part of the bag body, and when heated by a microwave oven, the weak seal portion peels off to form a water vapor discharge ventilation path (Patent Document 1). 【Prior Art Documents】 【Patent Documents】 【0005】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 10-095472 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0006】 However, in the configuration of Patent Document 1, a bag body in which a ventilation path is formed by peeling off a weak seal portion when heated in a microwave oven can be obtained, but in order to form such a weak seal portion, a plurality of steps for changing the peel strength and other complicated steps are required. 【0007】 Therefore, there was a need for a bag that could be manufactured using a simple process, reliably detached when heated in a microwave oven, and had a weak joint that did not detach during transport or storage. 【0008】 This invention has been made in view of the above points, and aims to provide a bag that can be manufactured with a simple work process and has a weak joint that reliably separates when heated in a microwave oven to serve as a ventilation channel for steam release, and does not separate during transport or storage. 【0009】 Furthermore, the present invention aims to provide a method for manufacturing a bag that can be produced through a simple process and has a weak joint that reliably separates during microwave heating to form a vent for steam release, while remaining intact during transport and storage. [Means for solving the problem] 【0010】 According to the present invention, A bag for containing microwave-safe food, It has a body made of folded film that forms a sealed internal space, The bag body is provided with a strip-shaped joining portion that seals the internal space of the bag body by overlapping and joining the films together. At least one of the strip-shaped joints includes, in part, a weak joint with lower joint strength than the strip-shaped joint. The weak joint portion is formed by a linear joint portion that is narrower than the strip-shaped joint portion and has a width of 0.2 mm to 0.7 mm, and has a substantially V-shape that converges toward the internal space. A bag characterized by the above is provided. 【0011】 In a preferred embodiment of the present invention, The aforementioned weak joint is set so that the distance between both ends is between 5 mm and 50 mm. 【0012】 In another preferred embodiment of the present invention, The angle of the top of the roughly V-shaped linear joint is set to 170 degrees or less. 【0013】 In another preferred embodiment of the present invention, the weak joint is provided at one or more and four or less locations. 【0014】 In another preferred embodiment of the present invention, the strip joint and the linear joint are heat seal joints or ultrasonic joints. 【0015】 In another preferred embodiment of the present invention, There is provided a method for manufacturing a bag body, characterized in that the above bag body is formed by an ultrasonic bonding method or a heat seal bonding method. 【Effects of the Invention】 【0016】 According to the present invention, there is provided a bag body having a weak joint that can be manufactured by a simple working process, surely peels off when heated by a microwave oven to form a ventilation path for water vapor discharge, and does not peel off during transportation or storage. 【0017】 According to the present invention, there is provided a method for manufacturing a bag body having a weak joint that can be manufactured by a simple working process, surely peels off when heated by a microwave oven to form a ventilation path for water vapor discharge, and does not peel off during transportation or storage. 【Brief Description of the Drawings】 【0018】 [Figure 1] It is a schematic plan view of a bag body for storing food compatible with a microwave oven according to a preferred embodiment of the present invention. [Figure 2] It is a schematic drawing for explaining the configuration of the weak joint of the bag body of FIG. 1. [Figure 3] It is a schematic drawing for explaining another arrangement state of the weak joint. [Figure 4] It is a schematic drawing for explaining another arrangement state of the weak joint. [Figure 5] It is a schematic drawing for explaining another arrangement state of the weak joint. [Figure 6] It is a schematic drawing for explaining a weak joint of another configuration. [Figure 7] It is a schematic drawing for explaining a weak joint portion with another configuration. [Figure 8] It is a schematic drawing showing the configuration of an ultrasonic bonding machine used for manufacturing the bag body of FIG. 1. [Figure 9] It is a perspective view schematically showing the configuration of an anvil used in the ultrasonic bonding machine of FIG. 8. 【Mode for Carrying Out the Invention】 【0019】 Hereinafter, a bag body for accommodating a microwave-compatible food of the present invention will be described. 【0020】 In the present application, the microwave-compatible food refers to a food in which cooked foods such as dumplings and meat buns are stored in a bag body and refrigerated, a food in which cooked foods such as dumplings, shumai, and fried chicken are stored in a bag body and frozen, and a food in which cooked foods such as meat buns are stored in a bag body and stored at room temperature, and can be served on the table by heating the entire bag body in a microwave oven. 【0021】 In addition, the microwave-compatible food may be stored in a bag body while being placed on a plastic tray as needed. Further, nitrogen gas may be filled in the bag body as needed. 【0022】 Hereinafter, along with FIG. 1, a bag body 10 for storing a microwave-compatible food of a preferred embodiment of the present invention will be described. FIG. 1 is a schematic plan view of a bag body 1 of a preferred embodiment of the present invention. The bag body 1 is a rectangular bag body in a plan view having a main body 10 with an internal space being a sealed space, for example, about 10 cm or more and 30 cm or less in length and 7 cm or more and 25 cm or less in width. 【0023】 The bag body 1 is formed by folding a horizontally elongated rectangular film 12 twice horizontally along a widthwise center line 14 extending in the vertical direction, sealing the top with a top seal portion 16, the bottom with a bottom seal portion 18, and the sides where the two ends of the film 12 overlap with side seal portions 20. The top seal portion 16, the bottom seal portion 18, and the side seal portions 20 are formed as strip-shaped joints of a predetermined width that extend along the edge of the bag body 1. The strip-shaped joints are heat-sealed joints or ultrasonic joints. In this application, the direction parallel to the top seal portion 16 is defined as the Y direction, and the direction perpendicular to the top seal portion 16 is defined as the X direction. 【0024】 In the bag 1 of this embodiment, the strip-shaped joints 16, 18, and 20 that form the top seal portion 16, the bottom seal portion 18, and the side seal portion 20 are formed by joining films 12 together. In the bag 1 of this embodiment, the width of each strip-shaped joint (length in the inward and outward direction of the bag) is 0.3 mm or more and 15 mm or less, preferably 0.4 mm or more and 13 mm or less, and more preferably 0.5 mm or more and 10 mm or less. A width of 0.3 mm or more ensures bonding strength, and a width of 15 mm or less enables efficient production. 【0025】 When forming a strip-shaped joint using ultrasonic bonding, the width is preferably 0.3 mm to 3 mm, preferably 0.4 mm to 2.5 mm, and more preferably 0.5 mm to 2 mm. By setting the width to 0.3 mm to 3 mm, both bonding strength and efficient production can be achieved. 【0026】 Furthermore, when forming the strip-shaped joint by heat sealing, the width is preferably 3 mm to 15 mm, preferably 4 mm to 13 mm, and more preferably 5 mm to 10 mm. By setting the width to 3 mm to 15 mm, both joint strength and efficient production can be achieved. 【0027】 The interior space of the bag 1 contains microwave-safe food 22. After the microwave-safe food 22 is placed inside the bag 1, it is sealed completely. 【0028】 The film 12 used in the bag 1 of this embodiment is preferably one that can be bonded by ultrasonic bonding or heat sealing. Specifically, examples include films made of polyethylene, polypropylene, polystyrene, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polycarbonate, styrene-acrylonitrile copolymer, or films laminated therefrom. Furthermore, paper that can be bonded by the above bonding methods can also be used as the film. In this invention, it is not necessary to use a film in which the bonding strength of the aforementioned weak joint is particularly reduced. 【0029】 The film 12 is preferably 15 μm or more and 150 μm or less in thickness, and more preferably 20 μm or more and 100 μm or less. If the film thickness is less than 15 μm, the strength of the bag may be insufficient, and if it exceeds 150 μm, it may be disadvantageous in terms of cost. The film may be transparent or opaque. Opaque packaging film may be used to prevent deterioration of the contents due to external light. Additionally, film with printed surfaces may be used to enhance aesthetic appeal. 【0030】 In the bag body 1 of this embodiment, a weak joint 24 is provided in a part of the top seal portion 16 formed by a strip-shaped joint, which is composed of a linear joint with lower joint strength than the strip-shaped joint. In the bag body 1 of this embodiment, the strip-shaped joint that constitutes the top seal portion 16 is interrupted, and the weak joint 24 is positioned in this interrupted portion. The weak joint 24 has a substantially V-shape, which converges toward the inside of the bag body, and is positioned so that its tip is located on the inside side of the bag body than the strip-shaped joint. The linear joint, which has a substantially V-shape, is narrower than the strip-shaped joint and has a width of 0.2 mm to 0.7 mm. 【0031】 The width of the linear joint portion that constitutes the weak joint portion 24 is set to be smaller than the width of the strip-shaped joint portion that constitutes the top seal portion 16. By setting it in this way, the linear joint portion 24 can be reliably separated during microwave cooking, and the resulting steam can be discharged. 【0032】 The ratio of the width of the linear joint to the width of the strip joint is preferably 0.013 or more and less than 1, more preferably 0.016 or more and 0.83 or less, and even more preferably 0.02 or more and 0.67 or less. Setting this ratio to 0.013 or more prevents peeling of the weak joint during transport and storage. Setting the ratio to less than 1 ensures that the steam generated when the linear joint 24 peels off during microwave cooking can be reliably discharged. 【0033】 The preferred value of this ratio varies depending on the method used to form the strip-shaped joint. For example, when the strip-shaped joint is formed by ultrasonic bonding, the preferred ratio is 0.067 or more and less than 1, more preferably 0.083 or more and 0.83 or less, and even more preferably 0.1 or more and 0.67 or less. 【0034】 When forming a strip-shaped joint by a heat-sealing method, this ratio is preferably 0.013 or more and 0.1 or less, more preferably 0.017 or more and 0.083 or less, and even more preferably 0.2 or more and 0.067 or less. 【0035】 Each end of the roughly V-shaped linear joint that constitutes the weak joint 24 is connected to the tips, i.e., the free ends, of the separated portions 16a and 16b of the separated top seal portion 16. As a result, the upper part of the bag 1 has a structure in which it is continuously sealed by the portions 16a and 16b of the strip-shaped joint and the weak joint 24 formed by the linear joint. This configuration makes the inside of the bag airtight during storage, preventing the intrusion of foreign matter and the influx of oxygen from the outside. 【0036】 As described above, the weak joint portion 24 is located in the interrupted part of the strip-shaped joint portion of the top seal portion 16. Therefore, when the film 12 that was joined at the weak joint portion 20 peels off, a ventilation passage for water vapor discharge is formed, connecting the inside and outside of the bag 1. 【0037】 Specifically, when a bag 1 containing microwave-safe food in a sealed state is placed in a microwave oven and heated, the internal pressure generated by steam from the food causes the films 12 to separate at the weak joint 24, forming a steam-releasing vent that connects the inside and outside of the bag 1 and crosses the top seal 16. 【0038】 In the bag body 10 of this embodiment, a weak joint portion 24 is provided in the top seal portion 16, but the weak joint portion may also be provided in other seal portions, such as the bottom seal portion or the side seal portion. Providing the weak joint portion in the top seal portion or the bottom seal portion is preferable because it makes it easier to form a ventilation passage for steam discharge when heated in a microwave oven. Furthermore, if the bag has a back-sealed portion (center seal portion), a weak joint may be provided in the back-sealed portion. 【0039】 Next, the configuration of the weak joint 24 will be explained with reference to Figure 2. Figure 2 is a schematic diagram illustrating the specific configuration of the weak joint 24 of the bag body 1 in Figure 1. In the bag body 1, as shown in Figure 2, a portion of the strip-shaped joint that constitutes the top seal portion 16 is divided, and a weak joint portion 24, which is composed of a roughly V-shaped linear joint, is positioned between these divided portions 16a and 16b. 【0040】 The linear joint portion 24, which is roughly V-shaped, has a distance between its two ends (length in the Y direction), i.e., the length of the V-shaped open end is set to be between 5 mm and 50 mm. This length is more preferably between 10 mm and 45 mm, and even more preferably between 15 mm and 40 mm. 【0041】 By setting the distance between the two ends of the roughly V-shape to 5 mm or more, it becomes possible to reliably discharge water vapor, and by setting it to 50 mm or less, it is possible to prevent the weakened part 20 from breaking during transport or storage. This configuration makes it possible to achieve both steam release during microwave cooking and prevention of delamination during transport and storage without using a method that sets the bonding strength per unit area of ​​the linear joint 24 to be particularly low. In other words, it is possible to achieve both steam release during microwave cooking and prevention of delamination during transport and storage without using a special film or a manufacturing method that forms the strip joint and linear joint separately. 【0042】 The linear joint portion 24, which is roughly V-shaped, has an angle θ at its apex that is set to 170 degrees or less. This angle is more preferably 45 degrees or more and 168 degrees or less, and even more preferably 90 degrees or more and 165 degrees or less. By setting this angle to 170 degrees or less, the linear joint 24 can be reliably separated during microwave cooking, and the resulting steam can be discharged. 【0043】 Furthermore, in this embodiment, the width of the linear joint, that is, the length in the direction perpendicular to the direction in which the straight portion constituting the V shape of the linear joint extends, is set to 0.2 mm or more and 0.7 mm or less. This width is preferably 0.25 mm or more and 0.6 mm or less, and more preferably 0.3 mm or more and 0.5 mm. By setting the width of the linear joint of the weak joint 20 to 0.2 mm, the breakage of the linear joint 24 during transport and storage of the bag is prevented, and by setting it to 0.7 mm or less, poor steam release during microwave cooking is prevented. 【0044】 In the above embodiment, the width of the linear joint is constant, but this width does not have to be constant. For example, the width of the linear joint 24 may be continuously increased from the apex of the roughly V-shape toward the connection to the strip-shaped joint. Specifically, one example is a configuration in which the width at the apex of the roughly V-shape is 0.2 mm, and this width is continuously increased toward the connection to the strip-shaped joint to 0.7 mm. 【0045】 The V-shaped weak joint portion 24 is preferably positioned such that the tip of the V is shifted by 0.3 mm to 5 mm in the X direction from the inner surface of the strip-shaped joint portion constituting the top seal portion 16 (the position X=0 shown by the dotted line in Figure 2), and more preferably by 0.5 mm to 3 mm. 【0046】 By setting the tip shift distance to 0.3 mm or more, the weak joint 24 will be reliably separated during microwave cooking. Furthermore, by setting it to 5 mm or less, it becomes possible to prevent the film joining device from becoming larger and to manufacture bags efficiently. This configuration makes it possible to more reliably prevent poor steam release during microwave cooking. 【0047】 The connection between the tips of the divided portions 16a and 16b of the strip-shaped joint and the weak joint 24, which is formed by the linear joint, is such that the linear joint is connected to the outer side edge of the bag body of the divided portions 16a and 16b of the strip-shaped joint. By adopting this shape, it becomes possible to set a smaller angle at the vertices of the roughly V-shape. 【0048】 With the above configuration, the steam generated during microwave cooking causes the vertices 26 of the linear joint 24 to peel off first. Once the vertices 26 begin to peel off, this peeling propagates to other parts, easily causing the linear joint 24 to peel further. In this embodiment, the peeling process is designed to begin at a single point on the V-shaped apex. When the apex of a continuous linear joint peels off, the linear portion also peels off subsequently. As a result, the weakly joined portion is reliably separated during microwave cooking. Therefore, in this embodiment, there is no need to form the weakly joined portion with dots. 【0049】 In the above embodiment, the approximate V shape is formed by arranging single-line linear joints 24 in a V shape, but the approximate V shape may also be formed by arranging two sets of linear joints 24 overlapping in the vertical direction. At least one end of each of the two sets of approximate V shapes is connected to a strip-shaped joint. In this case, the width of the linear joint constituting the straight section is preferably 0.2 mm to 0.4 mm, and the spacing (gap) between the two linear joints arranged in a double-line configuration is preferably 0.1 mm to 0.3 mm. The two V-shapes may have two lines with the same or different widths. However, the sum of the widths of the two lines and the sum of the spacing between the two straight lines shall be 0.7 mm or less. 【0050】 In the above embodiment, the substantially V-shape formed by the linear joint is symmetrical, but it may also be asymmetrical. Specifically, examples include shapes in which the position of the vertex of a roughly V-shape is shifted along the Y-axis, shapes in which the two straight sections of a roughly V-shape have different widths, shapes in which one of the two straight sections of a roughly V-shape is composed of a curve, and shapes in which one of the two straight sections of a roughly V-shape consists of two straight lines arranged in a double-track manner. 【0051】 Furthermore, as shown in the schematic diagrams of Figures 3 to 5, the bag may also have multiple weak joints 24. Even when multiple weak joints are provided, the location of the weak joints is not limited to the top seal area. For example, they can also be provided in the bottom seal area, side seal area, and back sealing area. For example, possible configurations include one with two weak joints in the top seal section, one with three weak joints in the side seal section, and one weak joint in both the top seal section and the bottom seal section. The number and placement of weak joints are determined appropriately, taking into account factors such as the size of the bag and the amount of internal pressure generated during microwave heating. 【0052】 Next, the configuration of a bag body of another embodiment of the present invention will be described with reference to Figure 6. Figure 6 is a schematic diagram illustrating the configuration of the weak joint of the bag body of another embodiment. 【0053】 The difference between the bag body of this embodiment and the bag body of the above embodiment lies in the shape of the weak joint. The weak joint of the bag body of this embodiment differs from that of the bag body of the above embodiment in that the substantially V-shaped linear joint 24 has an extended portion 28 which is an I-shaped linear joint that extends a predetermined distance in the X direction from the apex 26 of the V. By providing such an extended portion 28, the peeling of the weak joint formed by the linear joint during microwave cooking becomes more reliable. 【0054】 The length of the extension portion 28 in the X direction is preferably 0.2 mm to 3 mm, more preferably 0.3 mm to 2.5 mm, and even more preferably 0.5 mm to 2 mm. By making the length of the extension portion 0.2 mm or more, the linear joint portion 24 can be reliably separated during microwave cooking, and the resulting steam can be discharged. Furthermore, by making it 3 mm or less, it becomes possible to prevent the film joining device from becoming larger and to manufacture the bags efficiently. 【0055】 Next, the configuration of the bag body of another embodiment will be described with reference to Figure 7. Figure 7 is a schematic diagram illustrating the configuration of the weak joint portion 24 of the bag body of another embodiment. The bag body of this embodiment differs from the bag body of Figure 1 in that the linear joint portion constituting the roughly V-shaped weak joint portion is not composed of two straight lines, but of two curved portions 24a and 24b that curve so as to be convex toward the inside of the V shape. 【0056】 The curvature of the curved portion described above will now be explained. In the linear joint that constitutes the weak joint of the bag body in this embodiment, the angle θ(a) is defined as the angle between the two tangent lines L1 and L2 at points A1 and A2, which are located at a distance a from the position X=0 shown by the dotted line in Figure 7. The value of this angle θ(a) is a function of a. In this embodiment, the curved portions 24a and 24b are configured to have a curved shape such that θ(a) increases as the value of a decreases (i.e., as points A1 and A2 move from the inside to the outside of the bag). This configuration ensures that the linear joints separate reliably during microwave cooking, allowing the generated steam to be released. 【0057】 The strip-shaped and linear joints of the bag body in this embodiment are formed by ultrasonic bonding. Alternatively, these joints may be formed by heat sealing. An embodiment of the method for forming such a joint will be described. 【0058】 Figure 8 is a schematic diagram showing the configuration of an ultrasonic bonding machine 50 used in ultrasonic bonding. The ultrasonic bonding machine 50 is an ultrasonic bonding machine with a known basic configuration, comprising an ultrasonic oscillator 52 that converts commercial electricity of 50 Hz or 60 Hz into a high-frequency signal of about 15 to 70 kHz, a converter 54 that converts this signal into mechanical vibrations, a booster 56 that amplifies these mechanical vibrations, a flat plate-shaped horn 58 that transmits the amplified vibrations to the object to be welded, and a flat plate-shaped anvil 60 that sandwiches two films 12, 12 between the horn 58. 【0059】 The horn 58 has a smooth surface, and the anvil 60 has a surface with protrusions corresponding to the shape of the joint to be formed, as described later. The length of the horn 58 and anvil 60 is approximately 50 mm to 450 mm, and the width of the horn 58 and anvil 60 is approximately 7 mm to 25 mm. The horn 58 and anvil 60 are preferably made of known materials, particularly stainless steel or titanium alloy. 【0060】 The edges of the surfaces of the horn 58 and anvil 60 may be chamfered. Chamfering prevents the film 12 from being cut at this point. 【0061】 The anvil 60 moves up and down by a drive mechanism (not shown) to sandwich the two films 12 between itself and the horn 58. In this state, ultrasonic waves are applied to the horn 58 to simultaneously form a strip-shaped joint 14 and a linear joint 24 on the bag. When sandwiching the two films 12, 12, a pressure of approximately 20N to 500N is applied between the horn 58 and the anvil 60 by a pressure device (not shown). 【0062】 The bonding time is preferably between 0.01 seconds and 10 seconds, more preferably between 0.03 seconds and 5 seconds, and even more preferably between 0.05 seconds and 3 seconds. By setting the bonding time to 0.01 seconds or longer, sufficient bonding strength can be obtained. Furthermore, by setting the bonding time to 10 seconds or less, manufacturing efficiency is improved. 【0063】 Figure 9 is a schematic perspective view showing the configuration of an anvil 60 used in the ultrasonic bonding machine 50. The anvil 60 is flat, and its surface 62 has protrusions 64 corresponding to the strip-shaped bonding portion 23 and linear bonding portion 24 of the bag body 10. 【0064】 The height of the protrusion 64 is set to be between 0.2 mm and 1.0 mm. If the height of the protrusion 64 is less than 0.2 mm, the bonding strength between the strip-shaped joint and the linear joint may be insufficient, and if it exceeds 1.0 mm, the film may tear at the edges, resulting in improper bonding. The cross-sectional shape of the protrusion 64 is preferably rectangular, semi-circular, or trapezoidal, but semi-circular or trapezoidal is particularly preferred from the viewpoint of preventing the film from tearing at the edges. 【0065】 Next, we will explain the configuration of the heat seal bonding machine. In a heat seal bonding machine, two films are sandwiched between a heating plate and a support, or between two heating plates, and heat and pressure are applied to bond the films together. 【0066】 The heating plate is made of metal such as brass, iron, or stainless steel and has a built-in heater. The heating plate has a flat plate shape with a planar surface. The base is also made of metal such as brass, iron, or stainless steel. The base is also flat plate shaped, but has protrusions corresponding to the strip-shaped joint and the linear joint 24 arranged on its planar surface. 【0067】 The height of the protrusion is set to between 0.2 mm and 5 mm. If the height of the protrusion is less than 0.2 mm, the bonding strength between the strip-shaped joint and the linear joint may be insufficient, and if it exceeds 5 mm, the film may tear at the edges, resulting in an improper bond. The cross-sectional shape of the protrusion is preferably rectangular, semi-circular, or trapezoidal, but semi-circular or trapezoidal is particularly preferred from the viewpoint of preventing the film from tearing at the edges. 【0068】 The length of the heating plate and the base is approximately 50 mm to 150 mm, and the width of the heating plate and the base is approximately 7 mm to 35 mm. The edges of the heating plate and the support base may be chamfered. Chamfering prevents the film 12 from being cut at these points. 【0069】 In the film joining process, two films are overlapped and pressure is applied between the heating plate and the base. If the pressure is too low, the adhesive strength will be insufficient; if it is too high, the film may deform. If the temperature is too low, heat sealing may not be possible, resulting in a weak seal; if it is too high, there is a risk of film deformation. If the heating time is too short, the adhesive strength will be insufficient; if it is too long, the film may deform. The appropriate pressure, temperature, and time vary depending on the type and thickness of the film, so they should be determined appropriately considering the above conditions. The pressure is typically around 20N to 500N, the heating plate temperature is typically around 100°C to 200°C, and the pressurization time is typically around 0.01 seconds to 10 seconds. 【0070】 The bag of this embodiment can be manufactured, for example, by the following method. (1) Prepare the film. (2) The film is folded in half, and the overlapping side edges of the filters are heat-sealed or ultrasonically bonded to form a side seal. (3) Furthermore, the lower part of the film is heat-sealed or ultrasonically bonded to form a bottom seal. (4) Form the bag using the method described above. (5) From the open top, microwave-safe food or microwave-safe food placed on a tray is placed inside the bag. (6) The open top of the bag is joined using an ultrasonic bonding machine that has a flat anvil with irregularities on its surface corresponding to the strip-shaped and linear joints, and a flat horn with a smooth surface, thereby sealing the internal space of the bag. In this way, microwave-safe food products are manufactured in a bag of the present invention having a weakly joined portion at the top seal. 【0071】 The method for manufacturing the bag and microwave-safe food according to the present invention is not limited thereto; for example, the number of steam discharge ports and their positions can be changed as needed. 【0072】 The method for producing the bag of the present invention is not limited to the method described above. For example, the strip-shaped joint and the linear joint may be formed in two steps. Specifically, this could involve first forming the strip-shaped joint and then forming the linear joint, or forming the strip-shaped joint and the linear joint in the reverse order. 【0073】 In this case, the strip-shaped joint and the linear joint may be formed under different conditions. For example, when forming the strip-shaped joint and the linear joint using ultrasonic bonding, the bonding conditions for both may be changed. Specifically, one method is to set the peeling force per unit area of ​​the strip-shaped joint to be greater than the peeling force per unit area of ​​the linear joint. 【0074】 Furthermore, the strip-shaped joint and the linear joint may be formed by different methods. For example, the strip-shaped joint may be formed by a heat sealing method and the linear joint by an ultrasonic bonding method, or the strip-shaped joint may be formed by an ultrasonic bonding method and the linear joint by a heat sealing method. 【0075】 Of these methods, the method of forming the strip-shaped joint by heat sealing and the linear joint by ultrasonic bonding is preferred because it can efficiently form strip-shaped and linear joints with accurate shapes. 【0076】 Furthermore, it is possible to create a large number of bags with only side seals formed using a long film, which are then connected vertically, and use these to continuously produce multiple microwave-safe food items. In this case, steps (1) and (2) above are performed in one step, and steps (3) through (6) are repeated. As a further variation, the top seal portion of one bag and the bottom seal portion of the adjacent bag are formed simultaneously, and then the two bags are separated. In this case, (6) and (3) of the next bag are performed simultaneously using ultrasonic bonding. 【0077】 The present invention is not limited to the embodiments described above, and various modifications and variations are possible within the scope of the technical idea described in the claims. [Explanation of Symbols] 【0078】 10: Bag body 12: Film 16: Top seal section 18: Bottom seal section 20: Side seal section 22: Microwave-safe foods 24: Weak joint

Claims

[Claim 1] A bag for containing microwave-safe food, It has a body made of folded film that forms a sealed internal space, The bag body is provided with a strip-shaped joining portion that seals the internal space of the bag body by overlapping and joining the films together. At least one of the strip-shaped joints includes a weak joint in part, which has lower joint strength than the strip-shaped joint. The weak joint portion is formed by a linear joint portion that is narrower than the strip-shaped joint portion and has a width of 0.2 mm to 0.7 mm, and has a substantially V-shape that converges toward the internal space. A bag characterized by the following features. [Claim 2] The aforementioned weak joint is set so that the distance between both ends is between 5 mm and 50 mm. The bag according to claim 1. [Claim 3] The angle of the top of the roughly V-shaped linear joint is set to 170 degrees or less. The bag according to claim 1 or 2. [Claim 4] The aforementioned weak joints are provided in one to four locations. The bag according to claim 1 or 2. [Claim 5] The aforementioned strip-shaped joint and linear joint are heat-seal joints or ultrasonic joints. The bag according to claim 1 or 2. [Claim 6] A method for manufacturing a bag, characterized by forming the bag according to claim 1 by an ultrasonic bonding method or a heat seal bonding method.

Images