Food packaging sheets and packaged foods

Abstract

The present invention provides a food packaging sheet that prevents sheet-shaped food from becoming damp and allows for easy removal of the packaging. [Solution] The food packaging sheet 1 of the present invention comprises an outer film 2, an inner film 3 placed on top of the outer film, and a sheet-like food 4 sandwiched between the outer film and the inner film, wherein the outer film and the inner film are heat-sealed 11 around the outer circumference of the sheet-like food, the outer film has an outer groove 21 recessed from the surface of the outer film, the inner film has an inner groove 31 recessed from the surface of the inner film, an outer bank portion 22 raised from the surface of the outer film is formed on both sides of the outer groove, and an inner bank portion 32 raised from the surface of the inner film is formed on both sides of the inner groove.

Description

Technical Field

[0001] The present invention relates to a packaging sheet configured by sandwiching a sheet-shaped food between an inner film and an outer film, and capable of packaging foods such as rice balls, and a packaged food obtained by packaging a food with the packaging sheet.

Background Art

[0002] As a food packaging sheet for packaging foods such as rice balls sold at convenience stores, etc., a packaging sheet having a triple structure formed by sandwiching a sheet-shaped seaweed between an outer film and an inner film is widely known. Hereinafter, a packaging sheet for packaging a rice ball will be taken as an example for explanation.

[0003] A cut tape for dividing the outer film is attached to the center in the width direction of the outer film, and the inner film consists of two inner film pieces. A sheet-shaped seaweed is sandwiched between the outer film and the inner film pieces, and the inner ends of the two inner film pieces are heat-sealed to the outer film so as to overlap on the cut tape of the outer film, thereby producing a packaging sheet (see, for example, Patent Document 1).

[0004] For a packaged rice ball (packaged food) packaged with the above packaging sheet, after pulling the start end of the cut tape to divide the outer film into two, and then pulling one of the outer films outward, the inner film pieces are pulled out together with the outer film (see, for example, Patent Document 2).

[0005] Subsequently, by pulling the other outer film outward and pulling it out together with the remaining inner film pieces, a seaweed-wrapped rice ball in which the sheet-shaped seaweed is directly wound around the rice ball can be obtained, and this can be eaten.

[0006] Furthermore, Patent Document 3 discloses a food packaging sheet in which groove-shaped half-cuts are formed in the center of the width direction of both the outer film and the inner film. When an onigiri (rice ball) is wrapped in this food packaging sheet, the packaging can be opened by pulling the outer film and inner film in a direction perpendicular to the half-cuts, which separates the half-cuts. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-101832 [Patent Document 2] Japanese Utility Model Publication No. 6-8284 [Patent Document 3] Japanese Patent Publication No. 2008-100741 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0008] The inner films described in Patent Documents 1 and 2 are simply two inner film pieces with their inner edges overlapping. Consequently, during the manufacturing and distribution process, or after the rice balls are packaged, moisture can penetrate through the overlapping parts of the inner film pieces, causing the sheet-like nori to become damp. Furthermore, while the outer film and inner film pieces are heat-sealed around the periphery of the sheet-like nori, the portion of the periphery that overlaps with the starting and ending points of the cut tape is not heat-sealed in order to allow for separation by the cut tape. As a result, moisture can penetrate through this unsealed portion, causing the sheet-like nori to become damp. When the sheet-like nori becomes damp, it can become sticky, wrinkled, and wavy, resulting in an inferior appearance and taste, and there is a risk that it may tear when the packaged rice balls are unwrapped.

[0009] Furthermore, when unwrapping a packaged rice ball, it can be difficult to determine the starting point of the tape, or even if the starting point is known, it can be difficult to grasp it properly, resulting in the inability to unwrap the package. This is especially difficult for those eating packaged rice balls for the first time or for the elderly. If the packaged rice ball is unwrapped using an incorrect method, the sheet-like food may tear, and it may also be difficult to properly wrap the sheet-like food around the rice ball.

[0010] In the food packaging sheet described in Patent Document 3, when the outer film and inner film are pulled, they may be cut off from the half-cut. As a result, the cut points of the outer film and inner film may not align, or the outer film and inner film may not be completely separated, with parts remaining connected, making it difficult to properly unpack the packaging.

[0011] The object of the present invention is to provide a food packaging sheet that prevents sheet-like food from becoming damp and allows the packaging to be easily opened. [Means for solving the problem]

[0012] The food packaging sheet of the present invention is Outer film and An inner film is arranged on top of the outer film, A sheet-like food sandwiched between the outer film and the inner film, Includes, A food packaging sheet formed by heat-sealing the outer film and the inner film around the outer circumference of the sheet-like food, The outer film has an outer groove that is recessed more than the surface of the outer film. The inner film has an inner groove formed by laser processing that is recessed from the surface of the inner film, On both sides of the outer groove, an outer embankment portion is formed that is raised higher than the surface of the outer film. On both sides of the inner groove, an inner embankment is formed that is raised higher than the surface of the inner film.

[0013] The groove film thickness I1 of the outer film at the portion where the outer groove is formed is 1 / 4 to 3 / 4 of the thickness H1 of the outer film. It is desirable that the groove film thickness I2 of the inner film at the portion where the inner groove is formed is 1 / 4 to 3 / 4 of the thickness H2 of the inner film.

[0014] The thickness H1 of the outer film is 10 μm to 40 μm. The groove film thickness I1 of the outer film at the portion where the outer groove is formed is 5 μm to 30 μm. For the outer soil portion, the height L1 from the surface of the outer film is 3 μm to 30 μm. The thickness H2 of the inner film is 10 μm to 40 μm. The groove film thickness I2 of the inner film at the portion where the inner groove is formed is 5 μm to 30 μm. It is desirable that for the inner soil portion, the height L2 from the surface of the inner film is 3 μm to 30 μm.

[0015] It is desirable that heat welding is performed on the outer film and the inner film so as to entirely surround the outer periphery of the sheet-shaped food.

[0016] In the outer film, the outer groove and the outer soil portion are formed on the middle surface on the sheet-shaped food side. It is desirable that in the inner film, the inner groove and the inner soil portion are formed on the inner surface on the side opposite to the sheet-shaped food.

[0017] The outer groove and the inner groove can be wavy.

[0018] The outer film is composed of a single film. The inner film can be configured to be composed of a single film.

[0019] The outer film and the inner film can be configured to be composed of a single folded film.

[0020] The packaged food of the present invention is formed by packaging food with the food packaging sheet described above.

Advantages of the Invention

[0021] In the food packaging sheet according to the present invention, outer grooves are formed in the outer film, and inner grooves are formed in the inner film. On both sides of these outer grooves and inner grooves, outer ridge portions and inner ridge portions higher than the surfaces of the outer film and the inner film are respectively formed. By forming these outer ridge portions and inner ridge portions, the thickness of the outer film and the inner film is increased at this portion, and both sides of the outer grooves and the inner grooves are reinforced.

[0022] When the outer film and the inner film are pulled outward in a direction substantially orthogonal to the outer grooves and the inner grooves, the outer film and the inner film are separated starting from the thin outer grooves and inner grooves. In the present invention, both sides of the outer grooves and the inner grooves are reinforced by the outer ridge portions and the inner ridge portions. Therefore, the separation of the outer film and the inner film proceeds along the outer grooves and the inner grooves without deviation. As a result, the packaged food formed by packaging food with the packaging sheet can be easily unpacked by simply pulling the outer film and the inner film outward, and the breakage progresses along the outer grooves and the inner grooves, and the outer film and the inner film are separated.

[0023] The food packaging sheet of the present invention does not consist of two inner film pieces like the conventional one, so there is no intrusion of moisture from the overlapping portion of the inner film pieces. Therefore, it is possible to prevent the sheet-like food from getting damp. Furthermore, since the packaging sheet of the present invention does not employ a cut tape, the outer film and the inner film can be thermally welded at all their outer peripheries. As a result, there is no unsealed portion through which moisture can intrude at the outer periphery of the packaging sheet, so it is possible to prevent the sheet-like food from getting damp. Therefore, the sheet-like food can be maintained in a dry state, suppressing stickiness, wrinkles, undulations, deterioration in appearance and taste of the sheet-like food, and reducing the possibility of the sheet-like food being broken when unpacking the packaged food.

[0024] Furthermore, in the case of food packaging sheets that use cut tape, there are three pieces of waste: the outer film and inner film that are separated into left and right halves, and the outer film to which the cut tape is attached. However, in the food packaging sheet of the present invention, there are only two film blocks: the outer film and inner film that are separated into left and right halves, thus reducing the amount of waste. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 is an exploded perspective view of the rice ball packaging sheet according to the present invention. [Figure 2] Figure 2 is a plan view of the rice ball packaging sheet according to the present invention. [Figure 3] Figure 3 is a cross-sectional view along line AA in Figure 2. [Figure 4] Figure 4 shows (a) a cross-sectional view perpendicular to the outer groove of the outer film, and (b) a cross-sectional view perpendicular to the inner groove of the inner film. [Figure 5] Figure 5 is an enlarged view of the circled area B in Figure 3. [Figure 6] Figure 6 is a perspective view of a packaged rice ball, which is a rice ball wrapped in a packaging sheet. [Figure 7] Figure 7 is a perspective view of a packaged rice ball, seen from the back. [Figure 8] Figure 8 is a schematic diagram of the main components of a packaging sheet manufacturing apparatus. [Figure 9] Figure 9 is an exploded perspective view of another pattern of the packaging sheet according to the present invention. [Figure 10] Figure 10 shows the shape measurement results of the film of the invention example using a digital microscope. [Figure 11] Figure 11 shows the shape measurement results of the comparative example film using a digital microscope. [Figure 12] Figure 12 is a photograph of the outer film of the invention example with straight grooves formed after it has been cut. [Figure 13] Figure 13 is a photograph of the inner film after it has been cut, showing an example of the invention in which straight grooves have been formed. [Figure 14]Figure 14 is a photograph of the outer film of the invention example with a wavy groove formed after it has been cut. [Figure 15] Figure 15 is a photograph of the inner film after it has been cut, showing an example of the invention in which a wavy groove has been formed. [Figure 16] Figure 16 is a photograph of the outer film of a comparative example in which straight grooves were formed, after it was cut. [Figure 17] Figure 17 is a photograph of the inner film of a comparative example in which straight grooves were formed, after it was cut. [Figure 18] Figure 18 is a photograph of the outer film of a comparative example that formed a wavy groove after being cut. [Figure 19] Figure 19 is a photograph of the inner film of a comparative example that had a wavy groove formed, after it was cut. [Modes for carrying out the invention]

[0026] The food packaging sheet 1 of the present invention will be described below with reference to the drawings. In the following description, a rice ball 5 made from solidified cooked rice will be used as an example of the food 5.

[0027] As shown in Figure 1, the packaging sheet 1 for the rice ball 5 of the present invention consists of an outer film 2, a sheet-like food 4, and an inner film 3. The outer film 2 and the inner film 3 are layered so as to sandwich the sheet-like food 4. As shown in Figures 2 and 3, the outer film 2 and the inner film 3 are heat-sealed 11 to completely surround the outer periphery of the sheet-like food 4, and are integrated to form the packaging sheet 1. The packaging sheet 1 packages the rice ball 5 as shown in Figures 6 and 7, which will be described later. In the illustrated embodiment, the outer film 2 and the inner film 3 are each made from a single film.

[0028] <Outer film 2, Inner film 3> The outer film 2 and inner film 3 can be rectangular. In the illustrated embodiment, films 2 and 3 are rectangles approximately 23 cm long and 16 cm wide. Films 2 and 3 may also be polygonal in shape, such as by rounding off the corners.

[0029] The outer film 2 and inner film 3 can be made from common materials used for rice ball packaging sheets, such as polypropylene films (PP films) like CPP film (unoriented polypropylene film) or OPP film (oriented polypropylene film), or polyethylene films (PE films). The outer film 2 can be, for example, a transparent film, and the product name and ingredients can be printed on it as appropriate. The inner film 3 can be a transparent or opaque film.

[0030] The thicknesses H1 and H2 (see Figure 4) of the outer film 2 and inner film 3 are preferably 10 to 40 μm, and more preferably 20 to 30 μm. If the film thicknesses H1 and H2 are thinner than this, sufficient strength cannot be achieved, and if the film thicknesses H1 and H2 are thicker than this, it may become difficult to wrap the rice ball 5, and costs will increase.

[0031] The packaging sheet 1 of the present invention has grooves 21 and 31 that allow the outer film 2 and inner film 3 to be easily torn apart by pulling them to the left and right when unpacking, as shown in Figure 4. The groove formed in the outer film 2 is called the outer groove 21, and the groove formed in the inner film 3 is called the inner groove 31. On both sides of the outer groove 21, there are outer embankments 22 that are raised higher than the surface of the outer film 2, and on both sides of the inner groove 31, there are inner embankments 32 that are raised higher than the surface of the inner film 3.

[0032] The outer groove 21, with outer embankment portions 22 formed on both sides, and the inner groove 31, with inner embankment portions 32 formed on both sides, can be formed by, for example, irradiating films 2 and 3 with a laser beam, although this does not limit the manufacturing method. Specific embodiments of laser processing will be described later, but Figure 4(a) is an enlarged view of the outer groove 21 formed on the outer film 2 by laser processing, and Figure 4(b) is an enlarged view of the inner groove 31 formed on the inner film 3 by laser processing. As shown in the figures, it can be seen that a portion of the surface of the outer film 2 and inner film 3 melts and becomes thinner when irradiated with a laser. On both sides of the outer groove 21 and inner groove 31, a portion of the melted resin flows to the left and right, forming raised embankment portions 22 and 32.

[0033] As shown in Figures 6 and 7, the outer groove 21 and inner groove 31 can be formed along the entire length of the outer film 2 and inner film 3, following a line connecting one vertex of the rice ball 5 to the center of the opposite side when the rice ball 5 is wrapped. In the unfolded state, this corresponds to approximately the center in the short direction of the outer film 2 and inner film 3, as shown in Figures 1 and 2. Of course, the outer groove 21 and inner groove 31 may also be formed in the longitudinal direction of the outer film 2 and inner film 3, and the formation position is not limited to the center, but may be offset from the center.

[0034] The outer groove 21 and inner groove 31 are preferably formed such that the thickness of the film 2 and 3 in the portion where the outer groove 21 and inner groove 31 are formed (groove film thickness) I1 and I2 are approximately 1 / 4 to 3 / 4 of the film thickness H1 and H2, respectively, as shown in Figure 4, and more preferably 1 / 3 to 1 / 2. Specifically, the groove film thickness I1 and I2 are 5 μm to 30 μm, preferably 10 μm to 25 μm. If the groove film thickness I1 and I2 are thinner than this, the film 2 and 3 may tear during the production of the packaging sheet 1 or when packaging rice balls. On the other hand, if the groove film thickness I1 and I2 are thicker than this, the film 2 and 3 may not tear properly.

[0035] In the case of the groove film thicknesses I1 and I2 described above, as shown in Figure 4, the depths J1 and J2 of the outer groove 21 and inner groove 31, including the bank portions 22 and 32, are 10 μm to 25 μm, preferably 15 to 20 μm. At this time, the groove depths K1 and K2 from the film surface to the bottom of the outer groove 21 and inner groove 31 are 5 μm to 20 μm.

[0036] Furthermore, the heights L1 and L2 of the embankment sections 22 and 32 (embankment heights) are preferably around 3 μm to 30 μm, more preferably 3 μm to 20 μm, and most preferably 5 μm to 15 μm. The embankment sections 22 and 32 are necessary to have a predetermined height in order to serve as reinforcement to prevent the break from diverting towards the film side when the outer groove 21 and inner groove 31 are separated. When the embankment heights L1 and L2 are as described above, the embankment film thicknesses M1 and M2 in the parts where the embankment sections 22 and 32 are formed will be M1 = H1 + L1 and M2 = H2 + M2, respectively. Therefore, with the above film thickness, the embankment film thicknesses M1 and M2 will be 13 μm to 70 μm, respectively.

[0037] The outer grooves 21 and inner grooves 31 may be formed on either the outer film 2 or the inner film 3, respectively. Specifically, if it is the outer film 2, the outer grooves 21 can be formed on the outer surface that faces outward during packaging, or on the inner surface that faces the sheet-like food 4. If it is the inner film 3, the inner grooves 31 can be formed on the inner surface that faces the sheet-like food 4 during packaging, or on the inner surface that faces the rice ball 5.

[0038] On the other hand, for the reasons described below, as shown in Figure 5, which is an enlarged view of the circled area B in Figure 3, it is desirable that the outer groove 21 formed on the outer film 2 be formed on the inner surface 24 facing the sheet-like food 4, and the inner groove 31 formed on the inner film 3 be formed on the inner surface facing the rice ball 5.

[0039] As shown in Figure 4, the outer grooves 21 and inner grooves 31 formed on the outer film 2 and inner film 3 have raised edges 22 and 32 on both sides. With respect to the packaging sheet 1, if there are raised outer edges 22 on the outer surface 23 of the outer film 2, purchasers may feel uncomfortable when they touch it. Therefore, it is preferable to form the outer grooves 21 on the inner surface 24 of the outer film 2, as shown in Figure 5. Also, if the sheet-shaped food 4 is sheet-shaped seaweed, the sheet-shaped seaweed has a smooth, glossy surface 41 and a rough, non-glossy surface 42. To improve the appearance of the packaged rice ball 6, the sheet-shaped seaweed is placed in the packaging sheet 1 with the surface 41 facing outwards, that is, as shown in Figure 5, with the surface 41 facing the outer film 2 side and the back surface 42 facing the inner film 3 side. In this case, if the inner groove 31 of the inner film 3 is on the rough side of the sheet-like food 4, the inner edge 32 may catch on the rough sheet-like food 4 when unpacking, making it difficult to unpack. For this reason, as shown in Figure 5, it is preferable to form the inner groove 31 on the inner surface 34 that faces the rice ball 5 side of the inner film 3.

[0040] <Sheet-shaped food 4> The sheet-like food 4 sandwiched between the outer film 2 and the inner film 3 can be exemplified by sheet-like seaweed. The sheet-like food 4 can be roughly rectangular, but it can also be rectangular with beveled corners or with rounded corners. In the illustrated embodiment, the sheet-like food 4 has a length of approximately 19 cm in the longitudinal direction and a length of approximately 10 cm in the transverse direction.

[0041] The sheet-like food 4 is not limited to sheet-like seaweed; any thin food can be used, such as thinly rolled dried squid or kelp formed into a sheet.

[0042] <Packaging Sheet 1> As shown in Figure 1, the outer film 2, sheet-shaped food 4, and inner film 3 are assembled by placing the sheet-shaped food 4 approximately in the center of the inner side of the inner film 3, and then placing the outer film 2 on top of it. Then, as shown in Figures 2 and 3, the outer film 2 and inner film 3 are heat-sealed 11 together so as to completely surround the outer perimeter of the sheet-shaped food 4, thereby creating the packaging sheet 1.

[0043] The packaging sheet 1 consists of an outer film 2 and an inner film 3, both made from a single film. The outer film 2 has an external groove 21, eliminating the need for cutting tape. Furthermore, since the inner film 3 is not made of two overlapping inner film pieces, moisture intrusion can be prevented. Additionally, because cutting tape is unnecessary, the outer film 2 and inner film 3 can be heat-sealed around their entire perimeter. Therefore, moisture intrusion into the packaging sheet 1 is prevented, reducing the likelihood of the sheet-shaped food 4 becoming damp.

[0044] <Onigiri 5 (Food)> The food 5 packaged by the packaging sheet 1 described above can be made by solidifying white rice or mixed rice into flat or spherical rice balls, or into round or rectangular prism-shaped rice sticks. The rice ball 5 may be sprinkled with sesame seeds or other toppings, or ingredients may be placed on top, or ingredients may be sandwiched inside. In this embodiment, as shown in Figures 6 and 7, the rice ball 5 is triangular and flat, but it can also be made into round or square rice balls.

[0045] <6 packaged rice balls (packaged food)> The rice ball 5 is wrapped in the packaging sheet 1 with the above configuration to become a packaged rice ball 6. The rice ball 5 is packaged by placing the packaging sheet 1 with the inner film 3 facing upwards onto the rice ball 5, and then covering it with the packaging sheet 1 so as to wrap around the rice ball 5, as shown in Figures 6 and 7. The overlapping parts of the packaging sheet 1 are then secured with fastening means such as tape or heat sealing (not shown) to obtain the packaged rice ball 6.

[0046] <How to unwrap a packaged rice ball (size 6)> To unwrap the packaged rice ball 6 described above, pinch the outer film 2 and pull it with both hands outward (left and right in the diagram) approximately perpendicular to the outer groove 21 and inner groove 31, as shown by arrow C in Figure 6. This pulls the outer film 2, and simultaneously pulls the inner film 3 located inside it. As a result, the groove film thickness I1 and I2 of the outer groove 21 and inner groove 31 are thinner than the film thickness H1 and H2 of the outer film 2 and inner film 3. Therefore, when the outer film 2 and inner film 3 are pulled, they will break starting from the outer groove 21 and inner groove 31 where the film thickness is thinner. The starting point of the break is the outer groove 21 and inner groove 31 located on the bottom surface of the packaged rice ball 6.

[0047] If the outer film 2 and inner film 3 are pulled further to the left and right from this state, the outer film 2 and inner film 3 will rupture further. In this invention, the outer groove 21 and inner groove 31 each have outer and inner embankment portions 22 and 32 formed on both sides. As shown in Figure 4, the film thicknesses M1 and M2 of the embankment portions 22 and 32 are reinforced to be thicker than the film thicknesses I1 and I2 of the groove portions 21 and 31. Therefore, the film rupture proceeds along the outer and inner grooves 21 and 31 without deviating from them, and the outer film 2 and inner film 3 are completely ruptured and separated. Then, the sheet-like food 4 is pulled out from between the separated outer film 2 and inner film 3, and a nori-wrapped rice ball 5 can be obtained in which the rice ball 5 is wrapped in the sheet-like food 4.

[0048] In this invention, as described above, the tearing of films 2 and 3 proceeds along the outer groove 21 and inner groove 31. This prevents the tearing from deviating from the grooves, which could result in the separation points of the outer film 2 and inner film 3 not aligning, or the outer film 2 and inner film 3 not being completely separated, leaving parts connected. This reduces the problem of being unable to properly unpack the packaging.

[0049] Furthermore, in the packaging sheet 1 of the present invention, both the outer film 2 and the inner film 3 are single films, and the outer film 2 and the inner film 3 can be heat-sealed around their entire outer circumference. Therefore, moisture penetration into the packaging sheet 1 can be prevented, and thus the moisture absorption of the sheet-like food 4 can be reduced not only during the manufacturing and distribution process of the packaging sheet 1, but also in the state of the packaged rice ball 6 in which the rice ball 5 is wrapped.

[0050] According to the present invention, to unwrap the packaged rice ball 6, one only needs to pinch the outer film 2 and pull it outwards. In other words, since a cut tape is not required, there is no need to pinch the starting end of the cut tape or to pinch and pull the cut tape in order to unwrap the packaged rice ball 6. Furthermore, after unwrapping, the outer film 2 and inner film 3 are separated into two film pieces, which become waste fragments, and the number of fragments can be reduced compared to the three fragments that are produced when a cut tape is used.

[0051] <Laser processing and manufacturing method of packaging sheet 1> For laser processing of the outer grooves 21 and inner grooves 31 on the outer film 2 and inner film 3, and for manufacturing the packaging sheet 1, the packaging sheet manufacturing apparatus 7 shown in Figure 8 can be used. In the present invention, the packaging sheet manufacturing apparatus 7 includes laser irradiation units 28 and 38.

[0052] The packaging sheet manufacturing apparatus 7 is a device that manufactures a packaging sheet 1 by sandwiching a sheet of food 4 between a long outer film strip 20 and a long inner film strip 30, applying heat sealing 11 to the outer film strip 20 and the inner film strip 30, and cutting it to a predetermined length.

[0053] The packaging sheet manufacturing apparatus 7 has a sheet food stocker 43 on the upstream side where sheet food 4 (sheet-shaped seaweed) is stacked. The sheet food 4 is pulled out one sheet at a time from the sheet food stocker 43 and transported downstream by a sheet food transport means 44 such as a conveyor.

[0054] The inner film strip 30 is wound around the inner film roll 35 and appears downstream of the sheet-like food conveying means 44 while changing direction via rollers 36, 37, etc. Then, the sheet-like food 4 is placed at predetermined intervals on the inner surface 34 side (see Figure 5) of the inner film strip 30 and moves downstream together with the inner film strip 30.

[0055] The inner groove 31 formed in the inner film 3 can be formed in the inner film strip 30, for example, by arranging a laser irradiation unit 38 between rollers 36 and 37. The laser irradiation unit 38 has a head portion 38a that emits a laser beam 38b and irradiates the inner film strip 30 with the laser beam 38b. In the illustrated embodiment, the laser irradiation unit 38 is positioned so that the inner groove 31 is formed on the inner surface 34 side of the inner film strip 30 (see Figure 5), that is, on the side opposite to the sheet-like food 4.

[0056] The laser irradiation unit 38 can be exemplified as a unit that irradiates with a CO2 laser as the laser beam 38b, but the laser beam 38b is not limited to a CO2 laser. Furthermore, the output of the laser irradiation unit 38 is, for example, 10W to 30W, preferably 15W to 25W, on the inner film band 30 surface, and the width of the laser beam 38b is, for example, 50μm to 300μm, preferably 100μm to 250μm.

[0057] Furthermore, in order to stabilize the irradiation distance of the laser beam 38b to the moving inner film strip 30, it is preferable to provide a guide base 39 on the opposite side of the head unit 38a at the irradiation position of the laser beam 38b, while the inner film strip 30 is in contact with it as it travels. This allows the inner film strip 30 to travel stably without swaying, and the irradiation distance of the laser beam 38b can be kept constant.

[0058] The wavelength of the laser beam 38b is such that, depending on the material, thickness, and travel speed of the inner film strip 52, an inner groove 31 is formed with a predetermined groove depth K2 and leaving a groove film thickness I2 (see Figure 4). Additionally, an inner embankment 32 with an embankment height L2 is formed on both sides of the inner groove 31. For example, if the travel speed of the inner film strip 52 made of PP film is 15 to 25 m / min, then with the output and width of the laser beam 38b described above, an inner groove 31 of the above dimensions can be formed in the inner film strip 30 by setting the wavelength to 5 μm to 15 μm.

[0059] As shown in Figure 8, the inner film strip 30, which has an inner groove 31 formed on it, travels with its direction of travel changed horizontally by the roller 37. Sheet-shaped food 4 is placed at predetermined intervals on the inner surface 33 (see Figure 5) of the horizontally traveling inner film strip 30 with its surface 41 (see Figure 5) facing upwards from the sheet-shaped food conveying means 44, and further downstream it overlaps with the outer film strip 20.

[0060] The outer film strip 20 is wound around the outer film roll 25 and, via rollers 26, 27, etc., emerges from above onto the inner film strip 30 on which the sheet-like food 4 is placed.

[0061] The outer groove 21 formed in the outer film 2 can be formed in the outer film strip 20, for example, by arranging a laser irradiation unit 28 between rollers 26 and 27. The laser irradiation unit 28 has a head portion 28a that emits a laser beam 28b and irradiates the outer film strip 20 with the laser beam 28b. In the illustrated embodiment, the laser irradiation unit 28 is positioned so that the outer groove 21 is formed on the inner surface 24 side (see Figure 5) of the outer film strip 20, that is, on the side facing the sheet-like food 4.

[0062] The laser irradiation unit 28 can be exemplified as a unit that irradiates with a CO2 laser as the laser beam 28b, but the laser beam 28b is not limited to a CO2 laser. Furthermore, the output of the laser irradiation unit 28 is, for example, 10W to 30W, preferably 15W to 25W, on the outer film band 20 surfaces, and the width of the laser beam 28b is, for example, 50μm to 300μm, preferably 100μm to 250μm.

[0063] Furthermore, in order to stabilize the irradiation distance of the laser beam 28b with respect to the moving outer film strip 20, it is preferable to provide a guide base 29 on the opposite side of the head unit 28a at the irradiation position of the laser beam 28b, while the outer film strip 20 is in contact with it as it travels. This allows the outer film strip 20 to travel stably without swaying, and the irradiation distance of the laser beam 28b can be kept constant.

[0064] The wavelength of the laser beam 28b is determined according to the material, thickness, and travel speed of the outer film strip 20. An outer groove 21 is formed with a predetermined groove depth K1, leaving a groove film thickness I1 (see Figure 4) intact. Additionally, an outer embankment 22 with an embankment height L1 is formed on both sides of the outer groove 21. For example, if the travel speed of the inner film strip 52 made of PP film is 15 to 25 m / min, then with the output and width of the laser beam 28b described above, an outer groove 21 of the above dimensions can be formed on the outer film strip 20 by setting the wavelength to 5 μm to 15 μm.

[0065] The outer film strip 20, on which the outer groove 21 is formed, travels with its direction of travel changed horizontally by the roller 27. Then, as it travels horizontally, it covers the inner film strip 30 on which the sheet-like food 4 is placed, and travels downstream with the sheet-like food 4 sandwiched between the outer film strip 20 and the inner film strip 30.

[0066] Next, the outer film strip 20 and inner film strip 30, which sandwich the sheet-like food 4, enter a sealing device 71 located downstream. The sealing device 71 is a device that heat-seals 11 the outer film strip 20 and the inner film strip 30. The sealing device 71 can be composed of, for example, rotating heat-sealing rollers 72 and 73, and heat-seals 11 is applied to both the left and right ends in the width direction of the outer film strip 20 and the inner film strip 30, and to the front and back of the sheet-like food 4, respectively (see Figures 2 and 3).

[0067] The heat-sealed outer film strip 20 and inner film strip 30 are then transported to a cutting device 74. The cutting device 74 can consist of a movable blade 75 and a fixed blade 76, and cuts the outer film strip 20 and inner film strip 30 at approximately the midpoint of the heat-sealed area 11 between the sheet-like food products 4, 4. This allows for the production of the packaging sheet 1 shown in Figure 2, etc.

[0068] The manufactured packaging sheets 1 are transported by a packaging sheet transport means 77, such as a conveyor, located downstream of the cutting device 74, stacked in a stocker (not shown), and shipped out.

[0069] <Different embodiments of the outer groove 21 and inner groove 31> In Figure 2, etc., the outer groove 21 and inner groove 31 are formed in a straight line, but they may also be wavy as shown in Figure 9, or jagged, although not shown. Wavy or jagged outer grooves 21 and inner grooves 31 can be formed by moving the heads 28a and 38a that irradiate the laser beams 28b and 38b from side to side with respect to the direction of travel of the outer film strip 20 and inner film strip 30. Even in this case, outer embankments 22 and inner embankments 32 are formed on both sides of the outer groove 21 and inner groove 31 along the shape of the wavy or jagged grooves 21 and 31. By forming the outer groove 21 and outer embankment 22, and the inner groove 31 and inner embankment 32 in a wavy or jagged shape, the outer film 2 and inner film 3 can be torn more easily compared to a straight line, making it easier to unpack the packaged rice ball 6. Even in this case, the tearing of the outer film 2 and inner film 3 proceeds along the grooves 21 and 31, as shown in the embodiment. This prevents the tearing from deviating from the grooves, causing the separation points of the outer film 2 and inner film 3 to not align, or preventing the outer film 2 and inner film 3 from being completely separated and leaving parts connected, thereby mitigating the problem of not being able to properly unpack the packaging.

[0070] <Different embodiments of outer film 2 and inner film 3> In the above embodiment, the outer film 2 and the inner film 3 are each made from a single film. However, it is also possible to fold a single film in half down the middle and heat-seal the three open sides. In this case, the outer groove 21 and the inner groove 31 can be formed on the left and right surfaces that straddle the fold, respectively.

[0071] The above description is for the purpose of explaining the present invention and should not be interpreted as limiting or restricting the scope of the invention described in the claims. Furthermore, it goes without saying that the configuration of each part of the present invention is not limited to the above embodiments and can be modified in various ways within the technical scope described in the claims.

[0072] For example, the above description refers to a packaging sheet 1 for a rice ball 5, but the packaging sheet 1 can also be used for packaging rolled sushi with cylindrical or cone-shaped rice, or for packaging hand-rolled sushi with cone-shaped rice. In this case, if necessary, ear-shaped films to cover the ends of the cylindrical or cone-shaped rice can be attached to the packaging sheet separately by heat welding or the like. In this case, the packaged food 6 will be packaged rolled sushi or packaged hand-rolled sushi. [Examples]

[0073] <Example 1> Films were prepared with grooves having a raised edge (inventive example) and grooves without a raised edge (comparative example), and observed using a digital microscope.

[0074] The films used are as follows: Film: 25μm thick OPP film (stretched polypropylene film)

[0075] In the example invention, grooves were formed by laser processing, while in the comparative example, grooves were formed by a cutter (rotary circular blade). More specifically, in the example invention, a CO2 laser with an output of 20W and a wavelength of 10μm was used, and the laser was irradiated onto the film at a speed of 15-25m / min.

[0076] For the films of the inventive example and comparative example, a 3D profile and height graph were obtained using a digital microscope with respect to the measurement line passing through the groove. The results are shown in Figures 10 and 11.

[0077] Figures 10(a) and 10(b) show the shape measurement results of the film of the invention example. Referring to the figures, raised embankments were formed on both sides of the groove indicated by reference numeral 3, as indicated by reference numerals 1 and 2, which were higher than the film surface. More specifically, the height of the embankment in Figure 10(a) was approximately 3 μm, the height of the embankment in (b) was approximately 9 μm, and the height of the embankment in (c) was approximately 20 μm.

[0078] Figures 11(a) and (b) show the shape measurement results of the comparative example film. Referring to the figures, it can be confirmed that grooves were formed, but no raised embankments were formed that were higher than the film surface.

[0079] <Example 2> Outer film: 25μm thick OPP film (stretched polypropylene film) Inner film: 25μm thick OPP film (stretched polypropylene film) The materials were prepared, and grooves 21 and 31 were formed using laser processing (inventive example) and a cutter (comparative example), respectively. The materials were then actually cut and compared. The groove depth (corresponding to K1 and K2 in Figure 4) was approximately 12.5 μm, and the height of the embankment in the inventive example (L1 and L2 in Figure 4) was approximately 7 μm.

[0080] In both the inventive example and the comparative example, eight outer films and eight inner films were prepared, with straight grooves formed on four films and wavy grooves on four films. The processing conditions for the grooves were the same as in Example 1. In the inventive example, the grooves were straight for approximately 2-3 cm of the film edge, while in the comparative example, no grooves were formed for approximately 2-3 cm of the edge.

[0081] The outer film and inner film of the obtained inventive example, and the outer film and inner film of the comparative example were pulled in the direction perpendicular to the groove, by grasping both ends of the center in the longitudinal direction in this example, and pulling in the short direction, and photographs of the film after breakage were taken. The results are shown in Figures 12 to 19. Figure 12 shows the outer film of the inventive example with a straight groove, Figure 13 shows the inner film of the inventive example with a straight groove, Figure 14 shows the outer film of the inventive example with a wavy groove, and Figure 15 shows the inner film of the inventive example with a wavy groove. Also, Figure 16 shows the outer film of the comparative example with a straight groove, Figure 17 shows the inner film of the comparative example with a straight groove, Figure 18 shows the outer film of the comparative example with a wavy groove, and Figure 19 shows the inner film of the comparative example with a wavy groove.

[0082] Referring to Figures 12-15, both the outer and inner films of the invention could be separated along straight and wavy grooves, respectively. This is because the embankment reinforced both sides of the groove, allowing the fracture to proceed without deviation.

[0083] On the other hand, referring to Figures 16 to 19, both the outer and inner films of the comparative example deviated from the groove and fractured.

[0084] These results confirm that by forming a groove with a raised edge, the film can be divided as the fracture progresses along the groove. [Explanation of symbols]

[0085] 1 Packaging sheet 11 Heat welding 2. Outer film 21 Exterior ditch 22 Outer embankment section 3. Inner film 31 Internal groove 32 Inner embankment 4. Sheet-shaped foods (sheet-shaped seaweed) 5. Food (rice ball) 6. Packaged foods (packaged rice balls)

Claims

1. Outer film and An inner film is arranged on top of the outer film, A sheet-like food sandwiched between the outer film and the inner film, Includes, A food packaging sheet formed by heat-sealing the outer film and the inner film around the outer circumference of the sheet-like food, The outer film has an outer groove that is recessed more than the surface of the outer film. The inner film has an inner groove formed by laser processing that is recessed from the surface of the inner film, On both sides of the outer groove, an outer embankment portion is formed that is raised higher than the surface of the outer film. On both sides of the inner groove, an inner embankment is formed that is raised higher than the surface of the inner film. Food packaging sheets.

2. The groove film thickness I1 of the outer film in the portion where the outer groove is formed is 1 / 4 to 3 / 4 of the outer film thickness H1. The groove film thickness I2 of the inner film in the portion where the inner groove is formed is 1 / 4 to 3 / 4 of the inner film thickness H2. The food packaging sheet according to claim 1.

3. The thickness H1 of the outer film is 10 μm to 40 μm. The groove film thickness I1 of the outer film in the portion where the outer groove is formed is 5 μm to 30 μm. The outer embankment portion has a height L1 from the surface of the outer film of 3 μm to 30 μm. The thickness H2 of the inner film is 10 μm to 40 μm. The groove film thickness I2 of the inner film in the portion where the inner groove is formed is 5 μm to 30 μm. The inner embankment portion has a height L2 from the surface of the inner film of 3 μm to 30 μm. The food packaging sheet according to claim 1.

4. The outer film and the inner film are heat-sealed together so as to completely surround the outer periphery of the sheet-like food product. A food packaging sheet according to any one of claims 1 to 3.

5. The outer film has the outer groove and the outer edge formed on the inner surface of the sheet-like food side. The inner film has the inner groove and the inner bank formed on the inner surface opposite to the sheet-like food. A food packaging sheet according to any one of claims 1 to 3.

6. The outer groove and the inner groove are wavy in shape. A food packaging sheet according to any one of claims 1 to 3.

7. The aforementioned outer film consists of a single film, The aforementioned internal film consists of a single film. A food packaging sheet according to any one of claims 1 to 3.

8. The outer film and the inner film consist of a single folded film. A food packaging sheet according to any one of claims 1 to 3.

9. Food is packaged using a food packaging sheet according to any one of claims 1 to 3. packaged food.

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