Food packaging sheets and packaged foods

Abstract

The present invention provides a food packaging sheet that prevents sheet-type food from getting wet and allows the food to be easily unwrapped. [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, and is formed by heat-sealing 11 the outer film and the inner film around the periphery of the sheet-like food, wherein the outer film has an outer groove 21 recessed below the surface of the outer film, and the inner film has an inner groove 31 recessed below the surface of the inner film, and outer banks 22 raised above the surface of the outer film are formed on both sides of the outer groove, and inner banks 32 raised above the surface of the inner film are formed on both sides of the inner groove.

Description

[Technical Field]

[0001] The present invention relates to a packaging sheet that is constructed by sandwiching a sheet-like food between an inner film and an outer film and that can be used to package food such as rice balls, and to a packaged food product in which food is packaged in the packaging sheet. [Background technology]

[0002] A triple-layered packaging sheet, which is formed by sandwiching a sheet of nori seaweed between an outer film and an inner film, is widely known as a food packaging sheet used to package foods such as rice balls sold at convenience stores, etc. The following explanation will be given using a packaging sheet for rice balls as an example.

[0003] The outer film has a cutting tape attached to the center in the width direction for dividing the outer film, and the inner film consists of two inner film pieces. A sheet of nori seaweed is sandwiched between the outer film and the inner film pieces, and the inner edges of the two inner film pieces are heat-sealed to the outer film so that they overlap on the cutting tape of the outer film, to create a packaging sheet (see, for example, Patent Document 1).

[0004] When a packaged rice ball (packaged food) is made by packaging rice balls in the above-mentioned packaging sheet, the outer film is divided into two by pulling the starting end of the cutting tape, and then one side of the outer film is pulled outward, thereby pulling out the piece of inner film along with the outer film (see, for example, Patent Document 2).

[0005] Next, the other outer film is pulled outward and pulled out together with the remaining piece of inner film, thereby obtaining a rice ball wrapped in nori seaweed directly wrapped around the rice ball, which can then be eaten.

[0006] Patent Document 3 discloses a food packaging sheet in which groove-shaped half cuts are formed in the widthwise center of the outer and inner films. When rice balls are wrapped in this food packaging sheet, the half cuts are separated by pulling the outer and inner films in a direction perpendicular to the half cuts, allowing the rice balls to be unwrapped. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-101832 [Patent Document 2] Japanese Utility Model Application Publication No. 6-8284 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-100741 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0008] The inner film in Patent Documents 1 and 2 is simply formed by overlapping the inner edges of two inner film pieces. Therefore, during the manufacturing and distribution process, or after packaging rice balls, moisture can penetrate through the overlapping portions of the inner film pieces, causing the sheet of nori to become damp. Furthermore, while the outer film and inner film pieces are heat-sealed around the outer periphery of the sheet of nori, the portions of the periphery that overlap the starting and ending ends of the cutting tape are not heat-sealed to allow for separation with the cutting tape. Therefore, moisture can penetrate through these unsealed portions, causing the sheet of nori to become damp. When the sheet of nori becomes damp, it can become sticky, wrinkled, or wavy, resulting in poor appearance and taste, and it may even tear when the packaged rice ball is unwrapped.

[0009] Furthermore, when unwrapping a wrapped rice ball, it can be difficult to know where the tear-starting edge of the cutting tape is, or even if the tear-starting edge is known, it can be difficult to grasp the tear-starting edge properly, making it impossible to unwrap the rice ball. This is particularly difficult for people who are eating wrapped rice balls for the first time or for the elderly. If a wrapped rice ball is unwrapped using the wrong opening method, the sheet food may tear, or the sheet food may not be wrapped properly around the rice ball.

[0010] In the food packaging sheet of Patent Document 3, when the outer and inner films are pulled, they may deviate from the half-cut and be cut. As a result, the cut points of the outer and inner films may not match, or the outer and inner films may not be completely cut, leaving some parts connected, making it difficult to unwrap the packaging.

[0011] An object of the present invention is to provide a food packaging sheet that prevents sheet-type food from getting wet and allows the food to be easily unwrapped. [Means for solving the problem]

[0012] The food packaging sheet of the present invention comprises: The outer film and an inner film disposed over the outer film; a sheet-type food sandwiched between the outer film and the inner film; Including, A food packaging sheet formed by heat-sealing the outer film and the inner film around the outer periphery of the sheet-type food, the outer film has an outer groove recessed below the surface of the outer film, the inner film has an inner groove formed by laser processing that is recessed below the surface of the inner film, On both sides of the outer groove, an outer bank portion is formed that is raised higher than the surface of the outer film, On both sides of the inner groove, inner banks that rise higher than the surface of the inner film are formed.

[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, The groove film thickness I2 of the inner film at the portion where the inner groove is formed is preferably 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 in the portion where the outer groove is formed is 5 μm to 30 μm, the outer bank 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 bank portion preferably has a height L2 from the surface of the inner film of 3 μm to 30 μm.

[0015] It is desirable that the outer film and the inner film are heat-sealed so as to surround the entire outer periphery of the sheet-type food.

[0016] the outer film has the outer groove and the outer bank formed on the inner surface facing the sheet-type food; It is desirable that the inner groove and the inner bank portion of the inner film be formed on the inner surface opposite to the sheet-type food.

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

[0018] The outer film is made of one film, The inner film may be configured to consist of a single film.

[0019] The outer film and the inner film may each be formed from a single folded film.

[0020] The packaged food of the present invention is obtained by packaging food in the food packaging sheet described above. [Effects of the Invention]

[0021] The food packaging sheet according to the present invention has an outer groove formed in the outer film and an inner groove formed in the inner film, and on both sides of the outer groove and inner groove, an outer bank portion and an inner bank portion that are higher than the surfaces of the outer film and inner film, respectively. By forming these outer bank portions and inner bank portions, the thickness of the outer film and inner film is increased in these areas, reinforcing both sides of the outer groove and inner groove.

[0022] When the outer film and the inner film are pulled outward in a direction substantially perpendicular to the outer and inner grooves, the outer film and the inner film are torn apart starting from the thinner outer and inner grooves. In the present invention, both sides of the outer and inner grooves are reinforced by outer and inner bank portions. Therefore, the separation of the outer and inner films proceeds along the outer and inner grooves without deviation. As a result, packaged food in which food is packaged with this packaging sheet can be easily unpacked by simply pulling the outer and inner films outward, as the tearing proceeds along the outer and inner grooves and the outer and inner films are separated.

[0023] The food packaging sheet of the present invention does not have an inner film composed of two inner film pieces, as in conventional packaging, and therefore moisture does not penetrate through the overlapping area of ​​the inner film pieces. This prevents sheet-type foods from becoming damp. Furthermore, because the packaging sheet of the present invention does not use cutting tape, the outer and inner films can be heat-sealed all around the periphery. This leaves no unsealed areas around the periphery of the packaging sheet through which moisture can penetrate, preventing sheet-type foods from becoming damp. This allows sheet-type foods to be kept dry, preventing stickiness, wrinkling, rippling, and deterioration in appearance and taste of the sheet-type foods, and also reduces tearing of the sheet-type foods when unpacking the packaged foods.

[0024] Furthermore, in the case of food packaging sheets that use cutting tape, three pieces of waste are generated: the outer film divided into left and right halves, the inner film, and the outer film with the cutting tape attached. However, with the food packaging sheet of the present invention, only two film chunks are generated: the outer film divided into left and right halves, and the inner film, so the amount of waste can be reduced. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is an exploded perspective view of a rice ball packaging sheet according to the present invention. [Figure 2] FIG. 2 is a plan view of the rice ball packaging sheet according to the present invention. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. [Figure 4] FIG. 4(a) is a cross-sectional view of the outer film taken in a direction perpendicular to the outer groove, and (b) is a cross-sectional view of the inner film taken in a direction perpendicular to the inner groove. [Figure 5] FIG. 5 is an enlarged view of the circled portion B in FIG. [Figure 6] FIG. 6 is a perspective view of a wrapped rice ball wrapped in a wrapping sheet. [Figure 7] FIG. 7 is a perspective view of the packaged rice ball as seen from the rear side. [Figure 8] FIG. 8 is a schematic view of a main part of a packaging sheet manufacturing apparatus. [Figure 9] FIG. 9 is an exploded perspective view of another pattern of the packaging sheet according to the present invention. [Figure 10] FIG. 10 shows the results of shape measurement of the film of the invention using a digital microscope. [Figure 11] FIG. 11 shows the results of measuring the shape of the comparative film using a digital microscope. [Figure 12] FIG. 12 is a photograph of an example of the film of the present invention in which linear grooves have been formed, after cutting. [Figure 13] FIG. 13 is a photograph of the inner film of an example of the invention in which linear grooves have been formed after cutting. [Figure 14]FIG. 14 is a photograph of an example of the film of the present invention having wavy grooves formed therein after cutting. [Figure 15] FIG. 15 is a photograph of the inner film of an example of the invention, in which wavy grooves have been formed, after being cut. [Figure 16] FIG. 16 is a photograph of the outer film of the comparative example having linear grooves formed therein after cutting. [Figure 17] FIG. 17 is a photograph of the inner film of the comparative example having linear grooves formed therein after cutting. [Figure 18] FIG. 18 is a photograph of the outer film of the comparative example having wavy grooves formed therein after cutting. [Figure 19] FIG. 19 is a photograph of the inner film of the comparative example having wavy grooves formed therein after cutting. DETAILED DESCRIPTION OF THE INVENTION

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

[0027] As shown in Figure 1, packaging sheet 1 for rice ball 5 of the present invention is composed of outer film 2, sheet food 4, and inner film 3. Outer film 2 and inner film 3 are layered so as to sandwich sheet food 4. As shown in Figures 2 and 3, outer film 2 and inner film 3 are heat-sealed 11 so as to surround the entire periphery of sheet food 4, and are integrated to form packaging sheet 1. Packaging sheet 1 packages rice ball 5, as shown in Figures 6 and 7 described below. In the illustrated embodiment, outer film 2 and inner film 3 are each composed of 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, the films 2 and 3 are rectangular with a length of approximately 23 cm and a width of approximately 16 cm. However, the films 2 and 3 may also be polygonal, with rounded corners.

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

[0030] The thicknesses (film thicknesses) H1 and H2 (see FIG. 4) of the outer film 2 and the 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 obtained, and if the film thicknesses H1 and H2 are thicker than this, it may be difficult to wrap the rice balls 5 and may also result in increased costs.

[0031] The packaging sheet 1 of the present invention has grooves 21, 31 that can be easily torn by pulling the outer film 2 and the inner film 3 left and right when unpacking, as shown in Fig. 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 this outer groove 21, outer bank portions 22 that are raised higher than the surface of the outer film 2 are formed, and on both sides of the inner groove 31, inner bank portions 32 that are raised higher than the surface of the inner film 3 are formed.

[0032] The outer groove 21, with outer bank portions 22 formed on both sides, and the inner groove 31, with inner bank portions 32 formed on both sides, can be formed, for example, by irradiating the films 2 and 3 with a laser beam, although the manufacturing method is not limited thereto. Specific embodiments of laser processing will be described later. Fig. 4(a) is an enlarged view of the outer groove 21 formed in the outer film 2 by laser processing, and Fig. 4(b) is an enlarged view of the inner groove 31 formed in the inner film 3 by laser processing. As shown in the figures, it can be seen that the laser irradiation melts and thins the surfaces of the outer film 2 and the inner film 3, respectively. On both sides of the outer groove 21 and the inner groove 31, some of the melted resin flows to the left and right, forming raised bank portions 22 and 32.

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

[0034] To facilitate tearing of the films 2 and 3, the outer grooves 21 and inner grooves 31 are preferably formed so that the thicknesses I1 and I2 (groove film thicknesses) of the films 2 and 3 at the portions where the outer grooves 21 and inner grooves 31 are formed are approximately 1 / 4 to 3 / 4 of the film thicknesses H1 and H2, respectively, as shown in FIG. 4, and more preferably 1 / 3 to 1 / 2. Specifically, the groove film thicknesses I1 and I2 are 5 μm to 30 μm, preferably 10 μm to 25 μm. If the groove film thicknesses I1 and I2 are thinner than this, the films 2 and 3 may tear during the production of the packaging sheet 1 or during packaging of rice balls. On the other hand, if the groove film thicknesses I1 and I2 are thicker than this, the films 2 and 3 may not tear properly.

[0035] In the case of the above groove film thicknesses I1 and I2, 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, as shown in Fig. 4. In this case, 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] The heights (bank heights) L1 and L2 of the banks 22 and 32 are preferably approximately 3 μm to 30 μm, more preferably 3 μm to 20 μm, and most preferably 5 μm to 15 μm. Banks 22 and 32 require a certain height to act as reinforcement to prevent breakage from deviating toward the film when outer groove 21 and inner groove 31 are separated. When bank heights L1 and L2 are as described above, the bank film thicknesses M1 and M2 at the portions where banks 22 and 32 are formed are M1 = H1 + L1 and M2 = H2 + M2, respectively. Therefore, for the above film thicknesses, bank film thicknesses M1 and M2 are 13 μm to 70 μm.

[0037] The outer grooves 21 and the inner grooves 31 may be formed on either the outer film 2 or the inner film 3. Specifically, in the case of 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-type food 4. In the case of the inner film 3, the inner grooves 31 can be formed on the inner surface that faces the sheet-type 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, it is desirable that the outer groove 21 formed in the outer film 2 be formed on the inner surface 24 facing the sheet-type food 4, and the inner groove 31 formed in the inner film 3 be formed on the inner surface facing the rice ball 5, as shown in Figure 5, which is an enlarged view of the circled area B in Figure 3.

[0039] As shown in FIG. 4, the outer groove 21 and inner groove 31 formed in the outer film 2 and inner film 3 have raised banks 22, 32 on both sides. If the outer surface 23 of the outer film 2 of the packaging sheet 1 has raised outer banks 22, the customer may feel uncomfortable when touching it. Therefore, it is preferable to form the outer groove 21 in the outer film 2 on the inner surface 24 of the outer film 2, as shown in FIG. 5. Furthermore, when the sheet food 4 is a sheet of nori, the sheet of nori 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 of nori is placed in the packaging sheet 1 with the surface 41 facing outward, i.e., with the surface 41 facing the outer film 2 and the back surface 42 facing the inner film 3, as shown in FIG. 5. In this case, if the inner groove 31 of the inner film 3 is located on the rough side of the sheet-type food 4, the inner bank 32 may get caught on the rough sheet-type food 4 when unwrapping, making it difficult to unwrap. For this reason, it is preferable to form the inner groove 31 on the inner surface 34 of the inner film 3 that faces the rice ball 5, as shown in Figure 5.

[0040] <Sheet Food 4> The sheet food 4 sandwiched between the outer film 2 and the inner film 3 can be, for example, a sheet of nori seaweed. The sheet food 4 can be roughly rectangular, but it can also be rectangular with chamfered corners or rounded corners. In the illustrated embodiment, the sheet food 4 is approximately 19 cm long and 10 cm short.

[0041] The sheet-like food 4 is not limited to sheet-like nori seaweed, and thin foods such as thinly stretched dried mackerel or thinly formed oboro konbu kelp may also be used.

[0042] <Packaging sheet 1> As shown in Fig. 1, the outer film 2, sheet-type food 4, and inner film 3 are arranged such that the sheet-type food 4 is placed approximately in the center of the inside surface of the inner film 3, and the outer film 2 is then placed on top of it. Then, as shown in Figs. 2 and 3, the outer film 2 and the inner film 3 are heat-sealed 11 so as to completely surround the outer periphery of the sheet-type food 4, thereby producing a packaging sheet 1.

[0043] The packaging sheet 1 is made up of a single sheet of film, with both the outer film 2 and the inner film 3. The provision of the outer groove 21 in the outer film 2 eliminates the need for cutting tape. In addition, the inner film 3 is not made up of two overlapping pieces of inner film, which prevents moisture from entering. Furthermore, because cutting tape is not required, the outer film 2 and the inner film 3 can be heat-sealed around the entire periphery. Therefore, moisture can be prevented from entering the packaging sheet 1, which reduces the likelihood of the sheet-type food 4 becoming damp.

[0044] <Onigiri 5 (food)> The food 5 packaged in the packaging sheet 1 can be flattened or spherical rice balls made by solidifying white rice or seasoned rice, or circular or prismatic rice rods. The rice balls 5 can be partially or entirely sprinkled with sesame seeds or other toppings, or topped with ingredients, or the ingredients can be sandwiched inside. In this embodiment, the rice balls 5 have a flat triangular shape as shown in Figures 6 and 7, but they can also be round or square.

[0045] <Packaged rice ball 6 (packaged food)> Rice balls 5 are packaged in the packaging sheet 1 configured as described above to become packaged rice balls 6. Rice balls 5 can be packaged by placing the packaging sheet 1 on the rice balls 5 with the inner film 3 facing upward, and then covering the rice balls 5 with the packaging sheet 1 as shown in Figures 6 and 7. The overlapping portions of the packaging sheet 1 are then fastened with a fastening means (not shown) such as tape or heat welding, thereby obtaining packaged rice balls 6.

[0046] <How to unwrap wrapped rice ball 6> To unwrap the wrapped rice ball 6, the outer film 2 is grasped and pulled with both hands outward (left and right in the drawing), as shown by arrow C in FIG. 6 , approximately perpendicular to the outer groove 21 and inner groove 31. This pulls the outer film 2, and at the same time, the inner film 3 located on the inside is also pulled. As a result, the groove film thicknesses I1 and I2 of the outer film 2 and inner groove 31 are thinner than the film thicknesses 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 break starting from the outer groove 21 and inner groove 31, which have thinner film thicknesses. The starting points for the break are the outer groove 21 and inner groove 31, which are located on the bottom surface of the wrapped rice ball 6.

[0047] If the outer film 2 and the inner film 3 are further pulled left and right from this state, the tearing of the outer film 2 and the inner film 3 progresses. In the present invention, outer bank portions 22 and inner bank portions 32 are formed on both sides of the outer groove 21 and the inner groove 31, respectively. The bank film thicknesses M1 and M2 at the portions where these bank portions 22 and 32 are formed are reinforced so as to be thicker than the groove film thicknesses I1 and I2 at the portions where the grooves 21 and 31 are formed, as shown in FIG. 4 . Therefore, the tearing of the film progresses along the outer groove 21 and the inner groove 31 without deviating from them, and the outer film 2 and the inner film 3 are completely torn 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 wrapped in the sheet-like food 4 is obtained.

[0048] In the present invention, as described above, the breaking of the films 2 and 3 proceeds along the outer groove 21 and the inner groove 31, so it is possible to prevent the breaking from deviating from the grooves, causing the dividing points of the outer film 2 and the inner film 3 to not align, or the outer film 2 and the inner film 3 not to be completely divided, leaving some parts connected, thereby alleviating the problem of the package not being able to be unpacked properly.

[0049] Furthermore, in packaging sheet 1 of the present invention, both outer film 2 and inner film 3 are made of a single film, and outer film 2 and inner film 3 can be heat-sealed along the entire periphery. This prevents moisture from entering packaging sheet 1, reducing moisture in sheet-type food 4 not only during the manufacturing and distribution processes of packaging sheet 1, but also in the state of packaged rice balls 6 after packaging rice balls 5.

[0050] According to the present invention, wrapping of the wrapped rice ball 6 can be unwrapped simply by pinching the outer film 2 and pulling it outward. In other words, because no cutting tape is required, there is no need to pinch the tear-starting end of the cutting tape or pinch and pull the cutting tape to unwrap the wrapped rice ball 6. Furthermore, after unwrapping, the outer film 2 and inner film 3 are separated into two halves, left and right, which become waste pieces, reducing the number of pieces from three when cutting tape is used.

[0051] <Laser processing and manufacturing method of packaging sheet 1> A packaging sheet manufacturing apparatus 7 shown in Fig. 8 can be used to laser process the outer groove 21 and the inner groove 31 in the outer film 2 and the inner film 3 and to manufacture the packaging sheet 1. In the present invention, the packaging sheet manufacturing apparatus 7 includes laser irradiation units 28 and 38.

[0052] The packaging sheet manufacturing device 7 is a device that sandwiches a sheet-like food 4 between a long outer film band 20 and a long inner film band 30, applies heat welding 11 to the outer film band 20 and the inner film band 30, and cuts the film to a predetermined length to manufacture a packaging sheet 1.

[0053] Packaging sheet manufacturing apparatus 7 has sheet food storage 43 on the upstream side in which sheet food 4 (sheet-like seaweed) is stacked. Sheet food 4 is pulled out one by one from sheet food storage 43 and transported downstream by sheet food transport means 44 such as a conveyor.

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

[0055] The inner grooves 31 formed in the inner film 3 can be formed in the inner film strip 30, for example, by disposing 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 laser beam 38b toward the inner film strip 30. In the illustrated embodiment, the laser irradiation unit 38 is disposed so that the inner grooves 31 are formed on the inner surface 34 side of the inner film strip 30 (see FIG. 5), i.e., the surface opposite the sheet-type food 4.

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

[0057] In order to stabilize the irradiation distance of the laser beam 38b relative to the running inner filmstrip 30, it is preferable to provide a guide table 39, against which the inner filmstrip 30 runs, on the opposite side of the head 38a at the irradiation position of the laser beam 38b. This allows the inner filmstrip 30 to run stably without shaking, and the irradiation distance of the laser beam 38b can be made constant.

[0058] The wavelength of laser beam 38b is set according to the material, thickness, and running speed of inner film strip 52 to form inner groove 31 with a predetermined groove depth K2, leaving groove film thickness I2 (see Figure 4), and inner bank portions 32 with bank height L2 are formed on both sides of inner groove 31. For example, if the running speed of inner film strip 52 made of PP film is 15 to 25 m / min, and the output and width of laser beam 38b are as described above, an inner groove 31 of the above dimensions can be formed in 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 with the inner groove 31 formed therein is changed in its running direction to horizontal by rollers 37 and runs. Sheet-type food 4 is then placed at predetermined intervals by sheet-type food conveying means 44 on the inner surface 33 (see Figure 5) of the horizontally running inner film strip 30, with the surface 41 (see Figure 5) facing upward, and overlaps with the outer film strip 20 further downstream.

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

[0061] The outer grooves 21 formed in the outer film 2 can be formed in the outer film strip 20, for example, by disposing a laser irradiation unit 28 between the rollers 26 and 27. The laser irradiation unit 28 has a head 28a that emits a laser beam 28b, and irradiates the laser beam 28b toward the outer film strip 20. In the illustrated embodiment, the laser irradiation unit 28 is disposed so that the outer grooves 21 are formed on the middle surface 24 side of the outer film strip 20 (see FIG. 5), i.e., the surface facing the sheet-type food 4.

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

[0063] In order to stabilize the irradiation distance of the laser beam 28b relative to the running outer filmstrip 20, it is preferable to provide a guide table 29, against which the outer filmstrip 20 runs, on the opposite side of the head 28a at the irradiation position of the laser beam 28b. This allows the outer filmstrip 20 to run stably without shaking, and the irradiation distance of the laser beam 28b can be made constant.

[0064] The wavelength of the laser beam 28b is adjusted according to the material, thickness, and running speed of the outer film belt 20 to form an outer groove 21 with a predetermined groove depth K1, leaving a groove film thickness I1 (see Figure 4), and also forming outer bank portions 22 with a bank height L1 on both sides of the outer groove 21. For example, if the running speed of the inner film belt 52 made of PP film is 15 to 25 m / min, and the output and width of the laser beam 28b are as described above, an outer groove 21 of the above dimensions can be formed in the outer film belt 20 by setting the wavelength to 5 μm to 15 μm.

[0065] The outer film belt 20 with the outer groove 21 formed therein is changed in its running direction to horizontal by the roller 27 and continues to run. Then, running horizontally, it covers the inner film belt 30 on which the sheet-type food 4 is placed, and continues to run downstream with the sheet-type food 4 sandwiched between the outer film belt 20 and the inner film belt 30.

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

[0067] The heat-sealed outer film band 20 and inner film band 30 are then transported to a cutting device 74. The cutting device 74 can be composed of a movable blade 75 and a fixed blade 76, and cuts the outer film band 20 and inner film band 30 approximately midway along the heat seal 11 between the sheet-type foods 4, 4. This allows the packaging sheet 1 shown in Figure 2 and other figures to be obtained.

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

[0069] <Different embodiments of outer groove 21 and inner groove 31> In Figure 2 and other figures, the outer grooves 21 and the inner grooves 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 left and right relative to the running direction of the outer film strip 20 and the inner film strip 30. Even in this case, outer bank portions 22 and inner bank portions 32 are formed on both sides of the outer grooves 21 and inner grooves 31 in accordance with the shapes of the wavy or jagged grooves 21 and 31. Forming the outer grooves 21 and outer bank portions 22 and the inner grooves 31 and inner bank portions 32 in a wavy or jagged shape makes the outer film 2 and inner film 3 easier to tear than if they were straight, making it easier to unwrap the packaged rice balls 6. Even in this case, the tearing of the outer film 2 and the inner film 3 proceeds along the grooves 21, 31 as shown in the examples, so it is possible to prevent the tearing from deviating from the grooves, causing the separation points of the outer film 2 and the inner film 3 to not align, or the outer film 2 and the inner film 3 not to separate completely, leaving some parts connected, thereby alleviating the problem of the package not being able to be unpacked properly.

[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 of a single sheet of film, but they may also be made by folding a single film in half at the center and heat-welding the three open sides. In this case, the outer groove 21 and the inner groove 31 may be formed on the left and right surfaces that sandwich the fold.

[0071] The above description is for the purpose of explaining the present invention, and should not be construed as limiting the invention described in the claims or narrowing its scope. Furthermore, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications are possible within the technical scope described in the claims.

[0072] For example, the above describes packaging sheet 1 for onigiri, which packages rice balls 5 in the shape of rice balls. However, packaging sheet 1 can also be used as a packaging sheet for sushi rolls, which packages cylindrically shaped rice sticks, or for hand-rolled sushi, which packages cone-shaped rice. In this case, if necessary, a separate piece of film in the shape of a tab covering the edge of the cylindrical or cone-shaped rice can be attached to the packaging sheet by heat welding or the like. In this case, packaged food 6 becomes packaged sushi rolls or hand-rolled sushi. [Example]

[0073] Example 1 Films were prepared in which grooves with banks (invention example) and grooves without banks (comparison example) were formed, and were observed using a digital microscope.

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

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

[0076] For the inventive and comparative films, a digital microscope was used to obtain 3D profile and height graphs for a measurement line passing through the groove. The results are shown in Figures 10 and 11.

[0077] Figures 10(a) and 10(b) show the results of measuring the shape of the film of the invention example. Referring to the figures, it can be seen that on both sides of the groove indicated by reference numeral 3, there were raised banks that rose higher than the film surface, as indicated by reference numerals 1 and 2. More specifically, the height of the banks in Figure 10(a) was approximately 3 μm, that in (b) was approximately 9 μm, and that in (c) was approximately 20 μm.

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

[0079] <Example 2> Outer film: 25 μm thick OPP film (oriented polypropylene film) Inner film: 25 μm thick OPP film (oriented polypropylene film) The grooves 21 and 31 were formed by laser processing (example of the invention) and a cutter (comparison example), and then the sample was actually cut and compared. The groove depth (corresponding to K1 and K2 in Figure 4) was approximately 12.5 μm, and the bank height of the example of the invention (L1 and L2 in Figure 4) was approximately 7 μm.

[0080] For both the invention examples and the comparative examples, eight outer films and eight inner films were prepared, and straight grooves were formed in four of them and wavy grooves in four of them. The groove processing conditions were the same as in Example 1. Note that in all of the invention examples, the grooves were straight grooves for about 2 cm to 3 cm around the edge of the film, while in the comparative examples, no grooves were formed in the edge of about 2 cm to 3 cm.

[0081] The outer and inner films of the obtained example of the invention and the outer and inner films of the comparative example were pulled in a direction perpendicular to the grooves (in this example, both ends of the center in the longitudinal direction were grasped and pulled in the short direction), and photographs of the films after rupture were taken. The results are shown in Figures 12 to 19. Figure 12 shows the outer film of the example with linear grooves, Figure 13 shows the inner film of the example with linear grooves, Figure 14 shows the outer film of the example with wavy grooves, and Figure 15 shows the inner film of the example with wavy grooves. Figure 16 shows the outer film of the comparative example with linear grooves, Figure 17 shows the inner film of the comparative example with linear grooves, Figure 18 shows the outer film of the comparative example with wavy grooves, and Figure 19 shows the inner film of the comparative example with wavy grooves.

[0082] 12 to 15, both the outer and inner films of the inventive examples could be torn along the straight and wavy grooves. This is because the banks reinforced both sides of the grooves, allowing the fracture to proceed without deviation.

[0083] On the other hand, referring to FIGS. 16 to 19, in the comparative example, both the outer film and the inner film deviated from the groove and the breakage progressed.

[0084] These results confirmed that by forming grooves with banks, fracture progresses along the grooves, allowing the film to be divided. [Explanation of symbols]

[0085] 1 Packaging sheet 11 Heat welding 2 outer film 21 Outer ditch 22 Outer bank 3 Inner film 31 Inner groove 32 Inner bank 4. Sheet foods (sheet seaweed) 5. Food (rice balls) 6. Packaged foods (packaged rice balls)

Claims

1. With outer film, an inner film disposed over the outer film; a sheet-type food sandwiched between the outer film and the inner film; Including, The outer film and the inner film are heat-sealed to each other around the outer periphery of the sheet-type food, the outer film has an outer groove recessed below the surface of the outer film, the inner film has an inner groove formed by laser processing that is recessed below the surface of the inner film, On both sides of the outer groove, an outer bank portion is formed that is raised higher than the surface of the outer film, On both sides of the inner groove, inner bank portions that are raised higher than the surface of the inner film are formed, By pulling the outer film and the inner film outward in a direction perpendicular to the outer groove and the inner groove, the outer groove and the inner groove are torn along the outer bank portion and the inner bank portion, and the outer film and the inner film are broken. Onigiri wrapping sheet.

2. a 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; 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. The rice ball 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 bank 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 bank portion has a height L2 from the surface of the inner film of 3 μm to 30 μm. The rice ball packaging sheet according to claim 1.

4. The outer film and the inner film are heat-sealed to surround the entire outer periphery of the sheet-type food. The rice ball packaging sheet according to any one of claims 1 to 3.

5. the outer film has the outer groove and the outer bank formed on the inner surface facing the sheet-type food; The inner film has the inner groove and the inner bank portion formed on the inner surface opposite to the sheet-type food. The rice ball packaging sheet according to any one of claims 1 to 3.

6. The outer groove and the inner groove are wavy. The rice ball packaging sheet according to any one of claims 1 to 3.

7. The outer film is made of one film, The inner film is made of one film. The rice ball packaging sheet according to any one of claims 1 to 3.

8. The outer film and the inner film are made of a single folded film. The rice ball packaging sheet according to any one of claims 1 to 3.

9. A rice ball is packaged using the rice ball packaging sheet according to any one of claims 1 to 3. Wrapped rice balls.

10. A method for unwrapping the packaged rice balls according to claim 9, comprising: The rice ball has a flat triangular shape, and the rice ball packaging sheet covers the rice ball so that the outer groove and the inner groove are perpendicular to the width direction of the bottom surface of the rice ball. The outer films located on both sides of the bottom surface of the rice ball are pinched and pulled outward perpendicular to the outer groove, whereby the outer groove and the inner groove are torn along the outer bank portion and the inner bank portion, starting from the outer groove and the inner groove located on the bottom surface, and the outer film and the inner film are broken. How to unwrap wrapped rice balls.

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