JP7695865B2 - High frequency dielectric heating electrodes - Google Patents

Description

The present invention relates to an electrode for high-frequency dielectric heating.

Currently, various cylindrical packages made of resin film for packaging contents such as sausages have been proposed. For example, a technology has been proposed in which the inner surfaces of both edges of a film rolled into a cylindrical shape are joined together in a folded state to form a cylindrical casing and a seal part that protrudes radially outward from the casing and extends in the longitudinal direction, and the seal part is then folded down and welded together with the casing part to form a cylindrical package (see Patent Document 1). In recent years, a technology has also been proposed that achieves both easy opening and retort resistance by making the seal part formed by joining both edges of the film out of a specific material (see Patent Document 2).

Japanese Patent Application Publication No. 1-139356 JP 2015-164860 A

In the technology described in Patent Document 1 and Patent Document 2, so-called high-frequency welding may be used, in which the part to be sealed is sandwiched between electrodes and an electric field is applied to heat and weld the part. When such high-frequency welding is used, when the sealed part is cut to open the package, only the surface part of the film (the part located on the outermost side in the radial direction) may peel off, resulting in failure to open. That is, in the conventional package (cylindrical film), four resin films are stacked by placing a laminate film composed of two resin films on the outer side and the inner side in the radial direction, respectively, and all four films are welded to form the seal part. Therefore, when the sealed part is cut to open the package, there have been many cases where only the two radially outer films (the surface parts located on the outermost side in the radial direction and easily subjected to force) peel off, resulting in failure to open. For this reason, there has been a demand for an improved high-frequency welding technology to reduce the possibility of failure to open, and in particular, the development of an electrode for high-frequency dielectric heating has been eagerly awaited.

The present invention was made in consideration of the above circumstances, and aims to provide a high-frequency dielectric heating electrode that can reduce the possibility of the surface layer of the film peeling off and resulting in failure to open a resin tubular film when the sealed portion of the film is cut to open it.

In order to achieve the above object, the high-frequency dielectric heating electrode of the present invention is for forming an envelope-type tubular film by sandwiching the first and second regions of a laminated film formed by stacking two vinylidene chloride resin films, with the first and second regions being placed radially outside and inside, respectively, and performing high-frequency dielectric heating to form an envelope-type tubular film, and is provided with an external electrode placed radially outside the first region and an internal electrode placed radially inside the second region, and the external electrode is coated with a film made of an electrical insulator. As the electrical insulator, one or more inorganic electrical insulators selected from ceramics, mica, and glass can be used.

When this configuration is adopted, the first and second regions of the laminated film, which is made of two laminated vinylidene chloride resin films, are arranged radially outside and inside, respectively, and then high-frequency dielectric heating is performed between the first and second regions, sandwiching them between an external electrode arranged radially outside the first region and an internal electrode arranged radially inside the second region, to continuously weld the first and second regions, thereby forming an envelope-type tubular film that can be filled and sealed with various contents (e.g., minced fish, etc.). At this time, since a coating made of an electrical insulator is formed on the external electrode, the region where the temperature between the electrodes is the highest can be shifted to the external electrode side. Therefore, the two films constituting the first region arranged radially outside and one of the two films constituting the second region arranged radially inside, which is located radially outside, can be welded to form a seal portion. In other words, the seal can be formed by welding the three outermost films out of the four films, so that when the seal is cut to open the package, the film located on the radially outer side of the two films constituting the first region arranged on the radially outer side can be prevented from peeling off from the film located on the radially inner side. As a result, the possibility of failure in opening can be reduced.

In the high-frequency dielectric heating electrode according to the present invention, the line roughness of the portion of the external electrode that contacts the vinylidene chloride resin film can be set to a maximum height Rz of 100 (μm) or less and an arithmetic mean roughness Ra of 10 (μm) or less.

By adopting this configuration, the line roughness of the portion of the external electrode that contacts the vinylidene chloride resin film is set to a maximum height Rz of 100 (μm) or less and an arithmetic mean roughness Ra of 10 (μm) or less, so that the frictional resistance between the electrode and the film can be reduced, and continuous welding can be achieved, for example, at a film speed of 30 to 40 m/min. In other words, by setting the line roughness of the portion to a maximum height Rz of 100 (μm) or less and an arithmetic mean roughness Ra of 10 (μm) or more, it is possible to prevent situations in which the frictional resistance between the electrode and the film becomes large and causes the film to pulsate.

In the high-frequency dielectric heating electrode according to the present invention, the line roughness of the portion of the external electrode that contacts the vinylidene chloride resin film can be set to a maximum height Rz of 1 (μm) or more and an arithmetic mean roughness Ra of 0.5 (μm) or more.

When this configuration is adopted, the line roughness of the portion of the external electrode that contacts the vinylidene chloride resin film is set to a maximum height Rz1 (μm) or more and an arithmetic mean roughness Ra0.5 (μm) or more, so that the slipperiness with the film can be appropriately expressed. In other words, by setting the line roughness of the portion in question to a maximum height Rz1 (μm) or more and an arithmetic mean roughness Ra0.5 (μm) or more, it is possible to prevent the film from becoming too smooth, which would deteriorate the slipperiness with the film and increase the frictional resistance, causing the film to pulsate.

In the high-frequency dielectric heating electrode according to the present invention, the thickness of the coating can be set to 10 μm or more and 150 μm or less.

By adopting this configuration, the outermost three of the four vinylidene chloride resin films can be more reliably welded to form a seal. In other words, by making the thickness of the coating 10 μm or more, the region where the temperature between the electrodes is the highest can be shifted sufficiently toward the outer electrode, so that it is possible to prevent the two films constituting the first region arranged on the radial outside from welding to the two films constituting the second region arranged on the radial inside, making it impossible to ensure openability. In addition, by making the thickness of the coating 150 μm or less, the output for welding is not too large, and it is possible to prevent the occurrence of a situation in which a spark occurs due to a small fluctuation in the film.

In the high-frequency dielectric heating electrode according to the present invention, the thickness of the coating can be set to 40 μm or more and 90 μm or less.

By adopting this configuration, the three outermost sheets of the four vinylidene chloride resin films can be welded together more reliably to form a seal.

The present invention makes it possible to provide a high-frequency dielectric heating electrode that can reduce the possibility of the surface layer of a resin tubular film peeling off and causing failure to open the film when the sealed portion of the film is cut to open it.

1 is a configuration diagram of an automatic filling and packaging machine equipped with a high-frequency dielectric heating electrode according to an embodiment of the present invention. FIG. 1 is a diagram showing the configuration of a high-frequency dielectric heating electrode according to an embodiment of the present invention. 1 is a cross-sectional view of a tubular film formed by an automatic filling and packaging machine equipped with a high-frequency dielectric heating electrode according to an embodiment of the present invention. 1 is a plan view of a tubular film formed by an automatic filling and packaging machine equipped with a high-frequency dielectric heating electrode according to an embodiment of the present invention. FIG. 4 is an enlarged cross-sectional view of a sealed portion (V portion in FIG. 3) of a tubular film formed by an automatic filling and packaging machine equipped with a high-frequency dielectric heating electrode according to an embodiment of the present invention. FIG.

Below, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are merely preferred application examples, and the scope of application of the present invention is not limited to these.

First, the configuration of an automatic filling and packaging machine 1 equipped with a high-frequency dielectric heating electrode 20 according to this embodiment will be described with reference to Figures 1 and 2.

The automatic filling and packaging machine 1 automatically performs each of the following steps: a laminated film P is formed by stacking two vinylidene chloride resin films (hereinafter simply referred to as "films") F, with a first region _P1 and a second region _P2 of the laminated film P positioned radially outward and radially inward, respectively, and then high-frequency dielectric heating is performed between the first region _P1 and the second region _P2 to form an envelope-type tubular film 100 (see FIG. 3, etc.), the formed cylindrical film 100 is filled with contents C, and the cylindrical film 100 is sealed and cut at predetermined lengths to obtain packages 200 of predetermined lengths. As shown in FIG. 1, the automatic filling and packaging machine 1 is equipped with a film supply unit 10, a high-frequency dielectric heating electrode 20, a contents supply unit 30, a sealing unit 40, and a cutting unit 50.

The film supply unit 10 includes a roller 11 configured to rotate at a predetermined rotation speed with the laminate film P wound around it, thereby unwinding the laminate film P, a guide member group 12 that guides the laminate film P unwound by the roller 11 to a predetermined position, and a cylindrical body forming unit (not shown) that forms the laminate film P into an envelope-type cylindrical body by arranging and overlapping a first region _P1 and a second region _P2 of the laminate film P guided to the predetermined position on the radially outer side and the radially inner side, respectively. The rotation speed of the roller 11, the position of the guide member group 12, the configuration of the cylindrical body forming unit, etc. can be appropriately adjusted depending on the type of laminate film P, the required film supply speed, the position of the high-frequency dielectric heating electrode 20, etc.

The high-frequency dielectric heating electrode 20 is used to form the laminated film P, which is continuously supplied by the film supply unit 10 at a predetermined speed (e.g., 40 m/min), into a tubular film 100, and has an external electrode 21 arranged radially outward from a first region _P1 of the laminated film P that has been formed into a tubular body by the tubular body forming section of the film supply unit 10, and an internal electrode 22 arranged radially inward from a second region _P2 of the laminated film P, as shown in FIG.

As shown in FIG. 2, the external electrode 21 is provided with a coating 21A made of an electrical insulator. In the present embodiment, examples of the electrical insulator constituting the coating 21A include organic insulators such as polyamide resin, polyimide resin, polyester resin, polyethylene resin, polypropylene resin, polystyrene resin, fluorine resin, polyurethane resin, acrylic resin, polyphenylene ether resin, polyacetal resin, phenol resin, epoxy resin, and silicon resin. Examples of inorganic insulators include ceramics, mica, and glass. Inorganic insulators are preferred from the viewpoint of heat resistance and abrasion resistance, and among ceramics, alumina, zirconia, and silicon carbide, which have high hardness, are more preferred. Note that materials with high friction resistance, such as silicone rubber, are not preferred as electrical insulators constituting the coating 21A because they deteriorate the slipperiness with the film F.

The thickness of the coating 21A provided on the external electrode 21 is set to 10 μm or more and 150 μm or less. The thickness of the coating 21A is preferably 20 μm or more and 140 μm or less, more preferably 40 μm or more and 130 μm or less, and particularly preferably 40 μm or more and 90 μm or less. This makes it possible to shift the area A (see FIG. 2) where the temperature between the external electrode 21 and the internal electrode 22 is the highest toward the external electrode 21, and to more reliably weld the outermost three of the four films F to form the seal portion S (see FIG. 3 to FIG. 5).

That is, by making the thickness of the coating 21A 10 μm or more, the region A where the temperature between the external electrode 21 and the internal electrode 22 is the highest can be shifted sufficiently toward the external electrode 21 side, and therefore, it is possible to prevent the occurrence of a situation in which the two films F constituting the first region _P1 arranged on the radially outer side and the two films F constituting the second region _P2 arranged on the radially inner side are welded together, making it impossible to ensure the openability. Also, by making the thickness of the coating 21A 150 μm or less, it is possible to prevent the output for welding from becoming too large, and to prevent the occurrence of a situation in which a spark occurs due to a minute fluctuation of the film F. In particular, it is preferable to set the thickness of the coating 21A to 40 μm or more and 90 μm or less.

The line roughness of the portion of the external electrode 21 that contacts the film F (i.e., the surface 21Aa of the coating 21A) is set to a maximum height Rz of 1 (μm) or more and 100 (μm) or less and an arithmetic mean roughness Ra of 0.5 (μm) or more and 10 (μm) or less. This makes it possible to reduce the frictional resistance between the external electrode 21 and the film F, and to realize continuous welding at a film speed of, for example, 30 to 40 m/min, while also allowing the film F to exhibit an appropriate degree of slipperiness. In other words, by setting the line roughness of the portion (surface 21Aa of the coating 21A) to a maximum height Rz of 100 (μm) or less and an arithmetic mean roughness Ra of 10 (μm) or more, it is possible to prevent the film F from pulsating due to an increase in frictional resistance between the external electrode 21 and the film F. In addition, by making the line roughness of the portion (surface 21Aa of coating 21A) at least 1 μm in maximum height Rz and at least 0.5 μm in arithmetic mean roughness Ra, it is possible to prevent the surface from becoming too smooth, which would deteriorate the slipperiness with film F and increase frictional resistance, causing film F to pulsate.

The contents supply section 30 is for supplying contents (e.g., fish paste) C to the inside of the tubular film 100 formed by the high-frequency dielectric heating electrode 20, and has a cylinder 31 that has a diameter slightly smaller than the diameter of the tubular film 100 and is partially inserted into the inside of the tubular film 100, and a contents supply source (not shown) that supplies the contents C to the inside of the tubular film 100 via the cylinder 31.

The sealing unit 40 is for sealing the tubular film 100 filled with the contents C at predetermined lengths (e.g., 200 mm). In this embodiment, the sealing unit 40 employs a mechanism that uses a pair of aluminum wires 41 to tie and seal the tubular film 100 at predetermined lengths. The pair of aluminum wires 41 are attached to the tubular film 100 with a slight gap between them, and a cutter 51 of the cutting unit 50, described below, is inserted into the gap formed between the aluminum wires 41.

The cutting unit 50 is for cutting a predetermined length of the tubular film 100 that is filled with the contents C and sealed, to obtain a package 200 of a predetermined length. In this embodiment, the cutting unit 50 has a cutter 51 configured to cut the portion of the tubular film 100 between the pair of aluminum wires 41 of the sealing unit 40, and a drive mechanism (not shown) that drives the cutter 51.

Next, the configuration of the tubular film 100 formed by the automatic filling and packaging machine 1 equipped with the high-frequency dielectric heating electrode 20 according to this embodiment will be described with reference to Figures 3 to 5.

As shown in FIG. 3 , tubular film 100 is an envelope-type tubular film having a sealed portion S formed by sealing a laminated film P formed by stacking two films F, in which a first region _P1 and a second region _P2 are positioned radially outward and radially inward, respectively, and sealed in an overlapping state.

3 and other figures, in this embodiment, a region _{of a predetermined width slightly (by width W1) spaced from the outermost end of one edge portion P E1 of the} laminate film P is used as the first region P1 of the laminate film P, and a region of a predetermined width slightly (by width _W2 ) spaced from the outermost end of the other edge portion P _E2 of the laminate film P is used as the second region _P2 of the laminate film P. That is, the first region P ₁ is a region near the edge that does not include one edge portion P _E1 of the laminate film P, and the second region P ₂ is a region near the edge that does not include the other edge portion P _E2 of the laminate film P.

The size and thickness of the film F are determined according to the size of the contents C to be filled. The circumference of the film F is usually 15 to 400 mm, often 30 to 300 mm, and commonly 40 to 200 mm, while the length in the longitudinal direction of the film F is usually 50 to 400 mm, often 70 to 300 mm, and commonly 80 to 250 mm. The thickness of the film F is determined taking into consideration the strength and barrier properties of the film according to the contents C to be filled, but is usually 15 to 300 μm, often 18 to 200 μm, and commonly 20 to 150 μm. Within this range, a thickness of 15 to 25 μm is preferable because the film F has a moderate strength and is easy to cut.

3 and 5, the seal portion S is formed by welding two films F _1A , F _1B constituting a first region _P1 disposed on the radially outer side of the laminated film P, and one film F 2A located on the radially outer side of two films F _2A , F _2B constituting a second region _P2 disposed on the radially inner side of the laminated film P. In this embodiment, these three films F _1A , F _1B , F _2A are welded together by performing high-frequency dielectric heating using the high-frequency dielectric heating electrode ₂₀ already described.

In addition, the region P _A of a predetermined width W ₁ from the outermost end of the edge portion P _E close to the first region P ₁ arranged radially outward of the laminated film P is a non-sealed portion (outer ear portion) N that can be pinched by the user. Through holes H arranged at a predetermined interval d in the longitudinal direction are formed in the non-sealed portion N. The non-sealed portion N (region P _A ) in which the through holes H are formed in this manner is a region that serves as a starting point when cutting the sealed portion S, and is easily torn by the user's hands. In this embodiment, an example in which two rows of through holes H are provided is shown, but the through holes H may be provided in only one row, or three or more rows.

Next, we will explain how to create the package 200 using the automatic filling and packaging machine 1 in this embodiment.

First, the laminated film P is supplied at a predetermined speed to the high-frequency dielectric heating electrode 20 by the film supply unit 10 of the automatic filling and packaging machine 1, while the first region _P1 and the second region _P2 of the laminated film P are arranged radially outward and radially inward, respectively, and overlapped to form an envelope-type cylindrical body (film supplying process). Next, the first region _P1 and the second region _P2 overlapped in the film supplying process are sandwiched between the external electrode 21 arranged radially outward and the internal electrode 22 arranged radially inward, and high-frequency dielectric heating is performed to seal, thereby forming a cylindrical film 100 having a sealed portion S (cylindrical film forming process).

In the cylindrical film forming process, an external electrode 21 having a coating 21A of a predetermined thickness is disposed outside a first region _P1 of the laminated film P, so that the position of the region A (the darkest part in FIG. 2) that is most heated by high-frequency dielectric heating can be shifted radially outward, as shown in Fig. 2. This allows the two films _F1A , _F1B constituting the first region _P1 disposed radially outward of the laminated film P to be welded _to one film F2A located radially outward of the two films _F2A , _F2B constituting the second region _P2 disposed radially inward to form a seal portion S, as shown in Fig. 3.

Then, the contents supply unit 30 supplies and fills the inside of the tubular film 100 with contents (e.g., minced fish meat) C (contents filling process), the tubular film 100 filled with the contents C is sealed at the sealing unit 40 at predetermined lengths (e.g., 200 mm) (sealing process), and the tubular film 100 filled with the contents C and sealed at the cutting unit 50 at predetermined lengths is cut (cutting process). The package 200 obtained by the above process group is manufactured into a product through a retort process at 120°C for about 20 minutes, for example.

When opening the package 200, the user first pinches the non-sealed portion (outer ear portion) N of the package 200 with his/her fingers and applies a force to tear the non-sealed portion S along a direction (width direction) substantially perpendicular to the longitudinal direction of the package 200. When such a force is applied, the sealed portion S is cut along the width direction. At this time, the film F _1A located on the radially outer side of the two films F _1A and F _1B constituting the first region P ₁ does not peel off from the film F _1B located on the radially inner side, and the first region P ₁ can be separated from the second region P ₂ to reliably release the sealed state. After this, the user can open the package 200 by cutting the laminated film P along the width direction of the package 200 or cutting the sealed portion S along the longitudinal direction of the package 200.

In the high-frequency dielectric heating electrode 20 according to the embodiment described above, the first region _P1 and the second region P2 of the laminated film P, which is formed by stacking two vinylidene chloride resin films _F , are arranged radially outside and inside, respectively, and high-frequency dielectric heating is performed by sandwiching the first region _P1 and the second region _P2 between the external electrode 21 arranged radially outside the first region _P1 and the internal electrode 22 arranged radially inside the second region _P2 , thereby continuously fusing the first region _P1 and the second region _P2 , thereby producing an envelope-type tubular film 100 capable of filling and sealing various contents C (e.g., minced fish, etc.). At this time, since the coating 21A made of an electrical insulator is formed on the external electrode 21, the region A where the temperature between the electrodes is the highest can be shifted to the external electrode 21 side. Therefore, the two films F constituting the first region _P1 arranged on the radial outside and one film F located on the radial outside of the two films F constituting the second region _P2 arranged on the radial inside can be welded to form the sealed portion S. That is, since the sealed portion S can be formed by welding three of the four films F from the outside, when the sealed portion S is cut to open the package 100, the film F located on the radial outside of the two films F constituting the first region _P1 arranged on the radial outside can be prevented from peeling off from the film F located on the radial inside. As a result, the possibility of failure in opening can be reduced.

In addition, in the high-frequency dielectric heating electrode 20 according to the embodiment described above, the line roughness of the portion of the external electrode 21 that contacts the film F (surface 21Aa of the coating 21A) is set to a maximum height Rz of 1 (μm) or more and 100 (μm) or less, and an arithmetic mean roughness Ra of 0.5 (μm) or more and 10 (μm) or less, so that it is possible to reduce the frictional resistance between the external electrode 21 and the film F while exhibiting an appropriate degree of slipperiness with the film F, and it is possible to realize continuous welding at a film speed of, for example, 30 to 40 m/min.

In addition, in the high-frequency dielectric heating electrode 20 according to the embodiment described above, the thickness of the coating 21A is set to 10 μm or more and 150 μm or less, so that the outermost three of the four films can be more reliably welded to form the seal portion S.

Next, we will explain each embodiment of the present invention.

Example 1
A vinylidene chloride-vinyl chloride copolymer (vinylidene chloride content/vinyl chloride content=89% by mass/11% by mass, weight average molecular weight 125,000) was melted and extruded through a circular die to produce a circular film, which was then subjected to inflation biaxial stretching at a stretching temperature of 30° C., 3.0 times in the longitudinal direction and 4.0 times in the width direction, so that the inner sides of the circular films were overlapped with each other to obtain a raw film having a thickness of 43 μm (the thickness of two films each having a thickness of 21.5 μm). This was then unwound and cut to a width of 86 mm to obtain a strip-shaped laminated film.

The laminated film obtained by the above process was set in an automatic filling and packaging machine (manufactured by Asahi Kasei Corporation: product name "ADP (registered trademark)") having a configuration similar to that described in this embodiment, and fed out. Both side edges extending in the longitudinal direction were overlapped and rolled into an envelope-like cylinder, and while traveling downstream, the overlapped both side edges were sealed at high frequency using a high frequency dielectric heating electrode to form a cylindrical film. In this embodiment, a high frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating with a surface line roughness of maximum height Rz 40.0 μm, arithmetic mean roughness Ra 5.0 μm, and a thickness of 50 μm.

Example 2
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating having a surface line roughness of maximum height Rz 80.0 μm, arithmetic mean roughness Ra 7.0 μm, and a thickness of 80 μm. A cylindrical film was formed in the same manner as in Example 1, except that the surface line roughness was 80.0 μm.

Example 3
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating having a surface line roughness of maximum height Rz 4.0 μm, arithmetic mean roughness Ra 0.7 μm, and a thickness of 20 μm. A cylindrical film was formed in the same manner as in Example 1, except that the surface line roughness was 4.0 μm and the external electrode had a zirconia coating having a thickness of 20 μm.

Example 4
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating having a surface line roughness of maximum height Rz 41.5 μm, arithmetic mean roughness Ra 4.8 μm, and a thickness of 118 μm. A cylindrical film was formed in the same manner as in Example 1, except that the surface line roughness was 41.5 μm in maximum height Rz and 4.8 μm in arithmetic mean roughness Ra.

Example 5
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating having a surface line roughness of maximum height Rz 39.2 μm, arithmetic mean roughness Ra 4.7 μm, and a thickness of 23 μm. A cylindrical film was formed in the same manner as in Example 1, except that the surface roughness was 39.2 μm.

Example 6
A high-frequency dielectric heating electrode was used, which had an external electrode formed with an alumina coating having a surface line roughness of maximum height Rz 41.2 μm, arithmetic mean roughness Ra 4.4 μm, and a thickness of 49 μm. A cylindrical film was formed in the same manner as in Example 1.

Example 7
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating having a surface line roughness of maximum height Rz 2.5 μm, arithmetic mean roughness Ra 0.3 μm, and a thickness of 52 μm. A cylindrical film was formed in the same manner as in Example 1, except that the surface roughness was 2.5 μm and the external electrode had a zirconia coating having a thickness of 52 μm.

Example 8
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating having a surface line roughness of maximum height Rz 0.3 μm, arithmetic mean roughness Ra 0.2 μm, and a thickness of 51 μm. A cylindrical film was formed in the same manner as in Example 1, except that the surface roughness was 0.2 μm.

Example 9
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a polyester coating having a surface line roughness of maximum height Rz 0.5 μm and arithmetic mean roughness Ra 0.4 μm and a thickness of 50 μm. A cylindrical film was formed in the same manner as in Example 1.

Example 10
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a polyethylene coating having a surface line roughness of maximum height Rz 0.5 μm and arithmetic mean roughness Ra 0.4 μm and a thickness of 60 μm. A cylindrical film was formed in the same manner as in Example 1.

Comparative Example 1
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating having a surface line roughness of maximum height Rz 120.0 μm, arithmetic mean roughness Ra 11.0 μm, and a thickness of 50 μm. A cylindrical film was formed in the same manner as in Example 1, except that the surface line roughness was 120.0 μm and the external electrode had a zirconia coating having a thickness of 50 μm.

Comparative Example 2
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating having a surface line roughness of maximum height Rz 40.0 μm, arithmetic mean roughness Ra 5.0 μm, and a thickness of 170 μm. A cylindrical film was formed in the same manner as in Example 1, except that the surface line roughness was 40.0 μm and the external electrode had a zirconia coating having a thickness of 170 μm.

Comparative Example 3
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating having a surface line roughness of maximum height Rz 0.5 μm, arithmetic mean roughness Ra 0.4 μm, and a thickness of 5 μm. A cylindrical film was formed in the same manner as in Example 1, except that the surface line roughness was 0.5 μm and the external electrode had a zirconia coating having a thickness of 5 μm.

Comparative Example 4
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a zirconia coating having a surface line roughness of maximum height Rz 39.5 μm, arithmetic mean roughness Ra 4.8 μm, and a thickness of 8 μm. A cylindrical film was formed in the same manner as in Example 1, except that the surface roughness was 39.5 μm and the external electrode had a zirconia coating having a thickness of 8 μm.

[Reference example]
A high-frequency dielectric heating electrode was used, which had an external electrode formed with a silicone rubber coating having a surface line roughness of maximum height Rz 0.9 μm, arithmetic mean roughness Ra 0.3 μm, and a thickness of 10 μm. A cylindrical film was formed in the same manner as in Example 1.

[Line roughness]
In each of the above examples and comparative examples, a shape analysis laser microscope (manufactured by KEYENCE Corp.: product name "LASER MICROSCOPE VK-X1000") was used to measure the maximum height Rz (μm) and arithmetic mean roughness Ra (μm) of the portion where the external electrode contacted the film, and this was taken as the line roughness.
<Measurement preparation>
The "observation application" was started, and the external electrode was placed on the rotating stage of the shape analysis laser microscope with the film contact side facing up and the up and down direction of the monitor representing the length direction of the external electrode.
<Measurement method settings>
The magnification of the objective lens was set to 5 times, and after focusing on the surface of the external electrode, the image was switched from the camera image to the laser image on the operation panel.
<Creating 3D images>
From the "Basic Measurement" toolbar, the scan mode was set to "Laser Confocal" and the brightness was adjusted. The upper and lower limits of the external electrode surface to be measured were set and the measurement started. After the measurement was completed, the obtained 3D image was saved. "Laser Confocal" is a scanning method in which light irradiated from a laser is reflected on the sample surface, and the focal point position (height information) is detected from the intensity of the reflected light to measure the shape.
<Line roughness measurement>
The "Multi-File Analysis Application" was launched, and "Line Roughness" was selected from the toolbar, a vertical line was selected from the profile tools, and settings were made to measure areas with high height levels in the 3D display image, and the maximum height Rz (μm) and arithmetic mean roughness Ra (μm) were obtained.

[Coating thickness]
In each of the above examples and comparative examples, the dimensions of the external electrode before and after being coated with the electrical insulator were measured with a microgauge to measure the coating thickness. In this case, one side of an external electrode having a roughly rectangular parallelepiped shape with a width of 40 mm, a length of 40 mm, and a thickness of 2 mm was coated with the electrical insulator, and the dimensions were measured at a position 20 mm from the end of the coated side (i.e., a position approximately in the center of the side).

[Packaging suitability evaluation]
The cylindrical films obtained in the Examples and Comparative Examples were filled with fish paste and both ends were clipped with aluminum steel wire to produce packages having an outer ear (non-sealed portion) with a length of 200 mm between clips and a width of 7 mm at a speed of 200 packages/min. The above filling operation was carried out using 1,500 m of vinylidene chloride resin film, and the number of sparks that occurred during the operation was counted to evaluate the packaging suitability according to the following evaluation criteria.
(Evaluation Criteria)
○: Sparks occurred 0 times during the manufacturing process ×: Sparks occurred 1 or more times during the manufacturing process

[Retort resistance evaluation]
One thousand packages obtained in the above packaging suitability evaluation were subjected to retort treatment at 120°C for 20 minutes using a high-temperature, high-pressure cooking sterilizer (manufactured by Hisaka Works, Ltd.: product name "RCS-40TGN") under conditions of a gauge pressure inside the heating can of 0.20 MPa, to obtain sealed packages. Among the sealed packages after the retort treatment, the number of broken bags was counted, and the retort resistance was evaluated according to the following evaluation criteria.
(Evaluation Criteria)
○: 0 broken bags ×: 1 or more broken bags

[Easy-to-open evaluation]
Among the sealed packages after the retort treatment, 100 packages that did not break were randomly sampled. The obtained samples were evaluated by a sensory test to see how much force was required to open them by pinching the outer ear (non-sealed part) and manually opening them. Specifically, 10 panelists each opened 10 sealed package samples and evaluated each sealed package with a sensory test score of 0 to 2 points (2 points: anyone can easily open it, 1 point: anyone can open it with force, 0 point: cannot open it with bare hands). The average sensory test scores of the total of 100 packages were rounded off to the first decimal place to obtain an evaluation score, and the ease of opening was evaluated according to the following criteria based on the obtained evaluation scores.
(Evaluation Criteria)
◎: Average sensory test score is 2.0
○: The average score of the sensory test is 1.5 or more and less than 2. △: The average score of the sensory test is 1 or more and less than 1.5. ×: The average score of the sensory test is less than 1.

[Wear resistance evaluation]
In the same manner as in the evaluation of packaging suitability, two rolls of 1500 m of vinylidene chloride resin film were used, and then the abrasion resistance of the electrode was evaluated visually according to the following criteria.
(Evaluation Criteria)
〇: No abnormality in the electrode coating ×: Holes or wear are found in the electrode coating

The results of each performance evaluation are shown in the following Table 1 (Examples) and Table 2 (Comparative Examples).

As is clear from Table 1, in each of the examples (Examples 1 to 7) in which the surface roughness of the coating of the external electrode is a maximum height Rz of 1 μm to 100 μm and an arithmetic mean roughness Ra of 0.5 μm to 10 μm, and the thickness of the coating of the external electrode is 10 μm to 150 μm, an evaluation of "△" or higher was obtained for all performances. In addition, in each of the examples (Examples 8 to 10) in which the surface roughness of the coating of the external electrode is less than a maximum height Rz of 1 μm and an arithmetic mean roughness Ra of 0.5 μm or less, an evaluation of "△" or higher was obtained for all performances. In all of Examples 1 to 10, the surface roughness of the coating of the external electrode is a maximum height Rz of 100 μm or less and an arithmetic mean roughness Ra of 10 μm or less, and the thickness of the coating of the external electrode is 10 μm to 150 μm. On the other hand, in Comparative Example 1, where the surface roughness of the coating exceeds a maximum height Rz of 100 μm and an arithmetic mean roughness Ra of 10 μm, the packaging suitability and retort resistance were rated as "x", in Comparative Example 2, where the thickness of the coating exceeds 150 μm, the packaging suitability, retort suitability, and ease of opening were rated as "x", in Comparative Example 3, where the surface roughness of the coating is less than a maximum height Rz of 1 μm and an arithmetic mean roughness Ra of less than 0.5 μm, the ease of opening was rated as "x", and in Comparative Example 4, where the thickness of the coating is less than 10 μm, the ease of opening was also rated as "x". In addition, in the reference example, where the coating material is silicone rubber and the surface roughness of the coating is less than a maximum height Rz of 1 μm and an arithmetic mean roughness Ra of less than 0.5 μm, the packaging suitability evaluation was rated as "unsuitable for packaging".

The present invention is not limited to the above-described embodiments, and designs to which a person skilled in the art may make appropriate design changes are also included within the scope of the present invention as long as they include the characteristics of the present invention. In other words, the elements of the above-described embodiments and their arrangements, materials, conditions, shapes, sizes, etc. are not limited to those exemplified, but can be modified as appropriate. Furthermore, the elements of the above-described embodiments can be combined to the extent technically possible, and combinations of these are also included within the scope of the present invention as long as they include the characteristics of the present invention.

20: High-frequency dielectric heating electrode 21: External electrode 21A: Coating 21Aa: Surface of coating (part in contact with film)
22: Internal electrode 100: Cylindrical film S: Sealing portion F: Film made of vinylidene chloride resin P: Laminated film P ₁ : First region P ₂ : Second region

Claims (6)

A high-frequency dielectric heating electrode for forming an envelope-type tubular film by sandwiching a first region and a second region of a laminated film formed by stacking two vinylidene chloride-based resin films, the first region and the second region being placed radially outward and radially inward, respectively, and then performing high-frequency dielectric heating between the first region and the second region in a state where the first region and the second region are stacked,
an outer electrode disposed radially outward from the first region;
an internal electrode disposed radially inward from the second region,
a coating made of an electrical insulator is formed on the external electrode , while the coating is not formed on the internal electrode;
the line roughness of the portion of the external electrode that contacts the vinylidene chloride resin film is set to a maximum height Rz of 100 (μm) or less and an arithmetic mean roughness Ra of 10 (μm) or less;
A high-frequency dielectric heating electrode, wherein the thickness of the coating is set to be 10 μm or more and 150 μm or less. The high-frequency dielectric heating electrode according to claim 1, wherein the line roughness of the portion of the external electrode that contacts the vinylidene chloride resin film is set to a maximum height Rz of 1 (μm) or more and an arithmetic mean roughness Ra of 0.5 (μm) or more. The high-frequency dielectric heating electrode according to claim 1 or 2, wherein the thickness of the coating is set to 40 μm or more and 130 μm or less. The high-frequency dielectric heating electrode according to claim 3, wherein the thickness of the coating is set to 40 μm or more and 90 μm or less. The high-frequency dielectric heating electrode according to any one of claims 1 to 4, wherein the electrical insulator is one or more inorganic electrical insulators selected from ceramics, mica, and glass. The high-frequency dielectric heating electrode according to any one of claims 1 to 4, wherein the electrical insulator is one or more inorganic electrical insulators selected from the ceramics alumina, zirconia, and silicon carbide.

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