Patent Publication Number: US-2020277121-A1

Title: Sealing cover having opening tap for containers and method for manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This U.S. Non-provisional Patent Application is a continuation-in-part of U.S. patent application Ser. No. 14/222,970, filed on Mar. 24, 2014, which claims priority under 35 U.S.C. 119 to Korean Patent Application No. 10-2014-0005010, filed on Jan. 15, 2014, in the Korean Intellectual Property Office, the disclosures of which are herein incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The disclosure relates generally to sealing covers having opening tabs for containers and, more particularly, to a sealing cover for containers which has an increased adhesive area between an opening tab and the sealing cover so that a user can easily remove the sealing cover from a container, and a method for manufacturing the sealing cover. 
     DISCUSSION OF RELATED ART 
     Different kinds of sealing covers are used to seal apertures of containers. 
     Such sealing covers for containers have several functions such as a function of protecting the contents of a container, an easy-opening function, etc. The functions of the sealing covers also continue to evolve for the sake of consumer convenience. 
     Recently, high-frequency induction heating is mainly used to seal the aperture of a container with a sealing cover, whereby the sealability of the sealing cover can be enhanced. 
     In the high-frequency induction heating method, the sealing cover is disposed in a cap of the container before the container is coupled to the contents-filled container. Subsequently, the sealing cover adheres, through high-frequency induction heating, to a portion of the container that defines an aperture thereof. 
     However, in the above method, because the shape and size of the sealing cover that adheres to the container to seal the aperture are the same as those of the portion of the container that defines the aperture thereof, it is inconvenient for a user to remove the sealing cover from the container. 
     In an effort to overcome the above problem, several improved structures have been introduced. For example, there is a structure in which a tab protrudes outwards from a peripheral edge of the sealing cover, and a structure in which a semi-circular tab is provided on an upper surface of a sealing cover. 
     Particularly, as examples of the sealing cover having the semi-circular tab, products of Stanpac Inc. of Canada have been widely used and are being widely used. 
     However, the conventional sealing cover having the semi-circular tab is configured in such a way that an upper layer and a lower layer of the sealing cover adhere to each other only in a remaining semi-circular area of the sealing cover that is other than the tab. Therefore, if the strength with which the sealing cover adheres to the container is comparatively high, when a user grasps the semi-circular tab and pulls it to remove the sealing cover form the container, only the tab and a portion around the tab may be detached from the sealing cover rather than the entirety of the sealing cover being removed from the container. Moreover, there is a disadvantage in that, because of the problem, the size of the tab is limited. 
       FIGS. 1A and 1B  illustrate a conventional sealing cover. 
       FIG. 1A  shows a circular sealing cover  30  which is provided with at least one small tab  30   a  formed on a circumferential edge thereof so that a consumer can use the tab  30   a  to open a container  10 . 
       FIG. 1B  shows a sealing cover  30  in which a polyester film layer  32  is formed on an upper surface of the sealing cover  30 , wherein only a half of the polyester film layer  32  adheres to the sealing cover  30 , and the other half thereof is used as an opening tab  32   a.  When a consumer grasps the semi-circular opening tab  32   a  and pulls it in the y-axis direction, the sealing cover  30  is removed from the container  10 . 
     Particularly, the construction of the sealing cover ( 30 ;  32 ,  34 ) of  FIG. 1B  will be explained in detail below. The sealing cover  30  includes an upper layer  32  which is formed of a polyester film, and a lower layer  34  which adheres to a lower surface of the upper layer  32 . 
     After an adhesive is applied to the lower surface of the polyester film that is the upper layer  32 , a band-shaped film  36  or paper is interposed between the upper and lower layers  32  and  34  and bonded to the upper layer  32 , and then the lower layer  34  adheres to the upper layer  32 . Here, while an upper surface of the band-shaped film  36  first adheres to the upper layer  32 , a lower surface of the band-shaped film  36  does not adhere to the lower layer  34 . The portion of the upper layer  32  that does not adhere to the lower layer  34  due to the band-shaped film  36  forms the opening tab  32   a.    
     However, in this conventional technique, because only a half portion of the upper layer  32  that has a circular shape adheres to the lower layer  34 , the adhesive strength therebetween is not sufficient. Furthermore, if the strength with which the sealing cover  30  adheres to the container  10  is comparatively high, when the opening tab  32   a  is pulled, only the opening tab  32   a  may be separated from the sealing cover  30  rather than the sealing cover  30  being removed from the container  10 . 
     In other words, when the tab  32   a  is pulled in the y-axis direction, as shown in the right view of  FIG. 2 , a phenomenon of only the tab  32   a  being delaminated may be induced. 
     Meanwhile, in the case of a small sized sealing cover, as shown in  FIG. 3 , the opening tab  32   a  provided on the upper layer  32  may have almost circular shape, rather than having a semi-circular shape, so as to allow a user to easily grasp the opening tab  32   a.  In this case, the adhesive area between the polyester film that is the upper layer  32  and the lower layer  34  is further reduced. As a result, the delamination phenomenon is more easily caused. 
     SUMMARY 
     According to an embodiment, a sealing cover for containers in which the whole area of an upper layer provided with an opening tab substantially adheres to the lower layer with sufficient adhesive strength. The sealing cover can be easily and reliably removed from a container regardless of whether the opening tab has a semi-circular shape or a circular shape. 
     According to an embodiment, there is provided a method for manufacturing the sealing cover. 
     According to an embodiment, a sealing cover having an opening tab for a container includes a tab-forming layer provided with the opening tab and a sealing layer formed under the tab-forming layer. The sealing layer has a function of substantially sealing the container. 
     The sealing cover may further include an intermediate substrate layer interposed between the tab-forming layer and the sealing layer. The intermediate substrate layer provides a close contact function and a shock absorbing function when a cap is coupled to the container. 
     The sealing layer may include an aluminum foil layer isolating an interior of the container from an exterior thereof, the aluminum foil layer generating heat through high-frequency induction heating and a heat-sealing resin layer provided under the aluminum foil layer. The heat-sealing resin layer may be adhered to the container by heat generated from the aluminum foil layer. 
     A thickness of the aluminum foil layer may range from 0.009 mm to 0.05 mm. 
     The heat-sealing resin layer may be made of one among polyolefin, EVA (ethylene vinyl acetate), EMA (ethylene methacrylic acid) and ionomer depending on a material of the container so as to provide an easy peel seal function. 
     A thickness of the heat-sealing resin layer may range from 0.03 mm to 0.1 mm. 
     The heat-sealing resin layer may include a film produced by a blown film method or is formed by an extrusion coating method. 
     A lower surface of the intermediate substrate layer and the aluminum foil layer provided in an upper portion of the sealing layer may be adhered to each other by a dry lamination method using a solvent-based urethane adhesive or by an extrusion lamination method of melting a raw material containing polyethylene, EVA (ethylene vinyl acetate) or EMAA (ethylene-methacrylic acid-acrylate) and extrusion-laminating. 
     The tab-forming layer may include a surface layer formed of a PET (polyethylene terephthalate) or PP (polypropylene) film having no heat adhesive property, the surface layer having a thickness ranging from 0.012 mm to 0.05 mm, an inner or outer surface of the surface layer being printed by a gravure process, a first heat-adhesive resin layer formed under a lower surface of the surface layer, a folded film layer provided under a lower surface of the first heat-adhesive resin layer so as to form the opening tab, the folded film layer having a thickness ranging from 0.012 mm to 0.05 mm and being made of a PET (polyethylene terephthalate) or PP (polypropylene) film having no heat adhesive property, the folded film layer having a band shape formed in such a way that the PET or PP film folds double; and a second heat-adhesive resin layer adhering both to a lower surface of the folded film layer and to the first heat-adhesive resin layer that is exposed to an area other than the folded film layer. 
     The folded film layer may form the opening tab using a structure in which when the folded film layer is cut into a size capable of being inserted into a cap, inner surfaces of the folded film layer that face each other do not adhere to each other. 
     The folded film layer may be folded double on one side or both sides thereof. 
     The folded film layer may be folded double in such a way that a cylindrical film roll is pressed to be flat. 
     The first heat-adhesive resin layer and the second heat-adhesive resin layer may be formed by an extrusion lamination method and are made of any one among EVA (ethylene vinyl acetate), EMAA (ethylene-methacrylic acid-acrylate) and polyolefin-based adhesive resin containing polyethylene. 
     The first heat-adhesive resin layer and the second heat-adhesive resin layer may be made of ethylene-methacrylic acid-acrylate terpolymer resin which is produced by DuPont Inc. and sold in a brand name “Nucrel” that is able to adhere to the PET or PP film without conducting a separate chemical primer process. 
     In another aspect, the disclosure provides a method for manufacturing a sealing cover for a container, the sealing cover including: a tab-forming layer provided with an opening tab; and a sealing layer formed under the tab-forming layer, the sealing layer having a function of substantially sealing the container, the method including: preparing a folded film layer formed by folding a PET (polyethylene terephthalate) or PP (polypropylene) film double, the PET or PP film having no heat adhesive property and having a thickness ranging from 0.012 mm to 0.05 mm; preparing a surface layer made of a PET or PP film having no heat adhesive property, the surface layer having a thickness ranging from 0.012 mm to 0.05 mm, an inner or outer surface of the surface layer being printed by a gravure method; preparing a sealing layer to be adhered to the container to isolate an interior of the container from an exterior thereof; a first adhesion operation of adhering the surface layer to an upper surface of the folded film layer using a first heat-adhesive resin layer; a second adhesion operation, using a second heat-adhesive resin layer, of adhering the sealing layer both to a lower surface of the folded film layer and to a portion of the first heat-adhesive resin layer that is other than the lower surface of the folded film layer; and cutting an output of the second adhesion operation such that a portion of a side of the folded film layer is removed, and forming the opening tab using a portion of the folded film layer. 
     The first heat-adhesive resin layer may be formed by an extrusion lamination method of melting adhesive resin and extrusion-adhering the surface layer to the folded film layer. 
     The second heat-adhesive resin layer may be formed by an extrusion lamination method of melting adhesive resin equal to the adhesive resin forming the first heat-adhesive resin layer and extrusion-adhering the sealing layer both to the lower surface of the folded film layer and to the portion of the first heat-adhesive resin layer that is other than the lower surface of the folded film layer. 
     The folded film may form the opening tab using a structure in which when the folded film layer is cut into a size capable of being inserted into a cap, inner surfaces of the folded film layer that face each other do not adhere to each other. 
     The folded film layer may be folded double on one side or both sides thereof 
     The folded film layer may be folded double in such a way that a cylindrical film roll is pressed to be flat. 
     The first heat-adhesive resin layer and the second heat-adhesive resin layer may be made of any one among EVA (ethylene vinyl acetate), EMAA (ethylene-methacrylic acid-acrylate) and polyolefin-based adhesive resin containing polyethylene. 
     The first heat-adhesive resin layer and the second heat-adhesive resin layer may be made of ethylene-methacrylic acid-acrylate terpolymer resin which is produced by DuPont Inc. and sold in a brand name “Nucrel” that is able to adhere to the PET or PP film without conducting a separate chemical primer process. 
     According to an embodiment, a sealing cover includes a tab-forming layer, an intermediate substrate layer, and a sealing layer. The tab-forming layer includes a surface layer, a first adhesive layer under the surface layer, a folded layer under the first adhesive layer, and a second adhesive layer under the first adhesive layer and the folded layer. The intermediate substrate layer is formed under the tab-forming layer. The sealing layer is formed under the intermediate substrate layer. The folded layer includes an upper portion and a lower portion branched from one end of the folded layer, forming an opening tab. 
     The folded layer may include a folded PE film and a folded urethane layer surrounding the PE film. The urethane layer of the folded layer may be attached to the first adhesive layer and the second adhesive layer. 
     The folded layer may be folded substantially in a shape of “&lt;.” 
     When the container is a bottle, the sealing cover may be sized or shaped to correspond to a mouth of the bottle. 
     The surface layer and the folded layer may be formed of substantially the same material, and the first adhesive layer and the second adhesive layer may be formed of substantially the same material but different from, but strongly bonded to, the surface layer and the folded layer. 
     In a sealing cover for containers according to the disclosure, an opening tab which is provided on an upper surface of the sealing cover can not only have a semi-circular shape but can also have an almost circular shape. Therefore, a consumer can more conveniently and easily open the container. 
     Furthermore, with regard to adhesion between layers that forms the opening tab, unlike the conventional technique, in the sealing cover according to the disclosure, because the whole area of an upper layer that forms the opening tab substantially adhere to a lower layer, a delamination phenomenon in which only the opening tab is removed from the sealing cover when the container is opened can be prevented. Therefore, the disclosure can provide the container sealing cover that has a more reliable structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIGS. 1A and 1B  show a conventional sealing cover in a closed ( FIG. 2A ) and open ( FIG. 2B ) arrangement, respectively; 
         FIG. 2  shows a delamination phenomenon of the conventional sealing cover in which only an opening tab is removed therefrom; 
         FIG. 3A and 3B , respectively, are a plan view and side elevation view of an opening tab of a conventional sealing cover; 
         FIG. 4  is a perspective view illustrating a container provided with a sealing cover according to an embodiment of the disclosure; 
         FIGS. 5A and 5B  illustrate a method of removing the sealing cover from the container, according to an embodiment of the disclosure; 
         FIG. 6  is a view illustrating the construction of the sealing cover according to an embodiment of the disclosure; 
         FIGS. 7A, 7B, 7C, 8A, 8B, and 8C  are views illustrating a method for manufacturing the sealing cover according to an embodiment of the disclosure; 
         FIGS. 9A and 9B  are views schematically illustrating a method of cutting out the sealing cover according to an embodiment of the disclosure; 
         FIG. 10A  is a view illustrating a folded film layer included in a sealing cover according to an embodiment of the disclosure; 
         FIG. 10B  is a view illustrating an arrangement of a surface layer, a first heat-adhesive resin layer, and a folded film layer included in a sealing cover according to an embodiment; 
         FIG. 10C  is a view illustrating an arrangement of a tab-forming layer, an intermediate substrate layer, and a sealing layer included in a sealing cover according to an embodiment of the disclosure; 
         FIG. 10D  is a view illustrating a layered structure of a sealing cover according to an embodiment of the disclosure; 
         FIG. 10E  is a view illustrating an example operation of a sealing cover according to an embodiment of the disclosure; 
         FIG. 10F  is a view illustrating how attaching force works between the folded film layer and the layers on the side and bottom of the folded film layer the upon pulling the opening tab upwards as shown in  FIG. 10E ; 
         FIG. 11A  is a view illustrating a folded film layer included in a sealing cover according to an embodiment of the disclosure; 
         FIG. 11B  is a view illustrating an arrangement of a surface layer, a first heat-adhesive resin layer, and a folded film layer included in a sealing cover according to an embodiment; 
         FIGS. 11C and 11D  are views illustrating an example of arranging and attaching together a tab-forming layer, an intermediate substrate layer, and a sealing layer included in a sealing cover according to an embodiment of the disclosure; 
         FIGS. 11E, 11F, and 11G  are views illustrating an example of gradually lifting up the opening tab formed by cutting the layered structure of  FIG. 11D  off, at the middle thereof; 
         FIG. 11H  is a view illustrating an example of pulling up a the sealing cover attached to the mouth of the container; 
         FIG. 11I  is a view illustrating the attaching force applied to the opening tab when the sealing cover is pulled up from the container; 
         FIGS. 12A, 12B, and 12C  are views illustrating a process for manufacturing an opening tab by cutting a layered structure for a sealing cover, along lines denoted with B′ and B″, according to an embodiment of the disclosure; 
         FIGS. 12D and 12E  are views illustrating an example in which the opening tab formed as shown in  FIG. 12C  is gradually lifted up; 
         FIG. 12F  is a view illustrating an example in which the sealing cover attached to the container is pulled up and removed from the container by applying force; 
         FIG. 12G  is a view illustrating attaching force works in directions denoted with arrows between some components of a sealing cover when the opening tab is pulled up from the container; 
         FIG. 13A  is a perspective view illustrating an example in which a sealing cover is attached to a container according to an embodiment of the disclosure; 
         FIG. 13B  is a perspective view illustrating an example in which the sealing cover of  FIG. 13A  is removed from the container by pulling up with the opening tab; 
         FIG. 13C  illustrates a position where an opening tab according to the disclosure is positioned on the mouth of a container; and 
         FIG. 13D  illustrates attaching force working in directions denoted with arrows between some components of a sealing cover according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, embodiments of the disclosure are described in detail with reference to the attached drawings. 
       FIG. 4  is a perspective view illustrating a container provided with a container sealing cover (hereinafter, referred to as a sealing cover  400 ) according to an embodiment of the disclosure. 
     Referring to  FIG. 4 , the sealing cover  400  according to the disclosure has an opening tab  100   a  at the top. An aperture  12  (also referred to herein as a mouth) of the container  10  is sealed with the sealing cover  400 . Sealing the aperture  12  with the sealing cover  400  may be achieved by high-frequency induction heating. 
     For example, the sealing cover  400  may be thermally sealed to the container  10  by disposing the sealing cover  400  inside a container cap (not shown), closing the cap, and then performing high-frequency induction heating. 
       FIGS. 5A and 5B  illustrate a method of removing the sealing cover  400  from the container  10 . 
     A user may remove the sealing cover  400  from the aperture  12  and open the container  10  sealed with the sealing cover  400  by pulling up the semi-circular or circular opening tab  100   a  in the y-axis direction. 
       FIG. 6  is a view illustrating a construction of the sealing cover  400  according to an embodiment of the disclosure. 
     Referring to  FIG. 6 , the sealing cover  400  according to an embodiment of the disclosure includes three layers, e.g., a tab-forming layer  100 , an intermediate substrate layer  200 , and a sealing layer  300 . 
     The tab-forming layer  100  includes the opening tab  100   a.  The intermediate substrate layer  200  may function to ensure close contact between the container  10  and the sealing cover  400  when the cap (not shown) having the sealing cover  400  therein is tightened over the container  10  and to prevent heat generated from an aluminum foil layer by high-frequency induction heating from being transferred to the upper portion of the sealing cover  400 . The sealing layer  300  substantially seals the container  10  and isolates contents in the container  10  from the outside. 
     The tab-forming layer  100  includes a surface layer  102 , a first heat-adhesive resin layer  104 , a folded film layer  106 , and a second heat-adhesive resin layer  108 . 
     The surface layer  102  is formed of a polyethylene terephthalate (PET) or polypropylene (PP) film that has no heat adhesive property. The thickness of the surface layer  102  ranges from 0.012 mm to 0.05 mm. The inner or outer surface of the surface layer  102  can be printed by a gravure method. 
     The first heat-adhesive resin layer  104  adheres the folded film layer  106  to the surface layer  102 . 
     For example, the first heat-adhesive resin layer  104  may include a polyolefin-based resin, such as polyethylene (PE), ethylene vinyl acetate (EVA), or ethylene acrylic acid (EAA). For example, when the surface layer  102  and the folded film layer  106  are formed of PET films, ethylene-methacrylic acid-acrylate terpolymer resin (e.g., “Nucrel”, which is commercially available from DuPont Inc.) which can strongly adhere to a PET film without conducting a separate chemical primer process, may be used for the first heat-adhesive resin layer  104 . 
     The surface layer  102  and the tab-forming layer  100  may be attached together by extrusion-laminating the first heat-adhesive resin layer  104  therebetween. 
     The folded film layer  106  is provided to form the opening tab  100   a.  The folded film layer  106  is formed of a PET or PP film that has no heat adhesive property. The thickness of the folded film layer  106  ranges from 0.012 mm to 0.05 mm. The folded film layer  106  may be formed by folding a band-shaped PET or PP film to have a width ranging from 20 mm to 150 mm. 
     The width of the folded film layer  106  may be determined depending on, or corresponding to, the diameter of the aperture  12 . 
     The second heat-adhesive resin layer  108  is provided under the folded film layer  106 . For example, the second heat-adhesive resin layer  108  adheres to both the lower surface of the folded film layer  106  and the first heat-adhesive resin layer  104 . 
     The second heat-adhesive resin layer  108  may be formed of the same material, e.g., PE, EVA, EMAA, or Nucrel™, as the first heat-adhesive resin layer  104 . The surface layer  102  may be formed of the same material, e.g., PET or PP, as the folded film layer  106 . Thus, the folded film layer  106  may be strongly adhered to the surface layer  102  via the first heat-adhesive resin layer  104 , and the second heat-adhesive resin layer  108  may be strongly adhered to both the folded film layer  106  and the first heat-adhesive resin layer  104 . Such material composition of the tab-forming layer  100  enables strong, secure bonding of the layers  102 ,  104 ,  106 , and  108  and, thus, easy and clean removal of the seal cover from the container without failure, e.g., delamination. 
     The intermediate substrate layer  200  is interposed between the tab-forming layer  100  and the sealing layer  300 . The intermediate substrate layer  200  may provide a close contact and shock absorbing when the cap (not shown) is coupled to the rim of the container that defines the aperture  12  therein. The intermediate substrate layer  200  may prevent heat generated from the aluminum foil layer  302  formed under the sealing cover  400  from being transferred to the upper portion of the sealing cover when high-frequency induction heating adhesion is conducted. 
     The sealing layer  300  includes the aluminum foil layer  302  and a heat-sealing resin layer  304 . The aluminum foil layer  320  may substantially isolate the interior of the container  10  from the outside and generate heat through high-frequency induction heating. The heat-sealing resin layer  304  is provided under the aluminum foil layer  302  and is adhered to the rim that defines the aperture  12  therein by heat generated from the aluminum foil layer  302 . 
     For example, the heat-sealing resin layer  304  may be formed of a film which is produced by a blown film method or by extrusion coating. 
     Referring to  FIG. 6  again, both lower surface of the folded film layer  106  and a portion of the folded film layer  106  that adheres to the surface layer  102  form the opening tab  100   a.  Such a double structure of the opening tab  100   a  may increase the tensile strength of the opening tab  100   a,  thus preventing the opening tab  100   a  alone from tearing off the sealing cover  400  without removing the whole sealing cover  400  from the container  10  when pulled up. 
     Meanwhile, the length of the part of the folded film layer  106 , which forms the opening tab  100   a,  and the length of the part of the folded film layer  106 , which adheres to the second heat-adhesive resin layer  108 , are determined by a position where the folded film layer  106  is cut to form the sealing cover  400 . In other words, the position where the folded film layer  106  is cut when the sealing cover  400  is manufactured can be appropriately adjusted such that when the aperture has a relatively small area, both the length of the part that forms the opening tab  100   a  and the length of the part that adheres to the second heat-adhesive resin layer  108  are sufficiently large and, when the aperture has a relatively large area, the length of the part that forms the opening tab  100   a  is relatively small while the length of the part that adheres to the second heat-adhesive resin layer  108  is sufficiently large. 
       FIGS. 7 through 8  are views illustrating a method for manufacturing the sealing cover according to the disclosure. 
     To form the semi-circular or circular opening tab  100   a  at the top of the sealing cover  400 , as shown in (a- 1 ) of  FIG. 7A , a PET or PP film which has no heat adhesive property and has a thickness ranging from 0.012 mm to 0.05 mm and a width ranging from 20 mm to 150 mm may be folded on both sides thereof to form a folded film layer  106 - 1 . 
     Alternatively, as shown in (a- 2 ) of  FIG. 7A , the PET or PP film may be folded in half to form a folded film layer  106 - 2 . As a further alternative, as shown in (a- 3 ) of  FIG. 7A , the PET or PP film may be rolled in a cylindrical shape by bonding the opposite edges thereof to each other and may then be pressed to be flat, thus forming a folded film layer  106 - 3 . As used herein, when “A has a heat adhesive property,” A may have an adhesive force when heated, e.g., by high-frequency induction heating, and when “A has no heat adhesive property,” A has no adhesive force although heated. The width of the PET or PP film that is used to form the folded film layer can be appropriately determined depending on the diameter of the aperture of the container. 
     Thereafter, the surface layer  102 , the intermediate substrate layer  200 , and the sealing layer  300  are prepared. 
     Although the above-mentioned folded film layers  106  have different shapes, the final shape thereof becomes the same as that of  FIG. 7B , and it is only a matter of whether the folded film layer  106  is cut in a row or two rows when it is cut to have a predetermined size and circular shape in which the product is finally disposed in the cap. 
     The folded film layer  106  formed by the above-mentioned method adheres to the lower surface of the surface layer  102  that is the uppermost layer of the sealing cover  400 . The surface layer  102  is made of a PET or PP film which has no heat adhesive property but has a high tensile strength, and the thickness of which ranges 0.012 mm to 0.05 mm. The surface layer  102  and the folded film layer  106  may be adhered together by an extrusion lamination method in which an adhesive resin is melted and applied therebetween and they are adhered to each other by extruding. 
     In this embodiment, the first heat-adhesive resin layer  104  has a thickness ranging from 0.015 mm to 0.04 mm, and the first heat-adhesive resin layer  104  may include a polyolefin-based resin, such as polyethylene, ethylene vinyl acetate (EVA), or ethylene acrylic acid (EAA). The first heat-adhesive resin layer  104  may be formed by an extrusion lamination process. 
     For example, because the surface layer  102  and the folded film layer  106  that is disposed under the first heat-adhesive resin layer  104  are made of PET films, ethylene-methacrylic acid-acrylate terpolymer resin (e.g., “Nucrel”, which is commercially available from DuPont Inc.) which can strongly adhere to a PET film without conducting a separate chemical primer process, may be used for the first heat-adhesive resin layer  104 . 
     In an actual production process, as shown in (c- 2 ) of  FIG. 7B , e.g., for the purpose of mass production, several folded film layers  106  may be arranged apart from each other at appropriate intervals and adhere together to the lower surface of the surface layer  102  that is formed of a PET film having a relatively large width. 
     After the first-step extrusion laminating process using the first heat-adhesive resin layer  104  has been conducted, as shown in  FIGS. 8A-8C , the surface layer  102  and the folded film layer  106  that have adhered to each other through the first-step adhesion process adhere to the intermediate substrate layer  200 , thus forming a second-step adhesion product. 
     The intermediate substrate layer  200  is formed of a polyolefin-based film or foam that has a thickness ranging from 0.03 mm to 3 mm. 
     The adhesion in the second-step adhesion process may be performed by extrusion lamination using the second heat-adhesive resin layer  108  which is made of ethylene-methacrylic acid-acrylate terpolymer resin that is the same material as that of the first heat-adhesive resin layer  104 . 
     The tab-forming layer  100  and the intermediate substrate layer  200  that have been formed through the above-mentioned process adhere to the sealing layer  300  which may substantially seal the container. The sealing layer  300  includes the aluminum foil layer  302  which is disposed in an upper position, and a heat-sealing resin layer  304  which is disposed in a lower position and has an easy peel seal function such that it can be easily sealed to the container  10 . 
     The adhesion between the lower surface of the intermediate substrate layer  200  and the aluminum foil layer  302  of the sealing layer  300  may be performed by a dry lamination method which may be a typical method of adhering plastic films to each other using a solvent-based urethane adhesive, or an extrusion lamination method in which the layers are laminated by melting raw material containing polyethylene, EVA (ethylene vinyl acetate), EMAA (ethylene-methacrylic acid-acrylate), etc. and by extruding the layers with the melted raw material. 
     As shown in  FIG. 9 , the sealing cover  400  is formed in a circular shape corresponding to the size of the cap by cutting or punching the half-finished product manufactured through the above-mentioned process. 
       FIGS. 9A and 9B  are views schematically illustrating a method of cutting out the sealing cover  400  according to the disclosure. 
     Referring to  FIGS. 9A and 9B , the length of the part of the folded film layer  106 , which forms the opening tab  100   a,  and the length of the part of the folded film layer  106 , which adheres to the second heat-adhesive resin layer  108 , are determined by a position where the folded film layer  106  is cut to form the sealing cover  400 . 
     As shown in (b- 1 ) of  FIG. 9B , when the aperture has a relatively large area, the sealing cover  400  is formed such that the length of the part that forms the opening tab  100   a  is relatively small while the length of the part that adheres to the second heat-adhesive resin layer  108  is sufficiently large. 
     As shown in (b- 2 ) of  FIG. 9 , when the aperture has a relatively small area, the sealing cover  400  is formed such that both the length of the part that forms the opening tab  100   a  and the length of the part that adheres to the second heat-adhesive resin layer  108  are sufficiently large. 
       FIG. 10A  is a view illustrating a folded film layer included in a sealing cover according to an embodiment of the disclosure. 
     Referring to  FIG. 10A , a folded film layer  107  (e.g., the folded film layer  106 ) may include a polyester film  107   a  and a urethane layer  107   b  coated on the bottom surface of the polyester film  107   a.  The urethane layer  107   b  may be 0.001 mm thick or less. The folded film layer  107  may be folded so that the urethane layer  107   b  faces the outside or is exposed to the outside. 
     The urethane layer  107   b  may reinforce the adhesive strength of the folded film layer  107 . 
     In other words, the folded film layer  107  may be more strongly attached to the surface layer  102  via the urethane layer  107   b,  further reducing the likelihood that the opening tab alone is torn out of the sealing cover upon removing the sealing cover by holding and pulling up the opening tab. 
       FIG. 10B  is a view illustrating an arrangement of a surface layer, a first heat-adhesive resin layer, and a folded film layer included in a sealing cover according to an embodiment. 
     Referring to  FIG. 10B , the first heat-adhesive resin layer  104  is attached to the bottom of the surface layer  102 , and the folded film layer  107  is attached to the bottom of the first heat-adhesive resin layer  104 . As the folded film layer  107  is folded so that the urethane layer  107   b  faces the outside, the urethane layer  107   b  of the folded film layer  107  is attached to the bottom of the first heat-adhesive resin layer  104 . 
     By this configuration, stronger adhesion between the surface  102 , which is a polyester film layer, and the urethane layer  107   b  , may be obtained. 
       FIG. 10C  is a view illustrating an arrangement of a tab-forming layer, an intermediate substrate layer, and a sealing layer included in a sealing cover according to an embodiment of the disclosure. 
     Referring to  FIG. 10C , the second heat-adhesive resin layer  108  is attached to the bottom of the structure of  FIG. 10B , specifically, the bottom of the folded film layer  107  and the first heat-adhesive resin layer  104 . The intermediate substrate layer  200  is attached to the bottom of the second heat-adhesive resin layer  108 , and the sealing layer  300  is attached to the bottom of the intermediate substrate layer  200 . 
       FIG. 10D  is a view illustrating a layered structure of a sealing cover according to an embodiment of the disclosure. 
       FIG. 10D  illustrates a sealing cover which includes the tab-forming layer  102 ,  104 , and  107 , the intermediate layer  200 , and the sealing layer  302  and  304 . 
     The layered structure formed by attaching the layers  102 ,  104 ,  107 ,  108 ,  200 , and  300  together may be cut in the middle thereof, forming the sealing cover as shown in  FIG. 10D . The upper and lower pieces of the folded resin layer  107  are seamlessly coupled together at one end of the folded resin layer  107 , with the upper and lower pieces separated from each other at the other end of the folded resin layer  107 . The opening tab may be pulled up. 
       FIG. 10E  is a view illustrating an example operation of a sealing cover according to an embodiment of the disclosure. 
     Referring to  FIG. 10E , the sealing cover  400  which used to have been attached to the aperture  12  of the container  20  may be removed from the aperture  12  of the container  20  by holding and pulling up the opening tab. 
     As such, when the user holds and pulls up the opening tab, the overall seal cover may be removed from the container without failure—i.e., the delamination issue that the opening tab alone tears off the seal cover, with the underneath layers still left on the mouth of the container, may be addressed. 
       FIG. 10F  is a view illustrating how attaching force works between the folded film layer and the layers on the side and bottom of the folded film layer upon pulling the opening tab upwards as shown in  FIG. 10E . The attaching force is denoted with arrows. 
     It may be identified from  FIG. 10F  that the attaching force evenly works over the entire opening tab, providing prominent effects over the prior art thanks to the attaching force of the upright portion. 
     As such, the urethane layer ( 107   b )-coated folded film layer  107  may be more strongly attached to the first heat-adhesive resin layer  104  and the second heat-adhesive resin layer  108  than when the folded film layer  107  lacks the urethane layer  107   b.    
     Major reasons for coating the polyester folded film layer  107  with the urethane layer  107   b  are as follows. 
     The first heat-adhesive resin layer  104  and the second heat-adhesive resin layer  108  are formed of a special (or, high-cost) adhesive, such as EMAA or EVA, to provide strong adhesivity to a regular polyester film. 
     However, if the folded film layer  107  is coated with the urethane layer  107   b,  the first heat-adhesive resin layer  104  and the second heat-adhesive resin layer  108  may be formed of a low-cost heat adhesive resin, e.g., polyethylene (e.g., low-density polyethylene (LDPE)), which is commonly used in extrusion laminating because the polyethylene first heat-adhesive resin layer  104  and the polyethylene second heat-adhesive resin layer  108  may be well attached strongly to the polyester folded film layer  107  via the urethane layer  107   b.  Thus, cost savings may be achieved. Further, better or stronger adhesivity may be achieved when the first heat-adhesive resin layer  104  and the second heat-adhesive resin layer  108 , which are formed of polyethylene, are attached to the urethane layer-coated folded film layer  107  than when the first heat-adhesive resin layer  104  and the second heat-adhesive resin layer  108 , which are formed of EMAA or EVA, are attached to the urethane layer-free folded film layer  107 . 
       FIG. 11A  is a view illustrating a folded film layer included in a sealing cover according to an embodiment of the disclosure. 
     Referring to  FIG. 11A , a folded film layer  107  (e.g., the folded film layer  106 ) may include a polyester film  107   a  and a urethane layer  107   b  coated on the bottom surface of the polyester film  107   a.  The urethane layer  107   b  may be 0.001 mm thick or less. The folded film layer  107  may be folded so that the urethane layer  107   b  faces the outside or is exposed to the outside. Substantially the same method as that used in the embodiment described above in connection with  FIGS. 10A to 10F  may be applied. 
     The urethane layer  107   b  may reinforce the adhesive strength of the folded film layer  107 . 
     In other words, the folded film layer  107  may be more strongly attached to the surface layer  102  via the urethane layer  107   b,  further reducing the likelihood that the opening tab alone is torn out of the sealing cover upon removing the sealing cover by holding and pulling up the opening tab. 
       FIG. 11B  is a view illustrating an arrangement of a surface layer, a first heat-adhesive resin layer, and a folded film layer included in a sealing cover according to an embodiment. 
     Referring to  FIG. 11B , the first heat-adhesive resin layer  104  is attached to one surface of the urethane layer ( 107   b )-coated folded film layer  107 . 
     A urethane layer  102   b  is formed on the bottom of the surface layer  102 . 
     Thus, the urethane layer  102   b  on the bottom of the polyester surface layer  102 , along with the first heat-adhesive resin layer  104 , may be strongly attached to the urethane layer  107   b  of the polyester folded film layer  107 . 
       FIGS. 11C and 11D  are views illustrating an example of arranging and attaching together a tab-forming layer, an intermediate substrate layer, and a sealing layer included in a sealing cover according to an embodiment of the disclosure. 
     Referring to  FIGS. 11C and 11D , the second heat-adhesive resin layer  108  is attached onto the bottom of the layered structure of  FIG. 11B , and the intermediate substrate layer  200  and the sealing layer  300  (i.e., the aluminum foil layer  302  and the heat-sealing resin layer  304 ) are sequentially attached onto the bottom of the second heat-adhesive resin layer  108 . 
       FIGS. 11E, 11F, and 11G  are views illustrating an example of gradually lifting up the opening tab formed by cutting the layered structure of  FIG. 11D  off, at the middle thereof. 
       FIG. 11H  is a view illustrating an example of pulling up the sealing cover  400  attached to the mouth of the container. 
       FIG. 11I  is a view illustrating the attaching force applied to the opening tab when the sealing cover is pulled up from the container. The attaching force is denoted with arrows. It may be identified from  FIG. 11I  that much more attaching force may be obtained than the embodiment described above with  FIGS. 10A to 10F , not alone the prior art. 
     Substantially the same, or much better, effects as those described with reference to  FIGS. 10A to 10F  may be achieved by the embodiment described above with reference to  FIGS. 11A to 11I . 
     The first heat-adhesive resin layer  104  and the second heat-adhesive resin layer  108  are formed of a special (or, high-cost) adhesive, such as EMAA or EVA, to provide strong adhesivity to a regular polyester film. 
     However, if the folded film layer  107  is coated with the urethane layer  107   b,  the first heat-adhesive resin layer  104  and the second heat-adhesive resin layer  108  may be formed of a low-cost heat adhesive resin, e.g., polyethylene (e.g., low-density polyethylene (LDPE)), which is commonly used in extrusion laminating because the polyethylene first heat-adhesive resin layer  104  and the polyethylene second heat-adhesive resin layer  108  may be well attached more strongly to the polyester folded film layer  107  via the urethane layer  107   b.  Thus, cost savings may be achieved. Further, better or stronger adhesivity may be achieved when the first heat-adhesive resin layer  104  and the second heat-adhesive resin layer  108 , which are formed of polyethylene, are attached to the urethane layer-coated folded film layer  107  than when the first heat-adhesive resin layer  104  and the second heat-adhesive resin layer  108 , which are formed of EMAA or EVA, are attached to the urethane layer-free folded film layer  107 . 
       FIGS. 12A, 12B, and 12C  are views illustrating a process for manufacturing an opening tab by cutting a layered structure for a sealing cover, along lines denoted with B′ and B″, according to an embodiment of the disclosure. 
       FIGS. 12D and 12E  are views illustrating an example in which the opening tab formed as shown in  FIG. 12C  is gradually lifted up. 
       FIG. 12F  is a view illustrating an example in which the sealing cover attached to the container is pulled up and removed from the container by applying force. 
       FIG. 12G  is a view illustrating attaching force works in directions denoted with arrows between the components (e.g.,  102 ,  100 ,  107 , and  108 ) when the opening tab is pulled up from the container. 
       FIG. 13A  is a perspective view illustrating an example in which a sealing cover is attached to a container according to an embodiment of the disclosure. 
       FIG. 13B  is a perspective view illustrating an example in which the sealing cover of  FIG. 13A  is removed from the container by pulling up with the opening tab. 
       FIG. 13C  illustrates the mouth of the container of  FIG. 13A or 13B . 
       FIG. 13D  illustrates attaching force working in directions denoted with arrows between some components (e.g.,  108  and  200 ) of a sealing cover according to an embodiment of the disclosure. 
     Referring to  FIGS. 12A to 13D , the effects achieved by an embodiment of the disclosure are described below. 
     The inter-film bond strength may refer to a force value at which two films are attached together and may be typically measured by a tensile tester based on peel strength which is the force value at which two bonded samples are detached from each other when pulled away from each other in opposite directions. 
     The inter-film bond strength for packing materials is typically 600 gf/15 mm which means the force measured at the moment of peel-off according to the length of the bonded films (although it may be measured according to the area of the bonded films, the peel strength along the length is widely adopted internationally), and the peel strength typically ranges from 500 gf/15 mm to 1,500 gf/15 mm. For illustration purposes, the mean peel strength, e.g., 1,000 gf/15 mm, is used in the following description. 
     The sealing cover cut to have a circular shape, with the portion of the opening tab  102  larger in area than the rest thereof, is attached to the mouth  12  of the container  10  as shown in  FIG. 13A . When pulled up with the opening tab  102  gripped, the sealing cover is removed from the container  10  as shown in  FIG. 13B . 
     In this case when the mouth  12  of the container  10  has an outer diameter of 40 mm and an inner diameter of 34 mm as shown in  FIG. 13C , the sealing cover starts to detach off from one side thereof, with the most force applied along line “L”. The length of line “L” is 21 mm as shown in  FIG. 13C , and thus, a peel strength of 1,400 gf/21 mm may be needed to peel the sealing cover off, based on the typical peel strength of 1,000 gf/15 mm as described above. 
     The inter-film bond strength for packing materials is typically 600 gf/15 mm as described above. Thus, when the opening tab  102  is positioned at a side the distance of two ends of which is 30 mm as shown in  FIG. 13D , the inter-film bond strength is 1,200 gf/30 mm. In the structure according to embodiments of the disclosure, since the surface layer and the folded film layer are attached at two sides as shown in  FIG. 12G , a two times higher bond strength, i.e., 2,400 gf/30 mm (1680 gf/21 mm), may always be provided than the typical inter-film bond strength, i.e., 1,200 gf/30 mm, and this is much higher than the peel strength of 1,400 gf/21 mm, and thus, the sealing cover may be removed from the container in an easy and opening tab tear-free manner. 
     In other words, even when the opening tab is formed to be positioned away from the center and closer to a side as shown in  FIGS. 12A to 12F , the opening tab may be prevented from being broken before the entire sealing cover is removed from the mouth of the container as the opening tab is formed to be positioned at the center. 
     Unlike the conventional sealing cover having the semi-circular opening tab, in the sealing cover according to the disclosure, the opening tab which is provided at the top of the sealing cover may have a semi-circular shape or a substantially circular shape, Therefore, a consumer can more conveniently and easily open the container. 
     Furthermore, because the layers that form the opening tab in the sealing cover adhere to each other in the entire area thereof, delamination in which only the opening tab is removed from the sealing cover when the container is opened may be prevented. Therefore, the container sealing cover has a more reliable structure. 
     Although the container sealing cover having the opening tab and the method for manufacturing the sealing cover according to the embodiment of the disclosure have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.