JP2008265873A - Plastic cap provided with ic tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic cap having an IC tag wherein transmission and reception of information to and from the IC tag are not interrupted and product information is surely inputted and outputted to and from the IC tag. <P>SOLUTION: The upper surface of the top panel 21 of the plastic cap is provided with the IC tag 10 wherein product information is stored. The top panel 21 is composed of an annular flange section 35 and a recessed section 37. The recessed section 37 is composed of a side wall section 37a continuous to the inner circumference end of the annular flange section 35, and a bottom section 37b continuous to the lower end of the side wall section 37a. The IC tag 10 is attached to the annular flange section 35 to cover the recessed section 37. A gap between the IC tag 10 and the bottom section 37b is maintained as a gap by which signal transmission and reception to and from the IC tag 10 is not interrupted when the bottom surface of the bottom section 37b is brought into contact with water. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a plastic cap in which an IC tag storing product information is attached to a top plate.

  Conventionally, barcodes displaying product information such as date of manufacture, manufacturer / seller name, expiration date, etc. have been widely used for various products. By the way, since barcodes read the coded information with a reader, the barcode printing surface must be flat. For this reason, in the field of packaging materials such as bottles and caps, the barcode printing surface is There is a problem that the amount of information that can be encoded is limited.

  Therefore, recently, an information display technique using an IC tag has been used. An IC tag is also referred to as RFID (Radio Frequency Identification), and is an ultra-high frequency tag formed by embedding an IC chip storing predetermined information in a dielectric material such as resin or glass together with a wireless antenna. It is a small communication terminal. Such an IC tag reads product information stored in an IC chip by wireless communication. For example, data of several hundred bytes can be recorded in a memory of the IC chip, and a lot of product information is stored. There is an advantage that it can be recorded. In addition, IC tags can read information recorded in a non-contact manner, have no problems such as wear due to contact, and can be processed into a shape that matches the form of the product, or can be reduced in size and thickness. There is an advantage that it is possible.

As a cap provided with such an IC tag, Patent Documents 1 and 2 propose a cap in which an IC tag is embedded in a top plate.
JP 2006-62716 A JP 2005-321935 A

By the way, the IC tag as described above includes a type in which communication is performed by electromagnetic induction and a type in which communication is performed by a radio wave system. Although the electromagnetic induction type IC tag has an advantage that communication is not easily affected by moisture, it has a disadvantage that the area is large. On the other hand, the radio frequency type IC tag has a disadvantage that communication is easily affected by moisture. However, since it has an advantage of a small area, this radio wave type IC tag is currently being studied in the field of caps.
However, the cap with the IC tag provided on the top plate described above is a radio wave type IC tag when applied to a container filled with water-containing contents such as beverages. There was a problem that it became difficult to send and receive. That is, moisture contained in beverages or the like causes dielectric loss and impedance mismatch, and as a result, transmission / reception of information to / from the IC tag is hindered.

  Accordingly, an object of the present invention is to provide a plastic cap with an IC tag capable of reliably inputting product information to the IC tag and reliably outputting the input product information without disturbing transmission / reception of information to / from the IC tag. Is to provide.

According to the present invention, in the plastic cap having the top plate and the skirt wall descending from the peripheral edge of the top plate, the top surface of the top plate is provided with an IC tag storing product information,
The top plate is formed of an annular flange portion and a concave portion that is continuous with the inner peripheral edge of the annular flange portion, and a bottom portion that is continuous with the inner peripheral edge of the annular flange portion and the lower end of the side wall portion. Consists of
The IC tag is attached to the annular flange portion so as to cover the recess, and the interval between the IC tag and the bottom of the recess is such that the back surface of the bottom is in contact with water. A plastic cap is provided that is maintained at an interval that does not hinder the transmission and reception of signals to and from.

In the plastic cap of the present invention,
(1) The IC tag is attached by thermally welding the peripheral edge portion to the upper surface of the annular flange portion;
(2) A projection extending upward is formed on the upper surface of the bottom of the recess.
(3) An inner ring extending downward from a position between the skirt wall and the side wall portion of the recess is provided on the inner surface of the annular flange portion of the top plate, and the skirt wall and the inner ring are provided. Being fixed to the container mouth by fitting the container mouth into the space between
(4) The side wall portion of the concave portion of the top plate is composed of an upper large diameter portion having a relatively large outer diameter located above and a lower small diameter portion having a relatively small outer diameter located below, and the side wall portion An inner ring is formed at the lower portion of the upper large diameter portion of the lower outer diameter portion of the lower small diameter portion. The inner ring extends downward and is spaced apart from the lower small diameter portion. The container mouth is fitted into the space, thereby being fixed to the container mouth,
Is preferred.

  In the plastic cap of the present invention, a predetermined interval is maintained between the IC tag attached to the annular flange portion of the top plate and the bottom of the concave portion of the top plate. For this reason, even when this cap is applied to a container filled with a liquid content containing water, such as a beverage, a constant interval is maintained between the liquid level of the content liquid and the IC tag. The inconvenience that the liquid interferes with transmission and reception due to dielectric loss and impedance mismatch is prevented, and product information is transmitted (input) to the IC tag and input product information is received (output). Is possible.

  In the present invention, the IC tag can be securely and easily attached to the cap top plate by thermally welding the peripheral portion thereof to the upper surface of the annular flange portion of the cap top plate.

  Further, in the present invention, when a protrusion is provided on the upper surface of the bottom of the concave portion of the cap top plate, when an external force is accidentally applied from above, the IC tag is supported by the protrusion. Tag deformation and damage can be effectively avoided. Further, when discarding a used cap, the IC tag can be easily removed from the cap top plate by pressing the bottom of the recess upward from the back surface, which is advantageous in terms of separation and disposal.

  Furthermore, the plastic cap of the present invention is fixed to the container mouth by providing an inner ring on the inner surface of the top plate and fitting the container mouth between the inner ring and the skirt wall. Good sealability is ensured by adhering to the inner surface of the container mouth. In the present invention, the side wall portion of the concave portion of the top plate described above can have a function as a seal portion, but the seal portion is preferably provided as a member independent of the side wall portion of the concave portion. That is, when the side wall portion of the recess is to have a function as a seal portion, the container mouth portion is fitted into the space between the side wall portion and the skirt wall, but the lower end of the side wall portion is integrated with the bottom portion. This is because the flexibility of the side wall portion is poor, and as a result, it is difficult to fit the container mouth portion into the space between the side wall portion and the skirt wall. Further, the close contact between the side wall portion and the container mouth portion becomes unstable, and the sealing performance may be lowered. However, if the seal portion is provided as a member independent of the recess side wall portion, sufficient flexibility can be maintained, which is convenient for avoiding the above-described disadvantages.

  In order to make the seal portion a member independent of the recess side wall portion, for example, an inner ring can be provided at a position between the skirt wall and the recess side wall portion on the inner surface of the annular flange portion of the top plate. In the present invention, it is particularly preferable to form an inner ring as a seal portion in the middle of the side wall of the recess. Specifically, the recess side wall is formed so as to be composed of an upper large-diameter portion having a relatively large outer diameter positioned above and a lower small-diameter portion having a relatively small outer diameter positioned below, Preferably, an inner ring extending downward from the lower small-diameter portion on the outer peripheral side of the lower small-diameter portion is formed below the upper large-diameter portion of the portion. When the inner ring is provided in this way, even when the container liquid enters the space between the inner ring and the recess side wall, an appropriate size is provided between the IC tag and the container liquid. Since this space is maintained, interference of signal transmission to the IC tag by the liquid in the container can be effectively prevented.

The present invention will be described below based on specific examples shown in the accompanying drawings.
FIG. 1 is a side sectional view of an IC tag attached to a plastic cap of the present invention,
FIG. 2 is a half cross-sectional side view showing an example of the plastic cap of the present invention to which the IC tag of FIG.
FIG. 3 is a half cross-sectional side view showing another example of the plastic cap of the present invention together with a container mouth portion,
FIG. 4 is a half cross-sectional side view of an embodiment in which an inner ring is provided separately from the recessed sidewall in the plastic cap of the present invention,
FIG. 5 is a half sectional side view showing a preferred example of the plastic cap of the present invention in which an inner ring is provided in a form different from that of FIG.
FIG. 6 is a diagram showing a half-section side surface of the plastic cap of FIG.
FIG. 7 is a partially enlarged cross-sectional view showing the recessed side wall and the inner ring, which are the main parts of the plastic cap of FIG.

  Referring to FIG. 1, an IC tag (indicated by 10 as a whole) attached to a plastic cap of the present invention includes a dielectric substrate 1, and a metal antenna 3 and an IC chip are provided on the surface of the dielectric substrate 1. 5 is fixed.

  The dielectric substrate 1 is formed from a non-conductive material, but is generally formed from a thermoplastic resin that can be thermally welded. Such a thermoplastic resin is not particularly limited, but is generally made of the same resin as the resin base material constituting the plastic cap to which the IC tag 10 is attached. For example, a polypropylene cap is used. When the IC tag 10 is provided, the dielectric substrate 1 is preferably formed of polypropylene.

  In addition, an adhesive layer (not shown) can be formed on the surface of the dielectric substrate 1 if necessary, so that the metal antenna can be firmly bonded and fixed to the dielectric substrate 1. it can. As such an adhesive, an acid-modified olefin resin obtained by graft-modifying a polyolefin resin with an unsaturated carboxylic acid or a derivative thereof is generally preferable.

  The antenna 3 is usually made of a thin film (thickness of about 5 to 50 μm) of a low-resistance metal such as aluminum, copper, silver, or gold, has a predetermined pattern shape, and is used for signal transmission / reception. The

  As can be understood from FIG. 1, in order to bond and fix the IC tag to a top plate of a plastic cap, which will be described later, by thermal welding or the like, the peripheral portion of the substrate 1 is not covered with the antenna 3 and the upper surface thereof is covered. Is exposed.

  The IC chip 5 is provided so as to be electrically connected to the antenna 3 by flip chip mounting or the like, and stores information on a plastic cap to which the IC tag 10 is attached. By transmitting the signal via the predetermined information, predetermined information is stored, and information stored in the IC tag 10 is read via the antenna 3.

  Further, as shown in FIG. 1, the IC chip 5 is generally sealed and protected by a sealing agent 7 such as polyimide or bismaleimide resin.

  still. The thickness of the dielectric substrate 1 is not particularly limited as long as it exhibits such a strength that the operation of forming the antenna 3 on the surface and mounting the IC chip 5 can be performed, and is generally about 10 to 1000 μm. .

  Referring to FIG. 2 showing the structure of the plastic cap to which the IC tag 10 is attached, the plastic cap 20 as a whole has a top plate 21 and a skirt wall 23 descending from the peripheral edge of the top plate 21. It consists of.

  The inner surface of the skirt wall 23 is formed with a thread 25 that is threadedly engaged with a thread 71 provided on the outer surface of the mouth portion 70 of the container to which the cap 20 is mounted. A tamper evidence (TE) band 29 is provided via a breakable bridge 27, and an upward flap piece 30 is intermittently formed on the inner surface of the TE band 29.

  That is, the cap 20 is attached to the container mouth portion 70 by screw engagement by the thread 25, and the cap 20 attached to the container mouth portion 70 is removed from the container mouth portion 70 by rotating in the opening direction. At the time of opening, the flap piece 30 formed on the inner surface of the TE band 29 engages with the jaw 73 formed on the outer surface of the container mouth portion 70, the rise of the TE band 29 is restricted, and the bridge 27 is It breaks and is separated from the skirt wall 23. As a result, the general consumer can recognize the fact that the cap 20 has been once removed from the container mouth portion 70 from the fact that the TE band 29 is cut off.

  The first stopper pieces 31 are formed at appropriate intervals on the lower end surface of the skirt wall 23, and the second stopper pieces 33 are provided between the first stopper pieces 33 on the upper end surface of the TE band 29. It is provided at appropriate intervals so as to be positioned. That is, the first stopper piece 31 has an upright side surface in the closing direction, and when the cap 20 is attached to the container mouth portion 70, the upright side surface of the first stopper piece 31 is the TE band. The side surface on the plug opening direction side provided on the upper surface of 29 is in contact with the upright surface of the stopper standing upright, whereby the skirt wall 23 and the TE band rotate integrally in the closing direction, Breakage of the bridge 27 is effectively avoided. Further, the upper end surface of the second stopper piece 33 is a flat surface, and this surface abuts against the lower end surface of the skirt wall 23 at the time of closing, thereby lowering the upper end surface of the TE band 29 and the lower side of the skirt wall 23. A constant distance is maintained between the end face and the bridge 27 so that breakage of the bridge 27 at the time of closing is effectively prevented.

  On the other hand, the top plate 21 includes an annular flange portion 35 and a concave portion 37 that is continuous with the inner peripheral edge of the annular flange portion 35.

  The concave portion 37 is formed of a side wall portion 37a continuous with the inner peripheral edge of the annular flange portion 35 and a bottom portion 37b closing the lower end of the side wall portion 37a. The outer surface side is slightly bulging outward. On the other hand, an outer ring 39 is formed on the inner surface of the annular flange portion 35, and an annular small protrusion 50 is formed between the outer ring 39 and the base portion of the side wall portion 37a.

  That is, when the cap 20 is attached to the container mouth portion 70 by the screw engagement described above, the inner surface of the upper portion of the container mouth portion 70 is in close contact with the outer surface of the side wall portion 37a, and the outer surface side of the upper end portion of the container mouth portion 70 is the outer surface. The ring 39 is in close contact with the inner surface, and the upper end surface of the container mouth portion 70 is in close contact with the small protrusion 50, thereby ensuring a good seal.

  In the present invention, the peripheral portion of the IC tag 10 described above is thermally welded to the upper surface of the annular flange portion 35 of the top plate 21 so that the IC chip 5 is on the lower side. 10 is firmly fixed to the top plate 21, and the recess 37 is covered with the IC tag 10.

  That is, in the present invention, the formation of the concave portion 37 described above not only reliably prevents direct contact between the IC tag 10 and the liquid in the container, but also the signal transmission surface (the antenna 3 is formed) of the IC tag 10. A constant distance d is ensured between the bottom portion 37b of the recess 37 and the bottom portion 37b of the concave portion 37, so that interference of signal transmission due to moisture contained in the container liquid is effectively prevented. It is possible to reliably transmit a signal to the IC tag 10 (IC chip 5) or receive a signal from the IC tag 10 in a state where it is mounted on the unit 70, and effectively input and output product information. Can be performed.

  In the present invention, the size of the recess 37 described above may be such that transmission of signals to the IC tag 10 in a state where water is in contact with the bottom 37b of the recess 37 is not hindered by water. Although it depends on the frequency of the signal, the pattern of the antenna 3 and the like, it is generally sufficient that the depth of the recess 37 (the above-mentioned distance d) is set to be 7 mm or more.

  Further, it is preferable that a step 50 having a size corresponding to the thickness of the substrate 1 of the IC tag 10 is formed on the outer peripheral edge portion on the upper surface of the annular flange portion 35 to which the IC tag 10 is thermally welded. Thereby, the upper end surface of the cap 20 can be made into a smooth flat surface, and the external appearance of the cap 20 can be kept favorable.

  In the present invention, as shown in FIG. 3, a protrusion 60 for holding the IC tag 10 may be formed on the upper surface of the bottom 37b of the recess 37 described above.

  That is, as can be understood from FIG. 3, the protrusion 60 is located at the center of the upper surface of the bottom portion 37b, and the portion 7 where the IC chip 5 of the IC tag 10 is provided is placed on the upper end of the protrusion 60. It is in the state. Providing such a protrusion 60 that supports the IC tag 10 makes it possible to effectively prevent deformation and breakage of the IC tag 10 when an external force is applied from above the cap 20. Further, when the used cap 20 is discarded, the IC tag 10 is easily pressed from the top plate 21 of the cap 20 by pressing the bottom portion 37b of the concave portion 37 upward from the back surface side, whereby the IC tag 10 is pressed by the protrusion 60. It is also possible to remove them, and it is possible to ensure excellent separation and disposal.

  The protrusion 60 as described above is not necessarily in contact with, for example, the portion 7 where the IC chip 5 of the IC tag 10 is provided. For example, a slight amount is provided between the portion 7 and the upper end of the protrusion 60. A gap may be formed. In short, the protrusion 60 may be provided so that the IC tag 10 is not greatly deformed when an external force is applied from above. Therefore, the protrusion 60 is not limited to the aspect provided in the central portion of the bottom portion 37b. For example, a plurality of protrusions 60 are arranged in a point-symmetric manner in an annular manner around the center of the bottom portion 37b. It is also possible to adopt a structure in which the protrusion 60 supports the portion of the IC tag 10 where the antenna 3 is provided.

  In the present invention, the above-described IC tag 10 is preferably formed by thermally welding the surface peripheral portion of the substrate 1 to the upper surface of the annular flange portion 35. However, depending on the case, the annular flange portion may be fitted. It is also possible to mechanically fix the upper surface of the annular flange portion 35, and a protrusion is provided on the outer peripheral portion of the annular flange portion 35, and the IC tag 10 is placed on the upper surface of the annular flange portion 35. It is also possible to fix the peripheral portion of the IC tag 10 by bending. When the IC tag 10 is provided in this way, the substrate 1 of the IC tag 10 does not have to be formed of a heat-weldable material such as a thermoplastic resin, but is made of a dielectric material such as glass. It may be formed. In addition, the IC tag 10 can be fixed to the upper surface of the annular flange 35 by fitting.

  In the example described above, the cap 20 is fixed to the container mouth portion 70 by fitting the upper portion of the container mouth portion 70 into the space between the concave side wall portion 37a of the top plate 21 and the skirt wall 23, and the container mouth opening. The seal is secured by the close contact between the inner surface of the portion 70 and the recess side wall portion 37a, but an inner ring is provided as a member independent of the recess side wall portion 37a, and the inner ring has the above function. You can also.

  That is, the upper part of the container mouth part 70 is fitted into the space between the concave side wall part 37a and the skirt wall 23, or the outer surface of the side wall part 37a is brought into close contact with the inner surface of the container mouth part 70 to provide a sealing property. In the structure, since the bottom 37b is integrally connected to the lower end of the side wall 37a, the flexibility of the side wall 47a is lowered. For this reason, it may be difficult to fit the container opening 70. Further, the close contact between the side wall portion 37a and the container mouth portion 70 becomes insufficient, and the sealing performance may become unstable. However, an inner ring is provided completely separate from the concave side wall 37a, and the sealing performance is ensured by this inner ring, so that high flexibility is maintained, and the winding is poor when the cap 20 is wound around the container mouth portion 70. In addition, it is possible to effectively prevent a decrease in sealing performance.

A cap having such an inner ring is shown in FIGS.
The cap 20 shown in FIGS. 4 to 7 has basically the same structure as the cap 20 shown in FIG. 2 except that an inner ring is provided. Reference numerals will be used, and descriptions of the same members will be omitted.

  In FIG. 4, in the cap 20, an inner ring 63 is provided on the inner surface (lower surface) of the annular flange portion 35 of the top plate 21. That is, the inner ring 63 is located between the skirt wall 23 and the concave side wall 37a, and extends downward so as to be spaced from the skirt wall 23 and not to contact the outer surface of the concave side wall 37a. In addition, the outer surface of the inner ring 63 has a shape in which the central portion swells outward, and is configured to be able to adhere well to the inner surface of the container mouth portion 70.

  As understood from FIG. 4, the upper portion of the container mouth portion 70 is fitted into the space between the inner ring 63 and the skirt wall 23, whereby the outer surface of the inner ring 63 is brought into contact with the inner surface of the container mouth portion 70. It becomes possible to adhere and secure a good sealing property. That is, unlike the recessed side wall portion 37a, the lower end of the inner ring 63 is not constrained and thus exhibits high flexibility. As a result, the cap 20 can be easily and smoothly fitted into the container mouth portion 70, and the outer surface of the inner ring 63 is firmly attached to the inner surface of the container mouth portion 70, so that excellent sealing performance is stable. It will be held in.

  Further, the above example is an example in which the inner ring 63 is provided on the inner surface of the annular flange portion 35, but the half sectional side view shown in FIG. 5, the half sectional side view shown together with the container mouth portion in FIG. 6, and FIG. In the cap 20 in the enlarged view of the main part, an inner ring 63 is provided in the middle of the concave side wall 37a.

  That is, in the caps shown in FIGS. 5 to 7, the recess side wall portion 37a has an upper large-diameter portion A having a relatively large outer diameter positioned above and a lower portion having a relatively small outer diameter positioned below. An inner ring 63 is formed below the upper large-diameter portion A. The inner ring 63 extends downward from the lower small-diameter portion B on the outer peripheral side of the lower small-diameter portion B. . The inner ring 63 extends downward from the lower portion of the upper large-diameter portion A so as not to contact the small-diameter portion B below the side wall portion 37a.

  In the cap 20 provided with such an inner ring 63 as well as the cap of FIG. 4, the container mouth portion is formed in the space between the inner ring 63 and the upper large-diameter portion A of the recess side wall portion 37 a and the skirt wall 23. The upper portion of the inner ring 63 is fitted, and the lower end of the inner ring 63 (below the portion bulging outward of the inner ring 63) is not restrained. The flexibility is high, and therefore, the container mouth portion 70 can be easily and smoothly fitted. Further, the outer surface of the inner ring 63 and the inner surface of the container mouth portion 70 are firmly in contact with each other, and excellent sealing performance is achieved. It is kept stable.

  In the present invention, the cap 20 shown in FIGS. 5 to 7 is most preferable. That is, in the example of FIGS. 5 to 7, since the inner ring 63 extends from the middle of the concave side wall portion 37a, the space between the inner ring 63 and the concave side wall portion 37a can be reduced. This is because the moldability can be improved.

  In the example of FIGS. 5 to 7, a horizontal step 65 is provided in the middle of the concave side wall portion 37a to divide the side wall portion 37a into an upper upper large diameter portion A and a lower lower small diameter portion B. As long as the inner ring 63 is not constrained by contact with the outer surface of the side wall 37a, such a horizontal step 65 is not necessarily provided. For example, if the concave side wall portion 37a is formed so that the upper portion has a large diameter and the lower portion has a small diameter, and the inner surface of the inner ring 63 extends downward so as not to contact the outer surface of the lower small diameter portion, the horizontal step 63 exists. You don't have to.

  The cap 20 of the present invention shown in FIG. 2 to FIG. 7 is formed into a cap shape by injection molding, compression molding or the like of various plastics, and then the IC tag 10 is attached by means of the above-described heat welding or the like. Manufactured by.

The sectional side view of the IC tag attached to the plastic cap of this invention. The half section side view which shows an example of the plastic cap of this invention with which the IC tag of FIG. 1 was attached with a container mouth part. The cross-sectional side view which shows the other example of the plastic cap of this invention with a container opening part. The plastic cap of this invention WHEREIN: The half cross section side view of the aspect which provided the inner ring separately from the recessed part side wall part. FIG. 5 is a half sectional side view showing a preferred example of the plastic cap of the present invention in which an inner ring is provided in a form different from that of FIG. The figure which shows the half cross section side surface of the plastic cap of FIG. 5 with a container mouth part. The elements on larger scale which show the recessed part side wall part and inner ring which are the principal parts of the plastic cap of FIG.

Explanation of symbols

10: IC tag 21: Top plate 23: Skirt wall 35: Annular flange portion 37: Recessed portion 37a: Side wall portion 37b: Bottom portion 60: Projection 63: Inner ring A: Upper large diameter portion B: Lower small diameter portion

Claims (5)

In a plastic cap having a top plate and a skirt wall descending from the peripheral portion of the top plate, and an upper surface of the top plate is provided with an IC tag storing product information,
The top plate is formed of an annular flange portion and a concave portion that is continuous with the inner peripheral edge of the annular flange portion, and a bottom portion that is continuous with the inner peripheral edge of the annular flange portion and the lower end of the side wall portion. Consists of
The IC tag is attached to the annular flange portion so as to cover the recess, and the interval between the IC tag and the bottom of the recess is such that the back surface of the bottom is in contact with water. A plastic cap characterized by being held at an interval that does not interfere with transmission and reception of signals to and from.   The plastic cap according to claim 1, wherein the IC tag is attached by thermally welding a peripheral portion thereof to an upper surface of the annular flange portion.   The plastic cap according to claim 1, wherein a protrusion extending upward is formed on an upper surface of the bottom of the recess.   An inner ring extending downward from a position between the skirt wall and the side wall portion of the recess is provided on the inner surface of the annular flange portion of the top plate, and is provided between the skirt wall and the inner ring. The plastic cap according to any one of claims 1 to 3, which is fixed to the container mouth portion by fitting the container mouth portion into the space.   The side wall portion of the concave portion of the top plate is composed of an upper large-diameter portion having a relatively large outer diameter positioned above and a lower small-diameter portion having a relatively small outer diameter positioned below, and a large upper portion of the side wall portion. At the lower part of the diameter part, an inner ring is formed on the outer peripheral side of the lower small diameter part, and is separated from the lower small diameter part and extends downward, and is formed in a space between the skirt wall and the inner ring. The plastic cap according to any one of claims 1 to 3, wherein the plastic cap is fixed to the container mouth portion by fitting the container mouth portion.

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