JPH0670736B2 - In-mold label sticker label and labeled plastic container - Google Patents

Description

TECHNICAL FIELD The present invention relates to an in-mold label sticking label and a labeled plastic container using this label, and more specifically,
The present invention relates to an in-mold label-attached label which can eliminate blister due to inclusion of air bubbles at an adhesive interface between a plastic container and a label at the time of attaching an in-mold label, improve the appearance characteristics of the labeled container, and enhance the commercial value.

(Prior Art) Affixing a label for displaying contents on a hollow container has an important meaning in packaging technology because it enhances the commercial value of packaging products and motivates consumers to purchase.

It has been known for a long time to label a hollow container by in-mold label operation, and the label to be attached to the inner surface of the cavity of the molding die is held by means such as vacuum suction, and the plastic is placed in this die. A means for hollow molding a parison is generally adopted (for example, JP-A-61-202818).

As a label for in-mold label operation, a label based on a plastic film is desirable because it has advantages such as back surface printing, a clear image, and excellent stain resistance. , In terms of bonding using the heat of the plastic container wall that is being molded,
It is advantageous that at least the inner surface is made of a heat-bondable resin, that is, the back surface of the label is made of a heat-adhesive resin film or a heat-sensitive adhesive coat layer.

(Problems to be Solved by the Invention) When the label held on the surface of the mold cavity and the outer surface of the container being molded are combined by the label operation in the mold, the inner surface of the label (sticking surface) and the outer surface of the container It often causes air inclusions with the surface. The entrapped air is trapped between the label and the outer surface of the container, resulting in incomplete adhesion of this part.When the labeled container is taken out of the mold, compressed air bubbles are generated. It expands and becomes blister. When the label and the container are adhered from one side to the other side or from the label center part to the peripheral part in a certain order, even if such entrapment of air bubbles does not easily occur, the in-mold label attaching operation is performed. However, since it cannot be expected that the container wall and the label, which are being molded due to expansion or the like, are stuck in the above order, it is very difficult to prevent air from being caught. Moreover, in the case where there is a portion with a varying radius of curvature, a protruding portion or a concave portion on the outer surface of the container, the contact between the outer surface of the container and the inner surface of the label jumps over these portions or the boundary portion, so that the bubble It is inevitable to hug.

Then, when blisters are generated in the label due to air inclusion, the blisters are noticeable due to the smoothness and glossiness of the in-mold label sticking film, so the appearance characteristics of the labeled container are significantly impaired, and its commercial value is reduced. It will be.

Therefore, it is an object of the present invention to effectively eliminate the generation of blisters due to the inclusion of air when attaching a label in a mold, and as a result, it is possible to improve the appearance characteristics of the labeled container and increase its commercial value. To provide a label for attaching an in-mold label.

Another object of the present invention is to provide a portion where the radius of curvature changes, a protruding portion or a concave portion on the outer surface of the container, so that even if air entrapment occurs between the label and the outer surface of the container, the outside of the trapped air is reduced. It is possible to provide a labeled plastic container that can be opened to a container, and as a result, generation of blisters and defective adhesion can be eliminated.

Still another object of the present invention is to provide an in-mold label sticking label and a labeled container using the same, which enables the above-mentioned closed air to be released to the outside without impairing the aesthetic appearance and display function of the label. There is.

(Means for Solving the Problems) According to the present invention, a label is attached to the outer surface of a plastic container by in-mold label sticking, the label having at least the inner surface formed of a heat-bondable resin. By piercing at least a part of the label with a needle from the outer surface to the inner surface of the label, the cross-sectional shape is formed into a Y-shape or a V-shape, having a valve function, which is difficult to discriminate with the naked eye. Provided is an in-mold label sticking label, which is provided with a large number of small holes penetrating inside and outside of a certain size.

According to the present invention, there is also provided a labeled plastic container obtained by applying the above-mentioned label to the outer surface of the body of the plastic container by applying an in-mold label.

(Function) Since the label of the present invention is applied to the outer surface of the plastic container that is being molded by attaching the label inside the mold, at least the inner surface is formed of a heat-bondable resin.

At least a part of this label, that is, a portion where air is likely to be trapped when the in-mold label is attached to the container, is provided with a large number of holes extending from the inner surface of the label to the outer surface thereof, and the size of the holes can be visually observed. It is a feature of the present invention that the holes are small enough to be difficult to distinguish.

When the label of the present invention is used for sticking an in-mold label, even if air entrapment occurs between the label and the outer surface of the container that is being molded, this air causes the holes to be generated by the molding pressure applied to the wall surface of the container. Through and escapes between the outer label surface and the mold surface, resulting in a complete bond between the inner label surface and the outer plastic container surface without leaving blister. It has been found that a small hole that is difficult to be discerned by the naked eye is sufficient as a hole for removing the air that is trapped between the label and the outer surface of the container. According to the experiments conducted by the present inventors, the size of the blister formed by the inclusion of air varies depending on the shape and size of the container, but roughly speaking, the area is 20 to 1 mm ² and the volume is 30 to 0.5. mm ³
Even if it is a small hole that is difficult to distinguish with the naked eye, if this hole reaches from the inner surface of the label to the outer surface, air is extracted outside without being trapped and the label and container are separated. The bonding can be done completely. Also,
The distribution of the holes may be such that at least one hole is located for one of the blisters.

In the present invention, by providing a large number of holes as small holes that are difficult to discriminate with the naked eye, it is possible to effectively prevent label blister generation without impairing the aesthetic appearance and display function of the label. It is a thing.

The hole provided in the label is preferably a hole formed by piercing the label with a needle and having a valve function. This is because when the needle is pierced into the label, it is perforated without removing the label-constituting material such as film, and in the state where pressure is not applied due to the plasticity and resilience of the label film. This is because the holes are closed and open so that air is discharged when pressure is applied.

(Example) The label used in the present invention may have any layer structure as long as it is based on a film and has a printing layer. Some examples of this label are 1-A to 1-H
Shown by a figure. In FIG. 1-A, a label 1 comprises a plastic film substrate 2 and a printed layer 3 provided on the outer surface thereof. The plastic film substrate 2 may be a single-layer film or a multi-layer film, but the outer surface side must be heat-adhesive to the plastic container.
The label 1 of FIG. 1-B is the same as the label 1 shown in FIG. 1 except that an overcoat layer 4 is provided on the printed layer 3 to protect it.
-Similar to that of FIG. A transparent resin coat layer is used as the overcoat layer 4. In the label 1 of FIG. 1-C, an adhesive resin layer 5 having thermal adhesiveness is applied to the inner surface side of the film base material 2 by means such as coating. The label 1 of FIG. 1-D has an overcoat layer 4 on the printed layer 3 of FIG. 1-C. 1st-
The label 1 in FIG. E has a printing layer 3 on the inner surface side of the film substrate 2.
Is applied as so-called back printing, and the adhesive resin layer 5 is provided on the printed layer 3. Figure 1-F
An overcoat layer 4 is provided on the outer surface side of the film base material 2 of the label shown in FIG. 1-E. The label 1 in FIG. 1-G has a print layer 3 on the inner surface side of a film substrate 2, a thin metal layer 6 formed by vapor deposition or the like, and an adhesive resin layer 5 thereon. is there. This thin metal layer 6 serves to give the printed layer a metallic sheen. 1st-
FIG. H shows the film substrate 2 in the label of FIG. 1-G.
The overcoat layer 4 is provided on the outer surface side of the. The laminated structure of the label used in the present invention is, of course, not limited to the one exemplified above.

Examples of the plastic constituting the film substrate include crystalline polypropylene, crystalline propylene-ethylene copolymer, crystalline polypten-1, crystalline poly-4-methylpentene-1, low-, medium-, or high-density. Polyolefins such as polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ion-crosslinked olefin copolymer (ionomer); aromatics such as polystyrene and styrene-butadiene copolymer Group vinyl polymers; vinyl halide polymers such as polyvinyl chloride and vinylidene chloride resins; acrylonitrile-
Nitrile polymers such as styrene copolymers and acrylonitrile-styrene-butadiene copolymers: Polyamides such as nylon 6, nylon 6,6, para or metaxylylene adipamide: polyesters such as polyethylene terephthalate, polytetramethylene terephthalate Types: Various polycarbonates: Thermoplastic resins such as polyacetals such as polyoxymethylene can be mentioned. These film substrates may be unstretched or may be uniaxially or biaxially stretched. Further, this film may be an ordinary transparent film, a lightly foamed film, or a semitransparent or opaque film containing a filler or a pigment. The thickness of the film substrate is such that it can be attached to a curved surface or an uneven portion, and it is suitable that it is generally in the range of 20 to 250 μm, particularly 50 to 150 μm.

As the ink for forming the printing layer, an ink known per se used for film printing, for example, polyester urethane, vinyl urethane, acrylic urethane, epoxy urethane, epoxy vinyl, epoxy acrylate, chlorinated polypropylene, etc. as a vehicle, Inks containing colorants are used. Printing can be performed by means such as offset printing, gravure printing, letterpress printing, electrophotographic printing, hot stamping and the like.

Between the film used for the label and the plastic on the outer surface of the container, it is not particularly necessary when sufficient thermal adhesive strength can be obtained even directly at the time of hollow molding, but in general, via a hot melt adhesive resin, a stretched film substrate and It is preferable to perform thermal bonding with the outer wall plastic of the container. As such a hot-melt adhesive resin, an ethylene-vinyl acetate copolymer (EVA) having a vinyl acetate content of 5 to 40% by weight and an ethylene-ethyl acrylate copolymer having an acrylic acid content of 5 to 40% by weight are used. Combined (EEA), low density polyethylene (LDPE), E
An ethylene resin such as VA or EEA, or a mixture of 5 to 30% by weight of a tackifier such as rosin of these resins, terpene resin, petroleum resin or styrene resin is used.
Chlorinated polypropylene is also used. The hot melt adhesive resin is generally provided on the substrate film in a thickness of 3 to 40 μm, and particularly 5 to 15 μm.

For the overcoat layer, a resin having excellent transparency and scratch resistance, such as nitrocellulose, acrylic resin, acrylic-vinyl paint, acrylic-phenol paint, acrylic-amino paint, etc., is used. The overcoat layer is generally provided to a thickness of 1 to 20 μm, and particularly 2 to 10 μm. The thin metal layer can be provided by vapor deposition of metal such as aluminum or hot stamping (transfer),
This thickness is generally 0.005 to 15 μm, especially 0.01 to 9 μm
It should be in the range of m.

According to the present invention, at least a part of the above-mentioned label, that is, at least a portion where air is likely to be included in the container, is provided with a large number of small holes that are difficult to discern with the naked eye. The region where air is likely to be trapped is a portion on the outer surface of the container where the radius of curvature changes, a protruding portion or a concave portion, or a boundary portion thereof. A few examples will be described below.

FIGS. 2-A and 2-B are for explaining the inclusion of air into the hollow container when the in-mold label is operated in the hollow container having a flat body section. The container 10 in FIG. 2-A is the body
11, a bottom portion 12 connected to the lower end of the body portion 11, a shoulder portion 13 connected to the upper end of the body portion 11, and a neck portion 13a above the shoulder portion.
1 has a flat cross section as shown in FIG. 2-B, and connects the opposite long side wall portions 14 and 14 having a large radius of curvature, the opposite short side wall portions 15 and 15 having a small radius of curvature, and both wall portions. Large curvature corner 1
It consists of 6,16, ... For this hollow container 10,
The label 1 is applied so as to cover most of the long side wall portions 14 and 14 and to extend over the corner portions 16. The label 1 is held on the mold inner surfaces of the split molds 20a, 20b having cavities 21 corresponding to the outer shape of the container 10 so as to correspond to the long side wall portions 14 of the container. The hollow molding parison 22 is inserted and held in the cavity 21 of the split molds 20a and 20b, and the fluid pressure 23 is blown into the parison 22.
Causes the parison 22 to expand. In this case, in response to the flatness of the body portion 11, the parison portion 25 corresponding to the short side wall portion 15 is made thicker than the parison portion 24 corresponding to the long side wall portion 14, and the container is Make sure that the thickness of the body is uniform over the entire circumference. As the fluid is blown into the parison 22, the parison expands to a state shown in 22 ',
First, the central portion of the label 1 and the parison come into close contact with each other, and this close contact gradually spreads from the center of the label 1 to the periphery. When the expansion of the parison portion 25 occurs at a speed faster than this spreading speed, an air pocket 26 is formed between the label corresponding to the corner portion 16 and the vessel wall, which is when the labeled container is taken out of the mold. It becomes blister.

FIGS. 3-A and 3-B show the wrapping of air when operating the in-mold label of a container in which irregularities such as beads for decoration, reinforcement or deformation prevention are formed on the surface of the container body. It is for explanation. This container 10 is the second-A and the second
-Long side wall parts 14,14 and short side wall parts 15,15 as in the container shown in FIG.
With and with concave (convex) beads between them 1
7 and 17 are provided, and the label 1 is these beads 1
It is applied across 7, 17 ... When sticking the label in the mold, since the parison or the wall of the molding being formed and the label are closely contacted with each other over the boundaries 18 between the beads 17, 17, ... An air pocket 26 will also be formed between it and the vessel wall.

FIGS. 4-A and 4-B are for explaining the entrapment of air when operating the in-mold label of a container having a protrusion for decoration such as relief on the surface of the container body. This container
10 is also the long side wall portion, like the container shown in FIGS. 2-A and 2-B.
14 and 14 and the short side wall portions 15 and 15, but the long side wall portion 14 has a relief-like protrusion 19, and the label 1 is attached so as to cover the protrusion 19. It Even in this case, the protrusion
Since the label and the vessel wall are brought into close contact with each other over the boundary portion 18 of 19 and an air pocket 26 is formed between the label and the vessel wall corresponding to the boundary portion 18.

The hole provided in the label completely penetrates from the outer surface of the label toward the inner surface, but at least the inner surface side of the label is substantially closed in the state where pressure is applied,
It is preferably narrowed and has a structure such that the closed portion or the narrowed portion opens when pressure is applied. In FIG. 5 showing an example of such holes, the holes 7 in FIG. 5 are the outer surface 8 to the inner surface 9 of the label 1.
Although it completely penetrates toward, the cross section is Y-shaped and the inner surface side is substantially closed or narrowed in a pressureless state. In FIG. 6 showing another example of the hole, the hole 7 of FIG. 6 also completely penetrates from the outer surface 8 to the inner surface 9 of the label 1, but has a V-shaped cross section. The surface side is closed or narrowed in a pressureless state. Whether or not the holes 7 are substantially closed on the inner surface side of the label can be confirmed by the fact that when the water containing the surfactant is placed on the outer surface side of the label 1, the water does not seep to the inner surface side. The hole with such a valve function has a good appearance and complete prevention of blistering due to the escape of air when attaching the in-mold label, and the labeled container is left for a long time under dew condensation conditions such as refrigeration conditions. In this case, the advantage that the label is completely adhered to the container is provided.

To pierce the label, pierce the needle (needling),
It can be carried out by electric discharge machining or laser beam irradiation, but it is preferably carried out by needling, and it is particularly best carried out by piercing a needle from the outer surface side to the inner surface side of the label. That is, according to this method, not only the holes shown in FIGS. 5 and 6 are easily formed, but also the outer surface side of the label is not roughened, and the appearance characteristics of the label and the appearance of the finger when touched are touched. Excellent in smoothness.

Of course, in the present invention, since the hole 7 is so small that it is difficult to discriminate it with the naked eye, it goes without saying that the hole 7 may be a completely open hole that penetrates the label.

Number 7 showing the diameter (needle diameter) and arrangement of holes 7 provided in the label
In the figure, the hole D is a size that is difficult to discern with the naked eye, and for this purpose, the diameter of the hole 7 or the needle should be 1 mm or less, particularly 0.5 mm or less. In terms of workability, this hole 7
Alternatively, the needle is preferably 0.1 mm or more, particularly 0.2 mm or more. Further, the pitch P between the adjacent holes is such that the air in the label and the container wall can be discharged to the outside without leaving blister, and is generally provided at a pitch P of 1 to 7 mm, particularly 2 to 4 mm. It is preferable. The holes 7 can be arranged in a linear shape, a band shape, or over a certain area in a region where label blisters are likely to occur.

In the case of the labeled container shown in FIGS. 2-A and 2-B,
The holes 7 may be provided in one row or a plurality of rows in a portion 1 to 10 mm, particularly 2 to 6 mm from both ends of the label.
In the case of the labeled container shown in FIGS. A and 3-B, holes may be provided in one or a plurality of rows at the boundary of the concave or protruding ribs 17. The same applies to the case of FIGS. 4-A and 4-B.

In the present invention, it is not absolutely necessary that the position where blisters actually occur in the label when the hole is not provided and the position of the hole provided in the label exactly match. This is because the air entrapped between the label and the vessel wall causes a certain amount of flow even if compressed by the molding pressure applied to the vessel wall, causing air to escape through the holes.

In FIG. 8 which is an enlarged view of the label-attached portion of the labeled container of the present invention, the label 1 is firmly bonded to the container body 11 over its entire surface, but the outer surface 8 of the label 1 and the container body are There is substantially no step between the outer surface 27 and the outer surface 27 other than the label sticking portion, and they are flush with each other. That is,
The edge portion 28 of the label 1 is embedded in the container body portion 11 so as to prevent curling or the like due to stress concentration on the edge portion.

The container 10 is a resin that has already been described for the label film substrate, such as polyolefins, aromatic vinyl polymers,
It can be composed of vinyl halide polymers, nitrile polymers, polyamides, polyesters, polycarbonates, polyacetals and the like. The present invention is applicable to all of these plastic containers, but is particularly easy to apply to polyolefin containers. The container may have a single-layer structure or a multilayer structure. In FIG. 9 showing an example of a multilayer structure of a container, this container 10 is inserted between an oxygen barrier thermoplastic resin intermediate layer 29, moisture resistant thermoplastic resin inner and outer layers 30a and 30b and, if necessary, between both resins. It is composed of adhesive resin layers 31a and 31b.

In this case, the oxygen permeability coefficient (PO ₂ ) is 5.5 × 10 ^-12 cc · cm / cm ² · sec · cmHg (37 ° C,
0% RH) or less, especially 4.5 × 10 ^-12 cc ・ cm / cm ²・ sec ・ cmHg
It is desirable to use the following thermoplastic resins alone or a blend of the resins as the oxygen barrier resin.

The most preferable example of such a resin is an ethylene-vinyl alcohol copolymer, particularly one having a vinyl alcohol unit content of 40 to 85 mol%, particularly 50 to 80 mol%. Such an ethylene-vinyl alcohol copolymer is a combination of ethylene or a majority of ethylene and a minor component of an olefin such as propylene, and a vinyl ester of a low aliphatic acid such as vinyl formate, vinyl acetate and vinyl propionate. It is obtained by saponifying a copolymer, particularly an ethylene-vinyl acetate copolymer, so that the saponification degree is 96% or more, particularly 99% or more.

Other examples of the oxygen barrier resin include nylon resin,
Especially nylon 6, nylon 8, nylon 11, nylon 1
2, Nylon 6,6, Nylon 6,10, Nylon 10,6, or Nylon 6-6,6 copolymer can be mentioned.

Further, high nitrile resin, vinylidene chloride resin, vinyl chloride resin and the like can be used for this purpose.

The oxygen barrier resin can be used in the form of a so-called blend, for example, a blend of an ethylene-vinyl alcohol copolymer and a nylon resin can be used, and further, an ethylene-vinyl alcohol copolymer can be used. Other resins such as polyethylene, ethylene-vinyl acetate copolymer, and blends with ionomers can also be used for this purpose if the oxygen permeability coefficient is within the above range.

As the moisture-resistant thermoplastic resin, olefin-based resins such as low-, medium- or high-density polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer and ionomer are preferably used.

When there is no interlayer adhesion between the oxygen barrier resin and the moisture resistant resin, an adhesive layer is interposed between both resin layers.

As the adhesive resin (C), any resin that exhibits adhesiveness to both the oxygen barrier thermoplastic resin (A) and the moisture resistant thermoplastic resin (B) described above is used.
As the adhesive resin (C), generally, free carboxylic acid, carboxylic acid salt, carboxylic acid ester, carboxylic acid amide, carboxylic acid anhydride, carbonic acid ester, urethane,
Carbonyl group based on functional groups such as urea A thermoplastic polymer containing or a blend of these polymers with another thermoplastic polymer is used. The carbonyl group concentration in these thermoplastic polymers can vary, but generally the carbonyl group content is 10 to 1400 mmol / 100 g.
Polymers, especially those containing a concentration of 30 to 1200 mmol / 100 g polymer, are preferred. Suitable adhesives are polyolefins modified with at least one ethylenically unsaturated monomer of unsaturated carboxylic acids, acid anhydrides, esters, amides, etc., especially maleic acid, acrylic acid, methacrylic acid, crotonic acid. , Fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, ethyl acrylate, methyl methacrylate, ethyl maleate,
2-ethylhexyl acrylate, acrylic acid amide, methacrylic acid amide, coconut oil fatty acid amide, polypropylene modified with maleimide and the like, high density polyethylene, low density polyethylene, ethylene-vinyl acetate copolymer, etc. Examples thereof include acrylate copolymers, ionomers (Surrin A manufactured by DuPont), polyalkylene oxides, polyester block copolymers, carboxymethyl cellulose derivatives, and blends of these with polyolefins. It should be noted that any of these resins having a low carbonyl group content can be used as a moisture resistant resin itself.

The body of the container of the present invention can have a wide range of wall thickness, from a so-called rigid container to a collapsible container, for example, it can generally have a thickness of 0.2 μm to 3.0 mm.

In FIG. 10 for explaining the in-mold label operation, in step A, prior to the blow molding of the plastic parison, the blow split molds 32a, 32b are in an open state, and at least one of these cavity surfaces 33, Label 1 is applied in advance. That is, the cavity surface 33 has a portion for supporting the label 1, and the reduced pressure suction mechanism 34 is provided in this portion, and the label 1 is suctioned to the cavity surface 33.
Held in. In this case, the label has a positional relationship with the plastic inside. The application and fixing of the label 1 to the cavity surface 33 is not limited to suction,
For example, static electricity can be used.

Next, in step B, the molten plastic parison 36 is extruded from the die 35, the blow split molds 32a and 32b are closed, and pressurized gas is blown into the closed parison 36.

In step C, the parison that expands in the mold is held on the mold surface and pressed against the label 1 to bring them into close contact, and the expanded parison comes into contact with the mold surface and is cooled, whereby the labeled container 10 Becomes

Blow molding is performed by any blow molding method such as injection blow, two-stage blow, sheet forming, stretch blow, etc. in addition to the direct blow method using a horizontal rotary blow molding machine or a vertical rotary blow molding machine. be able to.

Of course, it should be understood that the molding of the labeled container of the present invention is not limited to the blow molding described above, and can be naturally applied to, for example, injection molding, vacuum molding, pressure molding, and the like.

(Effect of the invention) According to the present invention, at least a part of the in-mold label sticking label is provided with a large number of small holes which are difficult to be discerned by the naked eye, so that the curvature change portion and the uneven portion of the outer surface of the container Even if air is trapped between the label and the container wall, it is possible to remove the air, eliminate the blister on the label, and improve the appearance characteristics and product value of the labeled container. Became.

[Brief description of drawings]

Figures 1-A, 1-B, 1-C, 1-D, 1-E, 1-F, 1-G and 1-H show examples of the cross-sectional structure of the in-mold label sticking label of the present invention. 2-A and 2-B are a side view and a horizontal cross-sectional view for explaining air entrapment between the label and the container wall in the flat container, and FIGS. 3-A and 3-B are A side view and a horizontal cross-sectional view for explaining the inclusion of air between a label and a container wall in a container having a concave portion, and FIGS. 4-A and 4-B show air between the label and the container wall in a container having a protruding portion. A side view and a horizontal cross-sectional view for explaining the hugging, FIGS. 5 and 6 are cross-sectional views showing an example of the cross-sectional shape of the label holes, and FIG. 7 is a top view showing the arrangement of the label holes. Fig. 8 is an enlarged cross-sectional view of the label sticking part of the label sticking container, Fig. 9 is a cross-sectional view showing the cross-sectional structure of the multi-layered container, and Fig. 10 is an explanation showing the in-mold label sticking process It is a clear view. 1 is a label, 7 is a hole, and 10 is a container.

Claims (2)

[Claims] 1. A label to be bonded to an outer surface of a plastic container by applying an in-mold label, wherein at least an inner surface of the label is formed of a heat-bondable resin, and at least a part of the label has a label By piercing the needle from the outer surface toward the inner surface, the inner and outer portions are formed in a Y-shaped to V-shaped cross-section, have a valve function, and have a size that is difficult to discern with the naked eye. An in-mold label sticking label characterized by having a large number of small holes. 2. A labeled plastic container in which the label according to claim 1 is applied to the outer surface of the body of a plastic container by applying an in-mold label.