JP2007276461A - Heat shrinkable film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat shrinkable film having a pressure-sensitive adhesive layer causing no wrinkle even when a heat shrinkable substrate is heat-shrunk by heating. <P>SOLUTION: The heat shrinkable film of the present invention comprises a pressure-sensitive adhesive layer provided on at least one surface of a heat shrinkable substrate, wherein the pressure-sensitive adhesive layer includes a pressure-sensitive adhesive having a glass transition temperature of -30°C or more and has a preferable thickness of the pressure-sensitive adhesive layer in a range of 0.1 to 20 μm. The heat shrinkable film may also comprise a functional layer disposed on a surface provided with the pressure-sensitive adhesive layer of the heat shrinkable substance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat shrinkable film having an adhesive layer that does not cause wrinkles during heat shrinkage.

  In recent years, heat-shrinkable films using the property of shrinking by heating have been widely used for packaging various containers such as plastic bottles and plastic cases.

  A heat-shrinkable film is made of a heat-shrinkable film and is covered with a container such as a plastic bottle or a plastic case, or attached to a container as an adhesive label, and heat is applied to the container to heat-shrinkable film. Is contracted and brought into close contact with the container.

  In general, such heat-shrinkable films are not only used for packaging containers, but also provide specific functions such as container protection and image printing.

  As such a heat-shrinkable film, for example, a film capable of performing image processing on one side or both sides of a heat-shrinkable base material by offset printing, gravure printing, letterpress printing or the like has been proposed (Patent Document 1). ).

  According to such a printing method, it is suitable for mass production of heat-shrinkable films subjected to the same image processing, but since it must start from the plate making process of the printing plate, It was not very suitable.

  In view of this, a method has been proposed in which image processing is performed by an ink jet recording method that does not require a printing plate as described above and can produce a small variety of products. Such a heat-shrinkable film is certainly suitable for the production of a large variety of small quantities, but it causes new problems.

  That is, an image receiving layer for enabling ink jet printing is required. When the image receiving layer is applied directly to a heat-shrinkable substrate, the heat-shrinkable substrate shrinks due to heat when the image-receiving layer is dried. Therefore, it could not be provided directly. Therefore, after forming the image receiving layer on the separator, the pressure-sensitive adhesive layer is formed, and the pressure-sensitive adhesive layer is bonded to the heat-shrinkable substrate, and then the separator is peeled off to produce.

JP 2005-25145 A

  And when the heat-shrinkable film having the adhesive layer heats the heat-shrinkable film and heat-shrinks the heat-shrinkable substrate, the heat-shrinkable film wrinkles due to the adhesive layer. The image receiving layer existing above was also adversely affected.

  Such a phenomenon is not limited to the above-described image-receiving layer, and the same applies even when a functional layer capable of exhibiting a specific function such as scratch resistance or photocatalytic property is provided on the adhesive layer. Occurred.

  Then, regarding the heat-shrinkable film having the adhesive layer as described above, a heat-shrinkable film that does not cause wrinkles during heat shrinkage has been desired.

  As a result of intensive research to solve the above-mentioned problems, the present inventor does not properly follow the heat-shrinkable base material that causes the wrinkle at the time of heat shrinkage, and the non-shrinkable or hard-to-shrink adhesive layer easily heat shrinks. I found that there was something.

  That is, the pressure-sensitive adhesive layer using the conventional pressure-sensitive adhesive is not shrinkable or hardly shrunk even when heated, but has a strong holding power or tack, so when the heat-shrinkable film is heat shrunk. It was found that the pressure-sensitive adhesive layer was also involved and forcedly contracted, causing wrinkles.

  As a result of further diligent research on this point, the present inventors have determined that the heat-shrinkable substrate is heat-shrinkable because the holding power or tack of the adhesive layer is weakened by using a specific adhesive having a glass transition temperature as the adhesive layer. It was found that even if the adhesive layer was used, the adhesive layer was not involved in shrinkage, and an appropriate shift occurred between the adhesive layer and the heat-shrinkable base material (FIG. 1), thereby preventing wrinkles.

  This invention is made | formed in view of the above-mentioned situation, and it aims at providing the heat-shrinkable film which has the adhesion layer which does not produce a wrinkle at the time of heat shrink.

  That is, the heat-shrinkable film of the present invention has an adhesive layer on at least one surface of a heat-shrinkable substrate, and the adhesive layer has an adhesive having a glass transition temperature of −30 ° C. or higher. It is characterized by including.

  The heat-shrinkable film of the present invention is characterized in that the adhesive layer has a thickness of 0.1 to 20 μm.

  Moreover, the heat-shrinkable film of the present invention is characterized in that a functional layer is provided on the surface of the heat-shrinkable substrate having the adhesive layer.

  Moreover, the glass transition temperature of the binder resin of the functional layer which the heat-shrinkable film of this invention has is 30-150 degreeC, It is characterized by the above-mentioned.

  The functional layer of the heat-shrinkable film of the present invention is an image receiving layer.

  Moreover, the adhesive layer which the heat-shrinkable film of this invention has can be peeled from a heat-shrinkable base material, It is characterized by the above-mentioned. Furthermore, the adhesive force between the pressure-sensitive adhesive layer of the heat-shrinkable film of the present invention and the heat-shrinkable substrate before heat shrinking is 0.01 to 30 N / 25 mm.

  ADVANTAGE OF THE INVENTION According to this invention, the heat-shrinkable film which has an adhesion layer which does not produce a wrinkle at the time of heat shrink can be provided.

  Hereinafter, embodiments of the heat-shrinkable film of the present invention will be described.

  The heat-shrinkable film of the present invention has an adhesive layer on at least one surface of a heat-shrinkable substrate, and the adhesive layer contains an adhesive having a glass transition temperature of −30 ° C. or higher. It is a waste.

  The heat-shrinkable substrate used in the present invention refers to a material that has the ability to shrink by heating, such as olefin resin such as polyethylene or polypropylene, vinyl chloride resin, vinylidene chloride resin, polystyrene resin, polyester resin, polyamide resin, A conventionally known heat-shrinkable substrate obtained by stretching a plastic film made of nylon resin or other resin in at least a uniaxial direction can be used.

  The thickness of the heat-shrinkable substrate is not particularly limited, but is preferably about 10 to 300 μm.

  The heat shrinkage rate of the heat-shrinkable substrate is preferably about 20 to 80% and preferably about 30 to 60% when the heat-shrinkable substrate is shrunk in hot air at 80 ° C. for 10 seconds. More preferred. By setting it to 20% or more, it is possible to prevent problems such as sagging or wrinkling due to failure to follow the shape of the container when mounted on a container such as a PET bottle. Moreover, the deformation | transformation of the container by excessive shrinkage | contraction etc. can be prevented by setting it as 80% or less.

  Further, the shrinkage rate (natural shrinkage rate) of the heat-shrinkable base material in hot air at 40 ° C. in an environment for 7 days is preferably 5% or less, and more preferably 2% or less. By setting it to 5% or less, shrinkage can be prevented during transportation and storage of the heat-shrinkable substrate, and problems such as winding tightness and sagging can be prevented and the commercial value can be remarkably lowered.

  Next, the pressure-sensitive adhesive layer used in the present invention is provided on at least one surface of the heat-shrinkable substrate and contains a pressure-sensitive adhesive having a glass transition temperature of −30 ° C. or higher. In this way, by using an adhesive having a glass transition temperature of −30 ° C. or higher, the adhesive layer can have a lower holding power or tack than an ordinary adhesive layer, and thus the heat-shrinkable substrate is heated. Even if the adhesive layer is contracted, the adhesive layer does not get involved in the contraction, and there is a remarkable effect that a gap occurs between the adhesive layer and the heat-shrinkable base material (FIG. 1), and wrinkles are not generated. Note that the adhesive layer may be provided not only on one surface of the heat-shrinkable film but also on both surfaces.

  The glass transition temperature of the pressure-sensitive adhesive of the present invention is −30 ° C. or higher. By making the glass transition temperature higher than that of a normal pressure-sensitive adhesive in this way, the holding power or tack of the pressure-sensitive adhesive layer can be suppressed weakly, and the generation of wrinkles during heat-shrinking of the heat-shrinkable film is difficult to occur. be able to. From the viewpoint of exhibiting the effects of the present invention more remarkably, it is preferable that the glass transition temperature is preferably in the range of -20 to 0 ° C.

  Examples of the pressure-sensitive adhesive having a glass transition temperature of −30 ° C. or higher include polyester-based pressure-sensitive adhesives, polystyrene-based pressure-sensitive adhesives, olefin-based pressure-sensitive adhesives, and acrylic pressure-sensitive adhesives. Moreover, an acrylic adhesive is used suitably from a viewpoint of transparency and a weather resistance.

  The pressure-sensitive adhesive layer of the present invention is preferably cured from the viewpoint of sufficiently reducing the holding force or tack and reducing the occurrence of wrinkles in the heat-shrinkable film. Regarding the curing method, for example, if the pressure-sensitive adhesive is a thermosetting resin, it can be cured by heating, and if it is an ionizing radiation curable resin, it can be cured by irradiation with ionizing radiation. Further, in order to sufficiently cure the adhesive layer, a curing agent or a crosslinking agent may be separately contained in the adhesive layer. Examples of the curing agent and the crosslinking agent include isocyanate compounds, epoxy compounds, metal chelate compounds, metal salts, amine compounds, hydrazine compounds, and aldehyde compounds.

  Further, the adhesive layer of the present invention includes a saturated polyester, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinylidene chloride copolymer, polyvinyl pyrrolidone, polyvinyl alcohol, nitro, as long as the function as an adhesive layer is not impaired. Cellulose, other cellulose derivatives, polyamide polyester resins, acrylic resins, acrylic urethane resins, polyester acrylate resins, polyurethane acrylate resins, epoxy acrylate resins, urethane resins, epoxy resins, polycarbonate resins, melamine resins Conventionally known resins such as thermoplastic resins such as phenolic resins and silicone resins, thermosetting resins, and ionizing radiation curable resins can be contained.

  The content of the pressure-sensitive adhesive having a glass transition temperature of −30 ° C. or higher in the pressure-sensitive adhesive layer of the present invention is preferably 70% by weight or more and 90% by weight or higher from the viewpoint of sufficiently exerting the effects of the present invention. More preferably.

  Furthermore, in the adhesive layer, if necessary, a tackifier, an acid proliferating agent, a diluent solvent, a filler, a colorant, a matting agent, a slipper, an antistatic agent, a flame retardant, an antibacterial agent, an antifungal agent, and an ultraviolet ray. Absorbers, light stabilizers, antioxidants, plasticizers, leveling agents, pigment dispersants, flow regulators, antifoaming agents, and the like can be included.

  The thickness of the adhesive layer is preferably 0.1 to 20 μm, and more preferably 5 to 15 μm. Adhesive performance can be made sufficient by setting it as 0.1 micrometer or more. Further, when the thickness is 20 μm or less, the holding force or tack can be sufficiently weakened.

  In addition to providing a functional layer as described later on the adhesive layer, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyethylene, polypropylene, polystyrene, triacetyl cellulose, acrylic, polyvinyl chloride, norbornene compound, etc. There is no problem even if a conventionally known plastic substrate such as the above or a heat-shrinkable substrate as described above is provided.

  Next, a functional layer is formed as needed on the adhesion layer formed on the heat-shrinkable base material. In the present invention, since the heat-shrinkable film does not cause wrinkles during heat shrinkage, there is a remarkable effect that even if a functional layer is formed on the adhesive layer, the function of the functional layer is not inhibited. Demonstrated.

  The functional layer refers to a layer that can exhibit a specific function, and examples thereof include a hard coat layer, an image receiving layer, a photocatalyst layer, and a light diffusion layer.

  The hard coat layer exhibits a surface protecting function and contributes to strengthening the protection of the container. Such a hard coat layer can be obtained by coating a composition containing an ionizing radiation curable resin as a main component and irradiating with ionizing radiation to cure by crosslinking.

  As the ionizing radiation curable resin, a photopolymerizable prepolymer that can be crosslinked and cured by irradiation with ionizing radiation (ultraviolet ray or electron beam) can be used. An acrylic prepolymer having at least one acryloyl group and having a three-dimensional network structure by crosslinking and curing is particularly preferably used.

  As this acrylic prepolymer, urethane acrylate, polyester acrylate, epoxy acrylate, melamine acrylate and the like can be used.

  These can be used alone, but it is preferable to add a photopolymerizable monomer, a photopolymerization initiator, an ultraviolet sensitizer, etc., in order to further improve the crosslinkability and the hardness of the crosslinked cured coating film.

  Photopolymerizable monomers include trimethylolpropane trimethacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, neopentyl glycol diacrylate, tripropylene glycol triacrylate, diethylene glycol diacrylate, 1, A polyfunctional monomer such as 6-hexanediol diacrylate is exemplified.

  Examples of the photopolymerization initiator include acetophenone, benzophenone, Michler's ketone, benzoin, benzylmethyl ketal, benzoylbenzoate, α-acyloxime ester, thioxanthone, and the like, and examples of the ultraviolet sensitizer include n-butylamine, triethylamine, tri- and n-butylphosphine.

  The image receiving layer plays an important role in providing a decorative effect to a container such as a plastic bottle or forming an image that contributes to distinguishability from other companies' products. Since the image receiving layer is formed on the adhesive layer, it is very susceptible to wrinkles generated during heat shrinkage of the heat shrinkable film. However, according to the heat-shrinkable film of the present invention, wrinkles do not occur even at the time of heat-shrinking, so that a remarkable effect of not affecting the visibility of the image formed on the image receiving layer is exhibited. .

  As the image receiving layer, conventionally known ones can be used. Examples of such a layer include polyamide, polyacrylamide, polyvinylpyrrolidone, polyethyleneimine, polyvinylpyridium halide, melamine resin, polyurethane, carboxymethylcellulose, hydroxyethylcellulose, Hydrophilic synthetic polymers such as hydroxymethylcellulose, polyvinyl alcohol, polyester, sodium polyacrylate, and hydrophilic natural polymers such as gelatin, starch, cellulose derivative cellulose, casein, chitin, and chitosan, polyethylene oxide and copolymers thereof Super absorbent resin, polyvinyl butyral, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, acrylic resin, epoxy resin, polycarbonate DOO resins, phenol resins and the like.

  The above-described resin used as the image receiving layer may be crosslinked and cured with a phenol resin, an epoxy resin, a melamine resin, an isocyanate compound, a dialdehyde compound, or the like. By crosslinking and curing, the image-receiving layer can have good water resistance and chemical resistance.

  Further, a pigment may be contained in the image receiving layer in order to improve ink absorbability or prevent blocking. In addition to inorganic pigments such as silica, clay, talc, calcium carbonate, calcium sulfate, barium sulfate, aluminum silicate, titanium oxide, synthetic zeolite, alumina, smectite, styrene resin, urethane resin, benzoguanamine resin, silicone resin, Organic pigments such as resin beads made of acrylic resin or the like, or hollow resin beads made of these as raw materials can be mentioned, and these can be used alone or in admixture of two or more.

  The addition amount of the pigment is usually about 0.1 to 200 parts by weight with respect to 100 parts by weight of the total binder resin in the image receiving layer.

  In the image receiving layer, additives such as a leveling agent, an ultraviolet absorber, an antioxidant and a chelating agent may be added.

  The surface of the photocatalyst layer is highly hydrophilic, making it very easy to get wet with water, and exhibiting properties that make it difficult to get dirt, such as dust. A function called so-called self-cleaning, which is washed away, is exhibited and consists of a photocatalyst and a binder.

  Examples of the photocatalyst include anatase type titanium oxide, rutile type titanium oxide, brookite type titanium oxide, zinc oxide, tin oxide, ferric oxide, dibismuth trioxide, tungsten trioxide, strontium titanate and the like. Among these, anatase type titanium oxide is preferably used.

  It is preferable that the binder is mainly composed of an inorganic binder. As this inorganic binder, a binder made of a silicon compound, a binder made of a zirconium compound, a binder made of an aluminum compound, and a binder made of a titanium compound can be used. Among these binders, from the viewpoint of improving the high ultraviolet transmittance, low haze, and adhesiveness with the pressure-sensitive adhesive layer, the binder is preferably made of a silica-based or silicone-based binder.

  Examples of the binder composed of such a silicon compound include hydrolyzable silane derivatives, hydrolyzable silane derivative partial hydrolysates and dehydration polycondensates, or hydrolyzed silane derivative partial hydrolysates and tetramethoxysilane, Those prepared by dehydration condensation polymerization with a partial hydrolyzate such as tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, diethoxydimethoxysilane, or a silicone resin can be used.

  The light diffusion layer exhibits a function of diffusing light, and is mainly composed of a light diffusing agent and a binder resin.

  As light diffusing agents, extender pigments such as calcium carbonate, magnesium carbonate, barium sulfate, silica, aluminum hydroxide, kaolin, clay, talc, acrylic resin particles, polystyrene resin particles, polyurethane resin particles, polyethylene resin particles, benzoguanamine resin Examples thereof include synthetic resin particles such as particles and epoxy resin particles, and particle waxes such as hydrocarbon wax, fatty acid wax, and fatty acid amide wax.

  As binder resins, polyester resins, acrylic resins, polyester acrylate resins, polyurethane acrylate resins, epoxy acrylate resins, cellulose resins, acetal resins, vinyl resins, polyethylene resins, polystyrene resins, polypropylene resins Resin, polyamide resin, polyimide resin, melamine resin, phenolic resin, silicone resin, resin having optical transparency such as thermoplastic resin, thermosetting resin, ionizing radiation curable resin, etc. Is mentioned.

  The thickness of these functional layers is properly used depending on the application, but is usually in the range of 0.1 to 50 μm.

  Moreover, it is preferable that it is 30-150 degreeC, and, as for the glass transition temperature of the binder resin of a functional layer, it is more preferable that it is 50-100 degreeC. By setting the glass transition temperature to 30 ° C. or higher, stickiness and the like can be eliminated and workability can be improved. Moreover, by making glass transition temperature 150 degrees C or less, followable | trackability with an adhesion layer can be made favorable and it can prevent that peeling of a functional layer, etc. arise.

  The heat-shrinkable film of the present invention is obtained by applying a coating solution for an adhesive layer obtained by dissolving a material constituting the adhesive layer in a separator in a suitable solvent, for example, a bar coater, a blade coater, a spin coater, It is obtained by applying and drying by a roll coater, gravure coater, flow coater, spray, screen printing, etc., and then bonding to a heat-shrinkable substrate and peeling the separator.

  In addition, in the case of having a functional layer, a functional layer coating solution obtained by dissolving the material constituting the functional layer in the separator in an appropriate solvent is applied and dried by the above-described conventionally known method, Furthermore, after apply | coating and drying the coating liquid for adhesion layers which dissolves the material which comprises the adhesion layer in a suitable solvent, it bonds together to a heat-shrinkable base material, and is obtained by peeling a separator.

  Moreover, as for the heat-shrinkable film of this invention, it is more preferable that the adhesion layer mentioned above can peel from a heat-shrinkable base material before a heating. When the heat-shrinkable film of the present invention is put on a container such as a PET bottle and heated, not only the heat-shrinkable base material of the heat-shrinkable film but also the pressure-sensitive adhesive layer itself constitutes the pressure-sensitive adhesive layer. The resin may shrink due to the influence of the resin component. Then, due to the heat shrinkage of the adhesive layer itself, the adhesive layer cannot follow the shape at the part where the external shape change of the container such as the vicinity of the tip of the PET bottle is severe, and the heat shrinkable film may be wrinkled. is there.

  In general, it is difficult to design the container to follow the container completely without causing wrinkles. However, in the heat-shrinkable film of the present invention, the pressure-sensitive adhesive layer can be peeled off from the heat-shrinkable base material. By peeling off, the generation of wrinkles of the heat-shrinkable film, which has been a problem in the past, can be prevented in advance.

  Furthermore, even when the functional layer described above is laminated on the adhesive layer, the functional layer itself is thermally contracted by heating due to the influence of the resin component constituting the functional layer, and follows in a portion where the external shape change of the container is severe. Without shrinkage, the heat shrinkable film may wrinkle. And the function with which a functional layer is originally provided may not fully be exhibited by the influence of the wrinkle resulting from the resin component of the said functional layer. Also in this case, the heat-shrinkable film of the present invention has a pressure-sensitive adhesive layer and a functional layer corresponding to a portion where the external shape change of the container is severe before heating because the pressure-sensitive adhesive layer can be peeled off from the heat-shrinkable substrate. By peeling from the heat-shrinkable substrate, it is possible to prevent the occurrence of wrinkles in the heat-shrinkable film and the functional deterioration of the entire functional layer.

  In the case where the functional layer is an image receiving layer, when a resin such as polyvinyl alcohol or polyurethane is used, the generation of wrinkles and the deterioration of the function are particularly noticeable in a portion where the external shape change of the container is severe. However, according to the heat-shrinkable film of the present invention, it is possible to remarkably prevent the occurrence of wrinkles and the functional deterioration of the entire functional layer when such a resin is used.

  In the heat-shrinkable film of the present invention, the adhesive force between the adhesive layer and the heat-shrinkable substrate before heat shrinking is preferably 0.01 to 30 N / 25 mm, and 0.05 to 10 N / 25 mm. It is more preferable. When the adhesive force between the pressure-sensitive adhesive layer and the heat-shrinkable substrate is 0.01 N / 25 mm or more, the pressure-sensitive adhesive layer and the heat-shrinkable substrate can be bonded to such an extent that they do not easily fall off. Moreover, when the adhesive force between the adhesive layer and the heat-shrinkable substrate is 30 N / 25 mm or less, the adhesive layer can be peeled from the heat-shrinkable substrate without any influence such as cohesive failure. In addition, when a functional layer or a substrate is formed on the adhesive layer, the adhesive force between the adhesive layer and the functional layer is stronger than the adhesive force between the adhesive layer and the heat-shrinkable substrate. Cost.

  As the pressure-sensitive adhesive in the pressure-sensitive adhesive layer for obtaining the above-mentioned desired adhesive force, since it depends on the type of the heat-shrinkable substrate that is in close contact with the pressure-sensitive adhesive layer, it cannot be said unconditionally. It is preferable to use a polyester pressure sensitive adhesive or an acrylic pressure sensitive adhesive.

  For the method of peeling the adhesive layer from the heat-shrinkable substrate, for example, cut the adhesive layer with a cutter, knife, etc. so that the part to be removed can be peeled off, such as the part where the external shape change of the container is severe. The pressure-sensitive adhesive layer can be peeled and removed by putting it in place and sticking a pressure-sensitive adhesive tape on the part to be peeled and removed.

  In the heat-shrinkable film thus obtained, the pressure-sensitive adhesive layer on at least one surface of the heat-shrinkable substrate contains a pressure-sensitive adhesive having a glass transition temperature of −30 ° C. or higher. However, wrinkles are not generated in the heat-shrinkable film. Therefore, it can be suitably used for various containers such as PET bottles and bottles, and various lighting devices such as fluorescent lamps and incandescent lamps.

  The following examples further illustrate the present invention. “Parts” and “%” are based on weight unless otherwise specified.

1. Production of heat-shrinkable film [Example 1]
An image-receiving layer coating solution having the following composition is applied to a separator having a thickness of 50 μm and dried at 110 ° C. for 5 minutes to form an image-receiving layer having a thickness of 20 μm. The coating solution was applied and dried at 110 ° C. for 5 minutes to form an adhesive layer having a thickness of 10 μm.

<Coating liquid for image receiving layer of Example 1>
・ 20 parts of polyvinyl butyral (S-REC BM-S: Sekisui Chemical Co., Ltd., glass transition temperature 60 ° C.)
・ Methyl ethyl ketone 40 parts ・ Toluene 40 parts

<Coating liquid for adhesive layer of Example 1>
-20 parts acrylic adhesive (Rikabond AP360A: Chuo Rika Kogyo Co., Ltd., solid content 50%, glass transition temperature -11 ° C)
・ Epoxy hardener 1 part (Rikabond EX-8: Chuo Rika Kogyo Co., Ltd., solid content 55%)

  Next, the separator having the image-receiving layer and the adhesive layer produced as described above on one surface of a heat-shrinkable base material (space clean: Toyobo Co., Ltd.) having a thickness of 60 μm is combined with the adhesive layer and the heat-shrinkable base material. And the separator were peeled off to produce the heat-shrinkable film of Example 1.

[Example 2]
Example 1 except that the acrylic adhesive was changed to an acrylic adhesive (Rikabond AP368A: Chuo Rika Kogyo Co., Ltd., solid content 50%, glass transition temperature −11 ° C.) in the coating liquid for the adhesive layer of Example 1. Similarly, the heat-shrinkable film of Example 2 was produced.

[Example 3]
A heat-shrinkable film of Example 3 was produced in the same manner as in Example 1 except that the adhesive layer coating solution of Example 1 was changed to an adhesive layer coating solution having the following formulation.

<Coating liquid for adhesive layer of Example 3>
-11 parts polyester adhesive (Byron 55SS: Toyobo Co., Ltd., solid content 35%, glass transition temperature -17 ° C)
・ Isocyanate curing agent 1 part (Takenate D110N: Mitsui Chemicals Polyurethanes, 60% solid content)

[Example 4]
A heat-shrinkable film of Example 4 was produced in the same manner as in Example 1 except that the thickness of the adhesive layer of Example 1 was changed to 25 μm.

[Comparative Example 1]
Instead of the adhesive layer coating solution of Example 1, an acrylic adhesive (SK Dyne E-03H: Soken Chemical Co., Ltd., solid content 62%, glass transition temperature -58 ° C.) was directly applied to form an adhesive layer. A heat-shrinkable film of Comparative Example 1 was produced in the same manner as Example 1 except for the above.

[Comparative Example 2]
Instead of the adhesive layer coating solution of Example 1, an acrylic adhesive (SK Dyne EW2500: Soken Chemical Co., Ltd., solid content 49%, glass transition temperature -65 ° C.) was directly applied to form an adhesive layer. A heat-shrinkable film of Comparative Example 2 was produced in the same manner as Example 1.

[Comparative Example 3]
Instead of the adhesive layer coating solution of Example 1, an acrylic adhesive (SK Dyne E-1000: Soken Chemical Co., Ltd., solid content 60%, glass transition temperature -46 ° C.) was directly applied to form an adhesive layer. A heat-shrinkable film of Comparative Example 3 was produced in the same manner as Example 1 except for the above.

2. Evaluation The heat-shrinkable films obtained in the examples and comparative examples were evaluated as follows. The evaluation results are shown in Table 1.

  Inkjet printing was performed on the surface having the image receiving layer of the heat-shrinkable film using an inkjet printer (SOLJET SC-540: Roland DG). Thereafter, a heat-shrinkable film was wound into a cylindrical shape for a shrinkable label, and then covered with a 500 ml PET bottle, heated at 80 to 110 ° C., and adhered to the PET bottle.

(1) Existence of wrinkles Visually check the heat-shrinkable film in close contact with the PET bottle. What was doing was evaluated as "x".

(2) Image visibility The heat-shrinkable film in close contact with the PET bottle is visually confirmed, and “○” indicates that the image visibility is not affected. Those that slightly affected the property were evaluated as “Δ”.

  The heat-shrinkable films of Examples 1 to 3 have a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive having a glass transition temperature of −30 ° C. or higher on one surface of the heat-shrinkable substrate. Was within the range of 0.1 μm to 20 μm, so that even when heat-shrinked by heating, wrinkles were not generated, and the image visibility of the image receiving layer was not affected.

  Further, the heat-shrinkable film of Example 4 had a glass transition temperature of −30 ° C. or higher of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, but because the thickness of the pressure-sensitive adhesive layer was 25 μm, in the vicinity of the tip of the PET bottle, The shape of the tip portion could not be completely followed and a slight wrinkle occurred. On the other hand, the visibility of the image was not affected at all.

  On the other hand, since the heat-shrinkable films of the comparative examples all had a glass transition temperature of −30 ° C. or lower of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, The wrinkles were generated in the vicinity of the tip of the PET bottle without causing a gap between the layers of the photosensitive base material, and the visibility of the image of the image receiving layer was affected.

[Example 5]
For the heat-shrinkable film produced in Example 1, the image receiving layer and the adhesive layer were cut with a cutter so that the portion corresponding to the tip of the PET bottle could be peeled before heating, and the portion When cellophane adhesive tape is affixed to and peeled off, peeling occurs at the interface between the heat-shrinkable substrate and the adhesive layer, and the image receiving layer and adhesive layer corresponding to the tip of the PET bottle are peeled and removed. We were able to. After that, the heat-shrinkable film was put on a PET bottle and heat-shrinked by heating, but wrinkles did not occur as a whole heat-shrinkable film, and it has no influence on the image visibility of the image receiving layer did not become. The adhesive force between the heat-shrinkable substrate and the pressure-sensitive adhesive layer before heat shrinking was 7.00 N / 25 mm.

The state diagram showing the gap between the layers at the time of heat shrink of the heat shrinkable film of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Heat-shrinkable base material 2 ... Adhesive layer 3 ... Deviation

Claims (7)

  A heat-shrinkable film having an adhesive layer on at least one surface of a heat-shrinkable substrate, wherein the adhesive layer contains an adhesive having a glass transition temperature of −30 ° C. or higher. Shrink film.   The heat-shrinkable film according to claim 1, wherein the adhesive layer has a thickness of 0.1 to 20 μm.   The heat-shrinkable film according to claim 1 or 2, wherein a functional layer is provided on the surface of the heat-shrinkable substrate having an adhesive layer.   The heat-shrinkable film according to claim 3, wherein the binder resin of the functional layer has a glass transition temperature of 30 to 150 ° C.   The heat-shrinkable film according to claim 3 or 4, wherein the functional layer is an image receiving layer.   The heat-shrinkable film according to any one of claims 1 to 5, wherein the adhesive layer is peelable from the heat-shrinkable substrate.   The heat-shrinkable film according to claim 6, wherein the adhesive force between the pressure-sensitive adhesive layer and the heat-shrinkable substrate before heat shrinking is 0.01 to 30 N / 25 mm.

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