JP4578307B2 - Thermal label - Google Patents

Description

  The present invention relates to a thermal label attached to a container or the like, and more particularly to a thermal label using an emulsion type thermal adhesive.

  Tack labels are used as labels to be attached to polyethylene terephthalate containers (so-called PET bottles), plastic containers such as polypropylene and polyethylene, and glass bottles. In this label, the adhesive layer is used until the label is attached to the container. In addition to the need for a release paper for protection, the release paper is expensive, and since the release paper is thick, the number of labels per roll that can be installed on the labeler is limited, resulting in reduced work efficiency. In addition, there is a problem that the release paper becomes industrial waste after use. Therefore, heat-sensitive labels are widely used as labels that do not require such release paper.

On the other hand, the heat-sensitive label before being attached to the container is usually stored by wrapping or stacking the label, but stickiness occurs during long-term storage, the handling property is inferior, and the workability of attaching to the container is remarkable. There was a problem of being damaged. In order to deal with the above problem, a method for imparting anti-blocking property by adding an additive effective for anti-blocking to the adhesive of the heat-sensitive label has been attempted. For example, Japanese Patent Application Laid-Open No. 6-179855 discloses a plasticizer. JP-A-62-2835 discloses a heat-sensitive adhesive with a lubricant added thereto. However, an adhesive to which the above additives are added is not preferable because the adhesive strength is reduced or the film strength is weak and causes a residue of adhesive.
JP-A-6-179855 Japanese Examined Patent Publication No. 62-21835

An object of the present invention is to provide a heat-sensitive label and a container with a label that have excellent blocking resistance, have good labeler aptitude, are less likely to have adhesive residue at the time of peeling, and can be manufactured at low cost with few steps. .
Another object of the present invention is to provide a heat-sensitive label and a container with a label that are excellent in low-temperature tackiness in addition to the above properties and are less likely to deteriorate with time such as a decrease in adhesive strength.
Still another object of the present invention is to provide a thermosensitive label and a labeled container that are excellent in transparency and decorating properties.

  As a result of earnest studies to achieve the above object, the present inventors can improve the blocking resistance without reducing the adhesive strength by using an emulsion-type heat-sensitive adhesive having a specific configuration, In addition, the present inventors have found that a heat-sensitive label that does not easily deteriorate with time and does not leave adhesive residue at the time of peeling can be obtained at low cost.

That is, the present invention is a label in which an adhesive layer is formed on at least the surface of the substrate that is in contact with the adherend, and the adhesive layer has an ethylene content of 66 to 90% by weight. , An ethylene copolymer having a melting point of 60 to 90 ° C., and 10 to 30% by weight of a tackifier in the total solid content, and the content of the solid plasticizer and the lubricant with respect to the total solid content It is formed by applying an emulsion-type heat-sensitive adhesive that is 3% by weight or less and drying, and the average roughness (Ra) of the surface of the adhesive layer based on unevenness caused by the resin particles of the emulsion is 0.3 μm or more. Provide a thermal label. The present invention also provides a labeled container equipped with the thermosensitive label of the present invention. In the present specification, in addition to the above-described invention, a label in which an adhesive layer is formed on at least the surface of the substrate that contacts the adherend, and the adhesive layer is an emulsion-type heat-sensitive adhesive A thermal label having an average roughness (Ra) on the surface of the adhesive layer of 0.3 μm or more, and a labeled container on which multiple thermal labels are mounted will be described.

  The heat-sensitive label of the present invention is less likely to block during label storage, is excellent in labeler suitability, and can be adhered to the adherend with sufficient strength, so that no adhesive residue remains on the adherend after use. Can be peeled off. Moreover, since an adhesive bond layer can be formed in the same process as printing, a label can be manufactured at low cost.

  In the present invention, the average roughness (Ra) means the surface roughness measured according to JIS B 0601-1994.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the thermal label of the present invention. In the thermosensitive label 1 of FIG. 1, a printing layer 3 and an adhesive layer 4 are laminated in this order on one side of a label substrate 2. The heat-sensitive label of the present invention is preferably used as a wound heat-sensitive adhesive label that is attached to a container by winding. In the heat-sensitive label of the present invention, the printing layer 3 is not necessarily provided.

  The heat-sensitive label 1 of the present invention is mainly characterized in that the adhesive layer 4 is formed of an emulsion-type heat-sensitive adhesive, and the average roughness (Ra) of the surface of the adhesive layer 4 is 0.3 μm or more. Yes. Since the adhesive layer 4 in the present invention is formed of an emulsion-type heat-sensitive adhesive that is a dispersion in which a polymer component (solid content) is dispersed in a liquid form, the adhesive coating surface is caused by particles. It has minute unevenness. Since Ra on the surface of the adhesive layer 4 serving as an index of the unevenness is in the above range, blocking can be prevented and the efficiency of the sticking work by the labeler can be improved. The Ra can be controlled by appropriately selecting the composition of the adhesive forming the adhesive layer, the drying conditions after applying the adhesive, and the like.

The anti-blocking property is obtained, for example, by overlapping the surface of the label on the adhesive layer 4 side and the surface of the label base 2 and applying a pressure of about ² kg / cm ² (196 kPa), for example, in an atmosphere of 40 ° C. The sample stored for 24 hours can be evaluated as the adhesive strength to plastic by a test according to JIS K 6854-3 (T-type peeling) (peeling speed 200 mm / min). The adhesive strength of the adhesive layer 4 based on the above method to the plastic is, for example, less than 0.1 N / 15 mm. When the adhesive strength is 0.1 N / 15 mm or more, the anti-blocking property is inferior, so that stickiness tends to occur when the labels are wound or stacked, and the labeling suitability at the time of labeling is poor.

  The labeler suitability can be evaluated by a static friction coefficient between the label substrate 2 and the adhesive layer 4 by a test according to JIS K 7125. The static friction coefficient between the label substrate 2 and the adhesive layer 4 is, for example, 0. Is less than 5. When the coefficient of static friction is 0.5 or more, the overlapping labels are difficult to slip, and the labeler suitability tends to be reduced.

  The label substrate 2 can be appropriately selected in consideration of heat resistance, handleability, printability, etc., but a transparent substrate is preferable in that the printed layer 3 provided on the back side of the label substrate 2 can be seen. For example, a plastic film is used. Examples of the plastic film include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); polyolefin resins such as polyethylene and polypropylene; and styrene-butadiene copolymers. Examples thereof include films made of polystyrene resin; polyvinyl chloride resin, polyvinylidene chloride resin and the like. For the label base material of the wound heat-sensitive adhesive label, an unstretched film or a biaxially stretched film that is a non-heat-shrinkable film made of the above-described resin is preferably used, and in particular, a biaxially stretched polypropylene film (OPP) and PET films are used. These materials can be used alone or in admixture of two or more. The label substrate 2 may be a single layer or a laminate of two or more layers.

  The thickness of the label substrate 2 can be appropriately selected within the range not impairing the mechanical strength, the handleability of the label, etc. The thickness of the label substrate of the wound heat-sensitive adhesive label is, for example, about 5 to 50 μm, preferably 8 to It is about 40 μm.

  The stretching treatment is carried out using a tenter method, a tube method, or the like, for example, at a temperature of about 70 to 230 ° C., and 2.0 to 8.0 times in one direction (for example, the longitudinal direction; MD direction), preferably 3 In the case of biaxial stretching in the range of about 5 to 5.5 times, the film is further stretched in the other direction (for example, transverse direction; TD direction) by 2.0 to 8.0 times, preferably about 3.5 to 5.5 times. Is done. In addition, when using as a non-heat-shrinkable film, heat setting is performed after extending | stretching.

  In the case of a non-heat-shrinkable film, the label substrate 2 has a heat shrinkage rate of less than 5%, preferably less than 2% in both the MD direction and the TD direction under conditions of a glycerin bath at 100 ° C. for 5 seconds. That is, in the case of a biaxially stretched film, in any direction subjected to stretching treatment, it is less than 5%, preferably less than 2% under the conditions of a glycerin bath at 100 ° C. for 5 seconds. If the heat shrinkage rate is 5% or more, the label may shrink due to heat at the time of sticking, and wrinkles or misalignment may occur.

  The printing layer 3 is a layer in which a trade name, an illustration, handling precautions, and the like are printed and displayed by a known printing method such as letterpress printing, silk screen printing, and gravure printing. In the present invention, gravure printing is preferably used in that the printing layer 3 and the adhesive layer 4 can be formed in one step, the printing speed is high, and the production efficiency can be improved. The printing ink used for forming the printing layer 3 is, for example, an ink mainly composed of an acrylic resin, a polyurethane resin, or a mixture thereof so as not to be damaged by heat when the adhesive layer 4 is activated. It is preferable to use an ink in consideration of the heat resistance.

  In addition, in order to improve the adhesiveness with respect to the label base material 2 of the printing layer 3, you may provide a primer coat layer between the said 2 layers. The primer coat layer can be formed of a known primer such as an acrylic primer, a polyester primer, an isocyanate primer (two-component mixed primer, etc.), and the like. The thickness of a primer coat layer can be suitably selected in the range which does not impair transparency, the handleability of a label, etc., for example, is about 0.3-1.5 micrometers.

  The adhesive layer 4 is composed of an emulsion type heat sensitive adhesive. Emulsion-type heat-sensitive adhesive is an adhesive that does not exhibit tackiness at room temperature after application and drying, but develops tackiness upon heating, and contains a base polymer and a tackifier as constituent components. It is out. Since the adhesive layer is composed of an emulsion-type heat-sensitive adhesive, no release paper is required. Moreover, the emulsion-type heat-sensitive adhesive in the present invention is preferably substantially free of a solid plasticizer and a lubricant. Here, “substantially free of solid plasticizer” means that the content of the solid plasticizer and the lubricant is 3% by weight or less, preferably 1% by weight or less, based on the total solid content of the adhesive. Means. By substantially not including a solid plasticizer and a lubricant, it is possible to suppress deterioration with time of adhesive strength and transparency. Further, it is possible to avoid problems such as a decrease in film strength of the adhesive layer due to a solid plasticizer or a lubricant, and adhesive residue.

  As the base polymer, a conventional thermoplastic resin constituting a heat-sensitive adhesive can be used. For example, an ethylene copolymer, an acrylic polymer, a polyurethane polymer, a vinyl acetate polymer, a styrene polymer Conventional thermoplastic resins such as polymers can be used. Among these, an ethylene copolymer, an acrylic polymer, and a polyurethane polymer are preferable, and an ethylene copolymer is particularly preferably used. These base polymers may be used alone or in combination of two or more.

  Examples of the ethylene copolymer include ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid copolymer (EAA), ethylene-methacrylic acid copolymer (EMAA), and ethylene-ethyl acrylate. Examples thereof include ethylene-acrylic acid ester copolymers such as a copolymer (EEA) and ethylene-methacrylic acid ester copolymers such as an ethylene-methyl methacrylate copolymer (EMMA). Of these, EVA copolymers are preferably used. These can be used alone or in combination of two or more.

  Examples of the acrylic polymer include (meth) acrylic acid such as poly (meth) acrylic acid ester, styrene- (meth) acrylic acid ester copolymer, vinyl acetate- (meth) acrylic acid ester copolymer, or ( Examples thereof include polymers containing a meth) acrylic acid alkyl ester as a monomer component. The acrylic polymer can be used alone or in combination of two or more polymers having different monomer compositions.

  As the polyurethane polymer, known polyurethane polymers such as polyether polyurethane and polyester polyurethane can be used. Polyurethane polymers can be used alone or in combination of two or more.

  The tackifier exhibits an effect of improving adhesiveness. For example, rosin resin (rosin, polymerized rosin, hydrogenated rosin and derivatives thereof, resin acid dimer, etc.), terpene resin (terpene resin, aromatic modification) Terpene resin, hydrogenated terpene resin, terpene-phenol resin, etc.), petroleum resin (aliphatic, aromatic, alicyclic), coumarone-indene resin, styrene resin, phenol resin and the like. Of these, rosin resins and terpene resins are preferable, and terpene resins such as hydrogenated terpene resins are particularly preferable. A tackifier can be used individually or in combination of 2 or more types.

  The emulsion-type heat-sensitive adhesive may further contain an auxiliary agent. For example, when the base polymer is an ethylene copolymer, the auxiliary agent is composed of an acrylic resin or a polyurethane resin. These resins that make up the auxiliary agent are not themselves adhesive or tacky, they are also used as coating agents, and can be added to the adhesive layer to improve the film strength and at the time of peeling. Can prevent adhesive residue.

  As the acrylic resin, a known acrylic resin can be used, but an acrylic resin having a glass transition temperature (Tg) of 0 to 60 ° C. is preferably used. When the acrylic resin has a Tg of less than 0 ° C., the effect of improving the film strength due to the addition is hardly obtained. When the Tg exceeds 60 ° C., it is not preferable because a small amount of use tends to cause a decrease in adhesive strength. Acrylic resins can be used alone or in combination of two or more resins having different monomer compositions. The usage-amount of acrylic resin is 0.5-10 weight part with respect to 100 weight part of total amounts of a base polymer and a tackifier, Preferably it is about 0.5-5 weight part.

  As the polyurethane resin, known polyurethane resins can be used, and those having a thermal fluidity starting temperature (conforming to JIS K 7210-1976) of about 40 to 100 ° C. are preferably used. When the auxiliary agent is a polyurethane resin, the weight average molecular weight (Mw) of the polyurethane resin is preferably about 200 to 900. If Mw is too low, the blocking resistance is inferior, and adhesive residue due to a decrease in film strength is likely to occur. If Mw is too high, the adhesive force tends to decrease. Polyurethane resins can be used alone or in combination of two or more resins. The usage-amount of a polyurethane resin is 5-60 weight part with respect to 100 weight part of total amounts of a base polymer and a tackifier, Preferably it is about 30-60 weight part.

  As an auxiliary agent, an acrylic resin or a polyurethane resin may be used alone, or both may be used in combination.

As an example of a preferable adhesive layer in the present invention, an ethylene copolymer having an ethylene content of 66 to 90% by weight and a melting point of 60 to 90 ° C., and 10 to 30% by weight in the total solid content And an adhesive layer formed of an emulsion-type heat-sensitive adhesive containing a tackifier. According to such an adhesive layer can exhibit an excellent low-temperature tackiness and blocking resistance.

  In any case where the ethylene content of the ethylene copolymer is less than 66% by weight or more than 90% by weight, the low-temperature tack property tends to be remarkably lowered, and preferably about 66 to 90% by weight. Moreover, when the melting point of the ethylene copolymer is less than 60 ° C., the blocking resistance tends to be inferior, and when it exceeds 90 ° C., the temperature (activation temperature) that causes the adhesive layer 4 to become sticky is likely to increase, It becomes easy to damage an adherend and a label base material at the time of conversion. The melting point is preferably about 70 to 85 ° C.

  When the content of the tackifier is less than 10% by weight or more than 30% by weight, the low-temperature tackiness is inferior, it is difficult to obtain a sufficient adhesive force, and there are too many tackifiers. And adhesive residue is likely to occur. The content of the tackifier is preferably about 12 to 30% by weight, more preferably about 15 to 30% by weight.

  The low temperature tackiness refers to a property that can develop adhesive force by low temperature heating. For example, a sample obtained by bonding a label activated by heating to 80 ° C. to a plastic sheet similar to the container surface is JIS By the test according to K 6854-3 (T-type peeling) (peeling speed 200 mm / min), it can be evaluated as the adhesive strength to the container surface. The adhesive strength of the adhesive layer 4 based on the method to a plastic sheet similar to the container surface is, for example, 3 N / 15 mm or more. If the adhesive strength is less than 3 N / 15 mm, a mounting failure such as the label 1 being unable to adhere to the container tends to occur. The low temperature tackiness can be adjusted by the ethylene content and melting point in the ethylene polymer and the kind and content of the tackifier.

  The blocking resistance can be evaluated as described above. Moreover, blocking resistance can also be adjusted with the melting point of an ethylene-type copolymer, the kind and content of a tackifier, and adjuvant.

  The adhesive layer having the above-described configuration further has an advantage that the transparency and adhesive strength hardly change over time, and the quality hardly deteriorates even during long-term storage.

  As another example of a preferable adhesive layer, ethylene content is 66 to 90% by weight, melting point is 60 to 90 ° C., ethylene copolymer 70 to 90% by weight, and tackifier 30 to 10%. Formed with emulsion-type heat-sensitive adhesive containing 0.5 to 10 parts by weight of acrylic resin or 5 to 60 parts by weight of polyurethane resin as an auxiliary agent with respect to 100 parts by weight of the main agent. The adhesive layer made is mentioned. According to such an adhesive layer, excellent low-temperature tackiness and blocking resistance can be exhibited, and adhesive residue on the adherend during peeling can be prevented.

  By using an acrylic resin and a polyurethane resin as an auxiliary agent, blocking resistance is imparted and it is difficult for adhesive to remain on the adherend at the time of peeling. However, if the amount used is too large, the adhesive force decreases, which is not preferable. Specifically, the content of the acrylic resin is, for example, 0.5 to 10 parts by weight, preferably 1 to 10 parts by weight with respect to 100 parts by weight of the main agent. Moreover, content of a polyurethane resin is 5-60 weight part with respect to 100 weight part of main agents, Preferably it is 5-50 weight part.

  The adhesive residue preventing property is, for example, a method of visually observing whether or not adhesive remains on the surface of the plastic sheet when measuring the low-temperature tack property described above, or a label from a PET bottle actually attached with a label. It can be evaluated by a method of visually observing the presence or absence of adhesive residue when peeled. The adhesive residue preventing property can also be adjusted by the type and content of the ethylene copolymer, the tackifier and the adjuvant. In particular, when an ethylene copolymer having a high MFR is used, the effect of preventing adhesive residue can be improved without reducing the amount of tackifier used. Therefore, the adhesive strength can be prevented by improving the film strength while maintaining excellent coatability and sufficient adhesive force.

  Additives such as emulsifiers, waxes, stabilizers and modifiers may be added to the emulsion-type heat-sensitive adhesive as necessary, in addition to the above components.

  The emulsion-type heat-sensitive adhesive is used, for example, in a state where the above base polymer, tackifier, auxiliary agent as necessary, and other components are dispersed in water or a solvent by a conventional method. The (aqueous) emulsion-type heat-sensitive adhesive dispersed in water can be prepared, for example, by emulsion polymerization of a monomer containing ethylene corresponding to the ethylene-based polymer. (Solvent-based) emulsion-type heat-sensitive adhesives dispersed in a solvent include, for example, the above-mentioned components having low solubility in the above-mentioned components (poor solvents), for example, aliphatics such as n-hexane and n-heptane. It can be prepared by dispersing in a hydrocarbon solvent or the like. A water-based emulsion type heat-sensitive adhesive is preferably used because of its low environmental load.

  The emulsion-type heat-sensitive adhesive thus obtained is a dispersion in which a polymer component (solid content) is dispersed in the form of particles in a liquid. The solid content concentration of the emulsion-type heat-sensitive adhesive is, for example, about 30 to 60% by weight. When the solid content concentration exceeds 60% by weight, the coating workability is inferior, and when it is less than 30% by weight, it takes time to dry after coating, and the production efficiency tends to decrease. The size of the particles (resin particles) made of the polymer component dispersed in the dispersion is, for example, about 0.1 to 15 μm. The average particle diameter of the resin particles is usually about 2 μm. In the present invention, the size of the resin particles (average particle diameter and the like) is important in that it affects the average roughness of the adhesive layer surface. The size of the resin particles can be controlled by appropriately selecting the type of components (resin, solvent, etc.) constituting the adhesive, the solid content concentration of the adhesive, and the like.

  The adhesive layer 4 is formed by applying an emulsion type heat sensitive adhesive and drying it. The adhesive can be applied by a known printing method such as flexographic printing or gravure printing. In particular, gravure printing is preferable because the printing speed is high, the coating amount is stable, and the printing layer 3 and the adhesive layer 4 that are usually provided by gravure printing can be formed in one step. For printing, the emulsion-type heat-sensitive adhesive having the above-described configuration may be used as it is, or methanol or the like may be added to promote drying after printing. Thus, according to the emulsion-type heat-sensitive adhesive, application to the label base material (printing layer) can be easily performed using the same process as printing, and a separate process such as melt extrusion coating is unnecessary. Economically advantageous. And since an adhesive bond layer can be formed thinly, it is advantageous to the thickness reduction of a label, and adhesive residue can also be suppressed.

  The film thickness after application (before drying) can be appropriately selected in consideration of the thickness of the adhesive layer 4 formed after drying, the drying time, and the like, and is, for example, about 5 to 63 μm, preferably about 12 to 38 μm.

  Drying after applying the adhesive is performed by appropriately selecting conditions such that the average roughness of the surface of the adhesive layer falls within the above range. The drying temperature is appropriately selected according to the type of resin constituting the adhesive, but is usually set to a temperature lower than the activation temperature of the resin, for example, about 40 to 70 ° C., preferably about 50 to 70 ° C. . If the drying temperature is too low, the drying is insufficient and blocking due to the remaining moisture occurs, and the drying takes time and the production efficiency tends to decrease. If the temperature is too high, blocking due to the activation of the resin constituting the adhesive tends to occur. As the drying means, for example, a conventional heating means such as a heater or hot air can be used. When hot air is used as the drying means, the average roughness of the adhesive layer surface can be adjusted within the above range by controlling the strength of the hot air.

  The water content (residual water amount) of the adhesive layer 4 after drying is, for example, 1% by weight or less, preferably 0.1% by weight or less. When the water content exceeds 1% by weight, since drying is insufficient, blocking is easily caused by water contained in the adhesive layer 4.

  The thickness of the adhesive layer 4 can be appropriately selected in consideration of adhesiveness, appearance, cost, and the like, and is, for example, about 2 to 25 μm, preferably about 5 to 15 μm. If the thickness of the adhesive layer is too thick, cohesive failure occurs, the desired adhesive strength cannot be obtained, and if it is too thin, sufficient adhesiveness is difficult to obtain. In the present invention, the reduction rate of the thickness of the adhesive layer (after drying) relative to the thickness of the coating film (before drying) is, for example, less than 70% by volume (about 40 to 60% by volume). When the reduction rate is too large, the average roughness of the adhesive layer surface becomes less than 0.3 μm, and blocking tends to occur.

  When the average roughness of the surface of the adhesive layer 4 is less than 0.3 μm, the blocking resistance is inferior, and stickiness is produced when the labels are wound or stacked, and the labeler suitability at the time of labeling is poor. The adhesive layer in the conventional heat-sensitive label has a structure in which the surface irregularities are small, the average roughness Ra is less than 0.3 μm, and it is easy to block. On the other hand, since the heat sensitive label of the present invention has large irregularities on the surface of the adhesive layer 4 and an average roughness Ra of 0.3 μm or more, the blocking resistance and the like can be remarkably improved. The average roughness can be adjusted by appropriately selecting the size of the resin particles constituting the emulsion-type heat-sensitive adhesive, the film thickness after application of the adhesive, the drying conditions (temperature, hot air strength), and the like.

  Note that an adhesive layer may be provided on one side of the label substrate, and a printing layer may be provided on the other side. FIG. 2 is a schematic sectional view showing another example of the thermosensitive label of the present invention. In the thermosensitive label 1 'shown in FIG. 2, an adhesive layer 4 is laminated on one side of a label substrate 2', and a printed layer 3 and an overcoat layer 5 are laminated on the other side in this order.

  The label base material 2 'can be appropriately selected according to the printability and the like because the printing layer 3 is provided on the front side of the label base material 2'. In addition to the transparent base material exemplified as the label base material 2 in FIG. Furthermore, water-resistant paper such as opaque plastic film and coated paper, paper such as Japanese paper and synthetic paper, metal foil such as aluminum foil, or a laminate thereof can be used. The thickness of the label substrate 2 ′ can be selected as appropriate as long as it does not impair the mechanical strength, the handleability of the label, etc., but is generally about 5 to 50 μm, preferably about 8 to 40 μm. As the printing layer 3 and the adhesive layer 4, those exemplified above can be used.

  The overcoat layer 5 is a layer for protecting the printed layer 3 and giving gloss, and is a transparent ultraviolet curable varnish, polyester resin, acrylic resin, epoxy resin, and silicone resin to which a lubricant is added as required. Etc. can be formed by coating, printing or the like. The thickness of the overcoat layer is, for example, about 0.5 to 2 μm. The heat-sensitive label 1 'can be produced, for example, by forming the printed layer 3' and the overcoat layer 5 'on the surface of the label base material and then inverting and forming the adhesive layer on the other surface by printing. .

  Moreover, the thermosensitive label may have other layers (for example, an overlaminate layer, an anchor coat layer, a primer coat layer, etc.) other than a label base material, a printing layer, an adhesive layer, and an overcoat layer. These layers can be formed by a conventional coating method, laminating method or the like. The step of forming these layers is also preferably performed in the same step as the printing step.

  The total thickness of the thermosensitive label is, for example, 6 to 75 μm, preferably 8 to 60 μm, in terms of cost and appearance. In particular, the label tends to be thin because it gives a sense of unity with the container at the time of sticking and is excellent in decorating properties. However, if the thickness is too thin, the workability and workability at the time of sticking are inferior.

  The heat-sensitive label of the present invention is not limited to a wound heat-sensitive adhesive label, but a heat-shrinkable label base material is used. It may be a shrink label, a stretch label, a stretch shrink label, or the like.

  When the heat-sensitive label is a heat-shrinkable label such as a shrink label, for example, a heat-shrinkable film that has been stretched in at least one direction is used as a label substrate. As the heat-shrinkable film, a uniaxially stretched film made of a polyester resin, a polystyrene resin, a polyvinyl chloride resin, particularly a polyester resin is preferably used. The uniaxially stretched film is a film having an orientation in the main stretching direction and showing a large heat shrinkability in the direction, as long as it is stretched mainly in one direction (for example, MD direction), Stretching may be performed in the other direction (for example, the lateral direction) by about 1.01 to 1.1 times. The heat shrinkage rate in the main stretching direction of the uniaxially stretched film is, for example, 10% or more, preferably 30% or more under the conditions of a glycerin bath at 100 ° C. for 5 seconds. The thickness of the label base material as the heat-shrinkable film is generally about 20 to 100 μm, preferably about 25 to 60 μm. The configuration other than the label substrate in the heat-shrinkable label is the same as described above.

  In the labeled container of the present invention, the thermosensitive label of the present invention is mounted so that the adhesive layer side is in contact with the container. The thermosensitive label may be attached to the entire surface of the container or may be attached to a part thereof. The container is not particularly limited and may be any of plastic bottles, glass bottles, metal cans, etc., but polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, high density polyethylene, polypropylene A plastic container made of, for example, is suitable.

  The heat-sensitive label can be attached to the container by a known or conventional method. For example, the label is attached by superimposing the surface of the heat-sensitive label 1 on the adhesive layer 4 side on the surface of the container and pressing a hot plate from the label base material 2 side, The labeler (usually by a method such as suctioning, activating the adhesive layer by applying heat to the adhesive layer with heat from the drum or a heat source such as infrared rays, and then sticking it to the container by pressing, This is done using an automatic labeling machine.

  The heating temperature is set to a temperature equal to or higher than the activation temperature of the adhesive layer 4, and is, for example, about 60 to 150 ° C., preferably about 70 to 120 ° C. The adhesive layer 4 activated by heating has less irregularities on the surface of the layer and an average roughness Ra of less than 0.3. For this reason, good adhesiveness is expressed on the surface of the adhesive layer 4 after heating, and excellent low-temperature tackiness can be exhibited, so that the surface can be satisfactorily attached to the container surface.

  Since the labeled container thus obtained can reduce the thickness of the heat-sensitive label, the label and the container produce a sense of unity and are excellent in appearance.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The activation temperature of the heat-sensitive adhesive is such that the surface of the label on the adhesive layer side and the surface of the label base material are overlapped, stored for 24 hours under a pressure of ² kg / cm ² (196 kPa), and peeled off. It is the temperature at the time of storage when an adhesive strength of 0.1 N / 15 mm or more is produced when a test according to JIS K 6854-3 (T-type peeling) is performed under the condition of a speed of 200 mm / min, and an adhesive layer The average surface roughness is a surface roughness measured according to JIS B 0601-1994.

Example 1
A biaxially stretched polyethylene terephthalate film (trade name “Lumirror P60”, manufactured by Toray Industries, Inc.) (thickness: 12 μm) was used as the label substrate. The heat shrinkage rate in the machine direction (MD direction) and the transverse direction (TD direction) of this film were both less than 1% under the condition of being immersed in a glycerin bath at 100 ° C. for 5 seconds. On one surface of the film, various display designs were printed by gravure printing to form a printed layer (thickness 3 μm), and then an ethylene-vinyl acetate copolymer (EVA; ethylene content 72% by weight, melting point) 62 ° C., MFR 400 g / 10 min) 80 parts by weight, tackifier [terpene resin (trade name “YS Polystar T115”, manufactured by Yasuhara Chemical Co.)] 20 parts by weight of water-based emulsion type thermal adhesive (activation temperature about 70) C.) was applied by gravure printing to a thickness of 10 μm. After the application, a drying process was performed by applying dry hot air at a temperature of 60 ° C. for 1 second to form an adhesive layer having a thickness of 4 μm (water content of 1% by weight or less), and a label (total thickness 19 μm) was produced. The average roughness of the surface of the adhesive layer of the obtained label was 0.32 μm. An electron micrograph of the surface of the adhesive layer of the obtained label is shown in FIG.
The obtained label is heated from the label substrate side while adsorbed to the heating drum (temperature 100 ° C.) to activate the adhesive layer, and the surface on the adhesive layer side is made of a polyethylene terephthalate bottle (PET bottle). ) To obtain a labeled container. The average roughness of the adhesive layer surface when re-cured after heating was 0.22 μm (an electron micrograph is shown in FIG. 3B).

Comparative Example 1
In Example 1, 80 parts by weight of an ethylene-vinyl acetate copolymer (same as in Example 1) and 20 parts by weight of a tackifier (same as in Example 1) are replaced with toluene instead of the water-based emulsion-type heat-sensitive adhesive. The same operation as in Example 1 was performed except that a dissolved solvent-type heat-sensitive adhesive (activation temperature: about 70 ° C.) was used, and an adhesive layer having a thickness after drying of 4 μm (water content of 1% by weight or less) A label having a total thickness (total thickness: 19 μm) was prepared. The average roughness of the surface of the adhesive layer of the obtained label was 0.23 μm.
Using this label, a labeled container was produced by the same operation as in Example 1.

Comparative Example 2
In Example 1, except that the water-based emulsion-type heat-sensitive adhesive applied to the label substrate was dried with hot air at 70 ° C. instead of 60 ° C., the same operation as in Example 1 was performed, and the thickness after drying was A label (total thickness: 19 μm) having a 4 μm adhesive layer (water content of 1% by weight or less) was prepared. The average roughness of the surface of the adhesive layer of the obtained label was 0.15 μm.
Using this label, a labeled container was produced by the same operation as in Example 1.

(Evaluation test)
The following tests were conducted on the labels and containers with labels obtained in Examples and Comparative Examples. These results are shown in Table 1. In Table 1, the “average roughness” column shows the value of the adhesive layer before activation, and the value in the parenthesis shows the value of the adhesive layer after activation by heating at 100 ° C.

Anti-blocking property The adhesive layer side of the labels obtained in Examples and Comparative Examples was overlapped with the label base material side, and stored at 40 ° C. for 24 hours under a load of 2 kg / cm ² (196 kPa), and then JIS K 6854- A T-type peeling test (peeling speed 200 mm / min) was performed by the method according to 3, and the adhesive strength (N / 15 mm) of the label was measured. The case where these adhesive strengths were less than 0.1 N / 15 mm was evaluated as “◯”, and the case where they exceeded 0.1 N / 15 mm was evaluated as “x”.

Low temperature tack property The labels obtained in Examples and Comparative Examples were adhered to a polyethylene terephthalate (PET) sheet [manufactured by Toyobo Co., Ltd., trade name “A1101”, 100 μm (non-treated surface)] with an area of 15 mm × 10 mm. As described above, a sample obtained by bonding using a hot plate under the conditions of a temperature of 80 ° C., a pressure of 0.1 MPa, and a time of 1 second was subjected to a T-type peel test (peel rate of 200 mm / min by a method according to JIS K 6854-3). ) And the adhesive strength (N / 15 mm) was measured. The case where the adhesive strength was 1 N / 15 mm or more was evaluated as “◯”, and the case where it was less than 1 N / 15 mm was evaluated as “x”. The above evaluation is shown in the upper part of the “low temperature tack” column of Table 1, and the adhesive strength (N / 15 mm) is shown in the lower part.

Adhesiveness to container Among the 20 containers with labels obtained in the examples and comparative examples, “○” indicates that all of the containers can be mounted satisfactorily. ".

Adhesive residue When the low-temperature tackiness of the labels obtained in Examples and Comparative Examples was measured, the label was agglomerated and peeled, and the presence or absence of adhesive residue on the surface of the adherend (plastic sheet) was visually observed, and the agglomeration of the label was removed. The case where there was no adhesive residue was evaluated as “◯”, and the case where cohesive peeling or adhesive residue occurred on the label surface was evaluated as “X”.
Moreover, when the label was actually peeled off from the labeled container obtained in the example and comparative example corresponding to the label having the evaluation of “◯”, it was visually confirmed that no adhesive residue was generated.

It is a schematic sectional drawing which shows an example of the thermosensitive label of this invention. It is a schematic sectional drawing which shows the other example of the thermosensitive label of this invention. (A) is an electron micrograph of the surface of the adhesive layer of the thermosensitive label of Example 1, and (b) is an electron micrograph of the surface of the adhesive layer when the label of (a) is re-cured after heating.

Explanation of symbols

1,1 'label 2,2' label substrate 3 printed layer 4 adhesive layer 5 overcoat layer

Claims (2)

A label in which an adhesive layer is formed on at least a surface of a substrate that contacts an adherend, and the adhesive layer has an ethylene content of 66 to 90% by weight and a melting point of 60 to 90. An ethylene copolymer having a temperature of 10 ° C. and a tackifier of 10 to 30% by weight in the total solid content, and the content of the solid plasticizer and the lubricant is 3% by weight or less based on the total solid content A heat-sensitive label formed by applying an emulsion-type heat-sensitive adhesive and drying, and having an average roughness (Ra) on the surface of the adhesive layer based on irregularities due to resin particles of the emulsion of 0.3 μm or more.   A labeled container to which the heat-sensitive label according to claim 1 is attached.