JP2015210431A - Heat-shrinkable cylindrical label - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-shrinkable cylindrical label that can easily perform a desired display and prevents disappearance of the display even when it is rubbed.SOLUTION: A heart-shrinkable cylindrical label includes a polystyrene resin which satisfies conditions of the following (1) to (4-1). (1) In the differential thermal analysis curve obtained by simultaneous measurement of differential thermal and thermogravimetry (TG/DTA), two exothermic peaks (F1, F2) are provided, (2) The first exothermic peak (F1) is within a temperature range of 200°C to 250°C, (3) the second exothermic peak (F2) comes after the thermogravimetry is reduced equal to or more than 1 wt.%, and (4-1) the endothermic peak does not come after the second exothermic peak (F2).

Description

  The present invention relates to a cylindrical label used by being attached to a beverage container or the like.

The heat-shrinkable cylindrical label is one of packaging materials that can be attached to a beverage container or the like by heat shrinkage.
Heat-shrinkable cylindrical labels can be broadly classified into the following two types according to the mounting method for adherends such as containers.
The first heat-shrinkable cylindrical label is formed in a cylindrical shape by overlaying and bonding the back surface of the second side end portion to the surface of the first side end portion of the label substrate having the heat-shrinkable film. A cylindrical body. The first heat-shrinkable cylindrical label is heat-sealed after being externally fitted to the adherend, and thereby heat-shrink and adheres to the adherend.

  The second heat-shrinkable cylindrical label is bonded to the adherend on the back side of the first side end of the label base material having the heat-shrinkable film, and the label base material is wound around the adherend, It is the cylindrical body formed in the cylinder shape by adhere | attaching the back surface of the 2nd side edge part of a label base material on the surface of a 1st side edge part. The second heat-shrinkable cylindrical label is in a state of being externally fitted to the adherend as soon as it is formed into a cylindrical shape. To do.

By the way, although a design display is usually printed on the heat-shrinkable cylindrical label, a display regarding traceability such as a manufacturing date and a manufacturing code is also printed. The design display can be printed uniformly at the manufacturing stage of the label, but the traceability display is usually printed immediately before or after mounting the heat-shrinkable cylindrical label on the adherend.
Conventionally, it is known that the traceability display is printed by an ink jet method. In this case, if moisture or the like adheres to the printing surface, the ink does not adhere well or the attached ink bleeds. There is a point.

In this regard, Patent Document 1 discloses that a target film composed of a first thin film layer and a second thin film layer is irradiated with CO ₂ laser light having a wavelength of 9.3 μm or 9.6 μm to remove a part of the first thin film layer. Alternatively, it is disclosed that the desired indication is expressed by melting.
According to the laser marking, a desired display can be displayed on the surface of the film even if moisture or the like adheres to the printing surface.

  However, in the laser marking of Patent Document 1, a desired display may not be clearly seen depending on the material of the film.

JP 2005-319501 A

  An object of the present invention is to provide a heat-shrinkable cylindrical label capable of expressing a desired display relatively clearly with a laser beam.

  One of the heat-shrinkable cylindrical labels of the present invention has a heat-shrinkable film including a polystyrene-based resin layer, and the polystyrene-based resin layer has (1) simultaneous differential heat-thermogravimetric (TG / DTA) measurement. In the differential thermal analysis curve according to, there are two exothermic peaks (F1, F2), (2) the first exothermic peak (F1) is in the temperature range of 200 ° C. to 250 ° C., and (3) the second exothermic peak. (F2) is after the thermal weight has decreased by 1% by weight or more, and (4-1) no endothermic peak after the second exothermic peak (F2).

  Another heat-shrinkable cylindrical label of the present invention has a heat-shrinkable film including a polystyrene-based resin layer, and the polystyrene-based resin layer is (1) differential thermal-thermogravimetric simultaneous (TG / DTA). The differential thermal analysis curve by measurement has two exothermic peaks (F1, F2), (2) the first exothermic peak (F1) is in the temperature range of 200 ° C. to 250 ° C., and (3) the second exothermic peak. The peak (F2) is after the thermal weight has decreased by 1% by weight or more, and (4-2, 4-3) after the second exothermic peak (F2) until the thermal weight becomes 20%, Than an imaginary straight line (X) passing through the minimum value (A) before the first exothermic peak (F1) and the minimum value (B) from the first exothermic peak (F1) to the second exothermic peak (F2). Has a large endothermic peak (E1) or after the second exothermic peak (F2) Until the thermal weight reaches 20%, the minimum value (A) before the first exothermic peak (F1) and the minimum value from the first exothermic peak (F1) to the second exothermic peak (F2). The endothermic peak (E2) is smaller than the virtual straight line (X) passing through (B), the endothermic amount at the endothermic peak (E2) is smaller than 30 J / g, and the endothermic amount is the endothermic peak (E2). It is calculated | required by the area enclosed by the differential thermal analysis curve containing imaginary straight line (X).

  The heat-shrinkable cylindrical label of the present invention can represent a relatively clear display by irradiating laser light.

The top view of one label base material which comprises the heat-shrinkable cylindrical label of this invention. The II-II line expanded sectional view of FIG. However, illustration in the middle is omitted. The reference graph figure which shows the thermal property of the polystyrene-type resin layer which concerns on 1st Embodiment. The reference graph figure which shows the thermal property of the polystyrene-type resin layer which concerns on 2nd Embodiment. The reference graph figure which shows the thermal property of the polystyrene-type resin layer which concerns on 3rd Embodiment. The principal part expanded sectional view which cut | disconnected the label base material in which the cavity part produced in the thickness direction after irradiating a laser beam. The expanded sectional view which cut | disconnected the label base material which concerns on other embodiment in the thickness direction. However, illustration in the middle is omitted. The perspective view of a 1st heat-shrinkable cylindrical label. The front view which shows the formation process of a 2nd heat-shrinkable cylindrical label. The front view of the 2nd heat-shrinkable cylindrical label. The graph which shows the result of the differential thermal-thermogravimetric simultaneous measurement of the heat-shrinkable film of Example 1. FIG. The graph which shows the result of the differential thermal-thermogravimetric simultaneous measurement of the heat-shrinkable film of Example 2. FIG. The graph which shows the result of the differential thermal-thermogravimetric simultaneous measurement of the heat-shrinkable film of the comparative example 1. FIG. The graph which shows the result of the differential thermal-thermogravimetric simultaneous measurement of the heat-shrinkable film of the comparative example 2. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In this specification, the “surface” of a member refers to the outer surface of the cylinder when it is formed into a cylindrical shape (that is, when a heat-shrinkable cylindrical label is formed). "" Refers to the inner surface of the cylinder. The “planar shape” refers to a shape viewed from the vertical direction with respect to the surface of the heat-shrinkable film. In addition, “first”, “second”, and the like may be added in front of a term, but this term is added to distinguish terms, and does not mean superiority, inferiority, order, or the like. Furthermore, the description “PPP to QQQ” means “PPP or more and QQQ or less”.
In each figure, it should be noted that the thickness and ratio are different from the actual ones.

FIG. 1 is a plan view of a label substrate 1 having a heat-shrinkable film 2, which is a basic member constituting the heat-shrinkable cylindrical label of the present invention, and FIG. 2 is orthogonal to the main stretching direction. It is thickness sectional drawing cut | disconnected along the direction (2nd direction).
The label substrate 1 includes a heat-shrinkable film 2 including a polystyrene-based resin layer exhibiting predetermined thermal properties by differential thermal-thermogravimetric simultaneous (TG / DTA) measurement, a design printing layer (not shown), light And a reflective layer 3. The label base material 1 may have a functional layer other than these layers.
The predetermined thermal property will be described later. Hereinafter, a polystyrene resin layer exhibiting predetermined thermal properties is referred to as a predetermined polystyrene resin layer, and the main resin component of the resin layer is referred to as a predetermined polystyrene resin.
The heat-shrinkable film 2 has a predetermined polystyrene resin layer and is a film stretched at least in the first direction. The front and back surfaces of the heat-shrinkable film 2 are smooth.

Specifically, the design print layer is provided as necessary to represent a desired design. The design printing layer can be formed by printing a known printing ink on the front surface and / or the back surface of the heat-shrinkable film 2. Since it becomes difficult to be damaged, it is preferable to provide a design print layer on the back surface of the heat-shrinkable film 2.
When the design printing layer is provided on the back surface of the heat-shrinkable film 2, the back surface of the heat-shrinkable film 2 and the light-reflecting layer 3 are arranged so that the design display of the design printing layer is not hidden by the light-reflecting layer 3. A design printing layer is provided between them.

The heat-shrinkable film 2 is a film having heat-shrinkability at least in the first direction (the first direction becomes the circumferential direction when formed in a cylindrical shape).
The heat shrinkability refers to a property of shrinking when heated to a predetermined temperature (for example, 70 ° C. to 100 ° C.). As the heat-shrinkable film 2, a film that slightly shrinks or stretches in the second direction (the second direction is a direction perpendicular to the first direction in the plane of the film) may be used.
The heat shrinkage rate of the heat shrinkable film 2 is not particularly limited. The heat shrinkage rate in the first direction of the heat shrinkable film 2 when heated to 90 ° C. is, for example, 30% or more, preferably 40% or more, more preferably 50% or more.
In addition, when the heat-shrinkable film 2 is slightly heat-shrinked or stretched in the second direction, the heat shrinkage rate in the second direction when heated to 90 ° C. is, for example, −3% to 15%. The minus of the thermal contraction rate in the second direction means thermal expansion.

The heat shrinkage rate when heated to 90 ° C. is the length of the film before heating (original length) and the length of the film after being immersed in warm water of 90 ° C. for 10 seconds (after immersion). Length) and is obtained by substituting into the following equation.
Formula: heat shrinkage rate (%) = [{(original length in the first direction (or second direction)) − (length after immersion in the first direction (or second direction))} / (first Original length of direction (or second direction)]] × 100.

The heat-shrinkable film 2 is made of a transparent film so that the shape of the cavity in plan view generated in the heat-shrinkable film 2 can be visually recognized by laser light irradiation.
In the present invention, the transparent includes colored transparent or colorless and transparent, but is preferably colorless and transparent.
The degree of transparency of the heat-shrinkable film 2 is not particularly limited as long as the shape of the hollow portion in plan view (desired display) is visible from the surface side of the heat-shrinkable film 2. The total light transmittance in the visible light region of the heat-shrinkable film 2 is, for example, 70% or more, preferably 80% or more, and more preferably 90% or more. The total light transmittance refers to a value measured by a measuring method based on JIS K7105 (plastic optical property testing method).
The thickness of the heat-shrinkable film 2 is not particularly limited, but is generally 20 μm to 100 μm, preferably 30 μm to 70 μm.

The heat-shrinkable film 2 may be a single layer film, but is preferably a laminated film in which a plurality of layers are laminated and integrated. When the heat-shrinkable film 2 is composed of a single layer film, a film composed only of a predetermined polystyrene resin layer is used. When the heat-shrinkable film 2 is composed of a multilayer film, at least one layer is a predetermined layer. A laminated film which is a polystyrene-based resin layer is used, and preferably a laminated film having a predetermined polystyrene-based resin layer and a resin layer other than the predetermined polystyrene-based resin layer respectively provided on the front and back sides of the layer. Is used. In addition, this preferable laminated film may have a structure of four or more layers in addition to a three-layer structure described later.
When the heat-shrinkable film 2 is a laminated film having a plurality of layers, the heat-shrinkable film as a whole has heat-shrinkability in a part of the plurality of layers, provided that the heat-shrinkable film 2 has the heat-shrinkability. A non-performing layer may be included.

The heat-shrinkable film 2 in the illustrated example has a three-layer structure, a transparent surface layer 21, a transparent intermediate layer 22 laminated on the back surface of the surface layer 21, and a transparent back layer laminated on the back surface of the intermediate layer 22. 23. In the heat-shrinkable film 2 having the three-layer structure, all the layers 21, 22, and 23 may be predetermined polystyrene resin layers, and one or two layers selected from them may be predetermined polystyrene resin layers. May be. Preferably, at least the intermediate layer 22 is composed of a predetermined polystyrene resin layer. When the intermediate layer 22 is composed of a predetermined polystyrene resin layer, for example, the surface layer 21 and the back layer 23 are composed of a resin layer other than the predetermined polystyrene resin layer.
Although the thickness of the surface layer 21 and the back layer 23 is not specifically limited, For example, they are 3 micrometers-50 micrometers.
Although the thickness of the intermediate | middle layer 22 is not specifically limited, For example, they are 10 micrometers-90 micrometers, Preferably, they are 20 micrometers-60 micrometers. Although the thickness of the surface layer 21 and the back layer 23 is not specifically limited, For example, it is 3 micrometers-30 micrometers independently, for example.
The ratio of the thicknesses of the surface layer 21, the intermediate layer 22, and the back layer 23 can be set as appropriate. For example, when the heat-shrinkable film 2 has a three-layer structure, the intermediate layer 22 is preferably 0.5 to 0.8 when the thickness of the film 2 is 1.

The material for forming the surface layer 21 and the back layer 23 is not particularly limited as long as it does not substantially absorb the laser beam and is not melted or burned by the laser beam. For example, the surface layer 21 and the back layer 23 are each independently a polystyrene resin other than a predetermined polystyrene resin layer, a polyester resin such as polyethylene terephthalate and polylactic acid, an olefin resin such as polyethylene, polypropylene, and a cyclic olefin, One or a mixture of two or more selected from thermoplastic resins such as vinyl chloride resin is included as a main component. Preferably, the surface layer 21 and the back layer 23 are comprised from the layer which contains a polyester-type resin as a main resin component.
Examples of the polyester resin include polyethylene terephthalate resin, poly (ethylene-2,6-naphthalenedicarboxylate), polylactic acid, and the like. Preferably, polyethylene terephthalate resin is used. As the polyethylene terephthalate resin, polyethylene terephthalate (PET) using terephthalic acid as a dicarboxylic acid component, ethylene glycol as a diol component; terephthalic acid as a dicarboxylic acid component, ethylene glycol as a diol component as a main component, 1 Copolyester (CHDM copolymerized PET) using 1,4-cyclohexanedimethanol (CHDM) as a copolymer component, terephthalic acid as a dicarboxylic acid component, ethylene glycol as a main component as a diol component, neopentyl glycol (NPG) Polyester (NPG copolymerized PET) using terephthalic acid as a dicarboxylic acid component, ethylene glycol as a main component as a diol component, diethylene glycol Diol-modified PET such as copolyester used as copolymerization component; dicarboxylic acid component, dicarboxylic acid-modified PET modified with isophthalic acid and / or adipic acid with terephthalic acid as the main component; both dicarboxylic acid component and diol component And modified dicarboxylic acid and diol-modified PET.

The predetermined polystyrene-based resin layer exhibits any one of the following thermal properties (I) to (III) by differential thermal-thermogravimetric simultaneous (TG / DTA) measurement.
The polystyrene-based resin layer exhibiting thermal properties (I) satisfies all the following conditions (1) to (4-1) with reference to FIG.
(1) It has two exothermic peaks (F1, F2) in the differential thermal analysis curve by differential thermal-thermogravimetric simultaneous (TG / DTA) measurement.
(2) The first exothermic peak (F1) is in the temperature range of 200 ° C to 250 ° C.
(3) The second exothermic peak (F2) is after the thermal weight has decreased by 1% by weight or more.
(4-1) In the differential thermal analysis curve, there is no endothermic peak after the second exothermic peak (F2).
Note that the peak is a portion showing a large value locally and is also called an extreme value.

The polystyrene resin layer exhibiting the thermal property (II) satisfies all the following conditions (1) to (4-2) with reference to FIG.
(1) It has two exothermic peaks (F1, F2) in the differential thermal analysis curve by differential thermal-thermogravimetric simultaneous (TG / DTA) measurement.
(2) The first exothermic peak (F1) is in the temperature range of 200 ° C to 250 ° C.
(3) The second exothermic peak (F2) is after the thermal weight has decreased by 1% by weight or more.
(4-2) In the differential thermal analysis curve, the minimum value (A) before the first exothermic peak (F1) after the second exothermic peak (F2) until the thermal weight reaches 20%. And an endothermic peak (E1) larger than an imaginary straight line (X) passing through the minimum value (B) from the first exothermic peak (F1) to the second exothermic peak (F2).
In the differential thermal analysis curve, when a plurality of endothermic peaks larger than the imaginary straight line (X) are observed after the second exothermic peak (F2) until the thermogravimetric weight reaches 20%, the endothermic peak ( E1) indicates the minimum value among them.

The polystyrene resin layer showing the thermal property (III) satisfies all the following conditions (1) to (4-3) with reference to FIG.
(1) It has two exothermic peaks (F1, F2) in the differential thermal analysis curve by differential thermal-thermogravimetric simultaneous (TG / DTA) measurement.
(2) The first exothermic peak (F1) is in the temperature range of 200 ° C to 250 ° C.
(3) The second exothermic peak (F2) is after the thermal weight has decreased by 1% by weight or more.
(4-3) In the differential thermal analysis curve, the minimum value (A) before the first exothermic peak (F1) after the second exothermic peak (F2) until the thermal weight reaches 20%. And an endothermic peak (E2) smaller than an imaginary straight line (X) passing through the minimum value (B) from the first exothermic peak (F1) to the second exothermic peak (F2). The endothermic amount at is less than 30 J / g. However, the endothermic amount is obtained by an area (a region indicated by hatching in FIG. 5) surrounded by the differential thermal analysis curve including the endothermic peak (E2) and the virtual straight line (X).
In the differential thermal analysis curve, when a plurality of endothermic peaks smaller than the virtual straight line (X) are observed after the second exothermic peak (F2) until the thermogravimetric weight reaches 20%, the endothermic peak ( E2) indicates the minimum value among them.

The differential thermal-thermogravimetric (TG / DTA) measurement is a method in which thermogravimetry and differential thermal analysis are combined and measured simultaneously with a single device. The differential thermal-thermogravimetric simultaneous measurement is performed from 50 ° C. to 500 ° C. at a heating rate of 10 ° C./min and an air flow rate of 150 ml / min.
3 to 5 are graphs schematically showing the results of the simultaneous differential thermo-thermogravimetric measurement, with the horizontal axis representing temperature and the vertical axis representing thermogravimetric change [%] and differential heat [electromotive force μV]. is there. The differential thermal analysis curve has a smaller value on the lower side.
It should be noted that FIGS. 3 to 5 are reference diagrams for explanation only, and are different from actual measurement results.

As described above, at least the intermediate layer 22 of the heat-shrinkable film 2 is preferably composed of a predetermined polystyrene resin layer.
As the predetermined polystyrene resin which is the main resin component of the predetermined polystyrene resin layer, a homopolymer or copolymer of a styrene monomer such as general polystyrene (GPPS) which is a homopolymer of styrene; synthetic rubber High impact polystyrene (HIPS) with styrene grafted onto styrene; styrene monomers represented by styrene-butadiene block copolymers (SBS, etc.) and diene monomers (conjugated diene) such as butadiene and isoprene ) A styrene-conjugated diene copolymer which is a copolymer (particularly a block copolymer); a styrene-polymer which is a copolymer of a styrene monomer and a (meth) acrylate monomer, etc. Unsaturated carboxylic acid ester copolymer; styrene-conjugated diene-polymerizable unsaturated carboxylic acid ester copolymer; Body and (meth) acrylic acid ester monomer, a copolymer of a transparent, high-impact polystyrene obtained by graft-polymerizing (graft HIPS), and mixtures thereof. In these, it is preferable that a styrene-conjugated diene copolymer is included as a predetermined polystyrene resin. This styrene-conjugated diene copolymer contains the hydrogenated product.

  Although it does not specifically limit as said (meth) acrylic-ester type monomer, For example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, methacryl Examples include ethyl acetate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, stearyl methacrylate, and the like. The (meth) acrylic acid ester monomer can be used alone or in combination of two or more. The (meth) acryl means methacryl or acryl.

  Although it does not specifically limit as said styrene-type monomer, For example, styrene, alpha-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, p-isobutyl styrene, pt-butyl styrene, Examples include chloromethylstyrene. Among these, styrene is particularly preferable from the viewpoint of physical properties such as strength and moldability. In addition, these styrenic monomers may be used independently and may use 2 or more types together.

  The conjugated diene is not particularly limited. For example, 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, Examples include 1,3-hexadiene and chloroprene. Among these, 1,3-butadiene and isoprene are particularly preferable from the viewpoints of improving brittleness and imparting flexibility. In addition, these conjugated dienes may be used independently and may use 2 or more types together.

  The form of copolymerization of the styrene-conjugated diene copolymer is not particularly limited, such as a random copolymer, a block copolymer, and an alternating copolymer, but a block copolymer is preferable, and a styrene (S) -conjugated diene is preferred. Block (D) type, SDS type, DSD type, SDS type, etc. are mentioned.

Examples of the styrene-conjugated diene copolymer include hydrogenated or anhydrous styrene-butadiene block copolymer, hydrogenated or anhydrous styrene-isoprene block copolymer, hydrogenated or anhydrous styrene-butadiene. -An isoprene block copolymer etc. are mentioned. Of these, hydrogenated or anhydrous styrene-butadiene block copolymers are preferred. The hydrogenation means “hydrogenated” and the anhydrous means “not hydrogenated”.
Examples of the hydrogenated or anhydrous styrene-butadiene block copolymer include styrene-butadiene block copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and styrene-butadiene-butylene-styrene. Examples thereof include a copolymer (SBBS).

The surface layer 21, the intermediate layer 22, and the back layer 23 may contain a thermoplastic resin other than the resin as the main component and various additives as long as the effects of the present invention are not impaired. Examples of the additive include a filler, a heat stabilizer, an antioxidant, an antistatic agent, a lubricant, a nucleating agent, and a flame retardant.
When blending such other thermoplastic resins and additives, the amount is preferably more than 0 and not more than 50% by weight in the forming material.

In addition, the return material may be mix | blended with the heat-shrinkable film. By blending the return material, a cavity is likely to be generated when the laser beam is irradiated.
The return material is a recycled material that reuses the film breaks that occur during the manufacture of the heat-shrinkable film. The return material is obtained by collecting a film end piece, melting the end piece at a required temperature (for example, 200 ° C. to 250 ° C.), and re-pelletizing.
The amount of the return material is not particularly limited, but when the entire forming material of the target layer (for example, the intermediate layer 22) is 100 parts by weight, 20 to 60 parts by weight of the return material is blended. It is preferable.

  In the above, the heat-shrinkable film 2 having a three-layer structure has been illustrated, but for example, a one-layer structure, a two-layer structure, or a structure having four or more layers may be used (not shown).

Like the heat-shrinkable film 2 composed of the surface layer 21, the intermediate layer 22, and the back layer 23, the heat-shrinkable film composed of a plurality of layers has an extruder (in the case of three layers, 3 If the surface and back layers are made of the same material, they may be co-extruded from two extruders, formed into a film by pulling on a roll, and at least in the first direction (main heat shrink direction) ) And heat aging. If necessary, the film may be stretched in the first direction and the second direction after film formation. Moreover, also about the laminated | multilayer film of 1 layer structure or 2 layers or more, the heat-shrinkable film 2 can be obtained by extending | stretching similarly after film-forming and heat-aging.
Stretching can be performed by a known method such as a tenter method or a tubular method. The stretching treatment is usually performed at a temperature of 70 ° C. to 110 ° C. in the first direction by 2.0 to 8.0 times, preferably about 3.0 to 7.0 times. Furthermore, if necessary, the stretching process may also be performed in the second direction at a low magnification of, for example, 1.5 times or less.

The light reflecting layer 3 is laminated on the back surface of the heat-shrinkable film 2 as necessary in order to make the hollow portion visible from the front surface side of the heat-shrinkable film 2. Further, by providing the light reflecting layer 3, a cavity portion is easily generated when laser light is irradiated from the surface side of the heat shrinkable film 2. Although it is not clear that the light reflection layer 3 is easily provided with a cavity, the light reflection layer 3 is formed in the thickness direction of the heat-shrinkable film 2 by providing the light reflection layer 3 made of a white print layer or the like. A relatively large number of cavities are formed on the side closer to the surface.
As the light reflection layer 3, a background printing layer provided on the back surface of the heat-shrinkable film 2 by applying a predetermined color ink on the back surface of the heat-shrinkable film 2, and the back surface of the heat-shrinkable film 2 Examples thereof include a metal vapor deposition film such as an aluminum film deposited on the surface, and a metal foil such as an aluminum foil laminated on the back surface of the heat-shrinkable film 2.

The color of the background printing layer is not particularly limited as long as it reflects light, and is usually a light color such as white or light yellow or silver, and preferably white. The background printing layer exhibiting the white or light yellow color preferably contains titanium oxide, and more preferably contains 40 wt% to 80 wt% titanium oxide. Since titanium oxide hardly absorbs laser, the light reflecting layer 3 containing titanium oxide is hardly lost by laser irradiation. As the binder resin, resin components used in conventionally known printing inks can be used. For example, urethane resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, polyamide resin, Examples thereof include polyester resins and cellulose resins.
Although the thickness of a background printing layer is not specifically limited, For example, they are 0.2 micrometer-15 micrometers.

  By irradiating laser light from the front surface side or the back surface side of the label base material 1 (heat-shrinkable film 2), a part of the intermediate layer 22 is melted or burnt, and as shown in FIG. The cavity 5 is generated in the (predetermined polystyrene resin layer). Although not shown, when using a label base material on which a light-reflective layer is not provided on the heat-shrinkable film, laser light is irradiated from either the front side or the back side of the label base material. When using the label base material 1 in which the light reflection layer 3 is provided on the back surface of the heat-shrinkable film 2, laser light is irradiated from the front surface side of the label base material 1.

As the laser beam, a YAG laser beam (yttrium, aluminum, garnet laser beam, wavelength = 1,064 nm), a YVO ₄ laser beam (yttrium vanadate laser beam, wavelength = 1,064 nm), or the like can be used. Since a clear display can be formed, it is preferable to use a YAG laser beam or a YVO ₄ laser beam.
When a YAG laser beam or a YVO ₄ laser beam is used as the laser beam, the surface layer 21, the intermediate layer 22 and the back layer 23 of the heat-shrinkable film 2 are each preferably a layer mainly composed of a polystyrene-based resin. Further, the surface layer 21 and the back layer 23 are preferably formed of a material having a lower laser light absorption rate than the intermediate layer 22.
The irradiation condition of the laser beam is set as appropriate.
The frequency of the laser light is, for example, 20 kHz to 100 kHz, preferably 20 kHz to 40 kHz. If the frequency (energy) is too small, the inside of the heat-shrinkable film 2 (intermediate layer 22) is not sufficiently melted. On the other hand, if the frequency is too large, the heat-shrinkable film 2 may be burned and partially broken. .

Carbide is generated on the wall surface 5a around the cavity that forms the cavity 5. In addition, when the carbide | carbonized_material around the cavity part 5 exists in the whole surrounding wall surface 5a (when the whole wall surface 5a is carbonized), when the carbide | carbonized_material does not exist in a part of wall surface 5a. Including.
The carbide around the cavity portion 5 is generated by carbonization of the wall surface 5a itself of the cavity portion 5, or the film component itself existing at the cavity portion forming place before the laser beam irradiation is irradiated with the laser beam. It is presumed that the carbide is carbonized to produce a carbide, and the carbide adheres to the wall surface 5a of the cavity portion 5 formed at the same time.
Since the carbide is formed around the cavity 5, the planar view shape of the cavity 5 can be favorably visually recognized from the surface side of the heat-shrinkable film 2.

  In particular, since the light reflecting layer 3 is provided on the back surface of the heat-shrinkable film 2, the refractive index of light greatly changes in the cavity portion 5, and the cavity appears when viewed from the front surface side of the heat-shrinkable film 2. The boundary between the part 5 and the other part (that is, the wall surface 5a around the cavity part 5) becomes clear, and a desired display represented by the shape of the cavity part 5 in a plan view can be clearly recognized.

By irradiating the laser beam, the cavity 5 having a desired shape in plan view and having a carbide around the heat shrinkable film 2 can be formed. The hollow portion 5 is formed in the heat-shrinkable film 2 and is a recessed space that communicates with the outside or a closed space that does not communicate with the outside.
As described above, when the heat-shrinkable film 2 is a single-layer film (a film composed only of a predetermined polystyrene resin layer), a cavity 5 is generated inside the film 2 or the surface of the film 2 Alternatively, the cavity 5 may be generated including the back surface. Therefore, the cavity 5 generated inside the heat-shrinkable film 2 is a closed space, and the cavity 5 generated including the front surface or the back surface is a recessed space.
On the other hand, when the heat-shrinkable film 2 is a laminated film having a predetermined polystyrene resin layer and a resin layer other than the predetermined polystyrene resin layer respectively provided on the front and back sides of the layer, The resin layer which does not produce a hollow part substantially exists in the front and back side of the predetermined polystyrene-type resin layer which produces. The heat-shrinkable film 2 has a hollow portion 5 (hollow portion in the meaning of a closed space) formed inside by irradiation with laser light. Therefore, even if the surface or the back surface of the heat-shrinkable cylindrical label is rubbed, This has the effect that the display is hardly lost. In the conventional laser marking, since the surface of the film is made uneven to represent a desired display, the display may disappear or become thin when the surface of the film rubs against foreign matter in the distribution process. In this regard, the heat-shrinkable cylindrical label of the present invention can represent a desired display that is difficult to disappear while maintaining the smoothness of the front and back surfaces.
For example, in the heat-shrinkable film 2 having the three-layer structure, the cavity 5 is generated inside the heat-shrinkable film 2 without reaching the front and back surfaces. In that case, for example, the cavity 5 may be formed in the intermediate layer 22, or may be formed across the stacked interface between the surface layer 21 and the intermediate layer 22.
Although the height (length in the thickness direction) of the cavity 5 is not particularly limited, it is preferably 1 μm to 30 μm, and more preferably 1 μm to 20 μm. When the height of the cavity 5 is too small, the visibility of the cavity 5 is lowered. On the other hand, when the cavity 5 is too large, the heat-shrinkable film 2 that can be generated inside can be used. The cavities 5 may break through the surface or back surface of the film 2 over time, and a crater-like depression may occur on the surface or back surface of the heat-shrinkable film 2.

The shape in plan view of the cavity 5 having carbide around it constitutes the desired display. It should be noted that the desired display is not composed of one cavity portion 5, but microscopically, innumerable cavity portions 5 gather to constitute the desired display.
The planar view shape (desired display) of the cavity 5 is not particularly limited and can be set as appropriate.
The plan view shape of the cavity 5 may represent a predetermined design display such as a product name or a pattern, or may represent an on-demand display.
On-demand display includes, for example, display related to traceability such as the date of manufacture, expiry date, and manufacturing code, prize application ID when a prize campaign is being conducted, and habit indication such as Atari or Loss . Normally, such on-demand display is represented by numbers, letters, symbols, and the like.

The heat-shrinkable film constituting the heat-shrinkable cylindrical label of the present invention includes a predetermined polystyrene resin layer.
When a predetermined polystyrene resin layer is irradiated with laser light, the polystyrene resin is decomposed and carbonized by the energy, and air bubbles are generated, so that a cavity is formed in the polystyrene resin layer. Although it is not clear why the predetermined polystyrene-based resin layer is likely to generate a cavity by laser light, the present inventors presume as follows.
When the heat-shrinkable film is irradiated with laser light, the polystyrene resin starts to be decomposed by the energy, and as it progresses, a part of the decomposed resin is depolymerized and finally enters the polystyrene resin layer. This produces carbonized decomposed resin and bubbles accompanying decomposition. The depolymerization is considered to occur at the endothermic peak observed after the second exothermic peak (F2). Since much of the energy is absorbed during the depolymerization, the smaller the energy is, the more easily the energy of the laser light is consumed for decomposition of the polystyrene resin, carbonization, and generation of bubbles.
Since the polystyrene resin layer having the thermal property (I) does not have an endothermic peak after the second exothermic peak (F2), decomposition of the polystyrene resin, carbonization and bubbles are promoted by the energy of the laser beam, which is good. A visible display can be formed.
The polystyrene resin layer having the thermal properties (II) and (III) has an endothermic peak (E2) after the second exothermic peak (F2). The decomposition, carbonization, and bubbles of the polystyrene resin are promoted, and a display that can be visually recognized can be formed.

Furthermore, as shown in FIG. 7, the mat layer 7 may be laminated | stacked on the surface of the heat-shrinkable film 2 as needed. By providing the mat layer 7, when the laser beam is irradiated from the side where the mat layer 7 is laminated, a relatively large cavity 5 having a carbide is easily generated. By forming the relatively large cavity portion 5, a heat-shrinkable cylindrical label that makes it easier to visually recognize a desired display can be configured.
When the mat layer 7 is provided, a light reflecting layer may not be provided on the back surface of the heat-shrinkable film 2, but preferably, as shown in FIG. 7, the light reflecting layer such as the white background printing layer. 3 is provided. By using a label substrate 1 having a heat-shrinkable film 2, a light reflecting layer 3 provided on the back surface thereof, and a matte layer 7 provided on the surface thereof, the inside of the heat-shrinkable film 2 is provided. It has a carbide | carbonized_material and it is easy to form the bigger cavity part 5. FIG. Since the heat-shrinkable cylindrical label made of the label base material 1 having the heat-shrinkable film 2, the light reflecting layer 3 and the matte layer 7 can form a larger cavity 5, the desired display can be clearly recognized. A heat-shrinkable cylindrical label can be constructed.
7 illustrates the heat-shrinkable film 2 having a three-layer structure, but the heat-shrinkable film 2 in the case where the matte layer 7 is provided is not limited to the three-layer structure, and has two or four layers. The above multi-layer structure or single-layer structure (single layer) may be used. FIG. 7 shows the label substrate 1 in a state where the cavity 5 is formed by laser light irradiation.

  The mat layer 7 can be formed, for example, by printing a mat ink containing a matting agent and a transparent binder resin on the surface of the heat-shrinkable film 2. As the matting agent, extender pigments can be used. Examples of extender pigments include inorganic fine particles such as silica, barium sulfate, and talc, and resin fine particles such as acrylic beads and styrene beads. As said binder resin, what was illustrated above can be used suitably. The content of the extender pigment in the matte layer is not particularly limited, but is preferably 10% by weight to 40% by weight. The thickness of the matte layer 7 is not particularly limited, but is, for example, 0.1 μm to 3 μm. The mat layer 7 is provided to such an extent that the translucency is not impaired. Specifically, the mat ink and thickness are set so that the total light transmittance (JIS K7105) in the visible light region of the heat-shrinkable film 2 provided with the mat layer 7 is, for example, 70% or more.

  The heat-shrinkable cylindrical label of the present invention may be one that has been formed in a cylindrical shape before being externally fitted to the adherend (first heat-shrinkable cylindrical label), or may be attached to the adherend. It may be formed into a cylindrical shape at the same time as the fitting (second heat-shrinkable cylindrical label).

  For example, as shown in FIG. 8, the first heat-shrinkable cylindrical label 11 of the present invention is rolled with the back side of the label base material 1 having the heat-shrinkable film 2 inward, in the first direction (mainly The back surface of the second side end portion 1b is overlapped and bonded to the surface of the first side end portion 1a of the label base material 1 so that the heat shrinkage direction is the circumferential direction. .

Moreover, as shown in FIG. 10, the 2nd heat-shrinkable cylindrical label 12 of this invention has the back surface of the 1st side edge part 1a of the label base material 1 which has the said heat-shrinkable film 2 on the to-be-adhered body 6. The label base material 1 is wound around the adherend 6 so that the first direction (main heat shrinkage direction) of the heat-shrinkable film 2 is the circumferential direction, and then the first side end portion The back surface of the second side end portion 1b is overlapped and bonded to the surface of 1a to form a cylinder.
FIG. 9 shows the process of forming the second heat-shrinkable cylindrical label 12, the back surface of the first side end 1 a of the label base 1 is bonded to the adherend 6, and the label base 1 is attached to the adherend. 6 shows a state before winding.
The first side end 1a is one of both sides extending in the second direction on both sides in the first direction of the label substrate 1, and the second side end 1b is the other of the both sides. It is.

The first and second heat-shrinkable cylindrical labels 11 and 12 may form the cavity 5 by irradiating laser light before forming the label base material 1 into a cylindrical shape. After forming 1 into a cylindrical shape, the cavity 5 may be formed by irradiating laser light from the surface side.
The first heat-shrinkable cylindrical label 11 is usually formed into a tubular body by forming the label substrate 1 into a tubular shape, and then the cavity 5 is formed in the heat-shrinkable film 2 by irradiation with laser light. The
The second heat-shrinkable cylindrical label 12 is formed into a cylindrical shape using the adherend 6 using the label base material 1 in which the cavity 5 is formed inside the heat-shrinkable film 2.

After the first heat-shrinkable cylindrical label 11 is fitted on the adherend, the first heat-shrinkable cylindrical label 11 is contracted in the circumferential direction and is in close contact with the adherend by heating to a predetermined temperature.
Since the second heat-shrinkable cylindrical label 12 is already externally fitted to the adherend, it is shrunk in the circumferential direction and adhered to the adherend by heating to a predetermined temperature.
The adherend is not particularly limited, and representative examples include various containers such as beverage containers, seasoning containers, cosmetic containers, and pharmaceutical containers.

According to the heat-shrinkable cylindrical label of the present invention, a desired display can be expressed relatively clearly by laser light.
In particular, when the carbide is formed around the cavity, the light is greatly refracted in the cavity, so that a desired display (the shape of the carbide) can be easily recognized.
Further, since laser light is used, a desired display can be expressed even when the label is wet.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples.

[Example 1]
As the heat-shrinkable film, a monoaxially stretched polystyrene resin film having a single layer structure with a thickness of 50 μm was used. This polystyrene resin is a partially hydrogenated styrene-butadiene block copolymer.

[Example 2]
As the heat-shrinkable film, a monoaxially stretched polystyrene resin film having a single layer structure with a thickness of 50 μm was used. This polystyrene resin is a styrene-butadiene block copolymer (butadiene content: 20% by mass, measured by H-NMR).

[Comparative Example 1]
As the heat-shrinkable film, a monoaxially stretched polystyrene resin film having a single layer structure with a thickness of 50 μm was used. This polystyrene resin is a mixture of styrene-butadiene block copolymer and grafted HIPS (butadiene content 20% by mass, measured by H-NMR).

[Comparative Example 2]
As the heat-shrinkable film, a monoaxially stretched polystyrene resin film having a single layer structure with a thickness of 50 μm was used. This polystyrene resin is a styrene-butadiene block copolymer (butadiene content of 10% by mass, measured by H-NMR).

[Differential thermal-thermogravimetric simultaneous measurement]
The thermal properties of the heat-shrinkable films of each example and comparative example were measured by differential thermal-thermogravimetric simultaneous measurement according to JIS K7120 (plastic thermogravimetric measurement method).
Specifically, about 10 mg of an arbitrary portion of the heat-shrinkable film is cut out to prepare a test piece, which is put in an aluminum dish, and a TG / DTA simultaneous measurement device (manufactured by Shimadzu Corporation) as a thermal analyzer. (Trade name: DTG-60), and the temperature was measured at a temperature rising rate of 10 ° C./min, in an air atmosphere (air flow rate 150 ml / min), and at a measurement temperature of 50 ° C. to 500 ° C.
The measuring device automatically records the obtained differential heat and thermogravimetric change and graphs it.
The measurement results of the heat-shrinkable film of each example and comparative example are shown in FIGS. However, the first and second exothermic peaks (F1, F2), minimum values (A, B), endothermic peaks (E1, E2), and virtual line (X) are written in the graph of the measurement results. .
In addition, the endothermic amount calculated | required by the area (area | region shown with a shaded area) enclosed by the differential thermal analysis curve containing the endothermic peak (E2) of the heat-shrinkable film of the comparative example 1 and a virtual straight line (X) is about 37 J /. The heat absorption amount of the heat-shrinkable film of Comparative Example 2 was about 38 J / g.

[Laser irradiation test]
Laser light was irradiated from the surface side of the heat-shrinkable film of the example and comparative example (using the heat-shrinkable film itself as a label base material) from the surface side under the following irradiation conditions so as to draw a predetermined display (number 12345567890). Irradiated.
(Laser irradiation conditions)
Laser: YAG Laser (trade name “FAYb Laser Marker LP-ADP40” manufactured by Panasonic Device Sunx)
Scanning speed: 500 mm / sec Q-switch frequency: 40 kHz
Laser power: 80%

As a result, when the front and back surfaces of the heat-shrinkable films of Examples 1 and 2 were visually observed, it was possible to clearly confirm the numbers 12345567890, and there were no depressed portions such as craters on either side, Even after laser light irradiation, the film was smooth.
On the other hand, when the front and back surfaces of the heat-shrinkable films of Comparative Examples 1 and 2 were visually observed, the numbers for Comparative Example 1 appeared thin, and for Comparative Example 2, the number 12345567890 could not be confirmed.

The heat-shrinkable films of Examples 1 and 2 have a polystyrene resin layer that exhibits the thermal property (II). On the other hand, the heat-shrinkable films of Comparative Examples 1 and 2 have a polystyrene resin layer that does not satisfy the condition (4-3) among the thermal properties (III).
In each of the heat-shrinkable films of Examples and Comparative Examples, a peak of oxidation exotherm due to dehydrogenation (first exothermic peak (F1)) was observed at 220 ° C. to 240 ° C., and resin decomposition began to proceed, and thereafter Further, after the thermogravimetric weight is reduced by 1% by weight or more, an oxidation exothermic peak (second exothermic peak (F2)) is further observed, and it is understood that the resin decomposition becomes remarkable.
However, the heat-shrinkable films of Examples 1 and 2 could be printed, and the heat-shrinkable films of Comparative Examples 1 and 2 could not be printed substantially. This is estimated as follows.
The endothermic peak generated after the second exothermic peak (F2) is considered to be caused by the fact that a part of the decomposed resin undergoes depolymerization and absorbs heat at that time. If the degree of this endotherm is large, much of the laser irradiation energy is consumed in the endothermic reaction (depolymerization) accordingly, and the temperature of the polystyrene resin layer does not rise, and as a result, it is estimated that the polystyrene resin cannot be sufficiently carbonized. Is done. In this respect, the heat-shrinkable films of Examples 1 and 2 have an endothermic peak after the second exothermic peak (F2), but the degree of endotherm was relatively small, so it is considered that printing was possible. On the other hand, when the degree of endotherm at the endothermic peak after the second exothermic peak (F2) is relatively large as in the heat-shrinkable films of Comparative Examples 1 and 2, it is estimated that printing is difficult.

DESCRIPTION OF SYMBOLS 1 Label base material 2 Heat-shrinkable film 3 Light reflection layer 5 Cavity part 5a Wall surface around a cavity part 7 Matting layer 11,12 Heat-shrinkable cylindrical label

Claims (2)

A heat-shrinkable cylindrical label having a heat-shrinkable film including a polystyrene-based resin layer that satisfies the following conditions (1) to (4-1).
(1) In the differential thermal analysis curve by differential thermal-thermogravimetric simultaneous (TG / DTA) measurement, it has two exothermic peaks (F1, F2),
(2) The first exothermic peak (F1) is in the temperature range of 200 ° C to 250 ° C,
(3) The second exothermic peak (F2) is after the thermogravimetric weight is reduced by 1% by weight or more,
(4-1) No endothermic peak after the second exothermic peak (F2). A heat-shrinkable cylindrical label having a heat-shrinkable film including a polystyrene-based resin layer that satisfies the following conditions (1) to (4-2, 4-3).
(1) In the differential thermal analysis curve by differential thermal-thermogravimetric simultaneous (TG / DTA) measurement, it has two exothermic peaks (F1, F2),
(2) The first exothermic peak (F1) is in the temperature range of 200 ° C to 250 ° C,
(3) The second exothermic peak (F2) is after the thermogravimetric weight is reduced by 1% by weight or more,
(4-2, 4-3) The minimum value (A) before the first exothermic peak (F1) between the second exothermic peak (F2) and the thermal weight of 20%, and the It has an endothermic peak (E1) larger than a virtual line (X) passing through a minimum value (B) from the first exothermic peak (F1) to the second exothermic peak (F2), or the second exothermic peak (F2) ) Until the thermal weight reaches 20%, the minimum value (A) before the first exothermic peak (F1) and the first exothermic peak (F1) to the second exothermic peak (F2). Endothermic peak (E2) smaller than the imaginary straight line (X) passing through the minimum value (B), and the endothermic amount at the endothermic peak (E2) is smaller than 30 J / g, (E2) is calculated by the area surrounded by the differential thermal analysis curve including the virtual straight line (X). .

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