Heat-shrinkable multilayer film

Abstract

To provide a heat-shrinkable multilayer film having higher resistance to sebum whitening while maintaining rigidity.SOLUTION: The heat-shrinkable multilayer film includes a substrate, an intermediate layer, and a surface layer. The base material has a first surface and a second surface and contains a thermoplastic resin. The intermediate layer is laminated on at least one of the first surface and the second surface of the base material. The surface layer is laminated on the intermediate layer and contains a thermoplastic resin. The intermediate layer contains 50 mass% or more and 90 mass% or less of a cyclic olefin-based resin and 5 mass% or more and 35 mass% or less of a petroleum resin. The thickness of the surface layer is 10% or less of the thickness of the resin constituting the entire heat shrinkable multilayer film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to heat-shrinkable multilayer films. [Background technology]

[0002] Patent Document 1 discloses a heat-shrinkable multilayer film. The heat-shrinkable multilayer film disclosed in Patent Document 1 is formed by laminating an outermost layer containing a resin (A) having an alicyclic structure in its molecule and having a thickness of 1 μm or less, and an intermediate layer containing a thermoplastic resin (B) other than (A). Examples of the thermoplastic resin (B) include petroleum resins. According to Patent Document 1, this provides a heat-shrinkable multilayer film with a large shrinkage rate when heated and excellent sebum whitening properties. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-276516 Summary of the Invention [Problem to be solved by the invention]

[0004] According to Patent Document 1, the layer made of thermoplastic resin (B) preferably contains 70% by weight or more and 100% by weight or less of thermoplastic resin (B) based on all resin components constituting the layer. However, if the petroleum resin is contained in the above range, the toughness and rigidity of the heat-shrinkable multilayer film may decrease. This point is not taken into consideration in Patent Document 1.

[0005] The present disclosure aims to provide a heat-shrinkable multilayer film that is more resistant to sebum whitening while maintaining stiffness. [Means for solving the problem]

[0006] A heat-shrinkable multilayer film according to a first aspect comprises a substrate, an intermediate layer, and a surface layer. The substrate has a first side and a second side, and contains a thermoplastic resin. The intermediate layer is laminated on at least one of the first side and the second side of the substrate. The surface layer is laminated on the intermediate layer and contains a thermoplastic resin. The intermediate layer contains 50% by mass or more and 90% by mass or less of a cyclic olefin resin and 5% by mass or more and 35% by mass or less of a petroleum resin. The thickness of the surface layer is 10% or less of the thickness of the resins constituting the entire heat-shrinkable multilayer film.

[0007] A heat-shrinkable multilayer film according to a second aspect is the heat-shrinkable multilayer film according to the first aspect, wherein the intermediate layer further contains 30% by mass or less of an ethylene-based resin.

[0008] A heat-shrinkable multilayer film according to a third aspect is the heat-shrinkable multilayer film according to the first or second aspect, wherein the surface layer contains a cyclic olefin resin.

[0009] A heat-shrinkable multilayer film according to a fourth aspect is the heat-shrinkable multilayer film according to any one of the first to third aspects, wherein the intermediate layer contains 10% by mass or more and 30% by mass or less of a petroleum resin.

[0010] A heat-shrinkable multilayer film according to a fifth aspect is a heat-shrinkable multilayer film according to any one of the first aspect to the fourth aspect, in which an intermediate layer is laminated on each of the first and second surfaces of the substrate, and a surface layer is laminated on each intermediate layer.

[0011] A heat-shrinkable label according to a sixth aspect includes the heat-shrinkable multilayer film according to any one of the first to fifth aspects. [Effects of the Invention]

[0012] In view of the above, a heat-shrinkable multilayer film is provided that maintains rigidity and has higher resistance to sebum whitening. [Brief explanation of the drawings]

[0013] [Figure 1]1 is a cross-sectional view showing an example of a heat-shrinkable multilayer film according to an embodiment. [Figure 2] 1 is a cross-sectional view showing an example of a heat-shrinkable multilayer film according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, one embodiment of a heat-shrinkable multilayer film 100 according to the present disclosure will be described. This heat-shrinkable multilayer film 100 comprises a sheet-like substrate 1 having a first side and a second side, an intermediate layer 2 laminated on at least one of the first side and the second side of the substrate 1, and a surface layer 3 laminated on the intermediate layer 2. Therefore, as shown in FIG. 1, the heat-shrinkable multilayer film 100 can be configured in two ways: in which the intermediate layers 2 are laminated on both sides of the substrate 1 and the surface layer 3 is laminated on each intermediate layer 2; and in which the intermediate layer 2 is laminated on one side of the substrate 1 and the surface layer 3 is laminated on the intermediate layer 2, as shown in FIG. 2. Each component will be described in detail below. Note that a film formed from each material may be referred to as a film.

[0015] <1. Base material> The substrate 1 contains a thermoplastic resin. The thermoplastic resin may contain, for example, a propylene-based resin or a petroleum resin. This will be explained below.

[0016] <1-1. Propylene-based resin> From the viewpoint of exhibiting heat shrinkability, the propylene-based resin is preferably a binary or ternary random copolymer containing propylene as the main component and an α-olefin as a copolymerization component. Specific examples of the α-olefin include ethylene, 1-butene, 1-hexene, and 1-octene, and the resin may contain two or more types of α-olefins. The proportion of the α-olefin as a copolymerization component is preferably 1 to 10 mol %. Furthermore, the propylene-based resin may be a mixture of different propylene-α-olefin random copolymers.

[0017] Commercially available propylene-based resins such as those mentioned above include, for example, Adsyl (manufactured by Basell) and Novatec (manufactured by Japan Polypropylene Corporation).

[0018] The deflection temperature under load (0.45 MPa) of the propylene-based resin is preferably 110° C. or lower, and more preferably 90° C. or lower. When the propylene-based resin is a mixed resin containing two or more propylene-based resins with different deflection temperatures under load, the deflection temperature under load of the propylene-based resin refers to an apparent deflection temperature under load calculated by summing the products of the deflection temperatures under load of each propylene-based resin and the blending ratio (weight ratio).

[0019] The base material 1 preferably contains the above propylene-based resin in an amount of 65% by mass or more and 90% by mass or less, and more preferably 70% by mass or more and 85% by mass or less, relative to 100% by mass of the resin components constituting the base material 1.

[0020] <1-2. Petroleum resin> Petroleum resins are resins obtained by polymerizing C5 or C9 fractions produced by thermal cracking of naphtha, or mixtures of these, as well as hydrogenated products thereof. Among these, hydrogenated alicyclic hydrocarbon resins with partially or completely hydrogenated alicyclic structures are preferred from the viewpoints of suppressing softening of the film at temperatures below 100°C and ensuring transparency and rigidity. Furthermore, polymerized products obtained by purifying single or multiple components of C5 or C9 fractions can also be used.

[0021] Commercially available petroleum resins such as those mentioned above include, for example, Imave (manufactured by Idemitsu Kosan Co., Ltd.), Alcon (manufactured by Arakawa Chemical Industries Co., Ltd.), and Regalite (manufactured by Eastman Co., Ltd.).

[0022] The softening point of the petroleum resin is preferably 100° C. or higher and 150° C. or lower, and more preferably 120° C. or higher and 130° C. or lower. When the softening point of the petroleum resin is within the above range, the heat shrinkability can be kept within a good range.

[0023] The base material 1 preferably contains 10% by mass or more and 35% by mass or less of the above petroleum resin, and more preferably 15% by mass or more and 30% by mass or less, relative to 100% by mass of the resin components constituting the base material 1. When the content is within this range, the heat-shrinkable multilayer film can be imparted with high shrinkability and high rigidity. Furthermore, when the content of the petroleum resin is below the above upper limit, a decrease in elongation at low temperatures and delamination between layers can be suppressed.

[0024] <1-3. Thickness> The thickness of the substrate 1 is, for example, preferably 50% or more and 90% or less of the thickness of the resin that constitutes the entire heat-shrinkable multilayer film 100, more preferably 60% or more and 84% or less, and even more preferably 70% or more and 80% or less.

[0025] 2. Middle Class The intermediate layer 2 mainly contains a cyclic olefin resin and a petroleum resin, and may further contain an ethylene resin in addition to these.

[0026] <2-1. Cyclic olefin resin> The cyclic olefin resin not only increases the heat shrinkage rate but also improves the stretchability during production of the heat-shrinkable multilayer film 100. A preferred cyclic olefin resin is a cyclic olefin copolymer (COC). The cyclic olefin copolymer can be obtained, for example, by copolymerizing an α-olefin and a cyclic olefin.

[0027] The cyclic olefin is not particularly limited, and examples thereof include norbornene and derivatives thereof, such as norbornene, 6-methylnorbornene, 6-ethylnorbornene, 5-propylnorbornene, 6-n-butylnorbornene, 1-methylnorbornene, 7-methylnorbornene, 5,6-dimethylnorbornene, 5-phenylnorbornene, and 5-benzylnorbornene, as well as tetracyclododecene and derivatives thereof, such as tetracyclododecene, 8-methyltetracyclo-3-dodecene, 8-ethyltetracyclo-3-dodecene, and 5,10-dimethyltetracyclo-3-dodecene.

[0028] Commercially available products of the above-mentioned cyclic olefin resins include APEL (manufactured by Mitsui Chemicals, Inc.), TOPAS COC (manufactured by Polyplastics Co., Ltd.), and ZEONOR (manufactured by Zeon Corporation).

[0029] The number average molecular weight of the cyclic olefin resin measured by GPC (gel permeation chromatography) is preferably 1000 or more and 1 million or less. By keeping it within the above range, film formation becomes easy.

[0030] The glass transition temperature of the cyclic olefin resin is preferably 20°C or higher and 130°C or lower, and more preferably 50°C or higher and 100°C or lower. When the glass transition temperature is 20°C or higher, the heat resistance of the film surface is improved, which can prevent blocking between containers on the mounting line and keep the natural shrinkage within a good range. When the glass transition temperature is 130°C or lower, the thermal shrinkage in the transverse direction can be sufficiently increased.

[0031] The density of the cyclic olefin resin is 1000 kg / m 3 More than 1050kg / m 3 It is preferable that the saturation is 1010 kg / m or less. 3 More than 1040kg / m 3 More preferably, it is:

[0032] The intermediate layer 2 preferably contains 50% by mass or more and 90% by mass or less of the cyclic olefin resin, more preferably 55% by mass or more and 85% by mass or less, and even more preferably 60% by mass or more and 80% by mass or less, relative to 100% by mass of the resin components constituting the intermediate layer 2. When the content of the cyclic olefin resin is within the above range, the rigidity, heat shrinkability, and transparency of the heat-shrinkable multilayer film 100 can be improved.

[0033] <2-2. Ethylene-based resins> Examples of ethylene-based resins include branched low-density polyethylene resins, linear low-density polyethylene resins, ethylene-vinyl acetate copolymers, ionomer resins, and mixtures thereof. Also included are copolymers of ethylene and α-olefins. Examples of α-olefins include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. The copolymers may be random copolymers or block copolymers. It is particularly preferred that the mid layer 2 contain a linear low-density polyethylene resin.

[0034] Commercially available linear low-density polyethylene resins such as those described above include Evolue (manufactured by Prime Polymer Co., Ltd.), Yumerit (manufactured by Ube Maruzen Polyethylene Co., Ltd.), Novatec, etc. Commercially available low-density polyethylene resins include Sumikasen (manufactured by Sumitomo Chemical Co., Ltd.) and Novatec (manufactured by Japan Polyethylene Corporation).

[0035] The intermediate layer 2 preferably contains 3% by mass or more and 30% by mass or less of the ethylene-based resin, more preferably 5% by mass or more and 25% by mass or less, and even more preferably 8% by mass or more and 20% by mass or less, relative to 100% by mass of the resin components constituting the intermediate layer 2. When the content of the ethylene-based resin is within the above range, sebum whitening of the cyclic olefin-based resin can be preferably suppressed, and the sebum whitening resistance of the heat-shrinkable multilayer film 100 can be improved.

[0036] <2-3.Petroleum resin> The petroleum resin may be the same as that described in the description of the substrate 1. The intermediate layer 2 may contain the same petroleum resin as that of the substrate 1, or may contain a different petroleum resin. The intermediate layer 2 preferably contains 5% by mass or more and 35% by mass or less of the above petroleum resin, more preferably 10% by mass or more and 30% by mass or less, and even more preferably 15% by mass or more and 25% by mass or less, relative to 100% by mass of the resin components constituting the intermediate layer 2.

[0037] <2-4. Thickness> The thickness of the intermediate layer 2 is, for example, preferably 5% or more and 25% or less of the thickness of the resin that constitutes the entire heat-shrinkable multilayer film 100, more preferably 8% or more and 20% or less, and even more preferably 10% or more and 15% or less.

[0038] <3.Surface layer> The surface layer 3 contains a thermoplastic resin. Examples of the thermoplastic resin that can be used include styrene-based resins, polyester-based resins, ethylene-based resins, cyclic olefin-based resins, and the like, or a mixture of at least one of these. The surface layer 3 may further contain fine particles. The inclusion of such fine particles can form irregularities in the surface layer 3. As a result, the fine particles function as an antiblocking agent, and can reduce the blocking strength of the heat-shrinkable multilayer film 100. This is explained below.

[0039] <3-1. Styrene-based resin> Examples of the styrene-based resin that can be used include styrene-butadiene copolymer and hydrogenated styrene-based thermoplastic elastomer. Examples of commercially available styrene-based resins include Clearen (manufactured by Denka Co., Ltd.).

[0040] <3-2. Polyester resin> The polyester resin is not particularly limited, but glycol-modified polyethylene terephthalate is preferred.

[0041] <3-3. Ethylene-based resins> Examples of ethylene-based resins include linear low-density polyethylene resins, branched low-density polyethylene resins, ethylene-vinyl acetate copolymers, ionomer resins, and mixtures thereof. Commercially available products include those already exemplified in the description of the intermediate layer.

[0042] <3-4. Cyclic olefin resin> Details of the cyclic olefin resin are as described above. Using a cyclic olefin resin for the surface layer 3 can increase gloss and improve surface properties. Furthermore, in this embodiment, since the intermediate layer 2 also contains a cyclic olefin resin, using a cyclic olefin resin for the surface layer 3 improves the interlayer adhesive strength with the intermediate layer 2.

[0043] <3-5. Fine particles> The fine particles contained in the surface layer 3 can be either organic or inorganic. Examples of organic fine particles include acrylic resin fine particles, styrene resin fine particles, styrene-acrylic resin fine particles, urethane resin fine particles, and silicone resin fine particles. These may be crosslinked or uncrosslinked, but crosslinking is preferred to enhance the heat resistance of the fine particles. Among these, acrylic resin fine particles are preferred from the viewpoint of compatibility with the cyclic olefin resin, and polymethyl methacrylate crosslinked fine particles are more preferred. Commercially available organic fine particles include Techpolymer (manufactured by Sekisui Plastics Co., Ltd.), Finesphere (manufactured by Nippon Paint Co., Ltd.), Ganz Pearl (manufactured by Aica Kogyo Co., Ltd.), and Art Pearl (manufactured by Negami Chemical Industrial Co., Ltd.).

[0044] Examples of inorganic fine particles that can be used include silica, zeolite, and alumina.

[0045] The content of the fine particles is preferably 0.01 to 0.10 parts by weight, more preferably 0.03 to 0.08 parts by weight, relative to 100 parts by weight of the resin component constituting the surface layer 3.

[0046] <3-6. Thickness> The thickness of the surface layer 3 is preferably 0.1% to 10% of the thickness of the resin constituting the entire heat-shrinkable multilayer film 100, more preferably 0.3% to 8% and even more preferably 0.5% to 3%. By setting the thickness of the surface layer 3 within the above range, the heat-shrinkable multilayer film 100 can have improved resistance to sebum whitening.

[0047] <4. Thickness of heat-shrinkable multilayer film> The overall thickness of the heat-shrinkable multilayer film of the present invention is preferably 15 μm or more and 50 μm or less, more preferably 20 μm or more and 45 μm or less, and even more preferably 25 μm or more and 40 μm or less.

[0048] <5. Other ingredients> The substrate 1, the intermediate layer 2, and the surface layer 3 may contain additives such as antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, fluorescent brighteners, and colorants, as needed.

[0049] 6. Heat shrinkage performance of heat shrinkable multilayer film When the heat-shrinkable multilayer film 100 is immersed in 70°C hot water for 10 seconds, then immersed in 20°C water for 10 seconds, and then removed, the heat shrinkage in the main shrinkage direction (TD direction) is preferably 5% or more and preferably 30% or less. When the film is immersed in 80°C hot water for 10 seconds, then immersed in 20°C water for 10 seconds, and then removed, the heat shrinkage in the main shrinkage direction is preferably 30% or more and preferably 60% or less. When the film is immersed in 90°C hot water for 10 seconds, then immersed in 20°C water for 10 seconds, and then removed, the heat shrinkage in the main shrinkage direction is preferably 50% or more and preferably 70% or less. When the film is immersed in 98°C hot water for 10 seconds, then immersed in 20°C water for 10 seconds, and then removed, the heat shrinkage in the main shrinkage direction is preferably 60% or more and preferably 80% or less.

[0050] When the heat shrinkage rate is within the above range, heat shrinkage over a relatively wide temperature range becomes possible, and the film can be suitably used as a heat-shrinkable multilayer film.

[0051] 7. Young's Modulus of Heat-Shrinkable Multilayer Film The heat-shrinkable multilayer film 100 may be formed into a cylindrical shape with the main shrinkage direction as the circumferential direction, and used as a base film for labels or packaging materials to be attached to containers such as PET bottles and metal cans, although this is not limited thereto. For this reason, the heat-shrinkable multilayer film 100 is required to have a certain level of rigidity so that the cylindrical label or packaging material does not break or collapse when attached to the container. The Young's modulus of the heat-shrinkable multilayer film 100 in the direction perpendicular to the main shrinkage direction (MD direction) preferably exceeds 1.3 (GPa). Furthermore, the Young's modulus of the heat-shrinkable multilayer film 100 in the main shrinkage direction preferably exceeds 1.6 (GPa).

[0052] 8. Manufacturing method of heat-shrinkable multilayer film Although there are no particular limitations on the method for producing the heat-shrinkable multilayer film 100, a method in which each layer is simultaneously formed by co-extrusion is preferred. When the co-extrusion method is co-extrusion using a T-die, the lamination method may be any of a feed block method, a multi-manifold method, or a method combining these.

[0053] Specific examples of methods for producing the heat-shrinkable multilayer film 100 include a method in which the raw materials constituting the substrate 1, intermediate layer 2, and surface layer 3 are each fed into an extruder, extruded into a sheet through a die, cooled and solidified by a take-up roll, and then uniaxially or biaxially stretched. Examples of the stretching method that can be used include roll stretching, tenter stretching, or a combination of these. The stretching temperature varies depending on the softening temperature of the resins constituting the heat-shrinkable multilayer film 100, the shrinkage properties required of the heat-shrinkable multilayer film 100, and the like, but is preferably 65°C or higher, more preferably 70°C or higher, and preferably 120°C or lower, more preferably 115°C or lower.

[0054] The stretching ratio in the main shrinkage direction varies depending on the resin constituting the heat-shrinkable multilayer film 100, the stretching means, the stretching temperature, etc., but is preferably 3 times or more, more preferably 4 times or more, and is preferably 7 times or less, more preferably 6 times or less.

[0055] <9. Uses of heat-shrinkable multilayer films> The heat-shrinkable multilayer film 100 has excellent heat shrinkability, rigidity, transparency, and resistance to sebum blanching. Therefore, the use of the heat-shrinkable multilayer film 100 is not particularly limited, but it is suitably used, for example, as a heat-shrinkable label attached to containers such as PET bottles and metal cans, and as a base film for packaging. Such heat-shrinkable labels can be obtained, for example, by cutting the printed heat-shrinkable multilayer film 100 into an appropriate strip shape. The two ends of this heat-shrinkable label are overlapped and sealed with a solvent to form a cylindrical shape, which is then placed over a container and heated in a shrink tunnel, yielding a container with a heat-shrinkable label attached. As illustrated in this example, a heat-shrinkable label including the heat-shrinkable multilayer film according to the present disclosure also constitutes part of the present disclosure.

[0056] <10. Features> According to the heat-shrinkable multilayer film 100 of this embodiment, the thickness of the surface layer 3 is 0.1% or more and 10% or less of the thickness of the resin constituting the entire heat-shrinkable multilayer film 100, and the intermediate layer 2 contains an appropriate amount of petroleum resin. This prevents areas that come into contact with a person's hand from turning white due to sebum after heat shrinkage, which would have an undesirable effect on the appearance. Furthermore, petroleum resin tends to reduce the toughness and rigidity of heat-shrinkable multilayer films, but the heat-shrinkable multilayer film 100 is able to maintain its overall toughness and rigidity because the intermediate layer 2 contains appropriate amounts of both petroleum resin and cyclic olefin resin. [Example]

[0057] Examples of the present disclosure will be described in detail below, but the present disclosure is not limited to these examples.

[0058] <1. Preparation of Examples and Comparative Examples> Heat-shrinkable multilayer films according to Examples 1 to 9 and Comparative Examples 1 to 3 were prepared as follows: Examples 1 to 9 and Comparative Examples 1 to 3 had a five-layer structure as shown in FIG.

[0059] The components shown in Table 1 were used as raw materials for the substrate, intermediate layer, and surface layer, and these were mixed in the proportions shown in Table 1 to obtain raw material compositions for the substrate, intermediate layer, and surface layer of Examples 1 to 9 and Comparative Examples 1 to 3. The raw materials for the substrate were the same for Examples 1 to 9 and Comparative Examples 1 to 3, but the thicknesses were different. APEL APL6509T (manufactured by Mitsui Chemicals, Inc.) was used as the cyclic olefin-based resin for the surface layer and intermediate layer. EVOLUE SP1020 (manufactured by Prime Polymer Co., Ltd.) was used as the ethylene-based resin for the intermediate layer in Examples 1 to 8 and Comparative Examples 1 to 3. On the other hand, no ethylene-based resin was used for the intermediate layer in Example 9. ARKON P125 (manufactured by Arakawa Chemical Industries, Ltd.) was used as the petroleum resin for the intermediate layer and substrate. The antiblocking agent was the same for Examples 1 to 9 and Comparative Examples 1 to 3.

[0060] Next, the raw material compositions constituting the substrate, intermediate layer, and surface layer were melted using separate extruders at a barrel temperature of 180°C for the substrate, 210°C for the intermediate layer, and 210°C for the surface layer, and extruded through a T-die and cooled and solidified using rolls cooled to 30°C to produce an unstretched sheet. This was stretched 1.3 times in the MD direction using a roll-type stretching machine, and then stretched 5 times in the TD direction using a tenter-type stretching machine at a temperature of 110°C to produce a 40 μm thick heat-shrinkable multilayer film with each layer having a thickness shown in Table 1. Note that the "thickness (%) of the surface layer relative to the total thickness" shown in Table 1 refers to the thickness (%) of the resin constituting one surface layer relative to the thickness of the resin constituting the entire heat-shrinkable multilayer film.

[0061] [Table 1] The units for the materials constituting the surface layer, intermediate layer, and substrate are % by mass, and the unit for the antiblocking agent is parts by mass.

[0062] <2. Evaluation> The above Examples 1 to 9 and Comparative Examples 1 to 3 were evaluated as follows.

[0063] <2-1. Haze> Samples of the same size were cut out from the heat-shrinkable multilayer films according to Examples 1 to 9 and Comparative Examples 1 to 3, and the haze (%) was measured in accordance with JIS K7136.

[0064] <2-2. Resistance to sebum whitening> A mixed reagent consisting of 50% by mass of oleic acid, 40% by mass of stearyl palmitate, and 10% by mass of squalene as sebum equivalents was applied to both the front and back of a sample cut from a heat-shrinkable multilayer film and left to stand at 40°C for 30 minutes. The haze (%) was then measured according to JIS K7136 and compared with the haze before application of the mixed reagent. Samples with the smallest increase in haze from before application of the mixed reagent were ranked as Level 1, Level 2, and Level 3, respectively. In other words, Level 1 indicates relatively high resistance to sebum whitening, Level 2 indicates acceptable resistance to sebum whitening, and Level 3 indicates resistance to sebum whitening that does not meet the standard.

[0065] <2-3. Heat shrinkage rate> Three measurement samples measuring 100 mm length x 100 mm width (TD direction of the film is the longitudinal direction, MD direction is the transverse direction) were cut out from any position of each of the heat-shrinkable multilayer films according to Examples 1 to 9 and Comparative Examples 1 to 3. Each measurement sample was immersed in warm water for 10 seconds, and then in water at 20°C for 10 seconds. After being removed from the water, the length L1 in the TD direction and the length L2 in the MD direction of each measurement sample were measured, and the heat shrinkage in each direction was calculated according to the following formula, and the average value for the three samples was calculated. Heat shrinkage rate (%) = {(100-Ln) / 100} x 100 (n=1, 2) The hot water used was 70°C, 80°C, 90°C, and 98°C, and the heat shrinkage rate was calculated for each.

[0066] <2-4. Natural shrinkage rate> Measurement samples measuring 100 mm long x 100 mm wide (TD direction of the film is the longitudinal direction, MD direction is the transverse direction) were cut out from any position of each of the heat-shrinkable multilayer films according to Examples 1 to 9 and Comparative Examples 1 to 3. These were left to stand for 7 days in a low-temperature incubator (IL-82, manufactured by Yamato Scientific Co., Ltd.) adjusted to 40°C, and the natural shrinkage was calculated according to the same formula as for the thermal shrinkage.

[0067] <2-5.Young's Modulus> Measurement samples measuring 250 mm lengthwise and 5 mm widthwise (the MD direction of the film is the longitudinal direction, and the TD direction is the transverse direction) and 250 mm lengthwise and 5 mm widthwise (the TD direction of the film is the longitudinal direction, and the MD direction is the transverse direction) were cut out from arbitrary locations of each of the heat-shrinkable multilayer films of Examples 1 to 9 and Comparative Examples 1 to 3. The Young's moduli (GPa) in the MD and TD directions were measured using the measurement samples and a Strograph (VE-1D, manufactured by Toyo Seiki Seisaku-sho, Ltd.) according to ASTM D882.

[0068] <2-6. Tensile elongation at break> Measurement samples measuring 40 mm lengthwise and 10 mm widthwise (MD direction of the film is the machine direction, TD direction is the transverse direction) were cut out from any location of each of the heat-shrinkable multilayer films according to Examples 1 to 9 and Comparative Examples 1 to 3. The measurement samples were set in a Strograph (VE-1D, manufactured by Toyo Seiki Seisaku-sho, Ltd.), and the tensile elongation at break was measured in accordance with JIS K-6732. The temperature during measurement was 5°C, and the pulling speed was 100 mm / min. The tensile elongation at break (toughness) was evaluated as "pass" if the break occurred at 100% or more, and as "fail" if the break occurred at less than 100%.

[0069] <2-7. Blocking> Two measurement samples measuring 100 mm long x 30 mm wide (the TD direction of the film is the longitudinal direction, and the MD direction is the transverse direction) were cut from any location of each of the heat-shrinkable multilayer films of Examples 1 to 9 and Comparative Examples 1 to 3. Next, the two measurement samples were overlapped with each other on the same surface, with an area of ​​40 mm long x 30 mm wide. The overlapping measurement samples were then sandwiched between two glass plates, and a 5 kg weight was placed on the overlapping portion of the samples. The samples thus set were placed in a thermostatic oven at 40°C and left for 48 hours. The samples were then removed from the thermostatic oven and placed in a peel tester (Peeling Tester Heidon-17, manufactured by Shinto Scientific Co., Ltd.) and pulled at a 180° angle at a pulling rate of 200 mm / min. The peel adhesion strength at which the two samples peeled off was determined as the blocking strength. The blocking strength was evaluated as "passable" if it was 2000 g / cm or less, and as "failable" if it was over 2000 g / cm.

[0070] <2-8. Interlayer adhesion strength> Measurement samples measuring 100 mm length x 10 mm width (TD direction of the film is the longitudinal direction, MD direction is the transverse direction) were cut out from any location of each of the heat-shrinkable multilayer films of Examples 1 to 9 and Comparative Examples 1 to 3. The measurement samples were set in a peel tester (Peeling Tester Heidon-17, manufactured by Shinto Scientific Co., Ltd.), and the strength (N / 10 mm) was measured at 23°C when peeled in a 180° direction at a pulling rate of 500 mm / min. The interlayer adhesive strength was evaluated as "good" if the interlayer delamination occurred at the interface between the substrate and the intermediate layer, and as "fair" if the interlayer delamination occurred at the interface between the surface layer and the intermediate layer and was 0.20 N / 10 mm or more.

[0071] <2-9. Evaluation Results> The evaluation results are as follows: [Table 2]

[0072] The above results confirmed that Examples 1 to 9 had no manufacturing problems with rigidity, expressed as Young's modulus, and had sebum blushing resistance. Example 8 confirmed that, even when the ethylene-based resin content in the intermediate layer was relatively high, there were no manufacturing problems with rigidity and sebum blushing resistance, as with the other Examples, and no manufacturing problems with other parameters such as shrinkage, tensile break elongation, blocking, and interlayer adhesive strength. Furthermore, Example 9 confirmed that there were no manufacturing problems with rigidity, sebum blushing resistance, shrinkage, tensile break elongation, blocking, and interlayer adhesive strength, even when the intermediate layer did not contain an ethylene-based resin. In contrast, Comparative Example 1, in which the intermediate layer contained a low petroleum resin, resulted in poor sebum blushing resistance. On the other hand, Comparative Example 2, in which the intermediate layer contained a high petroleum resin, resulted in poor Young's modulus and tensile break elongation, confirming reduced rigidity and toughness. It is believed that Comparative Example 3 had poor sebum blushing resistance due to the large thickness ratio of the surface layer. The surface layers of Examples 6 and 7 did not contain a cyclic olefin resin. For this reason, it is believed that the interlayer adhesive strength between the surface layer and the intermediate layer was weaker than in the other examples, although it was within an acceptable range. [Explanation of symbols]

[0073] 1 Base material 2. Middle class 3 Surface layer

Claims

1. a substrate having a first surface and a second surface and containing a thermoplastic resin; an intermediate layer laminated on at least one of the first surface and the second surface of the substrate; a surface layer laminated on the intermediate layer and containing a thermoplastic resin; Equipped with the intermediate layer contains 50% by mass or more and 90% by mass or less of a cyclic olefin resin and 5% by mass or more and 35% by mass or less of a petroleum resin, The thickness of the surface layer is 10% or less of the thickness of the resin constituting the entire heat-shrinkable multilayer film. Heat-shrinkable multilayer film.

2. The intermediate layer further contains 30% by mass or less of an ethylene-based resin. The heat-shrinkable multilayer film according to claim 1 .

3. The surface layer contains a cyclic olefin resin. The heat-shrinkable multilayer film according to claim 1 or 2.

4. The intermediate layer contains 10% by mass or more and 30% by mass or less of the petroleum resin. The heat-shrinkable multilayer film according to any one of claims 1 to 3.

5. the intermediate layer is laminated on each of the first surface and the second surface of the substrate; The surface layer is laminated on each of the intermediate layers. The heat-shrinkable multilayer film according to any one of claims 1 to 4.

6. A heat-shrinkable label comprising the heat-shrinkable multilayer film according to any one of claims 1 to 5.

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