Thermally shrinkable polyester film

Abstract

[PROBLEM] To provide a heat-shrinkable polyester film in which the protrusions of the film surface are constant in a range in which the film roll obtained has high heat-shrinkage in the width direction as the main shrinkage direction, transparency, printability, and good appearance. [SOLUTION] A heat-shrinkable polyester film characterized by satisfying the following characteristics (1) to (5). (1) The hot water heat-shrinkage when the film is immersed in hot water at 90°C for 10 seconds is 40% or more and 80% or less in the film width direction (2) The hot water heat-shrinkage when the film is immersed in hot water at 90°C for 10 seconds is -5% or more and 10% or less in the film length direction (3) The maximum protrusion height Sp of at least one film surface is 0.8 μm or more and 3.0 μm or less (4) The arithmetic mean height Sa of at least one film surface is 0.03 μm or more and 0.2 μm or less (5) The outgassing time of the film surface / back surface to each other is 14 seconds or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a heat-shrinkable polyester film, and more particularly to a heat-shrinkable polyester film having transparency, less wrinkles in a roll shape, and being suitable for processing such as printing, a heat-shrinkable label, and a packaging body. BACKGROUND

[0002] In recent years, in the use for label packaging, cap sealing, integrated packaging, and the like, which serve as protection and indication of a product such as a glass bottle or a plastic bottle, a heat-shrinkable polyester film having high heat resistance, easy incineration, and excellent solvent resistance has been gradually widely used as a shrink label, and there is a tendency that the use amount increases with the increase in the size of a PET (polyethylene terephthalate) bottle container or the like.

[0003] Hitherto, as a label for covering a PET bottle, a thick heat-shrinkable film has been gradually used. However, the heat-shrinkable film used in packaging becomes simple garbage after use of the content. Therefore, with the increase in environmental awareness that garbage should be reduced as much as possible, in order to reduce the thickness of the label, film manufacturers have also attempted to reduce the thickness of the heat-shrinkable polyester film.

[0004] However, the present inventors and the like have found that if the thickness of the film is reduced, the stiffness of the film decreases, and air easily enters when the film is wound into a roll shape, and if the outgassing of the film is poor, an adverse situation in which wrinkles occur in the roll shape occurs.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent No. 5240387

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-117700 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In general, a heat-shrinkable film is uniaxially stretched, and the tensile strength at break in the main shrink direction as the stretching direction is high, and the tensile strength at break in the non-shrink direction (a direction orthogonal to the main shrink direction) is low. In contrast, in Patent Document 1, the tensile strength at break in both the length direction and the width direction of the heat-shrinkable polyester film is increased by performing biaxial stretching, and a film having high film strength is produced. However, compared to the production method of a general heat-shrinkable film, the production method of the film is very complicated, requires expansion of equipment, and has problems such as high initial investment costs.

[0011] In addition, in Patent Literature 2, the surface roughness and the inorganic particle content of the biaxially stretched polyester film are limited. Patent Literature 2 relates to a crystalline biaxially stretched polyester film, and the roughness generated by the surface protrusions of a heat-shrinkable polyester film using an amorphous raw material and subjected to only uniaxial stretching, and the degassing at the time of winding into a roll are different from those of the biaxially stretched polyester film.

[0012] Therefore, the present application has an object to provide a heat-shrinkable polyester film which is excellent in degassing, winding quality, and printability, and in which wrinkles are less likely to occur, even if the thickness is 15 μm to 50 μm.

[0013] Solution to the problem

[0014] The present application for solving the aforementioned problems comprises the following configuration.

[0015] 1. A heat-shrinkable polyester film, characterized by satisfying the following characteristics (1) to (5).

[0016] (1) The hot water shrinkage rate when the film is immersed in hot water at 90°C for 10 seconds is 40% or more and 80% or less in the film width direction

[0017] (2) The hot water shrinkage rate when the film is immersed in hot water at 90°C for 10 seconds is -5% or more and 10% or less in the film length direction

[0018] (3) The maximum protrusion height Sp of at least one film surface is 0.8 μm or more and 3.0 μm or less

[0019] (4) The arithmetic mean height Sa of at least one film surface is 0.03 μm or more and 0.2 μm or less

[0020] (5) The degassing time of the film surface / back surface to each other is 14 seconds or less.

[0021] 2. The heat-shrinkable polyester film according to 1, characterized in that the thickness of the film is 15 μm or more and 50 μm or less.

[0022] 3. The heat-shrinkable polyester film according to 1 or 2, characterized in that the haze when the film thickness is 30 μm is 2% or more and 11% or less.

[0023] 4. The heat-shrinkable polyester film according to any one of 1 to 3, characterized in that it is a laminated heat-shrinkable polyester film in which at least 2 or more layers are laminated.

[0024] 5. A heat-shrinkable label using the heat-shrinkable polyester film according to any one of 1 to 4.

[0025] 6. A packaging body, characterized in that it is formed by covering at least a portion of the outer periphery of the packaged object with the heat-shrinkable label described in 5 above and causing it to heat-shrink.

[0026] The effects of the invention

[0027] The heat-shrinkable polyester film of the present invention maintains transparency and printability by keeping the surface roughness and degassing within a constant range, and even when the film thickness is thin, it can maintain good wrinkles and printability when rolled into a roll. Attached Figure Description

[0028] Figure 1 A diagram illustrating the method for determining the degassing time according to the present invention. Detailed Implementation

[0029] The heat-shrinkable polyester film of the present invention will now be described in detail. It should be noted that the manufacturing method of the heat-shrinkable polyester film will be described in detail below, but heat-shrinkable films are generally obtained by transporting and stretching using rollers or the like. In this case, the transport direction (film-forming direction) of the film is referred to as the length direction, and the direction orthogonal to the aforementioned length direction is referred to as the film width direction.

[0030] The heat-shrinkable polyester film of the present invention is a heat-shrinkable polyester film, characterized in that it satisfies the following features (1) to (5).

[0031] (1) When the film is immersed in hot water at 90°C for 10 seconds, the hot water thermal shrinkage rate is more than 40% and less than 80% in the width direction of the film.

[0032] (2) When the film is immersed in hot water at 90°C for 10 seconds, the thermal shrinkage rate of the hot water is greater than -5% and less than 10% along the length of the film.

[0033] (3) The maximum protrusion height Sp of at least one thin film surface is greater than 0.8 μm and less than 3 μm.

[0034] (4) The arithmetic mean height Sa of at least one thin film surface is greater than 0.03 μm and less than 0.2 μm.

[0035] (5) The degassing time between the surface and back of the film is less than 14 seconds.

[0036] The polyester used in the heat-shrinkable polyester film of the present invention uses polyethylene terephthalate units as the main component. The polyethylene terephthalate units constitute 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more of the polyester constituent units in 100 mol% of the total polyester composition.

[0037] As the other dicarboxylic acid component constituting the polyester of the present application, there can be mentioned aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, 2,6-naphthalene dicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, decane dicarboxylic acid, and alicyclic dicarboxylic acids such as 1,4-cyclohexane dicarboxylic acid, and the like.

[0038] Further, it is preferable to include a polybasic acid of three or more (e.g., trimellitic acid, pyromellitic acid, and anhydrides thereof, and the like) in the polyester. In a heat-shrinkable polyester film using a polyester containing such a polybasic acid, it becomes difficult to achieve the desired high shrinkage.

[0039] As the diol component constituting the polyester, in addition to ethylene glycol, there can be mentioned 1,3-propanediol, 2,2-diethyl-l,3-propanediol, 2-n-butyl-2-ethyl-l,3-propanediol, 2,2-isopropyl-l,3-propanediol, 2,2-di-n-butyl-l,3-propanediol, 1,4-butanediol, hexanediol, neopentyl glycol, aliphatic diols such as hexanediol, alicyclic diols such as 1,4-cyclohexane dimethanol, aromatic diols such as bisphenol A, and the like.

[0040] Among these, it is preferable to use a cyclic diol such as 1,4-cyclohexane dimethanol, and a diol having a carbon number of 3 to 6 (e.g., 1,3-propanediol, 1,4-butanediol, neopentyl glycol, hexanediol, and the like). In particular, if 1,4-butanediol or neopentyl glycol is used, it becomes easy to obtain a polyester satisfying the necessary technical features of the present application.

[0041] Further, the total of the amorphous components in 100 mol% of the polyol component and in 100 mol% of the polybasic acid component (i.e., in total 200 mol%) in the entire polyester resin is 17 mol% or more, preferably 18 mol% or more, more preferably 19 mol% or more, and particularly preferably 20 mol% or more. Note that, as the monomers in the aforementioned monomer component that can become amorphous components, there can be mentioned, for example, neopentyl glycol, 1,4-cyclohexane dimethanol, isophthalic acid, 1,4-cyclohexane dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2,2-diethyl-l,3-propanediol, 2-n-butyl-2-ethyl-l,3-propanediol, 2,2-isopropyl-l,3-propanediol, 2,2-di-n-butyl-l,3-propanediol, and hexanediol. Further, the upper limit of the total of the amorphous components is not particularly limited, and is preferably set to 30 mol% or less. By setting the amount of the amorphous components to the above range, a polyester having a glass transition point (Tg) adjusted to 60 to 80°C is obtained.

[0042] Note that in the polyester, it is preferable that no diol having 8 or more carbon atoms (e.g., octanediol, etc.) or trihydric or higher polyhydric alcohol (e.g., trimethylolpropane, trimethylolethane, glycerol, diglycerol, etc.) be contained. In a heat-shrinkable polyester film obtained using a polyester containing such diol or polyhydric alcohol, it becomes difficult to achieve the desired high shrinkage. In addition, it is also preferable that no diethylene glycol, triethylene glycol, or polyethylene glycol be contained in the polyester as much as possible.

[0043] In the resin for forming the heat-shrinkable polyester film of the present application, various additives such as waxes, antioxidants, antistatic agents, crystallization nucleating agents, thickeners, heat stabilizers, pigments for coloring, coloring preventing agents, ultraviolet absorbers, etc. can be added as needed.

[0044] In the resin for forming the heat-shrinkable polyester film of the present application, in order to make the maximum protrusion height Sp, the arithmetic average height Sa, and the degassing time of the film surface / back surface each other within a prescribed range, it is preferable to add microparticles. As the microparticles, any of them can be selected, for example, as inorganic microparticles, there can be mentioned silica, alumina, titanium dioxide, calcium carbonate, kaolin, barium sulfate, etc., and as organic microparticles, there can be mentioned, for example, acrylic resin particles, melamine resin particles, silicone resin particles, crosslinked polystyrene particles, etc. The average particle diameter of the microparticles is within a range of 1.0 to 5.0 μm (when measured by a Coulter counter), preferably within a range of 2.0 to 5.0 μm, and can be appropriately selected as needed. As to the particle shape, it can be either spherical or amorphous, but the number of protrusions of the film surface becomes larger in the case of the spherical shape than in the case of the amorphous shape. However, the spherical shape is generally more expensive than the amorphous shape, and thus it is desirable to select them according to the purpose. The amount of the microparticles to be added in the surface layer / inner layer of the heat-shrinkable polyester film is preferably 350 ppm or more and 20,000 ppm or less. If the amount of the microparticles to be added is less than 350 ppm, the maximum protrusion height Sp and the arithmetic average height Sa of the film surface become low, and it becomes impossible to make the degassing time within a prescribed range, which is not preferable. Moreover, if the amount of the microparticles to be added is more than 20,000 ppm, the degassing time becomes short, which is preferable, but the maximum protrusion height Sp and the arithmetic average height Sa become high, and the transparency and the printability deteriorate, which is not preferable. It is more preferable that the amount of the microparticles to be added be 450 ppm or more and 19,000 ppm or less, and particularly preferably 550 ppm or more and 18,000 ppm or less.

[0045] By using the above-mentioned preferable microparticles in combination with the preferable production method described later, protrusions suitable for the present application are formed on the film surface, and it is possible to control the aforementioned maximum protrusion height Sp, the arithmetic average height Sa, and the degassing time within a prescribed range.

[0046] As a method of compounding the above-mentioned particles in a resin for forming a heat-shrinkable polyester film, for example, it can be added at any stage of manufacturing the polyester resin, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification, or after the end of the transesterification reaction, before the start of the polycondensation reaction, and the polycondensation reaction is promoted. Further, it is also preferable to use a method of compounding a slurry of particles dispersed in ethylene glycol or water or the like with polyester resin raw materials using a mixing extruder with a vent, or a method of compounding dried particles with polyester resin raw materials using a mixing extruder, or the like.

[0047] The heat-shrinkable polyester film of the present application can also be subjected to corona treatment, coating treatment, flame treatment, or the like to make the adhesion of the film surface good.

[0048] Note that the heat-shrinkable polyester film of the present application also includes a laminated polyester film having at least one polyester resin layer. When the polyester resin layers are laminated in two or more layers, the polyester resin layers can be the same polyester or different polyesters. Further, the other layers that can be laminated are not particularly limited as long as they are thermoplastic resin layers, and are preferably polystyrene resin layers in terms of price and heat-shrinkage characteristics.

[0049] In the lamination of two or more layers of polyester resin layers alone, the polyester resin layer containing the microparticles must be on the surface / back surface. This is because the surface / inner layer is overlapped in a film roll shape, and thus the aforementioned maximum protrusion height Sp, arithmetic mean height Sa on the film surface are regulated within a certain range, so that the wrinkles of the film roll can be suppressed. The layer configuration can be one 2-layer, two 3-layers, three 3-layers, three 5-layers, and the two 3-layer configuration is suitable for preventing the enlargement of the equipment, and for controlling the protrusions on the film surface, the transparency. In the two 3-layer configuration, it is preferable to form a polyester resin layer containing microparticles / polyester resin layer not containing microparticles / polyester resin layer containing microparticles. By forming the same polyester resin layer containing microparticles, the protrusions on the front and back of the film can be controlled identically. Further, by making the middle layer a layer not containing microparticles, the transparency can be optimized. In the two 3-layer configuration, the polyester resin layer containing microparticles that appears in the front and back is preferably 4% or more and 70% or less of the total thickness. When it is less than 4%, the thickness of the polyester resin layer on one side becomes less than 2%, and in the case where the thickness precision of the polyester resin layer containing microparticles during the production of the film is poor, the thickness of the polyester resin layer containing microparticles becomes thin, and the target surface protrusion cannot be obtained, so it is not preferable. Even if it is more than 70%, there is no problem, but if the polyester resin layer not containing microparticles becomes thick, the transparency deteriorates, so it is not preferable. The thickness ratio of the polyester resin layer containing microparticles in the two 3-layer configuration / polyester resin layer not containing microparticles / polyester resin layer containing microparticles is more preferably 8% or more and 60% or less, and particularly preferably 10% or more and 50% or less.

[0050] A thermoplastic resin and / or a rubber component are preferably added to the polystyrene-based resin. As the thermoplastic resin, a polystyrene having a random structure, an AS resin, an ABS resin, and the like styrene-based resins, a polyethylene terephthalate, a polyethylene naphthalate, a polybutylene terephthalate, and the like polyester-based resins, nylon 6, nylon 66, nylon 12, nylon 4, polyhexamethylene adipamide, and the like polyamide-based resins, polyethylene, polypropylene, polybutylene, and the like polyolefin-based resins, and the like can be given.

[0051] On the other hand, as the rubber component, a rubbery copolymer containing a styrene-based compound as a constituent component thereof is preferable, and a random, block, or graft copolymer in which one or more kinds of styrene and a rubber component are each selected and copolymerized can be given. As such a rubbery copolymer, for example, a styrene-butadiene copolymer rubber, a styrene-isoprene block copolymer, a rubber in which a part or all of the butadiene portion of these is hydrogenated, a methyl acrylate-butadiene-styrene copolymer rubber, an acrylonitrile-butadiene-styrene copolymer rubber, an acrylonitrile-alkyl acrylate-butadiene-styrene copolymer rubber, a methyl methacrylate-alkyl acrylate-butadiene-styrene copolymer rubber, and the like can be given. The rubbery copolymer containing the above-described styrene-based compound as a constituent component thereof has a styrene unit, and thus has good dispersibility for the polystyrene-based resin having a syndiotactic structure and a large plasticizing effect for the polystyrene-based resin. In addition, as the compatibility adjusting agent, the rubbery copolymer containing the above-described styrene-based compound as a constituent component thereof can be appropriately used.

[0052] On the other hand, as the rubber component, in addition, natural rubber, polybutadiene, polyisoprene, polyisobutylene, chloroprene rubber, ethylene-propylene copolymer rubber, urethane rubber, silicone rubber, acrylate rubber, polyether-ester rubber, polyester-ester rubber, and the like can be used.

[0053] In addition, the weight average molecular weight of the polystyrene-based resin is preferably 10,000 or more, and more preferably 50,000 or more. When the weight average molecular weight is less than 10,000, the strength and elongation properties of the film and the heat resistance tend to decrease, and thus are not preferable. The upper limit of the weight average molecular weight is not particularly limited, but when the weight average molecular weight is higher than 1,500,000, the film sometimes breaks or the like with an increase in the stretching tension, and thus is not preferable.

[0054] The polystyrene-based resin is commercially available from various manufacturers in various grades, and a commercially available product can be used. The other layer can be one layer or two or more layers.

[0055] In the multilayer with polystyrene, the polyester layer having excellent gloss and printability is made the outermost layer, and the film surface can be provided with a polyester layer / polystyrene layer / polyester layer. However, polyester and polystyrene are non-soluble resins, and thus, sometimes, an adverse situation of peeling occurs. Therefore, it is preferable to form a polyester layer / adhesive layer / polystyrene layer / adhesive layer / 3 layers sandwiching the polyester layer and the adhesive layer from the film surface.

[0056] In the 3-layer 5-layer, the polyester layer is preferably 20% or more and 80% or less of the total thickness. When it is less than 20%, the thickness of one side of the polyester layer becomes less than 10%, and the printability and gloss of the film are insufficient, and thus, it is not preferable. When it is more than 80%, the polystyrene layer becomes thin, and the effect of suppressing the shrinkage ratio in the length direction becomes small, and thus, it is not preferable. In the 3-layer 5-layer, the polyester layer is more preferably 25% or more and 75% or less of the total thickness, and particularly preferably 30% or more and 70% or less.

[0057] In the 3-layer 5-layer, the adhesive layer is preferably 1% or more and 14% or less of the total thickness. When it is less than 1%, the adhesiveness is reduced, and thus, it is not preferable. When it is more than 14%, the thickness of the polyester layer and the polystyrene layer becomes thin, and the heat shrinkage characteristics are reduced, and thus, it is not preferable. In the 3-layer 5-layer, the adhesive layer is more preferably 2% or more and 12% or less of the total thickness, and particularly preferably 3% or more and 10% or less.

[0058] In the 3-layer 5-layer, the polystyrene layer is preferably 20% or more and 80% or less of the total thickness. When it is less than 20%, the effect of suppressing the shrinkage ratio in the length direction becomes small, and thus, it is not preferable. When it is 80% or more, the thickness of one side of the polyester layer becomes less than 10%, and the printability and gloss of the film are insufficient, and thus, it is not preferable. In the 3-layer 5-layer, the polystyrene layer is more preferably 25% or more and 75% or less of the total thickness, and particularly preferably 30% or more and 70% or less.

[0059] For the heat-shrinkable polyester film of the present application, when the film is treated in hot water at 90°C for 10 seconds in a state without load, the heat shrinkage ratio in the main shrinkage direction, i.e., the width direction of the film, calculated from the length before and after shrinkage according to the following formula 1 (i.e., the hot water heat shrinkage ratio at 90°C) is preferably 40% or more and 80% or less.

[0060] Heat shrinkage ratio = {(length before shrinkage - length after shrinkage) / length before shrinkage} x 100 (%)

[0061] The hot water heat shrinkage in the main shrinkage direction at 90°C is preferably 40% or more, more preferably 43% or more, particularly preferably 46% or more, and most preferably 50% or more. If the hot water heat shrinkage in the main shrinkage direction at 90°C is less than 40%, the shrinkage amount is small in the case of using the film as a beverage label or a bento packaging, and therefore, the label after heat shrinkage is wrinkled or slackened, which is not preferable. The hot water shrinkage at 90°C is more preferably 43% or more, particularly preferably 46% or more, and most preferably 50% or more.

[0062] Even if the hot water heat shrinkage in the main shrinkage direction at 90°C is more than 80%, there is no problem, but in the present application, a film having a hot water heat shrinkage at 90°C of more than 80% cannot be obtained, and therefore, the upper limit is set to 80%.

[0063] The hot water heat shrinkage in the length direction orthogonal to the main shrinkage direction at 90°C of the heat-shrinkable polyester film of the present application is preferably -5% or more and 10% or less. If the hot water heat shrinkage in the length direction at 90°C is less than -5%, the label is elongated in the case of using the film as a beverage label, and the label height in a PET bottle is elongated, which is not preferable. The hot water heat shrinkage in the length direction at 90°C is more preferably -4% or more, and particularly preferably -3% or more.

[0064] If the hot water heat shrinkage in the length direction at 90°C is more than 10%, the label is shrunk in the case of using the film as a beverage label, and the label height in a PET bottle is shortened, which is not preferable. In addition, it becomes a cause of the strain of the label after shrinkage. The hot water heat shrinkage in the length direction at 90°C is more preferably 9% or less, further preferably 8% or less, particularly preferably 7% or less, and most preferably 6% or less.

[0065] The maximum protrusion height Sp of at least one face of the heat-shrinkable polyester film of the present application is preferably 3.0 μm or less, more preferably 2.5 μm or less, and further preferably 2.0 μm or less. If the maximum protrusion height Sp is more than 3.0 μm, the film quality is deteriorated due to poor print appearance such as print loss caused by the formation of coarse protrusions, poor design, and the like, which is not preferable.

[0066] The maximum protrusion height Sp of at least one face of the heat-shrinkable polyester film of the present application is preferably 0.8 μm or more, more preferably 1.2 μm or more, and further preferably 1.6 μm or more. If the maximum protrusion height Sp is less than 0.8 μm, the air mixed in during winding into a roll cannot be uniformly removed, and the appearance is likely to be deteriorated by wrinkles, acne on bubbles, and the like, and the winding property is likely to be deteriorated.

[0067] The arithmetic mean height Sa of at least one face of the heat-shrinkable polyester film of the present application is preferably 0.2 μm or less, more preferably 0.18 μm or less, and further preferably 0.16 μm or less. If the arithmetic mean height Sa is more than 0.2 μm, the film surface is rough, and there is a concern that the transparency or the printability is deteriorated.

[0068] The arithmetic average height Sa of at least one face of the heat-shrinkable polyester film of the present application is preferably 0.03 μm or more, more preferably 0.035 μm or more, and further preferably 0.04 μm or more. If the arithmetic average height Sa is less than 0.03 μm, air entrapped in the roll when the film is taken up as a roll cannot be uniformly removed, and appearance defects such as wrinkles, bubble-like pimples, and the like are likely to occur, and the rollability deteriorates.

[0069] The degassing time of the front face / back face of the heat-shrinkable polyester film of the present application is preferably 14 seconds or less, more preferably 13 seconds or less, further preferably 12 seconds or less, and particularly preferably 10 seconds or less. If the degassing time exceeds 14 seconds, air entrapped in the roll during the manufacturing process and when the film is taken up as a roll by unrolling, slitting, and the like cannot be uniformly removed, and appearance defects such as wrinkles, bubble-like pimples, and the like are likely to occur.

[0070] The haze at a film thickness of 30 μm of the heat-shrinkable polyester film of the present application is 11% or less, more preferably 9% or less, further preferably 7% or less, and particularly preferably 5% or less. If the haze at a film thickness of 30 μm exceeds 11%, the print appearance deteriorates, and in the process of advancing the processing at high speed, it becomes difficult to perform foreign matter detection, and it becomes difficult to obtain sufficient quality.

[0071] The thickness of the heat-shrinkable polyester film of the present application is preferably 15 μm or more and 50 μm or less. If the film thickness is less than 15 μm, the stiffness of the film significantly decreases, and thus, it is not preferable because wrinkles are likely to be introduced in the roll. On the other hand, even if the film thickness is thick, there is no problem in forming a film roll, but from the viewpoint of cost and environment, it is preferable to make the film thin. The thickness of the film is more preferably 17 μm or more and 45 μm or less, and particularly preferably 20 μm or more and 40 μm or less.

[0072] The heat-shrinkable polyester film of the present application can be obtained by melt-extruding the above polyester raw material using an extruder to form an unstretched film, and uniaxially stretching the unstretched film in the transverse direction using a prescribed method as described below and heat-treating it. In the case of layering, a plurality of extruders, a feed block, and a manifold can be used. Note that the polyester can be obtained by polycondensing the aforementioned suitable dicarboxylic acid component and a diol component in a known manner. Also, generally, two or more pieces of the polyester are mixed and used as the raw material of the film. In the case of layering, a plurality of extruders can be used.

[0073] When the raw material resin is melt-extruded, the polyester raw material is preferably dried using a drier such as a hopper drier or a paddle drier, or a vacuum drier. After the polyester raw material is dried, it is melted at a temperature of 200 to 300°C using an extruder, and extruded into a film shape. At the time of extrusion, any of the conventional methods such as a T-die method or a tube method can be used.

[0074] Then, the extruded sheet-like molten resin is quenched, whereby an unstretched film can be obtained. Note that, as a method for quenching the molten resin, a method in which the molten resin is cast onto a rotating drum from a nozzle and is quenched and solidified, whereby a substantially unoriented resin sheet is obtained, can be suitably used.

[0075] Further, the obtained unstretched film is stretched in the width direction under prescribed conditions as described later, whereby a heat-shrinkable polyester film of the present application can be obtained. Hereinafter, preferred stretching for obtaining the heat-shrinkable polyester film of the present application will be described. By using the preferred stretching method and conditions described later, a film surface state suitable for the present application can be formed.

[0076] A conventional heat-shrinkable polyester film is manufactured by stretching an unstretched film in a direction in which shrinkage is desired. Alternatively, there is a manufacturing method in which biaxial stretching is performed in which longitudinal stretching is performed first and then transverse stretching is performed, but in the case of biaxial stretching, a large apparatus is required. In the present application, uniaxial stretching is performed in the width direction which is the main shrinkage direction. Note that, the manufacturing means based on uniaxial stretching in the width (transverse) direction has the advantage that it can be manufactured with a simple apparatus without using a stretching apparatus in the length direction.

[0077] Stretching in the width direction is performed by fixing both ends of the film of the unstretched film with clamps, introducing it into a tenter device which can be heated, heating the film to a prescribed temperature using hot air, and then stretching it by widening the distance between the clamps while transporting it in the length direction.

[0078] The preheating temperature of the unstretched film is preferably a temperature of Tg + 10°C or higher and +80°C or lower. More preferably, it is Tg + 20°C or higher and +60°C or lower. If it is lower than Tg + 10°C, the preheating temperature is insufficient, the stretching force becomes high, and it becomes easy to cause breakage, so it is not preferred. In addition, if heating is performed at a temperature higher than Tg + 80°C, the stretching force of the unstretched sheet in the width direction decreases, and the thickness accuracy (thickness unevenness) in the width direction deteriorates, so it is not preferred. More preferably, it is Tg + 30°C or higher and +50°C or lower.

[0079] The film temperature at the time of stretching in the width direction is preferably Tg°C or higher and Tg+30°C or lower. If the film temperature is lower than Tg, the stretching force becomes excessively high, and the film is likely to be broken, which is not preferred. If the film temperature exceeds Tg+30°C, the stretching force becomes excessively low, and thus, as described above, the heat shrinkage ratio in the width direction measured at 90°C becomes low, which is not preferred. More preferably, it is Tg+3°C or higher and +25°C or lower, and further preferably, it is Tg+5°C or higher and +20°C or lower.

[0080] The stretching ratio in the width direction is preferably 3.5 times or higher and 6 times or lower. If the stretching ratio is lower than 3.5 times, the stretching force is insufficient, and the thickness accuracy (so-called thickness unevenness) of the film in the width direction becomes poor. In addition, if the stretching ratio exceeds 6 times, the risk of breakage during film formation becomes high, and in addition, the equipment becomes large, which is not preferred. More preferably, it is 3.7 times or higher and 5.5 times or lower. In addition, there is no particular limitation, and after stretching in the width direction, heat treatment can also be performed to adjust the shrinkage ratio. The film temperature at the time of heat setting is preferably the film stretching temperature in the width direction or higher and the film stretching temperature in the width direction+30°C or lower. If the film heat setting temperature is lower than the film stretching temperature in the width direction, the molecular relaxation in the width direction becomes insufficient, there is no effect of heat setting, and thus, it is not preferred. If the film heat setting temperature exceeds the film stretching temperature in the width direction+30°C, the film crystallizes and the shrinkage ratio becomes low, which is not preferred. More preferably, it is the film stretching temperature in the width direction+1°C or higher and the film stretching temperature in the width direction+25°C or lower, and further preferably, it is the film stretching temperature in the width direction+2°C or higher and the film stretching temperature in the width direction+20°C or lower.

[0081] The heat-shrinkable polyester film of the present application can be labeled according to a method known in the art. As an example, a heat-shrinkable polyester film cut to a desired width is subjected to appropriate printing, and the left and right ends of the film are overlapped and joined using solvent adhesion or the like to produce a tube film. The tube film is cut to an appropriate length to form a tubular label. As the organic solvent for adhesion, a cyclic ether such as 1,3-dioxolane or tetrahydrofuran is preferred. In addition, an aromatic hydrocarbon such as benzene, toluene, xylene, mesitylene, a halogenated hydrocarbon such as dichloromethane or chloroform, a phenol such as phenol, or a mixture thereof can also be used.

[0082] After forming a perforation line in the above-described label using a known method, the label is overlaid on a PET bottle, and the PET bottle is placed inside a shrinkage type (steam type) in which steam is blown or a shrinkage type (hot air type) in which hot air is blown using a belt conveyor or the like. These types are passed through, and the label is heat-shrunk, whereby the label is mounted on the bottle container such as a plastic bottle.

[0083] The package of the present application is formed by covering the label obtained from the heat-shrinkable polyester film of the present application having a perforation line or a cutout to at least a part of the outer circumference of a package object and heat-shrinking it, thereby forming. As the package object, various bottles, cans, snack, bento, and the like plastic containers, paper boxes, and the like can be cited as represented by a PET bottle for beverages. Note that in the case where the label obtained from the heat-shrinkable polyester film is heat-shrunk and covered on these package objects, the label is heat-shrunk by about 5 to 70% or so and is tightly adhered on the package. Note that printing can be performed on the label covered on the package object or can not be performed.

[0084] Examples

[0085] Next, the present application is specifically described using examples and comparative examples, but the present application is not limited in any way by the modes of these examples and can be appropriately changed within the scope not departing from the gist of the present application. Note that the evaluation method of the film is shown below.

[0086] [Heat shrinkage ratio (hot water heat shrinkage ratio)]

[0087] The film was cut into a square of 10 cm x 10 cm, and after heat-shrinking in a hot water of 90°C ± 0.5°C under a load-free state for 10 seconds, the film was immersed in water of 25°C ± 0.5°C for 10 seconds, and the length (vertical) and width (horizontal) of the film were measured after pulling out from the water, and the heat shrinkage ratio was calculated according to the following formula (1) for each. The direction having a larger heat shrinkage ratio was taken as the main shrinkage direction.

[0088] Heat shrinkage ratio = {(length before shrinkage - length after shrinkage) / length before shrinkage} x 100 (%)

[0089] [Arithmetic average height Sa, maximum height Sp]

[0090] According to ISO 25178, an area of 10 cm in length x 10 cm in width was cut out from the obtained film, and a white laser interferometer (NEW VIEW 8300) manufactured by Zygo Corporation was used to scan under the following observation conditions, and the arithmetic average height Sa (μm) and the maximum protrusion height Sp (μm) were measured. In the measurement, the surface excluding foreign matters such as unmelted substances and dust was taken as the object.

[0091] The measurement site was 10 points at an arbitrary site of the sample of 10 cm x 10 cm, and the average value was taken as the arithmetic average height Sa and the maximum protrusion height Sp, respectively.

[0092] (Observation conditions)

[0093] • Objective lens: 10 times

[0094] • Zoom lens: 1x

[0095] • Field of view: 0.82×0.82mm

[0096] • Sampling interval: 0.803μm

[0097] • Assuming measurement time: 4 seconds

[0098] Type: Surface

[0099] • Mode: CSI

[0100] • Z-resolution: High

[0101] • Scan length: 20μm

[0102] • Camera mode: 1024×1024@100Hz

[0103] • Shutter speed: 100%

[0104] ·Light quantity: 1.3%

[0105] • Optional: SureScan Off

[0106] SmartPsi Averages 4

[0107] Noise reduction

[0108] • Optional signal processing: Edge count analysis Advanced

[0109] Edge removal ON

[0110] [Degassing time]

[0111] like Figure 1 As shown, a film 4 is placed on the base 1. Next, a film plate 2 is placed above the film 4 and fixed in place, thereby applying tension to fix the film 4. Then, on the film plate 2, the surface of the film 4, which is the film 5, placed on the base 1 with the surface opposite to the upper surface facing downwards is placed. Then, a film plate 8 is placed on the film 5, and the film plate 8, 2, and base 1 are further fixed using threads 3.

[0112] Next, the cavity 2a provided in the film plate 2 is connected to the vacuum pump 6 via the hole 2c provided in the film plate 2 and the pipe 7. Then, if the vacuum pump 6 is driven, it is attracted by the cavity 2a, thereby applying tension to the film 5. In addition, at the same time, the overlapping surfaces of the film 4 and the film 5 are depressurized by means of the circumferentially provided hole 2d in the film plate 2, and the film 4 and the film 5 are sealed together from the outer periphery at their overlapping surfaces.

[0113] The appearance of adhesion can be easily known by observing interference fringes from the upper portion of the overlapped faces. Then, after interference fringes are generated in the outer peripheral portion of the overlapped faces of the film 4 and the film 5, the interference fringes are enlarged in front of the overlapped faces, and the time (seconds) until the movement stops is measured, and the time (seconds) is taken as the degassing time. Note that the measurement is repeated 5 times for 2 sheets of the film to be replaced, and the average value thereof is used.

[0114] [Thickness of film]

[0115] The measurement was performed using a caliper according to JIS K7130-1999 A method.

[0116] [Thickness of film]

[0117] The film was cut into a square shape of 10 cm on one side according to JIS K7361-1, and a haze meter NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. was used to perform the haze measurement. The measurement was performed at 3 places, and the average value thereof was taken as the measured value of the haze, and the haze converted to 30 μm was calculated according to the following formula (2).

[0118] Haze = Measured value of haze x 30 / thickness of film (% / 30 μm) Formula (2)

[0119] [Tg (glass transition point)]

[0120] A differential scanning calorimeter (Model: DSC220) manufactured by Seiko Instruments Inc. was used to find Tg according to JIS-K7121-1987. In detail, 10 mg of the unstretched film was warmed from -40°C to 120°C at a warming rate of 10°C / minute to measure the endothermic curve. Tangents were drawn before and after the inflection point of the obtained endothermic curve, and the intersection point thereof was taken as the glass transition point (Tg; °C).

[0121] [Intrinsic viscosity (IV)]

[0122] The polyester was dissolved in 50 ml of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60 / 40 (wt ratio)) to 0.2 g, and the measurement was performed at 30°C using an Ostwald viscometer. The unit is dl / g.

[0123] [Composition analysis]

[0124] The sample solution was prepared by dissolving each sample in a solvent prepared by mixing chloroform D (manufactured by Yurisop Co.) and trifluoroacetic acid Dl (manufactured by Yurisop Co.) at 10: 1 (volume ratio). The proton NMR of the sample solution was measured using NMR "GEMINI-200" (manufactured by Varian Co.) under the measurement conditions of a temperature of 23°C and a cumulative number of 64 times. In the NMR measurement, the peak intensity of the prescribed proton was calculated, and the component amount in 100 mole% of the diacid component and the component amount in 100 mole% of the polyol component were measured.

[0125] [Shrink finishing property]

[0126] The end portion of the heat-shrinkable film was welded with a pulse heat sealer (manufactured by FUJI IMPULSE CO., LTD.) to obtain a cylindrical label with the width direction as the circumferential direction. In addition, holes of 0.5 mm in size were introduced at intervals of 3 mm in the film length direction. Further, holes of 0.5 mm in size were introduced at intervals of 3 mm in the film length direction at intervals of 10 mm in the film width direction (so-called perforation line for easy peeling of the label). The diameter of the shrink direction of the label was 68 mm. This label was overlaid on a commercially available PET bottle of 500 ml (with contents; main body diameter 62 mm, minimum diameter of the neck portion 25 mm), and heat-shrunk by steam using a steam type (model; SH-1500-L) manufactured by Fuji Astec Inc. adjusted to 90°C (type through time 5 seconds). For the shrink finishing property of the label, visual evaluation was performed according to the following criteria. Visual evaluation was performed in 5 stages according to the following criteria. The defects described below refer to scattering, wrinkling, insufficient shrinkage, folding of the label end portion, shrink whitening, and the like. Three or more were recorded as acceptable.

[0127] 5: Finishing property is best (no defects)

[0128] 4: Finishing property is good (1 defect)

[0129] 3: 2 defects

[0130] 2: 3 to 5 defects

[0131] 1: A large number of defects (6 or more)

[0132] [Evaluation of wrinkles of film roll]

[0133] The heat-shrinkable polyester film produced by film formation was wound at a width of 500 mm and a roll length of 1000 m, and evaluation of wrinkles on the roll surface was performed visually according to the following criteria. ○ and Δ were recorded as acceptable.

[0134] O: No wrinkles

[0135] O: No wrinkle, even if a tension of about 20 N / m is applied to the pulled-out film

[0136] X: Strong wrinkle, even if a tension of about 20 N / m is applied to the pulled-out film, the wrinkle does not disappear

[0137] [Printability Evaluation]

[0138] A film roll having a width of 500 mm and a roll length of 1000 m was printed with a green ink manufactured by Toyo Ink Mfg. Co., Ltd. (1-color printing). The thickness of the ink after printing was 1 μm. For the printed film, 1 each of an area of 900 mm 2 (lengthwise direction: 30 mm, widthwise direction: 30 mm) was measured, and the absence of printed dots was investigated using a magnifying glass having a magnification of 5 times. The measurement positions were as follows: 3 points of the printed roll were arbitrarily measured in the widthwise direction. In addition, 3 points (total of 6 points) were measured in the widthwise direction at positions deviated by 50 m in the lengthwise direction from the positions measured in the widthwise direction, and the area of 900 mm 2 (lengthwise direction: 30 mm, widthwise direction: 30 mm) was measured using a magnifying glass having a magnification of 5 times, and the results were recorded as O, Δ, or X.

[0139] O: Absence of printed dots was less than 1%

[0140] Δ: Absence of printed dots was 1% or more and less than 3%

[0141] X: Absence of printed dots was 3% or more

[0142] [Preparation of Polyester Raw Material]

[0143] In a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser, dimethyl terephthalate (DMT) 100 mol% as a diacid component and ethylene glycol (EG) 100 mol% as a diol component were charged in a manner such that the diol was 2.2 times the methyl ester in terms of molar ratio, and zinc acetate 0.05 mol% (relative to the acid component) as an ester exchange catalyst was used, and an ester exchange reaction was performed while distilling and removing the generated methanol to the outside of the system. Thereafter, antimony trioxide 0.025 mol% (relative to the acid component) as a polycondensation catalyst was added, and a polycondensation reaction was performed at 280°C under a reduced pressure of 26.6 Pa (0.2 torr) to obtain a polyester (A) having an intrinsic viscosity of 0.75 dl / g. The polyester was polyethylene terephthalate.

[0144] Note that, at the time of production, polyester Bl to B8 were produced by adding SiO2 as a lubricant at a proportion of 8000 ppm relative to the polyester, and the intrinsic viscosity was 0.75 dl / g. The SiO2 was as follows: the shape of polyester Bl was spherical, and the weight average particle diameter was 1 μm, the shape of polyester B2 was amorphous, and the weight average particle diameter was 1.5 μm, the shape of polyester B3 was amorphous, and the weight average particle diameter was 2 μm, the shape of polyester B4 was amorphous, and the weight average particle diameter was 2.5 μm, the shape of polyester B5 was amorphous, and the weight average particle diameter was 3 μm, the shape of polyester B6 was amorphous, and the weight average particle diameter was 4 μm, the shape of polyester B7 was amorphous, and the weight average particle diameter was 5 μm, and the shape of polyester B8 was amorphous, and the weight average particle diameter was 6 μm.

[0145] In addition, according to the same method as described above, the polyesters (C, D, E) shown in Table 1 were synthesized. Note that, in the table, NPG is neopentyl glycol, CHDM is 1,4-cyclohexanedimethanol, and BD is 1,4-butanediol. The intrinsic viscosities of the polyesters C, D, and E were 0.75 dl / g, 0.75 dl / g, and 1.15 dl / g, respectively. Note that, each of the polyesters was suitably formed into small pieces.

[0146] The content of the raw material pieces used in the examples and comparative examples, the resin composition, layer constitution, and production conditions of the films in the examples and comparative examples are shown in Table 1 and Table 2, respectively.

[0147] [Table 1]

[0148]

[0149] [Table 2]

[0150]

[0151] Example 1

[0152] A core layer-forming resin and a skin layer-forming resin were melt-extruded from each of the extruders (first and second extruders), were laminated in a die (T-die), were wound on a rotating metal roll whose surface temperature was cooled to 30°C, and were quenched, thereby obtaining an unstretched film having a thickness of 138 μm, a two-layer constitution, and a constitution in which a skin layer was laminated on the outside of the core layer. At this time, the polyester A, the polyester C, and the polyester E were mixed at a weight ratio of 20:70:10 and were fed to the extruder in the core layer. The mixed resin was melted at 260°C. In one skin layer, the polyester A, the polyester B3, the polyester C, and the polyester E were mixed at a weight ratio of 12:8:70:10 and were fed to the extruder. The mixed resin was melted at 260°C. The thickness ratio of the skin layer / core layer / skin layer at this time was 1:2:1. The drawing speed (rotational speed of the metal roll) of the unstretched film at this time was about 30 m / min. In addition, the Tg of the unstretched film was 69°C.

[0153] The obtained unstretched film was introduced into a tenter (transverse stretching machine). The temperature of the preheating step was set to 95°C (Tg + 26°C), and the temperature of the stretching step was set to 78°C (Tg + 9°C), and the film was stretched to 4.6 times. The film after transverse stretching was heat-treated at 83°C (stretching temperature + 5°C) in a tensioned state for 8 seconds. Thereafter, the film was cooled, and the both edge portions were cut and removed, and was wound in a roll shape with a width of 800 mm, thereby continuously producing a stretched film having a thickness of 30 μm over a length of 2000 m. The properties of the obtained film were evaluated according to the above-described method. The evaluation results are shown in Table 3. It was a film having good wrinkles and shrinkage finishing properties of the film roll.

[0154] Example 2

[0155] Polyester B3 was changed to polyester B4, and otherwise, a film having a thickness of 30 μm was collected in the same manner as in Example 1. The evaluation results are shown in Table 3. The degassing time became shorter than in Example 1, and it was a film having good wrinkles and shrinkage finishing properties of the film roll.

[0156] Example 3

[0157] Polyester B3 was changed to polyester B5, and otherwise, a film having a thickness of 30 μm was collected in the same manner as in Example 1. The evaluation results are shown in Table 3. The degassing time became shorter than in Example 1, and it was a film having good wrinkles and shrinkage finishing properties of the film roll.

[0158] Example 4

[0159] Polyester B3 was changed to polyester B6, and otherwise, a film having a thickness of 30 μm was collected in the same manner as in Example 1. The evaluation results are shown in Table 3. The degassing time became shorter than in Example 1, and the haze was slightly high, but it was a film having good wrinkles and shrinkage finishing properties of the film roll.

[0160] Example 5

[0161] Polyester B3 was changed to polyester B7, and otherwise, a film having a thickness of 30 μm was collected in the same manner as in Example 1. The evaluation results are shown in Table 3. The degassing time became shorter than in Example 1, and the haze was slightly high, but it was a film having good wrinkles and shrinkage finishing properties of the film roll.

[0162] Example 6

[0163] The raw material of the core layer of Example 1 was changed to the same raw material as the skin layer, and was changed to one three-layer, and otherwise, a film having a thickness of 30 μm was collected in the same manner as in Example 1. The evaluation results are shown in Table 3. The haze was slightly high, but it was a film having good wrinkles and shrinkage finishing properties of the film roll.

[0164] Example 7

[0165] The core layer forming resin, the skin layer forming resin, and the adhesive layer forming resin were melted and extruded from each of the extruders (the first to third extruders), were laminated in the die (T-die), were wound around a rotating metal roll cooled to 30°C according to the air knife method, and were rapidly cooled, thereby obtaining an unstretched film (polystyrene-based resin laminate) having a thickness of 138 μm, a five-layer structure, and a structure in which intermediate layers (adhesive layers) were laminated on both sides of the core layer, and skin layers were respectively laminated on the outer sides of the intermediate layers. The method of forming each layer of the unstretched film (up to the melting and extruding step) is described below. Note that, in the following description, the front and back of the polystyrene-based mixed resin laminate are sequentially referred to as the first layer, the second layer, the third layer, the fourth layer, and the fifth layer (i.e., the surface of the fifth layer is the metal roll contact surface). The drawing speed of the unstretched film at this time (the rotation speed of the metal roll) was about 30 m / min.

[0166] • Formation of the first layer and the fifth layer (skin layer)

[0167] The dried polyester A, polyester B4, polyester C, and polyester E were mixed at a ratio of 12:8:70:10 and were fed into the first extruder. The mixed resin was melted and extruded at 260°C (melted and extruded in a manner of being laminated on the outer sides of the intermediate layers laminated on the front and back of the core layer). In order to stabilize the extrusion from the T-die, a helical type and parallel type gear pump was interposed between the extruder and the T-die.

[0168] • Formation of the second layer and the fourth layer (adhesive layer)

[0169] The above pellets F were pre-dried using a blender device, and the pre-dried pellets F were continuously fed to a hopper directly above the second extruder using a constant screw feeder. Then, the fed pellets D were melted and extruded from the T-die of the second extruder (melted and extruded in a manner of being laminated on the outer sides of the core layer). Note that the temperature of the second extruder was adjusted to 200°C. Also, in the same manner as the extrusion using the first extruder, a helical type and parallel type gear pump was interposed between the extruder and the T-die in order to stabilize the extrusion from the T-die.

[0170] • Formation of the third layer (core layer)

[0171] The above pellets G, H, and I were pre-dried using a blender device, respectively, and the pellets G, H, and I were fed into the third extruder at a mixing ratio of 43:43:14. The mixed resin was melted and extruded at 200°C. Also, in the same manner as the extrusion using the first extruder and the extrusion using the second extruder, a helical type and parallel type gear pump was interposed between the extruder and the T-die in order to stabilize the extrusion from the T-die.

[0172] Note that in the extrusion of the resins using the respective extruders, the discharge amounts of the first to third extruders in the formation of the unstretched film were adjusted in the thickness of the first layer / second layer / third layer / fourth layer / fifth layer in the order of 23 / 3 / 48 / 3 / 23.

[0173] A film having a thickness of 30 μm was produced in the same manner as in Example 1, except that the stretching temperature in the width direction of the obtained unstretched film was changed to 82°C. The evaluation results are shown in Table 3. It was a film in which the wrinkles of the film roll and the shrink finishing property were good.

[0174] Example 8

[0175] A film having a thickness of 30 μm was produced in the same manner as in Example 1, except that the polyester C was changed to polyester D. The Tg of the unstretched film was 69°C. The evaluation results are shown in Table 3. It was a film in which the wrinkles of the film roll and the shrink finishing property were good.

[0176] Example 9

[0177] A film having a thickness of 30 μm was produced in the same manner as in Example 1, except that the polyester B3 was changed to polyester Bl, and the weight ratio of the raw materials of the skin layer, the polyester A, the polyester Bl, the polyester C, and the polyester E was set to 4 / 16 / 70 / 10. In addition, the temperature of the preheating step in the stretching step in the width direction of the unstretched film was changed to 100°C, the temperature of the stretching step was changed to 85°C, and the heat treatment temperature was changed to 86°C, and a film having a thickness of 30 μm was produced in the same manner as in Example 1. The evaluation results are shown in Table 3. It was a film in which the wrinkles of the film roll and the shrink finishing property were good.

[0178] Comparative Example 1

[0179] A film having a thickness of 30 μm was produced in the same manner as in Example 1, except that the polyester B3 was changed to polyester Bl. The evaluation results are shown in Table 3. The degassing time became slower than in Example 1, and it was a film in which the wrinkles of the film roll were conspicuous.

[0180] Comparative Example 2

[0181] A film having a thickness of 30 μm was produced in the same manner as in Example 1, except that the polyester B3 was changed to polyester B2. The evaluation results are shown in Table 3. The degassing time became slower than in Example 1, and it was a film in which the wrinkles of the film roll were conspicuous.

[0182] Comparative Example 3

[0183] The polyester B3 was changed to the polyester B8, and otherwise, a film having a thickness of 30 μm was collected in the same manner as in Example 1. The evaluation results are shown in Table 3. The degassing time was short and the wrinkle was also good, but the maximum protrusion height Sp of the film surface and the arithmetic mean height of the film surface were high, and thus, there was a dot loss at the time of printing, and it was a film having poor printability.

[0184] Comparative Example 4

[0185] For the unstretched film, the temperature of the preheating step in the step of stretching in the width direction was changed to 95°C, the stretching temperature in the width direction was changed to 83°C, and the heat treatment temperature was changed to 88°C, and otherwise, a film having a thickness of 30 μm was collected in the same manner as in Example 9. The evaluation results are shown in Table 3. The degassing time became slower than in Example 1, and it was a film in which the wrinkle of the film roll was conspicuous.

[0186] Comparative Example 5

[0187] In the step of stretching the unstretched film in the width direction, the temperature of the preheating step and the stretching step was changed to 76°C (Tg + 7°C) compared to Example 1, and the heat treatment temperature was changed to 88°C, and otherwise, a film having a thickness of 30 μm was collected in the same manner as in Example 1. The evaluation results are shown in Table 3. The degassing time became slower than in Example 1, and it was a film in which the wrinkle of the film roll was conspicuous. It is considered that the stretching stress at the time of film stretching was not high, and thus, the lubricant became easily deformed.

[0188] [Table 3]

[0189]

[0190] Industrial Applicability

[0191] The heat-shrinkable polyester film of the present application has a high heat shrinkage rate, and excellent transparency and printability, and a short degassing time, and thus, a film roll having a good appearance can be obtained.

[0192] Explanation of Reference Numerals

[0193] 1. Base

[0194] 2, 8. Film presser

[0195] 2a. Slot hole

[0196] 3. Screw thread

[0197] 4, 5. Film

[0198] 6. Vacuum pump

[0199] 7. Pipe

[0200] X. Film overlapping portion

Claims

1. A heat-shrinkable polyester film, characterized in that, The heat-shrinkable polyester film is a single-layer or laminated heat-shrinkable polyester film having at least a polyester resin layer containing 350 ppm or more and 20,000 ppm or less of fine particles having an average particle diameter of 1.0 to 5.0 μm on the surface / back surface thereof; The heat-shrinkable polyester film satisfies the following characteristics (1) to (5), (1) a hot water heat shrinkage rate when the film is immersed in hot water at 90°C for 10 seconds is 40% or more and 80% or less in the film width direction, (2) a hot water heat shrinkage rate when the film is immersed in hot water at 90°C for 10 seconds is -5% or more and 10% or less in the film length direction, (3) a maximum protrusion height Sp of at least one film surface is 0.8 μm or more and 3.0 μm or less, (4) an arithmetic mean height Sa of at least one film surface is 0.03 μm or more and 0.2 μm or less, (5) a degassing time of the film surface / back surface to each other is 14 seconds or less.

2. The heat-shrinkable polyester film according to claim 1, wherein The film thickness is 15 μm or more and 50 μm or less.

3. The heat-shrinkable polyester film according to claim 1 or 2, wherein The haze of the film is 2% or more and 11% or less when the film thickness is 30 μm.

4. The heat-shrinkable polyester film according to any one of claims 1 to 3, characterized by It is a laminated heat-shrinkable polyester film laminated with at least 2 or more layers.

5. A heat-shrinkable label using the heat-shrinkable polyester film according to any one of claims 1 to 4.

6. A package characterized by It is formed by covering at least a part of the outer periphery of an object to be packaged with the heat-shrinkable label according to claim 5 and heat-shrinking it.

Images