JP2007001139A - Multi-layered heat shrinkable polyester-based film and label - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat shrinkable polyester-based film suitable particularly for the use of labels, very little in the generation of wrinkles, unevenness of shrinkage and distortion by heat shrink, and hard to cause insufficient shrinkage. <P>SOLUTION: The multi-layered heat shrinkable polyester-based film comprises at least two layers. It has a heat shrinkage rate of 5-60% in a treatment temperature of 70°C and a treatment time of 5 seconds and ≥75% in a treatment of 85°C and 5 seconds in the major shrinking direction, and ≤10% in a treatment of 85°C and 5 seconds in the direction perpendicular to the major shrinking direction. The curl of the film before the shrinkage is within 5 mm. When the film is shrunk by 10% to the major shrinking direction and further subjected to a treatment in hot water of 95°C for 5 seconds and when the shrinkage rates of the major shrinking direction at that time are indicated each by X0(%) and X10(%), the difference Δ(%) in the heat shrinkages, shown by the formula Δ=X0-X10 is 10-20% and the film curls to one surface side on shrinking. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable polyester film, and more particularly to a heat-shrinkable polyester film suitable for label applications. More specifically, the present invention relates to a heat-shrinkable polyester film that is used for full labeling of bottles, particularly for full labeling of PET bottles, and is extremely free of wrinkles, shrinkage spots, and distortions due to heat shrinkage and is less likely to cause shrinkage.

  As a heat-shrinkable film, particularly a heat-shrinkable film for labeling the body of a bottle, a film made of polyvinyl chloride, polystyrene or the like is mainly used. However, with regard to polyvinyl chloride, in recent years, there has been a problem of generation of chlorinated gas when incinerated at the time of disposal, and polyethylene has problems such as difficulty in printing. Furthermore, when collecting and recycling PET bottles, it is necessary to separate labels of resins other than polyethylene terephthalate such as polyvinyl chloride and polyethylene. For this reason, polyester-based heat-shrinkable films that do not have these problems are attracting attention.

  These heat-shrinkable films are once wound up into a roll after production, and are sent to a printing process of various designs in the form of this film roll. After the printing is finished, they are used for final products as necessary. It is slitted to fit the size of the label, etc., and the left and right ends of the film are overlapped and sealed by means such as solvent bonding to form a tubular body, and the tubular body is cut into a label, bag It is processed into the form. Then, attach a label or bag-like item to the container and blow the hot air to shrink it (hot air tunnel) or the steam blown shrink device (steam tunnel) to the conveyor belt etc. It is placed and allowed to pass, and is heat-shrinked so as to be in close contact with the container.

By the way, from the viewpoint of recycling, as the use of colored PET bottles is restricted, there is a demand for covering most of the side of the bottle with a label made of a heat-shrinkable polyester film instead of coloring the bottle itself. However, the side shape of PET bottles varies, and the outer diameter changes at an arbitrary height position. Therefore, even for one label that covers one bottle, the required degree of shrinkage varies depending on the height position of the bottle. In the conventional heat-shrinkable film, there may be a problem in the shrink finish. Especially for beverage bottles, etc., when the bottle full label is narrow and the diameter difference from the body is large, the conventional heat shrinkable film causes insufficient shrinkage at the top of the bottle (head and neck). Therefore, there is a demand for a heat-shrinkable polyester film that has better shrinkage characteristics than conventional products and can exhibit excellent shrinkage finish even when used for coating bottles with complex side shapes.
(For example, refer to Patent Document 1).
JP 2000-135737 A

  Furthermore, for example, in beverage bottles for beverages, in order to improve productivity, there are an increasing number of cases where label attachment and shrinkage are performed in a beverage filling line. Since such a filling line is high-speed, label mounting / shrinking is also fast, and shrinking tends to be performed in a short time. Therefore, the heat-shrinkable polyester film is also required to have physical properties that can withstand high-speed mounting and shrinkage performance that provides a high shrinkage rate in a short time.

  In addition, there is a problem in that a label that has elapsed from the printing process is liable to have a problem such as a part of the label being folded when contracted. Although the cause of this is not clear, it is considered that the organic solvent remaining in the printing ink has some influence.

In addition, recently, labels used for various containers such as PET bottles are also expected to reinforce these containers. However, conventional labels have not been able to satisfy such a reinforcing effect.
Thus, in the case of the full label use of a bottle, the performance was insufficient with the conventional polyester heat-shrinkable film.

  The present invention solves the above-mentioned problems, and the object of the present invention is a heat-shrinkable polyester film for full labeling of bottles, particularly for full labeling of PET bottles and glass bottles. In particular, there is very little generation of wrinkles, shrinkage spots, and distortion due to shrinkage, and heat shrinkage that is less likely to cause problems such as label folding over time after printing and that can reinforce shrink-coated containers. It is providing a property polyester film.

A multilayer heat-shrinkable polyester film comprising at least two layers, wherein the heat-shrink rate of the polyester film is 5 to 60% in a main shrinkage direction at a treatment temperature of 70 ° C. and a treatment time of 5 seconds, and 85 ° C.・ 75% or more in 5 seconds, 85 ° C. in the direction perpendicular to the main shrinkage direction, 10% or less in 5 seconds, and the maximum value of heat shrinkage stress in hot air at 90 ° C. in the main shrinkage direction exceeds 13 MPa Value, the curl of the film before shrinkage is within 5 mm, and the shrinkage rate in the main shrinkage direction when the film further heat-shrinked by 10% in the main shrinkage direction is further treated in warm water at 95 ° C. for 5 seconds, Multi-layer heat shrinkage characterized by curling to one side during shrinkage when the shrinkage difference Δ (%) shown by the following formula is 10 to 20% when X0 (%) and X10 (%) respectively. Polyester This can solve the problem.
Δ = X0−X10

The present invention achieves multi-functionality by forming a multilayer film composed of at least an A layer and a B layer and imparting different characteristics to the A layer and the B layer, respectively.
For example, the polyester elastomer content in the A layer is 7% by mass or more and 11% by mass or less. For example, the polyester elastomer content in the B layer is 3% by mass or more and less than 7% by mass. This makes it difficult to cause problems such as label folding failure.

  In this case, the polyester elastomer is, for example, a polyester block copolymer composed of a high melting crystalline polyester segment (Tm 200 ° C. or higher) and a low melting point soft polymer segment (Tm 80 ° C. or lower) having a molecular weight of 400 or more, preferably 400 to 800. A polyester elastomer using a polylactone such as poly-ε-caprolactone in the low melting point soft polymer segment is particularly preferable.

  In this case, it contains at least one monomer component that can be an amorphous component in 100 mol% of the polyhydric alcohol component in the total polyester resin, and the total amount is set to 16 mol% or more. It is easy to satisfy the secondary processing characteristics, and it is particularly preferably 18 mol% or more.

  In this case, it is preferable that the monomer capable of becoming an amorphous component in the total polyester resin component of the film is neopentyl glycol and / or 1,4-cyclohexanedimethanol.

  Furthermore, the curl of the film before shrinkage is preferably within 5 mm.

Furthermore, when the shrinkage rate in the main shrinkage direction is set to X0 (%) and X10 (%), respectively, when a film thermally contracted by 10% in the main shrinkage direction is further treated in 95 ° C. warm water for 5 seconds. The heat shrinkage difference Δ (%) represented by the following formula is preferably 10 to 20%.
Δ = X0−X10

  Furthermore, the thickness distribution is preferably 6% or less.

  Furthermore, the label produced using the said film is a use suitable for a bottle.

  Furthermore, in this case, a label produced using the film so that the A layer side is the inner surface and the B layer side is the outer surface is a suitable application for the bottle.

  When the multilayer heat-shrinkable polyester film of the present invention is used as a full label for a bottle, it is possible to achieve a good finish with very little occurrence of wrinkles, shrinkage spots, distortion and insufficient shrinkage due to heat shrinkage. Very useful.

Embodiments of the present invention will be specifically described below.
The heat-shrinkable polyester film can be obtained as follows. A polyester composed of a dicarboxylic acid component and a polyvalent glycol component is melt-extruded from an extruder and cooled with a conductive cooling roll (such as a casting roll) to form a film (unstretched film).

In the extrusion, the copolyester is extruded alone, or a plurality of polyesters (copolyester, homopolyester, etc.) are mixed and extruded. That is, the film contains a second alcohol component that is different from a base unit (such as a crystalline unit such as polyethylene terephthalate) and a polyvalent glycol component (such as an ethylene glycol component) that constitutes the base unit. In the present invention, it is preferable to use ethylene terephthalate as the base unit for the purpose of maintaining the mechanical strength and low back feeling of the film at a practical level.
In addition, the content rate of the acid component of this invention and a diol component is a content rate with respect to the acid component of the whole polyester, and a diol component, when mixing and using 2 or more types of polyester. It does not matter whether transesterification has taken place after mixing.

  Any of the above polyesters can be produced by polymerization according to a conventional method. For example, the polyester can be obtained by using a direct esterification method in which a dicarboxylic acid and a diol are directly reacted, or a transesterification method in which a dicarboxylic acid dimethyl ester is reacted with a diol. The polymerization may be performed by either a batch method or a continuous method.

  When a polyester film containing the second alcohol component is stretched, a heat-shrinkable polyester film can be obtained.

  As the second alcohol component, a diol component and a trivalent or higher alcohol component can be used. Examples of the diol component include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 2,2-diethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5- Alkylene glycols such as pentanediol, 2-methyl-1,5-pentanediol, 1,9-nonanediol and 1,10-decanediol; cyclic alcohols such as 1,4-cyclohexanedimethanol; diethylene glycol, collected ethylene glycol, Ether glycols such as polypropylene glycol, polyoxytetramethylene glycol, alkylene oxide adducts of bisphenol compounds or derivatives thereof; dimer diols and the like are included. Trivalent or higher alcohols include trimethylolpropane, glycerin, pentaerythritol and the like.

The total of at least one monomer component that can be an amorphous component in 100 mol% of the polyhydric alcohol component in all the polyester resins is preferably 16 mol% or more, and more preferably 18 mol% or more. preferable.
Here, it is preferable to use neopentyl glycol and / or 1,4-cyclohexanedimethanol as a monomer that can be an amorphous component.

  Further, in addition to a heat-shrinkable polyester film having particularly excellent shrinkage finish, in order to improve the shrink finish while having a high heat shrinkage rate, in 100 mol% of the polyhydric alcohol component in the total polyester resin, The amount of neopentyl glycol component and / or the amount of 1,4-cyclohexanedimethanol component is preferably 16 mol% or more, and particularly preferably 18 mol% or more.

  The heat-shrinkable film of the present invention is characterized by curling to one side at the time of heat-shrinking. In order to control the curl within an appropriate range, the difference in the degree of plane orientation of each layer is 0. It is preferably within the range of 005 to 0.03, and more preferably within the range of 0.006 to 0.28. When the difference in the degree of plane orientation is less than 0.005, curling does not occur at the time of heat shrinkage, and when it exceeds 0.03, the adhesive strength at the interface of the layer is lowered and peeling at the time of shrinkage occurs. In order to set the difference in the degree of plane orientation of each layer within the above range, it is preferable to adopt the raw material prescription, production method and conditions described later.

The polyester elastomer content in the A layer is preferably 7% by mass or more and 11% by mass or less, and the polyester elastomer content in the B layer is preferably 3% by mass or more and less than 7% by mass. Here, the polyester elastomer is a polyester block copolymer comprising, for example, a high melting crystalline polyester segment (Tm 200 ° C. or higher) and a low melting point soft polymer segment (Tm 80 ° C. or lower) having a molecular weight of 400 or more, preferably 400 to 800. And polyester elastomers using polylactones such as poly-ε-caprolactone in the low melting point soft polymer segment.
In other words, a multi-layer film composed of an A layer and a B layer is used, and multi-functionalization is achieved by imparting different characteristics to the A layer and the B layer, respectively.
With the above configuration, the resulting film can be controlled to curl to one side during heat shrinkage. For example, the non-curled surface can be printed on the inner surface side of the label to fold after time. It is possible to avoid defects.

  In the multilayer heat-shrinkable polyester film of the present invention, the curl degree of the film before shrinkage is preferably within 5 mm, more preferably within 3 mm, according to the evaluation method described later. When the curl exceeds 5 mm, for example, the end of the film is lifted during the center seal processing of the film, and problems such as wrinkles and poor adhesion are likely to occur, which is not preferable.

The curl amount of the film at the time of shrinkage is preferably 5% or more, more preferably 10% to 100% by the method described later. In the present invention, the curling of the film or label to one side when contracted means that the curl amount is 1% or more in the evaluation method described later.
Moreover, it is possible to make the shrinkage rate of the direction orthogonal to the main shrinkage | contraction direction appropriate by making a polyester elastomer into the said range and combining with the preferable manufacturing method and conditions mentioned later.

  As common to the A layer and the B layer, an aliphatic linear diol having 8 or more carbon atoms (for example, octanediol) or a trihydric or higher polyhydric alcohol (for example, trimethylolpropane, trimethylolethane, glycerin, Diglycerin and the like) are preferably not contained. In the heat-shrinkable polyester film obtained by using polyester containing these diols or polyhydric alcohols, it is difficult to achieve a necessary high shrinkage rate.

  Moreover, it is preferable not to contain diethylene glycol, triethylene glycol, and polyethylene glycol as much as possible. In particular, diethylene glycol is likely to be present because it is a by-product component during polyester polymerization. However, in the polyester used in the present invention, the content of diethylene glycol is preferably less than 4 mol%.

  Furthermore, in order to improve the slipperiness of the heat-shrinkable film, for example, an inorganic lubricant such as titanium dioxide, fine-particle silica, kaolin, calcium carbonate, or an organic lubricant such as a long-chain fatty acid ester may be included. preferable. Moreover, you may contain additives, such as a stabilizer, a coloring agent, antioxidant, an antifoamer, an antistatic agent, and an ultraviolet absorber, as needed.

[Intrinsic viscosity]
The heat-shrinkable polyester film of the present invention preferably has an intrinsic viscosity of 0.60 dl / g or more. If the intrinsic viscosity of the heat-shrinkable film is too small, the molecular weight of the polyester that composes the film will be low, which will reduce the durability of the shrinkage stress during heat shrinkage, resulting in defects such as shrinkage whitening and shrinkage spots. It becomes easy, and it becomes inferior to shrink finish and appearance. Moreover, if the molecular weight of polyester falls, the mechanical strength and tear resistance of a film will be reduced.

    The intrinsic viscosity is preferably 0.60 dl / g or more, more preferably 0.63 dl / g or more.

  As a method for increasing the intrinsic viscosity of the film, for example, (1) a method in which a high molecular weight polyester is used as the polyester that is the raw material of the film (for example, the intrinsic viscosity is 0.63 dl / g or more, preferably 0.68 dl / g More preferably, a method of using a polyester of 0.70 dl / g or more), (2) a method of suppressing thermal decomposition and hydrolysis when forming a film by extruding the polyester (for example, preliminarily using a polyester raw material) (3) A method of using a hydrolysis-resistant polyester as the polyester (for example, having an acid value of 25 eq / ton or less) (Method of using polyester), (4) antioxidant to polyester (for example, 0.01 to 1 quality) Such as% of content) is a method to the like.

  As the polymerization catalyst, various conventional catalysts can be used. For example, titanium-based catalyst, antimony-based catalyst, germanium-based catalyst, tin-based catalyst, cobalt-based catalyst, manganese-based catalyst, etc., preferably titanium-based catalyst (titanium tetrabutoxide) Etc.), antimony catalysts (such as antimony trioxide), germanium catalysts (such as germanium dioxide), cobalt catalysts (such as cobalt acetate), and the like.

[Heat shrinkage]
The multilayer heat-shrinkable polyester film of the present invention is treated with warm water in an unloaded state, and from the length before and after shrinkage, the heat shrinkage rate = ((length before shrinkage−length after shrinkage) / before shrinkage. Length) x 100 (%), the thermal shrinkage rate of the film is 5 to 60% at a treatment temperature of 70 ° C. and a treatment time of 5 seconds in the main shrinkage direction, preferably 10 to 30%. Yes, it is 75% or more at 85 ° C. for 5 seconds, preferably 75 to 95%. Further, in the direction orthogonal to the main shrinkage direction, it is 10% or less at 85 ° C. for 5 seconds, preferably 6% or less.

  When the heat shrinkage rate in the main shrinkage direction is less than 5% at 70 ° C. for 5 seconds, the low-temperature shrinkability is insufficient, and for example, it is necessary to increase the shrinkage temperature. On the other hand, if it exceeds 60%, for example, jumping of the label due to heat shrinkage tends to occur, which is not preferable.

  The thermal shrinkage rate at 85 ° C. for 5 seconds is preferably 75 to 95%, and when it is less than 75%, for example, the shrinkage of the head of the bottle is not preferable. On the other hand, if it exceeds 95%, the force for further shrinkage remains even after heat shrinkage, so that it is not preferred because problems such as the label being likely to jump up easily occur.

In addition, the multilayer heat-shrinkable polyester film of the present invention has a shrinkage rate in the main shrinkage direction when the film heat-shrinked 10% in the main shrinkage direction is further treated in warm water at 95 ° C. for 5 seconds. When X0 (%) and X10 (%), the heat shrinkage difference Δ (%) shown by the following formula
Is preferably 10 to 20%.
Δ = X0−X10
If the heat shrinkable polyester film has the heat shrinkage difference Δ within the above range, a heat shrinkable polyester label having a reinforcing effect on the coated container can be obtained.

A heat-shrinkable polyester-based label obtained from a heat-shrinkable polyester-based film having a heat shrinkage rate difference Δ that is less than the above range has an insufficient reinforcing effect on the container after coating shrinkage. In the heat-shrinkable polyester film of the present invention, the preferred heat shrinkage difference Δ is 17% or less. Note that the lower limit of the heat shrinkage difference Δ is a value measured by using the film having the heat shrinkage ratio X10 of 10% heat shrinkage, and does not fall below 10%.

  In the multilayer heat-shrinkable polyester film of the present invention, the maximum value of the heat shrinkage stress in 90 ° C. hot air after 10% heat shrinkage in the main shrinkage direction is preferably 7 MPa or more. If the maximum value of the above heat shrinkage stress is 7 MPa or more, a heat shrinkable label having a more excellent reinforcing effect of the covering container can be obtained. In a heat-shrink label obtained from a film having the maximum value of the heat-shrinkage stress below the above range, the effect of reinforcing the covering container tends to be reduced. The heat shrinkage stress value is preferably 10 MPa or more, and more preferably 11 MPa or more.

  Further, the maximum value of the heat shrinkage stress in hot air at 90 ° C. in the main shrinkage direction is preferably a value exceeding 13 MPa, more preferably 14 MPa or more, and further preferably 15 MPa or more. When the heat shrinkage stress value is less than the above range, the heat shrink label coated on the container is not sufficiently adhered, and such a problem that the label rotates when the cap is opened is not preferable.

  Next, although a specific example is demonstrated about the manufacturing method of the heat-shrinkable polyester film of this invention, it is not limited to this manufacturing method.

  The polyester raw material used in the present invention is dried using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer, melted at a temperature of 200 to 300 ° C., and extruded into a film. In extruding, any existing method such as a T-die method or a tubular method may be employed. After extrusion, it is cooled rapidly to obtain an unstretched film.

  The extrusion temperature is preferably in the range of 250 ° C to 290 ° C. When the extrusion temperature is lower than 250 ° C., for example, a load is excessively applied and normal extrusion becomes difficult. When the extrusion temperature exceeds 290 ° C, for example, the polyester resin is likely to be thermally deteriorated in the extruder, resulting in problems such as a decrease in mechanical strength of the resulting film and excessive shrinkage in the longitudinal shrinkage resulting in a decrease in shrink finish. Arise.

  Stretching in the transverse direction is performed at a predetermined temperature within a range of Tg-5 ° C to Tg + 15 ° C. In the film of the present invention, in order to make the maximum heat shrinkage stress value within the above range, stretching may be performed in two or more stages. Hereinafter, a case where stretching is performed in two stages will be described as an example.

  First, the first stage of stretching is performed. The stretching ratio is 4.4 times or more and 6.0 times or less, preferably 4.6 times or more and 5.5 times or less with respect to the unstretched film. The stretching temperature in the first stage is set to the above temperature (a predetermined temperature in the range of Tg−5 ° C. to Tg + 15 ° C.).

  Next, it is preferable to heat-fix the film. The heat setting temperature is the same as the first stage stretching temperature, or 1 to 5 ° C. lower than the first stage stretching temperature within the above temperature range, and the heat setting time is 0.5 seconds to 5 seconds. Hereinafter, it is preferably 1 second or more and 3 seconds or less. Moreover, you may heat-set in the state strained in the extending direction of the film. In that case, the tension rate is desirably 6% or less.

  Next, the second stage of stretching is performed. The draw ratio is 1.03 times or more and 1.5 times or less, preferably 1.05 times or more and 1.3 times or less with respect to the film after heat setting (after the first stage if heat setting is not performed). And The stretching temperature in the second stage is preferably the same as the heat setting temperature, or preferably about 1 to 5 ° C. lower than the heat setting temperature within the above temperature range.

  Thereafter, the film is cooled to obtain a heat-shrinkable polyester film, preferably with slight tension applied to the film. The tension rate during cooling is preferably 0.1 to 3% with respect to the width of the film after stretching in the second stage.

  In addition, when making the process of extending | stretching into 3 steps | paragraphs, it is desirable to put the said heat setting process between 2nd step | stretching and 3rd step | stretching. What is necessary is just to determine the conditions of a heat setting process according to said heat setting conditions. Further, the stretching conditions at the third stage may be determined according to the stretching conditions at the second stage.

  From the viewpoint of controlling the heat shrinkage stress of the film, it is preferable that the number of stretching steps is large. However, if the number of steps is too large, it is difficult to design a stretching facility in industrial production. It is desirable to have 4 or less steps.

  In this transverse stretching step, it is preferable to use equipment that can reduce fluctuations in the film surface temperature. That is, the stretching process includes a preheating process before stretching, a stretching process, a heat treatment process after stretching, a relaxation process process, a restretching process, etc., and in particular, a preheating process, a stretching process, and a heat treatment process after stretching. In this case, the fluctuation range of the surface temperature of the film measured at an arbitrary point is preferably within an average temperature ± 1 ° C., and more preferably within an average temperature ± 0.5 ° C. When the fluctuation range of the surface temperature of the film is small, the film is stretched or heat-treated at the same temperature over the entire length of the film, so that the heat shrinkage behavior and other physical properties can be made uniform.

  As a stretching method, not only lateral uniaxial stretching with a tenter, but also stretching in the longitudinal direction by 1.0 to 4.0 times, preferably 1.1 to 2.0 times may be performed. When biaxial stretching is performed in this way, either sequential biaxial stretching or simultaneous biaxial stretching may be performed, and restretching may be performed as necessary. Further, in the sequential biaxial stretching, any of stretching methods such as vertical and horizontal, horizontal and vertical, vertical and horizontal and horizontal and vertical and horizontal directions may be used. Even when these longitudinal stretching steps or biaxial stretching steps are adopted, it is preferable to reduce the fluctuation range of the film surface temperature as much as possible in the preheating step and the stretching step, similarly to the transverse stretching.

  In order to make the curl before shrinkage within 5 mm, it is possible to increase the thickness ratio of the B layer. The thickness ratio of the A layer / B layer is preferably 5 to 20/95 to 80.

[Melting resistivity]
The heat-shrinkable polyester film used in the present invention has a melting specific resistance value at a temperature of 275 ° C. of 0.70 × 10 ⁸ Ω · cm or less. When such a film is used, as will be described in detail below, the uniformity of the film thickness can be improved, and the printability on the film and the workability when processing the film into a form that can be mounted on a container. (Stable workability) can be improved.

  In order to control the melting specific resistance value within the above range, it is preferable to contain an alkaline earth metal compound and a phosphorus-containing compound in the film. The melting specific resistance value can be lowered only with the alkaline earth compound, but the melting specific resistance value can be remarkably lowered when the phosphorus-containing compound coexists. Although it is not clear why the specific melt resistance value can be remarkably lowered by combining the alkaline earth metal compound and the phosphorus-containing compound, the amount of foreign matter can be reduced by containing the phosphorus-containing compound, and the charge carrier It is estimated that the amount can be increased.

  There is no particular limitation on the timing of addition of the above-mentioned compounds for reducing the specific resistance value (alkali metal compounds, alkaline earth metal compounds, phosphorus-containing compounds, etc.), and polymerization is performed before esterification, during esterification, and after completion of esterification. It may be at any stage during polymerization, during polymerization, or after polymerization. It is preferably at any stage after the esterification step, more preferably from the end of esterification to the start of the polymerization step. When an alkaline earth metal compound and a phosphorus-containing compound (and an alkali metal compound if necessary) are added after the esterification step, the amount of foreign matter generated can be reduced as compared with the case where it is added before that.

[Thickness distribution value in the maximum shrinkage direction]
Even if the melt specific resistance value is lowered and the film thickness uniformity is increased as described above, it is not sufficient. That is, when forming a film roll, since the said film is elongate (for example, about 300-6000m), there exists a prisoner whose thickness uniformity falls depending on a measurement location.

  The uniformity of the thickness can be determined based on the thickness distribution value represented by the following formula.

Thickness distribution value = (maximum thickness−minimum thickness) / average thickness × 100
The maximum thickness, the minimum thickness, and the average thickness are obtained by cutting a test piece from a roll so that the length in the main shrinkage direction is 20 cm and the width is 5 cm, and the thickness is displaced with respect to the main shrinkage direction using a contact-type thickness meter. Can be determined by measuring.

  The heat-shrinkable polyester film of the present invention preferably has a film thickness distribution value calculated by the above formula of 6% or less. More preferably, it is 5% or less.

A film having a thickness distribution of 6% or less is easy to superimpose colors by, for example, three-color printing performed at the time of shrinkage finish evaluation, whereas a film exceeding 6% is preferable in terms of color superposition. Absent.

  In order for the sample at each location to have the predetermined thickness distribution value, it is not sufficient that the film forming process and the stretching process reach a steady state, and when the molten polyester is extruded and cooled with a cooling roll, It is necessary to stabilize the electrostatic adhesion of the film from the beginning to the end of film production. As the electrode used for the cooling, it is preferable to use an electrode provided with an electrode contaminated surface retracting means and an electrode contaminated surface supplying means. That is, when electricity is applied from an electrode during film formation of molten polyester and the film is electrostatically adhered, the polyester contains a plurality of types of polymers (homopolymers, copolymerized polymers, etc.) and monomers. Since it often contains molecular components, the low molecular components volatilize during melt extrusion and gradually contaminate the electrode. Therefore, if production of the film is continued, the contamination of the electrode gradually becomes severe, and it becomes impossible to apply sufficient electricity to the film, and there is a captive that the electrostatic adhesion of the film is lowered. Therefore, by using the specific electrode, electrode contamination can be saved, and a non-contaminated surface can be supplied instead, and the electrode surface can be maintained in a state with little contamination. Therefore, even if production of the film is continued, there is no prisoner that the electrostatic adhesion decreases, and the samples at each location have the predetermined thickness distribution.

  In order for the sample at each location to have the predetermined thickness distribution, (A) a method of homogenizing a polyester raw material during film production, together with the method of stabilizing electrostatic adhesion from the beginning to the end of film production It is desirable to employ (B) a method for stabilizing the production process and / or (C) a method for stabilizing the film stretching process.

(A) Method of homogenizing polyester raw material during film production Fine powder (fine powder polyester chip) generated by scraping raw material chips used promotes the occurrence of raw material segregation. Reduction in raw material segregation can also be achieved.

  The ratio of the fine powder in the polyester chip is preferably controlled within 1% by mass and more preferably within 0.5% by mass throughout the entire process until the raw material chip enters the extruder.

  As a method for reducing the fine powder, for example, a method of removing fine powder generated in the process (classification removal, etc.) can be adopted. For example, a method of passing a sieve at the time of chip formation by a strand cutter, a method of passing a cyclonic air filter when the raw material chips are fed by air, and the like can be adopted.

  Moreover, a method of using a funnel-shaped hopper as the final hopper and bringing its hypotenuse (side wall) closer to the vertical can be mentioned. If the hypotenuse (side wall) is brought closer to the vertical, a large chip can be easily dropped like a small chip, and the upper end of the content descends while maintaining a horizontal plane, which is effective in reducing raw material segregation. is there.

  The inclination angle of the hypotenuse (side wall) is, for example, 65 ° or more, preferably 70 ° or more. The inclination angle of the hypotenuse (side wall) is an angle between the funnel-like hypotenuse (side wall) and a horizontal line segment.

(B) Method for Stabilizing Film Formation Methods for stabilizing the film formation process include a method for suppressing fluctuations in the discharge amount from the extruder, a method for suppressing fluctuations in the rotation speed of the cooling roll (casting roll), and the like. It is done.

  In order to suppress the discharge amount fluctuation from the extruder, for example, it is preferable to stabilize the discharge amount within a range of ± 2% of the average discharge amount. In order to suppress the discharge amount fluctuation, for example, it is preferable to use a gear pump as the discharge means.

  In order to suppress the rotational speed fluctuation of the cooling roll (casting roll), for example, it is preferable to stabilize the rotational speed within a range of ± 2% of the average rotational speed. In order to suppress the rotational speed fluctuation, it is preferable to use, for example, a means for controlling the rotational accuracy of the roll drive system, for example, an inverter for controlling the rotational speed.

(C) Method of Stabilizing Film Stretching Process In order to impart heat shrinkability to the film, it is necessary to stretch the unstretched film. When stabilizing the stretching process of the film, various devices for stabilization are applied to a general stretching method.

  When controlling the stretching temperature, the stretching temperature is controlled so as not to become too high. If the stretching temperature is too high, the film thickness distribution value may become too large. If the stretching temperature is too high, the heat shrinkage rate of the film may be insufficient, and further, the strength of the film will be insufficient when the obtained heat-shrinkable film is mounted on a container (such as a bottle) at high speed. In some cases.

  The stretching temperature is preferably controlled to, for example, glass transition temperature (Tg) + 40 ° C. or lower (preferably + 15 ° C. or lower).

  Although the relationship with the thickness distribution value is small, the stretching temperature is preferably a glass transition temperature (Tg) of −20 ° C. or higher (preferably −5 ° C. or higher). If the stretching temperature is too low, the transparency of the film may decrease.

  When the internal heat generation of the film accompanying stretching is suppressed, the temperature unevenness of the film in the stretching direction (such as the width direction) can be reduced, and the uniformity of the thickness of the stretched film (heat-shrinkable film) can be enhanced.

  In order to control the internal heat generation, it is preferable to appropriately control the heating conditions (for example, to increase the supply speed of hot air) so that the film is easily heated. When there is an insufficiently heated portion, internal heat generation due to stretching orientation occurs. On the other hand, when the film is sufficiently heated, the molecular chain easily slips during stretching, so that internal heat generation hardly occurs.

When the heating condition is represented by a heat transfer condition, for example, the heat transfer coefficient is 0.0038 J / cm ² · sec · ° C. (0.0009 calories / cm ² · sec · ° C.) or more, preferably 0.0046 to 0.00. It is about 0071 J / cm ² · sec · ° C. (0.0011 to 0.0017 calories / cm ² · sec · ° C.).

(3) Control of preliminary preheating conditions When controlling the preliminary preheating conditions, it is preferable to control so that the film is gradually heated. When the film is gradually heated in the preliminary preheating step, the temperature distribution of the film can be made substantially uniform, so that the uniformity of the thickness of the stretched film (heat-shrinkable film) can be enhanced.

When the preheating condition is represented by a heat transfer condition, for example, the heat transfer coefficient is about 0.00054 J / cm ² · sec · ° C. (0.0013 calories / cm ² · sec · ° C.) or less. In the preheating, the film surface temperature is preferably heated until it reaches a temperature within the range of Tg + 0 ° C. to Tg + 60 ° C., and the temperature of the hot air is preferably about Tg + 10 ° C. to Tg 90 ° C.

  Examples of the method for achieving the heat transfer coefficient include a method of slowing the hot air supply rate.

(4) Soaking the surface temperature of the film during stretching When stretching the film, if the fluctuation of the surface temperature of the film is reduced (soaking), stretching or heat treatment is performed at the same temperature over the entire length of the film. The thickness distribution value and heat shrinkage behavior can be made uniform.

  As for the fluctuation range of the surface temperature, the temperature at each point when the surface temperature of the film is measured at an arbitrary point is preferably, for example, within the average temperature of the film ± 1 ° C., and the average temperature ± 0.5 ° C. More preferably, it is within.

  When stretching the film, some of these steps are used to stretch the film through various steps such as a preheating step before stretching, a stretching step, a heat treatment step after stretching, a relaxation treatment step, and a re-stretching step. In all, it is preferable to use equipment that can reduce the fluctuation range of the surface temperature of the film (equalize). In particular, in order to make the thickness distribution value uniform over the entire length of the film, in the preheating step and the stretching step (and in the heat treatment step after stretching if necessary), the equipment that can reduce the surface temperature fluctuation range of the film Is preferably used. In order to make the heat shrinkage behavior uniform, it is preferable to use equipment that can reduce the fluctuation range of the surface temperature of the film in the stretching step.

Examples of equipment that can reduce the fluctuation range of the film temperature include, for example, equipment equipped with a wind speed control means (such as an inverter) for controlling the supply speed of hot air for heating the film, and stably heating the air. Examples include equipment equipped with heating means for adjusting the hot air [heating means using low pressure steam of 500 kPa or less (5 kgf / cm ² or less) as a heat source].

  The heat-shrinkable label obtained using the multilayer heat-shrinkable polyester film of the present invention has a good shrink-finished appearance even when used for a full label (a label that requires a high shrinkage rate partially) such as a PET bottle. Can be presented. In addition, high shrinkage can be achieved in a short time. Furthermore, it also has an effect of reinforcing a container such as a PET bottle whose coating has been shrunk.

  In order to use the multilayer heat-shrinkable polyester film as a heat-shrinkable label, for example, the heat-shrinkable film before shrinkage is stored in a temperature / humidity controlled environment for a predetermined time and then taken out, and a known tubular molding is performed. Using an apparatus, an adhesive solvent is applied slightly inward from the edge of one side of one end of the film, the film is immediately rolled up, the ends are overlapped and bonded, and processed into a tube shape. This tube can be cut into a predetermined length to obtain the heat-shrinkable label of the present invention.

  The film can be bonded by using a melt bonding method in which a part of the film is melted, but it is preferable to use a solvent from the viewpoint of suppressing fluctuations in the heat shrinkability of the label. Examples of the solvent that can be used include aromatic hydrocarbons such as benzene, toluene, xylene, and trimethylbenzene, halogenated hydrocarbons such as methylene chloride, 1,1,1, -trichloroethane, and chloroform, and phenols such as phenol. Organic solvents such as francs such as tetrahydrofuran, oxolanes such as 1,3-dioxolane, and the like. Among these, 1,3-dioxolane is desirable because of its high safety.

  The heat-shrinkable label is attached to a container such as a PET bottle, and then thermally contracted by the heat-shrinking means (hot air tunnel, steam tunnel, etc.) as described above.

  The thickness of the heat-shrinkable polyester film is not particularly limited. For example, when used for labeling, it is about 10 to 200 μm, preferably about 20 to 100 μm.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples, unless the summary is exceeded.

  The evaluation method of the film of the present invention is as follows.

(1) Heat shrinkage rate The film was cut into a 10 cm × 10 cm square, heat-shrinked in warm water at a predetermined temperature ± 0.5 ° C. under no load for 5 seconds, and then longitudinal and transverse directions of the film. Were measured, and the thermal shrinkage rate was determined according to the following formula. The direction in which the heat shrinkage rate is large was taken as the main shrinkage direction.
Heat shrinkage rate (%) = 100 × (length before shrinkage−length after shrinkage) ÷ (length before shrinkage)
The direction with the largest shrinkage rate is defined as the main shrinkage direction.

(2) Thermal shrinkage difference Δ
A mold having two chucks facing each other is prepared so that only a pair of opposing ends of a rectangular film can be gripped. The heat-shrinkable polyester film is cut into a square or a rectangle parallel to the main shrinkage direction. The cut film is fixed with the above mold. Fixing is performed by gripping both ends of the film perpendicular to the main shrinkage direction with a chuck, and loosening the film so that the film length between the chucks and the distance between the chucks of the mold is 1: 0.9. . After that, the film fixed on the mold was immersed in warm water at 95 ° C. ± 0.5 ° C. under no load for 5 seconds and heat-shrinked, and then immediately immersed in water at 25 ° C. ± 0.5 ° C. under no load. Soak for 10 seconds and pull up. The film is removed from the mold and the adhering water is removed to obtain a film contracted by 10% in the main contraction direction. Thereafter, the film is placed in an airless environment at 25 ° C. or lower and subjected to the next step in as short a time as possible.

  This film was cut into a 10 cm × 10 cm square, immersed in warm water at 95 ° C. ± 0.5 ° C. for 5 seconds in a no-load state and thermally contracted, and then 10 ° C. in water at 25 ° C. ± 0.5 ° C. It is immersed for 2 seconds, pulled out from the water, and the lengths of the sample in the vertical and horizontal directions are measured, and the thermal contraction rate X10 in the main contraction direction is determined according to the above formula for calculating the thermal contraction rate. Further, the heat shrinkage rate at a hot water temperature of 95 ° C. obtained by the method of the above formula (1) is assumed to be X0. From these values, the heat shrinkage rate difference Δ is calculated according to the above equation (1).

(3) Heat shrinkage stress A sample having a length of 200 mm in the main shrinkage direction and a width of 20 mm was cut out from each film and measured using a tensile tester with a heating furnace (“Tensilon” manufactured by Toyo Seiki Co., Ltd.). The maximum value was obtained from the measurement chart and was defined as the heat shrinkage stress (MPa).

(4) Shrinkage Finishing Properties Three-color printing was performed in advance on a heat-shrinkable film using grass, gold, and white ink from Toyo Ink Manufacturing Co., Ltd. The printing surface was the A layer side of the film. A label was produced from the printed film with a folding diameter of 108.5 mm and a height of 195 mm. The label was printed on the inside.

Using a steam tunnel (model: SH-1500-L) manufactured by Fuji Astec Inc, with a transit time of 10 seconds and a zone temperature of 90 ° C., a 334 ml glass bottle (height 190 cm, center diameter 6.9 cm) (Asahi Breweries) (Both used for Steiny Super Dry) (number of measurements = 20).
Evaluation was made visually and the criteria were as follows.
○: No wrinkles, jumping up, or insufficient contraction occurred ×: Wrinkles, jumping up, or insufficient contraction occurred

(5) Label folding after lapse of printing time After aging the printed label at 20 ° C. for 2 months, using a steam tunnel (model: SH-1500-L) manufactured by Fuji Astec Inc., passing time of 5 seconds, zone The test was conducted at a temperature of 90 ° C. using a 334 ml glass bottle (height 190 cm, central diameter 6.9 cm) (bottle used for Asahi Breweries' Steiny Super Dry) (number of measurements = 20).
Evaluation was made visually and the criteria were as follows.
○: No folding at the top of the label ×: Folding at the top of the label

(6) Tg (glass transition point)
Using DSC (model: DSC220) manufactured by Seiko Denshi Kogyo Co., Ltd., 10 mg of an unstretched film was heated from −40 ° C. to 120 ° C. at a heating rate of 20 ° C./min. From the obtained endothermic curve Asked. A tangent line was drawn before and after the inflection point of the endothermic curve, and the intersection was defined as Tg (glass transition point).

(7) Thickness distribution Using a contact thickness meter (model: KG60 / A) manufactured by Anritsu Co., Ltd., the thickness of the sample of 5 cm in the vertical direction and 50 cm in the horizontal direction was measured (measurement number = 20). The thickness distribution (thickness variation) was determined by the following equation (2). Moreover, the average value (n = 50) of the thickness distribution was evaluated according to the following criteria.
Thickness distribution = ((maximum thickness−minimum thickness) / average thickness) × 100 (%) (2)
○: 6% or less △: greater than 6% and less than 10% ×: 10% or more

(8) Intrinsic Viscosity 0.1 g of a sample (film or chip) is precisely weighed and dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane = 3/2 (mass ratio), and then 30 ± 0.1 using an Ostwald viscometer. Measured at ° C. The intrinsic viscosity [η] is determined by the following formula (Huggins formula).

η _sp / c = [η] + k [η] ² c
k is a so-called Huggins constant and is a measure of hydrodynamic interaction between solute molecules.
[Η] is obtained by plotting η _{sp /} c against _c from viscosity measurements of several solutions having different concentrations and extrapolating the obtained straight line from c → 0.
η _sp is the specific viscosity when the concentration is c.

(9) Composition ratio of film composition copolyester Approximately 5 mg of polymer piece sample of the measurement target layer cut out from each side of the laminated film was dissolved in 0.7 ml of a mixed solution of deuterated chloroform and trifluoroacetic acid (volume ratio 9/1). 1H-NMR (manufactured by varian, UNITY 50) was used.

(10) Curling of film before shrinkage After cutting the film into a size of 29.7 cm in length and 21 cm in width in a direction perpendicular to the main shrinkage direction, the film rising height in the length direction is measured and evaluated according to the following criteria: did.
○: Curling is within 5 mm ×: Curling exceeds 5 mm

(11) Hot water curl rate The heat-shrinkable film is cut into a 10 cm × 10 cm square, cut into a length of 1 cm × width of 1 cm in a direction perpendicular to the main shrinkage direction, and then heated at 75 ± 0.5 ° C. In the above, heat treatment was performed by treating for 3 seconds in a no-load state. The curl rate was calculated from the following formula for the cut portion of the film.

Formula: Curling rate (%) = (L1 / L2) × 100

L1: Length (mm) connecting the corners of the cutting tip with straight lines
L2: Length of cut root part (mm)

○: Curled on one side (curl amount of 5% or more)
X: No curling (curl amount less than 5%)

(12) Container reinforcement effect A label having a folding diameter of 108.5 mm and a height of 140 mm was prepared from the heat-shrinkable film. Weight: 20.5 g of a 500 mL round PET bottle [height 210 mm, center (body) diameter 6.5 cm] was filled with 500 mL of water and sealed, and the above label was attached to it, and Fuji Astec Inc. Using a steam tunnel (model: SH-1500-L), the label was shrunk by passing it at a zone temperature of 80 ° C. with a passage time of 2.5 seconds.

The diameter (W1) of the center of the bottle when a weight of 15 kg is applied in the compression mode to the center of the side surface of the label-coated PET bottle obtained in this manner using “Strograph V10-C” manufactured by Toyo Seiki Co., Ltd. The bottle diameter change rate was determined according to the following formula.
Bottle diameter change rate (%) = 100 × (W1-W2) / W2
Here, W2 is the diameter of the central portion of the bottle before weighting.

(13) Difference in degree of orientation between front and back surfaces of film Using Atsube refractometer 1T manufactured by ATAGO, the refractive index was measured from each surface, and the degree of surface orientation was determined from the following formula, and the difference was determined.

Formula: AO = (Nx + Ny) / 2-Nz

AO: degree of plane orientation Nx: refractive index in the main shrinkage direction Ny: refractive index in a direction orthogonal to the main shrinkage direction Nz: refractive index in the film thickness direction

The polyester used in the examples is as follows.
Polyester A: Polyethylene terephthalate (Intrinsic viscosity (IV): 0.75 dl / g)
Polyester B: Polyester composed of 30 mol% neopentyl glycol, 70 mol% ethylene glycol and terephthalic acid (IV: 0.75 dl / g)
Polyester C: Polybutylene terephthalate (IV: 1.24 dl / g)
Polyester elastomer: Polyester comprising 70% by mass of polybutylene terephthalate and 30% by mass of ε-caprolactone (reduced viscosity (ηsp / c) 1.30)

Example 1
Polyester mixed with 10% by mass of polyester A, 81% by mass of polyester B and 9% by mass of polyester elastomer as the A layer, and polyester mixed with 10% by mass of polyester A, 85% by mass of polyester B and 5% by mass of polyester elastomer as the B layer, respectively. And was coextruded from a T die so that the layer thickness ratio was A layer / B layer = 10/90, and quenched with a chill roll to obtain an unstretched multilayer film having a thickness of 240 μm. The unstretched multilayer film had a Tg of 67 ° C.

  The unstretched film was preheated until the film temperature reached 90 ° C., and then stretched in the transverse direction with a tenter. The stretching was performed by stretching 4.75 times at 74 ° C. (first stage), and then heat setting was performed at 76 ° C. for 5 seconds with the width at the end of the first stage. Next, at 76 ° C., the film was stretched 1.1 times the width at the end of heat setting (second stage). Next, the film was cooled while applying a tension of 1% with respect to the film width at the end of the second stage drawing to obtain a film having a thickness of 45 μm.

(Example 2)
A film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that the layer thickness ratio was A layer / B layer = 15/85. The multilayer film had a Tg of 67 ° C.

(Comparative Example 1)
A polyester in which 15% by mass of polyester A, 75% by mass of polyester B and 10% by mass of polyester C were mixed was melted at 280 ° C., extruded from a T-die, and quenched with a chill roll to obtain an unstretched film having a thickness of 230 μm. The unstretched film had a Tg of 68 ° C.

  The unstretched film was preheated until the film temperature reached 90 ° C., and then stretched in the transverse direction with a tenter. The film was stretched 5 times at 74 ° C., and then heat-fixed at 74 ° C. for 5 seconds to obtain a film having a thickness of 45 μm.

(Comparative Example 2)
A film having a thickness of 45 μm was obtained in the same manner as in Comparative Example 1 except that the thickness of the unstretched film was 180 μm and the stretching was 4 times.

(Comparative Example 3)
Polyester mixed with 10% by mass of polyester A, 81% by mass of polyester B and 9% by mass of polyester elastomer as the A layer, and polyester mixed with 10% by mass of polyester A, 85% by mass of polyester B and 5% by mass of polyester elastomer as the B layer, respectively. And was coextruded from a T-die so that the layer thickness ratio was A / B = 50/50, and quenched with a chill roll to obtain an unstretched multilayer film having a thickness of 240 μm. The unstretched multilayer film had a Tg of 65 ° C.

  The unstretched film was preheated until the film temperature reached 90 ° C., and then stretched in the transverse direction with a tenter. The stretching was performed by stretching 4.75 times at 74 ° C. (first stage), and then heat setting was performed at 74 ° C. for 5 seconds with the width at the end of the first stage. Next, at 72 ° C., the film was stretched 1.1 times the width at the end of heat setting (second stage) to obtain a film having a thickness of 45 μm.

  Table 2 shows the evaluation results of the films obtained in Examples 1-2 and Comparative Examples 1-3. As is apparent from Table 2, the films obtained in Examples 1 and 2 all had good shrinkage finish. The thickness distribution was also good. Moreover, there was no label folding at the time of shrinkage after printing. In addition, the reinforcing effect after covering the container was also excellent. Thus, the multilayer heat-shrinkable polyester film of the present invention has high quality and high practicality, and is particularly suitable for shrink labels.

On the other hand, the heat-shrinkable film obtained in Comparative Example 1 was folded when the label contracted after printing. The film obtained in Comparative 2 was inferior in the container reinforcing effect due to insufficient heat shrinkage difference Δ. In Comparative Example 3, the curl before shrinkage was large and the processing suitability was poor. Thus, all the heat-shrinkable polyester films obtained in the comparative examples were inferior in quality and low in practicality.

  When the multilayer heat-shrinkable polyester film of the present invention is used as a label for a bottle, wrinkles, shrinkage spots, distortion, and insufficient shrinkage due to heat shrinkage occur even in a container that requires a high shrinkage rate partially. Therefore, it is possible to obtain a beautiful shrink-finished appearance with very little crease and no folding failure even after printing. Moreover, the heat-shrinkable label obtained from the multilayer heat-shrinkable film of the present invention is excellent in the reinforcing effect of the coated container.

Claims (8)

A multilayer heat-shrinkable polyester film comprising at least two layers, wherein the heat-shrinkage rate of the polyester-based film is 5 to 60% at a treatment temperature of 70 ° C. and a treatment time of 5 seconds in the main shrinkage direction. 75% or more in 5 seconds, 10% or less in 85 ° C · 5 seconds in the direction orthogonal to the main shrinkage direction, and the maximum value of the heat shrinkage stress in hot air at 90 ° C in the main shrinkage direction exceeds 13 MPa The shrinkage rate in the main shrinkage direction when the curl of the film before shrinkage is within 5 mm and heat-shrinked in the main shrinkage direction by 10% is further treated in warm water at 95 ° C. for 5 seconds. Multilayer heat shrinkability, characterized in that when X0 (%) and X10 (%), the difference in thermal shrinkage Δ (%) shown by the following formula is 10 to 20% and curls to one side when shrinking. Polyester the film.
Δ = X0−X10   2. The heat-shrinkable polyester film according to claim 1, wherein the maximum value of heat shrinkage stress in hot air at 90 ° C. is 7 MPa or more in the direction of the film after 10% heat shrinkage in the main shrinkage direction.   A monomer component which can be an amorphous component in all the polyester resin components constituting the film, wherein the monomer component is neopentyl glycol and / or 1,4-cyclohexanedimethanol. 2. A heat-shrinkable polyester film according to 2.   The heat-shrinkable polyester film according to claim 3, wherein the content of the monomer component that can be an amorphous component in all the polyester resin components is 16 mol% or more.   A polyester elastomer is contained in the film in an amount of 3% by mass or more, and the polyester elastomer has a high melting point crystalline polyester segment having a melting point of 200 ° C. or more and a low melting point soft polymer segment having a molecular weight of 400 or more and a melting point of 80 ° C. or less. The multilayer heat-shrinkable polyester film according to any one of claims 1 to 4, which is a polyester block copolymer.   The heat-shrinkable polyester film according to any one of claims 1 to 5, wherein a thickness distribution is 6% or less.   The label produced using the heat-shrinkable polyester-type film in any one of Claims 1-5.   A label produced by using the heat-shrinkable polyester film according to any one of claims 1 to 6 so as to curl to the outer surface side of the label when shrinking.