JP2010058366A - Heat-shrinkable polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-shrinkable polyester film which gives iridescent metallic glossiness, is joined using a solvent as a film covering a container such as a PET bottle, and controls the occurrence of a defect damaging the appearance of the film by partial shrinkage spots. <P>SOLUTION: In the film, first layers each containing a polyester (A) containing ethylene terephthalate as an indispensable component and second layers each containing a polyester (B) containing ethylene-2,6-naphthalene dicarboxylate as a main component, are laminated alternately to form 25-1,001 layers. The percentage of the total thickness of the first layers to the thickness of the entire film is 80-96%. The polyester (A) contains 40-80 mol% of ethylene glycol and 20-60 mol% of a second glycol component to the total glycol components of the polyester (A). The film has at least one reflection peak having a reflectance of 25% or more in a reflectance curve of 400-800 wavelength. The thermal shrinkage factor in the longitudinal or width direction of the film when it is immersed in warm water of 65°C for 10 s, is 15% or more and ≥0% and <10% in an absolute value in the direction crossing this direction rectangularly. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat-shrinkable polyester film rich in design that reflects light of a specific wavelength. More specifically, the present invention is rich in glossy design that reflects light of a specific wavelength, and at the same time, such as a PET bottle. The present invention relates to a heat-shrinkable polyester film that can be easily bonded using a solvent as a film covering the outer surface of a container or an electric wire and that has small shrinkage spots and is used for shrink labels, electric wire coverings, and the like.

  In recent years, various polyester films have been used as packaging for beverage containers, such as laminate films of metal cans and shrink films that can be coated on the outer surface of PET bottles. In addition, in packaging bags, etc., a method of using as a packaging bag, etc. a film in which a film printed with a gravure or the like with excellent printing quality is attached by heat-sealing in order to give a higher quality design. Etc. have been proposed.

Recently, in addition to improvements in heat shrinkage, handling, chemical resistance, etc. for shrink labels, more and more beautiful ones are being demanded.
Various films made of polyester have been studied as shrink label films. For example, Patent Document 1 contains a naphthalenedicarboxylic acid residue in order to suppress the occurrence of uneven shrinkage in a hot-air shrink tunnel. A heat shrinkable polyester film is disclosed. In addition, as a heat-shrinkable polyester film excellent in all of the perforation cutability, the adhesive portion strength, the impact resistance, and the design properties when bottled when labeled in Patent Document 2, a multilayer heat-shrinkable polyester film Has been proposed, and it is disclosed that polyesters having different blend ratios are used for each layer. On the other hand, the design property studied in Patent Document 2 is that the design property is not impaired by vertical draw when attached to a square bottle, and is about the surface appearance due to heat shrinkage, Beautiful design properties such as metallic luster have not been studied.

  On the other hand, as a glossy film, a polyester-based multilayer film focusing on light interference has been studied. For example, Patent Document 3 discloses alternating layers of polyethylene naphthalate and copolymer polyethylene naphthalate. A multilayer laminated film is disclosed which is laminated on the substrate and selectively reflects specific wavelengths by structural light interference between these layers. However, Patent Document 3 is intended to improve deflection and reflection characteristics suitable for a reflective polarizer or mirror, and has not been studied at all for heat shrink characteristics and solvent adhesion as a shrink label.

In Patent Document 4, a polyethylene-2,6-naphthalate layer and a layer made of a thermoplastic resin having a lower refractive index than polyethylene-2,6-naphthalate are alternately used for the purpose of selectively reflecting light in an arbitrary wavelength band. Although a multilayer laminated film in which at least 11 layers are laminated is disclosed, no consideration has been given to heat shrinkage properties and solvent adhesion.
Patent Document 5 discloses a laminated heat-shrinkable film having 11 or more layers having iridescent metallic luster, but does not disclose the adhesiveness (bonding) between films using a solvent.

As described above, most conventional heat-shrinkable polyester films are intended to improve the heat-shrinkability and handling properties required for shrink labels, and recently, heat-shrinkable with design characteristics. The nature of the polyester film has just started to be studied. However, these heat-shrinkable polyester films have insufficient film adhesive strength using a solvent due to the characteristics of the outermost polyester resin.
Accordingly, there is a need for a heat-shrinkable polyester film that has good metallic gloss, excellent film-bonding workability using a solvent, and excellent shrinkage characteristics without shrinkage spots.

Japanese Patent Laid-Open No. 9-174684 JP 2007-152943 A Japanese National Patent Publication No. 9-506837 JP 2002-160339 A JP 2007-237434 A

  The object of the present invention is to eliminate such problems of the prior art, to provide iridescent metallic luster, and to use a solvent as a film for covering a container such as a PET bottle, and due to partial shrinkage. An object of the present invention is to provide a heat-shrinkable polyester film having excellent heat-shrinkability that does not easily cause defects that impair the appearance.

  As a result of intensive studies to solve the above problems, the inventors of the present invention alternately laminated a plurality of resins having different refractive indexes, and each layer thickness of these resins and a layer containing ethylene terephthalate as an essential component for the film thickness. In addition to obtaining a shrinkable polyester film having an iridescent metallic luster by adjusting the ratio of the above, there is no occurrence of partial shrinkage spots, and it is possible to use a solvent for bonding during label production The inventors have found that a polyester containing ethylene terephthalate, which is a high proportion of the film as an essential component, can be solved by containing a certain amount or more of the second acid component derived from the glycol component, and completed the present invention.

  That is, according to the present invention, an object of the present invention is to provide a first layer containing a polyester (A) containing ethylene terephthalate as an essential component, and a polyester (B containing ethylene-2,6-naphthalenedicarboxylate as a main component). ), The total thickness of the first layer with respect to the total film thickness is 80% or more and 96% or less. The polyester (A) contains ethylene glycol in the range of 40 mol% to 80 mol% based on the total glycol component of the polyester (A), and the second in the range of 20 mol% to 60 mol%. In the reflectance curve in the wavelength range of 400 to 800 nm, the film has few reflection peaks with a reflectance of 25% or more. The thermal shrinkage rate when left in 65 ° C. warm water for 10 seconds is 15% or more in either the film longitudinal direction or the width direction, and the absolute value in the direction perpendicular to the direction is 0% or more 10 Achieved by a heat shrinkable polyester-based film that is less than%.

Moreover, the heat-shrinkable polyester film of the present invention has, as a preferred embodiment thereof, a laminated structure composed of an alternating laminate (I) and a thickness adjusting layer (II) arranged on both sides, and has a thickness. The adjustment layer (II) is composed of a first layer containing polyester (A ′) containing ethylene terephthalate as an essential component, and the average thickness of the first layer in the alternating laminate (I) is 0.02 to 0.4 μm. The first layer has an average thickness of 0.03 to 0.5 μm, the first layer includes a polyester (A) whose laminated structure contains ethylene terephthalate as an essential component, and ethylene-2,6-naphthalene. The second layer comprises only a laminated structure in which the second layers containing the polyester (B) containing a carboxylate as a main component are alternately laminated, and the average thickness of the first layer is 0.05 to 3.6 μm. Average of The film has a haze of 0.1 to 10%, the second glycol component constituting the polyester (A) is diethylene glycol, 1,4-butanediol, It includes at least one selected from the group consisting of 1,6-hexanediol, neopentyl glycol and 1,4-cyclohexanedimethanol.
Moreover, according to this invention, the shrink label which consists of a heat-shrinkable polyester film of this invention is provided.

  According to the present invention, it is possible to provide an iridescent metallic luster by being rich in glossy design that reflects light of a specific wavelength, and bonding using a solvent as a film covering a container such as a PET bottle. It is possible to provide a heat-shrinkable polyester-based film which is possible and hardly causes defects that impair the appearance due to partial shrinkage spots, and can be suitably used for a shrink label of a PET bottle. In addition, it can be suitably used for electric wire coating that requires heat shrinkability and design.

Hereinafter, the present invention will be described in detail.
[First layer]
The 1st layer in this invention consists of polyester (A) which has ethylene terephthalate as an essential component. The polyester (A) contains ethylene glycol in the range of 40 mol% to 80 mol% based on the total glycol component of the polyester (A), and the second diol component in the range of 20 mol% to 60 mol%. It is necessary to contain. Further, the lower limit of the proportion of the second glycol component constituting the polyester (A) is preferably 25 mol% based on the total glycol component, and the upper limit of the proportion of the second acid component is preferably all 55 mol% based on the glycol component. The polyester (A) constituting the first layer of the present invention is a polyester containing ethylene terephthalate as an essential component and containing the second glycol component in the above range, and is sufficient for performing shrink processing as a shrink label. In addition to exhibiting excellent shrinkage characteristics, it is possible to adhere a solvent at the time of label production, and to reduce shrinkage spots at the time of label mounting. When the ratio of the second glycol component is less than the lower limit, not only sufficient solvent adhesion is not obtained, but also defects such as whitening due to partial shrinkage spots, wrinkles, distortion and vertical shrinkage tend to occur. On the other hand, if the ratio of the second glycol component exceeds the upper limit value, the shrink property is impaired, or the glass transition point (Tg) of the polyester becomes too low, making film formation difficult.
The polyester (A) constituting the first layer may be a copolyester or may be blended with other types of polyester resins.

Examples of the glycol component of the copolymer component include diethylene glycol, 1,4-butanediol, 1,6-hexanediol, aliphatic diols such as neopentyl glycol, and alicyclic diols such as 1,4-cyclohexanedimethanol. It is preferable that it is at least one selected from these groups. Among these copolymer components, diethylene glycol and 1,4-butanediol are particularly preferable. These copolymer components may be used alone or in combination of two or more components.
When blending other polyester resins, polybutylene terephthalate is exemplified as a blend component.

  In addition, the main component of the dicarboxylic acid component of the polyester (A) of the present invention is terephthalic acid, and may include a subordinate component within a range of 0 mol% to 20 mol%. Moreover, such a subordinate component may be included as a copolymerization component, and may be included as a blend with another kind of polyester resin. As copolymerization component of dicarboxylic acid component, aromatic dicarboxylic acid such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, aliphatic dicarboxylic acid such as 1,10-decanedicarboxylic acid An acid can be illustrated.

The glass transition temperature (Tg ₁ ) of the polyester (A) having ethylene terephthalate as an essential component is preferably in the range of more than 60 ° C. and 80 ° C. or less. The glass transition temperature (Tg ₁ ) of the polyester (A) is more preferably 65 ° C. or higher and 78 ° C. or lower, and further preferably 65 ° C. or higher and 75 ° C. or lower. When the glass transition temperature (Tg ₁ ) of the polyester (A) is less than the lower limit, the other layer constituting the alternately laminated layer for expressing the metallic luster, that is, ethylene-2 constituting the second layer, The glass transition temperature difference with the polyester (B) containing 6-naphthalenedicarboxylate as a main component becomes too large, and film formability may be lowered. On the other hand, when the glass transition temperature (Tg ₁ ) of the polyester (A) exceeds the upper limit, sufficient shrinkage characteristics may not be obtained when shrink processing is performed as a shrink label.

  The first layer may contain a very small amount of a colorant, an antistatic agent, an antioxidant, an organic lubricant, a catalyst, an ultraviolet absorber and the like as long as the object of the present invention is not impaired.

  The polyester (A) containing ethylene terephthalate as an essential component can be produced by applying a known method. For example, it can be produced by a method in which terephthalic acid, ethylene glycol and, if necessary, a copolymerization component are esterified, and then a reaction product obtained is polycondensed to form a polyester. Alternatively, these raw material monomer derivatives may be transesterified, and then the resulting reaction product may be subjected to a polycondensation reaction to obtain a polyester. The polyester (A) containing ethylene terephthalate as an essential component can also be produced by a method of blending polyethylene terephthalate and another type of polyester resin and transesterifying with heat during melting.

  The intrinsic viscosity of the polyester (A) constituting the first layer is preferably 0.55 to 0.80 dl / g, more preferably 0.55 to 0.75 dl / g. When the intrinsic viscosity of the polyester (A) constituting the first layer is not within such a range, the film-forming property may be lowered although the film can be formed.

  When the heat-shrinkable polyester film of the present invention has a layer structure including a thickness adjusting layer (II), the thickness adjusting layer (II) comprises a polyester (A ′) containing ethylene terephthalate as an essential component, It constitutes a part of the first layer. Here, the polyester (A ′) containing ethylene terephthalate as an essential component conforms to the polyester defined in the polyester (A). The polyester (A ′) may have the same composition as the first layer in the alternating laminate (I) described later, or may have another composition defined in the polyester (A).

[Second layer]
The 2nd layer in this invention consists of polyester (B) which has ethylene-2,6- naphthalene dicarboxylate as a main component. Here, “main” refers to 80 mol% or more and 100 mol% or less based on the total acid components constituting the polyester (B). The lower limit of the ratio of the main component constituting the polyester (B) is preferably 85 mol% or more, more preferably 90 mol% or more, based on the total acid component.
The polyester (B) constituting the second layer of the present invention is a polyester mainly composed of ethylene-2,6-naphthalenedicarboxylate, so that the refractive index difference from the first layer is 0.05. Thus, in the case of an alternately laminated structure, a reflection peak with a reflectance of 30% or more appears in the reflectance curve in the wavelength range of 400 to 800 nm, and metal gloss is exhibited. In addition, the refractive index of polyester (A) which comprises a 1st layer is the range of 1.40-1.70, and the refractive index of polyester (B) which comprises a 2nd layer is 1.70-1. It is preferable that the refractive index of the second layer is in the range of 80, and the refractive index of the second layer is 0.05 or more larger than the refractive index of the first layer. In addition, since the polyester of the second layer is a polyester (B) having ethylene-2,6-naphthalenedicarboxylate as a main component, it is refracted as compared with the case where layers having polyethylene terephthalate as a main component are laminated. The rate difference increases and the reflectivity increases.

  Polyester (B) constituting the second layer may be polyethylene-2,6-naphthalenedicarboxylate alone, blended with a small proportion of other types of polyester resin, or copolymerized with other copolymer components. It may be what you did. Here, the small proportion refers to a proportion of 0 mol% or more and 20 mol% or less based on the total acid components constituting the polyester (B), and the preferred upper limit is 15 mol% or less, more preferably 10 mol% or less. .

  Examples of the dicarboxylic acid component of the copolymer component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, and terephthalic acid, and aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and 1,10-decanedicarboxylic acid. be able to. Examples of the diol component of the copolymer component include aliphatic diols such as diethylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol, and alicyclic diols such as 1,4-cyclohexanedimethanol. be able to. Among these copolymer components, isophthalic acid and terephthalic acid are preferable, but terephthalic acid has an advantage that the film forming property and the layer structure can be easily controlled because the component is close to the polyester constituting the first layer.

  When blending a small proportion of other polyester resins, examples of blend components include polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate.

The polyester (B) mainly composed of ethylene-2,6-naphthalenedicarboxylate constituting the second layer preferably has a glass transition temperature (Tg ₂ ) in the range of 95 ° C. or more and 125 ° C. or less. The lower limit value of the glass transition temperature (Tg ₂ ) of the polyester (B) is more preferably 100 ° C., more preferably 105 ° C., while the upper limit value of the glass transition temperature (Tg ₂ ) of the polyester (B) is more Preferably it is 120 degreeC. Due to the constitution of the main component and copolymer component of the polyester (B), the lower limit of the glass transition temperature (Tg ₂ ) of the polyester (B) is naturally limited to the above range. On the other hand, when the glass transition temperature (Tg ₂ ) of the polyester (B) exceeds the upper limit, the other layer constituting the laminated structure for expressing the metallic luster, that is, ethylene terephthalate constituting the first layer is essential. The difference in glass transition temperature from the component polyester (A) becomes too large, film-forming properties may decrease, and heat shrinkability may decrease.

  The second layer may contain a very small amount of a colorant, an antistatic agent, an antioxidant, an organic lubricant, a catalyst, an ultraviolet absorber and the like as long as the object of the present invention is not impaired.

  The polyester (B) having ethylene-2,6-naphthalenedicarboxylate as a main component can be produced by applying a known method. For example, it can be produced by a method in which ethylene-2,6-naphthalenedicarboxylic acid, ethylene glycol and, if necessary, a copolymerization component are esterified, and then the resulting reaction product is polycondensed to form a polyester. . Alternatively, these raw material monomer derivatives may be transesterified, and then the resulting reaction product may be subjected to a polycondensation reaction to obtain a polyester. Polyester (B) can also be produced by a method in which polyethylene-2,6-naphthalene dicarboxylate and another type of polyester resin are blended and subjected to a transesterification reaction with heat at the time of melting.

  The intrinsic viscosity of the polyester (B) constituting the second layer is preferably 0.40 to 0.65 dl / g, and more preferably in the range of 0.45 to 0.62 dl / g. When the intrinsic viscosity of the polyester (B) constituting the second layer is not within such a range, film formation may be possible although film formation is possible.

[Glass-transition temperature]
Glass transition temperature (Tg ₁ ) of polyester (A) having ethylene terephthalate of the present invention as an essential component and glass transition temperature (Tg ₂ ) of polyester (B) having ethylene-2,6-naphthalenedicarboxylate as a main component. ) Preferably satisfies the following formula (1).
−60 ° C. <(Tg ₁ −Tg ₂ ) <− 30 ° C. (1)

The glass transition temperature difference (Tg ₁ -Tg ₂ ) between the polyester (A) and the polyester (B) is more preferably −57 ° C. or more and −35 ° C. or less, and further preferably −55 ° C. or more and −35 ° C. or less.
When such a glass transition temperature difference (Tg 1 _{-Tg 2)} is less than the lower limit, the glass transition temperature difference becomes too large of a polyester constituting the laminated structure (A) and the polyester (B), reduced film formability There are things to do. Also the structure of the polyester component of each layer, the upper limit of the glass transition temperature difference (Tg 1 _{-Tg 2)} is limited to this range.

  In order to make the glass transition temperature difference within the above-mentioned range, the types of the main component, polyester (B) constituting the first layer, and polyester (B) constituting the second layer, It is achieved by using those component amounts in the ranges described above.

[Heat-shrinkable polyester film]
The heat-shrinkable polyester film of the present invention comprises a first layer containing a polyester (A) containing ethylene terephthalate as an essential component and a polyester (B) containing ethylene-2,6-naphthalenedicarboxylate as a main component. And a second layer including a stacked structure in which the second layer is alternately stacked in a range of 25 to 1001 layers. When the number of stacked layers is less than the lower limit, color does not develop because light interference is not sufficient. When the number of layers exceeds the upper limit, the thickness of each layer is thinner than the lower limit of the thickness per layer, the reflection wavelength is in the ultraviolet region, and no color develops.

  The lower limit of the number of layers in the laminated structure is preferably 45 layers, more preferably 75 layers. The upper limit of the total number of laminated structures is not particularly limited as long as it is in the range of 1001 layers or less, but from an industrial viewpoint, it is preferably 701 layers or less, more preferably 501 layers or less, and even more preferably 201 layers or less.

  The total thickness of the first layer with respect to the total film thickness is 80% or more and 96% or less. When the total thickness of the first layer is within such a range, the metallic gloss and heat shrinkability can be combined. When the total thickness of the first layer is less than the lower limit with respect to the total film thickness, sufficient heat shrinkability cannot be obtained at the shrink processing temperature. On the other hand, when the total thickness of the first layer exceeds the upper limit with respect to the total film thickness, the metallic gloss is not sufficiently exhibited.

  The total film thickness of the heat-shrinkable polyester film of the present invention is preferably 30 to 80 μm, more preferably 35 to 60 μm. When the total film thickness is less than the lower limit, the film loses its elasticity and may be inferior in handling at the time of processing. On the other hand, when the total film thickness exceeds the upper limit, the film may be too hard and the handling property during processing may deteriorate.

  In the heat-shrinkable polyester film of the present invention, at least one reflection peak having a reflectance of 25% or more is observed in the reflectance curve in the wavelength range of 400 to 800 nm. The reflectance of the reflection peak is preferably 30% or more, more preferably 50% or more, and further preferably 70% or more. The higher the reflectance, the clearer the metallic luster color developability. The reflectance of the reflection peak is preferably higher, but is at most 95%, further at most 90%.

  When the reflection peak is present in a range less than the wavelength of 400 nm, or when the reflection peak is present in a range exceeding the wavelength of 800 nm, the metallic luster color developability is not exhibited because the reflection peak deviates from the visible light region. Further, when the reflectance of the reflection peak is less than the lower limit, the reflected color cannot be sufficiently recognized.

  Here, the reflectance curve means that a spectrophotometer is used, and a polarizing plate is sandwiched between the film and the light receiving portion in accordance with the main orientation direction (sometimes referred to as a direction with a large shrinkage rate or a main shrinkage direction). It is a curve obtained by measuring the relative specular reflectance with an aluminum-deposited mirror at each wavelength of 800 nm. In the reflectance curve, the reflectance of 25% or more is a peak in the reflectance measured for each wavelength. It indicates that the reflectance becomes 25% or more.

  Means for achieving such reflectance characteristics excellent in metallic luster are polyester (A) and ethylene-2 containing ethylene terephthalate as essential components as resins having different refractive indexes in the first layer and the second layer. , 6-Naphthalenedicarboxylate as a main component, the polyester (B) is alternately laminated in a range of 25 layers or more and 1001 layers or less, and each layer thickness in the laminated structure is achieved within a certain range.

The heat-shrinkable polyester film of the present invention has a characteristic that the heat shrinkage rate when left in 65 ° C. warm water for 10 seconds is 15% or more in either the film longitudinal direction or the width direction. If the thermal shrinkage rate in the direction of large shrinkage when left in 65 ° C warm water for 10 seconds is less than the lower limit, the shrinkage amount in the processing temperature range of the shrink label is small, and the PET bottle as a shrink label is sufficiently adhered Does not show sex. The heat shrinkage rate when left in 65 ° C. warm water for 10 seconds is preferably larger within this range from the viewpoint of adhesion, but the upper limit is about 25% at maximum considering the appearance after shrinking.
As a means for achieving such heat shrinkage characteristics, the total thickness of the first layer is 80% or more with respect to the total film thickness, and the main shrink direction at a predetermined draw ratio of 2.5 to 4.5 times. This is achieved by stretching the film.

  Further, the heat-shrinkable polyester film of the present invention has a characteristic of an absolute value of 0% or more and less than 10% in the direction perpendicular to the direction in which the heat shrinkage rate when left in 65 ° C. warm water for 10 seconds is 15% or more. Have. When the absolute value of the thermal contraction rate in the direction in which the shrinkage rate is small when left in 65 ° C. warm water for 10 seconds exceeds the upper limit, shrinkage spots called vertical shrinkage occur. The absolute value of the thermal contraction rate in the direction of decreasing shrinkage when left in 65 ° C. hot water for 10 seconds is preferably smaller within this range, but it is usually 8% or less, more preferably 6% or less.

  Means for achieving such heat shrinkage characteristics include the types of polyester constituting the first layer and the ratio of the first layer in the total film layer, as well as the shrinkage in the direction perpendicular to the direction of the above-mentioned shrinkage. In order to reduce the rate, it is preferable not to stretch the film, and in order to increase the film strength, it is achieved by stretching at a low magnification of 1.5 times or less.

  The heat shrinkage rate when left in 65 ° C. warm water for 10 seconds means that the sample is cut into a 10 cm × 10 cm square, immersed in 65 ° C. hot water for 10 seconds, and then cooled in cold water between the marked lines. The length was measured, and the ratio of the shrinkage amount to the original dimension was obtained as a heat shrinkage rate.

The laminated structure of the heat-shrinkable polyester film of the present invention preferably has the following laminated structure.
(Laminated structure having alternating laminate (I) and thickness adjusting layer (II))
The laminated structure of the heat-shrinkable polyester film of the present invention comprises a first layer containing a polyester (A) containing ethylene terephthalate as an essential component, and a polyester containing ethylene-2,6-naphthalenedicarboxylate as a main component ( It is preferable to have a laminated structure composed of alternating laminates (I) in which second layers containing B) are alternately laminated, and thickness adjusting layers (II) arranged on both sides thereof.

The alternate laminate (I) includes a first layer containing a polyester (A) containing ethylene terephthalate as an essential component and a second layer containing a polyester (B) containing ethylene-2,6-naphthalenedicarboxylate as a main component. This is a laminated structure in which these layers are alternately laminated.
Such an alternate laminate (I) has a thickness of 0.02 to 0.4 μm per layer of the first layer and a thickness per layer of the second layer from the viewpoint of metallic luster coloring property due to light interference. Is in the range of 0.03 to 0.5 μm. In addition, the average thickness per one layer of each layer has the relationship which becomes thin according to the increase in the number of layers, and becomes thick according to the decrease in the number of layers.
When the thickness of each of the first layer and the second layer is within such a range, a reflection peak appears in the wavelength range of 400 to 800 nm, and a reflected color with visible light is expressed. When the thickness of each layer is less than the lower limit, the reflection wavelength is in the ultraviolet region, and no color is generated. On the other hand, when the thickness of each layer exceeds the upper limit, the reflection wavelength is in the infrared region, and no color is generated.

  The heat-shrinkable polyester film of the present invention has a uniform thickness in each layer of the first layer and the second layer within such a layer thickness range. The strength increases and the color developability can be improved.

The thickness adjusting layer (II) includes a polyester (A ′) containing ethylene terephthalate as an essential component and constitutes a part of the first layer. The thickness adjusting layer (II) in the present invention is a layer having a thickness of at least 5 times or more of the average thickness of the first layer and the average thickness of the second layer of the alternating laminate (I) based on the larger value. Defined by
The thickness adjusting layer (II) is provided to increase the thermal contraction rate in the vicinity of the temperature at which the shrink label of the PET bottle is shrunk, and more specifically, a certain amount of polyester having a glass transition temperature close to the shrinking processing temperature. It is provided for the purpose of making the thicknesses of the first layer and the second layer in the alternating laminate (I) uniform so as to include the above and to improve the metallic gloss. Moreover, since the surface of the outermost layer becomes smooth by disposing the thickness adjusting layer (II) on both outermost surfaces, the transparency of the film is increased and the amount of the second glycol component is 20 mol% or more 60 Since it is less than mol%, it is possible to perform adhesion processing using a solvent.

  When it has such a laminated structure, the total thickness of the first layer with respect to the total film thickness is preferably 86% or more and 96% or less. Here, the total thickness of the first layers in the stacked structure refers to the total thickness of the first layers and the thickness adjusting layer (II) in the alternate stacked body (I).

  In the case of this laminated structure, the total thickness of the thickness adjusting layer (II) with respect to the total film thickness is preferably 50 to 85%. When the total layer thickness of the thickness adjusting layer (II) is less than the lower limit with respect to the total film thickness, the ratio of the first layer in the alternating laminate (I) is relatively increased. ) May exceed the upper limit, and since the reflection wavelength is in the infrared region, color development may not occur. On the other hand, when the total thickness of the thickness adjusting layer (II) exceeds the upper limit with respect to the total film thickness, the proportion of the first layer in the alternating laminate (I) is relatively reduced, and the first layer The thickness may be less than the lower limit, and since the reflection wavelength is in the ultraviolet region, there may be no color development.

  When it has this laminated structure, it is preferable that the reflectance of the reflectance peak of the film observed in the reflectance curve in the wavelength range of 400 to 800 nm is 30% or more. The reason why the reflectance in the present laminated structure is 30% or more is that the first layer and the second layer are within a certain thickness range in addition to the difference in refractive index between the first layer and the second layer polyester. Is due to

  In addition, when the polyester (A) in the alternating laminate (I) and the polyester (A ′) constituting the thickness adjusting layer (II) have the same composition, the same extruder can be used in the film production process.

(Laminated structure without thickness adjustment layer)
The laminated structure of the heat-shrinkable polyester film of the present invention mainly comprises, as another aspect, a first layer containing polyester (A) containing ethylene terephthalate as an essential component and ethylene-2,6-naphthalenedicarboxylate. It is preferable to have a laminated structure consisting only of a laminated structure in which the second layer containing polyester (B) as a component is alternately laminated.

In this laminated structure, the average thickness of the first layer is 0.05 to 3.6 μm, and the average thickness of the second layer made of polyester (B) is 0.005 to 1.0 μm.
In the case of this laminated structure, it is preferable that each layer thickness of the 1st layer in this laminated structure is changing continuously in the thickness direction. When the thickness of each layer of the first layer is not continuously changed in the thickness direction and is uniform, only the very narrow wavelength range is selectively reflected due to the regularity of the optical thickness. It can be difficult to control.
When each layer thickness of the first layer in this laminated structure is continuously changing in the thickness direction, the average thickness per layer of the first layer is a value obtained by dividing the total thickness of each layer by the number of layers. Is required. In addition, in the case of the aspect in which each layer thickness of the first layer is continuously reduced from both surface layers of the film to the center layer, the vicinity of the film surface layer is the maximum thickness, and the film center layer is the minimum thickness, It is obtained by an average value of the maximum layer thickness and the minimum layer thickness.

  The lower limit of the average thickness per layer of the first layer is preferably 0.1 μm, more preferably 0.2 μm, still more preferably 0.3 μm, and particularly preferably 0.4 μm. The upper limit of the average thickness per layer of the first layer is preferably 3.0 μm, more preferably 1.0 μm. Note that the average thickness of each first layer is reduced as the number of layers is increased and increased as the number of layers is decreased.

  The thickness per layer of each of the first layer and the second layer is in such a range, and preferably, the first layer has a thickness gradient, so that a reflection peak appears in the wavelength range of 400 to 800 nm and is visible. Appears a reflected color with light. When the thickness of each layer is less than the lower limit, the reflection wavelength is in the ultraviolet region, and no color is generated. On the other hand, when the thickness of each layer exceeds the upper limit, the reflection wavelength is in the infrared region, and no color is generated.

  Here, “continuously changing in the thickness direction” means that when the film cross section in the film thickness direction is observed, each layer of the first layer gradually increases from one film surface layer to the other film surface layer. Refers to continuous change. Specifically, the thickness of each layer continuously increases or decreases from one film surface layer to the other film surface layer, or the thickness of each layer continuously from both surface layers to the inside. Refers to the state of increasing or decreasing. Note that “continuously changing” includes an equal ratio change, a step change, and a change with a slope.

When such a thickness change is represented by a thickness distribution curve, the maximum value and the minimum value of the thickness distribution are not limited to one, and may be plural. In the present invention, the maximum value of the thickness distribution curve may be referred to as the maximum thickness, and the minimum value of the thickness distribution curve may be referred to as the minimum thickness.
Among these aspects, the thickness of each layer of the first layer is preferably an aspect in which the layer thickness is continuously reduced from both surface layers to the central layer, in which case the maximum thickness is near the film surface layer and the minimum thickness is the film central layer. It becomes.

  The ratio obtained by dividing the maximum thickness by the minimum thickness is preferably more than 1.0 and 3.0 or less, more preferably a lower limit of 1.1 or more, and still more preferably an upper limit of 2.0 or less. If the ratio of the maximum thickness divided by the minimum thickness exceeds the upper limit, the reflection wavelength band becomes too wide, and sufficient reflectance may not be obtained. Each layer thickness of the first layer is adjusted by controlling each layer thickness of the feed block.

  In this laminated structure, it is difficult to control the reflection peak in the visible light region in the state of being uniformly laminated with the average thickness of the first layer, but even with the same average thickness as in the uniformly laminated state, The wavelength range of the reflection peak is broadened by continuously changing the thickness of each layer of the first layer in the thickness direction, and at least any peak including primary interference, secondary interference, and tertiary interference is visible. It is considered that coloration with a metallic luster is likely to occur due to the occurrence of the above.

  In the case of the first layer thickness as in this configuration, the main peak of reflectivity is in the infrared region, but the peaks such as the above-mentioned primary interference and secondary interference are visible because multiple reflection peaks occur. It occurs in the light region and the reflected color is observed. Although the reflectivity of each layer tends to be weaker than in the case of a layer configuration having a thickness adjusting layer, a plurality of peaks overlap so that the reflected color can be visually recognized.

  In the present laminated structure, the total thickness of the first layer with respect to the total film thickness is preferably 80% or more and 86% or less. When the total thickness of the first layer is less than the lower limit with respect to the total film thickness, sufficient shrinkage may not be obtained at the shrink processing temperature. On the other hand, when the total layer thickness of the first layer in the laminated structure exceeds the upper limit with respect to the total film thickness, the layer configuration near the film surface is disturbed to form irregularities on the film surface, resulting in a decrease in transparency. However, it may have a frosted glass appearance.

[particle]
The heat-shrinkable polyester film of the present invention does not contain particles from the viewpoint of enhancing the transparency of the film or is added in a very small range even if particles are contained for the purpose of imparting slipperiness to the film. Specifically, at least one of the first layer and the second layer preferably has a particle content in the range of 0 wt% or more and less than 0.1 wt%. The lower limit of the particle content is more preferably 0.005% by weight, still more preferably 0.01% by weight. The upper limit of the particle content is more preferably 0.08% by weight, and still more preferably 0.06% by weight.
Such particle content is expressed as a ratio (%) of the weight of particles contained in the layer, based on the weight of the particle-containing layer.

  As the types of particles, for example, inorganic particles such as calcium carbonate, silica, talc, clay, etc., organic particles composed of thermoplastic resins such as silicone and acrylic, and thermosetting resins can be used. Among these, spherical silica particles are preferable. Although it will not specifically limit if the average particle diameter of particle | grains is the range of 0.001-5 micrometers, It is more preferable that it is 0.01-3 micrometers.

[Production method]
Next, an example of the manufacturing method of the heat-shrinkable polyester film of the present invention will be described in detail.
The heat-shrinkable polyester film of the present invention includes a first layer polyester (A) supplied from a first extruder, and a second layer polyester (B) supplied from a second extruder. Are laminated in the range of 25 layers or more and 1001 layers or less alternately in a molten state using a multilayer feedblock device.
Then, it is set as a multilayer unstretched film by casting on the drum which rotates this molten laminated body using die | dye. The outermost layer in the laminated structure is the first layer in terms of solvent adhesion, and the first layer is an odd layer and the second layer is an even layer.

  The multilayer unstretched film thus obtained is stretched in any one axial direction of the film forming direction or the width direction which is the orthogonal direction. The stretching temperature is preferably in the range of the temperature (Tg) to Tg + 50 ° C. of the glass transition point of the polyester (A) constituting the first layer. The area magnification at this time is preferably 2 to 6 times, more preferably 2.5 to 5 times. The larger the draw ratio, the smaller the variation in layer thickness in the individual layers of the first layer and the second layer, due to the thinning by stretching, while the optical interference of the multilayer stretched film becomes uniform in the plane direction, For the shrinkage characteristics, if the draw ratio is too high, not only the shrinkage rate in the main shrinkage direction can be obtained by crystallization, but also the shrinkage rate in the direction perpendicular to the main shrinkage direction becomes large. The main shrinkage direction needs to be in a range of 2.5 to 4.5 times, and the orthogonal direction of the main shrinkage direction needs not to be stretched or needs to be stretched in a range of 1.5 times or less at the maximum. In order to increase the accuracy of the shrinkage rate, heat treatment may be further performed at a temperature of 70 ° C. or higher and lower than 80 ° C.

  When producing a heat-shrinkable polyester film having a laminated structure having a thickness adjusting layer, the first layer polyester (A) supplied from the first extruder and the second polyester supplied from the second extruder. The layer polyester (B) is laminated in a molten state using a multilayer feed block device alternately in the range of 25 to 1001 layers (alternate laminate (I)), The polyester (A ′) for the thickness adjusting layer (II) supplied from the extruder 3 is laminated on both sides of the alternating laminate (I) through the outermost feed block whose thickness is adjusted. When the polyester (A ′) for the thickness adjusting layer (II) is the same as the polyester (A) for the first layer, a part of the polyester (A) supplied from the first extruder is used as the thickness adjusting layer. What is necessary is just to laminate | stack on both surfaces of an alternating laminated body (I) through the feed block outermost layer adjusted in thickness. Then, the film forming method after casting this molten laminated body on the rotating drum using a die is based on the above-mentioned method.

  Moreover, when manufacturing the heat-shrinkable polyester-type film of the laminated structure which does not contain a thickness adjustment layer, it is supplied from the 1st layer polyester (A) supplied from the 1st extruder, and the 2nd extruder. The second layer polyester (B) is laminated in the molten state using a multi-layer feed block device alternately in the range of 25 to 1001 layers, and this is rotated using a die. It is set as a multilayer unstretched film by casting on a drum. The feed block is controlled such that when the first layer has a thickness gradient, each layer thickness of the first layer becomes a desired thickness gradient, and each layer thickness of the second layer becomes a uniform thickness. Be controlled. As a result, the first layer has a thickness gradient, and the second layer can eliminate variations in layer thickness. Then, the film forming method after casting this molten laminated body on the rotating drum using a die is based on the above-mentioned method.

  When applying a primer layer or the like during the above process, for example, a water-dispersible coating agent is applied to one or both sides of the film after longitudinal stretching, and dried before lateral stretching to form a film on the film. Is preferred. The coating method is not limited, but coating by a reverse roll coater is preferable.

Hereinafter, the present invention will be described more specifically with reference to examples.
In addition, the measuring method and evaluation method of the characteristic used in the Example and the comparative example are as follows.

(1) Thermal shrinkage A film sample was cut into a 10 cm × 10 cm square, immersed in 65 ° C. warm water, pulled up 10 seconds later, and placed in cold water. The length between the marked lines was measured, and the amount of shrinkage of the film was expressed as a percentage with respect to the original dimension.
S = 100 × (L ₀ −L) / L ₀
(In the above formula, S is the heat shrinkage rate (unit:%), L is the length between marked lines after heat treatment (unit: mm), L ₀ is the length between marked lines before heat treatment (unit: mm), respectively. Represent)

(2) Light reflectivity Using a spectrophotometer (manufactured by Shimadzu Corp., MPC-3100), a polarizing plate is sandwiched between the film and the light-receiving portion in accordance with the main orientation direction (the direction with a large shrinkage rate or the main shrinkage direction), The relative specular reflectance with the aluminum-deposited mirror at each wavelength is measured in the wavelength range of 400 nm to 800 nm. Among the measured reflectances, the maximum reflectance was taken as the maximum reflectance, and the wavelength was taken as the reflection wavelength.
Furthermore, about the design property, it evaluated by the following references | standards by visual evaluation.
○: Metal luster color tone is observed ×: Metal luster color tone is not observed

(3) Evaluation as a shrink film After making a film sample into a cylindrical shape as a shrink label, it is covered with a PET bottle, the first zone is 85 ° C. with a residence time of 5 seconds, and the second zone is 90 ° C. with a residence time of 5 It was shrunk through a shrink tunnel under the condition of seconds. The following four evaluation methods evaluated the solvent adhesiveness, shrink characteristics, and design properties when shrink processing was performed. The following four evaluation methods evaluated the solvent adhesiveness, shrink characteristics, and design properties when shrink processing was performed.

i) Tetrahydrofuran was applied to the end of the label with a width of 2 mm, and the both ends of the label were quickly overlapped and bonded before drying. The adhesion (joining) state at this time was evaluated according to the following criteria.
○: The label edge is completely adhered.
X: The label edge is adhered, but peels off with an extremely light force.
XX: Peeling is observed at the end of the label.
ii) After passing through the tunnel, whether or not the film was sufficiently adhered to the PET bottle was evaluated by visual evaluation based on the following criteria.
○: Close contact with the shape of the PET bottle, and no gap is observed between the PET bottle and X: Some gap is observed between the PET bottle and the bottle.
iii) Regarding the shrinkage unevenness of the film after passing through the shrink tunnel, whether the upper end portion or the lower end portion is slanted or distorted after shrinkage was determined by visual evaluation according to the following criteria.
○: Neither the upper end portion nor the lower end portion is observed to be oblique or distorted due to shrinkage spots, and the bottle body portion is not observed to have wrinkles due to shrinkage spots.
X: Either the upper end portion or the lower end portion is observed to be either slanted or distorted due to shrinkage spots, or wrinkles due to shrinkage spots on the bottle body.
XX: Oblique or distorted parts are observed due to shrinkage spots at either the upper end or the lower end
iv) Further, for the design properties of the film after passing through the shrink tunnel, the transparency and metal gloss were evaluated by visual evaluation based on the following criteria.
A: Metal gloss color tone is observed and the film is not turbid and transparent B: Metal gloss color tone is observed, but the film is turbid C: Metal gloss color tone is not observed, but the film is not turbid Transparent D: Metallic luster is not observed, and the film is turbid

(4) Thickness of each layer, number of layers The cross section of the film sample was observed with a scanning electron microscope (S-4300SE / N type) manufactured by Hitachi Science Systems, Ltd., and the first layer and the second layer near the center in the thickness direction. The thickness of each layer was measured by n = 3, and the average value was obtained. The layer thickness of the thickness adjusting layer (II) was also measured from each of the three layers using the same measuring device and determined from the average value.
In addition, when there is a thickness gradient in the first layer, for the first layer, three layers are measured in the vicinity of the film surface layer and in the vicinity of the center in the thickness direction at n = 3, and the average at both measurement positions is measured. The average thickness at both measurement positions was determined from the value.
Similarly, the number of layers was determined by observing the cross section of the film sample with a scanning electron microscope (S-4300SE / N type) manufactured by Hitachi Science Systems, Ltd.

(5) Total film thickness The total film thickness of the film was measured at 10 points with a needle pressure of 30 g using an electronic micrometer (trade name “K-312A type” manufactured by Anritsu Co., Ltd.). Asked.

(6) Total layer thickness of the first layer with respect to the total film thickness Multiply the first layer thickness obtained by the method of (4) by the first number of layers to obtain the total first layer thickness, Moreover, when it had a thickness adjustment layer, the sum total of the layer thickness of the layer which consists of polyester (A) was calculated | required using the layer thickness of the thickness adjustment layer (II) obtained by the method of (4). On the other hand, the total film thickness was determined according to the method of (5), and the total thickness (%) of the first layer (including the thickness adjusting layer) with respect to the total film thickness was calculated.

(7) Total thickness of thickness adjusting layer (II) with respect to total film thickness Layer thickness of thickness adjusting layer (II) obtained by method (4) and total film thickness obtained by method (5) Based on the above, the total thickness (%) of the thickness adjustment layer (II) with respect to the total film thickness was calculated.

(8) Haze According to JIS K7136, the haze value of the film was measured using a haze measuring device (NDH-2000) manufactured by Nippon Denshoku Industries Co., Ltd.

(9) Glass transition temperature About 10 mg of a film sample is sealed in an aluminum pan for measurement and attached to a differential calorimeter (DuPont V4.OB2000 type DSC), and is heated at a rate of 25 ° C. to 20 ° C./min. The temperature is raised to 0 ° C., held at 300 ° C. for 5 minutes, taken out, immediately transferred onto ice and rapidly cooled. The pan was again mounted on the differential calorimeter, and the glass transition temperature (Tg: ° C.) was measured by increasing the temperature from 25 ° C. to 20 ° C./min.

(10) Intrinsic viscosity Intrinsic viscosity ([η] dl / g) was measured with an o-chlorophenol solution at 25 ° C.

(11) Polyester component amount About each layer of the film sample, the component of the polyester, the copolymerization component, and the amount of each component were specified by ¹ H-NMR measurement.

[Example 1]
As the polyester for the first layer (A) and the thickness control layer (II) polyester for (A '), intrinsic viscosity 0.64 dl / g of the composition shown in Table 1, the glass transition temperature _(Tg 1) of 66 ° C. Polyester is prepared. Polyethylene-2,6-naphthalenedicarboxylate homopolymer having an intrinsic viscosity of 0.51 dl / g and a glass transition temperature (Tg ₂ ) of 117 ° C. is prepared as the polyester (B) for the second layer. Each of the pellets was heated at 110 ° C. for 10 hours with stirring to crystallize the surface. In addition, since polyester (A ') for thickness adjustment layers (II) is the same polymer as polyester (A) for 1st layers, it described as polyester (A) hereafter.

  After drying polyester (A) and polyester (B) at 170 ° C. for 4 hours, respectively, polyester (A) is fed to the first extruder and polyester (B) is fed to the second extruder, up to 290 ° C. It is heated and melted, and the polyester (A) is branched into 99 layers and 2 thickness adjusting layers as the first layer in the alternating laminate (I), and the polyester (B) is divided into 100 layers as the second layer. After branching, use a multi-layer feed block device in which the first layer and the second layer are alternately laminated to form a laminated melt, which is cast on a casting drum while maintaining the laminated state. Thus, an unstretched multilayer laminate film having an alternating laminate (I) composed of a total of 199 layers in which the first layer and the second layer were alternately laminated and a thickness adjusting layer on both sides thereof was prepared. The ratio of the extrusion amount is 87% polyester (A) (26% as the first layer in the alternate laminate (I), 61% as the thickness adjusting layer (II)) and 13% in the second layer polyester (B). It was adjusted. In addition, each layer thickness of the first layer of the feed block and each layer thickness of the second layer were controlled to be a uniform layer.

  This multilayer unstretched film was stretched 3.2 times in the width direction without stretching in the continuous film-forming direction at a temperature of 80 ° C., and heat-treated at 75 ° C. for 3 seconds to obtain a film having a thickness of 45 μm. The properties of the obtained film are shown in Table 2.

[Example 2]
The polyester (A) is a polyester having an intrinsic viscosity of 0.64 dl / g and a glass transition temperature (Tg ₁ ) of 62 ° C. with the composition shown in Table 1, and the ratio of the extrusion amount is 90% of the first layer polyester (A) ( Except for 27% as the first layer and 63% as the thickness adjusting layer (II) in the alternating laminate (I) and 10% of the second layer polyester (B), the same as in Example 1, A film having a thickness of 45 μm was obtained. The properties of the obtained film are shown in Table 2.

[Example 3]
The polyester for the first layer (A) is a polyester having an intrinsic viscosity of 0.67 dl / g and a glass transition temperature (Tg ₁ ) of 75 ° C. having the composition shown in Table 1, and the ratio of the extrusion amounts is the polyester for the first layer (A ) Was 92% (28% as the first layer and 64% as the thickness adjusting layer (II) in the alternating laminate (I)) and 8% of the second layer polyester (B). In the same manner as described above, a film having a thickness of 45 μm was obtained. The properties of the obtained film are shown in Table 2.

[Example 4]
The first layer polyester (A) is a polyester having an intrinsic viscosity of 0.59 dl / g and a glass transition temperature (Tg ₁ ) of 65 ° C. having the composition shown in Table 1, and the polyester (B) has an intrinsic viscosity of 0.58 dl / g. , A polyethylene naphthalate-terephthalate copolymer (terephthalic acid content: 8 mol%) with a glass transition temperature (Tg ₂ ) of 109 ° C., and a ratio of extrusion amount of 90% (alternately) for the first layer polyester (A) In the same manner as in Example 1 except that 27% as the first layer and 63% as the thickness adjusting layer (II) in the laminate (I) and 10% of the second layer polyester (B) were used. A film having a thickness of 45 μm was obtained. The properties of the obtained film are shown in Table 2.

[Example 5]
The polyester for the first layer (A) is a polyester having the composition shown in Table 1 having an intrinsic viscosity of 0.67 dl / g and a glass transition temperature (Tg ₁ ) of 76 ° C., and the ratio of the extrusion amounts is the polyester for the first layer (A ) 90% (27% as the first layer and 63% as the thickness adjusting layer (II) in the alternating laminate (I)) and 10% of the second layer polyester (B). In the same manner as described above, a film having a thickness of 45 μm was obtained. The properties of the obtained film are shown in Table 2.

[Example 6]
A polyester having an intrinsic viscosity of 0.62 dl / g and a glass transition temperature (Tg ₁ ) of 61 ° C. having a composition shown in Table 1 is prepared as the first layer polyester (A). Polyethylene-2,6-naphthalenedicarboxylate homopolymer having 51 dl / g and glass transition temperature (Tg ₂ ) of 117 ° C. was prepared, and the surface was crystallized by heating at 110 ° C. for 10 hours while stirring the pellets. Prepared.

After drying polyester (A) and polyester (B) at 170 ° C. for 4 hours, respectively, polyester (A) is fed to the first extruder and polyester (B) is fed to the second extruder, up to 290 ° C. After heating to a molten state, the polyester (A) is divided into 101 layers as the first layer and the polyester (B) is divided into 100 layers as the second layer, and then the first layer and the second layer alternately Using a multi-layer feed block device that performs lamination, a molten material in a laminated state is formed, and the first layer and the second layer are alternately laminated by casting on a casting drum while maintaining the laminated state. A total of 201 unstretched multilayer laminated films were prepared. The ratio of the extrusion amount was adjusted to 80% for the first layer polyester (A) and 20% for the second layer polyester (B). The thickness gradient of the first layer of the feed block is controlled so that the layer thickness continuously decreases from the surface layers of the film to the center layer, and the thickness ratio is 1.30. Control was made to be a uniform layer.
This multilayer unstretched film was stretched 3.2 times in the width direction without stretching in the continuous film-forming direction at a temperature of 80 ° C., and heat-treated at 75 ° C. for 3 seconds to obtain a film having a thickness of 45 μm. The properties of the obtained film are shown in Table 2.

[Comparative Example 1]
The polyester (A) is a polyester having an intrinsic viscosity of 0.70 dl / g and a glass transition temperature (Tg ₁ ) of 82 ° C. having the composition shown in Table 1, and the ratio of the extrusion amount is 92% of the first layer polyester (A) ( In the same manner as in Example 1 except that 28% as the first layer and 64% as the thickness adjusting layer (II) in the alternate laminate (I) and 8% of the second layer polyester (B) were used. A film having a thickness of 45 μm was obtained. The properties of the obtained film are shown in Table 2.

[Comparative Example 2]
The polyester (A) is a polyester having an intrinsic viscosity of 0.64 dl / g and a glass transition temperature (Tg ₁ ) of 75 ° C. having a composition shown in Table 1, and the ratio of the extrusion amount is 92% of the first layer polyester (A) ( In the same manner as in Example 1 except that 28% as the first layer and 64% as the thickness adjusting layer (II) in the alternate laminate (I) and 8% of the second layer polyester (B) were used. A film having a thickness of 45 μm was obtained. The properties of the obtained film are shown in Table 2.

[Comparative Example 3]
The polyester (A) is a polyester having an intrinsic viscosity of 0.60 dl / g and a glass transition temperature (Tg ₁ ) of 44 ° C. having the composition shown in Table 1, and the ratio of the extrusion amount is 87% of the first layer polyester (A) ( Made in the same manner as in Example 1 except that 26% as the first layer and 61% as the thickness adjusting layer (II) in the alternating laminate (I) and 13% as the second layer polyester (B). As a result of film formation, the glass transition temperature of polyester (A) was too low to form a film.

[Comparative Example 4]
The polyester (A) is a polyester having an intrinsic viscosity of 0.64 dl / g and a glass transition temperature (Tg ₁ ) of 64 ° C. having the composition shown in Table 1, and the ratio of the extrusion amount is 87% of the first layer polyester (A) ( In the alternate laminate (I), the first layer is 26%, the thickness adjusting layer (II) is 61%), the second layer polyester (B) is 13%, and the multilayer unstretched film is continuously at a temperature of 80 ° C. A film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that the film was stretched 3.2 times in the film forming direction and then stretched 3.2 times in the width direction at 110 ° C. The properties of the obtained film are shown in Table 2.

[Comparative Example 5]
The same polyester as in Comparative Example 4 was used, and the extrusion rate ratio was 75% for the first layer polyester (A) (25% as the first layer in the alternating laminate (I) and 50 as the thickness adjusting layer (II). %), And a film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that the second layer polyester (B) was changed to 25%. The properties of the obtained film are shown in Table 2.

[Comparative Example 6]
Using the same polyester as in Comparative Example 4, the ratio of the extrusion amount was 99% for the first layer polyester (A) (20% as the first layer in the alternating laminate (I), 79 as the thickness adjusting layer (II)). %), Except that the polyester (B) for the second layer was changed to 1%, the film was formed in the same manner as in Example 1, and the polyester could not be uniformly extruded in the width direction, and a film that could be evaluated was obtained. I couldn't.

[Comparative Example 7]
The same polyester as in Comparative Example 4 was used, and the ratio of the extrusion amount was 92% for the first layer polyester (A) (28% as the first layer in the alternate laminate (I), 64 as the thickness adjusting layer (II)). %), The polyester (B) for the second layer is 8%, the polyester (A) is branched into 503 layers and two thickness adjusting layers as the first layer, and the polyester (B) is 504 as the second layer. A film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that the film was branched into layers. The properties of the obtained film are shown in Table 2.

[Comparative Example 8]
The same polyester as in Comparative Example 4 was used, and the ratio of the extrusion amount was 92% for the first layer polyester (A) (28% as the first layer in the alternate laminate (I), 64 as the thickness adjusting layer (II)). %), The polyester (B) for the second layer is 8%, the polyester (A) is branched into 3 layers and 2 thickness adjusting layers as the first layer, and the polyester (B) is 4 as the second layer. A film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that the film was branched into layers. The properties of the obtained film are shown in Table 2.

[Comparative Example 9]
Using the same polyester as in Example 3, the ratio of the extrusion amount was 98% for the first layer polyester (A) (all amounts were used as the first layer in the alternating laminate (I), and the thickness adjusting layer (II)) When the film was formed in the same manner as in Example 6 except that the second layer polyester (B) was changed to 2%, the polyester could not be extruded uniformly in the width direction and could be evaluated. A film could not be obtained.

[Comparative Example 10]
The same polyester as in Example 3 was used, the ratio of the extrusion amount was 78% for the first layer polyester (A) (all amounts were used as the first layer in the alternating laminate (I), and the thickness adjusting layer (II)) A 45 μm-thick film was obtained in the same manner as in Example 6 except that the second layer polyester (B) was changed to 22%. The properties of the obtained film are shown in Table 2.

[Comparative Example 11]
A film having a thickness of 45 μm was formed in the same manner as in Example 6, except that the same polyester as in Example 3 was used and the thickness ratio was not provided in the first layer at the same extrusion rate ratio as in Example 6. Obtained. The properties of the obtained film are shown in Table 2.

[Comparative Example 12]
Polyester (A) and intrinsic viscosity 0.51 dl / g, a glass transition temperature (Tg ₂₎ 117 ℃ of polyethylene-2,6-naphthalene dicarboxylate homopolymer, intrinsic viscosity of the composition showing the polyester (B) in Table 1 The thickness is 45 μm in the same manner as in Example 6 except that the polyester is 0.62 dl / g and the glass transition temperature (Tg ₂ ) is 64 ° C., the thickness gradient is not provided in the first layer, and the stretching temperature is 135 ° C. Film was obtained. The properties of the obtained film are shown in Table 2.

  The present invention gives an iridescent metallic luster by being rich in glossy design that reflects light of a specific wavelength, and can be bonded using a solvent as a film covering a container such as a PET bottle, In addition, a heat-shrinkable polyester film having heat-shrinkability without partial shrinkage spots can be provided, and can be suitably used for a shrink label of a PET bottle. In addition, it can be suitably used for electric wire coating that requires heat shrinkability and design.

Claims (6)

  25 first layers containing a polyester (A) containing ethylene terephthalate as an essential component and 2nd layers containing a polyester (B) containing ethylene-2,6-naphthalenedicarboxylate as a main component alternately In the film having a laminated structure laminated in the range of 1001 or less, the total thickness of the first layer with respect to the total film thickness is 80% or more and 96% or less, and the polyester (A) is polyester (A). The ethylene glycol is contained in the range of 40 mol% or more and 80 mol% or less based on the total glycol component, and the second glycol component is contained in the range of 20 mol% or more and 60 mol% or less. It has at least one reflection peak with a reflectance of 25% or more in the reflectance curve in the range of 800 nm and is released in warm water at 65 ° C. for 10 seconds. A heat shrinkable polyester film having a thermal shrinkage ratio of 15% or more in any one of the longitudinal direction and the width direction of the film and 0% or more and less than 10% in absolute value in the direction perpendicular to the direction. .   The laminated structure is a laminated structure composed of an alternating laminate (I) and a thickness adjusting layer (II) disposed on both sides thereof, and the thickness adjusting layer (II) is a polyester (A ′ having ethylene terephthalate as an essential component) ) And the average thickness of the first layer in the alternating laminate (I) is 0.02 to 0.4 μm, and the average thickness of the second layer is 0.03 to 0.5 μm. The heat-shrinkable polyester film according to claim 1.   The first layer containing a polyester (A) whose laminated structure contains ethylene terephthalate as an essential component and the second layer containing a polyester (B) containing ethylene-2,6-naphthalenedicarboxylate as a main component are alternately arranged. 2. The heat according to claim 1, wherein the first layer has an average thickness of 0.05 to 3.6 μm, and the second layer has an average thickness of 0.005 to 1.0 μm. Shrinkable polyester film.   The heat-shrinkable polyester film according to any one of claims 1 to 3, wherein the haze of the film is 0.1 to 10%.   The second glycol component constituting the polyester (A) is at least one selected from the group consisting of diethylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and 1,4-cyclohexanedimethanol. The heat-shrinkable polyester film according to any one of claims 1 to 4.   The shrink label which consists of a heat-shrinkable laminated polyester film in any one of Claims 1-5.