Polyester resin film, laminated film, packaging material, and lid material

Abstract

To provide a polyester resin film, a laminated film, a packaging material, and a lid material that exhibit superior foldability retention and dimensional stability.SOLUTION: The present invention provides: a polyester resin film composed of a polyester resin and having a thickness of 10 μm or more and 100 μm or less, wherein a yield point exists in a tensile test (a chuck-to-chuck distance of 100 mm, an ambient temperature of 23°C, and a tensile speed of 10 mm / min) in a longitudinal direction and a width direction of the film, the stress at the yield point is 35 MPa or more and 60 MPa or less, and a strain at the yield point is 2% or more and 5% or less; and a laminated film formed by laminating the polyester resin film.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a polyester resin film having folding retention (dead-hold property). Specifically, the present invention relates to a polyester resin film, a laminated film, a packaging material, and a lid material that have excellent heat resistance, aroma retention, and water resistance of the polyester resin film while having good folding retention.

Background Art

[0002] The property of maintaining the folded state when the film is folded is called folding retention (dead-hold property). When packaging bags for foods and the like and lid materials for packaging containers such as instant noodles have folding retention, the opened portion can be simply resealed by folding it.

[0003] When these packaging materials do not have folding retention, in order to reseal, it is necessary to stop the opening with a rubber band, a clip, or the like, or to perform heat sealing again. However, all of them require other tools, and in particular, performing heat sealing again is not practical in ordinary households.

[0004] Since metal foils such as aluminum foil and paper have excellent folding retention, it has been common to impart folding retention to packaging materials and lid materials by laminating aluminum foil or paper. Patent Document 1 discloses a three-layer structure of a polyethylene terephthalate film / aluminum foil / heat-sealing layer. In such a packaging bag laminated with aluminum foil, folding retention is imparted by the excellent folding retention of the metal foil, and it is used as a packaging bag for foods such as instant noodle lid materials such as sprinkles and soup bases, and pharmaceuticals.

[0005] On the other hand, packaging bags laminated with metal foils such as aluminum foil are known to have problems such as being unable to be heated in a microwave oven and being unable to perform foreign matter inspection of the contents with a metal detector. In addition, it has been pointed out that the furnace is damaged during incineration. Furthermore, from the viewpoints of recycling and environmental load, aluminum-free packaging bags are required.

[0006] Therefore, as materials to replace aluminum foil, plastic films such as cellophane, polyolefin, and polyester have been conventionally studied.

[0007] Cellophane is widely used as various packaging materials and materials for adhesive tapes due to its excellent transparency, easy cutability, fold retention property, etc. However, since cellophane has hygroscopicity and its properties vary with seasons, it has been difficult to constantly supply a product with consistent quality.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] Since it has excellent properties such as toughness, heat resistance, water resistance, and transparency, it is known to use a polyester - based resin film, particularly a polyethylene terephthalate film, instead of a metal foil. However, a polyester - based resin film has problems that it is difficult to cut, when used as a packaging bag, it is difficult to make folds due to low fold retention property, and even when used as a lid material, there are problems with opening retention property and resealability. Patent Document 2 discloses a lid material for a cup - type food packaging using a biaxially stretched polyester film instead of an aluminum foil, but it imparts fold retention property by laminating paper on the polyester film, and the fold retention property when not laminating paper is not considered.

[0010] Therefore, an object of the present invention is to provide a polyester - based resin film that achieves both heat shrinkability and fold retention property without using a metal foil or paper.

Means for Solving the Problems

[0011] In order to solve the above problems, the present invention focuses on the fact that when the stress and strain at the yield point of a polyester resin film are within a certain range, plastic deformation is likely to occur when folding, and a polyester resin film with sufficient fold retention and dimensional stability can be provided.

[0012] The polyester resin film in one aspect of the present invention is made of a polyester resin, has a thickness of 10 μm or more and 100 μm or less, has a yield point in a tensile test in the longitudinal and width directions of the film (chuck distance 100 mm, ambient temperature 23°C, tensile speed 10 mm / min), the stress at the yield point is 35 MPa or more and 60 MPa or less, and the strain at the yield point is 2% or more and 5% or less. It is a polyester resin film characterized by this.

[0013] The polyester resin film in another aspect of the present invention has a density of 1.335 g / cm 3 or more and 1.400 g / cm 3 or less. It is a polyester resin film characterized by this.

[0014] The polyester resin film in another aspect of the present invention is a polyester resin film characterized in that in a heat shrinkage rate test conforming to JIS Z1709, the heat shrinkage rates in the longitudinal and width directions at a temperature of 100 ± 0.5°C are less than 5%.

[0015] Another aspect of the present invention is a laminated film in which another layer is laminated on the polyester resin film in one aspect of the present invention.

[0016] Another aspect of the present invention is a packaging material or a lid material containing the above-described film.

Advantages of the Invention

[0017] According to the present invention, there is provided a polyester-based resin film and a laminate thereof which have good fold retention and dimensional stability without laminating a metal foil such as an aluminum foil or paper, etc., and which have good opening retention when used as a lid material or a packaging bag and good resealability by re-closing after opening.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0019] The present invention will be described in detail below with reference to the drawings. Here, the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thicknesses of the respective layers, etc. are different from the actual ones.

[0020] FIG. 1 is a cross-sectional view showing a single-layer polyester-based resin film in an embodiment of the present invention.

[0021] <Polyester-based resin film> As the polyester resin film (11), a polyester resin film constituting a normal packaging material can be appropriately used, but those having mechanical strength and dimensional stability are preferred. For example, polybutylene naphthalate, polyethylene terephthalate, etc. can be used. Further, in the present embodiment, the polyester resin may be a mixture composed of a plurality of different polyester resins. When using a plurality of different polyester resins, the mixing method is not particularly limited, but mixing by dry blending is preferred because thermal degradation can be suppressed.

[0022] The polyester resin can be produced by polycondensing diols and dicarboxylic acids.

[0023] The diols used in the polyester resin film in the present embodiment are, for example, aliphatic diols. Specific examples of the aliphatic diol include ethylene glycol, hexamethylene glycol, neopentyl glycol, 1,4-butanediol, etc. Further, when producing a crystalline polyester resin, the diols may be used alone or in combination of two or more of the above-mentioned compounds.

[0024] The dicarboxylic acids used in the polyester resin film in the present embodiment are, for example, aromatic dicarboxylic acids. Specific examples of the aromatic dicarboxylic acid include isophthalic acid, terephthalic acid, anhydrides or lower alkyl esters of these acids, etc. When producing a polyester resin, the dicarboxylic acid may be used alone or in combination of two or more of the above-mentioned compounds.

[0025] The polyester resin film in this embodiment has a yield point in the stress-strain curve, and the stress at the yield point is 35 MPa or more and 60 MPa or less, and the strain at the yield point is 2% or more and 5% or less. Preferably, the stress at the yield point is 45 MPa or more and 50 MPa or less, and the strain at the yield point is 2% or more and 3.5% or less. When the strain at the yield point is within such a range, the deformation of the fold made on the film is maintained, and fold retention is obtained. Further, when the strain at the yield point is 5% or more, no plastic deformation occurs even when a fold is made, so the deformation is not maintained and it easily returns to the original shape. When the stress at the yield point is 60 MPa or more, plastic deformation does not occur with a force sufficient to make a fold by hand, and it becomes difficult to make a fold. Furthermore, when the stress at the yield point is 35 MPa or less or the strain at the yield point is 2% or less, the mechanical properties and breakability deteriorate, so it is not suitable for packaging materials or lid materials.

[0026] The stress and strain at the yield point of the polyester resin film in this embodiment can be obtained as follows. (1) For each film for which the test is to be conducted, prepare 5 strip-shaped test pieces with a length of 150 mm in the longitudinal direction and a width of 15 mm for measurement in the longitudinal direction, and 5 strip-shaped test pieces with a width of 150 mm in the width direction and a length of 15 mm for measurement in the width direction, respectively. (2) Using a universal tensile-compression testing machine AGS-X (manufactured by Shimadzu Corporation), after gripping each test piece with a width of 25 mm from both ends, conduct a tensile test under the conditions of a chuck distance of 100 mm, an ambient temperature of 23°C, and a tensile speed of 10 mm / min to obtain a stress-strain curve. (3) Regarding the stress and strain at the first peak apex (yield point) of the obtained stress-strain curve, average the results for 5 times in the longitudinal direction and 5 times in the width direction, and use them as the stress and strain at the yield point of the film.

[0027] The density of the polyester resin film in one embodiment is 1.335 g / cm 3 or more and 1.400 g / cm 3 or less, and may be 1.380 g / cm 3 or more and 1.390 g / cm 3The following are preferred. When the density of the polyester resin film exceeds 1.400 g / cm 3 it is because the folding retention of the film is significantly reduced.

[0028] In one embodiment, the heat shrinkage rate of the polyester resin film may be 5% or less, preferably 3% or less. When the heat shrinkage rate is 5% or less, shrinkage due to heat is small and dimensional stability is improved. On the other hand, when the heat shrinkage rate is 5% or more, dimensional stability is low, so problems are likely to occur in processes where heat such as heat sealing is applied.

[0029] The heat shrinkage rate of the polyester resin film in this embodiment can be measured under the condition of a temperature of 100 ± 0.5°C in a test conforming to JIS Z1709.

[0030] Since the polyester resin film (11) in this embodiment has barrier properties and heat sealability, it can be used as a single-layer film, but it may also be laminated with other base materials, films, etc. to form a laminated film.

[0031] Such a laminated film can obtain characteristics such as sealability, easy peelability, gas barrier properties, shielding properties, heat insulation properties, and printing suitability by other layers laminated on the polyester resin film (11). Also, the polymer constituting the other layer is not particularly limited, and the configuration of the laminated film can be appropriately determined according to applications such as packaging bags and lid materials.

[0032] Figures 2 to 5 show laminated films in different embodiments respectively.

[0033] In one embodiment, as shown in Figure 2, the laminated film is a laminated film in which a polyester resin film (11) is laminated on a base material layer (21).

[0034] In another embodiment, as shown in FIG. 3, the laminated film is a laminated film in which a base material layer (21) is laminated on one side of a polyester resin film (11), and a heat seal layer (31) is laminated on the other side.

[0035] In another embodiment, as shown in FIG. 4, the laminated film is a laminated film in which a base material layer (21) is laminated on one side of a polyester resin film (11), and a heat seal layer (31) and an easy peel layer (41) are laminated on the other side.

[0036] In another embodiment, as shown in FIG. 5, the laminated film is a laminated film in which a base material layer (21) and a gas barrier layer (51) are laminated on one side of a polyester resin film (11), and a heat seal layer (31) is laminated on the other side.

[0037] <Base material layer> The base material layer is a layer that imparts shielding properties, firmness, proper printability, etc. to the polyester resin film. As the base material layer, olefin resins such as polypropylene and polyethylene, or double art paper, single art paper, or double coated paper, single coated paper, etc. with a printing base coat layer laminated thereon can be used.

[0038] <Gas barrier layer> The gas barrier layer is a layer that imparts gas barrier properties to the polyester resin film. As the gas barrier layer, a metal vapor-deposited film or a film made of a polymer with high gas barrier properties such as polyamide or saponified ethylene-vinyl acetate copolymer can be used.

[0039] <Heat seal layer> The heat seal layer is a layer that imparts sealability to the polyester resin film. As the heat seal layer, polypropylene, polyethylene, etc., which are olefin resins, or low melting point polyester, etc. can be used.

[0040] <Easy peel layer> The easy-peel layer can impart easy-peelability (easy-release property) after sealing to the polyester-based resin film. As the easy-peel layer, a polyolefin-based resin, a styrene-vinyl acetate copolymer resin, a styrene-based copolymer resin, etc. can be used.

[0041] As described above, embodiments of the present invention have been illustrated, but the present invention is not limited to the above embodiments, and an adhesive layer may be provided between each layer in order to improve the adhesion between the layers. Also, the embodiments may be used in combination.

[0042] Regarding the polyester-based resin film and the laminated film in the present invention, a packaging bag can be formed by sealing with the surfaces of the polyester-based resin film (11) facing each other. Examples of the formed packaging bag include a standing pouch, a three-side bag, a clasp bag, a gusset bag, a pouch with a spout, a pouch with a beak, etc. Also, the bag-making style of the packaging bag is not particularly limited.

[0043] Also, regarding the single-layer film and the laminated film in these embodiments, by sealing the surface of the polyester-based resin film (11) to the container opening, it can also be used as a lid material.

[0044] <Film manufacturing method> The manufacturing method of the polyester-based resin film and the laminated film in the present invention is not particularly limited, but a method of forming a polyester-based resin layer by an extrusion lamination method, a method of laminating a laminated film obtained by a co-extrusion method to a previously formed film, etc. can be used.

Examples

[0045] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[0046] <Example 1> 60% by weight of a low-crystalline polyester resin SA-863JP (manufactured by Unitika Ltd.) and 40% by weight of an amorphous polyester resin MA-1340P (manufactured by Unitika Ltd.) were dry-blended and formed into a thickness of 30 μm by an extrusion molding method to obtain the polyester resin film of Example 1.

[0047] <Example 2> A polyester resin film of Example 2 was obtained in the same manner as in Example 1, except that SA-863JP was 50% by weight and MA-1340P was 50% by weight.

[0048] <Example 3> A polyester resin film of Example 3 was obtained in the same manner as in Example 1, except that SA-863JP was 40% by weight and MA-1340P was 60% by weight.

[0049] <Example 4> On a Ryu-o coat paper with a basis weight of 65 g / m 2 which is a paper substrate, the polyester resin film of Example 1 was laminated by an extrusion lamination method to obtain the laminated film of Example 4 shown in FIG. 2.

[0050] <Example 5> On a Ryu-o coat paper with a basis weight of 65 g / m 2 which is a paper substrate, the polyester resin film of Example 1 and a heat seal layer with a thickness of 10 μm were laminated by a co-extrusion method to obtain the laminated film of Example 5 shown in FIG. 3. As the heat seal layer, WH303-F (manufactured by Sumitomo Chemical Co., Ltd.), which is a polyolefin resin, was used.

[0051] <Example 6> On a Ryu-o coat paper with a basis weight of 65 g / m 2On the Rewritable coated paper, using the coextrusion method, the polyester resin film of Example 1, a heat seal layer with a thickness of 10 μm, and an easy peel layer with a thickness of 10 μm were laminated to obtain the laminated film of Example 6 shown in FIG. 4. As the heat seal layer, WH303-F, a polyolefin resin, was used, and as the easy peel layer, VN503 (manufactured by Mitsui Dow Polychemical Co., Ltd.) was used.

[0052] <Example 7> On the Rewritable coated paper with a basis weight of 65 g / m 2 Takelac A-3210 (manufactured by Mitsui Chemicals, Inc.) was applied as an anchor coating agent, and a barrier film GL-AR-NF (manufactured by Toppan Co., Ltd.) was laminated. Then, on the barrier film, by the coextrusion method, the polyester resin film of Example 1 and a heat seal layer with a thickness of 10 μm were laminated to obtain the polyester resin laminate of Example 7 having the configuration shown in FIG. 5. As the heat seal layer, WH303-F, a polyolefin resin, was used.

[0053] <Comparative Example 1> A polyester resin film of Comparative Example 1 was obtained in the same manner as in Example 1, except that SA-863JP was 80% by weight and MA-1340P was 20% by weight.

[0054] <Comparative Example 2> A polyester resin film of Comparative Example 2 was obtained in the same manner as in Example 1, except that SA-863JP was 90% by weight and MA-1340P was 10% by weight.

[0055] <Comparative Example 3> Using the extrusion lamination method, polyolefin resin LC600A (manufactured by Nippon Polyethylene Co., Ltd.) was formed to a thickness of 30 μm to obtain a polyolefin resin film of Comparative Example 3.

[0056] <Comparative Example 4> A laminated film of Comparative Example 4 was obtained in the same manner as in Example 4, except that the polyester resin film was used as the polyolefin resin film of Comparative Example 3.

[0057] <Comparative Example 5> A laminated film of Comparative Example 5 was obtained in the same manner as in Example 5, except that the polyester resin film was used as the polyolefin resin film of Comparative Example 3.

[0058] <Comparative Example 6> A laminated film of Comparative Example 6 was obtained in the same manner as in Example 6, except that the polyester resin film was used as the polyolefin resin film of Comparative Example 3.

[0059] <Comparative Example 7> A laminated film of Comparative Example 7 was obtained in the same manner as in Example 7, except that the polyester resin film was used as the polyolefin resin film of Comparative Example 3.

[0060] <Measurement of Yield Point Stress and Strain> For the width direction and longitudinal direction of each film of Examples 1 to 7 and Comparative Examples 1 to 7, the following was determined. (1) For measurement in the longitudinal direction, five strip-shaped test pieces with a longitudinal length of 150 mm and a width of 15 mm are prepared, and for measurement in the width direction, five strip-shaped test pieces with a width of 150 mm and a longitudinal length of 15 mm are prepared respectively. For Examples 4 to 7, only the polyester resin film (11) was peeled off to obtain test pieces, and for Comparative Examples 4 to 7, only the polyolefin resin film was peeled off to obtain test pieces. (2) Using a universal tensile compression testing machine AGS-X (manufactured by Shimadzu Corporation), after gripping each test piece with a width of 25 mm from both ends, a tensile test is performed under the conditions of a chuck distance of 100 mm, an ambient temperature of 23 °C, and a tensile speed of 10 mm / min to obtain a stress-strain curve. (3) Regarding the stress and strain at the first peak apex (yield point) of the obtained stress-strain curve, the measurement results for 5 times in the longitudinal direction and 5 times in the width direction are averaged to obtain the stress and strain at the yield point of the film.

[0061] When the stress at the yield point of the film is in the range of 35 MPa or more and 60 MPa or less, and the strain at the yield point is in the range of 2% or more and 5% or less, it is evaluated as good, and those outside the range are judged as defective.

[0062] <Folding Angle Measurement> For each film of Examples 1 to 7 and Comparative Examples 1 to 7, in an environment of 23°C and 50% RH, it was cut into a 10 cm × 10 cm square and folded in half to form a 5 cm × 10 cm rectangle. Then, it was sandwiched between a 15 cm Φ disc jig on a tabletop testing machine EX-SX (manufactured by Shimadzu Corporation) and compressed with a test force of 5 MPa for 10 seconds. Then, it was further folded in half to form a 5 cm × 5 cm square and compressed in the same manner as above. Finally, the angle at which the film opened with the resulting fold as the base point was measured and taken as the folding angle. Note that the state where the film was completely folded was 0°, and the angle at which the film was completely opened was 180°. A small folding angle means that the fold was maintained, that is, it indicates high folding retention. When the folding angle of the film was 60° or less, it was evaluated that the folding retention was good.

[0063] <Thermal Shrinkage Rate Measurement> The thermal shrinkage rate of the polyester resin film at a temperature of 100 ± 0.5°C was measured by a thermal shrinkage rate test conforming to JIS Z1709. For Examples 4 to 7, only the polyester resin film (11) was peeled off and measured, and for Comparative Examples 4 to 7, only the polyolefin resin film was peeled off and measured.

[0064] When the thermal shrinkage rate of the film was 5% or less, it was evaluated as good.

[0065] <Density Measurement> For each of the films of Examples 1 to 7 and Comparative Examples 1 to 7, the density was measured using a He gas replacement type density measuring device BELPycno (manufactured by Microtrack Bell Co., Ltd.). For Examples 4 to 7, only the polyester resin film (11) was peeled off for measurement, and for Comparative Examples 4 to 7, only the polyolefin resin film was peeled off for measurement.

[0066] When the density of the film is 1.335 g / m 3 or more and 1.400 g / cm 3 or less, it was judged to be good.

[0067] The measurement results and evaluation results of Examples 1 to 7 and Comparative Examples 1 to 7 are shown in Table 1.

[0068]

Table 1

[0069] <Evaluation Results> For the polyester resin films of Examples 1 to 3, since the folding angle was 30° or less and the heat shrinkage rate was 5% or less in all cases, the evaluation of the folding retention and heat shrinkage was "good", and it was found that they had excellent folding retention and heat shrinkage. Also, the stress at the yield point was 50 MPa or less and the strain at the yield point was 5% for all films.

[0070] Generally, for the same resin, it is known that the higher the density of the resin, the higher the crystallinity, the lower the heat shrinkage as the crystallinity increases, and the greater the force required for plastic deformation. Also, when the stress at the yield point of a film or the like exceeds 60 MPa, it is difficult to exceed the yield point with the folding force and elastic deformation occurs, making it difficult to make a crease. When comparing Example 1 with Examples 2 and 3, although the yield point stress of Example 1 increased, its folding retention property was better than those of Examples 2 and 3. Generally, when stress is applied to a film or the like, if the amount of deformation is the same, the smaller the strain at the yield point, the easier it is to undergo plastic deformation. Since the strain at the yield point of Example 1 is smaller than those of Examples 2 and 3, it can be said that if the amount of deformation is the same, the film of Example 1 is more likely to undergo plastic deformation than the films of Examples 2 and 3. Therefore, it is considered that the best result was obtained when the folding angle was 20°.

[0071] In Examples 4 to 7, which are laminated films using the polyester resin film of Example 1, the folding angle was 60° or less in each case, and the evaluation of the folding retention property was "good". This indicates that the folding retention property can be maintained even when other layers or substrates are laminated on the polyester resin film of this embodiment. When such a film is used as a packaging bag or a lid material, it can have the effect of improving the opening retention property at the time of opening and the resealability by returning it. Also, the stress at the yield point of the polyester resin film layer peeled from each of the laminated films of Examples 4 to 7 was 50 MPa or less and the strain at the yield point was 5% or less, which was equivalent to the film of Example 1.

[0072] On the other hand, in the polyester resin films of Comparative Examples 1 and 2, the heat shrinkage rate was 3% or less and the evaluation of the heat shrinkage property was good, but the folding angle exceeded 60°, and the evaluation of the folding retention property was "poor". This is presumably because although the strain at the yield point is smaller than those of Examples 2 and 3, the stress at the yield point is larger than the folding force in the folding angle test, so it could not undergo plastic deformation to form a fold.

[0073] Therefore, from the results of Examples 1 to 7 and Comparative Examples 1 and 2, it is expected that in order for the film to have good folding retention property, the stress at the yield point should be 60 MPa or less, and in order to form a fold by the folding force, the strain at the yield point should be 5% or less. In Comparative Example 1, although the yield stress increased significantly, the folding angle only slightly exceeded the "good" range by 2°. Therefore, it is considered that if it is near the median value of the yield stress of Example 1 and Comparative Example 1, the evaluation of the folding retention will be "good". Also, from the results of Examples 1 and 4 to 7 with the same composition, since there is at least a variation of about 3 MPa in each of the films of Example 1 and Comparative Example 1, it is considered that if the yield stress is 60 MPa or less, the film is likely to have folding retention.

[0074] In the polyolefin resin film of Comparative Example 3, the heat shrinkage rate was 10.8% and the folding angle was 120°, and the evaluations of both heat shrinkage and folding retention were "poor". From the results of Comparative Example 3, although the polyolefin resin film has a lower yield stress than the polyester resin film, the yield strain is very high at 12% or more. Therefore, it is considered that the folding force was applied in the direction in which the film deforms, and it became elastic deformation without exceeding the yield point.

[0075] In the laminated films of Comparative Examples 4 to 7, although there was variation, the folding angle exceeded 110° in all cases, and the evaluation of folding retention was "poor". This indicates that even when other layers and a base material are laminated, the folding retention is not improved, and it shows that it is difficult to provide folding retention to a film containing a polyolefin resin even when using a base material with folding retention such as paper.

[0076] From the above results, it is possible to provide a polyester resin film having folding retention and dimensional stability by using the polyester resin film of the present invention, and a laminate laminated with this.

[0077] Also, for example, the present invention can take the following configurations. (1) A polyester resin film made of a polyester resin, having a thickness of 10 μm or more and 100 μm or less, In the tensile test of the film in the longitudinal and width directions (distance between chucks: 100 mm, ambient temperature: 23°C, tensile speed: 10 mm / min), a yield point exists, the stress at the yield point is 35 MPa or more and 60 MPa or less, and the strain at the yield point is 2% or more and 5% or less. A polyester resin film characterized by this. (2) The density is 1.335 g / cm 3 or more and 1.400 g / cm 3 or less. The polyester resin film according to (1), characterized by this. (3) In the heat shrinkage rate test conforming to JIS Z1709, the heat shrinkage rate in the longitudinal and width directions at a temperature of 100 ± 0.5°C is less than 5%. The polyester resin film according to (1) or (2), characterized by this. (4) A laminated film characterized in that a base material layer and the polyester resin film according to any one of (1) to (3) are laminated in this order. (5) A laminated film characterized in that a base material layer, the polyester resin film according to any one of (1) to (3), and a heat seal layer are laminated in this order. (6) A laminated film characterized in that a base material layer, the polyester resin film according to any one of (1) to (3), a heat seal layer, and an easy peel layer are laminated in this order. (7) A laminated film characterized in that a base material layer, a gas barrier layer, the polyester resin film according to any one of (1) to (3), and a heat seal layer are laminated in this order. (8) A packaging material containing the polyester resin film according to any one of (1) to (3). (9) A lid material containing the polyester resin film according to any one of (1) to (3). (10) A packaging material containing the laminated film according to any one of (4) to (7). (11) A lid material containing the laminated film according to any one of (4) to (7).

Explanation of symbols

[0078] 11 ··· Polyester resin film 21 ··· Base material layer 31 ··· Heat seal layer 41 ··· Easy peel layer 51 ··· Gas barrier layer

Claims

1. A polyester resin film made of a polyester resin, having a thickness of 10 μm or more and 100 μm or less, in a tensile test (chuck distance 100 mm, ambient temperature 23°C, tensile speed 10 mm / min) in the longitudinal and width directions of the film, there is a yield point, the stress at the yield point is 35 MPa or more and 60 MPa or less, and the strain at the yield point is 2% or more and 5% or less. A polyester resin film characterized by this.

2. The density is 1.335 g / cm ３ or more and 1.400 g / cm ３ or less, and the polyester resin film according to claim 1, characterized in that it is as described above.

3. In a heat shrinkage rate test conforming to JIS Z1709, the heat shrinkage rate in the longitudinal and width directions at a temperature of 100 ± 0.5°C is less than 5%. The polyester resin film according to Claim 1, characterized by this.

4. A laminated film characterized in that a base material layer and the polyester resin film according to Claim 1 are laminated in this order.

5. A laminated film characterized in that a base material layer, the polyester resin film according to Claim 1, and a heat seal layer are laminated in this order.

6. A laminated film characterized in that a base material layer, the polyester resin film according to Claim 1, a heat seal layer, and an easy peel layer are laminated in this order.

7. A laminated film characterized in that a base material layer, a gas barrier layer, the polyester resin film according to Claim 1, and a heat seal layer are laminated in this order.

8. A packaging material containing the polyester resin film according to any one of Claims 1 to 3.

9. A lid material containing the polyester resin film according to any one of Claims 1 to 3.

10. A packaging material containing the laminated film according to any one of Claims 4 to 7.

11. A lid material containing the laminated film according to any one of Claims 4 to 7.

Images