Biaxially oriented polypropylene film and laminate using the same

Abstract

To provide a laminate that has an excellent lamination strength, an excellent appearance of a heat-sealed portion, and hardly causes staining on a guide roll, and a biaxially oriented polypropylene film capable of forming such a laminate.SOLUTION: There is provided a biaxially oriented polypropylene film, comprising: a base layer A made of a polypropylene-based resin composition; a surface layer B made of a polypropylene-based resin composition; and a surface layer C made of a polypropylene-based resin composition, the biaxially oriented polypropylene film satisfies the following (1) and (2). (1) The surface layer B and the surface layer C contain 25 mass% or more and 85 mass% or less of a polypropylene-based resin having a melting point of 130°C or higher and 158°C or lower. (2) A sum of a heat shrinkage rate at 150°C in a longitudinal direction and a heat shrinkage rate at 150°C in a transverse direction of the biaxially oriented polypropylene film is 0.0% or more and 25.0% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a biaxially oriented polypropylene film and a laminate using the same. [Background technology]

[0002] Biaxially oriented polypropylene films have been widely used as packaging materials for foods, textile products, and other articles because of their excellent transparency and mechanical properties.

[0003] Food packaging requires films with gas barrier properties. Biaxially oriented polypropylene films have poorer oxygen barrier properties than nylon and polyester films, so they are sometimes used with a gas barrier layer laminated on them. In addition, biaxially oriented polypropylene film is sometimes laminated with a printed layer to enhance the contents display and design of food packaging bags. That is, a laminate film formed by laminating a film in which a printed film and a gas barrier layer are laminated with a heat-sealable film (also called a sealant film) for heat sealing may be used as a laminate for food packaging. For example, Patent Document 1 discloses a laminate having a configuration of printing substrate layer / printing layer / adhesive layer / inorganic thin film layer / deposition substrate layer / adhesive layer / heat-sealable film, in which each substrate layer and the heat-sealable film are made of the same material, polypropylene, from the viewpoint of recycling.

[0004] When printing or vapor deposition is performed on biaxially oriented polypropylene film, the non-polar nature of polypropylene resin results in low surface energy, which can result in insufficient adhesion to printing inks, coating layers, inorganic thin film layers, etc.

[0005] As a biaxially oriented polypropylene film with improved adhesiveness to printing ink, for example, Patent Document 2 discloses a film having a surface layer with a predetermined surface roughness and wetting tension. Furthermore, in the case of providing an aluminum vapor-deposited film on biaxially oriented polypropylene, for example, Patent Document 3 discloses a film having a surface layer with a relatively small surface roughness and a predetermined wetting tension as a film with excellent adhesion to the aluminum vapor-deposited film. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2021 / 020400 [Patent Document 2] International Publication No. 2018 / 142983 [Patent Document 3] International Publication No. 2022 / 004340 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the inventors have found through their studies that laminates obtained by laminating conventional biaxially oriented polypropylene films and heat-sealable films sometimes have insufficient lamination strength between the films. It has also been found that wrinkles may occur at the heat-sealed portion formed when such laminates are heat-sealed. It has also been found that the antiblocking agent may fall off during winding of such laminates, causing stains on the guide roll.

[0008] Therefore, an object of the present invention is to provide a laminate that has excellent lamination strength, excellent appearance of the heat-sealed portion, and is less likely to stain the guide roll. Another object of the present invention is to provide a biaxially oriented polypropylene film that can be used to form such a laminate. [Means for solving the problem]

[0009] The biaxially oriented polypropylene film of the embodiment that can solve the above problems is as follows. [1] A biaxially oriented polypropylene film having a base layer A made of a polypropylene-based resin composition, a surface layer B made of a polypropylene-based resin composition, and a surface layer C made of a polypropylene-based resin composition, wherein the biaxially oriented polypropylene film satisfies the following (1) and (2): (1) The surface layer B and the surface layer C contain 25% by mass or more and 85% by mass or less of a polypropylene-based resin having a melting point of 130° C. or more and 158° C. or less. (2) The sum of the heat shrinkage rate at 150°C in the longitudinal direction and the heat shrinkage rate at 150°C in the transverse direction of the biaxially oriented polypropylene film is 0.0% or more and 25.0% or less. [2] The biaxially oriented polypropylene film according to [1], wherein the surface layer B, the surface layer C, or both of the surfaces thereof have a wetting tension of 36 mN / m or more. [3] The biaxially oriented polypropylene film according to [1] or [2], wherein the base layer A contains 70% by mass or more of a polypropylene resin having a mesopentad fraction ([mmmm]%) of 95.0 to 99.9% and a melting point of 160°C to 175°C. [4] The biaxially oriented polypropylene film according to [1] or [2], wherein the surface resistivity of the surface layer B, the surface layer C, or both of these surfaces is 14.0 Log Ω or more. [5] A laminate comprising the biaxially oriented polypropylene film according to any one of [1] to [4] and further comprising a heat-sealable polyolefin film, in which the surface layer B of the biaxially oriented polypropylene film, the base layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order. [6] A laminate comprising the biaxially oriented polypropylene film according to any one of [1] to [4], and further comprising a functional layer and a heat-sealable polyolefin film, in which the functional layer, the surface layer B of the biaxially oriented polypropylene film, the base layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order. [7] The laminate according to [6], wherein the functional layer is a printed layer, a vapor-deposited layer, or a coated layer. [8] The laminate according to [7], further comprising a stretched polyolefin film or a stretched polyester film, wherein the stretched polyolefin film or the stretched polyester film, the functional layer, the surface layer B, the surface layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order. [Effects of the Invention]

[0010] The above-mentioned configuration makes it possible to provide a laminate having excellent lamination strength, excellent appearance of the heat-sealed portion, and less likely to stain the guide roll, and also to provide a biaxially oriented polypropylene film capable of forming such a laminate. [Brief explanation of the drawings]

[0011] [Figure 1] An example of a 125x magnification image taken with a microscope of a water-based ink printed surface with uniform dot size and no ink repellency. [Figure 2] An example of a 125x magnification image taken with a microscope of a water-based ink printed surface with uniform dot size and ink repellency. [Figure 3] An example of a 125x magnification image taken with a microscope of a water-based ink printed surface with uneven dot size and ink repellency. [Figure 4] An enlarged view of the ink repellent area in Figure 2. DETAILED DESCRIPTION OF THE INVENTION

[0012] The biaxially oriented polypropylene film of the embodiment has a base layer A made of a polypropylene-based resin composition, a surface layer B made of a polypropylene-based resin composition, and a surface layer C made of a polypropylene-based resin composition. Each layer will be described in detail below.

[0013] (1) Base material layer A The base layer A is made of a polypropylene-based resin composition. The base layer A preferably enhances the thermal dimensional stability, mechanical strength, and transparency of the biaxially oriented polypropylene film. The polypropylene-based resin composition of the base layer A preferably contains a polypropylene-based resin in an amount of 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the entire base layer A. On the other hand, the polypropylene-based resin composition of the base layer A may contain a polypropylene-based resin in an amount of 100% by mass or less, 99.9% by mass or less, 99.8% by mass or less, or 99.6% by mass or less, based on the entire base layer A. When the polypropylene-based resin composition of the base layer A contains two or more types of polypropylene-based resins, the above content is the total value.

[0014] Various suitable physical properties of polypropylene-based resins are described below, but when two or more different polypropylene-based resins are used, it is preferable that the mass-average values of the physical properties of each polypropylene-based resin fall within the numerical ranges described below. For example, when a polypropylene-based resin composition contains 50 mass% of a polypropylene-based resin with a melting point of 160°C and 50 mass% of a polypropylene-based resin with a melting point of 170°C, the mass-average melting point of the polypropylene-based resin composition is 165°C. The same applies to mass-average values hereinafter.

[0015] The polypropylene resin contained in the base layer A preferably has a melting point of 160°C or higher and 175°C or lower, more preferably 164°C or higher and 173°C or lower, and even more preferably 166°C or higher and 171°C or lower. A melting point of 160°C or higher can improve thermal dimensional stability and mechanical strength. A melting point of 175°C or lower can easily prevent cost increases in polypropylene production and make the film less susceptible to breakage during film formation. The melting point can also be further increased by blending a nucleating agent with the polypropylene resin. The melting point can be measured by differential scanning calorimetry (DSC). Specifically, a 5 mg sample is placed in an aluminum pan, melted at 230°C for 5 minutes under a nitrogen atmosphere, cooled to 30°C at a scanning rate of -10°C / min, held there for 5 minutes, and then heated again at a scanning rate of 10°C / min. The melting point is the main endothermic peak temperature observed during melting.

[0016] The polypropylene resin contained in the base layer A preferably has a mesopentad fraction ([mmmm]%), an index of stereoregularity, of 95.0 to 99.9%, more preferably 97.0 to 99.7%, even more preferably 97.5 to 99.5%, and particularly preferably 98.0 to 99.3%. A mesopentad fraction of 95.0% or higher enhances the crystallinity of the polypropylene resin, improving the melting point, crystallinity, and crystalline orientation of the crystals in the base layer A, thereby enhancing thermal dimensional stability and mechanical strength. A mesopentad fraction of 99.9% or lower helps to reduce the cost of polypropylene production and reduces breakage during film formation. The mesopentad fraction is measured by nuclear magnetic resonance (NMR).

[0017] The melt flow rate (MFR) of the polypropylene resin contained in the base layer A, when measured in accordance with condition M (230°C, 2.16 kgf) of JIS K 7210 (1995), is preferably 4.0 to 30 g / 10 min, more preferably 4.5 to 25 g / 10 min, even more preferably 4.8 to 22 g / 10 min, particularly preferably 5.0 to 20 g / 10 min, and most preferably 5.5 to 10 g / 10 min. When the polypropylene resin has an MFR of 4.0 g / 10 min or more, the amount of low-molecular-weight components in the polypropylene resin contained in the base layer A increases, which further promotes oriented crystallization of the polypropylene resin, makes it easier to increase the crystallinity in the base layer A, and reduces entanglement of polypropylene molecular chains in the amorphous portion, thereby improving thermal dimensional stability and mechanical strength. Furthermore, when the polypropylene resin has an MFR of 30 g / 10 min or less, it is easy to maintain the film formability.

[0018] The polypropylene resin contained in the base layer A preferably has a weight average molecular weight (Mw) of 180,000 to 500,000. If Mw is less than 180,000, the melt viscosity is low, which may result in instability during casting and poor film formability. If Mw exceeds 500,000, the amount of components with a molecular weight of 100,000 or less will be reduced, which may result in a high heat shrinkage rate at high temperatures. Mw is more preferably 190,000 to 400,000, even more preferably 200,000 to 380,000, and particularly preferably 210,000 to 350,000.

[0019] The number average molecular weight (Mn) of the polypropylene resin contained in the base layer A is preferably 20,000 to 200,000. If it is less than 20,000, the melt viscosity is low, which may result in instability during casting and poor film formability. If it exceeds 200,000, the heat shrinkage rate at high temperatures may decrease. Mn is more preferably 30,000 to 120,000, even more preferably 40,000 to 110,000, particularly preferably 50,000 to 100,000, and most preferably 60,000 to 90,000.

[0020] The polypropylene resin contained in the base layer A preferably has an Mw / Mn ratio, an index of molecular weight distribution, of 2.8 to 10. It is more preferably 3.0 to 8.0, even more preferably 3.2 to 6.0, and particularly preferably 3.5 to 5.0. When the polypropylene resin has an Mw / Mn ratio of 2.8 or higher, the proportion of low-molecular-weight components in the polypropylene resin contained in the base layer A increases, which further promotes oriented crystallization of the polypropylene resin, increases the crystallinity of the base layer A, and reduces entanglement of polypropylene molecular chains in the amorphous portion, thereby improving thermal dimensional stability and mechanical strength. The molecular weight distribution of the polypropylene resin can be adjusted by polymerizing components of different molecular weights in a series of plants in multiple stages, blending components of different molecular weights offline in a kneader, blending catalysts with different performances, or using a catalyst that can achieve the desired molecular weight distribution.

[0021] (Polypropylene homopolymer) The polypropylene resin contained in the base layer A is preferably a polypropylene homopolymer. The polypropylene homopolymer is a polypropylene polymer that does not substantially contain α-olefin components other than propylene, specifically a polypropylene copolymer having more than 0% but not more than 1 mol% of α-olefin components other than propylene and 99 mol% or more of propylene as constituent units, or a polypropylene that does not contain any components other than propylene as constituent units. Thus, in the present disclosure, polypropylene homopolymers include not only polypropylene homopolymers that contain no α-olefin components other than propylene, but also polypropylene copolymers whose constituent units are more than 0% and 1 mol% or less of α-olefin components other than propylene and 99 mol% or more of propylene. Even when polypropylene homopolymers contain α-olefin components other than propylene, the content of α-olefin components other than propylene (the total amount of ethylene and α-olefins having 4 or more carbon atoms) is 1 mol% or less, as described above, preferably 0.3 mol% or less, more preferably 0.2 mol% or less, and even more preferably 0.1 mol% or less. Within the above range, crystallinity is likely to be improved. Examples of α-olefin components having 4 or more carbon atoms include 1-butene, 1-pentene, 3-methyl-1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 5-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, and 1-eicosene. As the polypropylene homopolymer, two or more different polypropylene homopolymers can also be used.

[0022] (Other than polypropylene homopolymer) The polypropylene-based resin composition constituting the base layer A may contain additives or other resins other than polypropylene homopolymer. Examples of additives include antioxidants, UV absorbers, nucleating agents, adhesives, anti-fogging agents, flame retardants, inorganic or organic fillers, and mixtures thereof. Examples of other resins include polyolefin resins other than the polypropylene homopolymer used in the base layer A, and various elastomers. These may be sequentially polymerized using a multi-stage reactor, blended with the polypropylene-based resin using a Henschel mixer, pre-prepared master pellets diluted with polypropylene to a predetermined concentration using a melt kneader, or pre-melted and kneaded in their entirety. If the surface resistivity of the polypropylene-based resin used in the base layer A is too high when used alone, a surfactant may be added to reduce the surface resistivity.

[0023] (2) Surface layer B, surface layer C When a functional layer such as a printed layer, an inorganic thin film layer, or a coating layer is provided on the surface, it is preferable that surface layer B, surface layer C, or both of these have high adhesion to the functional layer, and it is also preferable that they are provided with slip properties and anti-blocking properties. Note that the functional layer is a layer having at least one function such as adhesion, coating properties, design properties, water vapor barrier properties, oxygen barrier properties, thermal conductivity, low dielectric properties, high dielectric properties, and heat resistance. Examples of the functional layer include a printed layer, an inorganic thin film layer, and a coating layer, and the functional layer is preferably a printed layer, a vapor deposition layer, or a coating layer.

[0024] Surface layer B is made of a polypropylene-based resin composition. Surface layer C is made of a polypropylene-based resin composition. The raw material compositions and properties of surface layer B and surface layer C will be described in detail below, but the raw material compositions and properties of surface layer B and surface layer C may be the same or different. The raw material compositions and properties of surface layer B and surface layer C can be changed depending on the purpose of each layer. For example, if the surface adhesiveness of surface layer B is to be higher than that of surface layer C, it is preferable to blend more polypropylene-based resin with a melting point of 130°C or higher and 158°C or lower in surface layer B than polypropylene-based resin with a melting point of 130°C or higher and 158°C or lower in surface layer C. The reverse is also possible. Furthermore, by adjusting the type, particle size, and blending amount of the antiblocking agent blended in surface layer B and surface layer C, the gas barrier properties of the vapor deposition layer can be improved by reducing and smoothing the surface protrusions on one surface, and the surface protrusions on the other surface can be made larger to impart slip properties and antiblocking properties.

[0025] Surface layer B and surface layer C each preferably contain 25% by mass or more and 85% by mass or less of a polypropylene resin having a melting point of 130°C or more and 158°C or less. Surface layer B and surface layer C each preferably contain 15% by mass or more and 75% by mass or less of a polypropylene resin having a melting point of 159°C or more and 175°C or less. On the other hand, in surface layer B and surface layer C, the content of polypropylene resin having a melting point of 129°C or less is preferably low, specifically preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 1% by mass or less, and most preferably 0% by mass (no polypropylene resin of 129°C or less). In the following, the polypropylene resin contained in surface layer B and surface layer C and having a melting point of 159°C or more and 175°C or less may be referred to as a "high melting point polypropylene resin," the polypropylene resin having a melting point of 130°C or more and 158°C or less may be referred to as a "mid-melting point polypropylene resin," and the polypropylene resin having a melting point of 129°C or less may be referred to as a "low melting point polypropylene resin." The melting points of the polypropylene resins contained in surface layer B and surface layer C are rounded to one decimal place and are classified as high melting point polypropylene resin, mid-melting point polypropylene resin, or low melting point polypropylene resin. The high melting point polypropylene resin, mid-melting point polypropylene resin, and low melting point polypropylene resin may each be only one type of polypropylene resin, or two or more different types of polypropylene resins.

[0026] When surface layer B and surface layer C each contain a mid-melting point polypropylene resin in a content of 25% by mass or more and 85% by mass or less, adhesion to printed layers, vapor-deposited layers, coating layers, etc. can be further improved. By increasing the adhesiveness of both surfaces of surface layer B and surface layer C, the peel strength of a laminate obtained by laminating other components to both surfaces of a biaxially oriented polypropylene film can be dramatically increased. When the melting point of the mid-melting point polypropylene resin is 158°C or less, adhesion to the functional layer can be improved. When the melting point is 130°C or more, roughening of the film surface can be suppressed even when the longitudinal stretching temperature is increased during film formation, and increasing the longitudinal stretching temperature can suppress detachment of the antiblocking agent. The mid-melting point polypropylene resin preferably has a melting point of 134°C or more and 150°C or less, more preferably 138°C or more and 143°C or less. When the content of the mid-melting point polypropylene resin is 25% by mass or more, adhesion to heat-sealable films, printed layers, vapor-deposited layers, coating layers, etc. can be improved. By setting the content of the mid-melting point polypropylene resin to 85% by mass or less, productivity during film production can be ensured, the film surface can be prevented from becoming rough, and film production stability can be improved. Surface layer B and surface layer C each preferably contain the mid-melting point polypropylene resin in a content of 30% by mass or more and 80% by mass or less, and even more preferably 35% by mass or more and 75% by mass or less.

[0027] On the other hand, it is preferable that the surface layer B and the surface layer C each contain a high melting point polypropylene resin in order to maintain the thermal dimensional stability and mechanical strength of the biaxially oriented polypropylene film. The high-melting-point polypropylene resin has a melting point of 159° C. or more and 175° C. or less, preferably 160° C. or more and 170° C. or less, and more preferably 161° C. or more and 165° C. or less. Furthermore, surface layer B and surface layer C each preferably contain the high-melting-point polypropylene resin in an amount of 15% by mass or more and 75% by mass or less, more preferably 20% by mass or more and 70% by mass or less, and even more preferably 25% by mass or more and 65% by mass or less.

[0028] With respect to the total resin contained in surface layer B and surface layer C, the total of the high-melting point polypropylene resin and the mid-melting point polypropylene resin is preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, even more preferably 90 to 100 mass%, particularly preferably 95 to 100 mass%, and most preferably 98 to 100 mass%.

[0029] Various suitable physical properties of the mid-melting point polypropylene resin and the high-melting point polypropylene resin are described below. When two or more different polypropylene resins are used as the mid-melting point polypropylene resin, it is preferable that the mass-averaged physical property values of the respective polypropylene resins fall within the numerical ranges described below. When two or more different polypropylene resins are used as the high-melting point polypropylene resin, it is preferable that the mass-averaged physical property values of the respective polypropylene resins fall within the numerical ranges described below.

[0030] The melt flow rate (MFR; 230°C, 2.16 kgf) of the mid-melting point polypropylene resin is preferably 2.0 g / 10 min or more and 10 g / 10 min or less, more preferably 3.0 g / 10 min or more and 8.0 g / 10 min or less, and even more preferably 4.0 g / 10 min or more and 7.0 g / 10 min or less. The melt flow rate (MFR; 230°C, 2.16 kgf) of the high-melting point polypropylene resin is preferably 2.0 g / 10 min or more and 10 g / 10 min or less, and more preferably 3.0 g / 10 min or more and 6.0 g / 10 min or less. Furthermore, the difference between the MFR of the mid-melting point polypropylene resin and the MFR of the high-melting point polypropylene resin is preferably 2.0 g / 10 min or less, and more preferably 1.5 g / 10 min or less.

[0031] The weight-average molecular weight (Mw) of the mid-melting point polypropylene resin is preferably 180,000 to 500,000. It is more preferably 190,000 to 320,000, even more preferably 200,000 to 300,000, and particularly preferably 230,000 to 260,000. If Mw is less than 180,000, the melt viscosity is low, which can result in instability during casting and poor film formability. If Mw exceeds 500,000, the amount of components with a molecular weight of 100,000 or less becomes too small, which can result in a high heat shrinkage rate at high temperatures.

[0032] The Mw of the high-melting-point polypropylene resin is preferably 180,000 to 500,000. It is more preferably 210,000 to 400,000, even more preferably 240,000 to 350,000, and particularly preferably 270,000 to 320,000. If the Mw is less than 180,000, the melt viscosity is low, resulting in instability during casting and poor film formability. If the Mw exceeds 500,000, the amount of components with a molecular weight of 100,000 or less becomes too small, resulting in a high heat shrinkage rate at high temperatures. It is also preferable that the Mw of the high-melting-point polypropylene resin is higher than that of the mid-melting-point polypropylene resin.

[0033] The number average molecular weight (Mn) of the mid-melting point polypropylene resin is preferably 20,000 to 200,000. It is more preferably 30,000 to 80,000, even more preferably 40,000 to 70,000, and particularly preferably 45,000 to 55,000. If Mn is less than 20,000, the melt viscosity is low, which may result in instability during casting and poor film formability. If Mn exceeds 200,000, the heat shrinkage at high temperatures may increase.

[0034] The Mn of the high-melting point polypropylene resin is preferably 20,000 to 200,000. It is more preferably 30,000 to 80,000, even more preferably 40,000 to 70,000, and particularly preferably 50,000 to 60,000. If the Mn is less than 20,000, the melt viscosity is low, which may result in instability during casting and poor film formability. If the Mn exceeds 200,000, the heat shrinkage rate at high temperatures may increase. It is also preferable that the Mn of the high-melting point polypropylene resin is higher than the Mn of the mid-melting point polypropylene resin.

[0035] The molecular weight distribution (Mw / Mn) of the mid-melting point polypropylene resin is preferably 2.8 to 10, more preferably 3.2 to 9.0, even more preferably 3.5 to 9.0, particularly preferably 4.0 to 8.0, and most preferably 4.5 to 6.0. The molecular weight distribution (Mw / Mn) of the high-melting point polypropylene resin is preferably 2.8 to 10, more preferably 3.2 to 9.0, even more preferably 3.5 to 9.0, particularly preferably 3.7 to 8.0, and most preferably 4.0 to 6.0. It is also preferable that the Mw / Mn of the high-melting point polypropylene resin is larger than the Mw / Mn of the mid-melting point polypropylene resin.

[0036] High-melting-point polypropylene resins, mid-melting-point polypropylene resins, and low-melting-point polypropylene resins are obtained by polymerizing the raw material propylene using known catalysts such as Ziegler-Natta catalysts and metallocene catalysts. For example, to obtain a mid-melting-point polypropylene resin, propylene may be copolymerized with ethylene, an α-olefin having 4 or more carbon atoms, or both. Alternatively, a polypropylene resin with reduced stereoregularity may be used depending on the catalyst used. However, a mid-melting-point polypropylene resin can also be obtained without copolymerizing propylene with ethylene, an α-olefin having 4 or more carbon atoms, or both. The content of α-olefin components other than propylene in the mid-melting-point polypropylene resin (specifically, the total amount of ethylene and an α-olefin having 4 or more carbon atoms) is preferably 0 to 15 mol%, more preferably 2 to 10 mol%. Specifically, a propylene-ethylene-butene copolymer is preferred. A propylene-ethylene-butene copolymer contains at least propylene structural units, ethylene structural units, and butene structural units. Similarly, the content of α-olefin components other than propylene in the low melting point polypropylene resin is preferably 0 to 15 mol %, more preferably 2 to 10 mol %. Specifically, the low melting point polypropylene resin is preferably a propylene-ethylene copolymer. The propylene-ethylene copolymer contains at least propylene structural units and ethylene structural units. The high melting point polypropylene resin is preferably a polypropylene homopolymer. The polypropylene homopolymer is polypropylene that does not substantially contain α-olefin components other than propylene, specifically a polypropylene copolymer having more than 0 mol % and not more than 1 mol % of α-olefin components other than propylene and 99 mol % or more of propylene as structural units, or a polypropylene that does not contain any components other than propylene as structural units.

[0037] From the viewpoint of imparting slip properties and anti-blocking properties to the surface layer B, the surface layer C, or both, it is preferable that the surface layer B, the surface layer C, or both contain an anti-blocking agent. Furthermore, the surface layer B, the surface layer C, or both may contain additives other than the anti-blocking agent, or may contain resins other than polypropylene-based resins. Examples of other additives include antioxidants, UV absorbers, nucleating agents, adhesives, anti-fogging agents, flame retardants, inorganic or organic fillers, or mixtures thereof. Examples of other resins include polyolefin-based resins other than the polypropylene-based resin used in the surface layer B, the surface layer C, or both, and various elastomers. These may be sequentially polymerized using a multi-stage reactor, blended with a polypropylene-based resin using a Henschel mixer, or master pellets prepared in advance using a melt kneader may be diluted with polypropylene to a predetermined concentration, or the entire amount may be melt-kneaded in advance before use. With respect to the total resin contained in surface layer B, surface layer C, or both, the total content of the high-melting point polypropylene resin and the mid-melting point polypropylene resin is preferably 70 to 100 mass%, more preferably 80 to 100 mass%, even more preferably 90 to 100 mass%, particularly preferably 95 to 100 mass%, and most preferably 98 to 100 mass%.

[0038] The antiblocking agent is preferably a particle having a pore volume of 0.2 mL / g to 3 mL / g, more preferably 0.5 mL / g to 2.5 mL / g, and even more preferably 1.1 mL / g to 1.8 mL / g. The antiblocking agent can be appropriately selected from inorganic and organic particles. Among these, silicon compounds are particularly preferred. Examples of silicon compounds include silica, silicates, compounds having a main skeleton formed by siloxane bonds, and mixtures thereof. Porous silica particles are particularly preferred. The porous silica preferably has a pore volume of 0.8 mL / g to 2 mL / g, more preferably 1.1 mL / g to 1.8 mL / g. The particle shape may be spherical or irregular, but irregular shapes are preferred. The average particle size of the particles is preferably 1 μm to 5 μm, more preferably 2 μm to 4 μm. The average particle size is determined by taking a photograph using a scanning electron microscope, measuring the Feret's diameter in the horizontal direction using an image analyzer, and averaging the results. The use of the antiblocking agent is preferred in that it can reduce the rate at which the antiblocking agent falls off and suppress guide roll contamination.

[0039] The content of the antiblocking agent is preferably 100 ppm to 10,000 ppm, more preferably 300 ppm to 6,000 ppm, even more preferably 800 ppm to 4,000 ppm, and particularly preferably 1,200 ppm to 2,700 ppm, based on the total mass of surface layer B, surface layer C, or both. By adjusting the content within the above ranges, the three-dimensional average roughness of surface layer B, surface layer C, or both, can be adjusted to the specified range described below. By adjusting the content of the antiblocking agent to 100 ppm or more, a film with excellent slip properties and blocking resistance can be obtained. By adjusting the content of the antiblocking agent to 10,000 ppm or less, shedding of the antiblocking agent can be reduced, thereby suppressing guide roll contamination. In addition, there is little risk of a decrease in light transmittance, the antiblocking agent penetrating the functional layer when laminating the functional layer, or the functional layer formed near surface layer B becoming sparse due to the antiblocking agent protruding from surface layer B, surface layer C, or both, which makes it less likely to result in a decrease in barrier properties or poor adhesion.

[0040] The dropout rate of the antiblocking agent in surface layer B and surface layer C is 10% or less, preferably 8% or less, more preferably 6% or less, and even more preferably 4% or less. A dropout rate of 10% or less can prevent guide roll contamination during post-processing such as coating or vapor deposition. Furthermore, the generation of voids due to dropout of the antiblocking agent can be prevented, and a laminate with excellent gas barrier properties can be obtained when a metal, a metal oxide, or both are vapor-deposited. The lower limit of the dropout rate is not particularly limited, but is, for example, 0.3% or more. The dropout rate of the antiblocking agent can be adjusted to the above range by adjusting the film-forming conditions in addition to the type, pore volume, particle size, and content of the antiblocking agent.

[0041] (4) Layer structure and thickness structure of biaxially oriented polypropylene film When a biaxially oriented polypropylene film has a surface layer B on one side of a base layer A, the surface layer B may be laminated directly on the surface of the base layer A, or another layer may be interposed between the base layer A and the surface layer B. When a biaxially oriented polypropylene film has a surface layer C on the other side of the base layer A, the surface layer C may be laminated directly on the surface of the base layer A, or another layer may be interposed between the base layer A and the surface layer C. For example, a biaxially oriented polypropylene film may have a three-layer structure consisting of only the surface layer B / base layer A / surface layer C, or may have a multi-layer structure of four or more layers including layers other than the base layer A, surface layer B, and surface layer C. An example of a four-layer structure is surface layer B / intermediate layer D / base layer A / surface layer C, and an example of a five-layer structure is surface layer B / intermediate layer D / base layer A / intermediate layer D / surface layer C. By providing the intermediate layer D, the adhesive strength between the base layer A and the surface layer B, the surface layer C, or both can be increased.

[0042] The overall thickness of the biaxially oriented polypropylene film of the present invention is preferably 5 to 100 μm, more preferably 10 to 80 μm, and even more preferably 18 to 50 μm. Within the above range, the film has sufficient rigidity and is suitable as a substrate for packaging and industrial use.

[0043] The thickness of surface layer B and surface layer C is preferably 0.3 μm to 10 μm, more preferably 0.5 μm to 3 μm, and even more preferably 0.8 μm to 2 μm. A thickness of 0.3 μm or more can improve adhesion between surface layer B and surface layer C and the functional layer, making the film suitable for use as a substrate for packaging or industrial applications that require the addition of a functional layer by vapor deposition or coating. If the thickness of surface layer B is greater than 10 μm, the thickness ratio of substrate layer A may become relatively low, which may result in a decrease in the rigidity and thermal dimensional stability of the film.

[0044] The thickness of the base layer A is preferably 5 to 90 μm, more preferably 10 to 50 μm, and even more preferably 15 to 30 μm. A thickness of 5 μm or more can improve the thermal dimensional stability and mechanical strength of the film. If the thickness of the base layer A is greater than 90 μm, the thermal dimensional stability and mechanical strength can be improved, but these effects may become saturated. (5) Manufacturing method of biaxially oriented polypropylene film

[0045] The biaxially oriented polypropylene film of the present invention can be obtained by melt-extruding the polypropylene resin compositions constituting each of the base layer A, surface layer B, and surface layer C using separate extruders, co-extruding them through a die, and cooling them with a cooling roll to form an unstretched sheet, stretching the unstretched sheet in the longitudinal direction (MD) and transverse direction (TD), and then heat-setting the sheet.

[0046] The melt extrusion temperature is preferably about 200 to 280°C. When layers A, B, and C are co-extruded within this temperature range, to obtain a film with good appearance without layer disorder, it is preferable that the difference between the MFR of base layer A and the MFR of surface layers B and C (hereinafter referred to as MFR difference) is 5.0 g / 10 min or less. If the MFR difference is greater than 5.0 g / 10 min, the layers tend to become disordered, resulting in poor appearance. It is more preferably 4.0 g / 10 min or less, and even more preferably 3.0 g / 10 min or less. Furthermore, when surface layer C is included, it is preferable that the difference between the maximum and minimum MFRs of the three polypropylene resin compositions constituting base layer A, surface layer B, and surface layer C is 5.0 g / 10 min or less, and more preferably 3.0 g / 10 min or less.

[0047] The surface temperature of the cooling roll is preferably 20 to 50°C, more preferably 30 to 40°C, and even more preferably 30 to 35°C. When the cooling roll temperature is 50°C or less, crystallization of the unstretched sheet and growth of spherulites can be suppressed, allowing for a high stretch ratio and producing a film with a high tensile modulus. In addition, the occurrence of large surface irregularities due to spherulites can be suppressed, producing a film with an appropriate surface roughness.

[0048] The lower limit of the stretching ratio in the machine direction (MD) is preferably 3.5 times or more. The upper limit of the MD stretching ratio is preferably 8 times or less, more preferably 7 times or less. When the stretching ratio is 8 times or less, breakage is unlikely to occur in the subsequent TD stretching, making production easier.

[0049] The lower limit of the MD stretching temperature is preferably 120°C or higher, more preferably 130°C or higher, and even more preferably 135°C or higher. At 120°C or higher, thickness unevenness is less likely to increase and the film surface is less likely to become rough. A higher MD stretching temperature makes it less likely that voids will form around the antiblocking agent particles, preventing roll contamination during processing due to the antiblocking agent particles falling off the film surface. In addition, good gas barrier properties are obtained when aluminum is vapor-deposited.

[0050] The upper limit of the MD stretching temperature is preferably 150°C or less, more preferably 145°C or less, and even more preferably 140°C or less. If the MD stretching temperature is too high, the film may start to stick to the MD stretching rolls, causing stick-slip and resulting in spots and surface roughness on the film. If the MD stretching temperature is further increased, the film may stick to the stretching rolls, making it impossible to stretch.

[0051] The lower limit of the stretching ratio in the transverse direction (TD) is preferably 6 times or more, more preferably 7 times or more, and even more preferably 8 times or more. If it is 6 times or more, thickness unevenness is unlikely to become large. The upper limit of the TD stretching ratio is preferably 15 times or less, more preferably 13 times or less, and even more preferably 11 times or less. If it exceeds the above range, the heat shrinkage rate may become high and there may be a risk of frequent breakage during stretching.

[0052] It is preferable to heat the uniaxially stretched film after longitudinal stretching to sufficiently soften the polypropylene resin composition before the widthwise stretching step. The heating temperature in the preheating step is preferably 160°C or higher and 180°C or lower, and more preferably 165°C or higher and 175°C or lower. By setting the heating temperature in the preheating step to 160°C or higher, softening proceeds and widthwise stretching becomes easier. The lower limit of the TD stretching temperature is preferably 150°C or higher, more preferably 152°C or higher, even more preferably 154°C or higher, and particularly preferably 156°C or higher. At 150°C or higher, the film is sufficiently softened and is less likely to break or experience a high heat shrinkage rate. The upper limit of the TD stretching temperature is preferably 170°C or lower, more preferably 168°C or lower, and even more preferably 166°C or lower.

[0053] To reduce the heat shrinkage rate, a higher heat setting temperature is preferable, more preferably 160°C or higher, and even more preferably 162°C or higher. If the temperature is 160°C or higher, the heat shrinkage rate is less likely to increase. The upper limit of the heat setting temperature is preferably 180°C or lower, more preferably 175°C or lower. If the temperature is 180°C or lower, surface roughening and whitening of the film are less likely to occur.

[0054] It is preferable to relax the film during heat setting. The lower limit of the relaxation rate is preferably 2% or more, more preferably 3% or more, and even more preferably 5% or more. If it is 2% or more, the thermal shrinkage rate is unlikely to become high. The upper limit of the relaxation rate is preferably 10% or less, more preferably 8% or less. If it is 10% or less, thickness unevenness is unlikely to become large.

[0055] Furthermore, in order to reduce the thermal shrinkage rate, the film produced by the above process may be wound into a roll and then annealed offline.

[0056] The film thus obtained may be subjected to corona discharge, plasma treatment, flame treatment, etc., as required, and then wound up on a winder to obtain the biaxially oriented polypropylene film roll of the present invention. The method for producing the biaxially oriented polypropylene film of the present invention is not limited to the above-mentioned method.

[0057] (6) Various properties of biaxially oriented polypropylene film (Hayes) The haze of the biaxially oriented polypropylene film is preferably 8% or less, more preferably 5% or less, even more preferably 4% or less, and particularly preferably 3% or less. Within the above range, the film is easy to use in applications requiring transparency. The haze tends to deteriorate when the stretching temperature or heat setting temperature is too high, when the cooling roll temperature is high and the cooling rate of the unstretched (raw) sheet is slow, or when there is too much low-molecular-weight component with a molecular weight of 100,000 or less. By adjusting these conditions, the haze can be kept within the above range.

[0058] (tensile modulus) The tensile modulus of elasticity in the longitudinal direction of the biaxially oriented polypropylene film is preferably 1.0 GPa or more, more preferably 1.5 GPa or more, even more preferably 1.8 GPa or more, and particularly preferably 2.0 GPa or more. There is no particular upper limit, and it is, for example, 5.0 GPa or less. The tensile modulus of elasticity in the width direction of the biaxially oriented polypropylene film is preferably 3.0 GPa or more, more preferably 3.2 GPa or more, and even more preferably 3.5 GPa or more. There is no particular upper limit, and it is, for example, 10 GPa or less. The sum of the tensile moduli in the longitudinal and transverse directions of the biaxially oriented polypropylene film is preferably 5.8 to 12.0 Pa, more preferably 6.0 to 10.0 GPa. If the tensile modulus is within the above range, the film will be strong and can be used even if it is thin, which in turn makes it possible to reduce costs. In addition, the "longitudinal direction" of a biaxially oriented polypropylene film refers to the direction corresponding to the flow direction in the film manufacturing process, and the "width direction" refers to the direction perpendicular to the flow direction in the film manufacturing process, and the same applies below.

[0059] (Thermal shrinkage rate) The heat shrinkage rate of the biaxially oriented polypropylene film in the longitudinal direction at 150°C is preferably 15.0% or less, more preferably 9.0% or less, even more preferably 7.0% or less, and particularly preferably 5.0% or less. The lower limit of the heat shrinkage rate in the longitudinal direction at 150°C is preferably 0% or more. Within the above range, the film can be used in applications where it may be exposed to high temperatures. Furthermore, even when a functional layer is laminated on the film, the degradation of the barrier property of the functional layer can be suppressed, resulting in an improvement in the barrier property of the laminate. The heat shrinkage rate in the width direction of the biaxially oriented polypropylene film at 150°C is preferably 20.0% or less, more preferably 10.0% or less, and even more preferably 8.0% or less. The lower limit of the heat shrinkage rate in the width direction at 150°C is preferably 0% or more. If it is within the above range, it can be used in applications where it may be exposed to high temperatures. Furthermore, even when a functional layer is laminated on the film, the degradation of the barrier property of the functional layer can be suppressed, and as a result, the barrier property of the laminate can be improved. The sum of the heat shrinkage rates in the longitudinal and width directions of the biaxially oriented polypropylene film at 150°C is 25.0% or less, preferably 23.0% or less, more preferably 20.0% or less, even more preferably 15.0% or less, and particularly preferably 12.0% or less. The lower limit of the sum of the heat shrinkage rates in the longitudinal and width directions at 150°C is 0% or more. From the perspective of production productivity, 4% is preferred, and 8% is more preferred. Within the above range, the film can be used in applications where it may be exposed to high temperatures. Furthermore, even when a functional layer is laminated on the film, the degradation of the barrier property of the functional layer can be suppressed, resulting in improved barrier property of the laminate.

[0060] Similarly, when a heat-sealable film is bonded to surface layer B and / or surface layer C, the wetting tension may be set appropriately depending on the type of adhesive used for bonding, but setting it to 36 mN / m or more tends to improve adhesion. To make the wetting tension 36 mN / m or more, surface treatment such as corona treatment, flame treatment, anchor coating treatment, etc. can be carried out. If the wetting tension is too high, the slipperiness and anti-blocking properties may deteriorate, so it is preferable that the wetting tension is 46 mN / m or less.

[0061] (wetting tension) The wetting tension of the surface layer B, surface layer C, or both of the biaxially oriented polypropylene film is preferably 36 mN / m or more, more preferably 38 mN / m or more, and even more preferably 40 mN / m or more. The wetting tension may be appropriately set depending on the type of functional layer to be formed on surface layer B, surface layer C, or both. When an inorganic thin film layer such as an aluminum thin film layer is formed by a thermal vapor deposition method or the like, setting the surface to 36 mN / m or more tends to improve adhesion with the inorganic vapor deposition layer. Similarly, when a heat-sealable film sealant film is laminated on surface layer B, surface layer C, or both, the wetting tension may be appropriately set depending on the type of adhesive used for lamination, but setting it to 36 mN / m or more tends to improve adhesion. To achieve a wetting tension of 36 mN / m or more, surface treatments such as corona treatment, flame treatment, and anchor coating treatment can be performed. Since too high a wetting tension can deteriorate slip properties and anti-blocking properties, it is preferable that the wetting tension be 46 mN / m or less.

[0062] (surface resistance value) The surface resistance of the surface layer B and the surface layer C of the biaxially oriented polypropylene film is preferably 14 Log Ω or more, more preferably 14.5 Log Ω or more, and even more preferably 15 Log Ω or more. If the film contains additives or impurities such as antistatic agents, these may bleed out onto the film surface due to surface treatment, resulting in poor adhesion. A surface resistance of 14 Log Ω or more reduces the bleed-out of additives, etc. onto the film surface, which is preferable in terms of adhesion to the functional layer. Surface layer B and surface layer C The preferred upper limit of the surface resistance is not particularly limited, but is 18 Log Ω or less for manufacturing reasons.

[0063] (three-dimensional average roughness) (three-dimensional average roughness) The lower limit of the three-dimensional average roughness SRa of the surface layer B, the surface layer C, or both of the biaxially oriented polypropylene film is preferably 15 nm. It is more preferably 20 nm, even more preferably 25 nm, and even more preferably 30 nm. When the three-dimensional average roughness of the surface layer B, the surface layer C, or both of them is 15 nm or more, the film has good slipperiness and can suppress the occurrence of wrinkles when wound into a roll or during post-processing such as vapor deposition. Furthermore, the upper limit of the three-dimensional average roughness of the surface layer B, the surface layer C, or both of them is preferably 100 nm. When it is 100 nm or less, the film has good transparency and can suppress the film from becoming too slippery when wound into a roll or during post-processing such as vapor deposition, thereby preventing deterioration of workability. The three-dimensional average roughness SRa can be controlled by adjusting the type, particle size, amount, and film-forming conditions of the antiblocking agent. When a biaxially oriented polypropylene film is vapor-deposited to impart gas barrier properties, the gas barrier properties of the vapor-deposited layer can be improved by making the surface protrusions on the vapor-deposited surface small and smooth, while the surface protrusions on the other surface can be made large to impart slip properties and anti-blocking properties. In this case, the three-dimensional average roughness SRa of the vapor-deposited surface can be less than 15 nm.

[0064] (dynamic friction coefficient) The dynamic friction coefficient of the biaxially oriented polypropylene film is preferably 0.5 or less, more preferably 0.48 or less, and particularly preferably 0.45 or less. A dynamic friction coefficient of 0.5 or less allows the film to be smoothly unwound from a roll film, facilitating printing processing. The dynamic friction coefficient of the biaxially oriented polypropylene film can be adjusted by the raw material composition and film-forming conditions. In particular, it can be adjusted by the amount and particle size of the antiblocking agent blended in surface layer B, surface layer C, or both. The dynamic friction coefficient of the biaxially oriented polypropylene film is the dynamic friction coefficient when surface layer B and surface layer C are in contact with each other, and can be measured by the method described in the examples.

[0065] (Anti-blocking agent removal rate) The dropout rate of the antiblocking agent in surface layer B and surface layer C is preferably 10% or less, more preferably 8% or less, even more preferably 6% or less, and particularly preferably 4% or less. A dropout rate of 10% or less can prevent guide roll contamination during post-processing such as coating or vapor deposition. Furthermore, the generation of voids due to dropout of the antiblocking agent can be prevented, and a laminate with excellent gas barrier properties can be obtained when a metal, a metal oxide, or both are vapor-deposited. The lower limit of the dropout rate is not particularly limited, but is, for example, 0.3% or more.

[0066] (7) Laminate A laminate according to an embodiment includes a biaxially oriented polypropylene film according to any of the above-described embodiments. The laminate preferably further includes a functional layer on surface layer B, surface layer C, or both of the biaxially oriented polypropylene film. The functional layer is preferably a printed layer, a vapor-deposited layer, or a coating layer. The laminate more preferably includes a heat-sealable polyolefin film, with the functional layer, surface layer B, surface layer A, surface layer C, and heat-sealable polyolefin film laminated in this order. The laminate more preferably includes a stretched polyolefin film or a stretched polyester film, with the functional layer, surface layer B, surface layer A, surface layer C, heat-sealable polyolefin film, and stretched polyolefin film or stretched polyester film laminated in this order. The functional layer, heat-sealable film, and stretched film of the laminate are described below in order.

[0067] (7) Functional layer The biaxially oriented polypropylene film is not limited to packaging applications and can be used for industrial purposes. When it is desired to improve the gas barrier properties or design properties of the biaxially oriented polypropylene film of the present invention, it can be made into a laminate provided with a functional layer such as a printed layer, an inorganic thin film layer, or a coating layer.

[0068] A printed layer can be provided on biaxially oriented polypropylene film. Water-based ink is preferable from an environmental perspective. When using water-based ink, it is necessary that the printed layer does not repel water (printability) and that it has sufficient adhesion to the film. Biaxially oriented polypropylene film has excellent printability and adhesion to water-based ink. Gravure printing is carried out on the surface of the film using aqueous ink, the shapes of the printed dots are observed, and the dot size and the degree of ink repellency are evaluated. A uniform dot size is preferred, and a uniform dot size with no repellency is even more preferred.

[0069] When it is desired to improve the gas barrier property, it is preferable to laminate a vapor deposition layer, a coating layer, or both of these on a biaxially oriented polypropylene film. The vapor deposition layer can be produced by any known method, such as a PVD method (physical vapor deposition method) such as vacuum deposition, sputtering, or ion plating, or a CVD method (chemical vapor deposition method), but physical vapor deposition is preferred, and vacuum vapor deposition is more preferred. For example, in the vacuum vapor deposition method, aluminum, Al2O3, SiO2, etc. are used as vapor deposition materials. x (x<2), a mixture of Al2O3 and SiO2, a mixture of Al and SiO2, etc. can be used, and known methods such as resistance heating, high-frequency induction heating, and electron beam heating can be used as the heating method. Furthermore, oxygen, nitrogen, water vapor, etc. can be introduced as a reactive gas, and reactive vapor deposition using ozone addition, ion-assisted deposition, etc. can also be used. Furthermore, the production conditions can be changed as long as the objectives of the present disclosure are not impaired, such as by applying a bias to the biaxially oriented polypropylene film or by changing the temperature of the biaxially oriented polypropylene film. The same applies to other production methods such as sputtering and CVD.

[0070] When a vapor-deposited layer is provided on a biaxially oriented polypropylene film, the vapor-deposited layer preferably contains a metal, a metal oxide, or both, more preferably aluminum, Al2O3, SiOx (x<2), a mixture of Al2O3 and SiO2, or a mixture of Al and SiO2, and even more preferably a mixture of aluminum or Al and SiO2. The thickness of the vapor-deposited layer is preferably 5 to 40 nm, more preferably 10 to 30 nm. When a metal or inorganic oxide is vapor-deposited, it is preferably vapor-deposited on the side of the biaxially oriented polypropylene film with less surface roughness. Materials for the coating layer when gas barrier properties need to be improved include polyvinylidene chloride, nylon, butanediol-vinyl alcohol copolymer, ethylene-vinyl alcohol copolymer, and polyvinyl alcohol. In the case of the coating layer, the coating amount after drying is 0.03 to 3 g / m 2 It is preferable that the density is 0.1 to 0.3 g / m 2 It is more preferable that:

[0071] The upper limit of oxygen permeability of a laminate consisting of a biaxially oriented polypropylene film with an inorganic thin film layer or coating layer at a temperature of 23°C and a relative humidity of 65% is 50 mL / m 2 / day / MPa, more preferably 39 mL / m 2 / day / MPa, more preferably 30 mL / m 2 / day / MPa, and particularly preferably 25 mL / m 2 / day / MPa. The upper limit of oxygen permeability is 50 mL / m 2 The lower limit of the oxygen permeability of the vapor-deposited film at a temperature of 23°C and a relative humidity of 65% is not particularly limited, but from the viewpoint of productivity, it is preferably 0.1 mL / m 2 / day / MPa. In a laminate in which an inorganic thin film layer is provided on a biaxially oriented polypropylene film, it is preferable that the adhesion at the interface between the inorganic thin film layer or coating layer and the biaxially oriented polypropylene film is high, as high adhesion can keep the above-mentioned oxygen permeability low. The adhesiveness at the interface between the inorganic thin film layer or coating layer and the biaxially oriented polypropylene film is evaluated by attaching an adhesive tape to the inorganic thin film layer and evaluating the degree of peeling of the inorganic thin film layer or coating layer using the 90° peeling method. It is preferable that the inorganic thin film layer or coating layer only peels partially, and it is more preferable that the inorganic thin film layer or coating layer does not peel at all.

[0072] High adhesion between the vapor-deposited layer and the substrate layer of a vapor-deposited film is preferable, as high adhesion can reduce the oxygen permeability mentioned above. The adhesion of the vapor-deposited layer can be evaluated by attaching adhesive tape to the vapor-deposited layer of the film and measuring the degree of peeling of the vapor-deposited layer using the 90° peeling method. It can also be evaluated by measuring the oxygen permeability after subjecting the vapor-deposited surface of the vapor-deposited film to an abrasion test; it is preferable that there is no partial peeling of the aluminum vapor-deposited layer, and even more preferable that there is no peeling of the aluminum vapor-deposited layer.

[0073] A printed layer can be provided on biaxially oriented polypropylene film. Water-based ink is preferable from an environmental perspective. When using water-based ink, it is necessary that the printed layer does not repel water (printability) and that it has sufficient adhesion to the film. Biaxially oriented polypropylene film has excellent printability and adhesion to water-based ink.

[0074] (8) Heat-sealable film, stretchable film Biaxially oriented polypropylene films or laminates having a printed layer, an inorganic thin film layer, or a coating layer laminated thereon can be processed into packaging bags or the like by laminating a heat-sealable film thereon. The heat-sealable film laminated on the biaxially oriented polypropylene film is preferably a heat-sealable polyolefin film. When both surfaces of a biaxially oriented polypropylene film have excellent adhesive properties, it is preferable to use it as part of a laminate having a heat-sealable polyolefin film on the outermost surface side. It is particularly preferable to use a biaxially oriented polypropylene film as a laminate further having a stretched polyolefin film or stretched polyester film on the opposite side of the heat-sealable polyolefin film. For example, biaxially oriented polypropylene films are preferably used as a substrate in a laminate consisting of a substrate for a front printing layer / heat-sealable film, or as a substrate for a gas barrier film as an intermediate layer in a laminate consisting of a substrate for a back printing layer / gas barrier film / heat-sealable film. Examples of heat-sealable films include unstretched films, uniaxially stretched films, and biaxially stretched films made of polyolefins such as low-density polyethylene, linear low-density polyethylene, and polypropylene, ethylene-vinyl acetate copolymers, polyesters, or combinations thereof. Heat-sealable polyolefin films made of low-density polyethylene, linear low-density polyethylene, or polypropylene are particularly preferred, as are unstretched or uniaxially stretched films. Polypropylene is particularly preferred in terms of ease of recycling.

[0075] The surface of the biaxially oriented polypropylene film onto which the heat-sealable film is laminated may be either the surface layer B side or the surface layer C side. The heat-sealable film is preferably laminated via an adhesive layer. Examples of adhesives that can be used include ester-based adhesives, urethane-based adhesives, acrylic-based adhesives, and polyethyleneimine-based adhesives. Examples of lamination methods that can be used include dry lamination, extrusion lamination, and co-extrusion.

[0076] Packaging bags made from biaxially oriented polypropylene film or laminates formed by laminating a functional layer such as a printed layer, an inorganic thin film layer, or a coating layer, and a heat-sealable film such as a heat-sealable film, can be used as packaging containers with excellent suitability for filling and packaging and preserving various items such as food and beverages, pharmaceuticals, detergents, shampoos, oils, toothpaste, adhesives, and pressure-sensitive adhesives.

[0077] The lamination strength of the biaxially oriented polypropylene film, measured by the method described below, is 1.5 N / 15 mm or more, preferably 2.0 N / 15 mm or more, more preferably 2.5 N / 15 mm or more, even more preferably 2.7 N / 15 mm or more, and particularly preferably 2.8 N / 15 mm or more. There is no particular upper limit, but a strength of 10 N / 15 mm or less is sufficient. In this case, it is preferable to have a heat-sealable film on the surface layer C side. Furthermore, the laminate strength of the biaxially oriented polypropylene film of the present invention having a functional layer such as a printed layer, an inorganic thin film layer, or a coating layer, measured by the measurement method described below, is 1.5 N / 15 mm or more, preferably 2.0 N / 15 mm or more, more preferably 2.5 N / 15 mm or more, even more preferably 2.7 N / 15 mm or more, and particularly preferably 2.8 N / 15 mm or more. There is no particular upper limit, but a strength of 10 N / 15 mm or less is sufficient. In this case, it is preferable to have a heat-sealable film on the surface layer C side. The lamination strength of the biaxially oriented polypropylene film of the present invention or a laminate having the biaxially oriented polypropylene film and a functional layer such as a printed layer, an inorganic thin film layer, or a coating layer, and a heat-sealable film is preferably 1.5 N / 15 mm or more, more preferably 2.0 N / 15 mm or more, even more preferably 2.5 N / 15 mm or more, and particularly preferably 2.8 N / 15 mm or more. There is no particular upper limit, and it is, for example, 10 N / 15 mm or less.

[0078] Biaxially oriented polypropylene film or a laminate having a functional layer such as a printed layer, an inorganic thin film layer, or a coating layer on the biaxially oriented polypropylene film and a heat-sealable film is less likely to wrinkle in the sealed area when processed into packaging bags, even when the heat-sealing temperature is high. Because the sum of the heat shrinkage rate at 150°C in the longitudinal direction and the heat shrinkage rate at 150°C in the transverse direction of the biaxially oriented polypropylene film is 0.0% or more and 25.0% or less, even when the temperature of the sealing bar is increased, there is little wrinkling or deformation in the sealed area, allowing for faster bag production.

[0079] Examples of laminate configurations having functional layers and heat-sealable films on both sides of a biaxially oriented polypropylene film include a laminate in which a biaxially oriented polypropylene film of the present application having a gas barrier layer as a functional layer is placed between a biaxially oriented polypropylene film having a printed layer and a heat-sealable film such as a non-oriented polypropylene film or a non-oriented linear low-density polyethylene film. Examples include (OPP or PET / printed layer) / adhesive layer / (aluminum or inorganic oxide vapor-deposited layer / OPP*) / adhesive layer / (CPP or LLDPE), or (OPP or PET / printed layer) / adhesive layer / (gas barrier coating layer / OPP*) / adhesive layer / (CPP or LLDPE). Laminates can also be produced by laminating a heat-sealable film such as a non-oriented polypropylene film or a non-oriented linear low-density polyethylene film to a biaxially oriented polypropylene film of the present application having a printed layer as a functional layer. Examples include laminates used as a surface printing substrate, such as (printed layer / OPP*) / adhesive layer / (CPP or LLDPE). In the above layer structure, " / " indicates a boundary between different members, and the abbreviations used are as follows: OPP*: Biaxially oriented polypropylene film of the present disclosure OPP or PET: General biaxially oriented polypropylene film or biaxially oriented polyethylene terephthalate film CPP: Non-oriented polypropylene film LLDPE: Linear low density polyethylene film

[0080] This application claims the benefit of priority based on Japanese Patent Application No. 2024-011277, filed January 29, 2024, and Japanese Patent Application No. 2024-012918, filed January 31, 2024. The entire contents of the specifications of Japanese Patent Application No. 2024-011277, filed January 29, 2024, and Japanese Patent Application No. 2024-012918, filed January 31, 2024, are incorporated herein by reference. [Example]

[0081] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0082] (Measurement method) The physical properties of the raw materials used and the resulting films in the examples and comparative examples were measured by the following methods. Note that in the following 1) to 5) the physical properties of the polypropylene resin used in each layer were measured, and in 6) to 17) the physical properties of the biaxially oriented polypropylene film were measured. In 18) to 21) evaluations were made during post-processing, such as laminating other layers such as functional layers onto the biaxially oriented polypropylene film.

[0083] 1) Melting point Using a PerkinElmer DSC8500 differential scanning calorimeter, 5 mg of the sample was packed into an aluminum pan and set therein. The sample was melted at 230°C for 5 minutes under a nitrogen atmosphere, cooled to 30°C at a scanning rate of -10°C / min, held there for 5 minutes, and then heated again at a scanning rate of 10°C / min. The main endothermic peak temperature associated with melting was taken as the melting point (Tm).

[0084] 2) Mesopentad fraction (mmmm) The mesopentad fraction is measured by 13 The mesopentad fraction was calculated according to the method described in "Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973)". 13C-NMR measurement was performed using an AVANCE500 manufactured by BRUKER at 110°C by dissolving 200 mg of a sample in a mixed solution of o-dichlorobenzene and deuterated benzene at a volume ratio of 8:2 at 135°C.

[0085] 3) Melt flow rate (MFR) Measurement was carried out in accordance with JIS K7210 at a temperature of 230°C and a load of 2.16 kgf.

[0086] 4) Number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) The molecular weight and molecular weight distribution of the polypropylene resin were determined using gel permeation chromatography (GPC) with monodisperse polystyrene as the standard. The measurement conditions for the column, solvent, etc. used in the GPC measurement are as follows: Solvent: 1,2,4-trichlorobenzene Column: TSKgel GMHHR-H(20)HT x 3 Flow rate: 1.0ml / min Detector: RI Measurement temperature: 140℃

[0087] 5) The number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) are calculated by the molecular weight (M) at each elution position of the GPC curve obtained through the molecular weight calibration curve. i ) number of molecules (N i ) is defined by the following equation: Number average molecular weight: Mn=Σ(N i M i ) / ΣN i Weight average molecular weight: Mw=Σ(N i M i 2 ) / Σ(N i M i ) Molecular weight distribution: Mw / Mn When the baseline was unclear, it was set in the range up to the lowest point of the high molecular weight side base of the elution peak on the high molecular weight side closest to the elution peak of the standard substance.

[0088] 6) Thickness The cross section of the film solidified with the modified urethane resin was cut out with a microtome and observed with a differential interference microscope to measure the thickness of each layer.

[0089] 7) Hayes The haze of the film was measured at 23° C. using a haze meter (300A manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7105. The measurement was carried out twice, and the average value was calculated.

[0090] 8) Appearance The film surface was irradiated with a bromine light (VIDEO LIGHT VLG301 100V 300W manufactured by LPL) at an angle of about 45 degrees, and the appearance of the film was evaluated by visual observation according to the following criteria. A: No visible spots were observed that would cause problems for the product. B: Many irregularities in transparency due to stick-slip occurring in the longitudinal stretching rolls were observed. C: A large number of irregularities in transparency due to stick-slip occurring in the longitudinal stretching rolls were observed, and the level was not acceptable for the product.

[0091] 9) Tensile modulus A sample measuring 10 mm in width and 180 mm in length was cut from the film using a razor. Measurements were performed according to JIS K 7127. After leaving the film in an atmosphere of 23°C and 65% relative humidity for 12 hours, measurements were performed again under conditions of 23°C, 65% relative humidity, a chuck distance of 100 mm, and a pulling speed of 200 mm / min. The average value of five measurements was calculated and used as the longitudinal tensile modulus. The measuring device used was an Autograph AG5000A manufactured by Shimadzu Corporation. Furthermore, a sample measuring 180 mm in width and 10 mm in length was cut out from the film using a razor, and the tensile modulus in the width direction was determined using the same method as for the tensile modulus in the length direction.

[0092] 10) Heat shrinkage rate Measurement was performed according to JIS Z 1712 using the following method. The film was cut into 20 mm wide and 200 mm long samples along either the longitudinal or transverse direction of the film, and these were then hung in a hot air oven at 150°C for 5 minutes. The length of each sample after heating was measured, and the ratio of the shrunken length to the original length was taken as the heat shrinkage rate.

[0093] 11) Wetting tension (mN / m) According to JIS K 6768 (1999), the film was aged at 23°C and a relative humidity of 50% for 24 hours, and then the surface wetting tension of surface layer B and surface layer C was measured.

[0094] 12) Surface resistance According to JIS K 6911 (1995), the film was aged at 23° C. and a relative humidity of 65% for 24 hours, and then the surface resistance values of surface layer B and surface layer C were measured.

[0095] 13) Three-dimensional average roughness SRa The average roughness SRa of the surface layers B and C was measured by the stylus method under the following conditions using a contact-type three-dimensional surface roughness meter (manufactured by Kosaka Laboratory Co., Ltd.: Model ET-4000A). Stylus tip radius: 0.5μm Stylus pressure: 50μN Cutoff value: 800 μm Measurement length: 500μm Measurement speed: 0.1μm / sec Measurement interval: 5 μm

[0096] 14) Anti-blocking agent removal rate Using a universal tensile testing machine (Toyo Baldwin STM-T-50BP), a 0.5 kg weight (contact surface: 63 mm x 63 mm) with a bettin fabric attached was placed over the measurement surface of the film, and a friction test was conducted under the following conditions. Temperature: 23℃ Relative humidity: 50% Number of times of friction: Rub the part to be evaluated 5 times in a row Tensile speed: 200 mm / min

[0097] After the above treatment, the film was observed at a magnification of 600x using a tabletop microscope (Hitachi, Ltd., "TM3030Plus Miniscope"), and the number of all antiblocking agents in the observed film and the number of antiblocking agents that had fallen off the film were counted, and the rate of antiblocking agent loss was calculated using the following formula. Antiblocking agent detachment rate (%) = (number of antiblocking agents detached from the film) / (total number of antiblocking agents observed in the film and number of antiblocking agents detached from the film) × 100

[0098] 15) Coefficient of dynamic friction Two films were prepared, and the surface layer B of one film was superimposed on the surface layer C of the other film. Measurements were then carried out in accordance with JIS K 7125 (1999) using a universal tensile tester STM-T-50BP (manufactured by Toyo Baldwin) at 23°C and a relative humidity of 50%.

[0099] 16) Wrinkles in film rolls The biaxially oriented polypropylene film thus produced was wound up to a width of 600 mm and a length of 1500 m using a slitter to produce a film roll, and the wrinkles on the surface of the film roll were visually evaluated according to the following criteria. A+: No wrinkles A: There were some slight wrinkles, but the wrinkles disappeared when a tension of about 5 N / m was applied to the pulled-out film. B: There were slight wrinkles, but the wrinkles disappeared when a tension of about 20 N / m was applied to the pulled-out film. C: There were strong wrinkles, and the wrinkles did not disappear even when a tension of about 20 N / m was applied to the pulled-out film.

[0100] 17) Guide roll dirt After passing a 500 m length of film through a slitter (NS-SLITTER FN-105 manufactured by Nishimura Manufacturing Co., Ltd.), the contamination of the guide roll was evaluated, and a rating of A was deemed to be acceptable. A: The guide roll was not dirty. B: There was slight dirt on the guide roll in some places. C: The entire surface of the guide roll was dirty.

[0101] 18) Evaluation of water-based ink printability Gravure printing was carried out on the surface layer B of the film using a gravure printing machine (manufactured by Fuji Machine Industry Co., Ltd.) with water-based ink at a speed of 50 m / min. A process chart plate was used for the printing design. The inks and diluents used are listed below. Water-based ink: Toyo Ink Co., Ltd., product name JW291 Aquaecol R39 (registered trademark) Dilution solvent: Toyo Ink Co., Ltd. product name AQ602F

[0102] (Microscope observation) Using a KEYENCE Digital Microscope VHX-200, the shape of the printed dots was observed at 125x magnification, and the dot size and degree of ink repellency were evaluated. A three-level evaluation standard was shown. Figures 1 to 3 show examples of dot shapes for each evaluation. Regarding ink repellency, Figure 4 shows an enlarged view of the ink repellency area in Figure 2. A: The dot size is uniform and there is no ink repellency (Figure 1) B: The dot size is uniform, and there is ink repellency (Figure 2) C: Uneven dot size and ink repellency (Figure 3)

[0103] 19) Evaluation of water-based ink adhesion The adhesion of the gravure printed ink in 18) was evaluated by a grid peeling method (25 squares of 2 mm, 90° peeling method using 18 mm wide Nichiban Cellotape (registered trademark)), and the following ranking was made based on practicality. A: 0-5 cross-cut peeled areas B: 6-15 cross-cut peeled areas C: 15 or more cross-cut peeled areas

[0104] 20) Adhesion of aluminum vapor deposition film A 105 mm × 105 mm film was cut out from the obtained film roll, and vapor deposition was performed on the surface of surface layer B using a small vacuum deposition apparatus (VWR-400 / ERH manufactured by ULVAC) to a film thickness of 30 nm, yielding a vapor-deposited film having an aluminum vapor-deposited film on surface layer B. An 18 mm wide piece of Cellotape (registered trademark) manufactured by Nichiban Co., Ltd. was attached to the aluminum vapor-deposited film of the vapor-deposited film, and the adhesion of the aluminum vapor-deposited film was evaluated by the 90° peeling method. A: There was no peeling of the aluminum vapor deposition film. B: The aluminum vapor deposition film was partially peeled off. C: The aluminum vapor deposition film was peeled off over the entire surface.

[0105] 21) Oxygen permeability of aluminum vapor deposition film The oxygen permeability of the vapor-deposited film produced by the manufacturing method described in 20) above was measured in an atmosphere of 23°C and 65% relative humidity using an oxygen permeability measuring device (OX-TRAN 2 / 20 manufactured by MOCON) in accordance with the electrolytic sensor method (Appendix A) of JIS K 7126-2. The oxygen permeability was measured in the direction in which oxygen permeated from the substrate layer A side to the aluminum inorganic thin film layer.

[0106] 22) Laminate strength The laminate strength was measured by the following procedure. Step 1) Preparation of a (heat-sealable film) laminate of biaxially oriented polypropylene film and unstretched polypropylene film The following procedure was carried out using a continuous dry laminating machine. An adhesive was applied to the surface of the surface layer C of the biaxially oriented polypropylene film obtained in the Examples and Comparative Examples in a dry coating amount of 2.8 g / m 2After gravure coating so that the adhesive was applied, the film was introduced into a drying zone and dried at 80°C for 5 seconds. Subsequently, the film was laminated to a heat-sealable film between rolls provided downstream (roll pressure: 0.2 MPa, roll temperature: 50°C). The resulting laminated film was aged in a wound state at 40°C for 3 days. However, the film of Example 5 was corona-treated immediately before gravure coating with the adhesive so that the wetting tension of the surface layer C was 40 mN / m. The adhesive used was a urethane adhesive obtained by mixing 28.9% by mass of a base agent (TM569, manufactured by Toyo Morton Co., Ltd.), 4.00% by mass of a curing agent (CAT10L, manufactured by Toyo Morton Co., Ltd.), and 67.1% by mass of ethyl acetate, and the heat-sealable film used was a non-oriented polypropylene film (P1193, thickness 40 μm) manufactured by Toyobo Co., Ltd. Step 2) Measuring laminate strength The laminate film obtained above was cut into strips 200 mm long and 15 mm wide, with the longitudinal direction of the biaxially oriented polypropylene film as the long side, and the peel strength was measured using a tensile tester (Tensilon, manufactured by Orientec Co., Ltd.) at 23°C and a relative humidity of 65% at a tensile speed of 200 mm / min in a T-peel test. The measurement was performed three times, and the average value was used as the laminate strength.

[0107] 23) Appearance evaluation of heat-sealed area An adhesive (TM329 / CAT8B manufactured by Toyo-Morton Co., Ltd.) was applied to the obtained film, and then a 30 μm thick unstretched polypropylene film (P1128 manufactured by Toyobo Co., Ltd.) was dry-laminated as a heat-sealable film on a metal roll heated to 60°C, and aging was carried out at 40°C for 3 days to obtain a laminate for evaluation. The heat-sealable films of the laminate were heat-sealed together to form a three-sided sealed bag measuring 130 mm x 180 mm using a heat sealer. The pressure was 0.2 MPa for 1 second, the seal bar width was 10 mm, and the heat seal temperature was 150°C. The appearance of wrinkles at the heat-sealed portion was visually evaluated. A: No wrinkles can be seen in the heat-sealed area in either the width or length direction of the film. B: Wrinkles can be seen in the heat-sealed area of the film in only one of the width and length directions. C: Wrinkles can be seen in the heat-sealed area in both the width and length directions of the film.

[0108] (raw resin) Table 1 shows the details of polypropylene resins PP-1 to PP-6, which were raw materials used in the following examples and comparative examples. The antiblocking agent masterbatch (manufactured by Nippon Pigment Co., Ltd., hereinafter referred to as MB-1) used PP-3 shown in Table 1 as the polypropylene resin, and porous silica particles with an average particle size of 2.9 μm and a pore volume of 1.6 mL / g as the antiblocking agent (AB agent), and the content of the antiblocking agent in MB-1 was 5.0 mass%.

[0109] [Table 1]

[0110] Example 1 A blend of 70% by mass of PP-1 and 30% by mass of PP-2 was used for the base layer A. A blend of 26% by mass of PP-3, 20% by mass of PP-4, 50% by mass of PP-5, and 4% by mass of MB-1 was used for the surface layer B and surface layer C. The base layer A was produced using a 45 mm extruder, the surface layer B using a 25 mm extruder, and the surface layer C using a 20 mm extruder. The raw resins were melted at 250 ° C and co-extruded into a sheet from a T-die. The surface layer B was cooled and solidified by contacting a cooling roll at 30 ° C., and then stretched 4.5 times in the longitudinal direction (MD) at 135 ° C. Next, in a tenter, both ends of the film width direction were clamped with clips, preheated at 173 ° C., stretched 8.2 times in the transverse direction (TD) at 164 ° C., and heat-set at 171 ° C. while relaxing 6.7% in the transverse direction (TD) to obtain a three-layer laminate consisting of the surface layer B / base layer A / surface layer C. The surfaces of surface layer B and surface layer C of the laminate were subjected to corona treatment using a corona treater manufactured by Softal Corona & Plasma GmbH at an applied current of 0.75 A, and then the laminate was wound up on a winder to obtain a biaxially oriented polypropylene film. The resulting biaxially oriented polypropylene film had an overall thickness of 20 μm (thicknesses of surface layer B / base layer A / surface layer C were 1.3 μm / 17.4 μm / 1.3 μm).

[0111] Examples 2 to 7 A biaxially oriented polypropylene film was obtained in the same manner as in Example 1, except that the raw material compositions and film-forming conditions for surface layer B and surface layer C were as shown in Table 2.

[0112] (Comparative Examples 1, 3, and 4) A biaxially oriented polypropylene film was obtained under the same conditions as in Example 1, except that the raw material compositions of surface layer B and surface layer C were changed as shown in Table 2.

[0113] An attempt was made to obtain a biaxially oriented polypropylene film under the same conditions as in Example 1, except that the raw material composition of surface layer B and surface layer C was changed to 0 mass% PP-1, a polypropylene-based resin with a melting point of 163°C, 6 mass% PP-4, a polypropylene-based resin with a melting point of 159°C, and 90 mass% PP-5, a polypropylene-based resin with a melting point of 140°C. However, the longitudinal stretching was unstable and the film formation stability was poor.

[0114] (Comparative Example 2) The raw material composition was the same as in Comparative Example 3, and the film production conditions were the same as in Example 1 except that the longitudinal stretching temperature was lowered by 10°C to 125°C, the widthwise stretching preheating temperature was 167°C, and the heat setting temperature was changed to 169°C. A biaxially oriented polypropylene film was obtained.

[0115] (Comparative Example 5) A biaxially oriented polypropylene film was obtained under the same conditions as in Example 1, except that the raw material composition of the base layer A was changed as shown in Table 2 and only PP-4, a polypropylene resin with a melting point of 159°C, was used as the raw material for the base layer A.

[0116] The raw material composition of each layer of the films of the Examples and Comparative Examples, the thickness of each layer, and the film production conditions are shown in Table 2, and various physical properties and evaluations of the films of the Examples and Comparative Examples are shown in Table 3.

[0117] [Table 2]

[0118] [Table 3]

[0119] The biaxially oriented polypropylene films obtained in Examples 1 to 7 did not cause guide roll staining. Furthermore, the obtained film rolls had few wrinkles, and films cut from the film rolls had little water-based ink repellency on Layer B and good adhesion. Furthermore, when aluminum was vapor-deposited, the aluminum vapor-deposited film had excellent adhesion, and the oxygen permeability of the aluminum vapor-deposited film was low, resulting in excellent gas barrier properties. Furthermore, when an unstretched polypropylene film was further laminated on the surface layer C, the lamination strength with the unstretched polypropylene film was high, and the appearance of the heat-sealed portion was also good.

[0120] In contrast, the film of Comparative Example 1 had a low content of polypropylene resin with a melting point of 130°C or higher and 158°C or lower in surface layers B and C, and therefore had poor water-based ink printability and adhesion on surface layer B, and also had poor adhesion to the aluminum vapor-deposited film, and the oxygen barrier properties of the aluminum vapor-deposited film were inferior to those of the Examples. Furthermore, when an unstretched polypropylene film was further laminated on surface layer C, the lamination strength with the unstretched polypropylene film was poor.

[0121] In Comparative Example 2, the water-based ink printability and the adhesion of the aluminum vapor deposition film on the surface layer B were poor. In addition, the rate of fall-off of the antiblocking agent was high, and there was a lot of guide roll contamination.

[0122] In Comparative Example 3, surface layer B and surface layer C did not contain a polypropylene-based resin with a melting point of 130°C or higher and 158°C or lower, so the water-based ink printability and adhesion on surface layer B were poor, and the adhesion of the aluminum vapor-deposited film was also poor, and the oxygen barrier property of the aluminum vapor-deposited film was inferior to that of the Examples. Furthermore, when an unstretched polypropylene film was further laminated on surface layer C, the lamination strength with the unstretched polypropylene film was poor.

[0123] In Comparative Example 4, the surface layer C did not contain a polypropylene resin having a melting point of 130° C. or more and 158° C. or less, and therefore the laminate strength was low.

[0124] The film of Comparative Example 5 had a high sum of heat shrinkage at 150°C because the raw material for the base layer A was a polypropylene-based resin with a melting point of 159°C. As a result, the laminated laminate had many wrinkles in the heat-sealed area, resulting in a poor appearance and making it unusable as a packaging bag. Furthermore, the oxygen barrier properties of the aluminum vapor-deposited film were also inferior to those of the Examples. [Industrial Applicability]

[0125] The biaxially oriented polypropylene film of the embodiment has excellent lamination strength when functional layers such as printed layers, inorganic thin film layers, and coating layers, and heat-sealable films are laminated on both sides to form a laminate, and therefore can be used as a base film for laminates suitable for various uses such as food packaging, labels, and industrial applications, and is therefore industrially useful.

Claims

1. A biaxially oriented polypropylene film having a base layer A made of a polypropylene-based resin composition, a surface layer B made of a polypropylene-based resin composition, and a surface layer C made of a polypropylene-based resin composition, wherein the biaxially oriented polypropylene film satisfies the following (1) and (2): (1) The surface layer B and the surface layer C contain 25% by mass or more and 85% by mass or less of a polypropylene-based resin having a melting point of 130° C. or more and 158° C. or less. (2) The sum of the heat shrinkage rate at 150°C in the longitudinal direction and the heat shrinkage rate at 150°C in the transverse direction of the biaxially oriented polypropylene film is 0.0% or more and 25.0% or less.

2. 2. The biaxially oriented polypropylene film according to claim 1, wherein the surface layer B, the surface layer C, or both of these surface layers have a surface wetting tension of 36 mN / m or more.

3. 3. The biaxially oriented polypropylene film according to claim 1, wherein the base layer A contains 70% by mass or more of a polypropylene resin having a mesopentad fraction ([mmmm]%) of 95.0 to 99.9% and a melting point of 160°C to 175°C.

4. 3. The biaxially oriented polypropylene film according to claim 1, wherein the surface resistivity of the surface layer B, the surface layer C, or both of these surface layers is 14.0 Log Ω or more.

5. A laminate comprising the biaxially oriented polypropylene film according to any one of claims 1 to 4, and further comprising a heat-sealable polyolefin film, in which the surface layer B of the biaxially oriented polypropylene film, the base layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order.

6. A laminate comprising the biaxially oriented polypropylene film according to any one of claims 1 to 4, and further comprising a functional layer and a heat-sealable polyolefin film, in which the functional layer, the surface layer B of the biaxially oriented polypropylene film, the base layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order.

7. The laminate according to claim 6 , wherein the functional layer is a printed layer, a vapor-deposited layer, or a coated layer.

8. The laminate described in claim 7 further comprises a stretched polyolefin film or a stretched polyester film, and the stretched polyolefin film or stretched polyester film, the functional layer, the surface layer B, the surface layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in that order.

Images