Biaxially oriented polypropylene film

Abstract

Provided is a biaxially oriented polypropylene film that is suitable as a processing blank, which shows excellent adhesion in evaporation, coating, and lamination with other films, and which has excellent sliding properties and blocking resistance, without impairing the excellent transparency and mechanical properties of the biaxially oriented polypropylene film as originally possessed.[Solution] A biaxially oriented polypropylene film having a base layer (A) having a polypropylene-based resin as a main component, and a surface layer (B) having a polypropylene-based resin as a main component, which satisfies (1) to (4) below.(1) The number of protrusions of 500 nm or more in the surface area of 2000 μm 2 is 50 or more and 200 or less.(2) The wetting tension of the surface is 38 mN / m or more.(3) The Martens hardness of the surface is 350 N / mm 2 or less.(4) The arithmetic average roughness (Ra) of the surface is 1.5 nm or more and 3.0 nm or less.

Description

Technical Field

[0001] This invention relates to biaxially oriented polypropylene films. More specifically, it relates to biaxially oriented polypropylene films exhibiting excellent winding quality and superior adhesion to vapor-deposited layers, coating layers, and adhesive layers used in lamination with other component films. Background Technology

[0002] Previously, biaxially oriented polypropylene films were widely used as packaging materials for various items, including food and textile products, due to their excellent transparency and mechanical properties. However, a problem with polypropylene films is that, because polypropylene resins are non-polar, their surface energy is low. Consequently, it has been pointed out that the adhesion is insufficient in processing methods such as vapor deposition, coating, and lamination with other films, whether using inorganic or organic materials.

[0003] In particular, during the formation of thin film layers based on vapor deposition and coating, not only is there a lack of adhesion, but also problems arise at protruding areas caused by surface irregularities where film cannot form, leading to poor barrier properties. On the other hand, biaxially oriented polypropylene films, due to their excellent flexibility and planarity, lack slippage, causing the films to stick together. Therefore, anti-blocking agents are usually added to create surface irregularities. Consequently, at these surface irregularities, the formation of film based on vapor deposition and coating becomes insufficient, resulting in poor barrier properties.

[0004] As a countermeasure to such problems, various methods have been proposed, such as the following method disclosed: mixing branched polypropylene into acrylic resin to cause the β crystals of polypropylene to transform into α crystals, thereby forming an uneven surface on the film, which substantially does not use inorganic or organic anti-blocking agents and achieves good sliding properties (see, for example, Patent Document 1, etc.).

[0005] In addition, the following method is disclosed: using an anti-blocking agent to form irregularities on the surface layer of the film to improve the adhesion to ink and other component films during lamination (for example, see Patent Document 2, etc.).

[0006] However, further improvements are needed regarding the quality of thin film winding, the formation of vapor-deposited layers, and the gas barrier properties after coating.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: International Publication No. 2007 / 094072

[0010] Patent Document 2: International Publication No. 2018 / 142983 Summary of the Invention

[0011] The problem the invention aims to solve

[0012] The purpose of this invention is to provide a biaxially oriented polypropylene film that does not impair the excellent transparency and mechanical properties of the original biaxially oriented polypropylene film, has excellent film winding quality, and excellent adhesion to the adhesive layer in the lamination of the vapor-deposited layer, coating layer, and other component films.

[0013] Solution for solving the problem

[0014] The present invention that solves the above problems is a biaxially oriented polypropylene film having a substrate layer (A) in which a polypropylene resin is the main component, and a surface layer (B) that satisfies (1) to (4) below and has a polypropylene resin as the main component.

[0015] (1) Surface area 2000μm 2 The number of protrusions larger than 500nm is between 50 and 200.

[0016] (2) The wetting tension of the surface is above 38mN / m.

[0017] (3) The surface martensitic hardness is 350 N / mm. 2 the following.

[0018] (4) The arithmetic mean roughness of the surface is above 1.5 nm and below 3.0 nm.

[0019] In this case, it is suitable for the film to have a haze value of less than 6%.

[0020] In addition, in this case, it is suitable that the tensile modulus of the film in the longitudinal direction is 2.0 GPa or more and the tensile modulus in the width direction is 3.0 GPa or more.

[0021] Furthermore, in this case, it is suitable for the film thickness to be 5 μm or more and 200 μm or less.

[0022] Furthermore, it is also suitable to have a laminate, which is a laminate of any biaxially oriented polypropylene film and an unstretched polypropylene film as described above.

[0023] The effects of the invention

[0024] The biaxially oriented polypropylene film of the present invention does not impair its original excellent transparency and mechanical properties, exhibits excellent film winding quality, and demonstrates excellent adhesion to the vapor-deposited layer, coating layer, and adhesive layer in lamination with other films. Detailed Implementation

[0025] The biaxially oriented polypropylene film of the present invention has a substrate layer (A) in which a polypropylene resin is the main component, and a surface layer (B) in which a polypropylene resin is the main component, satisfying (1) to (4) below.

[0026] (1) Surface area 2000μm 2 The number of protrusions larger than 500nm is between 50 and 200.

[0027] (2) The wetting tension of the surface is above 38mN / m.

[0028] (3) The surface martensitic hardness is 350 N / mm. 2 the following.

[0029] (4) The arithmetic mean roughness (Ra) of the surface is above 1.5 nm and below 3.0 nm.

[0030] The surface area of ​​the surface layer (B) is 2000 μm. 2 If there are many protrusions larger than 500nm in the film, the contact area between the surface layer (B) and other surface layers will be smaller during the adhesion between the films and the sliding with metals, etc., thus improving the sliding properties and anti-adhesion properties, which in turn affects the improvement of the winding quality of the film.

[0031] The wetting tension of the surface layer (B) represents the surface tension (mN / m) of the mixed reagent that is determined to wet the surface layer (B), and is related to the wetting ease of the vapor-deposited layer, coating layer, and adhesive layer.

[0032] The Marsh hardness of the surface layer (B) is expressed as the hardness of the surface layer (B) when a needle tip with a radius of curvature of less than 0.1 μm is pressed into the surface to a depth of approximately 0.1 μm using a dynamic microhardness tester. A low Marsh hardness indicates that the surface layer (B) is soft and easily follows the movement of the vapor-deposited layer, coating layer, and adhesive layer stacked on its surface. This improves the adhesion between the surface layer (B) and the vapor-deposited layer, coating layer, and adhesive layer, which in turn improves the gas barrier properties.

[0033] The arithmetic mean roughness (Ra) of the surface layer (B) is determined using a scanning probe microscope (AFM) according to the definition of arithmetic mean roughness described in JIS-B0601 (1994). It is an index representing the surface unevenness of the relatively flat areas other than the larger peaks and valleys, and is related to the adhesion of the vapor-deposited layer, coating layer, and adhesive layer used in lamination with other components. If the arithmetic mean roughness (Ra) is small, the vapor-deposited layer, coating layer, and adhesive layer are uniformly stacked on the film surface, thereby improving gas barrier properties.

[0034] (1) Substrate layer (A)

[0035] The substrate layer (A) of the biaxially oriented polypropylene film of the present invention uses a polypropylene resin as the main component. The polypropylene resin constituting the substrate layer (A) can be a polypropylene homopolymer without copolymer components, or a polypropylene resin copolymerized with ethylene and / or α-olefins having 4 or more carbon atoms at a concentration of 0.5 mol% or less. The copolymer component is preferably 0.3 mol% or less, more preferably 0.1 mol% or less, and most preferably a polypropylene homopolymer without copolymer components.

[0036] If the copolymerization amount of ethylene and / or α-olefins with 4 or more carbon atoms is less than 0.5 mol%, the crystallinity and rigidity are not easily reduced, and the thermal shrinkage rate at high temperatures is not easily increased. These resins can also be blended and used. The term "main component" here refers to the component that has the highest content in the substrate layer (A), preferably 50% by weight or more, more preferably 55% by weight or more, further preferably 60% by weight or more, and most preferably 70% by weight or more.

[0037] The stereoregularity of the polypropylene resin in the substrate layer (A) constituting the biaxially oriented polypropylene film of the present invention is an index of the stereoregularity of the polypropylene resin. 13 The percentage of racemic pentamerous components ([mmmm]%) determined by C-NMR is preferably 97.5% or higher and 99.5% or lower. More preferably 98.0% or higher, and even more preferably 98.5% or higher. If the percentage of racemic pentamerous components in polypropylene resins is 97.5% or higher, the elastic modulus increases and the heat resistance is improved. 99.5% is a realistic upper limit.

[0038] The mass-average molecular weight (Mw) of the polypropylene resin constituting the substrate layer (A) of the biaxially oriented polypropylene film of the present invention is preferably 180,000 or more and 500,000 or less.

[0039] If the molecular weight (Mw) is less than 180,000, the melt viscosity is low, resulting in instability during casting and sometimes poor film formation. If the Mw exceeds 500,000, the amount of components with a molecular weight below 100,000 decreases, making it difficult to reduce the thermal shrinkage rate at high temperatures.

[0040] The preferred lower limit of Mw is 190,000, further preferred is 200,000, and particularly preferred is 220,000. The preferred upper limit of Mw is 350,000, further preferred is 340,000, and particularly preferred is 330,000.

[0041] The number average molecular weight (Mn) of the polypropylene resin constituting the substrate layer (A) of the biaxially oriented polypropylene film of the present invention is preferably 20,000 or more and 200,000 or less.

[0042] If the value is less than 20,000, the melt viscosity is low, resulting in instability during casting and sometimes poor film formation. If the value exceeds 200,000, the heat shrinkage rate at high temperatures is not easily reduced.

[0043] The preferred lower limit of Mn is 30,000, the further preferred is 40,000, the particularly preferred is 50,000, and the preferred upper limit of Mn is 100,000, the further preferred is 90,000, and the particularly preferred is 85,000.

[0044] Furthermore, regarding the Mw / Mn ratio, an indicator of molecular weight distribution, for the polypropylene resin constituting the substrate layer (A), a ratio of 2.5 or higher and 10.0 or lower is preferred. More preferably, it is 3.0 or higher and 9.0 or lower; even more preferably, it is 3.5 or higher and 7.0 or lower; and particularly preferably, it is 3.5 or higher and 6.0 or lower. If the Mw / Mn ratio is 2.5 or higher, the heat shrinkage rate at high temperatures is less likely to decrease.

[0045] It should be noted that the molecular weight distribution of polypropylene resins can be adjusted in the following ways: by polymerizing components of different molecular weights in a series of devices in multiple stages, or by blending components of different molecular weights offline in a mixer, or by blending and polymerizing catalysts with different properties, or by using a catalyst that can achieve the desired molecular weight distribution.

[0046] The melt flow rate (MFR; 230°C, 2.16 kgf) of the polypropylene resin constituting the substrate layer (A) of the biaxially oriented polypropylene film of the present invention is preferably 1.0 g / 10 min or more and 10 g / 10 min or less.

[0047] The lower limit of the MFR of the polypropylene resin in the substrate layer (A) is more preferably 1.2 g / 10 min, further preferably 1.5 g / 10 min, even more preferably 1.8 g / 10 min, and particularly preferably 2.0 g / 10 min. The upper limit of the MFR of the polypropylene resin in the substrate layer (A) is more preferably 9.0 g / 10 min, and further preferably 8.0 g / 10 min.

[0048] If the Mw / Mn and MFR of the polypropylene resin constituting the substrate layer (A) are within this range, the tensile modulus can be increased and the heat shrinkage rate at high temperature can be kept small.

[0049] The substrate layer (A) of the biaxially oriented polypropylene film of the present invention may also contain additives and other resins. Examples of additives include antioxidants, ultraviolet absorbers, nucleating agents, binders, antifogging agents, flame retardants, inorganic or organic fillers, etc. Examples of other resins include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers of propylene with ethylene and / or α-olefins having 4 or more carbon atoms, various elastomers, etc. These can be polymerized sequentially using a multi-stage reactor, blended with polypropylene resin in a Henschel mixer, diluted with polypropylene to a predetermined concentration using a melt-blending mill, or pre-melted and blended entirely before use. The surfactant added to reduce surface resistivity is preferably 6000 ppm or less, more preferably 1500 ppm, further preferably 500 ppm, and particularly preferably 100 ppm or less relative to the polypropylene resin constituting the substrate layer (A).

[0050] (2) Surface layer (B)

[0051] The surface layer (B) of the biaxially oriented polypropylene film of the present invention uses a polypropylene resin as the main component. The polypropylene resin constituting the surface layer (B) can be a polypropylene homopolymer without copolymer components, or a polypropylene resin copolymerized with ethylene and / or α-olefins having 4 or more carbon atoms at a concentration of 0.5 mol% or less. The copolymer component is preferably 0.3 mol% or less, more preferably 0.1 mol% or less, and most preferably a polypropylene homopolymer without copolymer components.

[0052] Examples of α-olefins with 4 or more carbon atoms include 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Additionally, polar maleic acid and other similar compounds can be used as copolymerizing components.

[0053] If the copolymerization amount of ethylene and / or α-olefins with 4 or more carbon atoms is less than 0.5 mol%, the crystallinity and rigidity are not easily reduced, and the thermal shrinkage rate at high temperatures is not easily increased. These resins can also be blended and used. The term "main component" here refers to the component with the highest content in the surface layer (B), preferably 50% by weight or more, more preferably 80% by weight or more, further preferably 90% by weight or more, and most preferably 95% by weight or more.

[0054] As the polypropylene resin constituting the surface layer (B), a mixture of two or more polypropylene resins with different melt flow rates (MFR) can also be used.

[0055] It is speculated that when the difference in melt flow rate (MFR) between two or more polypropylene resins in a mixture is small, the crystallization rate and crystallinity of each polypropylene resin will not differ significantly, and slight surface irregularities are easily formed. However, if the cooling rate of the unstretched sheet slows down during film manufacturing, the surface irregularities based on spherulites will increase. Excessively high stretching temperatures during longitudinal or transverse stretching can also exacerbate surface irregularities, therefore, caution is required.

[0056] As various polypropylene resins, polypropylene homopolymers without copolymer components and polypropylene resins copolymerized with ethylene and / or α-olefins having 4 or more carbon atoms at a rate of 0.5 mol% or less can be used. The copolymer component is preferably 0.3 mol% or less, more preferably 0.1 mol% or less, and most preferably a polypropylene homopolymer without copolymer components.

[0057] Examples of α-olefins with 4 or more carbon atoms include 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene. Additionally, polar maleic acid and other similar compounds can be used as copolymerizing components.

[0058] The total amount of ethylene and / or α-olefins with 4 or more carbon atoms, and other copolymer components is preferably less than 0.5 mol%.

[0059] The polypropylene resin used in this invention is obtained by polymerizing propylene from raw materials using known catalysts such as Ziegler-Natta catalysts and metallocene catalysts. In order to avoid the formation of heterogeneous bonds, a Ziegler-Natta catalyst is preferred, and a catalyst capable of high stereoregularity polymerization is used.

[0060] As a method for polymerizing propylene, any known method can be used. Examples include: polymerization in inactive solvents such as hexane, heptane, toluene, and xylene; polymerization in liquid monomers; polymerization in gaseous monomers with the addition of a catalyst in the gas phase; or polymerization by combining these methods; etc.

[0061] The stereoregularity of the polypropylene resin in the surface layer (B) of the biaxially oriented polypropylene film of the present invention is an indicator of its stereoregularity. 13 The percentage of racemic pentamerous components ([mmmm]%) determined by C-NMR is preferably 90.0% or more and 99.5% or less. The lower limit is more preferably 92.0% or more, further preferably 93.0% or more, and particularly preferably 93.5%. The upper limit is more preferably 99.0% or less, further preferably 98.5% or less, and particularly preferably 98.0% or less. If the percentage of racemic pentamerous components in the polypropylene resin is greater than 90.0%, the elastic modulus increases, and the heat resistance also improves.

[0062] The mass-average molecular weight (Mw) of the polypropylene resin constituting the surface layer (B) of the biaxially oriented polypropylene film of the present invention is preferably 200,000 or more and 500,000 or less.

[0063] If the molecular weight (Mw) is less than 200,000, the melt viscosity is low, resulting in instability during casting and sometimes poor film formation. If the Mw exceeds 500,000, the amount of components with a molecular weight below 100,000 decreases, making it difficult to reduce the thermal shrinkage rate at high temperatures.

[0064] The preferred lower limit of Mw is 220,000, the further preferred is 250,000, and the preferred upper limit of Mw is 400,000, the further preferred is 360,000, and the particularly preferred is 330,000.

[0065] The number average molecular weight (Mn) of the polypropylene resin constituting the surface layer (B) of the biaxially oriented polypropylene film of the present invention is preferably 20,000 or more and 200,000 or less.

[0066] If the value is less than 20,000, the melt viscosity is low, resulting in instability during casting and sometimes poor film formation. If the value exceeds 200,000, the heat shrinkage rate at high temperatures is not easily reduced.

[0067] The preferred lower limit of Mn is 30,000, the further preferred is 40,000, the particularly preferred is 50,000, and the preferred upper limit of Mn is 80,000, the further preferred is 70,000, and the particularly preferred is 60,000.

[0068] Furthermore, for the Mw / Mn ratio, which is an indicator of molecular weight distribution, the polypropylene resin constituting the surface layer (B) preferably has a ratio of 3.2 or higher and 10 or lower. More preferably, it has a ratio of 3.5 or higher and 8 or lower, even more preferably, it has a ratio of 4.0 or higher and 6 or lower, and particularly preferably, it has a ratio of 4.5 or higher and 6 or lower. If the Mw / Mn ratio is 3.2 or higher, the heat shrinkage rate at high temperatures is less likely to decrease.

[0069] It should be noted that the molecular weight distribution of polypropylene resins can be adjusted in the following ways: by polymerizing components of different molecular weights in a series of devices in multiple stages, or by blending components of different molecular weights offline in a mixer, or by blending and polymerizing catalysts with different properties, or by using a catalyst that can achieve the desired molecular weight distribution.

[0070] The melt flow rate (MFR; 230°C, 2.16 kgf) of the polypropylene resin constituting the surface layer (B) of the biaxially oriented polypropylene film of the present invention is preferably 1.0 g / 10 min or more and 8.0 g / 10 min or less.

[0071] The lower limit of the MFR of the polypropylene resin in the surface layer (B) is more preferably 1.5 g / 10 min, further preferably 2.0 g / 10 min, and particularly preferably 2.5 g / 10 min. The upper limit of the MFR of the polypropylene resin in the surface layer (B) is more preferably 8 g / 10 min, further preferably 7 g / 10 min, and even more preferably 6 g / 10 min or less.

[0072] If the Mw / Mn and MFR of the polypropylene resin constituting the surface layer (B) are within this range, the adhesion to the cooling roller is also good, which is conducive to the formation of suitable surface protrusions, which can improve the surface martensitic hardness and keep the thermal shrinkage rate at high temperature to a small level.

[0073] The surface layer (B) of the biaxially oriented polypropylene film of the present invention may also contain additives and other resins. Examples of additives include anti-blocking agents, antioxidants, ultraviolet absorbers, nucleating agents, adhesives, anti-fogging agents, flame retardants, and inorganic or organic fillers. Examples of other resins include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers of propylene with ethylene and / or α-olefins having four or more carbon atoms, and various elastomers. These can be polymerized sequentially using a multi-stage reactor, blended with polypropylene resin in a Henschel mixer, diluted with polypropylene to a predetermined concentration using a melt-blending mill, or pre-melted and melt-blended in total for use.

[0074] As an anti-blocking agent included in the surface layer (B), inorganic and organic particles can be suitably selected. Among these, silicon compounds are particularly preferred. Examples of silicon compounds include silicates, silica, and compounds having a main framework based on siloxane bonds. The particle shape can be spherical or amorphous. Among these particles, particles formed by a compound having a main framework based on siloxane bonds and acrylic acid (organosilicon particles) are preferred. It has been found that organosilicon particles have excellent compatibility and dispersibility with the polypropylene resin of the surface layer (B), thus exhibiting excellent transparency, excellent affinity with coating layers and vapor-deposited layers disposed on the surface layer (B), low repulsion of coating layers, or excellent adhesion to vapor-deposited layers.

[0075] The preferred average particle size is 1.0 μm or more and 3.0 μm or less, more preferably 1.5 μm or more and 2.7 μm or less. The average particle size is determined as follows: a photograph is taken using a scanning electron microscope, the horizontal Freette diameter is measured using an image analyzer device, and the average value is expressed as the average value.

[0076] The amount of particles added is preferably 400 ppm or more and 4000 ppm or less. The amount of anti-blocking agent added is more preferably 400 ppm or more and 2500 ppm or less, further preferably 800 ppm or more and 2500 ppm, and particularly preferably 1200 ppm or more and 2500 ppm or less. It is carried out in a manner where the number of surface protrusions and the Martens hardness are within the known range. When it is 500 ppm or more, the film has excellent sliding properties and anti-blocking properties. When it is 4000 ppm or less, it is less likely to cause devitrification due to excessive addition of anti-blocking agent, penetration of film layer caused by particles when applying aluminum vapor deposition, coating or other film layers, formation of film on the side of the protruding part, and it is less likely to become less barrier and poorly sealed.

[0077] The surfactant added to reduce surface resistivity is preferably 6000 ppm or less, more preferably 1500 ppm, further preferably 500 ppm, and particularly preferably 100 ppm or less.

[0078] (3) Biaxially oriented polypropylene film

[0079] The biaxially oriented polypropylene film of the present invention can be a two-layer structure of surface layer (B) / substrate layer (A), a three-layer structure of surface layer (B) / substrate layer (C) / substrate layer (A), a four-layer structure of surface layer (B) / substrate layer (A) / second surface layer (B), or a multilayer structure thereof. When the surface layer (B) is located on both sides of the film, one of them is the second surface layer (B), and the resins constituting each can be the same or different.

[0080] The overall thickness of the biaxially oriented polypropylene film of the present invention is preferably 1 μm or more, more preferably 2 μm or more, further preferably 5 μm or more, even more preferably 10 μm or more, and particularly preferably 15 μm or more.

[0081] The overall thickness of the biaxially oriented polypropylene film of the present invention is preferably less than 100 μm, more preferably less than 8 μm, further preferably less than 60 μm, and even more preferably less than 50 μm.

[0082] The thickness of all surface layers (B) in the biaxially oriented polypropylene film of the present invention is preferably 0.010 or more, more preferably 0.020 or more, further preferably 0.030 or more, and particularly preferably 0.040 or more.

[0083] As for the ratio of the thickness of the surface layer (B) to the overall thickness of the film in the biaxially oriented polypropylene film of the present invention, the ratio of the total surface layer (B) thickness to the overall film thickness is preferably 0.500 or less, more preferably 0.400 or less, further preferably 0.300 or less, even more preferably 0.200 or less, particularly preferably 0.115 or less, and most preferably 0.110 or less. If the ratio of the total surface layer (B) thickness to the overall film thickness is 0.500 or less, the shrinkage rate is smaller, which is therefore preferable.

[0084] The thickness of the surface layer (B) in the biaxially oriented polypropylene film of the present invention is preferably 0.02 or more, and more preferably 0.030 or more, compared with the overall thickness of the film.

[0085] If the thickness of the surface layer (B) is greater than or equal to the thickness of the film, the adhesion between the surface layer (B) and the vapor-deposited layer, the coating layer, and the adhesive layer is improved.

[0086] The thickness of the surface layer (B) in the biaxially oriented polypropylene film of the present invention is preferably 0.08 or less, more preferably 0.07 or less, further preferably 0.06 or less, and even more preferably 0.055 or less. If the thickness of the surface layer (B) is 0.08 or less, the shrinkage rate is smaller, which is therefore preferable.

[0087] In addition, the thickness of the substrate layer (A), or the total thickness of the substrate layer (A) and the intermediate layer (C) relative to the overall thickness of the film is preferably 0.50 or more and 0.99 or less, more preferably 0.60 or more and 0.97 or less, particularly preferably 0.7 or more and 0.90 or less, and most preferably 0.80 or more and 0.92 or less.

[0088] (4) Manufacturing method

[0089] The biaxially oriented polypropylene film of the present invention can be obtained by melt extruding a polypropylene resin composition constituting a substrate layer (A) and a polypropylene resin composition constituting a surface layer (B) using separate extruders, co-extruding from a die, cooling on a cooling roller to form an unstretched sheet, stretching the unstretched sheet along the longitudinal (MD) and width (TD) directions, and then performing a heat setting treatment. It should be noted that extrusion is preferably performed with the surface layer (B) in contact with the cooling roller. When the surface layer (B) is the opposite side to the cooling roller, the polypropylene resin is cooled slowly, resulting in increased crystallinity. Sometimes, due to surface unevenness caused by spherulites, the arithmetic mean roughness (Ra) of the surface layer (B) becomes excessively large.

[0090] The melt extrusion temperature is preferably around 200–280°C. Within this temperature range, to obtain a laminated film with a good appearance without causing layer disorder, the viscosity difference (MFR difference) between the polypropylene resin composition constituting the substrate layer (A) and the polypropylene resin composition constituting the surface layer (B) is preferably 6.5 g / 10 min or less. If the viscosity difference is greater than 5.0 g / 10 min, the layers become disordered and the appearance is easily poor. More preferably, it is 4.0 g / 10 min or less, and even more preferably, it is 3.0 g / 10 min or less.

[0091] The surface temperature of the cooling roller is preferably 25–50°C, more preferably 30–45°C. If the cooling roller temperature is below 50°C, the crystallinity of the polypropylene resin will not become excessively high, and the arithmetic mean roughness (Ra) of the surface layer (B) will not easily increase due to the unevenness of the surface of the formed spherulites.

[0092] The lower limit of the longitudinal (MD) stretching ratio is preferably 4 times, more preferably 4.2 times. If it is 4 times or more, it is less likely to cause film thickness unevenness. The upper limit of the MD stretching ratio is preferably 8 times, more preferably 7 times. If it is less than 8 times, it becomes easier to perform the subsequent TD stretching. The lower limit of the MD stretching temperature is preferably 118°C, more preferably 120°C, and even more preferably 122°C. If it is 118°C or more, the mechanical load is less likely to increase, the thickness unevenness is less likely to increase, and the surface roughness of the film is less likely to occur. The upper limit of the MD stretching temperature is preferably 135°C, more preferably 132°C, and even more preferably 128°C. Higher temperatures are preferred for reducing the heat shrinkage rate, but sometimes the film may adhere to the rollers and become impossible to stretch, or cause surface roughness.

[0093] The lower limit of the stretch ratio in the width direction (TD) is preferably 7 times, more preferably 7.5 times, and even more preferably 8 times. If it is 7 times or more, the thickness unevenness is less likely to increase. The upper limit of the TD stretch ratio is preferably 15 times, more preferably 12 times, and even more preferably 10 times. If it exceeds the above, the heat shrinkage rate may become high, or breakage may occur during stretching.

[0094] For the preheating temperature in TD stretching, in order to rapidly raise the film temperature to near the stretching temperature, it is preferably set to be 10-20°C higher than the stretching temperature. The lower limit of the TD stretching temperature is preferably 150°C, more preferably 152°C, further preferably 154°C, and particularly preferably 156°C. If it is above 150°C, it is easy to soften sufficiently, not easy to break, or the heat shrinkage rate is not easy to increase. The upper limit of the TD stretching temperature is preferably 164°C, more preferably 162°C, and further preferably 160°C. In order to reduce the heat shrinkage rate, a higher temperature is preferred, but if it is above 170°C, it is not easy to cause the melting and recrystallization of low molecular weight components, which leads to a decrease in orientation, nor is it easy to cause surface roughness and film whitening.

[0095] The stretched film is then heat-set. The lower limit of the heat-setting temperature is preferably 168°C, more preferably 170°C, and even more preferably 173°C. If the temperature is above 168°C, the heat shrinkage rate is less likely to increase, eliminating the need for prolonged processing to reduce heat shrinkage. The upper limit of the heat-setting temperature is preferably 180°C, more preferably 178°C. If the temperature is below 180°C, it is less likely to cause a decrease in orientation due to melting and recrystallization of low-molecular-weight components, and it is also less likely to cause surface roughness or film whitening.

[0096] During heat setting, relaxation is preferred. The lower limit of the relaxation rate is preferably 2%, more preferably 3%, and even more preferably 5%. If it is 2% or more, the heat shrinkage rate is less likely to increase. The upper limit of the relaxation rate is preferably 10%, more preferably 8%. If it is less than 10%, the thickness unevenness is less likely to increase.

[0097] Furthermore, in order to reduce the heat shrinkage rate, the film manufactured in the above process can be temporarily rolled into a roll and then annealed offline.

[0098] The biaxially oriented polypropylene film thus obtained can be wound up using a winding machine after corona discharge, plasma treatment, flame treatment, etc., as needed, thereby obtaining the biaxially oriented polypropylene film roll of the present invention.

[0099] (Thin film properties)

[0100] The biaxially oriented polypropylene film of the present invention is characterized by the following properties. Here, the "longitudinal direction" of the biaxially oriented polypropylene film of the present invention corresponds to the flow direction in the film manufacturing process, and the "width direction" is the direction orthogonal to the flow direction in the aforementioned film manufacturing process. For polypropylene films where the flow direction in the film manufacturing process is unclear, wide-angle X-rays are incident perpendicularly to the film surface, and the scattering peaks originating from the (110) plane of the α-type crystal are scanned in the circumferential direction. The direction with the highest diffraction intensity of the obtained diffraction intensity distribution is taken as the "longitudinal direction", and the direction orthogonal to it is taken as the "width direction".

[0101] The surface roughness of the surface layer (B) of the biaxially oriented polypropylene film of the present invention is 2000 μm based on a three-dimensional roughness meter. 2 The number of protrusions 500 nm or larger in the film is preferably 50 or more and 200 or less. The number of protrusions on the surface of the surface layer (B) is more preferably 60 or more, further preferably 70 or more, even more preferably 80 or more, particularly preferably 100 or more, and particularly preferably 120 or more. When the number of protrusions 500 nm or larger is 50 or more, the film has excellent sliding properties and anti-adhesion properties, and thus excellent winding quality.

[0102] The number of protrusions larger than 500 nm is more preferably 180 or less, further preferably 170 or less, and particularly preferably 160 or less. When the number of protrusions larger than 500 nm is 200 or less, it is less likely to cause the aluminum vapor-deposited layer or coating layer to penetrate due to the protrusions, or to prevent the formation of aluminum vapor-deposited layer or coating layer on the side of the protrusion, thus improving the adhesion. There are several methods to keep the size and number of protrusions in the surface layer (B) within a limited range, which can be adjusted by the type, average particle size, and amount of anti-blocking agent.

[0103] (Wetting tension)

[0104] The surface wetting tension of the surface layer (B) of the biaxially oriented polypropylene film of the present invention is preferably 38 mN / m or higher. If the wetting tension is 38 mN / m or higher, the adhesion to adhesives used in the lamination of vapor-deposited films, coated films, and films of other components is improved. To achieve a wetting tension of 38 mN / m or higher, additives such as antistatic agents and surfactants are typically used. Among these methods, physicochemical surface treatments such as corona treatment and flame treatment are preferred because they reduce surface resistivity.

[0105] For example, in corona treatment, it is preferable to use a preheating roller and a treatment roller to discharge in the air. The wetting tension is preferably 44 mN / m or less, more preferably 43 mN / m or less, and even more preferably 42 mN / m or less.

[0106] (Madall hardness)

[0107] The surface layer (B) of the biaxially oriented polypropylene film of the present invention preferably has a Martens hardness of 350 N / mm. 2 Below, more preferably 340 N / mm 2 The following is a further preferred value: 320 N / mm 2 The following is a preferred option: 310 N / mm 2 The optimal value is 300 N / mm. 2 the following.

[0108] The Martens hardness is 350 N / mm². 2 In the following cases, the adhesion between the vapor-deposited layer, the coating layer, and the surface layer (B) is improved. Furthermore, even by reducing the thickness of the surface layer (B) and its proportion to the thin film, adhesion is easily improved. To achieve a martensitic hardness of 350 N / mm... 2 The following can be achieved by adding ethylene and / or α-olefins with 4 or more carbon atoms, or other copolymer components. Additionally, the martensitic hardness can be reduced by decreasing the film's stretch ratio and decreasing the orientation of the molecular chains.

[0109] The surface layer (B) of the biaxially oriented polypropylene film of the present invention preferably has a Martens hardness of 150 N / mm.2 Above, or more preferably 180 N / mm 2 The above, further optimized, is 220N / mm. 2 The above, and even more preferably 240N / mm 2 The above, and even more preferably 260N / mm 2 above.

[0110] The Marlowon hardness of the surface layer (B) is expressed as the hardness of the surface layer (B) when a needle tip with a radius of curvature of less than 0.1 μm is pressed into the surface to a depth of approximately 0.1 μm using a dynamic microhardness tester. A higher Marlowon hardness indicates a harder surface layer (B), resulting in smaller depressions in the protrusions formed on the surface of the surface layer (B). This maintains a small contact area between the surface layer (B) and other surface layers, improving slip properties and anti-adhesion properties, which in turn affects the winding quality of the film.

[0111] (Arithmetic mean roughness (Ra))

[0112] The surface layer (B) of the biaxially oriented polypropylene film of the present invention has an arithmetic mean roughness (Ra) of 1.5 nm or more and 3.0 nm or less. More preferably, the arithmetic mean roughness (Ra) is 2.9 nm or less, more preferably 2.8 nm or less, and particularly preferably 2.7 nm or less. When the arithmetic mean roughness (Ra) is 3.0 nm or less, the vapor-deposited layer and coating layer are less prone to peeling off at protruding portions, exhibiting excellent gas barrier properties.

[0113] The arithmetic mean roughness (Ra) of the surface layer (B) is more preferably 1.8 nm or more, further preferably 2.0 nm or more, particularly preferably 2.2 nm or more, and most preferably 2.3 nm or more. If the arithmetic mean roughness (Ra) is 1.5 nm or more, the adhesion to the vapor-deposited layer and the coating layer is improved, and the gas barrier properties are excellent.

[0114] (Surface resistivity)

[0115] Regarding adhesion to vapor-deposited films, coated films, and adhesives, the surface resistivity of the surface layer (B) of the biaxially oriented polypropylene film of the present invention is more preferably 14 LogΩ or higher. The surface resistivity is further preferably 14.5 LogΩ or higher, and particularly preferably 15 LogΩ or higher. Therefore, it is preferable to contain surfactants and anti-fogging agents without excess. The surface resistivity is preferably 18 LogΩ or lower, and more preferably 17 LogΩ or lower.

[0116] (Haze)

[0117] The haze of the biaxially oriented polypropylene film of the present invention is preferably 6.0% or less, more preferably 0.2% or more and 5.0% or less, further preferably 0.3% or more and 4.5% or less, and particularly preferably 0.4% or more and 4.0% or less. If it falls within the above range, it can sometimes be easily used for applications requiring transparency. Haze tends to worsen, for example, when the stretching temperature or heat setting temperature is excessively high, when the cooling roller temperature is high, when the cooling rate of the unstretched (preform) sheet is slow, or when there is an excessive amount of low molecular weight components. By adjusting these factors, it can be set within the above range.

[0118] (Tensive modulus)

[0119] The longitudinal tensile modulus of the biaxially oriented polypropylene film of the present invention is preferably 1.5 GPa or more and 5.0 GPa or less, more preferably 1.8 GPa or more and 5.0 GPa or less, further preferably 2.0 GPa or more and 4.0 GPa or less, and particularly preferably 2.1 GPa or more and 3.5 GPa or less.

[0120] The tensile modulus in the width direction of the biaxially oriented polypropylene film of the present invention is preferably 3.0 GPa or more and 8.0 GPa or more, more preferably 3.2 GPa or more and 7.0 GPa or less, further preferably 3.5 GPa or more and 6.5 GPa or less, particularly preferably 3.8 GPa or more and 6.5 GPa or less, and most preferably 4.0 GPa or more and 6.5 GPa or less.

[0121] If the tensile modulus is within the above range, the stiffness is increased, and it can be used even with a small film thickness, thus reducing the amount of film used. The method for determining the tensile modulus is described later.

[0122] (Heat shrinkage rate)

[0123] In the biaxially oriented polypropylene film of the present invention, the longitudinal heat shrinkage rate at 150°C is preferably 0.2% or more and 15.0% or less, more preferably 0.3% or more and 13.0% or less, further preferably 0.5% or more and 9.0% or less, and particularly preferably 1.0% or more and 8.0% or less. If the heat shrinkage rate is within the above range, it can be considered a film with excellent heat resistance and can be used in applications where it may be exposed to high temperatures. It should be noted that if the heat shrinkage rate at 150°C is around 1.5%, it can be achieved, for example, by increasing the low molecular weight component, adjusting the stretching conditions, and the heat setting conditions.

[0124] In the biaxially oriented polypropylene film of the present invention, the heat shrinkage rate in the width direction at 150°C is preferably 0.5% or more and 20.0% or less, more preferably 1.0% or more and 15.0% or less, further preferably 1.5% or more and 10.0% or less, and particularly preferably 2.0% or more and 8.0% or less. If the heat shrinkage rate is within the above range, it can be considered a film with excellent heat resistance and can be used in applications where it may be exposed to high temperatures. It should be noted that if the heat shrinkage rate at 150°C is around 1.5%, it can be achieved, for example, by increasing the low molecular weight component, adjusting the stretching conditions, and the heat setting conditions.

[0125] (Laminated thin film)

[0126] To improve the gas barrier properties and designability of the biaxially oriented polypropylene film of the present invention, it is preferable to provide an evaporation layer and a coating layer.

[0127] Materials for vapor-deposited layers can include aluminum, Al2O3, SiOx (X<2), mixtures of Al2O3 and SiO2, mixtures of Al and SiO2, and so on.

[0128] Examples of materials for the coating layer include polyvinylidene chloride, nylon, ethylene-vinyl alcohol copolymer, and polyvinyl alcohol. The vapor-deposited layer and the coating layer are preferably thin film layers. In the case of a vapor-deposited layer, a thickness of 5–40 nm is preferred, more preferably 10–30 nm. In the case of a coating layer, a thickness of 0.05–0.5 g / m² is preferred. 2 The coating amount is more preferably 0.10–0.3 g / m². 2 The amount of coating.

[0129] The vapor-deposited layer disposed on the surface of the biaxially oriented polypropylene film of the present invention is preferably only partially peeled off, more preferably not peeled off at all. Furthermore, the coating layer disposed on the surface of the biaxially oriented polypropylene film of the present invention is preferably only partially repelled, more preferably not repelled.

[0130] (Method for fabricating vapor-deposited coatings)

[0131] When fabricating a vapor-deposited layer, known methods such as PVD (physical vapor deposition), sputtering, and ion plating, or CVD (chemical vapor deposition) are suitable, with physical vapor deposition being preferred and vacuum vapor deposition being more preferred. For example, in vacuum vapor deposition, aluminum, Al₂O₃, SiOₓ (X<2), mixtures of Al₂O₃ and SiO₂, or mixtures of Al and SiO₂ can be used as the vapor deposition source material. For the heating method, resistance heating, high-frequency induction heating, or electron beam heating can be used. Furthermore, oxygen, nitrogen, or water vapor can be introduced as reactive gases, or reactive vapor deposition using ozone addition, ion assistance, or other methods can be employed. Additionally, as long as the purpose of this invention is not impaired, the fabrication conditions can be changed by applying a bias voltage to the thin film substrate, or by raising or lowering the temperature of the thin film substrate. The same applies to fabrication methods other than sputtering and CVD.

[0132] The biaxially oriented polypropylene film of the present invention is not limited to packaging, but can also be used as an insulating film for capacitors, motors, etc., and as a base film for the backsheet of solar cells.

[0133] (Layered structure)

[0134] Packaging bags are preferably made from a laminate of the biaxially oriented polypropylene film of the present invention or a film having a vapor-deposited layer or a coating layer thereon, and an unstretched film, uniaxially stretched film, or biaxially stretched film formed from low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, or polyester.

[0135] (Method for fabricating laminated composites)

[0136] A laminate containing a heat-sealable polyolefin resin layer on a biaxially oriented polypropylene film of the present invention can be used to manufacture packaging containers with excellent filling and storage properties for chemicals such as food, pharmaceuticals, detergents, shampoos, oils, toothpaste, adhesives, and other chemicals or cosmetics.

[0137] As a heat-sealable polyolefin resin layer, films or sheets of resins that can be melted and fused together by heat can be used. Specifically, films or sheets of, for example, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear (linear) low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-propylene copolymer, methylpentene polymer, polybutene polymer, acid-modified polyolefin resins obtained by modifying polyolefin resins such as polyethylene or polypropylene with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, polyvinyl acetate resins, poly(meth)acrylic acid resins, polyvinyl chloride resins, and various other resins can be used. Representative examples are films or sheets formed from linear (linear) low-density polyethylene or polypropylene.

[0138] The upper limit of oxygen permeability of the laminate at 23°C and 65% relative humidity is preferably 50 mL / m³. 2 / day / MPa, more preferably 30mL / m 2 / day / MPa, further optimized to 20mL / m 2 / day / MPa, with a preferred 15mL / m 2 / day / MPa. If the upper limit of oxygen permeability is 50mL / m 2 At a pressure of / MPa / day, substances and foods that would otherwise deteriorate due to oxygen exhibit excellent preservation properties. There is no particular limitation on the lower limit of oxygen permeability for laminated polypropylene films at 23°C and 65% humidity, but 0.1 mL / m² is preferred. 2 / day / MPa. Additionally, from a manufacturing perspective, 0.1mL / m 2 / day / MPa is the lower limit.

[0139] Example

[0140] The present invention will be further described in detail below with reference to embodiments. However, the following embodiments do not limit the present invention. Any modifications made without departing from the spirit of the present invention are included in the present invention.

[0141] (Determination Method)

[0142] The raw materials used in the examples and comparative examples, and the methods for determining the physical properties of the resulting films, are described below.

[0143] 1) Meso-five-unit component ratio ([mmmm] unit: %)

[0144] Determination of the proportion of racemic five-unit components 13The C-NMR was performed. The proportions of the racemic pentagonal components were calculated according to the method described in "Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973)". 13 C-NMR determination was performed using a BRUKER AVANCE 500. 200 mg of the sample was dissolved in a mixture of o-dichlorobenzene and deuterated benzene in a volume ratio of 8:2 at 135 °C, and the determination was carried out at 110 °C.

[0145] 2) Melt flow rate ([MFR] g / 10 min)

[0146] The measurements were performed according to JIS K7210 at a temperature of 230℃ and a load of 2.16 kgf.

[0147] In the case of raw resin, the required amount of granules (powder) is measured directly and used.

[0148] In the case of a thin film, after cutting out the required amount, use a sample cut to approximately 5 mm square.

[0149] 3) Molecular weight and molecular weight distribution

[0150] The molecular weight and molecular weight distribution of the raw resin and film were determined using gel permeation chromatography (GPC) based on monodisperse polystyrene. The measurement conditions, including the column and solvent used in the GPC determination, are described below.

[0151] Solvent: 1,2,4-trichlorobenzene

[0152] Column: TSKgel GMHHR-H(20)HT×3

[0153] Flow rate: 1.0 ml / minute

[0154] Detector: RI

[0155] Measurement temperature: 140℃

[0156] Number-average molecular weight (Mn), mass-average molecular weight (Mw), and molecular weight distribution (Mw / Mn) are respectively determined based on the molecular weight (Mn) at each elution position of the GPC curve obtained using a molecular weight correction curve. i The number of molecules (N) i ), is defined by the following formula.

[0157] Number-average molecular weight: Mn=Σ(N i ·M i ) / ΣN i

[0158] Mass-average molecular weight: Mw=Σ(N i ·M i 2) / Σ(N i ·M i )

[0159] Molecular weight distribution: Mw / Mn

[0160] When the baseline is unclear, the baseline is set up to the lowest point of the base of the elution peak on the high molecular weight side that is closest to the elution peak of the standard substance.

[0161] 4) Melting peak temperature (°C), melting peak area (J / g)

[0162] The SII differential scanning calorimeter (DSC) was used for the determination of a sample amount of 10 mg and a heating rate of 20 °C / min. The melting endothermic peak temperature and melting peak area were determined from the DSC curve.

[0163] 5) Thickness (μm)

[0164] The thickness of each layer, including the substrate layer (A) and the surface layer (B), was determined by cutting out the cross section of the biaxially stretched laminated polypropylene film cured with modified polyurethane resin using a slicing machine, and then observing and measuring it using a differential interference microscope.

[0165] 6) Haze (%)

[0166] The measurements were performed according to JIS K 7105 at 23°C. A haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., 300A) was used. It should be noted that the measurements were performed twice, and the average value was calculated.

[0167] 7) Tensile modulus (GPa)

[0168] The measurements were performed according to JIS K 7127. Samples with a width of 10 mm and a length of 180 mm were cut along the longitudinal and width directions of the film using a razor. After being placed at 23°C and 65% RH for 12 hours, the measurements were performed at 23°C and 65% RH with a chuck spacing of 100 mm and a tensile speed of 200 mm / min. The average of five measurements was used. The measuring apparatus used was an Autograph AG5000A manufactured by Shimadzu Corporation.

[0169] 8) Thermal shrinkage rate

[0170] According to JIS Z 1712, the following method was used for measurement: The film was cut into sections 20 mm wide and 200 mm long along its longitudinal and width directions, and then suspended in a hot air oven at 150°C for 5 minutes. The length after heating was measured, and the heat shrinkage rate was calculated as the ratio of the shrunken length to the original length.

[0171] 9) Wetting tension (mN / m)

[0172] According to K 6768:1999, after the film was cured at 23°C and 50% relative humidity for 24 hours, the surface layer (B) of the film was measured according to the following steps.

[0173] Step 1)

[0174] The measurements were conducted in a standard laboratory atmosphere (refer to JIS K 7100) at a temperature of 23°C and a relative humidity of 50%.

[0175] Step 2)

[0176] Place the test piece on the substrate of the hand coating machine (4.1), add a few drops of the test mixture to the test piece, and immediately pull the wire bar to spread it.

[0177] When using a cotton swab or brush to spread the test solution, the liquid should spread rapidly to at least 6 cm. 2 The area above. The amount of liquid is set to a level that does not accumulate and forms a thin layer.

[0178] Observe the liquid film of the test mixture in a bright light, and determine the wetting tension after 3 seconds. Wetting is defined as the liquid film remaining intact for more than 3 seconds without breaking. If wetting is maintained for more than 3 seconds, proceed to the mixture with a high surface tension. Conversely, if the liquid film breaks in less than 3 seconds, proceed to the mixture with a low surface tension.

[0179] Repeat this process, selecting a mixture that can accurately wet the surface of the test piece within 3 seconds.

[0180] Step 3)

[0181] Use fresh cotton swabs in each test. For brushes or wire rods, residual liquid can alter composition and surface tension due to evaporation; therefore, clean with methanol and dry after each use.

[0182] Step 4)

[0183] Perform at least three operations to select a mixture capable of wetting the surface of the test piece within 3 seconds. Report the surface tension of the selected mixture as the wetting tension of the film.

[0184] 10) Martens hardness (N / mm) 2 )

[0185] The obtained film was cut into approximately 2 cm squares. The opposite sides of the test surface were then fixed to a glass plate approximately 1 mm thick using adhesive. The sample was then placed at 23°C and 50% RH for 12 hours to allow for humidity adjustment. The test surface was designated as surface layer (B). For this sample, a dynamic microhardness tester (Shimadzu DUH-211) was used, and measurements were performed according to the method based on ISO 14577-1 (2002) under the following conditions. Ten measurements were performed with the film position changed, and the average value of the eight points excluding the maximum and minimum values ​​was calculated.

[0186] <Measurement Conditions>

[0187] (set up)

[0188] • Measurement environment: Temperature 23℃ / Relative humidity 50%

[0189] • Test mode: Load-unloading test

[0190] • Use indenter: 115-degree angle between edges, triangular pyramid indenter

[0191] • Elastic modulus of the indenter: 1.140×10⁶ N / mm 2

[0192] • Poisson's ratio of pressure head: 0.07

[0193] • Cf-Ap, As correction: present

[0194] (condition)

[0195] • Test force: 0.10 mN

[0196] • Loading speed: 0.0050 mN / s

[0197] • Load holding time: 5 seconds

[0198] • Uninstallation retention time: 0 seconds

[0199] 11) Number of protrusions

[0200] The surface area of ​​the surface layer (B) of the obtained thin film is 2000 μm. 2 The number of protrusions larger than 500 nm was determined using a three-dimensional roughness tester (manufactured by Kosaka Research Institute Co., Ltd., model ET-30HK). Under a stylus pressure of 20 mg, the test was conducted with a measurement length of 1 mm in the X direction, a feed speed of 100 μm / s, a feed spacing of 2 μm in the Y direction, a measurement magnification of 20,000 times in the height direction, and a cutoff of 80 μm. The height from the reference height was calculated, and the number of protrusions larger than 500 nm was calculated.

[0201] For the number of protrusions, three trials were conducted, and the average value was used for evaluation.

[0202] 12) Arithmetic mean roughness (Ra) (nm)

[0203] The arithmetic mean roughness (Ra) of the surface layer (B) of the thin film was measured using a scanning probe microscope (Shimadzu SPM-9700). Measurements were performed in dynamic mode within a 2 μm measurement range in both the X and Y directions. After correcting the obtained images (slope adjustment, line fitting, noise removal), the arithmetic mean roughness was calculated according to the definition in JIS-B0601 (1994).

[0204] 13) Surface resistivity (LogΩ)

[0205] According to JIS K6911, after the film was cured at 23°C for 24 hours, the surface layer (B) of the film was measured.

[0206] 14) Evaluation of film roll wrinkles

[0207] The biaxially oriented polypropylene film is wound into rolls 600 mm wide and 1500 m long. The wrinkles on the surface of the roll are evaluated and judged visually according to the following criteria. ◎ and ○ are marked as acceptable.

[0208] ◎: No wrinkles.

[0209] 〇: Although there are weak wrinkles, the wrinkles disappear when a tension of about 5 N / m is applied to the stretched film.

[0210] △: Although there are weak wrinkles, the wrinkles disappear when a tension of about 20 N / m is applied to the stretched film.

[0211] ×: It has strong wrinkles, and even if a tension of about 20 N / m is applied to the stretched film, the wrinkles will not disappear.

[0212] 15) Coating suitability evaluation

[0213] A coating solution with a solid content of 5% was prepared by dissolving butanediol-vinyl alcohol copolymer (manufactured by Nichigo-G-ploymer-OKS-8049, Japan Synthetic Chemical Industry Co., Ltd.) in a 15% aqueous solution of isopropanol. The prepared coating solution was then dropped onto the surface layer (B) of the film cut from the film roll, using a Mayer rod #3, to achieve a dry coating of 0.2 g / m³. 2 The coating is applied using a specific coating amount. Afterwards, the solution is allowed to evaporate completely in a dryer, and the coating layer is visually evaluated for rejection. Marks of ◎ or ○ indicate acceptance.

[0214] ◎: Rejection without coating layer.

[0215] 0: 90% rejection without coating layer, but slight rejection.

[0216] △: The proportion of rejection in areas with coating is less than 90%, while the proportion of rejection in areas without coating is less than 90%.

[0217] ×: The repulsion of the coating layer is located on the entire surface.

[0218] 16) Evaluation of the adhesion of aluminum vapor-deposited film

[0219] Using a small vacuum evaporation apparatus (ULVAC Kiko Co., Ltd., VWR-400 / ERH), aluminum film was deposited on the surface layer (B) of the film unwound from the film roll with an aluminum film thickness of 30 nm. On the deposited surface of the resulting film, an 18 mm wide cellotape (registered trademark) manufactured by Nichiban Company Limited was used to evaluate the adhesion of the aluminum film using the 90° peel method. A score of 0 was recorded as acceptable.

[0220] ○: Peeling off aluminum-free vapor-deposited film.

[0221] △: Localized peeling of aluminum vapor-deposited film.

[0222] ×: There is peeling of aluminum vapor-deposited film on the entire surface.

[0223] (Raw material resin)

[0224] Details of the polypropylene resin raw materials used in the following examples and comparative examples, as well as the film-forming conditions, are shown in Tables 1 to 3.

[0225] The masterbatch of silicone particles used as an anti-blocking agent as listed in Table 2 is as follows: For the polypropylene resin, a propylene homopolymer (Novatec PP "FL203D" manufactured by Japan Polypropylene Corporation, registered trademark: 0 mol% comonomer; hereinafter abbreviated as "PP-1") with Mn=56000, Mw=310000, MFR=2.5 g / 10 min, and meso-pentamericanthropoietin component ratio [mmmm]=94.8% as shown in Table 1 is used. The silicone particles used as the anti-blocking agent have a particle size of 2.0 μm and an anti-blocking agent content of 50000 ppm. Additionally, the masterbatch of silica particles listed in Table 2 has a particle size of 2.7 μm and an anti-blocking agent content of 50000 ppm.

[0226] [Table 1]

[0227]

[0228] [Table 2]

[0229]

[0230] [Table 3]

[0231] Melting resin temperature (°C) 250 250 250 Cooling roller temperature (°C) 40 30 30 Longitudinal stretch ratio (times) 4.5 4.5 4.5 Longitudinal tensile temperature (°C) 125 125 125 Width-direction stretch ratio (times) 82 82 8.2 Width-direction stretching preheating temperature (°C) 174 168 175 Tensile temperature in the width direction (°C) 158 155 166 Heat setting temperature (°C) 175 165 171 Relaxation rate in the width direction (%) 6.7 6.7 6.7

[0232] (Example 1)

[0233] The substrate layer (A) uses a blend of: a propylene homopolymer (PP "FS2012" manufactured by Sumitomo Chemical Co., Ltd.: comonomer content of 0 mol%; hereinafter referred to as "PP-2") with Mn=81000, Mw=320000, MFR=2.2 g / 10 min and mesopentanoic pentanoic component ratio [mmmm]=99.2% as shown in Table 1, and a propylene homopolymer (PP "FLX80E4" manufactured by Sumitomo Chemical Co., Ltd.: comonomer content of 0 mol%; hereinafter referred to as "PP-3") with Mn=65000, Mw=240000, MFR=7.5 g / 10 min and mesopentanoic pentanoic component ratio [mmmm]=98.9% as shown in Table 1, and a propylene homopolymer (PP "FLX80E4" manufactured by Sumitomo Chemical Co., Ltd.: comonomer content of 0 mol%; hereinafter referred to as "PP-3") with Mn=65000, Mw=240000, MFR=7.5 g / 10 min and mesopentanoic pentanoic component ratio [mmmm]=98.9% as shown in Table 1.

[0234] In addition, the surface layer (B) uses a mixture of 24.8% by weight of a propylene polymer with Mn=55000, Mw=300000, MFR=5.6 g / 10 min (Novatec PP "FL4" manufactured by Japan Polypropylene Corporation: abbreviated as "PP-5"), 72.2% by weight of a propylene polymer with Mn=59000, Mw=310000, MFR=5.3 g / 10 min (Primepolypro "F-300SP" manufactured by Prime Polymer Co., Ltd.: abbreviated as "PP-6"), and 3.0% by weight of masterbatch A shown in Table 2.

[0235] The substrate layer (A) was extruded using a 45mm extruder, the surface layer (B) using a 25mm extruder, and the second surface layer (B) using a 20mm extruder. The raw resin was melted at 250°C and co-extruded in sheet form from a T-die. After cooling and curing with a 40°C cooling roller in contact with the surface layer (B), the film was stretched to 4.5 times its original length along the longitudinal direction (MD) at 125°C. Then, in a tenter frame, the film was clamped at both ends along the width direction (TD) and preheated to 174°C. It was then stretched to 8.2 times its original length along the width direction (TD) at 158°C, relaxed by 6.7% along the width direction (TD), and heat-set at 175°C. These film-forming conditions are denoted as film-forming condition a.

[0236] Thus, a biaxially oriented polypropylene film consisting of surface layer (B), substrate layer (A), and second surface layer (B) is obtained.

[0237] Using a corona treatment machine manufactured by SOFTAL Corona & Plasma GmbH, the surface of the surface layer (B) of a biaxially oriented polypropylene film was corona treated with an applied current of 0.75 A, and then wound up using a winding machine. The resulting film thickness was 20 μm (the thicknesses of the surface layer (B) / substrate layer (A) / second surface layer (B) were 1.0 μm / 18.0 μm / 1.0 μm).

[0238] (Example 2)

[0239] For surface layer (B) and second surface layer (B), a compound was prepared by mixing 4.0% by weight of masterbatch A shown in Table 2, 23.8% by weight of PP-5, and 72.2% by weight of PP-6, except that the conditions were the same as in Example 1, to obtain a 20 μm biaxially oriented polypropylene film.

[0240] (Example 3)

[0241] The surface layer (B) and the second surface layer (B) were prepared by blending 6.0 wt% of masterbatch B shown in Table 2, 55.3 wt% of PP-5, and 39.7 wt% of PP-6. Otherwise, under the same conditions as in Example 1, a 20 μm biaxially oriented polypropylene film was obtained.

[0242] (Comparative Example 1)

[0243] The substrate layer (A) uses a 100% by weight propylene homopolymer (PP "FL203D" manufactured by Japan Polypropylene Corporation: comonomer content is 0 mol%; hereinafter referred to as "PP-1") with Mn = 56000, Mw = 310000, MFR = 2.5 g / 10 min, and meso-five-unit component ratio [mmmm] = 94.8%, as shown in Table 1.

[0244] In addition, the surface layer (B) uses a mixture of 52% by weight of a propylene-ethylene copolymer (Wintec PP "WFX4M" manufactured by Japan Polypropylene Corporation, registered trademark, abbreviated as "PP-4") with Mn=80000, Mw=220000, and MFR=7.0 g / 10 min as shown in Table 1, 43.2% by weight of PP-1, and 4.8% by weight of masterbatch B as shown in Table 2.

[0245] The second surface layer (B) is made of a mixture of 93.6% by weight PP-1 and 6.4% by weight masterbatch B.

[0246] The substrate layer (A) was extruded using a 45mm extruder, the surface layer (B) using a 25mm extruder, and the second surface layer (B) using a 20mm extruder. The raw resin was melted at 250°C and co-extruded in sheet form from a T-die. After cooling and curing with a 30°C cooling roller in contact with the surface layer (B), it was stretched to 4.5 times its original length along the longitudinal direction (MD) at 125°C. Then, in a tenter frame, the film was clamped at both ends along the width direction (TD) and preheated to 168°C. It was then stretched to 8.2 times its original length along the width direction (TD) at 155°C, relaxed by 6.7% along the width direction (TD), and heat-set at 165°C. These film-forming conditions are denoted as film-forming condition b.

[0247] Thus, a biaxially oriented polypropylene film consisting of surface layer (B), substrate layer (A), and second surface layer (B) is obtained.

[0248] Using a corona treatment machine manufactured by SOFTAL Corona & Plasma GmbH, the surface of the surface layer (B) of a biaxially oriented polypropylene film was corona treated with an applied current of 0.75 A, and then wound up using a winding machine. The resulting film thickness was 20 μm (the thicknesses of the surface layer (B) / substrate layer (A) / second surface layer (B) were 1.3 μm / 17.7 μm / 1.0 μm).

[0249] (Comparative Example 2)

[0250] The discharge rate of the resin self-extruder was adjusted so that the thickness of the substrate layer (A) was 15.1 μm and the thickness of the surface layer (B) was 3.9 μm. Otherwise, the conditions were the same as those in Comparative Example 1, and a 20 μm biaxially oriented polypropylene film was obtained.

[0251] (Comparative Example 3)

[0252] The surface layer (B) was prepared by mixing polypropylene homopolymer PP-1 shown in Table 1 at a ratio of 45.0% by weight, ethylene copolymer polypropylene polymer PP-3 shown in Table 1 at a ratio of 52.0% by weight, and masterbatch B shown in Table 2 at a ratio of 3.0% by weight. Otherwise, the conditions were the same as those in Comparative Example 1, and a biaxially oriented polypropylene film with a diameter of 20 μm was obtained.

[0253] (Comparative Example 4)

[0254] The surface layer (B) was prepared by mixing polypropylene homopolymer PP-1 shown in Table 1 at a ratio of 1.2% by weight, ethylene copolymer polypropylene polymer PP-3 shown in Table 1 at a ratio of 94.0% by weight, and masterbatch B shown in Table 2 at a ratio of 4.8% by weight. Otherwise, the conditions were the same as those in Comparative Example 1, and a biaxially oriented polypropylene film with a diameter of 20 μm was obtained.

[0255] (Comparative Example 5)

[0256] By changing the film-forming conditions as described below, and otherwise setting them to the same conditions as Comparative Example 1, a 20 μm biaxially oriented polypropylene film was obtained.

[0257] The substrate layer (A) was extruded using a 45mm extruder, the surface layer (B) using a 25mm extruder, and the second surface layer (B) using a 20mm extruder. The raw resin was melted at 250°C and co-extruded in sheet form from a T-die. After cooling and curing with a 30°C cooling roller in contact with the surface layer (B), it was stretched to 4.5 times its original length in the longitudinal direction (MD) at 125°C. Then, in a tenter frame, the two ends of the film in the width direction (TD) were clamped with fixtures, preheated to 175°C, stretched to 8.2 times its original length in the width direction (TD) at 166°C, relaxed by 6.7% in the width direction (TD), and then heat-set at 171°C.

[0258] Let the film-forming conditions at this time be denoted as film-forming condition c.

[0259] (Comparative Example 6)

[0260] In surface layer B, PP-1 was mixed at a ratio of 95.2% by weight and masterbatch B at a ratio of 4.8% by weight. Otherwise, the conditions were the same as those in Comparative Example 1, and a 20 μm biaxially oriented polypropylene film was obtained.

[0261] The raw materials / manufacturing methods and physical properties of the films used in the above embodiments and comparative examples are shown in Tables 4 and 5.

[0262] [Table 4]

[0263]

[0264] [Table 5]

[0265]

[0266] The biaxially oriented polypropylene films obtained in Examples 1-3 exhibit excellent wrinkle-free properties in the film roll. Furthermore, there is no peeling of the aluminum vapor deposit and no rejection of the coating liquid, resulting in excellent adhesion.

[0267] In contrast, the film rolls of Comparative Examples 1 to 6 all had poor winding quality and / or poor adhesion.

[0268] Industrial availability

[0269] The biaxially oriented polypropylene film of the present invention does not impair the excellent transparency and mechanical properties of the original biaxially oriented polypropylene film, has excellent winding quality, and exhibits excellent adhesion to the adhesive layer in the lamination of the vapor-deposited layer, coating layer, and other component films.

[0270] Therefore, it is suitable for processing raw materials. It can be used for food packaging, labels, and industrial films, such as those used in snacks. In addition, the film can be manufactured inexpensively, making it useful in industry.

Claims

1. A biaxially oriented polypropylene film having a substrate layer (A) comprising 70% by weight or more of a polypropylene resin, wherein the polypropylene resin is at least one of a polypropylene homopolymer without copolymer components and a polypropylene resin copolymerized with ethylene and / or an α-olefin having 4 or more carbon atoms at less than 0.5 mol% Furthermore, the biaxially oriented polypropylene film has a surface layer (B) that satisfies the following (1) to (7) and contains more than 80% by weight of the polypropylene resin. (1) Surface area 2000μm 2 The number of protrusions larger than 500nm is between 50 and 200. (2) The surface wetting tension is above 38 mN / m. (3) The surface martensitic hardness is 350 N / mm. 2 the following, (4) The arithmetic mean roughness of the surface is greater than 1.5 nm and less than 3.0 nm. (5) Surface resistivity is above 14 LogΩ. (6) The surface layer (B) contains an anti-blocking agent, the amount of which is above 400 ppm and below 4000 ppm. (7) The surface layer (B) contains an anti-blocking agent with an average particle size of more than 1.0 μm and less than 3.0 μm.

2. The biaxially oriented polypropylene film according to claim 1, wherein, The haze value of the film is below 6%.

3. The biaxially oriented polypropylene film according to claim 1 or 2, wherein, The tensile modulus of the film in the longitudinal direction is above 2.0 GPa, and the tensile modulus in the width direction is above 3.0 GPa.

4. The biaxially oriented polypropylene film according to claim 1 or 2, wherein, The film thickness is greater than 5 μm and less than 200 μm.

5. A laminate, which is a laminate of a biaxially oriented polypropylene film and an unstretched polypropylene film as described in claim 1 or 2.

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