Biaxially oriented polypropylene film

Abstract

Provided is a biaxially oriented polypropylene film made of a polypropylene resin composition comprising 87-99 mass% polypropylene resin and 1-13 mass% alicyclic hydrocarbon resin, the biaxially oriented polypropylene film satisfying the following requirements (1) and (2). (1) To have a thickness of 65-200 μm. (2) To have a width-direction thickness unevenness of 8.0% or less per 1,000 mm.

Description

Biaxially oriented polypropylene film

[0001] The present invention relates to a biaxially oriented polypropylene film useful as a process film, a release film, an adhesive label, etc.

[0002] Traditionally, biaxially oriented polypropylene film has been used in a wide range of applications, including packaging for food and various other products, release films, adhesives, labels, surface protection, and electrical insulation. However, biaxially oriented polyester (PET) film is generally used as processing film, release film, and adhesive film. Biaxially oriented polypropylene film has a lower specific gravity than PET film, which allows for weight reduction. It is also expected to be more efficient to recycle, so its use as processing film is highly anticipated. However, with biaxially oriented polypropylene film, it is necessary to increase the film thickness and improve dimensional stability at high temperatures in order to achieve strong stiffness.

[0003] Patent Documents 1 to 3 disclose thick biaxially oriented polypropylene films. However, these films have poor dimensional stability at high temperatures and have large thickness variations and poor thickness uniformity. On the other hand, Patent Documents 4 and 5 disclose biaxially oriented polypropylene films for food packaging that have improved water vapor barrier properties by blending a hydrogenated petroleum resin. However, these documents do not describe thick biaxially oriented polypropylene films for use in resin sheet manufacturing processes.

[0004] Japanese Patent No. 3700995 JP 2008-111055 A JP 2008-189795 A JP 2018-167867 A JP 10-278198 A

[0005] The first object of the first invention is to solve the above-mentioned problems. That is, to stably obtain a thick biaxially oriented polypropylene film with strong stiffness and little thickness unevenness. In particular, to provide a thick biaxially oriented polypropylene film with little thickness unevenness that is suitable for use as a process film in the production of resin sheets such as polyurethane resins.

[0006] The second object of the second invention is to solve the above-mentioned problems. That is, to stably obtain a thick biaxially oriented polypropylene film with a strong stiffness and little thickness unevenness, and a matte finish. In particular, to provide a thick biaxially oriented polypropylene film with little thickness unevenness that is suitable for use as a process film in the production of resin sheets such as polyurethane resins.

[0007] As a result of extensive research to achieve the first object, the present inventors have arrived at the first invention described in [1] to [4] below. The present inventors have discovered that suppressing excessive crystallization of the polypropylene resin composition is effective in reducing thickness unevenness in biaxially oriented polypropylene films. Furthermore, by adjusting the content of the alicyclic hydrocarbon resin and the biaxial stretching conditions, they have been able to obtain biaxially oriented polypropylene films with strong stiffness, dimensional stability at high temperatures, and little thickness unevenness. [1] A biaxially oriented polypropylene film made from a polypropylene resin composition containing 87% by mass or more and 99% by mass or less of a polypropylene resin and 1% by mass or more and 13% by mass or less of an alicyclic hydrocarbon resin, wherein the biaxially oriented polypropylene film satisfies the following requirements (1) and (2): (1) The thickness is 65 μm or more and 200 μm or less. (2) The thickness unevenness within 1000 mm in the width direction is 8.0% or less. [2] The biaxially oriented polypropylene film according to [1], wherein the biaxially oriented polypropylene film satisfies the following requirements (3) and (4): (3) The heat shrinkage rate at 120°C in the longitudinal direction is 0.0% or more and 6.0% or less. (4) The heat shrinkage rate at 120°C in the width direction is -3.0% or more and 5.0% or less. [3] The biaxially oriented polypropylene film according to [1] or [2], wherein the biaxially oriented polypropylene film satisfies the following requirements (5) and (6): (5) The stress at 5% elongation in the longitudinal direction (F5MD) is 30 MPa or more and 60 MPa or less. (6) The stress at 5% elongation in the width direction (F5TD) is 40 MPa or more and 150 MPa or less. [4] The biaxially oriented polypropylene film according to any one of [1] to [3], wherein the melting point of the polypropylene resin is 155°C or more and 175°C or less.

[0008] As a result of extensive research to achieve the second object, the present inventors have arrived at the second invention described in [5] to

[13] below. The present inventors have discovered that suppressing excessive crystallization of the polypropylene resin composition is effective in reducing thickness unevenness in biaxially oriented polypropylene films. Furthermore, by adjusting the content of the alicyclic hydrocarbon resin and the biaxial stretching conditions, they have been able to obtain a biaxially oriented polypropylene film with strong stiffness, dimensional stability at high temperatures, and little thickness unevenness. [5] A biaxially oriented polypropylene film comprising a base layer made of a polypropylene resin composition containing 87% by mass or more and 99% by mass or less of a polypropylene resin and 1% by mass or more and 13% by mass or less of an alicyclic hydrocarbon resin, and a matte layer made of a resin composition laminated on at least one side thereof, the biaxially oriented polypropylene film satisfying the following requirements (7) to (9): (7) The thickness is 65 μm or more and 200 μm or less; and (8) The thickness unevenness within 1000 mm in the width direction is 8.0% or less. (9) The haze is 30% or more and 90% or less. [6] The biaxially oriented polypropylene film according to [5], which satisfies the requirements (10) and (11) below. (10) The heat shrinkage rate at 120°C in the longitudinal direction is 0.0% or more and 6.0% or less. (11) The heat shrinkage rate at 120°C in the width direction is -3.0% or more and 5.0% or less. [7] The biaxially oriented polypropylene film according to [5] or [6], which satisfies the requirements (12) and (13) below. (12) The stress at 5% elongation in the longitudinal direction (F5MD) is 30 MPa or more and 60 MPa or less. (13) The stress at 5% elongation in the width direction (F5TD) is 40 MPa or more and 150 MPa or less. [8] The biaxially oriented polypropylene film according to any one of [5] to [7], wherein the surface average roughness SRa of the surface of the matte layer is 0.20 μm or more and 1.50 μm or less. [9] The biaxially oriented polypropylene film according to any one of [5] to [8], wherein the resin composition constituting the matte layer contains 3% by mass or more and 60% by mass or less of a polyethylene resin.

[10] The biaxially oriented polypropylene film according to any one of [5] to [9], wherein the resin composition constituting the matte layer contains 3% by mass or more and 60% by mass or less of a polypropylene copolymer copolymerized with ethylene and / or an α-olefin other than propylene.

[11] The biaxially oriented polypropylene film according to any one of [5] to

[10] , wherein the melting point of the polypropylene resin is 155° C. or higher and 175° C. or lower.

[12] A process film using the biaxially oriented polypropylene film according to any one of [5] to

[11] .

[13] A release film using the biaxially oriented polypropylene film according to any one of [5] to

[11] .

[0009] According to the first invention, a biaxially oriented polypropylene film having a strong stiffness and little thickness unevenness can be stably obtained. The biaxially oriented polypropylene film of the present invention is expected to reduce the weight of process films, release films, adhesive films, etc. by replacing PET films.

[0010] According to the second invention, a biaxially oriented polypropylene film having a strong stiffness and little thickness unevenness and a matte finish can be stably obtained. The biaxially oriented polypropylene film of the present invention is expected to reduce the weight of process films, release films, adhesive films, etc. by replacing PET films.

[0011] (First Invention) As described below, the biaxially oriented polypropylene film of the present invention is made of a polypropylene resin composition containing 87% by mass or more and 99% by mass or less of a polypropylene resin and 1% by mass or more and 13% by mass or less of an alicyclic hydrocarbon resin. When the polypropylene resin content is 87% by mass or more, a biaxially oriented polypropylene film with strong stiffness can be obtained by adjusting the film-forming conditions. When the alicyclic hydrocarbon resin content is 1% by mass or more and 13% by mass or less, biaxially oriented polypropylene film with little thickness unevenness can be obtained by smoothly performing biaxial stretching. The lower limit of the alicyclic hydrocarbon resin content is more preferably 3% by mass, and even more preferably 5% by mass. The upper limit of the alicyclic hydrocarbon resin content is more preferably 11% by mass, and even more preferably 10% by mass. When the alicyclic hydrocarbon resin content is 13% by mass or less, the 120°C heat shrinkage rate is easily reduced. Furthermore, raw material costs may also be reduced.

[0012] (1) Polypropylene Resin Composition (1-1) Polypropylene Resin The polypropylene resin used in the present invention may be a polypropylene homopolymer or a polypropylene copolymer containing an α-olefin other than propylene. However, it is preferable to use a polypropylene polymer that is substantially free of α-olefin components other than propylene. Specifically, a "polypropylene polymer that is substantially free of α-olefin components other than propylene" refers to a polypropylene copolymer having 1 mol% or less of α-olefin components other than propylene and 99 mol% or more of propylene as structural units. Even when α-olefin components other than propylene are contained, 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 0.8 mol% or less, and more preferably 0.7 mol% or less. Within the above range, crystallization is facilitated, stiffness is increased, and the 120°C heat shrinkage rate is easily reduced. Examples of the α-olefin component 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.

[0013] The polypropylene resin used in the present invention may be a mixture of two or more different polypropylene polymers, for example, two or more different polypropylene homopolymers, a polypropylene copolymer containing two or more different α-olefins other than propylene, or a mixture of one or more polypropylene homopolymers and one or more polypropylene copolymers containing one or more α-olefins other than propylene. In the case of a mixture of two or more different polypropylene polymers, it is preferable that the total content of the polypropylene polymers in the polypropylene resin composition is within the above range. By setting it within the above range, the polypropylene resin composition is strengthened and the 120°C heat shrinkage rate is easily reduced.

[0014] The following describes various suitable physical properties of the polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present invention. When two or more different polypropylene resins are used, the physical property values ​​are the mass average values ​​of the physical properties of each polypropylene resin.

[0015] The melting point of the polypropylene resin used in the present invention is preferably 155°C or higher, more preferably 156°C or higher. The melting point of the polypropylene resin used in the present invention is preferably 175°C or lower, more preferably 170°C or lower, even more preferably 169°C or lower, particularly preferably 168°C or lower, and most preferably 167°C or lower. When the melting point of the polypropylene resin is 155°C or higher, the 120°C heat shrinkage rate is easily reduced. When the melting point of the polypropylene resin is 175°C or lower, thickness unevenness can be reduced and the film is less likely to break during film formation. The melting point of the polypropylene resin is the main peak temperature of the endothermic peak accompanying melting, which is observed when 5 mg of polypropylene resin is packed into an aluminum pan, set in a differential scanning calorimeter (DSC), heated from 30°C to 230°C at a heating rate of 10°C / min in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin, then cooled to 30°C at a heating rate of -10°C / min, held at 30°C for 5 minutes, and then heated at a heating rate of 10°C / min.

[0016] The crystallization temperature of the polypropylene resin used in the present invention is preferably 105°C or higher, more preferably 108°C or higher, even more preferably 110°C or higher, even more preferably 112°C or higher, particularly preferably 114°C or higher, and most preferably 116°C or higher. The crystallization temperature of the polypropylene resin used in the present invention is preferably 135°C or lower, more preferably 133°C or lower, even more preferably 132°C or lower, even more preferably 130°C or lower, particularly preferably 128°C or lower, more particularly preferably 127°C or lower, and most preferably 116°C or lower. If the crystallization temperature is 105°C or higher, crystallization is likely to proceed during width direction stretching and the subsequent cooling process, increasing the stiffness and reducing the 120°C heat shrinkage rate. If the crystallization temperature is 135°C or lower, thickness unevenness can be reduced and the film is less likely to break during production. The crystallization temperature of the polypropylene resin is the main peak temperature of the exothermic peak observed when 5 mg of the polypropylene resin is packed into an aluminum pan, set in a DSC, heated from 30°C to 230°C at a heating rate of 10°C / min in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin, and then cooled to 30°C at a cooling rate of -10°C / min.

[0017] The melting point and crystallization temperature can be increased by blending a nucleating agent into the polypropylene resin. When a nucleating agent is blended, it is preferable that the melting point and crystallization temperature of the polypropylene resin blended with the nucleating agent be within the above ranges.

[0018] The mesopentad fraction ([mmmm]%), which is an index of stereoregularity of the polypropylene resin used in the present invention, is preferably 92% or more, more preferably 94% or more, and even more preferably 96% or more. The mesopentad fraction ([mmmm]%), which is an index of stereoregularity of the polypropylene resin used in the present invention, is preferably 99% or less, more preferably 98% or less, and even more preferably 97% or less. When the mesopentad fraction of the polypropylene resin is 92% or more, the 120°C heat shrinkage rate is easily reduced. When the mesopentad fraction of the polypropylene resin is 99% or less, thickness unevenness can be reduced and the film is less likely to break during film formation. The mesopentad fraction is measured by nuclear magnetic resonance spectroscopy (NMR spectroscopy). To adjust the mesopentad fraction of the polypropylene resin to fall within the above-mentioned range, for example, methods such as washing the obtained polypropylene resin powder with a solvent such as n-heptane or using an appropriate catalyst and / or co-catalyst may be used. The mesopentad fraction ([mmmm]%) was measured by 13 The mesopentad fraction can be calculated using C-NMR according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973). 13 C-NMR measurement can be performed using an AVANCE 500 manufactured by BRUKER, by dissolving 200 mg of a sample in a 8:2 mixture of o-dichlorobenzene and deuterated benzene at 135°C and at 110°C.

[0019] The melt flow rate (MFR) of the polypropylene resin constituting the biaxially oriented polypropylene film of the present invention, when measured in accordance with JIS K 7210 (1995), condition M (230°C, 2.16 kgf), is preferably 4.0 g / 10 min or more, more preferably 4.5 g / 10 min or more, even more preferably 4.8 g / 10 min or more, even more preferably 5.0 g / 10 min or more, particularly preferably 6.0 g / 10 min or more, and most preferably 7.5 g / 10 min or more. The melt flow rate (MFR) of the polypropylene resin constituting the biaxially oriented polypropylene film of the present invention, when measured in accordance with JIS K 7210 (1995) condition M (230°C, 2.16 kgf), is preferably 30 g / 10 min or less, more preferably 25 g / 10 min or less, even more preferably 22 g / 10 min or less, even more preferably 20 g / 10 min or less, and most preferably 15 g / 10 min or less. When the MFR of the polypropylene resin is 4.0 g / 10 min or more, the 120°C heat shrinkage rate is easily reduced. Furthermore, when the MFR of the polypropylene resin is 30 g / 10 min or less, thickness unevenness can be reduced and the film is less likely to break during production.

[0020] (1-2) Alicyclic Hydrocarbon Resin Examples of alicyclic hydrocarbon resins used in the present invention include alicyclic saturated hydrocarbon resins, alicyclic unsaturated hydrocarbon resins, aliphatic unsaturated hydrocarbon resins, aliphatic saturated hydrocarbon resins, aromatic hydrocarbon resins, hydrogenated aromatic hydrocarbon resins, rosin ester resins, hydrogenated rosin ester resins, terpene phenol resins, hydrogenated terpene phenol resins, terpene resins, hydrogenated terpene resins, aromatic hydrocarbon-modified terpene resins, coumarone-indene resins, phenol resins, and xylene resins. These may be used alone or in combination of two or more. Alicyclic saturated hydrocarbon resins are particularly preferred. By incorporating an alicyclic hydrocarbon resin in an amount of 1% by mass to 13% by mass, biaxial stretching can be carried out smoothly, resulting in a biaxially oriented polypropylene film with minimal thickness unevenness. The lower limit of the alicyclic hydrocarbon resin content is more preferably 3% by mass, and even more preferably 5% by mass. The upper limit of the alicyclic hydrocarbon resin content is more preferably 11% by mass, and even more preferably 10% by mass. An alicyclic hydrocarbon resin content of 13% by mass is sufficient to smoothly perform biaxial stretching and obtain a biaxially oriented polypropylene film with little thickness unevenness, but if the alicyclic hydrocarbon resin content exceeds 13% by mass, the dimensional stability at high temperatures may deteriorate. Furthermore, raw material costs may also increase. It is believed that the alicyclic hydrocarbon resin enables smooth stretching by suppressing excessive crystallization of polypropylene during the process of obtaining an unstretched sheet and the process of stretching in the longitudinal and transverse directions during film production.

[0021] (1-3) Other Additives Additives and other resins may be added to the polypropylene resin composition of the present invention as needed. Examples of additives include antioxidants, UV absorbers, antistatic agents, lubricants, nucleating agents, adhesives, antifogging agents, flame retardants, antiblocking agents, and inorganic or organic fillers. Other resins include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers of ethylene and α-olefins, and various elastomers. These may be blended with the polypropylene resin using a Henschel mixer, 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 and used. When the biaxially oriented polypropylene film of the present invention is used as a substrate film for a film-forming process, releasability, easy lubricity, antiblocking properties, and antistatic properties may be required. Therefore, it is preferable to add a lubricant, antiblocking agent, or antistatic agent.

[0022] (2) Film-forming method for biaxially oriented polypropylene film The biaxially oriented polypropylene film of the present invention is preferably obtained by preparing an unstretched sheet made of a polypropylene resin composition containing the above-mentioned polypropylene resin as a main component, and then biaxially stretching the sheet. Regarding biaxial stretching, it is preferable to stretch the sheet in the longitudinal direction and then in the width direction, but it may also be stretched in the width direction and then in the longitudinal direction. Examples of biaxial stretching methods include inflation simultaneous biaxial stretching, tenter simultaneous biaxial stretching, tenter sequential biaxial stretching, and tube stretching. From the viewpoints of film formation stability and reduced thickness unevenness, tenter sequential biaxial stretching is preferred. Below, a method for producing a biaxially oriented polypropylene film of the present invention will be described. Hereinafter, a method for producing a biaxially oriented polypropylene film using tenter sequential biaxial stretching will be described, but the present invention is not limited to the following production method.

[0023] First, a polypropylene resin composition is heated and melted in a single-screw or twin-screw extruder, extruded through a T-die into a sheet, and then cooled and solidified by contacting it with a cooling roll to obtain an unstretched sheet. Next, this unstretched sheet is stretched in the longitudinal direction between two pairs of heated stretching rolls by increasing the rotation speed of the rear stretching roll to obtain a uniaxially stretched film. Subsequently, the uniaxially stretched film is heated in a preheating step, then stretched in the width direction while gripping the film edges in a tenter-type stretching machine, heat-treated, and finally cooled to obtain a biaxially oriented polypropylene film. Below, the extrusion step, longitudinal stretching step, preheating step, width stretching step, heat-treatment step, and cooling step are described in this order.

[0024] <Extrusion Process> First, a polypropylene resin composition containing a polypropylene resin as a main component is heated and melted in a range of 200°C to 300°C using a single-screw or twin-screw extruder, and the sheet-shaped molten polypropylene resin composition is extruded from a T-die. The molten polypropylene resin composition is then brought into close contact with a metal cooling roll using a contacting device such as an air knife, and cooled and solidified to obtain an unstretched sheet. The obtained unstretched sheet is preferably further placed in a water bath. It is also preferable to actively cool the unstretched sheet by spraying cooling water on the side opposite the cooling roll. The extrusion temperature is preferably 220°C or higher, more preferably 240°C or higher. The extrusion temperature is preferably 270°C or lower, more preferably 260°C or lower. An extrusion temperature of 220°C or higher results in an unstretched sheet with good stretchability. An extrusion temperature of 270°C or lower suppresses thermal degradation of the polypropylene resin composition. The temperature of the cooling roll, or the temperature of the cooling roll and water bath, is preferably 0°C or higher. The temperature of the cooling roll, or the cooling roll and water bath, is preferably 40° C. or less, more preferably 30° C. or less, and even more preferably 20° C. or less. If the temperature of the cooling roll, or the cooling roll and water bath, is 40° C. or less, an unstretched sheet with good stretchability can be obtained, and a thick biaxially oriented polypropylene film with little thickness unevenness can be obtained. The lower limit of the temperature of the cooling roll, or the cooling roll and water bath, is preferably 0° C. from the viewpoints of economy and prevention of condensation.

[0025] <Longitudinal Stretching Step> The longitudinal stretching temperature is preferably 110°C or higher, and more preferably 120°C or higher. The longitudinal stretching temperature is preferably 140°C or lower, and more preferably 130°C or lower. When the longitudinal stretching temperature is 110°C or higher, the subsequent widthwise stretching becomes easier and thickness unevenness tends to be reduced. Furthermore, when the longitudinal stretching temperature is 140°C or lower, the film is less likely to stick to the stretching rolls, making stretching difficult, or to become rough on the surface, resulting in a decrease in quality. The longitudinal stretching ratio is preferably 3.5 times or higher, more preferably 3.8 times or higher, and even more preferably 4.2 times or higher. The longitudinal stretching ratio is preferably 4.8 times or lower, more preferably 4.7 times or lower, and even more preferably 4.6 times or lower. When the longitudinal stretching ratio is 3.5 times or higher, strength is easily increased and thickness unevenness tends to be reduced. Furthermore, when the stretching ratio in the longitudinal direction is 4.8 times or less, the stretching in the width direction is easy to perform in the width direction stretching step, and productivity is easily improved. The longitudinal stretching may be performed in two or more stages using three or more pairs of stretching rolls, but it is preferable to perform stretching in one stage using two pairs of stretching rolls. When stretching in multiple stages, it is preferable that the highest stretching temperature is within the above range.

[0026] <Preheating Step> It is preferable to heat the uniaxially stretched film after longitudinal stretching in the preheating step 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, more preferably 165°C or higher. The heating temperature in the preheating step is preferably 180°C or lower, more preferably 175°C or lower, and even more preferably 170°C or lower. By setting the heating temperature in the preheating step to 160°C or higher, softening progresses, making widthwise stretching easier. Furthermore, by setting the heating temperature in the preheating step to 180°C or lower, orientation progresses during widthwise stretching, making it easier for the resulting film to exhibit stress at 5% elongation. The heating temperature in the preheating step may be referred to as the preheating temperature. Note that when the preheating step consists of multiple zones, the temperature of the zone with the highest temperature among them is referred to as the preheating temperature.

[0027] <Width Direction Stretching Step> The width direction stretching temperature is preferably 155°C or higher, more preferably 160°C or higher, and even more preferably 163°C or higher. The width direction stretching temperature is preferably equal to or lower than the heating temperature in the preheating step. Specifically, for example, the width direction stretching temperature is more preferably 170°C or lower, and even more preferably 167°C or lower. When the width direction stretching temperature is 155°C or higher, the 120°C heat shrinkage rate of the obtained film is easily reduced. Furthermore, when the width direction stretching temperature is equal to or lower than the heating temperature in the preheating step, stretching unevenness is less likely to occur. The width direction stretching ratio is preferably more than 8 times, more preferably 9 times or higher, and even more preferably 10 times or higher. The width direction stretching ratio is preferably 15 times or lower, more preferably 13 times or lower, and even more preferably 12 times or lower. When the width direction stretching ratio is more than 8 times, the rigidity in the width direction is easily increased and thickness unevenness is also easily reduced. Furthermore, if the stretching ratio in the width direction is 15 times or less, the heat shrinkage rate can be easily reduced, and the film is less likely to break when stretched in the width direction.

[0028] <Heat Treatment Step> Heat treatment is carried out after the width direction stretching step is completed. Specific means for heat treatment include a method of providing a zone with a higher temperature than the stretching zone after the width direction stretching is completed, a method of increasing the zone temperature in the latter half of stretching and passing the film through a zone of the same temperature after the stretching is completed, etc. Heating means include a method of blowing hot air or a method of heating with an infrared heater, but are not particularly limited as long as the method is capable of increasing the temperature of the film from that at the end of the width direction stretching step.

[0029] The heat treatment step is preferably carried out immediately after the width direction stretching step is completed (i.e., immediately after the width direction stretching reaches the final stretch ratio). The heating temperature in the heat treatment step is preferably higher than that at the end of the width direction stretching step, specifically, preferably the width direction stretching temperature + 1°C or more. The heating temperature in the heat treatment step may be referred to as the heat treatment temperature.

[0030] The heating temperature in the heat treatment step is preferably 151°C or higher, more preferably 153°C or higher, and even more preferably 155°C or higher. The heating temperature in the heat treatment step is preferably 180°C or lower, more preferably 170°C or lower, and even more preferably 165°C or lower. By heating in the heat treatment step after the stretching step, the molecular chain orientation formed during stretching is relaxed, and the heat shrinkage rate can be reduced. In the heat treatment step, the film may or may not be relaxed (relaxed) in the width direction. When the film is relaxed in the width direction, the relaxation rate is preferably 1% or higher, more preferably 3% or higher, and even more preferably 5% or higher. When the film is relaxed in the width direction, the relaxation rate is preferably 12% or lower, more preferably 10% or lower, and even more preferably 8% or lower. When the film is relaxed in the width direction, the relaxation rate within the above range makes it easy to reduce the 120°C heat shrinkage rate while maintaining the stress of the resulting film at 5% elongation. However, if it is desired to increase the stress of the resulting film at 5% elongation, the film does not need to be relaxed in the width direction.

[0031] <Cooling Step> It is preferable to cool the film immediately after the heat treatment step. The cooling temperature is preferably 10°C or higher, more preferably 15°C or higher, and even more preferably 20°C or higher. The cooling temperature is preferably 140°C or lower, more preferably 135°C or lower, even more preferably 130°C or lower, particularly preferably 80°C or lower, and most preferably 50°C or lower. By providing a cooling step, the state of molecular orientation within the film can be fixed.

[0032] The method for producing a biaxially oriented polypropylene film has been described above. The biaxially oriented polypropylene film of the present invention may have a functional layer (hereinafter referred to as a functional layer) laminated on at least one side, or may be used as a single layer. The functional layer may be laminated on only one side or on both sides. The lamination method is not particularly limited. For example, coextrusion using a feed block method or a multi-manifold method is preferred. When the biaxially oriented polypropylene film of the present invention is used as a substrate film for a film-forming process, it is preferable that the film has releasability, easy lubricity, antiblocking properties, and antistatic properties, and therefore it is preferable to add a lubricant, antiblocking agent, or antistatic agent to the functional layer.

[0033] The biaxially oriented polypropylene film of the present invention can be wound into a roll to form a film roll having a width of 2000 mm to 12000 mm and a length of about 1000 m to 50000 m, making it possible to obtain a long film roll. In addition, slits may be formed in the film to suit each application, and the film can also be made into a slit roll having a width of 300 mm to 2000 mm and a length of 500 m to 5000 m.

[0034] (3) Properties of Biaxially Oriented Polypropylene Film The biaxially oriented polypropylene film of the present invention preferably has the following properties. Here, the "longitudinal direction (MD direction)" of the biaxially oriented polypropylene film of the present invention refers to the direction corresponding to the flow direction in the film production process, and the "width direction (TD direction)" refers to the direction perpendicular to the flow direction in the film production process, and the same applies hereinafter. For polypropylene films whose flow direction in the film production process is unknown, wide-angle X-rays are incident perpendicular to the film surface, and the scattering peak derived from the (110) plane of the α-crystals is scanned in the circumferential direction. The direction with the greatest diffraction intensity in the obtained diffraction intensity distribution is defined as the "longitudinal direction," and the direction perpendicular to that is defined as the "width direction."

[0035] <Thickness> The thickness of the biaxially oriented polypropylene film of the present invention is 65 μm or more and 200 μm or less. A thickness of 65 μm or more provides sufficient stiffness for use as a process film or label. Furthermore, a thickness of 200 μm or less makes it easier to obtain a film with little thickness unevenness. The thickness of the biaxially oriented polypropylene film may be 70 μm or more, or 73 μm or more. The thickness of the biaxially oriented polypropylene film may be 150 μm or less, or 100 μm or less.

[0036] <Thickness Unevenness> Even in the case of a thick film, the biaxially oriented polypropylene film of the present invention has a thickness unevenness of 8.0% or less within 1000 mm in the width direction. A low thickness unevenness of 8.0% or less makes it easier to improve the thickness uniformity of a resin sheet when used as a process film in the production of a resin sheet. The thickness unevenness of the biaxially oriented polypropylene film within 1000 mm in the width direction may be 7.0% or less, or 6.0% or less. The thickness unevenness of the biaxially oriented polypropylene film within 1000 mm in the width direction may be 0.0% or more, or 1.0% or more. The measurement method was as follows. A 1000 mm x 40 mm test piece was cut out in the width direction of the film, and the film thickness was measured continuously over 1000 mm using a film feeder manufactured by Micron Measuring Instruments (product number: A90172) and a continuous film thickness measuring instrument manufactured by Anritsu Corporation (product name: K-313A wide-range high-sensitivity electronic micrometer), and the thickness unevenness was calculated using the following formula. Thickness unevenness (%) = [(maximum thickness - minimum thickness) / average thickness] x 100

[0037] <Heat shrinkage at 120°C> The heat shrinkage in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 120°C is preferably 6.0% or less, more preferably 5.5% or less, even more preferably 5.0% or less, and particularly preferably 4.7% or less. The heat shrinkage in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 120°C is preferably 0.0% or more, more preferably 1.5% or more, and particularly preferably 3.0% or more. When the heat shrinkage in the longitudinal direction of the biaxially oriented polypropylene film at 120°C is 6.0% or less, poor appearance such as vertical streaks is unlikely to occur when used as a processing film. A heat shrinkage in the longitudinal direction of the biaxially oriented polypropylene film of about 2.0% at 120°C is sufficient. The heat shrinkage in the width direction of the biaxially oriented polypropylene film at 120°C is 5.0% or less, preferably 4.0% or less, more preferably 3.0% or less, and particularly preferably 2.5% or less. The heat shrinkage rate in the width direction of the biaxially oriented polypropylene film of the present invention at 120°C is preferably -3.0% or more, more preferably -1.0% or more, and particularly preferably 1.0% or more. When the heat shrinkage rate in the width direction of the biaxially oriented polypropylene film at 120°C is 5.0% or less, wrinkles, dimensional changes, and deterioration of flatness due to heat during use are less likely to occur, improving the appearance quality. A heat shrinkage rate in the width direction of the biaxially oriented polypropylene film at 120°C of approximately 2.0% is sufficient. The heat shrinkage rate of the biaxially oriented polypropylene film at 120°C can be kept within the above range by adjusting the stretch ratio, stretching temperature, and heat setting temperature. In accordance with JIS Z1712, the heat shrinkage rates in the longitudinal and width directions of the film at 120°C can be measured using the following method. A film is cut so that the measurement direction is 200 mm and the direction perpendicular to this is 20 mm, and the film is hung in a hot air oven at 120°C and heated for 5 minutes. The length after heating is measured, and the heat shrinkage rate at 120°C can be calculated as the ratio of the shrunk length to the original length.

[0038] <F5: Stress at 5% Elongation at 23°C> The F5 in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 23°C is preferably 30 MPa or more, more preferably 32 Pa or more, even more preferably 33 Pa or more, and particularly preferably 34 Pa or more. When the F5 in the longitudinal direction at 23°C is 30 MPa or more, the film has high rigidity and therefore has excellent handleability when used as a process film. The F5 in the longitudinal direction at 23°C is preferably 60 MPa or less, more preferably 55 MPa or less, even more preferably 50 MPa or less, and particularly preferably 45 Pa or less. When the F5 in the longitudinal direction at 23°C is 60 MPa or less, practical production is easy. The F5 in the width direction of the biaxially oriented polypropylene film of the present invention at 23°C is 40 MPa or more, preferably 50 MPa or more, more preferably 55 MPa or more, and even more preferably 60 MPa or more. When the F5 in the width direction at 23°C is 40 MPa or more, the rigidity is high, resulting in excellent handleability when used as a process film. The F5 in the width direction at 23°C is preferably 150 MPa or less, more preferably 140 MPa or less, and even more preferably 130 MPa or less. When the F5 in the width direction at 23°C is 150 MPa or less, practical production is easy. The F5 can be adjusted within the above range by adjusting the stretch ratio and relaxation rate, or by adjusting the temperature during film formation. The stress (F5) at 5% elongation in the longitudinal and width directions of the film can be measured at 23°C in accordance with JIS K7127. A film is cut so that the measurement direction is 200 mm and the direction perpendicular thereto is 15 mm, and the film is set in a tensile tester (Instron 5965, a dual column tabletop tester manufactured by Instron Japan Company Limited) with a chuck width of 100 mm. The tensile test is then performed at a tensile speed of 200 mm / min. From the obtained strain-stress curve, the stress at 5% elongation can be determined as F5.

[0039] <Haze> The upper limit of the haze of the biaxially oriented polypropylene film of the present invention is preferably 10.0%, more preferably 7.5%, and even more preferably 5.0%. When the haze is 10.0% or less, a smooth sheet can be obtained when used as a process film in the production of resin sheets such as polyurethane resins. When used as a release film, adhesive film, or label, a beautiful appearance can be obtained. The lower limit of the haze is preferably 0.0%. From the standpoint of workability and ease of production, a lower limit of the haze of 1.0% is more preferable. On the other hand, when used as a process film or release film in the production of resin sheets, a higher haze may make the film easier to distinguish and improve workability, and a pigment such as titanium oxide may be added to increase the haze. The haze can be measured at 23°C using an NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7105.

[0040] <Breaking Strength> The lower limit of the breaking strength in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 23°C is preferably 90 MPa, more preferably 100 MPa, even more preferably 105 Pa, and particularly preferably 109 MPa. When the breaking strength in the longitudinal direction at 23°C is 90 MPa or more, the film has excellent handleability and is likely to break when used as a processing film. The lower limit of the breaking strength in the width direction of the biaxially oriented polypropylene film of the present invention at 23°C is 250 MPa, preferably 270 MPa, more preferably 280 MPa, and even more preferably 290 MPa. When the breaking strength in the width direction at 23°C is 250 MPa or more, the film is likely to break when used as a processing film. The breaking strength can be adjusted within the above range by adjusting the stretch ratio, relaxation rate, and the temperature of each step during film formation. <Break elongation> The lower limit of the break elongation in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 23°C is preferably 100%, more preferably 150%, and even more preferably 200%. If the break elongation in the longitudinal direction at 23°C is 100% or more, breakage is likely to be suppressed when used as a processing film. It is sufficient if the upper limit of the break elongation in the longitudinal direction at 23°C is 500%. The lower limit of the break elongation in the width direction of the biaxially oriented polypropylene film of the present invention at 23°C is 20%, preferably 30%, more preferably 35%, and even more preferably 40%. If the break elongation in the width direction at 23°C is 20% or more, breakage is likely to be suppressed when used as a processing film. It is sufficient if the upper limit of the break elongation in the width direction at 23°C is 200%. The break elongation can be kept within the above range by adjusting the draw ratio, relaxation rate, and the temperature of each step during film formation.

[0041] <Suitability of Process Film> For example, when used as a process film in urethane resin sheet molding, a rolled film is unwound, a urethane-based elastomer resin is applied to the film in a sheet form at about 200°C to a thickness of about 300 μm, and then the laminate of the film and urethane resin sheet is wound up to obtain a urethane resin sheet. In this case, a thin film is weak and therefore prone to fine wrinkles during unwinding. These wrinkles are transferred to the urethane resin sheet, resulting in a decrease in sheet quality. Furthermore, a film with significant thickness unevenness in the width direction is prone to sagging, which makes it impossible to coat the urethane resin sheet with a uniform thickness, resulting in a decrease in the thickness uniformity of the urethane resin sheet. Furthermore, a film with a large thermal shrinkage rate is prone to shrinkage during resin coating, resulting in streaks in the urethane resin sheet and a decrease in sheet quality.

[0042] (Second Invention) As described below, the biaxially oriented polypropylene film of the present invention has a substrate layer made of a polypropylene resin composition containing 87% by mass or more and 99% by mass or less of a polypropylene resin and 1% by mass or more and 13% by mass or less of an alicyclic hydrocarbon resin, and a matte layer made of the resin composition. This will be explained in detail below. (4) Substrate Layer: If the polypropylene resin composition constituting the substrate layer contains 87% by mass or more of a polypropylene resin, a biaxially oriented polypropylene film with strong stiffness can be obtained by adjusting the film-forming conditions. By adding 1% by mass or more and 13% by mass or less of an alicyclic hydrocarbon resin to the polypropylene resin composition constituting the substrate layer, biaxial stretching can be performed smoothly, resulting in a biaxially oriented polypropylene film with little thickness unevenness. The lower limit of the alicyclic hydrocarbon resin content is more preferably 3% by mass, and even more preferably 5% by mass. The upper limit of the alicyclic hydrocarbon resin content is more preferably 11% by mass, and even more preferably 10% by mass. If the alicyclic hydrocarbon resin content is 13% by mass or less, the 120°C heat shrinkage rate is easily reduced. Raw material costs may also be reduced.

[0043] (4-1) Polypropylene Resin The polypropylene resin used in the base layer of the present invention may be a polypropylene homopolymer or a polypropylene copolymer containing an α-olefin other than propylene. However, it is preferable to use a polypropylene polymer that is substantially free of α-olefin components other than propylene. Specifically, a "polypropylene polymer that is substantially free of α-olefin components other than propylene" refers to a polypropylene copolymer whose constituent units are 1 mol% or less of α-olefin components other than propylene and 99 mol% or more of propylene. Even when α-olefin components other than propylene are contained, 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 0.8 mol% or less, and more preferably 0.7 mol% or less. Within the above range, crystallization is facilitated, stiffness is increased, and the 120°C heat shrinkage rate is easily reduced. Examples of the α-olefin component 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.

[0044] The polypropylene resin used in the present invention may be a mixture of two or more different polypropylene polymers, for example, two or more different polypropylene homopolymers, a polypropylene copolymer containing two or more different α-olefins other than propylene, or a mixture of one or more polypropylene homopolymers and one or more polypropylene copolymers containing one or more α-olefins other than propylene. In the case of a mixture of two or more different polypropylene polymers, it is preferable that the total content of the polypropylene polymers in the polypropylene resin composition is within the above range. By setting it within the above range, the polypropylene resin composition is strengthened and the 120°C heat shrinkage rate is easily reduced.

[0045] Various suitable physical properties of the polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present invention, are described below. When two or more different polypropylene resins are used, the physical property values ​​are the mass average values ​​of the physical properties of each polypropylene resin.

[0046] The melting point of the polypropylene resin used in the base layer of the present invention is preferably 155°C or higher, more preferably 156°C or higher. The melting point of the polypropylene resin used in the base layer of the present invention is preferably 175°C or lower, more preferably 170°C or lower, even more preferably 169°C or lower, particularly preferably 168°C or lower, and most preferably 167°C or lower. When the melting point of the polypropylene resin used in the base layer is 155°C or higher, the 120°C heat shrinkage rate is easily reduced. When the melting point is 175°C or lower, thickness unevenness can be reduced and the film is less likely to break during production. The melting point of the polypropylene resin is the main peak temperature of the endothermic peak accompanying melting, which is observed when 5 mg of polypropylene resin is packed into an aluminum pan, set in a differential scanning calorimeter (DSC), heated from 30°C to 230°C at a heating rate of 10°C / min in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin, then cooled to 30°C at a heating rate of -10°C / min, held at 30°C for 5 minutes, and then heated at a heating rate of 10°C / min.

[0047] The crystallization temperature of the polypropylene resin used in the base layer of the present invention is preferably 105 ° C or higher, more preferably 108 ° C or higher, even more preferably 110 ° C or higher, even more preferably 112 ° C or higher, particularly preferably 114 ° C or higher, and most preferably 116 ° C or higher. The crystallization temperature of the polypropylene resin used in the base layer of the present invention is preferably 135 ° C or lower, more preferably 132 ° C or lower, even more preferably 130 ° C or lower, even more preferably 128 ° C or lower, particularly preferably 127 ° C or lower, and most preferably 116 ° C or lower. If the crystallization temperature is 105 ° C or higher, crystallization tends to proceed during width direction stretching and the subsequent cooling process, strengthening the film and reducing the 120 ° C heat shrinkage rate. If the crystallization temperature is 135 ° C or lower, thickness unevenness can be reduced and the film is less likely to break during production. The crystallization temperature of the polypropylene resin is the main peak temperature of the exothermic peak observed when 5 mg of the polypropylene resin is packed into an aluminum pan, set in a DSC, heated from 30°C to 230°C at a heating rate of 10°C / min in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin, and then cooled to 30°C at a cooling rate of -10°C / min.

[0048] The melting point and crystallization temperature can be increased by blending a nucleating agent into the polypropylene resin. When a nucleating agent is blended, it is preferable that the melting point and crystallization temperature of the polypropylene resin blended with the nucleating agent be within the above ranges.

[0049] The mesopentad fraction ([mmmm]%), which is an index of stereoregularity of the polypropylene resin used in the base layer of the present invention, is preferably 92% or more, more preferably 94% or more, and even more preferably 96% or more. The mesopentad fraction ([mmmm]%), which is an index of stereoregularity of the polypropylene resin used in the base layer of the present invention, is preferably 99% or less, more preferably 98% or less, and even more preferably 97% or less. When the mesopentad fraction of the polypropylene resin is 92% or more, the 120°C heat shrinkage rate is easily reduced. When the mesopentad fraction of the polypropylene resin is 99% or less, thickness unevenness can be reduced and breakage during film formation is less likely. The mesopentad fraction is measured by nuclear magnetic resonance spectroscopy (NMR spectroscopy). To achieve the mesopentad fraction of the polypropylene resin within the above range, for example, methods such as washing the obtained polypropylene resin powder with a solvent such as n-heptane or using an appropriate catalyst and / or co-catalyst may be used. The mesopentad fraction ([mmmm]%) was measured by 13 The mesopentad fraction can be calculated using C-NMR according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973). 13 C-NMR measurement can be performed using an AVANCE 500 manufactured by BRUKER, by dissolving 200 mg of a sample in a 8:2 mixture of o-dichlorobenzene and deuterated benzene at 135°C and at 110°C.

[0050] The melt flow rate (MFR) of the polypropylene resin constituting the base layer of the present invention, when measured in accordance with condition M (230°C, 2.16 kgf) of JIS K 7210 (1995), is preferably 4.0 g / 10 min or more, more preferably 4.5 g / 10 min or more, even more preferably 4.8 g / 10 min or more, still more preferably 5.0 g / 10 min or more, particularly preferably 6.0 g / 10 min or more, and most preferably 7.5 g / 10 min or more. The melt flow rate (MFR) of the polypropylene resin constituting the base layer of the present invention, when measured in accordance with condition M (230°C, 2.16 kgf) of JIS K 7210 (1995), is preferably 30 g / 10 min or less, more preferably 25 g / 10 min or less, even more preferably 22 g / 10 min or less, even more preferably 20 g / 10 min or less, and most preferably 15 g / 10 min or less. When the MFR of the polypropylene resin is 4.0 g / 10 min or more, the 120°C heat shrinkage rate is easily reduced. Furthermore, when the MFR of the polypropylene resin is 30 g / 10 min or less, thickness unevenness can be reduced and the film is less likely to break during production.

[0051] (4-2) Alicyclic Hydrocarbon Resin Examples of alicyclic hydrocarbon resins used in the present invention include alicyclic saturated hydrocarbon resins, alicyclic unsaturated hydrocarbon resins, aliphatic unsaturated hydrocarbon resins, aliphatic saturated hydrocarbon resins, aromatic hydrocarbon resins, hydrogenated aromatic hydrocarbon resins, rosin ester resins, hydrogenated rosin ester resins, terpene phenol resins, hydrogenated terpene phenol resins, terpene resins, hydrogenated terpene resins, aromatic hydrocarbon-modified terpene resins, coumarone-indene resins, phenol resins, and xylene resins. These may be used alone or in combination of two or more. Alicyclic saturated hydrocarbon resins are particularly preferred. By incorporating an alicyclic hydrocarbon resin in an amount of 1% by mass or more and 13% by mass or less, biaxial stretching can be carried out smoothly, resulting in a biaxially oriented polypropylene film with minimal thickness unevenness. The lower limit of the alicyclic hydrocarbon resin content is more preferably 3% by mass, and even more preferably 5% by mass. The upper limit of the alicyclic hydrocarbon resin content is more preferably 11% by mass, and even more preferably 10% by mass. An alicyclic hydrocarbon resin content of 13% by mass is sufficient to smoothly perform biaxial stretching and obtain a biaxially oriented polypropylene film with little thickness unevenness, but if the alicyclic hydrocarbon resin content exceeds 13% by mass, the dimensional stability at high temperatures may deteriorate. Furthermore, raw material costs may also increase. It is believed that the alicyclic hydrocarbon resin enables smooth stretching by suppressing excessive crystallization of polypropylene during the process of obtaining an unstretched sheet and the process of stretching in the longitudinal and transverse directions during film production.

[0052] (5) Matte Layer The matte layer in the present invention is made of a resin composition. The matte layer is laminated on at least one side of the substrate layer. That is, the matte layer may be laminated on only one side of the substrate layer, or on both sides of the substrate layer. The surface of the matte layer, i.e., the side on which the substrate layer is not laminated, preferably has a matte or matte finish. At the same time, if the matte layer is translucent, this is more preferable because it allows for easier visibility when used as a process film or release film. In addition, a high surface roughness is preferable because it improves workability when used as a process film. In this case, for example, when the process film is wound into a roll together with a melt-cast resin sheet, it can be smoothly wound and unwound.

[0053] The matte layer in the present invention can be produced from, for example, a resin composition containing two or more incompatible resins, a resin composition containing a resin and fine particles, or a resin composition containing both a resin composition containing two or more incompatible resins and fine particles. It is more preferable that the resin composition containing two or more incompatible resins has a sea-island structure. In terms of extending the cycle for replacing the polymer filter in the extrusion process, it is preferable that a resin composition having a sea-island structure, which is obtained by blending and melt-kneading two or more incompatible resins, is used for the matte layer.

[0054] When a resin composition containing two or more incompatible resins is used for the matte layer, it is preferable to use a resin composition containing a mixture of polypropylene resin and polyethylene resin. It is more preferable that the resin composition containing a mixture of polypropylene resin and polyethylene resin has a sea-island structure. The fine particles may be inorganic particles having an average particle size of 0.1 μm or more and 10 μm or less, such as silica, silica alumina, alumina, talc, calcium carbonate, or barium sulfate, or organic resin particles such as silicone resin, cross-linked polystyrene resin, or cross-linked acrylic resin.

[0055] When a resin composition containing a polypropylene resin and a polyethylene-based resin is used for the matte layer, the polypropylene resin may be a polypropylene homopolymer or a polypropylene copolymer copolymerized with an α-olefin other than ethylene and / or propylene. Examples of the α-olefin component 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. The polypropylene resin in the resin composition constituting the mat layer may be a mixture of two or more different polypropylene polymers. For example, it may be two or more different polypropylene homopolymers, a polypropylene copolymer containing two or more different α-olefins other than propylene, or a mixture of one or more polypropylene homopolymers and one or more polypropylene copolymers containing one or more α-olefins other than propylene. As the polypropylene resin in the resin composition constituting the mat layer, one or more of the above-mentioned resins may be used. As the polypropylene copolymer, it is particularly preferable to use a propylene-ethylene binary copolymer resin (Pr-Et copolymer) or a propylene-ethylene-1-butene terpolymer resin (Pr-Et-1-Bu copolymer).

[0056] Examples of the polyethylene resin in the resin composition constituting the mat layer include high-density polyethylene resin, medium-density polyethylene resin, low-density polyethylene resin, linear low-density polyethylene resin, and polyethylene copolymers copolymerized with α-olefin. As the polyethylene resin, one or more of the above resins can be used.

[0057] The content of polypropylene resin in the resin composition constituting the matte layer is preferably 3% by mass or more and 90% by mass or less. By making the content of polypropylene resin in the resin composition constituting the matte layer 3% by mass or more, sufficient adhesion can be obtained between the matte layer and the base layer. By making the content of polypropylene resin in the resin composition constituting the matte layer 90% by mass or less, visibility, matte finish, and workability can be improved. The content of polypropylene resin in the resin composition constituting the matte layer is more preferably 40% by mass or more.

[0058] The content of the polypropylene copolymer in which ethylene and / or an α-olefin other than propylene is copolymerized in the resin composition constituting the matte layer is preferably 3% by mass or more and 60% by mass or less. By making the content of the polypropylene copolymer 3% by mass or more, visibility, matte finish, and workability can be improved. By making the content of the polypropylene copolymer 60% by mass or less, stable film formation is possible, allowing for efficient production. The content of the polypropylene copolymer is more preferably 40% by mass or more.

[0059] The content of polyethylene resin in the resin composition constituting the matte layer is preferably 3% by mass or more and 60% by mass or less. By making the content of the polyethylene resin 3% by mass or more, visibility, matte finish, and workability can be improved. By making the content of the polyethylene resin 60% by mass or less, stable film formation is possible, allowing for efficient production. The content of the polyethylene resin is more preferably 50% by mass or less.

[0060] As the resin composition constituting the matte layer in the present invention, a resin composition containing a propylene-ethylene binary copolymer resin (Pr-Et copolymer), a propylene-ethylene-1-butene terpolymer (Pr-Et-1-Bu copolymer) resin, and a polyethylene resin is particularly preferred.

[0061] The resin composition constituting the matte layer preferably has a melt flow rate (MFR) of 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, and particularly preferably 1.0 g / 10 min or more. The resin composition constituting the matte layer preferably has a melt flow rate (MFR) of 100 g / 10 min or less, more preferably 20 g / 10 min or less, and particularly preferably 10 g / 10 min or less.

[0062] The thickness of the matte layer is preferably 0.5 μm or more and 1 / 3 or less of the total thickness of the film. If it is 0.5 μm or more, a uniform and sufficiently matte texture can be obtained. If the thickness of the matte layer exceeds 1 / 3 of the total thickness of the film, the thermal shrinkage rate increases, which is not preferable.

[0063] (6) Other Additives Additives and other resins may be added to the resin composition constituting the substrate layer and / or matte layer of the present invention, as needed. Examples of additives include antioxidants, UV absorbers, antistatic agents, lubricants, nucleating agents, adhesives, antifogging agents, flame retardants, antiblocking agents, inorganic or organic fillers, and other resins. Examples of other resins include polypropylene resins other than the polypropylene resin used in the present invention, polyolefin polymers, and various elastomers. These may be blended with the polypropylene resin using a Henschel mixer, 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 and used. When the biaxially oriented polypropylene film of the present invention is used as a substrate film for a film-forming process, peelability, easy lubricity, antiblocking properties, and antistatic properties may be required, so it is preferable to add a lubricant, antiblocking agent, or antistatic agent.

[0064] (7) Film-forming method for biaxially oriented polypropylene film The biaxially oriented polypropylene film of the present invention is preferably obtained by preparing an unstretched sheet in which a substrate layer made of a polypropylene resin composition containing a polypropylene resin as a main component and a matte layer made of a polypropylene resin composition are laminated, and then biaxially stretching the unstretched sheet. Regarding biaxial stretching, it is preferable to stretch the sheet in the longitudinal direction and then in the width direction, but it is also possible to stretch the sheet in the width direction and then in the longitudinal direction. Examples of biaxial stretching methods include inflation simultaneous biaxial stretching, tenter simultaneous biaxial stretching, tenter sequential biaxial stretching, and tube stretching. From the viewpoints of film formation stability and thickness unevenness, tenter sequential biaxial stretching is preferred. Below, the method for producing the biaxially oriented polypropylene film of the present invention, which is composed of a substrate layer and a matte layer, is described, but the method is not limited to the following production method.

[0065] First, the polypropylene resin composition used for the base layer and the resin composition used for the mat layer are fed, for example, from two extruders through different flow paths. The polypropylene resin composition and the resin composition melted at 200°C or higher and 300°C or lower are laminated in multiple layers using a multi-layer feed block, static mixer, multi-layer multi-manifold die, or the like, and co-extruded into a sheet from a T-die. Alternatively, it is possible to use only one extruder and install the above-mentioned multi-layering device in the melt line from the extruder to the T-die. From the viewpoint of stabilizing back pressure and suppressing thickness fluctuations, a method in which a gear pump is installed in the polymer flow path is preferred. The molten laminated sheet extruded into a sheet from the T-die is cooled and solidified by contacting it with a cooling roll to obtain an unstretched sheet. Next, the unstretched sheet is stretched in the longitudinal direction between two pairs of heated stretching rolls by increasing the rotation speed of the rear stretching roll to obtain a uniaxially stretched film. Next, the uniaxially stretched film is heated in a preheating step, then stretched in the width direction while holding the film edges in a tenter-type stretching machine, heat-treated, and finally cooled to obtain a biaxially oriented polypropylene film. Below, the extrusion step, longitudinal stretching step, preheating step, width-direction stretching step, heat-treatment step, and cooling step will be explained in this order.

[0066] <Extrusion Step> First, a polypropylene resin composition containing a polypropylene resin as a main component and a resin composition constituting the mat layer are heated and melted in a single-screw or twin-screw extruder at a temperature in the range of 200°C or higher and 300°C or lower. The sheet-shaped molten polypropylene resin composition and the resin composition constituting the mat layer are co-extruded from a T-die, brought into close contact with a metal cooling roll using a contacting device such as an air knife, and cooled and solidified to obtain an unstretched sheet. The obtained unstretched sheet is preferably further placed in a water tank. It is also preferable to actively cool the unstretched sheet by spraying cooling water on the side opposite the cooling roll. The extrusion temperature of the polypropylene resin composition is preferably 220°C or higher, more preferably 240°C or higher. The extrusion temperature of the polypropylene resin composition is preferably 270°C or lower, more preferably 260°C or lower. When the extrusion temperature of the polypropylene resin composition is 220°C or higher, an unstretched sheet with good stretchability is obtained. When the extrusion temperature of the polypropylene resin composition is 270°C or lower, thermal degradation of the polypropylene resin composition can be suppressed. The extrusion temperature of the resin composition constituting the mat layer is preferably 200°C or higher, more preferably 210°C or higher. The extrusion temperature of the resin composition constituting the mat layer is preferably 240°C or lower, more preferably 230°C or lower. The temperature of the cooling roll, or the cooling roll and water bath, is preferably 0°C or higher. The temperature of the cooling roll, or the cooling roll and water bath, is preferably 40°C or lower, more preferably 30°C or lower, and even more preferably 20°C or lower. If the temperature of the cooling roll, or the cooling roll and water bath, is 40°C or lower, an unstretched sheet with good stretchability can be obtained, and a thick biaxially oriented polypropylene film with little thickness unevenness can be obtained. The lower limit of the temperature of the cooling roll, or the cooling roll and water bath, is preferably 0°C from the standpoint of economy and prevention of condensation.

[0067] <Longitudinal Stretching Step> The longitudinal stretching temperature is preferably 110°C or higher, and more preferably 120°C or higher. The longitudinal stretching temperature is preferably 140°C or lower, and more preferably 130°C or lower. When the longitudinal stretching temperature is 110°C or higher, the subsequent widthwise stretching becomes easier and thickness unevenness tends to be reduced. Furthermore, when the longitudinal stretching temperature is 140°C or lower, the film is less likely to stick to the stretching rolls, making stretching difficult, or to become rough on the surface, resulting in a decrease in quality. The longitudinal stretching ratio is preferably 3.5 times or higher, more preferably 3.8 times or higher, and even more preferably 4.2 times or higher. The longitudinal stretching ratio is preferably 4.8 times or lower, more preferably 4.7 times or lower, and even more preferably 4.6 times or lower. When the longitudinal stretching ratio is 3.5 times or higher, strength is easily increased and thickness unevenness tends to be reduced. Furthermore, when the stretching ratio in the longitudinal direction is 4.8 times or less, the stretching in the width direction is easy to perform in the width direction stretching step, and productivity is easily improved. The longitudinal stretching may be performed in two or more stages using three or more pairs of stretching rolls, but it is preferable to perform stretching in one stage using two pairs of stretching rolls. When stretching in multiple stages, it is preferable that the highest stretching temperature is within the above range.

[0068] <Preheating Step> It is preferable to heat the uniaxially stretched film after longitudinal stretching in the preheating step 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, more preferably 165°C or higher. The heating temperature in the preheating step is preferably 180°C or lower, more preferably 175°C or lower, and even more preferably 170°C or lower. By setting the heating temperature in the preheating step to 160°C or higher, softening progresses, making widthwise stretching easier. Furthermore, by setting the heating temperature in the preheating step to 180°C or lower, orientation progresses during widthwise stretching, making it easier for the resulting film to exhibit stress at 5% elongation. The heating temperature in the preheating step may be referred to as the preheating temperature. Note that when the preheating step consists of multiple zones, the temperature of the zone with the highest temperature among them is referred to as the preheating temperature.

[0069] <Width Direction Stretching Step> The width direction stretching temperature is preferably 155°C or higher, more preferably 160°C or higher, and even more preferably 163°C or higher. The width direction stretching temperature is preferably equal to or lower than the heating temperature in the preheating step, more preferably 170°C or lower, and even more preferably 167°C or lower. When the width direction stretching temperature is 155°C or higher, the 120°C heat shrinkage rate of the obtained film is easily reduced. Furthermore, when the width direction stretching temperature is equal to or lower than the heating temperature in the preheating step, stretching unevenness is less likely to occur. The width direction stretching ratio is preferably more than 8 times, more preferably 9 times or higher, and even more preferably 10 times or higher. The width direction stretching ratio is preferably 15 times or lower, more preferably 13 times or lower, and even more preferably 12 times or lower. When it is greater than 8 times, the rigidity in the width direction is easily increased and thickness unevenness is easily reduced. Furthermore, when it is 15 times or lower, the heat shrinkage rate is easily reduced and the film is less likely to break during width direction stretching.

[0070] <Heat Treatment Step> Heat treatment is carried out after the width direction stretching step is completed. Specific means for heat treatment include a method of providing a zone with a higher temperature than the stretching zone after the width direction stretching is completed, a method of increasing the zone temperature in the latter half of stretching and passing the film through a zone of the same temperature after the stretching is completed, etc. Heating means include a method of blowing hot air or a method of heating with an infrared heater, but are not particularly limited as long as the method is capable of increasing the temperature of the film from that at the end of the width direction stretching step.

[0071] The heat treatment step is preferably carried out immediately after the width direction stretching step is completed (i.e., immediately after the width direction stretching reaches the final stretch ratio). The heating temperature in the heat treatment step is preferably higher than that at the end of the width direction stretching step, specifically, preferably the width direction stretching temperature + 1°C or more. The heating temperature in the heat treatment step may be referred to as the heat treatment temperature.

[0072] The heating temperature in the heat treatment step is preferably 151°C or higher, more preferably 153°C or higher, and even more preferably 155°C or higher. The heating temperature in the heat treatment step is preferably 180°C or lower, more preferably 170°C or lower, and even more preferably 165°C or lower. By heating in the heat treatment step after the stretching step, the molecular chain orientation formed during stretching is relaxed, and the heat shrinkage rate can be reduced. In the heat treatment step, the film may or may not be relaxed (relaxed) in the width direction. When the film is relaxed in the width direction, the relaxation rate is preferably 1% or higher, more preferably 3% or higher, and even more preferably 5% or higher. When the film is relaxed in the width direction, the relaxation rate is preferably 12% or lower, more preferably 10% or lower, and even more preferably 8% or lower. When the film is relaxed in the width direction, the relaxation rate within the above range makes it easy to reduce the 120°C heat shrinkage rate while maintaining the stress of the resulting film at 5% elongation. However, if it is desired to increase the stress of the resulting film at 5% elongation, the film does not need to be relaxed in the width direction.

[0073] <Cooling Step> It is preferable to cool the film immediately after the heat treatment step. The cooling temperature is preferably 10°C or higher, more preferably 15°C or higher, and even more preferably 20°C or higher. The cooling temperature is preferably 140°C or lower, more preferably 135°C or lower, even more preferably 130°C or lower, particularly preferably 80°C or lower, and most preferably 50°C or lower. By providing the cooling step, the state of molecular orientation in the film can be fixed.

[0074] The method for producing a biaxially oriented polypropylene film has been described above. However, the biaxially oriented polypropylene film of the present invention may have a functional layer (hereinafter referred to as a functional layer) laminated on the side opposite to the matte layer. The lamination method is not particularly limited. For example, coextrusion using a feed block method or a multi-manifold method is preferred. When the biaxially oriented polypropylene film of the present invention is used as a substrate film for a film-forming process, it is preferable that the film has releasability, easy lubricity, antiblocking properties, and antistatic properties, and therefore it is preferable to add a lubricant, antiblocking agent, or antistatic agent to the functional layer.

[0075] The biaxially oriented polypropylene film of the present invention can be wound into a roll to form a film roll having a width of 2000 mm to 12000 mm and a length of about 1000 m to 50000 m, making it possible to obtain a long film roll. In addition, slits may be formed in the film to suit each application, and the film can also be made into a slit roll having a width of 300 mm to 2000 mm and a length of 500 m to 5000 m.

[0076] (8) Properties of Biaxially Oriented Polypropylene Film The biaxially oriented polypropylene film of the present invention preferably has the following properties. Here, the "longitudinal direction (MD direction)" of the biaxially oriented polypropylene film of the present invention refers to the direction corresponding to the flow direction in the film production process, and the "width direction (TD direction)" refers to the direction perpendicular to the flow direction in the film production process, and the same applies hereinafter. For polypropylene films whose flow direction in the film production process is unknown, wide-angle X-rays are incident perpendicular to the film surface, and the scattering peak derived from the (110) plane of the α-crystals is scanned in the circumferential direction. The direction with the greatest diffraction intensity in the obtained diffraction intensity distribution is defined as the "longitudinal direction," and the direction perpendicular to that is defined as the "width direction."

[0077] <Thickness> The thickness of the biaxially oriented polypropylene film of the present invention is 65 μm or more and 200 μm or less. A thickness of 65 μm or more provides sufficient stiffness for use as a process film or label. Furthermore, a thickness of 200 μm or less makes it easier to obtain a film with little thickness unevenness. The thickness of the biaxially oriented polypropylene film may be 70 μm or more, or 73 μm or more. The thickness of the biaxially oriented polypropylene film may be 150 μm or less, or 100 μm or less.

[0078] <Thickness Unevenness> Even in the case of a thick film, the biaxially oriented polypropylene film of the present invention has a thickness unevenness of 8.0% or less within 1000 mm in the width direction. A low thickness unevenness of 8.0% or less makes it easier to improve the thickness uniformity of a resin sheet when used as a process film in the production of a resin sheet. The thickness unevenness of the biaxially oriented polypropylene film within 1000 mm in the width direction may be 7.0% or less, or 6.0% or less. The thickness unevenness of the biaxially oriented polypropylene film within 1000 mm in the width direction may be 0.0% or more, or 1.0% or more. The measurement method was as follows. A 1000 mm x 40 mm test piece was cut out in the width direction of the film, and the film thickness was measured continuously over 1000 mm using a film feeder manufactured by Micron Measuring Instruments (product number: A90172) and a continuous film thickness measuring instrument manufactured by Anritsu Corporation (product name: K-313A wide-range high-sensitivity electronic micrometer), and the thickness unevenness was calculated using the following formula. Thickness unevenness (%) = [(maximum thickness - minimum thickness) / average thickness] x 100

[0079] <Surface average roughness SRa of matte layer surface> The surface average roughness SRa of the matte layer surface of the biaxially oriented polypropylene film is preferably 0.20 μm or more and 1.50 μm or less. If the surface average roughness SRa of the matte layer surface is 0.20 μm or more, when it is used as a process film for resin sheet film formation and wound into a roll together with the formed film, it can be smoothly wound and unwound. Furthermore, if the surface average roughness SRa of the matte layer surface is 1.50 μm or less, when it is used as a process film for resin sheet film formation, a resin sheet with a uniform surface can be obtained.

[0080] <Haze> The haze of the biaxially oriented polypropylene film of the present invention is 30% or more and 90% or less. If the haze is 30% or more and 90% or less, when used as a processing film or a release film, visibility is good and workability is easy. The lower limit of the haze is more preferably 40%. The upper limit of the haze is more preferably 80%. The haze can be measured at 23°C according to JIS K7105 using an NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0081] <Heat shrinkage at 120°C> The heat shrinkage in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 120°C is preferably 6.0% or less, more preferably 5.5% or less, even more preferably 5.0% or less, and particularly preferably 4.7% or less. The heat shrinkage in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 120°C is preferably 0.0% or more, more preferably 1.5% or more, and particularly preferably 3.0% or more. When the heat shrinkage in the longitudinal direction of the biaxially oriented polypropylene film at 120°C is 6.0% or less, poor appearance such as vertical streaks is unlikely to occur when used as a processing film. A heat shrinkage in the longitudinal direction of the biaxially oriented polypropylene film of about 2.0% at 120°C is sufficient. The heat shrinkage in the width direction of the biaxially oriented polypropylene film at 120°C is 5.0% or less, preferably 4.0% or less, more preferably 3.0% or less, and particularly preferably 2.5% or less. The heat shrinkage rate in the width direction of the biaxially oriented polypropylene film of the present invention at 120°C is preferably -3.0% or more, more preferably -1.0% or more, and particularly preferably 1.0% or more. When the heat shrinkage rate in the width direction of the biaxially oriented polypropylene film at 120°C is 5.0% or less, wrinkles, dimensional changes, and deterioration of flatness due to heat during use are less likely to occur, improving the appearance quality. A heat shrinkage rate in the width direction of the biaxially oriented polypropylene film at 120°C of approximately 2.0% is sufficient. The heat shrinkage rate of the biaxially oriented polypropylene film at 120°C can be kept within the above range by adjusting the stretch ratio, stretching temperature, and heat setting temperature. In accordance with JIS Z1712, the heat shrinkage rates in the longitudinal and width directions of the film at 120°C can be measured using the following method. A film is cut so that the measurement direction is 200 mm and the direction perpendicular to this is 20 mm, and the film is hung in a hot air oven at 120°C and heated for 5 minutes. The length after heating is measured, and the heat shrinkage rate at 120°C can be calculated as the ratio of the shrunk length to the original length.

[0082] <F5: Stress at 5% Elongation at 23°C> The F5 in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 23°C is preferably 30 MPa or more, more preferably 31 Pa or more, even more preferably 32 Pa or more, and particularly preferably 33 Pa or more. When the F5 in the longitudinal direction at 23°C is 30 MPa or more, the film has high rigidity and therefore has excellent handleability when used as a process film. The F5 in the longitudinal direction at 23°C is preferably 60 MPa or less, more preferably 55 MPa or less, even more preferably 50 MPa or less, and particularly preferably 45 Pa or less. When the F5 in the longitudinal direction at 23°C is 60 MPa or less, practical production is easy. The F5 in the width direction of the biaxially oriented polypropylene film of the present invention at 23°C is 40 MPa or more, preferably 50 MPa or more, more preferably 55 MPa or more, and even more preferably 60 MPa or more. When the F5 in the width direction at 23°C is 40 MPa or more, the rigidity is high, resulting in excellent handleability when used as a process film. The F5 in the width direction at 23°C is preferably 150 MPa or less, more preferably 140 MPa or less, and even more preferably 130 MPa or less. When the F5 in the width direction at 23°C is 150 MPa or less, practical production is easy. The F5 can be adjusted within the above range by adjusting the stretch ratio and relaxation rate, or by adjusting the temperature during film formation. The stress (F5) at 5% elongation in the longitudinal and width directions of the film can be measured at 23°C in accordance with JIS K7127. A film is cut so that the measurement direction is 200 mm and the direction perpendicular thereto is 15 mm, and the film is set in a tensile tester (Instron 5965, a dual column tabletop tester manufactured by Instron Japan Company Limited) with a chuck width of 100 mm. The tensile test is then performed at a tensile speed of 200 mm / min. From the obtained strain-stress curve, the stress at 5% elongation can be determined as F5.

[0083] <Breaking Strength> The lower limit of the breaking strength in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 23°C is preferably 90 MPa, more preferably 100 MPa, even more preferably 105 Pa, and particularly preferably 107 MPa. When the breaking strength in the longitudinal direction at 23°C is 90 MPa or more, the film has excellent handleability and is likely to break when used as a processing film. The lower limit of the breaking strength in the width direction of the biaxially oriented polypropylene film of the present invention at 23°C is 250 MPa, preferably 260 MPa, more preferably 270 MPa, and even more preferably 280 MPa. When the breaking strength in the width direction at 23°C is 250 MPa or more, the film is likely to break when used as a processing film. The breaking strength can be adjusted within the above range by adjusting the stretch ratio, relaxation rate, and the temperature of each step during film formation.

[0084] <Break elongation> The lower limit of the break elongation in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 23°C is preferably 100%, more preferably 150%, and even more preferably 200%. If the break elongation in the longitudinal direction at 23°C is 100% or more, breakage is likely to be suppressed when used as a processing film. It is sufficient if the upper limit of the break elongation in the longitudinal direction at 23°C is 500%. The lower limit of the break elongation in the width direction of the biaxially oriented polypropylene film of the present invention at 23°C is 20%, preferably 30%, more preferably 35%, and even more preferably 40%. If the break elongation in the width direction at 23°C is 20% or more, breakage is likely to be suppressed when used as a processing film. It is sufficient if the upper limit of the break elongation in the width direction at 23°C is 200%. The break elongation can be kept within the above range by adjusting the draw ratio, relaxation rate, and the temperature of each step during film formation.

[0085] <Suitability of Process Film> For example, when used as a process film in urethane resin sheet molding, a rolled film is unwound, a urethane-based elastomer resin is applied to the film in a sheet form at about 200°C to a thickness of about 300 μm, and then the laminate of the film and urethane resin sheet is wound up to obtain a urethane resin sheet. In this case, a thin film is weak and therefore prone to fine wrinkles during unwinding. These wrinkles are transferred to the urethane resin sheet, resulting in a decrease in sheet quality. Furthermore, a film with significant thickness unevenness in the width direction is prone to sagging, which makes it impossible to coat the urethane resin sheet with a uniform thickness, resulting in a decrease in the thickness uniformity of the urethane resin sheet. Furthermore, a film with a large thermal shrinkage rate is prone to shrinkage during resin coating, resulting in streaks in the urethane resin sheet and a decrease in sheet quality.

[0086] This application claims the benefit of priority based on Japanese Patent Application No. 2023-195355 filed on November 16, 2023, Japanese Patent Application No. 2023-200752 filed on November 28, 2023, Japanese Patent Application No. 2023-200753 filed on December 28, 2023, and Japanese Patent Application No. 2023-223139 and Japanese Patent Application No. 2023-223140 filed on December 28, 2023. The entire contents of the specifications of Japanese Patent Application No. 2023-195355 filed on November 16, 2023, Japanese Patent Application No. 2023-200752 filed on November 28, 2023, Japanese Patent Application No. 2023-200753 filed on December 28, 2023, Japanese Patent Application No. 2023-223139 filed on December 28, 2023, and Japanese Patent Application No. 2023-223140 filed on December 28, 2023 are incorporated herein by reference.

[0087] The first invention will be described in detail below with reference to examples. The first invention is not limited to these examples. The evaluation methods used in each example and comparative example are as follows. Furthermore, the following (1) to (3) show methods for measuring various physical properties of polypropylene resins. For polypropylene resin compositions using two types of polypropylene resins, the mass average of the physical property values ​​of the individual polypropylene resins was used as the physical property value of the polypropylene resin composition.

[0088] (1) Melt Flow Rate The melt flow rate (MFR) was measured in accordance with JIS K7210 at a temperature of 230°C and a load of 2.16 kgf.

[0089] (2) Mesopentad fraction The mesopentad fraction ([mmmm]%) was measured by 13 The mesopentad fraction was calculated according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973). 13 C-NMR measurement was performed using an AVANCE 500 manufactured by BRUKER, by dissolving 200 mg of a sample in a 8:2 mixture of o-dichlorobenzene and deuterated benzene at 135°C and at 110°C.

[0090] (3) Melting Point Thermal measurements were performed under a nitrogen atmosphere using a PerkinElmer DSC8500 differential scanning calorimeter. Approximately 5 mg was cut out from a polypropylene resin pellet and sealed in an aluminum pan for measurement. After heating to 230°C and holding for 5 minutes, it was cooled to 30°C at a rate of -10°C / min, and the exothermic peak temperature was taken as the crystallization temperature (Tc). The sample was then held at 30°C for 5 minutes, heated to 230°C at 10°C / min, and the main endothermic peak temperature was taken as the melting temperature (Tm).

[0091] (4) Film Thickness The film thickness was measured using a Millitron 1202D manufactured by Seiko EM Corporation.

[0092] (5) Film Thickness Unevenness A test piece of 1000 mm x 40 mm was cut out in the width direction of the film, and the film thickness was measured continuously over 1000 mm using a film feeder manufactured by Micron Measuring Instruments (product number: A90172) and a continuous film thickness measuring instrument manufactured by Anritsu Corporation (product name: K-313A wide-range high-sensitivity electronic micrometer), and the thickness unevenness was calculated using the following formula: Thickness Unevenness (%) = [(maximum thickness - minimum thickness) / average thickness] x 100

[0093] (6) 120°C Heat Shrinkage Rate The heat shrinkage rate of the film in the longitudinal direction and width direction at 120°C was measured in accordance with JIS Z1712 by the following method. A film was cut so that the measurement direction was 200 mm and the direction perpendicular thereto was 20 mm, and the film was hung in a hot air oven at 120°C and heated for 5 minutes. The length after heating was measured, and the heat shrinkage rate at 120°C was calculated as the ratio of the shrunken length to the original length.

[0094] (7) Haze: Measured at 23° C. in accordance with JIS K7105 using an NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0095] (8) Breaking Strength, Breaking Elongation, and Stress at 5% Elongation (F5) The breaking strength, breaking elongation, and stress at 5% elongation (F5) in the longitudinal and transverse directions of the film were measured at 23°C according to JIS K7127. The film was cut so that the measurement direction was 200 mm and the direction perpendicular thereto was 15 mm, and the chuck width was 100 mm. The film was then set in a tensile tester (Instron 5965, a dual-column tabletop tester manufactured by Instron Japan Co., Ltd.). A tensile test was then performed at a tensile speed of 200 mm / min. From the obtained strain-stress curve, the strength at which the film broke was defined as breaking strength, the elongation as breaking elongation, and the stress at 5% elongation as F5.

[0096] (9) Evaluation of Suitability of Film for Processing The suitability of a film for processing in resin sheet molding was evaluated using the following procedure. A film wound into a roll was unwound, and a urethane-based elastomer resin was applied to the film in a sheet form with a thickness of 300 μm at 200° C., and then a laminate of the film and urethane resin sheet was wound into a roll. The rolled laminate was then unwound to obtain a urethane resin sheet, and its thickness uniformity and quality (wrinkles, streaks) were evaluated. A film with significant thickness unevenness in the width direction is prone to sagging, making it impossible to coat the urethane resin sheet with a uniform thickness, and the thickness uniformity of the urethane resin sheet is reduced. Furthermore, a film with a large thermal shrinkage rate is prone to shrinkage during urethane resin coating, which makes streaks likely to occur in the urethane resin sheet. A film with weak stiffness is prone to wrinkles in the urethane resin sheet.

[0097] (9-1) Thickness Uniformity of Urethane Resin Sheet A test piece measuring 500 mm in the width direction and 40 mm in the machine direction was cut out from the resin sheet prepared above, and the film thickness was measured at 10 mm intervals using a Millitron 1202D manufactured by Seiko EM Corporation. The thickness unevenness was calculated using the following formula, and the thickness uniformity was evaluated using this value. Thickness unevenness (%) = [(maximum thickness - minimum thickness) / average thickness] x 100 Evaluation: Good: Thickness unevenness is less than 8% Evaluation: Bad: Thickness unevenness is 8% or more (9-2) Wrinkles in Urethane Resin Sheet The resin sheet prepared above was cut into a piece of 500 mm x 500 mm, and the quality was confirmed visually. Evaluation: Good: No wrinkles were observed. Evaluation: Bad: Wrinkles were observed. (9-3) Streaks in Urethane Resin Sheet The resin sheet prepared above was cut into a piece of 500 mm x 500 mm, and the quality was confirmed visually. Evaluation: Good: No streaks were observed. Evaluation: ×: Streaks were observed.

[0098] (Raw Materials Used) The polypropylene resins constituting each layer used in the following Examples and Comparative Examples are as follows: PP-1: Propylene polymer [WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.] (copolymerized ethylene component: 0.6 mol%, melting point: 158°C, MFR: 7.5 g / 10 min). PP-2: A mixture of propylene polymer [WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.] (copolymerized ethylene component: 0.6 mol%, melting point: 158°C, MFR: 7.5 g / 10 min) containing a total of 2.0 mass% of stearyl diethanolamine monostearate, stearyl diethanolamine distearate, and stearyl diethanolamine as antistatic agents, and 0.17% of stearic acid monoglycerin ester. PP-3: A masterbatch containing 50% by mass of a propylene polymer (FS2011DG3 manufactured by Sumitomo Chemical Co., Ltd.) (copolymerized ethylene component: 0.6 mol%, melting point: 156°C, MFR: 2.5g / 10min) and a hydrogenated petroleum resin (Alcon P-125 manufactured by Arakawa Chemical Industries, Ltd.), which is an alicyclic hydrocarbon resin. PP-4: Antiblocking agent masterbatch: A masterbatch manufactured by Sumitomo Chemical Co., Ltd., containing 20% ​​by mass of polymethyl methacrylate-polystyrene crosslinked resin microparticles with an average particle size of 1.2μm in a polypropylene polymer (ethylene-propylene copolymer, MFR: 2.4g / 10min). PP-5: A masterbatch containing 50% by mass of a propylene polymer [FS2011DG3 manufactured by Sumitomo Chemical Co., Ltd.] (ethylene copolymer component: 0.6 mol%, melting point: 156°C, MFR: 2.5g / 10min) and an ethylene copolymer with 1-butene as the main component [Tafmer BL3110 manufactured by Mitsui Chemicals, Inc.]. PP-6: A masterbatch containing 50% by mass of a propylene polymer [FS2011DG3 manufactured by Sumitomo Chemical Co., Ltd.] (ethylene copolymer component: 0.6 mol%, melting point: 156°C, MFR: 2.5g / 10min) and poly4-methyl-1-pentene [TPX RT18 manufactured by Mitsui Chemicals, Inc.].

[0099] Example 1 A polypropylene resin composition containing 48% by mass of PP-1, 41% by mass of PP-2, 10% by mass of PP-3, and 1% by mass of PP-4 was used as raw materials. The polypropylene resin composition was heated and melted at 250°C in an extruder, extruded into a sheet from a T-die at 250°C, contacted with a cooling roll at 20°C, and then placed directly into a water bath at 20°C. The sheet was then stretched 4.5 times in the longitudinal direction at 130°C using two pairs of rolls. The ends were then clamped with clips, introduced into a hot air oven, preheated to 168°C, and stretched 10.0 times in the width direction at 165°C. The sheet was then heat-treated at 155°C and relaxed to a relaxation rate of 7% in the width direction. Finally, the sheet was cooled to room temperature. The thickness of the film thus obtained was 75 μm. Table 1 shows the film production conditions, and Table 1 shows the film properties. As shown in Table 1, a biaxially oriented polypropylene film with minimal thickness unevenness was obtained. Furthermore, the film was suitable for use as a process film.

[0100] (Examples 2 to 5) In Examples 2 to 5, the films were produced in the same manner as in Example 1, except that the film production conditions were changed to those shown in Table 1. Table 1 shows the film production conditions and film properties. As shown in Table 1, in Examples 2 to 5, biaxially oriented polypropylene films with small thickness variations were obtained. Furthermore, these films were suitable for use as process films.

[0101] (Comparative Examples 1 to 10) In Comparative Examples 1 to 10, films were produced in the same manner as in Example 1, except that the film production conditions were changed to those listed in Table 2. Table 2 shows the film production conditions and film properties. In Comparative Example 1, the absence of an alicyclic hydrocarbon resin resulted in uneven stretching, resulting in significant thickness variation. In Comparative Example 2, the high cooling roll temperature and water cooling temperature resulted in significant thickness variation. In Comparative Example 3, the small widthwise stretching ratio resulted in significant thickness variation. In Comparative Example 4, the large longitudinal stretching ratio resulted in significant thickness variation. In Comparative Example 5, a film with a thickness of 20 μm was produced under conditions similar to those described in Patent Document 4. The film of Comparative Example 5 had minimal thickness variation, but was weak and had a large longitudinal thermal shrinkage rate. In Comparative Example 6, a film with a thickness of 75 μm was produced under conditions similar to those described in Patent Document 4. The film of Comparative Example 6 had significant thickness variation. The thermal shrinkage in the longitudinal direction was also large. In Comparative Example 7, a film having a thickness of 35 μm was produced under conditions similar to those of Patent Document 5. The film of Comparative Example 7 had little thickness variation, but was weak and had a large thermal shrinkage in the longitudinal direction. In Comparative Example 8, a film having a thickness of 75 μm was produced under conditions similar to those of Patent Document 5. The film of Comparative Example 8 had large thickness variation. The thermal shrinkage in the longitudinal direction was also large. In Comparative Examples 9 and 10, polybutene-1 and polymethylpentene were added instead of the alicyclic hydrocarbon resin, and films were produced under conditions similar to those of Patent Documents 2 and 3. The obtained films had large thickness variation.

[0102]

[0103]

[0104] The second invention will be described in detail below with reference to examples. The second invention is not limited to these examples. The evaluation methods used in each example and comparative example are as follows. Furthermore, the following (10) to (12) show methods for measuring various physical properties of polypropylene resins. For polypropylene resin compositions using two types of polypropylene resins, the mass average of the physical property values ​​of the individual polypropylene resins was used as the physical property value of the polypropylene resin composition.

[0105] (10) Melt Flow Rate The melt flow rate (MFR) was measured in accordance with JIS K7210 at a temperature of 230°C and a load of 2.16 kgf.

[0106] (11) Mesopentad fraction The mesopentad fraction ([mmmm]%) was measured by 13 The mesopentad fraction was calculated according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973). 13 C-NMR measurement was performed using an AVANCE 500 manufactured by BRUKER, by dissolving 200 mg of a sample in a 8:2 mixture of o-dichlorobenzene and deuterated benzene at 135°C and at 110°C.

[0107] (12) Melting Point Thermal measurements were performed under a nitrogen atmosphere using a PerkinElmer DSC8500 differential scanning calorimeter. Approximately 5 mg was cut out from a polypropylene resin pellet and sealed in an aluminum pan for measurement. After heating to 230°C and holding for 5 minutes, it was cooled to 30°C at a rate of -10°C / min, and the exothermic peak temperature was taken as the crystallization temperature (Tc). The sample was then held at 30°C for 5 minutes, heated to 230°C at 10°C / min, and the main endothermic peak temperature was taken as the melting temperature (Tm).

[0108] (13) Film Thickness The film thickness was measured using a Millitron 1202D manufactured by Seiko EM Corporation.

[0109] (14) Film Thickness Unevenness A test piece of 1000 mm x 40 mm was cut out in the width direction of the film, and the film thickness was measured continuously over 1000 mm using a film feeder manufactured by Micron Measuring Instruments (product number: A90172) and a continuous film thickness measuring instrument manufactured by Anritsu Corporation (product name: K-313A wide-range high-sensitivity electronic micrometer), and the thickness unevenness was calculated using the following formula: Thickness Unevenness (%) = [(maximum thickness - minimum thickness) / average thickness] x 100

[0110] (15) 120°C Heat Shrinkage Rate The heat shrinkage rate of the film in the longitudinal direction and width direction at 120°C was measured in accordance with JIS Z1712 by the following method. A film was cut so that the measurement direction was 200 mm and the direction perpendicular thereto was 20 mm, and the film was hung in a hot air oven at 120°C and heated for 5 minutes. The length after heating was measured, and the heat shrinkage rate at 120°C was calculated as the ratio of the shrunken length to the original length.

[0111] (16) Haze: Measured at 23° C. in accordance with JIS K7105 using an NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0112] (17) Three-dimensional average surface roughness (SRa) The surface roughness of the film was measured by the following method: Using a three-dimensional roughness meter (manufactured by Kosaka Laboratory Co., Ltd., model number ET4000A), measurements were performed with a stylus pressure of 0.5 μN, a measurement length of 1 mm in the X direction, a feed speed of 100 μm / sec, a feed pitch of 2 μm in the Y direction, 101 recorded lines, a height direction magnification of 20,000 times, and a cutoff of 80 μm, and the surface roughness was calculated in accordance with the definition described in JIS B 0601 (1994).

[0113] (18) Breaking Strength, Breaking Elongation, and Stress at 5% Elongation (F5) The breaking strength, breaking elongation, and stress at 5% elongation (F5) in the longitudinal and transverse directions of the film were measured at 23°C according to JIS K7127. The film was cut so that the measurement direction was 200 mm and the direction perpendicular thereto was 15 mm, and the film was set in a tensile tester (Instron 5965, a dual-column tabletop tester manufactured by Instron Japan Co., Ltd.) with a chuck width of 100 mm. A tensile test was then performed at a tensile speed of 200 mm / min. From the obtained strain-stress curve, the strength at which the film broke was defined as breaking strength, the elongation as breaking elongation, and the stress at 5% elongation as F5.

[0114] (19) Evaluation of Suitability of Film for Processing The suitability of a film for processing in resin sheet molding was evaluated using the following procedure. A film wound into a roll was unwound, and a urethane-based elastomer resin was applied to the film in a sheet form with a thickness of 300 μm at 200° C., and then a laminate of the film and the urethane resin sheet was wound into a roll. The rolled laminate was then unwound to obtain a urethane resin sheet, and its thickness uniformity and quality (wrinkles, streaks) were evaluated. A film with significant thickness unevenness in the width direction is prone to sagging, making it impossible to coat the urethane resin sheet with a uniform thickness, and the thickness uniformity of the urethane resin sheet is reduced. Furthermore, a film with a large thermal shrinkage rate is prone to shrinkage during urethane resin coating, which makes streaks likely to occur in the urethane resin sheet. A film with weak stiffness is prone to wrinkles in the urethane resin sheet.

[0115] (19-1) Thickness Uniformity of Urethane Resin Sheet A test piece measuring 500 mm in the width direction and 40 mm in the machine direction was cut out from the resin sheet prepared above, and the film thickness was measured at 10 mm intervals using a Millitron 1202D manufactured by Seiko EM Corporation. The thickness unevenness was calculated using the following formula, and the thickness uniformity was evaluated using this value. Thickness Unevenness (%) = [(Maximum Thickness - Minimum Thickness) / Average Thickness] x 100 Evaluation: Good: Thickness unevenness is less than 8% Evaluation: Bad: Thickness unevenness is 8% or more (19-2) Wrinkles in Urethane Resin Sheet The resin sheet prepared above was cut into a piece of 500 mm x 500 mm, and the quality was confirmed visually. Evaluation: Good: No wrinkles occurred. Evaluation: Bad: Wrinkles occurred. (19-3) Streaks in Urethane Resin Sheet The resin sheet prepared above was cut into a piece of 500 mm x 500 mm, and the quality was confirmed visually. Evaluation: Good: No streaks occurred. Evaluation: ×: Streaks were observed.

[0116] (Raw Materials Used) The polypropylene resins constituting each layer used in the following Examples and Comparative Examples are as follows: PP-1: Propylene polymer [WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.] (copolymerized ethylene component: 0.6 mol%, melting point: 158°C, MFR: 7.5 g / 10 min). PP-2: A mixture of propylene polymer [WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.] (copolymerized ethylene component: 0.6 mol%, melting point: 158°C, MFR: 7.5 g / 10 min) containing a total of 2.0 mass% of stearyl diethanolamine monostearate, stearyl diethanolamine distearate, and stearyl diethanolamine as antistatic agents, and 0.17% of stearic acid monoglycerin ester. PP-3: A masterbatch containing 50% by mass of a propylene polymer [FS2011DG3 manufactured by Sumitomo Chemical Co., Ltd.] (copolymerized ethylene component: 0.6 mol%, melting point: 156°C, MFR: 2.5g / 10min) and a hydrogenated petroleum resin (Arcon P-125 manufactured by Arakawa Chemical Industries, Ltd.), which is an alicyclic hydrocarbon resin. PP-4: Antiblocking agent masterbatch: A masterbatch manufactured by Sumitomo Chemical Co., Ltd., containing 20% ​​by mass of polymethyl methacrylate-polystyrene crosslinked resin microparticles with an average particle size of 1.2μm in a polypropylene polymer (ethylene-propylene copolymer, MFR: 2.4g / 10min). PP-5: A masterbatch containing 50% by mass of a propylene polymer [FS2011DG3 manufactured by Sumitomo Chemical Co., Ltd.] (ethylene copolymer component: 0.6 mol%, melting point: 156°C, MFR: 2.5g / 10min) and an ethylene copolymer with 1-butene as the main component [Tafmer BL3110 manufactured by Mitsui Chemicals, Inc.]. PP-6: A masterbatch containing 50% by mass of a propylene polymer [FS2011DG3 manufactured by Sumitomo Chemical Co., Ltd.] (ethylene copolymer component: 0.6 mol%, melting point: 156°C, MFR: 2.5g / 10min) and poly4-methyl-1-pentene (TPX RT18 manufactured by Mitsui Chemicals, Inc.). PP-7: Matting agent masterbatch [FTX0876(N) manufactured by Japan Polypropylene Corporation] (masterbatch containing 50% by mass of propylene-ethylene-1-butene copolymer resin and 50% by mass of polyethylene resin).

[0117] (Example 6) (Base layer) A polypropylene-based resin composition containing 48% by mass of PP-1, 41% by mass of PP-2, 10% by mass of PP-3, and 1% by mass of PP-4 was used as the raw material. (Matte layer) A polypropylene-based resin composition containing 20% ​​by mass of PP-1 and 80% by mass of PP-7 was used as the raw material. (Film production) First, the polypropylene-based resin compositions constituting the base layer and matte layer were heated and melted at 250°C and 220°C, respectively, in an extruder. Using a multilayer feed block, the molten polypropylene-based resin compositions were laminated from a T-die at 250°C, and co-extruded so that the thicknesses of the base layer and matte layer were 72 μm and 3 μm, respectively. The base layer of the molten sheet was brought into contact with a cooling roll at 20°C and then placed directly into a water bath at 20°C. Subsequently, the film was stretched 4.5 times in the longitudinal direction at 130°C using the difference in peripheral speed between heated metal rolls, and then introduced into a tenter stretching machine, where, while held by clips, it was stretched 10 times in the width direction at a preheating temperature of 168°C and a stretching temperature of 165°C. It was then heat-treated at 155°C while being relaxed at a relaxation rate of 7% in the width direction. Finally, it was cooled to room temperature. The thickness of the film thus obtained was 75 μm. Table 3 shows the film production conditions, and Table 3 shows the film properties. As shown in Table 3, a biaxially oriented polypropylene film with minimal thickness unevenness was obtained. Furthermore, the film was suitable for use as a process film.

[0118] (Examples 7 to 10) In Examples 7 to 10, the films were produced in the same manner as in Example 6, except that the film production conditions were changed to those shown in Table 3. Table 3 shows the film production conditions and film properties. As shown in Table 3, in Examples 7 to 10, biaxially oriented polypropylene films with small thickness variations were obtained. Furthermore, these films were suitable for use as process films.

[0119] (Comparative Examples 11 to 20) In Comparative Examples 11 to 20, films were produced in the same manner as in Example 6, except that the film production conditions were changed to those listed in Table 4. Table 4 shows the film production conditions and film properties. In Comparative Example 11, the absence of an alicyclic hydrocarbon resin resulted in uneven stretching, resulting in significant thickness variation. In Comparative Example 12, the high cooling roll temperature and water cooling temperature resulted in significant thickness variation. In Comparative Example 13, the small widthwise stretching ratio resulted in significant thickness variation. In Comparative Example 14, the large longitudinal stretching ratio resulted in significant thickness variation. In Comparative Example 15, a 20 μm thick film was produced under conditions similar to those described in Patent Document 4. The film of Comparative Example 15 had minimal thickness variation, but was weak and had a large longitudinal heat shrinkage rate. In Comparative Example 16, a 75 μm thick film was produced under conditions similar to those described in Patent Document 4. The film of Comparative Example 16 had large thickness variations. It also had a large thermal shrinkage rate in the longitudinal direction. In Comparative Example 17, a film having a thickness of 35 μm was produced under conditions similar to those of Patent Document 5. The film of Comparative Example 17 had small thickness variations, but was weak and had a large thermal shrinkage rate in the longitudinal direction. In Comparative Example 18, a film having a thickness of 75 μm was produced under conditions similar to those of Patent Document 5. The film of Comparative Example 18 had large thickness variations. It also had a large thermal shrinkage rate in the longitudinal direction. In Comparative Examples 19 and 20, polybutene-1 and polymethylpentene were added instead of the alicyclic hydrocarbon resin, and films were produced under conditions similar to those of Patent Documents 2 and 3. The resulting films had large thickness variations.

[0120]

[0121]

[0122] The biaxially oriented polypropylene film of the first invention has a strong stiffness and little thickness unevenness. The biaxially oriented polypropylene film of the first invention can be used as a film for resin sheet production processes, a release film for manufacturing thermosetting resin parts such as epoxy resins and unsaturated polyesters, and fiber-reinforced plastics, as well as adhesive labels, adhesive tapes, cover films, protective films for construction and agricultural use, and insulating films.

[0123] The biaxially oriented polypropylene film of the second invention is a matte biaxially oriented polypropylene film with strong stiffness and little thickness unevenness. The biaxially oriented polypropylene film of the second invention can be used as a film for resin sheet production processes, a release film for manufacturing thermosetting resin parts such as epoxy resins and unsaturated polyesters, and fiber-reinforced plastics, as well as adhesive labels, adhesive tapes, cover films, protective films for construction and agricultural use, and insulating films.

Claims

1. A biaxially oriented polypropylene film made of a polypropylene resin composition containing 87% by mass or more and 99% by mass or less of a polypropylene resin and 1% by mass or more and 13% by mass or less of an alicyclic hydrocarbon resin, said biaxially oriented polypropylene film satisfying the following requirements (1) and (2): (1) The thickness is 65 μm or more and 200 μm or less. (2) The thickness unevenness within 1000 mm in the width direction is 8.0% or less.

2. The biaxially oriented polypropylene film according to claim 1, which satisfies the following requirements (3) and (4): (3) The heat shrinkage rate at 120°C in the longitudinal direction is 0.0% or more and 6.0% or less, and (4) The heat shrinkage rate at 120°C in the transverse direction is -3.0% or more and 5.0% or less.

3. The biaxially oriented polypropylene film according to claim 1 or 2, which satisfies the following requirements (5) and (6): (5) The stress at 5% elongation in the longitudinal direction (F5MD) is 30 MPa or more and 60 MPa or less, and (6) The stress at 5% elongation in the transverse direction (F5TD) is 40 MPa or more and 150 MPa or less.

4. A biaxially oriented polypropylene film according to claim 1 or 2, wherein the melting point of the polypropylene resin is 155°C or higher and 175°C or lower.

5. A biaxially oriented polypropylene film having a matte layer made of a resin composition laminated on at least one side of a base layer made of a polypropylene resin composition containing 87% by mass or more and 99% by mass or less of a polypropylene resin and 1% by mass or more and 13% by mass or less of an alicyclic hydrocarbon resin, the biaxially oriented polypropylene film satisfying the following requirements (7) to (9): (7) The thickness is 65 μm or more and 200 μm or less. (8) The thickness unevenness in the width direction of 1000 mm is 8.0% or less. (9) The haze is 30% or more and 90% or less.

6. The biaxially oriented polypropylene film according to claim 5, which satisfies the following requirements (10) and (11): (10) The heat shrinkage rate at 120°C in the longitudinal direction is 0.0% or more and 6.0% or less. (11) The heat shrinkage rate at 120°C in the transverse direction is -3.0% or more and 5.0% or less.

7. The biaxially oriented polypropylene film according to claim 5 or 6, which satisfies the following requirements (12) and (13): (12) The stress at 5% elongation in the longitudinal direction (F5MD) is 30 MPa or more and 60 MPa or less, and (13) The stress at 5% elongation in the transverse direction (F5TD) is 40 MPa or more and 150 MPa or less.

8. The biaxially oriented polypropylene film according to claim 5 or 6, wherein the surface average roughness SRa of the surface of the matte layer is 0.20 μm or more and 1.50 μm or less.

9. A biaxially oriented polypropylene film as described in claim 5 or 6, wherein the resin composition constituting the matte layer contains 3 mass % or more and 60 mass % or less of polyethylene resin.

10. A biaxially oriented polypropylene film as described in claim 5 or 6, wherein the resin composition constituting the matte layer contains 3 mass% or more and 60 mass% or less of a polypropylene copolymer copolymerized with ethylene and / or an α-olefin other than propylene.

11. The biaxially oriented polypropylene film according to claim 5 or 6, wherein the melting point of the polypropylene resin is 155°C or higher and 175°C or lower.

12. A process film using the biaxially oriented polypropylene film according to claim 5 or 6.

13. A release film using the biaxially oriented polypropylene film according to claim 5 or 6.

Images