Film, laminate, and method for producing film

Abstract

A film, when a skew Ssk is 5 or more and 0 or less, a load area ratio Smr2 is 70% or more and 98% or less, and a protrusion peak height Spk is 1 nm or more and 100 nm or less, at least one face is an A face. A film having no coarse protrusions, having a prescribed recess structure, excellent in mold releasability, rigidity, and heat resistance is provided.

Description

Technical Field

[0001] This invention relates to a method for manufacturing films, laminates, and resin composition films that exhibit excellent release properties, rigidity, and heat resistance. Background Technology

[0002] Films are used in various applications, including packaging, surface protection, support in the manufacturing processes of other components, hygiene products, agricultural products, construction products, medical products, and capacitors. Among these, films used for surface protection and support (hereinafter sometimes referred to as surface protective films or support films) are called process films because they are used in the manufacturing processes of optical components and electronic materials. In recent years, with the increasing demands for sophisticated and high-quality optical components and electronic materials, the required characteristics and quality of such process films have also increased.

[0003] In particular, when using a support film to manufacture a resin composition film for optical applications, the surface shape of the support film requires a high degree of control. For example, Patent Document 1 describes an example of improving the anti-glare properties of the optical film and suppressing glare by forming a phase separation structure on the surface of the support film and transferring it thereon.

[0004] Furthermore, from the viewpoint of suppressing dent transfer, a smooth surface is required for the support film. However, if the surface smoothness is too high, the slipability of the resin composition film formed on the support film may decrease, resulting in poor quality due to the generation of foreign matter and wrinkles caused by surface scraping. For example, Patent Document 2 describes an example of improving the slipability of optical films and reducing defects by adding fine particles to the surface of polyethylene terephthalate (PET) films and controlling the surface roughness to a specific level.

[0005] Furthermore, Patent Document 3 describes an example of improving high-temperature voltage resistance by controlling specific equipment and conditions during the casting process after polymer melt extrusion, thereby reducing the depth of the valleys and the volume of the valley-side voids on the film surface.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2018-173546

[0009] Patent Document 2: Japanese Patent Application Publication No. 2005-307038

[0010] Patent Document 3: Japanese Patent No. 6115687 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, in the method described in Patent Document 1, the surface of the transferred resin composition film sometimes has a large unevenness, resulting in poor optical properties and quality. Furthermore, in the method described in Patent Document 2, the surface of the transferred resin composition film has a low protrusion height and insufficient slipability. Moreover, in the method described in Patent Document 3, the surface protrusion height is sometimes high, resulting in a large depression depth on the surface of the transferred resin composition film, leading to poor optical properties and quality. Therefore, the objective of this invention is to solve the above problems. That is, to provide a film that, when used as a process film in the manufacturing process of a resin composition film, can simultaneously improve the optical properties and quality of the resulting resin composition film and its operability.

[0013] Methods for solving problems

[0014] To solve the above-mentioned problems, the membrane of the present invention has the following structure. That is,

[0015] A membrane, wherein at least one of its surfaces is a surface A, wherein the surface with a skewness Ssk of -5 or more and 0 or less, a loading area ratio Smr2 of 70% or more and 98% or less, and a protrusion peak height Spk of 1 nm or more and 100 nm or less is designated as surface A.

[0016] The laminate of the present invention has the following configuration. That is,

[0017] A laminate having a resin composition layer on surface A of the aforementioned membrane.

[0018] The method for manufacturing the resin composition film of the present invention has the following structure. That is,

[0019] A method for manufacturing a resin composition film, comprising at least the following steps 1 to 3 in sequence.

[0020] Step 1: The step of coating the above-mentioned film with a coating agent containing a resin composition on the above-mentioned surface A.

[0021] Step 2: Curing the coating agent containing the resin composition described above to form a resin composition layer, thereby producing a laminate.

[0022] Step 3: The step of peeling the resin composition layer from the above-mentioned laminate to obtain a resin composition film.

[0023] The membrane of the present invention preferably has a maximum valley depth Sv of 20 nm or more and 400 nm or less on the A-side.

[0024] The membrane of the present invention preferably has a dynamic friction coefficient μd between one surface and another surface of 0.20 or more and 0.80 or less.

[0025] The membrane of the present invention preferably has a Young's modulus of 100 MPa or more and 200 MPa or less in the MD direction at 130°C.

[0026] The membrane of the present invention preferably has a melting peak above 160°C when heated from 30°C to 260°C using a differential scanning calorimeter (DSC).

[0027] The membrane of the present invention preferably has an internal haze of 0.01% or more and 1.5% or less after being heated at 130°C for 10 minutes.

[0028] The membrane of the present invention preferably has a surface free energy of surface A of 15 mN / m or more and 35 mN / m or less.

[0029] The membrane of the present invention preferably has an olefin-based resin as the main component of its surface layer having the above-mentioned A side.

[0030] The membrane of the present invention preferably comprises at least one of an olefin-based elastomer resin and a polypropylene block copolymer.

[0031] The membrane of the present invention is preferably used as a process membrane.

[0032] The effects of the invention

[0033] This invention provides a membrane that, when used as a process membrane in the manufacturing process of resin composition films, can balance the optical properties, improved quality, and operability of the resulting resin composition film. Furthermore, because the membrane of this invention also exhibits excellent heat resistance and mold release properties, it is widely suitable for use as a process membrane for industrial materials, particularly as a protective film, support film, etc. Attached Figure Description

[0034] Figure 1 A diagram illustrating the load area ratio Smr2 and the peak height Spk of the protrusion. Detailed Implementation

[0035] In the membrane of the present invention, when the surface with a skewness Ssk of -5 or more and 0 or less, a loading area ratio Smr2 of 70% or more and 98% or less, and a peak height Spk of 1 nm or more and 100 nm or less is designated as surface A, at least one surface is surface A. By having surface A on at least one surface, the smoothness and workability of the resin composition film obtained by coating a coating agent containing a resin composition onto surface A, curing it, and peeling it off can be improved. Furthermore, hereafter, skewness Ssk, loading area ratio Smr2, and peak height Spk are sometimes simply referred to as Ssk, Smr2, and Spk, respectively.

[0036] Ssk is a parameter specified in ISO 25178-2:2012, also known as skewness. Details of the measurement conditions are shown in the examples. Generally, it is considered that fine peaks are more numerous when Ssk > 0, and fine valleys are more numerous when Ssk < 0. Most industrial membranes have protrusions on their surface to ensure slip resistance; membranes with recesses between these protrusions are very rare. Regarding the membrane of this invention, a greater number of recesses (valves) than protrusions (peaks) is important, corresponding to Ssk values ​​below 0.

[0037] When Ssk is greater than 0, the membrane surface exhibits more protrusions than depressions. Therefore, for example, when used as a support membrane, sometimes the resin composition membrane obtained by transferring a coating agent containing a resin composition onto the membrane, curing it, and then peeling it off has few protrusions, resulting in insufficient slip resistance and poor operability. On the other hand, when Ssk is less than -5, it indicates extremely few protrusions on the membrane surface. Therefore, sometimes during membrane fabrication, especially when processed as a support membrane, the slip resistance is low, reducing operability.

[0038] To achieve a Ssk value of -5 or higher and 0 or lower, methods can be employed such as setting the raw material composition of the membrane to the range described later, and setting the membrane forming conditions to the range described later. Specifically, in addition to the resin as the main component, the membrane contains at least one of an olefin-based elastomer resin and a polypropylene block copolymer. Initial longitudinal stretching is performed at a temperature above the softening temperature of the olefin-based elastomer resin and the polypropylene block copolymer formed in the resin as the main component. Then, secondary longitudinal stretching is performed at a temperature above the softening temperature of the resin as the main component of the membrane, thereby reducing the Ssk value.

[0039] In the film of the present invention, from the viewpoint of transferring and forming protrusions by coating a resin composition film containing a resin composition onto surface A, curing it, and peeling it off, the skewness Ssk of surface A is preferably -0.001 or less, more preferably -0.01 or less. Furthermore, from the viewpoint of increasing the protrusion height of the resin composition film obtained by the above method and improving operability, the Ssk of surface A is preferably -3 or more, more preferably -1.5 or more, and even more preferably -0.5 or more.

[0040] Smr2 is a parameter specified in ISO 25178-2:2012, and its detailed measurement conditions are shown in the examples. For example, a graph schematically showing the load area ratio Smr2 and the peak height Spk of the protrusion is provided. Figure 1As shown, Smr2 (symbol 1) refers to the load curve in the central part of the roughness curve (symbol 2), where the secant line of the load curve drawn to make the difference in load area ratio Smr ΔSmr 40% the gentlest slope is defined as the equivalent line (symbol 3). When the equivalent line intersects the vertical axis at two heights between the 0% and 100% load area ratio positions, which is considered the core region, the load area ratio at the point where the load curve intersects the boundary line of the protruding valley and the core region represents the proportion of the protruding valley. Furthermore, the load curve is a surface-related load curve, represented by the cut-off level as a function of the load area ratio.

[0041] Generally, a higher Smr2 value indicates a smaller core valley and finer surface depressions, while a lower Smr2 value indicates a larger core valley and coarser surface depressions. When Smr2 is greater than 98%, the depth of surface depressions becomes insufficient. Therefore, for example, when used as a support film, the height of the protrusions in the resin composition film obtained by transferring a coating agent containing a resin composition onto the film, curing it, and peeling it off is sometimes low, resulting in insufficient slip resistance and poor operability. On the other hand, when Smr2 is less than 70%, the core valleys are extremely large, and the flat core is few, resulting in an undulating surface. Therefore, for example, when used as a support film as described above, the transparency of the resulting resin composition film is sometimes compromised.

[0042] To achieve an Smr2 content of 70% or higher, one can, for example, increase the amount of olefin-based elastomer resin in the membrane, use an olefin-based elastomer with a lower softening temperature, and further increase the initial longitudinal stretching ratio during longitudinal stretching and lower the initial longitudinal stretching temperature.

[0043] In the film of the present invention, from the viewpoint of improving operability by transferring protrusions of a suitable height onto the resin composition film obtained by coating a coating agent containing a resin composition onto surface A, curing it, and peeling it off, the Smr2 of surface A is preferably 95% or less, more preferably 92% or less. Furthermore, from the viewpoint of the smoothness of the resin composition film obtained by the above method, the Smr2 of surface A is preferably 80% or more, more preferably 85% or more.

[0044] Spk is a parameter specified in ISO 25178-2:2012, and detailed measurement conditions are shown in the examples. For example, a graph schematically showing the load area ratio Smr2 and the peak height Spk of the protrusion is provided. Figure 1As shown, Spk (symbol 4) is the equivalent straight line (symbol 3) in the central part of the load curve with respect to the roughness curve (symbol 2), where the secant of the load curve with the difference ΔSmr of the load area ratio Smr is 40%. The average height of the protruding peak above the core is defined as the two height positions where the equivalent straight line intersects the vertical axis at the positions with load area ratios of 0% and 100%.

[0045] When Spk is higher than 100 nm, the protrusions on the membrane surface become coarse. Therefore, for example, when used as a support membrane, large depressions sometimes form on the resin composition membrane obtained by coating an agent containing a resin composition onto the membrane, curing it, and peeling it off. These depressions become the starting point for poor peeling when the resin composition membrane is peeled off, resulting in poor peeling and membrane breakage.

[0046] To achieve a Spk value of 1 nm or more but less than 100 nm, for example, methods can be used to configure the film's raw material composition within the range described later, and also to configure the film-forming conditions within the range described later. In particular, by including branched polypropylene resin to reduce the size of the spherulites formed during casting, by lowering the extrusion temperature and the temperature of the casting drum to increase cooling during casting, and by increasing the preheating temperature during longitudinal / transverse stretching to perform high-ratio stretching uniformly at a high ratio at a low temperature, a low Spk value can be achieved.

[0047] In the film of the present invention, from the viewpoint of improving the smoothness of the resin composition film obtained by coating an agent containing a resin composition onto surface A, curing it, and peeling it off, the Spk of surface A is preferably 70 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. Furthermore, a lower Spk of surface A is more preferred, but from the viewpoint of feasibility, a lower limit of 1 nm is desired.

[0048] From the viewpoint of balancing the smoothness and operability of the resulting resin composition film when used as a support film, the maximum valley depth Sv (hereinafter, sometimes simply referred to as Sv) on the A-side of the membrane of the present invention is preferably 20 nm or more and 400 nm or less. From the viewpoint of the smoothness of the resin composition film, the Sv on the A-side is more preferably 300 nm or less, and even more preferably 250 nm or less. Furthermore, from the viewpoint of the operability of the resin composition film, the Sv on the A-side is more preferably 30 nm or more, even more preferably 40 nm or more, and particularly preferably 50 nm or more. Sv is a parameter specified in ISO 25178-2:2012, representing the depth of the deepest pit from the average surface of the surface (the surface with the average height, corresponding to the baseline). Detailed measurement conditions are shown in the examples.

[0049] When the Sv is 20 nm or higher, excessively low depression depth on surface A can be prevented. Therefore, when used as a support film, as described above, a sufficiently high protrusion is formed in the resulting resin composition film, improving the slipperiness and operability of the resin composition film. On the other hand, when the Sv of surface A is 400 nm or lower, the size of depressions on surface A can be suppressed. Therefore, when used as a support film, for example, no large depressions are formed on the resin composition film obtained by coating a coating agent containing the resin composition onto surface A of the film, curing it, and peeling it off, thus improving the smoothness of the resin composition film. Furthermore, the transparency of the support film is also excellent, and defects during inspection using a defect inspection machine when bonded to the substrate are reduced.

[0050] To achieve a Sv of 20 nm or more and 400 nm or less, for example, methods can be used that specify the composition of the membrane raw materials within the range described later, and also specify the membrane forming conditions within the range described later. In particular, by reducing the viscosity of the olefin-based elastomer resin and the polypropylene block copolymer, and by pre-compositing the olefin-based elastomer resin and the polypropylene block copolymer with the resin that is the main component of each layer's raw material to microdisperse the rubber domain, a small Sv can be achieved.

[0051] From the viewpoint of improving quality, the membrane of the present invention preferably has a coefficient of kinetic friction μd (hereinafter, sometimes simply referred to as μd) between one surface and another surface of 0.20 or more and 0.80 or less. From the above viewpoint, μd between one surface and another surface is more preferably 0.70 or less, and even more preferably 0.60 or less. Furthermore, the lower the μd between one surface and another surface, the more preferred it is; there is no particular limitation on the lower limit, but from the viewpoint of feasibility, it is around 0.20. By making μd 0.80 or less, the slipperiness of the membrane is improved, thereby suppressing the occurrence of wrinkles and foreign matter scraping during membrane transport, and improving quality.

[0052] To achieve a μd between one surface and another surface that is 0.20 or higher and 0.80 or lower, for example, a method can be used that sets the raw material composition of the film to the range described later, and also sets the film-forming conditions to the range described later. In particular, by including branched polypropylene resin, it is effective to make the spherulites formed during casting smaller, thereby forming fine protrusions on the surface of the stretched film. In this case, by increasing the amount of branched polypropylene resin, the μd between one surface and another surface can be reduced.

[0053] The membrane of the present invention is sometimes coated with a coating agent comprising a resin composition and dried in a high-temperature oven at around 130°C. From the viewpoint of reducing wrinkles in such a high-temperature oven, it is preferable that the Young's modulus in the MD direction of the membrane (hereinafter, sometimes simply referred to as the Young's modulus in the MD direction) at 130°C is 100 MPa or more and 200 MPa or less. From the above viewpoint, the Young's modulus in the MD direction is more preferably 120 MPa or more, and even more preferably 140 MPa or more. A higher Young's modulus in the MD direction of the membrane at 130°C is preferred, and there is no particular limitation, but 200 MPa is an upper limit in terms of feasibility. In addition, the term "membrane MD direction" refers to the direction parallel to the direction in which the membrane is formed, and is also referred to as the film forming direction or length direction in other expressions. Furthermore, the term "membrane TD direction" refers to the direction orthogonal to the membrane MD direction within the membrane surface, and is also referred to as the width direction in other expressions. In addition, Young's modulus can be determined by performing a tensile test on the membrane after heating it at 130°C for 1 minute and then stretching it at a speed of 300 mm / min. The detailed test conditions will be described later.

[0054] Furthermore, when the MD direction of the membrane is unclear, the orthogonal direction to the main orientation direction of the membrane is defined as the MD direction. Here, the main orientation direction refers to the direction in which the Young's modulus is highest when measured in various directions forming angles of 0° to 175° at 5° intervals relative to any arbitrary direction within the membrane surface, with any direction set to 0°. When the Young's modulus in the MD direction of the membrane is 100 MPa or higher, for example, when used as a support membrane, applying a coating agent containing a resin composition and curing it in a high-temperature process can suppress membrane stretching, thereby reducing the formation of wrinkles.

[0055] To achieve a Young's modulus of 100 MPa or more and 200 MPa or less in the MD direction of the film at 130°C, methods can be used to make the raw material composition of the film within the range described later, and also to make the film forming conditions within the range described later. In particular, it is effective to use raw materials with high crystallinity, and to increase the preheating temperature during longitudinal / transverse stretching, and to perform high-ratio stretching uniformly at a high ratio at a low temperature.

[0056] From the viewpoint of improving heat resistance, the membrane of the present invention preferably has a melting peak at or above 160°C when heated from 30°C to 260°C using a differential scanning calorimeter (DSC), more preferably at or above 165°C, and even more preferably at or above 168°C. A higher melting peak temperature is preferred, and while there is no particular upper limit, 220°C is practically the upper limit. The phrase "having a melting peak at or above 160°C" here includes not only the case where there is only one melting peak at or above 160°C, but also the case where there are multiple melting peaks, at least one of which falls within the range of 160°C or above.

[0057] When a melting peak is present at temperatures above 160°C, for example when used as a support film, curing the coating agent containing the resin composition in a high-temperature process after application can reduce film breakage and deterioration of planarity. To achieve a melting peak temperature of 160°C or higher, methods can be used that specify the raw material composition of the film within the range described later, and also specify the film-forming conditions within the range described later. In particular, using a high-melting-point resin in the inner layer of the film is effective in improving the heat resistance of the inner layer.

[0058] From the viewpoint of transparency, the membrane of the present invention preferably has an internal haze (hereinafter, sometimes simply referred to as haze) of 0.01% or more and 1.5% or less after heating at 130°C for 10 minutes. From the above viewpoint, the haze after heating at 130°C for 10 minutes is more preferably 1.0% or less, and even more preferably 0.7% or less. Lower haze after heating at 130°C for 10 minutes is preferred, and there are no particular limitations, but 0.01% is desirable from the viewpoint of feasibility. Furthermore, the haze can be measured using a known haze meter, and detailed measurement conditions are shown in the examples.

[0059] By heating at 130°C for 10 minutes, the haze is reduced to 1.5% or less. Therefore, for example, when used as a support film, the transparency of the support film is maintained even after a high-temperature heat transfer process as described above, and defects during inspection with a defect inspection machine when bonded to the substrate are mitigated. The film of the present invention sometimes contains various additives such as antioxidants. Such films, in particular, are prone to having their transparency compromised if subjected to heat above 130°C, as these additives can leach to the film surface. Therefore, for such films, it is particularly advantageous to maintain a haze within the aforementioned range.

[0060] To achieve a haze of 0.01% to 1.5% after heating at 130°C for 10 minutes, methods can be used to configure the film's raw material composition as described later, and also to configure the film-forming conditions as described later. In particular, it is effective to achieve uniform stretching by including branched polypropylene resin, reducing the size of the spherulites formed during casting, lowering the extrusion temperature and casting drum temperature to increase cooling during casting, and increasing the preheating temperature during longitudinal / transverse stretching to perform stretching at low temperatures. Furthermore, using raw materials with high stereoregularity and low cold xylene soluble fraction (CXS) improves crystallinity; and heat treatment and relaxation after longitudinal and transverse stretching are also effective.

[0061] From the viewpoint of facilitating the peeling of the resin composition film formed on the surface of layer A when used as a support film, the surface free energy of the A-side of the membrane of the present invention is preferably 15 mN / m or more and 35 mN / m or less. From the above viewpoint, the surface free energy of the A-side is more preferably 32 mN / m or less, and even more preferably 29 mN / m or less. Lower surface free energy results in better release properties, which is preferred, but 15 mN / m is the lower limit from the viewpoint of feasibility. With a surface free energy of 35 mN / m or less, for example, when used as a support film, when a coating agent containing a resin composition is applied to the A-side and peeled off after curing to obtain a resin composition film, the peeling of the resin composition film becomes smooth, and the generation of film breakage and peel marks during peeling is reduced. Furthermore, the surface free energy can be measured using four liquids—water, ethylene glycol, formamide, and diiodomethane—as measuring solutions, and measured with a known contact angle meter; detailed measurement conditions are shown in the examples.

[0062] To achieve a surface free energy of 15 mN / m or more and 35 mN / m or less for surface A, for example, a method can be used that sets the raw material composition of the membrane to the range described later, and also sets the membrane forming conditions to the range described later. In particular, it is effective to make the main component of the membrane surface layer in contact with surface A (in the case of a single-layer structure, the membrane itself, hereinafter the same) a polyolefin resin and to provide a release coating layer on surface A. However, from the viewpoint of component movement in the resin composition membrane and cost, it is more preferable to make the main component of the membrane surface layer in contact with surface A a polyolefin resin.

[0063] The thickness of the film of the present invention is appropriately adjusted according to the application and is not particularly limited, but from an operational point of view, a thickness of 0.5 μm or more and 100 μm or less is preferred. When used as a release film, the upper limit of the thickness is more preferably 60 μm or less, further preferably 50 μm or less, and most preferably 40 μm or less. The lower limit is more preferably 4 μm or more, further preferably 8 μm or more, and most preferably 11 μm or more. The thickness can be adjusted by the screw speed of the extruder, the width of the unstretched sheet, the film forming speed, the stretch ratio, etc., without reducing other physical properties.

[0064] The raw materials of the membrane of the present invention will be described below, but are not necessarily limited thereto.

[0065] The composition of the film constituting the present invention is not particularly limited, but it is preferred that the main component is a thermoplastic resin. Examples of thermoplastic resins, besides polypropylene resin described later, include, for example, polyolefin resins such as polystyrene (PS) resin, styrene-based elastomer resin, polymethylpentene (PMP) resin, cyclic olefin (COP) resin, and cyclic olefin / copolymer (COC) resin; polyester resins such as polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, and polyethylene naphthalate (PEN) resin; polysulfone resins such as polysulfone (PSU) resin, polyethersulfone (PES) resin, and polyphenylene sulfone (PPSU) resin; polyphenylene sulfide (PPS) resin; polyphenylene sulfide ketone resin; polyphenylene sulfide sulfone resin; and polyphenylene sulfide ketone sulfone. Resins include polyarylene sulfide resins, polyetherketone (PEK) resins, polyetheretherketone (PEEK) resins, polyetherketoneketone (PEKK) resins, polyetheretherketoneketone (PEEKK) resins, polyetherketoneketoneketone (PEKEKK) resins, polytetrafluoroethylene (PTFE) resins (also known as tetrafluoroethylene resins), polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resins (also known as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resins), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resins (also known as tetrafluoroethylene-hexafluoropropylene copolymer resins), and tetrafluoroethylene-ethylene copolymer (ETFE) resins (also known as tetrafluoroethylene-ethylene copolymers). Fluoropolymer resins, polychlorotrifluoroethylene (PCTFE) resin (also known as trifluorochloroethylene resin), poly(1,1-difluoroethylene) (PVDE) resin (also known as 1,1-difluoroethylene resin), 1,1-difluoroethylene / tetrafluoroethylene / hexafluoropyrene copolymer resin, etc.; polyacetal resins; liquid crystal polymer (LCP) resins; polycarbonate (PC) resins; polyarylate (PAR) resins; acrylic resins; polymethyl methacrylate (PMMA) resins; polyurethane resins (PU); polyurethane acrylate resins; cellulose; cellulose derivatives (e.g., acetyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, etc.); petroleum... Resins, terpene resins, terpene phenolic resins, low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, low-crystallinity or amorphous ethylene / α-olefin copolymers, ethylene / propylene / diene terpolymers, crystalline polypropylene, polypropylene, propylene / ethylene copolymers (random copolymers and / or block copolymers), propylene / α-olefin copolymers, propylene / ethylene / α-olefin copolymers, polybutene, 4-methyl-1-pentene / α-olefin copolymers, ethylene / (meth)acrylate ethyl acrylate copolymers, ethylene / (meth)acrylate methyl acrylate copolymers, ethylene / (meth)acrylate n-butyl acrylate copolymers, ethylene / vinyl acetate copolymers, etc. These raw materials can also be modified, derived, and copolymerized with other compounds.Furthermore, these raw materials can be used alone or in combination of two or more. From the viewpoint of adjusting Ssk to 0 or below, polyolefin resins and polyester resins that are easy to biaxially stretch are preferred. In order to produce a microphase separation structure with an average domain diameter of 5 μm or less before stretching, it is preferable to contain at least one group of mutually incompatible components.

[0066] Furthermore, the membrane of the present invention may contain various additives, such as weathering agents, transparentizing agents, crystal nucleating agents, antioxidants, heat stabilizers, lubricants, antistatic agents, anti-blocking agents, fillers, viscosity modifiers, color-preventing agents, leveling agents, surfactants, release agents, etc., without impairing the purpose of the present invention.

[0067] From the viewpoints of release properties and cost, it is preferable that the surface layer having side A of the film of the present invention uses an olefin-based resin as the main component. For the purpose of improving release properties, sometimes resins with release properties, such as silicone resins, are coated onto PET films, etc. However, when peeling off after bonding with an adhered object, the silicone resin or other resin components sometimes migrate to the adhered object and become contaminated. On the other hand, although olefin-based resins have relatively low release properties, the migration to the adhered object is extremely rare; therefore, they are preferred for use in the surface layer having side A. In the present invention, "surface layer having side A" refers to the outermost layer on the side A when the film is a laminated structure, and to the film itself when the film is a single layer. "The surface layer having side A uses an olefin-based resin as the main component" means that the proportion of the olefin-based resin in all components constituting the surface layer having side A is more than 50% by mass and less than 100% by mass (hereinafter, the term "main component" can also be interpreted similarly). Furthermore, when the membrane is composed of multiple layers and both sides are A-sides, it can be considered that "the surface layer having the A-side has an olefin-based resin as its main component" as long as at least one of the surface layers having the A-side satisfies the above requirements. The content of the olefin-based resin in the surface layer having the A-side is more preferably 90% by mass or more and 100% by mass or less, further preferably 95% by mass or more and 100% by mass or less, even more preferably 96% by mass or more and 100% by mass or less, particularly preferably 97% by mass or more and 100% by mass or less, and most preferably 98% by mass or more and 100% by mass or less.

[0068] The term "olefin resin" here refers to a resin that contains more than 50 mol% and less than 100 mol% of olefin units when all the constituent units of the resin are set to 100 mol%. Specific examples of olefin resins include polyethylene, polypropylene, polybutene, polymethylpentene, and copolymers thereof. Furthermore, when multiple olefin resins are included, the content of the olefin resin is calculated by adding up all the olefin resins. That is, except for cases where a single olefin resin contains more than 50 mol% by mass, cases where each olefin resin contains less than 50 mol% by mass, but the total content of all olefin resins exceeds 50 mol% by mass, are also considered as "olefin resin as the main component".

[0069] From the viewpoints of mold release, flexibility, and cost, the membrane of the present invention preferably has not only an A-side surface layer but also, as a whole, an olefin-based resin as the main component. The amount of olefin-based resin in all components constituting the membrane is more preferably 90% by mass or more and 100% by mass or less, further preferably 95% by mass or more and 100% by mass or less, even more preferably 96% by mass or more and 100% by mass or less, particularly preferably 97% by mass or more and 100% by mass or less, and most preferably 98% by mass or more and 100% by mass or less. Specific examples of olefin-based resins include polyethylene resin, polypropylene resin, polybutene resin, polymethylpentene resin, and copolymers thereof.

[0070] Regarding the membrane of the present invention, from the viewpoint of transparency and heat resistance, it is preferable that the content of polypropylene resin in the resin constituting the membrane is 95% by mass or more and 100% by mass or less. From the above viewpoint, it is more preferable that it is 96% by mass or more, further preferably 97% by mass or more, and particularly preferably 98% by mass or more. Polypropylene resin, as referred to here, means a resin containing more than 50% by mass and less than 100% propylene units when all the constituent units constituting the resin are set to 100 mol%.

[0071] In the membrane of the present invention, the surface layer having side A is preferably composed of polypropylene resin as the main component, and the content of polyethylene resin in the entire layer is 3% by mass or less. From the viewpoint of membrane quality, the content of polyethylene resin in the surface layer having side A is more preferably 2% by mass or less, more preferably 1% by mass or less, and most preferably 0.5% by mass or less. Matte rough polypropylene membranes are often formed by blending polypropylene resin and polyethylene resin to create a rough surface. However, in this method, sometimes the quality deteriorates due to increased fisheyes in the polyethylene resin, sometimes due to increased foreign matter caused by scraping the membrane surface, etc. Therefore, it is preferable to suppress the content of polyethylene resin in the surface layer having side A to be within the above-mentioned range.

[0072] From the viewpoint of suppressing the formation of coarse protrusions on the surface of surface A and forming a recessed structure of a specified depth, the membrane of the present invention preferably comprises at least two of the following resins: polypropylene resin, branched polypropylene resin, low-crystallinity polyolefin resin, polymethylpentene resin, and resin containing a rubber domain.

[0073] The melting point of the polypropylene resin (hereinafter, sometimes referred to as polypropylene resin A) in the film of the present invention is preferably 155°C or higher, more preferably 160°C or higher, further preferably 163°C or higher, and most preferably 165°C or higher. By having the polypropylene resin melt point of 155°C or higher, the heat resistance of the film is improved. Therefore, for example, when used as a release film, when passing through a heated process after being bonded to an adherend, the softening of the film and its accompanying elongation in the tensile direction are reduced, thus suppressing deformation of the adherend.

[0074] As polypropylene resin A, linear polypropylene resin is preferred.

[0075] Furthermore, for polypropylene resin A, a melt flow rate (MFR) of 1 to 10 g / 10 min at 230°C and a load of 21.18 N is more preferred, even more preferred is 1 to 8 g / 10 min, and particularly preferred is 2 to 5 g / 10 min. By using such a polypropylene resin, film-forming properties and film strength are improved. To achieve a melt flow rate (MFR) of 1 to 10 g / 10 min or the aforementioned preferred values, it is preferable to adjust the hydrogen concentration during polymerization, appropriately select the catalyst and / or co-catalyst, and select the composition, etc.

[0076] Without impairing the purpose of the present invention, polypropylene resin A may contain copolymer components (copolymer units) formed from other unsaturated hydrocarbons. Examples of such copolymer components include ethylene, 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1, 1-hexene, 4-methylpentene-1, 5-ethylhexene-1, 1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl-2-norbornene, etc. From the perspective of dimensional stability, the copolymer content is 1 mol% or less. Furthermore, within the scope of not impairing the effects of the present invention, resins containing propylene and the above-mentioned copolymer components may also be blended into polypropylene resin A.

[0077] It is known that the branched polypropylene resin (hereinafter, sometimes referred to as branched polypropylene resin B) in the film of the present invention acts as a nucleating agent for the linear polypropylene resin, thereby suppressing the formation of coarse protrusions in the stretched film by miniaturizing the spherulites of the cast film after melt extrusion.

[0078] When branched polypropylene resin B is included, regarding the content of branched polypropylene resin B in this layer, when all components of the layer are set to 100% by mass, the upper limit of the content of branched polypropylene resin B is more preferably 50% by mass or less, further preferably 40% by mass or less, more preferably 30% by mass or less, and most preferably 25% by mass or less. Furthermore, the lower limit of the content of branched polypropylene resin B is more preferably 0.1% by mass or more, further preferably 1% by mass or more, more preferably 4% by mass or more, and most preferably 10% by mass or more.

[0079] From the viewpoint of extrusion stability, it is preferable that the molecular weight flow rate (MFR) of branched polypropylene resin B, measured at 230°C and a load of 21.18 N, is 0.5 g / 10 min or more and 9 g / 10 min or less. More preferably, the lower limit of the MFR of branched polypropylene resin B measured under the same conditions is in the range of 2 g / 10 min, and even more preferably, it is 6 g / 10 min or more. To achieve an MFR of branched polypropylene resin B of 0.5 g / 10 min or more and 9 g / 10 min or less, or the aforementioned preferred values, it is preferable to employ methods such as adjusting the hydrogen concentration during polymerization, appropriately selecting the catalyst and / or co-catalyst, and selecting the composition.

[0080] From the viewpoint of uniform tensile strength, a melt tension of 3 gf or more and 40 gf or less is preferred for branched polypropylene resin B. The lower limit of the melt tension is more preferably 4 gf, and even more preferably 6 gf. The upper limit is more preferably 30 gf, and even more preferably 25 gf. To achieve the above-mentioned melt tension values, methods such as controlling the average molecular weight, molecular weight distribution, and degree of branching in the polypropylene resin are employed. In particular, in the case of long-chain branches, the melt tension can be significantly increased, and preferred values ​​can be adjusted by modifying the molecular chain and degree of branching of the long-chain branches.

[0081] Although there are various branched polypropylene resins B available on the market, such as Ziegler-Natta catalysts and metallocene catalysts, metallocene catalysts with low molecular weight components, low high molecular weight components, and narrow molecular weight distribution are preferred.

[0082] The film of the present invention contains a low-crystallinity polyolefin resin (hereinafter, low-crystallinity polyolefin resin C), thereby reducing the crystallinity of the cast film after melt extrusion, and as a result, suppressing the formation of coarse protrusions in the stretched film. The low-crystallinity polyolefin resin C preferably has lower stereoregularity of the polymer molecular structure and / or lower crystallinity compared to polypropylene resin A. Examples of reducing crystallinity include copolymerization with comonomers. While resins without a melting point are also considered, in the case of resins with a melting point, the melting point of the low-crystallinity polyolefin resin C is preferably lower than that of polypropylene resin A, more preferably 50°C or higher and 135°C or lower, more preferably 60°C or higher and 130°C or lower, further preferably 60°C or higher and 120°C or lower, and most preferably 60°C or higher and 100°C or lower. Furthermore, it is also preferable to produce a laminated film in which at least one surface layer contains a low-crystallinity polyolefin resin with a melting point of 50°C or higher and 135°C or lower, or within the aforementioned preferred range.

[0083] When conveying the preheating / stretching rollers, from the viewpoint of preventing melting of the film surface and adhesion to the rollers, the melting point of the low-crystallinity polyolefin resin C is preferably 50°C or higher. Furthermore, from the viewpoint of partially melting and roughening the film surface during stretching, the melting point of the low-crystallinity polyolefin resin C is preferably 135°C or lower. When the film is a laminated structure and at least one surface layer contains low-crystallinity polyolefin resin C, regarding the content of low-crystallinity polyolefin resin C in the surface layer containing low-crystallinity polyolefin resin C, when all components of that layer are set to 100% by mass, the upper limit of the content of low-crystallinity polyolefin resin C is more preferably 80% by mass or lower, further preferably 70% by mass or lower, further preferably 40% by mass or lower, and most preferably 25% by mass or lower. Furthermore, the lower limit of the content of low-crystallinity polyolefin resin C is more preferably 5% by mass or higher, further preferably 15% by mass or higher, and most preferably 20% by mass or higher. As for the low-crystallinity polyolefin resin C, a low-crystallinity polypropylene resin compatible with polypropylene resin A is preferred. Examples include copolymers of propylene and α-olefins and polypropylene resins with low stereoregularity. For example, commercially available products such as "Wintec" (registered trademark) manufactured by Nippon Polypro Co., Ltd., which is a random copolymer of polypropylene, and "Elmode" (registered trademark) manufactured by Idemitsu Kosan Co., Ltd., which is a low-stereoregularity polypropylene resin, can be appropriately selected and used.

[0084] The membrane of the present invention preferably contains a rubber domain forming resin (hereinafter, sometimes referred to as rubber domain forming resin D). Here, a rubber domain forming resin refers to a resin in which rubber domains can be formed in the membrane by blending with polypropylene resin A. Examples include resins containing rubber domains, such as polypropylene block copolymers, and thermoplastic elastomers that do not completely incompatible with polypropylene resin A but form rubber domains in the matrix of polypropylene resin A. By adopting this form, the rubber domains are stretched significantly compared to the matrix resin during longitudinal stretching, thus forming a recessed structure on the membrane surface. The rubber domain forming resin D is not particularly limited as long as it is a resin in which rubber domains can be formed in the membrane, but it is preferably at least one of thermoplastic elastomers and polypropylene block copolymers, but polyolefin-based thermoplastic elastomers are particularly preferred from the perspective of high affinity with polypropylene resin A. In particular, a thermoplastic elastomer refers to an elastomer that has the property of softening and exhibiting fluidity when heated, and returning to a rubbery state when cooled. The upper limit of the preferred Vicat softening temperature of the rubber domain forming resin D is preferably 130°C or less, more preferably 122°C or less, and even more preferably 110°C or less. The lower limit of the Vicat softening temperature is preferably 50°C or more, more preferably 65°C or more, even more preferably 80°C or more, and most preferably 90°C or more.

[0085] When the rubber domain forming resin D is included, regarding the content of rubber domain forming resin D in the layer containing the rubber domain forming resin, when the total composition of the layer is set to 100% by mass, the upper limit of the content of rubber domain forming resin D is more preferably 35% by mass or less, further preferably 25% by mass or less, further preferably 17% by mass or less, and most preferably 12% by mass or less. Furthermore, the lower limit of the content of rubber domain forming resin D is more preferably 1% by mass or more, further preferably 4% by mass or more, further preferably 6% by mass or more, and most preferably 8% by mass or more.

[0086] In the polypropylene resin A, branched polypropylene resin B, low-crystallinity polyolefin resin C, and rubber domain forming resin D used in the membrane of the present invention, various additives may be contained, such as crystal nucleating agents, antioxidants, heat stabilizers, lubricants, antistatic agents, anti-blocking agents, fillers, viscosity modifiers, color-preventing agents, etc., without prejudice to the purpose of the present invention.

[0087] Among these, the selection of the type and amount of antioxidant is important from the viewpoint of antioxidant efflux. That is, as such antioxidants, sterically hindered phenolic antioxidants are preferred, at least one of which is a high molecular weight antioxidant with a molecular weight of 500 or more. As specific examples, various examples can be given, such as 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (e.g., BASF's "Irganox" (registered trademark) 1330: molecular weight 775.2) or tetra[methylene-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane (e.g., BASF's "Irganox" (registered trademark) 1010: molecular weight 1,177.7), etc.

[0088] In the polypropylene resin A used in the membrane of the present invention, a crystallizing nucleating agent may be added without departing from the purpose of the present invention. Specific examples include α-crystal nucleating agents (dibenzyl sorbitol derivatives, sodium benzoate, etc.) and β-crystal nucleating agents (potassium 1,2-hydroxystearate, magnesium benzoate, amide compounds such as N,N'-dicyclohexyl-2,6-naphthalenedicarboxylate, quinacridone compounds, etc.). Excessive addition of the above-mentioned nucleating agents can sometimes cause a decrease in tensile strength, void formation, and consequently a decrease in transparency and strength. Therefore, when the polypropylene resin A is set to 100 parts by weight, the amount added is typically 0.5 parts by weight or less, preferably 0.1 parts by weight or less, and more preferably 0.05 parts by weight or less.

[0089] Preferably, the surface layer having side A (the film itself in the case of a single-layer structure) of the film of the present invention does not contain organic or inorganic particles. Polypropylene resin has low affinity for organic and inorganic particles, which can sometimes cause particles to detach and contaminate processes and products. Furthermore, sometimes high-hardness particles can form large protrusions that unevenly transfer onto the resin layer of optical components, sometimes hindering its use as a protective film or support film for high-quality products such as display components.

[0090] The film of the present invention is preferably biaxially stretched based on the above-mentioned resin. As a method of biaxial stretching, it can be obtained by any of the following methods: simultaneous biaxial stretching with blow-up, simultaneous biaxial stretching with a tenter frame, and successive biaxial stretching with a tenter frame. Among these methods, the successive biaxial stretching with a tenter frame is preferred in terms of controlling film formation stability, thickness uniformity, high film rigidity, and dimensional stability.

[0091] The following describes one aspect of the membrane manufacturing method of the present invention as an example, but the membrane manufacturing method of the present invention is not necessarily limited to this.

[0092] First, 50 parts by weight of polypropylene resin A, 20 parts by weight of branched polypropylene resin B, 20 parts by weight of low-crystallinity polyolefin resin C, and 10 parts by weight of rubber domain forming resin D are fed from a metering hopper to a twin-screw extruder. The mixture is melt-blended at 260°C and discharged in strip form from the die. The discharged resin composition is cooled and cured in a water bath at 25°C and cut into sheets to obtain a resin composition for the surface layer (I). The resin composition for the surface layer (I) is fed to a single-screw extruder, and A1 and B1 are dry-blended at a 95:5 (mass ratio) and fed to a single-screw melt extruder for the inner layer (II). Melt extrusion is performed at 200–280°C, more preferably 220–280°C, and even more preferably 240–270°C. Furthermore, after removing foreign matter and modified polymers using a filter installed midway through the polymer tube, the layers are stacked using a multi-manifold type composite T-die in two configurations: layer I / layer II / layer I. The stacked layers are then discharged onto a casting drum to obtain a laminated unstretched sheet with a layer I / layer II / layer I configuration. In this case, the preferred layer thickness ratio is in the range of 1 / 8 / 1 to 1 / 60 / 1.

[0093] Furthermore, the surface temperature of the casting drum is preferably 10–45°C, more preferably 15–35°C, and even more preferably 15–25°C. It can also be configured as a two-layer stack of layer I / II, but in this case, the layer I side is tightly sealed to the casting drum. As a method for sealing to the casting drum, any of the following methods can be used: electrostatic application, sealing using the surface tension of water, air knife method, pressure roller method, underwater casting method, etc., but air knife method, which provides good planarity and allows for control of surface roughness, is preferred. The air temperature of the air knife is preferably 10°C–30°C, and the blowing air velocity is preferably 130 m / s–150 m / s. Furthermore, to prevent film vibration, the position of the air knife is preferably adjusted appropriately so that the airflow is directed to the downstream side of the film forming process.

[0094] The resulting unstretched sheet is fed into a longitudinal stretching process. In this process, a two-stage stretching process—initial longitudinal stretching at a low temperature and low ratio, followed by longitudinal stretching at a high temperature and high ratio—effectively forms a recessed structure on the surface of layer I. Initially, as the initial longitudinal stretching, low-ratio stretching is performed by preheating at a temperature higher than the softening temperature of the resin D forming the rubber domain. This effectively stretches the rubber domain significantly compared to the matrix resin, forming a recessed structure on the film surface. Preferably, this initial longitudinal stretching involves preheating the unstretched sheet by contacting it with multiple metal rollers maintained at 80°C or higher and 130°C or lower, preferably 90°C or higher and 120°C or lower, and more preferably 100°C or higher and 110°C or lower. The sheet is then stretched along its length at a ratio of 1.1 to 3.0 times, preferably 1.3 to 2.5 times, between rollers with a circumferential speed difference.

[0095] Then, by performing longitudinal stretching at a high ratio at a temperature higher than the initial longitudinal stretching temperature, a longitudinally uniaxially stretched film is obtained, which is preferred because it stabilizes the transverse stretching and results in low haze. More specifically, preheating is preferably performed by contacting a metal roller at a preheating temperature higher than the initial longitudinal stretching temperature and maintained at 110°C to 150°C, preferably 115°C to 140°C, and more preferably 120°C to 140°C, and the sheet is stretched between rollers with a circumferential speed difference. The total stretching ratio for the two-stage stretching is preferably 3.5 to 7 times, more preferably 4.5 to 5.5 times, and more preferably 4.5 to 5.0 times. If the total stretching ratio is less than 3 times, the orientation of the resulting film may become weaker and the strength may decrease.

[0096] Next, the longitudinally uniaxially stretched film is guided to a tenter frame, and after preheating by clamping the ends of the film with fixtures, it is stretched laterally in the width direction to 7 to 13 times its original size. It is important that the longitudinally uniaxially stretched film is preheated at a low temperature before being stretched laterally, so as not to damage the recessed structure formed on the film surface. Therefore, the preheating and stretching temperature is 120°C to 175°C, preferably 120°C to 165°C, and more preferably 140°C to 160°C. Furthermore, it is particularly preferable that the stretching temperature is low relative to the preheating temperature, preferably at least 3°C ​​lower, more preferably at least 5°C lower, and even more preferably at least 10°C lower.

[0097] In the subsequent heat treatment and relaxation processes, the film is relaxed along its width at a relaxation rate of 2% to 20%, more preferably 5% to 18%, and even more preferably 8% to 15%, while being held taut in the width direction by clamps. Simultaneously, heat setting is performed at a temperature of 140°C to 175°C, preferably 140°C to 170°C, more preferably 150°C to 170°C, and even more preferably 160°C to 170°C. Then, while still held taut in the width direction by clamps, the film undergoes a cooling process at 80°C to 100°C and is guided to the outside of the tenter frame. The clamps at both ends of the film in the width direction are released, and the film edges are cut during the winding process to wind the film product. By performing heat setting under the above conditions, residual stress within the film is alleviated, and the heat shrinkage rate is reduced.

[0098] The film obtained by the above-described process can be used in various industrial applications such as packaging films, surface protective films, support films, hygiene products, agricultural products, construction products, medical products, and capacitor films. However, it is particularly favored for process film applications due to its lack of large protrusions, its defined recessed structure, excellent release properties, rigidity, heat resistance, and slip resistance. Process films, as referred to here, include protective films that protect the film during transport, support films used as supports in the manufacture of resin composition films, and cover films that cover the non-supporting side of the resin composition film when molding the resin composition film on a support film.

[0099] Next, the manufacturing method of the laminated body and the resin composition film of the present invention will be described. The laminated body of the present invention has a resin composition layer on surface A of the film of the present invention. Because the film of the present invention does not have large protrusions and has a defined recessed structure, it exhibits excellent mold release properties, rigidity, and heat resistance. Therefore, it facilitates the manufacturing of a resin composition film obtained by forming a laminated body on surface A and then peeling off the resin composition layer. Furthermore, the manufacturing method of the resin composition film of the present invention includes at least the following steps 1 to 3 in sequence: Step 1: A step of coating the surface A of the film according to any one of claims 1 to 10 with a coating agent containing a resin composition. Step 2: A step of curing the coating agent containing the resin composition to form a resin composition layer, thereby forming a laminated body. Step 3: A step of peeling off the resin composition layer from the laminated body to obtain a resin composition film.

[0100] The following example illustrates the method for manufacturing the resin composition film of the present invention, using a method for manufacturing a polyurethane acrylate film as an example, but it is not necessarily limited to this.

[0101] The roll of film obtained by the above method is fed into a rod coater, and a coating agent consisting of 50 parts by weight of a resin composition made of commercially available urethane acrylate (viscosity at 25°C 600,000 mPa·s, weight average molecular weight Mw 1,600, glass transition temperature 10°C), 50 parts by weight of commercially available methyl ethyl ketone, and 3 parts by weight of commercially available 1-hydroxycyclohexylphenyl ketone is applied to surface A of the film to achieve a film thickness of 1 μm or more and 100 μm or less. The film is then fed into a hot air dryer and heated to 50°C or higher and 150°C or lower to remove the solvent. Next, the coating agent on the film is cured by irradiation with a UV lamp under a nitrogen atmosphere, resulting in a laminate made of a resin composition layer formed of polyurethane acrylate and a film. The laminate is then wound to obtain a roll having the resin composition layer on surface A of the film. A resin composition film formed of polyurethane acrylate can be obtained by peeling the resin composition layer off the film by rolling the laminate out of the laminate.

[0102] As an example of other resin composition films, a resin composition film formed from cellulose acetate propionate can be cited. A coating agent consisting of 100 parts by weight of commercially available cellulose acetate propionate (acetyl substitution degree + propionyl substitution degree = 2.5, weight average molecular weight = 180,000, Mw / Mn = 3.0), 8 parts by weight of triphenyl phosphate, 2 parts by weight of ethyl phthaloyl ethyl glycolate, 360 parts by weight of dichloromethane, 60 parts by weight of ethanol, 0.5 parts by weight of Tinuvin 109 (manufactured by Chiba Japan Co., Ltd.), and 0.5 parts by weight of Tinuvin 171 (manufactured by Chiba Japan Co., Ltd.) is applied to side A of the film to achieve a film thickness of 1 μm or more and 100 μm or less. The material is introduced into a hot air dryer and heated to a temperature between 10°C and 50°C to remove the solvent, thereby curing the coating agent on the membrane and obtaining a laminate consisting of a resin composition layer formed of cellulose acetate propionate and a membrane. The laminate is then wound to obtain a roll in which the resin composition layer is formed on surface A of the membrane. The laminate is unwound from the roll to peel the resin composition layer off the membrane, thus obtaining a resin composition membrane formed of cellulose acetate propionate.

[0103] As another example, a resin composition film formed from polyetherimide can be cited. A coating agent consisting of 15 parts by weight of commercially available polyetherimide resin (manufactured by SABIC, trade name "ULTEM" (registered trademark) 1010, Vicat softening point temperature 215°C) and 85 parts by weight of N-methyl-2-pyrrolidone is applied to surface A of a film to achieve a film thickness of 1 μm or more and 100 μm or less. This mixture is then placed in a hot air dryer and heated at 50°C or higher and 150°C or lower to remove the solvent, thereby curing the coating agent on the film and obtaining a laminate consisting of a resin composition layer formed from polyetherimide and a film. This laminate is then wound to obtain a roll containing the resin composition layer on surface A of the film. The laminate is then unwound from the film, and the resin composition layer is peeled off, thus obtaining a resin composition film formed from polyetherimide.

[0104] Example

[0105] The present invention will now be described in detail through examples. Furthermore, the methods for evaluating various properties, the resins used in the manufacture of the membranes, etc., will be described below.

[0106] (Evaluation methods for each characteristic)

[0107] (1) Film thickness

[0108] The thickness was measured using a micrometer manufactured by Anritsu Corporation. Specifically, a 10cm square sample of the membrane was taken, and the thickness of 5 randomly selected points was measured and the average value was calculated. The obtained value was set as the membrane thickness.

[0109] (2) Skewness Ssk, load area ratio Smr2, peak height Spk, maximum valley depth Sv

[0110] All parameters were measured and calculated according to ISO 25178 (2012). Measurements were performed using a scanning white interference microscope “VS1540” (manufactured by Hitachi Hitachi Systems Co., Ltd.; measurement conditions and apparatus configuration will be described later). Furthermore, the captured images were supplemented (fully supplemented) using the accompanying analysis software, and surface correction was performed using a fourth-order polynomial approximation. A median filter (3×3 pixels) was then applied to this image as the measured electromagnetic surface. The S-filter nesting index was set to 0.445. Measurements were performed on both sides of a 5cm×5cm square section of the membrane. The intersection of the diagonals was designated as measurement point 1. Points 1 cm apart, moving clockwise from the starting point towards each of the four corners, were designated as points 2, 3, 4, and 5. The midpoint of the line segment connecting points 2 and 3 was designated as point 6; the midpoint of the line segment connecting points 3 and 4 was designated as point 7; the midpoint of the line segment connecting points 4 and 5 was designated as point 8; and the midpoint of the line segment connecting points 5 and 2 was designated as point 9. A total of nine measurement points were identified (points 1 to 9), and measurements were taken at each point. Based on the measurement results, Ssk, Smr2, Spk, and Sv were calculated for each measurement location using the above steps. For each parameter, the average of the five values ​​obtained after removing the first, second, eighth, and ninth largest values ​​from the nine values ​​was used as the membrane's Ssk, Smr2, Spk, and Sv. Table 2 lists the values ​​of Ssk, Smr2, Spk, and Sv for the A-side of the membrane. For membranes with two A-sides, the values ​​for the side with the lower Spk value are listed. For membranes without an A-side, the values ​​for the side with the lower Spk value are listed. Furthermore, for membranes without an A-side and with equal Spk values ​​on both sides, the values ​​for the side with the smaller Ssk value are listed.

[0111] <Measurement conditions and apparatus configuration>

[0112] Objective lens: 10x

[0113] Lens tube: 1x

[0114] Variable focal length lens: 1x

[0115] Wavelength filter: 530nm white

[0116] Measurement mode: Wave

[0117] Measurement software: VS-Measure 10.0.4.0

[0118] Analysis software: VS-Viewer 10.0.3.0

[0119] Measurement area: 561.1 μm × 561.5 μm

[0120] Pixel count: 1,024 × 1,024.

[0121] (3) The coefficient of kinetic friction μd between one surface and another

[0122] The membrane was cut into pieces 6.5 cm wide and 12 cm long, and measured using a sliding testing machine manufactured by Toyo Seiki Kogyo Co., Ltd., according to JIS K7125 (1999), at 25°C and 65% RH. Furthermore, the measurement direction was set as the orthogonal direction of the principal orientation, and different surfaces were overlapped. The same measurement was performed five times on a single sample, and the average value was calculated and set as the coefficient of kinetic friction (μd) for that sample.

[0123] (4) Young's modulus at 130℃

[0124] The Young's modulus at 130°C was measured using an Olymtec film tensile strength tester (AMF / RTA-100) from Olymtec Corporation. The film was placed in an oven heated to 130°C along with its clamping pan and heated for 1 minute. Then, a tensile test was performed on the film at a stretching speed of 300 mm / min. A rectangle was cut out with a measurement direction (orthogonal to the main orientation axis) of 25 cm and a direction perpendicular to the measurement direction of 1 cm. The film was stretched to a length of 100 mm and a stretching speed of 300 mm / min, and the elongation was measured according to the method specified in JIS Z1702 (1994).

[0125] (5) Melting peak temperature

[0126] A sample of 5 mg of the film or raw material was placed in an aluminum dish and measured using a differential scanning calorimeter (Seiko Electronics Kogyo Co., Ltd. RDC220). The temperature was increased from 20°C to 260°C at a rate of 10°C / min under a nitrogen atmosphere, held for 5 minutes, then decreased from 260°C to 20°C at a rate of 10°C / min, and then increased again from 20°C to 260°C (second run). The temperature at the top of the melting curve observed at the highest temperature side was defined as the melting peak temperature.

[0127] (6) Internal haze after heat treatment

[0128] The membrane was cut into pieces 3.0 cm wide and 6.0 cm long, and the test pieces were sandwiched between pieces of paper. Under zero load, the samples were heated in an oven at 130°C for 10 minutes, then removed and cooled to room temperature. These were then used as samples. A haze meter (HGM-2DP) manufactured by Suga Testing Equipment Co., Ltd. was used for the measurements. The internal haze after heat treatment was determined by measuring the sample inserted into a quartz cell with a 1 cm optical path length filled with tetrahydronaphthalene.

[0129] (7) Evaluation of the slip properties of the resin composition film obtained by coating, curing, and peeling.

[0130] On side A of a 21cm × 30cm membrane, a coating agent consisting of 50 parts by weight of a resin composition comprising a commercially available urethane acrylate (viscosity at 25°C 600,000 mPa·s, weight-average molecular weight Mw 1,600, glass transition temperature 10°C), 50 parts by weight of a commercially available methyl ethyl ketone, and 3 parts by weight of a commercially available 1-hydroxycyclohexylphenyl ketone was applied to achieve a film thickness of 45 μm. The membrane was then placed in a hot air dryer and heated at 80°C to remove the solvent. Next, the coating agent on the membrane was cured by irradiation with a UV lamp under a nitrogen atmosphere. The resin composition layer was then peeled off to obtain a resin composition film formed from polyurethane acrylate. When both sides of the membrane are sides A, the same coating agent was applied to the side with the lower Spk value, and the same procedure was followed to obtain a resin composition film. For membranes without sides A, the same coating agent was applied to the side with the lower Spk value, and the same procedure was followed to obtain a resin composition film. Furthermore, for films without an A-side and with equal Spk values ​​on both sides, the above-mentioned coating agent was applied to the side with the smaller Ssk value, and the same steps were followed to obtain a resin composition film. This was repeated 5 times to obtain 5 resin composition films. Using a sliding testing machine manufactured by Toyo Seiki Kogyo Co., Ltd., according to JISK 7125 (1999), the kinetic friction coefficient μd of the resin composition films rubbing against each other along their length was determined by the method described in (3) with the surfaces in contact with each other being overlapped in a manner that the surfaces of the resin composition films obtained under a load of 200g, 25°C, and 65%RH in contact with each other. The sample was set as a rectangle with a width of 80mm and a length of 200mm, and 5 sets (10 pieces) were cut out. When cutting out the sample, one set was cut from one resin composition film, and the area 2cm from the end of the resin composition film was not used. Five measurements were performed, and the average value was taken as the value of the kinetic friction coefficient μd of the resin composition film. The slip properties (the effect of the film on the sliding properties of the film) of the resin composition were evaluated based on the value of the dynamic friction coefficient μd of the film.

[0131] Advantages: μd is below 0.50.

[0132] Good: μd is greater than 0.50 and less than 0.55.

[0133] Acceptable: μd is greater than 0.55 and less than 0.60.

[0134] Unacceptable: μd > 0.60.

[0135] (8) Evaluation of the transparency of resin composition films obtained by coating, curing, and peeling.

[0136] Two resin composition films were obtained using the method described in (7). The obtained resin composition films were sampled as squares with a width of 100 mm and a length of 100 mm. The side of the resin composition film in contact with the film was designated as the P-side, and the other side as the Q-side. The films were overlapped with the P-side and Q-side in contact, sandwiched between two acrylic sheets (100 mm wide and 100 mm long), and a 3 kg load was applied. The films were then left to stand at 23°C for 24 hours. After 24 hours, the Q-side, which was in contact with the P-side, was visually observed, and the smoothing effect of the process film was evaluated according to the following criteria.

[0137] Superior: Clean, as before the application of load.

[0138] Good: The surface was slightly uneven immediately after the load was released, but the unevenness was no longer visible after 10 minutes.

[0139] Acceptable: A weak bump or depression was also detected 10 minutes after the load was released.

[0140] Unacceptable: Strong embossed transfer was found.

[0141] (9) Surface free energy

[0142] Four liquids—water, ethylene glycol, formamide, and diiodomethane—were used as the test solutions. A contact angle meter (CA-D type) manufactured by Kyowa Interface Science Co., Ltd. was used to determine the static contact angle of each liquid relative to the A-side of the membrane. The static contact angle was measured 30 seconds after each liquid was added to the A-side of the membrane. The contact angles obtained for each liquid and the surface tension components of the test solution were substituted into the following equations, and the simultaneous equations consisting of these equations were solved for γSd, γSp, and γSh. For membranes with A-sides on both sides, the side with lower Spk was evaluated. For membranes without A-sides, the side with lower Spk was evaluated. Furthermore, for membranes without A-sides and with equal Spk on both sides, the side with lower Ssk value was evaluated.

[0143] (γSd·γLd) 1 / 2 +(γSp·γLp) 1 / 2 +(γSh·γLh) 1 / 2 =γL(1+COSθ) / 2

[0144] Where γS=γSd+γSp+γSh

[0145] γL=γLd+γLp+γLh

[0146] γS, γSd, γSp, and γSh represent the surface free energy, dispersion force component, polar force component, and hydrogen bond component of the membrane surface, respectively. Furthermore, γL, γLd, γLp, and γLh represent the surface free energy, dispersion force component, polar force component, and hydrogen bond component of the measured liquids used. Here, the surface tensions of the liquids used are values ​​proposed by Panzer (J. Panzer, J. Colloid Interface Sci., 44, 142 (1973)).

[0147] (10) Vicat softening temperature

[0148] Test samples were prepared by pressing each raw material into 3 mm thick shapes, and the Vicat softening temperature of each raw material was evaluated using a heat distortion tester (Yasuda Seiki Co., Ltd. "148-6-type") according to ASTM D1525.

[0149] (The resins, etc. used in the manufacture of membranes)

[0150] A1: Polypropylene resin (manufactured by Polymer Corporation, MFR: 3.0g / 10min, melting point: 164℃)

[0151] A2: Polypropylene resin (manufactured by Sumitomo Chemical Co., Ltd., MFR: 7.5g / 10min, melting point: 163℃)

[0152] A3: Polypropylene resin (manufactured by Polymer Corporation, MFR: 3.0g / 10min, melting point 161℃)

[0153] A4: Polypropylene resin (manufactured by Polymer Corporation, MFR: 4.0g / 10min, melting point 166℃)

[0154] B1: Branched polypropylene resin (WAYMAX MFX6, manufactured by Nippon Polypro Co., Ltd., MFR: 3.0g / 10 minutes)

[0155] B2: Branched polypropylene resin (WAYMAX MFX3, manufactured by Nippon Polypro Co., Ltd., MFR: 8.0g / 10 minutes)

[0156] B3: Branched polypropylene resin (Daploy (registered trademark) WB140HMS, manufactured by Voleaires Co., Ltd., MFR: 2.1g / 10 minutes)

[0157] C1: Random polypropylene resin (WINTEC (registered trademark) WFW4M manufactured by Polypro Co., Ltd., Japan, MFR: 7.0g / 10min, melting point 135℃) C2: Polypropylene resin (L-MODU (registered trademark) S901 manufactured by Idemitsu Kosan Co., Ltd., melting point 80℃)

[0158] D1: Thermoplastic elastomer resin (WELNEX RFX4V manufactured by Polypro Co., Ltd., Japan (registered trademark), Vicat softening temperature: 100℃)

[0159] D2: Block polypropylene resin (Sumitomo Chemical Co., Ltd. "Noblen" (registered trademark) AW564, Vicat softening temperature: 101℃)

[0160] D3: Thermoplastic elastomer resin (WELNEX RFX4VM manufactured by Polypro Co., Ltd., Japan (registered trademark), Vicat softening temperature: 115℃)

[0161] D4: Thermoplastic elastomer resin (Mitsui Chemicals Co., Ltd. "Tafmar" (registered trademark) XM7070, Vicat softening temperature: 67°C)

[0162] Polyester A: Polyester resin with an intrinsic viscosity of 0.68 obtained through the following steps.

[0163] Procedure: 100 parts by mass of dimethyl terephthalate and 60 parts by mass of ethylene glycol were used as starting materials. 0.09 parts by mass of magnesium acetate tetrahydrate was added to the reactor as a catalyst. The reaction was initiated at 150°C, and the temperature was slowly increased along with the removal of methanol by distillation, reaching 230°C after 3 hours. The transesterification reaction was essentially completed after 4 hours. Then, 0.04 parts by mass of ethyl phosphate and 0.04 parts by mass of antimony trioxide were added to the reaction mixture, and a condensation reaction was carried out for 4 hours. Specifically, the temperature was slowly increased from 230°C to 280°C. Simultaneously, the pressure was slowly decreased from atmospheric pressure, eventually reaching 0.3 mmHg. After the reaction started, the reaction was stopped at a point equivalent to an intrinsic viscosity of 0.68 by adjusting the stirring force of the reaction vessel, and the polymer was discharged under nitrogen pressure.

[0164] Polyester B: Polyester resin with an intrinsic viscosity of 0.67 obtained through the following steps.

[0165] Steps: In the manufacturing method of polyester A, after adding 0.04 parts by mass of ethyl phosphate, 0.3 parts by mass of synthetic calcium carbonate particles with an average particle size of 0.7 μm and a particle size distribution value of 1.70 dispersed in ethylene glycol and 0.04 parts by mass of antimony trioxide were added. The polycondensation reaction was stopped at a point equivalent to an intrinsic viscosity of 0.66. Otherwise, the same method as the manufacturing method of polyester A was used.

[0166] Polyester C: A polyester resin with an intrinsic viscosity of 0.67 obtained through the following steps.

[0167] Steps: In the manufacturing method of polyester B, the added particles are amorphous silica particles with an average particle size of 1.4 μm and a particle size distribution value of 2.5, and the addition amount is 0.1 parts. Otherwise, the same method as the manufacturing method of polyester B is used.

[0168] (Example 1)

[0169] The resin composition was fed from a metering hopper to a twin-screw extruder in the following manner: A1 as 50 parts by mass, B1 as 20 parts by mass, C1 as a low-crystallinity polyolefin resin as 20 parts by mass, and D1 as a rubber domain forming resin as 10 parts by mass. The mixture was melt-blended at 260°C and discharged in strip form from the die. The discharged resin composition was cooled and cured in a water bath at 25°C and cut into sheets to obtain a resin composition for the surface layer (I). The resin composition for the surface layer (I) was fed to a single-screw extruder, and A1 and B1 were dry-blended at a 95:5 (mass ratio) and fed to a single-screw melt extruder for the inner layer (II). Both were melt-extruded at 260°C. Next, foreign matter was removed from the molten resin compositions using a sintering filter with a 20μm cutoff. Then, using a feed block type composite T-die, the surface layer (I) / inner layer (II) / surface layer (I) were laminated at a thickness ratio of 1 / 24 / 1, and discharged into a casting drum with the surface temperature controlled at 20°C. An air knife was used to ensure tight adhesion between the sheet and the casting drum. Compressed air was then sprayed onto the side of the sheet opposite to the casting drum surface to cool it, resulting in an unstretched sheet. This unstretched sheet was then preheated to 90°C using ceramic rollers and initially stretched 1.3 times along its length between rollers at 90°C with a circumferential speed difference (stretching along the length is sometimes referred to as longitudinal stretching). Next, the initially stretched film was preheated to 140°C and subjected to a second longitudinal stretch at a ratio of 3.5 times. Next, the longitudinally stretched film was clamped at both ends along its width direction and fed into a tenter frame. After preheating at 160°C for 3 seconds, it was stretched to 9.8 times its original length along its width direction at 150°C. While allowing a 10% relaxation along its width direction, it was heat-treated at 165°C. Then, after a cooling process at 100°C, the film was guided to the outside of the tenter frame, the clamps at both ends along its width direction were released, and the film was wound onto a core, yielding a 12 μm thick biaxially oriented polypropylene film. The physical properties and evaluation results of the obtained biaxially oriented polypropylene film are shown in Table 1.

[0170]

[0171] (Examples 2-4, 6-7, Comparative Examples 1, 2, 4, 6)

[0172] The composition, layer structure, stack ratio, and film-forming conditions of each layer were as shown in Table 1. Except for these differences, the procedure was the same as in Example 1, and films with the thicknesses shown in Table 1 were obtained. The physical properties and evaluation results of the obtained films are also shown in Table 1. Furthermore, the film thickness was adjusted by adjusting the discharge rate during extrusion.

[0173] (Example 5)

[0174] As raw materials, 65 parts by mass of the aforementioned polypropylene raw material A1, 20 parts by mass of the aforementioned low-crystallinity polyolefin raw material C1, and 15 parts by mass of the aforementioned raw material containing rubber domains were dry-blended and fed into a single-screw melt extruder for single-layer applications. Melt extrusion was performed at 260°C. After removing foreign matter using a sintered filter with a 20 μm cutoff, the extruded material was discharged into a casting drum with a surface temperature controlled at 20°C. An air knife was used to seal the material against the casting drum. Then, compressed air was sprayed onto the uncooled drum surface of the sheet on the casting drum for cooling, resulting in an unstretched sheet. Next, the sheet was preheated to 125°C using ceramic rollers and initially stretched 1.2 times along the length of the film between rollers at 125°C with a circumferential speed difference. Then, it was preheated to 138°C and subjected to a second longitudinal stretch of 3.4 times. Next, the film end was clamped and fed into a tenter frame. After preheating at 168°C for 3 seconds, it was stretched to 7.5 times its original length at 163°C. While being relaxed by 16% along the width direction, it underwent heat treatment at 173°C. After a cooling process at 100°C, it was guided to the outside of the tenter frame, the clamps at the film end were released, and the film was wound onto a core, yielding a single-layer film with a thickness of 22 μm. The physical properties and evaluation results of the obtained film are shown in Table 1.

[0175] (Comparative Example 3)

[0176] Coating solution X was prepared by dissolving 5.65 parts by weight of an acrylic resin with polymerizable unsaturated side chains, 1.2 parts by weight of cellulose acetate propionate, 4 parts by weight of a multifunctional acrylic UV-curable compound, 2.77 parts by weight of an acrylic UV-curable compound, and 0.53 parts by weight of a photoinitiator in a mixed solvent of 25 parts by weight of methyl ethyl ketone (MEK) and 12.15 parts by weight of 1-butanol. Then, coating solution X was applied to the side of a biaxially stretched PET film that had undergone an easy-to-adhere surface treatment using a wire-bar coating method. The film was dried at 95°C for 2 minutes to form a 7 μm thick coating layer. Further, the film was irradiated with ultraviolet light from a high-pressure mercury lamp (manufactured by Igura Films Co., Ltd.) for approximately 10 seconds (cumulative irradiation intensity approximately 400 mJ / cm²). 2 The film was obtained by UV curing. The physical properties and evaluation results of the obtained film are shown in Table 1.

[0177] (Comparative Example 5)

[0178] 70 parts by weight of A3 and 30 parts by weight of D1 were dry-blended to prepare mixed raw material particles. These particles were fed from a hopper into a single-screw extruder A for melting and extruded as a single resin layer through a single-layer die. The extruded resin layer was cooled and solidified on a cooling drum controlled at 35°C while being pressed by air pressure from an air knife, resulting in a 900 μm thick unstretched film. Simultaneous biaxial stretching was performed using a Bluenear intermittent biaxial stretching machine, "KAROIV," relative to the obtained unstretched film. Using the following equipment settings and the stretching ratio of the unstretched film, a film with a total thickness of approximately 100 μm was obtained. The physical properties and evaluation results of the obtained film are shown in Table 1.

[0179] Device settings: Preheating temperature 165℃, preheating time 2 minutes, stretching temperature (longitudinal stretching temperature and transverse stretching temperature) 165℃, stretching speed 100% / second.

[0180] Stretching and heat treatment conditions for non-stretchable film: After simultaneous biaxial stretching at 3.3 times in the longitudinal direction and 3.3 times in the transverse direction, the longitudinal stretch is gradually reduced to 3 times and the transverse stretch is gradually reduced to 3 times in an oven at a set temperature of 170°C, and then heat-set for 20 seconds.

[0181] (Comparative Example 7)

[0182] Anhydrous magnesium chloride, decane, and 2-ethylhexanol were mixed, and phthalic anhydride was added to the heated solution, followed by further stirring. After cooling the solution, it was added dropwise to titanium tetrachloride cooled to -20°C. The mixture was then heated, and diisobutyl phthalate was added with stirring. The mixture was then filtered to obtain a solid. The resulting solid was washed with decane and hexane to obtain the titanium catalyst used in propylene polymerization.

[0183] Propylene polymerization was carried out using the aforementioned titanium catalyst, triethylaluminum as a co-catalyst, and hydrogen as a chain transfer agent. After deactivation, the resulting product was thoroughly washed with propylene monomer to obtain polypropylene resin. The MFR of this polypropylene resin was 2.5 g / 10 min, and the proportion of racemic pentamelidic components (mmmm) was 0.980.

[0184] After adding BHT as an antioxidant to 99.7% by mass of the obtained polypropylene resin in such a manner as 0.1% by mass and Irganox-1010 as an antioxidant in the same manner, the mixture was kneaded and granulated at a temperature of 260°C to obtain a polypropylene resin composition.

[0185] 100% by mass of the above polypropylene resin composition was fed into a single-screw melt extruder and melt extruded at 250°C. Foreign matter was removed using a sintered filter with a 25 μm cutoff. Furthermore, a shear rate of 300 seconds was applied in the T-die during extrusion. -1 The molten polypropylene resin composition discharged from the T-die is pressed together on four consecutive casting drums to obtain a molten sheet. The consecutive casting drums have the same diameter and are designated CD1, CD2, CD3, and CD4 from the upstream of the apparatus, forming a film pass where each surface of the cast sheet alternately contacts each casting drum. The surface temperatures of CD1 and CD2 are 30°C, and the surface temperatures of CD3 and CD4 are 90°C. Furthermore, the pressing time between each casting drum (CD1, CD2, CD3, CD4) and the molten sheet is 0.4 seconds. To ensure the sheet presses together on CD1, the initial casting drum, an air knife and end-point air are used. The air temperature of the air knife is adjusted to 30°C. Furthermore, the atmosphere temperature of the casting process is also adjusted to 30°C. Next, the cast sheet is preheated using heated rollers, heated to a film temperature of 145°C, and then stretched 5.5 times along its length. At this point, the length-direction stretching speed was 2,000,000% / min, and the necking rate was 98%. Next, the ends were clamped and stretched 10 times along the width direction at 30,000% / min at 155°C. Further, a heat treatment was performed at 158°C for 7 seconds, followed by a 12% relaxation along the width direction. Then, after slow cooling to room temperature, one side of the film was stretched at 25 W·min / m. 2 The membrane was subjected to corona discharge treatment, and the ear-like parts of the membrane held by the clamp were cut off. The side that was in contact with CD1 and underwent corona discharge treatment was designated as side A, and the side that was in contact with CD2 and not underwent corona discharge treatment was designated as side B. The membrane with the ends removed was wound using a winding machine to obtain a biaxially oriented polypropylene membrane with a thickness of 2.5 μm.

[0186] In addition, since Example 5 and Comparative Examples 5 and 7 are single-layered, there is no difference between the surface layer (I) and the inner layer (II). However, the composition of the films of Comparative Examples 5 and 7 is recorded in the column of surface layer (I) in Table 1.

[0187] Industry availability

[0188] The film of the present invention can be used in various industrial applications such as packaging film, surface protective film, support film, hygiene products, agricultural products, building products, medical products, and capacitor film. In particular, it is preferred as a support film (especially a process film in the manufacturing process of resin composition films) because it does not have large protrusions, has a specified recessed structure, and has excellent release properties, rigidity, and heat resistance.

[0189] Explanation of symbols

[0190] 1: Smr2

[0191] 2: Roughness curve

[0192] 3: Equivalent straight lines

[0193] 4: Spk.

Claims

1. A biaxially stretched film comprising linear polypropylene resin, branched polypropylene resin, low-crystallinity polyolefin resin, and rubber domain forming resin. The rubber domain forming resin is at least one of an olefin-based elastomer resin and a polypropylene block copolymer. When a surface with a skewness Ssk of -5 or higher and 0 or lower, a loading area ratio Smr2 of 70% or higher and 98% or lower, and a protrusion peak height Spk of 1 nm or higher and 100 nm or lower is designated as surface A, at least one of these surfaces is surface A. The surface layer having side A is mainly composed of olefin resin.

2. The biaxially stretched membrane according to claim 1, wherein the maximum valley depth Sv of surface A is greater than 20 nm and less than 400 nm.

3. The biaxially stretched membrane according to claim 1 or 2, wherein the coefficient of kinetic friction μd between one surface and the other surface is 0.20 or more and 0.80 or less.

4. The biaxially stretched membrane according to claim 1 or 2, wherein the Young's modulus in the MD direction of the membrane at 130°C is 100 MPa or more and 200 MPa or less.

5. The biaxially stretched film according to claim 1 or 2, when heated from 30°C to 260°C using differential scanning calorimetry (DSC), has a melting peak above 160°C.

6. The biaxially stretched film according to claim 1 or 2, wherein the internal haze after being heated at 130°C for 10 minutes is greater than 0.01% and less than 1.5%.

7. The biaxially stretched membrane according to claim 1 or 2, wherein the surface free energy of surface A is above 15 mN / m and below 35 mN / m.

8. The biaxially stretched film according to claim 1 or 2, which is used as a process film.

9. A laminate having a resin composition layer on said A surface of the biaxially stretched film according to any one of claims 1 to 8.

10. A method for manufacturing a resin composition film, comprising at least the following steps 1 to 3 in sequence. Step 1: The step of coating side A of the biaxially stretched film according to any one of claims 1 to 8 with a coating agent comprising a resin composition. Step 2: The step of curing the coating agent containing the resin composition to form a resin composition layer, thereby producing a laminate. Step 3: Step of peeling the resin composition layer from the laminate to obtain a resin composition film.

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