Laminated film for decoration

Abstract

To provide a laminated film for decoration which is formed by laminating an acrylic resin film and a vinylidene fluoride-based resin film, has high stretchability, and has good transparency, chemical resistance and scratch resistance of the vinylidene fluoride-based resin film even after stretching.SOLUTION: A laminated film for decoration is formed by laminating an acrylic (AC)-based resin film and a vinylidene fluoride (VDF)-based resin film. A ratio of the thickness of the VDF-based resin film to the thickness of the AC-based resin film is 1 / 20 to 1 / 4. As for the VDF-based resin film, a ratio of absorbance of a peak measured at 1,700 to 1,740 cm-1 to absorbance of a peak measured at 860 to 880 cm-1 in an IR spectrum is 0.120 or less. As the laminated film, a haze measured in a non-stretched manner is 0.0 to 10.0%, tensile elastic modulus is 500 to 1,500 MPa, and a haze stretched at 120°C and 140% in an MD direction is 0.0 to 10.0%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a decorative laminate film. [Background technology]

[0002] Decorative films are often applied to automobiles, home appliances, furniture, buildings, etc. to improve durability and decoration. In particular, for the interior and exterior of automobiles, replacing the conventional paint with decorative films is expected to improve design, reduce weight, simplify the manufacturing process, and reduce environmental pollution caused by solvents contained in paint.

[0003] As a decorative film, a highly transparent acrylic resin film (hereinafter, acrylic resin may be referred to as "AC resin" and acrylic resin film may be referred to as "AC resin film") is used so as not to impair the design expression of the base material. On the other hand, AC resin film has poor chemical resistance, so it is used as a laminate film laminated with a vinylidene fluoride resin film (hereinafter, vinylidene fluoride resin may be referred to as "VDF resin" and vinylidene fluoride resin film may be referred to as "VDF resin film"), which has excellent chemical resistance, weather resistance, scratch resistance, etc. (Patent Document 1, Patent Document 2, etc.).

[0004] Decorative films are attached to the surface of a substrate while being heated and stretched by methods such as vacuum forming, compressed air forming, etc. To improve stretchability during molding, acrylic resins are sometimes mixed into VDF-based resin films used in decorative films (Patent Document 1, Patent Document 2, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-187934 [Patent Document 2] International Publication No. 2021 / 161899 Summary of the Invention [Problem to be solved by the invention]

[0006] As described in Patent Documents 1 and 2, high stretchability is required for VDF-based resin films used in decorative laminate films. To improve stretchability, VDF-based resin films have been mixed with AC-based resins.

[0007] The high chemical resistance and scratch resistance expected of VDF-based resin films must be maintained even after they are stretched during molding. However, VDF-based resin films used in conventional decorative laminate films have poor chemical resistance and scratch resistance after stretching because the crystallinity of the VDF-based resin is reduced when mixed with AC-based resin. As a result, it has been extremely difficult to achieve both chemical resistance and scratch resistance (hardness) with stretchability in VDF-based resin films used in decorative laminate films.

[0008] Furthermore, although the transparency of a VDF-based resin film does not usually decrease (the haze does not increase) when stretched while heated, the inventors have found that a laminate film in which a VDF-based resin film is laminated with an AC-based resin film has a problem in that the transparency of the VDF-based resin film decreases when stretched while heated.

[0009] The present invention has been made in view of the above problems, and has an object to provide a decorative laminate film in which an AC-based resin film and a VDF-based resin film are laminated together, the laminate film having high stretchability and in which the transparency, chemical resistance, and scratch resistance of the VDF-based resin film are good even after stretching. [Means for solving the problem]

[0010] One embodiment of the present invention for solving the above problems relates to the following fluorine-containing resin films [1] to [6]. [1] A laminated film in which an acrylic resin film and a vinylidene fluoride resin film are laminated, wherein the ratio (T1 / T2) of the thickness (T1) of the vinylidene fluoride resin film to the thickness (T2) of the acrylic resin film is 1 / 20 or more and 1 / 4 or less, and the vinylidene fluoride resin film has an infrared absorption spectrum of 1700 cm -1 ~1740cm -1 The absorbance A of the peak measured in the range of 860 cm -1 ~880cm -1 a ratio (A / B) of the absorbance A of the peak measured in the range of A to the absorbance B of the peak measured in the range of B is 0.12 or less, the haze of the laminate film measured in an unstretched state is 0.0% or more and 10.0% or less, and the tensile modulus of elasticity at 23°C measured in an unstretched state is 500 MPa or more and 1500 MPa or less, and the haze of the laminate film when stretched to 140% at 120°C is 0.0% or more and 10.0% or less. [2] The decorative laminate film according to [1], wherein the vinylidene fluoride resin film has a scratch hardness (pencil method) measured in accordance with ISO 15184:2020 of HB or more and 6H or less. [3] The decorative laminate film according to either [1] or [2], which has a breaking elongation at 23°C of 100% or more and 400% or less. [4] The decorative laminate film according to any one of [1] to [3], wherein the vinylidene fluoride resin film has a thickness (T1) of 1 μm or more and 30 μm or less, and the acrylic resin film has a thickness (T2) of 25 μm or more and 200 μm or less. [5] The decorative laminate film according to any one of [1] to [4], wherein the vinylidene fluoride resin film contains a VDF resin having an inherent viscosity of 0.80 dl / g or more and 1.20 dl / g or less. [6] The decorative laminate film according to any one of [1] to [5], wherein the vinylidene fluoride resin film contains a vinylidene fluoride resin and 0.3 parts by mass or more and 5.0 parts by mass or less of an alkyl quaternary ammonium sulfate per 100 parts by mass of the vinylidene fluoride resin. [Effects of the Invention]

[0011] According to the present invention, there is provided a laminated film for decorative use, which is formed by laminating an AC-based resin film and a VDF-based resin film, and which has high stretchability and maintains the transparency, chemical resistance, and scratch resistance of the VDF-based resin film even after stretching. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Laminated film] One embodiment of the present invention relates to a decorative laminate film (hereinafter, sometimes simply referred to as a "laminate film") The laminate film is formed by laminating an AC-based resin film and a VDF-based resin film.

[0013] (VDF resin film) The VDF-based resin film is a film formed from a VDF-based resin.

[0014] VDF resin film has an infrared absorption spectrum of 1700 cm -1 ~1740cm -1 The absorbance A of the peak measured in the range of 860 cm -1 ~880cm -1 The ratio (A / B) of the absorbance A of the peak measured in the range of A to the absorbance B of the peak measured in the range of A / B is 0.12 or less. The absorbance A corresponds to the content of AC resin contained in the VDF resin film. The absorbance B corresponds to the content of VDF resin contained in the VDF resin film. VDF resin films have a small ratio A / B and a low content of AC resin, etc. Therefore, deterioration of chemical resistance and scratch resistance after stretching due to AC resin, etc. is unlikely to occur. The ratio A / B is preferably 0.01 or more and 0.120 or less, and more preferably 0.02 or more and 0.07 or less.

[0015] On the other hand, in this embodiment, the crystallinity of the VDF-based resin is maintained while the microstructure, such as the crystal size and crystal arrangement, is appropriately controlled by adding alkyl quaternary ammonium sulfate to the VDF-based resin, copolymerizing vinylidene fluoride with a fluorinated olefin, optimizing the inherent viscosity of the VDF-based resin, and optimizing the cooling rate of the film during production, etc. This reduces the tensile modulus and increases the breaking elongation while maintaining the hardness of the VDF-based resin film.

[0016] The transparency of a polymer film can be evaluated by its haze. Higher haze indicates lower transparency. VDF-based resin films are less likely to have high haze when stretched alone. On the other hand, when a VDF-based resin film is laminated with an AC-based resin film, the haze of the laminated film tends to increase during stretching. The increase in haze is primarily due to an increase in the haze of the VDF-based resin film. The reason why the haze of the laminated film increases upon stretching is unclear, but the inventors believe the reason is as follows: Because the VDF-based resin and AC-based resin are compatible at the interface of the laminated film, the polymer chains of the VDF-based resin are bound to the polymer chains of the AC-based resin. In particular, the constraint of the polymer chains between the crystals of the VDF-based resin prevents stress relaxation during stretching, resulting in stress concentration. In contrast, stress concentration due to stretching is low within the VDF-based resin film away from the interface. It is believed that the coexistence of areas in the film where stress concentration occurs during stretching and areas where stress concentration is relatively low creates voids between the molecular chains that make up the film, resulting in high haze in the VDF-based resin film.In contrast, in this embodiment, by appropriately controlling the microstructure, such as by loosening the arrangement of the VDF-based resin molecular chains, stress concentration is suppressed, and the occurrence of cracks and surface irregularities that increase haze when the laminate film is stretched is suppressed, thereby also suppressing a decrease in transparency after stretching.

[0017] The VDF-based resin may be a homopolymer of vinylidene fluoride (hereinafter sometimes abbreviated as "VDF") or a copolymer containing VDF as the main component. "Containing VDF as the main component" means that the mass ratio of VDF-derived structural units to the total mass of the VDF-based resin is 50 mass% or more. From the viewpoint of improving the stretchability of the laminated film, a copolymer is preferred. Examples of the copolymer include VDF-hexafluoropropylene copolymer, VDF-tetrafluoroethylene copolymer, and VDF-tetrafluoroethylene-hexafluoropropylene copolymer, with VDF-hexafluoropropylene copolymer being particularly preferred from the viewpoint of improving the stretchability. The content of other structural units (i.e., structural units derived from hexafluoropropylene or tetrafluoroethylene) in the copolymer is preferably 1.0 mass% or more and 5.0 mass% or less, more preferably 1.5 mass% or more and 3.0 mass% or less. When the content of other structural units is 1.0% by mass or more, the stretchability of the laminated film is improved, resulting in a high breaking elongation. Furthermore, since the crystallinity of the VDF-based resin is appropriately reduced, cracks are less likely to occur during stretching, and a decrease in transparency after stretching due to cracks (increases in internal and external haze) is less likely to occur. When the amount of other structural units is 5.0% by mass or less, slight irregularities caused by the cooling roll that comes into contact with the laminated film during production are less likely to form on the surface of the laminated film. These irregularities are less likely to spread during stretching, causing surface roughness and resulting in a decrease in transparency (increases in external haze). The VDF-based resin may be commercially available or may be obtained by polymerization using a conventional method.

[0018] The content of structural units derived from hexafluoropropylene (hereinafter sometimes abbreviated as "HFP") in a VDF-based resin is defined as the ratio of the content of fluorine atoms derived from HFP to the content of all fluorine atoms in the resin. 19 The content of structural units derived from HFP contained in the VDF-based resin can be determined by F-NMR measurement and calculated.

[0019] The inherent viscosity of the VDF-based resin is preferably 0.80 dl / g or more but 1.20 dl / g or less, and more preferably 0.80 dl / g or more but 1.05 dl / g or less. Generally, as the molecular weight decreases, thermal molecular motion tends to become easier. Even in polymer compounds, the lower the degree of polymerization, the easier the molecular chain motion. Therefore, the lower the inherent viscosity, the lower the degree of polymerization, which facilitates polymer chain rearrangement upon cooling, resulting in faster crystallization and easier crystal growth. Therefore, it tends to be difficult to control the microstructure, such as by loosening the molecular chains to alleviate stress concentration during stretching. If the inherent viscosity is 0.80 dl / g or less, it becomes difficult to control the microstructure. Stress concentration due to constraints at the interface of the laminated film during stretching tends to lead to the generation of microvoids in the VDF-based resin film, resulting in increased haze. If the inherent viscosity is 0.80 dl / g or more, the stretchability of the laminated film improves, resulting in a higher breaking elongation. If the inherent viscosity exceeds 1.20 dl / g, the stretchability of the laminated film decreases, resulting in a low elongation at break, which is undesirable.

[0020] The inherent viscosity of VDF-based resin is measured in accordance with JIS K 7367-1:2002. Specifically, 80 mg of VDF-based resin is dissolved in 20 ml of N,N-dimethylformamide, and the viscosity η of the polymer solution is measured using an Ubbelohde viscometer in a thermostatic bath at 30°C. The viscosity η of the polymer solution and the viscosity η of N,N-dimethylformamide used as a solvent are then calculated. o (dl / g), and the solution concentration C (g / dl), the inherent viscosity η is calculated using the following formula: i Calculate (dl / g). η i =(1 / C)·ln(η / η o ) Here, the concentration of the solution is 0.4 (g / dl)

[0021] The VDF resin film may contain an alkyl quaternary ammonium sulfate, which is a compound represented by the following formula (1):

[0022] [ka]

[0023] In formula (1), R 1 ~R 4 are independently alkyl groups having 1 to 10 carbon atoms. 1 ~R 4 Examples of the alkyl group in R include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group. 1 ~R 4 The total number of carbon atoms in the alkyl group is preferably 6 or more and 30 or less, more preferably 6 or more and 24 or less, and even more preferably 8 or more and 20 or less.

[0024] In formula (1), R 5 R is an alkyl group having 1 to 10 carbon atoms, a fluoroalkyl group having 1 to 10 carbon atoms, or a hydrogen atom. 5 Examples of the alkyl group in R include a methyl group and an ethyl group. 5 Examples of fluoroalkyl groups in R include CF3 and C2F5. 5 is preferably hydrogen.

[0025] Examples of alkyl quaternary ammonium sulfates include (C2H5)4N + , (C3H7)4N + , (C4H9)4N + , and (CH 11 )4N + and alkyl quaternary ammonium cations such as CF3SO4 - , CH3SO4 - , and HSO4 - These compounds may be used alone or in combination of two or more.

[0026] The alkyl quaternary ammonium sulfate is preferably an alkyl quaternary ammonium hydrogen sulfate. Examples of the alkyl quaternary ammonium hydrogen sulfate include tetraethylammonium hydrogen sulfate, tetrapropylammonium hydrogen sulfate, tetrabutylammonium hydrogen sulfate, tetrapentylammonium hydrogen sulfate, and tetrahexylammonium hydrogen sulfate.

[0027] The amount of alkyl quaternary ammonium sulfate is preferably 0.3 to 5.0 parts by weight, more preferably 0.4 to 2.0 parts by weight, and even more preferably 0.6 to 1.3 parts by weight, per 100 parts by weight of VDF-based resin. When the amount of alkyl quaternary ammonium sulfate is 0.3 parts by weight or more, the microstructure of the VDF-based resin is likely appropriately controlled, thereby improving the stretchability of the VDF-based resin film. Furthermore, appropriately controlling the microstructure of the VDF-based resin is thought to reduce the occurrence of cracks in the VDF-based resin film during stretching, thereby reducing the likelihood of a decrease in transparency (increase in internal haze and external haze) after stretching. When the amount of alkyl quaternary ammonium sulfate is 5.0 parts by weight or less, the alkyl quaternary ammonium sulfate and VDF-based resin can be thoroughly mixed during the production of the VDF-based resin.

[0028] The VDF resin film may contain antioxidants, ultraviolet absorbers, light stabilizers, lubricants, release agents, antistatic agents, flame retardants, reinforcing agents, nucleating agents, bluing agents, and the like, as long as the laminated film satisfies the properties described below.

[0029] The thickness (T1) of the VDF resin film is preferably 1 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, even more preferably 2 μm or more and 15 μm or less, and particularly preferably 2 μm or more and 10 μm or less. When the thickness (T1) is 1 μm or more, it is possible to prevent a decrease in transparency after stretching. When the thickness (T1) is 30 μm or less, it is possible to sufficiently increase the hardness of the laminated film.

[0030] (AC resin film) The AC-based resin film is a film formed from a known AC-based resin.

[0031] As the AC-based resin, a known homopolymer or copolymer of (meth)acrylic acid ester can be used. In this specification, (meth)acrylic means acrylic or methacrylic.

[0032] From the viewpoint of increasing the surface hardness of the laminated film, the AC-based resin is preferably a homopolymer or copolymer of a methacrylic acid ester. The methacrylic acid ester preferably has an alkyl group having from 1 to 4 carbon atoms, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, and t-butyl methacrylate, with methyl methacrylate being more preferred. The AC-based resin may be a copolymer of these methacrylic acid esters with other AC acid esters or vinyl monomers, but the amount of structural units derived from the methacrylic acid esters is preferably from 50 to 100% by mass, more preferably from 70 to 100% by mass, and even more preferably from 80 to 100% by mass. Commercially available AC-based resins may be used, or those obtained by polymerization using conventional methods may be used.

[0033] The AC-based resin film may contain a fluororesin such as a VDF-based resin or other resins, but the amount of AC-based resin in the AC-based resin film is from 50% to 100% by mass, preferably from 70% to 100% by mass, and more preferably from 80% to 100% by mass.

[0034] The AC resin film may contain ultraviolet absorbers, other resins, plasticizers, heat stabilizers, antioxidants, light stabilizers, crystal nucleating agents, antiblocking agents, sealability improvers, mold release agents, colorants, pigments, foaming agents, flame retardants, and the like, as long as the laminated film satisfies the properties described below.

[0035] The thickness (T2) of the AC resin film is preferably 25 μm or more and 200 μm or less, more preferably 25 μm or more and 150 μm or less, even more preferably 30 μm or more and 100 μm or less, and particularly preferably 30 μm or more and 75 μm or less. When the thickness is 25 μm or more, the hardness of the laminated film can be sufficiently increased. When the thickness is 200 μm or less, the formability, stretchability, and transparency of the laminated film can be improved.

[0036] (Laminated film) The laminated film is made by laminating an AC resin film and a VDF resin film in contact with each other, and by appropriately controlling the microstructure of the VDF resin in the VDF resin film, the hardness of the VDF resin film is maintained while the tensile modulus is lowered and the elongation at break is increased, thereby improving the stretchability.

[0037] The laminate film is attached to the surface of a preformed substrate by methods such as vacuum forming or pressure forming, while being heated and stretched. The laminate film has high stretchability, making it easy to attach to the surface shape of the substrate. Furthermore, despite its high stretchability, the laminate film also has high hardness, resulting in high scratch resistance after stretching. Furthermore, despite being laminated with an AC-based resin film, the transparency of the VDF-based resin film is not easily reduced even after stretching, so the laminate film maintains high transparency even after stretching. Furthermore, since the VDF-based resin film contains almost no AC resin, the laminate film also has high chemical resistance after attachment.

[0038] Specifically, the haze of the laminated film measured in an unstretched state is 0.0% or more and 10.0% or less, preferably 0.0% or more and 6.0% or less, and more preferably 0.0% or more and 4.0% or less.

[0039] The haze is a value measured based on JIS K 7136: 2000 (ISO 14782: 1999).

[0040] Furthermore, the laminated film has a tensile modulus at 23°C measured in an unstretched state in accordance with JIS K 7161-1:2014 (ISO 527-1:2012) of 500 MPa or more and 1500 MPa or less, preferably 800 MPa or more and 1400 MPa or less, and more preferably 1000 MPa or more and 1350 MPa or less.

[0041] Furthermore, the laminated film has a breaking elongation at 23°C measured in an unstretched state in accordance with JIS K 7161-1:2014 (ISO 527-1:2012) of 100% or more and 400% or less, preferably 100% or more and 300% or less, more preferably 130% or more and 300% or less, even more preferably 130% or more and 250% or less, and particularly preferably 130% or more and 200% or less.

[0042] Furthermore, the scratch hardness (pencil method) of the laminate film, measured on the VDF resin film side in an unstretched state in accordance with ISO 15184:2020, is preferably HB or more and 6H or less, more preferably HB or more and 2H or less, and even more preferably HB or more and F or less. By sufficiently increasing the hardness in the unstretched state, the scratch resistance after stretching can also be improved.

[0043] Furthermore, the ratio (T1 / T2) of the thickness of the VDF resin film (T1) to the thickness of the AC resin film (T2) of the laminate film is 1 / 20 or more and 1 / 4 or less, preferably 1 / 18 or more and 1 / 5 or less, more preferably 1 / 15 or more and 1 / 8 or less, and even more preferably 1 / 12 or more and 1 / 9 or less. Increasing T1 / T2 (increasing the proportion of the VDF resin film thickness) can improve the chemical resistance of the laminate film. Decreasing T1 / T2 (increasing the proportion of the AC resin film thickness) can improve the scratch resistance of the laminate film.

[0044] The thicknesses T1 and T2 are values ​​measured by observing the cross section of the laminated film cut with a single-edged knife perpendicular to the thickness direction so as to have a smooth cross section.

[0045] The haze of the laminated film when stretched 140% at 120°C is 0.0% or more and 10.0% or less, preferably 0.0% or more and 7.0% or less, more preferably 0.0% or more and 5.0% or less, and even more preferably 0.0% or more and 4.0% or less. The stretching direction at this time may be either the MD direction or the TD direction of the laminated film. In this embodiment, it is sufficient that the haze when stretched 140% at 120°C in at least one of the MD direction and the TD direction is within the above range.

[0046] [Laminated film manufacturing method] The method for producing the laminated film is not particularly limited, but a method in which a heat-molten AC resin film material and a heat-molten VDF resin film material are co-extruded and then cooled is preferred.

[0047] Specifically, the VDF resin is heated, melted, and kneaded in the first extruder. When the VDF resin film contains additives such as alkyl quaternary ammonium sulfate, these additives are also kneaded together with the VDF resin in the first extruder.

[0048] The heating temperature (cylinder temperature) in the first kneader is preferably 210°C or higher and 260°C or lower, and more preferably 210°C or higher and 240°C or lower. By setting the heating temperature to 210°C or higher, the VDF-based resin can be melted and thoroughly kneaded. By setting the heating temperature to 260°C or lower, yellowing and deterioration of transparency due to decomposition of alkyl quaternary ammonium sulfate and the like can be suppressed.

[0049] At the same time, the AC resin is heated and melted in the second extruder and kneaded. If the AC resin film contains additives, the additives are also kneaded together with the AC resin in the second extruder.

[0050] The heating temperature (cylinder temperature) in the second kneader is preferably 200°C or higher and 260°C or lower, and more preferably 200°C or higher and 240°C or lower. By setting the heating temperature to 200°C or higher, the AC-based resin can be melted and thoroughly kneaded. By setting the heating temperature to 260°C or lower, yellowing and deterioration of transparency due to decomposition of the AC-based resin and additives can be suppressed.

[0051] The melt-kneaded VDF resin and AC resin are then co-extruded through a feedblock T-die or multi-manifold T-die connected to the first and second extruders, resulting in a molten extrudate in which the VDF resin and AC resin are laminated.

[0052] The molten extrudate is then cooled by contacting it with a cooling roll while maintaining the temperature at 150°C or higher. The cooling roll can be a metallic mirror-finish touch roll or a metallic endless belt. The surface temperature of the cooling roll is preferably 125°C or lower, more preferably 30°C or higher and 100°C or lower. The VDF resin side of the molten extrudate is preferably brought into contact with the cooling roll. Rapid cooling of the VDF resin by contacting it with a cooling roll set at a relatively low temperature appropriately suppresses crystallization of the VDF resin, thereby appropriately controlling the crystalline structure of the VDF resin. This reduces the tensile modulus and increases the elongation at break while maintaining the hardness of the VDF resin film.

[0053] The laminated film that has been cooled and solidified can be wound into a roll for storage, transportation, and the like.

[0054] [Application] The laminated film described above can be used as a decorative film to be attached by vacuum forming or pressure forming to the surface of an interior or exterior substrate of an automobile, railcar, aircraft, ship, spacecraft, home appliance, furniture, building, etc. When attaching, the VDF-based resin film is attached to the surface of the substrate so that the VDF-based resin film side faces outward.

[0055] [Other embodiments] It should be noted that the above-described embodiments are exemplary embodiments of the present invention, and it goes without saying that the present invention may include embodiments other than the above-described embodiments within the scope of its core technical concept. [Example]

[0056] The present invention will be described in detail based on examples, but the present invention is not limited to these examples.

[0057] 1. Preparation of laminated film To 100 parts by mass of a VDF homopolymer having an inherent viscosity of 1.00 dl / g was added 1.0 part by mass of tetrabutylammonium hydrogen sulfate (manufactured by Koei Chemical Industry Co., Ltd.; hereinafter, sometimes abbreviated as "TBAHS") The VDF homopolymer to which TBAHS had been added was melt-kneaded at a cylinder temperature of 190°C using a co-rotating twin-screw extruder (manufactured by Shibaura Machine Co., Ltd., TEM-26) to obtain a pelletized VDF-based resin composition 1.

[0058] Various VDF-based resin compositions were obtained in the same manner by varying the inherent viscosity of the VDF-based polymer, the presence or absence and ratio of copolymerization with HFP, and the amount of TBAHS added.

[0059] The VDF-based resin composition 1 obtained above was thermally melted in a φ30 mm first extruder with a cylinder temperature set to 240°C. Furthermore, a methacrylic resin (Parapet GR-F, manufactured by Kuraray Co., Ltd.) was thermally melted in a φ30 mm second extruder with a cylinder temperature set to 240°C. The thermally melted VDF-based resin composition and methacrylic resin were then co-extruded from a multi-manifold T-die connected to the first and second extruders. The VDF-based resin composition side was brought into contact with a cooling roll whose surface was set to 98°C for cooling, yielding a laminated film 1 consisting of a 10 μm-thick VDF-based resin layer and a 45 μm-thick methacrylic resin layer (hereinafter abbreviated as "AC layer").

[0060] Laminated films 2 to 14 were obtained in the same manner except that the type of VDF-based resin composition and the thickness of each layer were changed.

[0061] The inherent viscosity of the VDF resin was measured in accordance with JIS K 7367-1:2002. Specifically, 80 mg of the VDF resin was dissolved in 20 ml of N,N-dimethylformamide, and the viscosity η of the polymer solution was measured using an Ubbelohde viscometer in a thermostatic bath at 30°C. The viscosity η of the polymer solution and the viscosity η of N,N-dimethylformamide used as the solvent were then calculated. o Based on the solution concentration C (g / dl), the inherent viscosity η is calculated using the following formula: i asked for. η i =(1 / C)·ln(η / η o ) Here, the concentration of the solution is 0.4 g / dl.

[0062] The content of structural units derived from HFP in a VDF-based resin is the ratio of the content of fluorine atoms derived from HFP to the content of all fluorine atoms in the resin. 19 The content of structural units derived from HFP contained in the VDF-based resin was determined by F-NMR.

[0063] 2. Evaluation of laminated film (before stretching) The obtained laminated film was evaluated as follows without being stretched.

[0064] 2-1.Thickness ratio The laminate film was cut perpendicular to the thickness direction using a single-edged knife so that the cross section was smooth. The film cross section was observed at 800x magnification using a digital microscope (Keyence Corporation, VHX-700F). The thicknesses of the VDF-based resin layer and the AC-based resin layer were measured, and the ratio (T1 / T2) of the thickness of the VDF-based resin layer (T1) to the thickness of the AC layer (T2) was calculated. The thickness ratio (T1 / T2) was measured at a total of five locations: a measurement point set in the center of the laminate film and four other locations set at least 50 mm away from the other measurement points. The average of these measurements was used as the thickness ratio of the laminate film.

[0065] 2-2. Absorbance ratio The infrared absorption spectrum of the VDF resin film side of the laminated film was measured using FT / IR-4100 and ATR PRO610P-S (both manufactured by JASCO Corporation) in the measurement range of 600 cm -1 ~4000cm -1 The transmittance spectrum was converted to an absorbance spectrum. -1 ~1740cm -1 The maximum absorbance of the peak due to the stretching vibration of the carbonyl group detected at 860 cm is the absorbance A, -1 ~880cm -1 The maximum absorbance value of the peak derived from the VDF resin detected in the graph was taken as absorbance B. No baseline was set, and the converted absorbance values ​​were used directly as absorbance A and absorbance B. The absorbance ratio (A / B) was then calculated by dividing absorbance A by absorbance B. The measurement was carried out at one location in the center of the laminated film.

[0066] 2-3. Tensile modulus and elongation at break Tensile tests were performed in accordance with JIS K 7161-1:2014 (ISO 527-1:2012) to measure the tensile modulus and elongation at break using a universal testing machine (Shimadzu Corporation, Autograph AGS-J) at a temperature of 23°C and a tensile speed of 50 mm / min.

[0067] 2-4. Hayes The haze of the laminated film was measured using a haze meter (NDH4000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136: 2000 (ISO 14782: 1999). Haze measurements were taken at a total of five locations: a measurement point set at the center of the laminated film and four other locations arbitrarily set at least 50 mm away from the other measurement points, and the average of these measurements was taken as the haze of the laminated film.

[0068] 2-5.Pencil hardness The pencil hardness of the VDF resin film side was evaluated in accordance with JIS K 5600-5-4 at an angle of 45° and a pressure of 750 g. The pencil hardness was evaluated at a total of five points: a measurement point set at the center of the laminated film and four other points set at random at least 50 mm away from the other measurement points, and the average of these points was taken as the pencil hardness of the laminated film.

[0069] 3. Evaluation of laminated film (after stretching) The obtained laminated film was stretched by 140% at 120° C. The laminated film after stretching was evaluated as follows.

[0070] 3-1. Hayes The haze was measured in the same manner as for the laminated film before stretching.

[0071] 3-2.Chemical resistance A small amount of sunscreen cream (Neutrogena UltraSheer SPF45, manufactured by Johnson & Johnson) was applied to the VDF resin film side of the laminated film, the applied area was covered with a cover glass, and the film was left to stand at 80°C for 1 hour. After leaving the film to stand, the adhering sunscreen cream was wiped off, the film was washed with water, and the appearance of the applied area was evaluated according to the following evaluation criteria. ○ No change in appearance is observed. △: Minor application marks or minor wrinkles are observed. × Whitening or obvious deterioration of the surface is observed.

[0072] 3-3. Scratch resistance A friction test was conducted on the VDF resin film side of the laminate film in accordance with JIS L 0849:2013 using a friction fastness tester (Gakushin-type friction tester RT-200, manufactured by Daiei Scientific Instruments Co., Ltd.). The laminate film was cut into a 220 mm long, 30 mm wide test sample. A No. 3 gold-plated cloth was used as the friction cloth, and the friction test was performed 50 times with a load of 9.8 N and a speed of 30 reciprocations per minute. After the friction test, the sample surface was observed at 100x magnification using a digital microscope (Keyence Corporation, VHX-700F), and the results were evaluated based on the following criteria within the microscope's field of view. No scratches longer than 500 μm were visible. △: 1 to 5 scratches having a length of 500 μm or more were visible. × Six or more scratches with a length of 500 μm or more were visible.

[0073] 4.Results Table 1 shows the preparation conditions and evaluation results of each laminated film.

[0074] [Table 1]

[0075] [Reference example] A VDF homopolymer having an inherent viscosity of 1.00 dl / g was melt-kneaded without adding TBAHS at a cylinder temperature of 190°C using a co-rotating twin-screw extruder (Shibaura Machine Co., Ltd., TEM-26) to obtain a pelletized VDF resin composition.

[0076] The VDF-based resin composition obtained above was heat-melted in a φ30 mm extruder with a cylinder temperature set to 240°C, extruded from a T-die connected to the extruder, and cooled by contacting the surface with a cooling roll set to 98°C, to obtain a single-layer film consisting of a 40 μm-thick VDF-based resin layer.

[0077] The haze of the obtained monolayer film was measured before and after stretching in the same manner as for the laminated film described above. The haze before stretching was 29.0%, and the haze after stretching was 14.0%.

[0078] The results of Comparative Examples 12 and 13 and Reference Example show that the haze of a VDF resin film does not normally increase when stretched while heated, but when laminated with an AC resin film and stretched while heated, the haze increases. In contrast, the results of Examples 1 to 10 show that by appropriately controlling the microstructure by adding TBAHS or copolymerizing with HFP, the haze does not increase even when stretched while heated. [Industrial Applicability]

[0079] The laminated film according to the present invention has high stretchability, and the VDF resin film has good transparency, chemical resistance and scratch resistance even after stretching.

Claims

1. A laminated film in which an acrylic resin film and a vinylidene fluoride resin film are laminated, a ratio (T1 / T2) of a thickness (T1) of the vinylidene fluoride resin film to a thickness (T2) of the acrylic resin film is 1 / 20 or more and 1 / 4 or less; The vinylidene fluoride resin film has an infrared absorption spectrum of 1700 cm －１ ~1740cm －１ and the absorbance A of the peak measured in the range of 860 cm －１ ~880cm －１ the ratio (A / B) of the absorbance B of the peak measured in the range of The laminated film has a haze of 0.0% or more and 10.0% or less when measured in an unstretched state, and a tensile modulus of elasticity at 23°C when measured in an unstretched state of 500 MPa or more and 1500 MPa or less, The laminated film has a haze of 0.0% or more and 10.0% or less when stretched to 140% at 120°C. Decorative laminated film.

2. The vinylidene fluoride resin film has a scratch hardness (pencil method) measured in accordance with ISO 15184:2020 of HB or more and 6H or less. The decorative laminate film according to claim 1 .

3. The breaking elongation at 23°C is 100% or more and 400% or less. The decorative laminate film according to claim 1 .

4. The vinylidene fluoride resin film has a thickness (T1) of 1 μm or more and 30 μm or less, The acrylic resin film has a thickness (T2) of 25 μm or more and 200 μm or less. The decorative laminate film according to claim 1 .

5. The vinylidene fluoride resin film contains a vinylidene fluoride resin having an inherent viscosity of 0.80 dL / g or more and 1.20 dL / g or less. The decorative laminate film according to claim 1 .

6. The vinylidene fluoride resin film contains a vinylidene fluoride resin and 0.3 parts by mass or more and 5.0 parts by mass or less of an alkyl quaternary ammonium sulfate relative to 100 parts by mass of the vinylidene fluoride resin. The decorative laminate film according to claim 1 .

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