Multilayer film

Abstract

The present invention provides a multilayer film which has a resin layer in at least one surface, and which is characterized in that: the resin layer satisfies at least one of the features A to C described below; and if Xs and Xc are the positive secondary ion normalized intensities of GCIB-TOF-SIMS of each component at the positions corresponding to 20% and 50% of the thickness from the surface layer of the resin layer, all components satisfy 0.5 ≤ Xs / Xc ≤ 2.0. Feature A: All of an acrylic resin, a polyester resin and a urethane resin are contained. Feature B: An acrylic modified polyester resin and a urethane resin are contained. Feature C: All of an acrylic skeleton, a polyester skeleton and a urethane skeleton are contained.　Consequently, the present invention provides a multilayer film which is excellent in terms of versatile adhesiveness to various functional materials, thereby achieving high adhesion to a functional material regardless of the temperature at which the multilayer film is used, in particular, in a low temperature environment (below the freezing point).

Description

Laminated Film

[0001] The present invention relates to a laminate film, more particularly to a laminate film used together with functional materials such as ethylene-vinyl acetate copolymer, polyvinyl alcohol, and polyvinyl butyral in applications such as solar cell members, laminated glass, and polarizer protection.

[0002] Combining films with other components via functional materials such as ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB) has been studied for many applications. For example, in the case of solar cell backsheets, EVA is provided on a laminated film to form a solar cell. In laminated glass applications, a film is inserted between two sheets of glass via PVB or EVA to form laminated glass. In addition, in polarizer protective film applications, the provision of films as protective layers on both sides of a polarizing PVA layer has been studied.

[0003] In particular, solar cells are rapidly becoming more widespread as solar power generation is gaining attention as a semi-permanent, pollution-free, next-generation energy source. Furthermore, laminated glass with functional films inserted is also being studied to provide functions such as heat insulation and visibility to window glass in automobiles and buildings. These components are often used outdoors, and therefore must be able to operate without problems in a variety of temperature environments, including high temperatures and humidity in the summer and low temperatures (below freezing) in cold regions.

[0004] However, when combining a film with other functional materials as described above, the adhesion between the film and the functional material becomes an issue, and for example, the films that have been studied so far have had the problem of insufficient adhesion to EVA, PVB, PVA, etc. Peeling off of these functional materials from the film makes it difficult to apply them to final products.

[0005] To address this problem, there is a method of providing a resin layer on the surface of the film to improve adhesion. Proposed methods include adding a water-soluble polymer such as PVA to the resin layer to approximate the surface energy of the functional material to be adhered (Patent Document 1), forming a hydrophilic easy-adhesion layer by an in-line coating method during the polyester film production process (Patent Document 2), and improving the flexibility and moist heat resistance of the easy-adhesion layer (Patent Document 3).

[0006] JP 2000-336309 A JP 2001-179913 A JP 2011-156848 A

[0007] However, the method of incorporating a water-soluble polymer into a coating film to be laminated on a film, as in Patent Document 1, improves adhesion by approximating the surface free energy between the coating film and the PVA. While the method exhibits good adhesion with PVA having a certain degree of saponification, it has problems with versatility, such as poor adhesion with other PVAs with different degrees of saponification. Furthermore, the coating film swells or shrinks depending on the temperature used, resulting in a decrease in adhesion depending on the temperature used. The method of laminating a hydrophilic adhesive layer by in-line coating, as in Patent Document 2, also has the same problems as the method of Patent Document 1. Furthermore, the method of improving the flexibility of the adhesive layer, as in Patent Document 3, has a problem in that the adhesiveness and hardness of the adhesive layer change significantly with temperature, resulting in a decrease in adhesion depending on the temperature used.

[0008] As described above, the conventional resin layers described in Patent Documents 1 to 3 do not have sufficient general adhesive properties with various functional materials, and furthermore, there is a problem in that the adhesive properties with functional materials deteriorate, particularly in low-temperature environments (below freezing points) assumed for outdoor use.

[0009] In order to solve these problems, the present invention aims to provide a laminated film that has excellent general-purpose adhesive properties with various functional materials and that has high adhesive properties with functional materials regardless of the temperature at which it is used, particularly in low-temperature environments (below freezing).

[0010] As a result of intensive research in view of the above-mentioned problems, the present inventors have found that by using a laminate film provided with a resin layer having specific physical properties, it is possible to obtain a laminate film having excellent adhesion between the resin layer and a functional material provided on the resin layer, and have completed the present invention. That is, the present invention has the following configuration.

[0011] A laminate film having a resin layer on at least one surface, wherein the resin layer satisfies at least one of the following characteristics A to C, and wherein, when Xs and Xc are the normalized positive secondary ion intensities of each component measured by GCIB-TOF-SIMS at positions 20% and 50% of the thickness from the surface of the resin layer, respectively, all components satisfy the relationship 0.5≦Xs / Xc≦2.0. Characteristic A: The film contains all of an acrylic resin, a polyester resin, and a urethane resin. Characteristic B: The film contains an acrylic-modified polyester resin and a urethane resin. Characteristic C: The film contains all of an acrylic skeleton, a polyester skeleton, and a urethane skeleton.

[0012] According to the present invention, it is possible to provide a laminated film that has excellent general-purpose adhesive properties with various functional materials, and further has high adhesive properties with various functional materials regardless of the temperature at which it is used, particularly even in low-temperature environments (below freezing).

[0013] The laminated film of the present invention will be described in detail below, but the present invention should not be construed as being limited to the embodiments including the following examples, and various embodiments that can achieve the object of the invention and do not deviate from the gist of the invention are naturally included in the scope of the present invention.

[0014] The laminate film of the present invention has a resin layer on at least one surface. Here, the term "film" refers to a sheet-like molded article whose main component is a thermoplastic resin. The term "main component" refers to a component that accounts for more than 50% by mass and not more than 100% by mass of all constituent components, and the same applies hereinafter. The material of the film is not particularly specified, and examples of the thermoplastic resin used in the laminate film include linear polyolefins such as polyethylene, polypropylene, poly(4-methylpentene-1), and polyacetal; alicyclic polyolefins that are ring-opening metathesis polymers of norbornenes, addition polymers, and addition copolymers with other olefins; biodegradable polymers such as polylactic acid and polybutyl succinate; polyamides such as nylon 6, nylon 11, nylon 12, and nylon 66; aramid; polymethyl methacrylate; polyvinyl chloride; polyvinylidene chloride; polyvinyl alcohol; polyvinyl butyral; and ethylene-vinyl acetate copolymers. Polyesters such as polyacetal, polyglycolic acid, polystyrene, styrene copolymerized polymethyl methacrylate, polycarbonate, polypropylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, as well as polyethersulfone, polyetheretherketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polyarylate, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinylidene fluoride can be used. Among these, polyesters are particularly preferred because of their excellent mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance. These resins may be copolymers or mixtures of two or more types of resins.

[0015] The term "laminated film" refers to a film in which two or more layers with different compositions are laminated together. The term "resin layer" generally refers to a primer layer provided on the surface of a film, which is a layer provided to bond the film to other components.

[0016] Polyester is a general term for polymers in which ester bonds are the main bonding chains in the main chain, and those containing at least one component selected from ethylene terephthalate, propylene terephthalate, ethylene-2,6-naphthalate, butylene terephthalate, propylene-2,6-naphthalate, ethylene-α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate, etc. as the main component can be preferably used. Herein, the term "main component" refers to a component (structural unit) that accounts for more than 50 mol% but not more than 100 mol%, when all the components (structural units) constituting the polymer are taken as 100 mol%. Hereinafter, a film containing a polyester resin as the main component may be referred to as a polyester film.

[0017] In the laminate film of the present invention, it is preferable that a resin layer be present on the surface of the substrate film. The type of substrate film is not particularly limited, but polyester film is preferably used, and polyethylene terephthalate film is more preferably used. Furthermore, when heat or shrinkage stress is applied to the laminate film, it is preferable to use polyethylene naphthalate film, which has excellent heat resistance and rigidity. Here, polyethylene terephthalate refers to polyester containing ethylene terephthalate as the main component, and polyethylene terephthalate film refers to a film containing more than 50% by mass but not more than 100% by mass of polyethylene terephthalate, assuming that all components constituting the film are 100% by mass. Polyethylene naphthalate and polyethylene naphthalate film can be interpreted similarly.

[0018] In addition, when a film contains multiple components corresponding to polyethylene terephthalate, the film is considered to be a polyethylene terephthalate film if the total amount of these components is more than 50% by mass but not more than 100% by mass. In this respect, a polyethylene naphthalate film can also be interpreted in the same way.

[0019] Furthermore, the polyester film for the substrate is preferably a biaxially oriented polyester film. A biaxially oriented polyester film refers to a polyester film that exhibits a biaxially oriented pattern in wide-angle X-ray diffraction. A biaxially oriented polyester film can generally be obtained by stretching an unstretched polyester sheet or film in two perpendicular directions (e.g., the longitudinal direction and the width direction) and completing the crystal orientation by heat treatment. The stretching ratio in this case is preferably 2.5 times or more and 5.0 times or less. When the polyester film for the substrate is a biaxially oriented polyester film, the thermal stability, particularly the dimensional stability and mechanical strength, of the laminated film is improved, and the flatness is also improved. The longitudinal direction refers to the direction in which the film runs during the manufacturing process, and in the case of a film roll, this corresponds to the winding direction. The width direction refers to the direction perpendicular to the longitudinal direction within the film plane.

[0020] Furthermore, various additives such as antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents, etc. may be added to the polyester film for the substrate to the extent that they do not deteriorate the properties of the film. These components may also be used in combination.

[0021] The thickness of the polyester film for the substrate is not particularly limited and is appropriately selected depending on the application and type, but is usually preferably 10 to 500 μm, more preferably 20 to 250 μm, and most preferably 30 to 150 μm in terms of mechanical strength, handleability, etc. The polyester film for the substrate may be a composite film obtained by coextrusion, or may be a film obtained by laminating obtained films by various methods.

[0022] The resin layer in the laminate film of the present invention satisfies at least one of Features A to C from the viewpoint of improving general adhesiveness in room temperature environments and adhesiveness in low temperature environments. Feature A: Contains all of an acrylic resin, a polyester resin, and a urethane resin. Feature B: Contains an acrylic-modified polyester resin and a urethane resin. Feature C: Contains all of an acrylic skeleton, a polyester skeleton, and a urethane skeleton.

[0023] From the above viewpoint, the laminate film satisfies 0.5≦Xs / Xc≦2.0 for all components, where Xs and Xc are the normalized positive secondary ion intensities of each component measured by GCIB-TOF-SIMS at positions 20% and 50% of the thickness from the surface of the resin layer, respectively. Furthermore, from the above viewpoint, the laminate film of the present invention preferably satisfies 0.5≦Xb / Xc≦2.0 for all components, where Xb is the normalized positive secondary ion intensity of each component measured by GCIB-TOF-SIMS at positions 80% of the thickness from the surface of the resin layer.

[0024] Here, GCIB is an abbreviation for gas cluster ion beam, and TOF-SIMS is an abbreviation for time-of-flight secondary ion mass spectrometry. In GCIB-TOF-SIMS analysis, in the embodiment of Feature A, ions derived from acrylic resin, polyester resin, and urethane resin are generated, while in the embodiment of Feature C, ions derived from acrylic skeleton, polyester skeleton, and urethane skeleton are generated. Furthermore, even in an embodiment containing an acrylic-modified polyester resin instead of an acrylic resin and a polyester resin (an embodiment satisfying Feature B), ions derived from acrylic and polyester are generated. Therefore, "all components" here refers to the acrylic component, polyester component, and urethane component, which are detected as ions in GCIB-TOF-SIMS analysis. As described above, ions derived from acrylic, polyester, and urethane are generated in any embodiment satisfying Features A to C, and therefore "all components" can be interpreted in the same way in any embodiment.

[0025] The resin layer in the laminate film of the present invention must satisfy at least one of Characteristics A to C from the viewpoint of general-purpose adhesion with various functional materials. The term "functional material" as used herein refers to a layer provided on the resin layer in the laminate film, which has functions such as sealing, adhesion, design, durability, weather resistance, and impact resistance. For example, a solar cell is generally constructed by laminating a power generation element (solar cell), a transparent substrate such as glass, and a resin sheet called a back sheet (back surface protective sheet). When laminating these components, a "sealant" that has functions such as protection from the external environment, such as moisture intrusion into the solar cell, and adhesion to the back sheet may be used as a functional material. Furthermore, when a laminate film is laminated to glass or inserted between two sheets of glass to be used as a glass construct, an "interlayer" that has functions such as adhesion between the glass and the laminate film, and design, durability, weather resistance, and impact resistance of the laminated glass may be used as a functional material. The functional material such as the sealing material and intermediate layer is not particularly limited, but examples thereof include EVA, PVB, PVA, etc., and details thereof will be described later.

[0026] The resin layer contains a urethane resin or a urethane skeleton, which allows hydrogen bonds to be formed with hydroxyl groups of EVA, PVB, PVA, etc., thereby enabling high adhesiveness to be exhibited. The resin layer contains a polyester resin or a polyester skeleton, which allows high adhesiveness to be achieved with functional materials such as EVA, PVB, PVA, etc. through hydrogen bonds with hydroxyl groups, and furthermore, when the substrate is a polyester film, it also enables good adhesiveness to the substrate. The resin layer contains an acrylic resin or an acrylic skeleton, which not only promotes curing of the resin layer when it is formed by coating, but also makes it easy to set the water droplet contact angle of the resin layer, described below, to between 65° and 90°.

[0027] In the laminated film of the present invention, even when the acrylic resin and the polyester resin are acrylic-modified polyester resins (in other words, when an acrylic-modified polyester resin is contained in place of a polyester resin and an acrylic resin), the same effects as those of a film containing a polyester resin and an acrylic resin, or a film containing a polyester skeleton and an acrylic skeleton, can be obtained.

[0028] The resin layer in the laminate film of the present invention may contain a polyester resin and a urethane resin in the form of a polyester-urethane copolymer. A layer containing an acrylic resin and a polyester-urethane copolymer can be considered to be a "layer containing all of an acrylic resin, a polyester resin, and a urethane resin" and a "layer containing all of an acrylic skeleton, a polyester skeleton, and a urethane skeleton," i.e., satisfying both Features A and C. A layer containing an acrylic-modified polyester resin and a polyester-urethane copolymer can be considered to be a "layer containing an acrylic-modified polyester resin and a urethane resin" and a "layer containing all of an acrylic skeleton, a polyester skeleton, and a urethane skeleton," i.e., satisfying both Features B and C.

[0029] In general, functional materials such as EVA, PVB, and PVA have a wide range of elastic moduli depending on the degree of saponification. Furthermore, even if these functional materials have a low elastic modulus and are relatively flexible at room temperature, their elastic moduli increase in a low-temperature environment, such as at −20°C, resulting in a large difference in the elastic modulus compared to room temperature. Therefore, even if the adhesion between the functional material and the resin layer is sufficient at room temperature, peeling is likely to occur at the interface between the functional material and the resin layer in a low-temperature environment. The elastic modulus of the resin layer is important in determining the adhesion between the functional material, which has such a wide range of elastic moduli, and it is known that the greater the elastic modulus of the resin layer (i.e., the harder it is), the worse the adhesion. Meanwhile, just as the elastic modulus of the functional material increases at a low-temperature environment of −20°C, the elastic modulus of the resin layer also generally increases in a low-temperature environment.

[0030] When controlling the elastic modulus of a resin layer, it is important to mix resins with different elastic moduli. Acrylic resins, polyester resins, urethane resins, acrylic-modified polyester resins, and polyester-urethane copolymers typically have different elastic moduli. More specifically, polyester resins generally have a high elastic modulus, urethane resins have a low elastic modulus, and acrylic resins have an intermediate elastic modulus. Therefore, the elastic modulus can be easily controlled by mixing these three types of resins. However, in the case of urethane resins, for example, between aliphatic urethane resins containing aliphatic groups as part of their structure and aromatic urethane resins containing aromatic groups as part of their structure, the elastic modulus of the aromatic urethane resin is higher due to the rigidity of the aromatic chain. Therefore, the elastic moduli of polyester resins, acrylic resins, and urethane resins may not necessarily follow the order described above. Furthermore, since acrylic-modified polyester resins possess the characteristics of acrylic resins and polyester resins, and polyester-urethane copolymers possess the characteristics of polyester resins and urethane resins, they generally have an intermediate elastic modulus between the two.

[0031] As described above, in order to enhance general-purpose adhesion and adhesion in low-temperature environments, the resin layer must satisfy at least one of Characteristics A to C. However, acrylic resins, polyester resins, and urethane resins differ in their properties due to their skeletons, with acrylic resins being hydrophobic and polyester resins being hydrophilic, followed by urethane resins. It is generally known that when a resin layer is formed by mixing a hydrophobic resin and a hydrophilic resin, a distribution occurs in the depth direction for each resin with its respective properties. Therefore, when these three types of resins are simply mixed, a bias in the component distribution occurs within the resin layer, for example, with a higher acrylic resin content on the surface side of the resin layer and a higher polyester or urethane resin content on the inner side. This bias in component distribution also occurs between acrylic-modified polyester resins and urethane resins, and between acrylic-modified polyester resins and polyester-urethane copolymers.

[0032] Therefore, as a result of extensive research, the inventors have found that by making the resin layer satisfy at least one of Features A to C, and further satisfying 0.5≦Xs / Xc≦2.0 for all components, where Xs and Xc are the normalized positive secondary ion intensities of each component measured by GCIB-TOF-SIMS at positions 20% and 50% of the thickness from the surface of the resin layer, respectively, the laminate film of the present invention exhibits excellent flexibility at room temperature, suppresses an increase in elastic modulus at low temperatures, and exhibits excellent adhesiveness in both environments. Furthermore, it is also preferable that the laminate film of the present invention satisfies 0.5≦Xb / Xc≦2.0 for all components, where Xb is the normalized positive secondary ion intensities of each component measured by GCIB-TOF-SIMS at positions 80% of the thickness from the surface of the resin layer.

[0033] The laminated film of the present invention satisfies 0.5≦Xs / Xc≦2.0, which means that each component is uniformly dispersed from the surface to the center of the resin layer, and 0.5≦Xb / Xc≦2.0, which means that each component is uniformly dispersed from the center of the resin layer to the vicinity of another layer (for example, a layer formed by a substrate film). That is, when Xs / Xc and Xb / Xc are both within the above ranges, it means that each component is uniformly dispersed in the thickness (depth) direction of the resin layer. Conversely, when Xs / Xc and Xb / Xc do not satisfy the above ranges, it means that there is a bias in the dispersion of each component in the depth direction of the resin layer.

[0034] It is particularly important that all components of the resin layer satisfy 0.5≦Xs / Xc≦2.0, as this contributes greatly to adhesion with functional materials. Furthermore, if all components of the resin layer also satisfy 0.5≦Xb / Xc≦2.0, the entire resin layer is uniform, and sufficient adhesiveness can be obtained in a room temperature environment, and a decrease in adhesiveness at low temperatures can be more easily reduced, which is preferable.

[0035] Xs, Xc, and Xb of the resin layer can be measured by GCIB-TOF-SIMS, and the specific measurement method and conditions will be described later. Furthermore, "a position 20% of the thickness from the surface of the resin layer" refers to a position 20% of the thickness when the surface of the resin layer is 0% and the interface between the resin layer and another layer is 100%. "A position 50% of the thickness from the surface of the resin layer" and "a position 80% of the thickness from the surface of the resin layer" can also be interpreted in the same way.

[0036] The laminated film of the present invention preferably satisfies at least one of Features A to C and incorporates a compound having both hydrophobic and hydrophilic properties. This configuration suppresses uneven distribution of each component in the depth direction, resulting in a more uniform resin layer. By dispersing each component more uniformly in the thickness direction, the elastic modulus of the entire resin layer becomes more uniform, improving general-purpose adhesion with various functional materials and achieving high adhesion even in low-temperature environments.

[0037] Furthermore, the laminate film of the present invention preferably has at least one of the following features 1 and 2, where P(T) is the AFM elastic modulus of the resin layer at a temperature T°C measured with an atomic force microscope (hereinafter referred to as AFM), ΔP is P(-20) - P(25), and P(-20) / P(25) is the elastic modulus ratio P'. Feature 1: ΔP is 0.2 GPa or more and 2.0 GPa or less. Feature 2: The elastic modulus ratio P' is 0.1 or more and 2.3 or less.

[0038] The AFM elastic modulus of the resin layer can be measured using a known measuring device, such as a NanoScope V manufactured by Bruker AXS Inc. The measurement method and procedure when using this device are described below. P(-20) is the AFM elastic modulus at -20°C, representing the AFM elastic modulus in a low-temperature environment intended for use in cold regions or desert areas. On the other hand, P(25) is the AFM elastic modulus at 25°C, i.e., in a room-temperature environment. In general, functional materials such as EVA, PVB, and PVA increase in elastic modulus in a low-temperature environment of -20°C, and it is known that the adhesion between the resin layer and the functional material (adherend) deteriorates as the elastic modulus of the functional material increases. Therefore, even if the adhesion between the functional material such as EVA, PVB, or PVA and the resin layer is sufficient in a room-temperature environment, peeling tends to occur at the interface between the functional material and the resin layer in a low-temperature environment.

[0039] When the laminate film of the present invention does not have Feature 2, a ΔP of 0.2 GPa or more ensures sufficient temperature-dependent changes in the state of the resin layer during thermal processing with the functional material, improving the adhesion between the laminate film and the functional material. Furthermore, when the laminate film of the present invention does not have Feature 2 and a ΔP of 2.0 or less, an increase in the elastic modulus at −20°C is suppressed, reducing the deterioration of adhesion to the functional material due to excessive curing of the resin layer. From the above perspective, a more preferred range for ΔP is 0.3 GPa or more and 1.7 GPa or less, and even more preferably 0.4 GPa or more and 1.3 GPa or less. In the prior art described in Patent Documents 1 to 3, even if the adhesiveness at 25°C is sufficient, there are cases where the elastic modulus of the adhesive layer changes when the temperature is reduced to −20°C, making it impossible to maintain sufficient adhesion.

[0040] When the laminate film of the present invention does not have Feature 1, an increase in the elastic modulus at −20°C is suppressed by having an elastic modulus ratio P′ of 0.1 or more, thereby reducing the decrease in adhesion to the functional material due to excessive curing of the resin layer. Furthermore, when the laminate film of the present invention does not have Feature 1 and has an elastic modulus ratio P′ of 2.3 or less, the resin layer undergoes sufficient temperature-dependent state change during thermal processing with the functional material, improving the adhesion between the laminate film and the functional material. Furthermore, since substrate films, which are generally sheet-shaped molded products primarily composed of thermoplastic resins, generally have an elastic modulus higher than that at 25°C when cooled to −20°C, or have values ​​similar before and after cooling, the elastic modulus ratio P′ is preferably in the range of 0.9 to 2.1, more preferably 1.1 to 2.0. By setting the elastic modulus ratio P′ within the above range, a decrease in adhesion to the functional material in low-temperature environments tends to be more effectively suppressed.

[0041] In addition, from the viewpoint of enhancing the adhesion of the resin layer to the functional material in a low-temperature environment, the laminate film of the present invention may have at least one of Features 1 and 2, but it is more preferable to have both Features 1 and 2. By having both Features 1 and 2, not only is it possible to reduce the decrease in adhesion to the functional material in a low-temperature environment, but it is also easy to ensure sufficient adhesion to the functional material in a room-temperature environment. As a method for providing at least one of Features 1 and 2 or for adjusting each of them to the preferred ranges, for example, a method of adjusting the glass transition temperature of the resin layer can be mentioned. More specifically, by setting the glass transition temperature of the resin layer to 30°C or higher, it is easy to reduce ΔP or adjust the elastic modulus ratio P' to a suitable range. Furthermore, by including an oxazoline compound or a chemical structure derived from an oxazoline compound in the resin layer A, it is also easy to reduce ΔP or adjust the elastic modulus ratio P' to a suitable range.

[0042] Furthermore, in the laminate film of the present invention, P(25) is preferably 0.2 GPa or more and 1.5 GPa or less. By adopting such an embodiment, the adhesion between the resin layer A of the laminate film of the present invention and the highly flexible functional material can be improved. From the above viewpoints, P(25) is more preferably 0.2 GPa or more and 1.3 GPa or less, and even more preferably 0.3 GPa or more and 0.9 GPa or less. By setting P(25) to 1.5 GPa or less, the resin layer is sufficiently flexible and adhesion with the highly flexible functional material can be ensured. By setting P(25) to 0.2 GPa or more, the resin layer does not become too flexible, and blocking when the film is wound up in a roll shape can be reduced.

[0043] Methods for adjusting P(25) to 0.2 GPa or more and 1.5 GPa or less, or within the above preferred range, are not particularly limited, but include, for example, a method of adjusting the glass transition temperature of the resin layer. Alternatively, a method can be used in which the urethane resin contained in the resin composition forming the resin layer satisfying Features A and B is an aliphatic urethane resin, or a polymer of an aliphatic polyisocyanate compound and a polyol compound. Furthermore, this can be easily achieved by adjusting the content of the urethane resin to 4% by mass or more and 60% by mass or less, preferably 4% by mass or more and 50% by mass or less, based on 100% by mass of the resin composition. Regarding the above points, when a resin layer satisfying Feature C is included, the same interpretation can be achieved by replacing urethane resin with a urethane skeleton. Furthermore, when a polyester-urethane copolymer is used as the urethane resin, the amount of polyisocyanate compound charged during copolymerization is considered to be the content of the urethane resin.

[0044] In the laminate film of the present invention, the glass transition temperature (hereinafter also referred to as Tg) of the resin layer is preferably 30°C or higher and 80°C or lower. When the Tg of the resin layer is 30°C or higher, an increase in ΔP is suppressed, and when it is 80°C or lower, sufficient adhesion to the functional material can be achieved regardless of the temperature environment or type. From the above viewpoints, the Tg of the resin layer is more preferably 30°C or higher and 70°C or lower, and even more preferably 30°C or higher and 55°C or lower. The glass transition temperature of the resin layer can be measured using a differential scanning calorimeter (DSC), and details of the conditions, etc. will be described later in the examples.

[0045] The glass transition temperature can be adjusted by adjusting the components contained in the resin layer. When the resin layer satisfies Feature B, the glass transition temperature of the resin layer can also be adjusted by adjusting the ratio of the acrylic resin component (acrylic units) to the polyester resin component (polyester units) in the acrylic-modified polyester resin.

[0046] In the laminate film of the present invention, the water droplet contact angle of the resin layer is preferably 65° to 90°. This configuration reduces the difference in hydrophilicity between the resin layer and the functional material, thereby improving adhesion between them. From the above perspective, the water droplet contact angle of the resin layer is more preferably 65° to 85°, and even more preferably 65° to 80°. The water droplet contact angle referred to in the present invention is determined by the sessile drop method described in JIS R3257:1999. More specifically, it is the value that can be determined by the following formula when a water droplet is placed on the surface of the resin layer and equilibrated in the atmosphere. Generally, it serves as an index for determining the wettability of the solid surface. That is, a smaller water droplet contact angle indicates better wettability of the solid surface, and a larger value indicates poorer wettability. The following formula is called "Young's equation," and in this formula, the angle between the liquid surface and the solid surface is defined as the "contact angle." A specific method for measuring the water droplet contact angle will be described later. γS = γL cos θ + γSL (In the above formula, γS is the surface tension of the solid, γL is the surface tension of the liquid, γSL is the interfacial tension between the solid and the liquid, and θ is the contact angle).

[0047] The method for adjusting the water droplet contact angle of the resin layer to 65° or more and 90° or less or the above preferred range is not particularly limited, but examples include a method of adjusting the ratio of highly hydrophobic components or skeletons in the resin layer. For example, the water droplet contact angle of the resin layer can be increased by increasing the ratio of acrylic resin (an embodiment satisfying Feature A), the ratio of acrylic skeleton (an embodiment satisfying Feature C), or the ratio of acrylic-modified polyester resin (an embodiment satisfying Feature B). In an embodiment satisfying Feature B, the water droplet contact angle of the resin layer can also be increased by increasing the ratio of acrylic resin components (acrylic units) in the acrylic-modified polyester resin. Another method for increasing the water droplet contact angle of the resin layer is to add an oxazoline compound to the resin layer. These methods may be used in combination as appropriate.

[0048] When the resin layer satisfies at least one of Features A and B, the urethane resin contained in the resin layer is preferably an aliphatic urethane resin, and more preferably an alicyclic urethane resin. Here, "aliphatic urethane resin" refers to a urethane resin having an aliphatic chain, and "alicyclic urethane resin" refers to an aliphatic urethane resin in which part of the aliphatic chain contains a cyclic structure. Because alicyclic urethane resins have a high glass transition point among aliphatic urethane resins, resin layers containing alicyclic urethane resins do not soften or melt when exposed to heat applied during thermal processing steps such as laminating glass or use in high-temperature, high-humidity environments. Furthermore, the occurrence of bleed-out of oligomers in the polyester film onto the resin layer surface is suppressed. Therefore, when the resin layer contains an alicyclic urethane resin, a resin layer with excellent adhesion, particularly in a humid and heat-resistant environment, can be obtained. Regarding the above points, in an embodiment in which the resin layer satisfies Feature C, the same interpretation can be achieved by replacing "urethane resin" with "urethane skeleton."

[0049] On the other hand, when the resin layer satisfies at least one of Features A and B, if an aromatic urethane resin containing aromatic groups as part of its structure is used instead of the aliphatic urethane resin, the resin composition containing the aromatic urethane resin will have a rigid resin layer due to the influence of the aromatic chain, and will not be able to follow the expansion and contraction of EVA or PVB, and sufficient adhesiveness may not be obtained. Furthermore, when the resin layer is exposed to light, problems such as yellowing and embrittlement of the resin layer may occur, and for example, when used in heat-blocking glass or window glass, the quality may be reduced due to the influence of external light. Regarding the above points, in an embodiment in which the resin layer satisfies Feature C, the same interpretation can be obtained by replacing the urethane resin with a urethane skeleton.

[0050] The acrylic-modified polyester resin that can be used in the laminate film of the present invention (an embodiment satisfying Feature B) is a resin in which an acrylic resin component and a polyester resin component are bonded to each other, and includes, for example, graft polymerization types and block copolymerization types. Furthermore, the copolymerization ratio of the acrylic resin component to the polyester resin component in the acrylic-modified polyester resin may be higher. The acrylic-modified polyester resin can be produced, for example, by adding a radical initiator to both ends of a polyester to polymerize the acrylic monomer, by adding a radical initiator to the side chain of a polyester to polymerize the acrylic monomer, or by adding a hydroxyl group to the side chain of an acrylic resin and reacting it with a polyester having an isocyanate group or a carboxyl group at its terminal. As mentioned above, it is preferable for the acrylic resin component and the polyester resin component to be bonded to each other from the viewpoint of the stability of the resin layer. Increasing the acrylic resin component in the acrylic-modified polyester resin can increase the water droplet contact angle of the resin layer, while decreasing the acrylic resin component can decrease the water droplet contact angle of the resin layer. In order to set the water droplet contact angle of the resin layer in the range of 65° or more and 90° or less as described below, the mass ratio of the acrylic resin to the polyester resin (acrylic resin content [parts by mass] / polyester resin content [parts by mass]) or the mass ratio of the acrylic resin component to the polyester resin component in the acrylic-modified polyester resin (acrylic resin component content [parts by mass] / polyester resin component content [parts by mass]) can be set to 15 / 85 or more and 85 / 15 or less.

[0051] In particular, when a polyester film is used as the substrate of the laminated film of the present invention, the polyester resin component of the acrylic-modified polyester resin can improve the adhesion between the resin layer and the polyester film substrate. Furthermore, a method for making the water droplet contact angle of the resin layer from 65° to 90° can also be used in which the amount of the oxazoline compound is from 30 to 90 parts by mass per 100 parts by mass of the total of the acrylic resin, polyester resin, and urethane resin (or the acrylic-modified polyester resin and the urethane resin).

[0052] Furthermore, it is preferable that the resin layer has at least one structure of the following formulas (1) to (5), and it is particularly preferable that the acrylic-modified polyester resin has at least one structure of the following formulas (1) to (5). Formulas (1) to (5) are polar groups that form hydrogen bonds with hydroxyl groups of the functional material. Therefore, by adopting such an embodiment, the resin layer can form hydrogen bonds with EVA, PVB, or PVA at the sites of formulas (1) to (5), thereby improving adhesion to the functional material.

[0053]

[0054] The acrylic resin component constituting the acrylic-modified polyester resin preferably has a hydrophilic radical-polymerizable vinyl monomer polymerized in the main chain of an acrylic resin composed of, specifically, alkyl methacrylate and / or alkyl acrylate. By including this hydrophilic radical-polymerizable vinyl monomer in the acrylic resin component, it is possible to impart at least one structure represented by the above formulas (1) to (5) to the acrylic-modified polyester.

[0055] When the total acrylic resin component is taken as 100 parts by mass, the amount of the hydrophilic radical polymerizable vinyl monomer is preferably 20 parts by mass or more and 50 parts by mass or less. By using the hydrophilic radical polymerizable vinyl monomer in an amount of 20 parts by mass or more and 50 parts by mass or less, it becomes easy to set the water droplet contact angle in the range of 65° or more and 90° or less, and adhesion to the functional material can be effectively improved.

[0056] As the acrylic resin component, alkyl methacrylate and / or alkyl acrylate is used, and specifically, it is preferable to use methacrylic acid, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, etc. These can be used alone or in combination of two or more.

[0057] Specific examples of hydrophilic radically polymerizable vinyl monomers having the structure of the above formula (1) include hydroxyacrylic acid esters such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate. Examples of monomers having the structure of the above formula (2) include glycol esters such as ethylene glycol acrylate, ethylene glycol methacrylate, polyethylene glycol acrylate, and polyethylene glycol methacrylate. Examples of monomers having the structure of the above formula (3) include acrylamide-based compounds such as acrylamide, methacrylamide, N-methylolacrylamide, and methoxymethylolacrylamide. Examples of monomers having the structure of the above formula (4) include cationic monomers such as aminoalkyl acrylate, aminoalkyl methacrylate esters, and quaternary ammonium salts thereof. Examples of monomers having the structure of the formula (5) include glycidyl acrylate-based compounds such as glycidyl acrylate and glycidyl methacrylate, as well as unsaturated acids and salts thereof such as acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, and crotonic acid. The hydrophilic radical polymerizable monomers may be used alone or in combination of several kinds. Furthermore, these hydrophilic monomers may be used in combination with other copolymerizable vinyl monomers.

[0058] Examples of other copolymerizable vinyl monomers include vinyl esters such as vinyl acetate and vinyl propionate, vinyl halides such as vinyl chloride and vinyl bromide, unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate, vinyl silanes such as dimethylvinylmethoxysilane and γ-methacryloxypropyltrimethoxysilane, and olefins and diolefin compounds such as ethylene, propylene, styrene, and butadiene.

[0059] The polyester resin component constituting the acrylic-modified polyester resin has an ester bond in the main chain or side chain and is composed of a dicarboxylic acid component and a diol component. The carboxylic acid component constituting the polyester resin can be an aromatic, aliphatic, or alicyclic dicarboxylic acid or a trivalent or higher polycarboxylic acid. Examples of aromatic dicarboxylic acids that can be used include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 5-sodium sulfoisophthalic acid, 1,4-naphthalenedicarboxylic acid, and their ester-forming derivatives.

[0060] Examples of the glycol component of the polyester resin that can be used include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and neopentyl glycol.

[0061] Furthermore, when the polyester resin component is dissolved or dispersed in an aqueous solvent and used as an aqueous resin composition, it is preferable to copolymerize a compound containing a sulfonate group or a compound containing a carboxylate group in order to make the polyester resin component water-soluble or water-dispersible.

[0062] Examples of the compound containing a carboxylate group include, but are not limited to, alkali metal salts, alkaline earth metal salts, and ammonium salts of trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, 4-methylcyclohexene-1,2,3-tricarboxylic acid, trimesic acid, 1,2,3,4-butanetetracarboxylic acid, and 1,2,3,4-pentanetetracarboxylic acid.

[0063] Examples of the compound containing a sulfonate group that can be used include, but are not limited to, alkali metal salts, alkaline earth metal salts, and ammonium salts of sulfoterephthalic acid, 5-sulfoisophthalic acid, 5-sodium sulfoisophthalic acid, and 4-sulfoisophthalic acid.

[0064] The acrylic-modified polyester resin used in the resin composition forming the resin layer of the present invention can be produced, for example, by the following production method. First, a polyester resin component is produced as follows. For example, it can be produced by a method of directly esterifying a dicarboxylic acid component with a glycol component, or by a production method that involves a first step of transesterifying a dicarboxylic acid component with a glycol component and a second step of polycondensing the reaction product of this first step. In this case, for example, an alkali metal, alkaline earth metal, manganese, cobalt, zinc, antimony, germanium, titanium compound, or the like can be used as a reaction catalyst.

[0065] Next, the polyester resin component is dispersed in a solvent, particularly in an aqueous solvent, by dissolving or dispersing the polyester resin under stirring in an aqueous solution of an alkaline compound such as ammonia water, sodium hydroxide, potassium hydroxide, various amines, etc. In this case, a water-soluble organic solvent such as methanol, ethanol, isopropanol, butyl cellosolve, or ethyl cellosolve may be used in combination.

[0066] Next, to produce the acrylic-modified polyester resin, a polymerization initiator and, if necessary, an emulsifying dispersant, etc. are added to the dispersion of the polyester resin component, and the acrylic resin component is gradually added while maintaining a constant temperature, followed by reaction for several hours to produce a dispersion of the acrylic-modified polyester. The resulting dispersion is a mixture of the acrylic-modified polyester resin component, the polyester resin component, and the acrylic resin component.

[0067] The polymerization initiator is not particularly limited, but a general radical polymerization initiator, for example, a water-soluble peroxide such as potassium persulfate, ammonium persulfate, or hydrogen peroxide, an oil-soluble peroxide such as benzoyl peroxide or t-butyl hydroperoxide, or an azo compound such as azodiisobutyronitrile, can be used.

[0068] When the resin layer satisfies at least one of Features A and B, the urethane resin contained in the resin composition forming the resin layer in the laminate film of the present invention is preferably an aliphatic urethane resin. The urethane resin used in the present invention is not particularly limited, but is preferably a polymer of an aliphatic polyisocyanate compound and a polyol compound. When the resin layer satisfies Feature C, it preferably has a skeleton similar to that of a urethane resin suitable for when the resin layer satisfies at least one of Features A and B.

[0069] First, the aliphatic polyisocyanate compound used in the resin composition will be described. Aliphatic polyisocyanate compounds preferably used in the resin composition include those having multiple isocyanate groups in the molecule, such as 1,6-hexane diisocyanate, isophorone diisocyanate, methylene bis(4-cyclohexyl isocyanate), 2,2,4-trimethylhexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, bis(2-isocyanatoethyl) fumarate, bis(4-isocyanatocyclohexyl)methane, dicyclohexylmethane 4,4-diisocyanatoridin diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated phenylmethane diisocyanate. The aliphatic polyisocyanate compound used in the present invention may be one type or two or more types.

[0070] In the present invention, any of the aliphatic polyisocyanate compounds described above can be suitably used, but it is particularly preferable to use an alicyclic polyisocyanate compound. Aliphatic urethane resins polymerized from alicyclic polyisocyanate compounds have a high glass transition point among aliphatic urethane resins. Therefore, they do not soften or melt in the resin layer when heated during lamination of a functional material or in a high-temperature, high-humidity environment, and they do not bleed out to the surface of the resin layer, remaining unchanged in the resin layer. Therefore, the adhesiveness between the resin layer and the functional material can be maintained, particularly in a heat-and-humidity adhesion test.

[0071] Next, the polyol compound used in the resin composition will be described. The polyol compound used in the resin composition is not particularly limited as long as it has a plurality of hydroxyl groups. Examples of such polyol compounds include aromatic polyether polyols, aliphatic polyether polyols, polyester polyols, polycarbonate polyols, and polycaprolactone polyols. Specific examples of these polyol compounds will be described below in order.

[0072] Examples of aromatic polyether polyols include ethylene oxide addition diol of bisphenol A, propylene oxide addition diol of bisphenol A, butylene oxide addition diol of bisphenol A, ethylene oxide addition diol of bisphenol F, propylene oxide addition diol of bisphenol F, propylene oxide addition diol of bisphenol F, alkylene oxide addition diol of hydroquinone, and alkylene oxide addition diol of naphthoquinone.

[0073] Examples of aliphatic polyether polyols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, 1,2-polybutylene glycol, polyisobutylene glycol, copolymer polyols of propylene oxide and tetrahydrofuran, copolymer polyols of ethylene oxide and tetrahydrofuran, copolymer polyols of ethylene oxide and propylene oxide, copolymer polyols of tetrahydrofuran and 3-methyltetrahydrofuran, and copolymer polyols of ethylene oxide and 1,2-butylene oxide. Among aliphatic polyether polyols, examples of alicyclic polyether polyols include ethylene oxide addition diol of hydrogenated bisphenol A, propylene oxide addition diol of hydrogenated bisphenol A, butylene oxide addition diol of hydrogenated bisphenol A, ethylene oxide addition diol of hydrogenated bisphenol F, propylene oxide addition diol of hydrogenated bisphenol F, butylene oxide addition diol of hydrogenated bisphenol F, dimethylol compounds of dicyclopentadiene, and tricyclodecane dimethanol.

[0074] Examples of polyester polyols include polyester polyols obtained by reacting polyhydric alcohols such as ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, tetramethylene glycol, polytetramethylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, and 2-methyl-1,8-octanediol with polybasic acids such as phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, adipic acid, and sebacic acid.

[0075] An example of the polycarbonate polyol is 1,6-hexane polycarbonate.

[0076] Examples of polycaprolactone polyols include polycaprolactone diols obtained by reacting ε-caprolactone with a dihydric diol such as ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, tetramethylene glycol, polytetramethylene glycol, 1,2-polybutylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, and 1,4-butanediol.

[0077] Other examples of polyol compounds that can be used in the resin composition include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, poly-β-methyl-δ-valerolactone, hydroxy-terminated polybutadiene, hydroxy-terminated hydrogenated polybutadiene, castor oil-modified polyol, polydimethylsiloxane terminal diol compound, polydimethylsiloxane carbitol-modified polyol, and the like.

[0078] In the resin composition, any of these polyol compounds can be suitably used, but it is preferable to use an aliphatic polyether polyol. The use of an aliphatic polyether polyol can make the aliphatic urethane resin flexible, making it easier to set the aforementioned P(25) to 0.2 GPa or more and 1.5 GPa or less, and making it possible to improve the general-purpose adhesiveness to EVA, PVB, and PVA under room temperature environments. The polyol compound used in the resin composition may be one type or two or more types.

[0079] From the above viewpoints, it is particularly preferable that the specific structure of the urethane resin used in the resin composition is composed of the following aliphatic polyisocyanate compound and aliphatic polyether polyol: Examples of the aliphatic polyisocyanate compound include 1,6-hexane diisocyanate, isophorone diisocyanate, methylene bis(4-cyclohexyl isocyanate), 2,2,4-trimethylhexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, bis(2-isocyanatoethyl) fumarate, bis(4-isocyanatocyclohexyl)methane, dicyclohexylmethane 4,4-diisocyanatoridin diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated phenylmethane diisocyanate.

[0080] Examples of the aliphatic polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, 1,2-polybutylene glycol, and polyisobutylene glycol.

[0081] The aliphatic urethane resin used in the resin composition is obtained by dissolving or dispersing an aliphatic polyisocyanate compound, a polyol compound, and optionally a chain extender in water, and is polymerized by a known method.

[0082] Examples of the chain extender include polyols such as ethylene glycol, 1,4-butanediol, trimethylolpropane, triisopropanolamine, N,N-bis(2-hydroxypropyl)aniline, hydroquinone-bis(β-hydroxyethyl)ether, and resorcinol-bis(β-hydroxyethyl)ether; polyamines such as ethylenediamine, propylenediamine, hexamethylenediamine, phenylenediamine, tolylenediamine, diphenyldiamine, diaminodiphenylmethane, diaminodiphenylmethane, diaminodicyclohexylmethane, piperazine, isophoronediamine, diethylenetriamine, and dipropylenetriamine; hydrazines; and water.

[0083] The content of the urethane resin in the resin composition is not particularly limited as long as it is within a range in which the urethane resin exhibits general-purpose adhesiveness to EVA, PVA, and PVB with a high degree of saponification, as well as moist heat resistant adhesiveness, but is preferably 4% by mass or more and 60% by mass or less, when the entire resin composition is taken as 100% by mass. From the above viewpoints, it is more preferably 4% by mass or more and 50% by mass or less, and even more preferably 5% by mass or more and 50% by mass or less. When a polyester-urethane copolymer is used, the amount of polyisocyanate compound charged during copolymerization is taken as the content of the urethane resin.

[0084] Furthermore, when the resin composition contains an acrylic-modified polyester resin and a urethane resin, the total content of the acrylic-modified polyester resin and the urethane resin in the resin composition is preferably 30% by mass or more and 90% by mass or less, when the total components of the resin composition are taken as 100% by mass. When the total content of these resins is 30% by mass or more, the resin composition exhibits good adhesion to EVA, PVB, and PVA having a wide range of saponification degrees, and can maintain good adhesion even in high-temperature, high-humidity environments. When the total content of these components is 90% by mass or less, the resin composition can contain 10% by mass or more of the compounds described below, melamine compounds, and / or compounds having a carbodiimide group, etc., which is preferable because the inclusion of these components improves adhesion to EVA, PVB, and PVA, as well as the flexibility and toughness of the resin layer.

[0085] When an acrylic resin and a polyester resin are separately contained instead of an acrylic-modified polyester resin, the total content of these components and the urethane resin is preferably 30% by mass or more and 90% by mass or less, when the total content of all components of the resin composition is 100% by mass. In this case, too, when the resin composition contains 10% by mass or more of the compounds described below, melamine compounds and / or compounds having a carbodiimide group, the inclusion of these components improves the adhesion to EVA, PVB, and PVA, as well as the flexibility and toughness of the resin layer.

[0086] Furthermore, when the resin composition contains an acrylic-modified polyester resin, the mass ratio of the acrylic-modified polyester resin to the urethane resin in the resin composition (content of acrylic-modified polyester resin [parts by mass] / content of urethane resin [parts by mass]) is preferably 50 / 50 to 90 / 10. By doing so, it becomes easier to adjust the glass transition temperature of the resin layer within a suitable range, and the change in elastic modulus (ΔP) of the resin layer at 25°C and -20°C can be reduced, thereby minimizing changes in adhesion to the functional material due to temperature. Note that, when the resin composition contains an acrylic resin and a polyester resin separately, rather than an acrylic-modified polyester resin, the mass ratio of the total of these components to the urethane resin is preferably within the above range. Furthermore, when a polyester-urethane copolymer is used, the amount of polyisocyanate compound charged during copolymerization is considered to be the content of the urethane resin, and the amount of polyester polyol compound charged during copolymerization is considered to be the content of the polyester resin.

[0087] As a result of extensive research by the inventors, the laminate film of the present invention has been found to contain a resin layer that contains an acrylic resin, a polyester resin, and a urethane resin (which may be an acrylic-modified polyester resin and a urethane resin, or all of an acrylic skeleton, a polyester skeleton, and a urethane skeleton), as well as a "compound or chemical structure that has both hydrophobic and hydrophilic properties," thereby suppressing separation in the depth direction of the resin layer and making it possible to easily form a uniform resin layer.

[0088] Examples of "compounds or chemical structures having both hydrophobic and hydrophilic properties" include oxazoline compounds and chemical structures derived from oxazoline compounds. That is, it is preferable that the resin layer in the laminate film of the present invention contains a chemical structure derived from an oxazoline compound or contains an oxazoline compound. When the resin layer contains an oxazoline compound or a chemical structure derived from an oxazoline compound, it becomes easy to satisfy the relationship 0.5≦Xs / Xc≦2.0 or 0.5≦Xb / Xc≦2.0. Here, the chemical structure derived from an oxazoline compound refers to a chemical structure (compound) that forms a crosslinked structure with the oxazoline compound contained in the resin layer. For example, when a crosslinked structure is formed with a carboxyl group, it refers to a chemical structure (compound) that forms an amide ester bond.

[0089] The oxazoline compound that can be used in the present invention is not particularly limited as long as it has an oxazoline group as a functional group. However, it is preferable to use an oxazoline group-containing copolymer containing at least one structural unit derived from a monomer containing an oxazoline group. Examples of monomers containing an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. These can be used alone or in mixtures of two or more. Of these, 2-isopropenyl-2-oxazoline is industrially readily available and is therefore preferred. The chemical structure derived from the oxazoline compound contained in the resin layer of the laminate film of the present invention is preferably derived from the above-mentioned oxazoline compound.

[0090] In the oxazoline compound, the other monomer used for the addition-polymerizable oxazoline, i.e., the monomer other than the monomer containing an oxazoline group for obtaining the oxazoline group-containing copolymer, is not particularly limited as long as it is a monomer copolymerizable with the monomer containing an oxazoline group, but is preferably a monomer having a hydrophobic skeleton. When the monomer other than the monomer containing an oxazoline group has a hydrophobic skeleton, the hydrophilic oxazoline group is polymerized, thereby making it possible to obtain an oxazoline compound having both hydrophobic and hydrophilic properties.

[0091] Examples of the monomer having a hydrophobic skeleton include acrylic acid esters or methacrylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid; unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated amides such as acrylamide, methacrylamide, N-methylol acrylamide, and N-methylol methacrylamide; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; olefins such as ethylene and propylene; halogen-containing α,β-unsaturated monomers such as vinyl chloride, vinylidene chloride, and vinyl fluoride; and α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. These may be used alone or as a mixture of two or more thereof.

[0092] Furthermore, by including an oxazoline compound or a chemical structure derived from an oxazoline compound in the resin layer, it is easy to achieve a ΔP of 0.2 GPa or more and 2.0 GPa or less, and a modulus of elasticity ratio P' of 0.1 or more and 2.3 or less. The oxazoline compound can form a crosslinked structure with each component of a urethane resin, polyester resin, acrylic resin, acrylic-modified polyester resin, or polyester-urethane copolymer to strengthen the resin layer while maintaining flexibility. Therefore, the ΔP and modulus of elasticity ratio P' can be set within a suitable range. Furthermore, since a portion of the oxazoline compound contained in the resin layer remains in the resin layer without forming a crosslinked structure, it reacts with the acetyl groups and hydroxyl groups of the functional material, contributing to improved adhesion.

[0093] The resin layer of the present invention preferably satisfies XO / Xs ≧ 1.0, where XO and XOs are the normalized positive secondary ion intensities of the oxazoline compound measured by GCIB-TOF-SIMS at the surface and 20% thickness of the resin layer, respectively. Satisfying XO / Xs ≧ 1.0 means that the oxazoline compound and chemical structures derived from the oxazoline compound remain on the surface side of the resin layer, thereby allowing the water droplet contact angle to be within a suitable range, resulting in increased affinity with functional materials and improved adhesion. From the above perspective, XO / Xs is more preferably 1.1 or greater and 3.0 or less, and even more preferably 1.2 or greater and 2.5 or less. When XO / Xs satisfies the above preferred range, not only is adhesion to the functional material improved, but blocking when the film is wound up in a roll can also be expected.

[0094] From the viewpoint of easily adjusting ΔP and the elastic modulus ratio P' within a preferred range, adjusting the water droplet contact angle within a preferred range, and easily satisfying XO / Xs≧1.0, the oxazoline compound is preferably contained in an amount of 30 to 90 parts by mass, more preferably 30 to 70 parts by mass, and particularly preferably 35 to 60 parts by mass, per 100 parts by mass of the total of acrylic resin, polyester resin, urethane resin, acrylic-modified polyester resin, and polyester-urethane copolymer in the resin composition used to form the resin layer. Furthermore, when the content of the oxazoline compound is within the above range, blocking can be expected to be reduced when the film is wound up in a roll. Note that, when the resin layer contains all of an acrylic skeleton, a polyester skeleton, and a urethane skeleton (when Feature C is satisfied), for the same reason, it is preferable that the mass ratio of the portion containing these skeletons to the portion containing a chemical structure derived from the oxazoline compound be within the above range.

[0095] The resin layer may also contain various additives, such as a melamine compound and / or a compound having a carbodiimide group, a lubricant, inorganic particles, organic particles, a surfactant, and a surface treatment agent, as described below. For example, the content of the melamine compound is preferably 40 parts by mass or less, more preferably less than 20% by mass, based on 100 parts by mass of the total of the acrylic resin, polyester resin, and urethane resin (or acrylic-modified polyester resin and urethane resin) in the resin composition used to form the resin layer. By having the content of the melamine compound and / or the compound having a carbodiimide group be 40 parts by mass or less, the resin layer can be improved in properties such as flexibility and toughness while maintaining adhesion to the hydrophilic material. Furthermore, a melamine compound is preferred because it can reduce blocking when the film is wound up in a roll. The melamine compound may exist in the resin layer as a single compound or as part of a crosslinked structure. This also applies to the compound having a carbodiimide group, described below.

[0096] The melamine compound that can be used in the resin layer of the laminated film of the present invention is not particularly limited as long as it has a melamine skeleton. However, from the viewpoint of solubility in the coating liquid and flatness of the resin layer, specifically, a compound obtained by etherifying a methylolmelamine derivative obtained by condensing melamine with formaldehyde through a dehydration condensation reaction with a lower alcohol such as methyl alcohol, ethyl alcohol, or isopropyl alcohol is preferred.

[0097] Examples of the methylol melamine derivatives include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine.

[0098] The compound having a carbodiimide group is not particularly limited as long as it has at least one carbodiimide structure represented by the following formula (6) per molecule. However, in terms of moisture- and heat-resistant adhesion, a polycarbodiimide compound having two or more carbodiimide groups per molecule is more preferred. In particular, the use of a polymeric isocyanate compound having multiple carbodiimide groups at the end or side chain of a polymer such as a polyester resin or acrylic resin is preferred because, when the resin layer used in the present invention is provided on a film to form a laminate film, not only the hardness of the resin layer is improved and oligomer precipitation is suppressed, but also adhesion to various inks and hard coating agents, moisture- and heat-resistant adhesion, flexibility, and toughness are improved. Formula (6) -N=C=N-

[0099] Known techniques can be applied to the production of compounds having carbodiimide groups, and they are generally obtained by polycondensing a diisocyanate compound in the presence of a catalyst. Examples of diisocyanate compounds that can be used as starting materials for polycarbodiimide compounds include aromatic, aliphatic, and alicyclic diisocyanates, such as tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, and dicyclohexyl diisocyanate. Furthermore, to improve the water solubility or water dispersibility of the polycarbodiimide compound, surfactants or hydrophilic monomers such as polyalkylene oxides, quaternary ammonium salts of dialkylamino alcohols, and hydroxyalkyl sulfonates may be added within the scope of the present invention.

[0100] Other compounds, for example, known crosslinking agents such as epoxy compounds and isocyanate compounds, can also be used as desired.

[0101] The laminate film of the present invention preferably has a laminated structure including at least 51 or more layers, each layer including a layer (A layer) primarily composed of a polyester resin (resin A) and a layer (B layer) primarily composed of a thermoplastic resin (resin B) different from resin A. The laminated structure herein refers to a region in which layers A and B are alternately stacked in a regular arrangement in the thickness direction, such as a regular arrangement such as A(BA)n (n is a natural number representing the number of repeating units). The laminated structure may also include a layer (C layer) made of a third thermoplastic resin, the arrangement of which is not particularly limited, but examples include layers stacked in a regular order, such as C(BA)nC, C(ABC)n, or C(ACBC)n (n is a natural number representing the number of repeating units). "51 or more layers" refers to a total number of repeated layers in the laminated structure, such as layers A and B, or layers A, B, and C, of ​​51 or more.

[0102] In order to obtain a laminate film having a laminated component of such an embodiment, it is preferable to use a film having the above-mentioned laminated component as a film for a substrate. Hereinafter, for the purpose of simplifying the explanation, some of the explanations will be given using as an example a laminated film having a structure in which layers A and B are alternately laminated, which is one of the preferred embodiments of the present invention, but the same should be understood even when three or more thermoplastic resins are used. Hereinafter, a film for a substrate having a laminated component of such an embodiment will sometimes be referred to as a multilayer film.

[0103] For example, by using such a multilayer film as a substrate film, the relationship between the difference in refractive index of each layer and the layer thickness makes it easy to achieve functions such as selectively reflecting light in a specific wavelength band through interference reflection or reflecting light of a specific polarization. As a result, by applying a laminate film using such a multilayer film as a substrate to a solar cell backsheet (a sheet for protecting the back surface of a solar cell), functions such as heat-shielding properties by reflecting infrared rays and deterioration prevention functions by reflecting ultraviolet rays can be imparted to the solar cell. In particular, improving the heat-shielding properties of the laminate film reduces the temperature rise of the solar cell due to direct sunlight and light reflected from the earth's surface, thereby suppressing deterioration of the solar cell due to heat and leading to improved and maintained power generation efficiency.

[0104] Other applications for laminated films using such multilayer films as a substrate include the following: By sandwiching a laminated film having functions such as heat insulation by reflecting infrared rays and deterioration prevention by reflecting ultraviolet rays between two sheets of glass, laminated glass capable of maintaining high heat insulation performance for a long period of time can be produced. Furthermore, by sandwiching a laminated film having the function of reflecting specifically polarized light between two sheets of glass, it can be produced as a component suitable for a display device that displays images using specifically polarized light.

[0105] Here, "resin A and resin B are different" means that resin A and resin B have different melting points or crystallization temperatures. "Different melting points or crystallization temperatures" means that either the melting point or the crystallization temperature determined by the measurement method described below differs by 3°C or more. Note that cases where one resin has a melting point and the other does not, or where one resin has a crystallization temperature and the other does not, are also considered to have different melting points or crystallization temperatures. It is more preferable that the combination of resin A and resin B has different melting points and different crystallization temperatures.

[0106] In the multilayer film used in the laminate film of the present invention, the difference in the in-plane average refractive index between layer A and layer B is preferably 0.03 or more. It is more preferably 0.05 or more, and even more preferably 0.10 or more. When the difference in the in-plane average refractive index between layer A and layer B is greater than 0.03, sufficient reflectance is obtained, thereby improving, for example, heat-blocking performance. One method for achieving the difference in the in-plane average refractive index between layer A and layer B within the above range is to use an embodiment in which one of resins A and B is crystalline and the other is amorphous. Crystallinity here refers to a melting enthalpy of 10 J / g or more in differential scanning calorimetry (DSC). Similarly, amorphousness refers to a melting enthalpy of less than 10 J / g. With such a resin combination, it is possible to easily achieve a refractive index difference during the stretching and heat treatment steps in film production.

[0107] The combination of resin A and resin B constituting the multilayer film used in the laminate film of the present invention is preferably a combination having the same basic skeleton. The basic skeleton here refers to the repeating unit that is most abundant among the repeating units constituting the resin. For example, when polyethylene terephthalate is used as one of the thermoplastic resins, it is preferable that the basic skeleton of the other thermoplastic resin is also an ethylene terephthalate unit, from the viewpoint of easily realizing a highly accurate laminate structure. When resins A and B have the same basic skeleton, the lamination precision is high and interlayer delamination at the lamination interface is less likely to occur.

[0108] Furthermore, a preferred combination of resin A and resin B for the multilayer film used in the laminate film of the present invention is one in which the difference in glass transition temperature between them is 20°C or less. If the difference in glass transition temperature between them is greater than 20°C, the thickness of the multilayer film may become less uniform during film formation, leading to poor appearance of the final laminate film, and problems such as overstretching may occur during molding of the multilayer film. It is also preferable that the glass transition temperature of the crystalline resin between resins A and B is lower than that of the amorphous resin. In this case, when the multilayer film is stretched at a stretching temperature appropriate for orienting and crystallizing the crystalline resin, the orientation of the amorphous resin can be suppressed compared to the crystalline resin, making it easy to achieve a difference in the in-plane average refractive index.

[0109] In the multilayer film used in the laminate film of the present invention, examples of dicarboxylic acid units of the polyester resin used in Resin A, Resin B, and Resin C, which is the main component of Layer C that can be provided as needed, include structural units such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acids (1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid), 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid, and ester-forming derivatives thereof. These acid components may be used alone or in combination, and may further be partially copolymerized with oxyacids such as hydroxybenzoic acid.

[0110] Furthermore, examples of diol units that can be used in these resins include structural units such as ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, diethylene glycol, polyalkylene glycol, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, isosorbate, 1,4-cyclohexanedimethanol, spiroglycol, neopentyl glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, triethylene glycol, tetraethylene glycol, polytetramethylene ether glycol, and ester-forming derivatives thereof.

[0111] Preferred examples of the dicarboxylic acid units constituting these resins include structural units such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, and isophthalic acid, and preferred examples of the diol units include structural units such as ethylene glycol, 1,4-cyclohexanedimethanol, polyalkylene glycol, polyethylene glycol, tetraethylene glycol, and polytetramethylene ether glycol. These diol components may be used alone or in combination of two or more.

[0112] An example of a suitable combination of resins A and B that satisfies the above glass transition temperature conditions is one in which one of resins A and B is polyethylene terephthalate or polyethylene naphthalate, and the other is a polyester containing a spiroglycol-derived polyester. Spiroglycol-derived polyester refers to a polyester that uses spiroglycol as a diol component, such as a copolymer with other ester structural units, a polyester that uses spiroglycol as the sole diol component, or a blend of these with other polyester resins, preferably a polyester in which spiroglycol residues account for more than half of all diol residues in the polyester resin. Spiroglycol-derived polyesters are preferred because they have a small difference in glass transition temperature from polyethylene terephthalate or polyethylene naphthalate, making them less susceptible to overstretching during molding and less susceptible to delamination.

[0113] From the above viewpoints, it is preferable that one of the resins A and B is polyethylene terephthalate or polyethylene naphthalate, and the other is a polyester using spiroglycol and cyclohexanedicarboxylic acid. When a polyester obtained using spiroglycol and cyclohexanedicarboxylic acid is used in one layer, the difference in in-plane refractive index between the polyester and polyethylene terephthalate or polyethylene naphthalate becomes large, and thus a high reflectance is easily obtained. Furthermore, since the difference in glass transition temperature between the polyester and polyethylene terephthalate or polyethylene naphthalate is small and the polyester has excellent adhesiveness, it is less likely to be overstretched during molding and less likely to delaminate.

[0114] Furthermore, in the multilayer film used in the laminate film of the present invention, it is also preferred that one of resins A and B is polyethylene terephthalate or polyethylene naphthalate, and the other is a polyester derived from cyclohexanedimethanol. A cyclohexanedimethanol-derived polyester refers to a polyester using cyclohexanedimethanol as a diol component, such as a copolymer with other ester structural units, a polyester using cyclohexanedimethanol as the sole diol component, or a polyester blended with other polyesters, in which cyclohexanedimethanol residues account for more than half of all diol residues. Polyesters derived from cyclohexanedimethanol have a small difference in glass transition temperature from polyethylene terephthalate and polyethylene naphthalate, making them less susceptible to overstretching during molding and less susceptible to delamination, making them suitable for use. More preferably, at least one thermoplastic resin is an ethylene terephthalate polycondensate in which the copolymerization amount of cyclohexanedimethanol is 15 mol% to 60 mol%.

[0115] By adopting such an embodiment, the film has high reflectivity, but exhibits minimal change in optical properties, particularly due to heating or aging, and is less susceptible to interlayer delamination. Furthermore, an ethylene terephthalate polycondensate having a copolymerization amount of cyclohexanedimethanol of 15 mol% to 60 mol% exhibits very strong adhesion to polyethylene terephthalate. Furthermore, the cyclohexanedimethanol group has geometric isomers, either cis or trans, and conformational isomers, either chair or boat, making it less susceptible to orientation and crystallization even when co-stretched with polyethylene terephthalate. Therefore, the resulting film has high reflectivity, even less change in optical properties due to thermal history, and is less susceptible to tearing during film formation.

[0116] Resins with different melting points and crystallization temperatures usually have different optical properties. Therefore, by alternately stacking such resins, it becomes easier to reflect light in a specific wavelength band due to the relationship between the difference in refractive index of each layer and the layer thickness. Furthermore, the more layers are stacked, the higher the reflectivity can be obtained over a wider band. From this perspective, the number of layers in the laminated structure is preferably 51, more preferably 201 or more, and even more preferably 401 or more. In such reflection (interference reflection), the greater the total number of A and B layers, the wider the wavelength band and the higher the reflectivity, resulting in a laminated structure with high light-blocking performance. Therefore, although there is no upper limit to the number of layers in the laminated structure, increasing the number of layers in the laminated structure increases the manufacturing cost due to the larger manufacturing equipment and the handling ability due to the thicker film. Therefore, in reality, the practical range is a total of 1001 layers or less.

[0117] From the viewpoint of enhancing reflective properties such as heat shielding properties, the laminate film of the present invention preferably has, on at least one surface, a wavelength at which the reflectance is 30% or more when light having a wavelength in the range of 300 nm to 2500 nm is incident at an incident angle of 10°, more preferably a wavelength at which the reflectance is 50% or more, and even more preferably a wavelength at which the reflectance is 80% or more. Furthermore, from the same viewpoint, it preferably has, on at least one surface, at least one reflection band in which the reflectance is 30% or more continuously over a wavelength width of 20 nm or more when light having a wavelength of 300 nm to 2500 nm is incident at an incident angle of 10°, more preferably a wavelength width of 100 nm or more, and even more preferably a wavelength width of 300 nm or more.

[0118] The reflectance at each wavelength can be measured as a relative reflectance using a white aluminum oxide plate as a reference, and details will be described later. The angle of incidence refers to the angle with the normal to the film surface. "On at least one surface" means that the requirements are met when the reflectance is measured by irradiating light onto at least one surface, and preferably when the reflectance is measured by irradiating light onto the surface on the resin layer side. Hereinafter, the same interpretation will be used for "on at least one surface" in measuring optical properties.

[0119] Such properties can be achieved by using a multilayer film as a substrate film and increasing the difference in the in-plane average refractive index between Layer A and Layer B. Therefore, when the multilayer film is to be a biaxially stretched film, it is preferable to use a multilayer polyester film in which layers containing a crystalline polyester resin as the main component and layers containing a low refractive index copolymer polyester as the main component that maintains its amorphous nature during stretching or is melted in a heat treatment step are alternately laminated.

[0120] The laminate film of the present invention preferably has, on at least one surface, an average reflectance of 15% or less in the wavelength range of 400 nm to 700 nm and 70% or more in the wavelength range of 850 nm to 1200 nm when light is incident at an incident angle of 10°. This configuration suppresses reflection in the visible range, reduces coloring and glare, and reflects infrared light. Therefore, this laminate film has excellent heat-shielding properties. For example, by sandwiching this laminate film between two sheets of glass, a laminated glass capable of maintaining high heat-shielding performance for a long period of time can be obtained.

[0121] A laminate film having an average reflectance of 70% or more in the wavelength range of 850 to 1200 nm can be obtained, for example, by using a multilayer film as the substrate film of the laminate film and increasing the total number of layers A and B and / or increasing the in-plane average refractive index difference between layers A and B. The total number of layers depends on the in-plane average refractive index difference between layers A and B (or the resins A and B that are the main components of these layers), but it is preferable that the total number of layers A and B is 201 or more. By increasing the total number of layers A and B to 201 or more, it becomes easy to achieve an average reflectance of 70% or more in the wavelength range of 850 to 1200 nm. Furthermore, when an average reflectance of 80% or more in the wavelength range of 850 to 1200 nm is desired, it is preferable that the total number of layers A and B is 401 or more.

[0122] To obtain such a laminate film, it is preferable that the sum of the optical thicknesses of adjacent layers for the majority of layers constituting the multilayer film (laminate component) used as the substrate of the laminate film is 400 to 700 nm. The optical thickness here refers to the product of the layer thickness of each layer and the refractive index of the resin constituting the layer, and the sum of the optical thicknesses of adjacent layers is a factor that determines the wavelength at which interference reflection occurs in the laminate film. Interference reflection from a laminate component in which the sum of the optical thicknesses of adjacent layers is 400 to 700 nm typically occurs in the wavelength range of approximately 800 to 1400 nm, making it easy to achieve an average reflectance of 70% or more in the wavelength range of 850 to 1200 nm. Furthermore, the magnitude of the reflectance increases with the number of layers and the difference in the in-plane average refractive index of adjacent layers. In a multilayer film having a laminate component in which the sum of the optical thicknesses of adjacent layers for the majority of layers is 400 to 700 nm, it becomes easy to efficiently improve the average reflectance in the wavelength range of 850 to 1200 nm.

[0123] For example, when polyethylene terephthalate with a refractive index of 1.66 and polyethylene terephthalate copolymerized with spiroglycol and cyclohexanedicarboxylic acid with a refractive index of 1.55 are used as resins A and B, the number of layers required to achieve an average reflectance of 70% or more in the wavelength range of 850 to 1200 nm, so that the sum of the optical thicknesses of adjacent layers is 400 to 700 nm, is approximately 201 or more. As the difference in the average in-plane refractive index between resins A and B increases, the number of layers required to achieve a maximum reflectance of 70% or more in the wavelength range of 850 to 1200 nm decreases, and sufficient reflectance can be achieved with approximately 51 layers as long as the in-plane average refractive index difference is 0.3 or more. Furthermore, when polyethylene terephthalate with a refractive index of 1.66 and polyethylene terephthalate copolymerized with spiroglycol and cyclohexanedicarboxylic acid with a refractive index of 1.55 are used as thermoplastic resins, the layer thickness range required to achieve a sum of the optical thicknesses of adjacent layers of 400 to 700 nm is approximately 120 to 220 nm.

[0124] Another example of a laminate film having an average reflectance of 70% or more in the wavelength band of 850 to 1200 nm is one in which the optical thicknesses of adjacent layers A and B simultaneously satisfy the following formulas (7) and (8):

[0125]

[0126]

[0127] where λ is the reflection wavelength, n α is the in-plane refractive index of layer A, d α is the thickness of layer A, n β is the in-plane refractive index of layer B, d β is the thickness of layer B. Having a layer thickness distribution that simultaneously satisfies both formulas (7) and (8) can eliminate even-order reflections. This allows for a high average reflectance in the wavelength range of 850 nm to 1200 nm while a low average reflectance in the visible light wavelength range of 400 to 700 nm, resulting in a transparent film with excellent heat-ray blocking performance. Generally, the refractive index of a film obtained by molding and stretching a thermoplastic resin is approximately 1.4 to 1.9. Therefore, by setting the thickness ratio of adjacent layers A and B (thickness of layer A / thickness of layer B) to 0.7 or more and 1.4 or less, a film with suppressed even-order reflections can be obtained. Therefore, it is preferable that the thickness ratio of adjacent layers A and B (thickness of layer A / thickness of layer B) be 0.7 or more and 1.4 or less. It is more preferable that the thickness ratio be 0.8 or more and 1.2 or less.

[0128] One embodiment of the multilayer film used in the laminate film of the present invention is one in which the refractive index of at least one surface of the laminate polyester film is 1.68 to 1.80. If the refractive index is lower than 1.68, it may be difficult to achieve a reflection band with a reflectance of 30% or more over 20 nm or more in the wavelength range of 300 nm to 2500 nm. If the refractive index is higher than 1.80, the difference in chemical structure becomes greater, which may deteriorate the lamination ability of resin A and resin B, resulting in clouding of the multilayer film and significant peeling at the interface between layer A and layer B.

[0129] An example of a method for achieving a refractive index of 1.68 or more and 1.80 or less on at least one surface of a multilayer film is a method in which the main dicarboxylic acid unit of resin A is a naphthalenedicarboxylic acid unit. By adopting such an embodiment, a refractive index difference between layer A and layer B can be established, making it easier to obtain a laminated polyester film with better reflective performance. Furthermore, in order to increase the refractive index difference between layer A and layer B, it is also preferable that resin B be an amorphous resin. To incorporate naphthalenedicarboxylic acid into resin A of the laminated polyester film of the present invention as a dicarboxylic acid constituent, a method can be used in which naphthalenedicarboxylic acid is included in the dicarboxylic acid constituent of the raw material polyester resin that constitutes resin A.

[0130] The laminate film of the present invention preferably has an average transmittance of 50% or more and 100% or less for visible light incident perpendicularly on at least one surface, and satisfies the relationship R20≦R40<R70, where R20, R40, and R70 are the average reflectances (%) of P waves with wavelengths of 400 nm to 700 nm when P wave light is incident at angles of 20°, 40°, and 70° with respect to the normal to the film surface.

[0131] Here, "perpendicular" means an angle of 0° with respect to the film surface itself or the tangent plane of the film surface. Since the average transmittance of visible light with a wavelength of 400 to 700 nm incident perpendicularly is 50% or more and 100% or less, the laminate film has transparency similar to that of transparent glass or a transparent resin film. Therefore, when a laminated glass having such a configuration is sandwiched between two pieces of glass to form a laminated glass, good visibility of the background can be obtained when the background is observed from a direction perpendicular to the laminated glass.

[0132] From the above viewpoints, the transmittance is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. If the transmittance is 90% or more, when the background is observed from a direction perpendicular to the laminated glass, the background can be seen without being aware of the presence of the laminated glass. From the viewpoint of feasibility, the upper limit of the transmittance is preferably 99%.

[0133] The transmittance of light incident perpendicularly to the laminated film can be measured by measuring the transmittance of light having a wavelength of 400 to 700 nm at an incident angle θ = 0° with a spectrophotometer in 1 nm increments and calculating the average value, although detailed measurement conditions will be described later in the Examples.

[0134] Furthermore, when the average reflectance (%) of P waves with wavelengths of 400 nm to 700 nm when P waves are incident at angles of 20°, 40°, and 70° relative to the normal to the film surface is R20, R40, and R70, an embodiment that satisfies the relationship R20≦R40<R70 is an embodiment in which the laminate film does not have an angle equivalent to Brewster's angle. In the case of a typical transparent substrate such as transparent glass or transparent resin film, as the incident angle relative to the normal to one surface of the transparent substrate gradually increases from 20°, the reflectance of P waves, which are one type of polarized light, decreases, reaching 0% at an angle known as Brewster's angle. Therefore, a typical transparent substrate transmits light in the front direction and has difficulty reflecting P waves from oblique directions.

[0135] When the reflectance of P waves incident on at least one surface of a laminate film at angles of 20°, 40°, and 70° relative to the normal to the film surface is R20, R40, and R70, respectively, and the relationship R20≦R40<R70 is satisfied, the laminate film is suitable for use in a display device that displays images using P waves from oblique angles. From the viewpoint of improving image display performance, R70 is preferably 30% or more, more preferably 50% or more. The higher R70, the better the display performance of the projected image when a P wave image is projected onto the surface of a projection image display member. The upper limit of R70 is not particularly limited, but from the viewpoint of feasibility, it is set to 99%.

[0136] The average reflectance (%) of P waves can be measured by measuring the reflectance of P waves in the wavelength range of 400 to 700 nm at incident angles θ = 20°, 40°, and 70° using a spectrophotometer in 1 nm increments and calculating the average value, although detailed measurement conditions will be described later in the Examples.

[0137] An example of a method for making a laminated polyester film such that the transmittance of visible light incident perpendicularly to the film surface is 50% or more and 100% or less, and the reflectance (%) of P waves incident at angles of 20°, 40°, and 70° to the normal to the film surface is R20, R40, and R70, respectively, satisfies the relationship R20≦R40<R70 and R70 is 10% or more, will be described in detail below.

[0138] The average transmittance of visible light incident perpendicularly to a laminated polyester film can be reduced by reducing the difference in refractive index between the two thermoplastic resin layers in the direction parallel to the film surface (in-plane direction). For example, if the number of layers in the laminated polyester film is within the above-mentioned range, the transmittance can be easily increased to 50% or more if the refractive index difference in the direction parallel to the film surface is 0.06 or less, to 70% or more if the refractive index difference is 0.04 or less, and to 80% or more if the refractive index difference is 0.02 or less. Note that the "refractive index difference in the direction parallel to the film surface" refers to the absolute value of the difference in in-plane refractive index between adjacent thermoplastic resin layers.

[0139] To obtain a laminated polyester film satisfying the relationship R20≦R40<R70, a method can be used to adjust the refractive index difference between the two thermoplastic resin layers in the direction perpendicular to the film surface and the number of layers. In this case, the greater the refractive index difference in the direction perpendicular to the film surface and the greater the number of layers, the greater the R70. For example, in a film with 801 layers, if the refractive index difference in the direction perpendicular to the film surface is 0.08 or more, the reflectance can be easily increased to 30% or more, and if the refractive index difference is 0.12 or more, the reflectance can be easily increased to 50% or more. As a result, when the reflectance (%) of P waves incident at angles of 20°, 40°, and 70° relative to the normal to the laminated polyester film is R20, R40, and R70, respectively, the relationship R20≦R40<R70 can be satisfied. Furthermore, even if the refractive index difference does not reach the above level, the reflectance can be increased to reach the above level by further increasing the number of layers. Hereinafter, the refractive index in the direction perpendicular to the film surface may be referred to as the in-plane refractive index.

[0140] Methods for adjusting the reflection wavelength of the laminated film to a wavelength range of 400 to 700 nm include adjusting the difference in refractive index perpendicular to the plane of the two thermoplastic resin layers, the number of layers stacked, the layer thickness distribution, and film-forming conditions (e.g., stretching ratio, stretching speed, stretching temperature, heat treatment temperature, and heat treatment time). It is preferable that the layer thickness distribution be such that the optical thicknesses of adjacent layers A and B satisfy formula (7). It is preferable that the crystalline thermoplastic resin in layer A and the amorphous thermoplastic resin in layer B are both polyesters.

[0141]

[0142] The layer thickness distribution of the multilayer film used in the laminate film of the present invention is preferably a constant layer thickness distribution from one side of the laminate polyester film to the opposite side, a layer thickness distribution that increases or decreases from one side of the laminate polyester film to the opposite side, a layer thickness distribution in which the layer thickness increases and then decreases from one side of the laminate polyester film to the center of the film, a layer thickness distribution in which the layer thickness decreases and then increases from one side of the laminate polyester film to the center of the film, or a combination of these distributions. As for the way in which the layer thickness distribution changes, a continuous change such as linear, geometric, or difference progression, or a change in layer thickness in a stepwise manner in which about 10 to 50 layers have approximately the same layer thickness, is preferred.

[0143] Both surface layers of the multilayer film used in the laminate film of the present invention can preferably be provided with protective layers whose thickness is 1% or more of the thickness of the multilayer film itself, and the thickness of each protective layer is preferably 4% or more of the total thickness of the multilayer film. Increasing the thickness of the protective layers leads to the suppression of flow marks during film formation, improved accuracy of the actual layer thickness relative to the design, suppression of deformation of thin layers in the multilayer film during lamination with other films or molded articles and after the lamination process, and improved pressure resistance. The upper limit of the thickness of the protective layer is 20% from the viewpoint of ensuring the laminated components necessary for the expression of interference reflection while suppressing an increase in the thickness of the multilayer film. The thickness of the multilayer film is not particularly limited, but is preferably 20 μm to 300 μm, for example. A thickness of 20 μm or more increases the rigidity of the multilayer film, ensuring ease of handling. Furthermore, a thickness of 300 μm or less prevents the rigidity of the multilayer film from becoming excessively strong, improving formability.

[0144] An example of a laminated polyester film preferably used in the present invention is one in which, when the direction parallel to the film surface and in which the average rate of change in thermal shrinkage measured by thermomechanical analysis in the range of 100°C to 150°C is the X direction, the average rate of change in thermal shrinkage in the X direction is 0.01% / °C or more and 0.1% / °C or less. Thermomechanical analysis here refers to a method in which a non-oscillating load is applied to a material while changing its temperature according to a controlled program, and the deformation of the material is measured as a function of temperature. This method is performed using a commercially available thermomechanical analyzer. The thermal shrinkage is defined by equation (9):

[0145] The average change in heat shrinkage here refers to the difference between the heat shrinkage at 100°C and 150°C divided by the temperature difference. By configuring the laminated polyester film in this manner, when the laminated polyester film is sandwiched between two intermediate layers and two panes of glass to form laminated glass, wrinkles and peeling are suppressed, resulting in a laminated glass with a good appearance. More preferably, the average change in heat shrinkage is 0.01% or more and less than 0.05%. It is also preferable that the direction perpendicular to the X direction is the Y direction, and the average change in heat shrinkage measured by thermomechanical analysis in the range of 100°C to 150°C in both the X and Y directions is 0.01% / °C or more and 0.1% / °C or less. In this case, the heat shrinkage changes isotropically, allowing it to appropriately follow changes in the heat shrinkage of the intermediate layer, thereby substantially suppressing the occurrence of wrinkles and peeling.

[0146] When the X direction of a laminate film is the direction parallel to the film surface and exhibits the greatest average rate of change in thermal shrinkage measured by thermomechanical analysis in the range of 100°C to 150°C, the average rate of change in thermal shrinkage in the X direction is 0.01% / °C or more and 0.1% / °C or less. To achieve this, it is preferable to enhance the orientation in the longitudinal direction of the film by adjusting the longitudinal stretching ratio and longitudinal stretching temperature during the production of the laminate film. For example, when a multilayer film is used as a substrate film for a laminate film, a desired multilayer film can be easily obtained by adjusting the longitudinal stretching temperature to 90°C or less or the longitudinal stretching ratio to 3.5 times or more. Similarly, it is also preferable to enhance the orientation in the direction perpendicular to the longitudinal direction by adjusting the transverse stretching temperature and transverse stretching ratio. For example, when a multilayer film is used as a substrate film for a laminate film, a desired multilayer film can be easily obtained by adjusting the transverse stretching temperature to 110°C or less or the transverse stretching ratio to 3.8 times or more. In addition, in order to suppress the difference in heat shrinkage behavior between the longitudinal direction of the multilayer film and the direction perpendicular thereto, it is desirable to adjust the longitudinal stretching conditions and transverse stretching conditions. Specifically, the heat shrinkage behavior is easily made isotropic by setting the difference between the longitudinal stretching ratio and the transverse stretching ratio to 0.3 times or less, or by setting the temperature difference between the longitudinal stretching temperature and the transverse stretching temperature to 20°C or more. These methods can be used in appropriate combination, and by using the multilayer film obtained in this way as a substrate film, a laminated film can be obtained in which the average change rate of the heat shrinkage in the X direction is 0.01% / °C or more and 0.1% / °C or less.

[0147] Furthermore, when there is a difference in melting point between resin A and resin B, it is also preferable to set the heat treatment temperature after stretching to a temperature between the melting points of both. In this case, the resin with the relatively higher melting point maintains a high orientation state, while the orientation of the other resin is relaxed, making it easy to create a refractive index difference between these resins, and also making it possible to impart high heat shrinkage behavior to the thermoplastic resin that maintains its orientation. Furthermore, when resin A is a crystalline polyester and resin B is a polyester resin composed of an amorphous polyester and a crystalline polyester, it is preferable that the heat treatment temperature be equal to or lower than the crystalline polyester contained in resin A and resin B. In this case, the orientation of the crystalline polyester contained in resin B is maintained in addition to the orientation of resin A, making it possible to impart high heat shrinkage behavior.

[0148] Furthermore, since the relaxation treatment is carried out to suppress heat shrinkage behavior, it is also preferable not to carry out the relaxation treatment, and the preferred degree of relaxation treatment is a ratio of the relaxation treatment to the film width before the relaxation treatment of 0% to 5% (a relaxation treatment ratio of 0% means that the relaxation treatment itself is not carried out). Although it depends on the types of resins A and B to be laminated, for example, in the case of polyethylene terephthalate and an amorphous polyester that is completely melted in the heat treatment step, a multilayer film with the best heat shrinkage behavior can be obtained when the relaxation treatment ratio to the film width before the relaxation treatment is in the range of about 0% to 1%.

[0149] Here, the longitudinal direction refers to the running direction of the sheet or film (the winding direction of the film in the case of a film roll), and the width direction refers to the direction perpendicular to the longitudinal direction within the film plane. Generally, the thermal shrinkage rate is large because it exists as a residual stress due to the stretching. Therefore, either the longitudinal direction or the width direction is the X direction, and the other is the Y direction.

[0150] The laminate film of the present invention preferably has a small endothermic peak measured by differential scanning calorimetry between 170°C and 210°C. The small endothermic peak corresponds to the thermal history corresponding to the heat treatment temperature during transverse stretching, as described below, and the thermal shrinkage of the laminate film varies depending on the temperature of the endothermic peak. By setting the small endothermic peak between 170°C and 210°C, the shrinkage of the laminate film is similar to that of EVA, PVB, and PVA, thereby suppressing the occurrence of wrinkles during thermal processing steps such as glass lamination. The small endothermic peak is usually observed below the melting point and near the melting point, and is observed in the first run of differential scanning calorimetry. Since it is not observed in the second run, in which the temperature is raised above the melting point to erase the thermal history, the position of the small endothermic peak can be confirmed by comparing the two peaks. The method for measuring the small endothermic peak will be described later.

[0151] A preferred method for producing a laminate film will be described below using as an example a multilayer film substrate film in which polyethylene terephthalate is used as resin A constituting Layer A and a polyethylene terephthalate copolymer (polyethylene terephthalate copolymerized with 20 to 40 mol % of a cyclohexanedimethanol component) is used as resin B constituting Layer B. Of course, the laminate film of the present invention is not intended to be limited to this example. Furthermore, the laminated portion of this multilayer film can be easily produced by a method similar to that described in paragraphs

[0053] to

[0063] of JP 2007-307893 A.

[0152] Each resin is prepared in the form of pellets or the like. The pellets are dried in hot air or under vacuum, as necessary, and then fed to separate extruders. The resins are heated and melted in the extruder at 280 to 300°C. The resin extrusion rate is uniformed using a gear pump or the like, and foreign matter and denatured resin are removed through a filter or the like. These resins are molded into the desired shape through a die and then discharged. The multilayered sheet discharged from the die is then extruded onto a cooling body such as a casting drum, where it is cooled and solidified to form a cast film. In this case, it is preferable to use a wire-, tape-, needle-, or knife-shaped electrode to electrostatically contact the cooling body such as a casting drum and rapidly solidify the film. Other preferable methods include blowing air from a slit-, spot-, or plane-shaped device to rapidly solidify the film by contacting the film with a cooling body such as a casting drum, or using a nip roll to rapidly solidify the film by contacting the film with the cooling body.

[0153] In this process, resins A and B are melt-kneaded in separate extruders and fed into a multi-layer lamination device through separate channels. While multi-manifold dies, feed blocks, static mixers, and the like can be used as multi-layer lamination devices, it is particularly preferable to use a feed block with 51 to 1,001 fine slits to efficiently achieve the configuration of the present invention. The use of such a feed block prevents the device from becoming excessively large, reduces the amount of foreign matter caused by thermal degradation, and enables high-precision lamination when the number of layers is 51 to 1,001. Furthermore, the lamination accuracy in the width direction is significantly improved compared to conventional techniques. Furthermore, with such a feed block, the thickness of each layer can be adjusted by the shape (length and width) of the slits, making it easy to achieve any desired layer thickness. The molten multi-layer laminate thus formed into the desired layer configuration is guided into a die, and a casting film is obtained as described above.

[0154] The cast film thus obtained is preferably biaxially stretched. Here, biaxial stretching refers to stretching in the longitudinal direction and the width direction. Stretching may be performed in the two directions sequentially or simultaneously. Furthermore, re-stretching may be performed in the longitudinal direction and / or the width direction.

[0155] First, the case of sequential biaxial stretching will be described. In the case of sequential biaxial stretching, stretching in the longitudinal direction (longitudinal stretching) is usually performed followed by stretching in the width direction (transverse stretching). Here, stretching in the longitudinal direction refers to stretching to impart molecular orientation to the film in the longitudinal direction, and is usually performed by varying the peripheral speed of rolls. This stretching may be performed in one stage, or may be performed in multiple stages using multiple pairs of rolls. The stretching ratio varies depending on the type of resin, but is usually preferably 2 to 15 times, and when polyethylene terephthalate is used as resin A, 2 to 7 times is particularly preferred. The stretching temperature is preferably the glass transition temperature of the resin constituting the film to the glass transition temperature + 100°C.

[0156] The uniaxially stretched film thus obtained is subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment as required, and then subjected to a step of coating with a resin composition to form a resin layer. The method for forming the resin layer will be described in detail later.

[0157] Next, widthwise stretching refers to stretching to impart widthwise orientation to the film. Typically, a uniaxially stretched film obtained by longitudinal stretching is conveyed using a tenter while holding both widthwise ends with multiple clips, and the film is stretched widthwise by widening the distance between the opposing clips. The stretching ratio varies depending on the type of resin, but is typically 2 to 15 times, and when polyethylene terephthalate is used as resin A, a ratio of 2 to 7 times is particularly preferred. In particular, for the laminated film of the present invention, the transverse stretching ratio is preferably 4 times or more, as increasing the transverse stretching ratio is effective in improving the uniformity of the reflection band and the average reflectance. The stretching temperature is preferably between the maximum glass transition temperature of the resins constituting the film and the maximum glass transition temperature + 120°C.

[0158] The biaxially stretched film is preferably heat-treated in a tenter at a temperature equal to or higher than the stretching temperature and equal to or lower than the melting point of thermoplastic resin A to impart flatness and dimensional stability. Heat treatment improves the dimensional stability of the film. After heat treatment, the film is uniformly and slowly cooled to room temperature and wound up. If necessary, a relaxation treatment or the like may be performed during the heat treatment and slow cooling.

[0159] Next, simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the obtained cast film is subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment as necessary, and then a resin layer is formed by in-line coating.

[0160] The cast film is then introduced into a simultaneous biaxial tenter, where it is conveyed while its widthwise ends are held with clips, and simultaneously and / or stepwise stretched in the longitudinal and widthwise directions. Tenter types that can be used as simultaneous biaxial stretching machines include pantograph, screw, drive motor, and linear motor types. Drive motor or linear motor types are preferred, as they allow for arbitrary change in stretching ratio and relaxation treatment at any location. The stretching ratio varies depending on the type of resin, but an area ratio of 6 to 50 times is generally preferred. When polyethylene terephthalate is used as the thermoplastic resin A, an area ratio of 8 to 30 times is particularly preferred. In particular, in the case of simultaneous biaxial stretching, it is preferable to make the stretching ratios in the longitudinal and width directions the same and to make the stretching speeds approximately equal in order to suppress in-plane orientation differences. Furthermore, the stretching temperature is preferably between the maximum glass transition temperature of the resins constituting the film and the maximum glass transition temperature + 120°C.

[0161] The biaxially stretched film is preferably subsequently heat-treated in a tenter at a temperature equal to or higher than the stretching temperature and lower than the melting point to impart flatness and dimensional stability. During this heat treatment, it is preferable to instantaneously relax the film in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone in order to suppress the distribution of the main orientation axis in the width direction. After the heat treatment, the film is uniformly and slowly cooled, then cooled to room temperature, and wound up. If necessary, relaxation treatment may be performed in the longitudinal and / or width directions during the slow cooling period following the heat treatment. Preferably, the film is instantly relaxed by 1 to 5% in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone.

[0162] A method for forming a resin layer on the multilayer film thus obtained can be to apply a resin composition to at least one surface of the multilayer film to form a resin layer. In this method, the resin composition contains a urethane resin and an acrylic-modified polyester resin (or an acrylic resin and a polyester resin). It is more preferable that the resin composition contains an oxazoline compound. When applying such a resin composition to a thermoplastic resin film, the resin composition may contain a solvent. That is, each resin component may be dissolved or dispersed in a solvent to form a coating liquid, which may then be applied to the multilayer film. After application, the solvent is dried and the resulting film is heated to obtain a laminate film having a resin layer laminated thereon. In the present invention, it is preferable to use an aqueous solvent as the solvent. The use of an aqueous solvent not only prevents rapid evaporation of the solvent during the heating process, allows for the formation of a uniform resin layer, but is also excellent in terms of environmental impact.

[0163] Here, the aqueous solvent refers to water or a mixture of water and a water-soluble organic solvent, such as an alcohol such as methanol, ethanol, isopropyl alcohol, or butanol, a ketone such as acetone or methyl ethyl ketone, or a glycol such as ethylene glycol, diethylene glycol, or propylene glycol, in any ratio.

[0164] The resin composition can be applied to a multilayer film by either an in-line coating method or an off-coating method, but the in-line coating method is preferred. The in-line coating method is a method in which coating is performed within the film production process. Specifically, it refers to a method in which coating is performed at any stage from melt extrusion of a thermoplastic resin to winding up. Typically, coating is performed on any of the following films: an unstretched (unoriented) polyester film (A film) in a substantially amorphous state obtained by melt extrusion and quenching, a uniaxially stretched (uniaxially oriented) polyester film (B film) that has been subsequently stretched in the longitudinal direction, or a biaxially stretched (biaxially oriented) polyester film (C film) that has been further stretched in the width direction and has not yet been heat-treated.

[0165] In the present invention, a method is preferably adopted in which a resin composition is applied to either the A film or the B film of a polyester film before the crystal orientation is completed, the solvent is evaporated, and then the polyester film is stretched uniaxially or biaxially and heated to complete the crystal orientation of the polyester film and provide a resin layer. This method has the advantage of being cost-effective because it allows the production of a substrate film, the application of the resin composition, the drying of the solvent, and the heating (i.e., the formation of the resin layer) to be performed simultaneously. In addition, it is easy to make the resin layer thinner by performing stretching after coating.

[0166] Among these, the method of applying the resin composition to a film (film B) uniaxially stretched in the longitudinal direction, drying the solvent, and then stretching the film in the width direction and heating is excellent. This is because, compared to the method of applying the resin composition to an unstretched film and then biaxially stretching it, this method requires one less stretching step after coating, making it less likely for defects or cracks to occur in the resin layer due to stretching, and making it possible to form a resin layer with excellent transparency and smoothness.

[0167] On the other hand, the offline coating method is a method in which the above-mentioned A film is uniaxially or biaxially stretched and heat-treated to complete the crystal orientation of the polyester film, or the A film is coated with a resin composition in a step separate from the film production step. In the present invention, in view of the various advantages described above, it is preferable to apply the resin composition by the inline coating method.

[0168] The best method for forming the resin layer in the present invention is to apply a resin composition using an aqueous solvent onto a polyester film by in-line coating, and then heat and dry the aqueous solvent.

[0169] When preparing a resin composition for forming a resin layer, it is preferable to use an aqueous solvent. The resin composition can be prepared by mixing and stirring an acrylic-modified polyester resin (acrylic resin and polyester resin) dispersed or solubilized in water as needed, a urethane resin, an oxazoline compound and / or a melamine compound, and an aqueous solvent in any order at a desired weight ratio. Next, various additives such as lubricants, inorganic particles, organic particles, surfactants, antioxidants, and thermal initiators can be added as needed, in any order so long as they do not deteriorate the properties of the resin layer formed from the resin composition. Mixing and stirring can be performed by shaking the container by hand, using a magnetic stirrer or stirring blade, ultrasonic irradiation, vibration dispersion, etc.

[0170] The resin composition can be applied to the laminate film by any known coating method, such as bar coating, reverse coating, gravure coating, die coating, blade coating, etc. From the viewpoint of appropriate coating thickness and viscosity, bar coating and gravure coating are preferred.

[0171] The thickness of the resin layer of the present invention is not particularly limited, but is preferably 20 to 500 nm. By making the resin layer thickness 20 nm or more, it becomes easy to provide a uniform resin layer on the substrate film. By making the resin layer thickness 500 nm or less, it is possible to maintain the quality of the laminated film without increasing the manufacturing cost and further suppress the occurrence of unevenness or streaks during application of the resin layer.

[0172] The thickness of the resin layer can be measured using a cross-sectional image taken with a transmission electron microscope (TEM), and details thereof will be described later. In the laminated film of the present invention, the method for adjusting the thickness of the resin layer is not particularly limited and can be appropriately selected from known methods, for example, a method of adjusting the concentration of solids in the resin composition.

[0173] Generally, a solar cell is constructed by laminating a transparent substrate such as glass and a resin sheet called a back sheet (a sheet for protecting the back surface) to a power generation element sealed with a transparent sealing material, and the laminated film of the present invention is suitable for use in a solar cell module having a structure in which a sealing material is directly laminated.Furthermore, the laminated film of the present invention is suitable for use in a solar cell module having two sealing materials (sealing materials 1 and 2), and comprising sealing material 1, a solar cell, sealing material 2, and the laminated film in this order.

[0174] Solar cells convert the light energy of sunlight that enters the interior through a transparent substrate into electrical energy using a power generation element. The resulting electrical energy is extracted through lead wires connected to the power generation element and used in various electrical devices. By improving the heat-shielding properties of the laminated polyester film, the temperature rise of the solar cell caused by direct sunlight and light reflected from the ground surface is reduced, which prevents the solar cell from deteriorating due to heat and leads to improved power generation efficiency.

[0175] The laminate film of the present invention includes an intermediate layer and glass, and is suitable for use in a glass structure in which the laminate film and the intermediate layer are adjacent to each other. Examples include a glass laminate in which the laminate film of the present invention is bonded to one surface of glass using an intermediate layer, and laminated glass in which a laminate film is inserted between two glass panes and two intermediate layers. Furthermore, the laminate film of the present invention is suitable for use in a glass structure (laminated glass) having two glass panes (glass panes 1 and 2) and two intermediate layers (intermediate layers 1 and 2), and including glass pane 1, intermediate layer 1, laminate film, intermediate layer 2, and glass pane 2 in this order.

[0176] The glass used in the glass construct of the present invention is not particularly limited, and commonly used transparent plate glass, etc., can be used, such as clear glass, float plate glass, polished plate glass, figured plate glass, wired plate glass, lined plate glass, infrared absorbing plate glass, infrared reflecting plate glass, green glass, etc.

[0177] The intermediate layer used in the glass construct of the present invention is not particularly limited, and examples thereof include vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate copolymers, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, polyvinyl ether, nitrile rubbers, styrene-butadiene rubbers, natural rubbers, chloroprene rubbers, polyamides, epoxy resins, polyurethanes, acrylic resins, cellulose, polyvinyl chloride, polyacrylic esters, and polyisobutylene. These intermediate layers may also contain adhesive modifiers, plasticizers, heat stabilizers, antioxidants, UV absorbers, antistatic agents, lubricants, colorants, crosslinking agents, and the like. The provision of an intermediate layer can improve the adhesion between the glass and the laminated film, and the design, durability, weather resistance, impact resistance, and other properties of the laminated glass.

[0178] The intermediate layer used in the glass construct of the present invention may contain a component that enhances design. Examples of the component that enhances design include colorants, such as azo pigments, polycyclic pigments, lake pigments, nitro pigments, nitroso pigments, aniline black, alkali blue, phthalocyanine pigments, cyanine pigments, azo dyes, anthraquinone dyes, quinophthalone dyes, methine dyes, condensed polycyclic dyes, reactive dyes, cationic dyes, lanthanum hexaboride, indium tin oxide, antimony tin oxide, and cesium tungsten oxide.

[0179] Methods for forming the interlayer include extrusion lamination, hot melt lamination, thermal lamination, press lamination, vacuum lamination, and autoclave lamination. Extrusion lamination is a method in which a molten laminate film and an interlayer are extruded from a die into a film shape and laminated onto glass, and the molded product is then passed through two rolls to form the laminate. Hot melt lamination is a molding method in which a heat-melted interlayer is applied to the laminate film or glass, and the laminate film and glass are laminated together. Thermal lamination is a molding method in which the laminate film, interlayer, and glass are heated and pressed together with a heated roll. Press lamination is a molding method in which the laminate film, interlayer, and glass are heated and pressed together in a press. Vacuum lamination is a molding method in which the laminate film, interlayer, and glass are heated, then the inside of the device is evacuated, and the laminate is pressed together to form the laminate. Autoclave lamination is a molding method in which a laminated film, an intermediate layer, and glass are heated, and then the inside of the apparatus is pressurized with gas or the like to laminate them.

[0180] The glass construct of the present invention preferably satisfies 3≦d1 / d2≦100, where d1 is the thickness of intermediate layer 1 and d2 is the thickness of intermediate layer 2. By setting the thicknesses of the two intermediate layers within a suitable range, double images in projected images can be suppressed when the glass construct is used in, for example, a projection image display member having P-wave reflection characteristics and a projection member such as a head-up display (HUD). The thickness of the intermediate layer is preferably 10 μm to 1 mm.

[0181] The glass construct of the present invention preferably satisfies 1.5≦d3 / d4≦10, where d3 is the thickness of glass 1 and d4 is the thickness of glass 2. By setting the thicknesses of the two glass sheets within a suitable range, double images in projected images can be suppressed when the glass construct is used in, for example, a projection image display component having P-wave reflection characteristics and a projection component such as a head-up display (HUD). The thickness of the glass is preferably 0.5 mm to 5.0 mm.

[0182] A glass construct using the laminated film thus obtained has, for example, excellent heat-shielding performance on the inside and excellent transparency, and is therefore particularly suitable as heat-shielding glass used in automobiles, building windows, etc. Furthermore, it is also suitable for display devices that have high display properties for projected images and good visibility of the surrounding scenery when used in projection components such as projection image display components having P-wave reflection characteristics and head-up displays (HUDs). That is, the automobile and building windows of the present invention comprise the glass construct of the present invention.

[0183] The laminated film of the present invention will be specifically described below using examples, but the laminated film of the present invention is not limited to these embodiments.

[0184] [Methods for Measuring Physical Properties and Evaluating Effects] The methods for evaluating physical properties and effects are as follows.

[0185] (1) Identification of the substrate The composition of the resin constituting the substrate was confirmed by the following method. First, the presence or absence of peaks derived from the bonds between the atoms in the resin structure was confirmed by Fourier transform infrared spectroscopy (FT-IR or ATR). Furthermore, proton nuclear magnetic resonance spectroscopy ( １ Using H-NMR, the chemical shift position derived from the position of hydrogen atoms in the resin structure and the proton absorption line area derived from the number of hydrogen atoms were confirmed. These results were combined and comprehensively confirmed to identify the substrate. Furthermore, mass peaks may be confirmed by gas chromatography mass spectrometry (GC-MS) if necessary. The above analysis was performed on samples scraped from the laminated film with a blade knife.

[0186] (2) Thickness of resin layer: The laminated film is made of RuO ４ and / or OsO ４The laminated film was then frozen and cut in the film thickness direction to obtain 10 ultrathin section samples for observing the cross section of the resin layer. The cross section of each sample was observed at 10,000 to 1,000,000 magnifications using a TEM (transmission electron microscope: H7100FA type manufactured by Hitachi, Ltd.), and a cross-sectional photograph was obtained. The thickness of the resin layer of each sample was measured from the cross-sectional photograph using the length measurement function of the microscope, and the measured values ​​of the resin layer thickness of the 10 samples were averaged to obtain the thickness of the resin layer of the laminated film.

[0187] (3) Derivation of Xs, Xc, Xb, XO, and XOs of the Resin Layer First, the composition distribution in the depth direction from the surface side of the resin layer of the laminated film was analyzed using the analytical method GCIB-TOF-SIMS (GCIB: gas cluster ion beam, TOF-SIMS: time-of-flight secondary ion mass spectrometry). The measurement conditions were as follows. <Sputtering conditions> Ion source: argon gas cluster ion beam (Ar-GCIB) <Detection conditions> Primary ions: Bi ３＋＋ (25 kV) Secondary ion polarity: positive Mass range: m / z 0 to 1500 Measurement range: 300 x 300 μm ２ Measurement vacuum degree: 4×10 －７ Pa or less. Measurements under the above conditions were performed to obtain a profile of the absolute positive secondary ion intensity of each component versus the sputtering time of the GCIB-TOF-SIMS. An approximate straight line of 100 consecutive points was calculated in the profile of the absolute positive secondary ion intensity corresponding to the main component of the substrate identified in (1), and the average value of the 100 points located closest to the inner layer (substrate side) among the 100 points with a slope of ±15 or less was taken as the "absolute substrate intensity." The sputtering time at which the intensity was half the "absolute substrate intensity" calculated above was derived and designated the "half intensity sputtering time," and this point was defined as the boundary between the resin layer and the substrate. In other words, the sputtering time from 0 to the half intensity sputtering time indicates the component distribution of the resin layer, and the period from the half intensity sputtering time onwards indicates the component distribution of the substrate.

[0188] Next, a method for converting the sputtering time of the GCIB-TOF-SIMS absolute positive ion intensity profile into the resin layer thickness will be described. The resin layer thickness obtained by the measurement in (2) above was divided by the half-intensity sputtering time calculated above to obtain the etching rate. The sputtering time was converted into the resin layer thickness based on this etching rate, thereby obtaining a profile of the absolute positive secondary ion intensity of each component relative to the resin layer thickness of the GCIB-TOF-SIMS.

[0189] Next, a method for converting the absolute positive secondary ion intensity of each component into the normalized positive secondary ion intensity of each component will be described. The substrate absolute intensity calculated by the above method is normalized as 1, and the normalized positive secondary ion intensity of each component is obtained from the absolute positive secondary ion intensity of each component. Of the normalized positive secondary ion intensities of each component, the normalized intensity at a position 20% of the thickness from the surface of the resin layer was designated Xs, the normalized intensity at a position 50% of the thickness from the surface of the resin layer was designated Xc, and the normalized intensity at a position 80% of the thickness from the surface of the resin layer was designated Xb. Furthermore, the normalized intensity of the oxazoline compound in the surface of the resin layer was designated XO, and the normalized intensity at a position 20% of the thickness from the surface of the resin layer was designated XOs.

[0190] In addition, the positive secondary ions of acrylic resin are, for example, ６９ C ４ H ５ O ＋ As the positive secondary ions of polyester resin, for example, １０４ C ７ H ４ O ＋ , the positive secondary ions of urethane resin are, for example, １２２ C ７ H ８ NO ＋ Positive secondary ions of oxazoline compounds or chemical structures derived from oxazoline compounds include, for example, １１２ C ６ H １０ NO ＋Here, "a position 20% in thickness from the surface of the resin layer" refers to a thickness position closest to 20 / 100 times the thickness of the resin layer when viewed from the surface of the resin layer. Similarly, "a position 50% in thickness from the surface of the resin layer" refers to a thickness position closest to 50 / 100 times the thickness of the resin layer when viewed from the surface of the resin layer, "a position 80% in thickness from the surface of the resin layer" refers to a thickness position closest to 80 / 100 times the thickness of the resin layer when viewed from the surface of the resin layer, and "the surface of the resin layer" refers to the surface of the resin layer.

[0191] (4) AFM Elastic Modulus of Resin Layer Measurement was performed using a NanoScope V manufactured by Bruker AXS Co., Ltd. Measurements were performed in accordance with the attached "Measurement Procedure PeakForce QNM" under the following measurement conditions. Measurements at 25 ° C were performed on samples left standing for 24 hours in a room temperature controlled at 25 ° C, and measurements at -20 ° C were performed immediately after removing the samples left standing for 24 hours in a portable freezer temperature controlled at -20 ° C. All measurements were performed in an atmosphere of room temperature 23 ° C and relative humidity 65%. This measurement was performed 10 times, and the average value was used as the AFM elastic modulus of the resin layer at each temperature (P (25), P (-20)), and the elastic modulus ratio P' (P (-20) / P (25)) was calculated. Probe: RTESPA-300 ScanSize: 1nm ScanRate: 1Hz PeakForce Setpoint: 40.00mN.

[0192] (5) Melting point, crystallization temperature, melting enthalpy, minute endothermic peak, glass transition temperature of resin layer 5 mg of sample was collected by scraping with a cutter or blade knife, and measured and calculated according to JIS-K-7122 (1987) using a differential scanning calorimeter (DSC) robot DSC-RDC220 manufactured by Seiko Electronics Co., Ltd. More specifically, the sample was heated from 25 ° C to 300 ° C at a rate of 5 ° C / min, and the peak near the melting point on the lower side than the melting point at this time was taken as the minute endothermic peak, and the integrated value from the baseline in the range of the melting point ± 20 ° C was taken as the melting enthalpy. The melting point here was taken as the point at which the difference from the baseline of the DSC chart was minimal. The crystallization temperature was taken as the point at which the difference from the baseline of the DSC chart was maximal in the exothermic peak on the lower side than the melting point. Since the small endothermic peak is observed in the first run of DSC and not observed in the second run in which the thermal history is erased by raising the temperature above the melting point, it can be confirmed by comparing the two DSC charts. The glass transition temperature of the resin layer was also measured and calculated in accordance with JIS-K-7122 (1987). More specifically, the glass transition temperature was determined as the temperature at the point where a line equidistant in the vertical direction from the line extending from the low-temperature baseline and the high-temperature baseline intersects with the curve of the stepwise change in the glass transition.

[0193] (6) Water Droplet Contact Angle The water drop contact angle was measured according to the sessile drop method described in JIS R3257:1999. First, the laminated film was left for 24 hours in an atmosphere of room temperature 23°C and relative humidity 65%. Then, under the same atmosphere, the contact angle of pure water on the surface side of the resin layer of the laminated film was measured at five points using a contact angle meter CA-D type (manufactured by Kyowa Interface Science Co., Ltd.) using the 2 / θ method. The measurement was carried out within 10 seconds after the pure water contacted the resin layer. The maximum and minimum values ​​of the five measured values ​​were excluded, and the three measured values ​​were averaged, and the value doubled was used as the water drop contact angle.

[0194] (7) Confirmation of Resin Layer Structure Confirmation of the resin layer structure was carried out by the following method. In order to identify the urethane structure and the structures of the following formulae (1) to (5), the weight peaks of the aliphatic isocyanate compound and polyol compound cleaved at the urethane bond were confirmed by gas chromatography mass spectrometry (GC-MS). The structures of the following formulae (1) to (5) were also confirmed to have the same weight peaks derived from the structure. Next, Fourier transform infrared spectroscopy (FT-IR) was used to confirm the presence or absence of peaks derived from the isocyanate compound component, the polyol compound, and the bonds between the atoms in the structures of the following formulae (1) to (5). Furthermore, proton nuclear magnetic resonance spectroscopy ( １ Using H-NMR, the positions of chemical shifts derived from the positions of hydrogen atoms in the isocyanate compound, polyol compound, oxazoline compound, and structures of the following formulas (1) to (5), and the areas of proton absorption lines derived from the number of hydrogen atoms were confirmed. These results were comprehensively confirmed to confirm the structure of the resin. The above analysis was performed on samples obtained by scraping the resin layer with a blade knife. Using methods similar to those in the above examples, the structures of the acrylic-modified polyester resin, oxazoline compound, and oxazoline compound-derived chemical structures, and melamine compound were also confirmed.

[0195]

[0196] (8) Preparation of samples used in peel strength tests (25 ° C, -20 ° C) of EVA and PVB. The laminated film was cut into a length of 10 cm x width of 3 cm, and EVA ("Soarnol" (registered trademark) DC3203 manufactured by Mitsubishi Chemical Corporation) and PVB ("Slec Film" HI manufactured by Sekisui Chemical Co., Ltd.) were cut into a length of 40 cm x width of 1 cm. EVA and PVB were stacked in the center of the width direction of the laminated film so that the long sides were parallel to each other, and the protruding portion was sandwiched with a protective film ("Cerapeel" (registered trademark) #25WZ (RX) manufactured by Toray Advanced Film Co., Ltd.). This was preheated for 1 minute in a hot air oven heated to 140 ° C. and then laminated at a speed of 300 mm / min using a laminator (MRK-600 manufactured by MCK Corporation) heated to 140 ° C. to obtain a sample.

[0197] (9) EVA and PVB Peel Force Test (25°C, -20°C) Measurements were performed using the VPA-2 adhesive / film peeling analyzer manufactured by Kyowa Interface Science Co., Ltd., according to the following procedure. First, the sample prepared in (8) was fixed to the measurement unit with tape along with the attached stainless steel plate, and the EVA and PVB portions of the sample that protruded from the laminated film portion were fixed to a sample fixing plate. The peel force was then measured under the following measurement conditions, and the average peel force was calculated over a 20 mm section of a 100 mm measurement distance, where the peel force was most uniform. Similar measurements were performed five times for each sample, and the average of the five measurements was taken as the peel force (N / mm) and evaluated according to the following criteria (◎ and ◯ were considered good results). The peel force test at 25°C was performed on samples that had been left standing for 24 hours in a room conditioned at 25°C. The peel force test at -20°C was performed immediately after the sample and the attached stainless steel plate were placed in a portable freezer conditioned at -20°C for 24 hours and removed. <Measurement conditions> Load cell: 100 N Peel speed: 300 mm / min Peel angle: 180° Sample width (tape width): 10 mm Measurement distance: 100 mm <Evaluation criteria> ◎: Higher than 1.0 N / mm ○: 0.8 N / mm or more and 1.0 N / mm or less ×: Less than 0.8 N / mm.

[0198] (10) Layer Thickness, Number of Laminates, and Laminate Structure The layer structure of the film was confirmed by observing a sample cut out of a cross section parallel to the thickness direction (thickness direction cross section) using a microtome with a transmission electron microscope (TEM). More specifically, a transmission electron microscope H-7100FA (manufactured by Hitachi, Ltd.) was used to observe the thickness direction cross section of the film at 10,000 to 40,000 times magnification under an acceleration voltage of 75 kV, and a photograph was taken. The layer structure was confirmed using the obtained image and the scale function of the TEM, and the thickness of each layer was measured. In some cases, in order to obtain high contrast, a known RuO ４ YaOsO ４ The thickness direction refers to the direction perpendicular to the film surface.

[0199] (11) Blocking Two pieces of film, each measuring 30 mm wide x 60 mm long, were overlapped vertically with the resin layer surfaces facing each other by 40 mm. A 30 mm wide x 40 mm long weight weighing 6 kg was placed on the overlapping portion and treated in an atmosphere of 60°C x 95% RH for 168 hours. After treatment, the overlapping films were peeled off and evaluated according to the following criteria (◎, ◯, △ were considered good results). In the evaluation, the resistance during peeling was evaluated by holding each of the two films in one hand and evaluating the resistance during peeling sensorily. Whitening and peeling were observed visually. <Evaluation Criteria> ◎: No resistance during peeling, and no whitening or peeling on the resin layer surface after peeling. ○: There was slight resistance during peeling, but no whitening or peeling on the resin layer surface after peeling. △: There was resistance during peeling, but no whitening or peeling on the resin layer surface after peeling. ×: There was resistance during peeling, and whitening or peeling was observed on the resin layer surface after peeling.

[0200] (12) Preparation of Laminated Glass Using LAMINATOR0303S manufactured by Nisshinbo, a transparent plate glass, an intermediate layer, a film of an example or comparative example, an intermediate layer, and a transparent plate glass were stacked in this order and placed, and pressed at a temperature of 140°C and a pressure of 1.5 MPa for 30 minutes to prepare laminated glass. The transparent plate glass was 100 mm wide x 100 mm long, and had thicknesses shown in Tables 3 and 4. A PVB film was used as the intermediate layer, and had a thickness shown in Tables 3 and 4.

[0201] (13) Preparation of Glass Laminate Using LAMINATOR0303S manufactured by Nisshinbo, a transparent plate glass, an intermediate layer, and the films of Examples 38 to 41 were stacked in this order and placed, and pressed at a temperature of 140°C and 1.5 MPa for 30 minutes to prepare a glass laminate. The transparent plate glass was 100 mm wide x 100 mm long, and had a thickness as shown in Tables 3 and 4. A PVB film was used as the intermediate layer, and had a thickness as shown in Tables 3 and 4.

[0202] (14) Appearance of Laminated Glass (Unevenness) The laminated glass prepared in (12) was placed under a fluorescent lamp, and the evaluation portion was visually evaluated from angles of 20°, 50°, and 70° relative to the normal direction of the evaluation portion. The evaluation criteria were as follows: ○: Unevenness was not visible or was only slightly visible. ×: Unevenness was visible.

[0203] (15) Reflectance A sample cut to 5 cm x 5 cm was subjected to reflectance measurement using a Hitachi spectrophotometer (U-4100 Spectrophotometer) with an integrating sphere attached. The measurement was performed using the aluminum oxide secondary white plate attached to the instrument as a reference. The sample was placed behind the integrating sphere with its longitudinal direction facing up and down, and the reflectance was measured under the following conditions, with the resin layer surface of the laminated film as the incident surface. The average reflectance in the wavelength ranges of 400 nm to 700 nm and 850 nm to 1200 nm was calculated. <Measurement Conditions> Slit: 2 nm (visible) / Automatic control (infrared) Gain: 2 Scanning speed: 600 nm / min Starting wavelength: 2600 nm Ending wavelength: 240 nm Sampling interval: 1 nm Incident angle: 10°

[0204] (16) Heat-shielding property The total energy transmittance (Tts) through the laminated glass prepared in (12) was measured in accordance with ISO 13837:2008 "Road vehicles -- Safety glazing materials -- Determination of solar transmittance." The total energy transmittance (Tts) through the laminated glass was evaluated on the following four-point scale. ◎: Total energy transmittance (Tts) through the laminated glass is 50% or less. ○: Total energy transmittance (Tts) through the laminated glass is more than 50% and less than 60%. △: Total energy transmittance (Tts) through the laminated glass is more than 60% and less than 70%. ×: Total energy transmittance (Tts) through the laminated glass is 70% or more.

[0205] (17) Transmittance Measurement was performed under the following conditions using a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. in the standard configuration (solid measurement system) with the resin layer surface of the laminated film as the incident surface, and the average transmittance was calculated. <Measurement conditions> Slit: 2 nm (visible) / automatic control (infrared) Gain: 2 Scanning speed: 600 nm / min Start wavelength: 700 nm End wavelength: 400 nm Sampling interval: 1 nm Incident angle: 0°.

[0206] (18) Measurement of R20, R40, and R70 A variable angle reflection unit and a Glan-Taylor polarizer were attached to a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd., and the reflectance of P waves was measured in 1 nm increments in the wavelength range of 400 to 700 nm at incident angles θ = 20°, 40°, and 70°, with the resin layer surface of the laminate film as the incident surface. From the obtained reflectances, R20, R40, and R70 were calculated as the average reflectance of P waves in the wavelength range of 400 to 700 nm at incident angles of 20°, 40°, and 70°.

[0207] (19) Visibility A sensory evaluation was performed on the laminated glass prepared in (12) and the glass bonded body prepared in (13) to determine the visibility of a white straight line reflected on a black background using a P-wave light source at an incident angle of 70°. The visual visibility was evaluated using the following three-point scale. In the case of the laminated glass, the thinner of the two intermediate layers was designated d2, and the thinner of the two glass sheets was designated d4. Light was incident from the intermediate layer side with a thickness of d2 and the glass side with a thickness of d4. In the case of the glass bonded body, light was incident from the laminated film side. In the case of the laminated glass, when the two intermediate layers and the two glass sheets had the same thickness, the results were similar regardless of the side from which the measurement was performed. ⊚: Visually visible. ◯: Visually visible, but slightly inferior in brightness. ×: Not visually visible.

[0208] (20) Double images When a white straight line was reflected on a black background using a P-wave light source at an incident angle of 70° on the laminated glass produced in (12) and the glass bonded body produced in (13), the number of white straight lines and their appearance were evaluated visually and rated on the following three-point scale: ◎: One straight line appeared slightly blurred. ○: Two straight lines were seen, but they were very close together. ×: Two straight lines were seen that were far apart.

[0209] (21) Average Change in Shrinkage Rate Measurement was performed using a Seiko Instruments Inc. heat, stress, and strain measuring device (TMA / SS6000) under the following measurement conditions. Samples were cut out in a random direction in a plane parallel to the film surface and in each direction rotated from that direction up to 180° in 5° intervals in an in-plane direction parallel to the film surface. At least one data point was obtained per 1°C, and the shrinkage rate S(T) at each temperature was calculated using formula (9). A thermal shrinkage curve was obtained by plotting the shrinkage rate on the vertical axis and the temperature on the horizontal axis. Measurements were performed three times in each direction, and the direction with the largest S(150) was designated the X direction. <Measurement Conditions> Sample size: width 4 mm, length 15 mm Temperature rise range: 25 to 200°C Heat rise rate: 10°C / min Measurement load: 19.8 N Temperature 23°C, relative humidity 65%, in air

[0210]

[0211] where L(T) is the sample length at T°C.

[0212] From the obtained shrinkage rate S(T), the average change rate of the shrinkage rate from 100° C. to 150° C. (average change rate of the shrinkage rate) was calculated using formula (10).

[0213]

[0214] [Resins used in the film] Resin 1: A crystalline polyethylene terephthalate resin exhibiting a glass transition temperature of 78°C, a melting point of 254°C, a crystallization temperature of 180°C, and a melting enthalpy of 40 J / g. Resin 2: An amorphous polyethylene terephthalate resin copolymerized with 33 mol% cyclohexanedimethanol exhibiting a glass transition temperature of 80°C. Resin 3: An amorphous polyethylene terephthalate resin blend exhibiting a glass transition temperature of 80°C, which is a 70:30 blend of polyethylene terephthalate resin copolymerized with 29 mol% spiroglycol and 21 mol% cyclohexanedicarboxylic acid and Resin 1. Resin 4: An amorphous copolymer polynaphthalate resin exhibiting a glass transition temperature of 81°C, which uses 70 mol% 2,6-naphthalenedicarboxylic acid and 30 mol% isophthalic acid as dicarboxylic acid components, and 98 mol% ethylene glycol and 2 mol% polyethylene glycol with a molecular weight of 400 as diol components.

[0215] Example 1 Coating Liquid Containing Acrylic-Modified Polyester Resin: 50 parts by mass of terephthalic acid, 50 parts by mass of isophthalic acid, 50 parts by mass of ethylene glycol, and 30 parts by mass of neopentyl glycol were charged into a nitrogen-purged reactor along with 0.3 parts by mass of antimony trioxide and 0.3 parts by mass of zinc acetate as polymerization catalysts. Subsequently, a polymerization reaction was carried out for 12 hours under normal pressure and a temperature of 190 to 220°C while removing water, to obtain a polyester glycol. Next, 5 parts by mass of 5-sodium sulfoisophthalic acid and xylene as a solvent were added to the obtained polyester glycol, and the resulting mixture was charged into the reactor. Polymerization was carried out for 3 hours under reduced pressure conditions of 0.2 mmHg and 260°C while distilling off the xylene, to obtain a polyester resin component. This polyester resin component was dissolved in water containing ammonia water and butyl cellulose, to obtain an aqueous dispersion containing the polyester resin component. Next, 40 parts by mass of methyl methacrylate and 10 parts by mass of methacrylamide (50 parts by mass in total) were added to the aqueous dispersion containing the polyester resin component described above so that the mass ratio of acrylic resin component / polyester resin component was 50 / 50. Further, 5 parts by mass of benzoyl peroxide was added as a polymerization initiator, and a polymerization reaction was carried out at 70 to 80°C for 3 hours in a nitrogen-purged reactor to obtain a coating liquid containing an acrylic-modified polyester resin.

[0216] Coating liquid containing urethane resin: 70 parts by mass of 1,6-hexane diisocyanate as an aliphatic polyisocyanate compound, 30 parts by mass of polyisobutylene glycol as a polyol compound, 60 parts by mass of acetonitrile, and 30 parts by mass of N-methylpyrrolidone as a solvent were charged into a four-neck flask equipped with a reflux condenser, a nitrogen inlet tube, a thermometer, and a stirrer. Next, under a nitrogen atmosphere, the reaction liquid temperature was adjusted to 75-78°C, and 0.06 parts by mass of stannous octoate was added as a reaction catalyst, and the reaction was allowed to proceed for 7 hours. This was then cooled to 30°C to obtain an isocyanate-terminated aliphatic urethane resin. Next, water was added to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing at 2000 rpm, the isocyanate-terminated aliphatic urethane resin was added and dispersed in water. Subsequently, the acetonitrile and a portion of the water were removed under reduced pressure to prepare a coating liquid containing a urethane resin (abbreviated as Urethane 1 in Table 1-1).

[0217] Coating liquid containing an oxazoline compound: A flask equipped with a reflux condenser, a nitrogen inlet tube, a thermometer, a stirrer, and a dropping funnel was charged with 782.4 parts by mass of deionized water and 128 parts by mass of a surfactant (a 15% by mass aqueous solution of "Hitenol" (registered trademark) N-08 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.). The pH was adjusted to 9 with aqueous ammonia (28%) and heated to 70°C while flowing nitrogen gas. 64 parts by mass of a 5% aqueous solution of potassium persulfate was poured into the flask, and then a monomer mixture of 320 parts by mass of methyl methacrylate, 160 parts by mass of ethyl acrylate, 32 parts by mass of styrene, and 128 parts by mass of 2-isopropenyl-2-oxazoline, which had been mixed and stirred in advance in a separate flask, was added dropwise over 3 hours. The temperature of the reaction liquid was maintained at 70°C under a nitrogen atmosphere during the reaction. After the dropwise addition was completed, the temperature was maintained for 2 hours, and then the temperature was raised to 80°C and stirring was continued for 1 hour to complete the reaction. Thereafter, the mixture was cooled and diluted with a mixed solvent of propylene glycol monomethyl ether and water (20 / 80 (mass ratio)) to prepare a coating liquid containing an oxazoline compound.

[0218] Resin composition: The resulting coating liquid containing an acrylic-modified polyester resin, the coating liquid containing a urethane resin, the coating liquid containing an oxazoline compound, and the melamine compound "Nicalac" (registered trademark) MW-035 (manufactured by Sanwa Chemical Co., Ltd.) were mixed so that the solids mass ratio was acrylic-modified polyester resin / urethane resin / oxazoline compound / melamine compound = 90 / 10 / 60 / 10, and the total solids content was adjusted to 10 mass%, thereby obtaining Coating Liquid A. Furthermore, in order to impart lubricity to the resin layer surface, 2 mass parts of silica particles having a number average particle size of 170 nm ("Snowtex" (registered trademark) MP-2040, manufactured by Nissan Chemical Industries, Ltd.) were added as inorganic particles, per 100 mass parts of the total solids content of Coating Liquid A. Furthermore, in order to improve the coatability of the resin composition onto polyester film, 0.03 mass parts of a fluorine-based surfactant ("Pluscoat" (registered trademark) RY-2, manufactured by GOO Chemical Co., Ltd.) was added per 100 mass parts of the total solids content of Coating Liquid A. Thereafter, the mixture was diluted with a mixed solvent of isopropyl alcohol and water (20 / 80 (mass ratio)) so that the solid content was 5 mass %, thereby obtaining a resin composition.

[0219] Laminated film: Resin 1 was used as the crystalline thermoplastic resin (hereinafter also referred to as Resin A) constituting Layer A, and Resin 2 was used as the thermoplastic resin (hereinafter also referred to as Resin B) constituting Layer B. Resins A and B were melted at 280°C in separate extruders, and foreign matter was removed using five FSS-type leaf disc filters. The two resins were then merged in a 401-layer feed block while being metered using a gear pump to achieve a resin A / resin B ratio of 1 / 1.07. A total of 401 layers of resin A and resin B were laminated alternately in the thickness direction, with resin A forming the outermost layer on both sides. The layer thicknesses of layers A and B were designed to provide a flat reflectance spectrum in the wavelength range from 380 nm to 780 nm. The resulting molten laminate was then fed into a T-die and molded into a sheet. It was then quenched and solidified on a casting drum maintained at a surface temperature of 25°C while an electrostatic voltage of 8 kV was applied using a wire, yielding an unstretched film. This unstretched film was longitudinally stretched by differential roll speed at a temperature of 90°C and a stretching ratio of 3.5x, then cooled to obtain a uniaxially stretched film. Subsequently, both sides of this uniaxially stretched film were subjected to a corona discharge treatment in air, and the treated surface was coated with a resin composition using a bar coater to a coating thickness of approximately 6 μm. The uniaxially stretched film was then guided into a tenter, gripped at both widthwise ends with clips, and transversely stretched at a temperature of 110°C and a stretching ratio of 4.3x, followed by heat treatment at 210°C and further relaxation in the width direction by 1.6%, to obtain an 80 μm thick laminated film (abbreviated as Laminated Film 1 in Table 1-3). The resulting laminated film reflected infrared light with wavelengths of 850 to 1200 nm, while possessing a flat reflectance distribution with almost no reflection in the visible light wavelength range of 400 to 700 nm. The evaluation results of the resulting laminated film are shown in Tables 1-1, 1-2, and 1-3, and the properties of Laminated Film 1 are shown in Table 2.

[0220] Example 2 A laminated film was produced under the same conditions as in Example 1, except that the acrylic resin in the acrylic-modified polyester resin was changed to 40 parts by mass of methyl methacrylate and 10 parts by mass of 2-hydroxyethyl methacrylate, totaling 50 parts by mass. The composition of the resin composition and the evaluation results of the obtained laminated film are shown in Tables 1-1, 1-2, and 1-3.

[0221] Example 3 A laminated film was produced under the same conditions as in Example 1, except that the acrylic resin in the acrylic-modified polyester resin was changed to 40 parts by mass of methyl methacrylate and 10 parts by mass of ethylene glycol methacrylate, totaling 50 parts by mass. The composition of the resin composition and the evaluation results of the obtained laminated film are shown in Tables 1-1, 1-2, and 1-3.

[0222] Example 4 A laminated film was produced under the same conditions as in Example 1, except that the acrylic resin in the acrylic-modified polyester resin was changed to 40 parts by mass of methyl methacrylate and 10 parts by mass of triethylamine acrylate, totaling 50 parts by mass. The composition of the resin composition and the evaluation results of the obtained laminated film are shown in Tables 1-1, 1-2, and 1-3.

[0223] Example 5 A laminated film was produced under the same conditions as in Example 1, except that the acrylic resin in the acrylic-modified polyester resin was changed to 40 parts by mass of methyl methacrylate and 10 parts by mass of glycidyl acrylate, totaling 50 parts by mass. The composition of the resin composition and the evaluation results of the obtained laminated film are shown in Tables 1-1, 1-2, and 1-3.

[0224] (Examples 6, 9 to 20, 22 to 28, Comparative Examples 1 to 6) Laminated films were produced under the same conditions as in Example 1, except that the formulation of the resin composition was changed as shown in Table 1-1. The evaluation results of the obtained laminated films are shown in Tables 1-2 and 1-3. The carbodiimide compound used was "Carbodilite" (registered trademark) V-04 (manufactured by Nisshinbo Chemical Inc.).

[0225] Examples 7 and 8 Laminated films were produced under the same conditions as in Example 1, except that the acrylic resin in the acrylic-modified polyester resin was changed to 50 parts by mass of methyl methacrylate and the composition of the resin composition was changed as shown in Table 1-1. The evaluation results of the obtained laminated films are shown in Tables 1-2 and 1-3. The polyester-urethane copolymer was obtained by the following procedure.

[0226] Coating liquid containing polyester-urethane copolymer: 100 parts by mass of polyester polyol (adipic acid / 3-methyl-1,5-pentanediol), 3.0 parts by mass of trimethylolpropane, 10 parts by mass of dimethylolpropionic acid, and 58 parts by mass of isophorone diisocyanate were reacted in methyl ethyl ketone (MEK) to obtain a polyester-urethane copolymer. 7.5 parts by mass of triethylamine was added to this mixture, and the mixture was poured into water to disperse the polyester-urethane copolymer in water. The mixture was then elongated with ethylenediamine to obtain a dispersion. The methyl ethyl ketone was distilled off to obtain a coating liquid containing a polyester-urethane copolymer with a nonvolatile content of 30% by mass.

[0227] Example 21 A coating liquid containing a urethane resin was prepared in the same manner as in Example 1, except that isophorone diisocyanate was used as the aliphatic polyisocyanate compound in the coating liquid containing a urethane resin (abbreviated as Urethane 2 in Table 1-1), and a film was produced under the same conditions as in Example 1, except that the formulation of the resin composition was changed as shown in Table 1-1. The evaluation results of the obtained film are shown in Tables 1-2 and 1-3.

[0228] (Comparative Example 7) The composition of the resin composition was Compound A: methyl methacrylate 70 mol% / ethyl acrylate 20 mol% / 2-hydroxyethyl methacrylate 10 mol%, Compound B: terephthalic acid 32 mol% / isophthalic acid 12 mol% / 5-sodium sulfoisophthalic acid 6 mol% / ethylene glycol 46 mol% / diethylene glycol 4 mol%, Compound C: 1,3-bis (N, N-diglycidylamine) cyclohexane, Compound D: polyoxyethylene (n = 7) lauryl ether, and the respective weight percentages of Compound A: Compound B: Compound C: Compound D = 43: 43: 4: 10 were mixed in water, and the solids concentration was 3% by mass. A laminate film was produced under the same conditions as in Example 1. The composition of the resin composition and the evaluation results of the obtained laminate film are shown in Tables 1-1, 1-2, and 1-3.

[0229]

[0230] In addition, since Examples 7 and 8 and Comparative Example 6 contain acrylic resin instead of acrylic-modified polyester resin, and Comparative Example 5 contains polyester resin instead of acrylic-modified polyester resin, in the tables, acrylic-modified polyester resin in these Examples and Comparative Examples should be read as acrylic resin and polyester resin, respectively.

[0231]

[0232]

[0233]

[0234] The number of layers in the table means the number of layers excluding the resin layer. Furthermore, Laminated Film 5 is a single-layer film because Resin A and Resin B are the same. Furthermore, since Examples 1 to 28 only changed the composition of the resin composition, the resulting laminated films exhibited the same properties as Laminated Film 1 in Table 2.

[0235] (Examples 29 to 32, 34 to 40) Laminated films were produced under the same conditions as in Example 1, except that the number of layers in the multilayer film and the resins used in the laminated films were changed as shown in Table 2 (Laminated Films 2 to 5, 7, and 8). The properties of the resin layer of the obtained laminated films were the same as those of Example 1 shown in Tables 1-2 and 1-3. The evaluation results of the obtained laminated films are shown in Table 2. The evaluation results of laminated glass made using laminated films 2 to 5, 7, and 8 with the configurations shown in Tables 3 and 4 are shown in Tables 3 and 4.

[0236] (Example 33) A laminate film (laminated film 6) was produced under the same conditions as in Example 1, except that the heat treatment temperature of the laminate film was changed to 235°C and the width direction relaxation was changed to 1.3%. The properties of the resin layer of the obtained laminate film were the same as those of Example 1 shown in Tables 1-2 and 1-3. The evaluation results of the obtained laminate film are shown in Table 2. The evaluation results of laminated glass using laminate film 6 are shown in Table 3.

[0237] Examples 41 to 44 Table 4 shows the evaluation results of the glass laminated bodies using the laminated film 7 and the laminated film 8.

[0238] Example 45: Resin 1 was used as the crystalline thermoplastic resin (hereinafter also referred to as Resin A) constituting Layer A, and Resin 2 was used as the thermoplastic resin (hereinafter also referred to as Resin B) constituting Layer B. Resins A and B were melted at 280°C in separate extruders, and foreign matter was removed using five FSS-type leaf disc filters. Then, while the gear pump was used to measure the discharge ratio of Resin A / Resin B = 1 / 1.07, the two were merged in a 401-layer feed block, and a total of 401 layers of Resin A and Resin B were laminated alternately in the thickness direction, with Resin A being the outermost layer on both sides. The layer thicknesses of Layers A and B were designed so that the reflectance spectrum in the wavelength range from 380 nm to 1200 nm was flat. The resulting molten laminate was then fed into a T-die and molded into a sheet. It was then quenched and solidified on a casting drum maintained at a surface temperature of 25°C while an electrostatic voltage of 8 kV was applied using a wire, yielding an unstretched film. Both surfaces of this laminate were subjected to a corona discharge treatment in air, and the resin composition was applied to the treated surface using a bar coater to a coating thickness of approximately 6 μm. The uniaxially stretched film was then introduced into a tenter, gripped at both widthwise ends with clips, and transversely stretched at 90°C and a stretching ratio of 5.0. It was then heat-treated at 180°C and further relaxed by 1.6% in the width direction to obtain an 80 μm-thick laminate film (Laminate Film 9). The resulting laminate film exhibited polarized reflectivity, reflecting 42% of P-polarized light and 10% of S-polarized light in the visible to infrared wavelength range of 380 to 1200 nm. The properties of the resulting laminate film 9 are shown in Table 2, and the evaluation results of laminated glass using laminate film 9 are shown in Table 4.

[0239]

[0240]

[0241] The present invention can provide a laminated film that has excellent general-purpose adhesiveness to various functional materials and further has high adhesiveness to various functional materials regardless of the temperature at which it is used, particularly in a low-temperature environment (below freezing point). Because the laminated film of the present invention has the above-mentioned excellent properties, it can be suitably used for solar cell members, laminated glass, polarizer protective films, etc.

Claims

1. A laminated film having a resin layer on at least one surface, wherein the resin layer satisfies at least one of the following features A to C, and when the positive secondary ion normalization intensities of GCIB-TOF-SIMS for each component at positions 20% and 50% of the thickness from the surface of the resin layer are Xs and Xc, respectively, all components satisfy 0.5 ≤ Xs / Xc ≤ 2.

0. Feature A: Contains acrylic resin, polyester resin, and urethane resin. Feature B: Contains acrylic-modified polyester resin and urethane resin. Feature C: Includes acrylic, polyester, and urethane skeletons.

2. The laminated film according to claim 1, wherein the resin layer includes a chemical structure derived from an oxazoline compound.

3. The laminated film according to claim 1, wherein the resin layer contains an oxazoline compound.

4. The laminated film according to claim 2 or 3, wherein when the positive secondary ion normalization intensities of the GCIB-TOF-SIMS of the oxazoline compound at the surface layer and at a thickness of 20% of the resin layer are XO and XOs, respectively, the condition XO / XOs ≥ 1.0 is met.

5. A laminated film according to any one of claims 1 to 3, wherein the AFM modulus of the resin layer at a temperature T°C is P(T), P(-20) - P(25) is ΔP, and P(-20) / P(25) is the modulus ratio P', and the laminated film has at least one of the following features 1 and 2. Feature 1: The ΔP is 0.2 GPa or more and 2.0 GPa or less. Feature 2: The elastic modulus ratio P' is 0.1 or more and 2.3 or less.

6. The laminated film according to any one of claims 1 to 3, wherein the glass transition temperature of the resin layer is 30°C or higher and 80°C or lower.

7. The laminated film according to any one of claims 1 to 3, wherein the water droplet contact angle of the resin layer is 65° or more and 90° or less.

8. The laminated film according to any one of claims 1 to 3, wherein the resin layer has at least one structure of the following formulas (1) to (5). 【Chemistry 1】

9. The laminated film according to any one of claims 1 to 3, wherein the resin layer contains a melamine compound.

10. A laminated film according to any one of claims 1 to 3, wherein when the positive second-order ion normalization intensity of each component of GCIB-TOF-SIMS at a position 80% of the thickness from the surface of the resin layer is Xb, all components satisfy 0.5 ≤ Xb / Xc ≤ 2.

0.

11. A laminated film according to any one of claims 1 to 3, having a laminated structure comprising at least 51 layers, each layer mainly composed of a polyester resin (resin A) (layer A) and a thermoplastic resin (resin B) different from resin A (layer B).

12. The laminated film according to any one of claims 1 to 3, wherein on at least one surface, when light with a wavelength of 300 nm to 2500 nm is incident at an incident angle of 10°, there is at least one reflective band in which the reflectance is continuous over a wavelength width of 20 nm or more.

13. A laminated film according to any one of claims 1 to 3, wherein, on at least one surface, when light is incident at an incident angle of 10°, the average reflectance in the wavelength band of 400 nm to 700 nm is 15% or less, and the average reflectance in the wavelength band of 850 nm to 1200 nm is 70% or more.

14. A laminated film according to any one of claims 1 to 3, wherein the average transmittance of visible light incident perpendicularly on at least one surface is 50% or more and 100% or less, and when P-wave light is incident at angles of 20°, 40°, and 70° with respect to the normal to the film surface, the average reflectance (%) of P-waves with wavelengths from 400 nm to 700 nm is R20, R40, and R70, respectively, and the relationship R20 ≤ R40 < R70 is satisfied.

15. A laminated film according to any one of claims 1 to 3, wherein, when the direction parallel to the film surface and where the average rate of change of thermal shrinkage measured by thermomechanical analysis in the range of 100°C to 150°C is greatest is defined as the X direction, the average rate of change of thermal shrinkage in the X direction is 0.01% / °C or more and 0.1% / °C or less.

16. A solar cell module having a configuration in which a laminated film and a sealing material according to any one of claims 1 to 3 are directly laminated.

17. The solar cell module according to claim 16, comprising two sealing materials (sealing materials 1 and 2), wherein the sealing material 1, a solar cell, the sealing material 2, and the laminated film are provided in this order.

18. A glass structure comprising a laminated film, an intermediate layer, and glass as described in claim 1, wherein the laminated film and the intermediate layer are adjacent to each other.

19. A glass structure comprising two glass panes (glass panes 1 and 2) and two intermediate layers (intermediate layers 1 and 2), wherein the glass pane 1, the intermediate layer 1, the laminated film described in claim 1, the intermediate layer 2, and the glass pane 2 are provided in this order.

20. The glass structure according to claim 19, wherein when the thickness of the intermediate layer 1 is d1 and the thickness of the intermediate layer 2 is d2, the condition 3 ≤ d1 / d2 ≤ 100 is satisfied.

21. The glass structure according to claim 19, wherein when the thickness of glass 1 is d3 and the thickness of glass 2 is d4, the condition 1.5 ≤ d3 / d4 ≤ 10 is satisfied.

22. An automobile comprising a glass structure according to any one of claims 18 to 21.

23. A building window comprising a glass component according to any one of claims 18 to 21.

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