Laminated film

Abstract

A laminated film according to the present invention has a configuration in which 51 or more layers of two or more different thermoplastic resin layers are systematically laminated, the laminated film being characterized in that when the highest glass transition temperature obtained by differential scanning calorimetry is denoted by TA and the contraction start temperature obtained from a TMA curve in a main alignment direction is denoted by TX, TX is 5°C to 30°C lower than TA.　Provided is a laminated film which, in a molded article in which an intermediate film and a support body are disposed on at least one surface of the laminated film, can reduce color unevenness and distortion, in a protruding-recessed shape, that result from heating and pressure molding, and can improve appearance and design properties when formed into a molded body.

Description

Laminated Film

[0001] The present invention relates to a laminated film.

[0002] A laminate film is known that selectively reflects light of a specific wavelength by utilizing the optical interference phenomenon that occurs when two or more materials with different optical properties are alternately laminated in layer thicknesses at the wavelength level of the light. Such laminate films can be provided with various properties by adjusting the refractive index, number of layers, thickness of each layer, etc. of the materials used, and are therefore used in applications such as cold mirrors, half mirrors, laser mirrors, dichroic filters, heat ray reflective films, near-infrared cut filters, monochrome filters, and polarized reflective films.

[0003] Molded articles obtained by laminating such laminated films onto rigid supports under heat and pressure are used as decorative materials such as decorative panels, various home appliances, building materials, automobile-related parts, etc. In particular, in recent years, in response to restrictions on carbon dioxide emissions for environmental protection, heat-cutting glass, which can suppress the inflow of heat from outside in the summer, particularly heat from sunlight, has attracted attention as window glass for vehicles such as automobiles and trains, and for buildings.

[0004] Examples of such heat-ray-cutting glass include glass in which a heat-ray absorbing material is contained in glass or an interlayer film used in laminated glass, and heat rays are blocked by the heat-ray absorbing material (e.g., Patent Document 1), glass in which a film formed by sputtering or the like to reflect and block heat rays is attached to glass (e.g., Patent Document 2), and glass in which a laminated film in which polymers with different refractive indices are alternately laminated is inserted between the glass and the interlayer film to reflect and block heat rays (e.g., Patent Document 3).

[0005] However, the method of Patent Document 1 converts sunlight incident from outside into thermal energy, which radiates the heat into the room, resulting in a decrease in heat ray blocking efficiency. In addition, this method causes the glass temperature to rise partially by absorbing heat rays, which can lead to damage to the glass itself due to the difference in temperature with the outside air temperature. The method of Patent Document 2 reflects not only heat rays but also visible light, making the glass prone to coloration. It also blocks electromagnetic waves, which can adversely affect the use of communication devices inside. On the other hand, the laminated film of Patent Document 3 allows the layer thickness to be controlled to select the wavelength to be reflected, thereby selectively reflecting light in the near-infrared region that contributes to temperature rise, thereby improving heat ray blocking performance while maintaining visible light transmittance. Furthermore, because it does not contain components that block radio waves, such as metals, it maintains excellent radio wave transmittance.

[0006] Furthermore, when a laminate film such as that shown in Patent Document 3 is obtained by melt extrusion, for reasons of transparency, heat resistance, weather resistance, chemical resistance, strength, and dimensional stability, a polyester resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) is used as the main component of one resin layer, and a thermoplastic resin (e.g., a copolymer polyester) having optical properties different from those of the polyester resin is used as the other resin layer (e.g., Patent Documents 4 to 6). In particular, when polyethylene naphthalate is used as the main component of one resin layer, the difference in refractive index between the low-refractive-index copolymer polyester and polyethylene naphthalate can be increased, resulting in a laminate film with high reflectance.

[0007] JP 2010-17854 A JP 2001-310407 A WO 2005 / 040868 A JP 2005-059332 A JP 2004-249587 A WO 2013 / 137288

[0008] Such heat-cutting glass is often used in places visible to the public, such as windowpanes in vehicles and buildings, so appearance is also an important factor. However, in the application of a laminate film as described in Patent Document 3, uneven thickness of the interlayer film used for lamination with the support causes uneven pressure and differences in thermal shrinkage stress between the interlayer film and the support, resulting in uneven distortion of the laminate film during molding, which can impair the appearance. In particular, since such laminate films utilize the interference reflection phenomenon achieved by controlling the layer thickness, variations in layer thickness due to uneven distortion can easily cause color unevenness and optical defects within the film surface. Furthermore, such laminate films are prone to wrinkling when laminated with a support or interlayer film and molded. This problem occurs mainly at the edges of the molded product due to the laminate film's inability to conform to the shape of the support during molding and differences in thermal shrinkage between the interlayer film and the support.

[0009] Furthermore, as described in Patent Documents 4 and 5, when a laminate film consisting of a layer mainly composed of polyethylene naphthalate and a layer of a copolymer polyester having a relatively low refractive index is produced by melt extrusion, the layer mainly composed of polyethylene naphthalate has a relatively high rigidity and is therefore difficult to deform, making it difficult to apply to applications in which the laminate film is deformed or processed. For example, when a support, an interlayer film, and a laminate film are laminated and molded, wrinkles and uneven distortions may occur, making it difficult to apply to a final product.

[0010] On the other hand, as described in Patent Document 6, when a laminate film consisting of a layer mainly composed of polyethylene terephthalate and a layer of a copolymer polyester having a relatively low refractive index is produced by melt extrusion, the rigidity of the layer is lower than that of polyethylene naphthalate, so it is more easily deformed and is more easily applicable to applications in which the laminate film is deformed and processed. However, because polyethylene terephthalate has a lower refractive index than polyethylene naphthalate, the reflectance of the laminate film is lower, resulting in inferior performance as a final product.

[0011] The present invention aims to solve the above problems and to provide a laminate film that can reduce the occurrence of uneven distortion and color unevenness caused by molding involving heating and pressure in a molded product in which an intermediate film and a support are arranged on at least one side of the laminate film, and can improve the appearance and design when formed into a molded product.

[0012] To solve the above problems, the present invention has the following configurations. [1] A laminate film having a configuration in which two or more different thermoplastic resin layers are regularly laminated in 51 or more layers, characterized in that, where TA is the highest glass transition temperature determined by differential scanning calorimetry (DSC) and TX is the shrinkage onset temperature determined from a TMA curve in the main orientation direction, TX is 5°C to 30°C lower than TA. [2] The laminate film according to [1], which has a heat shrinkage rate of 0.5% to 1.2% in at least one of the main orientation direction and the direction perpendicular to the main orientation direction under an atmosphere of TA. [3] The laminate film according to [1] or [2], which has a heat shrinkage rate of 1.5% to less than 4.0% in at least one of the main orientation direction and the direction perpendicular to the main orientation direction under an atmosphere of 150°C. [4] The laminate film according to any one of [1] to [3], which includes a layer mainly composed of a polyester having naphthalenedicarboxylic acid units as the main structural unit. [5] The laminate film according to any one of [1] to [4], wherein TY is the shrinkage initiation temperature determined from a TMA curve in the direction perpendicular to the main orientation, and the difference between TY and TX is 0°C or more and 10°C or less. [6] The laminate film according to any one of [1] to [5], wherein TY is 5°C or more and 30°C or less lower than TA. [7] The laminate film according to any one of [1] to [6], wherein S(150) / S(TA) is 1.5 or more and 5.0 or less, where S(150) is the average heat shrinkage at 150°C and S(TA) is the average heat shrinkage at TA. [8] The laminate film according to any one of [1] to [7], wherein S(120) / S(TA) is 1.5 or more and 5.0 or less, where S(120) is the average heat shrinkage at 120°C and S(TA) is the average heat shrinkage at TA. [9] The laminate film according to any one of [1] to [8], having a reflection band of 100 nm or more, in which the reflectance is 30% or more when light is incident on the film surface at an incident angle of 10° and a wavelength of 800 to 2000 nm.

[10] The laminate film according to any one of [1] to [9], having an average P-wave reflectance of 10% or more and 50% or less for a wavelength of 400 to 700 nm at an incident angle of 60°.

[11] The laminate film according to any one of [1] to

[10] , having an internal haze of 0.5% or less.

[12] The laminate film according to any one of [1] to

[11] , which is a film for laminated glass.

[13] A laminate comprising, in this order, a support 1, an intermediate layer 1, the laminate film of [1] or [2], an intermediate layer 2, and a support 2.

[14] Laminated glass, in which the support 1 and the support 2 in the laminate according to

[13] are both glass.

[0013] The present invention can provide a laminated film that reduces the occurrence of uneven distortion and color unevenness caused by molding involving heating and pressure, and can improve the appearance and design of the molded product.

[0014] The laminate film of the present invention is a laminate film having a structure in which two or more different thermoplastic resin layers are regularly laminated in 51 or more layers, and is characterized in that, when TA is the highest glass transition temperature determined by differential scanning calorimetry (DSC measurement) and TX is the shrinkage onset temperature determined from a TMA curve in the main orientation direction, TX is 5°C to 30°C lower than TA. Although the following describes embodiments of the present invention, the present invention should not be construed as being limited to the embodiments, including the following examples, and various modifications are naturally possible within the scope of the invention, as long as the object of the invention can be achieved and the gist of the invention is not deviated from. Furthermore, for the purpose of simplifying the explanation, some of the explanations will be given using an example of a laminate film in which two different polyester resin layers (referred to as layer A and layer B) are regularly laminated. However, the same should be understood when using three or more polyester resin layers or when using a thermoplastic resin layer other than polyester resin.

[0015] The laminate film of the present invention has a structure in which two or more different thermoplastic resin layers are regularly laminated in 51 or more layers, preferably in which two or more thermoplastic resin layers having different main components are regularly laminated in 51 or more layers. Here, the term "main component" refers to a component that is present in an amount of more than 50% by mass but not more than 100% by mass, where the total mass of all components constituting the thermoplastic resin layer is 100% by mass. The same interpretation applies hereinafter to "main component." The term "different thermoplastic resin layers" refers to a case in which, when comparing two thermoplastic resin layers, at least one of the following conditions 1 to 3 is satisfied, preferably at least the following condition 2 is satisfied. When three or more types of thermoplastic resin layers are present, all of the thermoplastic resin layers must satisfy at least one of the following conditions 1 to 3 when compared (the same applies when four or more types of thermoplastic resin layers are present). 1: The refractive index differs by 0.01 or more in the main orientation direction (the method for determining the main orientation direction is described below). 2: Having 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 thermoplastic resin layer has a melting point and the other thermoplastic resin layer does not have a melting point, or where one thermoplastic resin layer has a crystallization temperature and the other thermoplastic resin layer does not have a crystallization temperature are also considered to have different melting points or crystallization temperatures.) 3: The compositions analyzed by nuclear magnetic resonance spectroscopy or gas chromatography-mass spectrometry differ by 5% by mass or more.

[0016] In the laminate film of the present invention, the phrase "a structure in which 51 or more thermoplastic resin layers are regularly laminated" refers to a structure in which 51 or more thermoplastic resin layers of multiple types are laminated in the thickness direction with a certain regularity. Specific examples include, for example, when there are two different thermoplastic resin layers (layer A and layer B), the two types of layers are alternately laminated in the thickness direction, such as an A(BA)n structure or a B(AB)n structure (where the repeating units are in parentheses and n is a natural number representing the number of repeating units, the same applies below), where layer A and layer B are represented as A and B. Specific examples of when there are three different thermoplastic resin layers (layer A, layer B, layer C), such as an (ABCB)nA structure or an (ABC)nA structure, where layer A, layer B, and layer C are represented as A, B, and C, respectively. By regularly laminating different thermoplastic resin layers in this way, the laminate film can reflect light of a wavelength specified by the relationship between the difference in refractive index of each layer and the layer thickness.

[0017] Generally, in a laminate film having such a layer structure, based on the principle of interference reflection, the greater the number of constituent layers, the higher the reflectivity can be obtained over a wider band. Therefore, the number of regularly stacked layers is preferably 101 or more, more preferably 401 or more. For the above reasons, the greater the number of layers in the laminate film, the better. However, from the viewpoint of suppressing the increase in manufacturing costs due to the increase in the size of the manufacturing equipment as the number of layers increases and the deterioration of handleability due to the increase in the thickness of the laminate film itself, the practical range is 1001 or less.

[0018] From the viewpoint of use in heat ray reflection applications, the laminate film of the present invention preferably has a reflection band of 100 nm or more in which the reflectance is 30% or more when light is incident on the film surface at an incident angle of 10° and a wavelength of 800 to 2000 nm. "Having a reflection band of 100 nm or more in which the reflectance is 30% or more" means having at least one band in which the reflectance is 30% or more continuously over a wavelength of 100 nm or more.

[0019] Sunlight has an intensity distribution mainly in the visible light region, and the intensity distribution tends to become smaller as the wavelength increases. However, for use in applications requiring high transparency, such as heat-blocking glass, it is necessary to achieve both transparency and high heat-blocking performance. In this way, by efficiently reflecting light with wavelengths of 800 to 2000 nm, which is slightly longer than the visible light region, a laminated film can be obtained that achieves both transparency and high heat-blocking performance.

[0020] From the above viewpoint, the laminate film of the present invention more preferably has a reflection band in which the reflectance is 50% or more continuously over 200 nm or more in the wavelength range of 900 to 1200 nm, and even more preferably has a reflectance of 50% or more continuously over the entire wavelength range of 900 to 1200 nm. Furthermore, the average reflectance at wavelengths of 900 to 1200 nm is preferably 70% or more, and the average reflectance at wavelengths of 900 to 1200 nm is even more preferably 80% or more. As the average reflectance at wavelengths of 900 to 1200 nm increases, it becomes possible to impart high heat ray blocking performance to the laminate film.

[0021] Such a laminate film can be realized by increasing the difference in in-plane refractive index between two or more resins with different optical properties. Therefore, when a biaxially stretched film is produced, a laminate film in which layers mainly composed of a crystalline polyester resin and layers mainly composed of a thermoplastic resin that can maintain amorphousness even when stretched or that melts in a heat treatment step are alternately laminated (in other words, a laminate film in which layers mainly composed of a crystalline thermoplastic resin and layers mainly composed of a thermoplastic resin that can maintain amorphousness even when stretched or that melts in a heat treatment step are alternately laminated is preferred.) In addition, to produce a laminate film having a reflection band of 100 nm or more where the reflectance is 30% or more, it is effective to set the in-plane stretching ratio (the product of the stretching ratio in the longitudinal direction (film conveying direction, also referred to as the longitudinal direction) and the stretching ratio in the transverse direction (the width direction within the film plane in the conveying direction)) described below to 9.0 times or more and to increase the number of layers. In order to set the average reflectance at wavelengths of 900 to 1200 nm within the above preferred range, it is effective to increase the in-plane stretching ratio within the above range or to increase the number of layers.

[0022] Here, the in-plane refractive index is the average value of the refractive index in the main orientation direction and the refractive index in the direction perpendicular to the main orientation direction in the film plane (the direction perpendicular to the main orientation). If the thermoplastic resin layer not located on the outermost surface is amorphous, the in-plane refractive index may be determined in any two directions perpendicular to the main orientation direction using a sheet obtained by vacuum drying the thermoplastic resin and then pressing it. This is because amorphous resins typically do not have birefringence, and the refractive index in each direction does not change depending on whether or not the resin is stretched. The refractive index can be measured using a laser with a wavelength of 632.8 nm, and a measuring device such as the "SPA-4000" manufactured by SAIRON TECHNOLOGY, INC. can be used.

[0023] Here, "crystalline" refers to a heat of fusion of 5 J / g or more in differential scanning calorimetry (DSC). Similarly, "amorphous" refers to a heat of fusion of less than 5 J / g. Crystalline polyester resins can be oriented and crystallized in the stretching and heat treatment processes to achieve a higher in-plane refractive index than in the amorphous state before stretching. Meanwhile, in the case of amorphous polyester resins, heat treatment at a temperature far above the glass transition temperature in the heat treatment process can significantly alleviate any slight orientation that occurs in the stretching process, thereby maintaining the low refractive index of the amorphous state. This laminate structure allows for easy creation of a refractive index difference between the crystalline polyester resin and the amorphous polyester resin in the stretching and heat treatment processes in the production of laminated films.

[0024] In the case of a laminate film having a structure in which two types of layers each having a thermoplastic resin with a different crystallinity as a main component are alternately laminated, it is preferable that the outermost layers on both sides be layers with a relatively high crystallinity (layers having a crystalline thermoplastic resin as a main component) from the viewpoint of suppressing adhesion to rolls, etc., during film production. In the following, a laminate film having such a structure will be described, and unless otherwise specified, the layer with a relatively high crystallinity will be referred to as layer A and the layer with a low crystallinity will be referred to as layer B.

[0025] Here, it is preferable that the optical thicknesses of the adjacent A layer and B layer simultaneously satisfy the following formulas (1) and (2): Formula (1): λ / m=2(nα d α +n β d β ) Formula (2): n α d α = n β d β .

[0026] 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, and m is the order, which is a natural number. Having a layer thickness distribution that simultaneously satisfies both formulas (1) and (2) can eliminate even-order reflections. Therefore, it is possible to increase the average reflectance in the wavelength range of 900 nm to 1200 nm while decreasing the average reflectance in the visible light wavelength range of 400 to 800 nm, thereby obtaining a laminated film that has excellent transparency and high heat-ray blocking performance.

[0027] Generally, the in-plane refractive index of the film surface after molding and stretching a thermoplastic resin is approximately 1.4 to approximately 1.9. Therefore, by setting the thickness ratio of adjacent A layers to B layers (thickness of A layer / thickness of B layer) to 0.7 or more and 1.4 or less, a laminate film can be obtained that suppresses even-order reflection. Therefore, from the above perspective, the thickness ratio of adjacent A layers to B layers (thickness of A layer / thickness of B layer) is preferably 0.7 or more and 1.4 or less, more preferably 0.8 or more and 1.2 or less. By setting the thicknesses of adjacent A layers and B layers within this range, the average reflectance in the wavelength range of 400 to 800 nm can be preferably 20% or less, more preferably 15% or less. As a result, reflection in the visible light region of the laminate film can be suppressed, reducing coloring and glare.

[0028] In the laminate film of the present invention, if the main component of Layer A is thermoplastic resin A and the main component of Layer B is thermoplastic resin B, then thermoplastic resins A and B must be different from each other. Thermoplastic resins A and B can be polyester resins, acrylic resins, polycarbonate resins, etc. Among these, polyester resins are preferably used as thermoplastic resins A and B because of their excellent transparency and formability. Furthermore, if the laminate film further has Layer C and the main component of Layer C is thermoplastic resin C, then thermoplastic resin C is preferably also a polyester resin. Here, polyester resin refers to a polymer obtained by condensation polymerization of a dicarboxylic acid component and a diol component.

[0029] In the laminate film of the present invention, examples of the dicarboxylic acid unit of the polyester resin used for the thermoplastic resin A, thermoplastic resin B, and thermoplastic resin C 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'-diphenylsulfonedicarboxylic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid, and ester-forming derivatives thereof.

[0030] Examples of the diol unit of the polyester resin 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.

[0031] Preferred examples of the dicarboxylic acid units constituting the polyester resin include structural units such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, and isophthalic acid. 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.

[0032] A preferred embodiment of the laminate film of the present invention is one in which the in-plane refractive index of at least one surface of the laminate film is 1.68 or more and 1.80 or less. Generally, it is preferable for the surface layer to be a layer with relatively high crystallinity, taking into account factors such as ease of film formation. However, by making the in-plane refractive index of this surface layer 1.68 or more, the difference in in-plane refractive index between the surface layer and the layer with relatively low crystallinity can be increased. This makes it easy to make the laminate film have a reflection band of 100 nm or more where the reflectance is 30% or more. On the other hand, by making the in-plane refractive index of the surface layer lower than 1.80, deterioration of the adhesion between the two alternating layers is suppressed, and clouding of the laminate film and peeling at the interface are reduced.

[0033] From the above viewpoints, it is preferable that the laminate film of the present invention has, as its main component, a crystalline polyester in which naphthalenedicarboxylic acid units are the main structural units. By adopting such an embodiment, the reflectance at the surface of Layer A is increased, and it is easy to create a refractive index difference with Layer B, thereby obtaining a laminate film with better reflective performance. Incidentally, "having naphthalenedicarboxylic acid units as the main structural units" means that naphthalenedicarboxylic acid units account for more than 50 mol% and up to 100% by mass of all dicarboxylic acid structural units of the polyester resin.

[0034] Examples of naphthalenedicarboxylic acids that serve as structural units of the crystalline polyester resin in Layer A include 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,3-naphthalenedicarboxylic acid, with 2,6-naphthalenedicarboxylic acid being particularly preferred. When Layer B is primarily composed of an amorphous thermoplastic resin, the greater the amount of naphthalenedicarboxylic acid units in the crystalline polyester resin that is the primary component of Layer A, the easier it is to increase the refractive index difference between Layer A and Layer B. Therefore, the proportion of naphthalenedicarboxylic acid units in the dicarboxylic acid units of the crystalline polyester resin that is the primary component of Layer A is more preferably 80 mol% to 100 mass%, and even more preferably 95 mol% to 100 mass%. From the same perspective, the content of the crystalline polyester resin in Layer A, when the entire layer is taken as 100 mass%, is preferably 80 mol% to 100 mass%, and even more preferably 95 mol% to 100 mass%.

[0035] In the laminate film of the present invention, the difference in in-plane refractive index between layer A and layer B is preferably 0.05 or more, more preferably 0.12 or more, and even more preferably 0.14 to 0.35. If the difference in average in-plane refractive index is less than 0.05, it may be difficult to achieve a reflection band with a reflectance of 30% or more. One example of a method for achieving this is to use a crystalline polyester resin as the main component of layer A and an amorphous thermoplastic resin as the main component of layer B. In this case, the refractive index difference can be easily achieved during the stretching and heat treatment steps in the production of the laminate film.

[0036] From the viewpoint of reflectance, a larger difference in the in-plane refractive index between Layer A and Layer B is preferable, but increasing the difference in the in-plane refractive index requires that the chemical structures of the thermoplastic resins that are the main components of both layers be significantly different, which would deteriorate interlayer adhesion. In light of this, by keeping the difference in the average in-plane refractive index between Layer A and Layer B to 0.35 or less, lamination becomes easier and the heat resistance and handleability of the resulting laminated film are improved.

[0037] From the viewpoint of improving the appearance of the laminated film of the present invention when formed into a molded article such as laminated glass, when the highest glass transition temperature determined by differential scanning calorimetry (DSC) is TA and the shrinkage onset temperature determined from the TMA curve in the main orientation direction is TX, TX must be 5°C to 30°C lower than TA, in other words, TA - TX must be 5°C to 30°C. Here, the main orientation direction refers to the direction in the film plane with the greatest degree of molecular orientation, which can be determined by measurement with a known molecular orientation meter (details of the measurement method will be described later). The shrinkage onset temperature can be measured by TMA measurement, and details of the measurement method will be described later. DSC measurement can be performed based on JIS-K-7121 (1987), and details of the measurement method will be described later.

[0038] When a laminated film is laminated with a support and an interlayer to form laminated glass, heat and pressure are applied to enhance adhesion between the components. During this molding process, heat and pressure can cause uneven thickness in the interlayer and differences in thermal shrinkage stress between the interlayer and the laminated film, resulting in uneven distortion and thickness variations in the laminated film. Such uneven distortion and thickness variations can cause light scattering and diffuse reflection, as well as color unevenness within the film, resulting in poor appearance of the molded product. Meanwhile, because the glass support barely deforms during this process, the shape of the interlayer is hardly relaxed by the support. Because laminated films contain interfaces formed from different thermoplastic resin layers, in addition to light scattering and diffuse reflection from the film surface, additional scattering and reflection from the interface make unevenness more noticeable than films made of a single resin. Therefore, if a laminated film that is less prone to unevenness could be used, the problem of poor appearance of molded products could be resolved.

[0039] When laminating a laminated film with a support and an interlayer, it is common to first bond the laminated film and the interlayer at a low temperature (pre-lamination step (hereinafter sometimes referred to as pre-lamination step)), and then bond them to the support by applying pressure at a higher temperature (main pressure bonding step). The method of the pre-lamination step is not particularly limited, but it is common to sandwich the film between two interlayers and roll laminate at 90 to 100°C, which is a temperature slightly higher than the glass transition temperature of the polyester resin. The method of the main pressure bonding step is also not particularly limited, but it is common to sandwich the sheet after the pre-lamination step between supports such as glass and heat it in an autoclave (pressure-heating adhesion furnace) at 140 to 150°C for 20 to 30 minutes under a pressure of 12 to 14 kg / cm. ２ It is common to use a pressure bonding method.

[0040] During this process, the laminated film and interlayer film become flexible and shrink during the pre-lamination and final pressure-bonding processes, and if these flexibility and shrinkage behaviors differ significantly, this can cause bubbles, wrinkles, and in-plane color unevenness. Therefore, it is necessary for the laminated film to not only shrink during the final pressure-bonding process, which is formed at a higher temperature, but also to exhibit shrinkage behavior at lower temperatures such as in the pre-lamination process, i.e., for the shrinkage onset temperature to be lower than the glass transition temperature.

[0041] Generally, thermoplastic resin films are formed into sheets by melt extrusion from pellets and then stretched and processed at temperatures above the glass transition temperature. Therefore, the oriented crystals formed at temperatures above the glass transition temperature relax when reheated, resulting in rapid shrinkage. However, even if such films can follow the shrinkage of the interlayer film in either the main pressure bonding process or the pre-lamination process, they may shrink insufficiently or excessively at the other temperature, resulting in bubbles, wrinkles, and in-plane color unevenness. The present invention has discovered that the above-mentioned problems can be solved by designing a laminated film so that shrinkage begins at a temperature 5°C to 30°C lower than the highest glass transition temperature (in other words, by setting TA-TX to 5°C to 30°C).

[0042] When the glass transition temperature is TA and the shrinkage initiation temperature obtained from the TMA curve in the main orientation direction is TX, by having TX lower than TA by 5°C or more and 30°C or less, the occurrence of bubbles, wrinkles, and in-plane color unevenness can be suppressed, and a molded product with excellent appearance (particularly the appearance in the main orientation direction) can be obtained. From the above viewpoint, it is more preferably 10°C or more and 30°C or less. If TA-TX exceeds 30°C, the laminated film may become too flexible, resulting in poor productivity and poor handling during molding processing. Furthermore, if TA-TX is less than 5°C, bubbles and wrinkles are likely to occur, resulting in poor appearance.

[0043] In the laminate film of the present invention, when the shrinkage initiation temperature determined from the TMA curve in the direction perpendicular to the main orientation is TY, the difference between TY and TX is preferably 0°C or more and 10°C or less. By adopting such an embodiment, the appearance of the laminate film and a molded article using the same when observed from a direction perpendicular to the main orientation is also improved. Therefore, it is possible to obtain a laminate film and a molded article that have excellent appearance when viewed from various angles. Here, the direction perpendicular to the main orientation refers to the direction perpendicular to the main orientation direction in the film plane. Furthermore, the "difference between TY and TX" is calculated as an absolute value. By having the difference between TY and TX be 10°C or less, the laminate film of the present invention has an improved appearance not only when observed from the main orientation direction, but also when observed from a direction perpendicular to the main orientation direction.

[0044] For the same reasons as for the preferred range of TX, in the laminate film of the present invention, TY is preferably 5°C or more and 30°C or less lower than TA (in other words, TA-TY is 5°C or more and 30°C or less), and more preferably 10°C or more and 30°C or less.

[0045] The method for achieving a TX that is 5°C to 30°C lower than TA is not particularly limited. For example, when a laminated film is obtained by sequential biaxial stretching as described below, a method is to stretch the film in the width direction (TD direction), heat treat the film, and then perform slight stretching during the process of slow cooling to room temperature. Alternatively, it is also effective to perform pseudo slight stretching by increasing the tension (draw) during the winding process after slow cooling. Both of these methods make it possible to obtain a film that shrinks at a temperature lower than the glass transition temperature by slight stretching at a temperature lower than the glass transition temperature. It is also effective to control the heat treatment temperature and the cooling temperature after heat treatment within a suitable range. These methods can also be combined as needed.

[0046] From the viewpoint of improving the appearance of a molded article such as laminated glass, the laminate film of the present invention preferably has a heat shrinkage rate of 0.5% to 1.2% in at least one of the main orientation direction and the direction perpendicular to the main orientation direction under a TA atmosphere. Here, "under a TA atmosphere" refers to an environment where the temperature is TA. From the above viewpoint, the heat shrinkage rate of at least one of the main orientation direction and the direction perpendicular to the main orientation direction under a TA atmosphere is more preferably 0.7% to 1.2%, and even more preferably 0.9% to 1.2%. From the above viewpoint, the laminate film of the present invention preferably has a heat shrinkage rate of 0.5% to 1.2% in both the main orientation direction and the direction perpendicular to the main orientation direction, with the preferred ranges being as described above. The heat shrinkage rate can be calculated by measuring the dimensional change after heat treatment; the measurement method will be described in detail below.

[0047] In a TA atmosphere, if the thermal shrinkage rate in at least one of the main orientation direction and the direction perpendicular to the main orientation is 0.5% or more, bubbles, wrinkles, and in-plane color unevenness are less likely to occur during the laminating process, particularly the pre-lamination process. On the other hand, if the shrinkage rate in at least one of the above directions is 1.2% or less, excessive softening of the laminated film is suppressed, resulting in good productivity and easy handling during molding.

[0048] In order to set the thermal shrinkage rate in at least one of the main orientation direction and the direction perpendicular to the main orientation to 0.5% or more and 1.2% or less, or to the above-mentioned preferred range, in an atmosphere of TA, a method similar to the method for setting TX to be 5°C or more and 30°C or less lower than TA can be used.

[0049] From the viewpoint of improving the appearance when formed into a molded article such as laminated glass, the laminated film of the present invention preferably has a heat shrinkage rate in at least one of the main orientation direction and the direction perpendicular to the main orientation of 1.5% or more and less than 4.0%, more preferably 2.0% or more and less than 4.0%, and even more preferably 2.0% or more and less than 3.0%, in an atmosphere of 150° C. From the above viewpoint, it is more preferable that the heat shrinkage rates in both the main orientation direction and the direction perpendicular to the main orientation of 1.5% or more and less than 4.0%, or within the above-mentioned preferred range, in an atmosphere of 150° C.

[0050] When the heat shrinkage rate in at least one of the main orientation direction and the direction perpendicular to the main orientation is 1.5% or more in an atmosphere at 150° C., bubbles, wrinkles, and in-plane color unevenness are less likely to occur in the laminating process, particularly in the main pressure bonding process. On the other hand, when the heat shrinkage rate in at least one of the above directions is less than 4.0% in an atmosphere at 150° C., it is possible to reduce deterioration in productivity and handling during molding, the occurrence of color unevenness, and deterioration in appearance due to excessive flexibility of the laminated film.

[0051] In order to make the heat shrinkage rate in at least one of the main orientation direction and the direction perpendicular to the main orientation 1.5% or more and less than 4.0% in an atmosphere of 150°C, methods such as adjusting the stretching ratio or heat treatment temperature can be mentioned. More specifically, the heat shrinkage rate can be increased by increasing the stretching ratio of the film or by lowering the heat treatment temperature after stretching in the width direction. These methods can also be used in combination as appropriate.

[0052] More specifically, to obtain a laminated film having a heat shrinkage rate of 1.5% or more and less than 4.0% in at least one of the main orientation direction and the direction perpendicular to the main orientation in an atmosphere of 150°C, the in-plane stretching ratio is preferably 11.0 times or more and 18.0 times or less, and more preferably 12.0 times or more and 18.0 times or less. From the above viewpoints, it is particularly preferable that the longitudinal stretching ratio is 3.0 times or more and 3.8 times or less, and the transverse stretching ratio is 3.7 times or more and 4.2 times or less. When the in-plane stretching ratio is 11.0 times or more, it becomes easy to set the heat shrinkage rate in each direction in an atmosphere of 150°C to 1.5% or more and less than 4.0%. Furthermore, when the in-plane stretching ratio is 18.0 times or less, whitening during film formation due to excessive stretching and a decrease in productivity due to film breakage are suppressed.

[0053] The laminated film of the present invention follows the shrinkage of the interlayer film in both the pre-lamination process and the final pressure bonding process, making it less likely to produce bubbles, wrinkles, or in-plane color unevenness. Therefore, the ratio of the high-temperature heat shrinkage rate in the final pressure bonding process to the heat shrinkage rate at the glass transition temperature of the film used affects bubbles, wrinkles, and in-plane color unevenness. When glass is used as the support, the maximum temperature in the final pressure bonding process is generally 150°C. Therefore, if the heat shrinkage rate at the temperature at which the film shrinks most is significantly different from or too close to the heat shrinkage rate at the glass transition temperature, it becomes difficult to follow the shrinkage of the interlayer film in both the pre-lamination process and the final pressure bonding process.

[0054] From the above viewpoints, the laminate film of the present invention preferably has an S(150) / S(TA) ratio of 1.5 to 5.0, where S(150) is the average heat shrinkage at 150°C and S(TA) is the average heat shrinkage at TA. From the above viewpoints, S(150) / S(TA) is more preferably 1.5 to 4.0, and even more preferably 1.5 to 3.0. Here, S(150) refers to the average value of the heat shrinkage in the main orientation direction and the heat shrinkage in the direction perpendicular to the main orientation at 150°C. S(TA) and S(120) described below can be interpreted similarly, except that the temperature changes from 150°C to TA or 120°C. When S(150) / S(TA) is 5.0 or less, bubbles, wrinkles, and in-plane color unevenness caused by an excessively high heat shrinkage at 150°C or an excessively low heat shrinkage at the glass transition temperature (TA) of the laminate film can be suppressed. When S(150) / S(TA) is 1.5 or more, the interlayer film follows the shrinkage of the interlayer film in both the pre-lamination process and the main pressure bonding process when glass is used as the support, thereby reducing the occurrence of bubbles and wrinkles.

[0055] Similarly, when a resin such as acrylic or polycarbonate is used as the support, the temperature of the pressure-bonding step is generally lower than that of glass. Therefore, from the above viewpoint, when the average thermal shrinkage at 120°C is S(120) and the average thermal shrinkage at TA is S(TA), it is preferable that S(120) / S(TA) is 1.5 or more and 5.0 or less. From the above viewpoint, S(120) / S(TA) is more preferably 1.5 or more and 3.0 or less, and even more preferably 1.5 or more and 2.0 or less. When S(120) / S(TA) is 5.0 or less, bubbles, wrinkles, and in-plane color unevenness caused by an excessively high thermal shrinkage at 120°C or an excessively small thermal shrinkage at the glass transition temperature (TA) of the laminated film are suppressed. When S(120) / S(TA) is 1.5 or more, the film follows the shrinkage of the interlayer film in both the pre-laminating step and the main pressure bonding step when a resin such as acrylic or polycarbonate is used as the support, thereby reducing the occurrence of bubbles and wrinkles.

[0056] One effective method for achieving a ratio S(150) / S(TA) of 1.5 to 5.0 or a ratio S(120) / S(TA) of 1.5 to 5.0 is to lower S(TA). However, if the glass transition temperatures of the thermoplastic resins constituting the laminate film are close to 150°C or 120°C, the heat shrinkage coefficients of S(150) and S(120) tend to be similar, making it difficult to achieve a ratio of 1.5 or greater. Therefore, it is effective to set the higher of the glass transition temperatures Tg of the thermoplastic resins (thermoplastic resin A and thermoplastic resin B) that are the main components of the two layers (layer A and layer B) with different main components to 95°C to 105°C, preferably 100°C to 105°C. It is also effective to include a component with a low melting point in layer A or layer B, and in terms of processing, it is also effective to set the heat treatment temperature within the preferred range described below.

[0057] Methods for lowering the glass transition temperature Tg of a thermoplastic resin are not particularly limited, but examples include copolymerizing a thermoplastic resin with a low crystalline component and using a thermoplastic resin with a low glass transition temperature. An example of the former is polyethylene naphthalate (PEN), the most commonly used polyester containing naphthalenedicarboxylic acid as a dicarboxylic acid component, which has a glass transition temperature of approximately 120°C. However, it is possible to lower the glass transition temperature by copolymerizing PEN with a structural unit with lower crystallinity than the ethylene naphthalate unit. An example of the latter is using a thermoplastic resin (such as polyethylene terephthalate) with a glass transition temperature lower than 105°C. Using such a method makes it easy to lower the glass transition temperature to 105°C or lower. These methods may also be used in combination as appropriate.

[0058] The low-crystalline structural unit to be copolymerized is not particularly limited as long as it is a structural unit with lower crystallinity than the main structural unit, but in the case of a polyester resin, it is preferably a structural unit derived from a compound containing a chemical structure represented by the following formula (3). That is, when thermoplastic resin A or thermoplastic resin B is a polyester resin, it is preferable to copolymerize the chemical structure represented by formula (3) in order to lower the glass transition temperature. Alternatively, instead of copolymerization, a mixture in which a thermoplastic resin containing a structural unit represented by formula (3) is mixed in layer A or layer B may be used. In formula (3), m and n represent natural numbers such that m×n is 5 or greater. -O-(C ｎ H ２ｎ -O) ｍ -...Formula (3).

[0059] When the thermoplastic resin components constituting each layer are unknown, the presence or absence of the chemical structure represented by formula (3) can be confirmed, for example, by the following method. First, a weight peak is confirmed by gas chromatography mass spectrometry (GC-MS). Next, the presence or absence of peaks derived from the bonds between each atom in the estimated chemical structure is confirmed by Fourier transform infrared spectroscopy (FT-IR). Furthermore, proton nuclear magnetic resonance spectroscopy ( １ H-NMR, 13 Using C-NMR, the position of the chemical shift derived from the position of the hydrogen or carbon atom in the chemical structural formula and the area of ​​the proton absorption line derived from the number of hydrogen atoms are confirmed. From these results, it is possible to determine whether or not the chemical structure represented by formula (3) exists.

[0060] Here, m×n in formula (3) is preferably at least 6, and more preferably at least 8. Specific examples of compounds having a chemical structure represented by formula (3) include polyethylene glycol, tetraethylene glycol, polytetramethylene ether glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, tributylene glycol, and tetrabutylene glycol.

[0061] When at least one of the A layer and the B layer contains a copolymerized polyester resin having a chemical structure represented by formula (3) as a main component, the copolymerized polyester resin preferably contains 0.5 mol % to 40 mol % of structural units having a chemical structure represented by formula (3) relative to 100 mol % of all diol constituent components. When the diol units of formula (3) are contained in this range, it becomes easy to set the glass transition temperatures of thermoplastic resin A and thermoplastic resin B to 105° C. or less. Note that when the diol units of formula (3) are contained in both thermoplastic resin A and thermoplastic resin B by copolymerization, the amount can be appropriately adjusted within the above range, taking into consideration not only the glass transition temperature but also crystallinity. For example, when thermoplastic resin A is a PEN copolymer and thermoplastic resin B is a PET copolymer, the content of the diol unit of formula (3) in thermoplastic resin A is preferably 3 mol % or more and 20 mol % or less relative to 100 mol % of all diol constituent components, and the content of the diol unit in thermoplastic resin B is preferably 3 mol % or more and 20 mol % or less relative to 100 mol % of all diol constituent components.

[0062] Furthermore, a compound having a chemical structure represented by formula (3) may be contained in at least one of layer A and layer B. In this case, the amount of the compound is preferably adjusted to 0.5 mol % to 40 mol % relative to 100 mol % of all diol constituents of all polyester resins constituting layer A or B. Even when the compound structure represented by formula (3) is obtained by mixing, the same effect as when the glass transition temperature is lowered by copolymerization can be obtained.

[0063] On the other hand, when the chemical structure represented by formula (3) is obtained by mixing, the haze value tends to be high due to differences in the compatibility of the different resins, and heat resistance may be poor, so it is more preferable for Layer A and Layer B to incorporate the chemical structure represented by formula (3) by copolymerization into thermoplastic resin A or thermoplastic resin B rather than by mixing compounds. Furthermore, copolymerizing a diol constituent component having the chemical structure represented by formula (3) into thermoplastic resin A or thermoplastic resin B is also preferable in that it can prevent components having these chemical structures from leaking out of the laminate film system due to evaporation, sublimation, or the like.

[0064] Another method for achieving the same effect as setting the glass transition temperatures of thermoplastic resin A or thermoplastic resin B to 105°C or lower is to mix a polyester resin with a lower glass transition temperature than these thermoplastic resins into Layer A or Layer B. Examples of polyester resins with lower glass transition temperatures include dicarboxylic acid components such as terephthalic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid, and their ester-forming derivatives. Examples of diol components include the same components as those described above, with ethylene glycol, 1,4-cyclohexanedimethanol, and 1,4-butanediol being particularly preferred. Adding such components to Layer A or Layer B achieves the same effect as setting S(150) / S(TA) or S(120) / S(TA) within a suitable range, making it possible to suppress bubbles, wrinkles, and in-plane color unevenness during molding. However, compared to the above example using a copolymer, it is important to note that the reflectance is likely to be low due to the low refractive index of each thermoplastic resin layer, and that the internal haze of the film is likely to increase due to the mixing of different resins.

[0065] The laminate film of the present invention preferably has an internal haze of 0.5% or less. Internal haze is an index representing the haze (turbidity) inside the film, excluding light scattering at the film surface. By reducing the internal haze, a laminate film can be obtained that is transparent and reflects light of a specific wavelength. Such a laminate film can be widely used in applications requiring transparency, such as half mirrors and heat ray reflective films. From the above perspective, the internal haze of the laminate film is preferably 0.4% or less, and more preferably 0.3% or less. The internal haze of the laminate film can be measured by measuring the haze in accordance with JIS-K-7105 (1981) while the film is placed in a quartz cell filled with liquid paraffin (details of the measurement method will be described later).

[0066] The internal haze of the laminate film can be adjusted to the aforementioned range by adjusting the type and amount of components other than thermoplastic resin A in Layer A and the type and amount of components other than thermoplastic resin B in Layer B. This configuration allows for the addition of appropriate amounts of components that have excellent compatibility and dispersibility with each thermoplastic resin, thereby reducing internal haze. Internal haze can also be reduced by appropriately combining thermoplastic resin A and thermoplastic resin B. One example of such a combination of thermoplastic resin A and thermoplastic resin B is a combination of polyethylene naphthalate resin copolymerized with polyethylene glycol as thermoplastic resin A and polyethylene terephthalate resin copolymerized with cyclohexanedimethanol as thermoplastic resin B. Furthermore, internal haze can be reduced by reducing the number of resin layers or the thickness of the film.

[0067] From the viewpoint of use as a projection image display component such as a head-up display, the laminate film of the present invention preferably has an average P-wave reflectance of 10% to 50% for wavelengths of 400 to 700 nm at an incident angle of 60°. In the case of a typical transparent substrate such as transparent glass or a transparent resin film, as the incident angle gradually increases from 20° relative to the normal to the film surface, the reflectance of P-waves, a type of polarized light, decreases, reaching 0% at an angle known as the Brewster angle. The Brewster angle varies depending on the refractive index of the material, and is approximately 60° for polyester resin. Therefore, typical transparent substrates transmit P-waves from the front direction while having difficulty reflecting P-waves from oblique directions. The incident angle refers to the angle between the normal to the film surface and the direction of travel of the light ray.

[0068] In other words, an embodiment in which the average reflectance of P waves at wavelengths of 400 to 700 nm at an incident angle of 60° is 10% or more and 50% or less is an embodiment that does not have an angle equivalent to the Brewster angle. Therefore, this embodiment enables reflection of P waves incident at an oblique angle relative to the film surface. Having an average reflectance of P waves at wavelengths of 400 to 700 nm at an incident angle of 60° of 10% or more improves the display quality of the projected image when the P wave image is projected onto the laminate film. From the above perspective, the average reflectance of P waves at an incident angle of 60° is preferably 20% or more, more preferably 25% or more. On the other hand, having an average reflectance of P waves at an incident angle of 60° of 50% or less can prevent the average reflectance of P waves at incident angles of 20° to 50° from increasing as the average reflectance of P waves at an incident angle of 60° increases. This reduces glare in the projected image due to P waves, improving display quality. To achieve an average P-wave reflectance of 20% or more at an incident angle of 60°, the absolute value of the difference in the in-plane normal refractive index between the A layer and the B layer is preferably 0.11 or more and 0.20 or less, more preferably 0.13 or more and 0.20 or less. If the absolute value of the difference in the in-plane normal refractive index between the A layer and the B layer is 0.11 or more, the display quality of the projected image described below is improved. On the other hand, if this difference is kept to 0.20 or less, peeling at the interface between the A layer and the B layer is reduced.

[0069] To obtain such a laminate film, a method can be used in which the refractive index difference between the two thermoplastic resin layers in the direction perpendicular to the film plane and the number of layers are adjusted. In this case, the greater the refractive index difference in the direction perpendicular to the film plane and the greater the number of layers, the greater the P-wave average reflectance at an incident angle of 60°. The difference in refractive index perpendicular to the plane between Layer A and Layer B can be adjusted by adjusting the composition of the resins constituting each layer and the film-forming conditions (e.g., stretching ratio, stretching speed, stretching temperature, heat treatment temperature, and heat treatment time). Here, the refractive index perpendicular to the plane refers to the refractive index in the direction perpendicular to the plane of the multilayer laminate film. Examples of resin compositions constituting Layer A and Layer B include the aforementioned compositions of thermoplastic resin A and thermoplastic resin B. Among these, it is preferable to use polyethylene terephthalate as thermoplastic resin A and polyethylene terephthalate as thermoplastic resin B, in which 2,6-naphthalenedicarboxylic acid is copolymerized in an amount of 15 mol % to 35 mol % based on the total dicarboxylic acid components.

[0070] From the viewpoint of the visibility of the background when a P-wave image is projected, the laminate film of the present invention, which has an average P-wave reflectance of 10% to 50% for wavelengths of 400 to 700 nm at an incident angle of 60°, preferably has an average transmittance of 50% to 100% for wavelengths of 400 to 700 nm at an incident angle of 10°. Such a high average transmittance for light in the visible light region of 400 to 700 nm wavelengths provides transparency similar to that of transparent glass or a transparent resin film, and good visibility of the background can be obtained when the background is observed through the laminate film from a direction perpendicular to the surface of the laminate film.

[0071] From the above viewpoints, the average transmittance is preferably 70% or more, more preferably 80% or more, and even more preferably 85% or more. If the average transmittance is 85% or more, the user can see the background without feeling the presence of the laminate film. From the viewpoint of feasibility, the upper limit of the average transmittance is preferably 99%. Such a laminate film can be obtained by reducing the refractive index difference between the two thermoplastic resin layers in a direction parallel to the film surface. If the refractive index difference in the direction parallel to the film surface is 0.06 or less, the transmittance can be easily increased to 50% or more; if the refractive index difference is 0.04 or less, the transmittance can be increased to 70% or more; and if the refractive index difference is 0.02 or less, the transmittance can be easily increased to 80% or more. 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 layer A and layer B.

[0072] Next, a preferred method for producing the laminate film of the present invention will be described below using an example in which a crystalline polyester resin is used as the thermoplastic resin A (layer A) and an amorphous polyester resin is used as the thermoplastic resin B (layer B). Of course, the present invention is not limited to this example. Furthermore, the formation of the laminate structure of the laminate film itself can be realized by referring to the description in paragraphs

[0053] to

[0063] of JP-A-2007-307893. The same can be said for a laminate film consisting of three types of layers, including layer C.

[0073] Thermoplastic resin A and thermoplastic resin B are prepared in the form of pellets or the like. If necessary, the pellets are dried in hot air or under vacuum and then fed into separate extruders. In the extruder, thermoplastic resin A is heated and melted at a temperature above its melting point, and thermoplastic resin B is heated and melted at a temperature within ±30°C of the heating temperature of thermoplastic resin A so as to prevent uneven extrusion. The extrusion rate is then uniformized using a gear pump or the like, and the molten thermoplastic resin is extruded. Foreign matter and denatured resin are removed through a filter or the like. These molten thermoplastic resins are laminated to the desired layer structure using a lamination device, molded into the desired sheet shape using a die, and then discharged onto a casting drum. The multilayered molten sheet discharged from the die is then extruded onto a cooling body such as a casting drum and cooled and solidified to obtain a cast film. In this process, 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. Also preferred is a method in which air is blown from a slit-, spot-, or plane-shaped device to bring the mixture into close contact with a cooling body such as a casting drum to rapidly solidify, or a method in which the mixture is brought into close contact with a cooling body using nip rolls to rapidly solidify.

[0074] As the lamination device, a multi-manifold die, a feed block, a static mixer, etc. can be used. However, in order to efficiently obtain the configuration of the present invention, it is particularly preferable to use a feed block containing at least two or more separate members with a large number of fine slits. Using such a feed block prevents the device from becoming extremely large, reduces foreign matter due to thermal degradation, and enables high-precision lamination even when the number of layers is extremely large. Furthermore, the lamination accuracy in the width direction is also significantly improved compared to conventional technology. Furthermore, with this device, the thickness of each layer can be adjusted by the shape (length, width) of the slits, making it easy to achieve any layer thickness.

[0075] The cast film thus obtained is then preferably biaxially stretched. Here, biaxial stretching refers to stretching in the longitudinal direction and the width direction. Stretching may be performed in two directions sequentially or simultaneously. Furthermore, re-stretching may be performed in the longitudinal direction and / or the width direction. The longitudinal direction refers to the running direction of the film, and the width direction refers to the direction perpendicular to the longitudinal direction within the film plane.

[0076] First, we will explain the case of sequential biaxial stretching. Here, stretching in the longitudinal direction (longitudinal stretching) refers to stretching to impart longitudinal molecular orientation to a film. This is typically achieved by varying the peripheral speed of rolls. This stretching can be performed in one stage or in multiple stages using multiple pairs of rolls. The stretching ratio varies depending on the type of resin, but is typically preferably 2.0 to 9.0 times. When a polyethylene naphthalate copolymer resin is used as one of the resins constituting the laminate film, a ratio of 2.0 to 7.0 times is preferred. Considering the need to obtain a laminate film with a reflection band of 100 nm or more where the reflectance is 30% or more, and further with a thermal shrinkage rate of 1.5% or more in at least one of the main orientation direction and the direction perpendicular to the main orientation direction in a 150°C atmosphere, a longitudinal stretching ratio of 3.0 to 3.8 times is particularly preferred. The stretching temperature is preferably in the range of the glass transition temperature of the resin with the higher glass transition temperature constituting the laminate film to the glass transition temperature + 100°C.

[0077] The uniaxially stretched film thus obtained may be subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment as needed, and then may be imparted with properties such as easy slippage, easy adhesion, and antistatic properties by in-line coating.

[0078] Stretching in the width direction (transverse stretching) refers to stretching to impart widthwise orientation to a film. Typically, a tenter is used to convey a uniaxially stretched film while holding both ends with clips, thereby stretching it in the width direction. The stretching ratio varies depending on the type of resin, but is typically 2.0 to 9.0 times. When a polyethylene naphthalate copolymer resin is used as one of the resins constituting the laminate film, a ratio of 2.0 to 7.0 times is preferred. Considering the need to obtain a laminate film with a reflection band of 100 nm or more where the reflectance is 30% or more, and further with a thermal shrinkage rate of 1.5% or more and less than 4.0% in at least one of the main orientation direction and the direction perpendicular to the main orientation direction in a 150°C atmosphere, a transverse stretching ratio of 3.7 times or more and 4.2 times or less is particularly preferred. From the above perspective, the in-plane stretching ratio, which is the product of the longitudinal stretching ratio and the transverse stretching ratio, is preferably 11.0 times or more and 18.0 times or less, and more preferably 12.0 times or more and 18.0 times or less. The stretching temperature is preferably in the range of from the glass transition temperature of the resin having the higher glass transition temperature among the resins constituting the laminated film to the glass transition temperature + 120°C.

[0079] The biaxially stretched film thus obtained is preferably heat-treated in a tenter at a temperature above the stretching temperature and below the melting point of thermoplastic resin A to impart flatness and dimensional stability. Heat treatment improves the dimensional stability of the resulting laminate film. After heat treatment, the laminate film is preferably uniformly slowly cooled at a temperature above the glass transition temperature of thermoplastic resin A and below the heat treatment temperature. More specifically, the film is preferably slowly cooled at a temperature above 100°C and below 200°C, more preferably from 130°C to 180°C, and even more preferably from 150°C to 180°C. After slow cooling, the film is cooled to room temperature and wound up. Furthermore, additional stretching of 0.1% to 10% or relaxation treatment may be performed during the heat treatment and slow cooling process.

[0080] Furthermore, in the laminate film of the present invention, the heat treatment temperature after stretching is preferably set to be below the melting point of thermoplastic resin A and above the melting point of thermoplastic resin B. In this case, thermoplastic resin A maintains a high orientation state while the orientation of thermoplastic resin B is relaxed, so that a refractive index difference can be easily achieved between the layers (layer A, layer B) containing these resins as main components. Note that when an amorphous resin is used as either thermoplastic resin A or thermoplastic resin B, the heat treatment temperature is preferably below the melting point of the crystalline resin and in the range of the glass transition temperature of the crystalline resin to the glass transition temperature + 120°C. When at least one of thermoplastic resin A and thermoplastic resin B is a crystalline polyester having naphthalenedicarboxylic acid units as the main structural unit, from the viewpoint of controlling the thermal shrinkage rate in at least one of the main orientation direction and the direction perpendicular to the main orientation in TA-TX or in an atmosphere of 150°C within a suitable range, the heat treatment temperature is preferably 170°C or higher and lower than 220°C, more preferably 175°C or higher and 215°C or lower, even more preferably 175°C or higher and 210°C or lower, and particularly preferably 175°C or higher and 200°C or lower. When an amorphous resin is used for thermoplastic resin A and thermoplastic resin B, the heat treatment step is not necessary.

[0081] Next, simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the obtained cast film may be subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment as necessary, and then may be imparted with properties such as easy lubricity, easy adhesion, and antistatic properties by in-line coating.

[0082] Next, while holding both widthwise ends with clips, the cast film is introduced into a simultaneous biaxial tenter and conveyed there, where it is stretched simultaneously and / or stepwise in the longitudinal and widthwise directions. 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 stretching ratios and relaxation treatment at any location. The stretching ratio varies depending on the type of resin, but an area ratio of 6.0 to 30.0 times is typically preferred. When a polyethylene naphthalate copolymer resin is used as one of the resins constituting the laminate film, an area ratio of 9.0 to 18.0 times is particularly preferred. In particular, in the case of simultaneous biaxial stretching, it is preferable to maintain the same stretching ratio in the longitudinal and widthwise directions and to ensure that the stretching speeds are approximately equal in order to suppress in-plane orientation differences. Furthermore, the stretching temperature is preferably in the range of the glass transition temperature of the resin with the higher glass transition temperature constituting the laminate film to the glass transition temperature + 120°C.

[0083] The biaxially stretched film is then heat-treated, slowly cooled, and cooled to room temperature, as in the case of sequential biaxial stretching, and then wound up. During the heat treatment, it is preferable to instantly relax the film in the longitudinal direction just before and / or just after entering the heat treatment zone in order to suppress the distribution of the main orientation axis in the width direction.

[0084] Next, the laminate and laminated glass of the present invention will be described. The laminate of the present invention includes a support 1, an intermediate layer 1, a laminate film of the present invention, an intermediate layer 2, and a support 2, in this order. Furthermore, among the laminates of the present invention, a laminated glass of the present invention includes a support 1 and a support 2, both of which are glass. The laminate and laminated glass of the present invention may include a plurality of the above components, and other components may be present between the above components, as long as the above components are arranged in this order. Furthermore, the support 1 and the support 2 may be the same or different components, as well as the intermediate layer 1 and the intermediate layer 2. Such molded products and laminated glass have excellent strength, and laminated glass in particular has the characteristic of suppressing glass shattering and penetration of objects when an object hits the glass surface, compared to double-glazed glass (multi-glazed glass) that has an air layer between the two panes of glass. Therefore, the laminated glass of the present invention is suitable for use in applications requiring safety and security, such as window glass for automobiles and buildings. Furthermore, by including the laminated film of the present invention in the laminated glass, it is possible to impart functions such as heat-blocking, half-mirror, and color filter functions to the laminated glass.

[0085] A laminate using the laminate film of the present invention comprises, in this order, support 1, intermediate layer 1, the laminate film of the present invention, intermediate layer 2, and support 2. Support 1 and support 2 serve to increase the strength of the laminate. Examples of supports for obtaining the laminate of the present invention include resins, metals, glass, and ceramics. The surface of the support may be flat or curved, and may have any shape. Examples of resins used for support 1 and 2 include acrylic resins such as polycarbonate, cyclic polyolefin, polyarylate, polyethylene terephthalate, and polymethyl methacrylate, ABS resin, and triacetyl cellulose. Examples of glass used for support 1 and 2 include float glass, tempered glass, colored glass, and heat-shielding glass. Considering use in heat-reflecting applications or as projection components for head-up displays, support 1 and 2 are preferably transparent, and the thickness of the support is preferably 0.05 mm to 5 mm from the viewpoint of ensuring strength and reducing weight.

[0086] The intermediate layers 1 and 2 serve to bond the laminate film of the present invention to the substrates 1 and 2, and are preferably adhesive layers or film layers. Examples of adhesives 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 adhesives in film form or formed on the surface of a film can also be used as adhesives. These adhesives may also contain viscosity modifiers, plasticizers, heat stabilizers, antioxidants, UV absorbers, antistatic agents, lubricants, colorants, crosslinking agents, and the like.

[0087] The provision of an intermediate layer can improve adhesion between the substrate 1 or 2 and the laminate film of the present invention, as well as the design, durability, weather resistance, impact resistance, and other functions of the laminate. Addition of a colorant to the intermediate layer can be a method of improving the design of the laminate. Examples of colorants include 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. From the viewpoint of improving processability and adhesion as an intermediate layer, the thickness of the intermediate layer is preferably 10 μm to 1 mm.

[0088] Molding methods for obtaining laminates include extrusion lamination, hot melt lamination, thermal lamination, press lamination, vacuum lamination, and autoclave lamination. Extrusion lamination is a method in which molten resin compositions for obtaining a laminate film and an intermediate layer are extruded from a die into a film shape, laminated onto a support, and then molded by passing the molded product between two rolls. Hot melt lamination is a molding method in which a resin composition for forming an intermediate layer, melted by heat, is applied to a laminate film or a support, and the laminate film and the support are laminated. Thermal lamination is a molding method in which the laminate film, an intermediate layer sheet, and the support are heated and pressed together with a heated roll. Press lamination is a molding method in which the laminate film, an intermediate layer sheet, and the support are heated and pressed together in a press. Vacuum lamination is a molding method in which the laminate film, the intermediate layer sheet, and the support are heated, then the inside of the device is evacuated, and the laminate is pressed and laminated. Autoclave lamination is a lamination method in which a laminate film, an intermediate layer sheet, and a support are heated, and then the inside of the apparatus is pressurized with gas or the like to laminate them.

[0089] The laminated film of the present invention will be described in more detail below using examples, but the laminated film of the present invention is not limited to the embodiments shown below.

[0090] [Methods for Measuring Physical Properties and Evaluating Effects] The methods for evaluating property values ​​and effects are as follows.

[0091] (1) Layer Thickness, Number of Laminates, and Laminate Configuration The layer configuration and number of laminates of the laminate film were identified and the thickness of each layer was measured by observing a sample cut out of a cross section using a microtome with a transmission electron microscope (TEM) and using its length measurement function. Specifically, a transmission electron microscope H-7100FA (manufactured by Hitachi, Ltd.) was used to observe the cross section of the film at 10,000 to 40,000 times magnification under an acceleration voltage of 75 kV, and a cross-sectional photograph was taken, and the layer configuration and number of laminates were identified and the thickness of each layer was measured. In some cases, in order to increase the contrast between layers, RuO ４ YaOsO ４ A known staining technique using the above was used.

[0092] (2) Reflectance and Transmittance Using a sample cut to 5 cm x 5 cm, reflectance and transmittance were measured under the following measurement conditions using a Hitachi spectrophotometer (U-4100 Spectrophotometer) with an integrating sphere attached as a basic configuration. In the reflectance measurement, the sample was placed behind the integrating sphere with its longitudinal direction facing up and down, and reflectance was calculated as a relative reflectance based on the aluminum oxide secondary white plate attached to the instrument. The average reflectance for wavelengths of 900 to 1200 nm was calculated by averaging all reflectance values ​​every 1 nm. Measurements were performed on both sides of the sample, and the measurement result for the side with the higher average reflectance for wavelengths of 900 to 1200 nm was used. In the transmittance measurement, the sample was placed in front of the integrating sphere with its longitudinal direction facing up and down. The average transmittance for wavelengths from 400 to 700 nm was taken as the average value of all the transmittances in 1 nm increments, and measurements were taken on both sides of the sample, with the measurement result for the side with the higher average transmittance for wavelengths from 400 to 700 nm being used. <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°.

[0093] (3) 60° P-wave reflectance A Hitachi spectrophotometer (U-4100 Spectrophotometer) was equipped with an attached variable angle reflection unit and a Glan-Taylor polarizer, and the reflectance of P-waves in the wavelength range of 400 to 700 nm at an incident angle θ = 60° was measured in 1 nm increments relative to an azimuth angle of 60° clockwise from an azimuth angle of 0° in the main orientation direction of the film surface. From the obtained reflectances, the 60° P-wave reflectance was calculated as the average reflectance of P-waves in the wavelength range of 400 to 700 nm at an incident angle of 60° in each azimuth angle direction. <Measurement conditions> Slit: 2 nm (visible) / automatic control (infrared) Gain: 2 Scanning speed: 600 nm / min Starting wavelength: 700 nm Ending wavelength: 400 nm Sampling interval: 1 nm.

[0094] (4) Melting Point, Glass Transition Temperature TA, Crystallization Temperature, and Heat of Crystal Fusion A 5 g sample was collected, and the melting point, glass transition temperature, crystallization temperature, and heat of crystal fusion were measured and calculated using a differential scanning calorimeter (Robot DSC-RDC220, manufactured by Seiko Instruments Inc.) in accordance with JIS-K-7121 (1987). When multiple glass transition temperatures existed, the higher temperature was taken as the glass transition temperature TA. For the measurement, the sample was heated from 25°C to 290°C at a rate of 5°C / min.

[0095] (5) Internal Haze Three square laminate film samples, each 5 cm on a side, were prepared and left for 40 hours under normal conditions (23°C, 50% relative humidity). The internal haze of each sample was then measured in accordance with JIS-K-7105 (1981) using a turbidity meter "NDH5000" manufactured by Nippon Denshoku Industries Co., Ltd. The measurements were carried out in a quartz cell filled with liquid paraffin to eliminate light scattering due to surface irregularities of the laminate film sample. The internal haze measurements of each sample were averaged to determine the internal haze of the laminate film.

[0096] (6) Laminate Appearance (Laminate Preparation) A Nisshinbo LAMINATOR 0303S was used to prepare the laminate. First, 3 mm thick, 10 cm square glass plates were stacked on both sides of the laminate film as supports, and 0.76 mm thick PVB (polyvinyl butyral) was placed between the laminate film and the supports as an intermediate layer. The temperature of the laminated member was increased from 25 ° C to 150 ° C at 3 ° C / min, then the pressure was reduced to 600 mmHg for 5 minutes, and the member was pressed for 30 minutes at a pressure of 0.1 MPa. The member was then slowly cooled to 35 ° C at 3 ° C / min while still pressed, and the press was released to obtain a laminate (150 ° C). A laminate (120 ° C) was also obtained under the same conditions, except that the temperature was increased from 25 ° C to 120 ° C at 3 ° C / min.

[0097] (Color Unevenness Evaluation) A straight-tube white three-wavelength fluorescent lamp and the laminate were arranged parallel to the main orientation direction and fixed at a position 30 cm away from each other in the normal direction. 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, with S and A representing good results. S: No color unevenness was visible from any angle. A: When observed from at least one angle, very slight color unevenness was visible, but no clear color unevenness was visible in part or the entire molded body from any angle. C: When observed from at least one angle, clear color unevenness was visible in part or the entire molded body.

[0098] (Appearance Evaluation) A straight-tube white three-wavelength fluorescent lamp and the laminate were arranged parallel to the main orientation direction and fixed at a position 30 cm away from each other in the normal direction. 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, with S and A representing good results. Similar observations were also made when the fluorescent lamp was arranged horizontally in a direction perpendicular to the main orientation direction. S: No wrinkles or irregularities were visible from any angle. A: When observed from at least one angle, very slight wrinkles or irregularities were visible, but no clear wrinkles or irregularities were visible in part or all of the molded product from any angle. C: When observed from at least one angle, clear wrinkles or irregularities were visible in part or all of the molded product.

[0099] (7) Identification of the main orientation direction A sample of the laminated film having a size of 10 cm x 10 cm was cut out at the center of the film width direction. The degree of orientation was measured using a molecular orientation analyzer MOA-2001 manufactured by KS Systems Co., Ltd. (now Oji Scientific Instruments Co., Ltd.), and the direction with the highest degree of orientation was determined as the main orientation direction.

[0100] (8) Shrinkage Start Temperatures TX and TY A laminated film sample was cut into a rectangular shape measuring 40 mm in the main orientation direction (measurement direction) and 4 mm in the direction perpendicular to the main orientation direction, and measured using a Hitachi High-Tech Science Corporation "TMA SS6100" under the following measurement conditions. <Measurement Conditions> Heating temperature: 25°C to 200°C Heating rate: 10°C / min Hold time: 10 minutes Sampling: 2 seconds Thereafter, the temperature at which the output displacement TMA value changed from a positive value to a negative value in the range of 40 to 150°C was taken as the shrinkage start temperature TX. If the TMA value at 40°C was negative, the shrinkage start temperature TX was taken as 40°C. If there were multiple temperatures at which the value changed from positive to negative, the lowest temperature was taken as the shrinkage start temperature TX. This measurement was performed five times, and the average value was used as the shrinkage start temperature TX. The shrinkage starting temperature TY was measured in the same manner by cutting out a sample into a rectangular shape of 40 mm in the direction (measurement direction) perpendicular to the main orientation direction and 4 mm in the main orientation direction.

[0101] (9) Thermal Shrinkage (150°C Atmosphere, 120°C Atmosphere) A sample was cut into a rectangular shape measuring 150 mm (measurement direction) x 10 mm, and marks were made on the sample at 100 mm intervals in the measurement direction. The spacing between the marks was measured using a Nikon universal projector (Model V-16A), and this value was designated as A. Next, the sample was hung in a gear oven with a 3 g load applied and left in an atmosphere at 150°C or 120°C for 30 minutes. Next, the sample was removed and cooled, and the spacing between the marks was measured and designated as B. The thermal shrinkage in the measurement direction was calculated using the following formula (4). The measurement directions were the main orientation direction and the direction perpendicular to the main orientation, with the number of measurements in each direction being 3, and the average value was used as the thermal shrinkage value. Thermal shrinkage (%) = 100 x (A - B) / A ... formula (4).

[0102] (10) In-plane refractive index of surface (A layer) The in-plane refractive index of the surface layer (A layer) was measured under the following measurement conditions using a "SPA-4000" manufactured by SAIRON TECHNOLOGY, INC. The in-plane refractive index was determined as the average value of the refractive index in the main orientation direction and the direction perpendicular to the main orientation direction of the laminated polyester film sample. The main orientation direction was specified by the method in (7), and the direction perpendicular to the main orientation direction was the direction perpendicular to the main orientation direction in the film plane. Laser: wavelength 632.8 nm Prism: GGG prism.

[0103] (11) In-plane refractive index of layer B Since layer B is an internal layer of the laminate film, the in-plane refractive index was not measured on the film itself, but on a monolayer film of layer B produced under the same stretching and heat treatment conditions as the film, using an "SPA-4000" manufactured by SAIRON TECHNOLOGY, INC. under the following measurement conditions. However, unlike the resin of layer A, the resin of layer B is amorphous, and the degree of orientation does not change upon stretching, so there is no main orientation direction. Therefore, the average value of the refractive index in the longitudinal direction and the refractive index in the width direction of the monolayer film was taken as the in-plane refractive index. Laser: wavelength 632.8 nm Prism: GGG prism.

[0104] (12) Head-up display evaluation A display (SP-133CM) manufactured by Dreammaker was used as the light source. The projection image display member was installed so that the light from the light source was incident at an angle of 60° with respect to the normal direction of the projection image display member surface, and an image was projected from the light source onto the projection image display member using P waves or S waves. The display quality of the projected image was then evaluated visually. (Evaluation criteria for display quality of projected image) S: The projected image was very bright. A: The projected image was bright. C: The projected image was dark.

[0105] [Resins Used in the Production of Laminated Films] The following resins were used as the resins for the A layer and the B layer in the production of the laminated films.

[0106] (Resins for Layer A) PEN (1): Polyethylene 2,6-naphthalate copolymerized with 4 mol% of polyethylene glycol having an average molecular weight of 400 relative to all diol constituents (intrinsic viscosity: 0.64, melting point: 260°C, glass transition temperature: 104°C). PEN (2): Polyethylene 2,6-naphthalate copolymerized with 6 mol% of polyethylene glycol having an average molecular weight of 400 relative to all diol constituents (intrinsic viscosity: 0.64, melting point: 255°C, glass transition temperature: 97°C). PET (2): Polyethylene terephthalate (intrinsic viscosity: 0.65, melting point: 254°C, glass transition temperature: 78°C).

[0107] (Resins for Layer B) PET (1): A mixture of polyethylene terephthalate resin (intrinsic viscosity: 0.73, amorphous resin (no melting point), glass transition temperature: 79°C) copolymerized with 31 mol% of cyclohexanedimethanol (CHDM) based on all diol constituents and polyethylene terephthalate (manufactured by Toray Industries, Inc., intrinsic viscosity: 0.65, melting point: 256°C, glass transition temperature: 80°C) in a mass ratio of 82:18 (melting point: 225°C, glass transition temperature: 79°C). PET (3): A polyethylene terephthalate resin (intrinsic viscosity: 0.67, no melting point, glass transition temperature: 95°C) copolymerized with 30 mol% of 2,6-naphthalenedicarboxylic acid based on all dicarboxylic acid constituents.

[0108] Example 1 PEN (1) was used as the polyester resin (thermoplastic resin A) forming layer A, and PET (1) was used as the polyester resin (thermoplastic resin B) forming layer B. The polyester resins forming each layer were melted at 280°C in a vented twin-screw extruder, and then merged in a 449-layer feed block via a gear pump and filter. 449 layers of molten thermoplastic resin A and thermoplastic resin B were laminated alternately in the thickness direction, with the outermost layers on both sides being layer A. The resulting molten laminate was then introduced into a T-die, formed into a sheet, and extruded. The molten sheet was then quenched and solidified on a casting drum with a surface temperature of 25°C using electrostatic application, yielding a cast film. The extrusion rate was adjusted so that the mass ratio of thermoplastic resin A to thermoplastic resin B was approximately 1:1. Next, the resulting cast film was heated with a group of rolls set at a temperature equal to the glass transition temperature of thermoplastic resin A + 10 ° C., and then rapidly heated from both sides with a radiation heater within a 100 mm stretching section, stretched 3.2 times in the longitudinal direction (longitudinal direction), and then cooled. Then, both sides of this uniaxially stretched film were subjected to a corona discharge treatment in air to a wet tension of 55 mN / m, and a lamination film coating solution consisting of (polyester resin with a glass transition temperature of 18 ° C.) / (polyester resin with a glass transition temperature of 82 ° C.) / silica particles with an average particle size of 100 nm was applied to both sides to form a transparent, easy-to-adhere layer with good slipperiness. This uniaxially stretched film was then clamped at both widthwise ends with clips and introduced into a tenter, preheated with hot air at 100 ° C., and stretched 4.0 times in the transverse direction (widthwise direction) at a uniform stretching speed at a temperature equal to the glass transition temperature of thermoplastic resin A + 20 ° C. Furthermore, in the same tenter, the stretched film was heat-treated with hot air at 195°C and subjected to a 1% relaxation treatment in the width direction at the same temperature. After that, it was further stretched in the width direction by 1% in a cooling zone at 150°C, slowly cooled to room temperature, and wound up. The winder draw was 98%. Note that winder draw is the ratio of the tenter speed to the winder winding speed, and a winder draw of 98% indicates that the tenter speed was 2% slower than the winder winding speed. The thickness of the resulting laminated film was 90 μm. The evaluation results are shown in Tables 2-1, 2-2, 4-1, and 4-2.

[0109] (Examples 2 to 17, Comparative Examples 1 to 7) Laminated films were produced under the same conditions as in Example 1, except that the resin used in each layer, the number of layers, film-forming conditions, and thickness were changed as shown in Tables 1, 2-1, 2-2, 3, 4-1, and 4-2. The evaluation results of the obtained laminated films are shown in Tables 2-1, 2-2, 4-1, and 4-2. The number of layers was adjusted by adjusting the number of slits in the feed block, and the thickness was adjusted by changing the speed of the entire film-forming line, which is linked to the casting drum speed.

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[0115]

[0116] The present invention can be used in decorative materials such as decorative panels, various home appliances, building materials, automobile parts, etc., and can be particularly used as heat-blocking glass that can suppress the inflow of heat caused by sunlight.

Claims

1. A laminated film having a structure in which two or more different types of thermoplastic resin layers are regularly laminated in 51 or more layers, characterized in that, when the highest glass transition temperature determined by differential scanning calorimetry (DSC measurement) is TA and the shrinkage onset temperature determined from a TMA curve in the main orientation direction is TX, the laminated film is characterized in that TX is 5°C to 30°C lower than TA.

2. The laminated film according to claim 1, which has a thermal shrinkage rate of 0.5% or more and 1.2% or less in at least one of the main orientation direction and the direction perpendicular to the main orientation under the TA atmosphere.

3. A laminated film according to claim 1 or 2, which has a thermal shrinkage rate of 1.5% or more and less than 4.0% in at least one of the main orientation direction and the direction perpendicular to the main orientation in an atmosphere of 150°C.

4. The laminate film according to claim 1 or 2, which comprises a layer mainly composed of a polyester having naphthalenedicarboxylic acid units as main structural units.

5. A laminated film according to claim 1 or 2, characterized in that, when TY is the shrinkage start temperature obtained from a TMA curve in the direction perpendicular to the main orientation, the difference between said TY and said TX is 0°C or more and 10°C or less.

6. The laminated film according to claim 1 or 2, wherein the TY is lower than the TA by 5° C. or more and 30° C. or less.

7. A laminate film according to claim 1 or 2, in which S(150) / S(TA) is 1.5 or more and 5.0 or less, where S(150) is the average heat shrinkage at 150°C and S(TA) is the average heat shrinkage at said TA.

8. A laminated film according to claim 1 or 2, in which S(120) / S(TA) is 1.5 or more and 5.0 or less, where S(120) is the average heat shrinkage at 120°C and S(TA) is the average heat shrinkage at said TA.

9. The laminate film according to claim 1 or 2, which has a reflection band of 100 nm or more at which the reflectance is 30% or more when light is incident on the film surface at an incident angle of 10° and a wavelength of 800 to 2000 nm.

10. The laminate film according to claim 1 or 2, which has an average P-wave reflectance of 10% or more and 50% or less for wavelengths of 400 to 700 nm at an incident angle of 60°.

11. The laminated film according to claim 1 or 2, having an internal haze of 0.5% or less.

12. The laminated film according to claim 1 or 2, which is a film for laminated glass.

13. A laminate comprising a support 1, an intermediate layer 1, the laminate film of claim 1 or 2, an intermediate layer 2, and a support 2 in this order.

14. A laminated glass in which the substrate 1 and substrate 2 in the laminate according to claim 13 are both glass.

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