Laminated film

Abstract

A laminated film having a configuration in which 51 or more layers are regularly laminated from two or more different thermoplastic resin layers, the laminated film being characterized in that TA represents the highest glass transition temperature as determined by differential scanning calorimetry, and TX represents the shrinkage initiation temperature as determined from a TMA curve in the main orientation direction, and TX represents the shrinkage initiation temperature as determined from a TMA curve in the main orientation direction. The TX is lower than the TA by 5 DEG C or more and 30 DEG C or less. Provided is a laminated film in which, in a molded article in which an intermediate film and a support are disposed on at least one surface of the laminated film, uneven deformation and color unevenness caused by heat / pressure molding can be reduced, and the appearance and designability can be improved when the molded article is formed.

Description

Technical Field

[0001] This invention relates to laminated films. Background Technology

[0002] A multilayer film is known to selectively reflect light of a specific wavelength by utilizing the interference phenomenon of light caused by alternately stacking two or more materials with different optical properties at layer thicknesses at the wavelength level. Such multilayer films can possess various properties by adjusting the refractive index, number of layers, and thickness of each layer, and are therefore used in applications such as cold mirrors, half mirrors, laser mirrors, dichroic filters, thermal ray reflective films, near-infrared cutoff filters, monochromatic filters, and polarizing reflective films.

[0003] The molded body obtained by laminating such a laminated film with a rigid support under heat and pressure is used in decorative materials such as decorative panels, various household appliances, building components, and automotive-related parts. In recent years, due to carbon dioxide emission regulations imposed by environmental protection, heat-blocking glass, which can suppress the inflow of external heat, especially heat caused by sunlight, has attracted attention as window glass for vehicles such as automobiles and trams, as well as buildings.

[0004] Examples of such heat-blocking glasses include materials that contain heat-absorbing materials in the interlayer used in laminated glass to block heat rays (e.g., Patent Document 1), materials that bond a metal film formed by sputtering or the like to the glass to block heat rays by reflecting them (e.g., Patent Document 2), and materials that insert a laminated film of polymers with different refractive indices alternately between the glass and the interlayer to block heat rays by reflecting them (e.g., Patent Document 3).

[0005] However, the method in Patent Document 1 suffers from the problem that the sunlight incident from the outside is converted into heat energy, resulting in reduced heat radiation into the room and a decrease in heat ray blocking efficiency. Furthermore, this method sometimes causes the glass temperature to rise partially due to the absorption of heat rays, leading to breakage of the glass body due to the temperature difference with the outside air. The method in Patent Document 2 is prone to coloring because it reflects not only heat rays but also visible light; furthermore, it also shields electromagnetic waves, negatively impacting the use of internal communication equipment. On the other hand, the laminated film in Patent Document 3 allows for selective reflection of the reflected wavelength by controlling its layer thickness, thus selectively reflecting light in the near-infrared region that contributes to temperature increases, improving heat ray blocking performance while maintaining visible light transmittance. Moreover, since it does not contain components that block electromagnetic waves, such as metals, it maintains excellent electromagnetic wave transmittance.

[0006] Furthermore, when obtaining a laminated film like the one shown in Patent Document 3 using melt extrusion, based on reasons such as transparency, heat resistance, weather resistance, chemical resistance, strength, and dimensional stability, one resin layer uses a polyester resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) as its main component, while the other resin layer uses a thermoplastic resin (e.g., a copolyester) with optical properties different from that polyester resin (e.g., Patent Documents 4-6). In particular, when polyethylene naphthalate is used as the main component of one resin layer, since the refractive index difference with the low-refractive-index copolyester can be large, a laminated film with high reflectivity can be obtained.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2010-17854

[0010] Patent Document 2: Japanese Patent Application Publication No. 2001-310407

[0011] Patent Document 3: International Publication No. 2005 / 040868

[0012] Patent Document 4: Japanese Patent Application Publication No. 2005-059332

[0013] Patent Document 5: Japanese Patent Application Publication No. 2004-249587

[0014] Patent Document 6: International Publication No. 2013 / 137288 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] Such heat-blocking glass is often used in places where people's line of sight is visible, such as windows in vehicles and buildings, making appearance an important factor. However, in the laminated film method of Patent Document 3, uneven pressing caused by uneven thickness of the intermediate film used in the lamination with the support, and the difference in thermal shrinkage stress between the intermediate film and the support, result in uneven deformation of the laminated film during molding, which damages its appearance. In particular, since such laminated films utilize interference reflection phenomena caused by controlling the layer thickness, if the layer thickness changes due to uneven deformation, color inconsistencies and optical defects within the film surface are easily noticeable. Furthermore, in such laminated films, wrinkles are easily generated when laminated with a support and an intermediate film. This is mainly due to the laminated film's inability to follow the shape of the support during molding and the difference in thermal shrinkage rate between the intermediate film and the support, and the problem mainly occurs at the ends of the molded body.

[0017] Furthermore, as described in Patent Documents 4 and 5, when a laminated film consisting of a layer with polyethylene naphthalate as the main component and a layer of copolyester with a relatively low refractive index is produced by melt extrusion, the layer with polyethylene naphthalate as the main component is relatively rigid and therefore difficult to deform, making it difficult to apply to applications where the laminated film is deformed / processed. For example, when the support, intermediate film, and laminated film are laminated and formed, wrinkles and uneven deformations sometimes occur, making it difficult to use as a final product.

[0018] On the other hand, as described in Patent Document 6, when a laminated film consisting of a layer with polyethylene terephthalate as the main component and a layer of a copolyester with a relatively low refractive index is produced by melt extrusion, the layer is easier to deform due to its lower rigidity compared to polyethylene naphthalate, making it suitable for applications where the laminated film is deformed / processed. However, because polyethylene terephthalate has a lower refractive index than polyethylene naphthalate, the reflectivity of the laminated film is lower, resulting in poor performance as a final product.

[0019] To solve the above-mentioned problems, the present invention provides a laminated film as its subject matter. In a molded article in which an intermediate film and a support are disposed on at least one side of the laminated film, the occurrence of uneven deformation and color unevenness caused by molding accompanied by heating and pressure can be reduced, and the appearance and designability are improved when the molded article is manufactured.

[0020] Methods for solving problems

[0021] To solve the above-mentioned problems, the present invention has the following configuration.

[0022] [1] A laminated film, characterized in that it is a laminated film having 51 or more layers of two or more different thermoplastic resin layers regularly laminated, wherein when the highest glass transition temperature determined by differential scanning calorimetry (DSC measurement) is set as TA, and the shrinkage start temperature determined by the TMA curve of the main orientation direction is set as TX, the TX is 5°C or more and 30°C lower than the TA.

[0023] [2] According to the laminated film described in [1], under the above-mentioned TA atmosphere, the thermal shrinkage rate of at least one of the main orientation direction and the main orientation orthogonal direction is 0.5% or more and 1.2% or less.

[0024] [3] The laminated film according to [1] or [2] has a thermal shrinkage rate of at least one of the main orientation direction and the main orientation orthogonal direction at 150°C of more than 1.5% and less than 4.0%.

[0025] [4] The laminated film according to any one of [1] to [3] comprises a layer of polyester as the main component, wherein the polyester is a naphthalene dicarboxylic acid unit as the main structural unit.

[0026] [5] When the shrinkage start temperature of the laminated film according to any one of [1] to [4] is set as TY, the difference between TY and TX is 0°C or more and 10°C or less.

[0027] [6] The laminated film according to any one of [1] to [5], wherein the TY is 5°C or more lower and 30°C or less lower than the TA.

[0028] [7] When the average value of the heat shrinkage rate at 150°C of the laminated film according to any one of [1] to [6] is set as S(150) and the average value of the heat shrinkage rate at TA is set as S(TA), S(150) / S(TA) is 1.5 or more and 5.0 or less.

[0029] [8] When the average value of the heat shrinkage rate at 120°C of the laminated film according to any one of [1] to [7] is set as S(120) and the average value of the heat shrinkage rate at TA is set as S(TA), S(120) / S(TA) is 1.5 or more and 5.0 or less.

[0030] [9] The laminated film according to any one of [1] to [8] has a reflective band of 100 nm or more that has a reflectivity of 30% or more when light is incident on the film surface under the conditions of an incident angle of 10° and a wavelength of 800 to 2000 nm.

[0031]

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

[0032]

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

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

[0033]

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

[11] is a film for laminated glass.

[0034]

[13] A stacked body having, in sequence, a support 1, an intermediate layer 1, a stacked film of [1] or [2], an intermediate layer 2, and a support 2.

[0035]

[14] A laminated glass,

[13] wherein the support 1 and support 2 in the laminate are both glass.

[0036] The effects of the invention

[0037] This invention provides a laminated film that can reduce uneven deformation and color uniformity caused by molding accompanied by heating and pressurization, and improves the appearance and design when the molded body is formed. Detailed Implementation

[0038] The laminated film of the present invention is characterized by having a structure consisting of 51 or more layers of two or more different thermoplastic resins regularly laminated together. When the highest glass transition temperature determined by differential scanning calorimetry (DSC) is defined as TA, and the shrinkage onset temperature determined by the TMA curve along the main orientation direction is defined as TX, the TX is at least 5°C lower than TA and at least 30°C lower. Embodiments of the present invention will be described below, but the present invention is not limited to the embodiments included in the following examples. Various modifications can be made that achieve the purpose of the invention without departing from its scope. Furthermore, for the purpose of simplification, a laminated film in which two different polyester resin layers (designated as layer A and layer B) are regularly laminated is used as an example in part of the description, but this should also be understood in the case of using three or more polyester resin layers, or using thermoplastic resin layers other than polyester resins.

[0039] The laminated film of the present invention has a structure consisting of 51 or more layers of two or more different thermoplastic resin layers regularly laminated, preferably consisting of 51 or more layers of two or more thermoplastic resin layers with different main components. Here, "main component" refers to a component that, when all components constituting the thermoplastic resin layer are set to 100% by mass, contains more than 50% and less than 100% by mass. The same interpretation applies to main components below. "Different thermoplastic resin layers" means that when comparing two thermoplastic resin layers, they correspond to at least one of the following 1 to 3, preferably at least one of the following "2". Furthermore, when there are three or more thermoplastic resin layers, the term "all different" requires that when comparing two thermoplastic resin layers in any combination, they correspond to at least one of the following 1 to 3 (this also applies when there are four or more thermoplastic resin layers).

[0040] 1: The refractive index difference is greater than 0.01 in the main orientation direction (the specific method for the main orientation direction will be described later).

[0041] 2: Having different melting points or crystallization temperatures (different melting points or crystallization temperatures refer to a difference of more than 3°C between either the melting point or the crystallization temperature determined by the methods described later. Additionally, cases where one thermoplastic resin layer has a melting point and the other does not, or cases where one thermoplastic resin layer has a crystallization temperature and the other does not, are also considered to have different melting points or crystallization temperatures.)

[0042] 3: The components analyzed by nuclear magnetic resonance spectrometry and gas chromatography-mass spectrometry differ by more than 5% by mass.

[0043] In the laminated film of the present invention, the term "a configuration consisting of 51 or more thermoplastic resin layers regularly stacked" refers to a configuration in which 51 or more layers of various thermoplastic resin layers are stacked along the thickness direction in a certain regularity. As a specific example, when there are two different thermoplastic resin layers (layer A and layer B), a configuration where the two types of layers are alternately stacked along the thickness direction, such as A(BA)n or B(AB)n (where the units in parentheses are repeating units, and n is a natural number representing the number of repeating units, and the same applies below). Furthermore, as a specific example when there are three different thermoplastic resin layers (layer A, layer B, and layer C), configurations such as (ABCB)nA or (ABC)nA, where the layers A, B, and C are sequentially expressed as A, B, and C respectively, can be given. By regularly stacking different thermoplastic resin layers in this way, the laminated film can reflect light of a specific wavelength through the relationship between the difference in refractive index of each layer and the layer thickness.

[0044] Generally speaking, in a multilayer film composed of such layers, based on the principle of interference reflection, the more layers there are, the higher the reflectivity can be obtained over a wider band. Therefore, the number of regularly stacked layers is preferably 101 or more, and more preferably 401 or more. For the above reasons, the more layers in the multilayer film, the better. However, considering the need to suppress the increase in manufacturing costs due to the larger manufacturing apparatus as the number of layers increases, and the deterioration in operability due to the increased thickness of the multilayer film itself, layers of 1001 or less are practically applicable.

[0045] From the viewpoint of application for reflecting thermal rays, the laminated film of the present invention preferably has a reflective band of 100 nm or more with a reflectivity of 30% or more when light is incident on the film surface under conditions of an incident angle of 10° and a wavelength of 800 to 2000 nm. The phrase "having a reflective band of 100 nm or more with a reflectivity of 30% or more" means having at least one band with a continuous reflectivity of 30% or more in the wavelength range of 100 nm or more.

[0046] Sunlight primarily exhibits its intensity distribution in the visible light region, and its intensity distribution tends to decrease as the wavelength increases. However, in applications requiring high transparency, such as heat-blocking glass, a combination of transparency and high heat-blocking performance is necessary. Thus, by efficiently reflecting light with wavelengths slightly larger than the visible light region (800–2000 nm), a laminated film can be created that combines transparency and high heat-blocking performance.

[0047] From the above perspective, the multilayer film of the present invention preferably has a reflection band with a reflectivity of 50% or more continuously in the wavelength range of 900 to 1200 nm, where the reflectivity is 200 nm or more. More preferably, the reflectivity is 50% or more continuously throughout the entire wavelength range of 900 to 1200 nm. Furthermore, it is preferable that the average reflectivity in the wavelength range of 900 to 1200 nm is 70% or more, and more preferably, the average reflectivity in the wavelength range of 900 to 1200 nm is 80% or more. As the average reflectivity in the wavelength range of 900 to 1200 nm increases, the multilayer film can be endowed with high thermal radiation blocking performance.

[0048] Since such a laminated film can be achieved by maximizing the difference in in-plane refractive index between two or more resins with different optical properties, when manufacturing a biaxially stretched film, it is sufficient to manufacture a laminated film that alternately laminates layers with a crystalline polyester resin as the main component and layers with a thermoplastic resin as the main component that can remain amorphous during stretching or melt during heat treatment (in other words, it is preferable to manufacture a laminated film that alternately laminates layers with a crystalline thermoplastic resin as the main component and layers with a thermoplastic resin that can remain amorphous during stretching or melt during heat treatment). Furthermore, in order to manufacture a laminated film with a reflective band of 100 nm or more and a reflectivity of 30% or more, it is also effective to increase the number of layers to make the in-plane stretching ratio (the product of the stretching ratio in the longitudinal direction (also known as the film transport direction, length direction) and the stretching ratio in the transverse direction (width direction perpendicular to the transport direction in the film surface) 9.0 times or more and 18.0 times or less. In order to achieve an average reflectance within the preferred range of 900–1200 nm wavelengths, increasing the in-plane stretching ratio and the number of layers within this range is effective.

[0049] The in-plane refractive index referred to here is the average of the refractive index along the principal orientation direction and the refractive index along the direction orthogonal to the principal orientation direction within the film surface. When the thermoplastic resin layer not located on the outermost surface is amorphous, the in-plane refractive index can be determined using any two orthogonal directions within the film surface of a sheet that has been vacuum-dried and pressed. This is because amorphous resins typically do not exhibit birefringence, and the refractive index in each direction does not change with or without stretching. Alternatively, the refractive index can be measured using a 632.8 nm wavelength laser. For example, a measuring device such as the "SPA-4000" manufactured by SAIRON TECHNOLOGY, INC. can be used.

[0050] Here, crystallinity refers to a heat of fusion of 5 J / g or higher in differential scanning calorimetry (DSC). Conversely, amorphous refers to a heat of fusion of less than 5 J / g. Crystalline polyester resins, through orientation crystallization during the stretching / heat treatment process, can achieve a high in-plane refractive index compared to their amorphous state before stretching. Conversely, in the case of amorphous polyester resins, by performing heat treatment at a temperature far exceeding the glass transition temperature during the heat treatment process, some of the orientation occurring during the stretching process can be significantly mitigated, maintaining the low refractive index of the amorphous state. By forming such a laminated structure, a refractive index difference can be easily established between the crystalline and amorphous polyester resins during the stretching and heat treatment processes in the manufacture of the laminated film.

[0051] Furthermore, when manufacturing a laminated film consisting of alternating layers of two types of thermoplastic resins with different crystallinities as the main components, from the viewpoint of suppressing adhesion to rollers during film formation, it is preferable that the outermost layers on both sides are layers with relatively higher crystallinity (layers with crystalline thermoplastic resins as the main components). The laminated film with this configuration will be described below, but unless otherwise specified, the layer with relatively higher crystallinity will be referred to as layer A and the layer with relatively lower crystallinity as layer B.

[0052] Here, the optical thicknesses of adjacent layers A and B preferably satisfy the following equations (1) and (2).

[0053] Equation (1): λ / m=2(n α d α +n β d β )

[0054] Equation (2): n α d α =n β d β .

[0055] Here, λ is the reflection wavelength, and n α Let d be the in-plane refractive index of layer A. α Let n be the thickness of layer A. β Let d be the in-plane refractive index of layer B. β Let B be the thickness of layer B, m be the order, and is a natural number. By having a layer thickness distribution that simultaneously satisfies equations (1) and (2), even-order reflections can be eliminated. Therefore, the average reflectivity in the wavelength range of 900nm to 1200nm can be high, while the average reflectivity in the wavelength range of 400 to 800nm, which is the visible light region, can be low. Thus, a multilayer film with excellent transparency and high thermal radiation cutoff performance can be obtained.

[0056] Generally, since the in-plane refractive index of the film surface after stretching the thermoplastic resin molding is about 1.4 to about 1.9, a laminated film that suppresses even-order reflections can be obtained by making the thickness ratio of adjacent A layers to B layers (thickness of A layer / thickness of B layer) 0.7 or more and 1.4 or less. Therefore, from the above viewpoint, it is preferable that the thickness ratio of adjacent A layers to B layers (thickness of A layer / thickness of B layer) is 0.7 or more and 1.4 or less, more preferably 0.8 or more and 1.2 or less. By making the thickness of adjacent A layers and B layers within such a range, the average reflectance at wavelengths of 400 to 800 nm is preferably 20% or less, more preferably 15% or less. As a result, reflections in the visible light region of the laminated film can be suppressed, reducing coloration and glare.

[0057] In the laminated 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 need to be different from each other. Polyester resin, acrylic resin, polycarbonate resin, etc., can be used as thermoplastic resin A and thermoplastic resin B. Among these, polyester resin is preferred as thermoplastic resin A and thermoplastic resin B due to its excellent transparency and formability. Furthermore, if the laminated film further has a layer C, and the main component of layer C is thermoplastic resin C, then thermoplastic resin C is also preferably polyester resin. Here, polyester resin refers to a polymer obtained by the condensation polymerization of a dicarboxylic acid component and a diol component.

[0058] In the laminated film of the present invention, the dicarboxylic acid unit of the polyester resin used as thermoplastic resin A, thermoplastic resin B, and thermoplastic resin C can be exemplified by terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid (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 their ester-forming derivatives.

[0059] Examples of diol units in the aforementioned polyester resins include 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, isosorbide, 1,4-cyclohexanediol, spirocyclodiol, neopentyl glycol, polyethylene glycol, polypropylene glycol, polybutanediol, triethylene glycol, tetraethylene glycol, polytetramethylene ether glycol, and their ester-forming derivatives.

[0060] As the dicarboxylic acid unit constituting the above-mentioned polyester resin, preferably terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid and other structural units are preferred. As the diol unit, preferably ethylene glycol, 1,4-cyclohexanediethanol, polyalkylene glycol, polyethylene glycol, tetraethylene glycol, polytetramethylene ether glycol and other structural units are preferred.

[0061] As a preferred embodiment of the multilayer film of the present invention, an embodiment in which at least one surface of the multilayer film has an in-plane refractive index of 1.68 or higher and 1.80 or lower can be provided. Generally, the surface layer is preferably a layer with relatively high crystallinity, considering ease of film formation, etc. With an in-plane refractive index of 1.68 or higher for the surface layer, the in-plane refractive index difference with that of the layer with relatively low crystallinity can be large. Therefore, it is easy to make the multilayer film have a reflective band of 100 nm or more with a reflectivity of 30% or higher. On the other hand, with an in-plane refractive index of less than 1.80 for the surface layer, the deterioration of the interlayer adhesion of the two alternately stacked layers is suppressed, and the turbidity and interfacial peeling of the multilayer film are reduced.

[0062] From the above perspective, the laminated film of the present invention preferably uses crystalline polyester as the main component in layer A, and the crystalline polyester uses naphthalene dicarboxylic acid units as the main structural units. With this configuration, the reflectivity of the surface of layer A is increased, and it is easy to establish a refractive index difference with layer B, thus obtaining a laminated film with superior reflective properties. Furthermore, "using naphthalene dicarboxylic acid units as the main structural units" means that among all dicarboxylic acid structural units of the polyester resin, naphthalene dicarboxylic acid units account for more than 50 mol% and less than 100% by mass.

[0063] Examples of naphthalene dicarboxylic acids that serve as structural units of the crystalline polyester resin that forms layer A include 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, and 2,3-naphthalene dicarboxylic acid, with 2,6-naphthalene dicarboxylic acid being particularly preferred. When layer B is primarily composed of an amorphous thermoplastic resin, the more naphthalene dicarboxylic acid units are present in the crystalline polyester resin that forms the main component of layer A, the greater the refractive index difference between layer A and layer B. Therefore, the proportion of naphthalene dicarboxylic acid units in the dicarboxylic acid units of the crystalline polyester resin that forms the main component of layer A is more preferably 80 mol% or more and 100% by mass or less, and even more preferably 95 mol% or more and 100% by mass or less. Furthermore, from the same perspective, when the total content of this crystalline polyester resin in layer A is set to 100% by mass, it is preferably 80% by mass or more and 100% by mass or less, and more preferably 95% by mass or more and 100% by mass or less.

[0064] In the laminated film of the present invention, it is preferable that the difference in in-plane refractive index between layer A and layer B is 0.05 or more. More preferably, it is 0.12 or more, and even more preferably, it is 0.14 or more and 0.35 or less. When the difference in average in-plane refractive index is less than 0.05, it is sometimes difficult to have a reflective band with a reflectivity of 30% or more. As an example of this implementation method, the main component of layer A is a crystalline polyester resin, and the main component of layer B is an amorphous thermoplastic resin. In this case, the refractive index difference can be easily set in the stretching and heat treatment processes during the manufacture of the laminated film.

[0065] From a reflectivity perspective, a large difference in in-plane refractive index between layer A and layer B is preferable. However, to achieve such a large difference, the chemical structures of the thermoplastic resins, which are the main components of the two layers, need to be significantly different, which would worsen interlayer adhesion. Considering this, the average in-plane refractive index difference between layer A and layer B is limited to below 0.35, thus facilitating lamination and improving the heat resistance and workability of the resulting laminated film.

[0066] From the viewpoint of achieving a good appearance when the laminated glass or other molded products are manufactured, the laminated film of the present invention needs to have a maximum glass transition temperature (TA) determined by differential scanning calorimetry (DSC) and a shrinkage initiation temperature (TX) determined by the TMA curve of the main orientation direction, where TX is at least 5°C lower than TA and less than 30°C lower. In other words, TA-TX is at least 5°C lower than 30°C. Here, the main orientation direction refers to the direction in which the molecular orientation degree is greatest within the film surface, which can be identified by measurement using a known molecular orientation meter (details of the measurement method will be described later). In addition, the shrinkage initiation temperature can be determined by TMA measurement, the details of which will be described later. Furthermore, the DSC measurement can be performed based on JIS-K-7121 (1987), the details of which will be described later.

[0067] In laminated glass, where a laminated film is stacked with a support and an interlayer, heating and pressurization are applied to improve the seal between the components. During this heat and pressure process, uneven thickness of the interlayer and the difference in thermal shrinkage stress between the interlayer and the laminated film cause deformation and thickness variations in the laminated film. Such uneven deformation and thickness variations result in light scattering, diffuse reflection, and color inconsistencies within the film surface, leading to a deterioration in the appearance of the finished product. On the other hand, since the glass supporting the laminate is almost undeformed, the shape of the interlayer is hardly affected by the support. Because the laminated film contains interfaces formed by different types of thermoplastic resin layers, in addition to light scattering and diffuse reflection caused by the film surface, scattering and reflection caused by the interfaces also occur, making the unevenness more noticeable compared to a film formed from a single resin. Therefore, if a laminated film that is difficult to produce unevenness can be used, the problem of poor appearance in the finished product can be solved.

[0068] When a laminated film is formed by laminating a support and an interlayer, the laminated film and the interlayer are generally pre-laminated at a low temperature (pre-lamination process, sometimes referred to as the pre-lamination process), and then pressed at a higher temperature to bond with the support (formal pressing process). The method for the pre-lamination process is not particularly limited; generally, two interlayer films are sandwiched between the laminates, and roll lamination is performed at 90–100°C, slightly higher than the glass transition temperature of the polyester resin. The method for the formal pressing process is also not particularly limited; generally, the pre-laminated film is sandwiched between a support such as glass, and then pressed using an autoclave (pressure-heated bonding furnace) at 140–150°C for 20–30 minutes at a pressure of 12–14 kg / cm². 2 Perform crimping.

[0069] At this point, during the pre-lamination and formal lamination processes, the laminated film and intermediate film soften and shrink. If their softness and shrinkage behavior differ significantly, it can lead to bubbles, wrinkles, and uneven color within the surface. Therefore, it is required not only that shrinkage occur during the formal lamination process, which is formed at a higher temperature, but also that the laminated film exhibits shrinkage behavior at a lower temperature, such as during the pre-lamination process; that is, the shrinkage initiation temperature must be lower than the glass transition temperature.

[0070] Generally, thermoplastic resin films are processed from granules into sheets via melt extrusion and then stretched / processed at temperatures above the glass transition temperature. The oriented crystals formed at temperatures above the glass transition temperature are then reheated, which slows down shrinkage, resulting in rapid shrinkage. However, for such films, even if the shrinkage can follow the intermediate film in either the formal lamination or pre-lamination process, shrinkage becomes insufficient or excessive at the other temperature, leading to bubbles, wrinkles, and uneven color within the film. This invention addresses these issues by designing a laminated film that initiates shrinkage at a temperature 5°C to 30°C below the highest glass transition temperature (in other words, TA-TX is 5°C to 30°C below the highest glass transition temperature).

[0071] By setting its glass transition temperature (TA) to TA and its shrinkage initiation temperature (TX) derived from the TMA curve along the main orientation direction to TX, TX being 5°C or more lower than TA and 30°C or less lower than TA, the generation of bubbles, wrinkles, and uneven color within the surface can be suppressed, resulting in molded articles with excellent appearance (especially in the main orientation direction). From this perspective, 10°C or more and 30°C or less is more preferable. If TA-TX exceeds 30°C, the laminated film may become excessively soft, leading to decreased productivity and poor handling during molding. Furthermore, if TA-TX is less than 5°C, bubbles and wrinkles are more likely to form, resulting in poor appearance.

[0072] The laminated film of the present invention preferably has a shrinkage start temperature (TY) determined from the TMA curve of the main orientation orthogonal direction, where the difference between TY and TX is 0°C or more and 10°C or less. With this configuration, the appearance of the laminated film and the molded body using it is improved when viewed from a direction orthogonal to the main orientation direction. Therefore, it is possible to obtain a laminated film and a molded body with excellent appearance when visually recognized from various angles. Here, the main orientation orthogonal direction refers to a direction orthogonal to the main orientation direction within the film surface. Furthermore, the difference between TY and TX is calculated as an absolute value. The laminated film of the present invention, by having a difference between TY and TX of 10°C or less, improves not only its appearance when viewed from the main orientation direction but also its appearance when viewed from a direction orthogonal to the main orientation direction.

[0073] Furthermore, for the same reasons as the preferred range of TX, in the laminated film of the present invention, TY is preferably 5°C or more and 30°C lower than TA (in other words, TA-TY is 5°C or more and 30°C or less), more preferably 10°C or more and 30°C or less.

[0074] There are no particular limitations on the method for achieving a TX temperature that is at least 5°C lower than the TA temperature but less than 30°C. For example, in the case of obtaining a laminated film by successive biaxial stretching (described later), after stretching in the width direction (TD direction) followed by heat treatment, micro-stretching can be performed during slow cooling to room temperature. Alternatively, simulating micro-stretching by increasing the tension (traction) during the winding process after slow cooling is also effective. Both methods enable the obtaining of a film that shrinks at a temperature below the glass transition temperature by micro-stretching at a temperature below the glass transition temperature. Furthermore, controlling the heat treatment temperature and the cooling temperature after heat treatment within suitable ranges is also effective. Additionally, these methods can be appropriately combined as needed.

[0075] From the viewpoint of ensuring a good appearance when the laminated glass or other molded articles are manufactured, the laminated film of the present invention preferably has a thermal shrinkage rate of at least 0.5% and less than 1.2% in at least one of the main orientation direction and the orthogonal main orientation direction under a TA atmosphere. Here, "under a TA atmosphere" refers to an environment with a temperature of TA. From the above viewpoint, under a TA atmosphere, the thermal shrinkage rate of at least one of the main orientation direction and the orthogonal main orientation direction is more preferably 0.7% and less than 1.2%, and even more preferably 0.9% and less than 1.2%. Furthermore, from the above viewpoint, in the laminated film of the present invention, it is preferable that the thermal shrinkage rate in both the main orientation direction and the orthogonal main orientation direction is 0.5% and less than 1.2%, and the preferred range is also as described above. In addition, the thermal shrinkage rate can be calculated by measuring the dimensional change after heat treatment; the measurement method will be described in detail later.

[0076] If, under a TA atmosphere, the thermal shrinkage rate of at least one of the main orientation direction and the orthogonal direction to the main orientation is 0.5% or more, it is difficult to produce bubbles, wrinkles, or uneven color within the surface during the laminated glass process, especially the pre-lamination process. On the other hand, if the shrinkage rate is 1.2% or less in at least one of the aforementioned directions, excessive softening of the laminated film is suppressed, thus improving productivity and operability during molding and processing.

[0077] In order to achieve a thermal shrinkage rate of at least one of the main orientation direction and the main orientation orthogonal direction of TA in an atmosphere of 0.5% or more and 1.2% or less, or the above-mentioned preferred range, the same method as the method for achieving a TX temperature that is 5°C or more and 30°C lower than TA can be used.

[0078] From the viewpoint of ensuring a good appearance when the laminated glass or other molded articles are manufactured, the laminated film of the present invention preferably has a thermal shrinkage rate of at least one of the main orientation direction and the main orientation orthogonal direction at 150°C 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%. From the above viewpoint, it is more preferable that the thermal shrinkage rate of both the main orientation direction and the main orientation orthogonal direction at 150°C is 1.5% or more and less than 4.0%, or within the above-preferred range.

[0079] If, in an atmosphere at 150°C, at least one of the main orientation direction and the orthogonal direction to the main orientation has a thermal shrinkage rate of 1.5% or more, it is difficult to produce bubbles, wrinkles, or uneven color within the surface during the laminated glass process, especially the formal pressing process. On the other hand, by ensuring that, in an atmosphere at 150°C, at least one of the aforementioned directions has a thermal shrinkage rate of less than 4.0%, it is possible to mitigate the deterioration of productivity, operational difficulties during molding, uneven color, and deterioration of appearance caused by excessive softening of the laminated film.

[0080] To achieve a thermal shrinkage rate of at least 1.5% and less than 4.0% in at least one of the main orientation direction and the orthogonal direction of the main orientation at 150°C, methods such as adjusting the stretching ratio and heat treatment temperature can be employed. More specifically, this thermal shrinkage rate can be increased by using a high stretching ratio for the film and a low heat treatment temperature after stretching in the width direction. Furthermore, these methods can be appropriately combined.

[0081] More specifically, in order to produce a laminated film with a thermal shrinkage rate of at least 1.5% and less than 4.0% in the main orientation direction and the orthogonal direction of the main orientation at 150°C, it is preferable to have an in-plane stretch ratio of 11.0 times or more and 18.0 times or less, more preferably 12.0 times or more and 18.0 times or less. From the above perspective, it is preferable to have a longitudinal stretch ratio of 3.0 times or more and 3.8 times or less, and a transverse stretch ratio of 3.7 times or more and 4.2 times or less. If the in-plane stretch ratio is 11.0 times or more, it is easy to achieve a thermal shrinkage rate of 1.5% or more and less than 4.0% in each direction at 150°C. Furthermore, if the in-plane stretch ratio is 18.0 times or less, whitening during film formation caused by excessive stretching and a decrease in productivity caused by film rupture are suppressed.

[0082] The laminated film of this invention, by following the shrinkage of the intermediate film in both the pre-lamination and formal lamination processes, is less prone to bubbles, wrinkles, and uneven color within the film. Therefore, the ratio of the high-temperature thermal shrinkage rate in the formal lamination process to the thermal shrinkage rate at the glass transition temperature of the film used affects the formation of bubbles, wrinkles, and uneven color within the film. When glass is used as the support, the temperature of the formal lamination process is generally at a maximum of 150°C. Therefore, if the thermal shrinkage rate at the temperature of maximum shrinkage is significantly different from or too close to the thermal shrinkage rate at the glass transition temperature, it will be difficult to follow the shrinkage of the intermediate film in both the pre-lamination and formal lamination processes.

[0083] From the above perspective, when the average value of the thermal shrinkage rate at 150°C is set as S(150) and the average value of the thermal shrinkage rate at the glass transition temperature (TA) is set as S(TA), the ratio of S(150) / S(TA) is 1.5 or more and 5.0 or less. From the above perspective, S(150) / S(TA) is more preferably 1.5 or more and 4.0 or less, and even more preferably 1.5 or more and 3.0 or less. Here, S(150) refers to the average value of the thermal shrinkage rate in the main orientation direction and the thermal shrinkage rate in the main orientation orthogonal direction at 150°C. S(TA) and S(120) (described later) can be interpreted in the same way, except that the temperature changes from 150°C to TA or 120°C. If S(150) / S(TA) is 5.0 or less, bubbles, wrinkles, and uneven color within the surface caused by excessively high thermal shrinkage rate of the laminated film at 150°C or insufficient thermal shrinkage at the glass transition temperature (TA) can be suppressed. If S(150) / S(TA) is 1.5 or higher, the shrinkage of the intermediate film will be followed in both the pre-lamination process and the formal lamination process when glass is used as the support, thus reducing the generation of bubbles and wrinkles.

[0084] Similarly, when acrylic or polycarbonate resins are used as the support, the formal pressing process is generally carried out at a temperature lower than that of glass. Therefore, from the above perspective, it is preferable that when the average heat shrinkage rate at 120°C is set as S(120) and the average heat shrinkage rate at the glass transition temperature (TA) is set as S(TA), the ratio of S(120) / S(TA) is 1.5 or more and 5.0 or less. From the above perspective, 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. If S(120) / S(TA) is 5.0 or less, bubbles, wrinkles, and uneven color within the laminate caused by excessively high heat shrinkage rate of the laminate at 120°C or insufficient heat shrinkage at the glass transition temperature (TA) can be suppressed. If S(120) / S(TA) is 1.5 or higher, the shrinkage of the intermediate film will be followed in both the pre-lamination process and the formal lamination process when using acrylic resins, polycarbonate resins, etc. as support, thus reducing the generation of bubbles and wrinkles.

[0085] As a method to make S(150) / S(TA) 1.5 or more and 5.0 or less, and to make S(120) / S(TA) 1.5 or more and 5.0 or less, making S(TA) low is effective. However, if the glass transition temperature of the thermoplastic resin constituting the laminated film is close to 150°C or 120°C, the thermal shrinkage rates of S(150) and S(120) are likely to be close to each other, making it difficult to make their ratio 1.5 or more. Therefore, among 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, it is effective to make the Tg of the higher one 95°C or more and 105°C or less, preferably 100°C or more and 105°C or less. In addition, it is also effective to make layer A and layer B contain components with low melting points, and in terms of process, it is also effective to make the heat treatment temperature within the preferred range described later.

[0086] There are no particular limitations on the method for lowering the glass transition temperature (Tg) of thermoplastic resins. Examples include copolymerizing a component with low crystallinity with the thermoplastic resin, and using a thermoplastic resin with a low glass transition temperature. As an example of the former, polyethylene naphthalate (PEN), a polyester most commonly used as a dicarboxylic acid component containing naphthalene dicarboxylic acid, has a glass transition temperature of approximately 120°C. The glass transition temperature can be lowered by copolymerizing structural units with lower crystallinity compared to ethylene naphthalate units with PEN. Furthermore, as an example of the latter, a method using a thermoplastic resin (such as polyethylene terephthalate) with a glass transition temperature below 105°C can be cited. By using such methods, it is easy to achieve a glass transition temperature below 105°C. Additionally, these methods can be used in appropriate combinations.

[0087] As for the low-crystallinity structural unit used for copolymerization, there is no particular limitation as long as it is a structural unit with low crystallinity compared to the main structural unit. However, in the case of polyester resin, it is preferable to use a structural unit derived from a compound containing the chemical structure shown in formula (3) below. That is, when thermoplastic resin A and thermoplastic resin B are polyester resins, in order to lower the glass transition temperature, it is preferable to copolymerize the chemical structure shown in formula (3). In addition, instead of copolymerization, a mixture of thermoplastic resins containing the structural unit shown in formula (3) below can be used in layers A and B. In addition, in formula (3), m and n represent natural numbers where m×n is 5 or more.

[0088] -O-(C n H 2n -O) m - Equation (3).

[0089] When the composition of the thermoplastic resin constituting each layer is unclear, the presence or absence of the chemical structure shown in equation (3) can be confirmed, for example, by the following methods. First, the weight peaks are confirmed by gas chromatography-mass spectrometry (GC-MS). Next, the presence or absence of peaks originating from the interatomic bonds of the proposed chemical structure is confirmed by Fourier transform infrared spectroscopy (FT-IR). Furthermore, the presence or absence of peaks originating from the interatomic bonds of the proposed chemical structure is confirmed by proton nuclear magnetic resonance spectroscopy (FT-IR). 1 H-NMR, 13 C-NMR is used to confirm the position of the chemical shift of the hydrogen or carbon atom in the chemical structure and the area of ​​the proton absorption peak due to the number of hydrogen atoms. The presence or absence of the chemical structure shown in equation (3) can be determined from these results.

[0090] Here, m×n in formula (3) is preferably 6 or more, and more preferably 8 or more. Specific examples of compounds having the chemical structure shown in formula (3) include polyethylene glycol, tetraethylene glycol, polytetramethylene ether glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, tributylene glycol, and tetrabutylene glycol.

[0091] When at least one of layers A and B is a copolyester resin having the chemical structure shown in formula (3) as the main component, the copolyester resin preferably contains 0.5 mol% to 40 mol% of structural units having the chemical structure shown in formula (3) relative to 100 mol% of the total diol components. If the diol units of formula (3) are included within this range, it is easy to make the glass transition temperature of thermoplastic resin A and thermoplastic resin B 105°C or less. In addition, when both thermoplastic resin A and thermoplastic resin B contain the diol units of formula (3) through copolymerization, crystallinity can be considered in addition to the glass transition temperature, and the amount can be appropriately adjusted within the above range. For example, if thermoplastic resin A is a copolymer of PEN and thermoplastic resin B is a copolymer of PET, then the preferred content of diol units in formula (3) is 3 mol% or more and 20 mol% or less relative to 100 mol% of all diol components in thermoplastic resin A, and 3 mol% or more and 20 mol% or less relative to 100 mol% of all diol components in thermoplastic resin B.

[0092] Furthermore, a compound having the chemical structure shown in formula (3) can be contained in at least one of layer A and layer B. In this case, the amount of the compound is preferably adjusted to be 0.5 mol% or more and 40 mol% or less relative to 100 mol% of the total diol components of the total polyester resin constituting layer A or layer B. Even when the chemical structure shown in formula (3) is obtained through mixing, the same effect as when the glass transition temperature is lowered through copolymerization is obtained.

[0093] On the other hand, when the chemical structure shown in formula (3) is obtained through mixing, the haze value may easily become high and the heat resistance may be poor due to the different compatibility of different resins. Therefore, for layers A and B, it is more preferable to copolymerize thermoplastic resin A and thermoplastic resin B to contain the chemical structure shown in formula (3) than to mix the compounds. Furthermore, copolymerizing diol components having the chemical structure shown in formula (3) with thermoplastic resin A and thermoplastic resin B is also preferable in that it can prevent components having these chemical structures from flowing out of the laminated film system through evaporation, sublimation, etc.

[0094] As another method to achieve the same effect as setting the glass transition temperature of thermoplastic resin A and thermoplastic resin B to below 105°C, a method of mixing a polyester resin with a lower glass transition temperature than these thermoplastic resins into layers A and B can be cited. Examples of polyester resins with low glass transition temperatures include terephthalic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, dimer acids, cyclohexanedicarboxylic acid, and their ester-forming derivatives as dicarboxylic acid components. Examples of diol components are the same as those described above, but ethylene glycol, 1,4-cyclohexanediol, and 1,4-butanediol are preferred. By adding such components to layers A and B, the same effect as setting S(150) / S(TA) and S(120) / S(TA) within suitable ranges can be achieved, suppressing bubbles, wrinkles, and uneven coloring during molding. However, compared to the examples above that use copolymers, attention should be paid to the fact that the refractive index of each thermoplastic resin layer is lower, thus the reflectivity is more likely to be lower, and the internal haze of the film is more likely to be increased by mixing different resins.

[0095] The laminated film of the present invention preferably has an internal haze of 0.5% or less. Internal haze is an indicator of the haze (turbidity) inside the film after excluding light scattering from the film surface. By achieving low internal haze, a transparent laminated film that reflects light of specific wavelengths can be produced. Such laminated films can be widely used in applications requiring transparency, such as translucent mirrors and heat-reflecting films. From the above viewpoint, the internal haze of the laminated film is preferably 0.4% or less, and more preferably 0.3% or less. The internal haze of the laminated film can be measured according to JIS-K-7105 (1981) while it is placed in a quartz cell filled with liquid paraffin (details of the measurement method will be described later).

[0096] To achieve the internal haze of the laminated film within the aforementioned range, this is achieved by adjusting the types and amounts of components other than thermoplastic resin A in layer A, and by adjusting the types and amounts of components other than thermoplastic resin B in layer B. This configuration allows for the appropriate addition of components with excellent compatibility / dispersibility with each thermoplastic resin, thus reducing internal haze. Furthermore, by appropriately combining thermoplastic resin A and thermoplastic resin B, internal haze can also be reduced. An example of such a combination of thermoplastic resin A and thermoplastic resin B is using polyethylene naphthalate resin copolymerized with polyethylene glycol as thermoplastic resin A and polyethylene terephthalate resin copolymerized with cyclohexanediol as thermoplastic resin B. Furthermore, reducing the number of resin layers and thus the film thickness can also reduce internal haze.

[0097] From the viewpoint of use as a projection image display component such as a head-up display, the laminated film of the present invention preferably has an average P-wave reflectance of 10% or more and 50% or less at an incident angle of 60° for wavelengths of 400-700 nm. In the case of general transparent substrates such as transparent glass and transparent resin films, as the incident angle gradually increases from 20° relative to the normal of the film surface, the reflectance of P-waves, which are a type of polarized light, decreases, and the reflectance becomes 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° in the case of polyester resin. Therefore, for general transparent substrates, it is difficult to transmit P-waves from the front direction and reflect P-waves from the oblique direction. Furthermore, the incident angle refers to the angle formed by the normal of the film surface and the direction of light propagation.

[0098] A scheme with an average reflectance of 10% to 50% for P-waves with wavelengths of 400–700 nm at an incident angle of 60° is, in other words, a scheme that does not have an angle equivalent to Brewster's angle. Therefore, this scheme allows for the reflection of P-waves incident from a direction inclined relative to the film surface. With an average reflectance of 10% or more for P-waves with wavelengths of 400–700 nm at an incident angle of 60°, the display quality of the projected image when the image caused by P-waves is projected onto the laminated film is improved. From the above viewpoint, an average reflectance of 20% or more for P-waves at an incident angle of 60° is preferably preferred, and more preferably 25% or more. On the other hand, with an average reflectance of 50% or less for P-waves at an incident angle of 60°, the increase in the average reflectance of P-waves with incident angles of 20°–50°, which is associated with an increase in the average reflectance of P-waves at an incident angle of 60°, can be suppressed. Therefore, glare from the projected image caused by P-waves is reduced, and display quality is improved. To achieve an average P-wave reflectance of 20% or higher at an incident angle of 60°, it is preferable that the absolute value of the difference between the refractive indices perpendicular to the surfaces of layer A and layer B is 0.11 or higher and 0.20 or lower, more preferably 0.13 or higher and 0.20 or lower. If the absolute value of the difference between the refractive indices perpendicular to the surfaces of layer A and layer B is 0.11 or higher, the display quality of the projected image described later becomes higher. On the other hand, if this difference is suppressed to 0.20 or lower, delamination at the interface between layer A and layer B is reduced.

[0099] To obtain such a laminated film, the refractive index difference perpendicular to the film surface between the two thermoplastic resin layers and the number of layers can be adjusted. A larger refractive index difference perpendicular to the film surface and a greater number of layers will increase the average P-wave reflectance at an incident angle of 60°. The perpendicular refractive index difference between layer A and layer B can be controlled 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, heat treatment time). Here, perpendicular refractive index refers to the refractive index in the direction perpendicular to the surface of the multilayer laminated film. Examples of the resin compositions constituting layers A and B include the aforementioned thermoplastic resin A and thermoplastic resin B, but polyethylene terephthalate is preferably used as thermoplastic resin A, and polyethylene terephthalate with 15 mol% to 35 mol% of 2,6-naphthalenedicarboxylic acid copolymerized relative to the total dicarboxylic acid content is preferred as thermoplastic resin B.

[0100] From the viewpoint of visual recognizability of the background when a P-wave image is projected, the laminated film of the present invention, with an average reflectance of 10% to 50% for P-wave wavelengths of 400 to 700 nm at an incident angle of 60°, is preferably characterized by an average transmittance of 50% to 100% for P-wave wavelengths of 400 to 700 nm at an incident angle of 10°. This results in high average transmittance of light in the visible light region of 400 to 700 nm, thereby achieving transparency similar to transparent glass or transparent resin films. When observing the background through the laminated film from a direction perpendicular to the surface of the laminated film, good visual recognizability of the background can be obtained.

[0101] From the above perspective, the average transmittance is preferably 70% or higher, more preferably 80% or higher, and even more preferably 85% or higher. With an average transmittance of 85% or higher, the user can visually identify the background with almost no perception of the laminated film. Furthermore, from the viewpoint of feasibility, the upper limit of this average transmittance is preferably 99%. Such a laminated film can be obtained by reducing the refractive index difference between the two thermoplastic resin layers in the 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 is easily 50% or higher; if it is 0.04 or less, the transmittance is easily 70% or higher; and if the refractive index difference is 0.02 or less, the transmittance is easily 80% or higher. Furthermore, the term "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.

[0102] Next, the preferred manufacturing method of the laminated film of the present invention will be described using an example of using a crystalline polyester resin as thermoplastic resin A (layer A) and an amorphous polyester resin as thermoplastic resin B (layer B). Of course, the present invention is not limited to such an example. Furthermore, the formation of the laminated structure of the laminated film can be achieved by referring to paragraphs

[0053] to

[0063] of Japanese Patent Application Publication No. 2007-307893. Furthermore, the above description also applies to laminated films composed of three layers further including layer C.

[0103] Thermoplastic resin A and thermoplastic resin B are prepared in granular form. After drying the granules in hot air or under vacuum as needed, they are fed to various extruders. Inside the extruder, thermoplastic resin A is heated and melted at a temperature above its melting point, while thermoplastic resin B is heated and melted within ±30°C of the heating temperature of thermoplastic resin A at a temperature that does not cause uneven discharge. Next, the molten thermoplastic resin is extruded by homogenizing the extrusion volume using a gear pump or the like, and impurities and modified resins are removed by a filter or the like. These molten thermoplastic resins are then laminated into desired layers using a lamination device, formed into a sheet shape using a die, and discharged into a casting drum. Furthermore, the multi-layered molten sheet discharged from the die is extruded onto a cooling body such as a casting drum and cooled and solidified to obtain a cast film. At this time, it is preferable to use wire, strip, needle, or knife-shaped electrodes, which are electrostatically pressed into the cooling body such as the casting drum for rapid cooling and solidification. In addition, methods such as blowing air from a slit-shaped, dot-shaped, or surface-shaped device to make it come into close contact with a cooling body such as a casting drum for rapid cooling and solidification, or using rollers to make it come into close contact with a cooling body for rapid cooling and solidification, are also preferred.

[0104] As a lamination device, multi-manifold dies, feed blocks, static mixers, etc., can be used. In particular, to obtain the configuration of the present invention efficiently, it is preferable to use a feed block that comprises at least two components each having multiple micro-slits. Using such a feed block prevents the device from becoming extremely large, thus reducing foreign matter caused by thermal degradation and enabling high-precision lamination even with an extremely high number of layers. Furthermore, the lamination accuracy in the width direction is significantly improved compared to existing technologies. Moreover, with this device, since the thickness of each layer can be adjusted according to the shape (length, width) of the slits, arbitrary layer thicknesses can be easily achieved.

[0105] Then, the cast film obtained by this operation is preferably subjected to biaxial stretching. Biaxial stretching here refers to stretching along both the length and width directions. Stretching can be performed sequentially along both directions or simultaneously along both directions. Furthermore, further stretching can be performed along the length and / or width directions. The length direction refers to the direction of film movement, and the width direction refers to the direction orthogonal to the length direction within the film surface.

[0106] First, the case of successive biaxial stretching will be explained. Here, stretching along the length direction (longitudinal stretching) refers to stretching used to impart molecular orientation to the film along its length. This is typically performed by the difference in circumferential speed of the rollers. This stretching can be performed in one stage, or multiple stages can be performed using multiple rollers. The stretching ratio varies depending on the type of resin, but is generally preferred to be 2.0 to 9.0 times. If a copolymer resin of polyethylene naphthalate is used for any of the resins constituting the laminated film, a ratio of 2.0 to 7.0 times is preferred. If the goal is to produce a laminated film with a reflective band of 100 nm or more and a reflectivity of 30% or more, and a thermal shrinkage rate of at least one of the main orientation direction and the main orientation orthogonal direction at an atmosphere of 150°C of 1.5% or more, then the longitudinal stretching ratio is particularly preferred to be 3.0 times or more and 3.8 times or less. Furthermore, the stretching temperature is preferably in the range of the glass transition temperature to +100°C of the resin with a high glass transition temperature among the resins constituting the laminated film.

[0107] After performing surface treatments such as corona treatment, flame treatment, and plasma treatment on the uniaxially stretched film obtained through this operation, it can be endowed with functions such as slipperiness, easy adhesion, and antistatic properties through online coating.

[0108] Furthermore, the so-called width-direction stretching (lateral stretching) refers to stretching used to impart a width-direction orientation to the film. Typically, a tenter frame is used to hold both ends of the uniaxially stretched film with clamps while conveying it, stretching it along the width direction. The stretching ratio varies depending on the type of resin, but is generally preferred to be 2.0 to 9.0 times. If a copolymer resin of polyethylene naphthalate is used for any of the resins constituting the laminated film, a ratio of 2.0 to 7.0 times is preferred. If the goal is to produce a laminated film with a reflective band of 100 nm or more and a reflectivity of 30% or more, and a thermal shrinkage rate of at least one of the main orientation direction and the main orientation orthogonal direction at an atmosphere of 150°C of 1.5% or more and less than 4.0%, then the lateral stretching ratio is particularly preferably 3.7 times or more and 4.2 times or less. Furthermore, from the above perspective, the in-plane stretching ratio, which is the product of the longitudinal stretching ratio and the lateral stretching ratio, is preferably 11.0 times or more and 18.0 times or less, more preferably 12.0 times or more and 18.0 times or less. Furthermore, the preferred stretching temperature is the range of the glass transition temperature of the resin constituting the laminated film, which is the temperature of the resin with a high glass transition temperature, to the glass transition temperature + 120°C.

[0109] To impart planarity and dimensional stability to the biaxially stretched film obtained through this operation, heat treatment is preferably performed in a tenter frame at a temperature above the stretching temperature and below the melting point of the thermoplastic resin A. This heat treatment improves the dimensional stability of the resulting laminated film. After heat treatment, the laminated film is preferably cooled slowly and uniformly at a temperature above the glass transition temperature of the thermoplastic resin A and below the heat treatment temperature. More specifically, slow cooling is preferably performed at a temperature above 100°C and below 200°C, more preferably above 130°C and below 180°C, and even more preferably above 150°C and below 180°C. After slow cooling, the film is cooled to room temperature and then wound. Furthermore, additional stretching or relaxation treatments of 0.1% to 10% can be performed during slow cooling from the heat treatment.

[0110] Furthermore, in the laminated film of the present invention, it is preferable that the heat treatment temperature after stretching is 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 moderated, thus making it easy to set the refractive index difference between the layers (layer A, layer B) with these resins as the main components. Additionally, when an amorphous resin is used for either thermoplastic resin A or thermoplastic resin B, the heat treatment temperature is preferably below the melting point of the crystalline resin and within the range of the glass transition temperature of the crystalline resin to the glass transition temperature +120°C. Furthermore, when at least one of thermoplastic resin A and thermoplastic resin B is a crystalline polyester with naphthalene dicarboxylic acid units as the main structural unit, from the viewpoint of controlling the thermal shrinkage rate of at least one of TA-TX, the main orientation direction at 150°C, and the main orientation orthogonal direction within a suitable range, the heat treatment temperature is preferably 170°C or higher and less than 220°C, more preferably 175°C or higher and less than 215°C, even more preferably 175°C or higher and less than 210°C, and particularly preferably 175°C or higher and less than 200°C. When thermoplastic resin A and thermoplastic resin B are amorphous resins, a heat treatment process is not required.

[0111] Next, we will explain the case of simultaneous biaxial stretching. In the case of simultaneous biaxial stretching, the resulting cast film can be subjected to surface treatments such as corona treatment, flame treatment, and plasma treatment as needed, and then imparted with functions such as slip resistance, adhesion, and antistatic properties through online coating.

[0112] Next, while holding both ends in the width direction with clamps, the cast film is guided to a simultaneous biaxial tenter frame for conveying and stretching simultaneously and / or in stages along the length and width directions. Simultaneous biaxial stretching machines include pantograph type, screw type, drive motor type, and linear motor type. Drive motor type or linear motor type, which allows for arbitrary changes in the stretching ratio and enables relaxation processing in any location, are preferred. The stretching ratio varies depending on the type of resin, but generally, an area ratio of 6.0 to 30.0 times is preferred. When any of the resins constituting the laminated film is a copolymer resin of polyethylene naphthalate, an area ratio of 9.0 to 18.0 times is particularly preferred. Especially in the case of simultaneous biaxial stretching, to suppress in-plane orientation differences, it is preferable to have the same stretching ratio in the length and width directions, and the stretching speed is also approximately equal. Furthermore, the stretching temperature is preferably in the range of the glass transition temperature of the resin constituting the laminated film with a high glass transition temperature to the glass transition temperature +120°C.

[0113] The biaxially stretched film, as in the case of successive biaxial stretching, undergoes heat treatment, slow cooling, and is wound up after cooling to room temperature. Furthermore, during heat treatment, to suppress the distribution of the main orientation axis in the width direction, it is preferable to perform a relaxation treatment along the length direction momentarily before entering the heat treatment region and / or immediately after entering the heat treatment region.

[0114] The laminated body and laminated glass of the present invention will now be described. The laminated body of the present invention sequentially comprises a support 1, an intermediate layer 1, the laminated film of the present invention, an intermediate layer 2, and a support 2. Furthermore, in the laminated body of the present invention, if both support 1 and support 2 are glass, it is the laminated glass of the present invention. The laminated body and laminated glass of the present invention can include multiple of the above-mentioned components as long as they are arranged sequentially; additionally, other components can exist between the above-mentioned components. Furthermore, support 1 and support 2 can be the same component or different components, as can intermediate layer 1 and intermediate layer 2. Such a molded body and laminated glass exhibit excellent strength, especially regarding laminated glass, compared to double-glazed glass (multi-layered glass) with an air layer between two panes of glass, it has the characteristics of suppressing glass scattering and object penetration when an object collides with the glass surface. Therefore, the laminated glass of the present invention is suitable for use in applications requiring safety and crime prevention, such as windows in automobiles and buildings. Furthermore, by incorporating the laminated film of the present invention into the laminated glass, it is also possible to impart functions such as heat ray blocking, translucent mirror function, and color filter function to the laminated glass.

[0115] The laminated body using the laminated film of the present invention sequentially comprises a support 1, an intermediate layer 1, the laminated film of the present invention, an intermediate layer 2, and a support 2. Supports 1 and 2 serve to improve the strength of the laminated body. Examples of supports for obtaining the laminated body of the present invention include resins, metals, glass, and ceramics. The surface of the support can be flat or curved, and can take any shape. Examples of resins used for supports 1 and 2 include polycarbonate, cyclic polyolefins, polyarylates, polyethylene terephthalate, polymethyl methacrylate and other acrylic resins, ABS resin, triacetyl cellulose, etc. Examples of glass used for supports 1 and 2 include float glass, tempered glass, colored glass, and heat-insulating glass. If supports 1 and 2 are intended for use in applications such as heat ray reflection or projection components for head-up displays, they are preferably transparent. From the viewpoint of ensuring both strength and weight reduction, the thickness of the support is preferably 0.05 mm to 5 mm.

[0116] Intermediate layers 1 and 2 serve to bond the laminated film of the present invention to the support 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 resins, polyvinyl chloride, polyacrylates, polyisobutylene, etc. These can also be used as film-like substances or substances formed on the film surface instead of adhesives. Furthermore, adhesive modifiers, plasticizers, heat stabilizers, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, colorants, crosslinking agents, etc., can be added to these adhesives.

[0117] By providing an intermediate layer, the adhesion between the supports 1 and 2 and the laminated film of the present invention can be improved, as well as the designability, durability, weather resistance, and impact resistance of the laminate. As a method to improve the designability of the laminate, a colorant can be added to the intermediate layer. Examples of colorants include azo pigments, polycyclic pigments, lake pigments, nitro pigments, nitroso pigments, aniline black, basic blue, phthalocyanine pigments, cyanine pigments, azo dyes, anthraquinone dyes, quinoline dyes, methylene dyes, fused polycyclic dyes, reactive dyes, cationic dyes, lanthanum hexaboride, indium tin oxide, antimony tin oxide, and cesium tungsten oxide. Furthermore, 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.

[0118] Methods for obtaining laminated bodies include extrusion lamination, hot melt lamination, hot lamination, compression lamination, vacuum lamination, and autoclave lamination. Extrusion lamination involves extruding a molten resin composition for obtaining a laminated film and an intermediate layer separately from a die, laminating them with a support, and then forming the laminated article between two rollers. Hot melt lamination involves coating a laminated film or support with a resin composition for forming an intermediate layer that has melted with heat, and then laminating the laminated film with a support. Hot lamination involves heating the laminated film, the intermediate layer sheet, and the support with heated rollers while simultaneously pressing them together. Compression lamination involves heating the laminated film, the intermediate layer sheet, and the support, and then pressing them together using a press. Vacuum lamination involves heating the laminated film, the intermediate layer sheet, and the support, creating a vacuum within the apparatus, and then pressing them together. High-pressure autoclave lamination is a lamination method in which laminated films, intermediate sheets, and supports are heated and then pressurized with gas or other substances inside the apparatus.

[0119] Example

[0120] The laminated film of the present invention will be described in more detail below using examples. However, the laminated film of the present invention is not limited to the embodiments shown below.

[0121] [Methods for determining physical properties and methods for evaluating effects]

[0122] The evaluation methods for characteristic values ​​and effects are described below.

[0123] (1) Layer thickness, number of layers, and layer composition

[0124] The layer composition, number of layers, and thickness of each layer of the laminated membrane were determined using a microtome to cut cross-sections, and observation and length measurement were performed using a transmission electron microscope (TEM). Specifically, a H-7100FA TEM (manufactured by Hitachi, Ltd.) was used to magnify the membrane cross-section to 10,000–40,000 times under an accelerating voltage of 75 kV, and cross-sectional photographs were taken to determine the layer composition, number of layers, and thickness of each layer. Furthermore, to improve interlayer contrast, known staining techniques using RuO4, OsO4, etc., were employed as needed.

[0125] (2) Reflectivity and Transmittance

[0126] Using samples cut to 5cm x 5cm, reflectance and transmittance were measured under the following conditions using the integrating sphere of a Hitachi U-4100 spectrophotometer. For reflectance measurement, the sample was positioned vertically behind the integrating sphere. Reflectance was calculated as relative reflectance using an alumina sub-white plate attached to the apparatus as a reference. The average reflectance for wavelengths from 900 to 1200 nm was calculated by averaging the reflectance per 1 nm. Measurements were taken on both sides of the sample, and the result from the side with the higher average reflectance for wavelengths from 900 to 1200 nm was used. For transmittance measurement, the sample was positioned vertically in front of the integrating sphere. The average transmittance for wavelengths from 400 to 700 nm was calculated by averaging the transmittance per 1 nm. Measurements were taken on both sides of the sample, and the result from the side with the higher average transmittance for wavelengths from 400 to 700 nm was used.

[0127] <Measurement Conditions>

[0128] Slit: 2nm (visible) / Automatic control (infrared)

[0129] Gain: 2

[0130] Scanning speed: 600nm / minute

[0131] Starting wavelength: 2600nm

[0132] End wavelength: 240nm

[0133] Sampling interval: 1nm

[0134] Angle of incidence: 10°.

[0135] (3) Reflectivity of P-wave at 60°

[0136] By installing the variable-angle reflectance unit and Glan-Taylor polarizer of the Hitachi U-4100 Spectrophotometer, with the azimuth angle of the principal orientation direction of the film surface at 0° as a reference, the reflectance of P-waves in the wavelength range of 400–700 nm at an incident angle θ = 60° was measured every 1 nm along a clockwise azimuth direction. The reflectance of P-waves at 60° was then calculated by using the obtained reflectance as the average reflectance of P-waves in the wavelength range of 400–700 nm at an incident angle of 60° in each azimuth direction.

[0137] <Measurement Conditions>

[0138] Slit: 2nm (visible) / Automatic control (infrared)

[0139] Gain: 2

[0140] Scanning speed: 600nm / minute

[0141] Starting wavelength: 700nm

[0142] End wavelength: 400nm

[0143] Sampling interval: 1nm.

[0144] (4) Melting point, glass transition temperature (TA), crystallization temperature, heat of fusion

[0145] A 5g sample was taken, and the melting point, glass transition temperature, crystallization temperature, and heat of fusion were determined using a differential scanning calorimeter (Robot DSC-RDC220 manufactured by Seiko Electronics Co., Ltd.) according to JIS-K-7121 (1987). In cases where multiple glass transition temperatures exist, the higher temperature was designated as the glass transition temperature TA. During the measurement, the sample was heated from 25°C to 290°C at a rate of 5°C / min.

[0146] (5) Internal fog

[0147] Three square-shaped laminated membrane samples, each with one side measuring 5 cm, were prepared and placed in a normal environment (23°C, 50% relative humidity) for 40 hours. Then, the internal haze of each sample was measured using a NDH5000 turbidimeter manufactured by Nippon Denshoku Kogyo Co., Ltd., according to JIS-K-7105 (1981). To eliminate light scattering caused by the unevenness of the laminated membrane sample surface, the measurement was performed while the sample was immersed in a quartz cell filled with liquid paraffin. The average internal haze values ​​of each sample were taken as the internal haze of the laminated membrane.

[0148] (6) Appearance of the laminate

[0149] (Construction of layered structures)

[0150] Nisshinbo LAMINATOR 0303S was used in the fabrication of the laminate. First, 3mm thick, 10cm square glass plates were overlapped on both sides of the laminate as supports. A 0.76mm thick PVB (polyvinyl butyral) interlayer was placed between the laminate and the supports. The laminated component was then heated from 25°C to 150°C at a rate of 3°C / min, then depressurized at 600mmHg for 5 minutes, and pressed for 30 minutes at a pressure of 0.1MPa. It was then slowly cooled at 3°C / min until it reached 35°C, and the pressing was released to obtain the laminate (150°C). Furthermore, a laminate (120°C) was obtained under the same conditions, except that the temperature was increased from 25°C to 120°C at a rate of 3°C / min.

[0151] (Evaluation of uneven color)

[0152] A straight-tube white 3-wavelength fluorescent lamp and a laminate were horizontally positioned along the main orientation direction and fixed at a distance of 30 cm from each other along the normal direction. The evaluation section was visually evaluated at angles of 20°, 50°, and 70° relative to the normal direction of the evaluation section. The evaluation criteria are as follows, with S and A set as good results.

[0153] S: No color unevenness can be seen from any angle.

[0154] A: Although very slight color unevenness can be seen when viewed from at least one angle, no obvious color unevenness can be seen in any part or the whole of the molded body when viewed from any angle.

[0155] C: When observed from at least one angle, obvious color unevenness can be seen in part or the whole of the molded body.

[0156] (Appearance Evaluation)

[0157] A straight-tube white 3-wavelength fluorescent lamp and a laminate were horizontally positioned along the main orientation direction and fixed at a distance of 30 cm from each other along the normal direction. The evaluation section was visually evaluated at angles of 20°, 50°, and 70° relative to the normal direction of the evaluation section. The evaluation criteria are as follows, with S and A being considered good results. The same observation was also made when the fluorescent lamp was horizontally positioned in a direction orthogonal to the main orientation direction.

[0158] S: No wrinkles or bumps can be seen from any angle.

[0159] A: Although very slight wrinkles and bumps can be seen when viewed from at least one angle, no obvious wrinkles or bumps can be seen in any part or the whole of the molded body when viewed from any angle.

[0160] C: When observed from at least one angle, obvious wrinkles and unevenness can be seen in part or the whole of the molded body.

[0161] (7) Specific orientation direction

[0162] The sample size of the laminated membrane was set to 10cm × 10cm, and the sample was cut out at the center of the membrane width. The degree of orientation was measured using a molecular orientation meter MOA-2001 manufactured by KS Systems Co., Ltd. (now Oji Keiseki Kogyo Co., Ltd.), and the direction with the greatest degree of orientation was set as the main orientation direction.

[0163] (8) Shrinkage start temperature TX, TY

[0164] The laminated film sample was cut into a rectangular shape with a main orientation direction (measurement direction) of 40 mm and a direction orthogonal to the main orientation direction of 4 mm. The measurement was performed using a "TMA SS6100" manufactured by Hitachi Technology Co., Ltd., under the following measurement conditions.

[0165] <Measurement Conditions>

[0166] Heating temperature: 25℃~200℃

[0167] Heating rate: 10℃ / minute

[0168] Duration: 10 minutes

[0169] Sampling: 2 seconds

[0170] Then, the temperature at which the output displacement value TMA changes from positive to negative within the range of 40–150°C is set as the shrinkage initiation temperature TX. If the TMA value at 40°C is negative, the shrinkage initiation temperature TX is set to 40°C. If multiple temperatures show a change from positive to negative, the lowest temperature is set as the shrinkage initiation temperature TX. This measurement was performed five times, and the average value was used as the shrinkage initiation temperature TX. Regarding the shrinkage initiation temperature TY, the sample was cut into a rectangular shape with a diameter of 40 mm in the direction orthogonal to the main orientation direction (measurement direction) and 4 mm in the main orientation direction, and the measurement was performed similarly.

[0171] (9) Thermal shrinkage rate (at 150℃ and 120℃ atmospheres)

[0172] The sample was cut into a rectangle measuring 150 mm (measurement direction) × 10 mm, and marked at 100 mm intervals along the measurement direction of the sample. The interval of the marks was measured using a Nikon universal projector (Model V-16A), and this value was set as A. Next, the sample was suspended in a GIL aging chamber with a load of 3 g and placed in an atmosphere of 150 °C or 120 °C for 30 minutes. After the sample was removed and cooled, the interval of the previously marked marks was measured and set as B. The thermal shrinkage rate in the measurement direction was calculated using the following formula (4). In addition, the measurement direction was set as the main orientation direction and the main orientation orthogonal direction, and the n number of each direction was set to 3. The average value of these directions was used as the value of the thermal shrinkage rate.

[0173] Heat shrinkage rate (%) = 100 × (AB) / A Equation (4).

[0174] (10) In-plane refractive index of the surface (layer A)

[0175] The in-plane refractive index of the surface layer (layer A) was determined using a SAIRON TECHNOLOGY, INC. "SPA-4000" under the following conditions. The average of the refractive index in the principal orientation direction and the refractive index in the direction orthogonal to the principal orientation of the laminated polyester film sample was taken as the in-plane refractive index. In addition, the principal orientation direction was specified by method (7), and the direction orthogonal to the principal orientation direction was taken as the direction orthogonal to the principal orientation direction in the film surface.

[0176] Laser: Wavelength 632.8nm

[0177] Prism: GGG prism.

[0178] (11) In-plane refractive index of layer B

[0179] Since layer B is an inner layer of the laminated film, the measurement is not performed on the film itself. Instead, a single-layer film of layer B, fabricated under the same stretching / heat treatment conditions as the original film, is measured using a SAIRON TECHNOLOGY, INC. "SPA-4000" instrument under the following conditions. However, unlike the resin in layer A, the resin in layer B is amorphous, and stretching does not change its orientation; therefore, there is no dominant orientation direction. Thus, the average of the refractive index along the length and width of this single-layer film is taken as the in-plane refractive index.

[0180] Laser: Wavelength 632.8nm

[0181] Prism: GGG prism.

[0182] (12) Evaluation of Head-Up Displays

[0183] The light source used was a display (SP-133CM) manufactured by Dreame Manufacturing Co., Ltd. The projection image display component was positioned such that the angle of incidence of the light from the light source relative to the normal direction of the projection image display component surface was 60°. An image was projected from the light source onto the projection image display component via P-waves or S-waves. The display quality of the projected image was then evaluated visually.

[0184] (Evaluation criteria for the display performance of projected images)

[0185] S: The projected image is very bright.

[0186] A: The projected image is bright.

[0187] C: The projected image is dark.

[0188] [The resin used in the manufacture of laminated films]

[0189] The following resins were used as the resins for layer A and layer B in the manufacture of the laminated film.

[0190] (The resin used in layer A)

[0191] PEN(1): 4 mol% of polyethylene 2,6-naphthalenedicarboxylate (intrinsic viscosity: 0.64, melting point: 260℃, glass transition temperature: 104℃) was copolymerized with polyethylene glycol of average molecular weight 400 relative to all glycol components.

[0192] PEN(2): Polyethylene glycol with an average molecular weight of 400 was copolymerized with 6 mol% of polyethylene 2,6-naphthalenedicarboxylate (intrinsic viscosity: 0.64, melting point: 255℃, glass transition temperature: 97℃) relative to all glycol components.

[0193] PET(2): Polyethylene terephthalate (intrinsic viscosity: 0.65, melting point: 254℃, glass transition temperature: 78℃).

[0194] (Resin used for layer B)

[0195] 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% cyclohexanediol (CHDM) relative to all glycol components and polyethylene terephthalate (manufactured by Tore Co., Ltd., intrinsic viscosity: 0.65, melting point: 256°C, glass transition temperature: 80°C) at a mass ratio of 82:18 (melting point: 225°C, glass transition temperature: 79°C).

[0196] PET(3): Polyethylene terephthalate resin copolymerized with 30 mol% 2,6-naphthalenedicarboxylic acid relative to all dicarboxylic acid components (intrinsic viscosity: 0.67, no melting point, glass transition temperature: 95℃).

[0197] (Example 1)

[0198] PEN(1) was used as the polyester resin (thermoplastic resin A) to form layer A, and PET(1) was used as the polyester resin (thermoplastic resin B) to form layer B. The polyester resins forming each layer were melted at 280°C using a twin-screw extruder with vents. The melted resins were then combined using a 449-layer feed block via a gear pump and filter, with the outermost layers on both sides forming layer A. 449 layers of molten thermoplastic resin A and thermoplastic resin B were alternately stacked along the thickness direction. The resulting molten stack was then guided to a T-die to be formed into a sheet and discharged. The molten sheet was then electrostatically cooled and solidified on a casting drum at a surface temperature of 25°C to obtain a cast film. The discharge rate was adjusted to approximately a 1:1 mass ratio of thermoplastic resin A to thermoplastic resin B. Next, the resulting cast film was heated using rollers set to a temperature of +10°C the glass transition temperature of thermoplastic resin A. While being rapidly heated from both sides by a radiant heater within a 100mm stretching section, it was stretched 3.2 times longitudinally (length direction) and temporarily cooled. Then, both sides of the uniaxially stretched film were subjected to corona discharge treatment in air to achieve a wetting tension of 55mN / m. A 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 100nm was applied to both sides, forming a transparent and slip-resistant, easily bondable layer. The uniaxially stretched film was then held at both ends in the width direction by clamps and guided to a tenter frame. After preheating with hot air at 100°C, it was stretched 4.0 times transversely (width direction) at a uniform stretching speed at a temperature of +20°C the glass transition temperature of thermoplastic resin A. Further, in the same tenter frame, the stretched film was heat-treated with hot air at 195°C. After a 1% relaxation treatment along the width direction at the same temperature, it was further stretched by 1% along the width direction in a cooling zone at 150°C, and then slowly cooled to room temperature before being wound. The winding machine traction was set to 98%. The winding machine traction is the ratio of the tenter frame speed to the winding machine speed; 98% winding machine traction means the tenter frame speed is 2% slower than the winding machine speed. The resulting laminated film had a thickness of 90 μm. The evaluation results are shown in Tables 2-1, 2-2, 4-1, and 4-2.

[0199] (Examples 2-17, Comparative Examples 1-7)

[0200] The resins used for each layer, the number of layers, the film-forming conditions, and the thickness were changed as shown in Tables 1, 2-1, 2-2, 3, 4-1, and 4-2. Otherwise, the laminated films were produced under the same conditions as in Example 1. The evaluation results of the resulting laminated films are shown in Tables 2-1, 2-2, 4-1, and 4-2. Furthermore, the number of layers was adjusted by adjusting the number of slits in the feed block, and the thickness was adjusted by changing the overall speed of the film-forming production line, which is linked to the speed of the casting drum.

[0201]

[0202] Industry availability

[0203] This invention can be used in decorative materials such as decorative panels, various household appliances, building components, automotive-related parts, etc., and in particular, it can be used as heat-blocking glass that can suppress the inflow of heat caused by sunlight.

Claims

1. A laminated film, characterized in that, It is a laminated film consisting of 51 or more layers of two or more different thermoplastic resins regularly stacked together. When the highest glass transition temperature determined by differential scanning calorimetry (DSC) is set as TA, and the shrinkage start temperature determined by the TMA curve of the main orientation direction is set as TX, the TX is 5°C or more lower than the TA and 30°C or less.

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

3. The laminated film according to claim 1 or 2, wherein, in an atmosphere at 150°C, the thermal shrinkage rate of at least one of the main orientation direction and the main orientation orthogonal direction is more than 1.5% and less than 4.0%.

4. The laminated film according to claim 1 or 2, comprising a layer of polyester as the main component, wherein the polyester uses naphthalene dicarboxylic acid units as the main structural units.

5. The laminated film according to claim 1 or 2, characterized in that, When the shrinkage start temperature obtained from the TMA curve of the main orientation orthogonal direction is set as TY, the difference between TY and TX is above 0°C and below 10°C.

6. The laminated film according to claim 1 or 2, characterized in that, The TY is at least 5°C lower than the TA but less than 30°C.

7. In the laminated film according to claim 1 or 2, when the average value of its heat shrinkage rate at 150°C is set as S(150) and the average value of its heat shrinkage rate at TA is set as S(TA), S(150) / S(TA) is 1.5 or more and 5.0 or less.

8. In the laminated film according to claim 1 or 2, when the average value of its heat shrinkage rate at 120°C is set as S(120) and the average value of its heat shrinkage rate at TA is set as S(TA), S(120) / S(TA) is 1.5 or more and 5.0 or less.

9. The laminated film according to claim 1 or 2, wherein the film has a reflective band of 100 nm or more such that when light is incident on the film surface at an incident angle of 10° and a wavelength of 800 to 2000 nm, the reflectivity is 30% or more.

10. The laminated film according to claim 1 or 2, wherein the average reflectivity of P-waves with wavelengths of 400-700 nm at an incident angle of 60° is 10% or more and 50% or less.

11. The laminated film according to claim 1 or 2, wherein the internal haze is less than 0.5%.

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

13. A laminate comprising, in sequence, a support 1, an intermediate layer 1, a laminated film of claim 1 or 2, an intermediate layer 2, and a support 2.

14. A laminated glass, wherein the support 1 and support 2 in the laminate of claim 13 are both glass.

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