Laminated film

Abstract

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

Description

[Technical Field]

[0001] This invention relates to a laminated film. [Background technology]

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

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

[0004] Examples of such heat-cutting glass include glass in which a heat-absorbing material is incorporated into the glass or an interlayer used in laminated glass to block heat rays with the heat-absorbing material (for example, Patent Document 1), glass in which a metal film is formed by sputtering or the like to reflect and block heat rays and is bonded to the glass (for example, Patent Document 2), and glass in which a laminated film in which polymers with different refractive indices are alternately layered is inserted between the glass and the interlayer to reflect and block heat rays (for example, Patent Document 3).

[0005] However, the method described in Patent Document 1 has the problem that sunlight incident from the outside is converted into thermal energy, and this heat is radiated into the room, reducing the heat ray blocking efficiency. In addition, this method causes the glass temperature to rise partially due to the absorption of heat rays, and the glass itself may break due to the difference with the outside temperature. The method described in Patent Document 2 reflects not only heat rays but also visible light, making it prone to coloring, and it also shields against electromagnetic waves, which may adversely affect the use of communication equipment inside. On the other hand, the laminated film described in Patent Document 3 can select the wavelength to be reflected by controlling its layer thickness, so it can selectively reflect light in the near-infrared region that contributes to temperature rise, and can improve heat ray blocking performance while maintaining visible light transmittance. Furthermore, because it does not contain components that block radio waves, such as metals, it maintains excellent radio wave transmittance.

[0006] Furthermore, when obtaining laminated films such as those shown in Patent Document 3 by melt extrusion, for reasons such as transparency, heat resistance, weather resistance, chemical resistance, strength, and dimensional stability, a polyester resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) is used as the main component of one resin layer, and a thermoplastic resin with different optical properties from the polyester resin (e.g., copolymerized polyester) is used for the other resin layer (for example, Patent Documents 4-6). In particular, when polyethylene naphthalate is used as the main component of one resin layer, the refractive index difference with the low refractive index copolymerized polyester can be increased, making it possible to obtain laminated films with high reflectivity. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2010-17854 [Patent Document 2] Japanese Patent Publication No. 2001-310407 [Patent Document 3] International Publication No. 2005 / 040868 [Patent Document 4] Japanese Patent Publication No. 2005-059332 [Patent Document 5] Japanese Patent Publication No. 2004-249587 [Patent Document 6] International Publication No. 2013 / 137288 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Since such heat-cut glass is often used in places visible to people, such as windows in vehicles and buildings, appearance is an important factor. However, in the embodiment of lamination described in Patent Document 3, there is a problem in that unevenness in the laminated film occurs during molding due to uneven pressure caused by thickness variations in the interlayer used for lamination with the support, and differences in thermal shrinkage stress with the interlayer, which impairs the appearance. In particular, since such laminated films utilize interference reflection phenomena by controlling the layer thickness, changes in layer thickness due to uneven distortion make color variations and optical defects within the film surface more noticeable. Furthermore, in such laminated films, wrinkles tend to occur when they are laminated with a support or interlayer during molding. This is a problem that mainly occurs at the edges of the molded body, caused by the laminated film's inability to follow the shape of the support during molding and differences in thermal shrinkage rates with the interlayer.

[0009] Furthermore, as described in Patent Documents 4 and 5, when a laminated film is made by melt extrusion consisting of a layer mainly composed of polyethylene naphthalate and a layer of copolymerized polyester with a relatively low refractive index, the relatively high rigidity of the polyethylene naphthalate-dominant layer makes it difficult to deform, making it difficult to apply to applications where the laminated film is deformed and processed. For example, when a support, an interlayer, and a laminated film are laminated and formed, wrinkles and uneven distortions may occur, which presents a problem as it is difficult to apply to the final product.

[0010] On the other hand, as described in Patent Document 6, when a laminated film is made by melt extrusion consisting of a layer mainly composed of polyethylene terephthalate and a layer of copolymerized polyester with a relatively low refractive index, the layer has lower rigidity compared to polyethylene naphthalate, making it easier to deform and suitable for applications where the laminated film is deformed and processed. However, since polyethylene terephthalate has a lower refractive index than polyethylene naphthalate, the reflectivity of the laminated film is lower, resulting in inferior performance as a final product.

[0011] The present invention aims to solve the above problems and provide a laminated film in which an interlayer and a support are arranged on at least one surface of the laminated film, which reduces the occurrence of uneven distortion and color unevenness due to molding involving heating and pressurization, and improves the appearance and design when it is made into a molded product. [Means for solving the problem]

[0012] To solve the above problems, the present invention has the following configuration. [1] A laminated film having a structure in which 51 or more layers of two or more different thermoplastic resin layers are regularly stacked, characterized in that when the highest glass transition temperature determined by differential scanning calorimetry (DSC measurement) is denoted as TA and the shrinkage start temperature determined from the TMA curve in the main orientation direction is denoted as TX, the TX is 5°C or more and 30°C or less lower than the TA. [2] The laminated film according to [1], wherein, in the atmosphere of TA, the thermal shrinkage rate in at least one of the principal orientation direction and the direction perpendicular to the principal orientation is 0.5% or more and 1.2% or less. [3] The laminated film according to [1] or [2], wherein, in an atmosphere of 150°C, the thermal shrinkage rate in at least one of the principal orientation direction and the direction perpendicular to the principal orientation is 1.5% or more and less than 4.0%. [4] A laminated film according to any one of [1] to [3], comprising a layer mainly composed of polyester having naphthalenedicarboxylic acid units as its primary constituent units. [5] When the shrinkage start temperature obtained from the TMA curve in the direction orthogonal to the main alignment direction is TY, the laminated film according to any one of [1] to [4], wherein the difference between TY and TX is 0 ° C or more and 10 ° C or less. [6] The laminated film according to any one of [1] to [5], wherein TY is 5 ° C or more and 30 ° C or less lower than TA. [7] When the average value of the thermal shrinkage rate at 150 ° C is S(150) and the average value of the thermal shrinkage rate at TA is S(TA), the laminated film according to any one of [1] to [6], wherein S(150) / S(TA) is 1.5 or more and 5.0 or less. [8] When the average value of the thermal shrinkage rate at 120 ° C is S(120) and the average value of the thermal shrinkage rate at TA is S(TA), the laminated film according to any one of [1] to [7], wherein S(120) / S(TA) is 1.5 or more and 5.0 or less. [9] The laminated film according to any one of [1] to [8], which has a reflection band with a reflectance of 30% or more and a width of 100 nm 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.

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

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

[10] , wherein the internal haze is 0.5% or less.

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

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

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

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

[13] are glass.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a laminated film that can reduce the occurrence of uneven distortion and color unevenness due to molding involving heating and pressing, and can improve the appearance and designability when formed into a molded body. [Modes for carrying out the invention]

[0014] The laminated film of the present invention is a laminated film having a structure in which 51 or more layers of two or more different thermoplastic resin layers are regularly laminated, and is characterized in that when the highest glass transition temperature determined by differential scanning calorimetry (DSC measurement) is denoted as TA and the shrinkage start temperature determined from the TMA curve in the main orientation direction is denoted as TX, the TX is 5°C to 30°C lower than the TA. Embodiments of the present invention will be described below, but the present invention is not to be interpreted as being limited to embodiments including the following examples, and various modifications are naturally possible as long as the objective of the invention is achieved and the gist of the invention is not departed. Also, for the purpose of simplifying the explanation, some descriptions will use a laminated film in which two different polyester resin layers (referred to as layer A and layer B) are regularly laminated as an example, but the same should be understood when three or more polyester resin layers are used or when thermoplastic resin layers other than polyester resin are used.

[0015] The laminated film of the present invention has a structure in which 51 or more layers of two or more different thermoplastic resin layers are regularly laminated, preferably a structure in which 51 or more layers of two or more thermoplastic resin layers with different main components are regularly laminated. Here, "main component" refers to a component that is present in an amount exceeding 50% by mass and not exceeding 100% by mass when the total components constituting the thermoplastic resin layer are taken as 100% by mass, and the same interpretation can be applied to the main component hereafter. "The thermoplastic resin layers are different" means that when comparing two thermoplastic resin layers, at least one of the following 1 to 3 is met, preferably at least "2" below. Note that if there are three or more types of thermoplastic resin layers, for them to all be different, it is necessary that when comparing any combination of two thermoplastic resin layers, at least one of the following 1 to 3 is met (the same applies when there are four or more types of thermoplastic resin layers). 1: The refractive index differs by 0.01 or more in the principal orientation direction (the method for determining the principal orientation direction will be described later). 2: Having different melting points or crystallization temperatures (A "different melting point or crystallization temperature" means that either the melting point or the crystallization temperature, as determined by the measurement method described below, differs by 3°C or more. This also applies if one thermoplastic resin layer has a melting point and the other does not, or if one thermoplastic resin layer has a crystallization temperature and the other does not.) 3. The composition analyzed by nuclear magnetic resonance spectroscopy or gas chromatography-mass spectrometry differs by 5 mass% or more.

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

[0017] Generally, in laminated films with this type of layer structure, due to the principle of interference reflection, a higher reflectivity can be obtained over a wider bandwidth as the number of constituent layers increases. Therefore, the number of regularly stacked layers is preferably 101 or more, and more preferably 401 or more. For the reasons above, a higher number of layers in a laminated film is preferable, but in reality, the practical range is 1001 layers or less, considering the increase in manufacturing costs due to the need for larger manufacturing equipment as the number of layers increases, and the deterioration of handling due to the increased thickness of the laminated film itself.

[0018] From the viewpoint of use in heat ray reflection applications, the laminated film of the present invention preferably has a reflective band of 100 nm or more in which the reflectance is 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. "Having a reflective band of 100 nm or more in which the reflectance is 30% or more" means having at least one band in which the reflectance is 30% or more continuously over a wavelength of 100 nm or more.

[0019] Sunlight primarily exhibits an intensity distribution in the visible light region, with this distribution tending to decrease as the wavelength increases. However, for applications requiring high transparency, such as heat-cutting glass, both transparency and high heat-cutting performance are 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 achieves both transparency and high heat-cutting performance.

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

[0021] Such laminated films can be realized by increasing the difference in in-plane refractive index between two or more resins with different optical properties. For biaxially oriented films, it is preferable to have a laminated film in which layers mainly composed of crystalline polyester resin and layers mainly composed of thermoplastic resin that can maintain amorphousness even when stretched or that melts in the heat treatment process are alternately laminated (in other words, it is preferable to have a laminated film in which layers mainly composed of crystalline thermoplastic resin and layers of thermoplastic resin that can maintain amorphousness even when stretched or that melts in the heat treatment process are alternately laminated). Furthermore, in order to have a laminated film with a reflectivity of 30% or more and a reflectivity band of 100 nm or more, it is also effective to set the in-plane stretching ratio (product of the stretching ratio in the longitudinal direction (film transport direction, also called the longitudinal direction) and the stretching ratio in the transverse direction (width direction in the film plane in the transport direction)) to 9.0 times or more and to increase the number of layers. To achieve the above-mentioned preferred range for the average reflectance at wavelengths of 900 to 1200 nm, it is effective to increase the in-plane stretching ratio or the number of layers within that range.

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

[0023] As used herein, "crystalline" means that the heat of fusion is 5 J / g or more in differential scanning calorimetry (DSC). On the other hand, "amorphous" means that the heat of fusion is less than 5 J / g in the same manner. The crystalline polyester resin can have a higher in-plane refractive index than in the amorphous state before stretching by orientation crystallization in the stretching / heat treatment step. On the other hand, in the case of an amorphous polyester resin, by performing heat treatment at a temperature far exceeding the glass transition temperature in the heat treatment step, even the slight orientation generated in the stretching step can be greatly relaxed, and the low refractive index of the amorphous state can be maintained. By adopting such a laminated structure, a refractive index difference can be easily provided between the crystalline polyester resin and the amorphous polyester resin in the stretching and heat treatment steps in the production of the laminated film.

[0024] In the case of a laminated film having a structure in which two types of layers mainly composed of thermoplastic resins having different crystallinities are alternately laminated, from the viewpoint of suppressing adhesion to rolls or the like during film formation, it is preferable that the outermost layers on both sides be relatively highly crystalline layers (layers mainly composed of crystalline thermoplastic resins). Hereinafter, a laminated film having such a structure will be described. Unless otherwise specified, a relatively highly crystalline layer will be described as layer A and a lower layer as layer B.

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

[0026] Here, λ is the reflection wavelength, n α is the in-plane refractive index of layer A, d α is the thickness of layer A, n β is the in-plane refractive index of layer B, d βis the thickness of layer B, and m is the order, both of which are natural numbers. By having a layer thickness distribution that satisfies both equation (1) and equation (2) simultaneously, even-order reflections can be eliminated. Therefore, it is possible to increase the average reflectance in the wavelength range of 900 nm to 1200 nm while lowering the average reflectance in the visible light region, which is the wavelength range of 400 nm to 800 nm, thereby obtaining a laminated film with excellent transparency and high heat-cutting performance.

[0027] Generally, the in-plane refractive index of the film surface after molding and stretching a thermoplastic resin is approximately 1.4 to 1.9. Therefore, by setting the ratio of the thicknesses of adjacent A and B layers (thickness of A layer / thickness of B layer) to 0.7 or more and 1.4 or less, a laminated film with suppressed even-order reflections can be obtained. Accordingly, from the above viewpoint, it is preferable to set the ratio of the thicknesses of adjacent A and B layers (thickness of A layer / thickness of B layer) to 0.7 or more and 1.4 or less, and more preferably to 0.8 or more and 1.2 or less. By setting the thicknesses of adjacent A and B layers within this range, the average reflectance at wavelengths of 400 to 800 nm can be preferably 20% or less, and more preferably 15% or less. As a result, reflection in the visible light region of the laminated film can be suppressed, and coloration and glare can be reduced.

[0028] 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 must be different from each other. As thermoplastic resins A and B, polyester resin, acrylic resin, polycarbonate resin, etc., can be used. Among these, polyester resin is preferred as thermoplastic resin A and thermoplastic resin B because of its excellent transparency and moldability. Furthermore, if the laminated film further has a layer C, and the main component of layer C is thermoplastic resin C, then it is preferable that thermoplastic resin C is also a polyester resin. Here, polyester resin refers to a polymer obtained by condensation polymerization of dicarboxylic acid components and diol components.

[0029] In the laminated film of the present invention, examples of dicarboxylic acid units in the polyester resins used in thermoplastic resin A, thermoplastic resin B, and thermoplastic resin C include 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'-diphenylsulfondicarboxylic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid, and their ester-forming derivatives.

[0030] Examples of diol units in the above-mentioned polyester resin include ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, diethylene glycol, polyalkylene glycol, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, isosorbate, 1,4-cyclohexanedimethanol, spiroglycol, neopentyl glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, triethylene glycol, tetraethylene glycol, polytetramethylene ether glycol, and ester-forming derivatives thereof.

[0031] Preferred dicarboxylic acid units constituting the polyester resin include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, and other constituent units. Preferred diol units include ethylene glycol, 1,4-cyclohexanedimethanol, polyalkylene glycol, polyethylene glycol, tetraethylene glycol, and polytetramethylene ether glycol.

[0032] One preferred embodiment of the laminated film of the present invention is one in which the in-plane refractive index of at least one surface of the laminated film is 1.68 or more and 1.80 or less. Generally, the surface layer is preferably a layer with relatively high crystallinity considering ease of film formation, etc., but by having an in-plane refractive index of 1.68 or more for this surface layer, the difference in in-plane refractive index with the relatively less crystallinity layer can be made large. As a result, it becomes easy to make the laminated film having a reflectance band of 100 nm or more in which the reflectance is 30% or more. On the other hand, by having an in-plane refractive index of less than 1.80 for the surface layer, deterioration of inter-layer adhesion between the two layers that are alternately laminated is suppressed, and clouding of the laminated film and delamination at the interface are reduced.

[0033] From the above viewpoint, it is preferable that the laminated film of the present invention has a crystalline polyester as the main component of layer A, in which naphthalenedicarboxylic acid units are the main constituent units. By adopting this configuration, the reflectivity on the surface of layer A is increased, and it becomes easy to create a refractive index difference with layer B, so that a laminated film with superior reflectivity can be obtained. Note that "naphthalenedicarboxylic acid units as the main constituent units" means that naphthalenedicarboxylic acid units account for more than 50 mol% and up to 100% by mass of the total dicarboxylic acid constituent units of the polyester resin.

[0034] Examples of naphthalenedicarboxylic acids that form the constituent units of the crystalline polyester resin in layer A include 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,3-naphthalenedicarboxylic acid, with 2,6-naphthalenedicarboxylic acid being particularly preferred. When layer B is mainly composed of an amorphous thermoplastic resin, the more naphthalenedicarboxylic acid units there are in the crystalline polyester resin that is the main component of layer A, the easier it is to increase the refractive index difference between layer A and layer B. Therefore, the naphthalenedicarboxylic acid units in the dicarboxylic acid units of the crystalline polyester resin that is the main component of layer A are more preferably 80 mol% to 100% by mass, and even more preferably 95 mol% to 100% by mass. Also, from a similar viewpoint, the content of the crystalline polyester resin in layer A is preferably 80% to 100% by mass, and more preferably 95% to 100% by mass, when the entire layer is considered as 100% by mass.

[0035] 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 0.14 to 0.35. If the difference in the average in-plane refractive index is less than 0.05, it may be difficult to have a reflectivity band of 30% or more. An example of how to achieve this is to use a crystalline polyester resin as the main component of layer A and an amorphous thermoplastic resin as the main component of layer B. In this case, it is possible to easily create a refractive index difference in the stretching and heat treatment processes during the manufacturing of the laminated film.

[0036] From the viewpoint of reflectivity, a larger difference in in-plane refractive index between layer A and layer B is preferable. However, increasing the difference in in-plane refractive index would require significantly different chemical structures for the thermoplastic resins that are the main components of both layers, which would worsen interlayer adhesion. Considering this, keeping the difference in the average in-plane refractive index between layer A and layer B to 0.35 or less facilitates lamination and improves the heat resistance and handling properties of the resulting laminated film.

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

[0038] When laminated glass is formed by laminating a laminated film with a support and an interlayer, heating and pressurization are performed to improve the adhesion between each component. In this molding process, where heat and pressure are applied, unevenness in the interlayer thickness and differences in thermal shrinkage stress between the interlayer and the laminated film can cause uneven distortion and changes in thickness in the laminated film. When such uneven distortion and thickness variations occur, light scattering and diffuse reflection occur, as well as color unevenness within the film surface, resulting in a poor appearance of the molded product. On the other hand, since the glass support hardly deforms at this time, the shape of the interlayer is hardly relaxed by the support. Because laminated films have interfaces formed from different thermoplastic resin layers, scattering and reflection at the interfaces are added in addition to the scattering and diffuse reflection of light from the film surface, making unevenness more noticeable than in films made of a single type of resin. Therefore, if it is possible to use a laminated film that is less prone to unevenness, the problem of poor appearance of molded products can be resolved.

[0039] When forming a laminated film by laminating it with a support and an interlayer, it is common practice to first bond the laminated film and interlayer at a low temperature (pre-lamination process, sometimes referred to as the pre-lamination process), and then bond it to the support by applying pressure at a higher temperature (main bonding process). While there are no particular limitations on the pre-lamination method, it is common to sandwich the film between two interlayers and roll-laminate it at a temperature of 90-100°C, slightly higher than the glass transition temperature of the polyester resin. While there are no particular limitations on the main bonding method, it is common to sandwich the sheet after the pre-lamination process between a support such as glass and bond it in an autoclave (pressure-heated bonding furnace) at 140-150°C for 20-30 minutes under a pressure of 12-14 kg / cm². 2 It is common to crimp them together.

[0040] During this process, the laminated film and interlayer become more flexible and shrink during the pre-lamination and main bonding processes. Significant differences in these flexibility and shrinkage behaviors can lead to bubbles, wrinkles, and uneven coloring within the surface. Therefore, it is necessary for the laminated film to shrink not only during the main bonding process, which is performed at higher temperatures, but also at lower temperatures, such as during the pre-lamination process; in other words, the shrinkage initiation temperature must be lower than the glass transition temperature.

[0041] Generally, thermoplastic resin films are processed into sheets from pellets by melt extrusion and then stretched and processed at a temperature higher than the glass transition temperature. As a result, the oriented crystals formed at a temperature higher than the glass transition temperature are relaxed upon reheating, and shrinkage proceeds rapidly. However, in such films, even if it is possible to follow the shrinkage of the interlayer in either the main bonding process or the pre-lamination process, shrinkage will be insufficient or excessive at the other temperature, resulting in bubbles, wrinkles, and uneven coloring within the surface. The present invention has found that the above problems can be solved by designing the laminated film so that shrinkage begins at a temperature 5°C to 30°C lower than the highest glass transition temperature (in other words, setting TA-TX to 5°C to 30°C).

[0042] When the glass transition temperature is denoted as TA and the shrinkage onset temperature determined from the TMA curve in the main orientation direction as TX, if TX is 5°C to 30°C lower than TA, the occurrence of bubbles, wrinkles, and color unevenness within the plane can be suppressed, making it possible to obtain a molded article with excellent appearance (especially the appearance in the main orientation direction). From the above viewpoint, it is more preferable that TX be 10°C to 30°C. If TA-TX exceeds 30°C, the laminated film becomes too flexible, which can lead to poor productivity and poor handling during molding. Also, if TA-TX is below 5°C, bubbles and wrinkles are more likely to occur, resulting in poor appearance.

[0043] In the laminated film of the present invention, it is preferable that the difference between TY and TX is 0°C or more and 10°C or less, when TY is the shrinkage onset temperature determined from the TMA curve in the direction orthogonal to the main orientation. By adopting this configuration, the appearance when observing the laminated film or a molded article using it from a direction orthogonal to the main orientation direction is also improved. Therefore, it is possible to obtain a laminated film or molded article with excellent appearance when viewed from various angles. Here, the direction orthogonal to the main orientation refers to the direction in the film plane that is orthogonal to the main orientation direction. Also, the "difference between TY and TX" shall be calculated as an absolute value. In the laminated film of the present invention, by having a difference of TY and TX of 10°C or less, the appearance is improved not only when observed from the main orientation direction, but also when observed from a direction orthogonal to the main orientation direction.

[0044] Furthermore, for the same reasons as the preferred range for TX, in the laminated film of the present invention, it is preferable that TY is 5°C to 30°C lower than TA (in other words, TA-TY is 5°C to 30°C), and more preferably 10°C to 30°C.

[0045] There are no particular limitations on the methods for achieving a temperature (TX) that is 5°C to 30°C lower than the temperature (TA). For example, when obtaining a laminated film by sequential biaxial stretching as described later, one method is to perform micro-stretching during the slow cooling process after heat treatment following stretching in the width direction (TD direction). Alternatively, it is also effective to perform pseudo-micro-stretching by increasing the tension (draw) during the winding process after slow cooling. Both of these methods enable the acquisition of a film that shrinks at a temperature lower than the glass transition temperature by performing micro-stretching at a temperature lower than the glass transition temperature. It is also effective to control the heat treatment temperature and the cooling temperature after heat treatment within a suitable range. These methods can be combined as needed.

[0046] From the viewpoint of obtaining a good appearance when formed into a molded product such as laminated glass, it is preferable that the laminated film of the present invention has a thermal shrinkage rate of 0.5% or more and 1.2% or less in at least one of the main orientation direction and the direction orthogonal to the main orientation under a TA atmosphere. Here, "under a TA atmosphere" refers to an environment where the temperature is TA. From the above viewpoint, it is more preferable that the thermal shrinkage rate in at least one of the main orientation direction and the direction orthogonal to the main orientation under a TA atmosphere is 0.7% or more and 1.2% or less, and even more preferable is 0.9% or more and 1.2% or less. Furthermore, from the above viewpoint, it is preferable that the thermal shrinkage rate of the laminated film of the present invention is 0.5% or more and 1.2% or less in both the main orientation direction and the direction orthogonal to the main orientation, and the preferred range is as described above. The thermal shrinkage rate can be calculated by measuring the dimensional change after heat treatment, and details of the measurement method will be described later.

[0047] Under a TA atmosphere, if the thermal shrinkage rate in at least one of the main orientation direction and the direction perpendicular to the main orientation is 0.5% or higher, bubbles, wrinkles, and color unevenness within the surface are less likely to occur in the laminated glass process, especially the pre-lamination process. On the other hand, if the shrinkage rate in at least one of the above directions is 1.2% or lower, excessive flexibility of the laminated film is suppressed, resulting in improved productivity and handling during molding.

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

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

[0050] Under a 150°C atmosphere, if the thermal shrinkage rate in at least one of the main orientation direction and the direction perpendicular to the main orientation is 1.5% or more, it becomes less likely for bubbles, wrinkles, and color unevenness to occur in the laminated glass process, especially in the main bonding process. On the other hand, under a 150°C atmosphere, if the thermal shrinkage rate in at least one of the above directions is less than 4.0%, it is possible to reduce the deterioration of productivity and handling during molding due to excessive flexibility of the laminated film, as well as the occurrence of color unevenness and deterioration of appearance.

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

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

[0053] The laminated film of the present invention is less prone to generating bubbles, wrinkles, and color unevenness within the surface by following the shrinkage of the interlayer in both the pre-lamination and main bonding processes. Therefore, the ratio of the high-temperature thermal shrinkage rate in the main bonding process to the thermal shrinkage rate at the glass transition temperature of the film used affects bubbles, wrinkles, and color unevenness within the surface. When glass is used as the support, the maximum temperature in the main bonding process is generally 150°C. If the thermal shrinkage rate at the temperature of greatest shrinkage differs significantly from, or is too close to, the thermal shrinkage rate at the glass transition temperature, it becomes difficult to follow the shrinkage of the interlayer in both the pre-lamination and main bonding processes.

[0054] From the above viewpoint, it is preferable that the laminated film of the present invention has a ratio of S(150) / S(TA) of 1.5 or more and 5.0 or less, where S(150) is the average value of the thermal shrinkage rate at 150°C and S(TA) is the average value of the thermal shrinkage rate at TA. From the above viewpoint, it is more preferable that S(150) / S(TA) is 1.5 or more and 4.0 or less, and even more preferable that it is 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 direction orthogonal to the main orientation at 150°C, and S(TA) and S(120) described later can be interpreted similarly except that the temperature is TA or 120°C instead of 150°C. When S(150) / S(TA) is 5.0 or less, bubbles, wrinkles, and color unevenness within the surface that occur when the thermal shrinkage rate of the laminated film at 150°C is excessively high or when the thermal shrinkage at the glass transition temperature (TA) is excessively low are suppressed. When S(150) / S(TA) is 1.5 or higher, the interlayer shrinkage can be followed in both the pre-lamination and main bonding processes when glass is used as the support, thus reducing the occurrence of bubbles and wrinkles.

[0055] Similarly, when using resins such as acrylic or polycarbonate as the support, the temperature of this bonding process is generally lower than that of glass. Therefore, from the above viewpoint, when S(120) is the average value of the thermal shrinkage rate at 120°C and S(TA) is the average value of the thermal shrinkage rate at TA, it is preferable that S(120) / S(TA) is between 1.5 and 5.0. From the above viewpoint, S(120) / S(TA) is more preferably between 1.5 and 3.0, and even more preferably between 1.5 and 2.0. When S(120) / S(TA) is 5.0 or less, bubbles, wrinkles, and color unevenness within the surface that occur due to excessively high thermal shrinkage of the laminated film at 120°C or excessively low thermal shrinkage at the glass transition temperature (TA) are suppressed. When S(120) / S(TA) is 1.5 or higher, the interlayer shrinkage can be followed in both the pre-lamination and main bonding processes when resins such as acrylic or polycarbonate are used as the support, thereby reducing the occurrence of bubbles and wrinkles.

[0056] To achieve a ratio of S(150) / S(TA) between 1.5 and 5.0, or a ratio of S(120) / S(TA) between 1.5 and 5.0, lowering S(TA) 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 coefficients of S(150) and S(120) tend to be close, making it difficult to set these ratios to 1.5 or higher. Therefore, it is effective to set the higher of the two glass transition temperatures (Tg) of the thermoplastic resins (thermoplastic resin A and thermoplastic resin B) that are the main components of the two layers (layer A and layer B) with different main components to 95°C or higher and 105°C or lower, preferably 100°C or higher and 105°C or lower. It is also effective to include components with low melting points in layers A and B, and in terms of the process, it is also effective to set the heat treatment temperature within the preferred range described later.

[0057] There are no particularly limited methods for lowering the glass transition temperature (Tg) of thermoplastic resins. Examples include copolymerizing the thermoplastic resin with a less crystalline component or using a thermoplastic resin with a low glass transition temperature. As an example of the former, polyethylene naphthalate (PEN), the most commonly used polyester containing naphthalenedicarboxylic acid as a dicarboxylic acid component, has a glass transition temperature of approximately 120°C. However, it is possible to lower the glass transition temperature of PEN by copolymerizing it with a constituent unit that is less crystalline than ethylene naphthalate units. As an example of the latter, a method of using a thermoplastic resin (such as polyethylene terephthalate) with a glass transition temperature lower than 105°C is employed. By using such methods, it becomes easy to lower the glass transition temperature to 105°C or below. These methods may be used in combination as appropriate.

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

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

[0060] 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 represented by formula (3) include polyethylene glycol, tetraethylene glycol, polytetramethylene ether glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, tributylene glycol, and tetrabutylene glycol.

[0061] When at least one of layers A and B is mainly composed of a copolymer polyester resin having the chemical structure represented by formula (3), it is preferable that the copolymer polyester resin contains 0.5 mol% to 40 mol% of the constituent units having the chemical structure represented by formula (3) per 100 mol% of the total diol constituents. Including the diol units of formula (3) within this range makes it easy to set the glass transition temperature of thermoplastic resin A and thermoplastic resin B to 105°C or lower. When both thermoplastic resin A and thermoplastic resin B contain the diol units of formula (3) by copolymerization, the amount can be appropriately adjusted within the above range, taking into consideration crystallinity in addition to the glass transition temperature. For example, if thermoplastic resin A is a copolymer of PEN and thermoplastic resin B is a copolymer of PET, it is preferable that the content of the diol units of formula (3) is 3 mol% to 20 mol% per 100 mol% of the total diol constituents in thermoplastic resin A, and 3 mol% to 20 mol% per 100 mol% of the total diol constituents in thermoplastic resin B.

[0062] Furthermore, a compound having the chemical structure represented by formula (3) may be included in at least one of layer A or layer B. In this case, it is preferable to adjust the amount of the compound to be between 0.5 mol% and 40 mol% relative to 100 mol% of the total diol components of the total polyester resin constituting layer A or layer B. Even when the mixture has a compound structure represented by formula (3), the same effect as when the glass transition temperature is lowered by copolymerization can be obtained.

[0063] On the other hand, when a mixture has a chemical structure represented by formula (3), the haze value tends to be high due to differences in the compatibility of the different resins, and the heat resistance may be inferior. Therefore, for layers A and B, it is more preferable to copolymerize thermoplastic resin A and thermoplastic resin B to incorporate the chemical structure represented by formula (3) rather than mixing compounds. Furthermore, copolymerizing thermoplastic resin A and thermoplastic resin B with diol components having the chemical structure represented by formula (3) is also preferable because it can suppress the leakage of these components having chemical structures out of the laminated film system by evaporation or sublimation.

[0064] Another method to achieve the same effect as setting the glass transition temperature of thermoplastic resin A and thermoplastic resin B to 105°C or lower is to mix a polyester resin with a lower glass transition temperature than these thermoplastic resins into layers A and B. Examples of polyester resins with a low glass transition temperature include terephthalic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid and their ester-forming derivatives as dicarboxylic acid components. Examples of diol components include the same components as mentioned above, but ethylene glycol, 1,4-cyclohexanedimethanol, and 1,4-butanediol are particularly preferred. By adding such components to layers A and B, the same effect as setting S(150) / S(TA) and S(120) / S(TA) to a suitable range can be obtained, making it possible to suppress bubbles, wrinkles, and color unevenness within the surface during molding. However, compared to the above example using copolymers, it is important to note that the reflectivity tends to decrease due to the lower refractive index of each thermoplastic resin layer, and the internal haze of the film tends to increase due to the mixing of different resins.

[0065] The laminated film of the present invention preferably has an internal haze of 0.5% or less. Internal haze is an index representing the haze (turbidity) inside the film, excluding light scattering at the surface of the film. By lowering the internal haze, a laminated film that is transparent and reflects light of a specific wavelength can be made, and such a laminated film can be widely applied to applications where transparency is required, such as half mirrors and heat-reflective 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 by measuring the haze in accordance with JIS-K-7105 (1981) while the film is placed in a quartz cell filled with liquid paraffin (details of the measurement method will be described later).

[0066] To keep the internal haze of the laminated film within the aforementioned range, this can be achieved by adjusting the types and amounts of components other than thermoplastic resin A in layer A, or by adjusting the types and amounts of components other than thermoplastic resin B in layer B. By adopting such a configuration, it is possible to add an appropriate amount of components that have excellent compatibility and dispersibility with each thermoplastic resin, thereby reducing the internal haze. Furthermore, internal haze can also be reduced by using an appropriate combination of thermoplastic resin A and thermoplastic resin B. An example of such a combination of thermoplastic resin A and thermoplastic resin B is a combination in which polyethylene naphthalate resin copolymerized with polyethylene glycol is used as thermoplastic resin A, and polyethylene terephthalate resin copolymerized with cyclohexanedimethanol is used as thermoplastic resin B. In addition, internal haze can also be reduced by reducing the number of resin layers or by reducing the thickness of the film.

[0067] From the viewpoint of using the laminated film of the present invention as a projection image display member for head-up displays and the like, it is preferable that the average P-wave reflectance at an incident angle of 60° for wavelengths of 400 to 700 nm is 10% or more and 50% or less. In the case of general transparent substrates such as transparent glass and transparent resin films, as the incident angle gradually increases from 20° with respect to the normal to the film surface, the reflectance of P-waves, which are one type of polarized light, decreases, and the reflectance becomes 0% at an angle called the Brewster angle. The Brewster angle varies depending on the refractive index of the material, and in the case of polyester resin, it is about 60°. Therefore, in general transparent substrates, it is difficult to transmit P-waves from the front direction and reflect P-waves from an oblique direction. The incident angle refers to the angle between the normal to the film surface and the direction of propagation of the light ray.

[0068] The configuration in which the average P-wave reflectance for wavelengths of 400-700 nm at an incident angle of 60° is 10% or more and 50% or less is, in other words, a configuration that does not have an angle equivalent to the Brewster angle. Therefore, by adopting this configuration, it becomes possible to reflect P-waves incident on the film surface from an oblique direction. By having an average P-wave reflectance of 10% or more at an incident angle of 60° for wavelengths of 400-700 nm, the displayability of the projected image when a P-wave image is projected onto the laminated film is improved. From the above viewpoint, an average P-wave reflectance of 20% or more at an incident angle of 60° is preferable, and more preferably 25% or more. On the other hand, by having an average P-wave reflectance of 50% or less at an incident angle of 60°, it is possible to suppress the increase in the average reflectance of P-waves at incident angles of 20° to 50° that occurs when the average reflectance of P-waves at an incident angle of 60° is increased. Therefore, glare of the projected image due to P-waves is reduced and displayability is improved. To achieve a P-wave average reflectance of 20% or more at an incident angle of 60°, it is preferable that the absolute value of the difference in refractive indices perpendicular to the plane of layer A and layer B be between 0.11 and 0.20, and more preferably between 0.13 and 0.20. When the absolute value of the difference in refractive indices perpendicular to the plane of layer A and layer B is 0.11 or more, the displayability of the projected image, as described later, improves. On the other hand, if this difference is kept below 0.20, delamination at the interface between layer A and layer B is reduced.

[0069] To obtain such a laminated film, a method can be used to adjust the refractive index difference in the direction perpendicular to the film surface between the two thermoplastic resin layers and the number of layers. In this case, the larger the refractive index difference in the direction perpendicular to the film surface and the more layers are added, the greater the average P-wave reflectance at an incident angle of 60°. The refractive index difference perpendicular to the film surface between layer A and layer B can be adjusted by adjusting the composition of the resins constituting each layer and the film formation conditions (e.g., stretching ratio, stretching speed, stretching temperature, heat treatment temperature, heat treatment time). Here, the refractive index perpendicular to the film surface refers to the refractive index in the direction perpendicular to the multilayer laminated film surface. As for the composition of the resins constituting layer A and layer B, the compositions of thermoplastic resin A and thermoplastic resin B mentioned above can be used, but it is preferable to use polyethylene terephthalate as thermoplastic resin A and polyethylene terephthalate copolymerized with 2,6-naphthalenedicarboxylic acid at a concentration of 15 mol% to 35 mol% of the total dicarboxylic acid components as thermoplastic resin B.

[0070] From the viewpoint of background visibility when projecting P-wave images, it is preferable that the laminated film of the present invention, which has an average P-wave reflectance of 10% to 50% at an incident angle of 60° for wavelengths of 400 to 700 nm, has an average transmittance of 50% to 100% at an incident angle of 10° for wavelengths of 400 to 700 nm. This high average transmittance of light in the visible light region of 400 to 700 nm provides transparency similar to transparent glass or transparent resin film, and allows for good visibility of the background when observing it through the laminated film from a direction perpendicular to the laminated film surface.

[0071] From the above perspective, the average transmittance is preferably 70% or more, more preferably 80% or more, and even more preferably 85% or more. If the average transmittance is 85% or more, the user can see the background with almost no awareness of the presence of the laminated film. From the viewpoint of feasibility, the upper limit of the average transmittance is preferably 99%. Such a laminated film can be obtained by reducing the difference in refractive index in the direction parallel to the film plane between the two thermoplastic resin layers. If the difference in refractive index in the direction parallel to the film plane is 0.06 or less, the transmittance can be easily set to 50% or more; if it is 0.04 or less, the transmittance can be easily set to 70% or more; and if the difference in refractive index is 0.02 or less, the transmittance can be easily set to 80% or more. Note that "difference in refractive index in the direction parallel to the film plane" refers to the absolute value of the difference in in-plane refractive index between layer A and layer B.

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

[0053] to

[0063] of Japanese Patent Application Publication No. 2007-307893. The same interpretation also applies to a laminated film consisting of three types of layers, including layer C.

[0073] Thermoplastic resins A and B are prepared in the form of pellets or the like. If necessary, the pellets are dried in hot air or under vacuum and then supplied to separate extruders. Inside the extruder, thermoplastic resin A is heated and melted at a temperature above its melting point, and thermoplastic resin B is heated and melted at a temperature within ±30°C of the heating temperature of thermoplastic resin A, without causing uneven discharge. Next, the extrusion amount is made uniform using a gear pump or the like to extrude the molten thermoplastic resins, and foreign matter and modified resin are removed through a filter or the like. These molten thermoplastic resins are laminated in the desired layer configuration using a lamination device, molded into the desired sheet shape using a die, and then discharged into a casting drum. The multi-layered molten sheet discharged from the die is then extruded onto a cooling body such as a casting drum and cooled and solidified to obtain a casting film. At this time, it is preferable to use electrodes such as wire, tape, needle, or knife to rapidly cool and solidify the film by making it adhere to the cooling body such as a casting drum using electrostatic force. Furthermore, methods such as blowing air from a slit-shaped, spot-shaped, or surface-shaped device to rapidly cool and solidify the material by bringing it into close contact with a cooling body such as a casting drum, or using a nip roll to rapidly cool and solidify the material by bringing it into close contact with a cooling body, are also preferred.

[0074] While multi-manifold dies, feed blocks, and static mixers can be used as lamination devices, it is particularly preferable to use a feed block containing at least two separate components with numerous fine slits in order to efficiently obtain the configuration of the present invention. Using such a feed block prevents the device from becoming excessively large, resulting in less foreign matter due to thermal degradation and enabling high-precision lamination even when the number of layers is extremely large. Furthermore, the lamination accuracy in the width direction is significantly improved compared to conventional technology. In addition, with this device, the thickness of each layer can be adjusted by the shape (length and width) of the slits, making it easy to achieve any desired layer thickness.

[0075] Subsequently, it is preferable to biaxially stretch the casting film obtained in this manner. Here, biaxial stretching means stretching in the longitudinal direction and the width direction. Stretching may be performed sequentially in the two directions, or simultaneously in the two directions. Furthermore, re-stretching may be performed in the longitudinal direction and / or the width direction. The longitudinal direction refers to the direction in which the film travels, and the width direction refers to the direction perpendicular to the longitudinal direction within the film plane.

[0076] First, let's explain the case of sequential biaxial stretching. Here, longitudinal stretching (longitudinal stretching) refers to stretching to give the film a longitudinal molecular orientation, and is usually performed by the difference in peripheral speed of the rolls. This stretching may be performed in one stage or in multiple stages using multiple pairs of rolls. The stretching ratio varies depending on the type of resin, but is usually preferably 2.0 to 9.0 times, and when polyethylene naphthalate copolymer resin is used as one of the resins constituting the laminated film, 2.0 to 7.0 times is preferably used. Considering that the laminated film should have a reflectance band of 100 nm or more with a reflectance of 30% or more, and that the thermal shrinkage rate in at least one of the main orientation direction and the direction perpendicular to the main orientation is 1.5% or more in an atmosphere of 150°C, a longitudinal stretching ratio of 3.0 times to 3.8 times is particularly preferable. The stretching temperature is preferably in the range of the glass transition temperature of the resin with the higher glass transition temperature among the resins constituting the laminated film to the glass transition temperature + 100°C.

[0077] The uniaxially oriented film obtained in this manner may be subjected to surface treatments such as corona treatment, flame treatment, or plasma treatment as needed, and then given functions such as slipperiness, adhesion, and antistatic properties by in-line coating.

[0078] Furthermore, stretching in the width direction (transverse stretching) refers to stretching to give the film a width direction orientation. Typically, a tenter is used to stretch the uniaxially oriented film in the width direction by conveying it while gripping both ends with clips. The stretching ratio varies depending on the type of resin, but is usually preferably 2.0 to 9.0 times. When polyethylene naphthalate copolymer resin is used in one of the resins constituting the laminated film, a stretching ratio of 2.0 to 7.0 times is preferably used. Considering that the laminated film should have a reflectance band of 100 nm or more with a reflectance of 30% or more, and that the thermal shrinkage rate in at least one of the main orientation direction and the direction orthogonal to the main orientation is 1.5% or more and less than 4.0% in an atmosphere of 150°C, a transverse stretching ratio of 3.7 times or more and 4.2 times or less is particularly preferable. Also, from the above viewpoint, the in-plane stretching ratio, which is the product of the longitudinal stretching ratio and the transverse stretching ratio, is preferably 11.0 times or more and 18.0 times or less, and more preferably 12.0 times or more and 18.0 times or less. Furthermore, the preferred stretching temperature is within the range of the glass transition temperature of the resin with the higher glass transition temperature among the resins constituting the laminated film, up to the glass transition temperature + 120°C.

[0079] The biaxially oriented film thus obtained is preferably heat-treated in a tenter at a temperature above the stretching temperature and below the melting point of thermoplastic resin A in order to impart flatness and dimensional stability. Heat treatment improves the dimensional stability of the resulting laminated film. After heat treatment in this manner, the laminated film is preferably uniformly and slowly cooled at a temperature above the glass transition temperature of thermoplastic resin A and below the heat treatment temperature. More specifically, it is preferable to slowly cool it at a temperature higher than 100°C and 200°C or lower, more preferably between 130°C and 180°C, and even more preferably between 150°C and 180°C. After slow cooling, it is cooled to room temperature and wound up. In addition, a 0.1% to 10% additional stretching or relaxation treatment may be used in combination with the slow cooling after heat treatment.

[0080] Furthermore, in the laminated film of the present invention, it is preferable that the heat treatment temperature after stretching be below the melting point of thermoplastic resin A and above the melting point of thermoplastic resin B. In this case, thermoplastic resin A maintains a highly oriented state, while the orientation of thermoplastic resin B is relaxed, making it easy to create a refractive index difference between each layer (layer A, layer B) mainly composed of these resins. When an amorphous resin is used for either thermoplastic resin A or thermoplastic resin B, it is preferable that the heat treatment temperature be below the melting point of the crystalline resin and in the range of the glass transition temperature of the crystalline resin to the glass transition temperature + 120°C. Furthermore, if at least one of thermoplastic resins A and B is a crystalline polyester whose main constituent unit is naphthalenedicarboxylic acid, the heat treatment temperature is preferably 170°C or higher and less than 220°C, more preferably 175°C or higher and 215°C or lower, even more preferably 175°C or higher and 210°C or lower, and particularly preferably 175°C or higher and 200°C or lower, from the viewpoint of controlling the heat shrinkage rate in at least one of the main orientation direction and the direction orthogonal to the main orientation in a TA-TX or 150°C atmosphere to a suitable range. If amorphous resins are used for thermoplastic resins A and B, the heat treatment step is unnecessary.

[0081] Next, we will explain the case of simultaneous biaxial stretching. In the case of simultaneous biaxial stretching, the obtained cast film may be subjected to surface treatments such as corona treatment, flame treatment, or plasma treatment as needed, and then functions such as slipperiness, adhesion, and antistatic properties may be imparted by in-line coating.

[0082] Next, the cast film is guided to a simultaneous biaxial tenter while being held at both ends in the width direction with clips, and then transported and stretched simultaneously and / or in stages in the longitudinal and width directions. Simultaneous biaxial stretchers include pantograph type, screw type, drive motor type, and linear motor type, but the drive motor type or linear motor type is preferred because it is possible to arbitrarily change the stretching ratio and perform relaxation processing at any point. The stretching ratio varies depending on the type of resin, but usually an area ratio of 6.0 to 30.0 times is preferred, and when a copolymer resin of polyethylene naphthalate is used in one of the resins constituting the laminated film, an area ratio of 9.0 to 18.0 times is particularly preferred. In particular, in the case of simultaneous biaxial stretching, in order to suppress the orientation difference in the plane, it is preferable to make the stretching ratio in the longitudinal and width directions the same and to make the stretching speed approximately equal. Furthermore, the stretching temperature is preferably in the range of the glass transition temperature of the resin with the higher glass transition temperature among the resins constituting the laminated film to the glass transition temperature + 120°C.

[0083] The biaxially stretched film is then subjected to heat treatment, slow cooling, and cooling to room temperature, similar to the case of sequential biaxial stretching, and then wound up. It is preferable to instantly loosen the film in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone during the heat treatment process, in order to suppress the distribution of the principal orientation axis in the width direction.

[0084] Next, the laminate and laminated glass of the present invention will be described. The laminate of the present invention comprises a support 1, an intermediate layer 1, the laminated film of the present invention, an intermediate layer 2, and a support 2 in this order. Furthermore, among the laminates of the present invention, those in which both support 1 and support 2 are glass are the laminated glass of the present invention. The laminate and laminated glass of the present invention may have multiple of the above components, as long as the above components are arranged in this order, and other components may be present between the above components. Also, support 1 and support 2 may be the same component or different components, and the same applies to intermediate layer 1 and intermediate layer 2. Such molded bodies and laminated glass are superior in terms of strength, and in particular, laminated glass has the characteristic of suppressing glass shattering and penetration when an object collides with the glass surface, compared to double-glazed glass (insulated glass) which has an air layer between two panes of glass. For this reason, the laminated glass of the present invention is suitable for use in applications where safety and security are required, such as windows in automobiles and buildings. Furthermore, by incorporating the laminated film of the present invention into the laminated glass, it is possible to give the laminated glass functions such as heat ray cutting function, half mirror function, and color filter function.

[0085] The laminate using the laminated film of the present invention comprises a support 1, an intermediate layer 1, the laminated film of the present invention, an intermediate layer 2, and a support 2 in this order. Supports 1 and 2 play a role in increasing the strength of the laminate. Examples of supports for obtaining the laminate of the present invention include resins, metals, glass, and ceramics. The surface of the support may be flat or curved, and can take any shape. Examples of resins used for supports 1 and 2 include polycarbonate, cyclic polyolefins, polyarylate, polyethylene terephthalate, polymethyl methacrylate and other acrylic resins, ABS resin, and triacetylcellulose. Examples of glass used for supports 1 and 2 include float glass, tempered glass, colored glass, and heat-shielding glass. If supports 1 and 2 are intended for use in applications such as heat reflection or projection members for head-up displays, they are preferably transparent, and the thickness of the support is preferably 0.05 mm to 5 mm from the viewpoint of achieving both strength and weight reduction.

[0086] Intermediate layers 1 and 2 play a role in bonding the laminated film of the present invention to the support 1 and 2, and adhesive layers or film layers are preferred. 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, celluloses, polyvinyl chloride, polyacrylic acid esters, and polyisobutylene. These can also be used in the form of films or formed on the surface of films as an alternative to adhesives. Furthermore, these adhesives may contain tackiness modifiers, plasticizers, heat stabilizers, antioxidants, UV absorbers, antistatic agents, lubricants, colorants, crosslinking agents, etc.

[0087] By providing an intermediate layer, the adhesion between the support 1 or 2 and the laminated film of the present invention, as well as the aesthetic appeal, durability, weather resistance, and impact resistance of the laminate, can be enhanced. One way to enhance the aesthetic appeal of the laminate is to add a coloring agent to the intermediate layer. Examples of coloring agents include azo pigments, polycyclic pigments, lake pigments, nitro pigments, nitroso pigments, aniline black, alkali blue, phthalocyanine pigments, cyanine pigments, azo dyes, anthraquinone dyes, quinophthalone dyes, methine dyes, condensed polycyclic dyes, reactive dyes, cationic dyes, lanthanum hexaboride, indium tin oxide, antimony tin oxide, and cesium tungsten oxide. 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.

[0088] Methods for forming laminates include extrusion lamination, hot melt lamination, thermal lamination, press lamination, vacuum lamination, and autoclave lamination. Extrusion lamination is a method in which a molten resin composition for obtaining a laminated film and an intermediate layer is extruded from a die into a film shape and laminated onto a support, and the molded product is passed between two rolls. Hot melt lamination is a molding method in which a resin composition for forming an intermediate layer, which has been melted by heat, is applied to the laminated film or support, and the laminated film and support are laminated. Thermal lamination is a molding method in which the laminated film, the sheet for the intermediate layer, and the support are laminated by heating and pressing them together with a heating roll. Press lamination is a molding method in which the laminated film, the sheet for the intermediate layer, and the support are heated and pressed together with a press machine. Vacuum lamination is a molding method in which the laminated film, the sheet for the intermediate layer, and the support are heated, the inside of the apparatus is put into a vacuum state, and the laminated products are pressed together. Autoclave lamination is a lamination method in which a laminated film, an intermediate layer sheet, and a support are heated, and then the inside of the apparatus is pressurized with gas or other means to laminate them. [Examples]

[0089] 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.

[0090] [Methods for measuring physical properties and evaluating their effects] The methods for evaluating characteristic values ​​and effects are as follows:

[0091] (1) Layer thickness, number of layers, layer configuration The lamination structure and number of layers of the laminated film, as well as the thickness of each layer, were determined by observing samples obtained by cutting cross-sections using a microtome, and then using a transmission electron microscope (TEM) and its length-measuring function. Specifically, a transmission electron microscope H-7100FA (manufactured by Hitachi, Ltd.) was used to observe the cross-section of the film at 10,000 to 40,000 times magnification under an acceleration voltage of 75 kV, and cross-sectional photographs were taken to determine the layer structure and number of layers, and to measure the thickness of each layer. In some cases, known staining techniques using RuO4 or OsO4 were used to enhance the contrast between layers.

[0092] (2)Reflectance, transmittance Using a 5cm x 5cm sample, reflectance and transmittance were measured under the following conditions using a basic configuration with an integrating sphere attached to a Hitachi U-4100 Spectrophotometer. For reflectance measurements, the sample was placed behind the integrating sphere with its length oriented vertically, and the reflectance was calculated as a relative reflectance based on the aluminum oxide sub-white plate attached to the instrument. The average reflectance for wavelengths of 900-1200nm was calculated by averaging all reflectance values ​​for every 1nm, and measurements were taken on both sides of the sample. The measurement result from the side with the higher average reflectance for wavelengths of 900-1200nm was adopted. For transmittance measurements, the sample was placed in front of the integrating sphere with its length oriented vertically. The average transmittance for wavelengths of 400-700nm was calculated by averaging all transmittance values ​​for every 1nm, and measurements were taken on both sides of the sample. The measurement result from the side with the higher average transmittance for wavelengths of 400-700nm was adopted. <Measurement conditions> Slit: 2nm (visible) / Automatic control (infrared) Gain: 2 Scanning speed: 600 nm / min Starting wavelength: 2600nm Termination wavelength: 240nm Sampling interval: 1 nm Incident angle: 10°.

[0093] (3) Reflectance of P-waves at 60° A Hitachi U-4100 Spectrophotometer was fitted with an angle-adjustable reflective unit and a GranTerra polarizer. The reflectance of P-waves in the wavelength range of 400-700 nm at an incident angle θ=60° was measured in 1 nm increments for azimuth angles of 60° clockwise, with the azimuth angle of the film surface being 0° as the reference point. From the obtained reflectances, the reflectance of P-waves in the wavelength range of 400 nm-700 nm at an incident angle of 60° in each azimuth angle direction was determined as the average reflectance of P-waves in the wavelength range of 400 nm-700 nm at an incident angle of 60°. <Measurement conditions> Slit: 2nm (visible) / Automatic control (infrared) Gain: 2 Scanning speed: 600 nm / min Starting wavelength: 700nm Termination wavelength: 400nm Sampling interval: 1 nm.

[0094] (4) Melting point, glass transition temperature TA, crystallization temperature, heat of fusion A 5g sample was taken, and the melting point, glass transition temperature, crystallization temperature, and heat of fusion were measured and calculated using a differential scanning calorimetry analyzer (Robot DSC-RDC220, Seiko Electronics Industries, Ltd.) in accordance with JIS-K-7121 (1987). If multiple glass transition temperatures were present, the higher temperature was designated as the glass transition temperature TA. For measurement, the sample was heated from 25°C to 290°C at a rate of 5°C / min.

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

[0096] (6) Appearance of the laminate (Fabrication of laminates) Nisshinbo LAMINATOR0303S was used to fabricate the laminate. First, 3 mm thick, 10 cm square glass plates were placed on both sides of the laminated film as supports, and 0.76 mm thick PVB (polyvinyl butyral) was placed as an intermediate layer between the laminated film and the supports. The resulting laminated material was heated from 25°C to 150°C at a rate of 3°C / min, then the pressure was reduced to 600 mmHg for 5 minutes to 0.1 MPa, and it was pressed for 30 minutes. After that, it was slowly cooled at a rate of 3°C / min until it reached 35°C while still pressed, and the press was released to obtain the laminate (150°C). Similarly, 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.

[0097] (Color unevenness evaluation) A straight-tube white three-wavelength fluorescent lamp and a laminate were positioned horizontally to the main orientation direction and fixed at a distance of 30 cm in the normal direction. The evaluation area was visually inspected from angles of 20°, 50°, and 70° relative to the normal direction of the evaluation area. The evaluation criteria were as follows, with S and A indicating good results. S: No color inconsistencies were visible from any angle. A: When observed from at least one angle, very slight color unevenness was visible, but from any angle, no clear color unevenness was visible in part or in the whole of the molded body. C: When observed from at least one angle, clear color variations were visible in part or throughout the molded body.

[0098] (Appearance evaluation) A straight-tube white three-wavelength fluorescent lamp and a laminate were positioned horizontally to the main orientation direction and fixed at a distance of 30 cm in the normal direction. The evaluation area was visually inspected from angles of 20°, 50°, and 70° relative to the normal direction of the evaluation area. The evaluation criteria were as follows, with S and A indicating good results. The same observations were also performed when the fluorescent lamp was positioned horizontally in a direction perpendicular to the main orientation direction. S: No wrinkles or unevenness were visible from any angle. A: When observed from at least one angle, very slight wrinkles or irregularities were visible, but from any angle, no clear wrinkles or irregularities were visible in part or on the entire molded body. C: When observed from at least one angle, clear wrinkles or irregularities were visible in part or throughout the molded body.

[0099] (7) Identification of the principal orientation direction The laminated film sample size was set to 10 cm x 10 cm, and the sample was cut at the center in the film width direction. The degree of orientation was measured using a molecular orientation meter MOA-2001 manufactured by KS Systems Co., Ltd. (now Oji Keisokuki Co., Ltd.), and the direction with the greatest degree of orientation was designated as the main orientation direction.

[0100] (8) Contraction start temperature TX, TY The laminated film sample was cut into a rectangular shape measuring 40 mm in the main orientation direction (measurement direction) and 4 mm in the direction perpendicular to the main orientation direction. It was then measured using the "TMA SS6100" manufactured by Hitachi High-Tech Science Corporation under the following measurement conditions. <Measurement conditions> Heating temperature range: 25℃~200℃ Heating rate: 10°C / min Hold time: 10 minutes Sampling: 2 seconds Subsequently, the shrinkage initiation temperature TX was determined from the output displacement TMA value, specifically the temperature at which the value changed from positive to negative within the range of 40 to 150°C. If the TMA value at 40°C was negative, the shrinkage initiation temperature TX was set to 40°C. If there were multiple temperatures at which the value changed from positive to negative, the lowest temperature was used as the shrinkage initiation temperature TX. This measurement was performed five times, and the average value was adopted as the shrinkage initiation temperature TX. The shrinkage initiation temperature TY was measured similarly by cutting the sample into a rectangle with dimensions of 40 mm in the direction perpendicular to the main orientation direction (measurement direction) and 4 mm in the main orientation direction.

[0101] (9) Thermal shrinkage rate (under a 150°C atmosphere, under a 120°C atmosphere) A rectangular piece measuring 150 mm (measurement direction) x 10 mm was cut from the sample, and marks were made at 100 mm intervals in the measurement direction. The interval between the marks was measured using a Nikon universal projector (Model V-16A), and this value was designated as A. Next, the sample was suspended in a gear oven with a load of 3 g applied and left for 30 minutes in an atmosphere of 150°C or 120°C. After removing the sample and allowing it to cool, the interval between the marks made earlier was measured and designated as B, and the thermal shrinkage rate in the measurement direction was calculated using the following formula (4). The measurement directions were the principal orientation direction and the direction perpendicular to the principal orientation, with n being 3 in each direction, and the average value was adopted as the thermal shrinkage rate. Thermal shrinkage rate (%) = 100 × (AB) / A ... Equation (4).

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

[0103] (11) In-plane refractive index of layer B Since layer B is an internal layer of the laminated film, the measurement was performed not on the film itself, but on a single-layer film of layer B prepared under the same stretching and heat treatment conditions as the film, using a SAIRON TECHNOLOGY, INC. "SPA-4000" under the following measurement conditions. However, unlike the resin of layer A, the resin of layer B is amorphous, and its degree of orientation does not change with stretching, so there is no principal orientation direction. Therefore, the in-plane refractive index was defined as the average of the refractive index in the longitudinal direction and the refractive index in the width direction of the single-layer film. Laser: Wavelength 632.8nm Prism: GGG Prism.

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

[0105] [Resin used in the manufacture of laminated film] The following resins were used as the resins for layer A and layer B in the manufacture of the laminated film.

[0106] (Resin for layer A) PEN(1): Polyethylene 2,6-naphthalate obtained by copolymerizing polyethylene glycol with an average molecular weight of 400 at a 4 mol% ratio relative to the total diol components (intrinsic viscosity: 0.64, melting point: 260°C, glass transition temperature: 104°C). PEN(2): Polyethylene 2,6-naphthalate obtained by copolymerizing polyethylene glycol with an average molecular weight of 400 at a 6 mol% ratio relative to the total diol components (intrinsic viscosity: 0.64, melting point: 255°C, glass transition temperature: 97°C). PET(2): Polyethylene terephthalate (intrinsic viscosity: 0.65, melting point: 254°C, glass transition temperature: 78°C).

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

[0108] (Example 1) PEN(1) was used as the polyester resin (thermoplastic resin A) forming layer A, and PET(1) was used as the polyester resin (thermoplastic resin B) forming layer B. The polyester resins forming each layer were melted to 280°C in a twin-screw extruder with vents, then merged in a 449-layer feed block via a gear pump and filter, and the molten thermoplastic resins A and B were alternately laminated in the thickness direction for 449 layers so that the outermost layers on both sides were layer A. The resulting molten laminate was then guided to a T-die to be formed into a sheet and extruded, and the molten sheet was rapidly cooled and solidified on a casting drum with a surface temperature of 25°C using electrostatic application to obtain a cast film. At this time, the extrusion amount was adjusted so that the mass ratio of thermoplastic resin A to thermoplastic resin B was approximately 1:1. Next, the obtained cast film was heated in a group of rolls set to a temperature of thermoplastic resin A's glass transition temperature + 10°C, and then stretched 3.2 times in the longitudinal direction (longitudinal direction) while rapidly heating from both sides with a radiation heater over a stretching section length of 100 mm, and then cooled. Subsequently, corona discharge treatment was performed on both sides of the uniaxially oriented film in air to achieve a wetting tension of 55 mN / m. A laminated film coating solution consisting of (polyester resin with a glass transition temperature of 18°C) / (polyester resin with a glass transition temperature of 82°C) / silica particles with an average particle size of 100 nm was applied to both sides to form a transparent, easily adhesive layer with good lubrication. This uniaxially oriented film was guided into a tenter by clipping both ends in the width direction, preheated with hot air at 100°C, and then stretched 4.0 times in the lateral (width direction) direction at a uniform stretching speed at a temperature of glass transition temperature of thermoplastic resin A + 20°C. Furthermore, in the same tenter, the stretched film was heat-treated with hot air at 195°C, and after a 1% relaxation treatment in the width direction at the same temperature, it was further stretched by 1% in the width direction in a cooling zone at 150°C, slowly cooled to room temperature, and wound up. The winder draw was set to 98%. Note that winder draw is the ratio of tenter speed to winder winding speed, and a winder draw of 98% indicates that the tenter speed is 2% slower than the winder winding speed. The thickness of the obtained laminated film was 90 μm. The evaluation results are shown in Tables 2-1, 2-2, 4-1, and 4-2.

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

[0110] [Table 1]

[0111] [Table 2-1]

[0112] [Table 2-2]

[0113] [Table 3]

[0114] [Table 4-1]

[0115] [Table 4-2] [Industrial applicability]

[0116] This invention can be used in decorative materials such as decorative panels, various home appliances, building materials, and automotive parts, and can be particularly used as heat-cutting glass that can suppress the inflow of heat from sunlight.

Claims

1. A laminated film having a structure in which 51 or more layers of two different types of polyester resin layers (layer A, layer B) are laminated in an arrangement of A(BA)n, where layer A and layer B are represented as A and B, and characterized in that when the highest glass transition temperature determined by differential scanning calorimetry (DSC measurement) is TA and the shrinkage start temperature determined from the TMA curve in the main orientation direction is TX, then TX is 5°C to 30°C lower than TA. The term "different polyester resin layers" means that when comparing two polyester resin layers, at least one of the following conditions 1 or 2 applies: 1: The refractive index differs by 0.01 or more in the main orientation direction.

2. They have different melting points or crystallization temperatures. In the structure A(BA)n, the parentheses represent repeating units, and n is a natural number representing the number of repeating units.

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

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

4. A laminated film according to claim 1 or 2, comprising a layer mainly composed of polyester having naphthalenedicarboxylic acid units as its primary constituent units.

5. The laminated film according to claim 1 or 2, characterized in that when the shrinkage onset temperature determined from the TMA curve in the direction orthogonal to the principal orientation is denoted as TY, the difference between TY and TX is 0°C or more and 10°C or less.

6. The laminated film according to claim 1 or 2, characterized in that when the shrinkage onset temperature TY is determined from the TMA curve in the direction orthogonal to the main orientation, TY is 5°C or more and 30°C or less lower than TA.

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

8. The laminated film according to claim 1 or 2, wherein when the average value of the thermal shrinkage rate at 120°C is S(120) and the average value of the thermal shrinkage rate at TA is 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 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, it has a reflectance band of 100 nm or more in which the reflectance is 30% or more.

10. The laminated film according to claim 1 or 2, wherein the average P-wave reflectance at wavelengths of 400 to 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 0.5% or less.

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

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

14. Laminated glass, wherein both support 1 and support 2 in the laminate according to claim 13 are glass.

Images