Film and method for producing same, laminated structure, laminated glass, and automobile

Abstract

The present invention addresses the problem of providing a film that is highly suitable for processes for laminating functional layers involving heating and is capable of suppressing uneven warping resulting from heat press molding for obtaining laminated glass including an intermediate layer and a support body. The present invention provides a film that has at least one thermoplastic resin layer and is characterized in that when the rate of shrinkage at a temperature of TºC in a heat shrinkage curve is represented by S(T)% and a direction in which S(150) is the largest among one discretionary direction and directions reached by rotating by intervals of 5º to 180ºC in an in-plane direction parallel to the film surface from said one discretionary direction in a plane parallel to the film surface is designated as an X direction, 0.50 ≤ | S(150) - S(100)| and 0.00 ≤ |S(120) - S(100)| ≤ 0.40 are satisfied in the X direction.

Description

Film and manufacturing method thereof, laminated structure, laminated glass, automobile

[0001] The present invention relates to a film that can be suitably used for laminated glass and the like, a method for producing the same, and a laminated structure, laminated glass, and automobiles that use the film.

[0002] Many products, such as mobile phones, personal computer housings, electrical appliances, furniture, and automobiles, require exterior design, and in recent years, the demand for design in these products has also increased. Known methods for imparting design to these products include, for example, painting or printing, attaching a colored film, or transferring the printed surface of a printed film onto a substrate. Furthermore, in addition to the demand for design, the demand for functionality in the exterior of these products is also increasing. For example, a known method is to impart functions such as heat absorption, gas barrier properties, adhesiveness, and electrical conductivity to the exterior substrate via a heating process.

[0003] In recent years, in particular, in response to carbon dioxide emission restrictions for environmental protection, heat-cutting glass capable of suppressing the inflow of heat from the outside in summer, particularly from sunlight, has attracted attention, and attempts have been made to use it in window glass for vehicles such as automobiles and trains, and for buildings. Examples of such heat-cutting glass include glass in which a substrate having a heat-absorbing material-containing layer is incorporated into laminated glass using an interlayer film to block heat rays, and glass in which a substrate having a metal film formed by sputtering or the like is laminated with an interlayer film to reflect and block heat rays.

[0004] Such heat-cutting glass is usually used in places where it is visible to the public, so its appearance is important. Furthermore, because a substrate such as a film must be subjected to processing such as lamination of a functional layer or sputtering before being processed into heat-cutting glass, the substrate such as a film must also be suitable for this processing. For example, in the molding of laminated glass containing a substrate such as a film, there are known problems, such as uneven pressing caused by uneven thickness of the interlayer film used to laminate the glass support, or differences in thermal shrinkage stress between the interlayer film and the film, which can cause uneven distortion in the film during molding and impair the appearance. One known cause of this problem is the difference in thermal shrinkage between the interlayer film and the film under processing conditions, and it has been proposed to control this thermal shrinkage (e.g., Patent Documents 1 and 2).

[0005] International Publication No. 2013 / 137288 Japanese Patent Application Laid-Open No. 2012-30563

[0006] However, the proposals in Patent Documents 1 and 2 are specialized in suppressing unevenness after laminating glass (improving appearance), and are insufficient in terms of suitability for processes including heating of substrates such as films before laminating glass. An object of the present invention is to provide a film that is highly suitable for processes in which functional layers are laminated with heating, and that can further suppress uneven distortion caused by hot and pressure molding to obtain laminated glass having an intermediate layer and a support.

[0007] In the production of laminated glass, a support (glass), an intermediate layer, and a film are laminated together, and then heated and pressurized to enhance adhesion between the components. During this process, uneven thickness of the intermediate layer and differences in thermal shrinkage stress between the intermediate layer and the film cause uneven distortion in the film, resulting in light scattering and diffuse reflection, which deteriorates the appearance of the laminated glass. Because the support undergoes little deformation during this process, the shape of the intermediate layer is not affected by the support. Therefore, if a film that is less likely to cause unevenness can be used, the problem of poor appearance of laminated glass can be solved. Furthermore, when laminating and molding a support, an intermediate layer, and a film using a film (laminate construct) that has undergone a process of laminating a functional layer under heating, it is important to control the thermal shrinkage stress of the laminate construct or the film that constitutes it.

[0008] The present invention was arrived at as a result of investigating how to eliminate unevenness, since the poor appearance that occurs in laminated glass obtained by hot-pressing a support, an intermediate layer, and a film is caused by uneven distortion of the film.

[0009] In order to solve the above problems, the present invention has the following configuration: (1) A film having at least one thermoplastic resin layer, wherein, when the shrinkage percentage at temperature T°C in a heat shrinkage curve is S(T)%, and the direction in which S(150) is largest among any one direction in a plane parallel to the film surface and among directions rotated from that direction up to 180° at 5° intervals in an in-plane direction parallel to the film surface, is defined as the X direction, the relationship in the X direction satisfies 0.50≦|S(150)−S(100)| and 0.00≦|S(120)−S(100)|≦0.40. (2) The film according to (1), wherein the shrinkage onset temperature in the heat shrinkage curve in the X direction is 110°C or higher and 170°C or lower. (3) The film according to (1) or (2), wherein the average shrinkage percentage in the X direction from 100°C to 120°C in a heat shrinkage curve is -0.40% or more and 0.50% or less, and the absolute value of the average rate of change in shrinkage percentage from 120°C to 150°C is 0.04% / °C or more. (4) The film according to any one of (1) to (3), wherein the thermoplastic resin layers are stacked in a configuration of 51 or more layers. (5) The film according to any one of (1) to (4), wherein, when two thermoplastic resin layers having different main components are designated as layer A1 and layer B1, the film has the A1 layer and the B1 layer. (6) The film according to any one of (1) to (4), wherein, when three thermoplastic resin layers having different main components are designated as layer A2, layer B2, and layer C2, the film has a regular arrangement consisting of the A2 layer, the B2 layer, and the C2 layer. (7) The film according to any one of (1) to (6), wherein at least one of the thermoplastic resin layers is a polyester resin layer. (8) A method for producing a film according to any one of (1) to (7), comprising an off-annealing step of subjecting a sheet satisfying 0.50≦|S(150)−S(100)| to a heat treatment at a temperature of 110°C or higher and lower than 140°C. (9) The method for producing a film according to (8), wherein the sheet satisfies 0.40<|S(120)−S(100)|. (10) A laminated structure obtained by laminating a functional layer on at least one surface of the film according to any one of (1) to (7). (11) The laminated structure according to (10), wherein the functional layer is a conductive layer.(12) The laminate structure according to (10) or (11), wherein the functional layer comprises a plurality of layers, at least one of which is a second film having an absolute value of shrinkage at 120°C of 0.20% or less. (13) The laminate structure according to (12), wherein the layers are bonded together so that |θb-θf|≦30°, where θb is the orientation angle of the film and θf is the orientation angle of the second film. (14) The laminate structure according to any one of (10) to (13), wherein the functional layer is on both sides, one of the functional layers being a conductive layer and the other functional layer being a second film having an absolute value of shrinkage at 120°C of 0.20% or less. (15) The laminate structure according to any one of (10) to (14), wherein a reflectance profile measured from at least one side has at least one reflection band having a reflectance of 30% or more continuous over a wavelength width of 20 nm or more. (16) The laminate structure according to (15), wherein the reflection band is in a wavelength range of 850 nm to 1200 nm. (17) The laminate structure according to any one of (10) to (16), wherein the visible light transmittance is 70% or more. (18) A method for producing the laminate structure according to any one of (11) to (17), comprising a step of performing heat treatment at a temperature of 100°C or more and less than 130°C when forming the conductive layer. (19) A laminated glass comprising, in this order, glass 1, an intermediate layer 1, the laminate structure according to any one of (11) to (17), an intermediate layer 2, and glass 2. (20) The laminated glass according to (19), wherein glass 1 is located on the sunlight incidence side, and the conductive layer of the laminate structure is located on the intermediate layer 1 side. (21) An automobile comprising the laminated glass according to (19), wherein optical or thermal functions are exhibited by passing a current through the conductive layer of the laminated glass.

[0010] The present invention relates to a film that has excellent processability before and after processing into laminated glass and the like, and by using the film of the present invention, laminated glass that is excellent in appearance and design can be obtained.

[0011] The present invention will be described in detail below, but the present invention should not be construed as being limited to specific embodiments including the following examples, and various modifications that can achieve the object of the invention and do not deviate from the gist of the invention are included in the scope of the present invention.

[0012] The film of the present invention has at least one thermoplastic resin layer, and when the shrinkage percentage at temperature T°C in a heat shrinkage curve is S(T)%, and the direction in which S(150) is largest among any one direction in a plane parallel to the film surface and directions rotated from there up to 180° in an in-plane direction parallel to the film surface at 5° intervals is defined as the X direction, it is necessary for the X direction to satisfy 0.50≦|S(150)−S(100)| and 0.00≦|S(120)−S(100)|≦0.40. Here, the thermoplastic resin layer refers to a layer whose main component is a thermoplastic resin, i.e., a layer containing more than 50% by mass but not more than 100% by mass of thermoplastic resin when the entire layer is taken as 100% by mass.

[0013] Representative thermoplastic resins that can be used to form the thermoplastic resin layer of the film of the present invention are listed below, but the thermoplastic resins used in the present invention are not limited to those listed below. Examples of the thermoplastic resin layer of the film of the present invention include polyolefin resins typified by polyethylene, polypropylene, poly(1-butene), poly(4-methylpentene), polyisobutylene, polyisoprene, polybutadiene, polyvinylcyclohexane, polystyrene, poly(α-methylstyrene), poly(p-methylstyrene), polynorbornene, and polycyclopentene, polyamide resins typified by nylon 6, nylon 11, nylon 12, and nylon 66, copolymer resins of vinyl monomers typified by ethylene / propylene copolymer, ethylene / vinylcyclohexane copolymer, ethylene / vinylcyclohexene copolymer, ethylene / alkyl acrylate copolymer, ethylene / acrylic methacrylate copolymer, ethylene / norbornene copolymer, ethylene / vinyl acetate copolymer, propylene / butadiene copolymer, isobutylene / isoprene copolymer, and vinyl chloride / vinyl acetate copolymer, polyacrylate acrylic resins typified by polyisobutyl methacrylate, polymethacrylate, polymethyl methacrylate, polybutyl acrylate, polyacrylamide, polyacrylonitrile, and the like; polyester resins typified by polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, and the like; biodegradable polymers typified by polylactic acid, polybutyl succinate, and the like; and other polymers that can be used include polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyglycolic acid, polycarbonate, polyketone, polyether sulfone, polyether ether ketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polysiloxane, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, and the like.

[0014] In each thermoplastic resin layer, these thermoplastic resins may be used alone, or two or more types of thermoplastic resins may be used as a blend or alloy. By carrying out blending or alloying, physical / chemical properties that cannot be obtained from a single type of thermoplastic resin can be obtained. In addition, when thermoplastic resin layers having significantly different skeletal structures are laminated, if a component common to the polymer skeletal structure contained in the thermoplastic resin layer on one side of adjacent thermoplastic resin layers can be imparted as a copolymerization component to the thermoplastic resin layer on the opposite side, the interlayer adhesion at the interface can be improved.

[0015] In each thermoplastic resin layer constituting the film of the present invention, from the viewpoint of rheological properties such as strength, heat resistance, transparency, and lamination, the thermoplastic resin forming the thermoplastic resin layer is preferably selected from polyolefin resin, polyester resin, acrylic resin, polycarbonate resin, and polyamide resin. Among these, from the viewpoint of the above, polyester resin is more preferably used, and it is more preferable that at least one thermoplastic resin layer is a polyester resin layer. Even more preferable is a polyester resin obtained by polymerization of a monomer mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol.

[0016] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, and 4,4'-diphenylsulfonedicarboxylic acid. Examples of aliphatic dicarboxylic acids include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid, and ester derivatives thereof. Of these, terephthalic acid and 2,6-naphthalenedicarboxylic acid are preferred. These acid components may be used alone or in combination, and may further include partial copolymerization with oxyacids such as hydroxybenzoic acid.

[0017] Examples of diol components include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbate, and spiroglycol. Of these, ethylene glycol is preferred. These diol components may be used alone or in combination of two or more.

[0018] In each thermoplastic resin layer constituting the film of the present invention, it is particularly preferable to use a polyester resin selected from the above polyester resins, particularly polyethylene terephthalate and copolymers thereof, polyethylene naphthalate and copolymers thereof, polybutylene terephthalate and copolymers thereof, polybutylene naphthalate and copolymers thereof, polyhexamethylene terephthalate and copolymers thereof, and polyhexamethylene naphthalate and copolymers thereof.

[0019] The film of the present invention preferably has a structure in which 51 or more thermoplastic resin layers are laminated. By laminating thermoplastic resins, it is possible to impart a function to the film that cannot be achieved with only one thermoplastic resin layer. For example, in the case of a function such as light reflection, the more layers there are, the better the function can be, based on the principle of interference reflection. From the above perspective, the number of thermoplastic resin layers is more preferably 401 or more. By increasing the number of layers, the interference function derived from the lamination can be enhanced, and for example, heat ray blocking performance can be improved. From the viewpoint of increasing the size of the lamination device, the upper limit is about 5001 layers. A film having a structure in which 51 or more thermoplastic resin layers are laminated is considered a laminated film.

[0020] By forming the film of the present invention into the above-described laminate film, it becomes easy to realize the function of selectively reflecting light in a specific wavelength band by interference reflection, the function of reflecting light of a specific polarized light, etc., depending on the relationship between the difference in refractive index of each layer and the layer thickness. For example, when a laminate film having the function of reflecting infrared rays is formed, it can be sandwiched between two sheets of glass to form laminated glass with high heat-shielding performance. Alternatively, when a laminate film having the function of reflecting light of a specific polarized light is formed, it can be sandwiched between two sheets of glass to form a glass member suitable for a display device that displays images using light of a specific polarized light.

[0021] When two thermoplastic resin layers having different main components are designated as layer A1 and layer B1, the film of the present invention preferably has layer A1 and layer B1. When three thermoplastic resin layers having different main components are designated as layer A2, layer B2, and layer C2, the film of the present invention also preferably has a regular arrangement consisting of layer A2, layer B2, and layer C2.

[0022] In the film of the present invention, the term "main component" refers to a component contained in a layer at a concentration of more than 50% by mass and no more than 100% by mass. Examples of minor components that are not major components include inorganic components and low-molecular-weight organic components other than thermoplastic resins, such as light absorbers (ultraviolet absorbers, dyes, pigments, and heat absorbers), antioxidants, light stabilizers, quenchers, heat stabilizers, weather stabilizers, organic lubricants, fillers, antistatic agents, nucleating agents, and flame retardants. These minor components can be freely added to each layer to the extent that the film's inherent properties and functions are not impaired.

[0023] Among these minor components, depending on the type of thermoplastic resin constituting each thermoplastic resin layer, it may absorb high-energy ultraviolet light, accelerating degradation. Therefore, it is preferable to include an ultraviolet absorber in order to suppress photodegradation by causing reaction competition. Furthermore, light absorbers such as ultraviolet absorbers may themselves be affected by degradation due to heat or oxygen, or photodegradation due to reaction with ultraviolet light or oxygen, during the resin extrusion process in film production. Therefore, antioxidants for the former and light stabilizers or quenchers for the latter can be added as additives to layers containing thermoplastic resins that may be subject to degradation, to the extent that the original physical properties and functions of the film are not impaired.

[0024] In the film of the present invention, the thermoplastic resin layers are "different" in that they fall into at least one of the following categories: (1) they have different compositions; (2) they have different glass transition temperatures or melting points in differential scanning calorimetry (DSC); and (3) they have different contrasts in images after dyeing when cross-sectionally observed by transmission electron microscopy (TEM).

[0025] "Different compositions" means that the following conditions for "same composition" are not met: "Same composition" means that the repeating units of the chemical structures of the thermoplastic resins constituting each thermoplastic resin layer are 95 mol % or more and 100 mol % or less in common, or when comparing the constituent components of each thermoplastic resin layer, 95 mass % to 100 mass % or less of the components are common.

[0026] For example, in the former case, polyethylene terephthalate has as its main structural unit a structural unit (ethylene terephthalate unit) in which an ethylene glycol unit and a terephthalic acid unit are bonded by an ester bond, but when the resins constituting the layers share a common chemical structure, an ethylene terephthalate skeleton, but the amount of copolymerization component exceeds 5 mol%, such as a layer made of homopolyethylene terephthalate and a layer made of polyethylene terephthalate copolymerized with 10 mol% of isophthalic acid, the two are considered to have different compositions.Furthermore, in the latter case, when the same structural component is the main component but the components differ by more than 5 mass%, such as a layer made only of homopolyethylene terephthalate and a layer containing 90 mass% homopolyethylene terephthalate with the remaining 10 mass% being other components, the two are also considered to have different compositions. The repeating unit structure of the specific composition / chemical structure of each thermoplastic resin layer can be identified by determining the layer thickness of each thermoplastic resin layer according to the method described below in the layer structure measurement method, and then cutting and removing the thermoplastic resin layer, or by scraping the layer to expose the outermost layer, using infrared spectroscopy (FT-IR method or nano-IR method), a gas chromatograph / mass spectrometer (GC-MS), a nuclear magnetic resonance apparatus (NMR), or the like.

[0027] On the other hand, if it is difficult to identify the composition by the above method after extracting each thermoplastic resin layer, the thermoplastic resin layers constituting the laminate film can be determined to be "different" by showing different melting points and / or glass transition points in differential scanning calorimetry (DSC). In the present invention, "showing different melting points" and "showing different glass transition temperatures" means that the melting points and glass transition points differ by 0.1°C or more, preferably 2°C or more. On the other hand, there are cases where the thermoplastic resin layers do not show a glass transition point or melting point. However, if one thermoplastic resin layer shows a glass transition point or melting point and the other thermoplastic resin layer does not, the temperature difference cannot be calculated, but the thermoplastic resin layers are interpreted as being different. In the present invention, DSC measurements can be performed using the method of JIS-K-7122 (1987) with a measurement temperature range of 25°C to 300°C.

[0028] In the above two methods, it is necessary to separate the corresponding thermoplastic resin layer from the film for analysis, but separation of the layers can be difficult. Therefore, in the present invention, for the sake of simplicity, if it is possible to recognize the layer interface by contrast difference in the cross-sectional image observed by transmission electron microscope observation, and it is confirmed that the difference in the average brightness of two adjacent layers is greater than any of the standard deviations of brightness within each of the adjacent thermoplastic resin layers by the method described in the section on layer interface (contrast difference) in the measurement method described below, the contrast of the image after dyeing is considered to be different, and the compositions of the adjacent thermoplastic resin layers are determined to be "different."

[0029] This contrast difference arises due to differences in electron beam scattering, crystal diffraction, etc. between thermoplastic resin layers. Therefore, if the composition of the thermoplastic resin layers differs according to the above-mentioned criteria, the crystallinity and electron density state will differ depending on the type of thermoplastic resin constituting each thermoplastic resin layer and the copolymerization amount of the combined thermoplastic resin, and the electron staining state will also differ. In other words, if the laminate film has thermoplastic resin layers with different compositions, each thermoplastic resin layer can be visually recognized as a layer structure with a contrast difference in a cross-sectional image of the laminate film. The presence or absence of a contrast difference can be evaluated using the method described below.

[0030] When two types of thermoplastic resin layers having different main components are designated as the A1 layer and the B1 layer, the film of the present invention preferably has the A1 layer and the B1 layer. From the viewpoints of interlayer adhesion and the ease of realizing a highly accurate laminate structure, the two types of thermoplastic resin layers preferably contain thermoplastic resins having the same basic skeleton. The basic skeleton is the repeating unit most abundant in the molecular chain, for example, in the case of polyethylene terephthalate, this corresponds to the ethylene terephthalate unit, and in the case of polyethylene, this corresponds to the ethylene unit. In addition, in such an embodiment, when a structure in which 51 or more thermoplastic resin layers are laminated is formed, it is preferable to have a structure in which the A1 layer and the B1 layer are alternately laminated.

[0031] A preferred combination of thermoplastic resins used in the A1 layer and the B1 layer of the film of the present invention is one in which the thermoplastic resin as the main component of the A1 layer and the thermoplastic resin as the main component of the B1 layer have the same basic skeleton. When the thermoplastic resins as the main components of each layer have the same basic skeleton, lamination precision is high and delamination at the lamination interface is less likely to occur.

[0032] To endow thermoplastic resins with the same basic skeleton with different properties, it is preferable to use one of them as a copolymer, or to use both as copolymers with different types or amounts of copolymerized copolymerized units. An example of the former is a case where one thermoplastic resin is homopolyethylene terephthalate and the other thermoplastic resin is a resin composed of ethylene terephthalate units and repeating units having other ester bonds. The proportion of the other repeating units (sometimes referred to as the copolymerization amount) is preferably 5 mol% or more due to the need to achieve different properties, while less than 50 mol% is preferred because it provides excellent interlayer adhesion and small differences in thermal flow properties, resulting in excellent thickness accuracy and thickness uniformity for each layer. A ratio of 10 mol% to 45 mol% is even more preferred. An example of the latter is a case where the thermoplastic resin is a resin composed of ethylene terephthalate units and repeating units having other ester bonds, with the copolymerization amounts being different from each other. It is also desirable for the A1 layer and the B1 layer to each be a blend or alloy of multiple types of thermoplastic resins. By blending or alloying multiple types of thermoplastic resins, it is possible to obtain properties that cannot be obtained with a single type of thermoplastic resin.

[0033] In addition, a preferred combination of thermoplastic resins used as the main components of the A1 layer and the B1 layer of the film of the present invention is one in which the difference in glass transition temperature between the respective thermoplastic resins is 20° C. or less. A difference in glass transition temperature of 20° C. or less improves thickness uniformity during film formation of the laminated film, resulting in more uniform reflection characteristics. Furthermore, the occurrence of overstretching during film formation can be reduced.

[0034] When the film of the present invention has a layer structure in which A1 layers and B1 layers are alternately laminated and the A1 layers are disposed as the outermost layers on both sides, it is more preferable that the glass transition temperature of the thermoplastic resin A1 is higher than that of the thermoplastic resin B1 when the difference in glass transition temperature between the thermoplastic resin that is the main component of the A1 layer (thermoplastic resin A1) and the thermoplastic resin that is the main component of the B1 layer (thermoplastic resin B1) is greater than 5° C. The relatively high glass transition temperature of the outermost layer A1 reduces adhesion to rolls or clips during longitudinal stretching or transverse stretching, thereby suppressing deterioration in appearance quality.

[0035] In the film of the present invention, the difference in the in-plane average refractive index between layer A and layer B is preferably 0.03 or more. It is more preferably 0.05 or more, and even more preferably 0.10 or more. When the difference in the in-plane average refractive index between layer A and layer B is 0.03 or more, sufficient reflectance can be obtained, resulting in improved heat-blocking performance, for example. One method for achieving the difference in the in-plane average refractive index between layer A and layer B within the above range is to use a method in which one of resins A and B is crystalline and the other is amorphous. Crystallinity here refers to a melting enthalpy of 10 J / g or more in differential scanning calorimetry (DSC). Similarly, amorphousness refers to a melting enthalpy of less than 10 J / g. With such a resin combination, an in-plane refractive index difference can be easily achieved during the stretching and heat treatment steps in film production. In the case of amorphous resins, the refractive index usually remains unchanged during the stretching and heat treatment steps in film production. Therefore, the refractive index can also be measured by vacuum-drying the resin and then pressing it into a sheet, as needed. The in-plane refractive index refers to the average value of the refractive index in the X direction and the Y direction (described later) (the method for specifying each direction and the method for measuring the refractive index will be described in detail later).

[0036] As an example of a resin combination that satisfies the above conditions, in the film of the present invention, it is preferable that the A1 layer be primarily composed of polyethylene terephthalate or polyethylene naphthalate, and the B1 layer be primarily composed of a polyester having the same basic skeleton as the primary component of the A1 layer and containing spiroglycol. The spiroglycol-containing polyester refers to a copolyester copolymerized with spiroglycol, or a polyester blended with a copolyester copolymerized with spiroglycol. Spiroglycol-containing polyesters are preferred because they have a small difference in glass transition temperature from polyethylene terephthalate or polyethylene naphthalate, making them less susceptible to overstretching during molding and less susceptible to delamination. From the above perspective, a more preferable embodiment is one in which the A1 layer is primarily composed of polyethylene terephthalate or polyethylene naphthalate, and the B1 layer is primarily composed of a polyester having the same basic skeleton as the primary component of the A1 layer and containing spiroglycol and cyclohexanedicarboxylic acid. When the B1 layer is primarily composed of a polyester containing spiroglycol and cyclohexanedicarboxylic acid, the difference in in-plane refractive index between the B1 layer and polyethylene terephthalate or polyethylene naphthalate is large, making it easier to achieve high reflectance by alternately laminating the A1 layer and the B1 layer. Furthermore, such a polyester has a small difference in glass transition temperature between the B1 layer and polyethylene terephthalate or polyethylene naphthalate, and exhibits excellent adhesive properties. Therefore, the film is less likely to be overstretched during molding, and delamination between the A1 layer and the B1 layer can be reduced.

[0037] The copolymerization amount of the polyester containing spiro glycol and cyclohexanedicarboxylic acid is preferably 5 mol % to 30 mol % of spiro glycol and 5 mol % to 30 mol % of cyclohexanedicarboxylic acid. The copolymerization amount of the polyester containing spiro glycol is preferably 5 mol % or more and less than 50 mol %.

[0038] Furthermore, when the film of the present invention has a layer structure in which the A1 layer and the B1 layer are alternately laminated and the A1 layer is disposed as the outermost layer on both sides, it is also preferable that the A1 layer is mainly composed of a crystalline polyester and the A2 layer is mainly composed of an amorphous polyester. With such a resin combination, as described above, an in-plane refractive index difference can be easily established in the stretching and heat treatment steps in film production, and orientation can be alleviated by heat treatment at a temperature much higher than the glass transition temperature of the amorphous polyester and equal to or lower than the melting point of the crystalline polyester.

[0039] Other preferred embodiments include those in which the A1 layer contains a small amount of the resin that is the main component of the B1 layer, those in which the B1 layer contains a small amount of the resin that is the main component of the A1 layer, and those in which both of the above are combined. By blending small amounts of the resins that are the main components of either the A1 layer or the B1 layer, or both, high-precision lamination, improved interlayer adhesion, and improved stretchability during film formation can be achieved. The blending ratio is preferably in the range of 5% to 30% by mass, with the entire layer being taken as 100% by mass.

[0040] Furthermore, the film of the present invention preferably has a regular arrangement consisting of the A2 layer, the B2 layer, and the C2 layer, when the three thermoplastic resin layers have different main components and are designated as the A2 layer, the B2 layer, and the C2 layer, respectively. Here, the term "regular arrangement" refers to a laminate structure in which three "different" thermoplastic resin layers are laminated in a regular arrangement, as defined above. In this case, the three different thermoplastic resin layers may each be formed from a thermoplastic resin having a different skeletal structure, or two different thermoplastic resins with different skeletal structures may be used, and the three thermoplastic resin layers may be designed so that their blend ratios or copolymerization amounts are different. For convenience, hereafter in this specification, the different thermoplastic resin layers will be defined alphabetically as the A2 layer, the B2 layer, and the C2 layer in the order in which they first appear when viewed from the outermost surface of the film, and the thermoplastic resins that are the main components of each thermoplastic resin layer will be defined as the thermoplastic resin A2, the thermoplastic resin B2, and the thermoplastic resin C2.

[0041] When the different thermoplastic resin layers are defined as the A2 layer, the B2 layer, and the C2 layer in the order of arrangement from the outermost surface of the laminate film, examples of the regular arrangement possessed by the film of the present invention include (ABC)x, (ABCB)x, (ABAC)x, (ABCAB)x, (ABCAC)x, (ABABC)x, and (ABCBCB)x (the numbers in parentheses represent the regular arrangement, and x is a natural number indicating the number of repetitions. A, B, and C represent the A2 layer, the B2 layer, and the C2 layer, respectively. Note that similar notations may be used hereinafter in describing the regular arrangement consisting of the A2 layer, the B2 layer, and the C2 layer.) In particular, in order for a film made of thermoplastic resins with different physical / chemical properties such as skeletal structure and viscoelasticity / viscosity characteristics to maintain the laminate structure over a long period of time without interfacial peeling and without impairing necessary functions, it is necessary to consider a combination of thermoplastic resin layers that have good compatibility (compatibility, surface free energy, etc.) with the adjacent thermoplastic resin layers that form the interface between the different thermoplastic resin layers contained in the film.

[0042] Therefore, to avoid complicating the resin design of the entire film, it is preferable to limit the number of different interface combinations formed between adjacent thermoplastic resin layers. Specifically, the interfaces formed by three different types of thermoplastic resin layers include three types: the A2-B2 interface, the B2-C2 interface, and the C2-A2 interface. Among the regular arrangements, (ABCB)x and (ABCBCB)x are preferred because only two types exist: the A2-B2 interface and the B2-C2 interface. In such an embodiment, it is sufficient to design the resin so that delamination between the A2 layer and the B2 layer, and between the B2 layer and the C2 layer, is unlikely to occur, and the combination of the A2 layer and the C2 layer does not need to be given much consideration.

[0043] The film of the present invention must satisfy the following conditions in the X direction: 0.50≦|S(150)−S(100)| and 0.00≦|S(120)−S(100)|≦0.40, where S(T)% is the shrinkage percentage at temperature T°C in the heat shrinkage curve, and the direction in which S(150) is greatest among any one direction in a plane parallel to the film surface and directions rotated up to 180° at 5° intervals in an in-plane direction parallel to the film surface. The heat shrinkage curve here is measured by thermomechanical analysis at a temperature of 25°C to 200°C and a heating rate of 10°C / min, with a positive value indicating shrinkage and a negative value indicating expansion, based on the length at 25°C. More preferably, 0.50≦|S(150)−S(100)|≦2.60 and 0.00≦|S(120)−S(100)|≦0.30 are satisfied, even more preferably, 1.00≦|S(150)−S(100)|≦2.60 and 0.00≦|S(120)−S(100)|≦0.20 are satisfied, and particularly preferably, 1.00≦|S(150)−S(100)|≦2.60 and 0.00≦|S(120)−S(100)|≦0.19 are satisfied.

[0044] By satisfying 0.50≦|S(150)−S(100)| in the X direction of the film, uneven pressing due to uneven thickness of the intermediate layer and uneven distortion of the film due to differences in thermal shrinkage stress between the intermediate layer and the film, which occur when producing molded articles such as laminated glass, can be suppressed, improving the appearance of the laminated glass. Furthermore, by satisfying 0.00≦|S(120)−S(100)|≦0.40 in the X direction of the film, efficient and satisfactory processing is possible without film deformation or curling due to differences in shrinkage rate with the functional layer during the heating step when laminating the film to the film. Furthermore, when the direction rotated 90° from the X direction parallel to the film surface is defined as the Y direction, the ratio of the shrinkage rates in the X direction to the Y direction is preferably 0.5 or more and 2.0 or less. Poor balance in the shrinkage rates in the X direction and the Y direction may result in wrinkles during processing, but achieving a good balance allows for laminated glass with fewer wrinkles to be obtained.

[0045] The film of the present invention preferably has a shrinkage start temperature in the X direction in a heat shrinkage curve of 110°C or higher and 170°C or lower. Here, the shrinkage start temperature in the heat shrinkage curve is the temperature at which the shrinkage rate exceeds 0% relative to 25°C in the heat shrinkage curve of the film measured under conditions of a temperature of 25°C to 200°C and a heating rate of 10°C / min. Having a shrinkage start temperature of 110°C or higher can reduce deformation of the film and curling due to differences in shrinkage rate with the functional layer during the heating step when laminating the functional layer. Furthermore, having a shrinkage start temperature of 170°C or lower can suppress uneven pressing due to uneven thickness of the intermediate layer when producing a molded product such as laminated glass, and uneven distortion of the film due to differences in thermal shrinkage stress between the intermediate layer and the film. From the above viewpoints, the shrinkage start temperature in the X direction in the heat shrinkage curve is more preferably 110°C or higher and 150°C or lower, and even more preferably 110°C or higher and lower than 140°C.

[0046] The film of the present invention preferably has, in the X direction, an average shrinkage rate from 100°C to 120°C on a heat shrinkage curve of -0.40% to 0.50%, and an absolute value of the average rate of change in shrinkage rate from 120°C to 150°C of 0.04% / °C or more. Here, the "average shrinkage rate from 100°C to 120°C on a heat shrinkage curve" refers to the average value of all measured values ​​from 100°C to 120°C on the heat shrinkage curve, and the "absolute value of the average rate of change in shrinkage rate from 120°C to 150°C" refers to the absolute value of the difference between S(150) and S(120) divided by the temperature difference of 30°C between 120°C and 150°C. By adopting such an embodiment, the film is less likely to curl due to differences in shrinkage rate from the functional layer during the heating step when laminating the functional layer, and uneven distortion during subsequent processing to obtain a molded product such as laminated glass is reduced.

[0047] A specific example of a method for imparting the above-mentioned properties of 0.50≦|S(150)−S(100)| and 0.00≦|S(120)−S(100)|≦0.40 in the X direction to the film of the present invention will be described below, but it should not be construed as being limited to this method.

[0048] One method for imparting the above-mentioned properties of 0.50≦|S(150)−S(100)| and 0.00≦|S(120)−S(100)|≦0.40 in the X direction to the film of the present invention is to subject a sheet satisfying 0.50≦|S(150)−S(100)| to off-annealing treatment at a temperature of 100° C. or higher and 140° C. or lower, preferably 110° C. or higher and lower than 140° C., more preferably 125° C. or higher and lower than 140° C. In this case, preferably, a sheet satisfying 1.00≦|S(150)−S(100)|, more preferably 1.50≦|S(150)−S(100)|, and even more preferably 1.50≦|S(150)−S(100)|≦3.50 is used. By making |S(150)-S(100)|≦3.50, the sheet shrinks less when subjected to off-annealing treatment, and the occurrence of scratches and the like can be reduced.

[0049] Furthermore, it is preferable that the sheet satisfy 0.40<|S(120)-S(100)|. A method for obtaining the sheet will be described later. By obtaining a sheet that satisfies 0.40<|S(120)-S(100)|, it becomes easier to satisfy 0.50≦|S(150)-S(100)| and adjust |S(150)-S(100)| to the more preferable range described above. In this case, it is more preferable to use a sheet that satisfies 0.45<|S(120)-S(100)|<0.85. By satisfying |S(120)-S(100)|<0.85, the sheet shrinks less when subjected to off-annealing treatment, reducing the occurrence of scratches and the like.

[0050] Here, the sheet may be an unoriented sheet formed by a melt extrusion process or a casting process, or a biaxially oriented sheet obtained by subsequently biaxially stretching an unoriented sheet. Biaxial stretching refers to stretching in the longitudinal and width directions. Stretching may be performed in two directions sequentially or simultaneously. Furthermore, if necessary, further re-stretching may be performed in the longitudinal and / or width directions. Here, the longitudinal direction refers to the running direction of the sheet or film (the winding direction of the film in the case of a film roll), and the width direction refers to the direction perpendicular to the longitudinal direction within the film plane. In particular, in the present invention, it is preferable to use a biaxially oriented sheet from the viewpoint of isotropizing mechanical properties such as heat shrinkage behavior.

[0051] Next, a preferred production method for obtaining a biaxially oriented sheet satisfying 0.50≦|S(150)−S(100)|, which is suitable for the film of the present invention, will be explained below using a sequential biaxial stretching method as an example, but the present invention should not be construed as being limited to such an example.

[0052] First, the thermoplastic resin constituting each thermoplastic resin layer of the sheet is prepared in the form of pellets or the like. Here, when forming an alloy of amorphous polyester and crystalline polyester, it is preferable to prepare pellets kneaded in advance using a twin-screw extruder or the like. The dispersion state of the crystalline polyester can be controlled by selecting the screw of the twin-screw extruder, controlling the discharge rate, screw rotation speed, kneading temperature, etc., and can also be controlled by adding a compatibilizer such as a polyester elastomer. By preparing pellets kneaded in advance using a twin-screw extruder or the like in this way, it becomes possible to control the dispersion state and domain size of the crystalline polyester in the amorphous polyester.

[0053] The pellets are then dried in hot air or under vacuum as needed and then fed into separate extruders. The pellets are heated and melted in each extruder to a temperature above the melting point or between 250 and 330°C. The resin extrusion rate is then uniformized using a gear pump or the like, and foreign matter and denatured resin are removed from the molten resin through a filter or the like. The resin is then formed into a sheet using a die, discharged, and cooled and solidified on a cooling body such as a casting drum to obtain an unoriented sheet. In this process, it is preferable to use a wire-, tape-, needle-, or knife-shaped electrode to electrostatically adhere the molten sheet to a cooling body such as a casting drum, thereby rapidly solidifying it. Other preferable methods for adhering the molten sheet to a cooling body include blowing air from a slit-, spot-, or planar-shaped device to adhere the molten sheet to the cooling body, and using a nip roll to adhere the molten sheet to the cooling body. The surface temperature of the casting drum is preferably 20 to 50°C.

[0054] Furthermore, when producing a sheet consisting of multiple thermoplastic resin layers, multiple resins are fed from different channels using two or more extruders and then fed into a multi-layer lamination device. Multi-manifold dies, feed blocks, static mixers, etc. can be used as multi-layer lamination devices. However, in order to efficiently obtain a desirable layer structure in the film of the present invention, it is preferable to use a feed block containing at least two or more separate members with multiple fine slits. The use of such a feed block prevents the device from becoming excessively large, suppresses the generation of foreign matter due to thermal degradation, and enables high-precision lamination even when the number of layers is extremely large. Furthermore, the lamination accuracy in the width direction is significantly improved compared to conventional technology, and it is also easy to form an arbitrary layer thickness structure. This device allows the thickness of each layer to be adjusted by the shape (length, width) of the slits, making it easy to achieve an arbitrary layer thickness. The molten multi-layer laminate formed in this manner with the desired layer structure is introduced into a die, and an unoriented sheet is obtained in the same manner as described above.

[0055] The resulting unoriented sheet is then biaxially stretched in the longitudinal and width directions. Here, stretching in the longitudinal direction refers to uniaxial stretching to impart molecular orientation to the sheet in the longitudinal direction, and is typically performed by varying the peripheral speed of the longitudinal stretching machine rolls. This stretching can be performed in one step or in multiple steps using multiple pairs of rolls. The stretching ratio varies depending on the type of resin, but is typically preferably 2 to 10 times. For example, when using polyethylene terephthalate or polyethylene naphthalate, which are thermoplastic resins that form the crystalline thermoplastic resin layer preferably used in the film of the present invention, a ratio of 2 to 7 times is particularly preferred. If the stretching ratio is excessively large during the longitudinal stretching step, strong orientation can occur, resulting in neckdown in the width direction, making it impossible to obtain a sufficient sheet width, and can also result in significant thickness unevenness in the longitudinal and / or width directions after width stretching. Furthermore, the stretching temperature is preferably set within the range of the glass transition temperature of the thermoplastic resin layer with the highest glass transition temperature among the thermoplastic resin layers constituting the sheet to the glass transition temperature + 100°C.

[0056] The uniaxially stretched sheet is then stretched in the width direction. Prior to this, if necessary, surface treatments such as corona treatment, flame treatment, and plasma treatment may be performed, followed by the application of an easy-adhesion layer by in-line coating to provide properties such as slipperiness, adhesion, and antistatic properties. In the in-line coating process, the easy-adhesion layer may be applied to one side of the laminated film, or to both sides of the sheet simultaneously or sequentially. Width-direction stretching refers to stretching to impart width-direction orientation to the sheet. This is typically carried out by using a tenter to hold both widthwise ends of the sheet with clips and conveying the sheet while increasing the distance between the opposing clips. The stretching ratio varies depending on the type of resin, but is typically preferably 2 to 10 times. For example, when using polyethylene terephthalate or polyethylene naphthalate, which are thermoplastic resins that form the crystalline thermoplastic resin layer preferably used in the film of the present invention, a stretching ratio of 2 to 7 times is particularly preferred. The stretching temperature is preferably between the glass transition temperature of the resin with the highest glass transition temperature among the resins constituting the sheet and the glass transition temperature + 120°C.

[0057] The biaxially stretched sheet is then heat-treated in a tenter at a temperature equal to or higher than the stretching temperature but lower than the melting point of the thermoplastic resin layer with the highest melting point among the thermoplastic resin layers constituting the sheet, preferably at a temperature equal to or higher than the stretching temperature but lower than the melting point of the thermoplastic resin layer with the highest melting point among the thermoplastic resin layers constituting the sheet -30°C. The sheet is then uniformly and slowly cooled, then cooled to room temperature, and wound up. If necessary, a relaxation treatment or the like may be performed in the longitudinal and / or transverse directions between the heat treatment and the slowly cooling to impart thermal dimensional stability.

[0058] Here, in order to obtain a sheet satisfying the relationship 0.50≦|S(150)−S(100)|, which is suitable for the film of the present invention, it is preferable to strengthen the longitudinal orientation by adjusting the longitudinal stretching ratio and the longitudinal stretching temperature. For example, when polyethylene terephthalate (PET) is used as one of the thermoplastic resins, the desired sheet is easily obtained by adjusting the longitudinal stretching temperature to 95°C or less and / or the longitudinal stretching ratio to 3.5 times or more. Similarly, it is also preferable to strengthen the orientation in the direction perpendicular to the longitudinal direction (width direction) by adjusting the transverse stretching temperature and the transverse stretching ratio. For example, when PET is used as one of the thermoplastic resins, the desired sheet is easily obtained by adjusting the transverse stretching temperature to 110°C or less and / or the transverse stretching ratio to 3.8 times or more. Furthermore, in order to suppress the difference in the thermal shrinkage behavior of the sheet between the longitudinal direction and the direction perpendicular thereto, it is desirable to adjust the longitudinal stretching conditions and the transverse stretching conditions. Specifically, the heat shrinkage behavior can be made isotropic by setting the difference between the longitudinal stretching ratio and the transverse stretching ratio to 0.8 times or less, and by setting the temperature difference between the longitudinal stretching temperature and the transverse stretching temperature to 15°C or more and 50°C or less.

[0059] Furthermore, in a sheet manufacturing method suitable for the film of the present invention, it is preferable that the heat treatment temperature after stretching is below the melting point of at least one thermoplastic resin and above the melting point of at least one of the remaining thermoplastic resins. In this case, one thermoplastic resin maintains a high orientation state while the orientation of the other thermoplastic resin is relaxed, making it easy to achieve a refractive index difference between these resins, and also making it possible to impart high heat shrinkage behavior to the oriented thermoplastic resin. For example, in a film having two thermoplastic resin layers (A1 layer, B1 layer) with different main components, where the A1 layer is made of a crystalline polyester (crystalline polyester A1) and the B1 layer is made of an amorphous polyester and a crystalline polyester (crystalline polyester B1) different from the crystalline polyester A1, it is preferable that the heat treatment temperature be below the melting points of the crystalline polyester A1 and the crystalline polyester B1. In this case, the orientation of the crystalline polyester A1 and the orientation of the crystalline polyester B1 are maintained, thereby imparting more favorable heat shrinkage behavior.

[0060] Furthermore, since the relaxation treatment is carried out to suppress heat shrinkage behavior, it is also preferable not to perform a relaxation treatment on a sheet suitable for the film of the present invention, and the preferred degree of relaxation treatment is a ratio of the relaxation treatment to the sheet width before the relaxation treatment of 0% to 5%. Although it depends on the type of thermoplastic resin used, for example, in the case of polyethylene terephthalate and an amorphous polyester that is completely melted in the heat treatment step, a sheet with the best heat shrinkage behavior can be obtained by a ratio of the relaxation treatment to the film width before the relaxation treatment in the range of about 0% to 1%.

[0061] Next, a method for producing the film of the present invention will be described. The method for producing the film of the present invention includes an off-annealing step in which a sheet satisfying 0.50≦|S(150)−S(100)| is heat-treated at a temperature of 110°C or higher but lower than 140°C. More preferably, the off-annealing step includes the sheet satisfying 0.40<|S(120)−S(100)|. An off-annealing step suitable for obtaining the film of the present invention will be described below. The off-annealing step is a step in which a sheet that has been wound up is heat-treated again. Sheets obtained by the above-described method that satisfy 0.50≦|S(150)−S(100)| generally do not satisfy 0.00≦|S(120)−S(100)|≦0.40. However, by subjecting a sheet that satisfies 0.50≦|S(150)−S(100)| to a heat treatment at 110°C or higher but lower than 140°C, a film that satisfies 0.50≦|S(150)−S(100)| and 0.00≦|S(120)−S(100)|≦0.40 can be obtained.

[0062] Generally, when reducing the shrinkage at a certain temperature, reheating at a temperature 10°C or higher is effective. Therefore, annealing at a temperature of 110°C or higher is effective for reducing S(120), i.e., the shrinkage at 120°C. On the other hand, when annealing at a temperature of 140°C or higher, S(150), i.e., the shrinkage at 150°C, is also reduced, and the resulting film may not satisfy 0.50≦|S(150)−S(100)|. However, even when annealing at a temperature of 140°C or higher, if the annealing time is short (i.e., the sheet conveying speed is fast), 0.50≦|S(150)−S(100)| may be satisfied. Similarly, even when annealing at a temperature below 110°C, if the annealing time is sufficient, 0.00≦|S(120)−S(100)|≦0.40 may be satisfied. However, if the difference between the desired temperature at which the shrinkage rate should be reduced and the re-heat treatment temperature is too large, problems may arise in the flatness of the film and the controllability of the shrinkage rate, so the preferred heat treatment temperature in the off-annealing step is 110°C or higher and lower than 140°C.

[0063] Furthermore, the present invention has found that even when the sheet satisfies 0.40<|S(120)-S(100)|, reheating at 110°C or higher but lower than 140°C reduces S(120) while maintaining a high S(150), i.e., a film can be obtained that satisfies 0.50≦|S(150)-S(100)| and 0.00≦|S(120)-S(100)|≦0.40.

[0064] Furthermore, when the width direction is the X direction, the width direction is left free during the off-annealing process, i.e., the sheet is not restrained in the width direction, which makes it easy to keep the shrinkage rate in the width direction within the above range. Furthermore, when the longitudinal direction is the X direction, the shrinkage rate in the longitudinal direction can also be easily kept within the above range by slowing the winding speed in the longitudinal direction by 0.5 to 5% lower than the unwinding speed. Furthermore, the shrinkage rate can also be adjusted by providing a stepwise cooling zone after the heat treatment.

[0065] The film of the present invention is suitable for use as a laminated glass having an intermediate layer and a support after undergoing a process of laminating a functional layer with heating. That is, a laminated structure can be formed by laminating a functional layer on at least one surface of the film of the present invention. Here, the functional layer refers to a layer having a function not found in the film of the present invention, such as an easy-adhesion layer, a hard coat layer, an abrasion-resistant layer, a scratch-resistant layer, an anti-reflection layer, a color correction layer, an ultraviolet absorbing layer, a heat absorbing layer, a printing layer, a gas barrier layer, an adhesive layer, a conductive layer, or a protective layer.

[0066] When a functional layer is laminated on the film of the present invention to form a laminated structure, a coating agent that forms the functional layer may be applied to the film, and a heating step at 100°C or higher but lower than 130°C may be performed to remove the solvent and harden the film. In this case, if the film does not satisfy 0.00≦|S(120)−S(100)|≦0.40, i.e., if |S(120)−S(100)|>0.40, the film may become deformed, such as wrinkled, during the heating step. In this case, cracks, distortions, curls, etc. may also occur in the functional layer, and the function of the functional layer may not be fully realized. Therefore, a manufacturing method for obtaining the laminated structure of the present invention preferably includes a step of performing a heat treatment at a temperature of 100°C or higher but lower than 130°C.

[0067] In the laminated structure of the present invention, it is also preferable that at least one of the functional layers is a conductive layer. The conductive layer is not particularly limited as long as it acts when an electric current is applied, but it may be formed of conductive fibers such as silver nanowires or carbon nanotubes, or a combination thereof. It may also be a film containing Ag, Cu, or a metal oxide as a constituent component. These may be used alone or in combination of two or more types, and a conductive layer formed of these generally functions as a transparent electrode. As the metal oxide, ITO (In ２ O ３ :Sn), ATO(SnO ２ :Sb), FTO(SnO ２ Examples include ZnO (ZnO:F), AZO (ZnO:Al), GZO (ZnO:Ga), etc. Among these, Ag and Cu may be subject to deterioration due to oxidation, so the conductive layer is preferably a film containing metal oxide, particularly ITO, as the main component, where the main component refers to a component contained in the conductive film in an amount of more than 50 mass % and not more than 100 mass %.

[0068] Furthermore, in the laminate structure of the present invention, it is also preferable that the functional layer has a plurality of layers, at least one of which is a second film having an absolute value of shrinkage percentage of 0.20% or less at 120° C. Here, "at least one of the functional layers has an absolute value of shrinkage percentage of 0.20% or less at 120° C." ... means that the absolute values ​​of shrinkage percentage at 120° C. are 0.20% or less in any one direction within the plane of the second film and in each direction rotated from that direction up to 180° at 5° intervals in an in-plane direction parallel to the plane.

[0069] For example, when laminating a functional layer in the film of the present invention, a protective layer may be pre-laminated on the surface opposite to the surface on which the functional layer is to be laminated to prevent scratches or stains on the film due to handling or the like. Alternatively, even if a functional layer is not laminated, a protective layer may be laminated to prevent scratches or stains on the film due to handling or the like during the off-annealing process of the film of the present invention. This protective layer may be composed of a film separate from the film of the present invention, and the film constituting this protective layer is referred to as the second film in the present invention. By keeping the absolute value of the shrinkage rate of the second film at 120°C to 0.20% or less, curling due to the difference in shrinkage rate between the second film (protective layer) and the film of the present invention is suppressed during the heating process of laminating another functional layer on the opposite surface, and the functional layer on the surface opposite the protective layer can be easily laminated without impairing its function. Therefore, it is preferable that the absolute value of the shrinkage rate of the second film at 120°C is 0.20% or less.

[0070] Furthermore, a laminate structure is preferred in which the orientation angle of the film of the present invention is θb and the orientation angle of the second film is θf, such that |θb - θf| ≦ 30°. The orientation angle here refers to the direction in which the refractive index of the film is greatest, and is actually measured by optical techniques. Furthermore, |θb - θf| is the maximum value in the longitudinal direction and at both ends of the longitudinal direction of the laminated films. In the sequential biaxial stretching used in the production of typical biaxially stretched films, a clip-type tenter is used, particularly when stretching the film in the width direction. In this method, the film is stretched along the rails while both ends are held by clips, and the stress applied in the film flow direction is different between the center portion of the film and the portion near the clips, resulting in a difference in orientation angle in the width direction of the film. Biaxially stretched films produced in this manner tend to shrink in the direction of the orientation angle when heated. When the orientation angle θb of the film of the present invention and the orientation angle θf of the second film are |θb-θf|≦30°, this means that the difference in orientation angle between the film of the present invention and the second film is small, and the occurrence of curling due to the difference in orientation angle between the film of the present invention and the second film, which is the protective layer, is suppressed, and the functional layer on the side opposite the protective layer can be easily laminated without impairing its function.

[0071] There are no particular limitations on the method for controlling the orientation angle. However, when it is desired to increase the orientation angle of a film by sequential longitudinal and transverse biaxial stretching, it is effective to increase the orientation in the film flow direction of a uniaxially stretched film by lowering the longitudinal stretching temperature or increasing the longitudinal stretching ratio, or to weaken the orientation in the film width direction during the heat treatment process by lowering the transverse stretching temperature or increasing the heat treatment temperature.

[0072] Furthermore, when it is desired to reduce the orientation angle of a film, it is effective to weaken the orientation in the film machine direction of a uniaxially stretched film by increasing the longitudinal stretching temperature or decreasing the longitudinal stretching ratio, or to weaken the orientation in the film width direction by increasing the transverse stretching temperature or decreasing the heat treatment temperature. Furthermore, it is also effective to provide a difference in the transverse stretching speed or stretching temperature during the transverse stretching process. Specifically, when the transverse stretching section is divided into two, the stretch amount of the film at the midpoint of the transverse stretching section (film width at the measurement point - film width before stretching) is set to 60% or more of the stretch amount at the end of the transverse stretching section. It is also effective to gradually change the temperature during transverse stretching. Specifically, when the transverse stretching section is divided into two, it is effective to provide a difference of 20°C or more between the atmospheric temperatures of the first and second stretching sections from the midpoint of the transverse stretching section.

[0073] Furthermore, from the viewpoint of easily laminating the functional layer on the side opposite the protective layer without impairing its function, it is preferable that the laminated structure of the present invention has functional layers on both sides, one of which is a conductive layer, and the other functional layer is a second film having an absolute value of shrinkage rate at 120°C of 0.20% or less.

[0074] The laminate structure of the present invention preferably has at least one reflection band in which the reflectance is 30% or more over a wavelength width of 20 nm or more in a reflectance profile measured from at least one surface, more preferably over a wavelength width of 100 nm or more, and even more preferably over a wavelength width of 300 nm or more.

[0075] The reflectance at each wavelength can be measured as a relative reflectance using a white aluminum oxide plate as a reference, and details will be described later. "On at least one surface" means that the requirement must be met when the reflectance is measured by irradiating light onto at least one surface. As a means for obtaining a laminated structure having at least one reflection band with a reflectance of 30% or more over a wavelength width of 20 nm or more, a means for adjusting the number of layers of the film of the present invention constituting the laminated structure can be mentioned. More specifically, the width of the reflection band can be widened by increasing the number of layers.

[0076] The laminated structure of the present invention preferably has a reflection band in the wavelength range of 850 nm to 1200 nm. This configuration allows infrared light to be reflected, resulting in excellent heat-shielding properties. For example, by sandwiching such a laminated film between two sheets of glass, a laminated glass capable of maintaining high heat-shielding performance for a long period of time can be obtained.

[0077] The laminated structure of the present invention preferably has a visible light transmittance of 70% or more. By adopting such an embodiment, reflection in the visible region can be suppressed, coloring and glare can be reduced, and visibility can be improved. For example, by sandwiching such a laminated structure between two sheets of glass, a highly transparent laminated glass can be obtained, which can be used for automobile windshields, etc.

[0078] Such a laminate structure can be easily obtained by using the film of the present invention as the laminate film described above. For the majority of layers constituting the laminate film, the sum of the optical thicknesses of adjacent layers is preferably 400 nm to 700 nm. The optical thickness here refers to the product of the layer thickness of each layer and the refractive index of the resin constituting the layer, and the sum of the optical thicknesses of adjacent layers is a factor determining the wavelength at which interference reflection occurs in the laminate film. Interference reflection from a laminate film in which the sum of the optical thicknesses of adjacent layers is 400 nm to 700 nm typically occurs in the wavelength range of approximately 800 nm to 1400 nm, making it easy to achieve a reflection band in the wavelength range of 850 nm to 1200 nm. Furthermore, the magnitude of reflectance increases with the number of layers and the difference in the in-plane average refractive index of adjacent layers. A laminate film in which the sum of the optical thicknesses of adjacent layers for the majority of layers is 400 nm to 700 nm easily efficiently improves the average reflectance in the wavelength range of 850 nm to 1200 nm.

[0079] For example, if polyethylene terephthalate with a refractive index of 1.66 and polyethylene terephthalate copolymerized with spiroglycol and cyclohexanedicarboxylic acid with a refractive index of 1.55 are used as resins A and B, stacking approximately 201 or more layers will result in the sum of the optical thicknesses of adjacent layers being 400 to 700 nm, and a reflection band with a maximum reflectance of 70% or more can be located in a wavelength range of 850 to 1200 nm. As the in-plane refractive index difference between resins A and B increases, the maximum reflectance in the reflection band can be increased, and if the in-plane refractive index difference is 0.3 or more, sufficient reflectance can be achieved even with approximately 51 layers.

[0080] Furthermore, when polyethylene terephthalate with a refractive index of 1.66 and polyethylene terephthalate copolymerized with spiroglycol and cyclohexanedicarboxylic acid with a refractive index of 1.55 are used as resins A and B, the layer thickness range required to make the sum of the optical thicknesses of adjacent layers 400 to 700 nm is approximately 120 to 220 nm. Note that the higher the reflectance in the reflection band in the wavelength range from 850 nm to 1200 nm, the higher the heat-shielding performance of the film.

[0081] Another example of a laminated film having an average reflectance of 70% or more in the wavelength band of 850 to 1200 nm is one in which the optical thicknesses of adjacent layers A and B simultaneously satisfy the following formulas 1 and 2. Formula 1: λ=2(n α d α +n β d β ) Formula 2: n α d α = n β d β where λ is the reflection wavelength, n α is the in-plane refractive index of layer A, d α is the thickness of layer A, n β is the in-plane refractive index of layer B, d βis the thickness of layer B. Having a layer thickness distribution that simultaneously satisfies both Equation 1 and Equation 2 can eliminate even-order reflections. This allows for a high average reflectance in the wavelength range of 850 nm to 1200 nm while a low average reflectance in the visible light wavelength range of 400 to 700 nm, resulting in a transparent film with excellent heat-ray blocking performance. Generally, the refractive index of a film obtained by molding and stretching a thermoplastic resin is approximately 1.4 to 1.9. Therefore, by setting the thickness ratio of adjacent layers A and B (thickness of layer A / thickness of layer B) to 0.7 or more and 1.4 or less, a film with suppressed even-order reflections can be obtained. Therefore, it is preferable that the thickness ratio of adjacent layers A and B (thickness of layer A / thickness of layer B) be 0.7 or more and 1.4 or less. It is more preferable that the thickness ratio be 0.8 or more and 1.2 or less.

[0082] In one embodiment of the film of the present invention, the refractive index of at least one surface of the laminate film is 1.68 to 1.80. If the refractive index is lower than 1.68, it may be difficult to achieve a reflection band with a reflectance of 30% or more over a wavelength range of 20 nm or more in the 300 nm to 2500 nm wavelength range. If the refractive index is higher than 1.80, the difference in chemical structure becomes greater, which may deteriorate the lamination ability of resin A and resin B, resulting in clouding of the multilayer film and significant peeling at the interface between layer A and layer B.

[0083] An example of a method for setting the refractive index of at least one surface of the laminate film to 1.68 or more and 1.80 or less is a method in which the main dicarboxylic acid unit of resin A is a naphthalenedicarboxylic acid unit. By adopting such an embodiment, a difference in in-plane refractive index between layer A and layer B can be established, making it easier to obtain a laminated polyester film with better reflective performance. Furthermore, in order to increase the difference in in-plane refractive index between layer A and layer B, it is also preferable that resin B be an amorphous resin. To incorporate naphthalenedicarboxylic acid into the dicarboxylic acid constituents of resin A of the film of the present invention, a method can be used in which naphthalenedicarboxylic acid is included in the dicarboxylic acid constituents of the raw material polyester resin that constitutes resin A.

[0084] The film of the present invention is suitable as a film to be used as laminated glass having an intermediate layer and a support after undergoing a process of laminating a functional layer with heating. Laminated glass having an intermediate layer and a support laminated on at least one surface of a film is generally laminated under adhesion pressure, and a preferred method is pressure molding under heating at 120°C to 160°C. When pressure molding is performed under heating at 120°C to 160°C, if the film satisfies 0.50≦|S(150)−S(100)|, uneven pressure caused by uneven thickness of the intermediate layer during the production of laminated glass and uneven distortion of the film caused by differences in thermal shrinkage stress between the intermediate layer and the film can be suppressed, thereby enabling the production of laminated glass with a good appearance.

[0085] The film of the present invention can be suitably used for laminated glass. In particular, laminated glass is suitable, in which polyvinyl butyral as an intermediate layer and glass as a support are laminated on both sides of a laminated structure in which a functional layer is laminated on the film of the present invention. That is, the laminated glass is preferably provided with glass 1, intermediate layer 1, the laminated structure, intermediate layer 2, and glass 2 in this order. The laminated glass of the present invention is made using the film of the present invention. Here, "made using the film of the present invention" means that the laminated glass is made using at least one of the film of the present invention or the laminated structure of the present invention. The glass support is not particularly limited, and commonly used transparent plate glass can be used. Examples include clear glass, float glass, polished glass, figured glass, wired glass, lined glass, infrared-absorbing glass, infrared-reflecting glass, and green glass. The glass is preferably transparent, and its thickness is preferably 0.5 mm to 5.0 mm.

[0086] In the laminated glass formed using the laminated structure of the present invention, it is preferred that the glass 1 is located on the sunlight incident side and the conductive layer of the laminated structure is located on the intermediate layer 1 side. By placing the conductive layer on the sunlight incident side, sunlight can be reflected or absorbed by the conductive layer, and a laminated glass with high heat-shielding properties can be obtained, which is preferred.

[0087] The laminated glass of the present invention can be suitably used for windows of buildings and automobiles. In particular, an automobile including a laminated glass formed by laminating polyvinyl butyral as an intermediate layer and glass as a support on both sides of a laminated structure formed by laminating a functional layer on the film of the present invention is suitable. Furthermore, an automobile including a laminated glass formed by using a laminated structure in which a conductive layer is laminated as a functional layer, and which exhibits optical or thermal functions by passing electricity through the conductive layer, is suitable.

[0088] In addition to the above, examples of intermediate layers include vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate copolymers, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, polyvinyl ether, nitrile rubbers, styrene-butadiene rubbers, natural rubbers, chloroprene rubbers, polyamides, epoxy resins, polyurethanes, acrylic resins, cellulose, polyvinyl chloride, polyacrylic esters, and polyisobutylene. These intermediate layers may also contain adhesiveness adjusters, plasticizers, heat stabilizers, antioxidants, UV absorbers, antistatic agents, lubricants, colorants, crosslinking agents, and the like. The provision of an intermediate layer can improve adhesion between the support and the film, as well as the design, durability, weather resistance, and impact resistance of the laminated glass. The thickness of the intermediate layer is preferably 10 μm to 1 mm.

[0089] Colorants are components that enhance design, and examples thereof 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.

[0090] Methods for forming laminated glass include extrusion lamination, hot melt lamination, thermal lamination, press lamination, vacuum lamination, and autoclave lamination. Extrusion lamination is a method in which a molten film and an intermediate layer are extruded from a die into a film shape and laminated onto a support, and the molded product is then passed between two rolls to form the laminate. Hot melt lamination is a molding method in which a heat-melted intermediate layer is applied to a film or a support, and the film and support are laminated. Thermal lamination is a molding method in which the film, intermediate layer, and support are heated and pressed together with a heated roll. Press lamination is a molding method in which the film, intermediate layer, and support are heated and pressed together in a press. Vacuum lamination is a molding method in which the film, intermediate layer, and support are heated, then the inside of the device is evacuated, and the materials are pressed together to form the laminate. Autoclave lamination is a molding method in which a film, an intermediate layer, and a support are heated, and then the inside of the apparatus is pressurized with gas or the like to laminate them.

[0091] The film and laminate structure of the present invention can also be suitably used in molded articles other than laminated glass, as will be specifically described below. Examples of supports that can be used in molded articles made using the film or laminate structure of the present invention include resin supports, metal or ceramic supports, and the like. The surface of the support may be flat or curved, and may have any shape. Examples of resins include acrylic resins such as polycarbonate, cyclic polyolefin, polyarylate, polyethylene terephthalate, and polymethyl methacrylate, ABS, and triacetyl cellulose. Depending on the application of the molded article, the support is preferably transparent, and the thickness of the support is preferably 0.5 mm to 5.0 mm.

[0092] The film of the present invention will be described below with reference to specific examples. Even when a thermoplastic resin other than the thermoplastic resins specifically exemplified below is used, the film of the present invention can be obtained in the same manner as above, provided that the description of this specification, including the examples below, is taken into consideration.

[0093] [Methods for Measuring Physical Properties and Evaluating Effects] The methods for evaluating physical properties and effects are as follows.

[0094] (1) Shrinkage, Shrinkage Onset Temperature, and Average Rate of Change Measurements were performed using a Seiko Instruments Inc. heat, stress, and strain measurement device (TMA / SS6000) under the following conditions. Samples were cut out in a plane parallel to the film surface in an arbitrary direction and in each direction rotated from that direction up to 180° in an in-plane direction parallel to the film surface at 5° intervals. At least one data point was obtained per 1°C, and the shrinkage at each temperature was calculated using the following equation 3 to obtain a thermal shrinkage curve. Measurements were performed three times in each direction, and the direction with the largest S(150) was designated the X direction. Sample size: width 4 mm, length 15 mm Temperature rise range: 25 to 200°C Temperature rise rate: 10°C / min Measurement load: 19.8 N Temperature 23°C, relative humidity 65%, in air Formula 3: Shrinkage rate at temperature T°C S(T) = (L(25) - L(T)) / L(25) x 100 L(T): sample length at T°C.

[0095] From the obtained heat shrinkage curve, the temperature at which the shrinkage rate S(T) first exceeded 0% was defined as the shrinkage initiation temperature. From the obtained shrinkage rate S(T), the average change in shrinkage rate from 120°C to 150°C (average change in shrinkage rate) was calculated using the following formula 4. Formula 4: Average change in shrinkage rate = |S(150) - S(120)| / (150 - 120).

[0096] (2) Number of Layers The number of layers of the laminate film was determined by observing a sample sliced ​​using an ultramicrotome with a transmission electron microscope (TEM). Specifically, a transmission electron microscope JEM-1400 Plus (manufactured by JEOL Ltd.) was used to observe the cross section of the laminate film at an acceleration voltage of 100 kV, and the number of layers was determined by obtaining a cross-sectional image. In order to obtain a large contrast difference between each layer, an electron stain (RuO ４ In addition, depending on the thickness of each layer, observation was performed at a direct magnification of 40,000 times when the thin film layer thickness was less than 100 nm, at a direct magnification of 20,000 times when the thin film layer thickness was 100 nm or more but less than 500 nm, and at a direct magnification of 1,000 to 10,000 times when the thin film layer thickness was 500 nm or more, and the number of layers was identified based on the contrast difference in the obtained images.

[0097] (3) Layer Interface (Contrast Difference) The cross-sectional image obtained in the transmission electron microscope observation in (2) was converted to a compressed image file (JPEG) format, and position-brightness data was obtained by line profiling along the thickness direction of the laminate film using ImagePro-10 (sold by Hakuto Co., Ltd.). Subsequently, a five-point moving average was performed on the profile obtained by plotting the relationship between position and brightness using spreadsheet software (Microsoft Excel (registered trademark) 2016). The averaging process was performed by averaging brightness at five consecutive measurement positions, changing the position one point at a time, and repeatedly performing the same calculation to obtain an averaged position-brightness profile. In the obtained averaged position-brightness profile, the positions surrounded by inflection points where the slope changes from positive to negative or negative to positive were determined to be one layer. For each layer obtained using this method, position-brightness data was then obtained in the planar direction of the laminate film (the direction perpendicular to the thickness direction). After calculating the average and standard deviation of the brightness obtained for each layer, if the difference between the average brightness values ​​of two adjacent layers was greater than either of the standard deviations of the brightness values ​​of the adjacent thermoplastic resin layers, the two adjacent layers were determined to be different.

[0098] (4) Differential Scanning Calorimetry (DSC) A differential scanning calorimeter EXSTAR DSC6220 manufactured by Hitachi High-Technologies Corporation was used. Measurements and temperature readings were performed in accordance with JIS-K-7122 (1987). Specifically, approximately 5 mg of sample was placed on an aluminum pan and heated from 25°C to 300°C at a rate of 10°C / min. The intersection of the baseline when heated from room temperature and the tangent to the inflection point of the step transition portion was taken as the glass transition temperature Tg (°C). After heating, the sample was rapidly cooled with liquid nitrogen, and the endothermic peak observed on the highest temperature side when heated again under the same conditions was taken as the melting point (°C). The integrated value from the baseline within the range of the melting point ± 20°C was taken as the enthalpy of fusion (J / g).

[0099] (5) Orientation angle A retardation measuring device (KOBRA-21ADH) manufactured by Oji Scientific Instruments Co., Ltd. was used. A sample was cut out to 3.5 cm x 3.5 cm so that the longitudinal direction of the film was the vertical direction, and samples were taken from the center and both ends of the longitudinal direction of the sample and both ends in the direction perpendicular to the longitudinal direction, and the orientation angle at a wavelength of 590 nm at an incident angle of 0 ° was measured. From the obtained results, the orientation angle at the longitudinal position was defined as θ0, and the orientation angles at which the difference from θ0 was maximum were defined as θb and θf.

[0100] (6) Curl Test The degree of curl after heat treatment was evaluated, assuming the heating process that occurs when laminating the functional layer after laminating the protective layer. A PET film with an adhesive layer attached was used as the protective layer, and the film was attached using a hand mill to prevent air bubbles. The film with the protective layer attached was then cut into a size of 20 mm wide and 20 mm long and heat-treated at 120°C for 1 hour. A windless oven was used for the heat treatment. The degree of curl was evaluated by measuring the height of the four corners of the sample after heat treatment. The evaluation criteria are as follows. The following protective layers were used: <Evaluation Criteria> A: All four corners are 30 mm or less. B: One or two of the four corners are 30 mm or less, and the remaining two or three corners are greater than 30 mm and less than 50 mm. C: Other than A, B, and D. D: All four corners are greater than 50 mm. <Protective Layer> A heat shrinkage curve of the adhesive film was obtained according to the method described in (1). Measurements were performed three times in each direction, and the films with the following maximum absolute values ​​of shrinkage rate S(120) at 120°C were used. Adhesive film 1: Adhesive film with shrinkage rate at 120°C of 0.15% Adhesive film 2: Adhesive film with shrinkage rate at 120°C of 0.28% Adhesive film 3: Adhesive film with shrinkage rate at 120°C of 0.35%. <Bonding direction> The film and protective layer were bonded in the following two directions depending on the orientation angle measured according to the method in (5). Parallel direction: The direction in which the orientation angle θb of the film and the orientation angle θf of the protective layer are aligned. In this case, θb - θf is the difference between the absolute values ​​of θb and θf measured in (5). Cross direction: The direction in which the orientation angle θb of the film and the orientation angle θf of the protective layer are perpendicular. In this case, θb - θf is the sum of the absolute values ​​of θb and θf measured in (5).

[0101] (7) Preparation of Laminated Glass Using LAMINATOR0303S manufactured by Nisshinbo, glass 1, intermediate layer 1, the film and laminated structure of the example or comparative example, intermediate layer 2, and glass 2 were stacked in this order and pressed at a temperature of 140°C and 1.5 MPa for 30 minutes to prepare laminated glass. Transparent plate glass measuring 100 mm wide x 100 mm long x 2 mm thick was used as glass 1 and glass 2, and PVB films with a thickness of 0.4 mm were used as intermediate layer 1 and intermediate layer 2. When the functional layer was a protective layer, the protective layer was peeled off and laminated glass was prepared with the film. When the functional layer was a conductive layer, laminated glass was prepared with a laminated structure on which the conductive layer was laminated.

[0102] (8) Appearance of Laminated Glass (Unevenness) A molded article was placed under a fluorescent lamp and the evaluation portion was visually evaluated from angles of 20°, 50°, and 70° relative to the normal direction of the evaluation portion. The evaluation criteria are as follows: A: No unevenness is visible. B: Very slight unevenness is visible. C: Unevenness is visible.

[0103] (9) Preparation of Glass Laminate Using a LAMINATOR 0303S manufactured by Nisshinbo, a transparent plate glass, an intermediate layer, and the film of Example 30 were stacked in this order and placed, and pressed at a temperature of 140°C and 1.5 MPa for 30 minutes to prepare a glass laminate. The transparent plate glass used was 100 mm wide x 100 mm long x 2 mm thick. A PVB film with a thickness of 0.4 mm was used as the intermediate layer.

[0104] (10) Lamination of Conductive Layer 1 An ITO film was formed as the conductive layer 1 by sputtering using a DC power source (indium / tin=95 / 5 molar ratio, thickness 0.2 μm, ultimate vacuum level 1×10 －３ Pa, the degree of vacuum when introducing gas was 0.10 Pa, and the gas ratio was Ar / O ２ =99 / 1).

[0105] (11) Lamination of Conductive Layer 2 To form the conductive layer 2, the silver nanowire-containing coating liquid was applied using a spin coater at room temperature and 500 rpm, and then dried at 70°C for 10 minutes to form a silver nanowire-containing transparent conductive film.

[0106] (12) Conductive Layer Deformation Test After laminating conductive layer 1 by the method described in (10) and conductive layer 2 by the method described in (11), heat treatment was carried out for 1 hour in a windless oven at the temperatures shown in Tables 2-2 and 3-2, and deformation of the conductive layer was evaluated by visual inspection of the appearance. The evaluation criteria are as follows: A: No change in appearance before and after heat treatment. B: After heat treatment, slight changes in appearance such as whitening are observed in part of the sample. C: After heat treatment, slight changes in appearance such as whitening are observed over the entire sample. D: After heat treatment, noticeable changes in appearance such as whitening are observed over the entire sample.

[0107] (13) Lamination and deformation evaluation of hard coat layer Containing 60 weight parts of isocyanate compound consisting of isocyanurate of hexamethylene diisocyanate per 100 weight parts of polyester compound, and adjusting the solid concentration to 40% coating material prepared, and further adding cesium tungsten oxide particle Cs0.33WO3 solid concentration 18.5% slurry in a weight ratio of 3:5 to this coating material to form a coating material for heat ray absorption layer. After coating these coating materials on one side with a wire bar coater, dry at 110 ° C for 10 minutes, and then use a UV irradiation device to apply ultraviolet light at 500 mJ / cm ２ The coating film was cured by irradiation to form a hard coat layer. Deformation of the hard coat layer during the drying process during hard coat layer formation was evaluated visually. The evaluation criteria are as follows: A: No curling of the film or change in appearance of the hard coat layer was observed. B: Curling of the film or change in appearance of the hard coat layer was observed.

[0108] (14) Reflectance A sample cut to 5 cm x 5 cm was subjected to reflectance measurement using a Hitachi spectrophotometer (U-4100 Spectrophotometer) with an integrating sphere attached to the basic configuration. In this measurement, the measurement was performed using an aluminum oxide secondary white plate attached to the device as a reference. In the reflectance measurement, the sample was placed behind the integrating sphere with its longitudinal direction facing up and down, and the reflectance was measured under the following conditions, and the average reflectance in the wavelength range of 850 nm to 1200 nm was calculated. <Measurement conditions> Slit: 2 nm (visible) / automatic control (infrared) Gain: 2 Scanning speed: 600 nm / min Starting wavelength: 2600 nm Ending wavelength: 240 nm Sampling interval: 1 nm Incident angle: 10° <Incident plane> If the functional layer is a protective layer: film surface If the functional layer is a conductive layer (conductive layer 1 and conductive layer 2): conductive layer surface If one of the functional layers is a conductive layer and the other functional layer is a protective layer: conductive layer surface If the functional layer is a hard coat layer: hard coat layer surface.

[0109] (15) Transmittance Measurement was performed under the following conditions using a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. in the standard configuration (solid measurement system), and the average transmittance in the wavelength range of 400 nm to 700 nm was determined and used as the visible light transmittance. <Measurement conditions> Slit: 2 nm (visible) / automatic control (infrared) Gain: 2 Scanning speed: 600 nm / min Starting wavelength: 700 nm Ending wavelength: 400 nm Sampling interval: 1 nm Incident angle: 0°.

[0110] (16) Heat Shielding Property The total energy transmittance (Tts) through the laminated glass produced in (7) and the glass laminate produced in (9) was measured according to ISO 13837:2008 "Road vehicles -- Safety glazing materials -- Determination of solar transmittance," using glass 1 as the incident surface for the laminated glass and a transparent plate glass for the glass laminate. The total energy transmittance (Tts) through the laminated glass was evaluated using the following four levels. A: The total energy transmittance (Tts) through the laminated glass was 50% or less. B: The total energy transmittance (Tts) through the laminated glass was greater than 50% and less than 70%. C: The total energy transmittance (Tts) through the laminated glass was 70% or more and less than 80%. D: The total energy transmittance (Tts) through the laminated glass was 80% or more.

[0111] (17) Film Quality The quality of the film was evaluated by visual inspection to see if there were any scratches on the film. A: Almost no scratches were observed on the film. B: Some scratches were observed on the film.

[0112] (18) Refractive index of layer A of laminated film The refractive index of the outermost layer of the film was measured using a Prism Coupler SPA-400 manufactured by Cylon Technology Co., Ltd. The wavelength of the laser used for the measurement was 633 nm, and the in-plane refractive index was calculated by averaging the values ​​measured for both outermost layers in the X direction and in a direction rotated 90° from the X direction parallel to the film surface (Y direction).

[0113] (19) Refractive Index of Layers B and C of Laminate Film Because layers B and C are internal layers of the laminate film, the refractive index was measured not on the film itself, but on a single-layer film of layers B and C produced under the same stretching and heat treatment conditions as the film, using a Prism Coupler SPA-400 manufactured by Cylon Technology Co., Ltd. The wavelength of the laser used for the measurement was 633 nm, and the in-plane refractive index was calculated by averaging the values ​​measured in the X direction and in the direction rotated 90° from the X direction parallel to the film surface (Y direction).

[0114] (Resins used in the film) The resins used in the examples of the present invention are described below. The refractive index indicates the in-plane refractive index (average value of the refractive index in the X direction and the Y direction) when a sheet made of each resin is stretched under the stretching conditions described in the examples. Within the range of the stretching conditions described in the examples, all of the in-plane refractive indexes showed the same value. Resin 1: Crystalline homopolyethylene terephthalate resin (IV = 0.65, in-plane refractive index = 1.66) exhibiting a glass transition temperature of 78°C, a melting point of 254°C, and a melting enthalpy of 40 J / g. Resin 2: Amorphous polyethylene terephthalate copolymer resin (IV = 0.72, in-plane refractive index = 1.54) copolymerized with 20 mol% of a cyclohexanedicarboxylic acid component relative to the total acid components and 20 mol% of a spiroglycol component relative to the total diol components, exhibiting a glass transition temperature of 78°C. Resin 3: Crystalline polyethylene terephthalate resin copolymerized with 10 mol% of isophthalic acid, exhibiting a glass transition temperature of 79°C, a melting point of 230°C, and a melting enthalpy of 12 J / g. (IV = 0.65, in-plane refractive index = 1.62) Resin 4: Amorphous polyethylene terephthalate resin copolymerized with 33 mol% cyclohexanedimethanol, exhibiting a glass transition temperature of 80°C (IV = 0.73, in-plane refractive index = 1.57). Resin 5: Amorphous homo-polymethylene methacrylate resin exhibiting a glass transition temperature of 101°C (in-plane refractive index = 1.49).

[0115] Example 1 Two thermoplastic resin layers with different main components were designated as layer A1 and layer B1, respectively. Resin 1 was used as the thermoplastic resin constituting layer A1, and resin 2 was used as the thermoplastic resin constituting layer B1. Resins 1 and 2 were melted at 280°C in separate extruders, and foreign matter was removed through five FSS-type leaf disc filters. They were then extruded using a gear pump while being metered so that the discharge ratio (lamination ratio) was resin 1 / resin 2 = 1 / 1.07, and the flows were joined in a 501-layer feed block. The thickness of the final A1 layer was varied in a geometric progression from 130 nm to 180 nm, and the thickness of the final B1 layer was varied in a geometric progression from 137 nm to 190 nm, so that the adjacent A1 layer (made of Resin 1) and B1 layer (made of Resin 2) from one surface of the film to the opposite surface satisfied the above-mentioned formulas 1 and 2. (However, the thickness of the A1 layers located on both surface layers was adjusted to a final thickness of 10 μm.) The resulting molten laminate was then fed into a T-die and formed into a sheet. It was then quenched and solidified on a casting drum maintained at a surface temperature of 25°C while applying an electrostatic voltage of 8 kV with a wire, to obtain an unoriented sheet. This unoriented sheet was then longitudinally stretched by differential roll speeds at a temperature of 90°C and a stretch ratio of 3.3 to obtain a uniaxially oriented sheet. The resulting uniaxially oriented sheet was then clamped at both ends with clips and introduced into a tenter, where it was transversely stretched at 100°C and a stretch ratio of 4.0. It was then heat-treated at 205°C for 10 seconds, relaxed 3% in the width direction, and cooled at 150°C for 10 seconds to obtain a sheet with a thickness of 80 μm. The resulting sheet was then subjected to an off-annealing treatment in a hot air oven at 130°C under the conditions of a width-direction free state (the sheet was not restrained in the width direction) and a longitudinal winding tension of 60 N, with a passage time of 60 seconds, to obtain a film. The evaluation results of the resulting sheet and film are shown in Tables 1-1 and 1-2. The sheets were laminated in the parallel direction during the curl test.

[0116] (Examples 2 to 5, 8, 10 to 11, 14 to 17) Sheets and films were obtained and evaluated in the same manner as in Example 1, except that the heat treatment temperature, the presence or absence of off-annealing treatment and its temperature were as shown in Table 1-1, and the protective layer for the curl test was as shown in Table 1-2. The evaluation results are shown in Table 1-2.

[0117] Example 6 Sheets and films were obtained and evaluated in the same manner as in Example 1, except that only Resin 1 was fed into each extruder as the thermoplastic resin layer. The evaluation results are shown in Tables 1-1 and 1-2.

[0118] Example 7 Three types of thermoplastic resin layers with different main components were used, namely, A2 layer, B2 layer, and C2 layer. Resin 1 was used as the thermoplastic resin constituting the A2 layer, Resin 3 was used as the thermoplastic resin constituting the B2 layer, and Resin 4 was used as the thermoplastic resin constituting the C2 layer. Resins 1, 3, and 4 were melted in separate extruders at 270°C, 270°C, and 280°C, respectively, and passed through seven FSS-type leaf disc filters. Then, the resins were extruded using a gear pump while measuring the discharge ratio (lamination ratio) so that Resin 1 / Resin 3 was 0.98 and Resin 4 / Resin 3 was 1.02, and the mixture was merged in a 601-layer feed block. Note that both surface layers were made of Resin 1, and the layers were laminated in a regular arrangement of A2 layer / B2 layer / C2 layer / B2 layer in the thickness direction. The slit length and width in the feed block were designed so that the layer thickness monotonically increased from the outermost surface on one side to the outermost surface on the other side, excluding both outermost layers. The resulting molten laminate was then fed into a T-die and formed into a sheet. While applying an 8 kV electrostatic voltage via a wire, the laminate was rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25°C to obtain an unoriented sheet. This unoriented sheet was then longitudinally stretched at 80°C and a stretch ratio of 3.3 to obtain a uniaxially oriented sheet. The resulting uniaxially oriented sheet was then guided into a tenter, held at both ends with clips, and transversely stretched at 90°C and a stretch ratio of 3.6. The sheet was then heat-treated at 205°C for 10 seconds, relaxed 5% in the width direction, and cooled at 150°C for 10 seconds to obtain an 80 μm thick sheet. The resulting sheet was subjected to an off-annealing treatment under the same conditions as in Example 1 to obtain a film. The same adhesive film was also used for the curl test. The evaluation results of the resulting sheet and film are shown in Tables 1-1 and 1-2.

[0119] Example 9 A sheet and a film were obtained and evaluated in the same manner as in Example 1, except that Resin 5 was used as the thermoplastic resin constituting Layer B1, the melting temperature was 260° C., the stretching temperature for the unoriented sheet was 105° C., and the stretching temperature for the uniaxially oriented sheet was 110° C. The evaluation results are shown in Tables 1-1 and 1-2.

[0120] Example 18 A sheet and a film were obtained and evaluated in the same manner as in Example 1, except that the extruded resins were joined in a 51-layer feed block. The evaluation results are shown in Tables 1-1 and 1-2.

[0121] Example 19 A sheet and a film were obtained and evaluated in the same manner as in Example 1, except that the stretching ratio during transverse stretching was 3.2 times. The evaluation results are shown in Tables 1-1 and 1-2.

[0122] Example 20 A sheet and a film were obtained and evaluated in the same manner as in Example 1, except that the sheets were laminated in the cross direction during the curl test. The evaluation results are shown in Tables 1-1 and 1-2.

[0123] Comparative Example 1 A sheet obtained in the same manner as in Example 1 was formed into a film without being subjected to off-annealing treatment. The evaluation results of the obtained film are shown in Tables 1-1 and 1-2.

[0124] Comparative Example 2 A sheet obtained in the same manner as in Example 2 was formed into a film without being subjected to off-annealing treatment. The evaluation results of the obtained film are shown in Tables 1-1 and 1-2.

[0125] Comparative Example 3 A sheet was obtained in the same manner as in Example 1, except that the heat treatment temperature was 225° C., and was then formed into a film without being subjected to off-annealing treatment. The evaluation results of the obtained film are shown in Tables 1-1 and 1-2.

[0126] Comparative Example 4 A sheet was obtained in the same manner as in Example 1, except that the heat treatment temperature was 235° C., and was then formed into a film without being subjected to off-annealing treatment. The evaluation results of the obtained film are shown in Tables 1-1 and 1-2.

[0127] Comparative Example 5 A sheet obtained in the same manner as in Example 6 was made into a film without being subjected to off-annealing treatment. The evaluation results of the obtained sheet and film are shown in Tables 1-1 and 1-2.

[0128] Comparative Example 6 A sheet obtained in the same manner as in Example 7 was made into a film without being subjected to off-annealing treatment. The evaluation results of the obtained sheet and film are shown in Tables 1-1 and 1-2.

[0129] Comparative Example 7 A film was obtained in the same manner as in Example 3, except that the temperature of the hot air oven in the off-annealing treatment was set to 100° C. The evaluation results of the obtained sheet and film are shown in Tables 1-1 and 1-2.

[0130] Comparative Example 8 A film was obtained in the same manner as in Example 2, except that the temperature of the hot air oven in the off-annealing treatment was set to 150° C. The evaluation results of the obtained sheet and film are shown in Tables 1-1 and 1-2.

[0131] (Example 12) A sheet and a film were obtained in the same manner as in Example 1, and then a conductive layer 1 was laminated thereon by the method described in (8). The evaluation results of the obtained sheet, film, and conductive layer laminate are shown in Tables 2-1 and 2-2. When preparing the laminated glass, the conductive layer 1 side faced the glass 1 side.

[0132] (Example 13) A sheet and a film were obtained in the same manner as in Example 2, and then a conductive layer 1 was laminated thereon by the method described in (8). The evaluation results of the obtained sheet, film, and conductive layer laminate are shown in Tables 2-1 and 2-2. When preparing the laminated glass, the conductive layer 1 side faced the glass 1 side.

[0133] (Example 21) A sheet and a film were obtained and evaluated in the same manner as in Example 12, except that the temperature of the deformation test of the conductive layer 1 in (12) was set as shown in Table 2-2. The evaluation results are shown in Tables 2-1 and 2-2.

[0134] Example 22 A sheet and a film were obtained and evaluated in the same manner as in Example 12, except that, when preparing the laminated glass, the conductive layer 1 side was placed on the glass 2 side. The evaluation results are shown in Tables 2-1 and 2-2.

[0135] Example 23 A sheet and a film were obtained and evaluated in the same manner as in Example 12, except that the functional layer was the conductive layer 2. The evaluation results are shown in Tables 2-1 and 2-2.

[0136] Example 24 A sheet and a film were obtained and evaluated in the same manner as in Example 23, except that the conductive layer 2 side was placed on the glass 2 side when preparing the laminated glass. The evaluation results are shown in Tables 2-1 and 2-2.

[0137] Comparative Example 9 A conductive layer was laminated by the method described in (7) on the film of Comparative Example 2. The evaluation results of the obtained film and the conductive layer laminate are shown in Tables 2-1 and 2-2.

[0138] Comparative Example 10 A conductive layer was laminated on the film of Comparative Example 4 by the method described in (7). The evaluation results of the obtained film and the conductive layer laminate are shown in Tables 2-1 and 2-2.

[0139] Example 25 A sheet and a film were obtained and evaluated in the same manner as in Example 23, except that one functional layer was the conductive layer 2 and the other functional layer was the protective layer described in Table 3-2. The evaluation results are shown in Tables 3-1 and 3-2. In addition, in the curl test, the sheets were laminated in the parallel direction.

[0140] Example 26 A sheet and a film were obtained and evaluated in the same manner as in Example 25, except that the protective layer was changed to Protective Layer 2 shown in Table 3-2. The evaluation results are shown in Tables 3-1 and 3-2.

[0141] Example 27 A sheet and a film were obtained and evaluated in the same manner as in Example 25, except that the sheets were laminated in the cross direction during the curl test. The evaluation results are shown in Tables 3-1 and 3-2.

[0142] Example 28 A sheet and a film were obtained and evaluated in the same manner as in Example 26, except that the sheets were laminated in the cross direction during the curl test. The evaluation results are shown in Tables 3-1 and 3-2.

[0143] (Example 29) A sheet and a film were obtained and evaluated in the same manner as in Example 23, except that the temperature of the deformation test of the conductive layer 2 in (12) was set as shown in Table 3-2. The evaluation results are shown in Tables 3-1 and 3-2.

[0144] Example 30 Except for using a hard coat layer as the functional layer, a sheet and a film were obtained and evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 4-1 and 4-2.

[0145]

[0146] In the table, layers A1 and A2 are referred to as layers A, layers B1 and B2 as layers B, and layers C2 as layers C. The same applies to the following tables.

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154] According to the present invention, it is possible to obtain a film that has excellent processability before and after processing into laminated glass, etc. By using the film of the present invention, it is possible to obtain laminated glass that is excellent in appearance and design, and the laminated glass can be suitably used for windows, etc. of automobiles, buildings, etc.

Claims

1. A film having at least one thermoplastic resin layer, Let S(T)% be the shrinkage rate at temperature T°C in the thermal shrinkage curve. When, in a plane parallel to the film surface, one direction and the direction in which S(150) is greatest, rotated up to 180° at 5° intervals from that direction in a plane parallel to the film surface, the X direction is defined as the direction in which S(150) is greatest. In the X direction, the following conditions must be met: 0.50 ≤ |S(150) - S(100)| and 0.00 ≤ |S(120) - S(100)| ≤ 0.

40. A film in which, in the X direction, the average shrinkage rate in the heat shrinkage curve from 100°C to 120°C is -0.40% or more and 0.50% or less, and the absolute value of the average rate of change of shrinkage rate from 120°C to 150°C is 0.04% / °C or more.

2. The film according to claim 1, wherein in the X direction, the shrinkage initiation temperature in the thermal shrinkage curve is 110°C or higher and 170°C or lower.

3. The film according to claim 1, having a structure in which 51 or more of the thermoplastic resin layers are laminated.

4. The film according to claim 1, having two thermoplastic resin layers with different main components, designated as layer A1 and layer B1, respectively.

5. The film according to claim 1, wherein three thermoplastic resin layers with different main components are designated as A2 layer, B2 layer, and C2 layer, and the film has a regular arrangement consisting of the A2 layer, the B2 layer, and the C2 layer.

6. The film according to claim 1, wherein at least one of the thermoplastic resin layers is a polyester resin layer.

7. A method for manufacturing a film according to claim 1, comprising an off-annealing step of heat-treating a sheet satisfying 0.50 ≤ |S(150) - S(100)| at a temperature of 110°C or higher and less than 140°C.

8. The method for manufacturing a film according to claim 7, wherein the sheet satisfies 0.40 < |S(120) - S(100)|.

9. A laminated structure comprising a functional layer laminated on at least one surface of the film described in claim 1.

10. The laminated structure according to claim 9, wherein the functional layer is a conductive layer.

11. The laminated structure according to claim 9, wherein the functional layer comprises multiple layers, and at least one of them is a second film having an absolute value of 0.20% or less in shrinkage rate at 120°C.

12. The laminated structure according to claim 11, wherein the orientation angle of one film is θb and the orientation angle of the second film is θf, and the films are bonded together such that |θb - θf| ≤ 30°.

13. The laminated structure according to claim 9, having the functional layers on both sides, wherein one of the functional layers is a conductive layer and the other functional layer is a second film having an absolute value of 0.20% or less in shrinkage rate at 120°C.

14. The laminated structure according to claim 9, wherein the reflectance profile measured from at least one surface has at least one reflection band in which the reflectance of 30% or more is continuous over a wavelength width of 20 nm or more.

15. The laminated structure according to claim 14, wherein the reflection band is in the range of wavelengths from 850 nm to 1200 nm.

16. The laminated structure according to claim 9, wherein the visible light transmittance is 70% or more.

17. A method for manufacturing a laminated structure according to claim 10, comprising the step of performing heat treatment at a temperature of 100°C or more and less than 130°C when forming the conductive layer.

18. Laminated glass comprising, in this order: glass 1, intermediate layer 1, the laminated structure described in claim 10, intermediate layer 2, and glass 2.

19. The laminated glass according to claim 18, wherein the glass 1 is located on the side where sunlight is incident, and the conductive layer of the laminated structure is located on the side where the intermediate layer 1 is located.

20. An automobile comprising the laminated glass described in claim 18, wherein an optical or thermal function is exhibited by passing an electric current through the conductive layer of the laminated glass.