Laminate film

Abstract

To provide a laminate film that is transparent even after high-temperature and high-pressure treatment for a long time as in glass laminate processing and exerts high heat shielding performance.SOLUTION: There is provided a laminate film having laminate structure in which two types of thermoplastic resin layers having main constituents different from each other are laminated alternately by 51 layers or more, having two or more peaks of loss tangent tanδ at 60-140°C, a loss tangent tanδ(Ts) at the peak on the highest temperature side of the peaks of the loss tangent tanδ being 0.17-0.30 and a loss tangent tanδ(Tl) at the peak on the lowest temperature side being more than or equal to 0.10 and less than or equal to 0.20, and which has all of: a feature 1 in which an average reflectance Ra at a wavelength of 400-700 nm is 0.1-15.0%; a feature 2 in which a difference Rs between a maximum value Rb and a minimum value Rc of reflectance at a bandwidth of a wavelength of 500-600 nm is 1.3-3.0%; and a feature 3 in which an average reflectance Rd at a wavelength of 900-1200 nm is 70-100%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminated film that remains excellent in heat insulation properties and transparency even after long-term high-temperature, high-pressure processing such as processing of laminated glass. [Background technology]

[0002] In recent years, various efforts have been made to reduce greenhouse gas emissions as a measure against climate change. For example, expectations are high for radical, large-scale initiatives such as demonstration experiments of smart cities, where entire cities are designed to circulate energy in an environmentally friendly manner, and companies designing greenhouse gas reductions throughout their entire supply chains. However, these are long-term efforts that involve both the public and private sectors, and there is a widespread demand for more immediate measures.

[0003] Among these, the use of heat-shielding glass, which can suppress the inflow of heat from sunlight and improve air conditioning efficiency, in the windows of vehicles such as cars and trains, as well as buildings, is attracting attention as a way to reduce greenhouse gas emissions by saving on power consumption.

[0004] Examples of methods for imparting heat-shielding properties to window glass include a method in which heat-ray absorbing particles are incorporated into glass or an interlayer film used in laminated glass, and the heat rays are blocked by the heat-ray absorbing particles (e.g., Patent Document 1); a method in which a metal film is formed on the glass surface by sputtering or the like, thereby reflecting and blocking heat rays (e.g., Patent Document 2); a method in which a polymer multilayer laminate film, which is made by alternately laminating polymer layers with different refractive indices, is inserted between the glass and the interlayer film, thereby reflecting and blocking heat rays (e.g., Patent Document 3); and a method in which heat-shielding performance is enhanced by using heat-ray absorbing particles in addition to interference reflection by a polymer multilayer laminate film (e.g., Patent Document 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-17854 [Patent Document 2] JP 2001-310407 A [Patent Document 3] International Publication No. 2005 / 040868 [Patent Document 4] Special Publication No. 2010-501458 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the method using heat ray absorbing particles and the method of forming a metal film on the glass surface by sputtering or the like provide higher heat shielding performance than the method using only a polymer multilayer laminate film, they reflect visible light in addition to heat rays and are therefore prone to coloration, and therefore may not be applicable to the window glass of vehicles or buildings. In other words, the methods described in Patent Documents 1, 2, and 4 have the problem that the glass appears colored.

[0007] Furthermore, in the method described in Patent Document 3, which uses only a polymer multilayer laminate film, although there is room for control of the coloring of the film by appropriate layer design, there is a problem in that the color tone is easily changed by the high temperature and pressure and long-term treatment during the processing of laminated glass, and localized color spots are easily visible when used over a large area.

[0008] Therefore, an object of the present invention is to provide a laminated film that remains transparent even after long-term high-temperature and high-pressure treatment such as laminated glass processing, and that exhibits high heat-shielding properties. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention comprises the following configurations. (1) A laminated film having a laminated structure in which 51 or more layers (A layers) whose main component is thermoplastic resin A and layers (B layers) whose main component is thermoplastic resin B different from the thermoplastic resin A are alternately laminated, the film having two or more peaks of loss tangent tanδ in the range of 60°C to 140°C, and the loss tangent tanδ (Ts) of the highest peak of the loss tangent tanδ is 0.17 to 0.30, and the loss tangent tanδ (Tl) of the lowest peak of the loss tangent tanδ is 0.10 to 0.20, and the film has all of the following characteristics 1 to 3: Feature 1: The average reflectance Ra in the wavelength range of 400 to 700 nm is 0.1% or more and 15.0% or less. Feature 2: The difference Rs between the maximum value Rb and the minimum value Rc of reflectance in the wavelength band of 500 to 600 nm is 1.3% or more and 3.0% or less. Feature 3: The average reflectance Rd in the wavelength range of 900 to 1200 nm is 70% or more and 100% or less. (2) A laminated film as described in (1), in which the heat shrinkage rate when heated at 100°C for 30 minutes is 0.50% or more and 1.50% or less in both the main orientation direction and the direction perpendicular to the main orientation direction, and the heat shrinkage rate when heated at 150°C for 30 minutes is 2.20% or more and 4.50% or less in both the main orientation direction and the direction perpendicular to the main orientation direction. (3) The laminated film according to (1) or (2), having an internal haze of 0.00% or more and 0.50% or less. (4) A laminated film according to any one of (1) to (3), in which, when the temperature at which the Ts is given is Tp°C, the storage modulus E'h (MPa) at Tp+10°C and the storage modulus E'l (MPa) at Tp-10°C satisfy the following formula: 0.50≦E'h / E'l≦0.90 (5) The laminated film according to any one of (1) to (4), wherein the quartile deviation of the internal haze is 0.00% or more and 0.10% or less. (6) The laminated film according to any one of (1) to (5), wherein the thermoplastic resin A contains a naphthalenedicarboxylic acid unit. (7) The laminated film according to any one of (1) to (6), wherein the thermoplastic resin B contains at least one structural unit selected from a cyclohexanedimethanol unit, a neopentyl glycol unit, and a spiroglycol unit. (8) The laminated film according to any one of (1) to (8), which is used as laminated glass. (9) A laminated film roll obtained by winding the laminated film according to any one of (1) to (8), wherein the quartile deviation of the internal haze is 0.00 or more and 0.10 or less. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a laminated film that remains transparent even after long-term high-temperature and high-pressure treatment such as that used in laminated glass processing, and that exhibits high heat-shielding properties. DETAILED DESCRIPTION OF THE INVENTION

[0011] Although the present invention will be described below with reference to the following embodiments, the present invention should not be construed as being limited to these embodiments, including the following examples, and various modifications are possible within the scope of the invention, as long as the object of the invention can be achieved and the gist of the invention is not deviated from. Furthermore, for the purpose of simplifying the explanation, some of the explanations will be given using an example of a film formed by alternately laminating two types of thermoplastic resins with different optical properties, but the same should be understood when three or more types of thermoplastic resins are used.

[0012] The laminate film of the present invention must be made of a thermoplastic resin. Thermoplastic resins are generally cheaper than thermosetting resins and photocurable resins, and can be easily and continuously formed into films by a known melt extrusion method. Therefore, by using a thermoplastic resin, it is possible to obtain a laminate film at low cost.

[0013] The laminated film of the present invention has a laminated structure in which 51 or more layers (A layers) whose main component is thermoplastic resin A and layers (B layers) whose main component is a thermoplastic resin B different from the thermoplastic resin A are alternately laminated. "Alternately laminated" here means that the A layers and B layers are laminated in a regular arrangement in the thickness direction, for example, A(BA)n (n is a natural number representing the number of layers). Furthermore, the "main component" refers to a component that accounts for more than 50% by mass but not more than 100% by mass when all components constituting the layer are taken as 100% by mass. The "thickness direction" refers to the direction perpendicular to the film surface.

[0014] By alternately laminating thermoplastic resin layers with different main components in this way, it becomes possible to reflect light of a specific wavelength due to the relationship between the difference in the average in-plane refractive index of each layer and the layer thickness (this phenomenon is called interference reflection). Furthermore, if the number of layers is 50 or less, the laminated film will not exhibit high reflectance over a sufficient range in the infrared region and will not have sufficient heat-shielding performance.

[0015] From the viewpoint of achieving sufficient heat-shielding performance, the number of layers in the laminated structure is preferably 401 or more in total, more preferably 551 or more in total. The more layers there are, the higher the reflectivity of the aforementioned interference reflection can be achieved for light in a wider wavelength band, resulting in a laminated film with high heat-shielding performance. Furthermore, while there is no upper limit to the number of layers in the laminated structure from the viewpoint of heat-shielding performance, an increase in the number of layers increases the size of the manufacturing equipment, resulting in increased manufacturing costs, and the thickness of the laminated film increases, resulting in poor handling. As a result, for example, when the laminated film is used in laminated glass, process defects may occur during the glass lamination process, so a practical range is approximately 1001 layers in total.

[0016] "Thermoplastic resin A and thermoplastic resin B are different" means that thermoplastic resin A and thermoplastic resin B exhibit different melting points and / or glass transition temperatures in differential scanning calorimetry (DSC). In the present invention, "exhibiting different melting points" and "different glass transition temperatures" means that the melting points and glass transition temperatures differ by 0.1°C or more. The melting points and / or glass transition temperatures preferably differ by 2°C or more, and more preferably by 5°C or more. A larger difference in the melting points or glass transition temperatures between thermoplastic resin A and thermoplastic resin B makes it possible to more precisely control the orientation state of the individual layers, even in the form of a laminated polyester film.

[0017] Depending on the combination of thermoplastic resins A and B, only one of them may exhibit a glass transition temperature or melting point. In this case, the difference cannot be calculated as a temperature difference, but the thermoplastic resins are considered to be different. On the other hand, using thermoplastic resins that do not exhibit a glass transition temperature or melting point as both thermoplastic resins A and B implies that the laminate sheet cannot be stretched in the manufacturing process. As described below, the laminate film of the present invention is preferably a biaxially stretched film, but if thermoplastic resins A and B are combined in this way, biaxial stretching may be difficult due to adhesion to rolls or clips during stretching.

[0018] Thermoplastic resins with different melting points and glass transition temperatures usually have different optical properties, so by alternately laminating layers whose main components are different thermoplastic resins, it becomes easy to reflect light of a specific wavelength that is determined by the relationship between the difference in refractive index of each layer and the layer thickness.

[0019] Examples of the thermoplastic resins that can be used as the thermoplastic resins A and B in the laminated film of the present invention include linear polyolefins such as polyethylene, polypropylene, poly(4-methylpentene-1), and polyacetal; alicyclic polyolefins that are obtained by ring-opening metathesis polymerization or addition polymerization of norbornenes, or addition copolymers with other olefins; biodegradable polymers such as polylactic acid and polybutyl succinate; polyamides such as nylon 6, nylon 11, nylon 12, and nylon 66; aramid, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, and ethylene vinyl acetate copolymers. Examples of suitable thermoplastic resins include polyesters such as styrene copolymers, polyacetal, polyglycolic acid, polystyrene, styrene copolymerized polymethyl methacrylate, polycarbonate, polypropylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, as well as polyethersulfone, polyetheretherketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polyarylate, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinylidene fluoride. Among these, polyesters are preferred for thermoplastic resins A and B from the viewpoints of strength, heat resistance, transparency, and versatility. The thermoplastic resins may be homopolymers or copolymers.

[0020] The polyester used for the thermoplastic resins A and B is preferably a polyester obtained by polymerization of a monomer having, as the main constituent, an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol or an ester-forming derivative thereof.

[0021] 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 their ester derivatives. Among these, terephthalic acid and 2,6-naphthalenedicarboxylic acid are preferred, as they exhibit a high in-plane average refractive index. These acid components may be used alone or in combination, and may also be partially copolymerized with hydroxy acids such as hydroxybenzoic acid.

[0022] 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. Among these, ethylene glycol, cyclohexanedimethanol, spiroglycol, and neopentyl glycol are preferred. From the viewpoints of film-forming properties, interlayer adhesion, and refractive index, preferred embodiments include those in which the thermoplastic resin B contains at least one structural unit selected from cyclohexanedimethanol units, neopentyl glycol units, and spiroglycol units. These diol components may be used alone or in combination.

[0023] As the thermoplastic resins A and B in the laminated film of the present invention, for example, among the above polyesters, it is preferable to use polyethylene terephthalate and copolymers thereof, polyethylene naphthalate and copolymers thereof, polybutylene terephthalate and copolymers thereof, polybutylene naphthalate and copolymers thereof, and further polyhexamethylene terephthalate and copolymers thereof, polyhexamethylene naphthalate and copolymers thereof, etc. Among these, from the viewpoint of realizing a high in-plane average refractive index, it is preferable that the thermoplastic resin A contains a naphthalenedicarboxylic acid unit.

[0024] A preferred combination of thermoplastic resins A and B in the laminate film of the present invention is one containing the same repeating units, from the viewpoints of reducing delamination and improving lamination accuracy. For example, when polyethylene terephthalate is used as one of the thermoplastic resins, it is preferred that the other thermoplastic resin also contains ethylene terephthalate units. By combining thermoplastic resins A and B having a common chemical structure in this way, and further increasing the proportion of the common chemical structure, it becomes easier to achieve both reduced delamination and improved lamination accuracy.

[0025] Furthermore, a preferred combination of thermoplastic resins A and B used in the laminate film of the present invention is one in which the difference in glass transition temperature between the thermoplastic resins is 25°C or less, more preferably 20°C or less. Having a difference in glass transition temperature of 25°C or less improves thickness uniformity during film formation of the laminate film, thereby reducing variations in the heat-shielding performance of the resulting laminate film. This also alleviates problems such as overstretching during molding of the laminate film.

[0026] As an example of a resin combination that satisfies the above conditions, in the laminate film of the present invention, it is preferred that the main component of at least one thermoplastic resin layer comprises polyethylene terephthalate or polyethylene naphthalate, and the main component of at least one other thermoplastic resin layer is a polyester containing cyclohexanedimethanol units, spiroglycol carboxylate units, or polyethylene glycol. A polyester containing spiroglycol carboxylate units refers to a copolyester copolymerized with spiroglycol, or a homopolyester (the same applies to a polyester containing cyclohexanedimethanol carboxylate units, described below). A polyester containing polyethylene glycol refers to a polyester containing a structure derived from polyethylene glycol in its molecular chain.

[0027] Polyesters containing spiroglycol carboxylate units 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 preferred embodiment is one in which one of thermoplastic resins A and B is polyethylene terephthalate or polyethylene naphthalate, and the other is a polyester obtained using spiroglycol or cyclohexanedicarboxylic acid. This embodiment increases the in-plane refractive index difference between the polyester obtained using spiroglycol or cyclohexanedicarboxylic acid and polyethylene terephthalate or polyethylene naphthalate, making it easier to obtain a laminate film with high reflectivity. Furthermore, this embodiment also reduces the difference in glass transition temperature between thermoplastic resins A and B, and provides excellent adhesion between layer A and layer B, making them less susceptible to overstretching during molding and less susceptible to delamination.

[0028] Furthermore, in the laminate film of the present invention, when one of Layer A and Layer B is primarily composed of polyethylene terephthalate or polyethylene naphthalate, these resins may be homopolymers or copolymers of up to 10 mol % of other repeating units or polyalkylene glycol units having a molecular weight of 100 to 800, with the total diol units being 100 mol %. Alternatively, Layer A or Layer B may be a single component, or may be blended with a small amount of other polyester. In this case, the other layer preferably contains a polyester containing cyclohexanedimethanol carboxylate units as its primary component. Polyesters containing cyclohexanedimethanol carboxylate units 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.

[0029] The polyester containing cyclohexanedimethanol carboxylate units is more preferably an ethylene terephthalate polycondensate or an ethylene naphthalate polycondensate in which the copolymerization amount of cyclohexanedimethanol is 15 mol% to 60 mol% relative to 100 mol% of all glycol units. This configuration provides high reflectivity while minimizing changes in optical properties, particularly with heating or aging, and reducing interlayer delamination. Furthermore, an ethylene terephthalate polycondensate or an ethylene naphthalate polycondensate in which the copolymerization amount of cyclohexanedimethanol is 15 mol% to 60 mol% exhibits very strong adhesion to polyethylene terephthalate or polyethylene naphthalate. Furthermore, since the cyclohexanedimethanol group has geometric isomers (cis and trans) and conformational isomers (chair and boat), such an ethylene terephthalate polycondensate or an ethylene naphthalate polycondensate is less likely to undergo orientation crystallization even when co-stretched with polyethylene terephthalate or polyethylene naphthalate. Therefore, a laminated film using such a polyester can achieve a higher reflectance, and furthermore, it is less likely to suffer from changes in optical properties due to heat history or tearing during film formation.

[0030] In the laminate film of the present invention, it is preferable that the outermost layers on both sides in the film thickness direction are Layer A, and that the thermoplastic resin A is a crystalline polyester and the thermoplastic resin B is an amorphous polyester. Having Layer A, which is primarily composed of a crystalline polyester, on both sides of the laminate film can suppress adhesion to rolls during the film-forming process and blocking during storage as a product roll. Furthermore, having Thermoplastic Resin B be an amorphous polyester makes it easy to set the refractive index difference between Layer A and Layer B within a desired range and to produce a laminate film with favorable reflective performance in each desired wavelength band.

[0031] The reflection wavelength of a laminate film in which two different types of thermoplastic resin layers are alternately laminated, such as the laminate film of the present invention, is determined by the in-plane average refractive index and thickness of each layer according to the following formula 1, which is the principle of interference reflection. In the laminate film of the present invention, by designing the optical thickness ratio k defined by the following formula 2 to be 1, light with a wavelength of 900 nm to 1200 nm, which is the primary reflection, is reflected, and light with a wavelength of 400 nm to 700 nm, which is the secondary reflection, is suppressed because the reflected light from adjacent layers has an opposite phase and cancels out each other. The reflection wavelength can be adjusted by the in-plane average refractive index and thickness of each layer, and the reflection wavelength band can be adjusted by the thickness distribution of each layer. Formula 1: 2×(na·da+nb·db)=mλ Equation 2: |(na·da) / (nb·db)| = k na: Average in-plane refractive index of A layer nb: Average in-plane refractive index of B layer da: A layer thickness (nm) db: Layer thickness of layer B (nm) λ: Main reflection wavelength (reflection wavelength) k: ratio of optical thickness m:1, 2,...n (m:1=1st-order reflection, m:2=2nd-order reflection, ...m:n=nth-order reflection).

[0032] The laminated film of the present invention must have an average reflectance Ra of 0.1% or more and 15% or less at wavelengths of 400 nm to 700 nm. A laminated film of such an embodiment can be suitably used in applications where high transparency is required.

[0033] Such a laminate film can be obtained by precisely controlling the layer thickness so that the difference in optical thickness (refractive index of thermoplastic resin × layer thickness) between two adjacent layers is small (preferably equal). Ra can also be adjusted by adjusting the number of layers and the amount of inorganic components contained in the surface layers of the laminate film. Specifically, the more layers there are and the more the amount of inorganic components contained in the surface layers is reduced, the lower Ra can be. Furthermore, if thermoplastic resins A and B are crystalline and amorphous, respectively, increasing the lamination ratio of layers A to B (total total thickness of layers A / total total thickness of layers B) is also effective in lowering Ra. These methods for favorably adjusting Ra can be used in combination as appropriate.

[0034] From the viewpoint of transparency, Ra is preferably 0.1% or more and 13% or less, more preferably 0.1% or more and 11% or less. As Ra becomes smaller, higher transparency can be imparted, but from the viewpoint of productivity and measurement accuracy, the lower limit is 0.1%. Ra can be calculated from the reflectance at each wavelength measured using a known spectrophotometer, and the detailed measurement method will be described later (the same applies to Rd described later).

[0035] The laminate film of the present invention must have an average reflectance Rd of 70% or more and 100% or less in the wavelength range of 900 to 1200 nm. Sunlight has an intensity distribution mainly in the visible light range, and this intensity distribution tends to narrow as the wavelength increases. However, if the laminate film reflects light in the visible light range, although the heat-shielding properties are improved, a decrease in transparency and coloration are observed. Therefore, for use in applications requiring high transparency, by efficiently reflecting light in the wavelength range of 900 to 1200 nm (approximately 18% of the total sunlight intensity), which is slightly wider than the visible light range, the laminate film can be endowed with high heat-shielding properties while reducing the decrease in transparency. From the above viewpoints, Rd is preferably 80% or more and 100% or less, and more preferably 90% or more and 100% or less.

[0036] A laminate film with an Rd of 70% or more and 100% or less can be achieved by adjusting the reflection wavelength through layer thickness design according to the aforementioned formulas 1 and 2, by adjusting the difference in the in-plane average refractive index between two or more resins with different optical properties, the thickness of each layer, and the lamination ratio of layers A and B (total total thickness of layers A / total total thickness of layers B). Furthermore, when the laminate film is a biaxially stretched film, combining layers A and B with one composed primarily of a crystalline thermoplastic resin and the other composed primarily of a thermoplastic resin that maintains its amorphous nature during stretching or melts during heat treatment facilitates a higher in-plane average refractive index and thus a higher Rd for the laminate film. Rd can also be increased by increasing the number of layers or by reducing the amount of heat-absorbing components that lead to temperature increases. These methods can be used in combination as appropriate.

[0037] The laminate film of the present invention must have a difference Rs between the maximum reflectance Rb and the minimum reflectance Rc in the wavelength range of 500 to 600 nm of 1.3% or more and 3.0% or less. When the laminate film reflects light with wavelengths of 500 to 600 nm (in other words, when Rs exceeds 3.0%), for example, when glass incorporating the laminate film is actually used, it is often judged to be unsuitable due to a perceived blue-green tint. Furthermore, when the laminate film is subsequently processed into laminated glass, a similar coloration may occur, requiring improvement. On the other hand, when Rs is controlled to less than 1.3% to achieve colorless transparency, thickness changes due to heating and pressure after processing of the laminated glass can cause deviations in the optical path difference between the layers, resulting in partial in-plane coloration.

[0038] Therefore, while slight coloring caused by reflection of light with wavelengths of 500 to 600 nm is an issue that should be resolved, deliberately controlling Rs to 1.3% or more reduces coloring of the laminate film due to color change after processing at high temperatures and high pressures, such as during laminated glass processing. Therefore, we discovered that laminated glass using such laminated films exhibits reduced coloring and can be used suitably for applications requiring large size and transparency, such as automobile windows and large-format window glass for building materials, leading to the present invention. From the above perspective, the Rs of the laminated film is preferably 1.6% to 2.7%, even more preferably 1.7% to 2.5%, and particularly preferably 1.7% to 2.1%. If the Rs of the laminated film is less than 1.3%, coloring may occur after processing into laminated glass. If it is greater than 3.0%, the coloring of the laminated film alone may be so strong that the coloring may persist even after processing into laminated glass. By adjusting Rs within the above range, transparency due to color change caused during laminated glass processing can be achieved.

[0039] Here, one method for controlling Rs within a preferred range is to vary the lamination ratio of layers A and B (total total thickness of layers A / total total thickness of layers B) by 0.05 to 0.15 from the value at which Rs satisfies 0.0 to 1.5% (the preferred range of the lamination ratio of layers A and B is described below). Even if the layer design of the laminated film of the present invention does not provide reflection in the visible light region, visible light may be reflected as a secondary reflection at half the wavelength of the near-infrared region where heat-shielding properties are exhibited. Typically, this secondary reflection is eliminated by setting the lamination ratio of layers A and B appropriately to equalize the optical path length between the layers. However, when used in applications involving processing under high-temperature and high-pressure conditions, such as laminated glass, the uniformity of the optical path length of the laminated film is not guaranteed after processing, and the final processed product may become discolored due to the aforementioned mechanism. Therefore, in the laminated film of the present invention, by adjusting the lamination ratio of layer A to layer B to a region that is not normally preferred because secondary reflection occurs, fluctuations in the optical path length during processing can be controlled, thereby achieving more uniform decolorization of the final processed product.

[0040] The laminate film of the present invention must have two or more peaks of loss tangent tanδ in the range of 60°C to 140°C, and the loss tangent tanδ (Ts) of the highest peak of the loss tangent tanδ must be 0.17 to 0.30, and the loss tangent tanδ (Tl) of the lowest peak of the loss tangent tanδ must be 0.10 to 0.20. The loss tangent tanδ generally peaks at the glass transition temperature of the constituent components of the measurement sample. In the laminate film of the present invention, which is formed by alternately laminating layers composed mainly of thermoplastic resins having different glass transition temperatures, having two or more peaks of loss tangent tanδ in the range of 60°C to 140°C often corresponds to the fact that the thermoplastic resins that are the main components of each layer exhibit peaks of different glass transition temperatures in the range of 60°C to 140°C.

[0041] Furthermore, by setting Ts and Tl within the above ranges, it may be possible to appropriately control the degree of thermal deformation of each layer during processing at high temperatures and pressures. To explain this in more detail using laminated glass processing as an example, the temperature peaks at two points: one below the glass processing temperature (typically 100°C or higher) and one above it. Furthermore, by having a large difference in loss tangent tanδ, it is possible to intentionally create a difference in thermal deformation between the laminated layers during processing. As a result, the optical path length between layers A and B can be appropriately changed after processing, reducing reflection in the visible light range and achieving transparency. The temperatures at which Ts and Tl are achieved are designated Tp (°C) and Tb (°C), respectively.

[0042] From the above viewpoints, Ts is more preferably 0.22 or more and 0.30 or less, and even more preferably 0.22 or more and 0.27 or less. If Ts is less than 0.17, the change in lamination ratio during processing of the laminated glass may be small, making it difficult to eliminate discoloration. If Ts is greater than 0.30, severe discoloration beyond colorlessness may occur. Furthermore, Tl is more preferably 0.10 or more and 0.17 or less. If Tl is less than 0.10, the change in lamination ratio during processing of the laminated glass may be too large, making it difficult to eliminate discoloration. If Tl is greater than 0.20, the change in lamination ratio during processing of the laminated glass may be small, making it difficult to eliminate discoloration.

[0043] While there are no particular limitations on the method for satisfying this requirement, it is preferable to set the glass transition temperature of Layer A (the glass transition temperature of the thermoplastic resin that is the main component of Layer A) to 90°C or higher, and to include a step in which the film stress is set to 1.0 MPa or more and 20.0 MPa or less in the film transport direction and / or width direction after the step in which the highest temperature is reached during the film formation process. This configuration and step strengthens intermolecular constraint, increasing the efficiency of converting applied strain into thermal energy, thereby adjusting the value of the tan δ peak on the high-temperature side to within the above range. These methods can be used in combination as appropriate.

[0044] From the viewpoint of suitably adjusting Rs and Ts, the lamination ratio of layer A to layer B (total total thickness of layer A / total total thickness of layer B) is preferably 1.75 or more and 2.00 or less, more preferably 1.80 or more and 1.90 or less. By designing the layer thickness in this way, Rs and Ts can be suitably adjusted by adjusting the wavelength of the interference reflection in formula 1 and the high-order reflection in formula 2. Usually, the lamination ratio is designed so that the optical distances of layer A and layer B are equal, thereby suppressing the second-order reflection whose reflection wavelength is expressed in formula 1 above. However, by controlling the lamination ratio to a range different from the above-mentioned original design, which leaves the color of the laminated film, it may be possible to suppress coloring after processing.

[0045] From the viewpoint of reducing deterioration in appearance after heat treatment, it is preferable that the laminated film of the present invention has a heat shrinkage rate of 0.50% or more and 1.50% or less when heated at 100°C for 30 minutes in both the main orientation direction and the direction perpendicular to the main orientation direction, and a heat shrinkage rate of 2.20% or more and 4.50% or less when heated at 150°C for 30 minutes in both the main orientation direction and the direction perpendicular to the main orientation direction.

[0046] Because the laminate film of the present invention has excellent transparency, it can be suitably used in applications requiring transparency, such as laminated glass. However, in such applications, in addition to transparency, it is also necessary to reduce appearance irregularities. Examples of appearance irregularities that may occur in laminated glass in which a laminate film is sandwiched between panes of glass include fine internal irregularities resembling orange peel. This orange peel is thought to be a phenomenon resulting from differences in the thermal dimensional change behavior between the PVB (Polyvinylbutyral) used as the interlayer film in laminated glass and the laminate film. More specifically, because the glass transition temperature of PVB is relatively low compared to that of the laminate film, the difference in thermal dimensional change between the two at low temperatures is large; improving this aspect will lead to the reduction of orange peel.

[0047] From the above viewpoints, the laminated film of the present invention preferably has a heat shrinkage of 0.50% to 1.50% when heated at 100°C for 30 minutes in both the main orientation direction and the direction perpendicular to the main orientation direction. For example, when the laminated film of the present invention is used in a laminated glass having the above-described configuration, a heat shrinkage of 0.5% or more when heated at 100°C for 30 minutes reduces the difference in shrinkage with PVB and reduces the occurrence of orange peel. On the other hand, a heat shrinkage of 1.5% or less prevents excessive shrinkage and reduces the occurrence of wrinkles at the edges of the laminated glass. Furthermore, a heat shrinkage of 2.20% to 4.50% when heated at 150°C for 30 minutes in both the main orientation direction and the direction perpendicular to the main orientation direction is preferable because it is less likely to cause wrinkles due to shrinkage, particularly when applied to a curved surface, and can suppress the aforementioned wrinkles at the edges of the glass.

[0048] A preferred method for achieving the above-mentioned preferred range of heat shrinkage is, for example, stretching at a ratio of 0.7% to 10.0% in the film-forming process (particularly a low-temperature process at 100 to 150°C). Specifically, a method may be used in which the film is slightly stretched in the transverse direction (TD) at a ratio of 0.7% to 10.0% in a slow-cooling zone at 100 to 150°C for winding after the heat treatment process. By adopting these process conditions, it is possible to selectively increase the heat shrinkage in a low-temperature environment at 100°C while suppressing an increase in heat shrinkage in a high-temperature environment at 150°C, thereby favorably controlling the heat shrinkage behavior in both temperature ranges. It is also effective to set the heat treatment temperature within the preferred range described below. These methods can be used in combination as appropriate. The transverse direction (TD) refers to the direction perpendicular to the running direction (longitudinal direction (MD)) of the film within the film plane.

[0049] In the laminated film of the present invention, the main orientation direction and the direction perpendicular to the main orientation direction can be determined from the degree of orientation measured using a known molecular orientation meter. The heat shrinkage at 100°C and 150°C can be measured by suspending a 3g weight in hot air adjusted to a predetermined temperature and heating for 30 minutes. Details of the measurement methods for each item will be described later.

[0050] The laminate film of the present invention preferably has an internal haze of 0.00% or more and 0.50% or less. By subjecting the laminate film of the present invention to high-temperature, high-pressure treatment, dimensional changes in the thickness direction are induced, which may lead to changes in the optical path length and refractive index between layers A and B. By reducing the increase in internal haze caused by changes in refractive index associated with high-temperature, high-pressure treatment, the laminate film can be manufactured through processing involving high-temperature, high-pressure treatment and be suitably used in applications requiring transparency (e.g., laminated glass).

[0051] For example, when the laminate film of the present invention is used in laminated glass, transparency is impaired and commercial value is reduced, so it is preferable to control the internal haze of the laminate film to the aforementioned low value. By setting the internal haze of the laminate film to 0.50% or less, when used in laminated glass, it is possible to reduce the decrease in visibility in conditions with a large amount of light, such as in the setting sun. From the above viewpoint, the internal haze of the laminate film is more preferably 0.30% or less. From the above viewpoint, the lower the internal haze of the laminate film, the better, with the lower limit being 0.00%.

[0052] The laminate film of the present invention preferably has an internal haze quartile deviation of 0.00% or more and 0.10% or less. In a film such as the laminate film of the present invention, the reflected color tone derived from its internal laminate structure acts synergistically with changes in internal haze, which is also an optical element within the film, making color unevenness more visible. The internal haze quartile deviation is an index of internal haze variation excluding extreme outliers, and by setting it within the above range, better uniformity in appearance can be achieved. From the above perspective, the internal haze quartile deviation is more preferably 0.00% or more and 0.07% or less, and even more preferably 0.00% or more and 0.05% or less.

[0053] There are no particular limitations on the method for achieving the quartile deviation of internal haze within the above-mentioned preferred range. One example is a method of increasing the resin viscosity of the layer in contact with the tube wall after laminating different layers during extrusion (preferably increasing the intrinsic viscosity (IV) to more than 0.60) to enhance interface stability. Furthermore, internal haze can also be affected by minute disturbances at the layer interface, and the above characteristics can sometimes be achieved by reducing in-plane flow irregularities caused by the distance from the tube wall or differences in flow path. To increase resin viscosity, it is preferable to use a resin with a high melting point (preferably 245°C or higher). Furthermore, considering the need to stabilize the interface between the two layers and reduce deterioration of appearance, it is preferable to minimize the difference in resin viscosity between the layers to be laminated.

[0054] The internal haze of a laminated film can be measured using the total light transmittance measured in accordance with JIS "Testing methods for total light transmittance of plastic transparent materials" (K7361-1, 1997 edition) in a manner conforming to JIS "Determining the haze of transparent materials" (K7136, 2000 edition) (details of the measurement method and the method for calculating the quartile deviation are described later).

[0055] When determining the measurement points for calculating the quartile deviation, if the longitudinal and transverse directions of the film are unknown, the degree of orientation in each direction of the sample can be measured using a known molecular orientation meter (e.g., the molecular orientation meter MOA-7015 manufactured by Oji Scientific Instruments Co., Ltd.), and the direction with the greatest degree of orientation can be considered the longitudinal direction, and the direction perpendicular to that in the film plane can be considered the transverse direction.If it is difficult to measure the degree of orientation, measurements can be made in any direction and in the direction perpendicular to that in the film plane. Methods for adjusting the internal haze of the laminated film of the present invention to fall within the above-mentioned preferred range include using a polymer of a single composition in Layer A or Layer B (preferably both) without blending different polymers with low compatibility, increasing the resin temperature during extrusion to reduce unmelted polymer, and setting the heat treatment temperature during the film formation process to the stretching temperature or higher and the melting point of the film minus 20° C. or lower. These methods can be used in combination as appropriate.

[0056] From the viewpoint of widely using the laminated film of the present invention for processed products involving processing at high temperatures and high pressures, when the temperature at which Ts is obtained is Tp°C, it is preferable that the storage modulus E'h (MPa) at Tp+10°C and the storage modulus E'l (MPa) at Tp-10°C satisfy the following formula: 0.50≦E'h / E'l≦0.90.

[0057] For a laminated film to satisfy the above formula means that the storage modulus changes slowly in the temperature range where it changes most significantly during processing. This configuration prevents a rapid decrease in storage modulus with increasing temperature. For example, when the laminated film is used in laminated glass with PVB as an interlayer, sufficient resistance to deformation due to the difference in dimensional change between the laminated film and the PVB is achieved, preventing the occurrence or worsening of orange peel. From this perspective, it is more preferable for E'h / E'l to satisfy the following formula: 0.70≦E'h / E'l≦0.90.

[0058] The storage modulus of the laminated film can be measured by dynamic viscoelasticity measurement, the detailed conditions of which will be described later. There are no particular limitations on the method for making the laminated film of the present invention satisfy 0.50≦E'h / E'l≦0.90. For example, the layer with the relatively higher refractive index between the laminated A and B layers has a glass transition temperature of room temperature (20°C to 30°C) or lower, for example, a method in which the content of polyethylene glycol or the like is 10 mol% or less, preferably 5 mol% or less, of all structural units. A component with a low glass transition temperature may be added or copolymerized to the high refractive index layer to ensure stretchability and interlayer adhesion. Setting the ratio within a specific range may prevent a rapid decrease in the modulus of elasticity due to a local phase transition.

[0059] Next, a preferred method for producing the laminated film of the present invention will be described below, but the present invention is not limited to such an example. Furthermore, the laminated structure of the laminated film of the present invention can be produced based on the description in paragraphs

[0053] to

[0063] of JP-A-2007-307893.

[0060] First, thermoplastic resins A and B are prepared in the form of pellets or the like. Next, these pellets are dried in hot air or under vacuum as necessary, and then fed into separate extruders. In each extruder, thermoplastic resins A and B are heated and melted at a temperature above their melting points, and then extruded at a uniform extrusion rate using a gear pump or the like. At this time, foreign matter, modified substances, etc. are removed from each molten thermoplastic resin using a filter or the like.

[0061] The molten thermoplastic resins A and B are then fed through separate channels by two or more extruders and into a multi-layer lamination device before being extruded through a die onto a cooling body such as a casting drum. While a multi-manifold die, feed block, static mixer, or the like can be used as the multi-layer lamination device, it is particularly preferable to use a feed block containing at least two or more separate components with numerous fine slits to efficiently obtain the laminate film structure of the present invention. The use of such a feed block prevents the multi-layer lamination device from becoming excessively large, reduces the amount of foreign matter caused by 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, making it easy to form any layer thickness configuration. Furthermore, with such a multi-layer lamination device, the thickness of each layer can be adjusted by the shape (length and width) of the slits, making it easy to adjust the thickness of each layer.

[0062] The multilayered molten sheet material extruded from the die is then extruded onto a cooling body such as a casting drum, where it is cooled and solidified to form a cast film. In this case, it is preferable to use a wire-, tape-, needle-, or knife-shaped electrode to bring the sheet into close contact with a cooling body such as a casting drum by electrostatic force, thereby rapidly solidifying the sheet. Other preferred methods include spraying air from a slit-, spot-, or planar-shaped device to bring the sheet into close contact with a cooling body such as a casting drum, thereby rapidly solidifying the sheet, or using a nip roll to bring the sheet into close contact with a cooling body and rapidly solidify the sheet.

[0063] The cast film thus obtained is preferably biaxially stretched as needed. Here, biaxial stretching refers to stretching in the machine direction (MD) and the transverse direction (TD). During stretching, the film may be stretched in two directions sequentially or simultaneously. Furthermore, the film may be re-stretched in the machine direction and / or the transverse direction as needed.

[0064] First, the case of sequential biaxial stretching will be described. In the case of sequential biaxial stretching, a cast film is typically stretched in the longitudinal direction, and then the resulting uniaxially stretched film is stretched in the width direction. Here, stretching in the longitudinal direction refers to stretching to impart molecular orientation to the film in the longitudinal direction, and is typically performed by varying the peripheral speed of rolls. This stretching may be performed in one stage, or in multiple stages using multiple pairs of rolls. The stretching ratio varies depending on the types of thermoplastic resins A and B, but is typically preferably 2.0 to 15 times, and when polyethylene terephthalate is used as either thermoplastic resin A or B, a ratio of 2.0 to 7.0 times is particularly preferred. The stretching temperature is preferably from the glass transition temperature of the thermoplastic resin A or B, whichever has the higher glass transition temperature, −10°C to +50°C of that glass transition temperature.

[0065] The uniaxially stretched film thus obtained may be subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment as needed, and then may be imparted with properties such as easy slippage, easy adhesion, and antistatic properties by in-line coating.

[0066] Stretching in the width direction refers to stretching to impart widthwise orientation to the film, and is typically performed by using a tenter to convey the uniaxially stretched film while holding both widthwise ends with multiple clips, thereby stretching it in the width direction. The stretching ratio varies depending on the types of thermoplastic resins A and B, but is typically preferably 2.0 to 15 times, and when polyethylene terephthalate is used as either thermoplastic resin A or B, a ratio of 2.0 to 7.0 times is particularly preferred. The stretching temperature is preferably from the glass transition temperature of the thermoplastic resin A or B, whichever has the higher glass transition temperature, to that glass transition temperature + 120°C.

[0067] To impart flatness and dimensional stability to the biaxially stretched film thus obtained, it is preferable to heat-treat the film in a tenter at a temperature equal to or higher than the stretching temperature and equal to or lower than the melting point of the thermoplastic resin A or B, whichever has the higher melting point. To achieve a suitable range for the heat shrinkage percentage when heated at 100°C for 30 minutes and the heat shrinkage percentage when heated at 150°C for 30 minutes, the heat-treating temperature is preferably equal to or higher than the stretching temperature and equal to or lower than the melting point of the thermoplastic resin A or B, whichever has the higher melting point, minus 20°C. Heat-treating improves the dimensional stability of the resulting laminated film. After heat-treating, the biaxially stretched film is uniformly and slowly cooled, then cooled to room temperature, and wound up. If necessary, a relaxation treatment or the like may be performed during the heat-treatment and slowly cooling process.

[0068] To control the tan δ of the laminated film within a preferred range, it is preferable to include a step in which the film stress is adjusted to 1.0 MPa or more and 20.0 MPa or less in the longitudinal and / or transverse directions during slow cooling after the heat treatment reaches the maximum temperature. By including such a step, slight tension is applied to the state in which the molecular orientation is most relaxed by the relaxation treatment at the maximum temperature. This strengthens the intermolecular constraint caused by the micro-orientation, increasing the efficiency of converting the applied strain into thermal energy, which may result in a higher value, Ts, of the tan δ peak on the high-temperature side of the biaxially stretched film.

[0069] More specific process conditions include, for example, a method in which a slow cooling process is performed at 70°C to 150°C, preferably 100°C to 150°C, followed by a widthwise re-stretching of 0.5% to 5.0%; or a method in which the transport draw is set to 1.0002% to 1.0050% on the rolls from the heat treatment oven exit to winding. The former method enables fine orientation in the width direction, and the latter method enables fine orientation in the longitudinal direction. The higher the re-stretching ratio and transport draw within the above ranges, the better, since this allows for a more preferable range of tan δ(Ts). However, a higher re-stretching ratio can deteriorate flatness, potentially leading to wrinkles after processing into laminated glass. Therefore, the upper limits of these ratios are 5.0% and 1.0050%. The laminated film of the present invention obtained in this manner is cut parallel to the longitudinal direction as needed to the desired width and wound into a film roll.

[0070] Next, simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the cast film obtained by the above method may be subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment as necessary, and then may be imparted with properties such as easy lubricity, easy adhesion, and antistatic properties by in-line coating.

[0071] The cast film is then introduced into a simultaneous biaxial tenter, where it is conveyed while being held at both widthwise ends with clips, and simultaneously and / or stepwise stretched in the longitudinal and widthwise directions. Simultaneous biaxial stretching machines include pantograph, screw, drive motor, and linear motor types. Drive motor and linear motor types are preferred, as they allow for variable stretching ratios and relaxation treatment at any desired location. The stretching ratio varies depending on the type of resin, but an area ratio of 6.0 to 20 times is generally preferred. When polyethylene terephthalate is used as one of the resins constituting the laminate film, an area ratio of 8.0 to 15 times is particularly preferred. The stretching temperature is preferably between the glass transition temperature of the thermoplastic resin A or B, whichever has the higher glass transition temperature, and the glass transition temperature + 120°C.

[0072] In particular, in the case of simultaneous biaxial stretching, it is preferable to make the stretching ratios in the longitudinal direction and the width direction as close to the same as possible and to make the stretching speeds approximately equal in order to suppress in-plane orientation differences. In order to impart flatness and dimensional stability to the biaxially stretched film, it is preferable to subject the film to various treatments in the steps after heat treatment, as in the case of sequential stretching.

[0073] Next, the laminate film roll of the present invention will be described. The laminate film roll of the present invention is formed by winding the laminate film of the present invention, and has an internal haze quartile deviation of 0.00 or more and 0.10 or less. The laminate film of the present invention can be obtained by the methods described above, and the internal haze quartile deviation can be adjusted in the same manner (a measurement sample can be obtained by unwinding the laminate film roll).

[0074] The size of the laminated film roll of the present invention is not particularly limited, but from the viewpoint of maintaining favorable quality, for example, a winding length of 500 m to 3000 m, a core diameter of 50 mm to 500 mm, and a roll width of 100 mm to 5000 mm are preferred. Furthermore, from the viewpoint of maintaining production efficiency while reducing breakage and the like during the film formation process, the winding conditions are preferably a speed of 50 m / min to 500 m / min, a tension of 50 N / m to 100 N / m, and a surface pressure of 100 N / m to 500 N / m. [Example]

[0075] The present invention will be described in detail below with reference to examples, in which the respective property values ​​were measured by the following methods.

[0076] [Methods for measuring physical properties and evaluating effects] The evaluation methods for the characteristic values ​​and the effects are as follows.

[0077] (1) Number of layers and layer structure The layer structure of the film was identified by observing a cross section of the laminated film sample cut perpendicular to the film surface using a microtome with a transmission electron microscope (TEM). Specifically, a transmission electron microscope (TEM) H-7100FA (manufactured by Hitachi, Ltd.) was used to observe the cross section of the sample at 40,000 times magnification at an accelerating voltage of 75 kV, and cross-sectional photographs were taken to identify the number of layers and the layer structure. In some cases, known staining techniques using RuO4 or OsO4 were used to obtain high contrast between each layer.

[0078] (2) Calculation method for layer thickness The cross-sectional photographs obtained in section (1) were captured at 720 dpi using a "CanoScan" (registered trademark) D123U (Canon Inc.). The captured images were saved in compressed image file (JPEG) format on a personal computer. The image files were then opened and analyzed using image processing software Image-Pro Plus ver. 4 (distributor: Planetron Co., Ltd.). Image analysis was performed in vertical thick profile mode by reading the relationship between the thickness direction position and the average brightness of the region sandwiched between two width direction lines as numerical data. Then, using spreadsheet software ("Excel" (registered trademark) 2003, Microsoft Corporation), the position (nm) and brightness data were sampled at a sampling step of 6 (thinning 6), followed by numerical processing using a three-point moving average. Furthermore, the data thus obtained, which showed periodically changing brightness, were differentiated, and the maximum and minimum values ​​of the differential curve were read using a VBA (Visual Basic for Applications) program. The layer thickness was calculated by defining the distance between adjacent values ​​as the layer thickness. This procedure was carried out for each photograph, and the layer thickness was calculated for all layers.

[0079] (3) Crystalline, amorphous The melting point of the thermoplastic resin was determined in accordance with JIS K-7121:1987 using an EXSTAR DSC6220 manufactured by Seiko Instruments Inc. The measurement conditions were as follows: 5 mg of the thermoplastic resin was weighed out on an electronic balance and sandwiched between aluminum packing to form a sample, and the sample was heated from 25°C to 300°C at a rate of 20°C / min using the SC6220. If a melting point peak was confirmed in the obtained chart, it was judged to be crystalline, and if not, it was judged to be amorphous.

[0080] (4)Reflectance First, a 5 cm x 5 cm sample of the laminated film was cut. A Hitachi spectrophotometer (U-4100 Spectrophotometer) was fitted with a 12° specular reflectance attachment (P / N 134-0104) and the reflectance of the sample was measured at wavelengths of 250 to 2600 nm at an incident angle of φ = 12°. The measurement conditions were a slit of 2 nm (visible) / automatic control (infrared), a gain of 2, a measurement interval of 1 nm, and a scanning speed of 600 nm / min. The light incident surface was set to face the transparent substrate. From the reflectance data obtained at each wavelength, the average reflectance at wavelengths of 400 to 700 nm and 900 to 1200 nm was calculated and used as Ra (%) and Rd (%). Furthermore, from the reflectance data obtained at each wavelength, the maximum and minimum reflectance values ​​in the wavelength band of 500 to 600 nm were identified and designated as Rb (%) and Rc (%), respectively. Rs (%) was adopted as the difference between Rb (%) and Rc (%). The measurement surface was selected arbitrarily.

[0081] (5) Main orientation direction and direction perpendicular to the main orientation direction A 10 cm × 10 cm sample of the laminated film was cut out. The orientation degree in each direction of the sample was measured using a molecular orientation analyzer MOA-7015 manufactured by Oji Scientific Instruments Co., Ltd. The direction with the greatest orientation degree was defined as the main orientation direction, and the direction perpendicular to this in the film plane was defined as the direction perpendicular to the main orientation direction.

[0082] (6) Heat shrinkage at 100°C and 150°C The film's main orientation direction and the direction perpendicular to the main orientation direction were determined using the method described in (5), and rectangular samples measuring 150 mm long x 10 mm wide (the length direction corresponds to the corresponding direction) were cut out in each direction. Marked lines were drawn on the sample at 100 mm intervals (50 mm from the center to both ends), and the sample was heat-treated by hanging a 3 g weight and placing it in a hot air oven heated to a specified temperature for 30 minutes. The distance between the marks after heat treatment was measured, and the heat shrinkage was calculated from the change in the distance between the marks before and after heating using the following formula. Heat shrinkage rate (%) = {(gauge length before heat treatment) - (gauge length after heat treatment)} / (heat treatment) (Gauge distance before heat treatment) x 100.

[0083] (7) Loss tangent tanδ The film's main orientation direction and the direction perpendicular to the main orientation direction were determined using the method described in (5). Rectangular samples measuring 60 mm long x 5 mm wide were cut out in each direction (the length direction corresponds to the relevant direction). The loss tangent (tanδ) of the sample was measured using a dynamic viscoelasticity measuring device (Seiko Instruments, DMS6100) under the following measurement conditions, and a curve was obtained with temperature on the horizontal axis and tanδ on the vertical axis. The temperature at which tanδ peaked in the obtained curve was determined within the range of 60°C to 140°C. The average value of tanδ at the highest peak in the main orientation direction and the perpendicular direction was taken as Ts. Similarly, the loss tangent (tanδ) (Tl) at the lowest peak in the above temperature range was calculated in the same way. The peak of tanδ here refers to the point where the slope of the curve changes from positive to negative. Furthermore, if there were two or more points within a 5°C temperature range where the slope changed from positive to negative and the difference between the maximum and minimum values ​​of the loss tangent tanδ between those points was less than 0.01, then these were considered noise and were not judged to be peaks. <Measurement conditions> Frequency: 1Hz, test length: 20mm, minimum load: approximately 100mN, amplitude: 10μm, measurement temperature range: 20℃~230℃, heating rate: 5℃ / min.

[0084] (8) Storage modulus E' Measurement was performed using a dynamic viscoelasticity measuring device under the conditions described in (6) to determine the storage modulus E', and a curve was obtained with temperature on the horizontal axis and E' on the vertical axis. On the obtained curve, the temperature at which Ts was obtained was defined as Tp, and the storage moduli at Tp + 10°C and Tp - 10°C were read and used as E'h and E'l, respectively.

[0085] (9) Internal haze, quartile deviation of internal haze First, three square samples of laminated film, each 5 cm on a side, were prepared. Then, the samples were left at room temperature (23°C, 50% relative humidity) for 40 hours. For each sample, total light transmittance was measured using a Nippon Denshoku Industries Co., Ltd. NDH5000 turbidity meter according to JIS "Test Method for Total Light Transmittance of Plastic Transparent Materials" (K7361-1, 1997 edition). Haze was measured according to JIS "Determination of Haze for Transparent Materials" (K7136, 2000 edition). Internal haze was measured according to JIS-K-7105 (1981 edition), except that the samples were immersed in a quartz cell filled with liquid paraffin to eliminate light scattering due to sample surface irregularities. The average of the three values ​​for each sample was used as the internal haze value for the laminated film. Furthermore, five points were set at 100 mm intervals on a line parallel to the longitudinal direction of the film, and five points were set at 100 mm intervals on a line parallel to the width direction of the film, for a total of 10 points, and similar measurements were taken at each point. The quartile deviation was calculated from the obtained data, and the obtained value was taken as the quartile deviation of the internal haze.

[0086] (10) Transparency after lamination On both sides of a laminated film cut into a square shape with one side being 150 mm, a PVB sheet (thickness 0.38 mm) serving as an intermediate film cut into the same size and glass with a thickness of 3.2 mm formed into a square shape with one side being 100 mm were stacked in the order of glass, intermediate film, laminated film, intermediate film, and glass. After inserting these into a rubber pack, the pressure was reduced, and they were pre-bonded for 1 hour while heating at 90 °C. Further, the laminated body after pre-bonding was heated and pressurized at 130 °C and 13 atmospheres for 0.5 hours in an autoclave for main bonding. From the obtained laminated body, the intermediate film and laminated film protruding from the glass surface were cut to obtain a laminated glass sample. Also, for a laminated film cut into a square shape with one side being 650 mm, a glass plate (thickness 3.2 mm) in a square shape with one side being 600 mm was similarly bonded to obtain a laminated glass sample. For the obtained laminated glass sample in a square shape with one side being 100 mm, Rs(%) was evaluated by the measurement described in (4). Also, for the laminated glass sample in a square shape with one side being 600 mm, the state of color unevenness was visually evaluated, and C or above was regarded as passing according to the following evaluation criteria. Note that an angle of 70 degrees from the glass plane means that the angle formed with the normal line of the glass surface is 70 degrees. <Evaluation Criteria> A: 0 ≦ Rs ≦ 0.7, and color unevenness could not be visually recognized from the front and at an angle of 70 degrees from the glass plane. B: 0.7 < Rs ≦ 1.1, and color unevenness could not be visually recognized from the front and at an angle of 70 degrees from the glass plane. C: 1.1 < Rs ≦ 1.5, or color unevenness could be slightly visually recognized at least in one of the front and at an angle of 70 degrees from the glass plane. D: Did not fall under any of A to C.

[0087] (11) Heat insulation Using a XES-155S1 (Minae Electric Manufacturing Co., Ltd.), the surface temperature rise after 30 minutes of light irradiation on a black acrylic plate (size 450 mm x 450 mm, thickness 5 mm) was measured using a FLIRE4 thermography (FLIR). During the measurement, the distance between the light source and the black acrylic plate was 350 mm, and the light output at the position of the black acrylic plate was 1000 W / m 2 The laminated film (size 450mm x 450mm) was placed at a position 200mm away from the light source. The temperature rise was evaluated according to the following criteria, with a grade of C or higher being considered a pass. A: The temperature rise of the black acrylic plate was 15°C or less. B: The temperature rise of the black acrylic plate was more than 15°C and less than 20°C. C: The temperature rise of the black acrylic plate was more than 20°C and less than 25°C. D: The temperature of the black acrylic plate rose above 25°C.

[0088] (12) Appearance of laminated glass after processing For the evaluation, a square laminated glass with a side length of 600 mm, prepared by the method described in (8), was used. Light was irradiated from a three-wavelength fluorescent lamp at a position 40 cm away from the surface of the laminated glass, and the image of the fluorescent lamp reflected on the surface of the laminated glass was visually observed to evaluate the appearance of the laminated glass according to the following criteria (a grade of C or higher was considered to be acceptable). A: The fluorescent light was clearly visible without any fluctuations even when I changed my viewpoint. B: When changing the viewpoint, there were some areas where the edges of the fluorescent lights appeared to fluctuate slightly. C: A slight fluctuation was visible on the edge of the fluorescent light regardless of the viewpoint. D: The edge of the fluorescent light was clearly fluctuating regardless of the viewpoint.

[0089] (13) In-plane average refractive index The in-plane average refractive index of Layer A was measured using a Cylon Technology SPA-400 prism coupler for the laminate films obtained in the Examples and Comparative Examples described below. The laser wavelength 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 main orientation axis direction and the direction perpendicular to the main orientation axis direction. Regarding the in-plane average refractive index of Layer B, since the thermoplastic resin constituting Layer B in each Example and Comparative Example was an amorphous resin, an unstretched film was prepared using the thermoplastic resin constituting Layer B, and the in-plane average refractive index measured in the same manner was used as the in-plane average refractive index of Layer B. The unstretched film was prepared by melting the resin composition at 280°C in a vented twin-screw extruder, then passing it through a gear pump and filter into a T-die to form a sheet, followed by quenching and solidification on a casting drum maintained at a surface temperature of 25°C by electrostatic application, resulting in a film with a thickness of 100 μm.

[0090] (14) Film stress Measurements were carried out using a Bruckner KARO-V film stretcher. A laminated film having the film composition of each example and obtained under the film-forming conditions described in Comparative Example 5 was cut into a 100 mm square with the longitudinal and width directions as its sides, and simultaneously biaxially stretched at a stretching speed of 200% / min at the temperature of annealing zone 2 (downstream annealing zone) in each example, with the width direction stretch ratio equal to the re-stretching ratio after annealing and the longitudinal direction draw ratio equal to the winding draw ratio. The maximum film stress in the longitudinal and width directions during stretching was recorded as the film stress in each example.

[0091] (raw materials) The following polyesters were used in producing the laminated film: The copolymerization ratio of the glycol component was calculated assuming that the entire glycol component was 100 mol %.

[0092] (Polyester A) 100 parts by mass of dimethyl terephthalate, 57.5 parts by mass of ethylene glycol, 0.03 parts by mass of magnesium acetate dihydrate, and 0.03 parts by mass of antimony trioxide were melted at 150°C under a nitrogen atmosphere. The melt was heated to 230°C over 3 hours with stirring, and the methanol was distilled off to terminate the transesterification reaction. After the transesterification reaction was completed, an ethylene glycol solution (pH 5.0) containing 0.005 parts by mass of phosphoric acid dissolved in 0.5 parts by mass of ethylene glycol was added. The intrinsic viscosity of the composition at this stage was less than 0.2. Subsequently, a polymerization reaction was carried out at a final temperature of 285°C and a vacuum of 0.1 Torr to obtain crystalline polyethylene terephthalate with an intrinsic viscosity (IV) of 0.65 and a melting point of 256°C, designated Polyester A. After film formation under the conditions of Example 1, the in-plane average refractive index was 1.66.

[0093] (Polyester B) Amorphous polyethylene terephthalate with an intrinsic viscosity (IV) of 0.72, copolymerized with 21 mol% spiroglycol (SPG) with an intrinsic viscosity (IV) of 0.55 and 24 mol% cyclohexanedicarboxylic acid (CHDC). The in-plane average refractive index after film formation was 1.55.

[0094] (Polyester C) The amorphous copolymer polyethylene terephthalate (GN001, manufactured by Eastman Chemical Co.) was copolymerized with 33 mol% of 1,4-cyclohexanedimethanol. The intrinsic viscosity (IV) was 0.75, and the in-plane average refractive index after film formation was 1.58.

[0095] (Polyester D) Crystalline polyethylene 2,6-naphthalate (intrinsic viscosity (IV) 0.62, melting point 245°C) copolymerized with 6 mol% polyethylene glycol (average molecular weight 400).

[0096] (Polyester E) Crystalline polyethylene 2,6-naphthalate (intrinsic viscosity (IV) 0.62, melting point 250°C) copolymerized with 3 mol% polyethylene glycol (average molecular weight 400).

[0097] (Polyester F) Crystalline polyethylene 2,6-naphthalate (intrinsic viscosity (IV) 0.60, melting point 243°C) copolymerized with 6.5 mol% polyethylene glycol (average molecular weight 400).

[0098] Example 1 Polyester A and polyester B were each fed into separate single-screw extruders and melt-kneaded at 280°C. Each molten resin was then extruded and passed through five FSS-type leaf disc filters to remove any impurities. The resins were then metered using a gear pump to achieve an optical thickness ratio of polyester A / polyester B = 1.5, excluding the polyester thick layer, and merged in a 661-layer lamination device consisting of three slit plates with 221 slits (slit processing accuracy of ±2.8%) to form a laminate with 601 layers alternately stacked in the thickness direction. The laminate was fabricated according to the method described in JP 2007-307893 A, paragraphs

[0053] to

[0056] . Because some A layers were formed by overlapping each other, the total number of gaps in the slit plate was 661. Here, the slit lengths were all constant, and only the slit gaps were varied to create a gradient layer thickness distribution. The resulting laminate had a gradient structure with 331 layers of polyester A (A layers) and 330 layers of polyester B (B layers), alternately stacked in the thickness direction. The slit gaps were adjusted so that the thick layers, where the A layers were overlapped on both surface layers of the film and the three slit plates, were 20 times thicker than the adjacent layers. The width-expansion ratio within the die, calculated by dividing the film width direction length at the die lip by the film width direction length at the die inlet, was set to 2.5. The draft ratio was 3.2. The resulting cast film was preheated with a group of rolls set at 85°C, then passed through a stretching roll set at 93°C. It was rapidly heated on both sides of the film with a radiation heater within a 100 mm stretching section, stretched 3.6 times in the longitudinal direction, and then cooled. Next, both sides of this uniaxially stretched film were subjected to corona discharge treatment in air to set the wetting tension of the uniaxially stretched film to 55 mN / m, and a coating solution consisting of (polyester with a glass transition temperature of 18°C) / (polyester with a glass transition temperature of 82°C) / silica particles with an average particle size of 140 nm was applied to the treated surface to form a coating layer with excellent transparency, slipperiness, and adhesiveness. This uniaxially stretched film was introduced into a tenter, preheated with hot air at 100°C, and then stretched 3.8 times in the width direction at a temperature of 120°C.The stretched film was then heat-treated in a tenter with hot air at 210°C and 220°C in stages. It was then relaxed by 2% in the width direction at 220°C, rapidly cooled to 140°C and 110°C in stages, and then re-stretched by 1.0% in the width direction. The film was then wound from the tenter exit at a draw ratio of 1.0001x on the first roll to obtain a laminated film with a thickness of 80 μm. The resulting laminated film roll was then slit into a 1400 mm width and wound onto a 167 mm outer diameter plastic core (FWP Core, manufactured by Tenryu Composites Co., Ltd.) at a speed of 100 m / min, a tension of 100 N / m, and a surface pressure of 250 N / m to obtain a laminated film roll of 1500 m. The resulting laminated film was then used to obtain laminated glass of various sizes using the method described in "(8) Transparency after Lamination." Tables 1 and 2 show the evaluation results of the obtained laminated film, laminated film roll, and laminated glass (hereinafter, these three items may be collectively referred to as laminated film, etc.).

[0099] (Examples 2 to 5, 7 to 9, Comparative Examples 1 to 3) Laminated films and the like were obtained in the same manner as in Example 1, except that the raw materials and production conditions were as shown in Tables 1 and 2. The evaluation results of the obtained laminated films and the like are shown in Tables 1 and 2.

[0100] Example 6 A laminate film and the like were obtained in the same manner as in Example 2, except that the film was rapidly cooled to 120°C in the tenter and then re-stretched by 2.0% in the width direction. The evaluation results of the obtained laminate film and the like are shown in Tables 1 and 2.

[0101] Comparative Example 4 Laminated films and the like were obtained in the same manner as in Example 1, except that the thickness was 95 μm, using the raw materials and production conditions shown in Tables 1 and 2. The evaluation results of the obtained laminated films and the like are shown in Tables 1 and 2.

[0102] (Comparative Example 5) Laminated films and the like were obtained in the same manner as in Example 1, except that the raw materials and production conditions were as shown in Tables 1 and 2, and the re-stretching treatment in the tenter was 0.0%. The evaluation results of the obtained laminated films and the like are shown in Tables 1 and 2.

[0103] [Table 1]

[0104] [Table 2] [Industrial Applicability]

[0105] According to the present invention, it is possible to provide a laminated film that remains transparent and exhibits high heat-shielding properties even after long-term processing at high temperatures and pressures during laminated glass processing. Because the laminated film of the present invention has the above-mentioned excellent properties, it can be suitably used for windows in buildings, as well as windows, windshields, sunroofs, rear windows, etc. of vehicles that require heat-shielding properties and transparency.

Claims

1. A laminated film having a laminated structure in which 51 or more layers (A layers) containing a thermoplastic resin A as a main component and layers (B layers) containing a thermoplastic resin B as a main component different from the thermoplastic resin A are alternately laminated, the laminated film having two or more peaks of loss tangent tanδ in the region of 60°C or higher and 140°C or lower, the loss tangent tanδ (Ts) of the highest peak of the loss tangent tanδ being 0.17 or higher and 0.30 or lower, and the loss tangent tanδ (Tl) of the lowest peak of the loss tangent tanδ being 0.10 or higher and 0.20 or lower, and the laminated film having all of the following characteristics 1 to 3. Feature 1: The average reflectance Ra in the wavelength range of 400 to 700 nm is 0.1% or more and 15.0% or less. Feature 2: The difference Rs between the maximum value Rb and the minimum value Rc of the reflectance in the wavelength band of 500 to 600 nm is 1.3% or more and 3.0% or less. Feature 3: The average reflectance Rd in the wavelength range of 900 to 1200 nm is 70% or more and 100% or less.

2. 2. The laminated film according to claim 1, wherein the heat shrinkage rate when heated at 100°C for 30 minutes is 0.50% or more and 1.50% or less in both the main orientation direction and the direction perpendicular to the main orientation direction, and the heat shrinkage rate when heated at 150°C for 30 minutes is 2.20% or more and 4.50% or less in both the main orientation direction and the direction perpendicular to the main orientation direction.

3. 3. The laminated film according to claim 1, wherein the internal haze is 0.00% or more and 0.50% or less.

4. 3. The laminated film according to claim 1, wherein, when the temperature at which Ts is given is Tp ° C., the storage modulus E'h (MPa) at Tp + 10 ° C. and the storage modulus E'l (MPa) at Tp - 10 ° C. satisfy the following formula: 0.50≦E'h / E'l≦0.90

5. 3. The laminated film according to claim 1, wherein the quartile deviation of the internal haze is 0.00% or more and 0.10% or less.

6. The laminated film according to claim 1 or 2, wherein the thermoplastic resin A contains a naphthalenedicarboxylic acid unit.

7. 3. The laminate film according to claim 1, wherein the thermoplastic resin B contains at least one structural unit selected from the group consisting of a cyclohexanedimethanol unit, a neopentyl glycol unit, and a spiro glycol unit.

8. The laminated film according to claim 1 or 2, which is used as laminated glass.

9. A laminated film roll obtained by winding the laminated film according to claim 1 or 2, wherein the quartile deviation of internal haze is 0.00 or more and 0.10 or less.

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