film

Abstract

The present invention aims to provide a film that, when used in a projected image display member, can achieve good background visibility, heat shielding, and image display performance. [Solution] A film characterized by having a thermoplastic resin as its main component and possessing all of the following features A to C on at least one surface. Feature A: When light is incident at an incident angle of 10°, there is a continuous reflectivity band of 30% to 110% in the wavelength range of 850 nm and above, with a wavelength width of 20 nm or more. Feature B: When light is incident at an incident angle of 10°, the average reflectance of visible light is between 0% and 25%. Feature C: When P-wave light is incident on the film surface at angles of 20°, 40°, and 70° to the normal, and the average reflectance (%) in the wavelength band of 400-700 nm is denoted as R20, R40, and R70 respectively, then R20 ≤ R40.

Description

[Technical Field]

[0001] The present invention relates to a film, a projected image display member, a projected image display device, a head-up display, and a manned transportation system. [Background technology]

[0002] In recent years, in response to carbon dioxide emission regulations for environmental protection, heat-cutting glass, which can suppress the inflow of heat from sunlight, has attracted attention as window glass for vehicles such as automobiles and trains, as well as buildings. Furthermore, the installation of projection image display devices in automobiles and other transportation vehicles, which project images onto projection image display components such as laminated glass and overlay the projected image with the background viewed through the projection image display component, is also attracting attention.

[0003] Against this backdrop, examples of heat-cutting glass have been proposed, such as glass in which a heat-absorbing material is incorporated into an interlayer used in glass or laminated glass, thereby blocking heat rays (near-infrared rays) with the heat-absorbing material (Patent Document 1), and glass in which a metal film is formed on the glass surface by sputtering or the like to reflect and block near-infrared rays (for example, Patent Document 2).

[0004] Furthermore, as projection image display devices, methods have been proposed such as projecting an image onto laminated glass with an interlayer having a wedge angle (thickness gradient) using an image projector with an S-wave light source (for example, Patent Document 3), and placing a polarizing reflective film inside laminated glass and inducing P-wave light for projecting an image at or near the Brewster angle of the laminated glass (Patent Document 4). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-17854 [Patent Document 2] Japanese Patent Publication No. 2001-310407 [Patent Document 3] International Publication No. 2018 / 181687 [Patent Document 4] International Publication No. 2005 / 017600 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] However, any of the technologies disclosed in Patent Documents 1 to 4 has a problem in that only one of the characteristics of suppressing heat inflow or projecting an image can be exhibited. Furthermore, in the technology of Patent Document 3, an image is projected onto a projection image display member by S waves, and when wearing polarized sunglasses, the S waves are absorbed by the polarized sunglasses, resulting in a problem (blackout) where the image cannot be visually recognized. In the technology of Patent Document 4, although an image of P waves incident obliquely can be projected by a polarized reflection film, there is also a problem that the transmissivity of visible light in the front is poor and the visibility of the background through the projection image display member is inferior.

[0007] An object of the present invention is to provide a film that can achieve good background visibility, heat insulation properties, and image display properties when used for a projection image display member in order to solve such problems. [Means for Solving the Problems]

[0008] The present invention aims to solve the above problems and has the following configuration.

[0009] A film characterized by containing a thermoplastic resin as a main component and having all of the following characteristics A to C on at least one surface. Characteristic A: When light is incident at an incident angle of 10°, there is a reflection band in the wavelength band of 850 nm or more with a wavelength width of 20 nm or more where the reflectance is continuously 30% or more and 110% or less. Characteristic B: When light is incident at an incident angle of 10°, the average reflectance of visible light is 0% or more and 25% or less. Characteristic C: When P-wave light is incident at angles of 20°, 40°, and 70° with respect to the normal of the film surface, the average reflectance (%) in the wavelength band of 400 to 700 nm satisfies the relationship R20 ≤ R40 < R70, where R20, R40, and R70 are the average reflectances in order.

[0010] Moreover, the present invention can also be in the following aspects. As shown below, a projection image display member, a projection image display device, a head-up display, and a manned transportation vehicle can also be obtained using this. (1) A film characterized by containing a thermoplastic resin as a main component and having all of the following characteristics A to C on at least one surface. Characteristic A: When light is incident at an incident angle of 10°, there is a reflection band in the wavelength band of 850 nm or more where the reflectance is continuously 30% or more and 110% or less over a wavelength width of 20 nm or more. Characteristic B: When light is incident at an incident angle of 10°, the average reflectance of visible light is 0% or more and 25% or less. Characteristic C: When P-wave light is incident at angles of 20°, 40°, and 70° with respect to the normal of the film surface, the average reflectance (%) in the wavelength band of 400 to 700 nm satisfies the relationship R20 ≤ R40 < R70, where R20, R40, and R70 are the average reflectances in order. (2) The film according to (1), having two laminated units in which two or more types of thermoplastic resin layers having different main components are regularly laminated in 51 or more and 1001 or less layers. (3) The film according to (2), wherein both of the two laminated units are laminated units in which two types of thermoplastic resin layers having different main components are alternately laminated in 51 or more and 1001 or less layers, and one of the main components of the thermoplastic resin layers constituting the two laminated units is common to each other. (4) The film according to (2), wherein both of the two laminated units are laminated units in which two types of thermoplastic resin layers having different main components are alternately laminated in 51 or more and 1001 or less layers, and all of the main components of the thermoplastic resin layers constituting the two laminated units are different. (5) The film according to (2), wherein one of the two laminated units is a laminated unit in which 51 to 1001 layers of three types of thermoplastic resin layers having different main components are regularly laminated, and the other is a laminated unit in which 51 to 1001 layers of two types of thermoplastic resin layers having different main components are alternately laminated, and the main components of the thermoplastic resin layers constituting the two laminated units are all different. (6) The film according to any one of (2) to (5), having a resin layer 1 with a thickness of 1.0 μm or more and 800 μm or less between two of the laminated units. (7) A film according to any one of (1) to (6), wherein when the principal orientation axis of one surface is X1 and the principal orientation axis of the other surface is X2, the angle between X1 and X2 is 0° or more and 45° or less. (8) The film according to (6) or (7), wherein one of the laminated units satisfies feature A and the other satisfies feature B and feature C. (9) The film according to any one of (6) to (8), wherein the resin layer 1 includes a heat-absorbing material. (10) La measured with a C light source on at least one surface * b * Saturation C of transmitted light in color space * A film described in any of (1) to (9), wherein the value is 7.0 or less. (11) A film according to any one of (1) to (10), having the following feature D on at least one surface. Feature D: The R20 and R70 satisfy R70 - R20 > 10. (12) A film according to any one of (1) to (11), wherein, in at least one plane, the difference between the refractive index of the principal orientation axis and the refractive index of the direction perpendicular to it in the film plane is 0.03 or less. (13) A projection image display member comprising a transparent support 1, a resin layer 2, and a film described in any of (1) to (12) in this order. (14) A projection image display member comprising a transparent support 1, a resin layer 2, and a film, a resin layer 3, and a transparent support 2 according to any one of (1) to (12) in this order. (15) A projection image display device comprising an image projector and a projection image display member as described in (13) or (14), wherein an image is projected onto the projection image display member by light from the image projector. (16) The projection image display device according to (15), wherein the image projector irradiates P-wave light. (17) The projection image display device according to (15) or (16), wherein when the angle between the light emitted by the image projector and the normal to the image display surface of the projection image display member is θ(°), θ is 35° or more and 70° or less. (18) A head-up display comprising a projection image display device as described in any of (15) to (17). (19) A manned transport vehicle equipped with a projection image display device as described in any of (15) to (17). [Effects of the Invention]

[0011] The present invention provides a film that, when used in a projected image display member, can achieve good background visibility, heat shielding, and image display performance. By using the film of the present invention, it is possible to obtain a projected image display member that can suppress the inflow of heat from the outside, especially from sunlight, while also having good background visibility and being able to display an image superimposed on the background. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram illustrating the relationship between depth in the thickness direction and contrast difference (gray level) in a cross-sectional image in the thickness direction of a laminated unit in which thermoplastic resin layers are alternately stacked in an array of (AB)n (where n is a natural number representing the number of repeating units). [Modes for carrying out the invention]

[0013] The film of the present invention is mainly composed of a thermoplastic resin and is characterized by having all of the following features A to C on at least one surface. Feature A: When light is incident at an incident angle of 10°, there is a reflection band in the wavelength band of 850 nm or more with a wavelength width of 20 nm or more, where the reflectance is continuously 30% or more and 110% or less. Feature B: When light is incident at an incident angle of 10°, the average reflectance of visible light is 0% or more and 25% or less. Feature C: When P-wave light is incident at angles of 20°, 40°, and 70° with respect to the normal of the film surface, when the average reflectances (%) in the wavelength band of 400 - 700 nm are designated as R20, R40, and R70 in order, the relationship R20 ≤ R40 < R70 is satisfied.

[0014] The present invention will be described in detail below. However, the present invention is not to be construed as being limited to the embodiments including the following examples, and various aspects within the scope that can achieve the object of the invention and do not depart from the gist of the invention are naturally included in the scope of the present invention.

[0015] The film of the present invention is mainly composed of a thermoplastic resin. Here, "film" refers to a sheet-shaped molded body, and the main component refers to a component contained in an amount exceeding 50% by mass and not exceeding 100% by mass among all the constituent components. These can be interpreted in the same way hereinafter.

[0016] From the viewpoint of suppressing the inflow of heat by sunlight, having better visibility of the background, and superimposing and displaying an image on the background, the film of the present invention has all of the following features A to C. Feature A: When light is incident at an incident angle of 10°, there is a reflection band in the wavelength band of 850 nm or more with a wavelength width of 20 nm or more, where the reflectance is continuously 30% or more and 110% or less. Feature B: When light is incident at an incident angle of 10°, the average reflectance of visible light is 0% or more and 25% or less. Feature C: When P-wave light is incident at angles of 20°, 40°, and 70° with respect to the normal of the film surface, when the average reflectances (%) in the wavelength band of 400 - 700 nm are designated as R20, R40, and R70 in order, the relationship R20 ≤ R40 < R70 is satisfied.

[0017] Details of measuring each optical property will be described later, but the angle of incidence refers to the angle made with the normal to the film surface. "At least one surface" means that the requirement is met when light is shone on at least one surface and the reflectance is measured. Hereafter, "at least one surface" in the measurement of optical properties will be interpreted similarly. Furthermore, for objects that can take the form of a curved surface as well as a planar shape, such as the projection image display member described later, in the case of a curved surface, the definition of the angle of incidence shall be read as "normal to the film surface" instead of "normal to the tangent surface of the light irradiation point" (the same applies below).

[0018] The film of the present invention possesses the above-described feature A on at least one surface. That is, on at least one surface, when light is incident at an incident angle of 10°, there exists a reflective band with a wavelength of 30% to 110% continuously over a wavelength width of 20 nm or more in the wavelength band of 850 nm or more. From the viewpoint of improving heat shielding, the wavelength width of the reflective band is preferably 100 nm or more, and more preferably 300 nm or more. From the above viewpoint, a larger wavelength width of the reflective band is preferable, but from the viewpoint of feasibility, 800 nm is the upper limit. Here, the maximum value of the reflectance in the reflective band exceeds 100% because the reflectance referred to here is the relative reflectance based on a white aluminum oxide board (details of the measurement method will be described later). Furthermore, from the viewpoint of heat shielding, the average reflectance in the reflective band is preferably 70% or more, and more preferably 80% or more. On the other hand, the upper limit of the average reflectance is 105%, considering that the reflective band is defined as a "reflective band with a continuous reflectance of 30% to 110%" and from the viewpoint of feasibility.

[0019] The film's configuration means it can reflect infrared rays. Therefore, a film of this configuration has excellent heat-shielding properties. For example, by sandwiching such a film between two panes of glass, it is possible to obtain laminated glass that can maintain high heat-shielding performance for a long period of time.

[0020] The film of the present invention satisfies the above characteristic B on at least one surface, that is, on at least one surface, when light is incident at an incident angle of 10°, the average reflectance of visible light is 0% or more and 25% or less. Here, visible light refers to light with a wavelength of 400 to 700 nm. Since the average reflectance of visible light incident at an incident angle of 10° is 0% or more and 25% or less, the film will have excellent transparency. Therefore, when the film in such a form is made into laminated glass sandwiched between two pieces of glass, the background visibility from a direction perpendicular to the laminated glass will be good. From the above viewpoint, the reflectance is preferably 0% or more and 20% or less, and a reflectance of 0% means that the film does not reflect visible light at all. Although the details of the measurement method of the average reflectance will be described later, it can be measured by measuring the reflectance of light with a wavelength of 400 to 700 nm at an incident angle θ = 10° with a spectrophotometer at 1-nm intervals and calculating the average value.

[0021] From the viewpoint of displaying an image with P-wave light from an oblique direction, the film of the present invention satisfies the above characteristic C on at least one surface, that is, on at least one surface, when P-wave light is incident at angles of 20°, 40°, and 70° with respect to the normal of the film surface, it is important that the relationship R20 ≦ R40 < R70 is satisfied when the average reflectances (%) of P-waves with wavelengths of 400 to 700 nm are R20, R40, and R70.

[0022] The embodiment with the above characteristic C is an embodiment in which the film does not have an angle corresponding to the Brewster angle. In the case of a general transparent substrate such as transparent glass or a transparent resin film, as the incident angle is gradually increased from 20° with respect to the normal of the surface of the transparent substrate, the reflectance of the P-wave, which is one of the polarized lights, decreases and becomes 0% at an angle called the Brewster angle. Therefore, it is difficult for a general transparent substrate to transmit light from the front direction and reflect P-waves in an oblique direction. On the other hand, when the film satisfies the relationship R20 ≦ R40 < R70, it is suitable for a display device that displays an image with P-wave light from an oblique direction.

[0023] The film of the present invention may also preferably have the following feature D on at least one surface. Feature D: R20 and R70 satisfy R70 - R20 > 10.

[0024] By adopting this configuration, when the film is incorporated into the projection image display member surface and an image is projected using P-wave light, the image is displayed more brightly, resulting in improved display quality.

[0025] From the viewpoint of improving image display quality, R70 is preferably 30% or more, more preferably 50% or more, and as R70 increases, the display quality of the image when an image using P-wave light is projected onto the projection image display member surface improves. There is no particular upper limit to R70, but from the viewpoint of feasibility it is 99%, and preferably 80%.

[0026] The average reflectance (%) of this P-wave can be measured by measuring the reflectance of P-waves in the wavelength range of 400-700 nm at incident angles θ = 20°, 40°, and 70° in 1 nm increments using a spectrophotometer, as detailed in the examples below, and then calculating the average value.

[0027] As described above, by satisfying all of features A to C (preferably also satisfying feature D), the film of the present invention can transmit visible light from the front direction, have excellent transparency, reflect oblique P-wave visible light, and also possess near-infrared reflection capabilities. By using the film of the present invention, for example, a projection image display member can be obtained that can display an image superimposed on a background while suppressing the inflow of heat from sunlight and maintaining good background visibility.

[0028] The present invention provides a film that satisfies all of the above-described features A to C, and preferably a film that also satisfies feature D. The method for obtaining such a film is not particularly limited, but one example is a film having two laminated units, each consisting of 51 to 1001 layers of two or more thermoplastic resin layers with different main components (details will be described later).

[0029] From the viewpoint of easily satisfying features A to C (preferably feature D), the film of the present invention preferably has two laminated units in which 51 to 1001 layers of two or more thermoplastic resin layers with different main components are regularly laminated.

[0030] In this context, a laminated unit refers to a structural unit in which thermoplastic resin layers are regularly laminated in the thickness direction (the direction perpendicular to the film surface), and "regularly" means that they are laminated with a certain regularity. For example, as a laminated unit in which thermoplastic resin layers are regularly laminated, when two different types of thermoplastic resins, A and B, are the main components of layers A and B respectively, a structural unit in which layers A and B are alternately laminated in the thickness direction can be mentioned, or in other words, a structural unit in which layers are laminated in a regular arrangement such as A(BA)n (where n is a natural number representing the number of repeating units). Furthermore, if a third thermoplastic resin C is included as the main component (layer C), the arrangement is not particularly limited, but for example, a structural unit in which each layer is laminated in an arrangement such as C(ABC)n, C(ACBC)n, etc. (where n is a natural number representing the number of repeating units) can be mentioned. Note that the film of the present invention may have layers other than those that constitute the laminated unit.

[0031] Furthermore, "51 layers or more" here means that the total number of layers repeated in the lamination unit, in the example above, is 51 or more layers, such as layers A and B, or layers A, B, and C. In the film of the present invention, if the following conditions are met, the lamination unit is treated as different, and the number of different lamination units is defined as the number of lamination units. (1) The number of different types of layers that make up the laminated unit is different (e.g., there is a laminated unit consisting of two types of layers and a laminated unit consisting of three types of layers). (2) The arrangement of the layers constituting the stacked unit is different (for example, there is a stacked unit consisting of three different types of layers (layer A, layer B, and layer C) with different main components, arranged in a regular pattern C(ABC)n (where n is a natural number representing the number of repeating units, the same applies below), and a stacked unit consisting of the same A to C layers, arranged in a regular pattern C(ACBC)n). (3) At least one of the main components of the layers constituting the laminated unit is different (e.g., a laminated unit consisting of a layer mainly composed of thermoplastic resin A and a layer mainly composed of thermoplastic resin B1, and a laminated unit consisting of a layer mainly composed of thermoplastic resin A and a layer mainly composed of thermoplastic resin B2 (where thermoplastic resins A, B1, and B2 are all different)).

[0032] In the film of the present invention, it is preferable that each of the two laminated units is a laminated unit in which 51 to 1001 layers of two types of thermoplastic resin layers with different main components are alternately laminated, and that one of the main components of the thermoplastic resin layers constituting the two laminated units is common to each other. It is also preferable that each of the two laminated units is a laminated unit in which 51 to 1001 layers of two types of thermoplastic resin layers with different main components are alternately laminated, and that the main components of the thermoplastic resin layers constituting the two laminated units are all different.

[0033] Assuming that thermoplastic resins A1, A2, B1, and B2 are all different, an example of the former embodiment would be a laminated unit consisting of a layer mainly composed of thermoplastic resin A1 and a layer mainly composed of thermoplastic resin B1, and a laminated unit consisting of a layer mainly composed of thermoplastic resin A1 and a layer mainly composed of thermoplastic resin B2. On the other hand, an example of the latter embodiment would be a laminated unit consisting of a layer mainly composed of thermoplastic resin A1 and a layer mainly composed of thermoplastic resin B1, and a laminated unit consisting of a layer mainly composed of thermoplastic resin A2 and a layer mainly composed of thermoplastic resin B2.

[0034] The film of the present invention may further be configured such that one of the two laminated units is a laminated unit in which 51 to 1001 layers of three types of thermoplastic resin layers with different main components are regularly laminated, and the other is a laminated unit in which 51 to 1001 layers of two types of thermoplastic resin layers with different main components are alternately laminated, and the main components of the thermoplastic resin layers constituting the two laminated units are all different.

[0035] One method for producing such a film having two laminated units is to use a lamination device such as a feed block to laminate molten thermoplastic resin in a single step to create a layer structure with the desired two laminated units. Alternatively, one can pre-produce two films, each containing one laminated unit, using a lamination device such as a feed block, and then bond them together with an adhesive resin. Further details will be described later.

[0036] The following are typical thermoplastic resins used to form the thermoplastic resin layer of the film of the present invention, but the thermoplastic resin used in the present invention is not limited to those listed below. Examples of thermoplastic resins for the thermoplastic resin layer of the film of the present invention include polyolefin resins such as polyethylene, polypropylene, poly(1-butene), poly(4-methylpentene), polyisobutylene, polyisoprene, polybutadiene, polyvinylcyclohexane, polystyrene, poly(α-methylstyrene), poly(p-methylstyrene), polynorbornene, and polycyclopentene; polyamide resins such as nylon 6, nylon 11, nylon 12, and nylon 66; vinyl monomer copolymer resins such as 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; and polyacrylate. In addition, acrylic resins such as polyisobutyl methacrylate, polymethacrylate, polymethyl methacrylate, polybutyl acrylate, polyacrylamide, and polyacrylonitrile can be used; polyester resins such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate; biodegradable polymers such as polylactic acid and polybutyl succinate; and other materials such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyglycolic acid, polycarbonate, polyketone, polyethersulfone, polyetheretherketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polysiloxane, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloride resin, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinylidene fluoride can be used. These resins may contain copolymer units as needed.

[0037] In each thermoplastic resin layer, these thermoplastic resins may be used individually, or two or more types of thermoplastic resins may be used as a blend or alloy. Blending or alloying allows for obtaining physical / chemical properties that cannot be obtained from a single type of thermoplastic resin. Furthermore, when laminating layers mainly composed of thermoplastic resins with significantly different skeletal structures, the interlayer adhesion at the interface can be improved by including a copolymer unit in one of the adjacent thermoplastic resin layers that shares a common polymer skeletal structure with the thermoplastic resin layer on the opposite side.

[0038] In each thermoplastic resin layer constituting the film of the present invention, from the viewpoint of rheological properties relating to strength, heat resistance, transparency, and lamination, it is particularly preferable to select from polyolefin resin, polyester resin, acrylic resin, polycarbonate resin, and polyamide resin. From the viewpoint of the above, polyester resin is more preferably used, and it is even more preferable that at least one layer, preferably the entire layer, of the thermoplastic resin layer is a layer mainly composed of polyester resin. Even more preferably is a polyester resin obtained by polymerization from monomers mainly composed of aromatic dicarboxylic acid or aliphatic dicarboxylic acid and diol.

[0039] 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'-diphenylsulfondicarboxylic acid. Examples of aliphatic dicarboxylic acids include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedionic acid, cyclohexanedicarboxylic acid and their ester derivatives. Terephthalic acid and 2,6-naphthalenedicarboxylic acid are particularly preferred. These acid components may be used individually, in combination of two or more, or partially copolymerized with oxyacids such as hydroxybenzoic acid.

[0040] 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 is preferred. These diol components may be used individually or in combination of two or more.

[0041] In each thermoplastic resin layer constituting the film of the present invention, it is particularly preferable to use a polyester resin selected from among the above polyester resins, polyethylene terephthalate and its copolymer, polyethylene naphthalate and its copolymer, polybutylene terephthalate and its copolymer, polybutylene naphthalate and its copolymer, and polyhexamethylene terephthalate and its copolymer, as well as polyhexamethylene naphthalate and its copolymer.

[0042] A film having a laminated unit in which layers mainly composed of different thermoplastic resins as described above are regularly stacked makes it easy to exhibit functions such as selectively reflecting light in a specific wavelength band or reflecting light of a specific polarization through interference reflection resulting from the relationship between the difference in refractive index of each layer and the layer thickness.

[0043] In the film of the present invention, "the main components of the thermoplastic resin layers are different" means that the conditions for being considered to have "the same main components" as shown below are not met. While it is possible to determine that the main components of the thermoplastic resin layers are different by analyzing the composition and components of each layer, it is also possible to determine that the "main components of the thermoplastic resin layers are different" if at least one of the following conditions is met: (1) the glass transition temperature or melting point is different in differential scanning calorimetry (DSC), (2) the contrast of the stained image when observing the cross-section with transmission electron microscopy (TEM) is different, or (3) the dielectric constant (refractive index) of each thermoplastic resin layer obtained from electron energy loss spectroscopy (EELS measurement) is different.

[0044] The statement that thermoplastic resin layers have "the same main components" usually refers to a case where, when comparing the constituent components of each thermoplastic resin layer, more than 50% by mass but less than or equal to 100% by mass of the components are common. However, in determining the above requirement, differences of more than 0 mol% and less than or equal to 5 mol% in the repeating units of the thermoplastic resin are treated as nonexistent. That is, for example, if more than 95 mol% of the repeating units are common, even though some of the repeating units differ, such as polyethylene terephthalate copolymerized with 4 mol% homopolyethylene terephthalate and isophthalic acid, then the two are considered to have the same components. The specific composition / chemical structure of each thermoplastic resin layer and its repeating unit structure can be determined by first determining the layer thickness of each thermoplastic resin layer according to the layer structure method described later in the measurement method, then obtaining a sample by cutting and removing the thermoplastic resin layer or scraping the layer to expose the outermost layer, and analyzing it using infrared spectroscopy (FT-IR method or nano-IR method), gas chromatography / mass spectrometry (GC-MS), nuclear magnetic resonance (NMR), etc.

[0045] Next, taking a laminated unit in which two types of thermoplastic resin layers are alternately laminated as an example, we will explain "(1) Different glass transition temperatures and melting points in differential scanning calorimetry (DSC)". If it is difficult to identify the main component by the above method after extracting a sample from each thermoplastic resin layer constituting the laminated unit, it is possible to determine that "the main components are different" by differential scanning calorimetry (DSC) if the thermoplastic resin layers constituting the laminated unit exhibit different melting points and / or glass transition temperatures. In the film of the present invention, exhibiting different melting points and different glass transition temperatures means that at least one of the melting point and the glass transition temperature differs by 0.1°C or more, preferably 2.0°C or more (in other words, it means that at least one of the difference in the melting point and the difference in the glass transition temperature of the thermoplastic resin layers is 0.1°C or more, preferably 2.0°C or more).

[0046] The easiest example to interpret as satisfying the above requirements is when differential scanning calorimetry is performed on a laminated unit and two different glass transition points, crystallization temperatures (exothermic peaks), or melting points (endothermic peaks) are observed. On the other hand, in the measurement temperature range of 25°C to 300°C as described in the differential scanning calorimetry (DSC) section of the measurement method described later, the thermoplastic resin layer may 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, it can be interpreted that the main components are different, although this cannot be calculated as a temperature difference. For example, if two glass transition points are observed but only one melting point is observed, it can be interpreted that one of the two thermoplastic resin layers has an amorphous thermoplastic resin without a melting point as its main component. Furthermore, in another embodiment, if two melting points can be identified, but only one or fewer glass transition temperatures or crystallization temperatures can be identified within the above temperature range, it can be interpreted that the laminated unit contains a layer mainly composed of a thermoplastic resin in a low-temperature region outside the temperature range where the glass transition temperature or crystallization temperature exists. In this invention, DSC measurement can be performed using the method of JIS-K-7122 (1987), and details will be described later.

[0047] Next, we will explain "(2) The contrast of the stained image differs when observed in cross-section using a transmission electron microscope (TEM)." The two methods described above require the separation and analysis of the thermoplastic resin layer to be measured from the laminated unit, and separation and analysis of the layers can be difficult. Therefore, to improve simplicity, if the layer interface can be recognized by the contrast difference in the cross-sectional image observed using a transmission electron microscope, and if it can be confirmed that the difference in the average brightness of two adjacent layers is greater than any of the standard deviations of brightness within each layer of the adjacent thermoplastic resin layer using the method described in the section on layer interface (contrast difference) in the measurement method described later, then the contrast of the stained image can be considered different, and it can be determined that the main components of the adjacent thermoplastic resin layers are "different".

[0048] This contrast difference arises from differences in electron beam scattering, crystal diffraction, etc., between thermoplastic resin layers. Therefore, when the main components of the thermoplastic resin layers differ according to the aforementioned criteria, the crystallinity and electron density state will usually differ, and the electron staining state will also differ. Consequently, when there are multiple thermoplastic resin layers with different main components, it becomes possible to visualize each thermoplastic resin layer as a layer structure with contrast differences in a cross-sectional image of the laminated unit. In the case of a film having a laminated unit (hereinafter sometimes referred to as an AB order arrangement) in which two types of thermoplastic resin layers with different main components are alternately laminated, as in one preferred embodiment of the present invention, since the same thermoplastic resin layer exhibits a constant brightness, if the depth in the thickness direction is shown on the horizontal axis and the brightness / contrast (gray level in grayscale display) at each point is shown on the vertical axis, one laminated unit will have a graph that repeatedly moves up and down between the brightness of two points, as shown in Figure 1. In Figure 1, reference numerals 1 to 3 represent, in order, the graph showing the relationship between the depth in the thickness direction and the contrast (gray level) of a film having an AB order arrangement, the thickness of layer A, and the thickness of layer B (however, in this embodiment, layer A is assumed to be a layer with relatively high crystallinity).

[0049] Next, we will explain "(3) The dielectric constant (refractive index) of each thermoplastic resin layer obtained from electron energy loss spectroscopy (EELS measurement) is different." Furthermore, the laminated unit constituting the film of the present invention may also be judged to have "different main components" if the refractive index (dielectric constant) of the thermoplastic resin layer is different. Thermoplastic resin layers with different refractive indices are determined from the dielectric constant and refractive index of each thermoplastic resin layer obtained from electron energy loss spectroscopy (EELS measurement) according to the method described in the measurement method section below. More specifically, it can be determined by the following procedure. First, the main orientation axis direction of the laminated unit is identified using a phase difference measuring device (for example, the phase difference measuring device KOBRA-WPR manufactured by Oji Instruments Co., Ltd.), and a cross-sectional sample of the film is obtained so as to include that direction and the thickness direction of the laminated unit. Next, each thermoplastic resin layer in the cross-sectional sample is irradiated with an electron beam, and the dielectric constant at a loss energy of 2.5 eV is read by analyzing its dielectric constant. If the difference in the dielectric constant of the obtained thermoplastic resin layers is 0.01 or more, it is judged that the refractive index of the thermoplastic resin layer is "different".

[0050] According to Maxwell's electromagnetic theory, in non-magnetic materials that absorb little light, such as the thermoplastic resin (described above) that can be suitably used in the laminated unit constituting the film of the present invention, the dielectric constant is generally equal to the square of the refractive index. Therefore, if the dielectric constant of the thermoplastic resin layer is different, it can be determined that the refractive index of the thermoplastic resin layer is different, and the relative magnitudes of the dielectric constants of the thermoplastic resin layers correspond to the relative magnitudes of their refractive indices.

[0051] If the dielectric constant difference of each thermoplastic resin layer cannot be analyzed using a cross-sectional sample, the position corresponding to each thermoplastic resin layer can be identified using scanning transmission electron microscopy (STEM) observation, and a thin section sample can be obtained by cutting in a direction parallel to the film surface. The dielectric constant of each thermoplastic resin layer's thin section sample can then be analyzed using EELS measurement to determine that the refractive indices of the thermoplastic resin layers are "different".

[0052] The embodiment of the film of the present invention having two laminated units is not particularly limited, but an example is an embodiment in which a resin layer 1 having a thickness of 1.0 μm or more and 800 μm or less is placed between the two laminated units.

[0053] First, the resin layer 1 in the above embodiment will be described. The resin layer referred to here is a layer in which the resin component is 10% by mass or more and 100% by mass or less when the total components constituting the layer are taken as 100% by mass, and the main component is different from any of the layers constituting the laminated unit. The reason why the thickness is stated as "1.0 μm or more and 800 μm or less" is to distinguish it from the layers with a thickness at the nm level that constitute each laminated unit. The resin layer 1 may have one or more functions such as aesthetics, durability, weather resistance, heat absorption, impact resistance, scratch resistance, easy adhesion, and tackiness. Furthermore, the resin layer 1 may consist of one layer or two or more layers.

[0054] The resin layer 1 of the film of the present invention preferably has adhesive properties. Here, adhesive properties refer to the ability to adhere to other materials. The method for making the resin layer 1 adhesive is not particularly limited, but examples include applying an adhesive to the resin layer 1 such as a vinyl acetate resin system, a vinyl chloride / vinyl acetate copolymer system, an ethylene / vinyl acetate copolymer system, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, polyvinyl ether, nitrile rubber system, styrene / butadiene rubber system, natural rubber system, chloroprene rubber system, polyamide system, epoxy resin system, polyurethane system, acrylic resin system, cellulose system, polyvinyl chloride, polyacrylic acid ester, or polyisobutylene. These components may be used individually or in combination, and adhesive modifiers, plasticizers, heat stabilizers, antioxidants, UV absorbers, antistatic agents, lubricants, colorants, crosslinking agents, etc. may be added as needed. The pre-processing form of these adhesives may be liquid, gel, lump, powder, or film.

[0055] In the film of the present invention, it is preferable that the resin layer 1 has heat-absorbing properties. Heat-absorbing properties refer to having light-absorbing performance mainly in the near-infrared to far-infrared region with a wavelength exceeding 700 nm. By providing such a resin layer between two laminated units, the film of the present invention can be easily obtained, and its heat-shielding performance can be further enhanced.

[0056] The method for giving the resin layer 1 heat-absorbing properties is not particularly limited, but one example is that the resin layer 1 may contain a heat-absorbing material. Examples of applicable heat-absorbing materials include lanthanum-based particles, antimony-based particles, indium-based particles, tin-based particles, and tungsten-based particles. These are preferred from the viewpoint of ensuring transparency because they have low light absorption in the visible light region. Generally, lanthanum-based particles and tungsten-based particles have particularly high absorption performance in the wavelength range of 700 to 1500 nm, while antimony-based particles, indium-based particles, and tin-based particles have particularly high absorption performance in the wavelength range of 1500 nm and above. These heat-absorbing materials may be used alone or in combination, and in combination with the aforementioned adhesive is also preferable considering the improvement of adhesion between laminated units.

[0057] Another example of a method for giving heat-absorbing properties to the resin layer 1 is a method in which the resin layer 1 comprises an adhesive resin layer and a heat-absorbing resin layer. For example, in such a configuration, the resin constituting the heat-absorbing resin layer may be as follows, and the heat-absorbing material may be as described above. Suitable resins for such a heat-absorbing resin layer are preferably selected from acrylic resin, urethane resin, polyester resin, silanol, etc., and the type is not particularly limited; these can be used individually or in combination. To explain using acrylic resin as an example, it is preferable to use acrylic resin obtained by using monomers such as methacrylic acid, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, lauryl acrylate, 2-ethylhexyl glycidyl acrylate, glycidyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether, 4-hydroxybutyl methacrylate glycidyl ether, phenyl glycidyl acrylate, epoxy acrylate, epoxy methacrylate, dipentaerythritol hexaacrylate, etc. (The monomers may be used individually or in combination of multiple types).

[0058] Furthermore, resins that form a heat-absorbing resin layer, and mixtures that serve as precursors thereof, are preferable because curing is further accelerated when initiators, curing agents, and catalysts are used. Preferred initiators are those that can initiate or accelerate polymerization, condensation, or crosslinking reactions by anionic, cation, or radical reactions. Various initiators, curing agents, and catalysts can be used. Initiators, curing agents, and catalysts may be used individually, or multiple initiators, curing agents, and catalysts may be used simultaneously. In addition, acidic catalysts, thermal polymerization initiators, and photopolymerization initiators may be used in combination, but photopolymerization initiators are preferred.

[0059] Examples of acidic catalysts include aqueous hydrochloric acid, formic acid, and acetic acid. Examples of thermal polymerization initiators include peroxides and azo compounds. Examples of photopolymerization initiators include alkylphenone compounds, sulfur-containing compounds, acylphosphine oxide compounds, and amine compounds. From the viewpoint of curability, alkylphenone compounds are preferred as photopolymerization initiators. Specific examples of alkylphenone compounds include 1-hydroxycyclohexylphenyl ketone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1-(4-phenyl)-1-butane, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-(4-phenyl)-1-butane Examples include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butane, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butane, 1-cyclohydroxyl-phenyl ketone, 2-methyl-1-phenylpropan-1-one, and 1-[4-(2-ethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one.

[0060] One example of a method for creating a film having two laminated units is to first produce two types of films, each consisting of one laminated unit, and then laminate these two types of films via an adhesive resin layer 1 as described above (hereinafter, the film that fulfills the role of satisfying characteristic A may be referred to as film 1, and the film that fulfills the roles of characteristics B and C may be referred to as film 2). In such a method, the resin layer 1 may also have heat-absorbing properties in addition to adhesive properties. Another example is to laminate a heat-absorbing resin layer onto a film that fulfills one of the roles, and then laminate this film and the film that fulfills the other role via an adhesive resin layer that does not have heat-absorbing properties.

[0061] The following describes a method for obtaining films (film 1, film 2) that can be used as a laminated unit of the present invention. For the purpose of simplifying the explanation, some of the explanation will use as an example a film having a structure in which layers (layer A and layer B) made of two different types of thermoplastic resins are alternately laminated, which is one of the preferred embodiments of the present invention. However, the same should be understood when three or more types of thermoplastic resins are used. For convenience, film 1 will be described as one that contributes to improved heat shielding, and film 2 will be described as one that contributes to improved image projection. That is, assuming an embodiment in which one of the laminated units satisfies feature A and the other satisfies features B and C, film 1 will be described as satisfying feature A and film 2 will satisfy features B and C.

[0062] First, we will explain the layer structure of Film 1 and the resins that can be used in its manufacture. Sunlight has an intensity distribution mainly in the visible light region, and this intensity distribution tends to decrease as the wavelength increases. To use it in applications where high transparency is required, transparency and heat shielding can be achieved simultaneously by selectively reflecting light with wavelengths slightly larger than the visible light region, from 850 nm onwards. Furthermore, by selectively reflecting light with wavelengths of 850 to 1200 nm, which accounts for approximately 18% of the total intensity of sunlight, high heat shielding performance can be provided.

[0063] From the above viewpoint, the film 1 preferably has a reflection band with a reflectance of 30% or more that is continuous over a wavelength width of 300 nm or more, more preferably has an average reflectance of 70% or more in the reflection band, and even more preferably has the short wavelength end of the reflection band in the wavelength range of 850 nm to 1200 nm. A film having such a reflection band in the wavelength range of 850 nm or more can be obtained by increasing the total number of layers of layer A and layer B, or / or by increasing the in-plane average refractive index difference between layer A and layer B. The total number of layers also depends on the in-plane average refractive index difference between layer A and layer B (or the thermoplastic resins A and B which are the main components of these layers), but by making the total number of layers of layer A and layer B 401 or more, it becomes easy to make the average reflectance in the reflection band 80% or more.

[0064] The thermoplastic resin layers used in film 1 are preferably a combination in which the difference in in-plane average refractive index between layer A and layer B is 0.03 or more. More preferably it is 0.05 or more, and even more preferably 0.10 or more. When the difference in in-plane average refractive index between layer A and layer B is 0.03 or more, sufficient reflectivity is obtained, and for example, the heat-cutting performance is improved. Methods for setting the difference in in-plane average refractive index between layer A and layer B within the above range include, for example, a method in which one of the thermoplastic resins A and B, which are the main components of each layer, is crystalline and the other is amorphous, or a method of increasing the difference in enthalpy of melt of thermoplastic resins A and B. Note that the difference in enthalpy of melt can be adjusted by the difference in the amount of copolymerized component, for example, if the basic skeletons of thermoplastic resins A and B are the same.

[0065] The in-plane average refractive index is the average value of the refractive index in the direction of the principal orientation axis and the refractive index in the direction perpendicular to the principal orientation axis within the film plane, measured with laser light of wavelength 633 nm. Details of the measurement method will be described later. The difference in in-plane average refractive index can be determined as the absolute value of the difference in in-plane average refractive index of the layers if there are two types of layers constituting the laminated structure of film 1 (the same applies to film 2 described later), or as the absolute value of the difference in in-plane average refractive index of the layers with the largest and smallest in-plane average refractive index if there are three types of layers constituting the laminated structure.

[0066] Crystallinity, as used here, can be determined by cutting and extracting the thermoplastic resin layer and using a differential scanning calorimetry (DSC) device to confirm the presence or absence of a melting point (endothermic peak). In particular, in the film of the present invention, a thermoplastic resin exhibiting a melting enthalpy of 1 J / g or more, which is the integral of the melting point endothermic peak with the baseline, is defined as a crystalline thermoplastic resin. Amorphous thermoplastic resin is defined as one in which this melting enthalpy does not exist. With such a combination of resins, it becomes easy to create a refractive index difference in the stretching and heat treatment processes during film manufacturing.

[0067] To obtain film 1, it is preferable that the sum of the optical thicknesses of adjacent layers is 400 to 700 nm for the majority of the layers in the entire laminate. Here, optical thickness refers to the product of the layer thickness and the refractive index of each layer, and the sum of the optical thicknesses of adjacent layers is a factor that determines the wavelength at which interference reflection occurs in the laminated film. Interference reflection by a laminate where the sum of the optical thicknesses of adjacent layers is 400 to 700 nm usually occurs in the wavelength range of approximately 800 to 1400 nm, making it easy to make film 1 have a reflectance of 30% or more in the wavelength band of 850 to 1200 nm with a wavelength width of 300 nm or more. Furthermore, the magnitude of the reflectance increases as the number of layers and the difference in the in-plane average refractive index of adjacent layers increase, and in a laminated film where the sum of the optical thicknesses of adjacent layers is 400 to 700 nm for the majority of the layers, it becomes easy to efficiently make the reflectance of 30% or more in the wavelength band of 850 to 1200 nm with a wavelength width of 300 nm or more.

[0068] For example, when using polyethylene terephthalate with a refractive index of 1.66 and polyethylene terephthalate with a refractive index of 1.55 obtained by copolymerizing spiroglycol and cyclohexanedicarboxylic acid as thermoplastic resins A and B, approximately 401 or more layers are required for the sum of the optical thicknesses of adjacent layers to be 400 to 700 nm in order to achieve a reflectance of 30% or more in the 850 to 1200 nm wavelength band with a wavelength width of 300 nm or more. As the difference in the in-plane average refractive index of thermoplastic resins A and B increases, the number of layers required to achieve a reflectance of 30% or more in the 850 to 1200 nm wavelength band with a wavelength width of 300 nm or more decreases, and if the difference in in-plane average refractive index is 0.30 or more, sufficient reflectance can be achieved with only about 51 layers. Furthermore, when polyethylene terephthalate copolymerized with polyethylene terephthalate having a refractive index of 1.66 and spiroglycol with a refractive index of 1.55 and cyclohexanedicarboxylic acid is used as the thermoplastic resin, the range of layer thickness required to make the sum of the optical thicknesses of adjacent layers 400 to 700 nm is approximately 120 to 220 nm.

[0069] As another example of a laminated film having a reflectance of 30% or more in a wavelength band of 850 to 1200 nm and a wavelength width of 300 nm or more, the optical thicknesses of adjacent A layer and B layer satisfy the following formulas (1) and (2) simultaneously. λ = 2(n α d α + n β d β ) (1) n α d α = n β d β (2) Here, λ is the reflection wavelength, n α is the in-plane average refractive index of the A layer, d α is the thickness of the A layer, n β is the in-plane average refractive index of the B layer, d β is the thickness of the B layer. By having a layer thickness distribution that satisfies formulas (1) and (2) simultaneously, even-order reflections can be eliminated. Therefore, while increasing the reflectance in the wavelength range of 850 nm to 1200 nm, the average reflectance in the wavelength range of 400 to 700 nm, which is the visible light region, can be lowered, so that a film that is transparent and has high heat ray cut performance can be obtained. Generally, since the refractive indices of the A layer and B layer after molding a thermoplastic resin into a sheet shape and stretching are 1.4 to 1.9, a film with suppressed even-order reflections can be obtained by setting the ratio of the thicknesses of adjacent A layer and B layer (thickness of A layer / thickness of B layer) to 0.7 or more and 1.4 or less. Therefore, it is preferable to set the ratio of the thicknesses of adjacent A layer and B layer (thickness of A layer / thickness of B layer) to 0.7 or more and 1.4 or less. From the above viewpoints, it is more preferably 0.8 or more and 1.2 or less.

[0070] The combination of thermoplastic resins A and B constituting the film 1 of the present invention is preferably a combination having the same basic structure. The basic structure, as used here, refers to the repeating unit that is most abundant in the thermoplastic resin. For example, when polyethylene terephthalate is used as one of the thermoplastic resins, it is preferable that the other thermoplastic resin also has an ethylene terephthalate unit as its basic structure, from the viewpoint of easily achieving a high-precision laminated structure. Furthermore, if thermoplastic resins A and B contain the same basic structure, the lamination accuracy is increased and delamination at the lamination interface becomes less likely.

[0071] Furthermore, a preferred combination of thermoplastic resin A and thermoplastic resin B used in the film 1 of the present invention is one in which the difference in glass transition temperatures is 20°C or less. If the difference in glass transition temperatures between the two is greater than 20°C, the thickness of the film during film formation becomes more uneven, which can lead to a poor appearance of the final film, and problems such as over-stretching may occur when forming the film. In addition, if one of the thermoplastic resins A and B is crystalline and the other is amorphous, it is also preferable that the glass transition temperature of the crystalline resin is lower than that of the amorphous resin. In this case, when the film is stretched at a stretching temperature suitable for oriented and crystallized crystalline resin, the orientation of the amorphous resin can be suppressed compared to that of crystalline resin, and it becomes possible to easily create a difference in the in-plane average refractive index by stretching.

[0072] As an example of a suitable combination of thermoplastic resins A and B that satisfy the above glass transition temperature conditions, one of thermoplastic resins A and B is polyethylene terephthalate or polyethylene naphthalate, and the other is a polyester containing a spiroglycol-derived polyester. A spiroglycol-derived polyester is a polyester that uses spiroglycol as a diol component, and includes both copolymers containing spiroglycol units and polyesters containing spiroglycol units as single diol units. Preferably, it refers to a polyester in which spiroglycol units account for more than half of the total diol units in the polyester. Spiroglycol-derived polyesters are preferred because they have a small glass transition temperature difference with polyethylene terephthalate or polyethylene naphthalate, making them less prone to overstretching during molding and less prone to delamination. Alternatively, similar effects can be obtained by blending these polyesters with thermoplastic resins A and B.

[0073] From the above viewpoint, it is preferable that one of the thermoplastic resins A and B is polyethylene terephthalate or polyethylene naphthalate, and the other is a polyester made using spiroglycol and cyclohexanedicarboxylic acid. When a polyester obtained using spiroglycol and cyclohexanedicarboxylic acid is used in one of the layers, the difference in in-plane average refractive index with polyethylene terephthalate or polyethylene naphthalate becomes large, making it easier to obtain a high reflectivity. In addition, the difference in glass transition temperature with polyethylene terephthalate or polyethylene naphthalate is small, and the adhesion is excellent, so it is less likely to be overstretched during molding and less likely to delaminate between layers.

[0074] Furthermore, in the film 1 of the present invention, it is also preferable that one of the thermoplastic resins A and B is polyethylene terephthalate or polyethylene naphthalate, and the other is a polyester derived from cyclohexanedimethanol. A polyester derived from cyclohexanedimethanol refers to a polyester in which cyclohexanedimethanol residues account for more than half of the total diol residues. Polyesters derived from cyclohexanedimethanol are preferable because they have a small glass transition temperature difference with polyethylene terephthalate or polyethylene naphthalate, making them less prone to overstretching during molding and less prone to delamination. More preferably, at least one thermoplastic resin is an ethylene terephthalate polycondensate in which the copolymerization amount of cyclohexanedimethanol is 15 mol% or more and 60 mol% or less.

[0075] This configuration allows for high reflectivity while minimizing changes in optical properties, particularly due to heating and aging, and reducing the likelihood of delamination between layers. Furthermore, ethylene terephthalate polycondensates with a copolymer amount of cyclohexanedimethanol of 15 mol% to 60 mol% adhere very strongly to polyethylene terephthalate. In addition, the cyclohexanedimethanol group has geometric isomers (cis or trans) and conformational isomers (chair or boat), making it less prone to oriented crystallization even when co-stretched with polyethylene terephthalate. As a result, the resulting film has high reflectivity, even less change in optical properties due to thermal history, and is less susceptible to tearing during film formation.

[0076] Furthermore, one preferred embodiment of the film of the present invention will be described, in which the film 1 is composed of three types of thermoplastic resin layers with different main components. In this embodiment, the film 1 has a regular arrangement consisting of the A2, B2, and C2 layers, where the three types of thermoplastic resin layers with different main components are designated as layers A2, B2, and C2, respectively. Here, a regular arrangement refers to a laminated structure in which three "different" types of thermoplastic resin layers are laminated according to a certain regular arrangement, following the definition above. In this case, the three different types of thermoplastic resin layers may be formed from thermoplastic resins having different skeletal structures, or two types of thermoplastic resins having different skeletal structures may be used, and the three thermoplastic resin layers may be designed to have different mixing ratios or copolymerization amounts. Hereafter in this specification, for convenience, the different thermoplastic resin layers will be defined alphabetically as layers A2, B2, and C2 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 thermoplastic resin A2, thermoplastic resin B2, and thermoplastic resin C2.

[0077] If we define different thermoplastic resin layers as layers A2, B2, and C2 in the order they are arranged from the outermost surface of film 1, the regular arrangement of film 1 of the present invention can be, for example, (ABC)n, (ABCB)n, (ABAC)n, (ABCAB)n, (ABCAC)n, (ABABC)n, (ABCBCB)n (the part in parentheses represents the regular arrangement, and n is a natural number indicating the number of repetitions. A, B, and C represent layers A2, B2, and C2 respectively. The same notation may be used below in the description of the regular arrangement consisting of layers A2, B2, and C2). In particular, in order for a film using thermoplastic resins with different physical / chemical properties such as skeletal structure and viscoelastic / viscosity characteristics to maintain its laminated structure without interfacial delamination over a long period of time and without impairing the necessary functions, it is necessary to consider combinations of thermoplastic resin layers that have good compatibility (compatibility, surface free energy, etc.) with adjacent thermoplastic resin layers that form the interface between different thermoplastic resin layers contained in the film.

[0078] Therefore, in order to avoid complicating the resin design of the entire film, it is preferable to have a small number of combinations of interfaces formed by adjacent thermoplastic resin layers. Specifically, there are three types of interfaces formed from three different thermoplastic resin layers: A2-B2 interface, B2-C2 interface, and C2-A2 interface. However, among the regular arrangements, (ABCB)n and (ABCBCB)n are preferable because they only have two types: A2-B2 interface and B2-C2 interface. In such an embodiment, the resin design should be such that delamination between the A2 and B2 layers, and between the B2 and C2 layers, is unlikely to occur, and the combination of the A2 and C2 layers does not need to be considered to a great extent.

[0079] Thermoplastic resins with different melting points and crystallization temperatures typically have different optical properties. Therefore, by regularly laminating layers of thermoplastic resins with different melting points and crystallization temperatures, it becomes easy to reflect light in a specific wavelength band based on the relationship between the difference in the in-plane average refractive index of each layer and the layer thickness. Furthermore, the more layers that are laminated, the higher the reflectivity can be obtained over a wider bandwidth. From this viewpoint, the number of layers in film 1 is preferably 51 or more, and more preferably 401 or more. In interference reflection, which is the principle by which film 1 reflects light wavelength-selectively, the wider the wavelength band and the higher the reflectivity, as the total number of A2 and B2 or C2 layers increases, resulting in a film with high light-cutting performance. Therefore, although there is no upper limit to the number of layers in film 1, as the number of layers increases, the manufacturing cost increases due to the enlargement of the manufacturing equipment for film 1, and the handling deteriorates due to the increased thickness of film 1. In reality, a total of 1001 layers or less is within the practical range.

[0080] Next, an example of the layer structure of the film 2 and a thermoplastic resin that can be used in its manufacture will be described. When light is incident at an incident angle of 10°, in order to make the average reflectance of visible light 0% or more and 25% or less (in other words, to satisfy Feature B), it is effective to reduce the in-plane average refractive index difference between the two layers (Layer A and Layer B) made of thermoplastic resin. For example, if the number of layers of the laminate unit is within the above range, from the above perspective, if the in-plane average refractive index difference is 0.03 or less, the reflectance can be made 25% or less, and more preferably, if it is 0.02 or less, the reflectance can be made 20% or less. When the layers constituting the laminate unit are of three types (Layer A, Layer B, and Layer C), it is desirable that the difference in the in-plane average refractive index be within the above range for all of Layer A and Layer B, Layer B and Layer C, and Layer C and Layer A. The method for adjusting the in-plane average refractive index difference is as described above.

[0081] When P-wave light is incident at angles of 20°, 40°, and 70° with respect to the normal of the film surface, and the average reflectance (%) in the wavelength band of 400 to 700 nm is defined as R20, R40, and R70 in order, in order to obtain the film 2 that satisfies the relationship R20 ≦ R40 < R70 (in other words, to satisfy Feature C), a method of adjusting the refractive index difference and the number of layers in the direction perpendicular to the film surface between the two layers made of thermoplastic resin can be used. Increasing R70 leads to an improvement in the display quality of the image, and R70 can be increased by increasing the refractive index difference in the direction perpendicular to the film surface or by increasing the number of layers. From the above perspective, when the number of layers reaches 801 layers, if the refractive index in the direction perpendicular to the film surface (the refractive index difference perpendicular to the surface) is 0.08 or more, the reflectance can be made 30% or more, and if the refractive index difference is 0.12 or more, the reflectance can be made easily 50% or more. As a result, it is easier to satisfy the relationship R20 ≦ R40 < R70, which is more preferable. Even if the refractive index difference perpendicular to the surface does not reach the above level, the reflectance can be increased by further increasing the number of layers to reach the above level.

[0082] Furthermore, as mentioned above, interference reflection can achieve higher reflectivity for a wider wavelength range of light as the number of layers increases. Therefore, by increasing the number of layers in the laminated unit of film 2, the reflectivity of P-waves in the desired wavelength range can be increased, resulting in a larger R70. From the above viewpoint, the number of layers in the laminated unit of film 2 is preferably 101 layers or more, more preferably 401 layers or more, and even more preferably 801 layers or more. Although there is no upper limit to the number of layers, as the number of layers increases, manufacturing costs increase due to the enlargement of the manufacturing equipment, and handling deteriorates due to the increased film thickness. Therefore, in reality, around 1001 layers is within the practical range.

[0083] Methods for adjusting the P-wave reflection wavelength of film 2 to the range of 400-700 nm include adjusting the difference in refractive index perpendicular to the plane of the two thermoplastic resin layers, the number of layers, the layer thickness distribution, and the film formation conditions (e.g., stretching ratio, stretching speed, stretching temperature, heat treatment temperature, heat treatment time). It is preferable that the optical thickness of adjacent layers A and B satisfies equation (1) (the parameters in equation (1) are as described above). λ=2(n α d α +n β d β ) (1) If film 2 has a structure in which two different types of thermoplastic resin layers (layer A and layer B) are alternately laminated, and layer A is the outermost layer on both sides of film 2, it is preferable that layer A is mainly composed of a crystalline thermoplastic resin. In this case, it is preferable that layer B is mainly composed of an amorphous thermoplastic resin, or contains a crystalline thermoplastic resin with a melting point of 20°C or less than the thermoplastic resin that is the main component of layer A. More preferably, layer A is mainly composed of a crystalline thermoplastic resin and layer B is mainly composed of an amorphous thermoplastic resin, or layer B is mainly composed of a crystalline thermoplastic resin with a melting point of 20°C or less than the thermoplastic resin that is the main component of layer A. Hereinafter, the thermoplastic resins that are the main components of each layer may be referred to as thermoplastic resin A and thermoplastic resin B.

[0084] Furthermore, in film 2, it is preferable that the difference in glass transition temperatures between thermoplastic resins A and B is 20°C or less. If there are multiple glass transition temperatures, it is sufficient that the glass transition temperatures of the two points with higher temperatures are 20°C or less. Preferably, the glass transition temperature of film 2 is 90°C or less. Also, if there are multiple glass transition temperatures in film 2, it is preferable that all of the glass transition temperatures are 90°C or less. Generally, as orientation and crystallization progress, the refractive index in the direction parallel to the film surface increases, while in order to increase the refractive index of amorphous resin, it is necessary to include aromatics such as benzene rings and naphthalene rings.

[0085] Therefore, in order to make the refractive index difference in the direction parallel to the film surface of the different thermoplastic resins the same for film 2, it is necessary to laminate an oriented / crystalline resin with a low aromatic content and an amorphous resin with a high aromatic content. On the other hand, as the aromatic content increases, the glass transition temperature tends to increase, so in the case of the above resin combination, the glass transition temperature of the oriented / crystalline resin tends to be low, and the glass transition temperature of the amorphous resin tends to be high. In that case, depending on the selection of thermoplastic resins, it may be difficult to stretch the amorphous resin at the optimal film stretching temperature to promote orientation and crystallization, and a film with the desired reflectivity may not be obtained. Therefore, by setting the difference in glass transition temperatures of the thermoplastic resins constituting film 2 to 20°C or less, the thermoplastic resin to be oriented can be sufficiently oriented, and it becomes easy to increase R70. From the above viewpoint, more preferably, the difference in glass transition temperatures of thermoplastic resins A and B is 15°C, and even more preferably 5°C or less. As the difference in glass transition temperatures decreases, it becomes easier to adjust the stretching conditions, and it becomes easier to improve the desired optical performance.

[0086] Furthermore, by setting the glass transition temperature to 90°C or lower, it becomes easier to form films of crystalline thermoplastic resin and amorphous resin at a stretching temperature that promotes orientation and crystallization. This makes it easier to achieve both transparency perpendicular to the film surface and excellent reflectivity at a 70° angle to the film surface.

[0087] The layer thickness distribution of film 2 is preferably such that it is constant from one side of the film to the opposite side, increases or decreases from one side of the film to the opposite side, increases and then decreases from one side of the film to the center, decreases and then increases from one side of the film to the center, or a combination of these distributions. The way the layer thickness distribution changes is preferably such as linear, geometric, or difference sequence, or such that 10 to 50 layers have approximately the same thickness and the thickness changes in a step-like manner. The same applies to film 1.

[0088] Preferably, protective layers with a thickness of 1% or more of the film's own thickness can be provided on both surface layers of film 2, and the thickness of each protective layer is preferably 4% or more of the total film thickness. Increasing the thickness of the protective layers leads to suppression of flow marks during film formation, improved accuracy of the actual layer thickness of each layer relative to the design, suppression of deformation of the thin film layer in the film during and after the lamination process with other films or molded articles, and improved pressure resistance. The upper limit of the thickness of the protective layer is 20%, from the viewpoint of securing the laminated structure necessary for the expression of interference reflection while suppressing an increase in the film thickness. The thickness of film 1 and film 2 is not particularly limited, but is preferably, for example, 20 μm to 300 μm. If it is 20 μm or more, the rigidity of the film is increased and handling is ensured. If it is 300 μm or less, the rigidity of the film is not excessively strong, and moldability is improved. The same applies to film 1.

[0089] The preferred method for manufacturing film 1 will be described in detail below, using as an example a case in which polyethylene terephthalate is used as the thermoplastic resin A constituting layer A (which is also the outermost layer on both sides), and a copolymer of polyethylene terephthalate (polyethylene terephthalate copolymerized with 20-40 mol% cyclohexanedimethanol) is used as the thermoplastic resin B constituting layer B. Of course, film 1 is not limited to this example. Furthermore, this film can be easily realized by the same method as described in sections

[0053] to

[0063] of Japanese Patent Application Publication No. 2007-307893.

[0090] Each resin is prepared in the form of pellets or other materials. The pellets are dried in hot air or under vacuum as needed, and then supplied to separate extruders. Inside the extruder, the resin is heated and melted at 280-300°C, and the amount of resin extruded is made uniform using a gear pump or the like, and foreign matter and modified resin are removed through a filter or the like. These resins are then molded into the desired shape using a die and then extruded. The multi-layered sheets extruded from the die are then pushed onto a cooling body such as a casting drum, where they are cooled and solidified to form a casting film. At this time, it is preferable to use electrodes such as wire, tape, needle, or knife shapes to rapidly cool and solidify the film by using electrostatic force to make it adhere to the cooling body such as a casting drum. Alternatively, it is also preferable to blow air from a slit-shaped, spot-shaped, or surface-shaped device to make it adhere to the cooling body such as a casting drum and rapidly cool and solidify it, or to make it adhere to the cooling body using a nip roll and rapidly cool and solidify it.

[0091] At this time, thermoplastic resin A and thermoplastic resin B are melt-kneaded in separate extruders and fed to a multilayer lamination device through different channels. As the multilayer lamination device, a multi-manifold die, a feed block, a static mixer, etc., can be used, but in particular, in order to efficiently obtain the configuration of the present invention, it is preferable to use a feed block having 51 to 1001 fine slits. Using such a feed block does not make the device excessively large, so there is less foreign matter due to thermal degradation, and high-precision lamination is possible when the number of layers is 51 to 1001. In addition, the lamination accuracy in the width direction is also significantly improved compared to conventional technology. Furthermore, with such a feed block, the thickness of each layer can be adjusted by the shape (length, width) of the slits, so it is easy to achieve any layer thickness. A layer structure suitable for film 1 can be achieved by designing a feed block that can realize a layer thickness distribution (described above) suitable for film 1. The molten multilayer laminate formed in this way is guided to a die, and a casting film is obtained as described above.

[0092] The casting film obtained in this manner is preferably biaxially stretched. Here, biaxial stretching means stretching in the longitudinal direction and the width direction. Stretching may be performed sequentially in the two directions or simultaneously in the two directions. Furthermore, re-stretching may be performed in the longitudinal direction and / or the width direction. The longitudinal direction is the direction in which the film travels during the film-making process, and the width direction is the direction perpendicular to the longitudinal direction within the film plane.

[0093] First, let's explain the case of sequential biaxial stretching. In sequential biaxial stretching, stretching in the longitudinal direction (longitudinal stretching) is usually performed first, followed by stretching in the width direction (transverse stretching). Here, longitudinal stretching refers to stretching to give the film a longitudinal molecular orientation, and is usually performed by the difference in peripheral speed of the rolls. This stretching may be performed in one stage, or it may be performed in multiple stages using multiple pairs of rolls. The stretching ratio varies depending on the type of resin, but is usually preferably 2 to 15 times, and is particularly preferably 2 to 7 times when polyethylene terephthalate is used as thermoplastic resin A. The stretching temperature is preferably between the glass transition temperature of the resin constituting the film and the glass transition temperature + 100°C.

[0094] Next, stretching in the width direction refers to stretching to give the film a width-direction orientation. This is usually done by using a tenter to transport the uniaxially oriented film obtained by longitudinal stretching, gripping both ends in the width direction with multiple clips, and widening the spacing between opposing clips. The stretching ratio varies depending on the type of thermoplastic resin, but is usually preferably 2 to 15 times, and is particularly preferably 2 to 7 times when polyethylene terephthalate is used as thermoplastic resin A. In particular, in the laminated film of the present invention, the transverse stretching ratio is preferably 4 times or more, and increasing the transverse stretching ratio is effective in improving the uniformity of the reflectance band and the uniformity of the average reflectance. Furthermore, the stretching temperature is preferably from the maximum glass transition temperature of the thermoplastic resin constituting the film to the maximum glass transition temperature + 120°C.

[0095] The biaxially stretched film is preferably heat-treated in a tenter at a temperature above the stretching temperature but below the melting point of thermoplastic resin A in order to impart flatness and dimensional stability. Heat treatment improves the dimensional stability of the film. After heat treatment in this manner, the film is uniformly cooled slowly and then wound up after cooling to room temperature. If necessary, a relaxation treatment or other process may be used in conjunction with the slow cooling after heat treatment.

[0096] Next, the case of simultaneous biaxial stretching will be explained. As described above, a casting film is obtained, and the obtained casting film is guided to a simultaneous biaxial tenter, where it is conveyed while being gripped at both ends in the width direction with clips, and stretched simultaneously and / or in stages in the longitudinal and width directions. The tenter type that can be used as a simultaneous biaxial stretcher includes the pantograph type, screw type, drive motor type, and linear motor type, but the drive motor type or linear motor type is preferred because the stretching ratio can be changed arbitrarily and relaxation processing can be performed at any point. The stretching ratio varies depending on the type of resin, but usually an area ratio of 6 to 50 times is preferred, and when polyethylene terephthalate is used as thermoplastic resin A, an area ratio of 8 to 30 times is particularly preferred. In particular, in the case of simultaneous biaxial stretching, in order to suppress the orientation difference in the plane, it is preferable to make the stretching ratio in the longitudinal and width directions the same and to make the stretching speed approximately equal. In addition, the stretching temperature is preferably from the maximum glass transition temperature of the resin constituting the film to the maximum glass transition temperature + 120°C.

[0097] The biaxially stretched film is then preferably subjected to further heat treatment in a tenter, above the stretching temperature but below the melting point, to impart flatness and dimensional stability. During this heat treatment, it is preferable to instantly loosen the film longitudinally just before and / or immediately after entering the heat treatment zone to suppress the distribution of the principal orientation axis in the width direction. After heat treatment in this manner, the film is uniformly cooled slowly, cooled to room temperature, and then wound up. If necessary, loosening treatment may also be performed in the longitudinal and / or width directions during the slow cooling after heat treatment. Preferably, a 1-5% loosening treatment is performed instantaneously in the longitudinal direction just before and / or immediately after entering the heat treatment zone.

[0098] Film 2 can be manufactured in the same manner as the method for manufacturing film 1 described above, except that the thermoplastic resin used is selected to exhibit the properties of film 2.

[0099] Another example of a film having two lamination units is a method in which the thermoplastic resins constituting the lamination unit that plays the role of film 1 and the lamination unit that plays the role of film 2 are melted and kneaded in separate extruders and fed into a multilayer lamination apparatus from different channels to form a film (hereinafter sometimes referred to as "simultaneous film formation").

[0100] Below is an example of a single-step film formation process in which thermoplastic resin A and thermoplastic resin B are used as the thermoplastic resins constituting the laminated unit that plays the role of film 1, and thermoplastic resin A and thermoplastic resin C are used as the thermoplastic resins constituting the laminated unit that plays the role of film 2 (an example in which one of the main components of the thermoplastic resin layers constituting the two laminated units is common to each other).

[0101] Three extruders, A, B, and C, supply thermoplastic resins A, B, and C in a molten state. The molten thermoplastic resins from each channel are then laminated using a multi-manifold type feed block and a square mixer, or a comb type feed block, which are known lamination devices. The laminated units are designed to function as film 1, with a layer configuration of A(BA)n (where n is a natural number representing the number of repeating units), and are designed to function as film 2, with a layer configuration of A(CA)n (where n is a natural number representing the number of repeating units). The molten laminates are then extruded into a sheet using a T-type die or the like, and subsequently cooled and solidified on a casting drum to obtain a casting film. Note that each resin may be dried in hot air, vacuum, or nitrogen atmosphere as needed before being supplied to the extruder.

[0102] In particular, to efficiently obtain a multilayer laminated structure, it is preferable to use a feed block with fine slits. Using such a feed block does not require an extremely large apparatus, resulting in less foreign matter generation due to thermal degradation and enabling high-precision lamination even when the number of layers is extremely large. Furthermore, the lamination accuracy in the width direction is significantly improved compared to conventional technology. In addition, with this apparatus, the thickness of each layer can be adjusted by the shape (length and width) of the slits, making it possible to achieve any desired layer thickness. The molten multilayer laminated sheet formed in this way is guided to a die, where it is cooled and solidified on a casting drum to obtain a casting film. After obtaining the casting film, as described above, it can be stretched sequentially or simultaneously in two directions to obtain a biaxially oriented film by single-layer film formation.

[0103] Furthermore, an example is described in which thermoplastic resin A and thermoplastic resin B are used as the thermoplastic resins constituting the laminated unit that plays the role of film 1, and thermoplastic resin C and thermoplastic resin D are used as the thermoplastic resins constituting the laminated unit that plays the role of film 2 (an example in which the main components of the thermoplastic resin layers constituting the two laminated units are all different).

[0104] Except for supplying molten thermoplastic resins A, B, C, and D from four extruders, A, B, C, and D respectively, and laminating the molten thermoplastic resins from each channel using a known lamination device consisting only of a multi-manifold type feed block and a square mixer, or a comb type feed block, in a layer configuration designed to form a lamination unit that plays the role of film 1, resulting in a lamination unit A(BA)n (where n is a natural number representing the number of repeating units), and in a layer configuration designed to form a lamination unit that plays the role of film 2, resulting in a lamination unit C(DC)n (where n is a natural number representing the number of repeating units), a biaxially oriented film can be obtained by single-step film formation in the same manner as described above.

[0105] In the present invention, when the principal orientation axis of one side is X1 and the principal orientation axis of the other side is X2, it is preferable that the angle between X1 and X2 is between 0° and 45°. Here, the principal orientation axis refers to the direction with the largest refractive index among the directions obtained by rotating the film in any one direction parallel to the film surface and in directions parallel to the film surface at 5° intervals up to 180°. The specific measurement method will be described later. In sequential biaxial stretching, which is used in the manufacture of general biaxially oriented films, a clip-type tenter is used, especially when stretching in the film width direction. However, in this method, as the film is stretched along a rail with both ends held by clips, the stress applied in the film flow direction differs between the central part of the film and the part near the clips. As a result, a difference in the principal orientation axis occurs between the central part and the ends in the width direction, and when different films are manufactured, the principal orientation axis will be different for each. Biaxially oriented films manufactured in this way tend to shrink in the direction of the principal orientation axis when heated. In the film of the present invention, when the principal orientation axis of one surface is X1 and the principal orientation axis of the other surface is X2, the angle between X1 and X2 being 0° or more and 45° or less means that the difference in the angle of the principal orientation axes of one surface and the other surface of the film of the present invention is small. By adopting this configuration, the occurrence of curl due to the difference in the angle of the principal orientation axes is suppressed, and handling performance is improved.

[0106] In the film of the present invention, when the principal orientation axis of one surface is X1 and the principal orientation axis of the other surface is X2, the method for making the angle between X1 and X2 to be 0° or more and 45° or less is not particularly limited. For example, when obtaining the film of the present invention by a method of single-layer film formation or by laminating two laminated films via a resin layer 1, this can be achieved by controlling the direction in which the two laminated films are laminated.

[0107] As mentioned above, when two laminated films are obtained by sequential biaxial stretching, which is commonly used in the manufacture of biaxially oriented films, the principal orientation axes of the two films may differ. In this case, by laminating the two laminated films in a direction that minimizes the difference in angle between the principal orientation axis of one side of the two laminated films and the principal orientation axis of one side of the other laminated film (referred to as the "parallel direction"), the angle between the two principal orientation axes can be set to be between 0° and 45°. However, if the two laminated films are laminated in a direction that maximizes the angle between the principal orientation axis of one side of the two laminated films and the principal orientation axis of one side of the other laminated film (referred to as the "cross direction"), the angle between the two principal orientation axes will be greater than 45°.

[0108] There are no particular limitations on the method for controlling the principal orientation axis by sequential biaxial stretching. Examples include controlling the longitudinal orientation of a uniaxially oriented film by adjusting the longitudinal stretching temperature and longitudinal stretching ratio, or controlling the orientation in the film width direction during the heat treatment process by adjusting the transverse stretching temperature and heat treatment temperature. Furthermore, control can also be achieved by creating differences in the transverse stretching speed and stretching temperature during the transverse stretching process, or by gradually changing the temperature during transverse stretching.

[0109] In addition, in films obtained by sequential biaxial stretching, which is used in the general production of biaxially oriented films, the principal orientation axis of one side and the other side are the same. That is, when the film of the invention is obtained in a single process, the angle between X1 and X2 will inevitably be between 0° and 45°.

[0110] In the present invention, it is preferable that the difference in refractive index between the principal orientation axis and the direction perpendicular to it within the film plane is 0.03 or less on at least one surface of the film. With this configuration, when the film of the present invention is applied to a projected image display member or the like, the image can be displayed with a constant brightness regardless of the viewing direction.

[0111] The method for producing the film of the present invention such that the difference in refractive index between the principal orientation axis and the direction perpendicular to it within the film plane is 0.03 or less on at least one surface is not particularly limited, but examples include a method of producing a film in one step by general biaxial stretching, or a method of laminating film 1 and film 2, which have been produced by general biaxial stretching, with an adhesive resin layer 1.

[0112] The film of the present invention has at least one surface that is measured with a C light source, La * b * Saturation C of transmitted light in color space * It is preferable that it is 7.0 or less. * b * Saturation C of transmitted light in color space * " is simply saturation C * This is one such example. Here, saturation C * This refers to the saturation C measured according to JIS Z 8701 (1999). * This refers to saturation C. * Details of the measurement method will be described later. Saturation C * By setting the saturation C to 7.0 or less, when the film of the present invention is applied to a projected image display member, etc., there is less color distortion, and when used in a head-up display, etc., it is excellent in color recognition of external information such as scenery, and also in color display performance that accurately represents the image to be displayed. From the above viewpoint, saturation C * A value of 6.0 or less is more preferable, 5.5 or less is even more preferable, and 4.0 or less is even more preferable. Furthermore, from the above viewpoint, the saturation C of the projected image display member is also preferable. * A smaller value is preferable, but its lower limit is theoretically 0.

[0113] The film of the present invention has a saturation of C * The method for making it 7.0 or less is not particularly limited, but for example, when the film of the present invention is obtained by laminating two laminated films with a resin layer 1, the saturation C of the resin layer 1 *Methods for adjusting the properties include the following: For example, when giving the layer the heat-absorbing properties described above, it is effective to use a heat-absorbing material such as tin-doped indium oxide (ITO) or cesium tungsten oxide (CWO), which absorbs in the visible light region but has relatively low absorption performance and appears slightly bluish or grayish, and to further adjust the amount used. For example, when using cesium tungsten oxide (CWO), it is preferable to use an amount of less than 1.0% by mass of the entire resin layer 1.

[0114] The film of the present invention further comprises a resin layer and a transparent support, and is suitably used in projection image display members in which the film and resin layer are adjacent. Examples of the transparent support include a transparent resin substrate and glass, but for example, glass is used as the transparent support, and the projection image display member (interpolation method) has two pieces of glass (transparent support 1, 2) and two resin layers (resin layers 2, 3), and is suitably used in projection image display members (lamination method) that have transparent support 1, resin layer 2, the film of the present invention, resin layer 3, and transparent support 2 in this order, or transparent support 1, resin layer 2, and the film of the present invention in this order.

[0115] Suitable transparent supports for the projection image display member of the present invention include transparent resin substrates and glass. Preferred transparent resin substrates include, for example, polyethylene terephthalate, polycarbonate, acrylic, polyvinyl chloride, polyethylene, polypropylene, polymethylpentene and its copolymers, and acrylonitrile-butadiene-styrene copolymers. These transparent resin substrates may be single components or mixtures of multiple components.

[0116] The glass used is not particularly limited, and commonly used transparent plate glass can be used. Examples include clear glass, float glass, polished plate glass, patterned glass, wired plate glass, reinforced plate glass, infrared absorbing plate glass, infrared reflective plate glass, and green glass. Furthermore, when the projection image display member of the present invention is a laminated type, the glass used for the transparent support can be not only single-layer glass, but also laminated glass and tempered glass used in automobile windshields, side windows, and rear windows, as well as plate glass, tempered glass, double-glazed glass, and vacuum glass used in glass building materials.

[0117] Furthermore, the resin layer used in the projection image display member of the present invention is not particularly limited, and a layer similar to the resin layer 1 described above can be applied. Each resin layer may be the same, or they may all be different.

[0118] When the projection image display member of the present invention uses an interpolation method, it is preferable that 3 ≤ d2 / d3 ≤ 100 is satisfied when the thickness of resin layer 2 is d2 and the thickness of resin layer 3 is d3. By setting the thicknesses of the two resin layers within a suitable range, it is preferable that double images of the projected image can be suppressed when used in projection image display members with P-wave reflection characteristics, and in head-up displays (HUDs), for example. Furthermore, it is preferable that the thicknesses of resin layer 2 and resin layer 3 are 10 μm to 1 mm.

[0119] When the projection image display member of the present invention uses an interpolation method, it is preferable that 1.5 ≤ d4 / d5 ≤ 10 is satisfied when the thickness of the transparent support 1 is d4 and the thickness of the transparent support 2 is d5. It is preferable that the thicknesses of the two glass plates be within a suitable range, as this can suppress double images in the projected image when used in projection image display members with P-wave reflection characteristics, and in head-up displays (HUDs), for example. The thicknesses of the transparent support 1 and the transparent support 2 are preferably 0.5 mm to 5.0 mm.

[0120] The projection image display device of the present invention will now be described. The projection image display device of the present invention comprises a video projector and a projection image display member of the present invention, wherein an image is projected onto the projection image display member by light from the video projector. Furthermore, it is preferable that the video projector emits P-waves in the projection image display device of the present invention. With this configuration, the projected image can be viewed even when wearing polarized sunglasses.

[0121] Furthermore, in the projection image display device of the present invention, it is preferable that θ (°) is the angle (angle of incidence) between the light emitted by the image projector and the normal to the image display surface of the projection image display member, and that θ is between 35° and 70°. By setting the image projector and the projection image display member to the above angle, even when an image is projected widely across the entire surface of the projection image display member, the presence of ghost images reflected from the surface can be minimized, suppressing multiple images and making the main image clearer. Of course, by bringing the angle of incidence closer to the Brewster angle, reflection from the transparent support is reduced and multiple images become less visible, so θ is more preferably between 45° and 65°. Setting θ to 35° or more allows sufficient reflection from the projection image display member, and the amount of P-wave component reflected by the transparent support is suppressed, making multiple images less visible. On the other hand, setting θ to 70° or less suppresses the rapid increase in P-wave reflectivity, and the contrast ratio of ghost images to the main image is kept low, making multiple images less visible. Since θ coincides with the angle of incidence of light from the image projector, this can be adjusted by positioning the image projector and the projected image display member so that they form the above angle so that the light from the image projector reaches the observer's eye. If the projected image display member is curved, the normal to the tangent surface at the centroid of the image displayed on the projected image display member is treated as the "normal to the image display surface."

[0122] The projection image display device of the present invention obtained in this manner has high displayability of projected images and good visibility of the surrounding scenery, and can therefore be used in head-up displays and manned transportation vehicles. That is, the head-up display and manned transportation vehicle of the present invention are equipped with the projection image display device of the present invention. By equipping the projection image display device of the present invention, it is possible to display projected images using P-waves while suppressing the rise in temperature inside the transportation vehicle. [Examples]

[0123] The laminated film of the present invention will be described in detail below using examples. However, the laminated film of the present invention is not limited to these embodiments.

[0124] [Methods for measuring physical properties and evaluating their effects] The methods for evaluating physical properties and effects are as follows.

[0125] (1) Number of layers and layer thickness The number of layers and layer thickness of the laminated unit were determined by transmission electron microscopy (TEM) observation of samples thinned using an ultramicrotome. Specifically, a JEM-1400 Plus transmission electron microscope (manufactured by JEOL Ltd.) was used to capture and observe cross-sectional images of the laminated film under an acceleration voltage of 100kV, and the number of layers was determined by obtaining the cross-sectional images. In addition, staining techniques using electron staining agents (such as RuO4) were used to increase the contrast difference between each layer. Furthermore, depending on the thickness of each layer, observations were performed at direct magnification of 40,000x for thin film layers with a thickness of less than 100nm, 20,000x for thin film layers with a thickness of 100nm or more but less than 500nm, and 1,000x to 10,000x depending on the thickness for layers with a thickness of 500nm or more. The number of layers and layer thickness were determined based on the contrast difference of the obtained images.

[0126] (2) Layer interface (contrast difference) The cross-sectional images obtained from the transmission electron microscope observation in (1) were converted to compressed image file (JPEG) format, and position-luminance data was acquired by line profiling using ImagePro-10 (distributed by Hakuto Co., Ltd.) along the thickness direction of the laminated film. Subsequently, a 5-point moving average was applied to the profile obtained by plotting the relationship between position and luminance using spreadsheet software (Microsoft Excel® 2016). The moving average was performed by averaging the luminance for five consecutive measurement positions, changing the position of each point, and repeating the same calculation to obtain a moving-averaged position-luminance profile. In the obtained averaged position-luminance profile, the position enclosed by inflection points where the slope changes from positive to negative, or from negative to positive, was determined to be a single layer. For each layer obtained using this method, position-luminance data was then acquired in the planar direction of the laminated film (direction perpendicular to the thickness direction). After calculating the average value and standard deviation of the luminance obtained for each layer, if the difference between the average values ​​of the luminances of two adjacent layers is greater than either of the standard deviations of the luminances of the adjacent thermoplastic resin layers, then these two adjacent layers were determined to be different.

[0127] (3) 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 the sample was heated from 25°C to 300°C at a rate of 10°C / min on an aluminum tray. The intersection of the baseline when heating from room temperature and the tangent at the inflection point of the step transition was defined as the glass transition temperature Tg (°C). After heating, the sample was rapidly cooled with liquid nitrogen, and when heating was repeated under the same conditions, the endothermic peak observed at the highest temperature was defined as the melting point (°C). The integral value from the baseline within a range of ±20°C from the melting point was defined as the enthalpy of fusion (J / g).

[0128] (4)Reflectance Reflectance measurements were performed on 5cm x 5cm samples using a Hitachi U-4100 Spectrophotometer with an integrating sphere in a basic configuration. For these measurements, an aluminum oxide sub-plate provided with the instrument was used as a reference. For the reflectance measurements, the sample was placed behind the integrating sphere with its longitudinal direction facing up and down. The reflectance was measured under the following conditions to calculate the average reflectance in the 400nm to 700nm wavelength range, and to confirm the presence or absence of a reflectance band beyond 850nm (and, if such a band exists, its shorter wavelength end). <Measurement conditions> Slit: 2nm (visible) / Automatic control (infrared) Gain: 2 Scanning speed: 600 nm / min Starting wavelength: 2600nm Termination wavelength: 240nm Sampling interval: 1 nm Incident angle: 10°.

[0129] (5) R20, R40, R70 A variable-angle reflector unit and a GranTerra polarizer were attached to a Hitachi, Ltd. U-4100 Spectrophotometer, and the P-wave reflectance was measured at 1 nm intervals in the wavelength range of 400-700 nm at incident angles θ = 20°, 40°, and 70°. From the obtained reflectances, R20, R40, and R70 were determined as the average P-wave reflectances in the wavelength range of 400-700 nm at incident angles of 20°, 40°, and 70°.

[0130] (6) Refractive index and principal orientation axis The refractive index of the film surface was measured using a SPA-400 prism coupler manufactured by Cylon Technology, with a measurement laser wavelength of 633 nm. Measurements were performed in an arbitrary direction parallel to the film surface, and in each direction rotated from that direction in a direction parallel to the film surface at 5° intervals up to 180°. The directions with the largest refractive index were designated as the principal orientation axes X1 and X2. The orientation axis perpendicular to the principal orientation axis X1 was designated as Y1. The difference in refractive index between X1 and Y1 was calculated by subtracting the refractive index in the Y1 direction from the refractive index in the X1 direction.

[0131] (7)La * b * Saturation C of transmitted light in color space * Using the standard configuration (solid-state measurement system) of the Hitachi, Ltd. U-4100 Spectrophotometer, the transmission spectrum at an incident angle of 0°, the spectral distribution of the C light source, and the XYZ color matching functions of the XYZ system were used to determine the XYZ values ​​under the C light source, and the chrominance C was calculated using the XYZ values. * The values ​​were calculated (JIS Z 8701 1999).

[0132] (8) Fabrication of an interpolation-type projection image display member Using LAMINATOR0303S manufactured by Nisshinbo Co., Ltd., a glass-based interpolation type projection image display component was fabricated by stacking a transparent glass plate, resin layer 2, the film from Examples 1-23 or Comparative Examples 1-3, resin layer 3, and transparent glass plate in that order, and then pressing it for 30 minutes under conditions of 140°C and 1.5 MPa. The transparent glass plate used was 100 mm wide x 100 mm long with a thickness of 2.1 mm (indicated as "2.1 mm glass" in Table 3). In Examples 1-23 and Comparative Examples 1-3, the following resin layer 2-1 was used as resin layer 2, and the following resin layer 3-1 was used as resin layer 3. In Examples 24-30, the types of resin layer 2 and resin layer 3 were as described in Table 3. <Resin layer 2> Resin layer 2-1: PVB sheet without heat absorber, 380 μm thick, Tg 22℃. <Resin layer 3> Resin layer 3-1: PVB sheet without heat absorber, 380 μm thick, Tg 22℃. Resin layer 3-2: PVB sheet without heat absorber, 50 μm thick, Tg 22℃. Resin layer 3-3: PVB sheet containing cesium tungsten oxide particles as a heat-absorbing material, 380 μm thick, Tg 22℃.

[0133] (9) Fabrication of a projection image display member using a bonding method Using LAMINATOR0303S manufactured by Nisshinbo Co., Ltd., a laminated projection image display component using glass was fabricated by stacking a transparent glass plate, resin layer 4, and the films of Example 1 and Example 20 in that order, and then pressing them while holding them at a temperature of 140°C and 1.5 MPa for 30 minutes. The transparent glass plate used was 100 mm wide x 100 mm long with a thickness of 2.1 mm (indicated as "2.1 mm glass" in Table 4). The type and thickness of resin layer 4 were as described in Table 4. <Resin layer 4> Resin layer 4-1: PVB sheet without heat absorber, 380 μm thick, Tg 22℃. Resin layer 4-2: PVB sheet without heat absorber, 50 μm thick, Tg 22℃. Resin layer 4-3: An acrylic adhesive layer made by mixing DIC Corporation's "FineTack" (registered trademark) CT-6030 and DIC Corporation's "FineTack" (registered trademark) hardener DN in a solid content mass ratio of 100:1. Thickness: 10 μm.

[0134] (10) Performance evaluation of projected image display member Using a projection image display member, an image containing white lines on a black background was projected by a video projector emitting P-waves. The projection angle (the angle between the light emitted by the video projector and the normal to the image display surface of the projection image display member, the same applies hereinafter) was 60° (for all examples except Examples 29 and 35 and each comparative example) or 40° (for Examples 29 and 35 only). In evaluating the projection image display member, light was incident from the resin layer 3 side in the case of the interpolation method, and from the film side in the case of the lamination method.

[0135] (Brightness of the projected image) A sensory evaluation was conducted on the visibility of white lines, and visual visibility was evaluated on the following four-point scale, with a score of B or higher being considered a passing grade. S: The projected image was very bright. A: The projected image was too bright. B: The projected image was a little too bright. C: The projected image was not visible.

[0136] (Background visibility) A sensory evaluation was conducted to assess the visibility of the background, and visual visibility was evaluated on the following four-point scale, with a score of B or higher being considered a passing grade. S: The background was clearly visible. A: The background appeared dark enough that it didn't pose any practical problems. The background appeared darker than the B:A standard. C: The background was not visible.

[0137] (Projected image in color) A sensory evaluation was conducted on the coloring of the white lines, and they were visually evaluated on the following four-point scale. S: I could barely see any color. A: A very slight discoloration was visible, but it did not pose any practical problems. B: The color was visible to a degree exceeding that of A. C: The color was so strong that it posed practical problems.

[0138] (Double image in projected images) The number and appearance of the white lines were visually evaluated and assessed in the following two stages. S: A single straight line appeared clear or slightly blurred. A: I could see two straight lines, but they were very close together. B: Clearly, there were two straight lines visible, separated by a significant distance.

[0139] (11) Heat-shielding properties The total energy transmittance (Tts) through the projected image display member was measured according to ISO 13837:2008 "Road vehicles - Safety glazing materials - Method for measuring sunlight transmittance," and evaluated on the following five-point scale, with B or higher being considered acceptable. In the case of the interpolation method, light was incident from the resin layer 2 side, and in the case of the lamination method, light was incident from the transparent support 1 side. SS: The total energy transmittance (Tts) through the projected image display component was 50% or less. S: The total energy transmittance (Tts) through the projected image display member was greater than 50% and less than or equal to 60%. A: The total energy transmittance (Tts) through the projected image display member was greater than 60% and less than or equal to 70%. B: The total energy transmittance (Tts) through the projected image display member was greater than 70% but less than or equal to 80%. C: The total energy transmittance (Tts) through the projected image display component exceeded 80%.

[0140] (12) Flatness of the film The flatness of the film was evaluated by the degree of curl after heat treatment. Films from Examples 1-23 and Comparative Examples 1-3 were cut to a size of 20 mm in width and 20 mm in length, and heat-treated at 120°C for 30 minutes. A fanless oven was used for the heat treatment. The degree of curl was evaluated in the following three stages by measuring the height of the four corners of the sample after heat treatment. S: All four corners were 30mm or less. A: One or two of the four corners were 30mm or less, and the remaining two or three corners were greater than 30mm but 50mm or less. B: All four corners were larger than 50mm.

[0141] (13) Calculation of in-plane refractive index difference and perpendicular refractive index difference The in-plane and perpendicular refractive indices of layer A of the film were measured using a SPA-400 prism coupler manufactured by Cylon Technology. The wavelength of the laser used for measurement was 633 nm. The in-plane refractive index was the average of the values ​​measured in the direction along the principal orientation axis and the direction perpendicular to the principal orientation axis, while the perpendicular refractive index was the average of the value measured from the direction along the principal orientation axis and the value measured from the direction perpendicular to the principal orientation axis. Since layers B and C of the film are layers inside the laminated unit, they were measured and calculated in the same manner as above using films of only the B-layer resin or only the C-layer resin, which were manufactured under the same conditions as the laminated unit, rather than the laminated unit itself. The difference in in-plane refractive index and the difference in perpendicular refractive index were calculated as the absolute values ​​obtained by subtracting the refractive index obtained for each layer.

[0142] [Resin used in the film] Resin 1: A crystalline polyethylene terephthalate resin exhibiting a glass transition temperature of 78°C, a melting point of 254°C, a crystallization temperature of 180°C, and a melting enthalpy of 40 J / g. Resin 2: An amorphous polyethylene terephthalate resin blend obtained by blending Resin 1 with Resin 1 in a 70:30 ratio. Resin 2 is a polyethylene terephthalate resin copolymerized with 29 mol% spiroglycol and 21 mol% cyclohexanedicarboxylic acid, exhibiting a glass transition temperature of 80°C. Resin 3: A crystalline polyethylene terephthalate resin copolymerized with 20 mol% naphthalenedicarboxylic acid, exhibiting a glass transition temperature of 90°C, a melting point of 211°C, and a melting enthalpy of 1 J / g. Resin 4: A crystalline polyethylene naphthalate resin exhibiting a glass transition temperature of 124°C, a melting point of 262°C, a crystallization temperature of 200°C, and a melting enthalpy of 48 J / g. Resin 5: An amorphous polyethylene terephthalate resin copolymerized with 33 mol% cyclohexanedimethanol, exhibiting a glass transition temperature of 80°C. Resin 6: A crystalline copolymer polyethylene terephthalate resin with a glass transition temperature of 78°C, a melting point of 221°C, a crystallization temperature of 176°C, and a melting enthalpy of 35 J / g, using terephthalic acid (88 mol%) and isophthalic acid (12 mol%) as dicarboxylic acid components, and ethylene glycol as the diol component. Resin 7: An amorphous copolymer polynaphthalate resin with a glass transition temperature of 81°C, comprising 70 mol% 2,6-naphthalenedicarboxylic acid and 30 mol% isophthalic acid as dicarboxylic acid components, 98 mol% ethylene glycol as diol components, and 2 mol% polyethylene glycol with a molecular weight of 400. Resin 8: A crystalline polyethylene terephthalate resin copolymerized with 10 mol% isophthalic acid, exhibiting a glass transition temperature of 79°C, a melting point of 230°C, and a melting enthalpy of 12 J / g. Resin 9: An amorphous polyethylene terephthalate resin blend obtained by blending resin 1 and resin 5 in a ratio of 38:62, exhibiting a glass transition temperature of 79°C.

[0143] [Resin layer 1] Resin layer 1-1: An acrylic adhesive layer containing indium tin oxide (ITO) as a heat-absorbing material. Resin layer 1-2: An acrylic adhesive layer made by mixing DIC Corporation's "FineTack" (registered trademark) CT-6030 and DIC Corporation's "FineTack" (registered trademark) hardener DN in a solid content mass ratio of 100:1. Resin layer 1-3: Acrylic adhesive layer containing 1.0% by weight of cesium tungsten oxide particles as a heat-absorbing material. Resin layer 1-4: Acrylic adhesive layer containing 1.5% by weight of cesium tungsten oxide particles as a heat-absorbing material. Resin layer 1-5: Acrylic adhesive layer containing 0.5% by weight of tungsten cesium oxide particles as a heat-absorbing material. Resin layer 1-6: PVB sheet containing indium tin oxide (ITO) as a heat absorber, Tg 22℃. Resin layer 1-7: PVB sheet containing cesium tungsten oxide particles as a heat-absorbing material, Tg 22°C. Resin layer 1-8: PVB sheet without heat absorber, Tg 22℃. Resin layer 1-9: A mixture of DPHA (dipentaerythritol hexaacrylate), potassium tert-butoxide, and a photoinitiator (BASF Japan's "IRGACURE" (registered trademark) 184) in a mass ratio of 99:1:1 was prepared, and the solid content was adjusted to a concentration of 40% with MEK (methyl ethyl ketone) (coating agent A). Coating agent A and cesium tungsten oxide particles Cs 0.33 Coating agent B was prepared by mixing a slurry of WO3 with a solid content concentration of 20% by mass in a solid content mass ratio of 80:18.5.

[0144] Coating agent B was applied to one surface of the film described later using a wire bar coater, and then dried in a hot air oven at 80°C for 2 minutes. After that, ultraviolet light at 300 mJ / cm² was applied using a UV irradiation device. 2 Resin layer 1-9 was formed by curing the coating film by irradiation. The amount of resin applied was adjusted so that the thickness of resin layer 1-9 after drying was 2 μm. Resin layer 1-10: Resin layer 1-10 was formed in the same manner as resin layer 1-9, except that coating agent C was used instead of coating agent B. Coating agent C: Coating agent A and a slurry containing 20% ​​by mass of indium tin oxide powder were mixed in a solid content ratio of 80:18.5.

[0145] (Example 1) Film 1: Resin 1 was used as the crystalline thermoplastic resin A1 (hereinafter also referred to as resin A1) constituting layer A, and resin 2 was used as the thermoplastic resin B1 (hereinafter also referred to as resin B1) constituting layer B. Resins A1 and B1 were melted at 280°C in separate extruders, and foreign matter was removed by passing them through five FSS-type leaf disc filters. Then, while measuring with a gear pump so that the discharge ratio of resin A1 / resin B1 = 1 / 1.07, both were combined in a 501-layer feed block, and a total of 501 layers of resin A1 and resin B1 were laminated alternately in the thickness direction so that the outermost layers on both sides were resin A1. At this time, the layer thicknesses of layers A and B were designed so that the reflectance spectrum in the wavelength range of 380 nm to 780 nm was flat. Specifically, the thickness of the final A layer was varied geometrically from 130 nm to 180 nm, and the thickness of the final B layer from 137 nm to 190 nm, so that adjacent A and B layers satisfy equations (1) and (2) above, starting from one surface of the film and moving toward the opposite surface (however, the thickness of the A layer located on both surfaces was adjusted to ultimately be 10 μm). Next, the obtained molten laminate was supplied to a T-die and formed into a sheet, and then rapidly cooled 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 unstretched film. This unstretched film was longitudinally stretched by the difference in peripheral speed of the rolls at a temperature of 90°C and a magnification of 3.5 times, and then cooled to obtain a uniaxially oriented film. Subsequently, the uniaxially oriented film was guided to a tenter with both ends in the width direction gripped with clips, and transversely stretched at a temperature of 110°C and a magnification of 4.3x. After heat treatment at 210°C, a further 1.6% widthwise relaxation was performed to obtain film 1 with a thickness of 80 μm that satisfies characteristic A. The properties and evaluation results are shown in Table 1.

[0146] Film 2: Film 2 was fabricated in the same manner as Film 1, except that resin 1 was used as the crystalline thermoplastic resin A2 constituting layer A, resin 3 was used as the thermoplastic resin B2 constituting layer B, and the number of layers was 801. A film 2 with a thickness of 100 μm that satisfies characteristics B and C was obtained. The properties and evaluation results are shown in Table 1. The number of layers was adjusted by the number of slits in the feed block (the same applies to other examples and comparative examples below).

[0147] Film 3: The films 1 and 2 obtained above were bonded together using resin layer 1-1 as resin layer 1, in a direction that minimizes the angle between the principal orientation axes of both films (parallel direction). The characteristics and evaluation results are shown in Table 1. The projection image display member was evaluated using an interpolation type projection image display member with resin layer 2-1 as resin layer 2 and resin layer 3-1 as resin layer 3, with a projection installation angle of 60° (the same applies to Examples 2 to 23 and Comparative Examples 1 to 3 below).

[0148] (Examples 2-7, 9-14, 17-19) Except for the number of layers in the lamination unit and the resin used, as shown in Tables 1 and 2, films 1 to 3 were obtained and evaluated in the same manner as in Example 1. The characteristics and evaluation results are shown in Tables 1 and 2.

[0149] (Example 8) Except for setting the lamination direction to the direction in which the angle between the principal orientation axes of both films is largest (cross direction), films 1 to 3 were obtained and evaluated in the same manner as in Example 1. The characteristics and evaluation results are shown in Table 1.

[0150] (Example 15) Except for using the film shown below for film 1, films 1 to 3 were obtained and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0151] Film 1: Resin 1 was used as the thermoplastic resin A1 (hereinafter also referred to as resin A1) constituting layer A, resin 8 as the thermoplastic resin B1 (hereinafter also referred to as resin B1) constituting layer B, and resin 5 as the thermoplastic resin C1 (hereinafter also referred to as resin C1) constituting layer C. Resins A1, B1, and C1 were melted in separate extruders at 270°C, 270°C, and 280°C, respectively. After passing through seven FSS-type leaf disc filters, each was extruded using a gear pump while measuring so that the discharge ratio (layering ratio) was resin A1 / resin B1 = 0.98 and resin C1 / resin B1 = 1.02, and then merged in a 601-layer feed block. At this time, both surface layers were made of resin A1, and the layers were laminated in a regular arrangement of A / B / C / B in the thickness direction. Furthermore, the layer thicknesses of layers A, B, and C were designed so that the reflectance spectrum in the wavelength range of 380 nm to 780 nm was flat. Specifically, from one surface of the film toward the opposite surface, the thickness of the final A layer was varied geometrically from 130 nm to 180 nm, the thickness of the final B layer from 137 nm to 190 nm, and the thickness of the final C layer from 144 nm to 200 nm, so that adjacent A and B layers, B and C layers, and C and A layers would each satisfy equations (1) and (2) above (however, the thickness of the A layer located on both surfaces was adjusted to ultimately be 10 μm). From there, the film was fabricated in the same manner as in film 1 of Example 1, and a film with a thickness of 80 μm that satisfies characteristic A was obtained. Note that the explanation of equations (1) and (2) above is based on the assumption of a combination of A and B layers, but they should be interpreted and applied according to the combination.

[0152] (Example 16) Resin 1 was used as the thermoplastic resin A1 (hereinafter also referred to as resin A1) constituting the laminated unit that plays the role of film 1, and resin 2 was used as the thermoplastic resin B1 (hereinafter also referred to as resin B1) constituting the B layer. Resin 1 was used as the thermoplastic resin A2 (hereinafter also referred to as resin A2) constituting the laminated unit that plays the role of film 2, and resin 3 was used as the thermoplastic resin B2 (hereinafter also referred to as resin B2) constituting the B layer. Resin A1 (resin A2), resin B1, and resin B2 were melted at 280°C in three extruders, extruder A, extruder B, and extruder C, respectively, and foreign matter was removed by passing them through five FSS-type leaf disc filters. Subsequently, the resins from each channel were metered using a gear pump to achieve discharge ratios of resin A1 / resin B1 = 1 / 1.07 and resin A2 / resin B2 = 1 / 1.07. The mixture was then combined in a 901-layer feed block with configurations A1(B1A1)n (n=250) and (B2A2)m (m=200). A total of 901 layers of resin A1 and resin B1, and resin A2 and resin B2 were laminated alternately in the thickness direction, with the outermost layers on both sides being either resin A1 or resin A2 (both resin 1). The film was then manufactured in the same manner as in Example 1, yielding a 130 μm thick film (film 3) that satisfied characteristics A, B, and C. The characteristics and evaluation results are shown in Table 2. The thickness was adjusted by changing the discharge amount of each resin.

[0153] (Example 20) A resin layer 1-9 was formed on film 1 obtained in Example 1 using the method described above. Next, with the side on which resin layer 1-9 was formed facing film 2, film 3 was obtained by laminating it in a parallel direction using resin layer 1-2. The properties and evaluation results are shown in Table 2.

[0154] (Example 21) Film 3 was obtained in the same manner as in Example 20, except that resin layers 1-10 were formed on film 1 obtained in Example 1, and then evaluated. The properties and evaluation results are shown in Table 2.

[0155] (Examples 22, 23) Except for using resin layer 1-8 instead of resin layer 1-2, film 3 was obtained and evaluated in the same manner as in Examples 20 and 21. The properties and evaluation results are shown in Table 2.

[0156] (Comparative Examples 1-3) Films 1 to 3 were obtained in the same manner as in Example 1, except that the number of layers in the laminated unit and the resins used were as shown in Table 2. The properties and evaluation results are shown in Table 2. Note that Film 1 in Comparative Example 2 and Film 2 in Comparative Example 3 are single-layer films, as resins A1 and B1, and resins A2 and B2 are the same, respectively. Furthermore, the properties of Film 3 were the same regardless of which side was used for measurement.

[0157] [Table 1]

[0158] In the table, "film" in "film layer composition" and "film characteristics" refers to Film 3. The same applies to Table 2.

[0159] [Table 2]

[0160] In Comparative Example 3, the "colored projection image evaluation" could not be evaluated because the "brightness of the projection image" was "C: The projection image was not visible."

[0161] (Examples 24-30, Comparative Examples 4 and 5) A projection image display member was fabricated with the transparent supports 1 and 2, resin layers 2 and 3, and film (film 3) configured as shown in Table 3, and evaluated with the projection installation angle shown in Table 3. The evaluation results are shown in Table 3. Note that the configurations of Examples 24-27 and Comparative Examples 4 and 5 are the same as those of the projection image display members fabricated in Examples 1, 18, 20, 22 and Comparative Examples 1 and 2, respectively, but the "double image of the projection image" was additionally evaluated.

[0162] [Table 3]

[0163] The film used in the "Film" section of the evaluation configuration is Film 3 obtained in each example and each comparative example. The same applies to Table 4.

[0164] (Examples 31-35) A projection image display component was fabricated with the transparent support 1, resin layer 4, and film (film 3) configured as shown in Table 4, and evaluation was conducted with the projection installation angle as shown in Table 4. The evaluation results are shown in Table 4.

[0165] [Table 4] [Industrial applicability]

[0166] The present invention provides a film that, when used in a projected image display member, can achieve good background visibility, heat shielding, and image display performance. Because the film of the present invention has excellent properties as described above, it can be suitably used in projected image display members that can suppress the inflow of heat from the outside, especially from sunlight, while also having good background visibility and displaying an image superimposed on the background, and in projected image display devices using said projected image display members, and in a manned transportation system equipped with said projected image display device. [Explanation of symbols]

[0167] 1: A graph showing the relationship between the depth in the thickness direction and the change in contrast (gray level) of a laminated film with an AB regular arrangement. 2: Thickness of layer A 3: Thickness of layer B

Claims

1. A film characterized by having a thermoplastic resin as its main component and possessing all of the following features A to C on at least one surface. Feature A: When light is incident at an incident angle of 10°, there is a reflection band in the wavelength range of 850 nm or more, with a wavelength width of 20 nm or more, where the reflectance is between 30% and 110%. Feature B: When light is incident at an incident angle of 10°, the average reflectance of visible light is between 0% and 25%. Feature C: When P-wave light is incident on the film surface at angles of 20°, 40°, and 70° to the normal, the average reflectance (%) in the wavelength band of 400-700 nm is denoted as R20, R40, and R70, respectively, and the relationship R20 ≤ R40 < R70 is satisfied.

2. The film according to claim 1, having two laminated units in which 51 to 1001 layers of two or more thermoplastic resin layers with different main components are regularly laminated.

3. The film according to claim 2, wherein both of the laminated units are laminated units in which 51 to 1001 layers of two types of thermoplastic resin layers having different main components are alternately laminated, and one of the main components of the thermoplastic resin layers constituting the two laminated units is common to each other.

4. The film according to claim 2, wherein each of the two laminated units is a laminated unit in which 51 to 1001 layers of two types of thermoplastic resin layers having different main components are alternately laminated, and the main components of the thermoplastic resin layers constituting the two laminated units are all different.

5. The film according to claim 2, wherein one of the two laminated units is a laminated unit in which 51 to 1001 layers of three types of thermoplastic resin layers having different main components are regularly laminated, and the other is a laminated unit in which 51 to 1001 layers of two types of thermoplastic resin layers having different main components are alternately laminated, and the main components of the thermoplastic resin layers constituting the two laminated units are all different.

6. The film according to claim 2, wherein a resin layer 1 having a thickness of 1.0 μm or more and 800 μm or less is provided between two of the laminated units.

7. The film according to claim 1 or 2, wherein when the principal orientation axis of one surface is X1 and the principal orientation axis of the other surface is X2, the angle between X1 and X2 is 0° or more and 45° or less.

8. The film according to claim 6, wherein one of the laminated units satisfies feature A, and the other satisfies feature B and feature C.

9. The film according to claim 6, wherein the resin layer 1 includes a heat-absorbing material.

10. On at least one surface, La measured with a C light source ＊ b ＊ Saturation C of transmitted light in color space ＊ The film according to claim 1 or 2, wherein the ratio is 7.0 or less.

11. The film according to claim 1 or 2, having the following feature D on at least one surface. Feature D: R20 and R70 satisfy R70 - R20 > 10.

12. The film according to claim 1 or 2, wherein in at least one plane, the difference between the refractive index of the principal orientation axis and the refractive index of the direction perpendicular thereto within the film plane is 0.03 or less.

13. A projection image display member comprising, in this order, a transparent support 1, a resin layer 2, and the film described in claim 1 or 2.

14. A projection image display member comprising a transparent support 1, a resin layer 2, and the film, resin layer 3, and transparent support 2 according to claim 1 or 2, in that order.

15. A projection image display device comprising an image projector and a projection image display member as described in claim 13, wherein an image is projected onto the projection image display member by light from the image projector.

16. The projection image display device according to claim 15, wherein the image projector emits P-wave light.

17. The projection image display device according to claim 15, wherein when the angle between the light emitted by the image projector and the normal to the image display surface of the projection image display member is θ (°), θ is 35° or more and 70° or less.

18. A head-up display comprising the projection image display device described in claim 15.

19. A manned transport vehicle equipped with the projection image display device described in claim 15.

Images