JP2025128508A - Laminate film - Google Patents

Abstract

To provide a laminate that exhibits superior thermal shielding and that can also enhance appearance and design quality.SOLUTION: The laminate comprises a dielectric multilayer film having a colored layer on one side. When an average reflectance at a wavelength of 900-1000 nm is defined as Ra and an average reflectance at a wavelength of 400-700 nm is defined as Rb, Ra is 50% or more and 100% or less, the shortest wavelength in the 700-900 nm region at which an intermediate value between Ra and Rb occurs is 850 nm or more, and when a surface opposite to the colored layer is defined as an X surface, a water contact angle of the X surface is 5° or more and 60° or less.SELECTED DRAWING: None

Description

The present invention relates to a laminated film.

Laminate films are known that selectively reflect light of specific wavelengths by utilizing the optical interference phenomenon that occurs when two or more materials with different optical properties are regularly laminated together in layer thicknesses on the order of the wavelengths of light. Such laminate films can be given a variety of performance properties by adjusting the refractive index, number of layers, thickness of each layer, and their distribution, etc., of the materials used. Therefore, they are used in applications such as cold mirrors, half mirrors, laser mirrors, dichroic filters, heat ray reflective films, near-infrared cut filters, monochrome filters, and polarized reflective films.

Molded articles obtained by laminating such laminated films onto a rigid support under heat and pressure are used in decorative materials such as decorative panels, various home appliances, building materials, automotive parts, etc. In particular, in recent years, in response to carbon dioxide emission restrictions aimed at environmental protection, heat-blocking glass, which can reduce the inflow of heat from outside in the summer, particularly heat from sunlight, has been attracting attention as window glass for vehicles such as cars and trains, and buildings.

Examples of such heat-ray-cutting glass include glass in which a heat-ray absorbing material is incorporated into the glass or the interlayer film used in laminated glass, blocking heat rays with the heat-ray absorbing material (e.g., Patent Document 1), glass in which a metal film is formed on the glass surface by sputtering or the like, blocking heat rays by reflecting them (e.g., Patent Document 2), and glass in which a laminated film made of alternating layers of polymers with different refractive indices is inserted between the glass and the interlayer film, blocking heat rays by reflecting them (e.g., Patent Document 3).

However, the heat-cutting glass of Patent Document 1 converts sunlight incident from outside into thermal energy, which radiates that heat into the room, resulting in reduced heat-cutting efficiency. Additionally, this method causes the glass temperature to rise locally as heat rays are absorbed, potentially resulting in damage to the glass itself due to the temperature difference with the outside air temperature. The heat-cutting glass of Patent Document 2 reflects not only heat rays but also visible light, making it prone to coloration. It also blocks electromagnetic waves, which can adversely affect the use of communication devices inside. On the other hand, the laminated film that makes up the heat-cutting glass of Patent Document 3 allows for the selection of wavelengths to be reflected by controlling its layer thickness, thereby selectively reflecting light in the near-infrared region that contributes to temperature rise, improving heat-cutting performance while maintaining visible light transmittance. Furthermore, because it does not contain components that block radio waves, such as metals, it also maintains good radio wave transmittance.

Furthermore, when a laminate film such as that shown in Patent Document 3 is obtained by melt extrusion, for reasons of transparency, heat resistance, weather resistance, chemical resistance, strength, and dimensional stability, one resin layer is primarily made of a polyester resin such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), while the other resin layer is made of a thermoplastic resin (such as a copolymer polyester resin) with optical properties different from that of the polyester resin (e.g., Patent Documents 4 to 6). In particular, when polyethylene naphthalate is used as the primary component of one resin layer, the difference in refractive index between it and the copolymer polyester, which has a low refractive index, can be made large, resulting in a laminate film with high reflectance.

JP 2010-17854 A Japanese Patent Application Laid-Open No. 2001-310407 WO 2005/040868 Japanese Patent Application Laid-Open No. 2005-059332 Japanese Patent Application Laid-Open No. 2004-249587 International Publication No. 2013/137288

Because such heat-cutting glass is often used in places visible to the public, such as the windowpanes of vehicles and buildings, appearance is also an important factor. However, when the laminated films of Patent Documents 3 to 6 are used in applications with a colored layer (especially a black layer), such as automobile sunroofs or tinted or printed windowpanes, there is an issue in that water droplets that adhere to the glass during rain or cleaning appear colored red or yellow. The mechanism behind this issue is unclear, but it is thought to be due to the fact that near-infrared light, which is normally reflected due to the interference phenomenon of light, is reflected at a wider viewing angle due to the lens effect of the water droplets, resulting in the reflection of light of red wavelengths. In particular, heat-cutting glass for sunroofs is sometimes provided with a colored layer to prevent the temperature inside the vehicle from rising due to sunlight, and water droplets appear colored red or yellow during rain or cleaning, which is undesirable from an appearance perspective.

The objective of the present invention is to solve the above problems and provide a laminate that has excellent heat-shielding properties and can improve appearance and design.

In order to solve the above problems, the present invention has the following configuration. Specifically, the laminate film of the present invention is a laminate having a colored layer on one side of a dielectric multilayer film, and is characterized in that, where Ra is the average reflectance in the wavelength range of 900 to 1000 nm and Rb is the average reflectance in the wavelength range of 400 to 700 nm, Ra is 50% to 100%, the shortest wavelength in the wavelength range of 700 to 900 nm that is the intermediate value between Ra and Rb is 850 nm or longer, and when the surface opposite the colored layer is designated as the X-plane, the water contact angle of the X-plane is 5° to 60°.

The laminated film of the present invention can also be formed into the following embodiments, and can also be used to form laminated glass.
[1] A laminate having a colored layer on one side of a dielectric multilayer film, wherein, when Ra is the average reflectance in a wavelength range of 900 to 1000 nm and Rb is the average reflectance in a wavelength range of 400 to 700 nm, Ra is 50% or more and 100% or less, the shortest wavelength that is the intermediate value between Ra and Rb in the wavelength range of 700 to 900 nm is 850 nm or more, and when the surface opposite to the colored layer is the X-plane, the water contact angle of the X-plane is 5° or more and 60° or less. [2] The laminate according to [1], wherein the saturation of reflected light when the X-plane is irradiated with light is 20 or less.
[3] The laminate according to [1] or [2], wherein the difference between the Ra and the Rb is 20% or more and 90% or less.
[4] The laminate according to any one of [1] to [3], wherein the dielectric multilayer film is a laminate film containing a thermoplastic resin as a main component.
[5] The laminate according to [4], wherein the laminate film has a structure in which at least 51 layers of at least two or more types of layers each having a different thermoplastic resin as a main component are regularly laminated.
[6] The laminate according to any one of [1] to [5], wherein the distance from the X plane to the dielectric multilayer film is 0.001 mm or more and 2.0 mm or less.
[7] The laminate according to any one of [1] to [6], wherein the maximum reflectance Rd at a wavelength of 400 to 830 nm is 0.1% or more and 15% or less.
[8] The laminate according to any one of [1] to [7], wherein a weather-resistant resin layer, the dielectric multilayer film, an adhesive layer, and a colored layer are arranged in this order, and the colored layer is mainly composed of glass or resin.
[9] The laminate according to any one of [1] to [8], wherein a support, an intermediate layer 1, the dielectric multilayer film, an intermediate layer 2, and a colored layer are arranged in this order, and the colored layer and the support are mainly composed of glass or resin.

The present invention provides a laminate that has excellent heat-shielding properties and can improve appearance and design.

The laminate of the present invention is a laminate having a colored layer on one side of a dielectric multilayer film, and is characterized in that, when the average reflectance at wavelengths of 900 to 1000 nm is Ra and the average reflectance at wavelengths of 400 to 700 nm is Rb, Ra is 50% to 100%, the shortest wavelength in the wavelength range of 700 to 900 nm that is the intermediate value between Ra and Rb is 850 nm or longer, and when the surface opposite the colored layer is designated as the X-plane, the water contact angle of the X-plane is 5° to 60°.

While the following describes embodiments of the present invention, the present invention should not be construed as being limited to the following examples. Naturally, various modifications are possible within the scope of the invention, as long as the objectives of the invention can be achieved and the gist of the invention is not deviated from. Furthermore, for the purpose of simplifying the explanation, in cases where a laminate film in which at least two or more layers primarily composed of different thermoplastic resins are regularly laminated is used as the dielectric multilayer film, some explanations will be given using an example in which the dielectric multilayer film uses a laminate film in which two different thermoplastic resin layers (hereinafter referred to as layers A and B) are regularly laminated. However, this should be understood in the same way when the dielectric multilayer film uses a laminate film in which three or more thermoplastic resin layers are used, or two or more different metal layers are used.

In this invention, a dielectric multilayer film refers to a laminate consisting of two or more different layers stacked together, and refers to a multilayer film that has the function of reflecting, transmitting, and absorbing light of a desired wavelength by controlling the thickness of each layer.

The dielectric multilayer film constituting the laminate of the present invention is preferably a laminate film whose main component is a thermoplastic resin. Furthermore, the laminate film preferably has a configuration in which two or more different types of layers are regularly laminated together to form 51 or more layers, and more preferably has a configuration in which at least two or more types of layers whose main components are different thermoplastic resins are regularly laminated together to form 51 or more layers. Here, "main component" refers to a component that accounts for more than 50% by mass but not more than 100% by mass, when the total components constituting the thermoplastic resin layer are taken as 100% by mass. Hereinafter, "main component" can be interpreted in the same way.

"The thermoplastic resin layers are different" refers to a case where, when two thermoplastic resin layers are compared, at least one of the following 1 to 3 applies, and preferably at least the following "2" applies. Note that, when three or more types of thermoplastic resin layers are present, for all of them to be different, it is necessary that, when comparing the two thermoplastic resin layers in any combination, at least one of the following 1 to 3 applies (the same applies when there are four or more types of thermoplastic resin layers). Furthermore, when two or more different types of metal layers are used as layers constituting a dielectric multilayer film, the metal layers are considered to be different if the following 1 or 4 applies.
1: The refractive index differs by 0.01 or more in the main alignment direction (the method for specifying the main alignment direction will be described later).
2: Having different melting points or crystallization temperatures (different melting points or crystallization temperatures means that either the melting point or the crystallization temperature determined by the measurement method described below differs by 3°C or more. Note that cases where one thermoplastic resin layer has a melting point and the other thermoplastic resin layer does not have a melting point, or where one thermoplastic resin layer has a crystallization temperature and the other thermoplastic resin layer does not have a crystallization temperature are also considered to have different melting points or crystallization temperatures).
3: The composition analyzed by nuclear magnetic resonance spectroscopy or gas chromatography mass spectrometry differs by 5% by mass or more.
4: The composition of metal elements analyzed by ICP atomic emission spectrometry differs by 5 mass% or more.

In the dielectric multilayer film constituting the laminate of the present invention, "a structure in which at least two or more layers each having different thermoplastic resins as their main components are regularly stacked in 51 or more layers" refers to a structure in which 51 or more layers of multiple types of thermoplastic resins each having different main components are stacked in the thickness direction with a certain regularity. Specific examples include, for example, when there are two types of thermoplastic resin layers (layers A and B) each having a different main component, structures in which two types of thermoplastic resin layers are alternately stacked in the thickness direction, such as structures A(BA)n and B(AB)n (where the repeating units are in parentheses and n is a natural number representing the number of repeating units; the same applies hereinafter).

Specific examples of dielectric multilayer films that consist of three types of thermoplastic resin layers (A layer, B layer, and C layer) with different main components include an (ABCB)nA structure and an (ABC)nA structure, where A layer, B layer, and C layer are represented as A, B, and C, respectively. By stacking different thermoplastic resin layers in an order like this, the dielectric multilayer film is able to reflect light of a wavelength specified by the relationship between the difference in refractive index of each layer and the layer thickness. Below, unless otherwise specified, such dielectric multilayer films will be described using an example of a structure in which two layers, A layer and B layer, are stacked alternately.

Generally, in a dielectric multilayer film with such a layer structure, the principle of interference reflection dictates that the more layers it contains, the higher the reflectivity, and the wider the layer thickness distribution, the wider the reflection band. Therefore, from the perspective of increasing reflectivity, the total number of regularly stacked layers is preferably 101 or more, and more preferably 401 or more. For the reasons stated above, the greater the total number of layers in the dielectric multilayer film, the better. However, from the perspective of preventing increased manufacturing costs due to the larger manufacturing equipment as the number of layers increases, and preventing deterioration in handleability due to the thickness of the dielectric multilayer film itself, the practical range is 1001 layers or less.

From the perspective of using the laminate of the present invention in heat ray reflection applications, it is important that Ra, where Ra is the average reflectance in the wavelength range of 900 to 1000 nm, is 50% or more and 100% or less. Sunlight has an intensity distribution mainly in the visible light range, and as the wavelength increases, this intensity distribution tends to narrow. However, for use in applications requiring high colorless transparency, such as heat ray-blocking glass, it is necessary to achieve both colorless transparency and high heat ray-blocking performance. In this way, by efficiently reflecting light with wavelengths of 900 to 1000 nm, which is slightly longer than the visible light range, a laminate can be created that combines transparency and high heat ray-blocking performance.

From the above perspective, the laminate of the present invention more preferably has an Ra of 65% or more and 100% or less, and even more preferably 80% or more and 100% or less. By adopting such an embodiment, it is possible to impart high heat-shielding properties to the laminate of the present invention.

To obtain such a laminate, it is effective to increase the difference in in-plane refractive index between two or more thermoplastic resin layers or metal layers with different optical properties used in the dielectric multilayer film. For example, when using a biaxially stretched film having a configuration in which two types of thermoplastic resin layers are alternately laminated as the dielectric multilayer film, the dielectric multilayer film may be formed by alternately laminating layers primarily composed of a crystalline thermoplastic resin and layers primarily composed of a thermoplastic resin that can maintain its amorphous nature even when stretched or that melts in a heat treatment process. (In other words, a dielectric multilayer film is preferably formed by alternately laminating layers primarily composed of a crystalline thermoplastic resin and layers primarily composed of a thermoplastic resin that can maintain its amorphous nature even when stretched or that melts in a heat treatment process.) It is also effective to set the in-plane stretch ratio (the product of the stretch ratio in the machine direction (the film transport direction, also referred to as the longitudinal direction) and the stretch ratio in the transverse direction (the direction in the film plane perpendicular to the transport direction, also referred to as the width direction)) to 9.0 times or more and to increase the number of layers.

Here, the in-plane refractive index is the average of the refractive index in the main orientation direction and the refractive index in the direction perpendicular to the main orientation direction within the film plane. If the thermoplastic resin layer that is not located on the outermost surface is primarily composed of an amorphous thermoplastic resin, the in-plane refractive index can be determined in any two perpendicular directions within the plane using a sheet obtained by vacuum drying and then pressing the amorphous thermoplastic resin. This is because amorphous resins typically do not have birefringence, and the refractive index in each direction does not change depending on whether or not the resin is stretched.

The refractive index can be measured using a laser with a wavelength of 632.8 nm. A measuring device such as the SPA-4000 manufactured by SAIRON TECHNOLOGY, INC. can be used. The main orientation direction is the direction with the greatest degree of molecular orientation, and the degree of molecular orientation can be measured using, for example, a molecular orientation analyzer MOA-2001 manufactured by KS Systems Co., Ltd. (now Oji Scientific Instruments Co., Ltd.). When the dielectric multilayer film is a biaxially stretched film, the direction with the greatest stretch ratio is usually the main orientation direction. When the dielectric multilayer film is made of an amorphous resin or metal film and there is no molecular orientation, the degree of orientation will be approximately the same regardless of the angle, so there is no need to specify the main orientation direction. However, even in this case, the direction with the greatest degree of orientation measured by the molecular orientation analyzer can be treated as the main orientation direction.

As used here, "crystalline" refers to a heat of fusion of 5 J/g or more in differential scanning calorimetry (DSC). Similarly, "amorphous" refers to a heat of fusion of less than 5 J/g. Crystalline thermoplastic resins can be oriented and crystallized during the stretching and heat treatment processes to achieve a higher in-plane refractive index than in the amorphous state before stretching. Meanwhile, in the case of amorphous thermoplastic resins, heat treatment at a temperature far above the glass transition temperature during the heat treatment process can significantly alleviate any slight orientation that occurs during the stretching process, allowing the low refractive index of the amorphous state to be maintained. This layer structure makes it easy to create a refractive index difference between the crystalline thermoplastic resin and the amorphous thermoplastic resin during the stretching and heat treatment processes in the manufacture of dielectric multilayer films.

When the dielectric multilayer film is made into a laminate film having a structure in which two types of layers whose main components are thermoplastic resins with different crystallinity are alternately laminated, it is preferable that the outermost layers on both sides be layers with relatively high crystallinity (layers whose main component is a crystalline thermoplastic resin) in order to prevent adhesion to rolls, etc. during film production. Below, a laminate film having such a structure will be described, and unless otherwise specified, the layer with relatively high crystallinity will be referred to as Layer A and the layer with low crystallinity will be referred to as Layer B.

In such a laminated film, it is preferable that the optical thicknesses of the adjacent A layer and B layer simultaneously satisfy the following formulas (1) and (2).
Formula (1): λ/m=2(n _α d _α cosθa+n _β d _β cosθb)
Equation (2): n _α d _α = n _β d _β .

Here, λ is the reflection wavelength, _nα is the in-plane refractive index of layer A, _dα is the thickness of layer A, θa is the angle of light incident on layer A (incidence angle), _nβ is the in-plane refractive index of layer B, _dβ is the thickness of layer B, θb is the angle of light refracted in layer B (refraction angle), and m is the order, a natural number. By having a layer thickness distribution that simultaneously satisfies both formulas (1) and (2), the laminate film can eliminate even-order reflections. This allows for a high average reflectance in the 900-1000 nm wavelength range while lowering the average reflectance in the visible light range of 400-830 nm, making it particularly easy to achieve a maximum reflectance Rd of 0.1% or more and 15% or less in the 400-830 nm wavelength range. As a result, a laminate film with excellent transparency and heat-blocking performance can be obtained. The layer structure and number of layers of such a laminated film can be identified by observing a cross section in the direction perpendicular to the film surface (thickness direction) with a transmission electron microscope (TEM), and the thickness of each layer can be measured using the length measurement function of the TEM (details will be described later).

Generally, when a thermoplastic resin is formed into a sheet and stretched, the in-plane refractive index of the laminate film surface is approximately 1.4 to approximately 1.9. Therefore, by setting the thickness ratio of adjacent layers A and B (layer A thickness/layer B thickness) to between 0.7 and 1.4, a laminate film that suppresses even-order reflections can be obtained. Therefore, from the above perspective, the thickness ratio of adjacent layers A and B (layer A thickness/layer B thickness) is preferably between 0.7 and 1.4, and more preferably between 0.8 and 1.2. By setting the thicknesses of adjacent layers A and B within this range, it becomes easy to achieve a maximum reflectance Rd of 15% or less in the wavelength range of 400 to 830 nm (described below). As a result, reflection in the visible light region of the dielectric multilayer film can be suppressed, reducing coloring and glare.

When the average reflectance in the wavelength range of 900 to 1000 nm is Ra and the average reflectance in the wavelength range of 400 to 700 nm is Rb, it is important that the shortest wavelength that is the midpoint between Ra and Rb is 850 nm or longer. As mentioned above, when using the laminate in applications requiring high colorless transparency, such as heat-blocking glass, it is preferable to achieve both colorless transparency and high heat-blocking properties, so a high Ra and a low Rb are required.

On the other hand, if the shortest wavelength, which is the midpoint between Ra and Rb, is lower than 850 nm, the reflected wavelength becomes shorter when the laminate is observed obliquely, as shown in formula (1) above. This makes it easier to reflect light with yellow to red wavelengths between 600 and 800 nm, resulting in a yellow to orange coloration. Furthermore, when water droplets adhere to the surface of such a laminate, the angle of incidence, as shown in formula (1), becomes smaller, further shortening the reflected wavelength and making it easier to reflect light with yellow to red wavelengths between 600 and 800 nm, resulting in a more intense coloration. In other words, ensuring that the shortest wavelength, which is the midpoint between Ra and Rb, is 850 nm or longer reduces the phenomenon of the laminate appearing colored, which occurs due to the above mechanism. Ra, Rb, and other reflectances and transmittances can be measured using a known spectrophotometer; details of the measurement method are described below.

The inventors prepared laminate films with different reflection wavelength bands and water contact angles and thoroughly investigated the relationship between the coloring of water droplets. As a result, they found that, from the perspective of suppressing the coloring of attached water droplets, the shortest wavelength that is the midpoint between Ra and Rb is preferably 870 nm or longer, and even more preferably 890 nm or longer. To ensure that the shortest wavelength that is the midpoint between Ra and Rb is 850 nm or longer or within the above preferred range, it is effective to adjust the thickness, layer thickness distribution, and in-plane refractive index of Layer A and Layer B so that the reflection wavelength of Formula (1) is 850 nm or longer or within the above preferred range.

For the same reasons as above, it is preferable that the laminate of the present invention have a maximum reflectance Rd of 0.1% or more and 15% or less in the wavelength range of 400 to 830 nm. It is difficult to achieve an Rd lower than 0.1% due to reflection at the interface between the materials. On the other hand, by setting Rd to 15% or less, it becomes easier to set the saturation of reflected light when irradiating the X surface (described below) with light to 20 or less, and it also reduces coloring caused by the shift of reflection at a wavelength around 830 nm to lower wavelengths when water droplets adhere. From the above perspective, Rd is more preferably 0.1% or more and 13% or less, and even more preferably 0.1% or more and 11% or less.

To achieve an Rd of 0.1% or more and 15% or less, or within the preferred range described above, it is effective to use a laminate film in which two different thermoplastic resin layers (layers A and B) are regularly laminated in a dielectric multilayer film, and adjust the thickness, layer thickness distribution, and in-plane refractive index of layers A and B so that the reflection wavelength of formula (1) above is 830 nm or more and the reflectance at wavelengths of 400 to 830 nm is low.

From the viewpoint of achieving both colorless transparency and high heat-shielding properties, the laminate of the present invention preferably has a difference between Ra and Rb of 20% or more and 90% or less. A difference between Ra and Rb of 20% or more enables both colorless transparency and high heat-shielding properties to be achieved. On the other hand, taking into account reflection at the interface between air and the laminate, the upper limit of the difference between Ra and Rb is 90%. From the above viewpoint, the difference between Ra and Rb is more preferably 50% or more and 90% or less, and even more preferably 68% or more and 90% or less.

One method for achieving a difference between Ra and Rb of the laminate of the present invention of 20% to 90% or within the above-mentioned preferred range is, for example, to use a laminate film in which two different thermoplastic resin layers (layers A and B) are regularly laminated in a dielectric multilayer film, and adjust the number of layers in the regularly laminated portion. More specifically, by increasing the number of layers, the difference between Ra and Rb can be increased, and Ra can be particularly increased. Furthermore, by setting the thickness ratio of the aforementioned adjacent layers A and B (thickness of layer A/thickness of layer B) to 0.7 to 1.4, the difference between Ra and Rb can be increased, and Rb can be particularly reduced.

When a laminate film having a structure in which layers A and B are alternately laminated is used as the dielectric multilayer film of the present invention, where the main component of layer A is thermoplastic resin A and the main component of layer B is thermoplastic resin B, polyester resin, acrylic resin, polycarbonate resin, etc. can be used as thermoplastic resin A and thermoplastic resin B. Among these, polyester resins are preferably used as thermoplastic resin A and thermoplastic resin B because of their excellent transparency and formability. Furthermore, when the laminate film further has a layer C structure and the main component of layer C is thermoplastic resin C, it is preferable that thermoplastic resin C is also a polyester resin. Here, polyester resin refers to a polymer obtained by condensation polymerization of a dicarboxylic acid component and a diol component.

In the dielectric multilayer film of the present invention, examples of dicarboxylic acid units in the polyester resins used for thermoplastic resin A, thermoplastic resin B, and thermoplastic resin C include structural units such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acids (1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid), 4,4'-diphenyldicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid, and their ester-forming derivatives.

Examples of diol units in the polyester resin include structural units such as ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, diethylene glycol, polyalkylene glycol, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, isosorbate, 1,4-cyclohexanedimethanol, spiroglycol, neopentyl glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, triethylene glycol, tetraethylene glycol, polytetramethylene ether glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, tributylene glycol, tetrabutylene glycol, and ester-forming derivatives thereof.

Preferably, the dicarboxylic acid units constituting the polyester resin include structural units such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, and isophthalic acid. Preferably, the diol units include structural units such as ethylene glycol, 1,4-cyclohexanedimethanol, polyalkylene glycol, polyethylene glycol, tetraethylene glycol, and polytetramethylene ether glycol.

A preferred embodiment of the laminate film used in the dielectric multilayer film in the laminate of the present invention is one in which the in-plane refractive index of at least one surface of the dielectric multilayer film is 1.68 or more and 1.80 or less. Generally, it is preferable for the surface layer to be a layer with relatively high crystallinity, taking into account factors such as ease of film formation. However, by ensuring that the in-plane refractive index of this surface layer is 1.68 or more, the difference in in-plane refractive index between the surface layer and the layer with relatively low crystallinity can be increased. This makes it easier to achieve an average reflectance Ra of 50% or more and 100% or less at wavelengths of 900 to 1000 nm. On the other hand, by ensuring that the in-plane refractive index of the surface layer is lower than 1.80, deterioration of the adhesion between the two alternating layers is suppressed, reducing clouding of the dielectric multilayer film and delamination at the interface.

From the above perspectives, it is preferable that the thermoplastic resin A used in the dielectric multilayer film of the laminate of the present invention is a crystalline polyester resin whose main structural unit is naphthalenedicarboxylic acid units. This configuration increases the reflectivity on the surface of Layer A and makes it easier to achieve a refractive index difference with Layer B, resulting in a laminate film with superior reflective performance. Note that "having naphthalenedicarboxylic acid units as the main structural unit" means that naphthalenedicarboxylic acid units account for more than 50 mol % and no more than 100 mol % of all dicarboxylic acid structural units of the polyester resin.

When thermoplastic resin A is a crystalline polyester resin whose main structural unit is naphthalenedicarboxylic acid units, examples of the naphthalenedicarboxylic acid structural unit include 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,3-naphthalenedicarboxylic acid, with 2,6-naphthalenedicarboxylic acid being particularly preferred. Furthermore, when thermoplastic resin B is an amorphous thermoplastic resin, the more naphthalenedicarboxylic acid units there are in thermoplastic resin A, the easier it is to increase the refractive index difference between layers A and B.

From the above viewpoints, when thermoplastic resin A is a crystalline polyester resin having naphthalenedicarboxylic acid units as the main structural unit, the naphthalenedicarboxylic acid units more preferably account for 80 mol% to 100 mol%, and even more preferably 95 mol% to 100 mol% of the dicarboxylic acid units in thermoplastic resin A. From the same viewpoints, the content of thermoplastic resin A in layer A is preferably 80 mol% to 100 mol%, and more preferably 95 mol% to 100 mol%, when the entire layer is taken as 100 mol%.

In such a laminate film, the difference in in-plane refractive index between Layer A and Layer B is preferably 0.05 or more. It is more preferably 0.12 or more, and even more preferably 0.14 or more and 0.35 or less. When the difference in average in-plane refractive index is 0.05 or more, it becomes easy to achieve an average reflectance Ra of 50% or more and 100% or less at wavelengths of 900 to 1000 nm. One way to achieve this is to use a crystalline polyester resin as the main component of Layer A and an amorphous thermoplastic resin as the main component of Layer B. In this case, it becomes easy to achieve a refractive index difference during the stretching and heat treatment processes in the production of the laminate film.

From the perspective of increasing reflectivity, a larger difference in the in-plane refractive index between Layer A and Layer B is preferable; however, increasing the difference in in-plane refractive index requires that the chemical structures of the thermoplastic resins that are the main components of both layers be significantly different, which would result in poor interlayer adhesion. With this in mind, keeping the difference in the average in-plane refractive index between Layer A and Layer B to 0.35 or less facilitates lamination and improves the heat resistance and handleability of the resulting laminated film.

In the dielectric multilayer film constituting the laminate of the present invention, metal layers may be used as layers A and B. A dielectric multilayer film having a metal layer may have a multilayer structure in which metal layers and metal oxide layers are alternately stacked. Examples of materials constituting the metal layer include metals such as gold (Au), silver (Ag), copper (Cu), and aluminum (Al), as well as alloys made of these metals.

Among these, Ag or its alloys are particularly preferred, as they offer excellent visible light transmission and infrared reflection properties. Using Ag alloys can further reduce defects such as deterioration due to reactions with sulfur and oxygen, and aggregation that occurs during metal layer formation. Ag alloys containing at least one of Au, Cu, platinum (Pt), palladium (Pd), bismuth (Bi), nickel (Ni), magnesium (Mg), neodymium (Nd), ruthenium (Ru), Al, and zinc (Zn) in amounts greater than 0.05% by mass and less than 3.0% by mass are preferred, as they facilitate improved visible light transmission, infrared reflection, and corrosion resistance. The above elements added to silver are preferably in a total amount greater than 0.05% by mass and less than 3.0% by mass, based on the total alloy weight (100% by mass). Adding more than 0.05% by mass of these elements facilitates corrosion resistance, while adding less than 3.0% by mass facilitates maintaining infrared reflection properties due to free electrons.

It is preferable to use a metal oxide having a higher refractive index as the other metal layer to be laminated with the above metal layer. Examples of metal oxides include zinc oxide (ZnO)-based (which may be doped with Al, gallium (Ga), boron (B), indium (In), yttrium (Y), scandium (Sc), fluorine (F), vanadium (V), silicon (Si), germanium (Ge), titanium (Ti), zirconium (Zr), hafnium (Hf), etc.), tin oxide (SnO ₂ )-based (which may be doped with F, antimony (Sb), niobium (Nb), tantalum (Ta), etc.), indium oxide (In ₂ O ₃ )-based (which may be doped with tin (Sn), Ge, molybdenum (Mo), F, Ti, Zr, Hf, Nb, Ta, tungsten (W), tellurium (Te), etc.), and gallium oxide (Ga ₂ O _{3 ).} )-based (which may be doped with Sn or the like as a dopant), zirconium oxide ( _ZrO2 ) (which may contain Cu and Al as additives), titanium oxide ( _TiO2 ) (which may contain Cu and Al as additives), etc. can be used, and from the above-mentioned viewpoint, it is preferable to use SnO2 _- based, _{In2O3 -} based, and TiO2 _-based materials.

Metal layers and metal oxide layers can be formed by vacuum deposition (induction heating, electron beam heating), pulsed laser deposition, magnetron sputtering, and other sputtering methods. Metal oxide layers can also be formed by chemical vapor deposition (CVD) and metal-organic chemical vapor deposition (MOCVD). Furthermore, if the substrate on which the metal or metal oxide layer is formed is a long film or film-like material, they can also be formed using roll-to-roll vacuum deposition or sputtering.

It is important that the laminate of the present invention has a colored layer on one side of the dielectric multilayer film. In the present invention, the colored layer refers to a layer containing 1% by mass or more of the absorbent described below in the entire layer. The colored layer may be laminated directly to the dielectric multilayer film, or may be laminated to the dielectric multilayer film via an adhesive layer, an intermediate layer, a support, a weather-resistant resin layer, or the like. Preferred configurations include a configuration in which the support 1, intermediate layer, dielectric multilayer film, colored layer, and support 2 are arranged in this order, or a configuration in which the support, intermediate layer 1, dielectric multilayer film, intermediate layer 2, and colored layer are arranged in this order. This configuration is particularly suitable for use in automobile sunroofs, etc. Another preferred configuration is a configuration in which the weather-resistant resin layer, dielectric multilayer film, adhesive layer, and colored layer are arranged in this order. This configuration enables the laminate to be used in applications exposed to sunlight without using a configuration such as laminated glass with multiple supports, which is preferable from the standpoints of manufacturing cost and weight reduction. By configuring the laminate in this way and positioning the dielectric multilayer film on the outer side (sun side) of the colored layer, light such as sunlight is reflected by the dielectric multilayer film, and the light that is not reflected is absorbed by the colored layer, reducing the amount of infrared light absorbed by the colored layer and reducing heat generation and re-radiation by the colored layer. In the above configuration, supports 1 and 2 and intermediate layers 1 and 2 may be the same or different.

The laminate of the present invention preferably has an L* value in transmission of 1 or more and 40 or less. For example, when the laminate is used in an automobile sunroof, black or smoked colors are typically used to reduce glare and temperature rise caused by sunlight shining through the sunroof, and to protect privacy inside the vehicle. From the perspective of achieving the above objectives, the L* value is more preferably 30 or less, and even more preferably 20 or less. On the other hand, an L* value of 1 or more makes it easier to ensure sufficient visibility when viewing the outside from inside the vehicle. Furthermore, in recent years, light-controlling glass has been used as a sunroof, and when the laminate is such light-controlling glass, it is preferable that the L* value when the switch is turned OFF falls within the above range. The L* value can be measured using a known spectrophotometer; detailed measurement methods are described below.

To achieve an L* value between 1 and 40 or within the preferred range described above, it is effective to adjust the concentration of the absorber contained in the colored layer. Absorbers used in the colored layer include carbon black, titanium black, copper oxide, black pigments, black metals, and metal compounds, and these may be used alone or in combination. Examples of absorbers with coloring functionality include azo pigments, polycyclic pigments, lake pigments, nitro pigments, nitroso pigments, aniline black, alkali blue, phthalocyanine pigments, cyanine pigments, azo dyes, anthraquinone dyes, quinophthalone dyes, methine dyes, condensed polycyclic dyes, reactive dyes, and cationic dyes. Examples of absorbers with infrared absorption functionality include tungsten compounds, lanthanum compounds, antimony compounds, indium compounds, and tin compounds, with carbon black and tungsten oxide compounds being preferred. While these absorbers are preferably contained in the colored layer, they may also be added to materials used as adhesive layers, intermediate layers, or supports, as described below. Additionally, instead of metal layers that are easily stained, it is also effective to use a laminate film having an alternating stack of A and B layers as the dielectric multilayer film, and to set the thickness ratio of adjacent A and B layers (thickness of A layer/thickness of B layer) to 0.7 or more and 1.4 or less.

Supports for obtaining the laminate of the present invention include, for example, resins, metals, glass, ceramics, etc. The support may be flat or curved and may have any shape. Examples of resins used for the support include polycarbonate, cyclic polyolefins, acrylic resins such as polyarylate, polyethylene terephthalate, and polymethyl methacrylate, ABS resins, and triacetyl cellulose. These may be used alone or in combination. Examples of glass used for the support include float glass, tempered glass, colored glass, and heat-shielding glass. Considering its use for heat reflection purposes, the support is preferably transparent, but may also contain the aforementioned absorbent or a colorant described below. The thickness of the support is preferably 0.05 mm to 5 mm from the viewpoint of achieving both strength and weight reduction. Furthermore, when the laminate includes multiple supports, these supports may be the same or different.

The intermediate layer serves to bond the dielectric multilayer film of the present invention to the support, colored layer, etc. Examples of adhesives suitable for use as the intermediate layer include vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate copolymers, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, polyvinyl ether, nitrile rubbers, styrene-butadiene rubbers, natural rubbers, chloroprene rubbers, polyamides, epoxy resins, polyurethanes, acrylic resins, cellulose, polyvinyl chloride, polyacrylic esters, and polyisobutylene. These adhesives, either in film form or formed on the surface of a film, can also be used as an adhesive. These adhesives may also contain additives such as viscosity adjusters, plasticizers, heat stabilizers, antioxidants, UV absorbers, antistatic agents, lubricants, colorants, and crosslinking agents. When multiple intermediate layers are included in a laminate, these intermediate layers may be the same or different. By providing an intermediate layer, it is possible to improve the adhesion between the support or the like and the dielectric multilayer film, as well as the design, durability, weather resistance, impact resistance, and other functions of the laminate. Furthermore, from the perspective of improving processability and adhesion as an intermediate layer, it is preferable that the thickness of the intermediate layer be 10 μm to 1 mm.

The weather-resistant resin layer in the laminate of the present invention is a resin layer provided primarily for the purpose of protecting the dielectric multilayer film, and is preferably a resin layer that has ultraviolet absorbing properties. There are no particular limitations on the resin that forms the weather-resistant resin layer, and for example, acrylic resin, urethane resin, polyester resin, silanol, etc. can be used alone or in combination.

Taking acrylic resins as an example, it is preferable to use, alone or in combination, 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 acrylate, glycidyl acrylate, glycidyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether, 4-hydroxybutyl methacrylate glycidyl ether, phenyl glycidyl acrylate, epoxy acrylate, epoxy methacrylate, dipentaerythritol hexaacrylate, etc.

It is also preferable to polymerize a hydrophilic monomer into these acrylic resins to impart hydrophilicity, and for example, it is preferable to polymerize a radically polymerizable vinyl monomer. Examples of hydrophilic radically polymerizable vinyl monomers include hydroxyacrylic acid esters such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate; glycol esters such as ethylene glycol acrylate, ethylene glycol methacrylate, polyethylene glycol acrylate, and polyethylene glycol methacrylate; acrylamide compounds such as acrylamide, methacrylamide, N-methylolacrylamide, and methoxymethylolacrylamide; cationic monomers such as aminoalkyl acrylate, aminoalkyl methacrylate esters, and their quaternary ammonium salts; glycidyl acrylate compounds such as glycidyl acrylate and glycidyl methacrylate; and unsaturated acids and their salts, such as acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, and crotonic acid. These monomers may be polymerized singly or in combination.

Acrylic resins are also preferably formulated with initiators, curing agents, catalysts, etc., as this further accelerates curing. Initiators that can initiate or accelerate polymerization, condensation, or crosslinking reactions through anionic, cationic, or radical reactions are preferred. A variety of initiators, curing agents, and catalysts can be used. Among these, photopolymerization initiators are preferred, and alkylphenone compounds are preferred from the standpoint of curability. Specific examples of alkylphenone compounds include 1-hydroxy-cyclohexyl-phenyl-ketone, 2.2-dimethoxy-1.2-diphenylethane-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-phenyl)-1-butane, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-(4-phenyl)-1-. butane, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butane, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butane, 1-cyclohexyl-phenyl ketone, 2-methyl-1-phenylpropan-1-one, 1-[4-(2-ethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, etc. Examples of UV absorbers used in the weather-resistant resin layer include benzotriazole-based, benzophenone-based, benzoate-based, triazine-based, benzoxazinone-based, salicylic acid-based, and indole-based UV absorbers, with benzotriazole-based and triazine-based UV absorbers being preferred.

Molding methods for obtaining laminates using the above-mentioned support, intermediate layer, dielectric multilayer film, and colored layer include extrusion lamination, hot-melt lamination, thermal lamination, press lamination, vacuum lamination, and autoclave lamination. Extrusion lamination is a method in which the molten resin compositions for the dielectric multilayer film and intermediate layer are extruded from a die into a film shape and laminated onto the support, and then the molded product is passed between two rolls for molding. Hot-melt lamination is a molding method in which a thermally melted resin composition for forming the intermediate layer is applied to the dielectric multilayer film or support, and the dielectric multilayer film and support are laminated together. Thermal lamination is a molding method in which the dielectric multilayer film, intermediate layer sheet, and support are heated and pressed together with a heated roll. Press lamination is a molding method in which the dielectric multilayer film, intermediate layer sheet, and support are heated and pressed together with a press. Vacuum lamination is a molding method in which a dielectric multilayer film, intermediate layer sheets, and support are heated, then the inside of the device is evacuated and the films are pressed and laminated. Autoclave lamination is a lamination method in which a dielectric multilayer film, intermediate layer sheets, and support are heated, then the inside of the device is pressurized with gas or the like to laminate the films. Of these, press lamination, vacuum lamination, and autoclave lamination are preferably used.

When the surface opposite the colored layer of the laminate of the present invention is designated as the X-plane, it is important that the water contact angle of the X-plane be 5° or more and 60° or less. The inventors have thoroughly investigated the relationship between the reflection wavelength and the phenomenon of water droplets appearing colored. As a result, they have discovered that, as shown in formula (1) above, the effect of shortening the reflection wavelength when observed from an angle, making it easier to reflect light with wavelengths from yellow to red in the 600 to 800 nm wavelength range, becomes more pronounced as the water contact angle increases. The mechanism behind this is unclear, but it is speculated that it is because the angle of incidence and the angle of refraction in formula (1) above increase as the contact angle of the water droplet increases.

If the water contact angle of the X surface is higher than 60°, the water droplets will increase the angle of incidence as determined by formula (1), causing the water droplets to appear yellow to red, which is undesirable. Since the smaller the water contact angle of the X surface, the more mitigated the coloring. Therefore, the water contact angle of the X surface is preferably 50° or less, more preferably 40° or less, and particularly preferably 30° or less. If the water contact angle of the X surface is 30° or less, the coloring phenomenon caused by water droplets adhering to the X surface will almost completely disappear. On the other hand, if the water contact angle of the X surface is less than 5°, it will be difficult to remove water droplets adhering to the X surface when used in automobiles or window glass. Here, the "surface opposite the colored layer" refers to the outermost surface of the dielectric multilayer film opposite the side on which the colored layer is located, and this is the X surface. The water contact angle in this invention can be measured as the water contact angle of pure water after leaving the film in an atmosphere at room temperature of 23°C and a relative humidity of 65% for 24 hours. The detailed measurement method will be described later.

To achieve a water contact angle of 5° to 60° or within the preferred range described above, it is effective to use a highly hydrophilic material for forming the X-face. Generally, automobile sunroofs and windowpanes are coated with a water-repellent coating to increase the water contact angle above 60° in order to reduce staining caused by water droplets. However, this technique cannot be used in the present invention, which uses a dielectric multilayer film, due to the aforementioned discoloration caused by water droplets. For example, when a substrate or a coating layer on the substrate is located on the X-face of the laminate, polycarbonate is preferably used in automobile sunroof applications to reduce the vehicle's weight and center of gravity and improve processability. When using polycarbonate as the substrate, the water contact angle of the surface of these layers (corresponding to the X-face) can be increased to 5° to 60° by providing a hydrophilic hard coat layer (e.g., acrylic resin layer, polyester resin layer, urethane resin layer) on the surface or by forming a photocatalytic layer (e.g., titanium oxide layer, tin oxide layer) on the surface. Plasma treatment or corona discharge treatment is also effective in adjusting the water contact angle of the X surface to between 5° and 60°. When a weather-resistant resin layer is located on the outermost surface opposite the colored layer, it is preferable to use a resin in which the aforementioned hydrophilic monomer has been polymerized for the weather-resistant resin layer in order to adjust the water contact angle of the X surface to between 5° and 60°. For example, it is preferable to use a resin in which a radically polymerizable vinyl monomer has been polymerized. Even when glass is used as the support, the water contact angle of the X surface can be adjusted to between 5° and 60° by forming the aforementioned hydrophilic hard coat layer or photocatalytic layer.

The laminate of the present invention preferably has a saturation of 20 or less when the X surface is irradiated with light. As described above, the colored layer is preferably black, and therefore, when used as a sunroof, low saturation is required when viewed from outside the vehicle. Furthermore, from the perspective of suppressing the phenomenon of visible coloration when water droplets adhere, as described below, it is preferable to lower the saturation of the laminate itself. If the saturation of the reflected light when the X surface is irradiated with light is lower than 20, the coloring will be less noticeable when viewed from the X surface. From the above perspectives, the saturation is more preferably 15 or less, even more preferably 10 or less, and particularly preferably 5% or less.

In order to keep the saturation of the reflected light when light is irradiated onto the X surface at 20 or less or within the above preferred range, it is effective to use, for example, a laminated film that simultaneously satisfies the above formulas (1) and (2) as the dielectric multilayer film. Furthermore, when a metal layer is used as the dielectric multilayer film, the saturation of the reflected light can be reduced by using a light-colored component or by reducing the thickness. The saturation of the reflected light can be measured using a spectrophotometer; details of this measurement method are described below.

In the laminate of the present invention, the distance from the X surface to the dielectric multilayer film is preferably 0.001 mm or more and 2.0 mm or less. This configuration makes it possible to reduce the coloring that occurs when water droplets adhere to the X surface of the laminate. While the reason for this is unclear, it is believed that the longer the distance from the X surface to the dielectric multilayer film, the greater the angle of incidence of light incident on the dielectric multilayer film, making it easier to reflect light with wavelengths of 600 to 800 nm, from yellow to red. When the distance from the X surface to the dielectric multilayer film is 0.001 mm or more, the thickness of the member responsible for protecting the dielectric multilayer film is ensured. On the other hand, when the distance from the X surface to the dielectric multilayer film is 2.0 mm or less, the distance from the X surface to the dielectric multilayer film is shortened, thereby effectively reducing the coloring that occurs when water droplets adhere to the dielectric multilayer film. To achieve a distance from the X surface to the dielectric multilayer film of 0.001 mm or more and 2.0 mm or less, it is effective to keep the total thickness of the members located between the X surface and the dielectric multilayer film within the above range.

Next, a preferred method for manufacturing a laminate film that can be suitably used as the dielectric multilayer film of the laminate of the present invention will be described below using an example in which a crystalline polyester resin is used as thermoplastic resin A (layer A) and an amorphous polyester resin is used as thermoplastic resin B (layer B). Of course, the present invention is not limited to this example. Furthermore, the formation of the laminate film's layer structure can be achieved by referring to the description in paragraphs [0053] to [0063] of JP 2007-307893 A. The same can be said for a laminate film consisting of three types of layers, including layer C.

First, thermoplastic resins A and B are prepared in the form of pellets or other materials. If necessary, the pellets are dried in hot air or under vacuum and then fed into separate extruders. In the extruder, thermoplastic resin A is heated and melted at a temperature above its melting point, while thermoplastic resin B is heated and melted at a temperature within ±30°C of the heating temperature of thermoplastic resin A (this temperature range may be adjusted as needed to prevent uneven extrusion). The molten thermoplastic resins are then extruded using a gear pump or other device to equalize the extrusion rate, and foreign matter and denatured resins are removed using a filter or other device. These molten thermoplastic resins are laminated into the desired layer configuration using a lamination device, molded into the desired sheet shape using a die, and then discharged onto a casting drum. The multilayered molten sheet discharged from the die is then extruded onto a cooling body such as a casting drum and cooled to solidify, resulting in a cast film. Preferably, wire, tape, needle, or knife-shaped electrodes are used to electrostatically contact the casting drum or other cooling body for rapid solidification. Also preferred are methods in which air is blown from a slit-, spot-, or planar-shaped device to bring the molten sheet into close contact with a cooling body such as a casting drum, or methods in which the molten sheet is brought into close contact with a cooling body using nip rolls to bring the molten sheet into close contact with a cooling body. The surface temperature of the cooling body such as a casting drum is preferably 5°C or higher and 30°C or lower, from the viewpoint of rapidly cooling and solidifying the molten sheet.

While a multi-manifold die, feed block, static mixer, or other lamination device can be used, it is particularly preferable to use a feed block containing at least two separate members with numerous fine slits to efficiently achieve the configuration of the present invention. Using such a feed block prevents the device from becoming excessively large, reduces the amount of foreign matter caused by thermal degradation, and enables highly accurate lamination even when an extremely large number of layers are stacked. Furthermore, lamination accuracy in the width direction is significantly improved compared to conventional technology. Furthermore, with such a device, the thickness of each layer can be adjusted by the shape (length, width) of the slits, making it easy to achieve any desired layer thickness.

The cast film thus obtained is then preferably biaxially stretched. Here, biaxial stretching refers to stretching in the longitudinal and width directions. Stretching may be performed in two directions sequentially, or simultaneously. Further re-stretching may be performed in the longitudinal and/or width directions. The longitudinal direction refers to the running direction of the film, and the width direction refers to the direction perpendicular to the longitudinal direction within the film plane.

First, we will explain the case of sequential biaxial stretching. Here, stretching in the longitudinal direction (longitudinal stretching) refers to stretching to impart longitudinal molecular orientation to the film, and is usually performed by varying the peripheral speed of the rolls. This stretching can be performed in a single stage, or in multiple stages using multiple pairs of rolls. The stretching ratio varies depending on the type of thermoplastic resin constituting the laminate film, but is typically preferably 2.0 to 9.0 times. When a polyethylene naphthalate copolymer resin is used as one of the thermoplastic resins constituting the laminate film, a ratio of 2.0 to 7.0 times is preferred, with 3.0 to 3.8 times being more preferred. The film surface temperature during stretching should preferably be in the range of the glass transition temperature of the resin with the higher glass transition temperature constituting the laminate film to the glass transition temperature + 100°C.

The uniaxially stretched film obtained in this manner may be subjected to surface treatment such as corona treatment, flame treatment, or plasma treatment as needed, and then imparted with properties such as easy slip, easy adhesion, and antistatic properties by in-line coating.

Stretching in the width direction (transverse stretching) refers to stretching to impart widthwise orientation to the film. Typically, a tenter is used to convey the uniaxially stretched film while holding both ends with clips, stretching it in the width direction. The stretching ratio varies depending on the type of resin, but is typically 2.0 to 9.0 times. When a polyethylene naphthalate copolymer resin is used as one of the resins constituting the laminate film, a ratio of 2.0 to 7.0 times is preferred, with 3.7 to 4.2 times being more preferred. The in-plane stretching ratio, which is the product of the longitudinal stretching ratio and the transverse stretching ratio, is preferably 12.0 to 18.0 times. The stretching temperature is preferably in the range of the glass transition temperature of the resin with the higher glass transition temperature constituting the laminate film to the glass transition temperature + 120°C.

To impart flatness and dimensional stability to the biaxially stretched film obtained in this manner, it is preferable to subject it to heat treatment in a tenter at a temperature above the stretching temperature and below the melting point of thermoplastic resin A. Heat treatment improves the dimensional stability of the resulting laminated film. After heat treatment in this manner, the laminated film is gradually cooled uniformly at a temperature above the glass transition temperature of thermoplastic resin A but below the heat treatment temperature, then cooled to room temperature and wound up. Furthermore, additional stretching or relaxation treatment of 0.1% to 10% may be performed during the period from heat treatment to slow cooling.

In addition, in the laminate film of the present invention, the heat treatment temperature after stretching is preferably set to a temperature below the melting point of thermoplastic resin A and above the melting point of thermoplastic resin B. In this case, thermoplastic resin A maintains a high degree of orientation while the orientation of thermoplastic resin B is relaxed, making it easy to achieve a refractive index difference between the layers (layer A, layer B) primarily composed of these resins. If an amorphous resin is used for either thermoplastic resin A or thermoplastic resin B, the heat treatment temperature is preferably below the melting point of the crystalline resin and in the range of the glass transition temperature of the crystalline resin to the glass transition temperature + 120°C. If at least one of thermoplastic resin A and thermoplastic resin B is a crystalline polyester primarily composed of naphthalenedicarboxylic acid units, the heat treatment temperature is preferably 170°C or higher but lower than 220°C.

Next, we will explain the case of simultaneous biaxial stretching. In the case of simultaneous biaxial stretching, the obtained cast film may be subjected to surface treatment such as corona treatment, flame treatment, or plasma treatment as necessary, and then properties such as easy slip, easy adhesion, and antistatic properties may be imparted by in-line coating.

Next, while holding both widthwise ends with clips, the cast film is introduced into a simultaneous biaxial tenter and conveyed there, where it is stretched simultaneously and/or stepwise in the longitudinal and widthwise directions. Simultaneous biaxial stretching machines include pantograph, screw, drive motor, and linear motor types. Drive motor and linear motor types are preferred, as they allow for arbitrary stretching ratios and relaxation treatment at any location. The stretching ratio varies depending on the type of resin, but an area ratio of 6.0 to 30.0 times is typically preferred. When a polyethylene naphthalate copolymer resin is used as one of the resins constituting the laminate film, an area ratio of 9.0 to 18.0 times is particularly preferred. In particular, with simultaneous biaxial stretching, it is preferable to maintain the same stretching ratio in the longitudinal and widthwise directions and to ensure that the stretching speeds are approximately equal in order to suppress in-plane orientation differences. Furthermore, the stretching temperature is preferably in the range of the glass transition temperature of the resin with the higher glass transition temperature constituting the laminate film to the glass transition temperature + 120°C.

The biaxially stretched film is then heat-treated, slowly cooled, and cooled to room temperature, as in the case of sequential biaxial stretching, and then wound up. During heat treatment, it is preferable to instantly relax the film in the longitudinal direction immediately before and/or after entering the heat treatment zone, in order to suppress distribution of the main orientation axis in the width direction.

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

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

(1) Layer Thickness, Number of Stacked Layers, and Stacking Configuration The layer structure and number of stacked layers of the dielectric multilayer film were identified and the thickness of each layer was measured using a sample cut out of a cross section using a microtome, and the sample was observed with a transmission electron microscope (TEM) and its length measurement function. Specifically, a transmission electron microscope H-7100FA (manufactured by Hitachi, Ltd.) was used to observe the cross section of the film at 10,000 to 40,000 times magnification at an acceleration voltage of 75 kV, and cross-sectional photographs were taken to identify the layer structure and number of stacked layers and measure the thickness of each layer. In some cases, known staining techniques using _RuO4 , _OsO4 , etc. were used to enhance the contrast between layers.

(2) Reflectance Reflectance was measured under the following measurement conditions using a Hitachi spectrophotometer (U-4100 Spectrophotometer) with an integrating sphere attached as a basic configuration. In the reflectance measurement, the sample was placed behind the integrating sphere with its longitudinal direction facing up and down, and the reflectance was calculated as a relative reflectance based on the aluminum oxide secondary white plate attached to the device. The average reflectance was calculated by averaging all the reflectance values every 1 nm. Measurements were performed on both sides of the sample, and the measurement result of the side with the higher average reflectance at wavelengths of 900 to 1000 nm was used.
<Measurement conditions>
Slit: 2 nm (visible) / automatic control (infrared)
Gain: 2
Scanning speed: 600 nm/min Starting wavelength: 2600 nm
End wavelength: 240 nm
Sampling interval: 1 nm
Incident angle: 10°.

(3) Melting Point, Glass Transition Temperature, Crystallization Temperature, and Heat of Crystal Fusion Five grams of sample was collected, and the melting point, glass transition temperature, crystallization temperature, and heat of crystal fusion were measured and calculated using a differential scanning calorimeter (Robot DSC-RDC220, manufactured by Seiko Instruments Inc.) in accordance with JIS-K-7121 (1987). In the measurements, the sample was heated from 25°C to 290°C at a rate of 5°C/min.

(4) Water Contact Angle of X-Plane The laminate was left for 24 hours in an atmosphere at room temperature of 23°C and a relative humidity of 65%. Thereafter, in the same atmosphere, the water contact angle of pure water was measured at five arbitrarily selected points on the X-plane using a contact angle meter CA-D type (manufactured by Kyowa Interface Science Co., Ltd.). The average value of the three measured values excluding the maximum and minimum values of the five measured values was taken as the water contact angle of the X-plane.

(5) Appearance of laminate (observation when water droplets are attached)
The laminate was placed under a three-band fluorescent lamp, and the water droplets attached in (4) were visually observed at angles of 0°, 45°, and 70° relative to the normal direction, and evaluation was performed. The evaluation criteria were as follows, with ⊚ and ◯ representing good results.
⊚: The entire water droplet was colored and not visible.
○: Some of the water droplets appeared slightly colored.
×: The entire water droplet appeared to be colored, or only a portion of the water droplet appeared to be clearly colored.

(6) Colorimetry (reflection saturation, transmission L*)
A spectrophotometer CM-3600d manufactured by Konica Minolta Sensing Inc. was used. For reflection saturation, the saturation of the X-plane was measured using the SCI method in reflection object color measurement mode under conditions of a target mask with a measurement diameter of 8 mm, and the average value was calculated for an n number of 5. For transmission L*, L* was measured in transmission measurement mode under conditions of a target mask with a measurement diameter of 25.4 mm, and the average value was calculated for an n number of 5. Calibration was performed using the following white calibration plate and zero calibration box. D65 was selected as the light source used to calculate the colorimetric values.
White calibration plate: CM-A103
Zero calibration box: CM-A104.

(7) Temperature increase due to external light The laminate was placed parallel to the glass bulb of a Panasonic "RF100V200W-W/D" reflector bulb at a position 30 cm from the tip of the bulb, and was irradiated with light from the bulb at a temperature of 25°C and a humidity of 60% RH. A thermometer was inserted 2 cm from the laminate on the opposite side of the reflector bulb, and the temperature was measured 2 minutes after irradiation. [Resins used in manufacturing dielectric multilayer films]
In manufacturing the dielectric multilayer film, the following resins were used as thermoplastic resins for layers A and B. Note that among the thermoplastic resins used for layers A and B, all those not described as amorphous are crystalline thermoplastic resins.

(Thermoplastic resin for layer A)
PEN (1): Polyethylene 2,6-naphthalate copolymerized with 6 mol % of polyethylene glycol having an average molecular weight of 400 relative to the total diol constituents (intrinsic viscosity: 0.64, melting point: 255° C., glass transition temperature: 97° C.).

(Thermoplastic resin for layer B)
PET (1): A mixture of polyethylene terephthalate resin (intrinsic viscosity: 0.73, amorphous resin (no melting point), glass transition temperature: 79°C) copolymerized with 31 mol% cyclohexanedimethanol (CHDM) relative to all diol constituents, and polyethylene terephthalate (manufactured by Toray Industries, Inc., intrinsic viscosity: 0.65, melting point: 256°C, glass transition temperature: 80°C) in a mass ratio of 82:18 (melting point: 225°C, glass transition temperature: 79°C).
PET (2): A mixture of polyethylene terephthalate resin (intrinsic viscosity: 0.73, amorphous resin (no melting point), glass transition temperature: 79°C) copolymerized with 31 mol% cyclohexanedimethanol (CHDM) relative to all diol constituents, and polyethylene terephthalate (manufactured by Toray Industries, Inc., intrinsic viscosity: 0.65, melting point: 256°C, glass transition temperature: 80°C) in a mass ratio of 50:50 (melting point: 225°C, glass transition temperature: 79°C).
PET (3): A mixture of polyethylene terephthalate resin (intrinsic viscosity: 0.73, amorphous resin (no melting point), glass transition temperature: 79°C) copolymerized with 31 mol% cyclohexanedimethanol (CHDM) relative to all diol constituents, and polyethylene terephthalate (manufactured by Toray Industries, Inc., intrinsic viscosity: 0.65, melting point: 256°C, glass transition temperature: 80°C) in a mass ratio of 30:70 (melting point: 230°C, glass transition temperature: 80°C).
PET (4): Polyethylene terephthalate resin copolymerized with 30 mol % of 2,6-naphthalenedicarboxylic acid relative to all dicarboxylic acid constituents (intrinsic viscosity: 0.67, amorphous resin (no melting point), glass transition temperature: 95°C).

[Materials used as support]
The following materials were used as supports. In the preparation of a laminate having supports on the outermost surfaces on both sides, corona discharge treatment and formation of a hard coat layer were performed on only one surface of one of the supports, and the surface subjected to these treatments was positioned on the surface opposite the colored layer (X surface) (however, when these treatments were not performed, the outermost surface was arbitrary). In other words, the surface opposite the X surface was made of the following material that had not been subjected to these treatments.
PC (1): A 5 mm thick polycarbonate sheet was used. It was subjected to corona discharge treatment for 5 seconds, and the water contact angle was 58°.
PC (2): Polycarbonate with a thickness of 5 mm was used. Corona discharge treatment was performed for 30 seconds, and the water contact angle was 49°.
PC (3): A 5 mm thick polycarbonate was used. A mixture of 15% by weight of acrylic ester, 15% by weight of epoxy acrylate, 15% by weight of urethane acrylate, 1% by weight of the photoinitiator "Irgacure" (registered trademark) 184, 34% by weight of methyl ethyl ketone, and 20% by weight of propylene glycol monomethyl ether acetate was applied with a bar coater and irradiated with ultraviolet light to form a hard coat layer. The thickness of the hard coat layer was 3 μm, and the water contact angle was 38°.
PC (4): A 5 mm thick polycarbonate was used. A mixture of 35% by weight of 2-hydroxyethyl methacrylate, 10% by weight of urethane acrylate, 1% by weight of the photoinitiator "Irgacure" (registered trademark) 184, 34% by weight of methyl ethyl ketone, and 20% by weight of propylene glycol monomethyl ether acetate was applied with a bar coater, and a hard coat layer was formed by ultraviolet irradiation. The hard coat layer had a thickness of 3 μm and a water contact angle of 25°.
Glass (1): A 5 mm thick float glass was used. A mixture of 10% by weight of acrylic acid ester, 35% by weight of urethane acrylate, 1% by weight of the photoinitiator "Irgacure" (registered trademark) 184, 34% by weight of methyl ethyl ketone, and 20% by weight of propylene glycol monomethyl ether acetate was applied with a bar coater, and a hard coat layer was formed by ultraviolet irradiation. The thickness of the hard coat layer was 3 μm, and the water contact angle was 57°.
Glass (2): A 5 mm thick float glass was used. A mixture of 15% by weight of acrylic ester, 15% by weight of epoxy acrylate, 15% by weight of urethane acrylate, 1% by weight of the photoinitiator "Irgacure" (registered trademark) 184, 34% by weight of methyl ethyl ketone, and 20% by weight of propylene glycol monomethyl ether acetate was applied with a bar coater, and a hard coat layer was formed by ultraviolet irradiation. The thickness of the hard coat layer was 3 μm, and the water contact angle was 38°.
Glass (3): A 5 mm thick float glass was used. A mixture of 45% by weight of urethane acrylate, 1% by weight of the photoinitiator "Irgacure" (registered trademark) 184, 34% by weight of methyl ethyl ketone, and 20% by weight of propylene glycol monomethyl ether acetate was applied with a bar coater, and a hard coat layer was formed by ultraviolet irradiation. The hard coat layer had a thickness of 3 μm and a water contact angle of 64°.
Weather-resistant resin layer (1): A mixture of 45% by weight of urethane acrylate, 1% by weight of the photoinitiator "Irgacure" (registered trademark) 184, 34% by weight of methyl ethyl ketone, and 20% by weight of propylene glycol monomethyl ether acetate was applied with a bar coater and irradiated with ultraviolet light to form a weather-resistant resin layer. The thickness was 3 μm, and the water contact angle was 58°.
PC (5): Polycarbonate with a thickness of 3 mm was used. Corona discharge treatment was performed for 5 seconds, and the water contact angle was 58°.
PC (6): Polycarbonate with a thickness of 2 mm was used. Corona discharge treatment was performed for 5 seconds, and the water contact angle was 58°.
PC (7): Polycarbonate with a thickness of 5 mm was used. The water contact angle was 85°C.

[Colored layer]
Colored layer 1: PVB (polyvinyl butyral) with a thickness of 0.8 mm and containing dispersed carbon black was used.
Colored layer 2: Polycarbonate with carbon black dispersed therein and a thickness of 5 mm was used.
Colored layer 3: Float glass with a thickness of 5 mm and dispersed with carbon black was used.

Example 1
PEN (1) was used as the polyester resin (thermoplastic resin A) forming layer A, and PET (1) was used as the polyester resin (thermoplastic resin B) forming layer B. The polyester resins forming each layer were melted at 280°C in a vented twin-screw extruder, then merged in a 449-layer feed block via a gear pump and filter. A total of 449 layers of molten thermoplastic resin A and thermoplastic resin B were laminated alternately in the thickness direction, with layer A being the outermost layer on both sides. The resulting molten laminate was then introduced into a T-die, formed into a sheet, and extruded. The molten sheet was then quenched and solidified by electrostatic application on a casting drum at a surface temperature of 25°C to obtain a cast film. The extrusion rate was adjusted so that the thickness ratio of adjacent layers A and B (thickness of layer A/thickness of layer B) was approximately 0.9. The resulting cast film was then heated using a group of rolls set at a temperature equal to or higher than the glass transition temperature of thermoplastic resin A by 10°C. The film was then rapidly heated from both sides using a radiation heater within a 100 mm stretching section, stretched 3.2 times in the machine direction (longitudinal direction) while maintaining a film surface temperature equal to or higher than the glass transition temperature of thermoplastic resin A by 10°C. The film was then cooled. Both sides of the uniaxially stretched film were then subjected to a corona discharge treatment in air to adjust the wetting tension to 55 mN/m. A coating liquid for forming a laminate film was then applied to both sides, consisting of a polyester resin with a glass transition temperature of 18°C, a polyester resin with a glass transition temperature of 82°C, and silica particles with an average particle size of 100 nm (median diameter determined by the laser diffraction and scattering method according to JIS Z 8825 (2022)). This formed a transparent, easily slippery, and easily adhesive layer. This uniaxially stretched film was introduced into a tenter, its widthwise ends held with clips, and preheated with hot air at 100°C. It was then stretched 4.0 times in the transverse direction (widthwise direction) at a uniform stretching speed at a temperature 20°C above the glass transition temperature of thermoplastic resin A. Furthermore, in the same tenter, the stretched film was heat-treated with hot air at 195°C and subjected to a 1% relaxation treatment in the widthwise direction at the same temperature. It was then further stretched 1% in the widthwise direction in a cooling zone at 150°C, slowly cooled to room temperature, and wound up. The thickness of the resulting dielectric multilayer film was 90 μm.

Nisshinbo LAMINATOR 0303S was used to prepare the laminate. The temperature of the laminated members as shown in Table 1 was raised from 25°C to 150°C at a rate of 3°C/min, then the pressure was reduced to 600 mmHg for 5 minutes and pressed at a pressure of 0.1 MPa for 30 minutes. The members were then slowly cooled to 35°C at a rate of 3°C/min while still pressed, and the press was released to obtain a laminate. The evaluation results of the resulting laminate are shown in Table 1.

(Examples 2 to 9, 11 to 19, Comparative Examples 1 to 9)
Laminates were produced under the same conditions as in Example 1, except that the configuration of the dielectric multilayer film used for each layer and the configuration of the laminate were changed as shown in Tables 1 and 2. The evaluation results of the obtained laminates are shown in Tables 1 and 2. The number of layers was adjusted by adjusting the number of slits in the feed block, and the thickness was adjusted by changing the speed of the entire film production line, which is linked to the casting drum speed.

Example 10
A laminate was obtained under the same conditions as in Example 1, except that the weather-resistant resin layer (1) was provided on the dielectric multilayer film as described above. The evaluation results of the obtained laminate are shown in Table 1.

(Example 20)
A laminate was obtained under the same conditions as in Example 1, except that a 10 nm thick indium oxide layer (metal layer (1)), a 12 nm thick silver thin film layer (metal layer (2)), and a 20 nm thick indium oxide layer were formed in this order by sputtering on "Toughtop" (registered trademark) C0T0 (100 μm thick) manufactured by Toray Advanced Film Co., Ltd., which is a film having an acrylic hard coat. The evaluation results of the obtained laminate are shown in Table 1.

This invention can be used in decorative materials such as decorative panels, various home appliances, building materials, automotive parts, etc., and can be used particularly as heat-blocking glass that can suppress the inflow of heat caused by sunlight.

Claims (9)

A laminate having a colored layer on one side of a dielectric multilayer film, wherein Ra is the average reflectance in the wavelength range of 900 to 1000 nm, and Rb is the average reflectance in the wavelength range of 400 to 700 nm, and Ra is 50% or more and 100% or less; the shortest wavelength in the wavelength range of 700 to 900 nm that is the midpoint between Ra and Rb is 850 nm or more; and when the surface opposite the colored layer is designated as the X-plane, the water contact angle of the X-plane is 5° or more and 60° or less. The laminate described in claim 1, wherein the saturation of reflected light when light is irradiated onto the X-face is 20 or less. The laminate described in claim 1 or 2, wherein the difference between Ra and Rb is 20% or more and 90% or less. The laminate according to claim 1 or 2, wherein the dielectric multilayer film is a laminate film whose main component is a thermoplastic resin. The laminate described in claim 4, wherein the laminate film has a structure in which at least 51 layers of at least two types of layers each having a different thermoplastic resin as a main component are regularly laminated. The laminate described in claim 1 or 2, wherein the distance from the X-plane to the dielectric multilayer film is 0.001 mm or more and 2.0 mm or less. The laminate according to claim 1 or 2, wherein the maximum reflectance Rd at wavelengths of 400 to 830 nm is 0.1% or more and 15% or less. The laminate described in claim 1 or 2, wherein a weather-resistant resin layer, the dielectric multilayer film, an adhesive layer, and a colored layer are arranged in this order, and the colored layer is primarily composed of glass or resin. 3. The laminate according to claim 1, wherein the support, the intermediate layer 1, the dielectric multilayer film, the intermediate layer 2, and the colored layer are arranged in this order, and the colored layer and the support are mainly composed of glass or resin.