JP7634352B2 - Heat shielding film - Google Patents

Description

This disclosure relates to a heat shielding film.

Heat-shielding films are used to improve the heat resistance of various molded products made of synthetic resins. For example, resin plates can warp over time due to infrared light.
A decorative sheet having heat shielding properties for suppressing warping caused by infrared light has been proposed (see Patent Document 1). The decorative sheet described in Patent Document 1 has a printed layer and an overlay film layer laminated in this order on a thermoplastic resin substrate, and has an adhesive layer made of a urethane adhesive having a polyester resin as the main chain between the printed layer and the overlay film layer, and an anchor layer made of a urethane anchor agent having an acrylic resin as the main chain, in this order. The overlay film layer of the decorative sheet contains an ultraviolet absorbing agent, and the ultraviolet absorbing agent is made only of a triazine ultraviolet absorbing agent, and the printed layer contains a black pigment, and the black pigment is a perylene black pigment. It is described that the ultraviolet absorbing agent in the overlay film layer is only a triazine ultraviolet absorbing agent, so that an ultraviolet absorbing ability is improved and a decorative sheet having excellent weather-resistant adhesion in addition to heat-resistant adhesion can be obtained.

In addition, a heat-shielding film has been proposed that is made of a resin composition containing a resin with a refractive index of less than 1.52 and a fine powder filler with a refractive index of 1.60 or more, and has an average reflectance of 80% or more at wavelengths of 810 nm to 2100 nm (see Patent Document 2).
As a resin having a refractive index of less than 1.52, a polylactic acid polymer or the like having a low refractive index is considered to be preferable, and the reflectance of the film is improved by increasing the difference in refractive index between the resin and the fine powder filler.

JP 2016-165865 A JP 2007-88930 A

A decorative sheet containing an ultraviolet absorber absorbs the ultraviolet rays contained in external light such as sunlight and converts them into heat, thereby reducing the effect of the ultraviolet rays on a substrate covered with the decorative sheet. However, because the ultraviolet absorber converts the energy of ultraviolet rays into heat, there is a concern that the temperature of the decorative sheet itself will increase due to sunlight in the decorative sheet described in Patent Document 1, which will lead to an increase in the temperature of the substrate covered with the decorative sheet.
The heat-shielding film described in Patent Document 2 aims to improve heat insulation by increasing the reflectance through the combination of a specific resin with a defined reflectance and a specific filler, but there is still room for improvement in terms of the durability of the film, particularly its weather resistance.

The objective of one embodiment of the present invention is to provide a heat shielding film that has good weather resistance and suppresses temperature rise caused by light, including ultraviolet and infrared rays, such as sunlight.

The means for solving the problems include the following aspects.
<1> A heat-shielding film having at least a white reflective layer, the white reflective layer containing at least one synthetic resin selected from the group consisting of polyvinyl chloride resin, acrylic resin, and fluororesin, a white pigment, and 0.1% by mass to 5.0% by mass of a fluorescent brightening agent relative to the total solid content of the white reflective layer.

<2> The heat shielding film according to <1>, wherein the white reflective layer does not contain an ultraviolet absorbing agent.
<3> The heat shielding film according to <1> or <2>, wherein the synthetic resin includes at least one selected from the group consisting of polyvinyl chloride resins and acrylic resins.

<4> The heat shielding film according to any one of <1> to <3>, further comprising a colored transmitting layer containing a synthetic resin and a colorant on one surface of the white reflective layer, the colorant not containing carbon black.
<5> The heat shielding film according to <4>, wherein the synthetic resin contained in the colored transmitting layer includes at least one selected from the group consisting of polyvinyl chloride resins and acrylic resins.
<6> The heat shielding film according to any one of <1> to <5>, which is an exterior material for a vehicle.
<7> The heat shielding film according to any one of <1> to <5>, which is an exterior material for a building.

According to one embodiment of the present invention, it is possible to provide a heat shielding film that is excellent in weather resistance and that suppresses temperature rise caused by light, including ultraviolet and infrared rays, such as sunlight.

FIG. 2 is a schematic cross-sectional view showing an example of an embodiment of a heat shielding film of the present disclosure having a colored transmitting layer and a white reflective layer.

The heat shielding film of the present disclosure will be described in detail below.
The following description of the configuration elements may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments.
In the present disclosure, the use of "to" indicating a range of values means that the values before and after the range are included as the lower limit and upper limit.
In the numerical ranges described in the present disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples.
In the present disclosure, combinations of two or more preferred aspects are more preferred aspects.
In the present disclosure, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified.
In the present disclosure, the term "step" refers not only to an independent step, but also to a step that cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved.

In the present disclosure, the surface of a heat-shielding film refers to the side on which light such as sunlight that the heat-shielding film is intended to shield against is incident, and the back surface of a heat-shielding film refers to the side opposite to the side on which light is incident. When a heat-shielding film is used by being attached to the surface of an object to be protected, the side of the heat-shielding film that comes into contact with the object to be protected is sometimes referred to as the back surface, and the side of the heat-shielding film opposite to the side that comes into contact with the object to be protected is sometimes referred to as the front surface.
In the present disclosure, a "layer containing a resin" refers to a "layer formed containing a resin that is the main component of the layer." Here, the "resin that is the main component" refers to a resin that is contained in an amount of 60 mass% or more based on the total amount of the resin composition containing the component. In the present disclosure, the resin that is the main component constituting the layer is also referred to as the "base resin."
In the present disclosure, the "total solid content" of a composition refers to the total mass of all components of the composition excluding the solvent. When the composition contains a liquid component, such as a polymerizable monomer, the liquid component is included in the solid content.

[Heat-shielding film]
The heat shielding film of the present disclosure has at least a white reflective layer, and the white reflective layer contains at least one synthetic resin selected from the group consisting of polyvinyl chloride resin, acrylic resin, and fluororesin, a white pigment, and 0.1% by mass to 5.0% by mass of a fluorescent brightening agent relative to the total solid content of the white reflective layer.
The heat shielding film of the present disclosure contains a predetermined amount of fluorescent brightening agent in addition to a white pigment, thereby improving the UV reflectivity and suppressing heat generation and accumulation of the generated heat due to exposure to light, even without using an UV absorber which may generate heat when exposed to light.

(White Reflective Layer)
The heat shielding film of the present disclosure has at least one white reflective layer.
The white reflective layer in the present disclosure refers to a layer that is white when viewed visually and has a reflectance of 80% or more for light with a wavelength of 260 nm to 2500 nm.
The light reflectance can be measured as the diffuse reflectance of the white reflective layer at a wavelength of 260 nm to 2500 nm using an integrating sphere spectrophotometer (e.g., V-670, manufactured by JASCO Corporation) in accordance with the method described in JIS A 5759 (2008).
The heat shielding film may have two or more white reflective layers.
The white reflective layer contains at least one synthetic resin selected from the group consisting of polyvinyl chloride resin, acrylic resin, and fluororesin, a white pigment, and 0.1% by mass to 5.0% by mass of a fluorescent whitening agent relative to the total solid content of the white reflective layer.

-At least one synthetic resin selected from the group consisting of polyvinyl chloride resin, acrylic resin, and fluororesin-
The white reflective layer contains at least one synthetic resin (hereinafter also referred to as specific resin) selected from the group consisting of polyvinyl chloride resin, acrylic resin, and fluororesin. Since polyvinyl chloride resin, acrylic resin, and fluororesin all have good light transmittance, the effects of the white pigment and fluorescent whitening agent contained in the white reflective layer are more effectively exhibited. In addition, the synthetic resin is useful for forming a film as a film forming substrate.
In particular, from the viewpoint of better adhesion to different materials, the synthetic resin contained in the white reflective layer preferably contains at least one type selected from the group consisting of polyvinyl chloride resin and acrylic resin.

In addition to being used as a film on its own, the heat shielding film of the present disclosure can also be used by being attached to a substrate for use as the exterior of a vehicle, the exterior of a building, and the like. From this viewpoint, it is preferable that the synthetic resin have good adhesion to different materials.
Furthermore, polyvinyl chloride resin and acrylic resin are general-purpose resins and have the advantages of being easily processable, readily available, and inexpensive.

The polyvinyl chloride resin may be used without any particular limitation as long as it has good film-forming properties.Specific examples include vinyl chloride homopolymers having an average degree of polymerization of 650 to 2000, preferably about 650 to 1800, and further copolymers of vinyl chloride with ethylene, vinyl acetate, methacrylic acid ester, etc., which are mainly made of vinyl chloride.
Furthermore, a mixed resin of a vinyl chloride homopolymer or a copolymer containing vinyl chloride with a polyester resin, an epoxy resin, an acrylic resin, a vinyl acetate resin, a urethane resin, an acrylonitrile, a styrene-butadiene copolymer resin, a partially saponified vinyl alcohol, or the like can be used.

Specific examples of the acrylic resin include homopolymers or copolymers of methacrylic acid or methacrylic acid esters, such as polymethyl methacrylate (PMMA), and copolymers of alkyl methacrylate, alkyl acrylate, and styrene.
Acrylic resin has excellent weather resistance, stretchability, and flexibility, and has good adhesion to different materials. Therefore, when the white reflective layer contains acrylic resin, good shape conformity can be expected even when the heat shielding film is attached to a substrate as an exterior material for a vehicle or building. Furthermore, acrylic resin has the advantage of being less likely to discolor even when heated.

The fluororesin is not particularly limited as long as it is a resin obtained by polymerizing at least one type of monomer containing a fluorine atom as a polymerization component, but a resin obtained by polymerizing an olefin containing a fluorine atom is preferable. Examples of the fluororesin include a resin composed of a polymerization component selected from tetrafluoroethylene, trifluorochloroethylene, vinyl fluoride, and vinylidene fluoride.
More specific examples of the polymerizable composition include homopolymers of polymerization components containing fluorine atoms, such as tetrafluoroethylene resin, vinyl fluoride resin, and vinylidene fluoride resin, and copolymers containing the above-mentioned polymerization components, such as trifluorochloroethylene-vinylidene fluoride copolymer, vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer.

The white reflective layer may contain only one type of synthetic resin, or may contain two or more types of synthetic resin.
When the white reflective layer contains two or more types of synthetic resins, the synthetic resins may be different from each other, the synthetic resins may be the same type of resin but have different polymerization degrees, or the synthetic resins may contain copolymerization components derived from the same monomer but different copolymerization components.

- White pigment -
The white reflective layer contains a white pigment. When the white reflective layer contains a white pigment, the infrared reflectivity is improved and the heat storage effect of the white reflective layer and the heat storage effect of the heat shielding film having the white reflective layer can be suppressed.
There are no particular limitations on the white pigment, and any pigment that has good infrared reflectivity and appears white to the naked eye can be used.
Examples of white pigments include titanium oxide (also called titanium white), barium titanate, zinc oxide (also called zinc white), basic lead carbonate (also called lead white), basic lead sulfate, zinc sulfide, lithopone (a mixture of barium sulfate and zinc sulfide), Titanox (trade name: titanium dioxide particles, manufactured by Kronos Co., Ltd.), etc. Among these, titanium oxide and the like are preferred from the viewpoint of better light reflectivity.

The particle size of the white pigment is preferably in the range of 0.05 μm to 10 μm in average.
When the particle size of the white pigment is within the above range, the light reflectivity is good and a uniform white reflective layer can be easily formed, which is preferable.
The average particle size of the white pigment can be obtained by photographing the white pigment with an electron microscope, randomly selecting 50 particles within the viewing angle, measuring the particle size, and calculating the arithmetic mean. If the pigment is not spherical, the maximum particle size is measured.
In addition, regarding the average particle size of the white pigment, if the average particle size of the white pigment used is specified in the catalog value, the catalog value is used.

The white reflective layer may contain only one type of white pigment, or may contain two or more types of white pigment.
From the viewpoint of improving the light reflectivity of the heat-shielding film, the content of the white pigment is preferably in the range of 1 mass % to 30 mass %, more preferably in the range of 2 mass % to 20 mass %, and even more preferably in the range of 3 mass % to 10 mass %, relative to the total solid content of the white reflective layer.

-Fluorescent whitening agent-
The white reflective layer contains a fluorescent brightening agent. By containing the fluorescent brightening agent, the white reflective layer can effectively reflect ultraviolet rays and suppress the heat storage effect of the heat shielding film. The inventors believe that the fluorescent brightening agent replaces the ultraviolet absorbing agent and plays a role as an ultraviolet stabilizer in the heat shielding film.
The fluorescent whitening agent refers to an organic compound that absorbs ultraviolet light and emits fluorescence, specifically, an organic compound that absorbs ultraviolet light and emits a bluish-white light when viewed with the naked eye.
Examples of the fluorescent whitening agent include stilbene derivatives such as bis(triazinylamide)stilbene disulfonic acid derivatives, benzimidazole derivatives, coumarin derivatives, aminocoumarin derivatives, benzoxazole derivatives, etc. Among these, from the viewpoint of better suppression of heat storage effect, bis(triazinylamide)stilbene disulfonic acid derivatives and the like are preferred.

The white reflective layer may contain only one type of fluorescent brightening agent, or may contain two or more types of fluorescent brightening agents.
The content of the fluorescent brightener is preferably in the range of 0.1% by mass to 6.0% by mass, relative to the total solid content of the white reflective layer, and from the viewpoint of obtaining a better effect of suppressing the heat storage action of the heat shielding film, is more preferably in the range of 0.5% by mass to 5.0% by mass, and even more preferably in the range of 1.0% by mass to 5.0% by mass.

The white reflective layer can be formed by preparing a composition for forming a white reflective layer containing a specific resin, a white pigment, a predetermined amount of a fluorescent brightener, and other additives that are used as desired, and molding the resulting composition for forming a white reflective layer into a film.
The composition for forming a white reflective layer may contain known additives within the range that does not impair the effect.

Additives that may be contained in the composition for forming a white reflective layer include plasticizers, heat stabilizers such as Ba/Zn-based heat stabilizers for vinyl chloride, Ba/Zn-based heat stabilizers for vinyl chloride, lubricants such as fatty acid ester-based lubricants, fillers, colorants, film-forming aids, flame retardants, and the like.
The flame retardancy of the white reflective layer can be improved by adding a known flame retardant such as a phosphorus-based, halogen-based, or inorganic metal-based flame retardant to the composition for forming the white reflective layer. In addition, when a polyvinyl chloride resin is used as the specific resin, the processability and the feel of the resulting white reflective layer can be further improved by adding a plasticizer.

The white reflective layer according to the present disclosure has excellent heat shielding properties and excellent protection of a substrate when attached to the substrate, and therefore does not particularly need to contain an ultraviolet absorbing agent.
The white reflective layer may contain an ultraviolet absorbing agent. However, when the obtained white reflective layer contains an ultraviolet absorbing agent, when the white reflective layer is irradiated with light, particularly ultraviolet light, the ultraviolet absorbing agent may convert the energy of the ultraviolet light into heat, and the temperature of the white reflective layer may increase. Therefore, from the viewpoint of the heat shielding effect, it is preferable that the white reflective layer does not contain an ultraviolet absorbing agent.

There is no particular limitation on the method for forming the white reflective layer, and any known film-forming method can be applied as long as it is possible to form the white reflective layer into a sheet shape.
To form a white reflective layer, a composition for forming a white reflective layer is first prepared, which contains a synthetic resin, a white pigment, a fluorescent brightener, and optionally other additives, and the resulting composition for forming a white reflective layer is then formed into a sheet-like film.
The composition for forming the white reflective layer used for forming the white reflective layer may be prepared by dissolving a synthetic resin in an appropriate solvent, but from the viewpoint of uniformity of the white reflective layer to be formed, it is preferable to heat and melt the synthetic resin, and melt-mix the white pigment, the fluorescent whitening agent, and additives contained as desired to prepare a uniform composition. As a method for forming the white reflective layer, a method of preparing a melt-mixed composition and forming it into a sheet is preferable.
Examples of the method for forming the sheet include a calendar method, an extrusion method, a casting method, etc. Among these, the calendar method is preferred from the viewpoint of good processability.

The thickness of the white reflective layer is preferably from 40 μm to 200 μm, and more preferably from 50 μm to 80 μm, from the viewpoint of maintaining the strength of the film.
The heat-shielding film of the present disclosure has at least one white reflective layer. The heat-shielding film may have two or more white reflective layers. When the heat-shielding film has two or more white reflective layers, the compositions of the white reflective layers may be the same or different from each other.
Even when the heat shielding film has two or more white reflective layers, the total thickness of the plurality of white reflective layers is preferably within the above range.
The thickness of the white reflective layer and the thickness of any layer in the heat-shielding film described below, for example, the thickness of each layer such as the colored transparent layer, can be measured by observing a cut surface obtained by cutting the heat-shielding film perpendicularly to the surface direction. In the present disclosure, the thickness of the white reflective layer is determined by measuring the thickness of five randomly selected points on the cut surface and arithmetically averaging the measured thickness. The thicknesses of the other layers can also be measured in the same manner.

(Colored transparent layer)
The heat shielding film of the present disclosure has a colored transmitting layer containing a synthetic resin and a colorant on one surface of the white reflective layer, and the colorant preferably does not contain carbon black.
The colored transparent layer can be provided in order to impart a hue to the heat shielding film and improve its design. The colored transparent layer is a colored layer containing a colorant, and the colored transparent layer of the heat shielding film of the present disclosure does not include a layer that is colorless when viewed with the naked eye.
The colored transmitting layer is preferably a layer that makes the presence of the white reflective layer invisible when the heat shielding film is viewed from the side having the colored transmitting layer.
From the viewpoint of not impairing the effect of the white reflective layer, the colored transmitting layer is preferably a layer that transmits light in the infrared and ultraviolet regions that are reflected by the white reflective layer to suppress the heat storage effect.
Therefore, the colored transmitting layer may be a dark color layer such as black, through which the white reflective layer cannot be seen. That is, the colored transmitting layer may be a layer having a low transmittance of light in the visible light region, but is preferably a layer capable of transmitting light in the infrared region and the ultraviolet region.

From the viewpoint of fully obtaining the effect of the white reflective layer, the light transmittance of the colored transmitting layer is preferably 45% or more for both infrared light with a wavelength of 780 nm to 2500 nm and ultraviolet light with a wavelength of 260 nm to 380 nm, and more preferably 50% or more for both of the above wavelengths.
The light transmittance of the colored transmission layer can be measured, for example, using an ultraviolet-visible-infrared spectrophotometer (model number: UV-3100PC, manufactured by Shimadzu Corporation). The light transmittance in each of the above wavelength ranges is measured at wavelength intervals of 10 nm, and the average value of the transmittance measurement results can be regarded as the average transmittance in that wavelength range.

Fig. 1 is a schematic cross-sectional view showing one example of an embodiment of a heat-shielding film according to the present disclosure having a colored transmitting layer and a white reflective layer. The heat-shielding film 10 shown in Fig. 1 has, in this order from the light-receiving side, a colored transmitting layer 12, a white reflective layer 14, and an adhesive layer 16. As described above, the white reflective layer 14 is an essential layer in the heat-shielding film according to the present disclosure, and the colored transmitting layer 12 and the adhesive layer 16 are optional layers that are provided as desired.
The heat-shielding film 10 shown in FIG. 1 has an adhesive layer 16 that is useful for adhering to a substrate, and by having a colored transparent layer 12, it is possible to impart a hue to the appearance of the heat-shielding film 10 and provide good design properties without impairing the heat-shielding properties of the white reflective layer 14.

- Synthetic resin -
The synthetic resin contained in the colored transmitting layer is a resin that can be molded into a sheet, and a synthetic resin that provides good transparency to the formed sheet-like resin layer, i.e., good transmittance to infrared light, visible light, and ultraviolet light, can be preferably used.
Examples of synthetic resins contained in the colored transmitting layer include polyvinyl chloride resin, acrylic resin, fluororesin, polyester resin, silicone resin, polyolefin resin, polystyrene elastomer, urethane resin, etc. Among them, from the viewpoint of better transparency and weather resistance, polyvinyl chloride resin, acrylic resin, and fluororesin are preferred, and it is more preferred to contain at least one selected from the group consisting of polyvinyl chloride resin and acrylic resin.

The synthetic resin contained in the colored transmitting layer may be the same type of resin as the synthetic resin contained in the white reflective layer described above or a different type of resin. Among them, from the viewpoint of adhesion between the white reflective layer and the colored transmitting layer, it is preferable that the colored transmitting layer contains the same type of synthetic resin as the synthetic resin contained in the white reflective layer.
Examples of the same type of synthetic resin include, for example, when the white reflective layer contains a polyvinyl chloride resin, the colored transparent layer also contains a polyvinyl chloride resin, and when the white reflective layer contains an acrylic resin, the colored transparent layer also contains an acrylic resin. Note that the same type of synthetic resin is not necessarily limited to resins of the same composition, and resins containing the same structural units as structural units constituting the main skeleton, resins containing the same structural units as copolymerization components, etc. are also included in the above-mentioned same type of resin.

- Coloring agent -
The colored transparent layer contains a colorant. When the colored transparent layer contains a colorant, any hue can be imparted to the heat shielding film.
The colorant may be a known colorant that is suitable for use depending on the desired hue. Examples of the colorant include dyes and pigments, and pigments are preferred from the viewpoint of better durability.
Examples of colorants include inorganic pigments such as titanium dioxide, zinc white, ultramarine, cobalt blue, red iron oxide, vermilion, chrome yellow, titanium yellow, and iron black; organic pigments such as quinacridone, isoindolinone, Hansa Yellow A, phthalocyanine blue, aniline black, and perylene black; metal pigments selected from the group consisting of foil powder of metals such as aluminum and brass; and pearlescent (pearl) pigments selected from the group consisting of titanium dioxide-coated mica and foil powder of basic lead carbonate.
In addition, when carbon black, which is a black pigment, is used, heat absorption by infrared light can cause a heat storage effect and reduce heat-shielding properties. Therefore, it is preferable that the colorant in the colored transmitting layer does not contain carbon black, or even if it does, the content of carbon black relative to the total solids content of the colorant in the colored transmitting layer is 0.1 mass% or less, and it is more preferable that the colorant does not contain carbon black.
When imparting a blackish hue to the colored transparent layer, it is preferable to use perylene black, iron black, aniline black, etc. as a pigment that can replace carbon black as a colorant, or to combine a plurality of colored pigments with different absorption wavelengths to achieve a blackish hue.

The colored transparent layer may contain only one type of colorant, or may contain two or more types of colorants for the purpose of achieving a desired hue.
The content of the colorant in the colored transmitting layer can be appropriately selected in consideration of the light transmittance and coloring effect of the colored transmitting layer. In general, from the viewpoint of achieving both the light transmittance and coloring effect of the colored transmitting layer, the content of the colorant can be, for example, in the range of 0.5% by mass to 20% by mass, and preferably in the range of 5% by mass to 15% by mass, based on the total solid content of the colored transmitting layer.

There is no particular limitation on the method for forming the colored transmitting layer, and any known film-forming method can be applied as long as the colored transmitting layer can be formed into a sheet.
To form a colored transmitting layer, a composition for forming a colored transmitting layer is first prepared, which contains a synthetic resin, a colorant, and optionally other additives, and the resulting composition for forming a colored transmitting layer is then formed into a sheet-like film.
The composition for forming the colored transmitting layer can be formed into a film in the same manner as in the above-mentioned white reflective layer.
Examples of methods for forming the sheet include a calendar method, an extrusion method, and a casting method.

The thickness of the colored transparent layer is preferably 40 μm to 200 μm, and more preferably 50 μm to 80 μm, from the viewpoint of improving the hiding power of the white reflective layer and the design of the heat shielding film.

[Other layers]
The heat shielding film of the present disclosure may further include an optional layer other than the white reflective layer and the colored transparent layer (hereinafter, these layers may be referred to as "other layers").
Examples of the other layers include an adhesive layer, a primer layer, an intermediate layer, a substrate layer, and a surface treatment layer.

(Adhesive Layer)
The heat shielding film of the present disclosure may have an adhesive layer.
When the heat-shielding film is used by being attached to a substrate such as a vehicle or a building, the adhesive layer can be provided on the surface of the heat-shielding film that contacts the substrate to improve the adhesion between the substrate and the heat-shielding film. When the heat-shielding film is composed of only a white reflective layer, the adhesive layer can be provided on one surface of the white reflective layer. When the heat-shielding film has a white reflective layer and a colored transparent layer, the adhesive layer can be provided on the surface of the white reflective layer opposite to the side having the colored transparent layer.
The adhesive constituting the adhesive layer is not particularly limited, and examples thereof include adhesives containing resins such as acrylic resins, silicone resins, urethane resins, polyisocyanurates, polyvinyl chloride, polyvinylidene chloride, and polystyrene.
Among these, acrylic resin, silicone resin, and urethane resin are preferred, and acrylic resin is more preferred from the viewpoint of better adhesion durability. Acrylic resin also has the advantages of good adhesion and low cost.

The adhesive layer can be formed, for example, by applying a viscosity-adjusted adhesive to one surface of the white reflective layer.
There is no particular limitation on the method for applying the adhesive, and the adhesive layer can be formed by applying a known application method.
Examples of the application method include gravure printing, coating, etc. From the viewpoint of better viscosity of the adhesive forming the adhesive layer and better smoothness of the obtained adhesive layer, it is preferable to form the adhesive layer by the coating method.
The thickness of the adhesive layer is preferably from 20 μm to 150 μm, and more preferably from 30 μm to 100 μm, from the viewpoint of further improving the adhesion between the heat shielding film and the substrate.
The thickness of the adhesive layer can be controlled by the amount of adhesive applied.

The heat-shielding film of the present disclosure has excellent heat-shielding properties because it effectively reflects ultraviolet light and infrared light and suppresses the heat storage effect of the heat-shielding film itself, and even when attached to a substrate for use, it can suppress the effects of heat on the substrate.
Applications of the heat shielding film of the present disclosure include exterior materials for vehicles such as automobiles and trains, exterior materials for buildings, and interior materials such as wall materials, and the like, and the film can be suitably used to shield various substrates from heat.
INDUSTRIAL APPLICABILITY The heat shielding film of the present disclosure has a wide range of applications since it has a suppressed heat storage effect in the film itself and has good heat shielding properties against substrates.

The skin material of the present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to the following specific examples.
In the following examples, the percentages indicating the concentrations and contents of each component are based on mass unless otherwise specified.

Example 1
(I: Formation of Colored Transparent Layer)
A PVC resin composition was obtained by thoroughly mixing 100 kg of polyvinyl chloride resin (hereinafter referred to as PVC resin, and written as "PVC" in Tables 1 and 2) having an average degree of polymerization of 1,300 with 20 kg of a plasticizer consisting of a phthalate ester and epoxidized soybean oil, 3 kg of a fatty acid ester as a lubricant, and 3 kg of a Ba/Zn-based heat stabilizer.
To the obtained PVC resin composition, 10 kg of an organic pigment consisting of phthalocyanine blue, quinacridone, and indolinone was added as a colorant, and the mixture was heated to 150°C, melt-kneaded, and formed into a sheet having a thickness of 80 μm by a calendar method to form a colored transparent layer.
The colored transmitting layer containing the colored pigment had a black hue. The light transmittance of the obtained colored transmitting layer was measured by the above-mentioned method using an ultraviolet-visible-infrared spectrophotometer (model number: UV-3100PC, manufactured by Shimadzu Corporation), and the transmittance of infrared light having a wavelength of 780 nm to 2500 nm was 45% or more, and the transmittance of ultraviolet light having a wavelength of 260 nm to 380 nm was 45% or more.

(II: Formation of White Reflective Layer)
A PVC resin composition was prepared in the same manner as in I: Colored transparent layer. 126 kg of the obtained PVC resin composition was mixed with 6 kg of titanium oxide (PO-KL White: product name, Nikko Bix Co., Ltd., average particle size 1 μm) as a white pigment, and 3 kg of bis(triazinylamide)stilbenedisulfonic acid derivative as a fluorescent whitening agent, and the mixture was heated to 150° C., melt-kneaded, and formed into a sheet having a thickness of 80 μm by a calendar method to form a white reflective layer.
The white reflective layer thus obtained was visually white. The light reflectance of the white reflective layer was measured by the method described above in accordance with JIS A 5759 (2008), and the light reflectance in the wavelength range of 260 nm to 2500 nm was 83%.

(III: Formation of Laminate)
The white reflective layer and the colored transparent layer obtained above were superposed, and the colored transparent layer side was brought into contact with a squeeze roll to perform laminate embossing, thereby forming a laminate of the white reflective layer and the colored transparent layer. The heating temperature during laminate embossing was 130°C.

(IV: Formation of adhesive layer)
An acrylic adhesive (Tg: -40°C, molecular weight 800,000, storage modulus at 25°C: 30 x ¹⁰⁴ Pa) was applied in an amount of 120 g/ ^m2 to the surface of the laminate formed in step III opposite the side having the colored transparent layer, forming an adhesive layer with a dry thickness of 40 μm, thereby obtaining the heat-shielding film of Example 1.
When observed from the surface, the heat-shielding film of Example 1 was a black film reflecting the hue of the colored transparent layer. In the heat-shielding film of Example 1, the white reflective layer located below was not visible through the black colored transparent layer containing the colored pigment.

Example 2
A heat shielding film of Example 2 was obtained in the same manner as in Example 1, except that in the formation of II: white reflective layer in Example 1, the content of the fluorescent whitening agent was changed from 3 kg to 4.5 kg.

Example 3
A heat shielding film of Example 3 was obtained in the same manner as in Example 1, except that in the formation of II: white reflective layer in Example 1, the content of the fluorescent whitening agent was changed from 3 kg to 6 kg.

Example 4
The heat-shielding film of Example 4 was obtained in the same manner as in Example 1, except that the PVC resin used to form I: colored transparent layer and II: white reflective layer in Example 1 was changed to an acrylic resin (ACRYLPET (registered trademark) MF, Mitsubishi Chemical Corporation; listed as "Acrylic" in Tables 1 and 2).

Example 5
A heat shielding film of Example 5 was obtained in the same manner as in Example 1, except that in the formation of II: white reflective layer in Example 1, the content of the white pigment was changed from 6 kg to 12 kg.

Example 6
A heat-shielding film of Example 6 was obtained in the same manner as in Example 1, except that in the formation of II: white reflective layer in Example 1, 1 kg of a benzotriazole-based ultraviolet absorber (RUVA-93 (product name), Otsuka Chemical Co., Ltd.; described as "benzotriazole-based" in Tables 1 and 2) was further added.

Comparative Example 1
A heat-shielding film of Comparative Example 1 was obtained in the same manner as in Example 1, except that in forming II: white reflective layer in Example 1, no fluorescent whitening agent was used and 3 kg of the benzotriazole-based ultraviolet absorber used in Example 6 was added.

Comparative Example 2
A heat shielding film of Comparative Example 2 was obtained in the same manner as in Example 1, except that in the formation of II: white reflective layer in Example 1, no fluorescent whitening agent was added.

Comparative Example 3
A heat shielding film of Comparative Example 3 was obtained in the same manner as in Example 1, except that in the formation of II: white reflective layer in Example 1, the white pigment was not added.

[Evaluation of heat shielding film]
The obtained heat shielding films were evaluated according to the following criteria. The results are shown in Tables 1 and 2 below.

(1. Heat insulation properties)
A temperature sensor was fixed onto a 30 mm thick polystyrene foam base, and a 12 cm x 12 cm piece of heat shielding film was attached to the temperature sensor via an adhesive layer.
Using a xenon weather meter (manufactured by Suga Test Instruments Co., Ltd.; emitting light extremely similar to sunlight), the heat-shielding film was irradiated with xenon light having an intensity of 160 W/ ^m2 from a distance of 15 cm directly above the heat-shielding film for 15 minutes in an environment of 20°C and 65% RH, and the temperature of the heat-shielding film after irradiation was measured using the temperature sensor described above.
The temperature of the heat-shielding film of Comparative Example 1 was measured in the same manner as above, and the temperature difference between the control example and the heat-shielding film of each Example and Comparative Example was measured using the control example (reference value) and evaluated according to the following evaluation criteria. Evaluation A was evaluated as a level at which the heat-shielding effect in the present disclosure is exhibited.
(Evaluation Criteria)
A: The temperature is lower than that of the control heat shielding film.
B: The temperature is equal to or higher than that of the control heat shielding film.

(2. Weather resistance)
In accordance with JIS K5602 (2008), an accelerated weather resistance test of the heat shielding film was conducted using a metal halide lamp type ultra-accelerated weather resistance tester (manufactured by Daipla Wintes Co., Ltd.), and the heat shielding film after the light resistance test was visually evaluated according to the following criteria.
The accelerated light resistance test was carried out using the above-mentioned device under conditions of a metal halide lamp irradiance of 650 W/m ² and a black panel temperature (test piece temperature) of 53° C. Grade A was evaluated as a level with no practical problems.
(Evaluation Criteria)
A: No change in appearance was observed in the test piece after the accelerated weather resistance test compared to the test piece before the accelerated weather resistance test.
B: After the accelerated weather resistance test, changes such as the occurrence of visually observable cracks and delamination were observed in the test piece.

The results in Tables 1 and 2 show that the heat shielding films of Examples 1 to 6 all contain an ultraviolet absorbing agent and have superior heat shielding properties compared to the heat shielding film of Comparative Example 1, which does not contain a fluorescent brightening agent. In addition, all of the heat shielding films had good weather resistance, which was at a level that did not pose any practical problems.

In contrast, the heat shielding film of Comparative Example 2, which did not contain a fluorescent brightening agent or an ultraviolet absorbing agent, had weather resistance at a level that was problematic for practical use, and the heat shielding film of Comparative Example 3, which did not contain a white pigment, had poor heat shielding properties.

10 heat shielding film 12 colored transparent layer 14 white reflective layer 16 adhesive layer

Claims (7)

At least a white reflective layer is included,
the white reflective layer contains at least one synthetic resin selected from the group consisting of polyvinyl chloride resin, acrylic resin, and fluororesin, a white pigment, and 0.1% by mass to 5.0% by mass of a fluorescent whitening agent relative to the total solid content of the white reflective layer ;
A heat shielding film having a colored transmitting layer containing a synthetic resin and a colorant on one surface of the white reflective layer . The heat shielding film according to claim 1, wherein the white reflective layer does not contain an ultraviolet absorbing agent. 3. The heat shielding film according to claim 1, wherein the synthetic resin contained in the white reflective layer comprises at least one selected from the group consisting of polyvinyl chloride resins and acrylic resins. The heat shielding film according to any one of claims 1 to 3, wherein the colorant does not contain carbon black. The heat shielding film according to any one of claims 1 to 4, wherein the synthetic resin contained in the colored transparent layer includes at least one selected from the group consisting of polyvinyl chloride resin and acrylic resin. The heat shielding film according to any one of claims 1 to 5, which is used as an exterior material for a vehicle. The heat shielding film according to any one of claims 1 to 5, which is used as an exterior material for a building.