JP4968491B1 - Infrared reflective film - Google Patents

Abstract

An object of the present invention is to provide an infrared reflective film having high infrared reflectivity, high visible light transmittance, and excellent heat resistance.
A high refractive index layer containing a high refractive index pigment and a binding polymer compound, and a low refractive index layer containing a low refractive index pigment and a binding polymer compound are laminated on a substrate. In the infrared reflective film thus obtained, the above object is achieved by the infrared reflective film characterized in that the xerogel compound is contained in both the high refractive index layer and the low refractive index layer or one of the layers.
[Selection] Figure 1

Description

  The present invention relates to an infrared reflective film.

  Infrared reflective films that reflect infrared rays can be used to shield infrared rays that are incident on buildings or vehicles, for example, by sticking to the walls or windows of buildings or vehicles. It is possible to prevent the rise and reduce the energy spent for cooling in summer. In particular, when used in a transparent part such as a window, an infrared reflective film having wavelength selectivity that reflects infrared rays but transmits visible rays is desired.

  So far, a method for producing an infrared reflective film by an evaporation method in which an inorganic compound having a high refractive index and an inorganic compound having a low refractive index are alternately deposited is known (Patent Document 1). Further, after applying a slurry in which titanium oxide particles are dispersed, drying is performed to form a high refractive index layer, and after applying a silica sol slurry on the high refractive index layer, drying is performed to form a low refractive index layer. A method for producing an infrared reflective film by a coating method is known (Patent Document 2).

JP 2007-65232 A JP 2003-266578 A

The manufacturing method of the infrared reflective film by the vapor deposition method described in Patent Document 1 requires a large-scale vacuum apparatus when the vapor deposition is continuously performed a plurality of times, and the initial cost is high.
In the method of alternately repeating vapor deposition in batch processing, the number of steps increases as the number of layers increases, resulting in an increase in cost.
Patent Document 2 describes that a slurry of titanium oxide or silica sol is used and the coating process and the drying process are sequentially repeated. However, this method is too costly and is not suitable for mass production.

Furthermore, the high refractive index layer and the low refractive index layer of the infrared reflective film of Patent Document 1 or Patent Document 2 are formed using only an inorganic compound or a metal oxide. Therefore, when formed on a flexible substrate, since there is no binding substance, when the film is bent, the inorganic compound and the metal oxide are easily peeled off.
However, when a high molecular compound binder is used, the inorganic compound and the metal oxide are difficult to peel off, but there is a possibility that the heat resistance may deteriorate due to discoloration during long-term use.
An object of the present invention is to obtain an infrared reflective film with little discoloration even when heated using a binder of a polymer compound.

In the first invention, a high refractive index layer containing a high refractive index pigment and a binding polymer compound, and a low refractive index layer containing a low refractive index pigment and a binding polymer compound are laminated on a substrate. In the infrared reflective film, the infrared reflective film is characterized in that a silicone acrylic copolymer and a xerogel compound are contained in both or one of the high refractive index layer and the low refractive index layer.

  In the second invention, the xerogel compound is at least one xerogel compound selected from gelatin, agar, carrageenan, xanthan gum, gum arabic, and guar gum. It is a sex film.

  The infrared reflective film of the present invention is excellent in heat resistance with little discoloration even when heated.

Schematic diagram showing an example of simultaneous multilayer coating method Cross-sectional schematic diagram of the infrared reflective film of Example 1 Reflection spectrum and sunlight irradiation spectrum of the infrared reflective film obtained in Example 1 and Example 2

According to a first aspect of the present invention, a high refractive index layer containing a high refractive index pigment and a binding polymer compound, and a low refractive index layer containing a low refractive index pigment and a binding polymer compound are formed on a substrate. In the laminated infrared reflective film, the infrared reflective film is characterized by containing a silicone acrylic copolymer and a xerogel compound in both the high refractive index layer and the low refractive index layer or one of the layers. .

  In a second aspect of the present invention, the xerogel compound is at least one xerogel compound selected from gelatin, agar, carrageenan, xanthan gum, gum arabic, and guar gum. Infrared reflective film.

The infrared reflective film is an infrared reflective film in which two or more layers having different refractive indexes are laminated on a light-transmitting substrate, and the refractive index difference between adjacent layers is 0.1 to 0.4. It is preferable that it is the range of these.
In the case of an infrared reflective film in which three or more layers are laminated, the difference in refractive index between adjacent layers may be within the above range, and the difference in refractive index between all adjacent layers need not be the same.

  The incident light side of the infrared reflective film is a high refractive index layer. The thicknesses of the high refractive index layer and the low refractive index layer are preferably about ¼ of the wavelength λ of the reflected infrared light. In order to reflect infrared rays having a wavelength near 1200 nm, the thickness of the high refractive index layer and the low refractive index layer is preferably about 300 nm.

  In addition, if the change in the refractive index at the boundary between the high refractive index layer and the low refractive index layer is not clear, the infrared reflection performance deteriorates. In the method of sequentially applying the ink for forming the high refractive index layer and the ink for forming the low refractive index layer, the lower layer dissolves when the upper layer is applied while the layers are successively applied in layers. The ink for forming the high refractive index layer and the ink for forming the low refractive index layer are mixed at the boundary between the refractive index layer and the low refractive index layer, and it is difficult to obtain good infrared reflection performance over a wide area.

  In order to form a plurality of layers so that the high refractive index layer and the low refractive index layer are thin films and are not mixed with each other, the selection of both ink compositions and the coating method are important. The simultaneous multilayer coating method is a method in which a plurality of layers are coated in a single coating process, but an additional component such as a polymer compound is required in accordance with the high refractive index pigment and the low refractive index pigment.

  High refractive index pigments and low refractive index pigments are inorganic compounds, so they do not change color when heated, but when high molecular compounds and additive components are organic compounds, they are colored by heating and transmit visible light. Will be reduced. Therefore, the composition of the ink must be selected so as not to impair the heat resistance of the manufactured infrared reflective film. The present inventor has found that there is little discoloration even when the infrared reflective film is heated by including xerogel in the high refractive index layer or the low refractive index layer of the infrared reflective film, and has reached the present invention. is there.

  As a method of forming a plurality of layers, preparing a high refractive index layer forming ink and a low refractive index layer forming ink, forming a high refractive index layer forming ink liquid layer from the high refractive index layer forming ink, An ink liquid layer for forming a low refractive index layer is formed from an ink for forming a low refractive index layer, an ink liquid layer for forming a high refractive index layer, an ink liquid layer for forming a low refractive index layer, and an ink liquid layer for forming a high refractive index layer. There is a simultaneous multi-layer coating method in which a multi-layered structure is formed and simultaneously applied to a substrate while maintaining the stacked structure. However, if the ink liquid layers are simply overlapped, the overlapping ink liquid layers are mixed with each other, and an infrared reflective film with a clear change in the refractive index at the boundary between the high refractive index layer and the low refractive index layer is obtained. I can't. Ink composition is important to solve the problem of ink mixing.

  One method of preventing mixing between the ink liquid layers when forming the above laminated structure is to include a gelling agent in either or either of the high refractive index layer forming ink and the low refractive index layer forming ink, Immediately after the simultaneous application to the substrate while maintaining the laminated structure, the laminated structure is cooled to reduce the fluidity of the ink liquid layer containing the gelling agent. This is a method for preventing mixing of the refractive index layer forming ink liquid layer.

  Another method for preventing mixing between the ink liquid layers when forming the above laminated structure is to include a reactive polymer compound in the high refractive index layer forming ink and a crosslinkable compound in the low refractive index layer forming ink. When an ink liquid layer for forming a high refractive index layer and an ink liquid layer for forming a low refractive index layer are superimposed, a reactive polymer compound and a crosslinkable compound react with each other to cause a hardly soluble substance to have a high refractive index. This is a method in which mixing between the ink liquid layer for forming the high refractive index layer and the ink liquid layer for forming the low refractive index layer is prevented by forming the ink liquid layer for forming the layer and the ink liquid layer for forming the low refractive index layer. The hardly soluble substance means a substance in which at least a part of a reaction product of a reactive polymer compound and a crosslinkable compound becomes insoluble and hinders the flow of liquid in the ink liquid layer.

  A reactive polymer compound may be contained in the low refractive index layer forming ink, and a crosslinkable compound may be contained in the high refractive index layer forming ink.

  In addition, as a method for preventing the mixing of the high refractive index layer forming ink liquid layer and the low refractive index layer forming ink liquid layer, a method of adding a gelling agent to the above ink and a reaction of a hardly soluble substance by reaction. You may combine the method to produce | generate.

≪Application method≫
FIG. 1 is a schematic view showing an example of a simultaneous multilayer coating method.
A die coating unit 11 has slits 1, 2, and 3 for extruding ink. The number of slits is not limited to 3 and can be any number.

  Each ink is stored in the tank 1t, the tank 2t, and the tank 3t. The ink that is pushed out by the ink supply pump 1p, the ink supply pump 2p, and the ink supply pump 3p and flows out from each slit is an ink liquid on the slide slope of the die coating unit. The ink liquid layers are stacked on the slide slope of the die coating unit 11 so that the upper ink liquid layer runs on the lower ink liquid layer.

The method of stacking the ink liquid layer includes a method in which a plurality of slit nozzles are arranged above the slide slope, the solution is poured in the form of a curtain from above and stacked on the slide slope, and is not limited to the coating method of FIG.

1s, 2s and 3s are ink liquid layers made of each ink. When the ink liquid layers of 1s, 2s and 3s are stacked on the slide slope, each ink liquid layer is mixed when adjacent ink liquid layers come into contact with each other. The method for preventing the fit is as described above. Although the apparatus and the like are not shown in the drawing, the ink liquid layer can be overlapped with 4s, 5s, 6s, 7s,.

The substrate 5 wound around the coating roll 4 is guided to the rotating coating roll, scoops up the stacked ink liquid layer which is about to flow down from the end of the die coating unit, and the ink liquid layer stacked on the substrate is removed. After being applied, the ink is dried in the drying zone 7 to produce a laminate. In the method using a gelling agent, a cooling zone 6 is provided before the drying zone to cool the ink liquid layer.

≪High refractive index pigment, low refractive index pigment≫
The inorganic compound particles are used for adjusting the refractive index of the high refractive index layer and the low refractive index layer, and the refractive index of the inorganic compound particles is not particularly limited, but may be in the range of 1.3 to 7.0. preferable. Examples of the inorganic compound include metal and metalloid oxides, phosphorus oxides, nitrides, carbides, halides, and the like.

  Examples of the high refractive index pigment used for the inorganic compound particles in the high refractive index layer include titanium oxide, lead oxide, iron oxide, tungsten oxide, indium oxide, tin oxide, zinc oxide, cerium oxide, bismuth oxide, zirconium oxide, and niobium oxide. , Tantalum oxide, composite compounds thereof, and compounds doped with other elements. Titanium oxide and tin oxide are particularly preferable.

  Examples of the low refractive index pigment used for the inorganic compound particles of the low refractive index layer include, for example, silicon oxide, aluminum oxide, sodium fluoride, magnesium fluoride, lithium fluoride, calcium fluoride, composite compounds thereof, and other elements. And silicon oxide and aluminum oxide are particularly preferable.

Inorganic compound particles may be used alone or in combination of two or more. Also,
Although there is no restriction | limiting in particular in the shape of an inorganic compound particle, It is preferable that a particle size is 0.1 nm-400 nm from an infrared reflectiveness and transparency viewpoint, and it is more preferable that it is 0.5 nm-50 nm.

  Liquids in which the inorganic compound particles are already dispersed as fine particles are commercially available, and it is convenient and preferable to use these commercially available products. Examples of the commercially available products include AERODISP series such as “AERODISP (registered trademark) -W740” (manufactured by Nippon Aerosil Co., Ltd., aqueous dispersion), “Sun colloid (registered trademark) HX-M5” (manufactured by Nissan Chemical Industries, Ltd.). Sun colloid series, such as "Optlake (registered trademark) 1120Z 8RU-25" (manufactured by JGC Catalysts and Chemicals), or "Ludox (registered trademark) HS-40" (manufactured by DuPont), etc. Such as the Ludox series.

≪Aqueous solvent≫
In the present invention, an infrared reflective film is produced using water-based ink. For water-based ink, a mixed solution of water and an organic solvent having an affinity for water is used in addition to water. A mixed solution of water and the organic solvent is referred to as an aqueous solvent.
Examples of organic solvents having an affinity for water include lower alcohols such as methanol, ethanol, propyl alcohol, isopropyl alcohol, and butyl alcohol, ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone, ethylene glycol Glycols such as propylene glycol, cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, ethers such as dioxane and tetrahydrofuran, dimethylformamide and the like.

≪High molecular weight compound≫
A polymer compound that binds a high refractive index pigment or a low refractive index pigment is used by being contained in water-based ink. The polymer compound is not particularly limited as long as it can be dissolved or dispersed in an aqueous solvent and can form a film upon drying.

  Examples of organic synthetic polymer compounds that are generally highly soluble in the aqueous solvent include, for example, hydroxymethylcellulose, hydroxyethylcellulose, methylcellulose, ethylcellulose, carboxymethylcellulose, carboxyethylcellulose, hydroxypropylcellulose, and a saponification degree of 50 mol% or more (preferably Is 70 mol% or more) polyvinyl alcohol (PVA) and its derivatives, polystyrene sulfonic acid having a sulfonation degree of 50 mol% or more (preferably 70 mol% or more), and a saponification degree of 50 mol% or more (preferably 70 mol% or more). Ethylene-vinyl alcohol copolymer, polyacrylic acid and salts thereof, aqueous acrylic resin, polyvinyl pyrrolidone, polyethylene glycol, alginates, aqueous polyester resin, aqueous polyurethane Butter, aqueous epoxy resin, aqueous polyolefin resin, aqueous phenolic resin, poly-para vinylphenol and the like. These may be used individually by 1 type and may use 2 or more types together. “Aqueous” means water-soluble, and the production method is not particularly limited, but in any case, it is easy to use commercially available products.

Examples of the aqueous acrylic resin include a copolymer of acrylic acid and (meth) acrylic acid alkyl ester or other polymerizable monomer. Examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isopropyl (meth) acrylate, (meth) Examples include isobutyl acrylate, 2-ethylhexyl (meth) acrylate, n-hexyl (meth) acrylate, and lauryl (meth) acrylate. Other polymerizable monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, acrylamide, N-methylol acrylamide, diacetone acrylamide, glycidyl (meth) acrylate, styrene, vinyl toluene, Examples include vinyl acetate, acrylonitrile, vinyl alcohol, and ethylene. For example, commercially available products such as “Watersol (registered trademark)” series manufactured by DIC Corporation may be used.
In addition, in this invention, (meth) acrylic acid ... means both methacrylic acid ... and acrylic acid ....

  The water-based polyester resin includes, for example, polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxypropyl ether, glycerin, trimethylolethane, and trimethylolpropane. , Dehydration condensation with polybasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, succinic anhydride, adipic acid, sebacic acid, maleic anhydride, itaconic acid, fumaric acid, etc. It can be obtained by adding and dispersing in water. In addition, for example, commercially available products such as “Vylonal (registered trademark)” series manufactured by Toyobo Co., Ltd. may be used.

Polyparavinylphenol is a homopolymer of paravinylphenol, and a commercially available product can be used. Examples of the commercially available products include “Marcalinker (registered trademark)” series manufactured by Maruzen Petrochemical Co., Ltd.
Specific examples of the polyvinyl alcohol derivative include carboxylated polyvinyl alcohol, sulfonated polyvinyl alcohol, acetoacetylated polyvinyl alcohol, and mixtures thereof.
Silicone acrylic-modified resin emulsions include the Charine E (registered trademark) series of silicone acrylic aqueous dispersions manufactured by Nissin Chemical Industry Co., Ltd.

  The binding polymer compound is preferably a polymer compound modified with an inorganic compound. This is because when the polymer compound has a portion modified with an inorganic compound, the affinity between the inorganic compound particle and the polymer compound is improved, and the inorganic compound particles can be bonded well. Examples of the modification of the inorganic compound include silicon compound modification such as silicone modification, tin compound modification, titanium compound modification, and aluminum compound modification. The polymer compound modified with an inorganic compound may be a graft polymer of an inorganic compound and a polymer compound, or may be a copolymer of an inorganic compound and a polymer compound. In particular, a silicone acrylic copolymer is preferably used from the viewpoint of affinity with an inorganic compound and transparency.

  The binding polymer compound may be a xerogel compound obtained from a gelling agent described below.

  The weight average molecular weight of the organic synthetic polymer compound is preferably 5,000 to 1,000,000, more preferably 10,000 to 100,000, and still more preferably 10,000 to 50,000. In the present specification, the weight average molecular weight is a value in terms of polystyrene measured by gel permeation chromatography (GPC).

≪Gelling agent≫
The component that reduces the fluidity of the ink liquid layer when cooled is not particularly limited as long as it exhibits its function. Since the handling in manufacture is easy, a gelling agent can be used suitably. A gelling agent is a material that transitions from a highly fluid sol state to a less fluid gel state by cooling. As a gelling agent, it has good solubility or dispersibility in aqueous solvents, supplements moisture by hydrogen bonding, and has the effect of increasing the viscosity of aqueous inks even in small amounts, so gelatin, agar, carrageenan, xanthan gum, Gum arabic and guar gum are particularly preferred. Gelatin has a gelation temperature of about 15 to 20 ° C. and is easy to handle in production, so that gelatin is most preferably used. However, other gelling agents are particularly considered if they are produced in consideration of the respective gelation temperatures. There is no problem.
In addition, a gelatinizer becomes a xerogel compound by apply | coating and drying, and shows the effect which reduces the discoloration of the infrared reflective film by heating.

≪Compounds that form insoluble substances≫
Although it does not restrict | limit especially as a reactive high molecular compound, The high molecular compound which has a hydroxyl group, a carboxyl group, etc., for example, polyvinyl alcohol, polyphenol, polycarboxylic acid etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. From the viewpoint of solubility in a solvent, the crosslinkable polymer compound preferably has a weight average molecular weight of 5,000 to 300,000, more preferably 30,000 to 200,000, and more preferably 50,000 to 150,000. Further preferred.

  As the crosslinkable compound, for example, a crosslinkable titanium compound such as boric acid, titanium hydroxide, or an organic titanium compound can be used, and the polymer compound can be made insoluble or insoluble by crosslinking. When the polymer compound has a ligand, crosslinking by chelation is possible. For example, it is difficult to chelate the polymer compound with chelate crosslinking with aluminum sulfate, cobalt sulfate, cobalt acetate, calcium hydroxide, magnesium hydroxide, etc. It can be solubilized or insolubilized.

≪Base body≫
Examples of the substrate on which the high refractive index layer and the low refractive index layer of the present invention are applied include, for example, polyethylene terephthalate film, polybutylene terephthalate film, polyester film such as polyethylene naphthalate film, polyolefin film such as polypropylene film, and diacetyl cellulose. Films, cellulose films such as triacetylcellulose film and acetylcellulose butyrate film, vinyl chloride films such as polyvinyl chloride film and polyvinylidene chloride film, vinyl alcohol films such as polyvinyl alcohol film and ethylene-vinyl acetate copolymer film Copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyetheretherketone Irumu, polyether sulfone film, polyether film such as polyetherimide film, a polyimide film, a fluororesin film, a polyamide film, an acrylic resin film, norbornene resin film, cycloolefin resin films or the like. Among these, a polyethylene terephthalate film and a triacetyl cellulose film are preferable from the viewpoint of transparency and production cost.
Although there is no restriction | limiting in particular in the thickness of a light-transmitting base material, Although it selects suitably according to a condition, Usually, Preferably it is 10-300 micrometers, More preferably, it is the range of 30-200 micrometers, More preferably, it is 50-125 micrometers.

  Moreover, this base | substrate can be surface-treated by the oxidation method, the uneven | corrugated method, etc. on one side or both surfaces as needed for the purpose of improving the adhesiveness with the layer provided in the surface. Examples of the oxidation method include corona discharge treatment, chromic acid treatment (wet), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment and the like, and examples of the unevenness method include a sand blast method and a solvent treatment method. Is mentioned. These surface treatment methods are appropriately selected according to the type of the light-transmitting substrate, but in general, the corona discharge treatment method is preferably used from the viewpoints of effects and operability.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited at all by these examples. In each example, the following light-transmitting substrate was used as the substrate. Furthermore, the visible light transmittance and infrared transmittance of the infrared reflective film obtained in each example were measured as follows.

(Light transmissive substrate)
A polyethylene terephthalate film “Cosmo Shine A4100” (manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm was used as a light-transmitting substrate.
(Measurement method of visible light transmittance)
The visible light transmittance was measured in accordance with JIS R3106 (1998). In addition, the visible light was irradiated from the opposite side to the light-transmitting substrate of the infrared reflective film.
(Measurement method of infrared reflectance)
Infrared reflectance was measured according to JIS R3106 (1998). In addition, infrared rays were irradiated from the opposite side to the light transmissive base material of an infrared reflective film.
(Measurement method of heat resistance)
The color difference between the sample before heating and the color of the sample heated in an oven at 100 ° C. for 12 hours is measured with a colorimetric color difference meter ZE-2000 manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS K7105 and JIS Z8722. Compared. The smaller the color difference, the smaller the color change and the better the heat resistance.

Example 1
Ink A for forming a high refractive index layer was obtained from the following composition. In addition, all the compositions of the examples were heated and stirred with a mechanical stirrer in a constant temperature water bath at 40 ° C., and the 5 μm mesh filter “Minisalto 17594K” (manufactured by Hitech Co., Ltd.) was used with care not to lower the temperature. The foreign matter was removed through.

Titanium oxide aqueous dispersion: 60 parts by weight “AERODISP (registered trademark) -W740”
(Nippon Aerosil Co., Ltd., solid content 40%)
Silicone acrylic aqueous dispersion: 120 parts by weight “Charine (registered trademark) FE-230N”
(Nissin Chemical Industry Co., Ltd., solid content 10%)
Gelatin: 12 parts by weight “gelatin type B derived from alkali-treated cattle”
(Nitta Gelatin Co., Ltd., 100% solid content)
Organo-titanium compound: 3 parts by weight “Orgachix (registered trademark) ТC-310”
(Matsumoto Fine Chemical Co., Ltd., solid content 42%)
Ion exchange water: 485 parts by weight

  In order to measure the refractive index, the above high refractive index layer forming ink A was applied to a polyester film having a thickness of 100 μm using a wire bar, and then dried in an oven at 120 ° C. for 3 minutes to have a thickness of 3 μm. A layer was formed, and the refractive index of the coating film was measured using a refractometer “DVA-36L type” (manufactured by Mizoji Optical Co., Ltd.). The refractive index was 1.60.

Ink B for forming a low refractive index layer was obtained from the following composition.

Silicon oxide aqueous dispersion: 60 parts by weight “Ludox (registered trademark) HS-40”
(DuPont, solid content 40%)
Silicone acrylic aqueous dispersion: 120 parts by weight “Charine (registered trademark) FE-230N”
(Nissin Chemical Industry Co., Ltd., solid content 10%)
Gelatin: 12 parts by weight “gelatin type B derived from alkali-treated cattle”
(Nitta Gelatin Co., Ltd., 100% solid content)
Polyvinyl alcohol: 12 parts by weight “GOHSENOL (registered trademark) KL-03”
(Nippon Synthetic Chemical Industry Co., Ltd., solid content 100%)
Ion exchange water: 596 parts by weight

  For the measurement of the refractive index, the low refractive index layer forming ink B was applied to a polyester film having a thickness of 100 μm using a wire bar, and then dried in an oven at 120 ° C. for 3 minutes to have a thickness of 3 μm. When a layer was formed and the refractive index of the coating film was measured using a refractometer “DVA-36L type” (manufactured by Mizoji Optical Co., Ltd.), the refractive index was 1.40 (for forming a high refractive index layer). The refractive index difference from the case of using ink A was 0.20).

Using the coating apparatus of FIG. 1 (however, the tank 4t, the ink supply pump 4p, and the slit 4 and the subsequent portions are not shown), the high refractive index layer forming ink A heated to 40 ° C. is added to the tanks 1t, 3t, After filling the tanks 2t, 4t, and 6t with the low refractive index layer forming ink B filled in 5t and 7t and heated to 40 ° C., the ink supply pumps 1p to 7p are operated and the slit 1 of the coating die unit 11 is operated. Each ink was extruded from ~ 7.
The stacked ink liquid layers 1 s to 7 s flowing down the coating die unit 11 heated to 40 ° C. are applied to the easy-adhesion treated surface of the substrate 5 conveyed by the coating roll 4 and cooled in the cooling zone 6 at 5 ° C. Then, it was dried in a drying zone 7 at 80 ° C. As a result, seven layers of high refractive index layer / low refractive index layer / high refractive index layer / low refractive index layer / high refractive index layer / low refractive index layer / high refractive index layer were formed on the PET film substrate. The infrared reflective film of Example 1 was obtained. The thickness of the seven layers obtained by subtracting the thickness of the substrate from the thickness of the infrared reflective film was about 2.1 μm.

In Example 1, the organic titanium compound contained in the high refractive index layer forming ink A and the polyvinyl alcohol contained in the low refractive index layer forming ink B undergo a crosslinking reaction to form a crosslinked polyvinyl alcohol-titanium. To do. The polyvinyl alcohol contained in the low refractive index layer forming ink B also has a function of bonding silicon oxide particles. Moreover, gelatin is contained in the high refractive index layer and the low refractive index layer as dried xerogel.
When the cross section of the obtained infrared reflective film was observed with an electron microscope, it was confirmed that the layer structure could be identified, the thickness of each high refractive index layer was about 0.3 μm, and the thickness of each low refractive index layer was It was about 0.3 μm. The presence of a crosslinked polyvinyl alcohol-titanium between the high refractive index layer and the low refractive index layer could not be confirmed with an electron microscope.

In FIG. 3, 31 is the reflection spectrum of the infrared reflective film obtained in Example 1, 32 is the reflection spectrum of the infrared reflective film obtained in Example 2 below, and 33 is the irradiation spectrum of sunlight. From FIG. 3, the infrared reflective films obtained in Example 1 and Example 2 have high infrared reflectivity and high visible light transmittance, so that the infrared reflectivity and visible light transmittance are good. Recognize.
The infrared reflective film obtained in Example 1 has an infrared reflectance at a wavelength of 1000 nm of 55%, a total infrared reflectance of 19% in the range of 780 nm to 2100 nm, and a total visible light transmittance in the range of wavelengths of 350 nm to 780 nm. 87%.

(Example 2)
Ink C for forming a high refractive index layer was obtained from the following composition.

Titanium oxide aqueous dispersion: 60 parts by weight “AERODISP (registered trademark) -W740”
(Nippon Aerosil Co., Ltd., solid content 40%)
Gelatin: 20 parts by weight “gelatin type B derived from alkali-treated cattle”
(Nitta Gelatin Co., Ltd., 100% solid content)
Ion exchange water: 560 parts by weight

Ink D for forming a low refractive index layer was obtained from the following composition.

Silicon oxide aqueous dispersion: 60 parts by weight “Ludox (registered trademark) HS-40”
(DuPont, solid content 40%)
Gelatin: 20 parts by weight “gelatin type B derived from alkali-treated cattle”
(Nitta Gelatin Co., Ltd., 100% solid content)
Ion exchange water: 560 parts by weight

Using the coating apparatus of FIG. 1, the high refractive index layer forming ink C heated to about 40 ° C. is filled in the tanks 1 t and 3 t, and the low refractive index layer forming ink D heated to about 40 ° C. is stored in the tank. After filling in 2t, each ink was extruded from the slits 1 to 3 of the coating die unit 11 which was heated to about 40 ° C. by operating the ink supply pumps 1p to 3p.
After the stacked ink liquid layers 1 s to 3 s flowing down the coating die unit 11 are applied on the easy-adhesion-treated surface of the substrate 5 conveyed by the coating roll 4, the coating is cooled in a cooling zone 6 at 5 ° C. and further 80 ° C. The drying zone 7 was dried. Thus, an infrared reflective film of Example 2 in which a three-layer structure of a high refractive index layer / a low refractive index layer / a high refractive index layer was formed on the PET film substrate was obtained. The thickness of the three layers obtained by subtracting the thickness of the substrate from the thickness of the infrared reflective film was about 0.9 μm.

  In Example 2, the fluidity of the ink liquid layer is lowered by cooling the gelatin contained in the high refractive index layer forming ink C and the low refractive index layer forming ink D after coating. The gelatin after drying has a function of binding inorganic compound particles as a xerogel. When the cross section of the obtained infrared reflective film was observed with an electron microscope, it was confirmed that the layer structure could be identified, the thickness of each high refractive index layer was about 0.3 μm, and the thickness of the low refractive index layer was about It was 0.3 μm.

  As shown in FIG. 3, the infrared reflective film obtained in Example 2 has an infrared reflectance at a wavelength of 1000 nm of 49%, a total infrared reflectance in the range of 780 nm to 2100 nm, 16%, and a wavelength in the range of 350 nm to 780 nm. The total visible light transmittance was 89%.

(Comparative Example 1)
Ink F for forming a high refractive index layer was obtained from the following composition.

Titanium oxide aqueous dispersion: 60 parts by weight “AERODISP (registered trademark) -W740”
(Nippon Aerosil Co., Ltd., solid content 40%)
Silicone acrylic aqueous dispersion: 240 parts by weight “Charine (registered trademark) FE-230N”
(Nissin Chemical Industry Co., Ltd., solid content 10%)
Organo-titanium compound: 3 parts by weight “Orgachix (registered trademark) ТC-310”
(Matsumoto Fine Chemical Co., Ltd., solid content 42%)
Ion exchange water: 370 parts by weight

An ink G for forming a low refractive index layer was obtained from the following composition.

Silicon oxide aqueous dispersion: 60 parts by weight “Ludox (registered trademark) HS-40”
(DuPont, solid content 40%)
Silicone acrylic aqueous dispersion: 240 parts by weight “Charine (registered trademark) FE-230N”
(Nissin Chemical Industry Co., Ltd., solid content 10%)
Polyvinyl alcohol: 12 parts by weight “GOHSENOL (registered trademark) KL-03”
(Nippon Synthetic Chemical Industry Co., Ltd., solid content 100%)
Ion exchange water: 470 parts by weight

Using the coating apparatus of FIG. 1, after filling the tanks 1t and 3t with the high refractive index layer forming ink F and filling the tank 2t with the low refractive index layer forming ink G, the ink supply pumps 1p to 3p are operated. Then, each ink was extruded from the slits 1 to 3 of the coating die unit 11.
After the stacked ink liquid layers 1 s to 3 s flowing down the coating die unit 11 were applied on the easy-adhesion treated surface of the substrate 5 conveyed by the coating roll 4, they were dried in a drying zone 7 at 80 ° C. Thus, an infrared reflective film of Comparative Example 1 in which a three-layer structure of a high refractive index layer / low refractive index layer / high refractive index layer was formed on the PET film substrate was obtained. The thickness of the three layers obtained by subtracting the thickness of the substrate from the thickness of the infrared reflective film was about 0.9 μm.

  In Comparative Example 1, the organic titanium compound contained in the high refractive index layer forming ink F and the polyvinyl alcohol contained in the low refractive index layer forming ink G undergo a crosslinking reaction to form a crosslinked polyvinyl alcohol-titanium. . When the cross section of the obtained infrared reflective film was observed with an electron microscope, it was confirmed that the layer structure could be identified, the thickness of each high refractive index layer was about 0.3 μm, and the thickness of each low refractive index layer was It was about 0.3 μm.

≪Results of heat resistance measurement≫
Table 1 shows the color differences of the infrared reflective films obtained in Example 1, Example 2, and Comparative Example 1 measured before heating and after the acceleration test. The minimum and maximum values measured at 5 points are shown.
Thereby, it turns out that the heat resistance of the infrared reflective film containing a xerogel is excellent.

  The infrared reflective film of the present invention can be used, for example, to stick to a window glass of a building or vehicle (automobile, train, bus, aircraft, ship, etc.) to prevent temperature rise in the building or vehicle.

1t: tank 2t: tank 3t: tank 1p: ink supply pump 2p: ink supply pump 3p: ink supply pump 1: slit 2: slit 3: slit 1s: ink liquid layer 2s: ink liquid layer 3s: ink liquid layer 4: Coating roll 5: Substrate 6: Cooling zone 7: Drying zone 11: Coating die unit 22: High refractive index layer 23: Low refractive index layer 31: Reflection spectrum 32 of the infrared reflective film of Example 1 Infrared ray of Example 2 Reflection spectrum 33 of reflective film: irradiation spectrum of sunlight

Claims (2)

In an infrared reflective film in which a high refractive index layer containing a high refractive index pigment and a binding polymer compound, and a low refractive index layer containing a low refractive index pigment and a binding polymer compound are laminated on a substrate,
An infrared reflective film characterized by containing a silicone acrylic copolymer and a xerogel compound in both or one of the high refractive index layer and the low refractive index layer.   The infrared reflective film according to claim 1, wherein the xerogel compound is at least one xerogel compound selected from gelatin, agar, carrageenan, xanthan gum, gum arabic, and guar gum.

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