JP2014070255A - Metal flat plate particle dispersion, its manufacturing method and heat-ray shielding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal flat plate particle dispersion capable of manufacturing a heat-ray shielding material excellent in heat-shielding performance.SOLUTION: A metal flat plate particle dispersion contains metal flat plate particles, and has a ratio of an average particle diameter of primary particles of the metal flat plate particles and the average particle diameter of second particles made by aggregation of the primary particles (the particle diameter of the secondary particles/the particle diameter of the primary particles) of 1.0 to 3.0, pH of 5 to 10 and the content of the metal flat plate particles of 22 g/L or less.

Description

  The present invention relates to a metal tabular grain dispersion, a production method thereof, and a heat ray shielding material. More specifically, the present invention relates to a metal tabular grain dispersion capable of producing a heat ray shielding material having excellent heat shielding performance, a method for producing the same, and a heat ray shielding material produced using the metal tabular grain dispersion.

  In recent years, heat ray shielding materials for automobiles and building windows have been developed as one of energy saving measures for reducing carbon dioxide. From the viewpoint of the heat ray shielding property (acquisition rate of solar heat), the heat ray reflection type without re-radiation is better than the heat ray absorption type with re-radiation of absorbed light into the room (about 1/3 of the absorbed solar energy). Various proposals have been made.

  For example, Patent Document 1 has 60% by number or more of hexagonal or circular tabular metal particles, and the main plane of the hexagonal or circular tabular metal particles is one surface of the metal particle-containing layer. With a heat ray shielding material that is plane-oriented in the range of 0 ° to ± 30 ° on the average, it has a high reflection wavelength selectivity and a reflection band selectivity, and is a heat ray reflection type that is excellent in visible light transmission and radio wave transmission. It is described that a heat ray shielding material can be provided. In Patent Document 1, the orientation state of the metal tabular grains in the coating film is specified, but the state of the dispersion of the metal tabular grains and the state of the silver tabular grains in the dispersion are not specified. For example, in the example of Patent Document 1, only the addition of water after synthesizing a metal tabular particle dispersion, centrifugation, and removal of the supernatant is described, and the conditions of the redispersion step are almost described. There wasn't. Moreover, although patent document 1 mentions the primary particle diameter of a metal tabular grain, there was no description about the secondary particle diameter.

  As an example of examining the dispersion state of fine particles, Patent Document 2 specifies the ratio of secondary particle size to primary particle size (secondary particle size / primary particle size) of pigment fine particles made of a polyhalogenated zinc phthalocyanine compound. A method for suppressing secondary aggregation is described. However, the pigment fine particles used in Patent Document 2 are not metal particles, and no mention is made of particles other than pigments. In the method described in Patent Document 2, secondary aggregation is suppressed by controlling the ratio of the secondary particle diameter to the primary particle diameter at the time of pigment build-up, and particles having a specific shape are synthesized as in Patent Document 1. There was no mention of controlling the ratio of the secondary particle size to the primary particle size when the particles after being redispersed after centrifugation.

JP 2011-118347 A JP 2011-68837 A

  When the present inventors prepared a dispersion of tabular metal particles by the method described in the example of Patent Document 1, it was found that the dispersibility was not good. Moreover, it turned out that the heat ray shielding material produced from the metal tabular grain dispersion liquid in which such a dispersed state is not so good becomes low in heat ray shielding ability (heat ray reflectivity).

  The problem to be solved by the present invention is to provide a metal tabular grain dispersion liquid capable of producing a heat ray shielding material having excellent heat shielding performance.

  In order to solve the above-mentioned problems, the present inventors diligently studied to find that the ratio of the secondary particle diameter to the primary particle diameter, the pH, and the content of the metal tabular grains are in a specific range, and the metal is in a well dispersed state. To find that a metal tabular grain coating film prepared from a tabular grain dispersion exhibits excellent heat ray shielding properties and to provide a metal tabular grain dispersion capable of producing a heat ray shielding material having excellent heat shielding performance. It came.

The present invention which is a specific means for solving the above-described problems is as follows.
[1] The ratio of the average particle size of the primary particles of the metal tabular particles, including the metal tabular particles, to the average particle size of the secondary particles formed by aggregation of the primary particles (secondary particle size / primary particles The particle size distribution is 1.0 to 3.0, the pH is 5 to 10, and the content of the metal tabular grains is 22 g / L or less.
[2] In the metal tabular grain dispersion liquid according to [1], the metal tabular grain preferably contains at least silver.
[3] The metal tabular grain dispersion liquid according to [1] or [2] preferably further contains gelatin.
[4] A heat ray shielding material comprising a metal particle-containing layer formed using the metal tabular grain dispersion described in any one of [1] to [3].
[5] In the heat ray shielding material according to [4], it is preferable that an RMS granularity of the metal tabular grain in the metal particle-containing layer is 15 or less.

  ADVANTAGE OF THE INVENTION According to this invention, the metal tabular grain dispersion liquid which can manufacture the heat ray shielding material excellent in heat insulation performance can be provided.

FIG. 1 is a schematic diagram of a configuration of a dynamic light scattering apparatus that measures the average particle diameter of secondary particles. FIG. 2 is an SEM image of the heat ray shielding material of Example 1. FIG. 3A is an image of the heat ray shielding material of Example 1 before the RMS patch processing. 3B is an image after the RMS patch processing of the heat ray shielding material of Example 1. FIG. FIG. 3C is a diagram illustrating a histogram calculated from an image after the RMS patch processing of the heat ray shielding material according to the first embodiment. FIG. 4 is a schematic view showing an example of the heat ray shielding material of the present invention. FIG. 5A is a schematic view showing another example of the heat ray shielding material of the present invention. FIG. 5B is a schematic view showing another example of the heat ray shielding material of the present invention. FIG. 5C is a schematic view showing another example of the heat ray shielding material of the present invention. FIG. 6A is a schematic perspective view showing an example of the shape of tabular grains contained in the heat ray shielding material of the present invention, and shows circular tabular metal particles. FIG. 6B is a schematic perspective view showing an example of the shape of a tabular grain contained in the heat ray shielding material of the present invention, and shows hexagonal tabular metal particles. FIG. 7A is a schematic cross-sectional view showing the existence state of a metal particle-containing layer containing metal tabular grains in the heat ray shielding material of the present invention, and is a metal particle-containing layer containing metal tabular grains (parallel to the plane of the substrate). ) And the main plane of the metal tabular grain (the plane that determines the equivalent circle diameter D). FIG. 7B is a schematic cross-sectional view showing the existence state of the metal particle-containing layer containing metal tabular grains in the heat ray shielding material of the present invention, and the metal tabular grains in the depth direction of the heat ray shielding material of the metal particle-containing layer. FIG. FIG. 7C is a schematic cross-sectional view showing an example of the presence state of a metal particle-containing layer containing metal tabular grains in the heat ray shielding material of the present invention. FIG. 7D is a schematic cross-sectional view showing another example of the existence state of the metal particle-containing layer containing the metal tabular grains in the heat ray shielding material of the present invention. FIG. 7E is a schematic cross-sectional view showing another example of the existence state of the metal particle-containing layer containing the metal tabular grains in the heat ray shielding material of the present invention. FIG. 8 shows the ratio of the secondary particle diameter of the metal tabular grains contained in the metal tabular grain dispersion liquid of each Example and Comparative Example to the primary particle diameter and the RMS granularity of the metal tabular grains contained in the heat ray shielding material. It is a scatter diagram showing correlation.

Hereinafter, the heat ray shielding material of the present invention will be described in detail.
The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

[Metal tabular grain dispersion]
The tabular metal particle dispersion of the present invention contains tabular metal particles, and the ratio of the average particle diameter of primary particles of the metal tabular grains to the average particle diameter of secondary particles formed by aggregation of the primary particles (two Secondary particle diameter / primary particle diameter) is 1.0 to 3.0, pH is 5 to 10, and the content of the metal tabular grains is 22 g / L or less.
With such a configuration, when the metal tabular grain dispersion of the present invention is used, a heat ray shielding material excellent in heat shielding performance can be produced.
Hereinafter, preferred embodiments of the metal tabular grain dispersion of the present invention will be described.

<Metal tabular grains>
The tabular metal particle dispersion of the present invention contains tabular metal particles, and the ratio of the average particle diameter of primary particles of the metal tabular grains to the average particle diameter of secondary particles formed by aggregation of the primary particles (two Secondary particle diameter / primary particle diameter) is 1.0 to 3.0.

(Shape of metal tabular grain)
-Average particle size of primary particles-
The average particle size of the primary particles of the metal tabular grains contained in the metal tabular grain dispersion of the present invention is preferably from 70 nm to 500 nm, more preferably from 100 nm to 400 nm. When the average particle size is 70 nm or more, the absorption contribution of the tabular silver particles is smaller than the contribution of reflection, so that sufficient heat ray reflectivity is obtained, and when it is 500 nm or less, haze (scattering) is reduced. It is advantageous in terms of the peak wavelength of the transmission spectrum when the average particle size of the metal tabular grains is within the more preferable range.

  Unless otherwise specified, the average particle diameter of the primary particles (equivalent circle diameter, synonymous with equivalent circle diameter) is the average of values obtained by measuring with a microscope as the projected area equivalent circle diameter defined in JIS Z 8901. Mean value. In the present specification, specifically, it means an average value of main plane diameters (maximum lengths) of 200 tabular grains arbitrarily selected from images obtained by observing grains with a TEM.

-Average particle size of secondary particles-
Moreover, the average particle diameter of the secondary particle of the metal tabular grain contained in the metal tabular grain dispersion of the present invention is 1.0 to 3.0 times the average particle diameter of the primary particle, and is 1.0 to 2.8. It is preferable that it is 2 times, and it is more preferable that it is 1.0 to 2.5 times. If the average particle diameter is outside this range, the dispersibility of the primary particles may become unstable and the primary particles may aggregate.

Unless otherwise specified, the measurement of the average particle diameter of the secondary particles is a dynamic light having a metal tabular grain dispersion of 1 g / L to 50 g / L and having a Mach-Zehnder interferometer and a low coherence light source. It means a value measured using a scatterometer. Specifically, the light emitted from the low-coherence light source is divided into two, one of the divided lights is used as reference light, and the other is used as scattered light through a medium containing particles. Preferably, the measurement is performed by a dynamic light scattering measuring device having means for combining the two lights.
FIG. 1 is an apparatus configuration diagram schematically showing one embodiment of a dynamic light scattering measurement apparatus that can be used in the present invention using a Mach-Zehnder interferometer. As a light source of the dynamic light scattering measurement apparatus 10, a low coherence light source (SLD) 1 is used. F1, F2, F3, F4, F5, F6, and F7 are optical fibers (light propagation paths). 3 is an optical coupler (optical branching mechanism). Reference numerals 6a, 6b and 6c denote collimator lenses (joiners of fibers and air in the light propagation path). Reference numeral 7 denotes a phase modulator (modulator). Reference numeral 2 denotes a circulator (the light coming from the optical fiber F3 is extracted into the optical fiber F4, and the light entering from the optical fiber F4 is guided to the optical fiber F6. An optical path changer). Reference numeral 12 denotes an objective lens (condenser). S is a scattering medium sample containing particles s1 in the medium s2. Reference numeral 4 denotes an optical coupler (optical coupling mechanism). Reference numeral 5 denotes a balance detector (detector). C is a BNC cable (electric cable). Reference numeral 8 denotes an A / D board (electric signal reading unit). Reference numeral 9 denotes a PC (data processing / analysis unit).
Although the wavelength of the light of the SLD light source 1 employed in the present embodiment is not particularly limited, for example, it is preferably 0.125 to 2 μm, and more preferably 0.250 to 1.5 μm. F1 to F7 may be replaced with an optical fiber, for example, a method of spatial propagation. The branching ratio of the optical coupler 3 can be changed according to the object to be measured. The modulation section 17 including the collimator lenses 6a and 6b and the modulator 7 may be a mechanism for performing modulation in the fiber or modulating in the fiber. Alternatively, the modulation unit 17 may be structured to include the circulator 2, the optical fiber F4, and the objective lens 12 employed in the other optical path, and the sample (scattering medium) S may be replaced with a oscillating mirror to perform modulation. is there. The objective lens 12 can be changed according to the measurement system. If the particle size is large, the objective lens need not be used. It is also considered necessary to adjust the light quantity by interposing an attenuator between the optical fibers F2 and F5. The A / D board 8 and the PC 9 can be replaced with a spectrum analyzer or the like. As the circulator 2, a 1: 1 coupler can be used, and the incident light path and the output light path can be separated.
The light of the low-coherence light source 1 propagates through the optical fiber F1, enters the optical coupler 3, and is split into two lights by the optical coupler 3. One of the divided lights is converted into parallel rays by the collimator lens 6a through the optical fiber F2, passes through the phase modulator 7, enters the optical fiber F5 by the collimator lens 6b, passes through the optical fiber F5, and the optical coupler-4. To reach. This light is called “reference light”. If the one-way optical path length from the optical coupler 3 to the optical coupler 4 is dref, the optical path of the reference light is the optical path length dref.
The other light split by the optical coupler 3 passes through the optical fiber F3, passes through the optical fiber F4 by the circulator 2, is collimated by the collimator 6c, and is incident on the scattering medium S in the sample cell by the condenser 12. The Backscattered light from the scattering medium passes through the condenser 12, the collimator lens 6c, and the optical fiber F4 again, and passes through the optical fiber F6 by the circulator 2 and enters the optical coupler 4. This light is called “scattered light”. The optical path length d1 from the optical coupler 3 to the spot where scattering occurs in the scattering medium S (the distance to the scattering medium may be defined according to the measurement condition and target, for example, it can be determined up to the condensing position). If the total of the optical path length d2 from the location where scattering occurs in the scattering medium S to the optical coupler 4 is defined as dsca, the optical path of the scattered light is optical path length dsca = d1 + d2.
The reference light and scattered light incident on the optical coupler 4 pass through an optical fiber F7 and are incident on a light receiving diode (PD; Photo Detector) 5, and this electrical conversion signal passes through a BNC cable C, and the A / D board. 8 outputs a power spectrum of the light interference intensity on the personal computer 9. This spectrum is called “heterodyne spectrum”. On the other hand, a power spectrum obtained by blocking the optical path of the reference light and detecting the intensity of only the scattered light is called “homodyne spectrum”. JP, 2005-121600, A can be referred to for details, such as a coherence function of a low-coherence light source concerning these series of measurements and calculations, a power spectrum of interference light intensity, and a scattered light spectrum.
Embodiments of the measurement apparatus and measurement method that can be used in the present invention are not limited to the above-described embodiments. For example, in addition to the interferometer using an optical fiber, a space propagation type interferometer can be used. Various other changes can be made.

The metal tabular grain dispersion of the present invention contains tabular metal grains, and preferably contains hexagonal or circular tabular metal grains.
The metal tabular grain is not particularly limited as long as it is a grain composed of two main planes (see FIGS. 6A and 6B), and can be appropriately selected according to the purpose. For example, hexagonal, circular, triangular Examples include shape. Among these, in terms of high visible light transmittance, a hexagonal or more polygonal shape to a circular shape is more preferable, and a hexagonal shape or a circular shape is particularly preferable.
In the present specification, the circular shape means 0 per side of a metal tabular grain having a length of 50% or more of the average equivalent circle diameter of a tabular metal grain (synonymous with tabular metal grain) described later. Say the shape that is. The circular tabular metal grains are not particularly limited as long as they have no corners and round shapes when observed from above the main plane with a transmission electron microscope (TEM), depending on the purpose. It can be selected appropriately.
In the present specification, the hexagonal shape means a shape in which the number of sides having a length of 20% or more of the average equivalent circle diameter of the metal tabular grains described later is 6 per one metal tabular grain. The same applies to other polygons. The hexagonal metal tabular grain is not particularly limited as long as it is a hexagonal shape when the metal tabular grain is observed from above the main plane with a transmission electron microscope (TEM), and is appropriately selected according to the purpose. For example, the hexagonal corner may be acute or dull, but the corner is preferably dull in that the absorption in the visible light region can be reduced. There is no restriction | limiting in particular as a grade of the dullness of an angle, According to the objective, it can select suitably.

  In the metal tabular grain dispersion, hexagonal or circular tabular metal particles are preferably 60% by number or more, more preferably 65% by number or more based on the total number of metal particles. 70% by number or more is particularly preferable. When the ratio of the hexagonal to circular plate-like metal particles is 60% by number or more, the visible light transmittance tends to increase.

-Thickness of metal tabular grains-
The hexagonal or circular plate-like metal particles preferably have a thickness of 20 nm or less, and more preferably 14 nm or less.

The aspect ratio of the hexagonal or circular plate-like metal particles is not particularly limited and may be appropriately selected depending on the intended purpose. However, the reflectance in the infrared light region with a wavelength of 800 nm to 1,800 nm is not limited. From the point which becomes high, 6-40 are preferable and 8-30 are more preferable. When the aspect ratio is less than 8, the reflection wavelength becomes smaller than 800 nm, and when it exceeds 40, the reflection wavelength becomes longer than 1,800 nm and sufficient heat ray reflectivity may not be obtained.
The aspect ratio means a value obtained by dividing the average particle size (average equivalent circle diameter) of primary particles of tabular metal grains by the average grain thickness of tabular metal grains. The average grain thickness corresponds to the distance between the main planes of the metal tabular grain, and is, for example, as shown in FIGS. 6A and 6B and can be measured by an atomic force microscope (AFM).
The method for measuring the average particle thickness by the AFM is not particularly limited and can be appropriately selected depending on the purpose.For example, a particle dispersion containing metal tabular particles is dropped onto a glass substrate and dried. For example, a method of measuring the thickness of one particle may be used.

(Material of tabular metal particles)
There is no restriction | limiting in particular as a material of the said metal tabular grain, Although it can select suitably according to the objective, From the point with the high reflectance of a heat ray (near infrared rays), silver, gold | metal | money, aluminum, copper, rhodium, nickel Platinum is preferred, and at least silver is more preferred.

(Metal tabular grain content)
In the metal tabular grain dispersion of the present invention, the content of the metal tabular grains is 22 g / L or less, and more preferably 1 to 22 g / L.

<Gel (gelatin)>
When producing the metal tabular grain dispersion of the present invention, it is preferable to add a gel during synthesis of the metal particles. The gel is not particularly limited, but is preferably a hydrophilic colloid.
Examples of the hydrophilic colloid include gelatin, colloidal albumin, agar, gum arabic, alginic acid, hydrolyzed cellulose acetate, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose and other cellulose derivatives, synthetic binders such as polyvinyl alcohol, and partial saponification. Polyvinyl acetate, polyacrylamide, poly N, N-dimethylacrylamide, poly N-vinyl pyrrolidone, U.S. Pat. Nos. 3,847,620, 3,655,389, 3,341,332, 3, 615,424, 3,860,428 and the like, water-soluble polymers as described in U.S. Pat. Nos. 2,614,928 and 2,525,753, phenylcarbamyl as described in U.S. Pat. Gelatin, acylated gelatin Polymerization of gelatin derivatives such as phthalated gelatin, acrylic acid (ester), methacrylic acid (ester), acrylonitrile, etc. as described in US Pat. Nos. 2,548,520 and 2,831,767 Examples thereof include those obtained by graft copolymerization of a monomer having an ethylene group with gelatin. These binders can be used as a compatible mixture of two or more as required.

Among these, gelatin is preferable, and water-soluble gelatin is more preferable from the viewpoint that it can be added as an aqueous solution. That is, the metal tabular grain dispersion of the present invention preferably further contains gelatin.
The molecular weight of the gelatin is not particularly limited, but gelatin having an average molecular weight of 1 to 300,000 is preferably used, and gelatin having 20,000 to 150,000 is more preferably used.
Two or more kinds of gelatins may be used. When two or more kinds of gelatins are used, 0.1 to 1.5% by mass of gelatin having an average molecular weight of 10,000 to 50,000 is averaged based on the amount of all gelatins. It is preferable to contain 0.1 to 1.5% by mass of gelatin having a molecular weight of 60,000 to 300,000.

<PH of tabular metal particle dispersion>
The pH of the metal tabular grain dispersion of the present invention is 5 to 10, more preferably 5 to 8. If the pH is less than 5, the particles will approach the isoelectric point of gelatin and no charge repulsion of the particles will occur, and further hydrolysis will proceed, so that the protective colloid properties of gelatin will deteriorate and the particles will aggregate. Even when the pH is 10 or more, the protective colloid property of gelatin is lowered due to the progress of hydrolysis, and the dispersibility of the particles is lowered.

(Preparation of metal tabular grains)
Although there is no restriction | limiting in particular as a method of synthesize | combining a metal tabular grain, For example, liquid phase methods, such as a chemical reduction method, a photochemical reduction method, an electrochemical reduction method, etc. are mentioned. Among these, a liquid phase method such as a chemical reduction method or a photochemical reduction method is particularly preferable in terms of shape and size controllability.

  In addition, after synthesizing hexagonal to triangular metal tabular grains, for example, by performing etching treatment with a dissolved species that dissolves silver such as nitric acid and sodium sulfite, aging treatment by heating, etc., hexagonal to triangular metal The corners of the tabular grains may be blunted to obtain hexagonal or circular tabular metal grains.

  As a method for synthesizing the metal tabular grains, in addition to the above, a seed crystal may be previously fixed on the surface of a transparent substrate such as a film or glass, and then metal grains (for example, Ag) may be grown in a tabular form.

  When the metal tabular grain dispersion of the present invention is produced, a pH buffer such as an alkali metal carbonate, borate or phosphate, chloride salt, bromide salt, iodide is used during the synthesis of the metal particles. Additives such as salts, benzimidazoles, benzothiazoles or mercapto compounds may be used.

  The metal tabular grain may be subjected to further treatment in order to impart desired properties. The further treatment is not particularly limited and may be appropriately selected depending on the purpose. For example, the formation of a high refractive index shell layer, the addition of various additives such as a dispersant and an antioxidant may be included. Can be mentioned.

In order to further improve the visible light region transparency, the metal tabular grain may be coated with a high refractive index material having high visible light region transparency.
As the high refractive index material is not particularly limited and may be appropriately selected depending on the purpose, for example, TiO _x, BaTiO _3, ZnO, etc. SnO _2, ZrO _2, NbO _x and the like.

There is no restriction | limiting in particular as said coating method, According to the objective, it can select suitably, For example, Langmuir, 2000, 16 volumes, p. As reported in 2731-2735, a method of forming a TiO _x layer on the surface of silver metal tabular grains by hydrolyzing tetrabutoxytitanium may be used.

Further, when it is difficult to form a high refractive index metal oxide layer shell directly on the metal tabular grain, after synthesizing the metal tabular grain as described above, an SiO ₂ or polymer shell layer is appropriately formed, The metal oxide layer may be formed on the shell layer. When TiO _x is used as a material for the high refractive index metal oxide layer, since TiO _x has photocatalytic activity, there is a concern of deteriorating the matrix in which the metal tabular grains are dispersed. After forming the TiO _x layer on the tabular grains, an SiO ₂ layer may be appropriately formed.

The metal tabular grains may adsorb an antioxidant such as mercaptotetrazole or ascorbic acid in order to prevent oxidation of metals such as silver constituting the metal tabular grains. Further, an oxidation sacrificial layer such as Ni may be formed on the surface of the metal tabular grain for the purpose of preventing oxidation. Moreover, it may be covered with a metal oxide film such as SiO ₂ for the purpose of blocking oxygen.
For the purpose of imparting dispersibility, the metal tabular grain is, for example, a low molecular weight dispersant or a high molecular weight dispersant containing at least one of N elements such as quaternary ammonium salts and amines, S elements, and P elements. A dispersant may be added.

-Purification and concentration of tabular metal grains-
In addition, the metal tabular grain dispersion of the present invention can be purified by removing impurities other than the coexisting metal tabular grains and impurities such as a residual reducing agent after the preparation of the tabular metal grains, and at the same time concentrate the tabular metal grains.
The purification / concentration method can be any method such as centrifugation, decantation, suction filtration, etc., but it is preferable to perform centrifugation from the viewpoint of heat ray shielding performance when a heat ray shielding material is produced. .

-Stirring (redispersion)-
The method for producing a metal tabular grain dispersion of the present invention comprises adding an aqueous NaOH solution, and then adding an average particle diameter of primary particles of the metal tabular grains and an average particle diameter of secondary particles formed by aggregation of the primary particles. And stirring (hereinafter also referred to as redispersion) until the ratio (secondary particle size / primary particle size) becomes 1.0 to 3.0.
Although there is no restriction | limiting in particular as a stirring method, It is preferable to use a stirring bar and a desktop homogenizer, and it is more preferable to use a desktop homogenizer. As stirring (redispersion) conditions, for example, dispersion can be performed at 10,000 to 18000 rpm, and dispersion is preferably performed at 13,000 to 16000 rpm.
The stirring time is not particularly limited, and the ratio between the average particle size of primary particles of the metal tabular particles and the average particle size of secondary particles formed by aggregation of the primary particles (secondary particle size / primary particle size). It is preferable to stir until the (diameter) becomes 1.0 to 3.0. For example, in the above-described stirring (redispersion) conditions, 2 to 50 minutes are preferable, 3 to 40 minutes are more preferable, and 5 to 30 minutes are particularly preferable.

  The metal tabular grain dispersion after stirring (redispersion) is preferably adjusted to pH to produce the metal tabular grain dispersion of the present invention. The preferred pH range is the same as the preferred pH range of the metal tabular grain dispersion of the present invention. There is no restriction | limiting in particular as a method of adjusting pH.

The metal tabular particle dispersion after stirring (redispersion) is preferably filtered after pH adjustment. There is no restriction | limiting in particular as the method of filtration, It can filter by an appropriate method according to the primary particle size of the metal tabular grain contained in the metal tabular grain dispersion liquid before re-dispersion. For example, when the primary particle size of the metal tabular grain is 70 to 500 nm, a filter having a filtration accuracy of 1 to 10 μm can be used.
Further, the yield of the metal tabular particle dispersion (percentage of liquid mass ratio before and after filtration) by the method for producing a metal tabular grain dispersion of the present invention is preferably 85% or more, and preferably 90% or more. More preferably, it is particularly preferably 95% or more.

[Heat ray shielding material]
The heat ray shielding material of the present invention has a metal particle-containing layer formed using the metal tabular particle dispersion of the present invention.

As for the heat ray shielding material of this invention, it is preferable that the RMS granularity of a metal tabular grain is 30 or less. The RMS granularity in the present invention refers to a metal tabular grain with respect to the RMS granularity in the silver salt photograph described in P504 of “Basics of Revised Photo Engineering—Silver Salt Photo Edition— (Corona, 1998)”. The metal tabular grains were extracted from the electron micrograph of the above, and the opening diameter was 0.6 μm □. RMS is an abbreviation for root mean square.
The method for obtaining the RMS granularity in the present invention is as follows.
(1) Take an electron micrograph of tabular metal grains,
(2) Binarize the photo to extract metal tabular grains,
(3) Average the density with a 0.6 μm square mesh,
(4) The coefficient of variation of the density of this mesh is obtained, and this is used as the RMS granularity in the present invention.
In the heat ray shielding material of the present invention, the RMS granularity of the metal tabular grains is preferably 25 or less, more preferably 20 or less, and particularly preferably 15 or less. On the other hand, in the heat ray shielding material of the present invention, from the viewpoint of heat ray shielding, the RMS granularity of the metal tabular grains is preferably 1 or more, more preferably 2 or more, and particularly preferably 4 or more.

  In addition to the metal particle-containing layer, the heat ray shielding material of the present invention may preferably have other layers such as an adhesive layer, an ultraviolet absorption layer, a base material, and a metal oxide particle-containing layer as necessary.

As shown in FIG. 4, the layer structure of the heat ray shielding material 10 has a metal particle-containing layer 2 containing at least one kind of metal particles, and the metal tabular grains 3 are unevenly distributed on the surface thereof. Can be mentioned.
Moreover, as shown to FIG. 5A, the aspect which has the base material 1, the metal particle content layer 2 on this base material, and the adhesion layer 11 on this metal particle content layer is mentioned suitably.
5B, the base material 1, the metal particle-containing layer 2 on the base material, the overcoat layer 4 on the metal particle-containing layer, and the adhesive layer 11 on the overcoat layer. The aspect which has is mentioned suitably.
Moreover, as shown to FIG. 5C, the aspect which has the metal oxide fine particle content layer 12 and the hard-coat layer 5 on it on the opposite side to the side which has the metal particle content layer 2 of the base material 1 is also suitable. Can be mentioned.

<Metal particle content layer>
The metal particle-containing layer is a layer formed using the metal tabular particle dispersion of the present invention.
When the thickness of the metal particle-containing layer is d, 80% by number or more of the hexagonal or circular plate-like metal particles are present in the range of d / 2 from the surface of the metal particle-containing layer. It is preferable that it exists in the range of d / 3 from the surface of the said metal-particle content layer. It is not limited to any theory, and the heat ray shielding material of the present invention is not limited to the following production method, but a specific polymer (preferably latex) is used when producing the metal particle-containing layer. By adding it, the metal tabular grains can be segregated on one surface of the metal particle-containing layer.

(Plane orientation)
In the heat ray shielding material of the present invention, the hexagonal or circular flat plate-like metal particles have a principal plane whose one surface is the surface of the metal particle-containing layer (if the heat ray shielding material has a substrate, the surface of the substrate). On the other hand, it is preferably plane-oriented in the range of 0 ° to ± 30 ° on average, more preferably plane-oriented in the range of 0 ° to ± 20 ° on average, and 0 ° to ± 10 ° on average. It is particularly preferable that the surface orientation be in the range of.
The presence state of the metal tabular grains is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably arranged as shown in FIGS. 7D and 7E to be described later.

Here, FIGS. 7A to 7E are schematic cross-sectional views showing the existence state of the metal particle-containing layer containing the metal tabular grains in the heat ray shielding material of the present invention, and the metal tabular grains 3 in the metal particle-containing layer 2. Indicates the presence state of. FIG. 7A is a diagram for explaining an angle (± θ) formed by the plane of the substrate 1 and the main plane of the tabular metal particle 3 (the plane that determines the equivalent circle diameter D). FIG. 7B shows the existence region in the depth direction of the heat ray shielding material of the metal particle-containing layer 2.
In FIG. 7A, the angle (± θ) formed between the surface of the substrate 1 and the main plane of the metal tabular grain 3 or an extension line of the main plane corresponds to a predetermined range in the plane orientation. That is, the plane orientation means a state where the inclination angle (± θ) shown in FIG. 7A is small when the cross section of the heat ray shielding material is observed. In particular, FIG. 7D shows the main surface of the substrate 1 and the metal tabular grain 3. A state where the flat surface is in contact, that is, a state where θ is 0 ° is shown. When the angle of the plane orientation of the main plane of the metal tabular grain 3 relative to the surface of the substrate 1, that is, θ in FIG. 7A exceeds ± 30 °, a predetermined wavelength of the heat ray shielding material (for example, near the visible light region long wavelength side) The reflectance in the infrared light region is reduced.

  There is no particular limitation on the evaluation of whether or not the main plane of the metal tabular grain is plane-oriented with respect to one surface of the metal particle-containing layer (the surface of the substrate when the heat ray shielding material has a substrate). , Can be selected appropriately according to the purpose. For example, an appropriate cross section is prepared, and a metal particle-containing layer (a base material when the heat ray shielding material has a base material) and a flat metal particle are observed in this section. It may be a method of evaluating. Specifically, as a heat ray shielding material, a microtome or a focused ion beam (FIB) is used to prepare a cross-section sample or a cross-section sample of the heat ray shielding material, and this is used for various microscopes (for example, a field emission scanning electron microscope ( FE-SEM) etc.) and the method of evaluating from images obtained by observation.

In the heat ray shielding material of the present invention, as shown in FIG. 7B, the plasmon resonance wavelength of the metal constituting the metal tabular grain 3 in the metal particle-containing layer 2 is λ, and the refractive index of the medium in the metal particle-containing layer 2 is n. When doing, it is preferable that the said metal-particle content layer 2 exists in the range of ((lambda) / n) / 4 in the depth direction from the horizontal surface of a heat ray shielding material. Within this range, the effect of increasing the amplitude of the reflected wave by the phase of the reflected wave at the interface between the upper and lower metal particle-containing layers of the heat ray shielding material is sufficiently large, and the visible light transmittance and the maximum heat ray Reflectivity is good.
The plasmon resonance wavelength λ of the metal constituting the metal tabular grain in the metal particle-containing layer is not particularly limited and can be appropriately selected according to the purpose. However, in terms of imparting heat ray reflection performance, 400 nm to 2, The thickness is preferably 500 nm, and more preferably 700 nm to 2,500 nm from the viewpoint of imparting visible light transmittance.

(Medium of metal particle containing layer)
There is no restriction | limiting in particular as a medium in the said metal particle content layer, According to the objective, it can select suitably. In the heat ray shielding material of the present invention, the metal-containing layer preferably contains a polymer, and more preferably contains a transparent polymer. Examples of the polymer include polyvinyl acetal resin, polyvinyl alcohol resin, polyvinyl butyral resin, polyacrylate resin, polymethyl methacrylate resin, polycarbonate resin, polyvinyl chloride resin, (saturated) polyester resin, polyurethane resin, gelatin, and cellulose. And polymers such as natural polymers. Among them, in the present invention, the main polymer of the polymer is preferably a polyvinyl alcohol resin, a polyvinyl butyral resin, a polyvinyl chloride resin, a (saturated) polyester resin, a polyurethane resin, and is preferably a polyester resin or a polyurethane resin. 80% by number or more of hexagonal or circular plate-like metal particles are more preferable from the viewpoint of being easily present in the range of d / 2 from the surface of the metal particle-containing layer, and the heat ray shielding of the present invention is a polyester resin. This is particularly preferable from the viewpoint of further improving the rubbing resistance of the material.
Among the polyester resins, a saturated polyester resin is more particularly preferable from the viewpoint of imparting excellent weather resistance since it does not contain a double bond. Moreover, it is more preferable to have a hydroxyl group or a carboxyl group at the molecular terminal from the viewpoint of obtaining high hardness, durability, and heat resistance by curing with a water-soluble / water-dispersible curing agent or the like.
Commercially available polymers can be preferably used as the polymer, and examples thereof include Plus Coat Z-867, which is a water-soluble polyester resin manufactured by Kyoyo Chemical Industry Co., Ltd.
Moreover, in this specification, the main polymer of the polymer contained in the metal-containing layer refers to a polymer component occupying 50% by mass or more of the polymer contained in the metal-containing layer.
It is preferable that content of the said polyester resin with respect to the said metal particle contained in the said metal particle content layer is 1-10000 mass%, It is more preferable that it is 10-1000 mass%, It is 20-500 mass% Is particularly preferred. By setting the binder contained in the metal particle-containing layer to be in the above range or more, physical properties such as rubbing resistance can be improved.
The refractive index n of the medium is preferably 1.4 to 1.7.

(Area ratio of tabular metal grains)
The total area of the metal tabular grains relative to the area A of the base material when viewed from above (the total projected area A of the metal particle-containing layer when viewed from the direction perpendicular to the metal particle-containing layer) The area ratio [(B / A) × 100], which is the ratio of the value B, is preferably 15% or more, and more preferably 20% or more. When the area ratio is less than 15%, the maximum reflectance of the heat ray is lowered, and the heat shielding effect may not be sufficiently obtained.
Here, the area ratio can be measured, for example, by performing image processing on an image obtained by SEM observation of the heat ray shielding base material from above or an image obtained by AFM (atomic force microscope) observation. .

(Average distance between tabular grains)
The average inter-particle distance between the metal tabular grains adjacent in the horizontal direction in the metal particle-containing layer is preferably 1/10 or more of the average particle diameter of the metal tabular grains in terms of visible light transmittance and maximum heat ray reflectance. .
When the horizontal average inter-grain distance of the metal tabular grains is less than 1/10 of the average grain diameter of the metal tabular grains, the maximum reflectance of the heat rays is lowered. Further, the average interparticle distance in the horizontal direction is preferably non-uniform (random) in terms of visible light transmittance. If it is not random, that is, if it is uniform, absorption of visible light occurs, and the transmittance may decrease.

  Here, the horizontal average interparticle distance of the metal tabular grains means an average value of interparticle distances between two adjacent grains. In addition, the average inter-particle distance is random as follows: “When taking a two-dimensional autocorrelation of luminance values when binarizing an SEM image including 100 or more metal tabular grains, other than the origin. It has no significant local maximum.

(Layer structure of metal particle-containing layer)
In the heat ray shielding material of the present invention, the metal tabular grains are arranged in the form of a metal particle-containing layer containing metal tabular grains as shown in FIGS. 7A to 7E.
The metal particle-containing layer may be composed of a single layer as shown in FIGS. 7A to 7E or may be composed of a plurality of metal particle-containing layers. When comprised with a several metal particle content layer, it becomes possible to provide the shielding performance according to the wavelength range | band which wants to provide heat insulation performance.

(Thickness of metal particle containing layer)
In the heat ray shielding material of the present invention, the metal particle-containing layer preferably has a thickness of 10 to 80 nm. The thickness of the metal particle-containing layer is more preferably 20 to 80 nm, and particularly preferably 30 to 50 nm.

  Here, the thickness of each layer of the metal particle-containing layer can be measured, for example, from an image obtained by SEM observation of a cross-sectional sample of the heat ray shielding material.

(Addition of various additives)
In the heat ray shielding material of the present invention, when the metal particle-containing layer contains a polymer and the main polymer of the polymer is a polyester resin, it is preferable to add a crosslinking agent from the viewpoint of film strength. The crosslinking agent is not particularly limited, and examples thereof include epoxy-based, isocyanate-based, melamine-based, carbodiimide-based, and oxazoline-based crosslinking agents. Of these, carbodiimide and oxazoline crosslinking agents are preferred. Specific examples of the carbodiimide-based crosslinking agent include, for example, Carbodilite V-02-L2 (manufactured by Nisshinbo Industries, Ltd.). It is preferable to contain a component derived from 1 to 20% by mass of the crosslinking agent with respect to the total binder in the metal particle-containing layer, and more preferably 2 to 20% by mass.
Moreover, in the heat ray shielding material of this invention, when the said metal particle content layer contains a polymer, it is preferable from a viewpoint from which generation | occurrence | production of surfactant suppresses generation | occurrence | production of a repellency and a favorable planar layer is obtained. As the surfactant, a specific example of a surfactant that can use a known surfactant such as an anionic or nonionic surfactant is, for example, Lapisol A-90 (manufactured by NOF Corporation), Narrow Acty HN-100 (manufactured by Sanyo Chemical Industries, Ltd.). It is preferable to contain 0.05-10 mass% surfactant with respect to all the binders in the said metal-particle content layer, More preferably, it is 0.1-5 mass%.

<Other layers>
<< Adhesive layer >>
The heat ray shielding material of the present invention preferably has an adhesive layer. The adhesive layer may include an ultraviolet absorber.
The material that can be used for forming the adhesive layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, polyvinyl butyral (PVB) resin, acrylic resin, styrene / acrylic resin, urethane resin, polyester Examples thereof include resins and silicone resins. These may be used individually by 1 type and may use 2 or more types together. An adhesive layer made of these materials can be formed by coating.
Furthermore, an antistatic agent, a lubricant, an antiblocking agent and the like may be added to the adhesive layer.
The thickness of the adhesive layer is preferably 0.1 μm to 10 μm.

<< Base material >>
The heat ray shielding material of the present invention preferably has a base material.
The substrate is not particularly limited as long as it is an optically transparent substrate, and can be appropriately selected according to the purpose. For example, the substrate has a visible light transmittance of 70% or more, preferably 80% or more. And those with high transmittance in the near infrared region.
There is no restriction | limiting in particular about the shape, a structure, a magnitude | size, material, etc. as said base material, According to the objective, it can select suitably. Examples of the shape include a flat plate shape, and the structure may be a single layer structure or a laminated structure, and the size may be the size of the heat ray shielding material. It can be appropriately selected according to the above.
The material for the substrate is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include polyolefin resins such as polyethylene, polypropylene, poly-4-methylpentene-1, and polybutene-1, polyethylene terephthalate, Polyester resins such as polyethylene naphthalate; polycarbonate resins, polyvinyl chloride resins, polyphenylene sulfide resins, polyether sulfone resins, polyethylene sulfide resins, polyphenylene ether resins, styrene resins, acrylic resins, polyamides Examples thereof include a film made of a cellulose resin such as a cellulose resin, a polyimide resin, and cellulose acetate, or a laminated film thereof. Among these, a polyethylene terephthalate film is particularly preferable.
There is no restriction | limiting in particular as thickness of this base film, It can select suitably according to the intended purpose of a solar radiation shielding film, Usually, they are about 10 micrometers-500 micrometers, 12 micrometers-300 micrometers are preferable, and 16 micrometers-125 micrometers are more. preferable.

<< Hard coat layer >>
In order to add scratch resistance, it is also preferable that the functional film includes a hard coat layer having hard coat properties. The hard coat layer can contain metal oxide particles.
There is no restriction | limiting in particular as said hard-coat layer, The kind and formation method can be selected suitably according to the objective, for example, acrylic resin, silicone resin, melamine resin, urethane resin, alkyd resin And thermosetting or photocurable resins such as fluorine-based resins. There is no restriction | limiting in particular as thickness of the said hard-coat layer, Although it can select suitably according to the objective, 1 micrometer-50 micrometers are preferable. When an antireflection layer and / or an antiglare layer are further formed on the hard coat layer, a functional film having antireflection properties and / or antiglare properties in addition to scratch resistance is preferably obtained.

<< Overcoat layer >>
In the heat ray shielding material of the present invention, in order to prevent oxidation and sulfidation of the metal tabular grains due to mass transfer and to provide scratch resistance, the heat ray shielding material of the present invention comprises the hexagonal or circular tabular metal particles. You may have the overcoat layer closely_contact | adhered to the surface of the said metal particle content layer of the exposed one. Moreover, you may have an overcoat layer between the said metal-particle content layer and the below-mentioned ultraviolet absorption layer. The heat ray shielding material of the present invention, particularly when the metal tabular grains are unevenly distributed on the surface of the metal particle-containing layer, prevents contamination of the production process due to peeling of the metal tabular grains, prevents the disorder of the arrangement of the metal tabular grains at the time of coating another layer, etc. Therefore, it may have an overcoat layer.
The overcoat layer may contain an ultraviolet absorber.
The overcoat layer is not particularly limited and may be appropriately selected depending on the intended purpose.For example, the overcoat layer contains a binder, a matting agent, and a surfactant, and further contains other components as necessary. It becomes.
The binder is not particularly limited and may be appropriately selected depending on the purpose. For example, thermosetting of acrylic resin, silicone resin, melamine resin, urethane resin, alkyd resin, fluorine resin, etc. Mold or photo-curable resin.
The thickness of the overcoat layer is preferably 0.01 μm to 1,000 μm, more preferably 0.02 μm to 500 μm, particularly preferably 0.1 to 10 μm, and particularly preferably 0.2 to 5 μm.

<< UV absorber >>
The heat ray shielding material of the present invention preferably has a layer containing an ultraviolet absorber.
The layer containing the ultraviolet absorber can be appropriately selected depending on the purpose, and may be an adhesive layer, or a layer (for example, an overcoat) between the adhesive layer and the metal particle-containing layer. Layer). In any case, the ultraviolet absorber is preferably added to a layer disposed on the side irradiated with sunlight with respect to the metal particle-containing layer.

  The ultraviolet absorber is not particularly limited and may be appropriately selected depending on the purpose. For example, a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a triazine ultraviolet absorber, a salicylate ultraviolet absorber, Examples include cyanoacrylate ultraviolet absorbers. These may be used individually by 1 type and may use 2 or more types together.

<< Metal oxide particles >>
The heat ray shielding material of the present invention is preferable from the viewpoint of balance between heat ray shielding and production cost even if it contains at least one kind of metal oxide particles in order to absorb long wave infrared rays. In this case, you may have the metal oxide particle content layer 12 independently, and the hard-coat layer 5 may contain the metal oxide particle. The hard coat layer 5 may be laminated with the metal particle-containing layer 2 via the substrate 1. When the heat ray shielding material of the present invention is arranged so that the metal particle-containing layer 2 is on the incident direction side of heat rays such as sunlight, a part (or all) of the heat rays is reflected by the metal particle-containing layer 2. After that, the hard coat layer 5 will absorb a part of the heat rays, and the amount of heat directly received inside the heat ray shielding material due to the heat rays that are not absorbed by the metal oxide particle-containing layer and pass through the heat ray shielding material, The amount of heat as the total amount of heat absorbed by the metal oxide particle-containing layer of the heat ray shielding material and indirectly transmitted to the inside of the heat ray shielding material can be reduced.
There is no restriction | limiting in particular as a material of the said metal oxide particle, According to the objective, it can select suitably, For example, a tin dope indium oxide (henceforth "ITO"), a tin dope antimony oxide (henceforth). , Abbreviated as “ATO”), zinc oxide, titanium oxide, indium oxide, tin oxide, antimony oxide, glass ceramics, and the like. Among these, ITO, ATO, and zinc oxide are more preferable, and infrared rays having a wavelength of 1,200 nm or more are preferably 90 in that they have excellent heat ray absorption ability and can produce a heat ray shielding material having a wide range of heat ray absorption ability when combined with metal tabular grains. In particular, ITO is preferable in that it has a visible light transmittance of 90% or more.
The volume average particle size of the primary particles of the metal oxide particles is preferably 0.1 μm or less in order not to reduce the visible light transmittance.
There is no restriction | limiting in particular as a shape of the said metal oxide particle, According to the objective, it can select suitably, For example, spherical shape, needle shape, plate shape, etc. are mentioned.

<Method for producing heat ray shielding material>
There is no restriction | limiting in particular as a manufacturing method of the heat ray shielding material of this invention, According to the objective, it can select suitably, For example, the said metal particle content layer and the said ultraviolet absorption layer are applied to the surface of the said base material by the apply | coating method. In addition, a method of forming other layers as necessary may be mentioned.

-Method for forming metal particle-containing layer-
The method for forming the metal particle-containing layer of the present invention is not particularly limited and may be appropriately selected depending on the purpose. May be applied by a dip coater, a die coater, a slit coater, a bar coater, a gravure coater, or the like, or may be subjected to surface orientation by a method such as an LB film method, a self-organization method, or spray coating. When the heat ray shielding material of the present invention is produced, the composition of the metal particle-containing layer used in the examples described later is used, and by adding latex or the like, the hexagonal or circular tabular metal particles 80 The number% or more is made to exist in the range of d / 2 from the surface of the metal particle-containing layer. It is preferable that 80% by number or more of the metal tabular grains of the hexagonal or circular tabular metal particles exist in a range of d / 3 from the surface of the metal particle-containing layer. Although there is no restriction | limiting in particular in the addition amount of the said latex, For example, it is preferable to add 1-10000 mass% with respect to a metal tabular grain.

  In addition, in order to accelerate | stimulate plane orientation, after apply | coating a metal tabular grain, you may accelerate | stimulate by passing through pressure bonding rollers, such as a calender roller and a laminating roller.

<Characteristics of heat ray shielding material>
The shielding coefficient of the heat ray shielding material of the present invention is preferably 0.8 or less, and more preferably 0.7 or less.
The haze of the heat ray shielding material of the present invention is preferably 3% or less, more preferably 2% or less, and particularly preferably 1% or less. As a result of producing the heat ray shielding material of the present invention using the metal tabular grain dispersion of the present invention, haze (scattering) can also be reduced.
The visible light transmittance of the heat ray shielding material of the present invention is preferably 60% or more and more preferably 70% or more when the shielding coefficient is 0.68. When the visible light transmittance is less than 60%, for example, when used as automotive glass or building glass, the outside may be difficult to see.

<Use aspect of heat ray shielding material>
When using the heat ray shielding material of the present invention to provide functionality to existing window glass, an adhesive is laminated and attached to the indoor side of the glass. At that time, the reflective layer is directed to the sunlight side as much as possible to prevent heat generation. Therefore, the adhesive layer is laminated on the metal tabular particle-containing layer, and the surface is bonded to the window glass. Is appropriate.

The heat-shielding material of the present invention can be bonded to either glass or plastic to produce a bonded structure.
There is no restriction | limiting in particular as a manufacturing method of the said bonding structure, According to the objective, it can select suitably, The heat ray shielding material of this invention manufactured as mentioned above is glass or plastics for vehicles, such as a motor vehicle. And a method of bonding to glass or plastic for building materials.

The heat ray shielding material of the present invention is not particularly limited as long as it is an embodiment used for selectively reflecting or absorbing heat rays (near infrared rays), and may be appropriately selected according to the purpose. Examples include films and laminated structures, building material films and laminated structures, agricultural films, and the like. Among these, in terms of energy saving effect, a vehicle film and a laminated structure, a building material film and a laminated structure are preferable.
In addition, in this invention, a heat ray (near infrared rays) means the near infrared rays (780 nm-1,800 nm) contained about 50% in sunlight.

The features of the present invention will be described more specifically with reference to examples.
The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Production Example 1]
-Synthesis of silver tabular grain A1-
To 308 mL of pure water, 24.5 mL of 1% sodium citrate aqueous solution and 16.7 mL of 8 g / L sodium polystyrenesulfonate aqueous solution were added and heated to 35 ° C. To this solution, 1 mL of 2.3 wt% aqueous sodium borohydride solution was added, and 363 mL of 0.5 mM aqueous silver nitrate solution (Ag-1) was added with stirring. After stirring this solution for 30 minutes, 24.5 mL of 1% sodium citrate aqueous solution, 33 mL of 10 mM aqueous ascorbic acid solution, and 211 mL of pure water were added. Furthermore, 199 mL of 0.5 mM aqueous silver nitrate solution (Ag-2) was added with stirring. After stirring for 30 minutes, 197 mL of a 7.7% potassium hydroquinonesulfonate aqueous solution, 33 g of inert gelatin having an average molecular weight of 100,000, and 22 g of inert gelatin having an average molecular weight of 20,000 in 480 mL of pure water were added to a reaction kettle. Added. Next, after adding 4.4 mL of 1N nitric acid, a white precipitate mixed solution of silver sulfite obtained by mixing 64 mL of 13.5% sodium sulfite aqueous solution and 217 mL of 10% silver nitrate aqueous solution and 351 mL of pure water in advance is added. Added. After stirring this solution for 300 minutes, 145 mL of 1N NaOH was added, and silver tabular grain dispersion liquid A1 was obtained.

[Production Example 2]
-Synthesis of silver tabular grain A2-
When preparing the silver tabular grain dispersion A1, a white precipitate mixed solution of silver sulfite formed by mixing 64 mL of 13.5% sodium sulfite aqueous solution, 217 mL of 10% silver nitrate aqueous solution and 351 mL of pure water is added. The same as the silver tabular grain dispersion liquid A1 except that a white precipitate mixed solution of silver sulfite obtained by mixing 134 mL of 13.5% aqueous sodium sulfite solution, 454 mL of 10% aqueous silver nitrate solution and 734 mL of pure water was added. Thus, silver tabular grain dispersion liquid A2 was synthesized.

[Production Example 3]
-Synthesis of silver tabular grain A3-
When preparing the silver tabular grain dispersion A1, a white precipitate mixed solution of silver sulfite formed by mixing 64 mL of 13.5% sodium sulfite aqueous solution, 217 mL of 10% silver nitrate aqueous solution and 351 mL of pure water is added. The same as the silver tabular grain dispersion liquid A1, except that a white precipitate mixed solution of silver sulfite obtained by mixing 204 mL of 13.5% sodium sulfite aqueous solution, 690 mL of 10% aqueous silver nitrate solution and 1117 mL of pure water was added. Thus, a tabular silver particle dispersion A3 was synthesized.

[Examples 1-11, Comparative Examples 1-10]
<Preparation of silver tabular grain dispersion>
-Preparation of silver tabular grain dispersion B1-
The silver tabular grain dispersion A1 (800 mL) was kept at 40 ° C. and adjusted to pH = 10 using 1N NaOH and / or 1N sulfuric acid. This was centrifuged at 9000 rpm for 60 minutes with a centrifuge (manufactured by Hitachi Koki Co., Ltd., angle rotor), and 760 mL of the supernatant was discarded. The precipitated silver tabular grains were transferred to a desktop homogenizer (SpinMix08, Mitsui Denki Seiki Co., Ltd.), and 360 mL of 0.2 mmol / L NaOH aqueous solution was added and dispersed at 12000 rpm for 20 minutes. After adjusting to pH = 4.5 using 1N NaOH and / or 1N sulfuric acid, a 1 μm cartridge filter (manufactured by Nippon Pole Co., Ltd., Profile II) was passed through to produce silver tabular grain dispersion liquid B1. This was used as the silver tabular grain dispersion of Comparative Example 1.

-Preparation of silver tabular grain dispersion B2-
When preparing the tabular silver particle dispersion B1, the tabular silver particle dispersion B2 is the same as the tabular silver particle dispersion B1, except that the pH is not adjusted to 4.5 but adjusted to pH = 5. Was made. This was used as the silver tabular grain dispersion of Example 2.

-Preparation of silver tabular grain dispersion B3-
When preparing the tabular silver particle dispersion B1, the tabular silver particle dispersion B3 is the same as the tabular silver particle dispersion B1, except that the pH is not adjusted to 4.5 but adjusted to pH = 6. Was made. This was used as the silver tabular grain dispersion of Example 1.

-Preparation of silver tabular grain dispersion B4-
When preparing the tabular silver particle dispersion B1, the tabular silver particle dispersion B4 is the same as the tabular silver particle dispersion B1, except that the pH is not adjusted to 4.5 but adjusted to pH = 8. Was made. This was used as the silver tabular grain dispersion of Example 3.

-Preparation of silver tabular grain dispersion B5-
When preparing the tabular silver particle dispersion B1, the tabular silver particle dispersion B5 is the same as the tabular silver particle dispersion B1 except that the pH is adjusted to 10 instead of adjusting to pH = 4.5. Was made. This was used as the silver tabular grain dispersion of Example 4.

-Preparation of silver tabular grain dispersion B6-
When preparing the tabular silver particle dispersion B1, the tabular silver particle dispersion was the same as that of the tabular silver particle dispersion B1, except that the pH was not adjusted to 4.5 but adjusted to pH = 10.5. Liquid B6 was produced. This was used as the silver tabular grain dispersion of Comparative Example 2.

-Preparation of silver tabular grain dispersion B7-
When preparing the silver tabular grain dispersion liquid B3, it was the same as the silver tabular grain dispersion liquid B3, except that 360 mL of a 0.2 mmol / L aqueous NaOH solution was not added, but 760 mL of a 0.2 mmol / L aqueous NaOH solution was added. Thus, a tabular silver particle dispersion B7 was produced. This was designated as the silver tabular grain dispersion of Example 5.

-Preparation of silver tabular grain dispersion B8-
When preparing the silver tabular grain dispersion liquid B3, it was the same as the silver tabular grain dispersion liquid B3, except that 160 mL of 0.2 mmol / L aqueous NaOH solution was added instead of adding 360 mL of 0.2 mmol / L aqueous NaOH solution. Thus, a tabular silver particle dispersion B8 was produced. This was used as the silver tabular grain dispersion liquid of Example 6.

-Preparation of silver tabular grain dispersion B9-
When preparing the silver tabular grain dispersion liquid B3, it was the same as the silver tabular grain dispersion liquid B3 except that 360 mL of a 0.2 mmol / L aqueous NaOH solution was not added, but 60 mL of a 0.2 mmol / L aqueous NaOH solution was added. Thus, a tabular silver particle dispersion B9 was produced. This was used as the silver tabular grain dispersion of Comparative Example 3.

-Preparation of silver tabular grain dispersion B10-
When preparing the tabular silver particle dispersion B3, the tabular silver particle dispersion B10 was prepared in the same manner as the tabular silver particle dispersion B3, except that the tabular homogenizer did not disperse for 20 minutes but dispersed for 60 minutes. did. This was used as the silver tabular grain dispersion of Comparative Example 4.

-Preparation of silver tabular grain dispersion B11-
When preparing the silver tabular grain dispersion B3, a silver tabular grain dispersion B11 was prepared in the same manner as the silver tabular grain dispersion B3, except that it was not dispersed for 20 minutes with a desktop homogenizer but for 10 minutes. did. This was designated as the silver tabular grain dispersion of Example 7.

-Preparation of silver tabular grain dispersion B12-
The silver tabular grain dispersion B12 was prepared in the same manner as the silver tabular grain dispersion B3, except that when the silver tabular grain dispersion B3 was prepared, it was not dispersed for 20 minutes with a desktop homogenizer, but for 5 minutes. did. This was used as the silver tabular grain dispersion liquid of Example 8.

-Preparation of silver tabular grain dispersion B13-
The silver tabular grain dispersion B3 was prepared in the same manner as the silver tabular grain dispersion B3, except that the silver tabular grain dispersion B3 was not dispersed with a desktop homogenizer for 20 minutes, but was redispersed with a stirrer for 1 hour. Liquid B13 was produced. This was designated as the silver tabular grain dispersion of Example 9.

-Preparation of silver tabular grain dispersion B14-
When preparing the silver tabular grain dispersion B3, the silver tabular grain dispersion was the same as the silver tabular grain dispersion B3, except that it was not dispersed for 20 minutes with a tabletop homogenizer, but was redispersed for 5 minutes by hand stirring. Liquid B14 was produced. This was used as the silver tabular grain dispersion of Comparative Example 5.

-Preparation of silver tabular grain dispersion B15-
A silver tabular grain dispersion B15 was produced in the same manner as the silver tabular grain dispersion B3, except that when the silver tabular grain dispersion B3 was prepared, it was not dispersed again for 20 minutes with a desktop homogenizer. did. This was used as the silver tabular grain dispersion of Comparative Example 6.

-Preparation of silver tabular grain dispersion B16-
The silver tabular grain dispersion A2 (800 mL) was kept at 40 ° C. and adjusted to pH = 10 using 1N NaOH and / or 1N sulfuric acid. This was centrifuged at 9000 rpm for 60 minutes with a centrifuge (manufactured by Hitachi Koki Co., Ltd., angle rotor), and 760 mL of the supernatant was discarded. The precipitated silver tabular grains were transferred to a desktop homogenizer (SpinMix08, Mitsui Denki Seiki Co., Ltd.), and 360 mL of 0.2 mmol / L NaOH aqueous solution was added and dispersed at 12000 rpm for 20 minutes. After adjusting to pH = 6 using 1N NaOH and / or 1N sulfuric acid, a 2 μm cartridge filter (Nippon Pole Co., Ltd., Profile II) was passed through to produce a tabular silver particle dispersion B1. This was designated as the silver tabular grain dispersion of Example 10.

-Preparation of silver tabular grain dispersion B17-
When preparing the tabular silver particle dispersion B16, the tabular silver particle dispersion B17 was prepared in the same manner as the tabular silver particle dispersion B16 except that the pH was adjusted to 4 instead of adjusting to pH = 6. did. This was used as the silver tabular grain dispersion of Comparative Example 7.

-Preparation of silver tabular grain dispersion B18-
When preparing the tabular silver particle dispersion B16, the tabular silver particle dispersion B18 was prepared in the same manner as the tabular silver particle dispersion B16 except that the pH was adjusted to 11 instead of adjusting to pH = 6. did. This was used as the silver tabular grain dispersion of Comparative Example 8.

-Preparation of silver tabular grain dispersion B19-
The silver tabular grain dispersion liquid A3 (800 mL) was kept at 40 ° C., and adjusted to pH = 10 using 1N NaOH and / or 1N sulfuric acid. This was centrifuged at 9000 rpm for 60 minutes with a centrifuge (manufactured by Hitachi Koki Co., Ltd., angle rotor), and 760 mL of the supernatant was discarded. The precipitated silver tabular grains were transferred to a desktop homogenizer (SpinMix08, Mitsui Denki Seiki Co., Ltd.), and 360 mL of 0.2 mmol / L NaOH aqueous solution was added and dispersed at 12000 rpm for 20 minutes. After adjusting to pH = 6 using 1N NaOH and / or 1N sulfuric acid, a silver tabular grain dispersion liquid B19 was prepared through a 3 μm cartridge filter (Nippon Pole Co., Ltd., Profile II). This was used as the silver tabular grain dispersion liquid of Example 11.

-Preparation of silver tabular grain dispersion B20-
When preparing the tabular silver particle dispersion B19, the tabular silver particle dispersion B20 was prepared in the same manner as the tabular silver particle dispersion B19 except that the pH was adjusted to 4 instead of adjusting to pH = 6. did. This was used as the silver tabular grain dispersion of Comparative Example 9.

-Preparation of silver tabular grain dispersion B21-
When preparing the tabular silver particle dispersion B19, the tabular silver particle dispersion B21 was prepared in the same manner as the tabular silver particle dispersion B19 except that the pH was adjusted to 11 instead of adjusting to pH = 6. did. This was used as the silver tabular grain dispersion of Comparative Example 10.

<Evaluation of silver particles>
-Ratio of tabular grains, average grain size (average equivalent circle diameter), coefficient of variation-
A TEM image of 400 grains in the silver tabular grain dispersion A1 was observed, and image analysis was performed with A as the tabular grains mainly having a hexagonal shape and B as other irregular grains. The ratio of the number of particles (number%) was 91%. The average particle size of the particles corresponding to A in the tabular silver particle dispersion A1 was (average equivalent circle diameter) 120 nm. The average equivalent circle diameter (coefficient of variation) of the tabular grains A obtained by dividing the standard deviation of the particle size distribution in the silver tabular grain dispersion A1 by the average equivalent circle diameter was 18%.
Similarly, when the silver tabular grain dispersion liquid A2 was measured, the ratio (number%) of the number of grains corresponding to A in the silver tabular grain dispersion liquid A2 was 92%, the average grain size was 240 nm, and the variation coefficient was 21%. It was.
Similarly, when the silver tabular grain dispersion A3 was measured, the ratio (number%) of the number of grains corresponding to A in the silver tabular grain dispersion A3 was 91%, the average grain size was 360 nm, and the coefficient of variation was 25%. It was.

-Average particle thickness-
The obtained silver tabular silver dispersions A1, A2 and A3 were dropped onto a glass substrate and dried, and the thickness of 100 silver tabular grains was measured using an atomic force microscope (AFM) (Nanocute II, manufactured by Seiko Instruments Inc.). ) And the average value was defined as the average thickness. The measurement conditions using the AFM were a self-detecting sensor, DFM mode, a measurement range of 5 μm, a scanning speed of 180 seconds / frame, and a data point of 256 × 256.
The average thicknesses of the silver tabular grains in the silver tabular grain dispersions A1, A2 and A3 were 10.1 nm, 12.1 nm and 13.2 nm, respectively.

-Aspect ratio-
From the average equivalent circle diameter (average primary particle diameter) and average particle thickness of the obtained silver tabular grains, the average equivalent circle diameter was divided by the average grain thickness to calculate the aspect ratio.
The aspect ratios of the silver tabular grains in the silver tabular grain dispersions A1, A2 and A3 were 11.9, 19.8 and 27.3, respectively.

<Evaluation of silver tabular grain dispersion>
-Silver tabular grain concentration-
The density | concentration of the silver tabular grain in the silver tabular grain dispersion liquid of each Example and a comparative example was measured with the following method.
The value converted from the silver amount measurement result of ICP measurement (Optima 7300 DV, manufactured by Perkin Elmer Co., Ltd.) of a solution obtained by diluting the silver tabular particle dispersion with 10 to 20% ethylenediaminetetraacetic acid ammonium ammonium aqueous solution was defined as the silver tabular grain concentration. The obtained results are shown in Table 1 below.

-Yield of filtration-
The yield was determined by measuring the liquid mass ratio before and after passing through the cartridge filter at the time of preparing the silver tabular grain dispersion liquid of each Example and Comparative Example. The obtained results were expressed in percentage and the results are shown in Table 1 below.

<Production of heat ray shielding material of Example 1>
A silver tabular grain coating liquid containing the silver tabular grain dispersion liquid B3 having the composition shown below was prepared.
Polyurethane aqueous solution: Hydran HW-350
(Manufactured by DIC Corporation, solid content concentration 30% by mass) 1.08 parts by mass Surfactant A: F Ripar 8780P
(Manufactured by Lion Corporation, solid content 1% by mass) 0.96 parts by mass Surfactant B: NAROACTY CL-95
(Manufactured by Sanyo Chemical Industries, Ltd., solid content 1% by mass) 1.19 parts by mass Silver tabular grain dispersion B3 32.74 parts by mass 1- (5-methylureidophenyl) -5-mercaptotetrazole (Wako Pure Chemical ( Co., Ltd., solid content 2% by mass) 0.61 parts by mass water 33.42 parts by mass methanol 30 parts by mass

Using a wire bar on the surface of a PET film (Fujipet, manufactured by Fuji Film Co., Ltd., thickness: 188 μm) using this coating solution as a base material, the average thickness after drying is 0.08 μm. did. Then, it heated at 150 degreeC for 10 minute (s), dried and solidified, and formed the silver tabular grain content layer.
After depositing a carbon thin film on the obtained PET film so as to have a thickness of 20 nm, SEM observation (manufactured by Hitachi, FE-SEM, S-4300, 2 kV, 20,000 times) was performed. It was found that the Ag hexagonal tabular grains were fixed without aggregation on the PET film, and the area ratio of the Ag hexagonal tabular grains measured on the substrate surface as measured below was 23%. The heat ray shielding material of Example 1 was produced by the above.

-Evaluation of area ratio-
About the obtained heat ray shielding material of Example 1, the SEM image obtained by observing with a scanning electron microscope (SEM) is binarized, and the area A of the substrate when the heat ray shielding material is viewed from above (the heat ray shielding material) The area ratio [(B / A) × 100], which is the ratio of the total area B of the silver tabular grains to the total projected area A) of the heat ray shielding material when viewed from the vertical direction, was determined.

<Production of heat ray shielding material of Example 2>
In Example 1, the heat ray shielding material of Example 2 was produced like Example 1 except having replaced silver tabular grain dispersion liquid B3 with silver tabular grain B2.

<Production of heat ray shielding material of Example 3>
In Example 1, the heat ray shielding material of Example 3 was produced like Example 1 except having replaced silver tabular grain dispersion liquid B3 with silver tabular grain B4.

<Production of heat ray shielding material of Example 4>
In Example 1, the heat ray shielding material of Example 4 was produced like Example 1 except having replaced silver tabular grain dispersion liquid B3 with silver tabular grain B5.

<Production of heat ray shielding material of Example 5>
In Example 1, 32.74 parts by mass of silver tabular grain dispersion liquid B3 was replaced with 65.48 parts by mass of silver tabular grain B7, and the excess and deficiency were prepared in the same manner as in Example 1 except that it was prepared with water. 5 heat ray shielding material was produced.

<Production of heat ray shielding material of Example 6>
In Example 1, 32.74 parts by mass of silver tabular grain dispersion B3 was replaced with 16.37 parts by mass of silver tabular grain B8, and the excess and deficiency were prepared in the same manner as in Example 1 except that it was prepared with water. 6 heat ray shielding material was produced.

<Preparation of heat ray shielding material of Example 7>
In Example 1, the heat ray shielding material of Example 7 was produced like Example 1 except having replaced silver tabular grain dispersion liquid B3 with silver tabular grain B11.

<Production of heat ray shielding material of Example 8>
In Example 1, the heat ray shielding material of Example 8 was produced like Example 1 except having replaced silver tabular grain dispersion liquid B3 with silver tabular grain B12.

<Production of heat ray shielding material of Example 9>
In Example 1, the heat ray shielding material of Example 9 was produced in the same manner as in Example 1 except that the silver tabular grain dispersion B3 was replaced with the silver tabular grain B13.

<Production of heat ray shielding material of Example 10>
In Example 1, the heat ray shielding material of Example 10 was produced like Example 1 except having replaced silver tabular grain dispersion liquid B3 with silver tabular grain B16.

<Production of heat ray shielding material of Example 11>
In Example 1, the heat ray shielding material of Example 11 was produced in the same manner as in Example 1 except that the silver tabular grain dispersion B3 was replaced with the silver tabular grain B19.

<Production of heat ray shielding material of Comparative Example 1>
In Example 1, the heat ray shielding material of Example 1 was produced like Example 1 except having replaced silver tabular grain dispersion liquid B3 with silver tabular grain B1.

<Production of heat ray shielding material of Comparative Example 2>
In Example 1, the heat ray shielding material of Example 2 was produced like Example 1 except having replaced silver tabular grain dispersion liquid B3 with silver tabular grain B6.

<Production of heat ray shielding material of Comparative Example 3>
In Example 1, 32.74 parts by mass of silver tabular grain dispersion liquid B3 was replaced with 8.18 parts by mass of silver tabular grain B9, and excess and deficiency were prepared with water in the same manner as in Example 1 and Comparative Example. 3 heat ray shielding material was produced.

<Production of heat ray shielding material of Comparative Example 4>
In Example 1, the heat ray shielding material of Comparative Example 4 was produced in the same manner as in Example 1 except that the silver tabular grain dispersion B3 was replaced with the silver tabular grain B10.

<Production of heat ray shielding material of Comparative Example 5>
In Example 1, the heat ray shielding material of Comparative Example 5 was produced in the same manner as in Example 1 except that the silver tabular grain dispersion B3 was replaced with the silver tabular grain B14.

<Production of heat ray shielding material of Comparative Example 6>
A heat ray shielding material of Comparative Example 6 was produced in the same manner as in Example 1 except that the silver tabular grain dispersion B3 was replaced with the silver tabular grain B15 in Example 1.

<Production of heat ray shielding material of Comparative Example 7>
In Example 1, the heat ray shielding material of Comparative Example 7 was produced in the same manner as in Example 1 except that the silver tabular grain dispersion B3 was replaced with the silver tabular grain B17.

<Production of heat ray shielding material of Comparative Example 8>
In Example 1, the heat ray shielding material of Comparative Example 8 was produced in the same manner as in Example 1 except that the silver tabular grain dispersion B3 was replaced with the silver tabular grain B18.

<Production of heat ray shielding material of Comparative Example 9>
A heat ray shielding material of Comparative Example 9 was produced in the same manner as in Example 1 except that the silver tabular grain dispersion B3 was replaced with the silver tabular grain B20 in Example 1.

<Production of heat ray shielding material of Comparative Example 10>
In Example 1, the heat ray shielding material of Comparative Example 10 was produced in the same manner as in Example 1 except that the silver tabular grain dispersion B3 was replaced with the silver tabular grain B21.

<Evaluation of heat ray shielding material>
Next, various characteristics of the obtained heat ray shielding material were evaluated as follows.

-Heat shielding performance-
When the same dispersion is used, the relationship between the visible light transmittance and the shielding coefficient of each heat ray shielding material changes with a certain inclination depending on the coating amount. Therefore, a large number of heat ray shielding materials were produced for each Example and Comparative Example by changing the amount of the silver tabular grain dispersion liquid of each Example and Comparative Example.
For the heat ray shielding performance, the visible light transmittance and shielding coefficient are measured by the following method, the visible light transmittance and shielding coefficient are set with the x axis as the visible light transmittance (unit%) and the y axis as the shielding coefficient (no unit). The graph which plotted the relation of was made. The obtained plot is approximated to a linear curve (straight line), and the obtained linear curve is extrapolated to obtain an x-intercept value specific to each heat ray shielding material (visible light transmittance value when the shielding coefficient is 0 (unit%)) )
(1) Measuring method of visible light transmittance About each produced heat ray shielding material, the value which correct | amended the transmittance | permeability of each wavelength measured to 380-780 nm with the spectral visibility of each wavelength was made visible light transmittance.
(2) Measurement method of shielding coefficient About each produced heat ray shielding material, the shielding coefficient was calculated | required based on the method of JIS5759 from the transmittance | permeability of each wavelength measured to 350-2,100 nm.
"Evaluation criteria"
A: x intercept is + 1% or more with reference to the x intercept of the primary curve in the graph of the heat ray shielding material produced using the silver tabular grain dispersion of Example 1.
(Circle): x intercept is -1% or more and less than + 1% on the basis of x intercept of the primary curve in the graph of the heat ray shielding material produced using the silver tabular grain dispersion liquid of Example 1.
X: The x intercept is -4% or more and less than -1% based on the x intercept of the primary curve in the graph of the heat ray shielding material produced using the silver tabular grain dispersion of Example 1.
Xx: x intercept is less than -4% on the basis of the x intercept of the primary curve in the graph of the heat ray shielding material produced using the silver tabular grain dispersion of Example 1.
The obtained results are shown in Table 1 below.
In addition, the heat-shielding coefficient of the heat ray shielding material produced using the silver tabular grain dispersion liquid of Example 1 was 0.68.

-Haze-
Using a haze meter (NDH-5000, manufactured by Nippon Denshoku Industries Co., Ltd.), the haze (%) of the heat shield film obtained as described above was measured.
"Evaluation criteria"
A: + 10% or less of the reference value based on the heat ray shielding material produced using the silver tabular grain dispersion liquid of Example 1.
◯: Within + 20% of the reference value based on the heat ray shielding material produced using the silver tabular grain dispersion liquid of Example 1.
(Triangle | delta): Based on the heat ray shielding material produced using the silver tabular grain dispersion liquid of Example 1, it is less than + 40% of a reference value.
X: + 40% or more of the reference value based on the heat ray shielding material produced using the silver tabular grain dispersion liquid of Example 1.
The obtained results are shown in Table 1 below.
In addition, the haze produced using the silver tabular grain dispersion liquid of Example 1 was 0.9%.

-RMS granularity of tabular silver grains-
About the produced heat ray shielding material of Example 1, the surface of the heat ray shielding material was observed with a scanning electron microscope (SEM), the obtained SEM image was binarized, and the metal tabular grain and the substrate were separated. The result is shown in FIG. 3A as an image before RMS patch processing. Then, the image is divided into 0.6 μm square meshes, and an image in which the density in the mesh is averaged is created. This is shown in FIG. 3B as an image after RMS patch processing. A value obtained by averaging the density in the mesh was obtained from FIG. 3B, and a histogram shown in FIG. 3C was created. The average concentration variation coefficient calculated from the histogram shown in FIG. 3C was used as the RMS granularity of the silver tabular grains of the heat ray shielding material of Example 1.
In addition, about the heat ray shielding material of each other Example and the comparative example, it carried out similarly to Example 1, and calculated | required RMS granularity of the silver tabular grain.
The results of RMS granularity of the obtained silver tabular grains are shown in Table 1 below.
Moreover, the average particle diameter of the primary particle of the metal tabular grain of the RMS granularity of the silver tabular grain in the heat ray shielding material of each Example and Comparative Example, and the average particle of the secondary particle formed by aggregation of the primary particle FIG. 8 below shows the relationship between the ratio and the ratio (secondary particle size / primary particle size) in a scatter diagram. FIG. 8 shows that the ratio (secondary particle size / primary particle size) of the average particle size of primary particles of metal tabular particles to the average particle size of secondary particles formed by aggregation of the primary particles is 1. It turned out that the RMS granularity of the silver tabular grain in the manufactured heat ray shielding material becomes it low that it is 0-3.0.

It turned out that the heat ray shielding material manufactured using the metal tabular grain dispersion liquid of this invention is excellent in heat insulation performance. Moreover, the heat ray shielding material manufactured using the metal tabular grain dispersion of the present invention had low haze.
On the other hand, from each comparative example, the ratio between the average particle size of the primary particles of the metal tabular grains and the average particle size of the secondary particles formed by aggregation of the primary particles (secondary particle size / primary particle size) Is in the range of 1.0 to 3.0, pH is in the range of 5 to 10, and the content of the tabular metal particles is outside the range of 22 g / L or less, the heat ray shielding material produced using the tabular metal particle dispersion is It was found that the heat shielding performance was poor. In particular, Comparative Example 6 is an embodiment in which re-dispersion was performed by imitating the method described in Examples of Japanese Patent Application Laid-Open No. 2011-118347. However, in this method, the pH and the metal tabular grain content are within the ranges. However, the ratio (secondary particle size / primary particle size) of the average particle size of the primary particles of the metal tabular particle to the average particle size of the secondary particles formed by aggregation of the primary particles is 1. It turned out that the 0-3.0 metal tabular grain dispersion liquid cannot be obtained.

  Since the heat ray shielding material of the present invention is excellent in heat shielding performance, it is required to prevent the transmission of heat rays, for example, as a film for automobiles, buses, etc., a laminated structure, a film for building materials, a laminated structure, etc. It can be suitably used as various members.

DESCRIPTION OF SYMBOLS 1 Base material 2 Metal particle content layer 2a Surface of metal particle content layer 3 Metal flat particle 4 Overcoat layer 5 Hard coat layer 10 Heat ray shielding material 11 Adhesion layer 12 Metal oxide particle content layer D Diameter L Thickness F (λ) Particle Existence area thickness

Claims (5)

Containing metal tabular grains,
The ratio (secondary particle diameter / primary particle diameter) of the average particle diameter of primary particles of the metal tabular grains to the average diameter of secondary particles formed by aggregation of the primary particles is 1.0 to 3 .0,
pH is 5-10,
Content of the said metal tabular grain is 22 g / L or less, The metal tabular grain dispersion liquid characterized by the above-mentioned.   The metal tabular grain dispersion liquid according to claim 1, wherein the metal tabular grain contains at least silver.   Furthermore, gelatin is contained, The metal tabular grain dispersion liquid of Claim 1 or 2 characterized by the above-mentioned.   It has a metal-particle content layer formed using the metal tabular grain dispersion liquid described in any one of Claims 1-3, The heat ray shielding material characterized by the above-mentioned.   The heat ray shielding material according to claim 4, wherein an RMS granularity of the metal tabular grains in the metal particle-containing layer is 15 or less.