JP2012193245A - Near infrared ray-absorbing particle, method for producing the same, dispersion liquid, resin composition, article having near infrared ray-absorbing coating film and near infrared ray-absorbing article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a near infrared ray-absorbing particle which is high in the transmittance of a visible light region, is low in the transmittance of a near infrared region, steeply changes the transmittance in a wavelength region of 630-700 nm, and is excellent in moisture resistance; a method for producing the same; a dispersion liquid; a resin composition; an article having a near infrared ray-absorbing coating film; and a near infrared ray-absorbing article.SOLUTION: The near infrared ray-absorbing particle comprises a core particle comprising a crystallite of ACuPO, and a shell covering the surface of the core particle and containing silicon oxide as a main component. In the formula, A is one or more selected from the group consisting of alkali metals (Li, Na, K, Rb, Cs), alkaline earth metals (Mg, Ca, Sr, Ba) and NH; n is 1 when A is an alkali metal or NH4, or 2 when A is an alkaline earth metal.

Description

  The present invention relates to near-infrared absorbing particles that absorb light in the near-infrared region, a method for producing the same, a dispersion containing near-infrared absorbing particles, a resin composition, an article having a near-infrared absorbing coating film, and a near-infrared absorbing article.

  Sensitivity of imaging devices such as cameras (CCD, CMOS, etc.) and light receiving devices such as automatic exposure meters ranges from the visible light region to the near infrared region. On the other hand, human visibility is only in the visible light region. Therefore, for example, in a camera, a near-infrared filter that transmits light in the visible light region (420 to 630 nm) and absorbs or reflects light in the near-infrared region (700 to 1100 nm) is interposed between the lens and the image sensor. By providing, the sensitivity of the image sensor is corrected so as to approach the human visibility. In order to make it closer to human visibility, the near-infrared filter is required to have a sharp change in transmittance between wavelengths of 630 to 700 nm.

As a near-infrared filter, a filter having a near-infrared absorbing coating formed by applying a paint obtained by adding a binder resin or the like to a dispersion obtained by dispersing near-infrared absorbing particles in a dispersion medium on the surface of a glass substrate. Are known.
Some near infrared absorbing particles containing copper and phosphoric acid have been proposed.
(1) The wavelength of 700 was obtained by treating the surface of near-infrared absorbing particles having a CuO / P ₂ O ₅ molar ratio of 0.05 to 4 in terms of copper as CuO and phosphoric acid as P ₂ O ₅ with an aluminum compound. Near-infrared absorbing particles that absorb light of ˜1100 nm (Patent Document 1).
(2) A dispersion in which copper phosphate is dispersed in a dispersion medium using a dispersant (Patent Document 2).

  It has been confirmed that the near-infrared absorbing coating film formed using both the near-infrared absorbing particles (1) and the dispersion liquid (2) absorb near-infrared rays having a wavelength of 800 nm or more. However, the transmittance of the near-infrared absorbing film does not change sharply between wavelengths of 630 to 700 nm, and does not sufficiently satisfy the performance required for the near-infrared filter.

Japanese Patent Application Laid-Open No. 07-070548 JP 2004-231708 A

Therefore, the inventors of the present invention have a near-infrared absorbing particle composed of a crystallite of the compound represented by the following formula (1) that has a high transmittance in the visible light region, a low transmittance in the near-infrared region, and a wavelength of 630 to 630. It has been found that the transmittance changes sharply between 700 nm (Japanese Patent Application No. 2009-227554).
A _{1 / n} CuPO ₄ (1).
However, A is an alkali metal (Li, Na, K, Rb , Cs), alkaline earth metal and a (Mg, Ca, Sr, Ba ) and one or more selected from the group consisting of NH _4,
n is 1 when A is an alkali metal or NH ₄ , and 2 when A is an alkaline earth metal.

However, since the near-infrared absorbing particles become a hydrate represented by A _{1 / n} CuPO ₄ .H ₂ O when exposed to water vapor and moisture, the crystal structure of the crystallite is A _{1 / n} CuPO ₄ . Cannot be maintained, the transmittance in the visible light region is low, and the transmittance in the near infrared region is high.

  The present invention relates to a near-infrared absorbing particle having high transmittance in the visible light region, low transmittance in the near-infrared region, a sharp change in transmittance between wavelengths of 630 to 700 nm, and excellent moisture resistance, and a method for producing the same , A dispersion, a resin composition, an article having a near-infrared absorbing coating film, and a near-infrared absorbing article.

The near-infrared absorbing particles of the present invention include core particles composed of crystallites of a compound represented by the following formula (1), and a shell mainly composed of silicon oxide that covers the surface of the core particles. .
A _{1 / n} CuPO ₄ (1).
However, A is an alkali metal (Li, Na, K, Rb , Cs), alkaline earth metal and a (Mg, Ca, Sr, Ba ) and one or more selected from the group consisting of NH _4,
n is 1 when A is an alkali metal or NH ₄ , and 2 when A is an alkaline earth metal.

  In the near-infrared absorbing particles of the present invention, the crystallite size determined from X-ray diffraction is 5 to 50 nm, the number-average aggregated particle diameter of the near-infrared absorbing particles is 20 to 200 nm, The reflectance at a wavelength of 450 nm in the diffuse reflection spectrum of the infrared absorbing particles is preferably 80% or more.

The near-infrared absorbing particles of the present invention preferably have a reflectance change amount D represented by the following formula (2) of -0.41 or less.
D (% / nm) = [ _R700 (%)- _R600 (%)] / [700 (nm) -600 (nm)] (2).
However, R ₇₀₀ is a reflectance at a wavelength of 700 nm in the diffuse reflection spectrum of the near-infrared absorbing particles, and R ₆₀₀ is a reflectance at a wavelength of 600 nm in the diffuse reflection spectrum of the near-infrared absorbing particles.

  In the near-infrared absorbing particles of the present invention, the reflectance at a wavelength of 715 nm in the diffuse reflection spectrum of the near-infrared absorbing particles is preferably 19% or less, and the reflectance at a wavelength of 500 nm is preferably 85% or more.

The manufacturing method of the near-infrared absorption particle | grains of this invention has the following process (d), It is characterized by the above-mentioned.
(D) A step of surface-treating the core particles made of crystallites of the compound represented by the formula (1) with alkoxysilane to form a shell mainly composed of silicon oxide on the surface of the core particles.

The step (d) is preferably the following step (d ′).
(D ′) A liquid containing core particles composed of crystallites of the compound represented by the formula (1) and alkoxysilane is irradiated with microwaves, and the surface of the core particles is mainly composed of silicon oxide. Forming a shell;

It is preferable that the manufacturing method of the near-infrared absorption particle | grains of this invention further has the following process (a)-process (c).
At (a) in a solvent, a salt containing ^{Cu 2+,} a salt or an organic material containing _PO ^{4 3-,} _PO ^{4 3-} molar ratio with respect to _{^{Cu 2+ (PO 4 3- / Cu}} 2+) 10-20 And A ^{n +} (where A is an alkali metal (Li, Na, K, Rb, Cs), alkaline earth metal (Mg, Ca, Sr, Ba) and NH ₄ ) 1 or more selected, and n is 1 when A is an alkali metal or NH ₄ , and 2 when A is an alkaline earth metal). Is a step of dispersing a raw material in a dispersion medium to obtain a raw material slurry.
(B) A step of introducing particles of the raw material slurry obtained in the step (a) into thermal plasma or flame and cooling the resulting product to obtain particles.
(C) A step of obtaining core particles composed of crystallites of the compound represented by the formula (1) by heat-treating the particles obtained in the step (b) at 300 to 700 ° C.

The dispersion of the present invention is characterized in that the near-infrared absorbing particles of the present invention are dispersed in a dispersion medium.
The resin composition of the present invention is characterized in that the near-infrared absorbing particles of the present invention are dispersed in a resin.
The article having the near-infrared absorbing coating film of the present invention is characterized by having a near-infrared absorbing coating film containing the near-infrared absorbing particles of the present invention on the surface of a substrate.
The near-infrared absorbing article of the present invention includes the near-infrared absorbing particles of the present invention.

The near-infrared absorbing particles of the present invention have a high transmittance in the visible light region, a low transmittance in the near-infrared region, a sharp change in wavelength between 630 to 700 nm, and excellent moisture resistance.
According to the method for producing near-infrared absorbing particles of the present invention, the transmittance in the visible light region is high, the transmittance in the near-infrared region is low, the transmittance sharply changes between wavelengths of 630 to 700 nm, and the moisture resistance. It is possible to produce near-infrared absorbing particles that are superior to the above.
The dispersion of the present invention has a high transmittance in the visible light region, a low transmittance in the near-infrared region, a sharp change in transmittance between wavelengths of 630 to 700 nm, and an excellent near-infrared absorbing coating film. It is useful for the formation of
The resin composition of the present invention has a high transmittance in the visible light region, a low transmittance in the near-infrared region, a sharp change in transmittance between wavelengths of 630 to 700 nm, and excellent near-infrared absorption coating. It is useful for forming films and near infrared absorbing articles.
The article having the near-infrared absorbing coating film of the present invention has a high transmittance in the visible light region, a low transmittance in the near-infrared region, a sharp change in transmittance between wavelengths of 630 to 700 nm, and Excellent moisture resistance.
The near-infrared absorbing article of the present invention has a high transmittance in the visible light region, a low transmittance in the near-infrared region, a sharp change in wavelength between 630 and 700 nm, and excellent moisture resistance.

FIG. 3 is a diagram showing the results of X-ray diffraction of core particles of Example 1. 2 is a diffuse reflection spectrum of near-infrared absorbing particles before and after the moisture resistance test of Example 1. 2 is a diffuse reflection spectrum of near-infrared absorbing particles before and after the moisture resistance test of Example 2. 4 is a diffuse reflection spectrum of near-infrared absorbing particles before and after the moisture resistance test of Example 3. 6 is a diffuse reflection spectrum of near-infrared absorbing particles before and after the moisture resistance test of Example 4. 6 is a diffuse reflection spectrum of near-infrared absorbing particles before and after the moisture resistance test of Example 5.

<Near-infrared absorbing particles>
The near-infrared absorbing particles of the present invention have core particles made of crystallites of a compound represented by the following formula (1), and a shell mainly composed of silicon oxide that covers the surface of the core particles.
A _{1 / n} CuPO ₄ (1).
However, A is an alkali metal (Li, Na, K, Rb , Cs), alkaline earth metal and a (Mg, Ca, Sr, Ba ) and one or more selected from the group consisting of NH _4,
n is 1 when A is an alkali metal or NH ₄ , and 2 when A is an alkaline earth metal.

“Crystallite” means a unit crystal that can be regarded as a single crystal, and “particle” is composed of a plurality of crystallites.
"Consisting crystallites of the compound represented by formula (1)", for example, as shown in FIG. 1, you can see the crystal structure of A _{1 / n} CuPO ₄ by X-ray diffraction, essentially A _{1 / n} It means that it consists of crystallites CuPO ₄ have been identified by X-ray diffraction, and "consisting of crystallites substantially _a 1 / n CuPO _4" is crystallite _a 1 / n CuPO ₄ This means that impurities may be contained within a range in which the crystal structure of A _{1 / n} CuPO ₄ can be confirmed by X-ray diffraction.
X-ray diffraction is measured with a X-ray diffractometer on powdered near-infrared absorbing particles.

The reason why alkali metal, alkaline earth metal or NH ₄ is used as A in the present invention is as follows (i) to (iii).
(I) The crystal structure of the crystallite in the near-infrared absorbing particles of the present invention is a network-like three-dimensional skeleton composed of alternating bonds of PO ₄ ³⁻ and Cu ^2+, and has a space inside the skeleton. The size of the space is alkali metal ion (Li ⁺ : 0.90Å, Na ⁺ : 1.16Å, K ⁺ : 1.52Å, Rb ⁺ : 1.66 ：, Cs ⁺ : 1.81Å), alkaline earth metal In order to match the ionic radius of ions (Mg ²⁺ : 0.86 Å, Ca ²⁺ : 1.14 Å, Sr ²⁺ : 1.32 Å, Ba ²⁺ : 1.49 Å) and NH ₄ ⁺ (1.66 Å) Sufficiently maintain.

(Ii) Alkali metal ions, alkaline earth metal ions, and NH ₄ ⁺ can stably exist as monovalent or divalent cations in the solution, and therefore, when the precursor is generated in the production process of near-infrared absorbing particles. Cations are easily incorporated into the crystal structure.
(Iii) A cation having a strong coordination bond with PO ₄ ³⁻ , such as a transition metal ion, may give a crystal structure different from the crystal structure in the present invention that exhibits sufficient near infrared absorption characteristics.
As A, the cation size is most suitable as an ion taken into the skeleton composed of PO ₄ ³⁻ and Cu ^2+, and K is particularly preferable from the viewpoint of taking a thermodynamically stable structure.

In the near-infrared absorbing particles of the present invention, it is confirmed by particle observation with a transmission electron microscope that the core particles made of crystallites of A _{1 / n} CuPO ₄ are covered with a shell mainly composed of silicon oxide. .

  The shell is mainly composed of silicon oxide, and is preferably 90% by mass or more and particularly preferably 100% by mass in the shell (100% by mass) from the viewpoint of moisture resistance, chemical resistance and the like.

The thickness of the shell is preferably 1.0 to 50.0 nm, and more preferably 5.0 to 30.0 nm. If the thickness of the shell is 1.0 nm or more, moisture resistance, chemical resistance, and the like are further improved. When the thickness of the shell is 50.0 nm or less, the near-infrared absorption characteristics of the core particles are sufficiently exhibited.
The thickness of the shell can appropriately adjust the amount of alkoxysilane, microwave output, irradiation time, etc. in the production method described later.
The thickness of the shell is determined by observing near-infrared absorbing particles with a transmission electron microscope, randomly selecting 20 particles, measuring the thickness of the shell of each particle, and measuring the thickness of the shell of 20 particles. Is an average value.

5-50 nm is preferable and, as for the magnitude | size of the crystallite in the near-infrared absorption particle | grains of this invention, 10-30 nm is more preferable. If the crystallite size is 5 nm or more, the crystallite can sufficiently maintain the crystal structure of A _{1 / n} CuPO ₄ , and as a result, sufficient near infrared absorption characteristics can be exhibited. If the crystallite size is 50 nm or less, the number-average aggregated particle diameter of the near-infrared absorbing particles can be kept small, and the haze of the dispersion, the resin composition, and the near-infrared absorbing coating film formed using them can be reduced. Is kept low.
The size of the crystallite is a value obtained by performing X-ray diffraction on the near-infrared absorbing particles in a powder state and calculating by the Scherrer method.

The number average aggregate particle diameter of the near infrared ray absorbing particles of the present invention is preferably 20 to 200 nm, more preferably 20 to 150 nm. If the number average aggregate particle diameter is 20 nm or more, the crystallite can sufficiently maintain the crystal structure of A _{1 / n} CuPO ₄ , and as a result, sufficient near infrared absorption characteristics can be exhibited. If the number average agglomerated particle diameter is 200 nm or less, the haze of the dispersion, the resin composition, and the near-infrared absorbing coating film formed using these will be low, that is, the transmittance will be high. It is suitable for use of a filter.
The number average agglomerated particle diameter is a value measured using a dynamic light scattering particle size distribution measuring apparatus for a particle diameter measurement dispersion in which near-infrared absorbing particles are dispersed in a dispersion medium.

The reflectance at a wavelength of 450 nm in the diffuse reflection spectrum of the near-infrared absorbing particles of the present invention is preferably 80% or more, and more preferably 81% or more.
High reflectivity of near infrared absorbing particles means that light absorption by near infrared absorbing particles is low, and low reflectivity of near infrared absorbing particles means that light absorption by near infrared absorbing particles is high. ing. The reflectance at a wavelength of 450 nm can be regarded as corresponding to the transmittance at a wavelength of 420 nm on the short wavelength side in the visible light region in the transmission spectrum of the film containing particles. That is, in the present invention, the absorption of light of the near-infrared absorbing particles is not performed using the reflectance of the wavelength 450 nm, which is a relatively small change amount of the diffuse reflection spectrum with respect to the wavelength, but the wavelength of 420 nm. Judging that there are few. That is, if the reflectance at a wavelength of 450 nm is 80% or more, the transmittance at a wavelength of 420 nm in the transmission spectrum of the film containing the particles is sufficiently high, and the near-infrared absorbing particles sufficiently absorb light in the visible light region. For example, it is suitable for a near infrared absorption filter of a camera.

In order to keep the near-infrared absorbing coating film haze low, if the near-infrared absorbing particles are excessively pulverized to reduce the number-average aggregated particle diameter of the near-infrared absorbing particles, the crystallites constituting the core particles are A. The crystal structure of _{1 / n} CuPO ₄ cannot be sufficiently maintained, and the reflectance at a wavelength of 450 nm in the diffuse reflection spectrum tends to be small. Therefore, if the reflectance at a wavelength of 450 nm is 80% or more, the crystallites can sufficiently maintain the crystal structure of A _{1 / n} CuPO ₄ even if the number average aggregate diameter of the near infrared absorbing particles is 200 nm or less. It becomes a standard of being. Further, in order to sufficiently maintain the crystal structure of the A _{1 / n} CuPO ₄ crystallite, near-infrared absorbing particles having a sufficiently small number average agglomerated particle diameter can be obtained without excessive pulverization. The method for producing near-infrared absorbing particles described later (steps (a) to (c)) is suitable.

The reflectance change amount D represented by the following formula (2) of the near-infrared absorbing particles of the present invention is preferably −0.41 or less, more preferably −0.45 or less.
D (% / nm) = [ _R700 (%)- _R600 (%)] / [700 (nm) -600 (nm)] (2).
However, R ₇₀₀ is a reflectance at a wavelength of 700 nm in the diffuse reflection spectrum of the near-infrared absorbing particles, and R ₆₀₀ is a reflectance at a wavelength of 600 nm in the diffuse reflection spectrum of the near-infrared absorbing particles.

In diffuse reflection spectrum measurement of particles with light absorption, since the intensity of light absorption varies depending on the optical path length at the light absorption wavelength, a weak absorption band in the transmission spectrum of the film containing particles is observed relatively strongly in the diffuse reflection spectrum. . Therefore, the reflectance change rate calculation in this specification uses a reflectance value of 600 to 700 nm, which is a range in which the reflectance changes in the same manner as the transmittance change in the transmission spectrum of the film including particles.
When the reflectance change amount D is −0.41 or less, the transmittance change between wavelengths of 630 to 700 nm is sufficiently steep, and a near-infrared absorbing coating film formed using this is, for example, a camera It is suitable for the near infrared absorption filter.

19% or less is preferable and the reflectance of the wavelength of 715 nm in the diffuse reflection spectrum of the near-infrared absorbing particles of the present invention is more preferably 18% or less. If the reflectance at a wavelength of 715 nm is 19% or less, the transmittance in the near infrared region is sufficiently low.
The reflectance of the wavelength of 500 nm in the diffuse reflection spectrum of the near-infrared absorbing particles of the present invention is preferably 85% or more, and more preferably 86% or more. If the reflectance at a wavelength of 500 nm is 85% or more, the transmittance in the visible light region is sufficiently high.
The diffuse reflection spectrum is measured using a UV-visible spectrophotometer for powdered near-infrared absorbing particles.

In the near-infrared absorbing particles of the present invention, when the crystal structure other than A _{1 / n} CuPO ₄ , for example, A _{1 / n} Cu ₄ (PO ₄ ) ₃ increases, the transmittance changes between wavelengths of 630 to 700 nm. The near-infrared absorbing coating film formed by using this is slow and is not suitable for a near-infrared absorbing filter of a camera.
Therefore, it is necessary to have been identified by X-ray diffraction to be substantially composed of A _{1 / n} CuPO ₄ crystallites.

(Function and effect)
The near-infrared absorbing particles of the present invention described above are near-infrared absorbing particles having core particles composed of crystallites of a compound represented by A _{1 / n} CuPO ₄ , and thus have high transmittance in the visible light region. The transmittance of the film containing the near-infrared absorbing particles is steeply changed between the wavelengths of 630 and 700 nm.
In addition, the near-infrared absorbing particles of the present invention described above have excellent moisture resistance because they have a shell mainly composed of silicon oxide covering the surface of the core particles made of crystallites of A _{1 / n} CuPO _4. .

<Method for producing near-infrared absorbing particles>
The manufacturing method of the near-infrared absorbing particles of the present invention is a method having the following step (d), and the following step (a) from the point that near-infrared absorbing particles having a sufficiently small number average aggregated particle diameter can be obtained. ) To (d) are preferred.
At (a) in a solvent, a salt containing ^{Cu 2+,} a salt or an organic material containing _PO ^{4 3-,} _PO ^{4 3-} molar ratio with respect to _{^{Cu 2+ (PO 4 3- / Cu}} 2+) 10-20 A step of obtaining a raw material slurry by dispersing a raw material powder obtained by mixing in the presence of ^{An +} in a dispersion medium.
(B) A step of introducing particles of the raw material slurry obtained in the step (a) into thermal plasma or flame and cooling the resulting product to obtain particles.
(C) A step of heat-treating the particles obtained in the step (b) at 300 to 700 ° C. to obtain core particles made of A _{1 / n} CuPO ₄ crystallites.
(D) A step of surface-treating the core particles made of A _{1 / n} CuPO ₄ crystallites with alkoxysilane to form a shell mainly composed of silicon oxide on the surface of the core particles.

(Process (a))
^Examples of salts containing Cu ²⁺ include copper (II) sulfate pentahydrate, copper (II) chloride dihydrate, copper (II) acetate monohydrate, copper (II) bromide, and copper (II) nitrate. And trihydrate.
Examples of the salt or organic substance containing PO ₄ ^3- include alkali metal phosphates, ammonium phosphates, alkaline earth metal phosphates, phosphoric acid, and the like.

Examples of alkali metal phosphate or alkaline earth metal phosphate include dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, disodium hydrogen phosphate dodecahydrate, sodium dihydrogen phosphate Examples thereof include dihydrate, trisodium phosphate dodecahydrate, lithium phosphate, calcium hydrogen phosphate, magnesium hydrogen phosphate trihydrate, and magnesium phosphate octahydrate.
Examples of the ammonium salt of phosphoric acid include diammonium hydrogen phosphate, ammonium dihydrogen phosphate, sodium ammonium hydrogen phosphate tetrahydrate, and ammonium phosphate trihydrate.

As a method for allowing ^{An +} to exist, a method using an alkali metal phosphate, an ammonium phosphate, an alkaline earth metal phosphate, or the like as a salt containing PO ₄ ^3- ; a salt containing Cu ²⁺ and PO _{4 When} a salt containing ^3- or an organic substance is mixed, a method of adding a salt containing ^{An +} is exemplified.
Salts containing ^{An +} include alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal chlorides, alkaline earth metal chlorides, alkali metal bromides, alkaline earth metal bromides, Examples thereof include alkali metal nitrates, alkaline earth metal nitrates, alkali metal carbonates, alkaline earth metal carbonates, alkali metal sulfates, alkaline earth metal sulfates, and the like.

Mixing of the salt containing Cu ²⁺ and the salt or organic substance containing PO ₄ ^3- is performed in a solvent. As the solvent, a salt containing Cu ²⁺ and a salt containing PO ₄ ³⁻ or a solvent capable of dissolving an organic substance is preferable. When a salt containing ^{An +} is used, the solvent is preferably a solvent that can also dissolve a salt containing ^{An +} . As the solvent, water is particularly preferable.

Ratio of the salt or organic containing salt and _PO ^{4 3-} and containing Cu ²⁺ is, _PO ^{4 3-} molar ratio with respect to ^{_{Cu 2+ (PO 4 3- / Cu}} 2+) 10-20, preferably 12-18 and The ratio is as follows. If PO ₄ ³⁻ / Cu ²⁺ is 10 or more, even if A _{1 / n} Cu ₄ (PO ₄ ) ₃ is not by-produced or by-produced in the step (b), the amount of crystallites is A _{1. Since} the crystal structure of _{/ n} CuPO ₄ can be sufficiently maintained, near-infrared absorbing particles in which the change in transmittance between wavelengths of 630 to 700 nm is sufficiently steep are obtained. If PO ₄ ³⁻ / Cu ²⁺ is 20 or less, impurities other than A _{1 / n} CuPO ₄ are not by-produced in the step (b), or even if they are by-produced, the amount of crystallites is A _{1 / n.} Since the crystal structure of CuPO ₄ is sufficiently maintained, near-infrared absorbing particles in which the change in transmittance between wavelengths of 630 to 700 nm is sufficiently steep can be obtained.

Temperature at the time of mixing the salt or organic containing salt and _PO ^{4 3-} and containing Cu ²⁺ is preferably 10 to 95 ° C., and more preferably from 15 to 40 ° C.. If the temperature is too high, the solute is concentrated by evaporation of the solvent, and impurities other than the target product may be mixed. If the temperature is too low, the reaction rate becomes slow and the reaction time becomes long.

In a solvent, a salt containing ^{Cu 2+,} a salt or an organic material containing _PO ^{4 3-,} _PO ^{4 3-} molar ratio with respect to _{^{Cu 2+ (PO 4 3- / Cu}} 2+) to become 10 to 20 The raw material powder obtained by mixing in a small proportion and in the presence of ^{An +} is solid-liquid separated and dried as necessary, and dispersed in a dispersion medium to obtain a raw material slurry.

  Examples of the dispersion medium for the raw slurry include water, alcohol, ketone, ether, ester, aldehyde, amine, aliphatic hydrocarbon, alicyclic hydrocarbon, and aromatic hydrocarbon. A dispersion medium may be used individually by 1 type, and may use 2 or more types together. As the dispersion medium, alcohols such as methanol, ethanol, and isopropanol are preferable because they are easy to handle and contain an oxygen atom that becomes an oxygen source when passing through thermal plasma.

  Since the particle diameter of the near-infrared absorbing particles obtained in the step (b) varies depending on the solid content concentration in the raw material slurry, it is necessary to adjust the solid content concentration of the raw material slurry as necessary. That is, the higher the solid content concentration in the raw slurry, the higher the crystal nucleus concentration when passing through the thermal plasma, the crystal growth occurs, and the near infrared absorbing particles having a large particle diameter can be obtained. The lower the solid content concentration in the raw material slurry, the lower the crystal nucleus concentration when passing through the thermal plasma, the crystal growth is suppressed, and the near-infrared absorbing particles having a small particle diameter can be obtained. The amount of the dispersion medium is preferably 50 to 95% by mass in the dispersion (100% by mass).

  The raw material slurry can be prepared by mixing raw material powder, a dispersion medium, and if necessary, zirconia beads and the like, and stirring with a rotation / revolution mixer, a bead mill, a planetary mill, an ultrasonic homogenizer or the like. In order to obtain a uniform near-infrared absorbing particle having a small particle size, the particle size of the raw material powder in the raw material slurry needs to be small and uniform. Stirring may be performed continuously or intermittently.

(Process (b))
Methods for introducing raw slurry into thermal plasma or flame and cooling the resulting product to obtain particles are described in JP-A-2005-170760, JP-A-4420690, and the like.
Therefore, except using the raw material slurry obtained in step (a) as the raw material slurry, using the apparatus described in Japanese Patent Application Laid-Open No. 2005-170760, Japanese Patent No. 4420690, etc., Japanese Patent Application Laid-Open No. 2005-170760, The particles may be produced by appropriately changing the conditions described in Japanese Patent No. 4420690.

  For example, plasma gas (argon gas, etc.) is supplied into a plasma torch, and while generating thermal plasma in the plasma torch, the raw material slurry is sprayed together with a carrier gas (oxygen gas, etc.) from a nozzle provided in the plasma torch. By doing so, droplets of the raw slurry are introduced into the thermal plasma. While the solvent of the raw material slurry is evaporated in the thermal plasma, the raw material contained in the raw material slurry is reacted, and the product generated from the thermal plasma is moved to a chamber adjacent to the lower part of the plasma torch. The product from the thermal plasma is crystallized by quenching in the chamber to produce particles.

(Process (c))
The particles obtained in the step (b) may have oxygen defects in the crystal structure. Since particles having an oxygen defect in the crystal structure have a low transmittance in the visible light region, it is preferable to perform heat treatment to reduce the oxygen defect in the crystal structure.

The heat treatment temperature is 300 to 700 ° C, preferably 300 to 500 ° C. If the heat treatment temperature is 300 ° C. or higher, oxygen defects in the crystal structure can be sufficiently reduced. If heat processing temperature is 700 degrees C or less, decomposition | disassembly by a heat | fever can be suppressed.
The heat treatment time is preferably 0.5 to 300 minutes, more preferably 1 to 10 minutes. If the heat treatment time is 0.5 minutes or more, oxygen defects in the crystal structure can be sufficiently reduced. If the heat treatment time is 300 minutes or less, crystal growth due to the heat treatment can be suppressed.
When an infrared image furnace is used, rapid heating and rapid cooling are possible, which is effective in suppressing crystal growth. A rotary kiln furnace that can be fired while flowing particles is also effective in suppressing crystal growth.

(Process (d))
A known method may be used as a method of surface-treating the core particles made of A _{1 / n} CuPO ₄ crystallites with alkoxysilane. As the step (d), the following step (d ′) is preferable for the following reasons.
(D ′) A liquid containing core particles composed of crystallites of the compound represented by the formula (1) and alkoxysilane is irradiated with microwaves, and the surface of the core particles is mainly composed of silicon oxide. Forming a shell;

  Reason: The core particles can be selectively heated to a high temperature (100 ° C. or higher). Therefore, even if the entire liquid becomes high temperature (100 ° C. or higher), since the core particles are heated to a higher temperature, hydrolysis of alkoxysilane proceeds preferentially on the surface of the core particles, Silicon oxide is selectively deposited on the surface. Therefore, the amount of silicon oxide precipitated alone other than the surface of the core particle can be suppressed. Further, since the shell can be formed under high temperature conditions, a dense shell can be formed in a short time.

Specifically, the step (d ′) includes the following steps (d1) to (d3).
(A) A step of preparing a raw material liquid by adding alkoxysilane, water, an organic solvent, an alkali or an acid, a curing catalyst, or the like to a dispersion of core particles in which the core particles are dispersed in a dispersion medium.
(B) The raw material liquid is irradiated with microwaves to heat the raw material liquid, and the alkoxysilane is hydrolyzed with an alkali or an acid to precipitate silicon oxide on the surface of the core particles to form a shell. A step of obtaining a dispersion of near-infrared absorbing particles having a structure.
(C) A step of removing the dispersion medium from the dispersion of near-infrared absorbing particles and collecting near-infrared absorbing particles as necessary.

Step (d1):
Examples of the dispersion medium include water, alcohol (methanol, ethanol, isopropanol, etc.), ketone (acetone, methyl ethyl ketone, etc.), ether (tetrahydrofuran, 1,4-dioxane, etc.), ester (ethyl acetate, methyl acetate, etc.), glycol ether ( Ethylene glycol monoalkyl ether), nitrogen-containing compounds (N, N-dimethylacetamide, N, N-dimethylformamide, etc.), sulfur-containing compounds (dimethyl sulfoxide, etc.) and the like.
Since the dispersion medium requires water for hydrolysis of alkoxysilane, it is preferable that 5 to 100% by mass of water is contained in 100% by mass of the dispersion medium.

  The concentration of the core particles in the dispersion is preferably 0.1 to 40% by mass, and more preferably 0.5 to 20% by mass in the core particle dispersion (100% by mass). If the density | concentration of a core particle is 0.1 mass% or more, the manufacturing efficiency of a near-infrared absorption particle will become favorable. When the concentration of the core particles is 40% by mass or less, the core particles hardly aggregate.

  Examples of the alkoxysilane include tetramethoxysilane, tetraethoxysilane (hereinafter referred to as TEOS), tetra n-propoxysilane, tetraisopropoxysilane, and the like, and TEOS is preferable from the viewpoint of an appropriate reaction rate.

The amount of alkoxysilane is preferably such that the shell thickness is 1.0 to 50.0 nm, and more preferably the shell thickness is 5.0 to 30.0 nm.
Specifically, the amount of alkoxysilane (in terms of metal oxide) is preferably 0.1 to 10,000 parts by mass with respect to 100 parts by mass of the core particles.

Examples of the alkali include potassium hydroxide, sodium hydroxide, ammonia, ammonium carbonate, ammonium hydrogen carbonate, dimethylamine, triethylamine, aniline and the like. Ammonia is preferable because it can be removed by heating.
The amount of the alkali is preferably such that the pH of the raw material liquid is 8.5 to 10.5 from the viewpoint that the alkoxysilane is three-dimensionally polymerized to form a dense shell. Is preferred.

Examples of the acid include hydrochloric acid and nitric acid.
The amount of the acid is preferably such that the pH of the raw material liquid is 3.5 to 5.5.

Examples of the curing catalyst include metal chelate compounds, organotin compounds, metal alcoholates, metal fatty acid salts, and the like. From the viewpoint of shell strength, metal chelate compounds and organotin compounds are preferred, and metal chelate compounds are particularly preferred.
The amount of the curing catalyst (in terms of metal oxide) is preferably 0.1 to 20.0 parts by mass, and preferably 0.2 to 8.0 parts by mass, based on 100 parts by mass of the alkoxysilane (in terms of metal oxide). Is more preferable.

Step (d2):
The microwave usually refers to an electromagnetic wave having a frequency of 1 G to 100 GHz. Usually, a microwave having a frequency of 2.45 ± 0.05 GHz is used, but a microwave of 5.8 ± 0.075 GHz, 24.125 ± 0.125 GHz, or the like may be used.
The microwave output is preferably an output in which the raw material liquid is heated to 100 to 500 ° C., and an output in which the raw material liquid is heated to 120 to 300 ° C. is more preferable. Specifically, 100 to 5000 W is preferable, and 500 to 3000 W is more preferable.
If the temperature of the raw material liquid is 100 ° C. or higher, a dense shell can be formed in a short time. When the temperature of the raw material liquid is 500 ° C. or lower, the amount of silicon oxide precipitated on the surface other than the core particle surface can be suppressed.

  What is necessary is just to adjust the irradiation time of a microwave to the time when the shell of desired thickness is formed according to the output (temperature of a raw material liquid) of a microwave, for example, is 10 second-60 minutes.

Step (d3):
Examples of a method for removing the dispersion medium from the dispersion of the near-infrared absorbing particles having the core-shell structure and recovering the near-infrared absorbing particles include the following methods.
-A method of volatilizing a dispersion medium by heating a dispersion of near-infrared absorbing particles.
A method of solid-liquid separation of a dispersion of near-infrared absorbing particles and drying the solid content.
-A method of spraying a dispersion of near-infrared absorbing particles in a heated gas using a spray dryer to volatilize the dispersion medium or the like (spray drying method).
A method (freeze-drying method) in which a dispersion medium or the like is sublimated by cooling and depressurizing the dispersion of near-infrared absorbing particles.

(Other surface treatment)
The near-infrared absorbing particles obtained as described above are further subjected to surface treatment by a known method for the purpose of improving weather resistance, acid resistance, water resistance, etc. and improving compatibility with the binder resin by surface modification. May be.
As a surface treatment method, a surface treatment agent or a surface treatment agent diluted with a solvent is added to a dispersion containing near-infrared absorbing particles, the mixture is stirred and treated, and then the solvent is removed and dried (wet method). ); A method (dry method) in which a surface treatment agent diluted with a surface treatment agent or a solvent is jetted with dry air or nitrogen gas and then dried while stirring the near infrared absorbing particles (dry method).
Examples of the surface treatment agent include a surfactant and a coupling agent.

(Function and effect)
In the method for producing near-infrared absorbing particles of the present invention described above, in the step (d), the core particles composed of crystallites of the compound represented by A _{1 / n} CuPO ₄ are surface-treated with alkoxysilane, Since a shell mainly composed of silicon oxide is formed on the surface of the core particle, the transmittance in the visible light region is high, the transmittance in the near infrared region is low, and the transmittance is steep between wavelengths of 630 to 700 nm. Near-infrared absorbing particles that change and have excellent moisture resistance can be produced.

  In addition, in the step (b), the raw material slurry passes through thermal plasma or flame, so that the raw material particles contained in the raw material slurry are rapidly heated and vaporized to an atomic state, and then rapidly cooled. Therefore, particle growth due to bonding between adjacent crystal nuclei is suppressed, and a product having a crystallite size of 5 to 50 nm obtained from X-ray diffraction can be easily obtained. Further, by subjecting the product to a heat treatment in step (c), particle growth due to the heat treatment is suppressed, and particles having few structural defects and high transmittance in the visible light region are obtained. That is, the number average aggregate particle diameter of the particles is 20 to 200 nm without excessive pulverization.

  On the other hand, when not using the method which has process (a)-(c), in order to make the number average aggregated particle diameter of a near-infrared absorption particle 20-200 nm, processes, such as wet grinding | pulverization, are required. However, an excessive pulverization treatment may partially destroy the crystal structure of the particles and reduce the transmittance in the visible light region. That is, when the method having the steps (a) to (c) is not used, an excessive pulverization process is required, and therefore the number-average aggregated particle diameter is small, but the near-infrared absorbing particles having a low visible light region transmittance There is a case. In addition, pulverization for as long as possible is preferable because pulverization for a long time reduces productivity efficiency.

From the above, in the method having the steps (a) to (c), the crystallite size obtained from X-ray diffraction is 5 to 50 nm without excessive pulverization, and the number average aggregated particles Core particles made of crystallites of A _{1 / n} CuPO ₄ having a diameter of 20 to 200 nm can be produced.

<Application>
The near-infrared absorbing particles of the present invention may be dispersed in a dispersion medium and used as a dispersion, or may be dispersed in a resin and used as a resin composition.

<Dispersion>
The dispersion liquid of the present invention includes a dispersion medium and the near-infrared absorbing particles of the present invention dispersed in the dispersion medium, and optionally includes a dispersant, a binder resin, and other light absorbing materials.
The amount of near-infrared absorbing particles is preferably 5 to 50% by mass in the dispersion (100% by mass). If the amount of near-infrared absorbing particles is 5% by mass or more, sufficient near-infrared absorbing characteristics can be exhibited. If the amount of near-infrared absorbing particles is 50% by mass or less, the transmittance in the visible light region can be maintained high.

(Dispersion medium)
Examples of the dispersion medium include water, alcohol, ketone, ether, ester, aldehyde, amine, aliphatic hydrocarbon, alicyclic hydrocarbon, and aromatic hydrocarbon. A dispersion medium may be used individually by 1 type, and may use 2 or more types together. The amount of the dispersion medium is preferably 50 to 95% by mass in the dispersion (100% by mass) from the viewpoint of maintaining the dispersibility of the near-infrared absorbing particles.

(Dispersant)
Dispersing agents that have a modification effect on the surface of near-infrared absorbing particles, such as surfactants, silanes, silicone resins, titanate coupling agents, aluminum coupling agents, zircoaluminate couplings Agents and the like.

  Surfactants include anionic surfactants (special polycarboxylic acid type polymer surfactants, alkyl phosphate esters, etc.), nonionic surfactants (polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxy Ethylene carboxylic acid esters, sorbitan higher carboxylic acid esters, etc.), cationic surfactants (polyoxyethylene alkylamine carboxylic acid esters, alkylamines, alkylammonium salts, etc.), and amphoteric surfactants (higher alkylbetaines, etc.). .

Examples of silane include a silane coupling agent, chlorosilane, alkoxysilane, and silazane. Examples of the silane coupling agent include alkoxysilanes having a functional group (glycidoxy group, vinyl group, amino group, alkenyl group, epoxy group, mercapto group, chloro group, ammonium group, acryloxy group, methacryloxy group, etc.).
Examples of the silicone resin include methyl silicone resin and methylphenyl silicone resin.

Examples of titanate coupling agents include those having an acyloxy group, phosphoxy group, pyrophosphoxy group, sulfoxy group, aryloxy group, and the like.
Examples of the aluminum coupling agent include acetoalkoxyaluminum diisopropylate.
Examples of the zircoaluminate coupling agent include those having an amino group, a mercapto group, an alkyl group, an alkenyl group, and the like.

  Although the quantity of a dispersing agent is based also on the kind of dispersing agent, 0.5-10 mass% is preferable among dispersion liquids (100 mass%). If the amount of the dispersant is within the above range, the dispersibility of the near-infrared absorbing particles becomes good, the transparency is not impaired, and the near-infrared absorbing particles are prevented from settling with time.

(Binder resin)
Binder resins include thermoplastic resins (polyester resins, acrylic resins, polycarbonate resins, polyamide resins, alkyd resins, etc.), thermosetting resins (epoxy resins, thermosetting acrylic resins, silsesquioxy). Sun resin). When the near-infrared absorbing coating film needs transparency, the binder resin is preferably an acrylic resin or a polyester resin. As for the quantity of binder resin, 10-90 mass% is preferable among solid content (100 mass%) of a dispersion liquid.

(Other light absorbers)
Examples of other light absorbing materials include ultraviolet absorbing materials and other infrared absorbing materials.
Examples of the ultraviolet absorber include zinc oxide, titanium oxide, cerium oxide, zirconium oxide, mica, kaolin, and sericite.
Examples of other infrared absorbing materials include ITO (Indium Tin Oxide), ATO (Antimony doped Tin Oxide), and the like. ITO has a high transmittance in the visible light region and has a wide range of electromagnetic wave absorptivity including a radio wave region exceeding 1100 nm. Therefore, ITO is particularly preferable when radio wave shielding is required.
The number average aggregated particle diameter of the other light absorbing material is preferably 100 nm or less from the viewpoint of transparency.

(Preparation of dispersion)
The dispersion of the present invention is mixed with the near-infrared absorbing particles of the present invention, a dispersion medium, a dispersant, a binder resin, etc., if necessary, and stirred by a rotation / revolution mixer, a bead mill, a planetary mill, an ultrasonic homogenizer, or the like. Can be prepared. In order to ensure high transparency, it is necessary to sufficiently stir. Stirring may be performed continuously or intermittently.

(Function and effect)
In the dispersion of the present invention described above, since the near-infrared absorbing particles of the present invention are dispersed in a dispersion medium, the transmittance in the visible light region is high, the transmittance in the near-infrared region is low, It is useful for forming a near-infrared absorbing coating film having a sharp change in transmittance between wavelengths of 630 and 700 nm and excellent moisture resistance.

<Resin composition>
The resin composition of the present invention includes a resin and the near-infrared absorbing particles of the present invention dispersed in the resin, and optionally includes a dispersant and other light absorbing materials.
The amount of near-infrared absorbing particles is preferably 10 to 60% by mass in the resin composition (100% by mass). If the amount of near-infrared absorbing particles is 10% by mass or more, sufficient near-infrared absorbing characteristics can be expressed. When the amount of the near-infrared absorbing particles is 60% by mass or less, the transmittance in the visible light region can be maintained high.

(resin)
Resins include thermoplastic resins (polyester resins, acrylic resins, polycarbonate resins, polyamide resins, alkyd resins, etc.), thermosetting resins (epoxy resins, thermosetting acrylic resins, silsesquioxanes). Resin). When the near-infrared absorbing coating film needs transparency, the resin is preferably an acrylic resin or a polyester resin. The amount of the resin is preferably 40 to 90% by mass in the resin composition (100% by mass).

(Dispersant)
As the dispersant, those having a modification effect on the surface of the near infrared absorbing particles, for example, the above-mentioned surfactant, silane, silicone resin, titanate coupling agent, aluminum coupling agent, zircoaluminate type. A coupling agent etc. are mentioned.

(Other light absorbers)
Examples of the other light absorbing material include the above-described ultraviolet absorbing material and other infrared absorbing materials.

(Preparation of resin composition)
The resin composition of the present invention is a mixture of the near-infrared absorbing particles of the present invention, a resin, and a solvent and a dispersing agent as required, and a rotation / revolution mixer, a bead mill, a planetary mill, a mixer-type kneader, and a three-roll It can prepare by kneading | mixing by etc. In order to ensure high transparency, it is necessary to knead sufficiently. Kneading may be performed continuously or intermittently.

(Function and effect)
In the resin composition of the present invention described above, since the near-infrared absorbing particles of the present invention are dispersed in the resin, the transmittance in the visible light region is high, the transmittance in the near-infrared region is low, It is useful for the formation of a near-infrared absorbing coating film and a near-infrared absorbing article having a sharp change in transmittance between wavelengths of 630 to 700 nm and excellent in moisture resistance.

<Articles with near infrared absorption coating>
The article having the near infrared absorbing coating film of the present invention has a near infrared absorbing coating film containing the near infrared absorbing particles of the present invention on the surface of the substrate.
The article having the near-infrared absorbing coating film of the present invention is required by applying the dispersion liquid of the present invention to the surface of the substrate and drying, or applying the resin composition of the present invention to the surface of the substrate. Can be produced by curing.

Examples of the article having a near-infrared absorbing coating include a near-infrared filter for a camera, an optical filter for a plasma display, a glass window for a vehicle (such as an automobile), a lamp, and the like.
The shape of the substrate may be a film shape or a plate shape. Examples of the material for the base material include glass, polyethylene terephthalate (PET), acrylic resin, urethane resin, polycarbonate, polyethylene, ethylene vinyl acetate copolymer, vinyl chloride, and fluororesin. From the viewpoint of transparency and heat resistance Glass is preferred.

The transmittance change amount D ′ represented by the following formula (3) of the near-infrared absorbing coating film is preferably −0.36 or less, and more preferably −0.37 or less.
D ′ (% / nm) = [T ₇₀₀ (%) − T ₆₃₀ (%)] / [700 (nm) −630 (nm)] (3).
_{However, T 700} is the transmittance at a wavelength of 700nm near infrared absorbing _{coating, T 630} is a transmittance at a wavelength of 630nm near infrared absorbing coating.

When the transmittance change amount D ′ is −0.36 or less, the transmittance change between wavelengths of 630 to 700 nm is sufficiently steep, which is suitable for a near-infrared absorption filter of a camera.
The transmittance of the near-infrared absorbing coating film at a wavelength of 600 nm is preferably 70% or more, and more preferably 75% or more. If the transmittance at a wavelength of 600 nm is 70% or more, red light absorption is sufficiently suppressed, which is suitable for a near-infrared absorption filter of a camera.
The transmittance of the near-infrared absorbing coating film at a wavelength of 450 nm is preferably 75% or more, and more preferably 80% or more. If the transmittance at a wavelength of 450 nm is 75% or more, light absorption in the visible light region is small, which is suitable for a near infrared absorption filter of a camera.

The transmittance of the near-infrared absorbing coating film at a wavelength of 715 nm is preferably 10% or less, and more preferably 5% or less.
The transmittance of the near-infrared absorbing coating film at a wavelength of 500 nm is preferably 80% or more, and more preferably 85% or more.
The transmittance of the near infrared absorbing coating film is measured as follows.
When the resin is a polyester-based resin, a dispersion containing 31% by mass of near-infrared absorbing particles and 69% by mass of resin as a solid content is applied to a glass substrate to form a near-infrared absorbing coating film having a thickness of 70 μm. When the resin is an acrylic resin, a dispersion containing 50% by mass of near-infrared absorbing particles and 50% by mass of resin as a solid content is applied to a glass substrate to form a near-infrared absorbing coating film having a thickness of 20 μm. The transmittance of the near-infrared absorbing coating film is measured using an ultraviolet-visible spectrophotometer.

<Near-infrared absorbing article>
The near-infrared absorbing article of the present invention includes the near-infrared absorbing particles of the present invention.
The near-infrared absorbing article of the present invention can be produced by molding the resin composition of the present invention by a known molding method.
Examples of the molding method include an extrusion molding method, an injection molding method, a calendar method, and a casting method.
Examples of the shape of the article include a film shape, a plate shape, and a coating film on the substrate.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
Examples 1 to 3 are examples, and examples 4 and 5 are comparative examples.

(X-ray diffraction)
About the near-infrared absorption particle | grains of a powder state, the X-ray-diffraction measurement was performed using the X-ray-diffraction apparatus (the RIGAKU company make, RINT-TTR-III), and the crystal structure was identified. Further, the size of the crystallite was obtained by calculation according to Scherrer's method for reflection at 2θ = 14 °.

(Number average agglomerated particle size)
About a dispersion for particle size measurement (solid content concentration: 5% by mass) in which near-infrared absorbing particles are dispersed in water, a dynamic light scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., Microtrac Ultrafine Particle Size Analyzer UPA-) 150) was used to measure the number average aggregate particle size.

(Reflectance)
About the near-infrared absorption particle | grains of a powder state, the diffuse reflection spectrum (reflectance) was measured using the ultraviolet visible spectrophotometer (the Hitachi High-Technologies company make, U-4100 type). Barium sulfate was used as the baseline.

(Transmittance)
About the near-infrared absorption coating film, the transmission spectrum (transmittance) was measured using the ultraviolet visible spectrophotometer (Hitachi High-Technologies company make, U-4100 type).

(Haze)
About the near-infrared absorption coating film used for the transmittance | permeability measurement, the haze was measured using the haze meter (the BYK Gardner company make, gaze-gard plus).

[Example 1]
Step (a):
To 500 g of 52 mass% dipotassium hydrogen phosphate (made by Junsei Kagaku), 500 g of 5 mass% copper sulfate pentahydrate (made by Junsei Chemical) aqueous solution is added with stirring and stirred at room temperature for 5 hours or more. As a result, a light blue reaction solution was obtained. Table 4 shows PO ₄ ³⁻ / Cu ²⁺ (molar ratio) during the reaction. The light blue reaction solution was subjected to solid-liquid separation using a desktop centrifuge to obtain a light blue precipitate. The light blue sediment was dispersed in acetone, subjected to ultrasonic treatment, and then subjected to solid-liquid separation using a desktop centrifuge. The obtained precipitate was dried at 150 ° C. for 2 hours and then dispersed in ethanol to obtain a raw material slurry.

Step (b):
Using the apparatus described in JP-A-2005-170760, the raw material slurry obtained in step (a) is introduced into the thermal plasma in the plasma torch, and the resulting product is cooled in the chamber to dark green. Obtained particles.

Step (c):
The particles obtained in the step (b) were transferred to a flat plate and heat-treated at 500 ° C. for 5 minutes in the air to obtain light blue-green core particles. An infrared image furnace was used for the heat treatment.
The obtained core particles were confirmed by observation with a scanning electron microscope to have an average particle diameter of about 70 nm and a small particle size distribution. Further, X-ray diffraction was measured for the core particles. The results are shown in FIG. From the result of X-ray diffraction, the crystal structure of KCuPO ₄ could be confirmed, and it was identified that the particle was a core particle substantially composed of a crystallite of KCuPO ₄ .

Step (d):
In a 200 mL quartz pressure vessel, 1.00 g of core particles, 7.72 g of TEOS (concentration of solid content in terms of silicon oxide: 28.8% by mass), 31.20 g of isopropanol, 0 of 28% by mass of aqueous ammonia solution. .50 g was added to prepare a raw material solution.
After sealing the pressure vessel, a microwave heating device (Milestone General, Micro SYNTH) is used to irradiate the raw material liquid with a microwave with a maximum output of 1000 W and a frequency of 2.45 GHz at a setting of an ultimate temperature of 150 ° C. Then, TEOS was hydrolyzed to deposit silicon oxide on the surface of the core particles to form a shell, thereby obtaining a dispersion of near-infrared absorbing particles. The obtained dispersion was subjected to solid-liquid separation using a desktop centrifuge. The obtained precipitate was dried at 150 ° C. for 2 hours to obtain an infrared absorbing fine particle powder surface-coated with silicon oxide. From the observation result using a transmission electron microscope, the thickness of the shell made of silicon oxide was about 10 nm.

Further, X-ray diffraction was measured for the near infrared absorbing particles. From the result of X-ray diffraction, the crystal structure of KCuPO ₄ was confirmed, and it was identified that the particle was a near-infrared absorbing particle substantially composed of a crystallite of KCuPO ₄ even after passing through the step (d). . The crystallite size is shown in Table 1.
Also, a dispersion for measuring the particle size of near infrared absorbing particles was prepared, and the number average aggregated particle size was measured. The results are shown in Table 1.
Moreover, the diffuse reflection spectrum (reflectance) of near-infrared absorbing particles was measured. The results are shown in Table 1. Further, the diffuse reflection spectrum is shown by a solid line in FIG.

Moisture resistance test:
Near-infrared absorbing particles were placed in a crucible and subjected to a moisture resistance test. As a tester, a thermo-hygrostat (manufactured by ESPEC Co., Ltd., a small environmental tester LH-113) was used. The test conditions were set to 85 ° C. and relative humidity 85%, and the tester was exposed for 1000 hours. X-ray diffraction was measured for the near-infrared absorbing particles after the test. From the results of X-ray diffraction, it was confirmed that the crystal structure of KCuPO ₄ was retained after the test.
Moreover, the diffuse reflection spectrum (reflectance) of the near-infrared absorbing particles after the test was measured. The results are shown by broken lines in FIG. The result of the diffuse reflection spectrum agrees with the diffuse reflection spectrum of the near-infrared absorbing particles before the test shown by the solid line in FIG. Moreover, the following was employ | adopted as a comparative evaluation method. The results are shown in Table 1.
In the measurement results of diffuse reflection at wavelengths of 300 nm to 2600 nm, the maximum of (reflectance at each wavelength of near-infrared absorbing fine particles after test (%) − reflectance at each wavelength of infrared absorbing fine particles before test) (%) The case where the absolute value of the value was less than 15% was marked as ◯. When the said value was 15% or more, it was set as x.

Dispersion, coating:
The near-infrared absorbing particles and a 25% by mass cyclohexanone solution of polyester resin (manufactured by Osaka Gas Chemical Co., Ltd., OKP4HT) are mixed so that the solid content is 31% by mass of the near-infrared absorbing particles and 69% by mass of the polyester-based resin. The mixture was mixed at a ratio and stirred with a rotation / revolution mixer to obtain a dispersion. The dispersion was applied to a glass substrate, dried with a nitrogen-substituted desiccator for 15 minutes or more, and heated at 150 ° C. for 10 minutes to form a near-infrared absorbing coating film having a thickness of 70 μm.

  The transmittance and haze of the near infrared absorbing coating film were measured. In addition, a moisture resistance test was performed. As a tester, a thermo-hygrostat (manufactured by ESPEC Co., Ltd., a small environmental tester LH-113) was used. The test conditions were 85 ° C. and relative humidity 85%, and exposure was performed for 100 hours. The transmittance and haze of the near-infrared absorbing coating film after the test were measured and compared with those before the test. The results are shown in Table 1. In addition, the following was employ | adopted as a comparative evaluation method.

About the transmittance | permeability spectrum of the near-infrared absorptive coating film after 100-hour humidity resistance test, (100- (800 nm transmittance | permeability (%) of the near-infrared absorptive coating after a test)) (100- (near before test) When the value divided by 800 nm transmittance (%) of the infrared absorbing coating film is 0.95 or more, it was evaluated as ◯. When the above value was 0.90 or more and less than 0.95, Δ and When the above value was less than 0.90, it was marked as x.
For the haze of the near-infrared absorbing coating film after 100 hours of the moisture resistance test, (100- (haze (%) of the near-infrared absorbing coating film after the test)) (100- (of the near-infrared absorbing coating film before the test) When the value divided by haze (%) is 0.95 or more, the result is ◯, and when the value is 0.90 or more and less than 0.95, the result is △. When it was less than, it was set as x.

[Example 2]
Near-infrared absorbing particles were obtained in the same manner as in Example 1 except that the ultimate temperature in the step (d) was set to 160 ° C. From the observation result using a transmission electron microscope, the thickness of the shell made of silicon oxide was approximately 15 nm.
X-ray diffraction was measured for the near-infrared absorbing particles. From the result of X-ray diffraction, the crystal structure of KCuPO ₄ was confirmed, and it was identified that the particle was a near-infrared absorbing particle substantially composed of a crystallite of KCuPO ₄ even after passing through the step (d). . The crystallite size is shown in Table 1.
Also, a dispersion for measuring the particle size of near infrared absorbing particles was prepared, and the number average aggregated particle size was measured. The results are shown in Table 1.
Moreover, the diffuse reflection spectrum (reflectance) of near-infrared absorbing particles was measured. The results are shown in Table 1. Further, the diffuse reflection spectrum is shown by a solid line in FIG.

Moisture resistance test:
Near-infrared absorbing particles were placed in a crucible and subjected to a moisture resistance test in the same manner as in Example 1. About the near-infrared absorption particle | grains after this test, the diffuse reflection spectrum (reflectance) was measured and it confirmed that a near-infrared absorption characteristic was hold | maintained after a moisture resistance test. The results are shown in Table 1. Further, the diffuse reflection spectrum is shown by a broken line in FIG.

Dispersion, coating:
A near-infrared absorbing coating film was formed in the same manner as in Example 1 using near-infrared absorbing particles. The near-infrared absorbing coating film was subjected to a moisture resistance test in the same manner as in Example 1, and a comparative evaluation was conducted on changes in transmittance and haze before and after the test. The results are shown in Table 1.

[Example 3]
Near-infrared absorbing particles surface-treated in the same manner as in Example 1 were obtained except that the ultimate temperature in the step (d) was set to 170 ° C. From the observation result using a transmission electron microscope, the thickness of the shell made of silicon oxide was approximately 15 nm.
X-ray diffraction was measured for the near-infrared absorbing particles. From the result of X-ray diffraction, the crystal structure of KCuPO ₄ was confirmed, and it was identified that the particle was a near-infrared absorbing particle substantially composed of a crystallite of KCuPO ₄ even after passing through the step (d). . The crystallite size is shown in Table 1.
Also, a dispersion for measuring the particle size of near infrared absorbing particles was prepared, and the number average aggregated particle size was measured. The results are shown in Table 1.
Moreover, the diffuse reflection spectrum (reflectance) of near-infrared absorbing particles was measured. The results are shown in Table 1. The diffuse reflection spectrum is shown by a solid line in FIG.

Moisture resistance test:
Near-infrared absorbing particles were placed in a crucible and subjected to a moisture resistance test in the same manner as in Example 1. About the near-infrared absorption particle | grains after this test, the diffuse reflection spectrum (reflectance) was measured and it confirmed that a near-infrared absorption characteristic was hold | maintained after a moisture resistance test. The results are shown in Table 1. Further, the diffuse reflection spectrum is shown by a broken line in FIG.

Dispersion, coating:
A near-infrared absorbing coating film was formed in the same manner as in Example 1 using near-infrared absorbing particles. The near-infrared absorbing coating film was subjected to a moisture resistance test in the same manner as in Example 1, and a comparative evaluation was conducted on changes in transmittance and haze before and after the test. The results are shown in Table 1.

[Example 4]
X-ray diffraction was measured for the core particles obtained in step (c) of Example 1. Table 2 shows the crystallite size.
Also, a dispersion for measuring the particle size of the core particles was prepared, and the number average aggregate particle size was measured. The results are shown in Table 2.
Further, the diffuse reflection spectrum (reflectance) of the core particles was measured. The results are shown in Table 2. The diffuse reflection spectrum is shown by a solid line in FIG.

Moisture resistance test:
The core particles obtained in the step (c) of Example 1 were put in a crucible, and a moisture resistance test was conducted in the same manner as in Example 1. X-ray diffraction was measured for the core particles after the test. From the result of X-ray diffraction, since it is different from the X-ray diffraction of the core particle before the test shown in FIG. 1, it was confirmed that the crystal structure of KCuPO ₄ was destroyed after the test.

  Further, the diffuse reflection spectrum (reflectance) of the core particles after the test was measured. The results are shown in Table 2. Further, the diffuse reflection spectrum is shown by a broken line in FIG. From the result of the diffuse reflectance spectrum, unlike the diffuse reflectance spectrum of the core particle before the test shown by a solid line in FIG. 5, the reflectance on the long wavelength side of the visible light wavelength range decreases after the test, Reflectivity increased. That is, the test showed that the near-infrared absorption characteristics of the core particles were impaired.

Dispersion, coating:
A near-infrared absorbing coating film was formed in the same manner as in Example 1 using the core particles obtained in the step (c) of Example 1. The near-infrared absorbing coating film was subjected to a moisture resistance test in the same manner as in Example 1, and a comparative evaluation was conducted on changes in transmittance and haze before and after the test. The results are shown in Table 2.

[Example 5]
In the step (d), near-infrared absorbing particles were obtained in the same manner as in Example 1 except that the reaction solution was stirred at room temperature for 24 hours without performing microwave irradiation. The shell made of silicon oxide was not confirmed from the observation result using the transmission electron microscope.
X-ray diffraction was measured for the near-infrared absorbing particles. From the result of X-ray diffraction, the crystal structure of KCuPO ₄ was confirmed, and it was identified that the particle was a near-infrared absorbing particle substantially composed of a crystallite of KCuPO ₄ even after passing through the step (d). . The crystallite size is shown in Table 2.
Also, a dispersion for measuring the particle size of near infrared absorbing particles was prepared, and the number average aggregated particle size was measured. The results are shown in Table 2.
Moreover, the diffuse reflection spectrum (reflectance) of near-infrared absorbing particles was measured. The results are shown in Table 2. Further, the diffuse reflection spectrum is shown by a solid line in FIG.

Moisture resistance test:
Near-infrared absorbing particles were placed in a crucible and subjected to a moisture resistance test in the same manner as in Example 1. About the near-infrared absorption particle | grains after this test, the diffuse reflection spectrum (reflectance) was measured. The results are shown in Table 2. Further, the diffuse reflection spectrum is shown by a broken line in FIG.

Dispersion, coating:
A near-infrared absorbing coating film was formed in the same manner as in Example 1 using near-infrared absorbing particles. The near-infrared absorbing coating film was subjected to a moisture resistance test in the same manner as in Example 1, and a comparative evaluation was conducted on changes in transmittance and haze before and after the test. The results are shown in Table 2.

  The near-infrared absorbing particles of the present invention are useful as near-infrared absorbing materials contained in near-infrared absorbing coatings such as near-infrared filters for cameras, optical filters for plasma displays, glass windows for vehicles (automobiles, etc.), lamps, etc. It is.

Claims (11)

Core particles composed of crystallites of the compound represented by the following formula (1);
A near-infrared absorbing particle comprising: a shell mainly composed of silicon oxide covering a surface of the core particle.
A _{1 / n} CuPO ₄ (1).
However, A is an alkali metal (Li, Na, K, Rb , Cs), alkaline earth metal and a (Mg, Ca, Sr, Ba ) and one or more selected from the group consisting of NH _4,
n is 1 when A is an alkali metal or NH ₄ , and 2 when A is an alkaline earth metal. The size of the crystallite obtained from X-ray diffraction is 5 to 50 nm,
The number-average aggregated particle diameter of the near-infrared absorbing particles is 20 to 200 nm,
The near-infrared absorbing particles according to claim 1, wherein a reflectance at a wavelength of 450 nm in the diffuse reflection spectrum of the near-infrared absorbing particles is 80% or more. The near-infrared absorbing particles according to claim 1 or 2, wherein a change amount D of reflectance represented by the following formula (2) is -0.41 or less.
D (% / nm) = [ _R700 (%)- _R600 (%)] / [700 (nm) -600 (nm)] (2).
However, R ₇₀₀ is a reflectance at a wavelength of 700 nm in the diffuse reflection spectrum of the near-infrared absorbing particles, and R ₆₀₀ is a reflectance at a wavelength of 600 nm in the diffuse reflection spectrum of the near-infrared absorbing particles.   The reflectance at a wavelength of 715 nm in the diffuse reflectance spectrum of the near-infrared absorbing particles is 19% or less, and the reflectance at a wavelength of 500 nm is 85% or more. Near-infrared absorbing particles. A method for producing near-infrared absorbing particles according to any one of claims 1 to 4,
The manufacturing method of near-infrared absorption particles which has the following process (d).
(D) A step of surface-treating the core particles made of crystallites of the compound represented by the formula (1) with alkoxysilane to form a shell mainly composed of silicon oxide on the surface of the core particles. The method for producing near-infrared absorbing particles according to claim 5, wherein the step (d) is the following step (d ′).
(D ′) A liquid containing core particles composed of crystallites of the compound represented by the formula (1) and alkoxysilane is irradiated with microwaves, and the surface of the core particles is mainly composed of silicon oxide. Forming a shell; The method for producing near-infrared absorbing particles according to claim 5 or 6, further comprising the following steps (a) to (c).
At (a) in a solvent, a salt containing ^{Cu 2+,} a salt or an organic material containing _PO ^{4 3-,} _PO ^{4 3-} molar ratio with respect to ^{_{Cu 2+ (PO 4 3- / Cu}} 2+) 10-20 And A ^{n +} (where A is an alkali metal (Li, Na, K, Rb, Cs), alkaline earth metal (Mg, Ca, Sr, Ba) and NH ₄ ) 1 or more selected, and n is 1 when A is an alkali metal or NH ₄ , and 2 when A is an alkaline earth metal). Is a step of dispersing a raw material in a dispersion medium to obtain a raw material slurry.
(B) A step of introducing particles of the raw material slurry obtained in the step (a) into thermal plasma or flame and cooling the resulting product to obtain particles.
(C) A step of obtaining core particles composed of crystallites of the compound represented by the formula (1) by heat-treating the particles obtained in the step (b) at 300 to 700 ° C.   The dispersion liquid which disperse | distributed the near-infrared absorption particle in any one of Claims 1-4 to the dispersion medium.   The resin composition which disperse | distributed the near-infrared absorption particle in any one of Claims 1-4 to resin.   The article which has a near-infrared absorption coating film which has the near-infrared absorption coating film containing the near-infrared absorption particle in any one of Claims 1-4 on the surface of a base material.   The near-infrared absorptive article containing the near-infrared absorptive particle in any one of Claims 1-4.

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