JP5891580B2 - Method for producing near-infrared absorbing particles, method for producing dispersion, and method for producing resin composition - Google Patents

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, and a resin composition.

  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

  The present invention relates to near-infrared absorbing particles having a high transmittance in the visible light region, a low transmittance in the near-infrared region, and a sharp change in transmittance between wavelengths of 630 to 700 nm, a production method thereof, a dispersion, and a resin A composition is provided.

The method for producing near-infrared absorbing particles of the present invention comprises crystallites of a compound represented by the following formula (1) having a size determined from X-ray diffraction of 5 to 50 nm, and a number average aggregate particle size of 20 to 200 nm. , and the method for manufacturing a near-infrared-absorbing particles reflectance wavelength 450nm is 80% or more in the diffuse reflectance spectrum, that having a following step (a) ~ step (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 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) The process of heat-processing the particle | grains obtained at the said process (b) at 300-700 degreeC.
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 near-infrared absorbing particles 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.

The near-infrared-absorbing particles, the reflectance of the wavelength of 715nm in the diffusion reflection spectrum, is 19% or less, and the reflectance of the wavelength of 500nm is preferably 85% or more.
The near-infrared absorbing particle has a peak near 1600 cm −1 attributed to water, based on the absorption intensity of a peak near 1000 cm −1 attributed to a phosphate group in a microscopic IR spectrum (100%). Is preferably 8% or less, and the peak absorption intensity in the vicinity of 3750 cm −1 attributed to a hydroxyl group satisfies the condition of 26% or less.

The method for producing a dispersion of the present invention comprises a step of producing the near infrared absorbing particles by the production method of the present invention, and a step of obtaining a dispersion by dispersing the near infrared absorbing particles in a dispersion medium. And
The method for producing a resin composition of the present invention comprises the steps of producing the near-infrared absorbing particles by the production method of the invention and obtaining the resin composition by dispersing the near-infrared absorbing particles in a resin. Features.

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, and a sharp change in wavelength between 630 and 700 nm.
According to the method for producing near-infrared absorbing particles of the present invention, the near-infrared absorption has a high transmittance in the visible light region, a low transmittance in the near-infrared region, and a sharp change in transmittance between wavelengths of 630 to 700 nm. Particles can be produced.
The dispersion of the present invention is useful for forming a near-infrared absorbing coating film having high transmittance in the visible light region, low transmittance in the near-infrared region, and a sharp change in transmittance between wavelengths of 630 to 700 nm. is there.
The resin composition of the present invention is useful for forming a near-infrared absorbing coating film that has a high transmittance in the visible light region, a low transmittance in the near-infrared region, and a sharp change in transmittance between wavelengths of 630 to 700 nm. It is.

FIG. 4 is a diagram showing the results of X-ray diffraction of near-infrared absorbing particles of Example 1. 2 is a diffuse reflection spectrum of near-infrared absorbing particles of Example 1. 2 is a transmission spectrum of the near-infrared absorbing coating film of Example 1. FIG. 4 is a diagram showing the results of X-ray diffraction of a fired product of Example 2. 3 is a diffuse reflection spectrum of near-infrared absorbing particles of Example 2. 2 is a transmission spectrum of a near infrared absorbing coating film of Example 2. 4 is a diffuse reflection spectrum of near-infrared absorbing particles of Example 3. 4 is a transmission spectrum of a near infrared absorbing coating film of Example 3. It is a figure which shows the result of the X-ray diffraction of the crushed material of Example 4. 7 is a diffuse reflection spectrum of near-infrared absorbing particles of Example 4. 6 is a transmission spectrum of a near infrared absorbing coating film of Example 4. FIG. 6 is a diagram showing the results of X-ray diffraction of the fired product of Example 5. 7 is a diffuse reflection spectrum of near-infrared absorbing particles of Example 5. 6 is a transmission spectrum of the near infrared absorption coating film of Example 5. 7 is a transmission spectrum of the near-infrared absorbing coating film of Example 6.

<Near-infrared absorbing particles>
The near-infrared absorbing particles of the present invention are particles composed of crystallites of a compound represented by the following formula (1).
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 can be sufficiently maintained (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 strong coordination bond with PO ₄ ^3- (for example, a transition metal ion or the like) 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.

The crystallite size in the near-infrared absorbing particles of the present invention is 5 to 50 nm, preferably 10 to 30 nm. 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 agglomerated particle diameter of the near-infrared absorbing particles of the present invention is 20 to 200 nm, 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 applications such as absorption filters.
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 near-infrared absorbing particles of the present invention have a reflectance at a wavelength of 450 nm in the diffuse reflection spectrum of 80% or 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 low in haze, 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 particles are A _1. The crystal structure of _{/ 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 manufacturing method of the near-infrared absorption coating film mentioned later 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.

The near-infrared absorbing particles of the present invention can exhibit sufficient near-infrared absorbing characteristics when the crystallites sufficiently maintain the crystal structure of A _{1 / n} CuPO ₄ . Therefore, when water or a hydroxyl group adheres to the surface of the crystallite, the crystal structure of A _{1 / n} CuPO ₄ cannot be maintained, so that the difference in transmittance between the visible light region and the near infrared region is reduced. The near-infrared absorbing coating film formed in this way is not suitable for a near-infrared absorbing filter of a camera.

Therefore, the near-infrared absorbing particles of the present invention have a 1600 cm ⁻ attributed to water when the absorption intensity of a peak near 1000 cm ⁻¹ attributed to a phosphate group is used as a reference (100%) in a microscopic IR spectrum. The absorption intensity of a peak near ¹ is 8% or less, and the absorption intensity of a peak near 3750 cm ⁻¹ attributed to a hydroxyl group is preferably 26% or less. The absorption intensity of a peak near 1600 cm ⁻¹ attributed to water Is 5% or less, and the absorption intensity of a peak near 3750 cm ⁻¹ attributed to a hydroxyl group is more preferably 15% or less.
The microscopic IR spectrum is measured with a Fourier transform infrared spectrophotometer for powdered near-infrared absorbing particles. Specifically, for example, using a Fourier transform infrared spectrophotometer Magna760 manufactured by Thermo Fisher Scientific, 50-100 μg of near infrared absorbing particles are placed on the diamond plate, flattened with a roller, and microscopic FT-IR Measure by the method.

Moreover, 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 between wavelengths of 630 to 700 nm is increased. The change becomes slow, and the near-infrared absorbing coating film formed using this is not suitable for the near-infrared absorbing filter of the 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 comprising crystallites of a compound represented by A _{1 / n} CuPO ₄ , and the size of the crystallites determined by X-ray diffraction is Since the near-infrared absorbing particles have a number average aggregate particle diameter of 20 to 200 nm and the reflectance at a wavelength of 450 nm in the diffuse reflection spectrum of the near-infrared absorbing particles is 80% or more, the transmission in the visible light region is 5 to 50 nm. The transmittance is high, the transmittance in the near-infrared region is low, and the transmittance of the film containing the near-infrared absorbing particles changes sharply between wavelengths of 630 to 700 nm.

<Method for producing near-infrared absorbing particles>
The manufacturing method of the near-infrared absorption particle | grains of this invention is a method which has the following process (a)-(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 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) The process of heat-processing the particle | grains obtained at the said process (b) at 300-700 degreeC.

(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 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.

(surface treatment)
The near-infrared absorbing particles obtained as described above are surface-treated by a known method for the purpose of improving the weather resistance, acid resistance, water resistance, etc. and improving the 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 general, if the number average aggregation diameter of the particles is 1/10 or less of the wavelength, the contribution of Rayleigh scattering is lost, and the haze of the dispersion or composition containing the particles is almost eliminated. Preferably used. Therefore, the number average aggregate diameter of the near-infrared absorbing particles in the present invention needs to be 20 to 200 nm. At the same time, near-infrared filters such as cameras are desired to have a high transmittance in the visible light region, a low transmittance in the near-infrared region, and a sharp change in transmittance between wavelengths of 630 to 700 nm. .
In the method for producing near-infrared absorbing particles of the present invention, the raw material slurry contained in the raw material slurry is rapidly heated and vaporized to an atomic state by passing the raw material slurry through thermal plasma or flame in the step (b). And then cooled rapidly. 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. In addition, by subjecting the product to a heat treatment by the method described in step (c), near-infrared absorbing particles that suppress particle growth due to the heat treatment and that have few structural defects and high transmittance in the visible light region are obtained. can get. That is, in the method for producing near-infrared absorbing particles of the present invention, the near-infrared light having a number average aggregated particle diameter of 20 to 200 nm and high transmittance in the visible light region without excessive pulverization. Absorbent particles are obtained.
On the other hand, when not using the manufacturing method of the near-infrared absorption particle | grains of this invention, 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 for producing near-infrared absorbing particles of the present invention is not used, excessive pulverization is required, and thus the number-average aggregated particle diameter is small, but the near-infrared absorbing particles having a low visible light region transmittance are obtained. There is a case. Further, since pulverization for a long time lowers the efficiency of productivity, it is preferable that the pulverization process be as short as possible.
From the above, in the method for producing near-infrared absorbing particles of the present invention, the crystallite size obtained from X-ray diffraction is 5 to 50 nm without excessive pulverization, Near-infrared absorbing particles composed of crystallites of the compound represented by the formula (1) having a number average aggregate particle diameter of 20 to 200 nm can be produced. That is, near-infrared absorbing particles having a high transmittance in the visible light region, a low transmittance in the near-infrared region, and a sharp change in transmittance between wavelengths of 630 to 700 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 dispersion medium is preferably water or alcohol from the viewpoint of the working environment. 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, Moreover, it is useful for forming a near-infrared absorbing coating film in which the transmittance changes sharply between wavelengths of 630 to 700 nm.

<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, Moreover, it is useful for forming a near-infrared-absorbing coating film and a near-infrared-absorbing article whose transmittance changes sharply between wavelengths of 630 to 700 nm.

<Articles with near infrared absorption coating>
By applying the dispersion of the present invention to the surface of the substrate and drying, or by applying the resin composition of the present invention to the surface of the substrate (and curing as necessary), the near-infrared absorbing coating An article having a membrane is obtained.

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)] (2).
_{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>
It is good also as a near-infrared absorption article by shape | molding the resin composition of this invention with a well-known shaping | 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.
Example 1 is an example, and Examples 2 to 6 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 near infrared absorbing particles. An infrared image furnace was used for the heat treatment.

Near-infrared absorbing particles:
X-ray diffraction was measured for the obtained near-infrared absorbing 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 particles were near-infrared absorbing particles substantially consisting of crystallites of KCuPO ₄ . 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. A diffuse reflection spectrum is shown in FIG.

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. The results are shown in Table 1. The transmission spectrum is shown in FIG.

[Example 2]
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. did. PO ₄ ³⁻ / Cu ²⁺ (molar ratio) is shown in Table 1.
The product was separated from the resulting light blue solution by suction filtration and washed with water and acetone to give a light blue product. The product was transferred to a crucible and vacuum dried at 100 ° C. for 2 hours. The dried product was subjected to dry pulverization for 30 seconds twice using a wonder blender (manufactured by Osaka Chemical Co., Ltd.).

The powdered product was transferred to a crucible and baked in the atmosphere at 600 ° C. for 8 hours to obtain a yellow-green baked product. The fired product was subjected to dry grinding for 30 seconds twice using a wonder blender. The obtained yellowish green fired product was 15.4 g, and the yield based on the number of moles of copper sulfate pentahydrate was 78%.
X-ray diffraction was measured for the fired product. The results are shown in FIG. From the result of X-ray diffraction, the crystal structure of KCuPO ₄ could be confirmed, and the fired product was identified as particles substantially consisting of crystallites of KCuPO ₄ .

The obtained baked product is dispersed in water to form a dispersion having a solid content of 10% by mass, treated with an ultrasonic homogenizer, and then wet pulverized using a wet micronizer (Sugino Machine, Starburst Mini). went. The number of times the dispersion passes through the orifice diameter is defined as the number of wet pulverization treatments. In this example, the number of wet pulverization treatments was 50.
The crushed material was centrifuged from the dispersion after wet pulverization, transferred to a crucible, and dried at 150 ° C. to obtain a yellow-green crushed material. About the crushed material, 30 seconds of dry-type grinding | pulverization was performed twice using the wonder blender.

Near-infrared absorbing particles:
X-ray diffraction of the crushed material was measured. From the result of X-ray diffraction, the crystal structure of KCuPO ₄ could be confirmed, and the crushed material was identified to be near-infrared absorbing particles substantially consisting of KCuPO ₄ crystallites. 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 in FIG.

Dispersion, coating:
A ratio in which the near-infrared absorbing particles and a 25% by mass cyclohexanone solution of a polyester-based resin (byron 103, manufactured by Toyobo Co., Ltd.) have a solid content of 31% by mass of the near-infrared absorbing particles and 69% by mass of the polyester-based resin And stirred with a rotating / revolving 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 20 μm. The transmittance and haze of the near infrared absorbing coating film were measured. The results are shown in Table 1. The transmission spectrum is shown in FIG.

[Example 3]
A crushed material was obtained in the same manner as in Example 2 except that the number of wet pulverization treatments was changed to 10.

Near-infrared absorbing particles:
X-ray diffraction of the crushed material was measured. From the result of X-ray diffraction, the crystal structure of KCuPO ₄ could be confirmed, and the crushed material was identified to be near-infrared absorbing particles substantially consisting of KCuPO ₄ crystallites. 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. A diffuse reflection spectrum is shown in FIG.

Dispersion, coating:
A dispersion and a near-infrared absorbing coating film were obtained in the same manner as in Example 2 except that the near-infrared absorbing particles were changed. The transmittance and haze of the near infrared absorbing coating film were measured. The results are shown in Table 1. The transmission spectrum is shown in FIG.

[Example 4]
The yellow-green fired product of Example 2 was dispersed in cyclohexanone to obtain a dispersion having a solid content of 9% by mass, and wet pulverized using a ball mill for 233 hours.
The crushed material was centrifuged from the dispersion after wet pulverization, transferred to a crucible and dried at 150 ° C. to obtain a green crushed material.

When the microscopic IR spectrum was measured for the yellow-green fired product of Example 2 and the green pulverized product after ball milling of Example 4, in the yellow-green fired product of Example 2, around 1000 cm ⁻¹ attributed to the phosphate group. The peak absorption intensity near 1600 cm ⁻¹ attributed to water is 2.0%, and the peak near 3750 cm ⁻¹ attributed to a hydroxyl group when the absorption intensity of the peak at 100% is taken as a reference (100%) Was 9.6%. On the other hand, in the green crushed material after the ball mill of Example 4, absorption derived from water and a hydroxyl group was confirmed, and when the absorption intensity of a peak near 1000 cm ⁻¹ attributed to a phosphate group was used as a reference (100%) In addition, the absorption intensity of a peak near 1600 cm ⁻¹ attributed to water was 8.7%, and the absorption intensity of a peak near 3750 cm ⁻¹ attributed to a hydroxyl group was 26.7%.

X-ray diffraction was measured for the green crushed material after the ball mill. The results are shown in FIG. The peak position was similar to Example 2, but the peak was broad as a whole. Further, there were peaks not observed in Example 2 at 2θ = 14.2 °, 35.7 °, and the like. These are because the crystal structure collapses due to water adhesion, and KCuPO ₄ is no longer the main crystal structure.

  A crushed product was obtained in the same manner as in Example 2 except that the green crushed product after the ball mill of Example 4 was used instead of the fired product of Example 2 and the number of wet pulverization treatments was changed to 20.

Near-infrared absorbing particles:
X-ray diffraction of the crushed material was measured. From the results of X-ray diffraction, it was confirmed that the crushed material had its crystal structure collapsed due to water adhesion, and KCuPO ₄ was not the main crystal structure. 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. The diffuse reflection spectrum is shown in FIG.

Dispersion, coating:
A dispersion and a near-infrared absorbing coating film were obtained in the same manner as in Example 2 except that the near-infrared absorbing particles were changed. The transmittance and haze of the near infrared absorbing coating film were measured. The results are shown in Table 2. A transmission spectrum is shown in FIG.

[Example 5]
In Example 2, a yellow-green fired product was obtained in the same manner as in Example 2 except that the mixing ratio of the raw materials was changed so that PO ₄ ³⁻ / Cu ²⁺ (molar ratio) was 7.
X-ray diffraction was measured for the fired product. The results are shown in FIG. Many peaks not found in Example 2 were observed (for example, 2θ = 12.5 °, 12.8 °, 15.3 °, etc.). Since the X-ray diffraction of Example 5 is similar to the diffraction pattern of KCu ₄ (PO ₄ ) ₃ reported in the past, the main component was identified as KCu ₄ (PO ₄ ) ₃ .

  A pulverized product was obtained in the same manner as in Example 2 except that the baked product of Example 5 was used instead of the baked product of Example 2 and the number of wet pulverization treatments was changed to 20.

Near-infrared absorbing particles:
X-ray diffraction of the crushed material was measured. From the result of X-ray diffraction, it was identified that the main component of the crushed material was KCu ₄ (PO ₄ ) ₃ . 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. A diffuse reflection spectrum is shown in FIG.

Dispersion, coating:
A dispersion and a near-infrared absorbing coating film were obtained in the same manner as in Example 2 except that the near-infrared absorbing particles were changed. The transmittance and haze of the near infrared absorbing coating film were measured. The results are shown in Table 2. A transmission spectrum is shown in FIG.

[Example 6]
In Example 2, a yellow-green fired product was obtained in the same manner as in Example 2 except that the mixing ratio of the raw materials was changed so that PO ₄ ³⁻ / Cu ²⁺ (molar ratio) was 0.5.
X-ray diffraction was measured for the fired product. Since the X-ray diffraction of Example 6 is similar to the diffraction pattern of KCu ₄ (PO ₄ ) ₃ reported in the past, the main component was estimated to be KCu ₄ (PO ₄ ) ₃ .

  A pulverized product was obtained in the same manner as in Example 2 except that the baked product of Example 6 was used instead of the baked product of Example 2 and the number of wet pulverization treatments was changed to 20.

Near-infrared absorbing particles:
X-ray diffraction of the crushed material was measured. From the result of X-ray diffraction, the crushed material was estimated to be KCu ₄ (PO ₄ ) ₃ . 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.

Dispersion, coating:
A dispersion and a near-infrared absorbing coating film were obtained in the same manner as in Example 2 except that the near-infrared absorbing particles were changed. The transmittance and haze of the near infrared absorbing coating film were measured. The results are shown in Table 2. A transmission spectrum is shown in FIG.

Since the near-infrared absorbing coating film of Example 1 contains the near-infrared absorbing particles of the present invention, the transmittance at a wavelength of 500 nm is high, the transmittance at a wavelength of 715 nm is low, and the change D ′ in transmittance is steep.
The near-infrared absorbing coating film of Example 2 had a small number-average aggregated particle diameter of near-infrared absorbing particles and a low haze, but the crystallites constituting the particles sufficiently maintained the crystal structure of KCuPO ₄ by excessive grinding treatment. It became impossible and the transmittance | permeability by the short wavelength side (500 nm or less) of visible region became low.
The near-infrared absorbing coating film of Example 3 had a high haze because the number-average aggregated particle diameter of the near-infrared absorbing particles was large.
Since the near-infrared absorbing coating films of Examples 4 to 6 have a crystal structure of near-infrared absorbing particles different from that of the present invention, the transmittance at a wavelength of 500 nm is low, the transmittance at a wavelength of 715 nm is high, and the transmittance change amount D ′. Was slow.

  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 (6)

Ri Do from crystallites of the compound represented by the following formula size calculated from X-ray diffraction is 5 to 50 nm (1), the number-average aggregate particle diameter of 20 to 200 nm, the reflection wavelength 450nm in diffuse reflectance spectrum A method for producing near-infrared absorbing particles having a rate of 80% or more ,
A method for producing near-infrared absorbing particles , 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) The process of heat-processing the particle | grains obtained at the said process (b) at 300-700 degreeC.
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 method for producing near-infrared absorbing particles according to claim 1, wherein the reflectance change amount D represented by the following formula (2) of the near-infrared absorbing particles 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 near-infrared absorbing particles according to claim 1 or 2, wherein a reflectance at a wavelength of 715 nm in the diffuse reflectance spectrum of the near-infrared absorbing particles is 19% or less and a reflectance at a wavelength of 500 nm is 85% or more . Manufacturing method . The near-infrared absorbing particles have a peak near 1600 cm ⁻¹ attributed to water when the absorption intensity of the peak near 1000 cm ⁻¹ attributed to the phosphate group is taken as a reference (100%) in the microscopic IR spectrum. The near-infrared absorption as described in any one of Claims 1-3 which satisfy | fills the conditions of the absorption intensity of the peak of 3750cm < ^-1 > vicinity assigned to a hydroxyl group satisfying the conditions of the absorption intensity of 26% or less being 8% or less of Particle manufacturing method . And a step of manufacturing the near-infrared-absorbing particles in the manufacturing method according to any one of claims 1 to 4, and a step of obtaining a dispersion by dispersing the near infrared absorbing particles in a dispersion medium, dispersion Manufacturing method . The resin composition which has the process of manufacturing the said near-infrared absorption particle by the manufacturing method as described in any one of Claims 1-4, and the process of obtaining the resin composition by disperse | distributing the said near-infrared absorption particle in resin. Manufacturing method .

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