JP6226198B2 - Infrared absorbing fine particles, infrared absorbing fine particle dispersion, and infrared absorbing fine particle dispersion using them, infrared absorbing laminated transparent base material, infrared absorbing film, infrared absorbing glass - Google Patents

Description

  The present invention provides an infrared-absorbing fine particle having good visible light transmittance and absorbing near-infrared light, an infrared-absorbing fine particle dispersion, an infrared-absorbing fine particle dispersion using the same, an infrared-absorbing laminated transparent substrate, an infrared-absorbing material. The present invention relates to a film and infrared absorbing glass.

  Near-infrared absorption filters are used in image sensors such as CCDs. This is because by using a near-infrared absorption filter for the image sensor, the near-infrared light incident on the image sensor is blocked, so that the spectral sensitivity of the image sensor can be made closer to the visual sensitivity. And the near-infrared absorption filter contains near-infrared shielding particles. Conventionally, cyanine compounds, porphyrin compounds, indoline compounds, quinacridone compounds, perylene compounds, azo compounds, oxime or thiol metal complexes, naphthoquinone compounds, diimmonium compounds, phthalocyanine compounds, and naphthalocyanine compounds are known as the near-infrared absorbing particles. ing.

  Further, as inorganic infrared absorbing materials that can be used as infrared absorbing materials, for example, Patent Documents 1 and 2 disclose metal borides, and Patent Document 3 discloses tungsten compounds and composite tungsten compounds. Patent Document 4 discloses a method of producing metal hexaboride fine particles by a thermal plasma method using metal boride and boron as raw materials.

Patent Document 1: Japanese Patent No. 4058822 Patent Document 2: Japanese Patent Application Laid-Open No. 2004-237250 Patent Document 3: Japanese Patent No. 4096205 Patent Document 4: Japanese Patent No. 4356313

  According to the study by the present inventors, the near-infrared absorbing material that is an organic compound has been found to have a low light fastness. On the other hand, near-infrared absorbers that are inorganic compounds such as metal borides, tungsten compounds, and composite tungsten compounds described in Patent Documents 1 to 4 do not satisfy the absorption characteristics in the near-infrared region of wavelength 700 to 900 nm. It was.

  The present invention has been made under the above-mentioned circumstances, and the problem to be solved is an inorganic compound having excellent weather resistance, and infrared absorbing fine particles that absorb near-infrared light having a wavelength of 700 to 900 nm. It is to provide an infrared absorbing fine particle dispersion, an infrared absorbing fine particle dispersion using them, an infrared absorbing laminated transparent substrate, an infrared absorbing film, and an infrared absorbing glass.

The present inventors conducted research in order to solve the above problems.
From the simulation calculation, it was conceived that the metal boride fine particles may have an absorption peak in the near-infrared light region having a wavelength of 700 to 900 nm by making the shape of the fine particles spherical. However, for example, the lanthanum hexaboride fine particles manufactured by the thermal plasma method according to the conventional technique described in Patent Document 4 have a shape close to a sphere, and the near-infrared region having a wavelength of 700 to 900 nm as described above. The absorption characteristics at were not satisfactory.
Here, the inventors of the present invention further studied the X-ray diffraction (XRD) pattern of the lanthanum hexaboride fine particles produced by the thermal plasma method according to the prior art, and the normal bulk lanthanum hexaboride. It was found that the XRD pattern was different. Specifically, in the XRD pattern of lanthanum hexaboride fine particles measured by the θ-2θ method, the lanthanum hexaboride fine particles produced by the thermal plasma method according to the prior art and the usual bulk lanthanum hexaboride lanthanum And the peak intensity value of the (100) plane of the lanthanum hexaboride fine particles produced by the thermal plasma method according to the prior art is the peak of the (100) plane of the normal bulk lanthanum hexaboride. It was found to be lower than the strength value. That is, the value of the X-ray diffraction peak intensity ratio (I) defined by Formula 1 is 45% or more and 75% or less, for example 54%, in the conventional bulk lanthanum hexaboride, whereas the conventional technology It was found that, for example, the lanthanum hexaboride fine particles produced by the thermal plasma method according to the present invention is 35%.
I = metal hexaboride fine particle (100) face / metal hexaboride fine particle (110) face × 100% Formula 1
The average particle diameter of the lanthanum hexaboride fine particles is as small as 100 nm, and the number of crystals contributing to X-ray diffraction is very large. For this reason, there is almost no measurement error due to the packing method of the sample, which is generally referred to in the measurement of the X-ray diffraction pattern, and it is considered that the above-described difference in intensity ratio is obtained with very good reproducibility. In other words, the difference in intensity ratio between the normal bulk lanthanum hexaboride and the lanthanum hexaboride fine particles produced by the thermal plasma method according to the prior art is due to the difference in crystal structure between the two. it was thought. That is, it is considered that the crystal structure of the lanthanum hexaboride fine particles manufactured by the thermal plasma method according to the conventional technique has strain and anisotropy.

The present inventors have found that the difference in crystal structure that appears as a difference in XRD pattern between lanthanum hexaboride fine particles produced by a thermal plasma method according to the prior art and a normal bulk lanthanum hexaboride is optical We thought that it might affect the characteristics, and conducted further research.
Then, the inventors have come up with a production method for producing metal boride fine particles having a predetermined spherical shape by a thermal plasma method using metal boride powder such as lanthanum hexaboride powder as a raw material. The XRD pattern of the obtained metal boride fine particles having a predetermined spherical shape almost coincides with the XRD pattern of the bulk metal boride, and the X-ray diffraction peak intensity ratio (I ) Was 45% or more and 75% or less, and the present invention was completed by obtaining the epoch-making knowledge that its optical characteristics have sharp absorption characteristics in the near-infrared region of wavelength 700 to 900 nm.

That is, the first invention for solving the above-described problem is
Metal hexaboride fine particles,
The aspect ratio [(major axis length) / (minor axis length)] when the fine particle shape is regarded as a spheroid is 1.0 or more and 1.5 or less,
X-ray diffraction peak intensity ratio (I) defined by Formula 1 is 45% or more and 75% or less,
I = [metal hexaboride fine particle (100) face / metal hexaboride fine particle (110) face] × 100% Formula 1
The absorption peak position of near-infrared light is in the wavelength range of 700 to 900 nm,
The ratio of the absorbance of light at a wavelength of 550 nm to the absorbance of light at the absorption peak position of near infrared light [(absorbance of light at the absorption peak position) / (absorbance of light at a wavelength of 550 nm)] is 5.0 or more and 20 It is an infrared absorbing fine particle characterized by being 0.0 or less.
The second invention is
The metal hexaboride fine particles are infrared absorbing fine particles, wherein the metal hexaboride fine particles are lanthanum hexaboride fine particles.
The third invention is
The infrared-absorbing fine particles, wherein the infrared-absorbing fine particles have an average particle size of 1 nm or more and 100 nm or less.
The fourth invention is:
The infrared absorbing fine particles according to any one of the first to third inventions are dispersed in a liquid medium, and the liquid medium is water, an organic solvent, an oil or fat, a liquid resin, a liquid An infrared-absorbing fine particle dispersion characterized by being selected from plasticizers for plastics or mixtures thereof.
The fifth invention is:
The infrared-absorbing fine particle dispersion is characterized in that the content of the infrared-absorbing fine particles contained in the liquid medium is 0.0004% by mass or more and 4% by mass or less.
The sixth invention is:
When the infrared ray absorbing fine particle dispersion according to the fourth or fifth invention is diluted with the liquid medium or concentrated by removing the liquid medium to have a visible light transmittance of 70%, light having a wavelength of 700 to 900 nm An infrared-absorbing fine particle dispersion having a minimum transmittance of 15% or less.
The seventh invention
An infrared-absorbing fine particle dispersion comprising the infrared-absorbing fine particles according to any one of the first to third inventions and a thermoplastic resin.
The eighth invention
The thermoplastic resin is polyethylene terephthalate resin, polycarbonate resin, acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluororesin, ethylene / vinyl acetate copolymer, polyvinyl One resin selected from the resin group called acetal resin, a mixture of two or more resins selected from the resin group, or a copolymer of two or more resins selected from the resin group, An infrared-absorbing fine particle dispersion characterized by being any one of the following.
The ninth invention
Infrared absorbing fine particle dispersion comprising 0.002% by mass or more and 80.0% by mass or less of the infrared absorbing fine particles.
The tenth invention is
The infrared-absorbing fine particle dispersion is in the form of a sheet, a board or a film.
The eleventh invention is
An infrared-absorbing fine particle dispersion, wherein the content of the infrared-absorbing fine particles per unit projected area contained in the infrared-absorbing fine particle dispersion is 0.01 g / m ² or more and 0.5 g / m ² or less. is there.
The twelfth invention
When the visible light transmittance is 70%, the infrared ray absorbing fine particle dispersion has a minimum transmittance of 15% or less for light having a wavelength of 700 to 900 nm.
The thirteenth invention
An infrared absorbing laminated transparent substrate characterized in that the infrared absorbing fine particle dispersion described in any one of the seventh to twelfth inventions is present between a plurality of transparent substrates.
The fourteenth invention is
It has a coating layer on at least one surface of a transparent substrate selected from a transparent film substrate or a transparent glass substrate, and the coating layer contains the infrared absorbing fine particles according to any one of the first to third inventions. An infrared absorbing film or an infrared absorbing glass, which is a binder resin.
The fifteenth invention
The infrared ray absorbing film or infrared ray absorbing glass according to the fourteenth aspect, wherein the binder resin is a UV curable resin binder.
The sixteenth invention is
The infrared-absorbing film or infrared-absorbing glass according to the fourteenth or fifteenth invention, wherein the coating layer has a thickness of 1 μm or more and 10 μm or less.
The seventeenth invention
The infrared-absorbing film according to any one of the fourteenth to sixteenth inventions, wherein the transparent film substrate is a polyester film.
The eighteenth invention
Any one of the fourteenth to seventeenth inventions, wherein a content per unit projected area of the infrared absorbing fine particles contained in the coating layer is 0.01 g / m ² or more and 0.5 g / m ² or less. The infrared absorbing film or infrared absorbing glass according to claim 1.
The nineteenth invention
The infrared-absorbing film or the infrared-absorbing glass according to any one of the fourteenth to eighteenth inventions, wherein the infrared-absorbing fine particle dispersion described in the twelfth invention is provided as a coating layer.

  According to the present invention, infrared absorbing fine particles that absorb near-infrared light having a wavelength of 700 to 900 nm while having excellent weather resistance and visible light transmittance, infrared absorbing fine particle dispersions, and infrared absorbing fine particle dispersions using them Body, infrared absorbing laminated transparent base material, infrared absorbing film, and infrared absorbing glass were obtained.

It is a schematic diagram which shows an example of the metal hexaboride fine particle manufacturing apparatus which concerns on this invention. 2 is an XRD pattern of LaB ₆ fine particles according to Example 1. FIG. 2 is a transmission electron micrograph of LaB ₆ fine particles according to Example 1. FIG. 2 is a permeation profile of a dispersion containing LaB ₆ fine particles according to Example 1 and Comparative Example 1. 2 is a permeation profile of a coating film containing LaB ₆ fine particles according to Example 1 and Comparative Example 1.

  Hereinafter, with respect to the embodiments of the present invention, [a] infrared absorbing fine particles, [b] a method for producing infrared absorbing fine particles, [c] an infrared absorbing fine particle dispersion and its production method, [d] infrared absorbing fine particle dispersion and its [E] Infrared absorbing fine particle dispersion in sheet form or film and manufacturing method thereof, [f] Infrared absorbing laminated transparent substrate and manufacturing method thereof [g] Infrared absorbing film, infrared absorbing glass and manufacturing method thereof It explains in order.

[a] Infrared absorbing fine particles The infrared absorbing fine particles according to the present invention are metal hexaboride fine particles having a predetermined spherical shape.
Examples of metal hexaboride include La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Yb, Lu, Sr and Ca hexaboride. However, lanthanum hexaboride (LaB ₆ ) is preferred. In addition, as the said hexaboride, the ratio of a metal and a boron does not need to be strictly 6, and should just be the range of 5.8-6.2.

The predetermined spherical shape of the infrared absorbing fine particles will be described.
The predetermined spherical shape of the infrared-absorbing fine particles is the aspect ratio [(major axis length) / (minor axis length) of the spheroid when the particle shape of the infrared-absorbing fine particles is approximately regarded as a spheroid. ))] Is 1.0 or more and 1.5 or less. Incidentally, the closer the aspect ratio is to 1.0, the closer to a true sphere.
Here, when the particle shape is approximately regarded as a spheroid, 100 or more, preferably 200 or more infrared absorbing fine particles are identified from a TEM photograph of the infrared absorbing fine particles. Then, three-dimensional image analysis is performed on each identified infrared absorbing fine particle by TEM tomography analysis, and the shape of the infrared absorbing fine particle is approximately regarded as a spheroid. In addition, the direction of the major axis and the minor axis is determined for each identified infrared absorbing fine particle (the longest axis orthogonal to each other is the major axis and the shortest axis is the minor axis), and the lengths of both the major and minor axes are determined. And the aspect ratio is calculated from the measured value.

The average particle diameter of the infrared absorbing fine particles is preferably 1 nm or more and 100 nm or less, more preferably 10 nm or more and 40 nm or less.
According to the study by the present inventors, the particle diameter of the infrared absorbing fine particles affects the intensity of the near infrared absorption peak, and the near infrared absorption peak tends to be stronger as the particle diameter of the fine particles is smaller. On the other hand, if the particle diameter of the fine particles is 1 nm or more, preferably 10 nm or more, the crystallinity of the infrared absorbing fine particles can be ensured, and a sufficient near infrared absorption peak can be ensured.

Further, when XRD is measured by the θ-2θ method for the infrared absorbing fine particles, the value of the XRD peak intensity ratio (I) between the (100) plane and the (110) plane defined by the following formula is 45 % To 75%.
I = [metal hexaboride fine particle (100) face / metal hexaboride fine particle (110) face] × 100% Formula 1
The value of the XRD peak intensity ratio (I) indicates that the metal hexaboride fine particles according to the present invention have a crystal structure close to the bulk crystal structure.
On the other hand, for example, the lanthanum hexaboride fine particles produced by the method described in Patent Document 4 have a smaller value of the (100) plane peak intensity than the lanthanum hexaboride fine particles according to the present invention, for example, I = 35%. It was a thing.
From the measurement, the metal hexaboride fine particles according to the present invention have a crystal structure close to the bulk crystal structure, whereas the lanthanum hexaboride fine particles produced by the method described in Patent Document 4 are strained in the crystal structure. Or anisotropy.

In contrast, the metal hexaboride fine particles according to the present invention have a predetermined spherical shape and a crystal structure close to a bulk crystal structure. As a result, the near-infrared absorption peak position of the infrared-absorbing fine particles according to the present invention is in the range of 700 to 900 nm, and the ratio of the absorbance of light having a wavelength of 550 nm to the absorbance of light at the near-infrared absorption peak position [(absorption The value of absorbance of light at the peak position / (absorbance at a wavelength of 550 nm)] was 5.0 or more and 20.0 or less.
The absorbance of the infrared absorbing fine particles is measured in the state of a dispersion in which the infrared absorbing fine particles are dispersed in a medium. Specifically, using a spectrophotometer, the dispersion is placed in a glass cell for a liquid sample and measured. At that time, the absorbance of the infrared-absorbing fine particles can be obtained by measuring in advance a glass cell containing only the medium and using it as a baseline.

  The infrared absorption peak position of the infrared absorbing fine particles depends on the shape of the infrared absorbing fine particles. And the main infrared absorption peak shifts to the lower wavelength side as the shape of the infrared absorbing fine particles is closer to a true sphere. Therefore, it is possible to arbitrarily set the infrared absorption peak position within the aforementioned range by controlling the particle shape of the infrared absorbing fine particles.

[B] Method for Producing Infrared Absorbing Fine Particles An example of the method for producing infrared absorbing fine particles according to the present invention will be described below.
(1) Raw material A metal hexaboride powder is used as a raw material for synthesizing the infrared absorbing fine particles according to the present invention by a thermal plasma method.
As the metal hexaboride powder, it is usually preferable to use commercially available micron order powder. Specifically, a micron-order raw material powder having a particle size range of 1 to 10 μm, which can be stably supplied by a feeder, can be preferably used. By using high-purity metal hexaboride fine particles as the raw material powder, near-infrared absorbing fine particles having the same XRD pattern as that of the bulk metal hexaboride can be obtained.

(2) Treatment by thermal plasma method After the inside of the reaction vessel is evacuated by a vacuum pump, argon (Ar) gas is introduced and evacuated. The exhaust and introduction of Ar gas are repeated to exhaust the residual atmosphere in the reaction vessel, and the exhaust and introduction are preferably performed three or more times.
Thereafter, any gas selected from argon gas, a mixed gas of argon and helium (Ar—He mixed gas), or a mixed gas of argon and nitrogen (Ar—N ₂ mixed gas) as a plasma gas in the reaction vessel At a flow rate of 15 to 25 liters / minute. On the other hand, an Ar—He mixed gas is introduced at a flow rate of 20 to 25 liters / minute as a sheath gas that flows just outside the plasma region.
Then, an alternating current is applied to the high frequency coil to generate thermal plasma by a high frequency electromagnetic field (frequency 4 MHz). At this time, plate power shall be 30-40 kW.
By mixing helium having high thermal conductivity into the sheath gas, the temperature of the inner wall surface of the quartz torch in the reaction vessel is lowered. Furthermore, since the temperature drop of the thermal plasma increases as the sheath gas flow rate increases, the plate power can be increased without melting the quartz torch. Therefore, when the particle shape is approximately regarded as a spheroid, the aspect ratio [(major axis length) / (minor axis length)] of the spheroid is 1.0 or more and 1.5 or less. It is preferable from the viewpoint of producing infrared absorbing fine particles.
However, in order to avoid generation of unreacted raw material powder and a reduction in the recovery rate of infrared absorbing fine particles, the plasma gas and sheath gas flow rates are preferably 25 liters / minute or less, respectively.

The carrier gas species for supplying the raw material powder may be the same as the plasma gas species, and the flow rate may be 1 to 3 liters / minute. The metal hexaboride powder is continuously fed into the thermal plasma little by little by an inert gas for the carrier.
The metal boride powder supplied as a raw material powder into the thermal plasma is heated at an ultra-high temperature portion (about 10,000 to 15000 ° C.) at the center of the thermal plasma, and then the core of the metal hexaboride in the thermal plasma. Is formed, the nucleus grows while moving with the flow of the thermal plasma, and the aspect ratio [(major axis length) / (minor axis length)] value is 1.0 or more and 1.5 or less. Absorbing particulates are synthesized.

[C] Infrared absorbing fine particle dispersion and method for producing the same The infrared absorbing fine particle dispersion according to the present invention can be produced by dispersing the infrared absorbing fine particles according to the present invention in a liquid medium.

  Hereinafter, a method for producing the infrared-absorbing fine particle dispersion will be described. In the present invention, the infrared-absorbing fine particle dispersion may be simply referred to as “dispersion”.

  The infrared-absorbing fine particle dispersion according to the present invention is obtained by adding the infrared-absorbing fine particles according to the present invention and, if desired, an appropriate amount of a dispersant, a coupling agent, a surfactant, etc. to the liquid medium and performing a dispersion treatment. Can do. The medium of the infrared-absorbing fine particle dispersion is required to have a function for maintaining the dispersibility of the infrared-absorbing fine particles and a function for preventing defects when the infrared-absorbing fine particle dispersion is used.

(1) Medium As the medium, water, an organic solvent, oils and fats, a liquid resin, a liquid plasticizer for plastics, or a mixture thereof can be selected to produce an infrared absorbing fine particle dispersion. Various organic solvents such as alcohols, ketones, hydrocarbons, glycols, and water can be selected as organic solvents that satisfy the above requirements. Specifically, alcohol solvents such as methanol, ethanol, 1-propanol, isopropanol, butanol, pentanol, benzyl alcohol and diacetone alcohol; ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone Solvents such as 3-methyl-methoxy-propionate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol methyl ether acetate, propylene Glycol derivatives such as glycol ethyl ether acetate; Amides such as N-methylformamide, dimethylformamide, dimethylacetamide and N-methyl-2-pyrrolidone; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as ethylene chloride and chlorobenzene Can be mentioned. Among these, organic solvents having low polarity are preferable, and isopropyl alcohol, ethanol, 1-methoxy-2-propanol, dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether acetate, n-butyl acetate and the like are more preferable. preferable. These solvents can be used alone or in combination of two or more.

  As the liquid resin, methyl methacrylate and the like are preferable. Liquid plasticizers include plasticizers that are compounds of monohydric alcohols and organic acid esters, ester plasticizers such as polyhydric alcohol organic acid ester compounds, and phosphorus compounds such as organic phosphate plasticizers. A preferable example is an acid plasticizer. Of these, triethylene glycol di-2-ethyl hexaonate, triethylene glycol di-2-ethyl butyrate, and tetraethylene glycol di-2-ethyl hexaonate are more preferable because of their low hydrolyzability.

(2) Dispersant, coupling agent, surfactant Dispersant, coupling agent, surfactant can be selected according to the application, but amine-containing group, hydroxyl group, carboxyl group, or epoxy group It is preferable to have it as a functional group. These functional groups are adsorbed on the surface of the infrared absorbing fine particles, prevent aggregation of the infrared absorbing fine particles, and have an effect of uniformly dispersing the infrared absorbing fine particles according to the present invention in the infrared absorbing film.

  Suitable dispersants include, but are not limited to, phosphate ester compounds, polymeric dispersants, silane coupling agents, titanate coupling agents, aluminum coupling agents, and the like. It is not a thing. Examples of the polymer dispersant include an acrylic polymer dispersant, a urethane polymer dispersant, an acrylic block copolymer polymer dispersant, a polyether dispersant, and a polyester polymer dispersant.

  The addition amount of the dispersant is desirably in the range of 10 parts by weight to 1000 parts by weight, and more preferably in the range of 20 parts by weight to 200 parts by weight with respect to 100 parts by weight of the infrared absorbing fine particles. When the added amount of the dispersant is in the above range, the infrared absorbing fine particles do not aggregate in the liquid, and dispersion stability is maintained.

(3) Method for producing infrared-absorbing fine particle dispersion The dispersion treatment method can be arbitrarily selected from known methods as long as the infrared-absorbing fine particles are uniformly dispersed in a liquid medium. For example, a bead mill, a ball mill, a sand mill, Methods such as sonic dispersion can be used.
In order to obtain a uniform infrared-absorbing fine particle dispersion, various additives and dispersants may be added, or the pH may be adjusted.

(4) Infrared absorbing fine particle dispersion The content of the infrared absorbing fine particles in the above-described infrared absorbing fine particle dispersion is preferably 0.002% by mass to 25% by mass. If it is 0.002 mass% or more, it can be used suitably for manufacture of the coating film mentioned later, a plastic molding, etc., and if it is 25 mass% or less, industrial production is easy. More preferably, it is 0.5 mass% or more and 20 mass% or less.

The infrared-absorbing fine particle dispersion according to the present invention in which such infrared-absorbing fine particles are dispersed in a liquid medium is placed in a suitable transparent container, and the light transmittance is measured as a function of wavelength using a spectrophotometer. be able to. The infrared-absorbing fine particle dispersion according to the present invention has an absorption peak at a wavelength of 700 to 900 nm, and a ratio of the light absorbance at a wavelength of 550 nm to the light absorbance at the absorption peak position [(absorbance of light at the absorption peak position) / (wavelength The absorbance at 550 nm)] is 5.0 or more and 20.0 or less.
In this measurement, the transmittance of the infrared-absorbing fine particle dispersion is easily adjusted by diluting with a dispersion solvent or an appropriate solvent compatible with the dispersion solvent.

[D] Infrared absorbing fine particle dispersion and method for producing the same The infrared absorbing fine particle dispersion comprises the infrared absorbing fine particles and a thermoplastic resin.
There are no particular restrictions on the thermoplastic resin, but polyethylene terephthalate resin, polycarbonate resin, acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluororesin, ethylene / vinyl acetate 1 type of resin selected from the resin group called a copolymer and a polyvinyl acetal resin,
Or a mixture of two or more resins selected from the resin group,
Or it is preferable that it is either the copolymer of 2 or more types of resin selected from the said resin group.
The amount of the infrared absorbing fine particles contained in the infrared absorbing fine particle dispersion is preferably 0.002% by mass or more and 80.0% by mass or less, more preferably 0.01% by mass or more and 50% by mass or less. preferable. When the infrared absorbing fine particles are less than 0.002% by mass, it is necessary to increase the thickness in order to obtain a necessary infrared shielding effect. When the infrared absorbing fine particles exceeds 80% by mass, the thermoplastic resin component is reduced, and the infrared rays are reduced. The strength of the absorbing fine particle dispersion may be weakened.
The content of infrared absorbing fine particles contained per unit projected area in the infrared absorbing fine particle dispersion is preferably 0.01 g / m ² or more and 0.5 g / m ² or less. If the infrared absorbing fine particles are less than 0.01 g / m ^{2, it} is necessary to increase the thickness in order to obtain the necessary infrared shielding effect. If the infrared absorbing fine particles exceed 0.5 g / m ² , the thermoplastic resin component is increased. In some cases, the strength of the infrared-absorbing fine particle dispersion becomes weak.
The “content per unit projected area” means the weight of the infrared absorbing fine particles contained in the thickness direction per unit area (m ² ) through which light passes in the infrared absorbing fine particle dispersion according to the present invention. (G).
The infrared absorbing fine particle dispersion can be applied to various uses by processing into a sheet shape, a board shape or a film shape.

The method for producing the infrared absorbing fine particle dispersion will be described below.
After mixing the infrared absorbing fine particle dispersion and the thermoplastic resin, by removing the solvent component, a dispersion powder or a plasticizer dispersion containing the infrared absorbing fine particles can be obtained. As a method for removing the solvent component from the infrared absorbing fine particle dispersion, the infrared absorbing fine particle dispersion is preferably dried under reduced pressure. Specifically, the infrared absorbing fine particle dispersion is dried under reduced pressure while stirring to separate the infrared absorbing fine particle-containing composition from the solvent component. Examples of the apparatus used for the reduced-pressure drying include a vacuum agitation type dryer, but any apparatus having the above functions may be used, and the apparatus is not particularly limited. Moreover, the pressure value at the time of pressure reduction in the drying step is appropriately selected.

  By using the reduced-pressure drying method, the removal efficiency of the solvent from the infrared-absorbing fine particle dispersion is improved, and the dispersion powder and the plasticizer dispersion are not exposed to high temperature for a long time. It is preferable that the infrared absorbing fine particles dispersed in the agent dispersion do not aggregate. Furthermore, the productivity of the dispersion powder and the plasticizer dispersion is improved, and it is easy to collect the evaporated solvent, which is preferable from the environmental consideration.

In the dispersion powder or plasticizer dispersion obtained after the drying step, the remaining solvent is preferably 5% by mass or less. If the remaining solvent is 5% by mass or less, bubbles are not generated when the dispersion powder or plasticizer dispersion is processed into, for example, a laminated transparent base material, and the appearance and optical characteristics are kept good. is there.
Moreover, a masterbatch can be obtained by disperse | distributing infrared absorption fine particles and dispersion | distribution powder in resin, and pelletizing the said resin.

  Further, after uniformly mixing the infrared-absorbing fine particles and the dispersion powder, thermoplastic resin granules or pellets, and other additives as necessary, kneaded in a vent type uniaxial or biaxial extruder, A master batch can also be obtained by processing into a pellet by a general method of cutting a melt-extruded strand. In this case, examples of the shape include a columnar shape and a prismatic shape. It is also possible to adopt a so-called hot cut method in which the molten extrudate is directly cut. In this case, it is common to take a shape close to a sphere.

[e] Sheet-like or film-like infrared-absorbing fine particle dispersion and production method thereof The sheet-like or film according to the present invention is obtained by uniformly mixing the dispersion powder, plasticizer dispersion, or masterbatch into a transparent resin. Infrared absorbing fine particle dispersion can be produced. From the sheet-like or film-like infrared-absorbing fine particle dispersion, an infrared-absorbing sheet or an infrared-absorbing film that selectively absorbs near-infrared light having a wavelength of 700 to 900 nm can be produced.

When manufacturing a sheet-like or film-like infrared-absorbing fine particle dispersion, various thermoplastic resins can be used as the resin constituting the sheet or film. And considering that the sheet-like or film-like infrared-absorbing fine particle dispersion is applied to the optical filter, it is preferably a thermoplastic resin having sufficient transparency.
Specifically, resin groups such as polyethylene terephthalate resin, polycarbonate resin, acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluorine resin, ethylene / vinyl acetate copolymer A preferred resin can be selected from a resin selected from the group consisting of two or more resins selected from the resin group, or a copolymer of two or more resins selected from the resin group. .

In addition, when a sheet-like or film-like infrared-absorbing fine particle dispersion is used as an intermediate layer, the thermoplastic resin constituting the sheet or film alone has sufficient flexibility and adhesion to a transparent substrate. For example, when the thermoplastic resin is a polyvinyl acetal resin, it is preferable to add a plasticizer.
As a plasticizer, the substance used as a plasticizer with respect to the thermoplastic resin which concerns on this invention can be used. For example, as a plasticizer used for an infrared absorbing film composed of a polyvinyl acetal resin, a plasticizer that is a compound of a monohydric alcohol and an organic acid ester, a plasticizer that is an ester system such as a polyhydric alcohol organic acid ester compound, Examples include phosphoric acid plasticizers such as organic phosphoric acid plasticizers. Any plasticizer is preferably liquid at room temperature. Among these, a plasticizer that is an ester compound synthesized from a polyhydric alcohol and a fatty acid is preferable.

After kneading the dispersion powder or plasticizer dispersion or masterbatch, the thermoplastic resin, and plasticizer and other additives as desired, the kneaded product is obtained by a known method such as an extrusion molding method or an injection molding method. For example, a sheet-like infrared-absorbing fine particle dispersion formed into a flat shape or a curved shape can be produced.
A known method can be used as a method for forming the sheet-like or film-like infrared-absorbing fine particle dispersion. For example, a calendar roll method, an extrusion method, a casting method, an inflation method, or the like can be used.

[F] Infrared absorbing laminated transparent base material and method for producing the same Infrared comprising a sheet-like or film-like infrared-absorbing fine particle dispersion interposed as an intermediate layer between a plurality of transparent base materials made of a sheet glass or plastic material. The absorption-matched transparent substrate will be described.
The infrared absorbing laminated transparent base material is obtained by sandwiching an intermediate layer from both sides using a transparent base material. As the transparent substrate, plate glass transparent in the visible light region, plate-like plastic, or film-like plastic is used. The material of the plastic is not particularly limited and can be selected according to the application, polycarbonate resin, acrylic resin, polyethylene terephthalate resin, PET resin, polyamide resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, A fluororesin can be used.

  The infrared-absorbing laminated transparent base material according to the present invention is a method in which a plurality of opposing transparent base materials that are sandwiched by the sheet- or film-shaped infrared-absorbing fine particle dispersion according to the present invention are bonded together by a known method. Can also be obtained.

As for the optical characteristics of the sheet-like or film-like infrared-absorbing fine particle dispersion or infrared-absorbing laminated structure according to the present invention, when the visible light transmittance is 70%, the minimum transmittance for light having a wavelength of 700 to 900 nm is 15%. It is as follows.
Here, adjusting the visible light transmittance to 70% is to prepare the resin composition, the concentration of infrared absorbing fine particles contained in the above-described infrared absorbing fine particle dispersion, dispersion powder, plasticizer dispersion or masterbatch. It is easy to adjust the amount of the infrared absorbing fine particles, the dispersed powder, the plasticizer dispersion or the master batch, and the film thickness of the film or sheet.

[G] Infrared absorbing film and infrared absorbing glass and method for producing the same Using the above-described infrared absorbing fine particle dispersion, a coating layer containing infrared absorbing fine particles is formed on a transparent substrate selected from a substrate film or a substrate glass. Thus, an infrared absorbing film or an infrared absorbing glass can be produced.

The above infrared absorbing fine particle dispersion is mixed with a plastic or a monomer to prepare a coating solution, and a coating film is formed on a transparent substrate by a known method to prepare an infrared absorbing film or infrared absorbing glass. Can do.
For example, the infrared absorbing film can be produced as follows.
A medium resin is added to the above-described infrared absorbing fine particle dispersion to obtain a coating solution. After coating the coating liquid on the surface of the film substrate, if the solvent is evaporated and the resin is cured by a predetermined method, a coating film in which the infrared absorbing fine particles are dispersed in the medium can be formed.

As the medium resin for the coating film, for example, a UV curable resin, a thermosetting resin, an electron beam curable resin, a room temperature curable resin, a thermoplastic resin, or the like can be selected according to the purpose. Specifically, polyethylene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol resin, polystyrene resin, polypropylene resin, ethylene vinyl acetate copolymer, polyester resin, polyethylene terephthalate resin, fluorine resin, polycarbonate resin, acrylic resin And polyvinyl butyral resin.
These resins may be used alone or in combination. However, among the media for the coating layer, it is particularly preferable to use a UV curable resin binder from the viewpoint of productivity, apparatus cost, and the like.

Also, a binder using a metal alkoxide can be used. Typical examples of the metal alkoxide include alkoxides such as Si, Ti, Al, and Zr. Binders using these metal alkoxides can be subjected to hydrolysis and polycondensation by heating or the like to form a coating layer made of an oxide film.
In addition to the above method, the infrared absorbing fine particle dispersion may be applied onto a substrate film or substrate glass, and then a coating layer may be formed by further applying a binder using a medium resin or a metal alkoxide.

  In addition, the film base material mentioned above is not limited to a film shape, For example, a board form or a sheet form may be sufficient. As the film base material, PET, acrylic, urethane, polycarbonate, polyethylene, ethylene vinyl acetate copolymer, vinyl chloride, fluorine resin, and the like can be used according to various purposes. However, the infrared absorbing film is preferably a polyester film, and more preferably a PET film.

Further, the surface of the film substrate is preferably subjected to a surface treatment in order to realize easy adhesion of the coating layer. In order to improve the adhesion between the glass substrate or the film substrate and the coating layer, it is also preferable to form an intermediate layer on the glass substrate or the film substrate and form the coating layer on the intermediate layer. The configuration of the intermediate layer is not particularly limited, and may be composed of, for example, a polymer film, a metal layer, an inorganic layer (for example, an inorganic oxide layer such as silica, titania, zirconia), an organic / inorganic composite layer, or the like. .
The method for providing the coating layer on the substrate film or the substrate glass is not particularly limited as long as the infrared absorbing fine particle dispersion can be uniformly applied to the surface of the substrate. For example, a bar coating method, a gravure coating method, a spray coating method, a dip coating method, and the like can be given.

  For example, according to the bar coating method using a UV curable resin, a coating liquid in which the liquid concentration and additives are appropriately adjusted so as to have an appropriate leveling property is used for the purpose of the thickness of the coating film and the content of the infrared absorbing fine particles. A coating film can be formed on a substrate film or substrate glass using a wire bar having a bar number that can be filled. And after removing the solvent contained in a coating liquid by drying, a coating layer can be formed on a board | substrate film or board | substrate glass by irradiating and hardening | curing an ultraviolet-ray. At this time, the drying condition of the coating film varies depending on the components, the type of solvent, and the use ratio, but is usually about 20 seconds to 10 minutes at a temperature of 60 ° C to 140 ° C. There is no restriction | limiting in particular in ultraviolet irradiation, For example, UV exposure machines, such as an ultrahigh pressure mercury lamp, can be used suitably.

  In addition, the adhesion between the substrate and the coating layer, the smoothness of the coating film at the time of coating, the drying property of the organic solvent, and the like can be controlled by the pre- and post-processes of forming the coating layer. Examples of the pre- and post-processes include a substrate surface treatment process, a pre-bake (substrate pre-heating) process, a post-bake (substrate post-heating) process, and the like, and can be appropriately selected. The heating temperature in the pre-baking step and / or the post-baking step is preferably 80 ° C. to 200 ° C., and the heating time is preferably 30 seconds to 240 seconds.

The thickness of the coating layer on the substrate film or the substrate glass is not particularly limited, but is practically preferably 10 μm or less, and more preferably 6 μm or less. If the thickness of the coating layer is 10 μm or less, in addition to exhibiting sufficient pencil hardness and scratch resistance, warping of the substrate film occurs when the coating layer is stripped of the solvent and the binder is cured. This is because the occurrence of process abnormalities such as these can be avoided.
The amount of infrared absorbing fine particles contained per unit projected area in the coating layer is preferably 0.01 g / m ² or more and 0.5 g / m ² or less.

  Regarding the optical characteristics of the manufactured infrared absorbing film and infrared absorbing glass, the minimum transmittance at a wavelength of 700 to 900 nm is 15% or less when the visible light transmittance is 70%. The visible light transmittance can be easily adjusted to 70% by adjusting the concentration of infrared absorbing fine particles in the coating liquid or adjusting the thickness of the coating layer.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not necessarily limited to these Examples.

Example 1
The apparatus shown in FIG. 1 is used as a reaction vessel, and the raw material powder is continuously supplied with a carrier gas into the thermal plasma of the Ar—He mixed gas generated in the reaction vessel, whereby the aspect ratio [(long axis length Spherical lanthanum hexaboride fine particles having a value of (sa) / (short axis length)] of 1.0 or more and 1.5 or less were produced.

(1) Raw Material Powder A dry powder of lanthanum hexaboride (LaB ₆ ) having an average particle diameter of 1 to 10 μm and a purity of 98% was prepared as a raw material powder.

(2) Reaction vessel The reaction vessel will be described with reference to FIG.
In FIG. 1, a high frequency coil 2 for generating thermal plasma is wound around an upper outer wall of a reaction vessel 6. The upper outer wall around which the high-frequency coil 2 is wound is a cylindrical double tube (quartz torch) made of quartz glass or the like, and cooling water is passed through the gap to prevent the quartz glass from melting by thermal plasma. doing.
In addition, a sheath gas supply nozzle 3 and a plasma gas supply nozzle 4 are provided in the upper part of the reaction vessel 6 together with the raw material powder supply nozzle 5. The powder raw material sent by the carrier gas from the raw material powder feeder is supplied into the thermal plasma 1 through the raw material powder supply nozzle 5. The raw material powder supply nozzle 5 does not necessarily have to be installed above the thermal plasma 1 as shown in FIG. 1, and the nozzle can be installed in the lateral direction of the thermal plasma 1.

  The reaction vessel 6 plays a role of maintaining the pressure in the plasma reaction part and suppressing the dispersion of the produced fine powder. A suction pipe 7 is connected to the lower part of the reaction vessel 6, and a filter 8 for collecting the synthesized fine powder is installed in the middle of the suction pipe 7. The pressure in the reaction vessel 6 is adjusted by the suction capacity of a pump installed on the downstream side of the filter 8.

(3) Synthesis of lanthanum hexaboride fine particles After evacuating the inside of the reaction vessel with a vacuum pump, Ar gas was introduced to bring the inside of the reaction vessel to atmospheric pressure. This operation of exhausting and introducing Ar gas was repeated three times to exhaust the residual air in the reaction vessel.
Thereafter, Ar—He mixed gas as a plasma gas is introduced into the reaction vessel at a rate of 20 liters / minute, and Ar—He mixed gas as a sheath gas is introduced at a flow rate of 25 liters / minute. Thermal plasma was generated by (frequency 4 MHz). The plate output power at this time was 35 kW. The carrier gas for supplying the raw material powder was Ar gas having a flow rate of 2 liters / minute.
The synthesized lanthanum hexaboride fine particles were collected with a filter.

(4) Measurement of synthesized lanthanum hexaboride fine particles A TEM photograph of the synthesized lanthanum hexaboride fine particles is shown in FIG. From FIG. 3, it was found that all the synthesized lanthanum hexaboride fine particles were fine nanoparticles. When 534 lanthanum hexaboride fine particles were selected from the TEM photograph of a total of 5 visual fields including FIG. 3 and the other 4 visual fields, the number average particle diameter of the lanthanum hexaboride fine particles was determined to be 27 nm. Further, the TEM photograph is subjected to three-dimensional image analysis by TEM tomography analysis, the shape of the lanthanum hexaboride fine particles is approximately regarded as a spheroid, the short axis and the long axis are determined, and the aspect ratio [(long axis length ) / (Minor axis length)] was calculated and found to be 1.0 or more and 1.5 or less for all the confirmed fine particles.

  For the recovered lanthanum hexaboride fine particles, identification of the crystal phase and analysis of the crystal structure are performed using a powder XRD apparatus (X'Pert-PRO / MPD manufactured by Spectaly Co., Ltd. PANalytical) using CuKα rays by the θ-2θ method. went. The composition analysis of the lanthanum hexaboride fine particles was performed by ICP emission spectrometry (ICPE-9000, manufactured by Shimadzu Corporation). Further, observation of the particle shape of the lanthanum hexaboride fine particles and measurement of the particle size distribution were performed using a transmission electron microscope (HF-2200 manufactured by Hitachi, Ltd.).

  FIG. 2 shows the XRD pattern of the synthesized lanthanum hexaboride fine particles. From FIG. 2, it was confirmed that the obtained lanthanum hexaboride fine particles were a single phase of lanthanum hexaboride. Further, it was found that the value of the ratio of the peak intensity of the (100) plane near 2θ = 21.4 ° to the peak intensity of the (110) plane at 2θ = 30.4 °: I = 62%. It was confirmed that the crystal structure of the lanthanum hexaboride fine particles was close to the crystal structure of bulk lanthanum hexaboride.

  The composition of the synthesized lanthanum hexaboride fine particles was examined by ICP emission spectrometry. As a result, it was confirmed that the total concentration of B and La was 90% by mass or more, the balance was oxygen, and no other impurities contained at 1% by mass or more were present.

(5) Measurement of optical properties of lanthanum hexaboride fine particles 10 parts by weight of the produced lanthanum hexaboride fine particles, 80 parts by weight of toluene, and 10 parts by weight of a dispersant (an acrylic polymer dispersant having an amino group) were mixed. A 3 kg slurry was prepared. This slurry was put into a medium stirring mill together with the beads, and the slurry was circulated for pulverization and dispersion treatment for 10 hours.
The medium stirring mill used was a horizontal cylindrical annular type (manufactured by Ashizawa Corporation), and the inner wall of the vessel and the rotor (rotary stirring portion) were made of ZrO ₂ . Also, beads made of YSZ (Yttria-Stabilized Zirconia) having a diameter of 0.3 mm were used.
The rotation speed of the rotor was 13 rpm / second, and pulverization dispersion treatment was performed at a slurry flow rate of 1 kg / min to obtain a dispersion.

The resulting dispersion was diluted with the solvent toluene. At this time, the concentration of the dispersion was adjusted so that the visible light transmittance of the dispersion was 70% in the transmittance measurement described later. After adjusting the concentration by dilution with toluene, the dispersion was put into a glass cell having a bottom surface of 1 cm square and a height of 5 cm.
The light transmittance of the dispersion in the glass cell was measured with a spectrophotometer (U-4100, manufactured by Hitachi, Ltd.) at an interval of 1 nm in a wavelength range of 300 nm to 1600 nm. As a result, that is, the permeation profile of the dispersion is shown by a solid line in FIG.
For comparison, the result of measuring the light transmittance of the dispersion using the lanthanum hexaboride fine particles produced by the production method by the breakdown method described in Patent Document 2 is shown by a broken line in FIG.
In the measurement, the light incident direction of the spectrophotometer was a direction perpendicular to the side surface of the glass cell. Moreover, the blank liquid which put only toluene of the solvent in this glass cell was made into the baseline of the light transmittance.

  From the transmission profile of the dispersion liquid of the present invention in FIG. 4, the absorption peak position of the dispersion liquid according to Example 1 is in the wavelength range of 700 to 900 nm, and the ratio of the light absorbance at the wavelength 550 nm to the light absorbance at the absorption peak position. It was confirmed that the value of [(absorbance of light at the absorption peak position) / (absorbance at a wavelength of 550 nm)] was 12.7. Further, the absorption peak position in Patent Document 2 described as a comparison does not exist in the wavelength range of 700 nm to 900 nm, exists near 1000 nm on the longer wavelength side, and the value of the absorbance ratio is 6. The difference between the dispersion of the present invention and the dispersion produced by the method described in Patent Document 2 is clear. In the permeation profile measurement, a blank liquid containing only toluene as a solvent is used as the base line of the transmissivity, and therefore, the permeation profile in FIG. 4 almost matches the optical characteristics of the lanthanum hexaboride fine particles in the dispersion. That is, it was confirmed that the lanthanum hexaboride fine particles in the dispersion had the optical characteristics described above.

  Further, the dispersion obtained in the paragraph [0065] is mixed with an ultraviolet curable resin and a toluene solvent, and coated on a glass substrate with a bar coater (IMC-700 manufactured by Imoto Seisakusho) to form a coating film. After the solvent was evaporated from the film, the coating film was cured by irradiation with ultraviolet rays. At this time, the concentration of the dispersion was adjusted in advance by dilution with toluene as a solvent so that the visible light transmittance of the coating film was 70%.

The result of measuring the light transmittance of the coating film according to Example 1 obtained in the same manner as the above-described transmittance measurement of the dispersion liquid, that is, the transmission profile of the coating film is shown by a solid line in FIG.
As a comparison, the result of measuring the light transmittance of the coating film of the dispersion using the lanthanum hexaboride fine particles produced by the manufacturing method by the breakdown method described in Patent Document 2 is shown by a broken line in FIG. .

  From the transmission profile of the coating film of FIG. 5, it was confirmed that the minimum transmittance for light having a wavelength of 700 to 900 nm was 5% and 15% or less. The minimum transmittance of light having a wavelength of 700 nm to 900 nm of the coating film of the dispersion liquid described in Patent Document 2 as a comparison is 22%, and the minimum transmittance at the absorption peak position near the wavelength of 1000 nm is 20%. The difference between the coating film of the present invention and the coating film of the dispersion produced by the method described in Patent Document 2 is clear.

(Comparative Example 1)
(1) Raw material powder La ₂ O ₃ powder (average particle size 1 to 10 μm, purity 99%), B (boron) powder (average particle size about 15 μm, purity 99%), C (carbon) powder (average) A particle size of about 1 μm and a purity of 99%) was prepared.

(2) to (3) Reaction vessel, synthesis of lanthanum hexaboride fine particles, measurement of synthesized lanthanum hexaboride fine particles,
Using the reaction vessel described in Example 1 as a reaction vessel, lanthanum hexaboride fine particles according to Comparative Example 1 were synthesized under the same production conditions as in Example 1.

(5) Measurement of optical properties of synthesized lanthanum hexaboride fine particles Using the synthesized lanthanum hexaboride fine particles according to Comparative Example 1, a dispersion according to Comparative Example 1 was prepared in the same manner as in Example 1, and light was measured. The transmittance of was measured.
The results of measuring the light transmittance of the obtained dispersion liquid according to Comparative Example 1 are shown by a one-dot chain line in FIG.
Next, using the synthesized lanthanum hexaboride fine particles according to Comparative Example 1, a coating film according to Comparative Example 1 was prepared in the same manner as in Example 1, and the light transmittance was measured.
The result of having measured the light transmittance of the coating film which concerns on the obtained comparative example 1 is shown with a dashed-dotted line in FIG.

  From the transmission profile of FIG. 4, the ratio of the absorption peak position of the dispersion according to Comparative Example 1 indicated by the alternate long and short dash line to the absorbance of light at a wavelength of 550 nm to the absorbance of light at the absorption peak position [(absorbance of light at the absorption peak position) / It was confirmed that the value of (absorbance at wavelength 550 nm) was 1.4. That is, it was confirmed that the lanthanum hexaboride fine particles in the coating film did not have sufficient optical properties.

1 Thermal Plasma 2 High Frequency Coil 3 Sheath Gas Supply Nozzle 4 Plasma Gas Supply Nozzle 5 Raw Material Powder Supply Nozzle 6 Reaction Vessel 7 Suction Pipe 8 Filter

Claims (19)

Metal hexaboride fine particles,
The aspect ratio [(major axis length) / (minor axis length)] when the fine particle shape is regarded as a spheroid is 1.0 or more and 1.5 or less,
X-ray diffraction peak intensity ratio (I) defined by Formula 1 is 45% or more and 75% or less,
I = [metal hexaboride fine particle (100) face / metal hexaboride fine particle (110) face] × 100% Formula 1
The absorption peak position of near-infrared light is in the wavelength range of 700 to 900 nm,
The ratio of the absorbance of light at a wavelength of 550 nm to the absorbance of light at the absorption peak position of near infrared light [(absorbance of light at the absorption peak position) / (absorbance of light at a wavelength of 550 nm)] is 5.0 or more and 20 Infrared-absorbing fine particles characterized by being 0.0 or less.   The infrared absorbing fine particles according to claim 1, wherein the metal hexaboride fine particles are lanthanum hexaboride fine particles.   The infrared-absorbing fine particles according to claim 1 or 2, wherein the infrared-absorbing fine particles have an average particle diameter of 1 nm or more and 100 nm or less.   A dispersion liquid in which the infrared absorbing fine particles according to any one of claims 1 to 3 are dispersed and contained in a liquid medium, wherein the liquid medium is for water, an organic solvent, an oil, a liquid resin, or a liquid plastic. An infrared-absorbing fine particle dispersion, which is selected from a plasticizer or a mixture thereof.   The infrared-absorbing fine particle dispersion according to claim 4, wherein the content of the infrared-absorbing fine particles contained in the liquid medium is 0.0004% by mass or more and 4% by mass or less.   When the infrared-absorbing fine particle dispersion according to claim 4 or 5 is diluted with the liquid medium or concentrated by removing the liquid medium to have a visible light transmittance of 70%, the minimum with respect to light having a wavelength of 700 to 900 nm An infrared-absorbing fine particle dispersion having a transmittance of 15% or less.   An infrared-absorbing fine particle dispersion comprising the infrared-absorbing fine particles according to any one of claims 1 to 3 and a thermoplastic resin.   The thermoplastic resin is polyethylene terephthalate resin, polycarbonate resin, acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluororesin, ethylene / vinyl acetate copolymer, polyvinyl One resin selected from the resin group called acetal resin, a mixture of two or more resins selected from the resin group, or a copolymer of two or more resins selected from the resin group, The infrared-absorbing fine particle dispersion according to claim 7, which is any one of the following.   The infrared-absorbing fine particle dispersion according to any one of claims 7 and 8, wherein the infrared-absorbing fine particles are contained in an amount of 0.002% by mass or more and 80.0% by mass or less.   The infrared absorbing fine particle dispersion according to any one of claims 7 to 9, wherein the infrared absorbing fine particle dispersion has a sheet shape, a board shape, or a film shape. The content of the infrared absorbing fine particles per unit projected area contained in the infrared absorbing fine particle dispersion is 0.01 g / m ² or more and 0.5 g / m ² or less. The infrared absorbing fine particle dispersion according to any one of the above.   The infrared-absorbing fine particle dispersion according to any one of claims 7 to 11, wherein the minimum transmittance for light having a wavelength of 700 to 900 nm is 15% or less when the visible light transmittance is 70%.   An infrared-absorbing laminated transparent substrate, wherein the infrared-absorbing fine particle dispersion according to any one of claims 7 to 12 is present between a plurality of transparent substrates.   A binder resin comprising a coating layer on at least one surface of a transparent substrate selected from a transparent film substrate or a transparent glass substrate, wherein the coating layer comprises infrared absorbing fine particles according to any one of claims 1 to 3. An infrared absorbing film or an infrared absorbing glass, characterized in that   The infrared absorbing film or the infrared absorbing glass according to claim 14, wherein the binder resin is a UV curable resin binder.   The infrared absorbing film or infrared absorbing glass according to claim 14 or 15, wherein the coating layer has a thickness of 1 µm or more and 10 µm or less.   The infrared-absorbing film according to claim 14, wherein the transparent film substrate is a polyester film. 18. The infrared absorbing film according to claim 14, wherein a content per unit projected area of the infrared absorbing fine particles contained in the coating layer is 0.01 g / m ² or more and 0.5 g / m ² or less. Or infrared absorbing glass.   The infrared absorbing film or infrared absorbing glass according to any one of claims 14 to 18, wherein the infrared absorbing fine particle dispersion according to claim 12 is provided as the coating layer.