JP2017122041A - Boride particle and boride particle dispersion liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boride particle which can be easily pulverized.SOLUTION: A boride particle is represented by general formula XB(where, X is one or more metal element selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sr, and Ca, and m is a number showing an amount of boron in the general formula). When measured by a combustion-infrared absorption method, an amount of carbon included in the boride particle is 0.2 mass% or less.SELECTED DRAWING: None

Description

  The present invention relates to boride particles and boride particle dispersions.

  Conventionally, rare earth element boride particles such as La are synthesized by a solid phase reaction method and then pulverized by a dry pulverization method, and in particular, a method of pulverizing particles by colliding with a high-speed air stream such as a jet mill. Is common. Among rare earth element boride particles, for example, lanthanum hexaboride is obtained by heating lanthanum oxide and boron oxide to a high temperature in the presence of carbon, and then pulverized by a dry pulverizer. A method for finely pulverizing powder using a jet mill is disclosed in Patent Document 1, for example.

  These boride particles have been conventionally used in thick film resistance pastes and the like, and when fine particles are used, they can be used as an optical material for solar radiation shielding. That is, a film in which boride particles are dispersed is suitable as a solar radiation shielding material to be applied to a window of a house or a car because it can efficiently block near infrared rays that transmit visible light and act as heat energy. It is known (see, for example, Patent Documents 2 and 3).

  However, since borides of rare earth elements such as La are hard, it is difficult to pulverize them into fine particles by a dry pulverization method using a jet mill or the like, and only relatively large particles of about 1 μm to 3 μm can be obtained. There was a problem. In addition, boride particles obtained by the dry pulverization method are difficult to suppress reaggregation.

  In subsequent studies, it was found that the average dispersed particle size of boride particles can be reduced to 200 nm or less by treating with a medium stirring mill (see, for example, Patent Document 4). Thereby, boride particles having an average dispersed particle diameter of about 200 nm can be obtained economically. If boride particles having an average dispersed particle size of 200 nm or less are used, geometrical scattering or Mie scattering that occurs when the particle size is larger than 200 nm can be reduced. For this reason, the phenomenon which scatters the light of the visible light region of 400 nm-780 nm, and becomes like a frosted glass can be prevented, and the optical member which attached importance to transparency came to be obtained.

  However, as an infrared shielding particle, the infrared shielding optical member in which the boride particles are dispersed is a phenomenon that turns blue-white when irradiated with strong light such as sunlight or a spotlight (hereinafter referred to as “blue”). May be described as “haze”). When such blue haze is generated, there is a problem that the beauty of the infrared shielding optical member may be impaired.

  It is known that when the average dispersed particle size of boride particles is 200 nm or less, geometrical scattering or Mie scattering is reduced, and most of the scattering follows Rayleigh scattering whose scattering coefficient is defined by the following formula (1). .

S = [16π ⁵ r ⁶ / 3λ ⁴ ] · [(m ² −1) / (m ² +2)] ² · [m] (1)
[In the above formula (1), S is the scattering coefficient, λ is the wavelength, r is the particle diameter, m = n ₁ / n ₀ , n ₀ is the refractive index of the substrate, and n ₁ is the refractive index of the dispersed material. Is]
The Rayleigh scattering is light scattering by particles having a size smaller than the wavelength of light. From the above formula (1), it is understood that Rayleigh scattering is inversely proportional to the fourth power of the wavelength (λ), and therefore, a large amount of blue light having a short wavelength is scattered and discolored to bluish white.

  In the Rayleigh scattering region, the scattered light is proportional to the sixth power of the particle diameter (r) from the above formula (1). Therefore, by reducing the particle diameter, the Rayleigh scattering is reduced and the generation of blue haze is reduced. It is understood that it can be suppressed.

  For example, Patent Document 5 discloses an example in which the generation of blue haze can be suppressed by setting the average dispersed particle diameter to 85 nm or less.

Japanese Patent Laid-Open No. 2001-314776 JP 2000-096034 A JP-A-11-181336 JP 2004-237250 A JP 2009-150979 A

V. Domnich et al., J. Am. Ceram. Soc., (2011) vol.94, Issue 11, pp.3605-3628 X.H.Zhao et al., App. Mech. Mater., (2011) vol.55-57, pp.1436-1440

  However, if the conventionally used boride particles are pulverized until the average dispersed particle diameter is 85 nm or less by the pulverization method using a medium stirring mill disclosed in Patent Document 4, the viscosity of the slurry becomes In some cases, the pulverization was difficult due to the increase in the height.

  Therefore, in order to continue the pulverization process to further reduce the average dispersed particle size and suppress blue haze, it is necessary to extremely reduce the concentration of boride particles in the slurry to lower the viscosity, resulting in poor pulverization efficiency and uneconomical efficiency. There was a problem that it was.

  Then, in view of the problem of the above-described conventional technology, an object of one aspect of the present invention is to provide boride particles that can be easily pulverized.

In order to solve the above problems, according to one aspect of the present invention,
General formula XB _m (where X is one or more selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sr, Ca) A metal element, m is a boride particle represented by a number indicating the amount of boron in the general formula),
Provided is a boride particle in which the amount of carbon contained in the boride particle as measured by a combustion-infrared absorption method is 0.2% by mass or less.

  According to one embodiment of the present invention, boride particles that can be easily pulverized can be provided.

Explanatory drawing (the 1) of the measurement principle of a diffuse transmission profile in an Example and a comparative example. Explanatory drawing of the measurement principle of a diffuse transmission profile in an Example and a comparative example (the 2).

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments, and the following embodiments are not departed from the scope of the present invention. Various modifications and substitutions can be made.
(Boride particles)
In the present embodiment, first, a configuration example of boride particles will be described.

The boride particles of the present embodiment have the general formula XB _m (where X is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sr. , One or more metal elements selected from Ca, and m is a boride particle represented by the following formula: And the carbon amount contained in the said boride particle | grains when measured by a combustion-infrared absorption method can be 0.2 mass% or less.

  The inventors of the present invention have intensively studied boride particles that can be easily pulverized, that is, pulverized into fine particles. And the boric acid particle | grains which can be easily pulverized by making the carbon amount (carbon concentration) in boride particle | grains below into a predetermined value were discovered, and the present invention was completed.

Boride particles of this embodiment may be particles of boride of the general formula XB _m as described above.

In the boride particles of the present embodiment represented by the above general formula XBm, _m , which is the elemental ratio (molar ratio) (B / X) of boron (B) to metal element (X), is particularly limited. Although it is not a thing, it is preferable that it is 3.0-20.0.

The boride constituting the boride particles represented by the general formula XB _m, e.g. _{XB 4, XB 6, XB 12,} and the like. However, from the viewpoint of selectively and efficiently reducing the light transmittance in the near-infrared region near the wavelength of 1000 nm, the boride particles of the present embodiment are preferably mainly composed of XB ₄ or XB _6. , XB ₁₂ may be partially included.

For this reason, in the general formula XBm, _m , which is an element ratio (B / X) of boron (B) to metal element (X), is more preferably 4.0 or more and 6.2 or less.

The above (B / X) if there is a 4.0 or higher, XB and, it is possible to suppress the formation of such XB _2, the reason is not clear, it is possible to improve the solar radiation shielding properties. Moreover, when (B / X) is 6.2 or less, the content ratio of hexaboride having particularly excellent solar radiation shielding properties can be increased, and the solar radiation shielding properties are improved, which is preferable.

In particular, the boride particles of the present embodiment are preferably mainly composed of XB ₆ because of the high absorption ability of near infrared rays in borides.

Therefore, in the boride particles of the present embodiment represented by the general formula XBm, _m , which is the element ratio (B / X) of boron (B) to metal element (X), is 5.8 or more and 6.2. More preferably, it is as follows.

In addition, when boride particles are produced, the obtained powder containing boride particles is not composed only of boride particles having a single composition, but is a particle containing boride having a plurality of compositions. be able to. Specifically, for example, particles of a mixture of borides such as XB ₄ , XB ₆ , and XB ₁₂ can be used.

  Therefore, for example, when X-ray diffraction measurement is performed on hexaboride particles, which are typical boride particles, even in the case of a single phase, a very small amount is actually measured. It is thought that other phases are included.

Therefore, _m in the general formula XB _m of the boride particles of the present embodiment is, for example, obtained by chemical analysis of the obtained powder containing boride particles by ICP emission spectroscopy (high frequency inductively coupled plasma emission spectroscopy) or the like. In this case, the atomic ratio of boron (B) to one atom of X element can be used.

  The metal element (X) of the boride particles of the present embodiment is not particularly limited as shown in the general formula. For example, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy , Ho, Er, Tm, Yb, Lu, Sr, Ca can be used as one or more metal elements.

  However, since lanthanum hexaboride, which is a hexaboride of lanthanum, has particularly high near-infrared absorptivity, the boride particles of this embodiment preferably include lanthanum hexaboride particles.

  As described above, according to the study by the inventors of the present invention, boride particles that can be easily pulverized can be obtained by setting the carbon amount (carbon concentration) in the boride particles to a predetermined value or less. be able to. The reason for this will be described below.

  According to the study of the inventors of the present invention, the carbon contained in the boride particles may form a carbon compound with the component of the boride particles, or the carbon compound contained in the raw material may remain.

Examples of such a carbon compound include LaB ₂ C ₂ , LaB ₂ C ₄ , B ₄ C, B _4.5 C, B _5.6 C, B _6.5 C, B _7.7 C, and B _9. C etc. are mentioned.

According to Non-Patent Document 1, among the above-mentioned carbon compounds, B ₄ C, B _4.5 C, B _5.6 C, B _6.5 C, B _7.7 C, and B ₉ C The Young's modulus as an index is a high hardness carbon compound of 472 GPa, 463 GPa, 462 GPa, 446 GPa, 352 GPa, and 348 GPa, respectively.

  On the other hand, Non-Patent Document 2 reports that, for example, the Young's modulus of lanthanum hexaboride is 194 GPa. In addition, it is presumed that other boride particles have similar Young's modulus.

  As described above, the carbon compound mixed as an impurity may have a higher Young's modulus than the target boride particles. For this reason, in order to obtain boride particles that can be easily pulverized, it is required to suppress the mixing of these carbon compounds.

  And since the mixing amount (content) of these carbon compounds has a correlation with the carbon amount in the boride particles, as described above, the carbon amount in the boride particles is set to a predetermined value or less, It is believed that boride particles can be easily pulverized.

  The amount of carbon contained in the boride particles of the present embodiment can be measured by a combustion-infrared absorption method. And it is preferable that it is 0.2 mass% or less, and, as for the carbon content contained in the boride particle | grains of this embodiment measured by the combustion-infrared absorption method, it is more preferable that it is 0.1 mass% or less.

Particularly, in the boride particles, B ₄ C (boron carbide) among the above-mentioned carbon compounds is easily generated, and therefore the boride particles of the present embodiment can suppress the amount of B ₄ C contained. preferable. For example, the B ₄ C content (content ratio) of the boride particles of the present embodiment is preferably 1.0% by mass or less.

By setting the amount of B ₄ C contained in the boride particles of the present embodiment, that is, the content ratio of B ₄ C to 1.0% by mass or less, the content of other carbon compounds can also be suppressed. The boride particles can be pulverized, which is preferable.

The amount of B ₄ C contained in the boride particles of the present embodiment can be measured by ICP analysis by performing a pretreatment of nitric acid dissolution and filtration separation.

It is known that B ₄ C hardly dissolves in nitric acid. On the other hand, boride particles are known to dissolve in nitric acid.

Therefore, when evaluating the amount of B ₄ C in the boride particles, the boride particles are added to nitric acid, the boride particles are dissolved, and then the undissolved residue is separated by filtration, whereby the B in the boride particles is separated. Only ₄ C particles can be removed. Then, the separated B _{4 C} particles were dissolved by sodium carbonate, by measuring the boron concentration by ICP analysis, it is possible to calculate the B 4 _C concentration.

At this time, in order to confirm that the undissolved residue obtained after the filtration and separation is B ₄ C, a sample that was processed in the same way until the filtration and separation was prepared in parallel, and the sample obtained after the filtration and separation was prepared. It is desirable to confirm that the undissolved residue is a B ₄ C single phase by XRD measurement.

  By the way, boride particles such as hexaboride particles are a powder colored dark blue-purple, etc., but pulverized so that the particle size is sufficiently smaller than the wavelength of visible light, and in the state dispersed in the film, Visible light transparency occurs. At the same time, an infrared shielding function appears.

  Although the reason for this has not been elucidated in detail, these boride materials have a relatively large number of free electrons, and absorption due to interband transition between 4f-5d and electron-electron and electron-phonon interaction is near-red. It is thought that it originates in existing in an outside field.

  According to the experiment, in a film in which these boride particles are sufficiently finely and uniformly dispersed, the transmittance of the film has a maximum value in a wavelength range of 400 nm to 700 nm and a wavelength range of 700 nm to 1800 nm. It is confirmed to have a local minimum. Considering that the visible light wavelength is 380 nm or more and 780 nm or less and the visibility is a bell-shaped peak with a peak at around 550 nm, such a film effectively transmits visible light and other sunlight is effectively used. It can be understood that it absorbs and reflects.

  The average dispersed particle size of the boride particles of this embodiment is preferably 100 nm or less, and more preferably 85 nm or less. The average dispersed particle diameter here can be measured by a particle size measuring apparatus based on a dynamic light scattering method.

  The lower limit of the average dispersed particle size of the boride particles is not particularly limited, but is preferably 1 nm or more, for example. This is because it is industrially difficult to make the average dispersed particle diameter of boride particles less than 1 nm.

Since the boride particles of the present embodiment described above have a carbon content of a predetermined value or less, they can be easily pulverized so that, for example, the average dispersed particle diameter is 100 nm or less, particularly 85 nm or less. For this reason, the infrared shielding optical member in which the boride particles of the present embodiment are dispersed can suppress the occurrence of blue haze even when strong light such as sunlight or spotlight is irradiated.
(Method for producing boride particles)
Next, one structural example of the boride particle manufacturing method of the present embodiment will be described.

As a method for producing boride particles of the present embodiment, the obtained boride particles are represented by the general formula XB _m (where X is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho). , Er, Tm, Yb, Lu, Sr, Ca), and the amount of carbon contained in the boride particles as measured by the combustion-infrared absorption method (carbon concentration) If it is 0.2 mass% or less, it will not specifically limit.

  As one configuration example of the method for producing boride particles of the present embodiment, for example, a solid phase reaction method using carbon or boron carbide as a reducing agent can be mentioned. Hereinafter, a case where boride particles using lanthanum as a metal element is manufactured will be described as an example.

  For example, boride particles using lanthanum as a metal element can be produced by firing a mixture of a boron source, a reducing agent, and a lanthanum source.

  Specifically, for example, when producing lanthanum boride particles using boron carbide as a boron source and a reducing agent and lanthanum oxide as a lanthanum source, first, a raw material mixture of boron carbide and lanthanum oxide is prepared. Next, the raw material mixture is baked at a temperature of 1500 ° C. or higher in an inert atmosphere, whereby lanthanum oxide is reduced by carbon in boron carbide, carbon monoxide and carbon dioxide are generated, and carbon is removed. . Furthermore, lanthanum boride is obtained from the remaining lanthanum and boron.

  In addition, carbon derived from boron carbide is not completely removed as carbon monoxide and carbon dioxide, but part of it remains in the lanthanum boride particles and becomes impurity carbon. Therefore, when the proportion of boron carbide in the raw material is increased, the impurity carbon concentration in the obtained lanthanum boride particles is increased.

As described above, the obtained powder containing boride particles is not composed only of boride particles having a single composition, but particles of a mixture with LaB ₄ , LaB ₆ , LaB ₁₂ and the like. Become. Therefore, when X-ray diffraction measurement is performed on the obtained powder containing boride particles, even if it is a single phase of boride in the analysis of X-ray diffraction, the other phase is actually contained in a trace amount. It is considered to contain.

  Here, when producing boride particles using lanthanum as a metal element as described above, the element ratio B / La of boron in the raw material boron source and lanthanum in the lanthanum source is not particularly limited. However, it is preferably 3.0 or more and 20.0 or less.

In particular, when the element ratio B / La of boron in the source boron source and the lanthanum element in the lanthanum source is 4.0 or more, the production of LaB, LaB _{2 and the} like can be suppressed. Moreover, although the reason is not clear, the solar radiation shielding characteristic can be improved.

  On the other hand, when the element ratio B / La of boron in the raw material boron source and lanthanum in the lanthanum source is 6.2 or less, generation of boron oxide particles in addition to boride particles is suppressed. Since boron oxide particles are hygroscopic, if boron oxide particles are mixed into the powder containing boride particles, the moisture resistance of the powder containing boride particles decreases, and the solar radiation shielding characteristics deteriorate over time. .

  For this reason, it is preferable to suppress the generation of boron oxide particles by setting the element ratio B / La of boron in the raw material boron source and lanthanum in the lanthanum source to 6.2 or less. Further, when the element ratio B / La is 6.2 or less, the content ratio of the hexaboride having particularly excellent solar radiation shielding characteristics can be increased, and the solar radiation shielding characteristics are improved, which is preferable.

  In order to further reduce the impurity carbon concentration, it is effective to reduce the proportion of boron carbide in the raw material as much as possible. Thus, for example, by generating lanthanum boride particles with B / La of 6.2 or less, a powder containing lanthanum boride particles having an impurity carbon concentration of 0.2 mass% or less can be obtained more reliably.

  As described above, when boride particles using lanthanum as a metal element are produced, the element ratio (molar ratio) B / La between boron in the boron source and lanthanum in the lanthanum source is 4.0 or more and 6 .2 or less is more preferable. By making the composition of the raw material within the above range, the powder containing lanthanum boride particles that can suppress the impurity carbon concentration in the powder containing the lanthanum boride particles obtained and at the same time exhibits high solar shading properties is obtained. be able to.

In particular, the particles of lanthanum boride obtained is preferably LaB ₆ is in principal. This is because LaB ₆ has particularly high near infrared absorption ability.

  For this reason, the element ratio B / La of boron in the source boron source and the lanthanum element in the lanthanum source is more preferably 5.8 or more and 6.2 or less.

  In addition, although the case where the boron source and the reducing agent were used to produce the lanthanum boride particles by using boron carbide as the lanthanum source and the lanthanum oxide as the lanthanum source was described as an example, the embodiment is not limited thereto. For example, boron or boron oxide can be used as the boron source, carbon can be used as the reducing agent, and lanthanum oxide can be used as the lanthanum source. In this case, it is preferable to perform a preliminary test or the like so as to select a mixing ratio of each component so that excess carbon or oxygen does not remain in the product.

  For example, according to the metal element X which the boride particle | grains to manufacture contain, the compound containing the metal element X instead of a lanthanum oxide can also be used. Examples of the compound containing the metal element X include one or more selected from a hydroxide of the metal element X, a hydrate of the metal element X, and an oxide of the metal element X. The method for producing the compound containing the metal element X is not particularly limited. For example, a solution containing the compound containing the metal element X and an alkaline solution are reacted with stirring to generate a precipitate, and the precipitate is obtained from the precipitate. be able to.

  As described above, even in the case of using a compound containing the metal element X instead of lanthanum oxide, a preliminary test or the like is performed so that excess carbon or oxygen does not remain in the product, and the mixing ratio of each component Is preferably selected. For example, the element ratio of boron in the boron source and the metal element X in the metal element X source may be the same as the element ratio of the boron in the boron source and the lanthanum element in the lanthanum source. it can.

The obtained boride particles can be formed into boride particles having a desired average dispersed particle size by, for example, wet grinding.
(Boride particle dispersion)
Next, a configuration example of the boride particle dispersion of this embodiment will be described.

  The boride particle dispersion of this embodiment can contain the boride particles described above and a liquid medium. The boride particles are preferably dispersed in a liquid medium, for example.

  The liquid medium used for the boride particle dispersion may include one or more selected from water, organic solvents, oils and fats, liquid resins, and plasticizers.

  The organic solvent preferably has a function for maintaining the dispersibility of the boride particles and a function for preventing application defects when the dispersion is applied. Examples of the organic solvent include methanol (MA), ethanol (EA), 1-propanol (NPA), isopropanol (IPA), butanol, pentanol, benzyl alcohol, diacetone alcohol and other alcohol solvents, acetone, methyl ethyl ketone (MEK). ), Ketone solvents such as methyl propyl ketone, methyl isobutyl ketone (MIBK), cyclohexanone, isophorone, ester solvents such as 3-methyl-methoxy-propionate (MMP), ethylene glycol monomethyl ether (MCS), ethylene glycol monoethyl Ether (ECS), ethylene glycol isopropyl ether (IPC), propylene glycol methyl ether (PGM), propylene glycol ethyl ether (PE), propylene group Glycol derivatives such as coal methyl ether acetate (PGMEA) and propylene glycol ethyl ether acetate (PE-AC), formamide (FA), N-methylformamide, dimethylformamide (DMF), dimethylacetamide, N-methyl-2- Examples include amides such as pyrrolidone (NMP), aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as ethylene chloride and chlorobenzene, and the like, one selected from these, or 2 More than one type can be used in combination.

  Among the above, organic solvents such as ketones such as MIBK and MEK, aromatic hydrocarbons such as toluene and xylene, glycol ether acetates such as PGMEA and PE-AC, and the like are more highly hydrophobic. preferable. Therefore, it is preferable to use one or two or more selected from these in combination.

  Examples of fats and oils include drying oils such as linseed oil, sunflower oil, tung oil, semi-drying oils such as sesame oil, cottonseed oil, rapeseed oil, soybean oil, rice bran oil, and non-drying oils such as olive oil, coconut oil, palm oil, and dehydrated castor oil. Fatty acid monoesters obtained by direct ester reaction of fatty acids and monoalcohols of vegetable oils, ethers, Isopar E, Exol Hexane, Exol Heptane, Exol E, Exol D30, Exol D40, Exol D60, Exol D80, Exol D95, Exol D110, One or more types selected from petroleum solvents such as Exol D130 (exxon mobile) can be used.

  As the liquid resin, for example, one or more selected from a liquid acrylic resin, a liquid epoxy resin, a liquid polyester resin, and a liquid urethane resin can be used.

  As the plasticizer, for example, a plasticizer for liquid plastic can be used. The plasticizer for the liquid plastic was selected from, for example, phthalic acid plasticizers such as DEHP and DINP, adipic acid plasticizers such as DINA and DOA, phosphoric acid plasticizers, epoxy plasticizers, and polyester plasticizers. One or more types can be used.

  Moreover, the liquid medium used for the boride particle dispersion liquid of the present embodiment can contain, for example, a dispersant, a coupling agent, a surfactant and the like in addition to the above-described components. The dispersant, the coupling agent, and the surfactant can be selected according to the use, but may have an amine-containing group, a hydroxyl group, a carboxyl group, or an epoxy group as a functional group. preferable. These functional groups are adsorbed on the surface of the boride particles and can prevent aggregation of the boride particles. For example, in the boride particle dispersion prepared using the boride particle dispersion, the boride particles are uniformly distributed. Demonstrate the effect of dispersing.

  As the dispersant, the coupling agent, and the surfactant, for example, a phosphate ester compound, a polymer dispersant, a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, and the like are preferably used. However, it is not limited to these. Examples of the polymer dispersant include acrylic polymer dispersants, urethane polymer dispersants, acrylic / block copolymer polymer dispersants, polyether dispersants, and polyester polymer dispersants.

  The addition amount of one or more materials selected from a dispersant, a coupling agent, and a surfactant to the boride particle dispersion is in the range of 10 parts by weight to 1000 parts by weight with respect to 100 parts by weight of the boride particles. It is preferable that it is in the range of 20 parts by weight or more and 200 parts by weight or less. If the added amount of the dispersant or the like is in the above range, the boride particles can suppress aggregation in the dispersion and can keep the dispersion stability high, which is preferable.

  The method for dispersing boride particles in the liquid medium is not particularly limited. For example, a method of dispersing a boride particle dispersion raw material mixture using a wet medium mill such as a bead mill, a ball mill, or a sand mill can be used. In particular, the boride particle dispersion of the present embodiment preferably has a state in which boride particles having an average dispersed particle diameter of 100 nm or less are dispersed in a liquid medium, and the boride particles have an average dispersed particle diameter of 85 nm. The following is more preferable. Therefore, it is preferable to prepare a dispersion by dispersing boride particles by a wet pulverization method using a medium stirring mill such as a bead mill.

  When preparing a boride particle dispersion in which boride particles are dispersed in a dispersion medium (liquid medium) as a boride particle dispersion, boride particles, a dispersant, and the like, which are raw materials as described above, Examples thereof include a method of adding to a liquid medium such as water, an organic solvent, fats and oils, a liquid resin, a plasticizer, and the like, followed by a dispersion treatment using a medium stirring mill or the like.

  Also, a boride particle dispersion can be prepared by the following procedure. Here, a case where a boride particle plasticizer dispersion is prepared will be described as an example.

  Specifically, first, a boride particle dispersion in which boride particles are dispersed in an organic solvent is prepared in advance using the above-described organic solvent as a liquid medium. Next, a boride particle plasticizer dispersion can be obtained by adding a plasticizer to the boride particle dispersion and removing the organic solvent.

  In addition, as a method of removing an organic solvent, the method of drying a boride particle dispersion liquid under reduced pressure is mentioned, for example.

  Specifically, a boride particle dispersion liquid containing an organic solvent as a liquid medium, to which a plasticizer is added, is dried under reduced pressure while stirring to separate an organic 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. The pressure value at the time of decompression is appropriately selected.

  By using the reduced-pressure drying method, it is possible to improve the removal efficiency of the organic solvent from the boride particle dispersion using the organic solvent to which the plasticizer is added as a liquid medium, so that in the boride particle plasticizer dispersion Aggregation of dispersed boride particles does not occur, which is preferable. Furthermore, the productivity of the boride particle plasticizer dispersion is increased, and it is easy to recover the evaporated organic solvent, which is preferable from the environmental consideration.

  In order to obtain a uniform boride particle dispersion, various additives and a dispersant may be added as described above, or the pH may be adjusted.

  In addition, here, the case of preparing a boride particle plasticizer dispersion using a plasticizer as a dispersion medium has been described as an example. However, the present invention is not limited to such a form, and instead of the plasticizer, water, an organic solvent, an oil and fat By using other dispersion media (liquid media) such as liquid resins, dispersions in which boride particles are dispersed in various dispersion media can be obtained.

  The content of boride particles in the boride particle dispersion, that is, the concentration is not particularly limited, but is preferably 0.01% by mass to 30% by mass, for example.

  This is because if the content of boride particles is 0.01% by mass or more, a boride particle dispersion having sufficient infrared shielding ability can be obtained.

  Moreover, if the content of boride particles is 30% by mass or less, it is preferable because the viscosity of the boride particle dispersion does not become too high and the dispersion stability can be maintained. In particular, the content of boride particles in the boride particle dispersion is more preferably 1% by mass or more and 30% by mass or less.

  The boride particles in the boride particle dispersion are preferably dispersed with an average dispersed particle diameter measured by a dynamic light scattering method of 100 nm or less, and more preferably 85 nm or less. If the average dispersed particle diameter of boride particles is 100 nm or less, the generation of blue haze in the infrared shielding film produced using the boride particle dispersion according to this embodiment is suppressed, and the optical characteristics are improved. It is because it can be made. Moreover, it is because generation | occurrence | production of the blue haze in an infrared shielding film can be suppressed especially when this average dispersed particle diameter is 85 nm or less.

  When a boride particle dispersion is prepared using the boride particles described above, the average dispersed particle diameter is 100 nm efficiently without causing problems such as gelation of the boride particle dispersion (slurry). In the following, the inventors of the present invention infer that the reason why pulverization is possible to 85 nm or less is as follows.

  Since the boride particles are hard, when they are pulverized using a wet medium agitation mill, wear debris such as fine powder with worn media beads and fine bead pieces with broken media beads are mixed in the slurry. At this time, since the hardness of boride particles increases with an increase in carbon concentration, when boride particles having a carbon concentration higher than 0.2% by mass are used as raw materials, a large amount of media beads wear residue is slurried. It gets mixed in. The mixing of the wear debris of the media beads increases the viscosity of the slurry.

The concentration ratio between the wear debris and boride of the media beads in the slurry can be used as an index of the wear amount of the media beads. For example, when yttria-stabilized zirconia beads (also simply referred to as “zirconia beads”) known as high wear resistance are used as media beads, Zr derived from zirconia beads in a slurry and a boron represented by the general formula XB _m The concentration ratio Zr / X of the weight concentration (mass%) with the metal element X in the compound can be used as an index of the wear amount of the media beads.

When the carbon concentration containing the boride particles is higher than 0.2 mass%, in the resulting slurry, the metal element X in boride represented by zirconium general formula XB _m from zirconia beads The concentration ratio Zr / X is greater than 1.5. That is, it shows that the amount of wear of the media beads is very large. The wear debris of the media beads increases the viscosity of the slurry.

  On the other hand, by using boride particles having a carbon concentration of 0.2% by mass or less as a raw material, yttria-stabilized zirconia beads are used as media beads, and the average dispersed particle size is 100 nm or less, particularly 85 nm or less. When pulverizing, the concentration ratio Zr / X in the resulting slurry can be made 1.5 or less. That is, since the amount of wear debris in the media beads is greatly reduced, it is assumed that the slurry can be efficiently pulverized without deteriorating the viscosity of the slurry. However, there are many unexplained points about the increase in the viscosity of the slurry, and there is a possibility that actions other than those described above are working, and therefore, it is not limited to the above actions.

Incidentally, the zirconia beads used as the media beads, when carrying out the dispersion treatment of the boride particle dispersion, the metal element in the boride represented by Zr and the general formula XB _m from zirconia beads boride particle dispersion The concentration ratio Zr / X with X is preferably 1.5 or less. That is, the boride particle dispersion can contain zirconia derived from the media beads used at the time of pulverization, and the weight concentration of Zr is 1.5 times the weight concentration of the metal element X in the boride particle dispersion. The following is preferable. This is because when the concentration ratio Zr / X in the boride particle dispersion obtained as described above is 1.5 or less, an increase in viscosity of the boride particles can be sufficiently suppressed.

  The boride particle dispersion liquid of the present embodiment described above can be used for various applications as an infrared shielding particle dispersion liquid. And the boride particle | grain dispersion liquid of this embodiment contains the boride particle | grains mentioned above, and can make an average dispersed particle diameter 100 nm or less, especially 85 nm or less easily. For this reason, it can suppress that a blue haze arises.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

Here, first, evaluation methods of samples in the following examples and comparative examples will be described.
(Boride particle composition)
The obtained boride particles, ICP (Shimadzu Model: ICPE9000) was analyzed using the element ratio of boron (B) to the metal element X when expressed by the general formula XB _m (mole ratio), i.e. The value of m, which is the element ratio (B / X) between boron (B) and metal element X in the boride particles, was calculated.
(Carbon concentration in boride particles)
The amount of carbon (carbon concentration) in boride particles produced in each of the following experimental examples was measured by a combustion-infrared absorption method.
(B ₄ C concentration in boride particles)
Among the obtained boride particles, the sample for measuring the B ₄ C concentration was divided into two, each weighed in a platinum crucible, 7N nitric acid was added and heated to 50 ° C. to dissolve the boride particles. . After standing to cool, pure water was added, and the undissolved residue (B ₄ C) was separated by filtration through a cellulose acetate membrane filter having a pore size of 0.2 μm.

  One undissolved residue obtained was put in the original platinum crucible, wetted with a saturated aqueous solution of calcium hydroxide to prevent volatilization of boron, and then dried in a dryer at about 80 ° C. After drying, sodium carbonate was added and mixed well before melting. After standing to cool, the molten salt in the crucible was dissolved in warm water and transferred to a Teflon (registered trademark) beaker. After adding nitric acid, the sample was heated and boiled to remove carbon dioxide, and then used as a sample solution for ICP. The boron concentration in the obtained sample solution was analyzed by ICP.

Also, other undissolved residue obtained subjected to XRD measurement for undissolved residue was confirmed whether the B _{4 C} single phase. When it was a B ₄ C single phase, the B ₄ C concentration was calculated from the boron concentration analyzed by ICP.
(Average dispersed particle size)
The average dispersed particle size was measured by a particle size measuring device based on a dynamic light scattering method (model: ELS-8000 manufactured by Otsuka Electronics Co., Ltd.). The particle refractive index was 1.81, and the particle shape was non-spherical. The background was measured with toluene, and the solvent refractive index was 1.50.
(Weight concentration ratio of Zr and metal element X in boride particle dispersion (Zr / X))
The weight concentration ratio (Zr / X) between Zr and metal element X in the boride particle dispersion was measured by ICP (Shimadzu Corporation model: ICPE9000) and calculated from the measured value.
(Maximum diffuse transmission profile)
Here, a blue haze evaluation method will be described.

  There is no known method for directly measuring blue haze. However, the applicant of the present invention finds the diffuse transmittance for each wavelength by paying attention to the linear incident light and the scattered light as the components of the transmitted light when light is applied to the infrared shielding material particle dispersion as a sample. Has already proposed a method for evaluating “blue haze” (see Patent Document 5). Hereinafter, the principle of measuring the diffuse transmittance for each wavelength (that is, the diffuse transmission profile) will be described with reference to FIGS.

  First, a measuring apparatus for measuring a diffuse transmission profile will be described with reference to FIGS. 1 and 2.

  As shown in FIGS. 1 and 2, the measuring apparatus 10 includes an integrating sphere 14. The integrating sphere 14 has a diffused reflectivity on the inner surface of the spherical body, and a second opening 141 to which the measurement sample 12 (see FIG. 2) is attached, the standard reflector 15 or the light trap component 16 is attached. It has the opening part 142 and the 3rd opening part 143 to which the light receiver 13 is attached.

  A light source 11 that emits linear light that enters the spherical space through the first opening 141; and a spectroscope (not shown) that is attached to the light receiver 13 and that separates the received reflected or scattered light. A data storage means (not shown) that is connected to the spectrometer and stores spectral data of the reflected or scattered light that is spectrally dispersed, and the diffuse transmitted light intensity from the stored spectral data of the blank transmitted light intensity and the diffuse transmitted light intensity. And a calculation means (not shown) that obtains the diffuse transmittance for each wavelength by calculating the ratio of each of the transmitted light intensity and the blank transmitted light intensity.

  Here, the integrating sphere 14 has a diffuse reflection property by applying barium sulfate or Spectralon (registered trademark) or the like to the inner surface of the spherical main body, and the incident angle to the standard reflector 15 is the standard side, the control. Both sides can be, for example, 10 °. As the light receiver 13, for example, a photomultiplier tube (ultraviolet / visible region) or a cooled lead sulfide (near infrared region) can be used. In addition, a spectroscope (not shown) attached to the light receiver 13 requires a wavelength measurement range in the ultraviolet / visible region and photometric accuracy (± 0.002 Abs).

  Next, as the light source 11 that emits linear light that enters the spherical space, for example, a deuterium lamp can be applied in the ultraviolet region, and a 50 W halogen lamp can be applied in the visible / near infrared region.

  The standard reflector 15 can be a white plate made of, for example, Spectralon, and the light trap component 16 must have a function of trapping incident linear light without reflecting it. For example, a dark box that absorbs incident linear light almost completely is used.

  Then, using the diffuse transmission profile measuring device, the maximum value of the diffuse transmission profile of the boride particle dispersion liquid of the examples and comparative examples which are measurement samples, the blank transmitted light intensity measurement step, and the diffuse transmitted light intensity measurement It can be evaluated by each step of the step and the diffuse transmittance calculation step.

  First, in the blank transmitted light intensity measurement step, the standard reflector 15 is attached to the second opening 142 of the integrating sphere 14 and the measurement sample is not attached to the first opening 141 as shown in FIG. Are incident on the spherical space through the first opening 141. Then, the reflected light reflected by the standard reflecting plate 15 is received by the light receiver 13 and dispersed by a spectroscope (not shown) attached to the light receiver 13 to obtain spectral data of the reflected light. As a spectroscope, a spectrophotometer (Hitachi High-Technologies Corporation model: U-4100) was used. The spectral data at this time is the blank transmitted light intensity.

  Next, in the diffuse transmitted light intensity measurement step, the light trap component 16 is attached to the second opening 142 of the integrating sphere 14 as shown in FIG. Then, with the measurement sample 12 attached to the first opening 141, linear light from the light source 11 enters the spherical space through the measurement sample 12 and the first opening 141 and is trapped by the light trap component 16. The scattered light other than the received light is received by the light receiver 13. At this time, the spectral data of the scattered light is obtained by performing spectroscopy with a spectroscope (not shown) attached to the light receiver 13. The spectral data at this time is the diffused transmitted light intensity.

  Then, in the diffuse transmittance calculation step, based on the spectral data of the blank transmitted light intensity and the diffuse transmitted light intensity stored by the data storage means (not shown) not shown, While calculating the ratio of the blank transmitted light intensity for each wavelength to obtain the diffuse transmittance for each wavelength, the maximum in the wavelength range of 360 nm to 500 nm in the diffuse transmission profile of the measurement sample 12 from the obtained diffuse transmittance for each wavelength. The value can be determined.

  The boride particle dispersions prepared in the following examples and comparative examples were adjusted so that the visible light (wavelength of 400 nm or more and 780 nm or less) transmittance was 50%, and diffused transmission in a region of wavelengths of 360 nm or more and 500 nm or less. The maximum value of the profile was measured.

  For the measurement sample, the boride particle dispersions prepared in each Example and Comparative Example were diluted with a main solvent so as to have the above-described visible light transmittance, and placed in a 10 mm square glass cell for measurement.

  When the maximum value of the diffuse transmission profile measured is 1.5% or less, it is confirmed that blue haze is hardly observed in the infrared shielding particle dispersion produced using the boride particle dispersion.

  In the measurement, the visible light transmittance of the boride particle dispersion is set to 50% or less in order to specify the measurement conditions of the diffuse transmittance (diffuse transmittance profile), and the diffuse transmittance is visible light transmittance. The range is set to be proportional to the rate. The reason why the diffuse transmittance (diffuse transmittance profile) in the region of wavelength 360 nm or more and 500 nm or less is measured is that scattering in that region is the cause of blue haze.

Hereinafter, sample preparation conditions and evaluation results in each example and comparative example will be described.
[Example 1]
Boron carbide was used as a boron source and a reducing agent, and lanthanum oxide was used as a lanthanum source. These were weighed and mixed so that B / La, which is the element ratio of lanthanum and boron, was 5.90. Thereafter, it was calcined for 6 hours under a temperature condition of 1600 ± 50 ° C. in an argon atmosphere to obtain a powder containing lanthanum hexaboride particles.

The carbon content of the obtained lanthanum hexaboride particle-containing powder was measured by a combustion-infrared absorption method, and the carbon content was 0.05% by mass. Further, when the composition of the obtained lanthanum hexaboride particles was evaluated by ICP, m, which is the elemental ratio (B / La) of boron (B) to lanthanum element (La) in the general formula LaB _m , It was confirmed that it was 5.8.

Further, the obtained lanthanum hexaboride particle-containing powder was measured for the B ₄ C concentration of the lanthanum hexaboride particle-containing powder by the method for evaluating the B ₄ C concentration in the boride particles described above. It was 2 mass%.

  Next, the produced lanthanum hexaboride particle-containing powder (infrared shielding material) is in a ratio of 10 parts by weight, toluene 80 parts by weight, and dispersant (acrylic polymer dispersant having an amino group) 10 parts by weight. Weighed and mixed to prepare 3 kg slurry. This slurry was put into a medium stirring mill together with the beads, and the slurry was circulated, and pulverized and dispersed for 20 hours.

The medium stirring mill used was a horizontal cylindrical annular type (manufactured by Ashizawa Corporation), and the material of the inner wall of the vessel and the rotor (rotating stirring portion) was ZrO ₂ . In addition, beads made of YSZ (Ytria-Stabilized Zirconia) having a diameter of 0.3 mm were used as the beads. The rotation speed of the rotor was 13 m / sec, and the slurry was pulverized at a slurry flow rate of 1 kg / min. It was 70 nm when the average dispersion | distribution particle diameter of the boride particle | grains in the obtained boride particle | grain dispersion liquid was measured.

  Further, the dispersion was evaluated for the weight concentration ratio (Zr / La) of Zr and La in the boride particle dispersion and the maximum value of the diffusion transmission profile as described above.

The results are shown in Table 1.
[Example 2]
A lanthanum hexaboride particle-containing powder was obtained in the same manner as in Example 1 except that boron carbide and lanthanum oxide were weighed and mixed so that the element ratio B / La between lanthanum and boron was 5.95. .

When the carbon content of the obtained lanthanum hexaboride particle-containing powder was measured by a combustion-infrared absorption method, the carbon content was 0.1% by mass. Further, when the composition of the obtained lanthanum hexaboride particles was evaluated by ICP, m, which is the elemental ratio (B / La) of boron (B) to lanthanum element (La) in the general formula LaB _m , It was confirmed that it was 5.9.

Further, the obtained lanthanum hexaboride particle-containing powder was measured for the B ₄ C concentration of the lanthanum hexaboride particle-containing powder by the method for evaluating the B ₄ C concentration in the boride particles described above. It was 5 mass%.

  A boride particle dispersion was prepared in the same manner as in Example 1 except that the lanthanum hexaboride particle-containing powder was used.

Evaluation similar to Example 1 was performed about the obtained dispersion liquid. The results are shown in Table 1.
[Example 3]
A lanthanum hexaboride particle-containing powder was obtained in the same manner as in Example 1 except that boron carbide and lanthanum oxide were weighed and mixed so that the element ratio B / La of lanthanum and boron was 6.00. .

When the carbon concentration of the obtained lanthanum hexaboride particle-containing powder was measured by a combustion-infrared absorption method, the carbon content was 0.2% by mass. Further, when the composition of the obtained lanthanum hexaboride particles was evaluated by ICP, m, which is the elemental ratio (B / La) of boron (B) to lanthanum element (La) in the general formula LaB _m , It was confirmed that it was 5.9.

Further, the obtained lanthanum hexaboride particle-containing powder was measured for the B ₄ C concentration of the lanthanum hexaboride particle-containing powder by the method for evaluating the B ₄ C concentration in the boride particles described above. It was 9% by mass.

  A boride particle dispersion was prepared in the same manner as in Example 1 except that the lanthanum hexaboride particle-containing powder was used.

Evaluation similar to Example 1 was performed about the obtained dispersion liquid. The results are shown in Table 1.
[Example 4]
A lanthanum hexaboride particle-containing powder was obtained in the same manner as in Example 1 except that boron carbide and lanthanum oxide were weighed and mixed so that the element ratio B / La of lanthanum and boron was 6.10. .

When the carbon concentration of the obtained lanthanum hexaboride particle-containing powder was measured by a combustion-infrared absorption method, the carbon content was 0.2% by mass. Further, when the composition of the obtained lanthanum hexaboride particles was evaluated by ICP, m, which is the elemental ratio (B / La) of boron (B) to lanthanum element (La) in the general formula LaB _m , It was confirmed that it was 6.0.

Further, the obtained lanthanum hexaboride particle-containing powder was measured for the B ₄ C concentration of the lanthanum hexaboride particle-containing powder by the method for evaluating the B ₄ C concentration in the boride particles described above. It was 9% by mass.

  A boride particle dispersion was prepared in the same manner as in Example 1 except that the lanthanum hexaboride particle-containing powder was used.

Evaluation similar to Example 1 was performed about the obtained dispersion liquid. The results are shown in Table 1.
[Example 5]
Boron carbide and lanthanum oxide were weighed and mixed so that the element ratio B / La of lanthanum to boron was 6.20, and the same as in Example 1 except that it was fired at a temperature of 1650 ± 50 ° C. A powder containing lanthanum hexaboride particles was obtained.

When the carbon concentration of the obtained lanthanum hexaboride particle-containing powder was measured by a combustion-infrared absorption method, the carbon content was 0.2% by mass. Further, when the composition of the obtained lanthanum hexaboride particles was evaluated by ICP, m, which is the elemental ratio (B / La) of boron (B) to lanthanum element (La) in the general formula LaB _m , It was confirmed that it was 6.0.

Further, the obtained lanthanum hexaboride particle-containing powder was measured for the B ₄ C concentration of the lanthanum hexaboride particle-containing powder by the method for evaluating the B ₄ C concentration in the boride particles described above. It was 9% by mass.

  A boride particle dispersion was prepared in the same manner as in Example 1 except that the lanthanum hexaboride particle-containing powder was used.

Evaluation similar to Example 1 was performed about the obtained dispersion liquid. The results are shown in Table 1.
[Example 6]
Example 1 except that boron oxide was used as the boron source, lanthanum oxide was used as the lanthanum source, carbon (graphite) was used as the reducing agent, and the element ratio B / La between lanthanum and boron was 6.10. In the same manner as above, a powder containing lanthanum hexaboride particles was obtained. However, 60 parts by weight of carbon was weighed and mixed with 100 parts by weight of boron oxide.

When the carbon content of the obtained lanthanum hexaboride particle-containing powder was measured by a combustion-infrared absorption method, the carbon content was 0.1% by mass. Further, when the composition of the obtained lanthanum hexaboride particles was evaluated by ICP, m, which is the elemental ratio (B / La) of boron (B) to lanthanum element (La) in the general formula LaB _m , It was confirmed that it was 6.0.

Further, the obtained lanthanum hexaboride particle-containing powder was measured for the B ₄ C concentration of the lanthanum hexaboride particle-containing powder by the method for evaluating the B ₄ C concentration in the boride particles described above. It was 4% by mass.

  A boride particle dispersion was prepared in the same manner as in Example 1 except that the lanthanum hexaboride particle-containing powder was used.

Evaluation similar to Example 1 was performed about the obtained dispersion liquid. The results are shown in Table 1.
[Example 7]
A cerium hexaboride particle-containing powder was obtained in the same manner as in Example 1 except that cerium oxide was used instead of lanthanum oxide so that the element ratio B / Ce of cerium and boron was 6.10. It was.

When the carbon concentration of the obtained cerium hexaboride particle-containing powder was measured by a combustion-infrared absorption method, the carbon content was 0.2% by mass. Also were evaluated by ICP for the composition of the obtained cerium hexaboride particles, in the general formula CeB _m, an element ratio of boron (B) with respect to the cerium element (Ce) (B / Ce) m, It was confirmed that it was 6.0.

Further, the cerium hexaboride particles containing powder obtained, where the evaluation method of B _{4 C} concentration in aforementioned boride particles were measured B _{4 C} concentration of cerium hexaboride particles containing powder, 0. It was 9% by mass.

  A boride particle dispersion was prepared in the same manner as in Example 1 except that the cerium hexaboride particle-containing powder was used.

Evaluation similar to Example 1 was performed about the obtained dispersion liquid. The results are shown in Table 1.
[Comparative Example 1]
Boron carbide was used as a boron source and a reducing agent, and lanthanum oxide was used as a lanthanum source. These were weighed and mixed so that the element ratio B / La of lanthanum and boron was 6.10. Thereafter, it was calcined in an argon atmosphere at a temperature of 1480 ± 50 ° C. for 6 hours to obtain a lanthanum hexaboride particle-containing powder.

When the carbon content of the obtained lanthanum hexaboride particle-containing powder was measured by a combustion-infrared absorption method, the carbon content was 0.6% by mass. Further, when the composition of the obtained lanthanum hexaboride particles was evaluated by ICP, m, which is the elemental ratio (B / La) of boron (B) to lanthanum element (La) in the general formula LaB _m , It was confirmed that it was 6.0.

Further, the obtained lanthanum hexaboride particle-containing powder was measured for the B ₄ C concentration of the lanthanum hexaboride particle-containing powder by the method for evaluating the B ₄ C concentration in the boride particles described above. It was 6% by mass.

  A boride particle dispersion was prepared in the same manner as in Example 1 except that the lanthanum hexaboride particle-containing powder was used.

  Evaluation similar to Example 1 was performed about the obtained dispersion liquid. The results are shown in Table 1.

  In addition, in order to prepare the dispersion, the average dispersed particle size was 105 nm and larger than 100 nm at the time when the grinding treatment was performed for 20 hours. It was judged that it was difficult to obtain a particle size of 100 nm or less even if the process was continued.

  In addition, Zr / La in the obtained boride particle dispersion is 1.8, which is higher than in the case of Examples 1 to 7, and the media beads are worn out and mixed into the slurry. I understand.

Furthermore, the diffuse transmittance peak value is 1.8%, which is higher than those in Examples 1 to 7, and there is a concern that blue haze is strongly observed when an optical member is produced using this. The
[Comparative Example 2]
A lanthanum hexaboride particle-containing powder was obtained in the same manner as in Comparative Example 1 except that boron carbide and lanthanum oxide were weighed and mixed so that the element ratio B / La between lanthanum and boron was 6.20. .

When the carbon content of the obtained lanthanum hexaboride particle-containing powder was measured by a combustion-infrared absorption method, the carbon content was 0.8% by mass. Further, when the composition of the obtained lanthanum hexaboride particles was evaluated by ICP, m, which is the elemental ratio (B / La) of boron (B) to lanthanum element (La) in the general formula LaB _m , It was confirmed to be 6.1.

Further, the obtained lanthanum hexaboride particle-containing powder was measured for the B ₄ C concentration of the lanthanum hexaboride particle-containing powder by the method for evaluating the B ₄ C concentration in the boride particles described above. It was 7 mass%.

  A boride particle dispersion was prepared in the same manner as in Example 1 except that the lanthanum hexaboride particle-containing powder was used.

  Evaluation similar to Example 1 was performed about the obtained dispersion liquid. The results are shown in Table 1.

  In addition, in order to prepare the dispersion, the average dispersed particle size was 111 nm and larger than 100 nm when the grinding process was performed for 20 hours. However, since the grinding efficiency was remarkably lowered due to the increase in slurry viscosity, the further grinding process was performed. It was judged that it was difficult to obtain a particle size of 100 nm or less even if the process was continued.

  In addition, Zr / La in the obtained boride particle dispersion is 2.0, which is higher than those in Examples 1 to 8, and the media beads are worn out and mixed into the slurry. I understand.

Furthermore, the diffuse transmittance peak value is 2.4%, which is higher than those in Examples 1 to 7, and there is a concern that blue haze is strongly observed when an optical member is produced using this. The
[Comparative Example 3]
Except that boron oxide was used as the boron source, lanthanum oxide was used as the lanthanum source, carbon (graphite) was used as the reducing agent, and the element ratio B / La of lanthanum and boron was weighed and mixed to be 6.10. In the same manner as in Example 1, a lanthanum hexaboride particle-containing powder was obtained. However, 60 parts by weight of carbon was weighed and mixed with 100 parts by weight of boron oxide.

The carbon content of the obtained lanthanum hexaboride particle-containing powder was measured by a combustion-infrared absorption method, and the carbon content was 0.7% by mass. Further, when the composition of the obtained lanthanum hexaboride particles was evaluated by ICP, m, which is the elemental ratio (B / La) of boron (B) to lanthanum element (La) in the general formula LaB _m , It was confirmed that it was 6.0.

Further, the obtained lanthanum hexaboride particle-containing powder was measured for the B ₄ C concentration of the lanthanum hexaboride particle-containing powder by the method for evaluating the B ₄ C concentration in the boride particles described above. It was 4% by mass.

  A boride particle dispersion was prepared in the same manner as in Example 1 except that the lanthanum hexaboride particle-containing powder was used.

Evaluation similar to Example 1 was performed about the obtained dispersion liquid. The results are shown in Table 1.
[Comparative Example 4]
A cerium hexaboride particle-containing powder was obtained in the same manner as in Comparative Example 1 except that cerium oxide was used instead of lanthanum oxide so that the element ratio B / Ce of cerium and boron was 6.10. It was.

When the carbon concentration of the obtained cerium hexaboride particle-containing powder was measured by a combustion-infrared absorption method, the carbon content was 0.9% by mass. Also were evaluated by ICP for the composition of the obtained cerium hexaboride particles, in the general formula CeB _m, an element ratio of boron (B) with respect to the cerium element (Ce) (B / Ce) m, It was confirmed that it was 6.0.

Furthermore, when the obtained cerium hexaboride particle-containing powder was measured for the B ₄ C concentration of the cerium hexaboride particle-containing powder by the method for evaluating the B ₄ C concentration in the boride particles described above, 4. It was 4% by mass.

  A boride particle dispersion was prepared in the same manner as in Example 1 except that the cerium hexaboride particle-containing powder was used.

  Evaluation similar to Example 1 was performed about the obtained dispersion liquid. The results are shown in Table 1.

実施例１〜実施例７では、固相反応等により得られたホウ化物粒子を、比較的簡単かつ経済的に、平均分散粒子径を１００ｎｍ以下、特に８５ｎｍ以下にまで粉砕して微細化することができることが確認できた。また、実施例１〜実施例７では、得られるホウ化物粒子は平均分散粒子径が１００ｎｍ以下、特に８５ｎｍ以下となるため、その粒子または分散液を用いて作製した赤外線遮蔽膜に人口太陽光を照射しても青白色に着色しない。すなわち、ブルーヘイズが抑制される。従って、実施例１〜実施例７のホウ化物粒子分散液を用いて作製した、赤外線遮蔽光学部材は、建材用の窓ガラスや車の窓ガラス等に好適に用いられることが確認できた。

In Examples 1 to 7, boride particles obtained by a solid phase reaction or the like are pulverized and refined relatively easily and economically to an average dispersed particle size of 100 nm or less, particularly 85 nm or less. I was able to confirm. In Examples 1 to 7, since the boride particles obtained have an average dispersed particle size of 100 nm or less, particularly 85 nm or less, artificial sunlight is applied to the infrared shielding film produced using the particles or dispersion. Even if irradiated, it does not color blue-white. That is, blue haze is suppressed. Therefore, it was confirmed that the infrared shielding optical member produced using the boride particle dispersion liquid of Examples 1 to 7 was suitably used for window glass for building materials, window glass for cars, and the like.

  On the other hand, in Comparative Examples 1 to 4 using boride particle-containing powder having a carbon concentration higher than 0.2% by mass as a raw material, the average dispersed particle diameter is larger than 100 nm and the viscosity is increased in 20 hours of pulverization treatment. Therefore, it was confirmed that it was difficult to obtain a particle size of 100 nm or less even when the pulverization was further advanced. For this reason, it has confirmed that generation | occurrence | production of blue haze was anxious about the infrared shielding optical member produced using the boride particle | grain dispersion liquid which concerns.

Claims (9)

General formula XB _m (where X is one or more selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sr, Ca) A metal element, m is a boride particle represented by a number indicating the amount of boron in the general formula),
The boride particle | grains whose carbon amount contained in the said boride particle | grains when measured by a combustion-infrared absorption method is 0.2 mass% or less. The boride particle according to claim 1, wherein _m in the general formula XBm is 4.0 or more and 6.2 or less.   The boride particles according to claim 1 or 2, comprising lanthanum hexaboride particles. The boride particle according to any one of claims 1 to 3, wherein the content of B ₄ C is 1.0 mass% or less.   A boride particle dispersion liquid comprising the boride particles according to claim 1 and a liquid medium.   The boride particle dispersion liquid according to claim 5, wherein the liquid medium contains one or more selected from water, organic solvents, oils and fats, liquid resins, and plasticizers.   The boride particle dispersion according to claim 5 or 6, wherein an average dispersed particle diameter of boride particles measured by a dynamic light scattering method is 85 nm or less.   The boride particle dispersion liquid according to any one of claims 5 to 7, wherein a concentration of the boride particles is 0.01% by mass or more and 30% by mass or less.   The boride particle dispersion according to any one of claims 5 to 8, wherein the weight concentration of Zr is 1.5 times or less of the weight concentration of the metal element X.

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