JP6544299B2 - Method of selecting elements in boride particles and method of producing boride particles - Google Patents

Description

  The present invention relates to a method of selecting elements in boride particles, and a method of producing boride particles.

  In recent years, by giving a heat ray shielding function to a window material applied to a car or a building opening, etc., a method is considered to reduce the cooling load and the heat sensation of a person by blocking the solar energy incident from the window material. It is done.

  As a method of imparting a heat ray shielding function to a window material, for example, a method of applying a coating solution containing particles having infrared absorptivity to a window material or the like and curing the coating solution is studied.

  For example, the inventors of the present invention disclosed in Patent Document 1 ruthenium oxide particles, titanium nitride particles, tantalum nitride particles, titanium silicide particles, silicon silicide molybdenum particles, lanthanum boride particles, iron oxide particles, which have an average particle diameter of 100 nm or less. Disclosed is a coating liquid for a selective permeation membrane, characterized in that at least one of iron (III) oxide hydroxide fine particles is dispersed.

  The boride particles such as lanthanum hexaboride mentioned as fine particles to be added to the coating solution for selective transmission film in Patent Document 1 are high for light in the near infrared region by localized surface plasmon resonance of conductor particles. It exhibits an absorption coefficient and also has visible light transparency.

  Among the borides, since lanthanum hexaboride has a high light absorption coefficient to light in the near infrared region as described above, it has very high heat shielding properties, and good heat shielding properties can be obtained with a small amount used. . Furthermore, it has excellent properties such as weather resistance, ease of production process, and easy availability of raw materials. For this reason, lanthanum hexaboride is widely used industrially.

  By the way, regarding particles having infrared absorptivity, particles having higher light transmittance in the visible region and higher heat ray shielding properties have been required, and this tendency is considered to become more remarkable in the future. Be

  This is because, by applying a material having a higher light transmittance in the visible region and a higher heat ray shielding property to, for example, a car window of an electric car, the load on the air conditioner can be reduced and the traveling distance can be extended. is there. Moreover, when the material which concerns is applied to the window material of a building, it is because an air-conditioner load can be reduced and the power consumption of summer can be suppressed.

Unexamined-Japanese-Patent No. 11-181336

  However, lanthanum hexaboride absorbs a part of light in the visible region because the bottom of the absorption curve having a peak in light in the near infrared region partially extends on the long wavelength side of visible light. Therefore, from the viewpoint of improving the light transmittance in the visible region, boride particles having a high heat ray shielding function to replace hexaboride particles are required.

  Phthalocyanine compounds, cyanine compounds, porphyrin compounds, naphthalocyanine compounds, indoline compounds, quinacridone compounds, perylene compounds, azo compounds belonging to organic compounds and having absorption in the ultraviolet to visible light and near infrared regions. Etc. can change the functional group in the structure, and if it is a metal complex, it is possible to manipulate the absorption wavelength by changing the structure of the central metal element etc.

  However, the boride particle has an electronic structure dependent on its crystal structure and constituent elements, and the dielectric function inherent to the substance resulting from the electronic structure causes absorption by causing plasmon resonance to a specific light wavelength. For this reason, it was difficult to change the absorption characteristics (absorption wavelength, absorption intensity) by changing the chemical structure of the substance itself unlike the case of the above-mentioned pigment compound, as for the boride particle.

  Therefore, as in the case of the dye compound described above, it has been difficult to obtain boride particles having high light transmittance in the visible region and having a heat ray shielding function higher than that of the hexaboride particles.

  Therefore, the inventors of the present invention maximize the peak of light absorption in the near infrared region while maintaining the visible light transmittance characteristics of the boride particles by selecting the element in the boride particles. It was investigated.

  In addition, the method of selecting the element which can maximize the absorption peak of light in the near infrared region while maintaining the visible light transmittance characteristic of the boride particles is not known, and from the viewpoint of the efficiency of the experiment, etc. There has been a need for a method of selecting the elements of boride particles.

  Therefore, in view of the problems of the prior art, according to one aspect of the present invention, it is possible to maximize the absorption peak of light in the near infrared region while maintaining the visible light transmittance characteristics of the boride particles. The purpose is to provide a method of selecting an element.

According to one aspect of the present invention for solving the above problems, the general formula XB a element selection method indicated by X boride in particles represented by _m, boride particles XB _m by first-principles calculation The energy band structure calculation step of calculating the energy band structure of the metal, the dielectric function calculation step of calculating the dielectric function of the boride particle XB _m by the calculated energy band structure, and the boride by the scattering theory from the calculated dielectric function A transmittance curve calculating step for calculating a transmittance curve of the particle XB _m, a transmittance calculating step for calculating a visible light transmittance and a near infrared light transmittance of the boride particle XB _m , and a visible light transmittance Is 96% or more, the near infrared light transmittance is in a wavelength range of 1400 to 1700 nm, and the percentage of the near infrared light transmittance divided by the visible light transmittance is 80.0% or less of If it meets the matter, a method of selecting an element of the boride in the particles having, a determination step to pass the element represented by the X, can be provided.

  According to one aspect of the present invention, there is provided a method of selecting an element in boride particles capable of maximizing the absorption peak of light in the near infrared region while maintaining the visible light transmittance characteristics of the boride particles. it can.

It is a figure which shows the transmittance | permeability curve of an Example and a prior art example.

Hereinafter, although the form for carrying out the present invention is explained with reference to drawings, the present invention is not limited to the following embodiment, and does not deviate from the scope of the present invention. Various modifications and substitutions may be made.
[Method of selecting element X of boride particles]
In the present embodiment, first, an example of a method for selecting the element X of boride particles will be described. The method of selecting the element X of the boride particle XB _m of the present invention includes an energy band structure calculating step, a dielectric function calculating step, a transmittance curve calculating step, a transmittance calculating step, and a determining step. In addition, the boride particle is represented by XB _m , and a specific value arbitrarily selected is used during the above process (for example, 5.2 ≦ m ≦ 6.5 can be made).

In the energy band structure calculating step, the energy band structure of the boride particle represented by the general formula XB _m containing the element X to be provided for calculation can be calculated using the first principle calculation. In this first principle calculation, it is preferable to use one or more kinds of plane wave basis first principle calculations selected from the screened exchange method, the hybrid functional method, and the GW method. According to such plane wave basis first principle calculation, a band structure with high accuracy can be obtained to an extent that the actual measurement value is sufficiently reproduced.

In the dielectric function calculation step, the dielectric function of the boride particle XB _m described above can be calculated from the calculated energy band structure. The dielectric function of the boride particle XB _m is preferably calculated as the dielectric function including the Lorentz term and the Drude term.

In addition, the method described in Lihua xiao et al. Applied Physics Letters 101, 041913 (2012) can be referred to for the method of calculating the dielectric function from the energy band structure calculated by the first principle calculation. Specifically, the dielectric function is obtained from the following (A) formula by determining the direct transition from the valence band lower than Fermi energy to the conduction band higher than Fermi energy in the obtained energy band structure: The imaginary part ε _{2 of} n can be calculated.

Also, the Kramers-Kronig conversion is performed as shown in the following equation (B), for the direct transition from the valence band lower than Fermi energy to the conduction band higher than Fermi energy in the obtained energy band structure. Thus, the real part ε ₁ of the dielectric function can be calculated.

In the transmittance curve calculation step, the transmittance curve can be calculated from the calculated dielectric function, and the absorption wavelength of the boride particle XB _m can be calculated. The absorption wavelength of the boride particle XB _m can be calculated by one or more kinds of scattering theory selected from Mie scattering and Rayleigh scattering. The transmittance curve was calculated from wavelengths 300 nm to 2100 nm.

  As a method of calculating the absorption wavelength from the dielectric function, the method described in K. Adachi, M. Miratsu, T. Asahi, J. Mater. Res., 25, 510 (2010) can be referred to .

In the transmittance calculation step, the transmittance of visible light of the boride particle XB _m and the transmittance of near infrared light are calculated. The transmittance of visible light (hereinafter referred to as visible light transmittance) can be calculated as an average value in the wavelength range of 380 nm to 800 nm. Moreover, the transmittance | permeability of near-infrared light (henceforth a near-infrared light transmittance) can make the transmittance | permeability in the arbitrary wavelength of a wavelength range of 1400 nm-1700 nm the transmittance | permeability of near-infrared light. For example, the transmittance at a wavelength of 1600 nm can be the transmittance of near infrared light. The reason why the transmittance of near-infrared light is the transmittance at an arbitrary wavelength in the range of 1400 nm to 1700 nm is that the boride particle tends to show an absorption peak in the wavelength in this range.

In the determination step, an element X having a visible light transmittance of 96% or more and a percentage obtained by dividing the near infrared light transmittance by the visible light transmittance is 80.0% or less is regarded as a pass. The term "pass" means that the material is excellent in visible light transmittance and also excellent in heat ray shielding properties. That is, when the visible light transmittance (96% or more) is A and the near infrared light transmittance (within the range of 1400 to 1700 nm) is B, the boride particle XB _m is satisfied so as to satisfy the following formula (C) Select the element X in
80 ≧ B ÷ A × 100 (C)
The reason for setting the visible light transmittance (average value of 380 nm to 800 nm) to 96% or more is that when the visible light transmittance is in the range of 96% or more, it can be judged that the visible light transparency is good. When the visible light transmittance is less than 96%, the brightness that can be taken into the room is dark, and it is not transparent, and the color tends to look different.

  Further, the percentage (B ÷ A × 100) obtained by dividing the near infrared light transmittance by the visible light transmittance is set to 80.0% or less in the range of the heat ray shielding function and the visible light transparency in this range. It is because it can be compatible. When the percentage (B ÷ A × 100) exceeds 80.0%, the transmittance of near infrared light to visible light is high, so the heat shield ratio tends to decrease.

In addition, when there are a plurality of candidates for the element X, each step from the energy band structure calculation step to the transmittance calculation step described above may be repeatedly performed with the element X changed to select the optimum element X (Repetitive process).
[Method of producing boride particles]
In addition, the method of producing boride particles has a selection step and a synthesis step.

In the selection step, the element X is selected. It is preferable to use the selection method which selects the element X in the boride particle | grains XB _m mentioned above for the selection method of the element X.

In the synthesis step, the boride particles XB _m are synthesized using the element X selected in the selection step. As the synthesis method, various production methods can be adopted according to the selected element.

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

The element X of the boride particle XB _m capable of maximizing the absorption peak of light in the near infrared region while maintaining the visible light transmittance characteristics of the boride particle was calculated and selected according to the following procedure.

The transmittance curve of the boride particle XB _m is shown in FIG. 1 below, and the value of the transmittance of the near infrared light of the boride particle XB _{m to} the transmittance of the visible light is shown in Table 1.
Example 1
Ac was selected as the element X, and evaluation was performed on boride particles represented by the general formula AcB ₆ containing the element X. Specifically, first, the energy band structure of boride particles was calculated by the first principle calculation based on the screened exchange method (energy band structure calculation step). The first principle calculation used plane wave basis first calculation software VASP (Vienna Ab initio Simulation Package).

The dielectric function of the boride particles AcB ₆ was calculated from the calculated energy band structure (dielectric function calculation step). From the calculated dielectric function, a transmittance curve was calculated based on Mie's scattering theory (transmittance curve calculation step). From the calculated transmittance curve, the transmittance of visible light of the boride particle was calculated as an average value of 380 nm to 800 nm, and the transmittance of near infrared light at a wavelength of 1600 nm was calculated as the transmittance of near infrared light ( Transmittance calculation step).

And, AcB ₆ has a visible light transmittance (average value of 380 nm to 800 nm) of 96% or more, a visible light transmittance (96% or more) of A, and a near infrared light transmittance (wavelength of 1600 nm) When position B is B, it can be confirmed that the condition of 80 ≧ B 位置 A × 100 is satisfied, and it is regarded as a pass (determination step).
Example 2
Sc was selected as the element X, and in the same manner as in Example 1, the boride particles represented by ScB ₆ containing this element X were evaluated. In the determination step, it was confirmed that ScB ₆ was a failure.
<Conventional example>
With respect to LaB ₆ used conventionally, up to the transmittance calculation step was carried out in the same manner as in Example 1 for comparison.

  The results of Example 1, Example 2, and Conventional Example are shown in Table 1.

First, in the conventional example (LaB ₆ ), the transmittance of near infrared light at a wavelength of 1600 nm was 80%. Moreover, the visible light transmittance | permeability (380 nm-800 nm average value) is 99%, and the transmittance | permeability curve which shows that visible light transparency is high was obtained. However, the percentage of the transmittance B of the near infrared light (wavelength 1600 nm) to the transmittance of the visible light A (B ÷ A × 100) was 80.8%.

On the other hand, in Example 1 (AcB ₆ ), the transmittance of near-infrared light at a wavelength of 1600 nm was 75%, and it was found that the absorption characteristics of near-infrared light were superior to LaB ₆ . Also, a 99% visible light transmittance (mean value of 380 nm to 800 nm), the transmittance curve shows a comparably high visible light transparency and LaB ₆ was obtained. Further, B ÷ A × 100 was a low value of 75.8%, which is lower than that of LaB ₆ , and it was confirmed that it was suitable as a heat ray shielding material having an excellent heat shielding function.

In Example 2 (ScB ₆ ), the near-infrared light transmittance at a wavelength of 1600 nm is 94%, the near-infrared light absorption is weak, and the visible light transmittance (average value of 380 nm to 800 nm) is 98. %, And a transmittance curve showing visible light transparency as high as that of LaB ₆ was obtained. The transmittance of near infrared light / visible light transmittance was 95.9%, which confirmed that it was not suitable.

As described above, by using the hexaboride fine particles of Example 1 (AcB _6), excellent heat ray shielding material to visible light transparency than LaB ₆ which has been conventionally used that is obtained was confirmed.

Claims (2)

A method of selecting an element represented by X in a boride particle represented by the general formula XB _m ,
An energy band structure calculating step of calculating an energy band structure of the boride particle XB _m by the first principle calculation;
A dielectric function calculating step of calculating a dielectric function of the boride particle XB _{m from} the calculated energy band structure;
A transmittance curve calculation step of calculating a transmittance curve of the boride particle XB _m from the calculated dielectric function according to the scattering theory;
A transmittance calculation step of calculating transmittance of visible light and transmittance of near infrared light of the boride particle XB _m ;
The element represented by X when the visible light transmittance is 96% or more and the percentage of the near infrared light transmittance divided by the visible light transmittance satisfies 80.0% or less And a determination step of passing the step of selecting the element in the boride particle. Selecting the element represented by X according to the selection method according to claim 1;
Synthesizing a boride particle using the selected element;
A method of producing boride particles having