JP4626284B2 - Method for producing tungsten oxide fine particles for forming solar shield, and tungsten oxide fine particles for forming solar shield - Google Patents

Description

  The present invention relates to a method for producing a tungsten oxide fine particle for forming a solar radiation shield that is transparent in the visible light region and has an absorption in the infrared region, a tungsten oxide fine particle for forming the solar radiation shield, and the tungsten oxide for forming the solar radiation shield. The present invention relates to a dispersion for forming a solar radiation shielding body in which fine particles are dispersed, and a solar radiation shielding body.

  As a method for removing and reducing the heat component from an external light source such as sunlight or a light bulb, conventionally, a coating made of a material that reflects infrared rays is formed on the glass surface or the like to form a heat ray reflective glass, and the heat ray reflective glass is used as an external light source. The heat component was removed and reduced from this. As the infrared reflecting material, metal oxides such as FeOx, CoOx, CrOx, and TiOx, and metal materials such as Ag, Au, Cu, Ni, and Al have been selected.

  However, since these metal oxides and metal materials have the property of simultaneously reflecting or absorbing visible light in addition to infrared rays that greatly contribute to the thermal effect, there is a problem that the visible light transmittance of the heat ray reflective glass is lowered. there were. In particular, base materials used for building materials, vehicles, telephone boxes, etc. require high transmittance in the visible light region. Therefore, when using materials such as the above metal oxides, the film thickness is extremely low. I had to make it thinner. For this reason, a method of forming a thin film having a thickness of 10 nm using a physical film forming method such as spray baking, CVD method, sputtering method or vacuum vapor deposition method is employed.

  However, these film formation methods require a large-scale apparatus and vacuum equipment, and there are problems in productivity and increase in area, and there is a problem in that the manufacturing cost of the film increases. In addition, if these materials are used to increase the solar shading characteristics, the reflectance in the visible light region tends to increase at the same time, giving a glimmery appearance like a mirror and detracting from aesthetics. There was also. Furthermore, the film formed with these materials has a relatively low electrical resistance value and high reflection with respect to radio waves. For example, the radio waves of mobile phones, televisions, radios, etc. are reflected and cannot be received. There were also problems such as causing radio interference in the area.

In order to improve such problems, the physical properties of the film are such that the light reflectance in the visible light region is low, the reflectance in the infrared region is high, and the surface resistance value of the film is approximately 10 ⁶ Ω / □ or more. It is considered that a controllable membrane is necessary.

  Further, antimony tin oxide (hereinafter abbreviated as ATO) and indium tin oxide (hereinafter abbreviated as ITO) are known as materials having high visible light transmittance and excellent solar radiation shielding function. These materials do not give a glaring appearance due to their relatively low visible light reflectivity. However, since the plasma frequency is in the near infrared region, the reflection / absorption effect is not yet sufficient in the near infrared region closer to visible light. Furthermore, since these materials have a low solar radiation shielding power per unit weight, there is a problem that the amount used is increased and the raw material cost is expensive in order to obtain a high shielding function.

  Furthermore, as an infrared shielding film material having a solar radiation shielding function, a film obtained by slightly reducing tungsten oxide, molybdenum oxide, or vanadium oxide can be given. Although these films are materials used as so-called electrochromic materials, they are transparent in a sufficiently oxidized state, and when they are reduced by an electrochemical method, absorption occurs from the long wavelength visible light region to the near infrared region. It becomes like this.

  In Patent Document 1, on a transparent glass substrate, at least one metal ion selected from the group consisting of Group IIIa, Group IVa, Group Vb, Group VIb and Group VIIb of the periodic table as the first layer from the substrate side. A composite tungsten oxide film containing, a transparent dielectric film as a second layer on the first layer, a third layer on the second layer as a group IIIa, IVa group, Vb group of the periodic table, A composite tungsten oxide film containing at least one metal ion selected from the group consisting of group VIb and group VIIb is provided, and the refractive index of the transparent dielectric film of the second layer is the first layer and the third layer. There has been proposed a heat-shielding glass having a refractive index lower than that of the composite tungsten oxide film of the layer. Further, according to the document, it is described that the composite tungsten oxide film containing metal ions is formed by a sputtering method particularly from the viewpoint of increasing the area and productivity.

  In Patent Document 2, a first dielectric film is provided as a first layer from the substrate side on a transparent glass substrate in the same manner as in Patent Document 1, and oxidized as a second layer on the first layer. There has been proposed a heat ray shielding glass in which a tungsten film is provided and a second dielectric film is provided as a third layer on the second layer.

  In Patent Document 3, a composite tungsten oxide film containing the same metal element is provided as a first layer from the substrate side on the transparent substrate in the same manner as in Patent Document 1, and the first layer is formed on the first layer. A heat ray shielding glass provided with a transparent dielectric film as two layers has been proposed.

  Further, in Patent Document 4, a tungsten oxide film having high heat shielding properties and uniform in-plane optical characteristics can be stably produced by sputtering in an atmosphere containing carbon dioxide using a target made of tungsten. A method of forming a radio wave transmission type heat ray shielding film has been proposed.

JP-A-8-59300 JP-A-8-12378 JP-A-8-283044 Japanese Patent Laid-Open No. 10-183334

  For example, as described in Patent Documents 1 to 4, a sputtering method has conventionally been used as a method for manufacturing an infrared shielding layer containing a tungsten compound. However, such a physical film formation method requires a large-scale apparatus and vacuum equipment, and has a problem from the viewpoint of productivity. Even though it is technically possible to increase the area, the manufacturing cost of the film is low. There was also a problem of becoming higher. In addition, from the viewpoint of a solar radiation shield, there is a problem that the light transmittance in the visible light region is further improved without deteriorating the shielding performance in the infrared region and near infrared region. From the viewpoint of productivity, when the infrared shielding layer is a single layer film, the durability of the infrared shielding layer is likely to be oxidized and easily damaged.

  Then, the place made into the subject of this invention used the tungsten oxide microparticles | fine-particles used for the solar radiation shielding body which can make the transmittance | permeability of infrared rays low, maintaining visible light transmittance | permeability high, its manufacturing method, and the said tungsten oxide microparticles | fine-particles. The object is to provide a dispersion for forming a sunscreen and a sunscreen.

  As a result of intensive studies, the inventors have obtained tungsten oxide fine particles that can be applied to solar radiation shields with low infrared transmittance while maintaining high visible light transmittance. Then, when a fine particle dispersion of the tungsten oxide was prepared, a solar shading film could be produced by forming a solar shading film by a simple coating method, etc. without using a high-cost physical film forming method. Improve the light transmittance in the visible light range without degrading the shielding performance in the infrared and near infrared regions, and also improve the durability due to the ease of oxidation and scratching of the solar radiation shielding layer It was found that it is possible to plan. Furthermore, the fine particles of the tungsten oxide are excellent in light transmittance in the visible light region without reducing the shielding performance in the infrared region and near infrared region by a simple method such as kneading into an appropriate resin. The inventors have found that a solar radiation shielding body can be formed, and have reached the present invention.

That is, according to the first aspect of the present invention, tungstic acid (H ₂ WO ₄ ) or a mixture of tungstic acid (H ₂ WO ₄ ) and tungsten trioxide fine particles is converted into an inert gas or an inert gas and a reducing property. By firing in a mixed gas atmosphere with a gas, it is represented by the general formula WyOz (where W is tungsten, O is oxygen, 2.2 ≦ z / y ≦ 2.999) and has a particle diameter of 1 nm to 800 nm. thereby generating a tungsten oxide microparticles you is a manufacturing method for forming a solar radiation-shielding body for tungsten oxide nanoparticles, wherein.

According to a second aspect of the present invention, tungstic acid (H ₂ WO ₄ ), a mixture of tungstic acid (H ₂ WO ₄ ) and tungsten trioxide fine particles, an oxide of M element and / or a hydroxide ( Where M is alkali metal, alkaline earth metal, rare earth element, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, One or more types selected from Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re A mixed powder of
Or / and tungstic acid (H ₂ WO ₄ ), or a mixture of tungstic acid (H ₂ WO ₄ ) and tungsten trioxide fine particles, and an aqueous solution of a metal salt, a colloidal solution of a metal oxide of the M element, alkoxy A dry powder obtained by mixing and drying at least one selected from solutions is baked in an atmosphere of an inert gas or a mixed gas of an inert gas and a reducing gas to obtain a general formula MxWyOz ( Where M is the element M, W is tungsten, O is oxygen, 0.001 ≦ x / y ≦ 1, 2.2 ≦ z / y ≦ 3.0), and has a particle diameter of 1 nm to 800 nm. The production method of the tungsten oxide fine particles for forming a solar shading body is characterized by producing tungsten oxide fine particles.

The third invention of the present invention is manufactured by the method for manufacturing the tungsten oxide fine particles for forming a solar radiation shield described in the second invention, and its powder color is recommended by the International Commission on Illumination (CIE). In the powder color in the L ^* a ^* b ^* color system (JIS Z8729), L ^* is in the range of 25-80, a ^* is in the range of -10 to 10, and b ^* is in the range of -15 to 15 , and 1 nm to 800 nm. It is a tungsten oxide fine particle for solar radiation shielding body characterized by having a particle diameter .

A fourth invention of the present invention is a tungsten oxide fine particle for forming a solar radiation shield as described in the third invention, and its powder color is L ^* a recommended by the International Commission on Illumination (CIE). ^* b ^{* In} the powder color in the color system (JIS Z8729), L ^* is 25 to 80, a ^* is in the range of -10 to 10, and b ^* is in the range of -15 to 15. It is a tungsten oxide fine particle for body formation.

  According to a fifth aspect of the present invention, there is provided a dispersion for forming a solar shading material, characterized in that the tungsten oxide fine particles for forming the solar shading material according to the third or fourth invention are dispersed in a solvent. .

  According to a sixth aspect of the present invention, there is provided a solar shading body characterized in that the tungsten oxide fine particles for forming the solar shading body described in the third or fourth aspect are dispersed in a resin.

  According to the present invention, it is possible to easily produce tungsten oxide fine particles exhibiting an excellent function as a solar radiation shielding film and a solar radiation shielding body, in which infrared transmittance can be lowered while keeping visible light transmittance high. Then, a tungsten oxide fine particle dispersion is prepared using the tungsten oxide fine particles, and a simple coating method or the like is used without using an expensive physical film forming method using the tungsten oxide fine particle dispersion. Thus, a solar radiation shielding film having excellent light transmittance in the visible light region can be produced at a low production cost without forming a solar radiation shielding film and reducing the shielding performance in the infrared region and near infrared region. Furthermore, by dispersing the tungsten oxide fine particles in an appropriate resin by a kneading method or the like, the solar radiation shielding body is excellent in light transmittance in the visible light range without deteriorating the shielding performance in the infrared region or near infrared region. Can be manufactured at a low production cost.

Hereinafter, embodiments of the present invention will be specifically described.
As the tungsten oxide that can reduce the transmittance of infrared rays while keeping the visible light transmittance high,
(A) General formula WyOz (provided by firing tungstic acid (H ₂ WO ₄ ) or / and tungsten trioxide fine particles in an inert gas or a mixed gas atmosphere of an inert gas and a reducing gas, W is tungsten, O is oxygen, and tungsten oxide fine particles represented by 2.2 ≦ z / y ≦ 2.999),
(B) Tungstic acid (H ₂ WO ₄ ) or / and tungsten trioxide fine particles and oxide or / and hydroxide of M element (where M is an alkali metal, alkaline earth metal, rare earth element, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, One or more elements selected from F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, and Re (referred to as M elements in this specification)). Mixed powder,
Or / and
Tungstic acid (H ₂ WO ₄ ) or / and tungsten trioxide fine particles are mixed with one or more selected from an aqueous solution of a metal salt, a colloidal solution of a metal oxide, and an alkoxy solution of the M element. The dried dry powder is calcined in an inert gas or a mixed gas atmosphere of an inert gas and a reducing gas to obtain a general formula MxWyOz (where M is the M element, W: tungsten, O: Oxygen, tungsten oxide fine particles represented by 0.001 ≦ x / y ≦ 1, 2.2 ≦ z / y ≦ 3.0) have been conceived.

  Using the tungsten oxide fine particles described in the above (A) and (B) and the tungsten oxide fine particle dispersion produced by using the tungsten oxide fine particles, simple coating without using a high-cost physical film forming method. The solar shading film or the solar shading body can be formed by using the method or the kneading method. The solar shading film and the solar shading body improve the light transmittance in the visible light region without degrading the shielding performance in the infrared region and near infrared region, which has been a problem in the past, and are easy to oxidize. Durability was improved with the ease of scratching, and this will be described in the order of steps.

1. Production of tungsten oxide fine particles 1- (A). Production of tungsten oxide fine particles represented by the general formula WyOz (W is tungsten, O is oxygen, 2.2 ≦ z / y ≦ 2.999) Tungstic acid (H ₂ WO ₄ ) and / or tungsten trioxide By firing the fine particles in an inert gas alone or in a mixed gas atmosphere of an inert gas and a reducing gas, the general formula WyOz (W is tungsten, O is oxygen, 2.2 ≦ z / y ≦ 2) .999) will be described.

The tungstic acid (H ₂ WO ₄ ) used as a raw material is not particularly limited as long as it becomes an oxide by firing. As the tungsten trioxide used as a raw material, tungsten trioxide fine particles obtained by firing the tungstic acid (H ₂ WO ₄ ) may be used, or commercially available products may be used. Here, from the viewpoint of the optical properties of the manufactured tungsten-shielding tungsten oxide fine particles, it is preferable to use an oxide obtained by firing tungstic acid (H ₂ WO ₄ ) used as a raw material. From the viewpoint of properties, tungsten trioxide fine particles such as commercially available products can be used. From the same viewpoint, a mixture of both may be used.

When the tungstic acid (H ₂ WO ₄ ) is fired and used as tungsten trioxide fine particles, the treatment temperature during firing is preferably 200 ° C. or higher from the viewpoint of desired properties and optical characteristics of the tungsten trioxide fine particles. On the other hand, if the treatment temperature during firing exceeds 1000 ° C., the effect of firing is saturated, and if it is 1000 ° C. or less, it is preferable to use 1000 ° C. or less because grain growth that causes a decrease in optical properties can be avoided. The treatment time during firing may be appropriately selected according to the treatment temperature, but may be 10 minutes or more and 5 hours or less.

Next, in order to generate oxygen vacancies in tungstic acid (H ₂ WO ₄ ) and / or tungsten trioxide fine particles, the fine particles are used in an inert gas alone or in a mixed gas atmosphere of an inert gas and a reducing gas. Is fired. As an atmosphere for the firing, an inert gas such as nitrogen, argon, or helium, or a mixed gas of the inert gas and a reducing gas such as hydrogen or alcohol can be used. When firing in a mixed gas atmosphere of an inert gas and a reducing gas, the concentration of the reducing gas in the inert gas may be appropriately selected according to the firing temperature, and is not particularly limited, for example, 20 vol% or less, Preferably it is 10 vol% or less, More preferably, it is 7 vol% or less. This is because if the concentration of the reducing gas is 20 vol% or less, it is possible to avoid the generation of WO ₂ that does not have the solar radiation shielding function due to rapid reduction.

The treatment temperature at the time of firing may be appropriately selected according to the atmosphere, but when the atmosphere is an inert gas alone, it exceeds 650 ° C. from the viewpoint of crystallinity and hiding power of the particles of the sun-shielding fine particles to be fired. It is 1200 degrees C or less, More preferably, it is 1100 degrees C or less, More preferably, it is 1000 degrees C or less. When the atmosphere is a mixed gas of an inert gas and a reducing gas, a temperature at which WO ₂ is not generated due to the presence of the reducing gas may be selected as appropriate.

  Moreover, although the said baking may be implemented under the process temperature of 1 step as mentioned above, it is good also as multiple steps which change atmosphere and baking temperature in the middle of baking. For example, by firing at 100 ° C. or more and 650 ° C. or less in a mixed gas atmosphere of an inert gas and a reducing gas in the first step, and firing at 650 ° C. and exceeding 1200 ° C. in an inert gas atmosphere in the second step. It is a preferable configuration because it is possible to obtain solar shading fine particles having excellent solar shading characteristics. The firing treatment time may be appropriately selected depending on the temperature, but may be 5 minutes or more and 5 hours or less.

The resulting tungsten oxide particles, in the powder colors in Commission Internationale de I'Eclairage (CIE) recommended to have L ^* a ^* b ^* colorimetric system (JIS Z8729), L ^* is 25 to 80, a ^* is -10 to 10 and b ^* are preferably in the range of -15 to 15.

1- (B). Tungsten oxide fine particles represented by the general formula MxWyOz (where M is the M element, W is tungsten, O is oxygen, 0.001 ≦ x / y ≦ 1, 2.2 ≦ z / y ≦ 3.0) Production of Tungstic Acid (H ₂ WO ₄ ) and M Element Oxide and / or Hydroxide Mixed Powder, or Tungsten Trioxide Fine Particles, M Element Oxide and / or Hydroxide Or a mixed powder obtained by mixing tungstic acid (H ₂ WO ₄ ) and tungsten trioxide fine particles and an oxide or / and hydroxide of M element, or tungsten. Mixing and drying acid (H ₂ WO ₄ ) and / or tungsten trioxide fine particles and one or more elements selected from an aqueous solution of metal salt, colloidal solution of metal oxide and alkoxy solution of M element Dry Powder is obtained by firing in an inert gas or a mixed gas atmosphere of an inert gas and a reducing gas. The general formula MxWyOz (where M is the M element, W is tungsten, O is oxygen, 0 It is characterized by obtaining tungsten oxide fine particles for forming a solar radiation shielding material represented by .001 ≦ x / y ≦ 1, 2.2 ≦ z / y ≦ 3.0). The firing conditions are the same as those for the tungsten oxide fine particles represented by the general formula WyOz described in “1. Production of tungsten oxide fine particles”.

Here, the tungsten compound used in the present invention is preferably tungstic acid from the viewpoint of raw material costs and exhaust gas treatment.
When tungsten trioxide is used as a raw material, tungstic acid (H ₂ WO ₄ ) is baked and used as tungsten trioxide fine particles, as described in “1. Production of tungsten oxide fine particles”. Alternatively, a commercially available product may be used. When tungstic acid (H ₂ WO ₄ ) is fired and used as tungsten trioxide fine particles, it may be produced in the same manner as described in “1. Production of tungsten oxide fine particles”.

The kind of the raw material when added is preferably an oxide or / and a hydroxide. The M element oxide and hydroxide are mixed with tungstic acid (H ₂ WO ₄ ) and / or tungsten trioxide fine particles. The mixing step may be performed with a commercially available machine, kneader, ball mill, sand mill, paint shaker or the like.

Also, tungstic acid (H ₂ WO ₄ ) or / and tungsten trioxide fine particles, and at least one selected from an aqueous solution of a metal salt, a colloidal solution of a metal oxide, and an alkoxy solution of the M element, When using dry powder that has been mixed and dried, the partner ion for forming the salt is not particularly limited, and examples thereof include nitrate ion, sulfate ion, chloride ion, carbonate ion and the like. The drying temperature and time are not particularly limited.

Next, in order to generate oxygen vacancies in the mixture or dry powder, the mixture is fired in an inert gas alone or in a mixed gas atmosphere of an inert gas and a reducing gas. As an atmosphere for the firing, an inert gas such as nitrogen, argon, or helium, or a mixed gas of the inert gas and a reducing gas such as hydrogen or alcohol can be used. When firing in a mixed gas atmosphere of an inert gas and a reducing gas, the concentration of the reducing gas in the inert gas may be appropriately selected according to the firing temperature, and is not particularly limited, for example, 20 vol% or less, Preferably it is 10 vol% or less, More preferably, it is 7 vol% or less. This is because if the concentration of the reducing gas is 20 vol% or less, the production of WO ₂ that does not have a solar radiation shielding function due to rapid reduction can be avoided.

The treatment temperature at the time of firing may be appropriately selected according to the atmosphere. However, when the atmosphere is an inert gas alone, it is 650 ° C. from the viewpoint of crystallinity and hiding power of the particles of the sunscreening fine particles to be fired. Exceeding 1200 ° C., more preferably 1100 ° C. or less, and still more preferably 1000 ° C. or less. When the atmosphere is a mixed gas of an inert gas and a reducing gas, a temperature at which WO ₂ is not generated due to the presence of the reducing gas may be selected as appropriate.
Moreover, although the said baking may be implemented under the process temperature of 1 step as mentioned above, it is good also as multiple steps which change atmosphere and baking temperature in the middle of baking. For example, in the first step, firing is performed at 100 ° C. or more and 650 ° C. or less in a mixed gas atmosphere of an inert gas and a reducing gas, and in the second step, firing is performed at 650 ° C. or more and 1200 ° C. or less in an inert gas atmosphere. By doing so, it is possible to obtain solar shading fine particles excellent in solar shading characteristics, which is a preferable configuration. The firing treatment time may be appropriately selected depending on the temperature, but may be 5 minutes or more and 5 hours or less.

The resulting tungsten oxide particles, in the powder colors in the International Commission on Illumination (CIE) recommended to have L ^* a ^* b ^* color system (JIS Z8729), L ^* is 25 to 80, a ^* is -10 to 10 and b ^* are preferably in the range of -15 to 15. The tungsten oxide fine particles having the powder color exhibit a sufficient solar radiation shielding function.

2. Tungsten oxide fine particles 1- (A). 1- (B). The tungsten oxide fine particles obtained by the step are tungsten oxide fine particles represented by the general formula WyOz (where W is tungsten, O is oxygen, 2.2 ≦ z / y ≦ 2.999), or general Tungsten oxide fine particles represented by the formula MxWyOz (where M is the M element, W is tungsten, O is oxygen, 0.001 ≦ x / y ≦ 1, 2.2 ≦ z / y ≦ 3.0) is there.
The tungsten oxide fine particles represented by WyOz are solar radiation shielding fine particles having a characteristic of shielding infrared rays while maintaining high visible light transmittance, and the value of z / y is 2.2 or more. For example, the generation of WO ₂ having no solar radiation shielding function is avoided, and if it is 2.999 or less, sufficient conduction electrons are generated, so that the sufficient solar radiation shielding function is exhibited.

In addition, the tungsten oxide fine particles represented by MxWyOz is preferable if the value of x is 0.001 or more because sufficient conduction electrons are generated, and if it is 1 or less, generation of impurities can be avoided. That is, a sufficient solar radiation shielding function is exhibited in this range. Moreover, if the value of z / y is 2.2 or more, generation of WO ₂ having no solar radiation shielding function can be avoided, and if it is 2.999 or less, sufficient conduction electrons are generated. As a result, a sufficient solar radiation shielding function is exhibited in this range. Here, the element M is alkali metal, alkaline earth metal, rare earth metal, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, 1 selected from Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re It is preferable that it is an element more than a kind. In addition, from the viewpoint of improving the solar radiation shielding characteristics, the metal belonging to the element M is preferably an alkali metal, an alkaline earth metal, or a transition metal. Further, from the viewpoint of improving the weather resistance, a group 3B element or a group 4A element Those belonging to Group 4B elements and Group 5B elements are preferred.

  Moreover, the particle diameter of the tungsten oxide fine particles of the present invention can be appropriately selected depending on the purpose of use of the fine particles. For example, when used for an application that maintains the transparency of the solar shading material, the particle diameter is preferably 800 nm or less. This is because particles having a particle diameter smaller than 800 nm do not completely block light, so that visibility in the visible light region can be maintained, and at the same time, transparency can be efficiently maintained.

  Furthermore, when importance is attached to transparency in the visible light region, it is necessary to consider light scattering by particles. When importance is attached to transparency, the particle diameter is 200 nm or less, preferably 100 nm or less. The reason is that if the particle size of the particles is large, light in the visible light region of 400 nm to 780 nm is scattered by geometrical scattering or Mie scattering, and the appearance of the solar shading material becomes like a frosted glass, and clear transparency is obtained. It is because it becomes difficult to be done. When the particle diameter is 200 nm or less, the scattering is reduced and a Rayleigh scattering region is obtained. In the Rayleigh scattering region, the scattered light decreases in inverse proportion to the sixth power of the particle diameter, so that the scattering is reduced and the transparency is improved as the particle diameter decreases. Furthermore, when the thickness is 100 nm or less, the scattered light is preferably very small. Further, the tungsten oxide fine particles having a particle diameter of 1 nm or more are easy to produce industrially.

  By selecting the particle size described above, the haze value of the solar shading material fine particle dispersion in which the tungsten oxide fine particles are dispersed in the medium can be set to a visible light transmittance of 85% or less and a haze of 30% or less. . If the haze is less than 30%, clear transparency can be obtained. Since the thus obtained tungsten oxide fine particles for forming a sunscreen have the above-mentioned characteristics, they exhibit excellent optical properties as sunscreen fine particles.

3. Sunscreener-forming dispersion The sunscreener-forming dispersion according to the present invention is obtained by mixing and dispersing the sunscreener-forming tungsten oxide fine particles in an appropriate solvent. The said solvent is not specifically limited, What is necessary is just to select suitably according to the said binder, when coating / kneading conditions, application | coating / kneading environment, and also the inorganic binder and the resin binder are contained. For example, water, ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, diacetone alcohol and other alcohols, ethers such as methyl ether, ethyl ether, propyl ether, esters, acetone, methyl ethyl ketone, diethyl ketone, cyclohexanone, isobutyl Various organic solvents such as ketones such as ketones and aromatic hydrocarbons such as toluene can be used. If necessary, pH may be adjusted by adding an acid or an alkali. Furthermore, in order to further improve the dispersion stability of the fine particles in the dispersion, it is of course possible to add various surfactants and coupling agents.

  The characteristics of the dispersion for forming a solar radiation shield according to the present invention can be confirmed by measuring the dispersion state of the tungsten oxide fine particles when the tungsten oxide fine particles are dispersed in a solvent. For example, the sample can be confirmed by sampling a sample from a liquid in which the tungsten oxide fine particles according to the present invention exist in a solvent as particles and agglomerated states of the particles, and measuring with various commercially available particle size distribution analyzers Can do. As the particle size distribution analyzer, for example, ELS-8000 manufactured by Otsuka Electronics Co., Ltd. based on the dynamic light scattering method can be used.

  The dispersed particle diameter of the tungsten oxide fine particles is preferably sufficiently fine and uniformly dispersed to 400 nm or less from the viewpoint of optical characteristics. This is because if the particle size is 400 nm or less, it is possible to prevent the solar shading film and the molded body (plate, sheet, etc.) from becoming a gray type having a monotonously reduced transmittance. In addition, the tungsten oxide fine particles are aggregated to form coarse particles, and if there are a large number of the coarse particles, the coarse particles become a light scattering source, and cloudiness (haze) increases when it becomes a solar shading film or a molded body. Since it may cause a decrease in the visible light transmittance, it is preferable to avoid the generation of coarse particles. In the specification, “dispersed particle size” means “aggregated particle size”.

  The method for dispersing the tungsten oxide fine particles in the solvent is not particularly limited as long as the fine particles are uniformly dispersed in the dispersion, and examples thereof include a bead mill, a ball mill, a sand mill, a paint shaker, and an ultrasonic homogenizer. Through the dispersion treatment process using these equipments, the tungsten oxide particles are dispersed in the solvent, and at the same time, the fine particles are produced by collision of the tungsten oxide particles, and the tungsten oxide particles are further finely dispersed. (That is, it can be pulverized and dispersed).

4). Manufacture of solar radiation shield 4- (A). In the case of application operation The application method in the case of forming a film by applying the dispersion for forming a solar shield on an appropriate transparent substrate is, for example, spin coating, bar coating, spray coating, dip coating. Any method may be used as long as the dispersion can be applied flatly, thinly and uniformly, such as screen printing, roll coating, and flow coating.

  Further, when the dispersion for forming the solar radiation shielding body is a dispersion containing an element such as silicon, zirconium, titanium, or aluminum as an inorganic binder as a metal alkoxide and a hydrolysis polymer thereof, after application of the dispersion The substrate heating temperature is preferably 100 ° C. or higher. By setting the substrate temperature to 100 ° C. or higher, the polymerization reaction of the alkoxide or its hydrolysis polymer contained in the coating film can be completed, and water or an organic solvent remains in the film and is heated. This is because it can be avoided that the visible light transmittance of the film is reduced. Furthermore, for the same reason, when the boiling point of the solvent is 100 ° C. or higher, it is desirable to heat at the boiling point or higher of the solvent.

  Moreover, when the said dispersion liquid for solar radiation shielding body is a dispersion liquid containing a resin binder, what is necessary is just to harden | cure according to the hardening method of each resin, after apply | coating the said dispersion liquid to a base material. For example, if the resin binder is an ultraviolet curable resin, ultraviolet rays may be appropriately irradiated. If the resin binder is a room temperature curable resin, the resin binder may be left as it is after application. For this reason, the dispersion for solar radiation shielding body which has the said structure can be apply | coated to the existing window glass etc. on the spot.

4- (B). In the case of kneading operation When kneading the dispersion for forming the solar shading body into a resin, it is heated and mixed at a temperature near the melting point of the resin (around 200 to 300 ° C.). And after mixing a solar radiation shielding body with resin, this can be pelletized and a file and a board can be formed by each system. As the forming method, for example, an extrusion molding method, an inflation molding method, a solution casting method, a casting method, or the like can be applied. The thickness of the film or board at this time may be appropriately selected according to the purpose of use. The amount of tungsten oxide fine particles added to the resin can be appropriately selected according to the thickness of the base material, required optical characteristics, and mechanical characteristics. It is preferable to set the weight% or less.

  The resin for kneading the solar shading body is not particularly limited and can be selected depending on the application. For example, PET resin, acrylic resin, polyamide resin, vinyl chloride resin, polycarbonate resin, olefin resin, epoxy resin, Examples include polyimide resin, fluororesin, polyethylene, polyvinylidene chloride resin, polyvinyl alcohol resin, ethylene vinyl acetate copolymer, polystyrene resin, polypropylene resin, and polyvinyl butyral resin.

5. The solar shading effect of the solar shading body The solar shading body in which the dispersed particle diameter of the tungsten oxide fine particles is sufficiently fine and uniformly dispersed is 800 nm or less, and the light transmittance has a maximum value at a wavelength of 350 nm to 600 nm and a wavelength of 600 to 1500 nm. When the maximum value and minimum value of transmittance are expressed as percentages, the maximum value (%) − minimum value (%) ≧ 15 (points), that is, the difference between the maximum value and the minimum value is A solar shading body having a characteristic of 5 points or more in percentage is obtained.

  As for the difference between the maximum value and the minimum value of the transmittance in the solar radiation shielding body, the larger the difference value, the better the solar radiation shielding characteristics. This is because the transmission profile of the tungsten oxide fine particles has a maximum value at a wavelength of 350 nm to 600 nm and a minimum value at a wavelength of 600 to 1500 nm, while the visible light wavelength range is 380 nm to 780 nm, and human visibility. Is a bell shape having a peak near 550 nm. That is, it is understood that the solar radiation shielding body according to the present invention having the transmission characteristics effectively transmits visible light and effectively reflects and absorbs other infrared rays.

6). Other In order to further impart an ultraviolet shielding function to the solar radiation shielding body according to the present invention, particles of inorganic titanium oxide, zinc oxide, cerium oxide, etc., one or more of organic benzophenone, benzotriazole and the like are added. It may be added.
Moreover, in order to improve the transmittance | permeability of the solar radiation shielding body which concerns on this invention, you may mix particles, such as ATO, ITO, and aluminum addition zinc oxide. When an appropriate amount of these transparent particles is added to the solar shading body, the transmittance near 750 nm is increased and the infrared ray is shielded, so that a solar shading body having high visible light transmittance and higher solar shading characteristics can be obtained. .

  Moreover, if the dispersion liquid for forming the solar radiation shield according to the present invention is added to the dispersion liquid in which particles such as ATO, ITO, and aluminum-added zinc oxide are dispersed, the tungsten oxide constituting the solar radiation shield according to the present invention is added. Since the film color is blue, it is possible to color the film of ATO, ITO, aluminum-added zinc oxide, etc., and at the same time assist the solar radiation shielding effect. In this case, the solar radiation shielding effect can be assisted by adding only a slight amount of the solar radiation shielding dispersion according to the present invention to ATO, ITO, aluminum-added zinc oxide or the like as the main component. As a result, the required addition amount of ATO, ITO, etc. with high raw material costs can be significantly reduced, and the dispersion cost can be reduced.

In addition, since the formation of the solar shield using the dispersion for forming the solar shield according to the present invention does not use a decomposition reaction of a liquid component due to heat during firing or a chemical reaction, the characteristics are stable. A solar shading body can be formed.
Furthermore, since the tungsten oxide fine particles that exhibit the excellent solar shading effect as described above are inorganic materials, they are superior in weather resistance compared to organic materials, and are used, for example, in areas exposed to sunlight (ultraviolet rays). However, there is almost no deterioration of color and functions. As a result, solar panels, laminated glass, plastics, textiles and other solar radiation used in window materials for vehicles, buildings, offices, ordinary houses, telephone boxes, show windows, lighting lamps, transparent cases, etc. It can be used in a wide range of fields such as a solar radiation shield that requires a shielding function.

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

[Example 1]
A quartz boat containing 50 g of tungstic acid (H ₂ WO ₄ ) was set in a box-type electric furnace and fired in the atmosphere at a temperature of 600 ° C. for 1 hour to obtain a fired powder. Next, the quartz boat containing 20 g of the fired powder is set in a 25 mmφ quartz tubular furnace, heated while supplying 5% H ₂ gas with N ₂ gas as a carrier, and at a temperature of 600 ° C. for 1 hour. The fine particles (a) were obtained by performing the reduction treatment.
Next, 5% by weight of the fine particles (a), 5% by weight of a polymeric dispersant, and 90% by weight of toluene are weighed and pulverized and dispersed for 6 hours in a paint shaker containing 0.3 mmφZrO ₂ beads. A dispersion for forming a solar shading body (Liquid A) was prepared. Here, when the dispersion particle diameter of the tungsten oxide fine particles in the dispersion liquid (A liquid) for solar radiation shielding body measurement was measured, it was 69 nm due to the effect of the pulverization / dispersion treatment.

  Next, 1.6 g of the obtained dispersion (Liquid A), 0.5 g of UV curable resin, and the remaining toluene were weighed, mixed and stirred to prepare a dispersion for solar radiation shielding body (Liquid B). Then, using a bar coater of bar No. 12, a dispersion liquid (B liquid) for forming a solar shading body was applied onto a PET (polyethylene terephthalate) film having a thickness of 50 μm, and then high pressure was applied at 70 ° C. for 1 minute. Irradiation with a mercury lamp gave a solar radiation shield A according to Example 1.

  Here, using a spectrophotometer U-4000 manufactured by Hitachi, Ltd., the visible light transmittance and the solar radiation shielding characteristic were measured as the optical characteristics of the solar radiation shielding body A. The solar shading characteristic evaluation in the measurement is obtained by expressing the transmittance of the solar shading body as a percentage and calculating the difference between the maximum value and the minimum value of the percentage as a point. As a result of measuring the visible light transmittance and the solar shading characteristics of the solar shading body A, the visible light transmittance was 59%, and the difference between the local maximum value and the local minimum value was 41.6 points. This value is shown in FIG.

[Example 2]
The solar shading body B was obtained in the same manner as in Example 1 except that the dispersion liquid for forming the solar shading body (liquid B) prepared in Example 1 was applied onto a PET film using a bar coater of bar No8. .
And with respect to the solar radiation shielding body B, the visible light transmittance and the solar radiation shielding characteristics were measured in the same manner as in Example 1. This value is shown in FIG.

[Example 3]
Barium hydroxide was added to 32.3 g of tungstic acid similar to that in Example 1 and mixed well. The amount of barium hydroxide added was set so that the weight ratio of Ba in barium hydroxide to 0.01 in the tungsten trioxide was 0.01. And fine particle (c) and the solar radiation shielding body C were obtained like Example 1 except having set the mixture 20g in the quartz tubular furnace.
And the visible light transmittance | permeability and the solar radiation shielding characteristic were measured with respect to the solar radiation shielding body C like Example 1. FIG. This value is shown in FIG.

[Example 4]
An aqueous barium nitrate solution was added to 32.3 g of tungstic acid similar to that in Example 1, and heated to 110 ° C. with stirring to evaporate to dryness. The addition amount of the barium nitrate aqueous solution was set so that the weight ratio of Ba in the barium nitrate aqueous solution was 0.01 with respect to the weight of W in tungsten trioxide. And fine particle (d) and the solar radiation shield D were obtained like Example 1 except having set the mixture 20g in the quartz tubular furnace.
And the visible light transmittance | permeability and the solar radiation shielding characteristic were measured with respect to the solar radiation shielding body D like Example 1. FIG. This value is shown in FIG.

[Example 5]
A lanthanum nitrate aqueous solution was added to 32.3 g of tungstic acid as in Example 1, and the mixture was heated to 110 ° C. with stirring and evaporated to dryness. The addition amount of the barium nitrate aqueous solution was set such that the weight ratio of La in the lanthanum nitrate aqueous solution to 0.01 wt% of tungsten in the tungsten trioxide was 0.01. Then, fine particles (e) and solar shield E were obtained in the same manner as in Example 1 except that 20 g of the mixture was set in a quartz tube furnace.
And with respect to the solar radiation shielding body E, the visible light transmittance and the solar radiation shielding characteristic were measured in the same manner as in Example 1. This value is shown in FIG.

[Example 6]
An aqueous copper chloride solution was added to 32.3 g of tungstic acid similar to Example 1, and the mixture was heated to 110 ° C. with stirring and evaporated to dryness. The amount of copper chloride aqueous solution added was such that the weight ratio of Cu in the copper chloride aqueous solution was 0.01 with respect to the weight of W in tungsten trioxide. And the fine particle (f) and the solar radiation shielding body F were obtained like Example 1 except having set the said mixture 20g in the quartz tubular furnace.
And with respect to the solar radiation shielding body F, the visible light transmittance and the solar radiation shielding characteristic were measured in the same manner as in Example 1. This value is shown in FIG.

[Example 7]
An aqueous cerium nitrate solution was added to 32.3 g of tungstic acid similar to that in Example 1, and the mixture was heated to 110 ° C. with stirring and evaporated to dryness. The amount of the cerium nitrate aqueous solution added was such that the weight ratio of Ce in the cerium nitrate aqueous solution to 0.01 wt. And the fine particle (g) and the solar radiation shielding body G were obtained like Example 1 except having set the mixture 20g in the quartz tubular furnace.
And with respect to the solar radiation shielding body G, the visible light transmittance and the solar radiation shielding characteristics were measured in the same manner as in Example 1. This value is shown in FIG.

[Example 8]
Magnesium nitrate aqueous solution was added to 32.3 g of tungstic acid similar to Example 1, and heated to 110 ° C. with stirring to evaporate to dryness. The amount of magnesium nitrate aqueous solution added was such that the weight ratio of Mg in the magnesium nitrate aqueous solution to 0.01 wt. And fine particle (h) and the solar radiation shielding body H were obtained like Example 1 except having set 20 g of the said mixture in the quartz tubular furnace.
And the visible light transmittance | permeability and the solar radiation shielding characteristic were measured with respect to the solar radiation shielding body H like Example 1. FIG. This value is shown in FIG.

[Example 9]
An aluminum nitrate aqueous solution was added to 32.3 g of tungstic acid as in Example 1, and the mixture was heated to 110 ° C. with stirring and evaporated to dryness. The amount of the aluminum nitrate aqueous solution added was such that the weight ratio of Al in the aluminum nitrate aqueous solution to the weight of W in tungstic acid was 0.1. Then, 20 g of the mixture was set in a quartz tubular furnace, and fine particles (i) and a solar shield I were obtained in the same manner as in Example 1 except that a bar coater of bar No. 24 was used.
In addition, it was 150 nm when the dispersion particle diameter was measured. And with respect to the solar radiation shielding body I, the visible light transmittance and the solar radiation shielding characteristic were measured in the same manner as in Example 1. This value is shown in FIG.

[Example 10]
A silver nitrate aqueous solution was added to 32.3 g of tungstic acid similar to that in Example 1, and the mixture was heated to 110 ° C. with stirring and evaporated to dryness. The amount of silver nitrate aqueous solution added was such that the weight ratio of Ag in the silver nitrate aqueous solution was 0.05 with respect to the weight of W in tungstic acid. And fine particle (j) and the solar radiation shield J were obtained like Example 1 except having set the said mixture 20g in the quartz tubular furnace.
And the visible light transmittance | permeability and the solar radiation shielding characteristic were measured with respect to the solar radiation shielding body J like Example 1. FIG. This value is shown in FIG.

[Example 11]
In Example 1, the fine particles (k) and solar shield K are the same as in Example 1 except that 5% H ₂ gas using N ₂ gas supplied to the quartz tube furnace as a carrier is replaced with N ₂ gas alone. And got.
And the visible light transmittance | permeability and the solar radiation shielding characteristic were measured with respect to the solar radiation shielding body K like Example 1. FIG. This value is shown in FIG.

[Comparative Example 1]
In Example 1, the fine particles (l) and the solar radiation shield L were obtained in the same manner as in Example 1 except that 5% H ₂ gas using N ₂ gas supplied to the quartz tube furnace as a carrier was replaced with air. It was.
And the visible light transmittance | permeability and the solar radiation shielding characteristic were measured with respect to the solar radiation shielding body L like Example 1. FIG. This value is shown in FIG.

[Example 12]
Using the same tungstic acid as in Example 1, heating was performed while supplying 5% H ₂ gas with N ₂ gas as an atmosphere, and a reduction treatment was performed at a temperature of 600 ° C. for 1 hour to obtain fine particles (a). Obtained. Next, the fine particles (a) are treated with N ₂ gas at a temperature of 800 ° C. for 1 hour, and after the treatment, the obtained object is pulverized and dispersed with a paint shaker for 3 hours. To obtain fine particles (m). A solar radiation shield M was obtained in the same manner as in Example 1 except that the fine particles (m) were used.
And the visible light transmittance | permeability and the solar radiation shielding characteristic were measured with respect to the solar radiation shielding body M like Example 1. FIG. This value is shown in FIG.

[Example 13]
In Example 12, as a bar coater, bar no. Except that 8 was used, a solar radiation shield N was obtained in the same manner as in Example 12.
And with respect to the solar radiation shielding body N, the visible light transmittance and the solar radiation shielding characteristics were measured in the same manner as in Example 1. This value is shown in FIG.

[Example 14]
In Example 12, as a bar coater, bar no. Except having used 16, the solar radiation shielding body O was obtained like Example 12. FIG.
Then, the visible light transmittance and the solar radiation shielding characteristics were measured for the solar radiation shielding body O in the same manner as in Example 1. This value is shown in FIG.

[Example 15]
2.8 g of Snotex N (manufactured by Nissan Chemical Industries, Ltd.) was added to 54.2 g of H ₂ WO ₄ and sufficiently stirred, and then dried. The dried product was heated while supplying 2% H ₂ gas with N ₂ gas as a carrier and baked at a temperature of 800 ° C. for 30 minutes, and then the gas was switched to N ₂ gas, and further 90 ° C. at the same temperature. Fine particles n were obtained by baking for a minute. Powder color of the microparticles n is, L ^* is 35.4446, a ^* is 2.0391, b ^* is -7.4738, result of identification of the crystal phase by powder X-ray _{diffraction, Si 0.043} WO _{2 839} single phase. A solar radiation shield P was obtained in the same manner as in Example 1 except that the fine particles n were prepared as described above and used.
And the visible light transmittance | permeability and the solar radiation shielding characteristic were measured with respect to the solar radiation shielding body P like Example 1. FIG. This value is shown in FIG.

[Example 16]
10.8 g of Cs ₂ CO ₃ was dissolved in 16.5 g of water, the solution was added to 50 g of H ₂ WO _{4, and the} mixture was sufficiently stirred and then dried. The dried product is heated while supplying 2% H ₂ gas using N ₂ gas as a carrier, baked at a temperature of 800 ° C. for 30 minutes, then switched to the gas N ₂ gas, and baked at the same temperature for another 90 minutes. Thus, fine particles o were obtained. The powder color of the fine particles o is 37.4562 L ^* , −0.3485 a ^* , and −4.6939 b ^*. As a result of identifying the crystal phase by powder X-ray diffraction, Cs _0.33 WO _{There were 3} single phases. A solar shading body Q was obtained in the same manner as in Example 1 except that the fine particles o were prepared as described above and used.
And the visible light transmittance | permeability and the solar radiation shielding characteristic were measured with respect to the solar radiation shielding body Q like Example 1. FIG. This value is shown in FIG.

[Example 17]
After adding 9.8 g of Cs ₂ CO ₃ to 100 g of water and adding 2.4 g of SNO-TEX N (Nissan Chemical Co., Ltd.) to 45.3 g of H ₂ WO ₄ and stirring sufficiently , Dried. The dried product was heated while supplying 2% H ₂ gas with N ₂ gas as a carrier, and baked at a temperature of 800 ° C. for 30 minutes. Then, the gas was switched to N ₂ gas, and the temperature was further changed to 90 minutes. The fine particles p were obtained by firing. Powder color of the fine particles p is, L ^* is 41.1780, a ^* is -1.6699, b ^* is -8.5722, result of identification of the crystal phase by powder X-ray diffraction, _{Cs 0.33} WO _{There were 3} single phases. A solar radiation shield R was obtained in the same manner as in Example 1 except that the fine particles p were prepared as described above and used.
And with respect to the solar radiation shield R, the visible light transmittance and the solar radiation shielding characteristic were measured in the same manner as in Example 1. This value is shown in FIG.

As is clear from the results shown in FIG. 1, in the solar shields AK and MR according to Examples 1 to 17, the solar shield characteristics evaluated by the difference between the maximum value and the minimum value of the transmittance are as follows: All were 15 points or more in percentage. On the other hand, in the solar radiation shielding body L which concerns on the comparative example 1, the said solar radiation shielding characteristic was less than 15 points.
From the above, the solar radiation shield prepared from the tungsten oxide fine particles obtained by the production method according to the present invention that is easy and low in production cost is the percentage difference between the maximum value and the minimum value of the transmittance. It was found to have excellent optical properties of 15 points or more.

It is a measurement result table | surface of the optical characteristic of the solar radiation shield which concerns on this invention.

Claims (3)

Baking tungstic acid (H ₂ WO ₄ ) or a mixture of tungstic acid (H ₂ WO ₄ ) and tungsten trioxide fine particles in an inert gas or a mixed gas atmosphere of an inert gas and a reducing gas. According to general formula WyOz (W is tungsten, O is oxygen, 2.2 ≦ z / y ≦ 2.999), tungsten oxide fine particles having a particle diameter of 1 nm to 800 nm are generated. The manufacturing method of the tungsten oxide microparticles | fine-particles for solar radiation shielding body to perform. Tungstic acid (H ₂ WO ₄ ), or a mixture of tungstic acid (H ₂ WO ₄ ) and tungsten trioxide fine particles, and an oxide or / and hydroxide of M element (where M is an alkali metal, an alkali Earth metal, rare earth element, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge , Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re)) powder,
Or / and tungstic acid (H ₂ WO ₄ ), or a mixture of tungstic acid (H ₂ WO ₄ ) and tungsten trioxide fine particles, and an aqueous solution of a metal salt, a colloidal solution of a metal oxide of the M element, alkoxy A dry powder obtained by mixing and drying at least one selected from solutions is baked in an atmosphere of an inert gas or a mixed gas of an inert gas and a reducing gas to obtain a general formula MxWyOz ( However, M is the M element, W is tungsten, O is oxygen, 0.001 ≦ x / y ≦ 1, 2.2 ≦ z / y ≦ 3.0), and tungsten having a particle diameter of 1 nm to 800 nm A method for producing tungsten oxide fine particles for forming a solar radiation shielding body, characterized by producing oxide fine particles. The L ^* a ^* b ^* color system produced by the method for producing a tungsten oxide fine particle for forming a solar shading body according to claim 2 and whose powder color is recommended by the International Commission on Illumination (CIE) ( In the powder color in JIS Z8729), solar radiation is characterized in that L ^* is 25 to 80, a ^* is -10 to 10, b ^* is -15 to 15 and has a particle diameter of 1 nm to 800 nm. Tungsten oxide fine particles for shielding formation.

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