JP2006193670A - Hexaborate particulate coated with silica film, method for producing the same, coating liquid for optical component produced by using the particulate and optical component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide hexaborate particulate having improved moisture resistance, free from the deterioration of properties and suitable as a sun screening material, etc., a coating liquid for optical components produced by using the particulate and a sun screening optical component. <P>SOLUTION: The particulate is produced by forming a primary coating film on the surface of a hexaborate particulate with a surface-modifying agent such as a silane coupling agent and forming a secondary coating film composed mainly of silica by using a silicic acid compound. The silica-coated hexaborate particulate has a nearly spherical form and excellent moisture resistance. The sun screening optical component is produced by coating a substrate with a coating liquid containing the silica-coated hexaborate particulate dispersed in the liquid or dispersing the silica-coated hexaborate particulate in a liquid medium or a solid medium and forming in the form of a film or a board. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hexaboride fine particle coated with a silica film suitable as a solar shading material, a method for producing the same, a coating solution for an optical member using the same, and an optical member for solar shading.

Conventionally, as a solar radiation shielding film that removes and reduces heat components from sunlight, metal oxides and metal thin films that reflect visible and infrared wavelengths are formed on the surface of resin films and glass. It was. As the solar shading material used for such a solar shading film, in inorganic systems, metal oxides such as FeO _x , CoO _x , CrO _x , TiO _x, and metals having a large amount of free electrons such as Ag, Au, and aluminum Material was used. Moreover, in the organic type, there are a phthalocyanine type and a metal complex type, and those added to the resin binder are often used.

  However, the above-described conventional inorganic solar radiation shielding material has a property of reflecting or absorbing light in the visible light region at the same time, in addition to the near infrared ray that greatly contributes to the thermal effect, particularly with sunlight. For this reason, there is a drawback in that a lustrous appearance such as a mirror is given and the aesthetic appearance is impaired, and the visible light transmittance is lowered.

  In particular, transparent substrates used in houses, buildings, vehicles, etc. require high transmittance in the visible light region, so when using inorganic solar shading materials, the operation is to make the film thickness very thin. Is required. Therefore, it has been necessary to form a very thin film of 10 nm level using a physical film forming method such as spray baking, CVD, sputtering, or vacuum deposition. For this reason, a large-scale apparatus and vacuum equipment are required, resulting in high film formation costs, difficulty in increasing the area, and inferior productivity.

  In addition, these inorganic solar shading materials often have high film conductivity, making it impossible to receive by reflecting radio waves from mobile phones, TV reception, car navigation systems equipped with antennas in the car, There was a fault that caused radio interference in the surrounding area.

  On the other hand, the above-mentioned conventional organic solar shading materials are significantly deteriorated by heat and humidity as compared with inorganic materials, and have a fatal defect in moisture resistance. In addition, when the visible light transmittance is increased, the solar shading characteristic is lowered, and conversely, when the solar shading characteristic is increased, the visible light transmittance is lowered.

  Other solar radiation shielding materials include antimony-containing tin oxide (ATO) and tin-containing indium oxide (ITO), which have relatively low light absorption / reflectance in the visible light region and high transparency to the human eye. There is an advantage. However, since the solar radiation shielding power per unit mass is low and a large amount of material is required to obtain a sufficient solar radiation shielding effect, the solar radiation shielding film using this is very expensive. In particular, since ATO has a low free electron concentration, it has a weak near-infrared shielding power and insufficient solar radiation shielding properties. In addition, even when an ATO or ITO solar shielding film is formed by a physical film forming method, there is a drawback that the conductivity of the film is increased and the radio wave is disturbed by reflection.

As a method for solving the drawbacks of the above-mentioned conventional solar shading material, Japanese Patent Application Laid-Open No. 2000-169765 discloses a light transmittance in the visible region that is high and a reflectance that is low, and a light transmittance in the near infrared region. However, it is described that the hexaboride which has a low amount of free electrons and has a large amount of free electrons is focused on and used in combination with ATO or ITO. According to this method, the solar shading characteristics are improved compared to using each material alone, the amount of ATO or ITO used is reduced, the material cost is reduced, and the surface resistance value is 10 ⁶ Ω / □ or more. There is an advantage that a controllable film can be formed by a simple coating method.

  However, it is known that the surface of the hexaboride particles is decomposed by water vapor or moisture in the air. In particular, since the surface area is increased with respect to the volume in the state of fine particles, the surface of the hexaboride fine particles is easily decomposed with water vapor or moisture, and the ratio of changing to oxides or hydroxide compounds is large. As a result, there was a drawback that the original characteristics of hexaboride gradually deteriorated. For example, in a coating film using hexaboride fine particles and the like, when applied to an application that shields light in the near infrared region using its optical characteristics, the transmittance in the 200 to 2600 nm region is affected by the influence of water vapor and moisture. It is known that the solar radiation shielding performance gradually deteriorates.

  As a method for preventing this, Japanese Patent Application Laid-Open No. 2004-043764 describes surface treatment of hexaboride fine particles with amorphous silica. Further, hexaboride fine particles surface-treated with amorphous silica are further bonded together with amorphous silica as a binder to grow into particles of about 1 to 100 μm, and then the particles are pulverized to obtain an average particle size. It is also disclosed to make 0.1-30 μm hexaboride composite particles. However, it is difficult to completely suppress the decomposition of hexaboride by water vapor or moisture, and it is also difficult to maintain moisture resistance because the silica film is broken during pulverization.

JP 2000-169765 A JP 2004-043764 A

  The present invention has been made in view of the above-described conventional circumstances, and provides hexaboride fine particles that are excellent in moisture resistance and have no deterioration in solar shading properties, and a coating liquid for optical members using the same. An object of the present invention is to provide an optical member.

  In order to achieve the above-mentioned object, the present invention has, on the surface of hexaboride fine particles, a primary coating film by a surface modifier and a secondary coating film mainly composed of silica on the primary coating film, The present invention provides a silica film-coated hexaboride fine particle characterized by having a substantially spherical outer shape.

  In the above-described silica film-coated hexaboride fine particles of the present invention, the hexaboride fine particles are Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu. It is preferably a hexaboride of at least one element selected from the group consisting of Sr, Ca. The hexaboride fine particles preferably have a particle diameter of 2 nm to 10 μm.

  In the silica film-coated hexaboride fine particles of the present invention, the total thickness of the primary coating film and the secondary coating film is preferably 1 to 100 nm. The surface modifier is preferably a silane coupling agent.

  In the above-described method for producing silica film-coated hexaboride fine particles of the present invention, a surface modifier is added to a liquid in which hexaboride fine particles are dispersed to form a primary coating film with the surface modifier on the particle surface, and then A secondary coating film mainly composed of silica is formed on the primary coating film by adding an acid compound and subjecting it to hydrolysis polymerization.

  In the method for producing silica film-coated hexaboride fine particles of the present invention, the surface modifier is a silane coupling agent, and the ratio of the surface modifier to the hexaboride fine particles is 6 boron in terms of silicon contained in the silane coupling agent. It is preferable that it is 0.01-10 weight part with respect to 1 weight part of compound fine particles. Moreover, it is preferable that the ratio with respect to the hexaboride microparticles | fine-particles of the said silicate compound is 0.01-100 weight part with respect to 1 weight part of hexaboride microparticles | fine-particles in conversion of the silicon contained in a silicate compound.

  The present invention also provides a coating solution for an optical member, wherein the silica film-coated hexaboride fine particles of the present invention are dispersed in a liquid. In the optical member coating solution, the liquid is preferably an organic solvent and / or water, or an organic solvent and / or water in which at least one of a resin and a metal alkoxide is dissolved or dispersed.

  The present invention provides an optical member, the first of which is characterized in that the optical member coating liquid of the present invention described above is applied to a substrate surface and cured. This optical member is also characterized in that a coating film comprising a dispersion for an optical member in which the above-described silica film-coated hexaboride fine particles of the present invention are dispersed in a solid medium is formed on the surface of the substrate. It is.

  Furthermore, the second optical member of the present invention is composed of a dispersion for an optical member in which the above-described silica film-coated hexaboride fine particles of the present invention are dispersed in a solid medium, and is formed into a film or a board. And

  In the second optical member, it is preferable that the solid medium is either resin or glass. Moreover, it is preferable that the thickness of the film or board which consists of the said optical dispersion is 0.1 micrometer-50 mm.

  In the third optical member of the present invention, a dispersion for an optical member in which the above-described silica film-coated hexaboride fine particles of the present invention are dispersed in a liquid medium is enclosed between a film or a board. It is a feature.

  According to the present invention, a coating film is formed by first forming a thin primary coating film with a surface modifier on the surface of hexaboride fine particles and then forming a secondary coating film of silica using a silicate compound. In some cases, aggregation between particles does not occur, and silica film-coated hexaboride particles having a substantially spherical outer shape centered on hexaboride particles whose surface is completely covered with a uniform silica film can be obtained.

  The hexaboride fine particles with a substantially spherical silica film covering the outer shape are not only completely coated with a silica film having a uniform surface, but also have high dispersibility, so that pulverization is unnecessary or light pulverization is required. Since the shape is smooth and approximately spherical, the silica film is not damaged. Therefore, the moisture resistance of hexaboride fine particles is dramatically improved, and silica film-coated hexaboride fine particles having excellent moisture resistance suitable as a solar radiation shielding material, and an optical member coating solution and an optical member using the same are provided. can do.

As described above, the hexaboride fine particles having solar radiation shielding characteristics have a problem that the surface changes to oxide or hydroxide due to moisture in the air and the like, and the original characteristics of hexaboride deteriorate. Therefore, attempts have been made to improve the moisture resistance of the hexaboride fine particles by physically or chemically coating the surface of the hexaboride fine particles with a surface treatment agent. For example, as described in the above-mentioned JP-A-2004-043764, hexaboride fine particles are directly applied to No. 3 sodium silicate (SiO ₂ content: 28.5%), tetraethyl silicate, tetramethyl silicate, tetrapropyl. There is a method of hydrolyzing a silicic acid compound such as silicate, tetraalkyl silicate such as tetrabutyl silicate, or a partial condensate thereof, and coating with amorphous, amorphous silica.

  However, the hexaboride fine particles coated with silica by such a method have poor dispersibility, and there is a problem that the particles are aggregated and bound at the time of coating. Therefore, when the bound particles are pulverized in order to obtain optical characteristics, the silica coating layer is broken, resulting in deterioration of moisture resistance. Further, since the silica adhering to the surface of the hexaboride fine particles is not smooth and has a rough coating film, it is easy to impregnate moisture, and it is difficult to obtain satisfactory moisture resistance.

  In the present invention, a thin primary coating film is previously formed on the surface of hexaboride fine particles with a surface modifier such as a silane coupling agent, and then a round secondary coating mainly composed of silica with a silicate compound. A film is formed. According to this method, aggregation between particles does not occur during coating, and the surface of hexaboride fine particles can be covered with a uniform silica film while maintaining high dispersibility. Therefore, the pulverization for removing the agglomeration is unnecessary or light pulverization, and since the shape is smooth and the outer shape is substantially spherical, the silica film is hardly damaged and the moisture resistance is remarkably improved.

  The silica film-coated hexaboride fine particles according to the present invention have a primary coating film made of a surface modifier and a secondary coating film mainly composed of silica on the surface of the hexaboride fine particles, and the outer shape is substantially spherical. . The total thickness of the primary coating film and the secondary coating film on the surface of the hexaboride fine particles is preferably in the range of 1 to 100 nm. If the film thickness is thinner than 1 nm, the moisture resistance is lowered, and conversely if it exceeds 100 nm, aggregation tends to occur, which is not preferable. A transmission electron microscope (abbreviated as TEM) photograph of silica film-coated hexaboride fine particles having a substantially spherical outer shape according to the present invention is shown in FIG.

  The silica film-coated hexaboride fine particles according to the present invention have solar radiation shielding properties derived from the electronic structure unique to hexaboride. That is, since hexaboride has plasmon resonance of free electrons particularly near 1000 nm, light (near infrared rays) in this region is broadly absorbed and reflected. At the same time, since there is little absorption in the visible light region of 380 to 780 nm, it is suitable for use as an optical member that transmits visible light and blocks near infrared light. Accordingly, the heat insulating optical filter to which the silica film-coated hexaboride fine particles of the present invention are applied can be applied to, for example, houses and automobile window materials, greenhouses, etc., thereby shielding the near infrared rays around 1000 nm of sunlight. A high heat insulating effect is obtained, and at the same time, visibility is ensured.

In addition, the usage-amount of the silica film coating | coated hexaboride microparticles | fine-particles in optical members, such as an optical filter for heat insulation, can be suitably changed with the characteristic calculated | required. Specifically, in the case of an adiabatic optical filter that transmits the visible light region and shields near infrared rays, for example, in LaB ₆ , an effective heat insulation effect is obtained when the filler amount per 1 m ² is 0.01 g or more. The upper limit of the amount used can be appropriately determined according to the required optical characteristics, but it is possible to absorb and shield about 50% of the solar energy at 0.1 g per m ² , so that the heat insulation efficiency in unit weight Is excellent.

  The hexaboride fine particles used in the present invention may be conventionally known for solar radiation shielding, but Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm It is preferably a hexaboride of at least one element selected from the group consisting of Yb, Lu, Sr, and Ca.

  The particle diameter of the hexaboride fine particles is appropriately set within the range of 2 nm to 10 μm depending on the purpose of optical use. For example, when importance is attached to transparency such as an optical selective transmission film (a film that transmits light in the visible light region and shields light in the near infrared region), the particle size of the hexaboride fine particles is preferably 200 nm or less, preferably Is 100 nm or less. The reason is that when the particle diameter exceeds 200 nm, the light in the visible light region of 380 to 780 nm is scattered by geometrical scattering or Mie scattering to become a frosted glass, and clear transparency cannot be achieved. .

  When the particle size of the hexaboride fine particles 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 transparency improves as the particle diameter decreases. Further, when the thickness is 100 nm or less, the scattered light is extremely reduced and the transmittance is further improved. However, since transparency may not be required depending on the application, it may be appropriately set within a range of 2 nm to 10 μm. Fine particles having a particle size smaller than 2 nm are difficult to obtain because the hexaboride is hard, and if the particle size exceeds 10 μm, it is difficult to form a smooth film, which is not preferable.

  In the method of the present invention, it is preferable to use a wet method in order to sequentially form a primary coating film with a surface modifier and a secondary coating film mainly composed of silica on the surface of hexaboride fine particles. According to this method, hexaboride fine particles are dispersed in a liquid, a surface modifier is added therein to coat the surface of the hexaboride fine particles with a monomolecular layer, and then a silicate compound is added, By the hydrolysis polymerization, it is possible to form a coating film mainly composed of amorphous or amorphous silica.

  The surface modifier for forming the primary coating film may be any one that chemically or physically coats the surface of the hexaboride fine particles. Among them, an organosilicon compound having a functional group chemically bonded to an inorganic substance and an organic substance in one molecule, such as a silane coupling agent, is preferable. Preferred silane coupling agents include amino, ureido, epoxy, isocyanate, vinyl, methacrylic, mercapto and the like.

  The ratio of the silane coupling agent to the hexaboride fine particles is preferably 0.01 to 10 parts by weight with respect to 1 part by weight of the hexaboride fine particles in terms of silicon contained in the silane coupling agent. This is because if the ratio of the silane coupling agent is less than 0.01 parts by weight, the effect of forming the primary coating film by the coupling agent cannot be obtained, and if it exceeds 10 parts by weight, aggregation tends to occur.

As the silicate compound for forming the secondary coating film, No. 3 sodium silicate (SiO ₂ content: 28.5%), tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxy Silane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, alkoxysilane such as dimethyldiethoxysilane, or a partial condensate thereof can be used. Here, alkoxysilane such as tetraethoxysilane is the same substance as tetraalkyl silicate such as tetraethyl silicate described in JP-A-2004-043764.

The secondary coating film mainly composed of silica is formed by hydrolysis polymerization of the silicate compound. For example, in the hydrolysis polymerization of tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) and water (H ₂ O), the ethoxy group is gradually removed as ethanol, and Si—O—H bonds to each other to form Si. A -O-Si structure is formed. By this hydrolysis polymerization, a secondary coating film mainly composed of amorphous or amorphous silica is formed. In order to control this hydrolysis polymerization reaction, an acid such as HCl or HNO ₃ or an alkali such as NH ₄ OH can be added as a catalyst.

  The ratio of the silicate compound to the hexaboride fine particles is preferably in the range of 0.01 to 100 parts by weight with respect to 1 part by weight of the hexaboride fine particles in terms of silicon contained in the silicate compound. This is because if the ratio of the silicate compound is less than 0.01 parts by weight, it is difficult to form a secondary coating film, and conversely if it exceeds 100 parts by weight, aggregation between particles occurs.

  The surface modifier described above efficiently covers the surface of the hexaboride fine particles in the liquid to form a primary coating film and prevents aggregation of the hexaboride fine particles in the liquid. At the same time, the primary coating film promotes the silica precursor to be preferentially formed on the surface of the hexaboride fine particles during the hydrolysis polymerization of the silicate compound during the formation of the secondary coating film. Suppressing the use of the body on surfaces other than the surface, for example, forming silica single particles in a liquid or binding between hexaboride fine particles.

  That is, the surface modifier becomes the silica-forming nuclei of the silica precursor to form silica on the surface of the hexaboride fine particles, which further becomes the next nuclei only on the surface of the hexaboride fine particles from the silica precursor one after another. Nucleation occurs and a secondary coating of silica is formed. As a result, the formation of single silica particles from the silica precursor and the formation of bridging silica between the particles leading to the binding between the particles can be suppressed. Further, when a silica coating film is formed on the surface of the hexaboride fine particles, the electric repulsive force between the particles is increased as compared with the bare hexaboride fine particles, and aggregation is less likely to occur.

  The thus obtained silica film-coated hexaboride fine particles having a substantially spherical outer shape are used as raw materials for solar shading products or the like as they are or after heat drying. In particular, the heat treatment is advantageous in that the silica film becomes dense and the moisture resistance is further improved. The heat treatment temperature is determined by the heat resistance temperature of the hexaboride and the heating atmosphere, but in an atmosphere in which oxygen exists, particularly in the air, hexaboride is oxidized from around 600 ° C., so in an atmosphere in which oxygen exists. It is preferable that the temperature be 600 ° C. or lower.

  Next, an optical member for solar radiation shielding using the silica film-coated hexaboride fine particles of the present invention will be described. First, as one means for producing an optical member such as a solar shading product, there is a coating solution for an optical member in which silica film-coated hexaboride fine particles are dispersed in a liquid. The liquid for dispersing the silica film-coated hexaboride fine particles is preferably an organic solvent such as alcohol and / or water, or an organic solvent and / or water in which at least one of resin and metal alkoxide is dissolved or dispersed. . As a resin component, what is necessary is just to select according to a use, and ultraviolet curable resin, thermosetting resin, normal temperature curable resin, a thermoplastic resin etc. can be used.

  By applying this optical member coating solution to the substrate surface and curing, a coating film of the optical member dispersion in which the silica film-coated hexaboride fine particles are dispersed in a solid medium can be formed. For example, when the optical member coating solution contains a resin or a metal alkoxide, the coating solution is applied to the substrate surface, and the solvent such as an organic solvent or water is evaporated, and the resin or the metal alkoxide is cured, An optical member having a coating film in which silica film-coated hexaboride fine particles are dispersed in a solid medium on the surface of the substrate can be easily produced.

  Further, when the coating liquid for optical members does not contain a resin and a metal alkoxide, a film in which silica film-coated hexaboride fine particles are deposited on the surface of the substrate is obtained by evaporating a solvent such as an organic solvent or water after coating. It is formed. In this case, an optical member similar to the above can be obtained by laminating silica film-coated hexaboride particles on the surface of the substrate and then applying a liquid medium containing a component such as a resin. In addition, another base material may be superposed on the silica film-coated hexaboride fine particle layer deposited on the base material surface.

  Here, the moisture resistance of the coating film in which the silica film-coated hexaboride fine particles are dispersed in the solid medium is improved by heat treatment later. In particular, when silica film-coated hexaboride fine particles that have not been subjected to heat treatment in advance are applied, the heat treatment makes the coating dense and further improves moisture resistance. As described above, the heat treatment temperature is determined by the heat resistance temperature of the hexaboride and the heating atmosphere. However, in an atmosphere where oxygen exists, particularly in the air, the temperature is set to 600 ° C. or less in order to prevent oxidation of the hexaboride fine particles. preferable.

  As another type of optical member, there is one in which a dispersion for an optical member in which the silica film-coated hexaboride fine particles of the present invention are dispersed in a solid medium is formed into a film or a board. The film or board in which the silica film-coated hexaboride fine particles are dispersed in a solid medium preferably has a thickness in the range of 0.1 μm to 50 mm. This is because if the thickness of the film or board is less than 0.1 μm, the strength becomes weak, and if it exceeds 50 mm, the processing becomes difficult.

  As the solid medium serving as a base of the film or board, resin or glass is preferable. The resin to be used is not particularly limited and can be selected in accordance with the intended use. However, considering moisture resistance, a fluororesin is effective. In addition, low-cost, high-transparency, and versatile resins compared to fluororesins include PET resin, acrylic resin, polyamide resin, vinyl chloride resin, polycarbonate resin, olefin resin, epoxy resin, and polyimide resin. Can be mentioned.

  As a method for producing an optical member composed of a film or board in which the silica film-coated hexaboride fine particles are dispersed in a solid medium, for example, the silica film-coated hexaboride fine particles are directly kneaded into a resin to form a film or board shape. The method of forming into a general shape is common. Alternatively, a dispersion in which silica film-coated hexaboride fine particles are dispersed in a liquid medium may be mixed with a resin, or a powdery dispersion in which silica film-coated hexaboride fine particles are dispersed in a solid medium may be used as the liquid medium. It is also possible to add and further mix with the resin.

  Generally, when kneading into a resin, it is heated and mixed at a temperature near the melting point of the resin (for example, around 200 to 300 ° C.). It is also possible to form a film or a board after mixing with resin and pelletizing. For example, it is possible to mold by an extrusion molding method, an inflation molding method, a solution casting method, a casting method or the like. The amount of filler relative to the resin, that is, the blending amount of the silica film-coated hexaboride fine particles can be changed according to the thickness of the film or board, the required optical properties and mechanical properties, 50 weight% or less is preferable.

  Furthermore, the optical member dispersion in which the silica film-coated hexaboride fine particles are dispersed in a liquid medium may be enclosed between a film or a board to form an optical member. The film or board in this case may also be resin or glass.

  The present invention will be specifically described below, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, the average dispersed particle diameter is an average value measured by a measuring device using a dynamic light scattering method (ELS-800, manufactured by Otsuka Electronics Co., Ltd.).

The visible light transmittance is an integrated value of the amount of transmitted light obtained by normalizing the amount of transmitted light in the wavelength region 380 to 780 nm with the visibility of the human eye, and is a value that represents the brightness perceived by the human eye. . Visible light transmittance is JISA
It was measured by a method according to 5759 (however, it was measured only with a film without being attached to glass). The haze value of the film was measured based on JIS K 7105.

  Furthermore, the evaluation method of moisture resistance is that a sample having a visible light transmittance of 60% to 70% and having an increase in transmittance of 1% or less when stored in an environment of 60 ° C. and 90% humidity for 3000 hours is regarded as good. Those exceeding 1% were regarded as defective.

[Example 1]
16 g of LaB ₆ fine particles having an average particle size of 80 nm are stirred and mixed with 1 g of γ-aminopropyltriethoxysilane as a silane coupling agent and 783 g of water, and γ-aminopropyltriethoxysilane is adsorbed on the surface of LaB ₆ fine particles. Modified. Next, after removing water with a centrifugal separator, 90 g of tetraethoxysilane was added to a mixed solvent of LaB ₆ fine particles with surface modification, 560 g of ethanol and 140 g of water, and silica was added to the surface of LaB ₆ fine particles by hydrolysis polymerization. A coating film was formed.

Then, after removing alcohol and water with a centrifuge, it was dried and further subjected to heat treatment at 450 ° C. for 30 minutes to obtain silica film-coated lanthanum hexaboride fine particles. As a result of TEM observation of the obtained silica film-coated lanthanum hexaboride fine particles, a silica-coated film having a thickness of about 20 nm was formed on the surface of monodispersed LaB ₆ fine particles, and the outer shape was substantially spherical. Observed.

  Since the substantially spherical silica film-coated lanthanum hexaboride fine particles were monodispersed, no particular pulverization was performed. This silica film-coated lanthanum hexaboride fine particle is 5% by weight, an organic polymer dispersant (made of an acrylic polymer, not containing an inorganic component) is 2% by weight, an ultraviolet curable resin (manufactured by Toagosei Co., Ltd., UV3701). Was mixed in toluene so as to be 26% by weight to prepare a coating solution. This coating solution was applied onto a 50 μm thick PET film using a bar coater, dried at 70 ° C. for 1 minute to evaporate the solvent, and then irradiated with ultraviolet rays from a high pressure mercury lamp to cure the coating.

  The total visible light transmittance of the obtained coating film and PET film was 65.6%, and the haze value was 1.4%. Further, after storing this film in an environment of 90% humidity at 60 ° C. for 3000 hours, the visible light transmittance was measured to be 65.7%, the increase in visible light transmittance was 0%, and the moisture resistance was extremely high. It was good.

[Example 2]
Silica film-coated lanthanum boride fine particles were obtained in the same manner as in Example 1 except that γ-aminopropyltrimethoxysilane was used as the silane coupling agent. As a result of TEM observation of the obtained silica film-coated lanthanum hexaboride fine particles, a silica-coated film having a thickness of about 20 nm was formed on the surface of monodispersed LaB ₆ fine particles, and the outer shape was substantially spherical. Observed.

Since the silica film-coated LaB ₆ fine particles were monodispersed, no particular pulverization was performed. Using this silica film-coated lanthanum hexaboride fine particles, a coating solution was prepared in the same manner as in Example 1. Further, a coating film was formed on the PET film using this coating solution in the same manner as in Example 1.

  The total visible light transmittance of the obtained coating film and PET film was 66.1%, and the haze value was 1.4%. The film was stored in an environment of 90% humidity at 60 ° C. for 3000 hours, and the visible light transmittance was measured to be 66.1%. The increase in visible light transmittance was 0% and the moisture resistance was extremely high. It was good.

[Example 3]
Silica film-coated lanthanum hexaboride fine particles were obtained in the same manner as in Example 1 except that γ-mercaptopropyltrimethoxysilane was used as the silane coupling agent. As a result of TEM observation of the obtained silica film-coated lanthanum hexaboride fine particles, a silica-coated film having a thickness of about 20 nm was formed on the surface of monodispersed LaB ₆ fine particles, and the outer shape was substantially spherical. Observed.

Since the silica film-coated LaB ₆ fine particles were monodispersed, no particular pulverization was performed. Using this silica film-coated lanthanum hexaboride fine particles, a coating solution was prepared in the same manner as in Example 1. Further, a coating film was formed on the PET film using this coating solution in the same manner as in Example 1.

  The total visible light transmittance of the obtained coating film and PET film was 65.3%, and the haze value was 1.4%. The film was stored at 60 ° C. in a 90% humidity environment for 3000 hours, and its visible light transmittance was measured to be 65.3%. The increase in visible light transmittance was 0% and the moisture resistance was extremely high. It was good.

[Example 4]
Silica film-coated lanthanum hexaboride fine particles were obtained in the same manner as in Example 1 except that γ-glycidoxypropyltrimethoxysilane was used as the silane coupling agent. As a result of TEM observation of the obtained silica film-coated lanthanum hexaboride fine particles, a silica-coated film having a thickness of about 20 nm was formed on the surface of monodispersed LaB ₆ fine particles, and the outer shape was substantially spherical. Observed.

Since the silica film-coated LaB ₆ fine particles were monodispersed, no particular pulverization was performed. Using this silica film-coated lanthanum hexaboride fine particles, a coating solution was prepared in the same manner as in Example 1. Further, a coating film was formed on the PET film using this coating solution in the same manner as in Example 1.

  The total visible light transmittance of the obtained coating film and PET film was 66.3%, and the haze value was 1.4%. The film was stored in an environment of 90% humidity at 60 ° C. for 3000 hours, and the visible light transmittance was measured to be 66.3%. The increase in visible light transmittance was 0% and the moisture resistance was extremely high. It was good.

[Example 5]
Example 3 except that No. 3 sodium silicate (SiO ₂ content: 28.5%) was used in place of tetraethoxysilane as the silicate compound, and the treatment was performed in water instead of the mixed solvent of ethanol and water. Thus, silica film-coated lanthanum hexaboride fine particles were obtained.

As a result of TEM observation of the obtained silica film-coated lanthanum hexaboride fine particles, a silica-coated film having a thickness of about 5 nm was formed on the surface of monodispersed LaB ₆ fine particles, and the outer shape was substantially spherical. Observed.

Since the silica film-coated LaB ₆ fine particles were monodispersed, no particular pulverization was performed. Using this silica film-coated lanthanum hexaboride fine particles, a coating solution was prepared in the same manner as in Example 1. Further, a coating film was formed on the PET film using this coating solution in the same manner as in Example 1.

  The total visible light transmittance of the obtained coating film and PET film was 67.5%, and the haze value was 1.3%. The film was stored in an environment of 90% humidity at 60 ° C. for 3000 hours, and the visible light transmittance was measured to be 67.7%. The increase in visible light transmittance was 0.2% and moisture resistance. Was very good.

[Example 6]
Silica film-coated 6-lanthanum boride fine particles were obtained in the same manner as in Example 1 except that No. 3 sodium silicate (SiO ₂ content: 28.5%) and tetraethoxysilane were sequentially added as a silicate compound. . As a result of TEM observation of the obtained silica film-coated lanthanum hexaboride fine particles, a silica-coated film having a thickness of about 20 nm was formed on the surface of monodispersed LaB ₆ fine particles, and the outer shape was substantially spherical. Observed.

Since the silica film-coated LaB ₆ fine particles were monodispersed, no particular pulverization was performed. Using the substantially spherical silica film-coated lanthanum hexaboride fine particles, a coating solution was prepared in the same manner as in Example 1. Further, a coating film was formed on the PET film using this coating solution in the same manner as in Example 1.

  The total visible light transmittance of the obtained coating film and PET film was 68.5%, and the haze value was 1.4%. The film was stored in an environment of 90% humidity at 60 ° C. for 3000 hours, and the visible light transmittance was measured to be 68.5%. The increase in visible light transmittance was 0% and the humidity resistance was very good. there were.

[Example 7]
Silica film-coated lanthanum boride fine particles were obtained in the same manner as in Example 1 except that No. 3 sodium silicate (SiO ₂ content: 28.5%) was added after the addition of the silane coupling agent. As a result of TEM observation of the obtained silica film-coated lanthanum hexaboride fine particles, a silica-coated film having a thickness of about 20 nm was formed on the surface of monodispersed LaB ₆ fine particles, and the outer shape was substantially spherical. Observed.

Since the silica film-coated LaB ₆ fine particles were monodispersed, no particular pulverization was performed. Using this silica film-coated lanthanum hexaboride fine particles, a coating solution was prepared in the same manner as in Example 1. Further, a coating film was formed on the PET film using this coating solution in the same manner as in Example 1.

  The total visible light transmittance of the obtained coating film and PET film was 68.6%, and the haze value was 1.4%. The film was stored at 60 ° C. in a 90% humidity environment for 3000 hours, and the visible light transmittance was measured to be 68.6%. The increase in visible light transmittance was 0% and the moisture resistance was extremely high. It was good.

[Example 8]
Silica film-coated lanthanum hexaboride fine particles were obtained in the same manner as in Example 1 except that tetramethoxysilane was used as the silicate compound. As a result of TEM observation of the obtained silica film-coated lanthanum hexaboride fine particles, a silica-coated film having a thickness of about 20 nm was formed on the surface of monodispersed LaB ₆ fine particles, and the outer shape was substantially spherical. Observed.

Since the silica film-coated LaB ₆ fine particles were monodispersed, no particular pulverization was performed. Using this silica film-coated lanthanum hexaboride fine particles, a coating solution was prepared in the same manner as in Example 1. Further, a coating film was formed on the PET film using this coating solution in the same manner as in Example 1.

  The total visible light transmittance of the obtained coating film and PET film was 65.5%, and the haze value was 1.4%. The film was stored in an environment of 90% humidity at 60 ° C. for 3000 hours, and the visible light transmittance was measured to be 65.5%. The increase in visible light transmittance was 0% and the moisture resistance was extremely high. It was good.

[Comparative Example 1]
16 g of LaB ₆ fine particles having an average particle diameter of 80 nm are 5% by weight, an organic polymer dispersant (made of an acrylic polymer and not containing an inorganic component) is 2% by weight, an ultraviolet curable resin (manufactured by Toagosei Co., Ltd., UV3701). Was mixed in toluene so as to be 26% by weight to prepare a coating solution. This coating solution was applied onto a 50 μm thick PET film using a bar coater, dried at 70 ° C. for 1 minute to evaporate the solvent, and then irradiated with ultraviolet rays from a high pressure mercury lamp to cure the coating.

  The total visible light transmittance of the obtained coating film and PET film was 66.6%, and the haze value was 1%. The film was stored in an environment of 90% humidity at 60 ° C. for 66 hours, and the visible light transmittance was measured to be 72.6% and the increase in visible light transmittance was 6%. Further, after storage for 3000 hours, the visible light transmittance was measured to be 82.7%, and the increase in visible light transmittance was 16.1%.

[Comparative Example 2]
16 g of LaB ₆ fine particles having an average particle diameter of 80 nm were mixed in a mixed solvent of 570 g of ethanol and 140 g of water, 90 g of tetraethoxysilane was added, and a silica coating film was formed on the surface of the LaB ₆ fine particles by hydrolysis polymerization. This solution was dried to remove the alcohol solvent, and further heat-treated at 450 ° C. for 30 minutes to obtain silica film-coated lanthanum hexaboride fine particles.

Since the obtained silica film-coated lanthanum hexaboride fine particles were in the form of aggregates, they were pulverized by a paint shaker (manufactured by Asada Tekko Co., Ltd.). Subsequent TEM observation revealed that the agglomeration was proceeding, but the silica film on the surface of the LaB ₆ fine particles was not uniform.

  This silica film-coated lanthanum hexaboride fine particle is 5% by weight, an organic polymer dispersant (made of an acrylic polymer, not containing an inorganic component) is 2% by weight, an ultraviolet curable resin (manufactured by Toagosei Co., Ltd., UV3701). Was mixed in toluene so as to be 26% by weight to prepare a coating solution.

  This coating solution was applied onto a 50 μm thick PET film using a bar coater, dried at 70 ° C. for 1 minute to evaporate the solvent, and then irradiated with ultraviolet rays from a high pressure mercury lamp to cure the coating.

  The total visible light transmittance of the obtained coating film and PET film was 63.6%, and the haze value was 20.3%. The film was stored in an environment with a humidity of 90% at 60 ° C. for 3000 hours, and the visible light transmittance was measured to be 66.8%. The increase in visible light transmittance was 3.2%. .

2 is a transmission electron micrograph of silica film-coated hexaboride fine particles having a substantially spherical outer shape according to the present invention.

Claims (16)

  It has a primary coating film by a surface modifier and a secondary coating film mainly composed of silica on the primary coating film on the surface of hexaboride fine particles, and the outer shape is substantially spherical. Silica film coated hexaboride fine particles.   The hexaboride fine particles are at least one selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sr, and Ca. The silica film-coated hexaboride fine particles according to claim 1, which are hexaboride of the element described above.   The silica film-coated hexaboride fine particles according to claim 1 or 2, wherein the hexaboride fine particles have a particle diameter of 2 nm to 10 µm.   The total thickness of the said primary coating film and a secondary coating film is 1-100 nm, The silica film coating | coated hexaboride microparticles | fine-particles in any one of Claims 1-3 characterized by the above-mentioned.   The silica film-coated hexaboride fine particles according to any one of claims 1 to 4, wherein the surface modifier is a silane coupling agent.   A primary coating film is formed by adding a surface modifier to a liquid in which hexaboride fine particles are dispersed to form a primary coating film by the surface modifier on the particle surface, and then adding a silicic acid compound to cause hydrolytic polymerization. A method for producing fine particles of hexaboride coated with silica film, wherein a secondary coating film mainly composed of silica is formed thereon.   The surface modifier is a silane coupling agent, and the ratio to the hexaboride fine particles is 0.01 to 10 parts by weight with respect to 1 part by weight of the hexaboride fine particles in terms of silicon contained in the silane coupling agent. The method for producing fine particles of hexaboride coated with silica film according to claim 6.   The ratio of the silicate compound to hexaboride fine particles is 0.01 to 100 parts by weight with respect to 1 part by weight of the hexaboride fine particles in terms of silicon contained in the silicate compound. Or the method for producing silica film-coated hexaboride microparticles according to 7.   A coating solution for an optical member, wherein the silica film-coated hexaboride fine particles according to any one of claims 1 to 5 are dispersed in a liquid.   The optical member according to claim 9, wherein the liquid is an organic solvent and / or water, or an organic solvent and / or water in which at least one of a resin and a metal alkoxide is dissolved or dispersed. Coating liquid.   An optical member formed by applying the coating liquid for an optical member according to claim 9 or 10 to the surface of the substrate and curing it.   6. An optical member comprising a substrate surface formed with a coating film comprising a dispersion for an optical member in which the silica film-coated hexaboride fine particles according to claim 1 are dispersed in a solid medium. .   An optical member comprising a dispersion for an optical member in which the silica film-coated hexaboride fine particles according to claim 1 are dispersed in a solid medium, and formed into a film or a board.   The optical member according to claim 13, wherein the solid medium is either resin or glass.   The optical member according to claim 13 or 14, wherein a film or board made of the optical dispersion has a thickness of 0.1 µm to 50 mm. An optical member, wherein the dispersion for an optical member in which the silica film-coated hexaboride fine particles according to any one of claims 1 to 5 are dispersed in a liquid medium is enclosed between a film or a board.