JP2006193376A - Surface-coated hexaboride particulate and method for producing the same - Google Patents
Surface-coated hexaboride particulate and method for producing the same Download PDFInfo
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本発明は、日射遮蔽材料として好適な表面被覆された六ホウ化微粒子、及びその製造方法に関する。 The present invention relates to a surface-coated hexaboride fine particle suitable as a solar shading material and a method for producing the same.
ＬａＢ６等で代表される六ホウ化物微粒子は、近赤外領域における光の透過率が低いという特性を有すると共に、可視光領域における光の透過率が高く且つ反射率が低いため、近年では日射遮蔽材料として利用されている（特開２０００−１６９７６５号公報参照）。 In recent years, hexaboride fine particles represented by LaB 6 and the like have the characteristics of low light transmittance in the near-infrared region and high light transmittance and low reflectance in the visible light region. It is used as a shielding material (see JP 2000-169765 A).
しかしながら、上記六ホウ化物は、空気中の水蒸気や水分によって表面が分解されることが知られている。特に、微細な粒子の状態で存在する場合には、体積に対して表面積が増加しているため、六ホウ化物微粒子表面は水蒸気や水分により簡単に分解し、酸化物や水酸化物などの化合物に変化してしまい、六ホウ化物本来の特性が徐々に低下するという現象が現れる。 However, it is known that the surface of the hexaboride is decomposed by water vapor or moisture in the air. In particular, when present in the form of fine particles, the surface area increases with respect to the volume, so the surface of the hexaboride fine particles is easily decomposed by water vapor or moisture, and compounds such as oxides and hydroxides And the phenomenon that the original properties of hexaboride gradually decline appears.
例えば、六ホウ化物微粒子を用いた塗膜等の光学特性を利用して、近赤外領域における光を遮蔽する用途に適用した場合、上記の現象によって塗膜中の六ホウ化物微粒子が水蒸気や水分の影響を受け、波長２００〜２６００ｎｍ領域の透過率が上昇してしまい、日射遮蔽性能が徐々に劣化するという問題があった。 For example, when it is applied to an application for shielding light in the near-infrared region by utilizing the optical properties of a coating film using hexaboride fine particles, the hexaboride fine particles in the coating film are caused by water vapor and Under the influence of moisture, there is a problem that the transmittance in the wavelength range of 200 to 2600 nm is increased, and the solar shading performance is gradually deteriorated.
そのため、六ホウ化物微粒子の水蒸気や水分による影響をなくし、本来の日射遮蔽性能を維持するための対策が求められている。その対策の一つとして、特開２００４−１１５５９３号公報には、六ホウ化物微粒子の表面をＳｉ、Ｔｉ、Ａｌ、Ｚｒのいずれか１種以上の金属酸化物で被覆することが記載されている。これらの金属化合物は基本的に透明であり、六ホウ化物微粒子表面を被覆したことによって可視光透過率を低下させることはなく、耐水性を向上させる。 Therefore, there is a demand for measures for eliminating the influence of water vapor and moisture on the hexaboride fine particles and maintaining the original solar shading performance. As one of the countermeasures, Japanese Patent Application Laid-Open No. 2004-115593 describes that the surface of hexaboride fine particles is coated with one or more metal oxides of Si, Ti, Al, and Zr. . These metal compounds are basically transparent, and by covering the surface of the hexaboride fine particles, the visible light transmittance is not lowered and the water resistance is improved.
また、六ホウ化物微粒子の耐水性を向上させるために、特開２００３−２７７０４５号公報には、Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、Ｓｒ、Ｃａから選ばれた１種以上の元素の六ホウ化物微粒子について、Ｓｉを含有する表面処理剤を用いて表面を被覆することが記載されている。上記表面処理剤としては、シラザン系処理剤、クロロシラン系処理剤、アルコキシ基を分子構造中に有する無機系処理剤、又はアルコキシ基を分子末端若しくは側鎖に有する有機系処理剤があり、加水分解重合してケイ素酸化物の被覆層を形成する。これらは基本的に透明であり、六ホウ化物微粒子の表面を被覆して耐水性を向上させることが記載されている。 In order to improve the water resistance of the hexaboride fine particles, Japanese Patent Application Laid-Open No. 2003-277045 discloses Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm. It describes that the surface of a hexaboride fine particle of one or more elements selected from Yb, Lu, Sr, and Ca is coated with a surface treatment agent containing Si. Examples of the surface treatment agent include a silazane treatment agent, a chlorosilane treatment agent, an inorganic treatment agent having an alkoxy group in the molecular structure, or an organic treatment agent having an alkoxy group at the molecular end or side chain, and hydrolysis. Polymerization forms a coating layer of silicon oxide. These are basically transparent and are described to improve the water resistance by covering the surface of the hexaboride fine particles.
上記したようにケイ素などの金属酸化物で表面を被覆することによって、六ホウ化物微粒子は空気中の水蒸気や水分による影響を受けなくなり、その表面の分解を防ぐことができる。しかしながら、上記被覆処理は、湿式法によるものであり、加水分解重合反応を促進するため水の添加が一般的に行われ、仮に有機溶剤中で処理する場合でも有機溶媒に水分が含まれる。そのため、被覆処理の際に溶媒中の水分によって六ホウ化物微粒子の表面が分解し、酸化物や水酸化物等の化合物に変化することが避けられなかった。 By covering the surface with a metal oxide such as silicon as described above, the hexaboride fine particles are not affected by water vapor or moisture in the air, and the surface can be prevented from being decomposed. However, the coating treatment is based on a wet method, and water is generally added to accelerate the hydrolysis polymerization reaction. Even when the treatment is performed in an organic solvent, the organic solvent contains moisture. For this reason, it is inevitable that the surface of the hexaboride microparticles is decomposed by moisture in the solvent during the coating treatment and changes to a compound such as an oxide or hydroxide.
本発明は、このような事情に鑑みてなされたものであり、湿式法により金属酸化物で表面被覆を行う際に、その溶媒中の水分による六ホウ化物微粒子表面の分解を防ぐことができる表面被覆六ホウ化物微粒子の製造方法、並びに耐水性に優れ、日射遮蔽材料として好適に利用される表面被覆六ホウ化物微粒子を提供することを目的とする。 The present invention has been made in view of such circumstances, and when surface coating with a metal oxide is performed by a wet method, a surface capable of preventing the decomposition of the surface of hexaboride fine particles due to moisture in the solvent. An object of the present invention is to provide a method for producing coated hexaboride fine particles, and surface-coated hexaboride fine particles that are excellent in water resistance and are suitably used as a solar shading material.
発明者は、上述した湿式法での表面被覆の際に六ホウ化物微粒子の表面が水分によって分解する問題について検討を重ね、この分解は六ホウ化物微粒子のホウ素が水分を含む液体中に溶け出すことが原因であることを見出した。更に、この水分を含む液体へのホウ素の溶け出しは、水分を含む液体に予めホウ素を溶解させておくことにより抑制できることを見出し、本発明を完成させるに至ったものである。 The inventor has repeatedly investigated the problem that the surface of the hexaboride fine particles is decomposed by moisture during the surface coating by the above-described wet method, and this decomposition causes the boron of the hexaboride fine particles to dissolve in the liquid containing water. I found out that this is the cause. Furthermore, it has been found that the dissolution of boron into a liquid containing water can be suppressed by previously dissolving boron in the liquid containing water, and the present invention has been completed.
即ち、本発明が提供する表面被覆六ホウ化物微粒子の製造方法は、Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、Ｓｒ、Ｃａの群から選ばれた少なくとも１種の元素の六ホウ化物からなる微粒子を溶媒に分散させ、その六ホウ化物微粒子が分散した溶媒に表面処理剤を添加混合し、その添加と同時に若しくはその前又は後にホウ素を含む水溶液を添加して、六ホウ化物微粒子の表面に被覆層を形成することを特徴とする。 That is, the method for producing surface-coated hexaboride fine particles provided by the present invention includes Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sr, Fine particles composed of hexaboride of at least one element selected from the group of Ca are dispersed in a solvent, and a surface treatment agent is added and mixed in the solvent in which the hexaboride fine particles are dispersed, and at the same time or before the addition. Alternatively, an aqueous solution containing boron is added later to form a coating layer on the surface of the hexaboride fine particles.
上記本発明による表面被覆六ホウ化物微粒子の製造方法において、前記表面処理剤は、Ｓｉ、Ｔｉ、Ａｌ、Ｚｒから選ばれた少なくとも１種の金属を含む、金属アルコキシド、金属アセチルアセトネート、金属カルボキシレート、硝酸塩、塩化物、オキシ塩化物から選ばれた少なくとも１種であることが好ましい。また、前記被覆層は、Ｓｉ、Ｔｉ、Ａｌ、Ｚｒから選ばれた少なくとも１種の金属の酸化物を主成分とする被覆化合物からなることが好ましい。 In the method for producing surface-coated hexaboride fine particles according to the present invention, the surface treatment agent includes at least one metal selected from Si, Ti, Al, and Zr, a metal alkoxide, a metal acetylacetonate, and a metal carboxy. It is preferably at least one selected from rate, nitrate, chloride, and oxychloride. Moreover, it is preferable that the said coating layer consists of a coating compound which has as a main component the oxide of the at least 1 sort (s) of metal chosen from Si, Ti, Al, and Zr.
上記本発明による表面被覆六ホウ化物微粒子の製造方法において、前記ホウ素を含む水溶液は、被覆処理温度におけるホウ酸の溶解度を超えない範囲でホウ酸又は無水ホウ酸を水に溶解したものであることが好ましい。また、前記溶媒としては、水及び／又は有機溶媒を用いることができる。 In the method for producing surface-coated hexaboride fine particles according to the present invention, the aqueous solution containing boron is obtained by dissolving boric acid or boric anhydride in water within a range not exceeding the solubility of boric acid at the coating treatment temperature. Is preferred. As the solvent, water and / or an organic solvent can be used.
本発明は、また、上記本発明による表面被覆六ホウ化物微粒子の製造方法により得られた表面被覆六ホウ化物微粒子を提供するものである。この本発明の表面被覆六ホウ化物微粒子の粒子径は、２ｎｍ〜１０μｍであることが好ましい。 The present invention also provides surface-coated hexaboride fine particles obtained by the method for producing surface-coated hexaboride fine particles according to the present invention. The particle diameter of the surface-coated hexaboride fine particles of the present invention is preferably 2 nm to 10 μm.
本発明によれば、六ホウ化物微粒子が分散した溶媒中に表面処理剤を添加し、六ホウ化物微粒子の表面に物理的若しくは化学的に被覆層を形成する際に、その溶媒中に含まれる水分による六ホウ化物微粒子の分解ないし溶解を抑制して、耐水性に優れた表面被覆六ホウ化物微粒子を高い収率で得ることができる。得られた表面被覆六ホウ化物微粒子は、近赤外領域の透過率が低く、可視光領域の透過率が高く且つ反射率が低い特性を有し、しかも耐水性に優れているため、日射遮蔽材料として利用したとき、長期にわたって優れた日射遮蔽性能を維持することができる。 According to the present invention, when a surface treatment agent is added to a solvent in which hexaboride fine particles are dispersed to form a coating layer physically or chemically on the surface of the hexaboride fine particles, it is contained in the solvent. The surface-coated hexaboride fine particles having excellent water resistance can be obtained in high yield by suppressing the decomposition or dissolution of the hexaboride fine particles due to moisture. The resulting surface-coated hexaboride fine particles have low transmittance in the near-infrared region, high transmittance in the visible light region, low reflectance, and excellent water resistance. When used as a material, excellent solar shading performance can be maintained over a long period of time.
本発明で用いる六ホウ化物微粒子は、Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、Ｓｒ、Ｃａから選ばれた少なくとも１種の元素の六ホウ化物である。六ホウ化物微粒子の粒子径は、その用途に応じて、２ｎｍ〜１０μｍの範囲内で適宜設定できる。例えば、光学的選択透過膜（可視光領域の光を透過させ且つ近赤外領域の光を遮蔽させる膜）に応用する場合には、粒子による光の散乱が少なく、透明性に優れることが必要であるかため、六ホウ化物微粒子の粒子径は２００ｎｍ以下が好ましく、１００ｎｍ以下が更に好ましい。 The hexaboride fine particles used in the present invention are at least one selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sr, and Ca. The hexaboride of the element. The particle size of the hexaboride fine particles can be appropriately set within the range of 2 nm to 10 μm depending on the application. For example, when applied to an optically selective transmission film (a film that transmits light in the visible light region and shields light in the near infrared region), it is necessary to have little transparency of particles and excellent transparency. Therefore, the particle size of the hexaboride fine particles is preferably 200 nm or less, and more preferably 100 nm or less.
その理由は、微粒子の粒子径が２００ｎｍを超えて大きいと、幾何学散乱若しくはミー散乱によって、３８０〜７８０ｎｍの可視光線領域の光を散乱して曇りガラスのようになり、鮮明な透明性が得られないからである。粒子径が２００ｎｍ以下になると、上記幾何学散乱及びミー散乱が低減して、レイリー散乱領域になる。レイリー散乱領域では、散乱光は粒子径の６乗に反比例して低減するため、粒子径の減少に伴い散乱が低減して透明性が向上する。更に粒子径が１００ｎｍ以下になると、散乱光は非常に少なくなり、透過性が一層向上する。ただし、用途によっては透明性が要求されない場合もあるため、２ｎｍ〜１０μｍの範囲内で粒子径を適宜設定すればよい。 The reason for this is that when the particle size of the fine particles exceeds 200 nm, the light in the visible light region of 380 to 780 nm is scattered by the geometric scattering or Mie scattering to become a frosted glass, and clear transparency is obtained. Because it is not possible. When the particle diameter is 200 nm or less, the geometric scattering and Mie scattering are 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. Further, when the particle diameter 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, the particle diameter may be appropriately set within the range of 2 nm to 10 μm.
上記した六ホウ化物微粒子の表面を被覆するには、従来から行われている湿式法を用いる。即ち、六ホウ化物微粒子を溶媒に分散させ、その溶媒にＳｉなどの金属を含む表面処理剤を添加混合することにより、六ホウ化物微粒子表面をＳｉなどの金属の酸化物からなる被覆層で物理的又は化学的に被覆することができる（特開２００４−１１５５９３号公報及び特開２００３−２７７０４５号公報参照）。被覆処理の溶媒としては、水又はアルコール等の有機溶媒、あるいは水と有機溶媒の混合物を用いることができる。 In order to coat the surface of the hexaboride fine particles described above, a conventional wet method is used. That is, the hexaboride fine particles are dispersed in a solvent, and a surface treatment agent containing a metal such as Si is added to and mixed with the solvent, whereby the surface of the hexaboride fine particles is physically covered with a coating layer made of an oxide of a metal such as Si. It is possible to coat the film manually or chemically (see Japanese Patent Application Laid-Open Nos. 2004-115593 and 2003-277045). As a solvent for the coating treatment, an organic solvent such as water or alcohol, or a mixture of water and an organic solvent can be used.
六ホウ化物微粒子表面に被覆層を形成する被覆化合物は、Ｓｉ、Ｔｉ、Ａｌ、Ｚｒから選ばれた少なくとも１種の金属酸化物であることが好ましい。これらの金属酸化物による被覆層は、ゾルゲル法により容易に形成することができる。例えば、Ｓｉの金属酸化物の場合は、六ホウ化物微粒子を分散させた有機溶媒に、表面処理剤としてシリカゾルのような含水酸化物ゾルを添加混合することにより、含水酸化物ゾルが化学的に脱水して、ＳｉＯ２のような金属酸化物を主成分とする被覆層を形成して、六ホウ化物微粒子表面を被覆する。Ｔｉ、Ａｌ及びＺｒの金属酸化物の場合も、ＳｉＯ２の場合と同様に、ＴｉＯ２、Ａｌ２Ｏ３及びＺｒＯ２のような金属酸化物を主成分とする被覆層を形成して、六ホウ化物微粒子表面を被覆することができる。 The coating compound that forms the coating layer on the surface of the hexaboride fine particles is preferably at least one metal oxide selected from Si, Ti, Al, and Zr. These metal oxide coating layers can be easily formed by a sol-gel method. For example, in the case of an Si metal oxide, a hydrous oxide sol such as silica sol as a surface treatment agent is added to and mixed with an organic solvent in which hexaboride fine particles are dispersed. Dehydration is performed to form a coating layer mainly composed of a metal oxide such as SiO 2 to coat the surface of the hexaboride fine particles. In the case of Ti, Al and Zr metal oxides, as in the case of SiO 2 , a coating layer mainly composed of metal oxides such as TiO 2 , Al 2 O 3 and ZrO 2 is formed. The boride fine particle surface can be coated.
詳しくは、上記被覆化合物からなる被覆層で六ホウ化物微粒子表面を被覆するための表面処理剤は、Ｓｉ、Ｔｉ、Ａｌ、Ｚｒから選ばれた少なくとも１種の金属を含む金属有機化合物又は金属無機化合物であり、金属アルコキシド、金属アセチルアセトネート、金属カルボキシレート、硝酸塩、塩化物、オキシ塩化物などが好ましい。例えば、Ｓｉを含む表面処理剤としては、シラザン系処理剤、クロロシラン系処理剤、アルコキシ基を分子構造中に有する無機系処理剤、アルコキシ基を分子末端又は側鎖に有する有機系処理剤のいずれか１種、又は２種以上を用いることができる。 Specifically, the surface treatment agent for coating the surface of the hexaboride fine particles with the coating layer made of the above coating compound is a metal organic compound or metal inorganic containing at least one metal selected from Si, Ti, Al, and Zr. It is a compound, and metal alkoxide, metal acetylacetonate, metal carboxylate, nitrate, chloride, oxychloride and the like are preferable. For example, as a surface treatment agent containing Si, any of a silazane treatment agent, a chlorosilane treatment agent, an inorganic treatment agent having an alkoxy group in the molecular structure, and an organic treatment agent having an alkoxy group at the molecular end or side chain 1 type, or 2 or more types can be used.
これらの表面処理剤のうち、金属アルコキシドとしては、アルコキシシラン、クロロシラン、シラザン、若しくはこれらの加水分解重合物が好ましく、市販されているものを用いることができる。アルコキシシランは、そのアルコキシ基が六ホウ化物と粒子表面で共有結合を形成し、微粒子表面に化学的に結合する。同時に、アルコキシシランは加水分解重合して、非結晶性ないし無定形のシリカを主体とする表面被覆を形成する。例えば、メチルトリメトキシシラン（ＣＨ３Ｓｉ(ＯＣＨ３)３）は水（Ｈ２Ｏ）と反応して徐々にメトキシ基がメタノールとして除かれ、更にＳｉ−Ｏ−Ｈ同士が結合してＳｉ−Ｏ−Ｓｉ構造が形成される。尚、加水分解重合反応のための水は、溶媒が水を含まない場合でも、本発明において被覆処理時に添加するホウ素を含む水溶液から供給することができる。 Among these surface treatment agents, as the metal alkoxide, alkoxysilane, chlorosilane, silazane, or a hydrolysis polymer thereof is preferable, and commercially available products can be used. In the alkoxysilane, the alkoxy group forms a covalent bond with the hexaboride on the particle surface and is chemically bonded to the fine particle surface. At the same time, the alkoxysilane undergoes hydrolytic polymerization to form a surface coating mainly composed of amorphous or amorphous silica. For example, methyltrimethoxysilane (CH 3 Si (OCH 3 ) 3 ) reacts with water (H 2 O) to gradually remove methoxy groups as methanol, and Si—O—H bonds to each other to form Si— An O-Si structure is formed. In addition, even when a solvent does not contain water, the water for hydrolysis polymerization reaction can be supplied from the aqueous solution containing the boron added at the time of a coating process in this invention.
表面処理剤として好ましいアルコキシシランには、テトラメトキシシラン、メチルトリメトキシシラン、ジメチルジメトキシシラン、フェニルトリメトキシシラン、ジフェニルジメトキシシラン、テトラエトキシシラン、メチルトリエトキシシラン、ジメチルジエトキシシラン、フェニルトリエトキシシラン、ジフェニルジエトキシシラン、ヘキシルトリメトキシシラン、ヘキシルトリエトキシシラン、デシルトリエトキシシラン、デシルトリメトキシシラン、トリウルオロプロピルトリメトキシシラン、ヘプタデカトリフルオロデシルトリメトキシシランなどがある。 Preferred alkoxysilanes as surface treatment agents include tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, and phenyltriethoxysilane. Diphenyldiethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltriethoxysilane, decyltrimethoxysilane, triuropropyltrimethoxysilane, heptadecatrifluorodecyltrimethoxysilane, and the like.
また、表面処理剤としての金属アルコキシドのうち、クロロシランは、そのクロロ基が六ホウ化物と共有結合を形成し、同時に加水分解重合して、非結晶性ないし無定形のシリカを主体とする表面被覆を形成する。代表的なクロロシランとしては、メチルトリクロロシラン、メチルジクロロシラン、ジメチルジクロロシラン、トリメチルクロロシラン、フェニルトリクロロシラン、ジフェニルジクロロシラン、トリフロロプロピルトリクロロシラン、ヘプタデカフロロデシルトリクロロシランなどがある。 Of the metal alkoxides as surface treatment agents, chlorosilane has a surface coating mainly composed of amorphous or amorphous silica, in which the chloro group forms a covalent bond with hexaboride and simultaneously undergoes hydrolytic polymerization. Form. Typical chlorosilanes include methyltrichlorosilane, methyldichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, trifluoropropyltrichlorosilane, heptadecafluorodecyltrichlorosilane, and the like.
更に、表面処理剤としての金属アルコキシドのうち、シラザンは、反応性が強く、加水分解重合して六ホウ化物と共有結合を形成し、微粒子表面を被覆する。また、シラザンは親油性であり、分子構造が小さいため緻密に粒子表面を覆うことができ、最外郭が疎水性となるため耐水性向上に有効である。好ましいシラザンとしては、ヘキサメチルジシラザン、サイクリックシラザン、Ｎ，Ｎ−ビス（トリメチルシリル）ウレア、Ｎ−トリメチルシリルアセトアミド、ジメチルトリメチルシリルアミン、ジエチルトリメチルシリルアミン、トリメチルシリルイミダゾール、Ｎ−トリメチルシリルフェニルウレアなどが挙げられる。 Furthermore, among the metal alkoxides as the surface treatment agent, silazane is highly reactive and hydrolytically polymerizes to form a covalent bond with the hexaboride and coats the surface of the fine particles. Silazane is lipophilic and has a small molecular structure, so that the particle surface can be densely covered, and the outermost wall is hydrophobic, which is effective for improving water resistance. Preferred silazanes include hexamethyldisilazane, cyclic silazane, N, N-bis (trimethylsilyl) urea, N-trimethylsilylacetamide, dimethyltrimethylsilylamine, diethyltrimethylsilylamine, trimethylsilylimidazole, N-trimethylsilylphenylurea and the like.
また、上記したＳｉを含む金属アルコキシドのほかにも、Ｔｉ、Ａｌ又はＺｒを含む金属アルコキシド、例えば、Ｔｉ(ｉｓｏ−ＯＣ３Ｈ７)４、Ａｌ(ＯＣ３Ｈ７)３、Ｚｒ(ＯＣＨ３)４などを用いることができる。適当な金属アルコキシドがない場合、即ち、非常に合成が難しかったり、通常溶媒として用いる水やアルコールに溶けなかったりする場合には、金属アセチルアセトネートや金属カルボキシレートを用いることもできる。例えば、金属アセチルアセトネートとしては、Ｚｒ(Ｃ５Ｈ７Ｏ２)４などが挙げられる。また、金属カルボキシレートとしては、ＺｒＯ(ＣＨ３ＣＯＯ)２などが挙げられる。 In addition to the above-described metal alkoxide containing Si, metal alkoxide containing Ti, Al or Zr, for example, Ti (iso-OC 3 H 7 ) 4 , Al (OC 3 H 7 ) 3 , Zr (OCH 3 4 ) can be used. When there is no suitable metal alkoxide, that is, when it is very difficult to synthesize or insoluble in water or alcohol usually used as a solvent, metal acetylacetonate or metal carboxylate can also be used. For example, examples of the metal acetylacetonate include Zr (C 5 H 7 O 2 ) 4 . Examples of the metal carboxylate include ZrO (CH 3 COO) 2 .
また、上記した金属アルコキシドやその他の金属有機化合物を使用せず、Ｓｉ、Ｔｉ、Ａｌ、Ｚｒを含む硝酸塩、塩化物、オキシ塩化物などの金属無機化合物を使用することもできる。この場合、その加水分解、重合反応を用いたゾルゲル法により、ＳｉＯ２、ＴｉＯ２、Ａｌ２Ｏ３、ＺｒＯ２を主成分とする被覆化合物の被覆層を形成することができる。例えば、硝酸塩としては、Ａｌ(ＮＯ３)３・９Ｈ２Ｏ、ＺｒＯ(ＮＯ３)２・２Ｈ２Ｏなどがある。また、塩化物としては、ＴｉＣｌ４などが挙げられる。更に、オキシ塩化物としては、ＡｌＯＣｌ、ＺｒＯＣｌ２などが挙げられる。尚、これらの金属無機化合物を用いることによって、被覆層形成の原料費を安くすることができる。 In addition, metal inorganic compounds such as nitrates, chlorides, and oxychlorides containing Si, Ti, Al, and Zr can be used without using the above-described metal alkoxide and other metal organic compounds. In this case, a coating layer of a coating compound containing SiO 2 , TiO 2 , Al 2 O 3 , and ZrO 2 as a main component can be formed by a sol-gel method using the hydrolysis and polymerization reaction. For example, nitrates include Al (NO 3 ) 3 · 9H 2 O, ZrO (NO 3 ) 2 · 2H 2 O, and the like. Examples of the chloride include TiCl 4 . Furthermore, as the oxychlorides, AlOCl, like ZrOCl 2. In addition, the raw material cost of coating layer formation can be made cheap by using these metal inorganic compounds.
本発明では、上記被覆処理を行う際に、表面処理剤の添加と同時に、若しくはその添加の前又は後に、ホウ素を含む水溶液を添加する。このホウ素を含む水溶液の添加により、溶媒中に含まれる水分による六ホウ化物微粒子の分解を抑制することができ、粒子表面を簡単に且つ効率よく被覆して、高い収率で表面被覆六ホウ化物微粒子を得ることができる。また、被覆処理に上記アルコキシシランなどの表面処理剤を用いた場合には、ホウ素を含む水溶液の水分によって加水分解重合反応を促進させるという効果もある。 In the present invention, when performing the coating treatment, an aqueous solution containing boron is added simultaneously with the addition of the surface treatment agent, or before or after the addition. By adding this aqueous solution containing boron, decomposition of hexaboride fine particles due to moisture contained in the solvent can be suppressed, and the surface of the particles can be easily and efficiently coated, and the surface-coated hexaboride can be obtained in a high yield. Fine particles can be obtained. In addition, when a surface treatment agent such as alkoxysilane is used for the coating treatment, there is also an effect that the hydrolysis polymerization reaction is promoted by moisture of an aqueous solution containing boron.
ホウ素を含む水溶液としては、ホウ酸（Ｈ３ＢＯ３）や無水ホウ酸（Ｂ２Ｏ３）を水に溶かしたものが好ましい。ただし、上記以外のホウ酸塩その他のホウ素含有化合物であっても、水に溶解してホウ素を供給し得るものであれば、特に制限なしに用いることができる。また、ホウ素を含む水溶液は、低濃度でも効果が得られるが、ホウ酸濃度が高いほど有効である。しかしながら、ホウ素を含む水溶液の濃度は、被覆処理温度におけるホウ酸の溶解度を超えない範囲が好ましい。溶解せずに残ったホウ酸は目視できる程度に大きい粒であるため、これを含む表面被覆六ホウ化物微粒子及びその成膜用塗布液は日射遮蔽材料のような光学部材用途において実用に供し得ないからである。 As an aqueous solution containing boron, a solution obtained by dissolving boric acid (H 3 BO 3 ) or boric anhydride (B 2 O 3 ) in water is preferable. However, borate and other boron-containing compounds other than those described above can be used without particular limitation as long as they can be dissolved in water and supplied with boron. An aqueous solution containing boron can be effective even at a low concentration, but the higher the boric acid concentration, the more effective. However, the concentration of the aqueous solution containing boron is preferably in a range not exceeding the solubility of boric acid at the coating treatment temperature. Since the boric acid remaining without being dissolved is a particle that is large enough to be visually observed, the surface-coated hexaboride fine particles containing the boric acid and the coating liquid for film formation thereof can be put to practical use in optical member applications such as solar shading materials. Because there is no.
従って、ホウ素を含む水溶液を調整する際には、被覆処理時の溶媒温度における水のホウ酸溶解度から算出して、ホウ素を含む水溶液のホウ酸濃度をホウ素が析出しない濃度以下とすることが望ましい。例えば、水のホウ酸溶解度（水１００ｇ中に溶解するホウ酸の量（ｇ））は、概ね、０℃で２.８ｇ、２０℃で４.９ｇ、３０℃で７.０ｇ、４０℃で８.９ｇ、６０℃で１４.９ｇ、８０℃で２３.６ｇである。この溶解度から、例えば３０℃の水１００ｇに溶解するときは、ホウ酸の添加量を７.０ｇ以下とすべきであり、７.０ｇを超えて添加すると溶解しないホウ酸が水溶液中に残ることになる。 Therefore, when adjusting the aqueous solution containing boron, it is desirable to calculate the boric acid concentration of the aqueous solution containing boron below the concentration at which boron does not precipitate, calculated from the boric acid solubility of water at the solvent temperature during the coating treatment. . For example, the solubility of boric acid in water (the amount of boric acid dissolved in 100 g of water (g)) is approximately 2.8 g at 0 ° C., 4.9 g at 20 ° C., 7.0 g at 30 ° C., and 40 g at 40 ° C. 8.9 g, 14.9 g at 60 ° C. and 23.6 g at 80 ° C. From this solubility, for example, when dissolving in 100 g of water at 30 ° C., the amount of boric acid added should be 7.0 g or less, and if added over 7.0 g, undissolved boric acid remains in the aqueous solution. become.
上記のような本発明方法で得られる表面被覆六ホウ化物微粒子は、被覆処理の際の溶媒中に水分が含まれていても六ホウ化物微粒子表面の分解が抑制され、六ホウ化物の溶解による収率の低下を防ぐことができる。このことにより、全ての六ホウ化物微粒子の表面を効率よく被覆でき、日射遮蔽材料として耐水性に優れた表面被覆六ホウ化物微粒子が容易に得られるのである。 The surface-coated hexaboride fine particles obtained by the method of the present invention as described above are prevented from being decomposed on the surface of the hexaboride fine particles even if water is contained in the solvent during the coating treatment. A decrease in yield can be prevented. As a result, the surface of all hexaboride fine particles can be efficiently coated, and surface-coated hexaboride fine particles having excellent water resistance as a solar radiation shielding material can be easily obtained.
また、表面被覆六ホウ化物微粒子の粒子径は、その光学的用途に応じて適宜選択できるが、２ｎｍ〜１０μｍであることが好ましい。例えば、光学的選択透過膜（可視光領域の光を透過させ近赤外領域の光を遮蔽させる上述の膜）に応用する場合には、粒子による散乱を考慮する必要があり、特に透明性を重視するときの粒子径は２００ｎｍ以下、好ましくは１００ｎｍ以下がよい。 The particle diameter of the surface-coated hexaboride fine particles can be appropriately selected according to the optical application, but is preferably 2 nm to 10 μm. For example, when it is applied to an optical selective transmission film (the above-mentioned film that transmits light in the visible light region and shields light in the near infrared region), it is necessary to consider scattering by particles. The particle size when emphasizing is 200 nm or less, preferably 100 nm or less.
上記表面被覆六ホウ化物微粒子は、可視光線領域を透過し且つ近赤外線を遮蔽する光学特性を有するため、日射遮蔽製品の原料として粒子状態のまま、あるいは液体媒質若しくは固体媒質に分散された状態で利用することができる。例えば住宅や自動車の窓材、温室などに適用すれば、高い断熱効果が得られると同時に視認性が確保される利点を有する。 The above surface-coated hexaboride fine particles have optical properties that transmit the visible light region and shield near infrared rays. Therefore, the surface-coated hexaboride fine particles remain in a particulate state as a raw material for solar radiation shielding products, or dispersed in a liquid medium or solid medium. Can be used. For example, when it is applied to a window material for a house or a car, a greenhouse, etc., there is an advantage that a high heat insulating effect can be obtained and at the same time visibility is secured.
以下、本発明の実施例について具体的に説明する。実施例中の可視光透過率とは、波長領域３８０ｎｍ〜７８０ｎｍの光の透過率であり、ＪＩＳＡ ５７５９に準ずる方法で測定した（ただし、ガラスに貼付せずに測定を行った）。また、被膜のヘイズ値は、ＪＩＳ Ｋ ７１０５に基づいて測定した。平均分散粒子径は、動的光散乱法を用いた測定装置（大塚電子株式会社製 ＥＬＳ−８００）により測定した測定粒径の平均値を用いた。 Examples of the present invention will be specifically described below. Visible light transmittance in the examples is light transmittance in a wavelength region of 380 nm to 780 nm, and was measured by a method according to JISA 5759 (however, measurement was performed without attaching to glass). Moreover, the haze value of the film was measured based on JIS K7105. As the average dispersed particle diameter, an average value of measured particle diameters measured by a measuring device using a dynamic light scattering method (ELS-800 manufactured by Otsuka Electronics Co., Ltd.) was used.
［基準例］
六ホウ化物微粒子の水分による影響を評価する基準として、水分を含まないトルエンを溶媒とする分散液を調整した。即ち、六ホウ化ランタン（ＬａＢ６）微粒子２ｇと、溶媒としてのトルエン９８ｇとを撹拌混合し、これを分散処理して平均分散粒子径１００ｎｍの六ホウ化ランタン微粒子分散液を得た。得られた分散液を溶媒のトルエンで８００倍に希釈し、可視光透過率を測定したところ６４.９８％であった。
[Standard example]
As a standard for evaluating the influence of water on the hexaboride fine particles, a dispersion using toluene containing no water as a solvent was prepared. That is, 2 g of lanthanum hexaboride (LaB 6 ) fine particles and 98 g of toluene as a solvent were mixed with stirring and dispersed to obtain a lanthanum hexaboride fine particle dispersion having an average dispersed particle size of 100 nm. The obtained dispersion was diluted 800 times with toluene as a solvent, and the visible light transmittance was measured to be 64.98%.
この分散液３ｇを紫外線硬化樹脂（ＵＶ３７０１、東亞合成(株)社製）４ｇと混合して、塗布液とした。この塗布液を、基材である厚さ５０μｍのＰＥＴフィルム上に、バーコーターを用いて塗布成膜した。これを７０℃で１分間乾燥し、溶媒を蒸発させた後、高圧水銀ランプを用いて紫外線を照射して、膜を硬化させた。得られた被膜とＰＥＴフィルムの合計の可視光透過率は６９.２％、ヘイズは２.５％であった。 3 g of this dispersion was mixed with 4 g of an ultraviolet curable resin (UV3701, manufactured by Toagosei Co., Ltd.) to prepare a coating solution. This coating solution was applied and formed on a PET film having a thickness of 50 μm as a substrate using a bar coater. This was dried at 70 ° C. for 1 minute to evaporate the solvent, and then irradiated with ultraviolet rays using a high-pressure mercury lamp to cure the film. The total visible light transmittance of the obtained coating film and PET film was 69.2%, and haze was 2.5%.
また、耐水性を評価するため、被膜を形成したＰＥＴフィルムを６０℃で湿度９０％の環境に４日間放置し、その後再び可視光透過率を測定した。上記環境での放置前後の透過率の差から、透過率の上昇が５ポイント以下のものは耐水性が良好であると評価した。放置後の可視光透過率は７５.６％であり、従って透過率の上昇は６.４ポイントとなるため、被覆処理していない基準例の六ホウ化物微粒子の耐水性は不良である。 Moreover, in order to evaluate water resistance, the PET film on which the film was formed was left in an environment of 90% humidity at 60 ° C. for 4 days, and then the visible light transmittance was measured again. From the difference in transmittance before and after standing in the above-mentioned environment, those having an increase in transmittance of 5 points or less were evaluated as having good water resistance. The visible light transmittance after being left is 75.6%, and therefore the increase in transmittance is 6.4 points. Therefore, the water resistance of the hexaboride fine particles of the reference example which is not coated is poor.
［実施例１］
六ホウ化ランタン微粒子２ｇと、メチルトリメトキシシラン１０ｇと、溶媒としてのエタノール５０ｇと、水３１ｇにホウ酸７ｇを溶解した水溶液とを撹拌混合し、これを分散処理して平均分散粒子径１００ｎｍの表面被覆六ホウ化ランタン微粒子分散液を調製した。尚、このときの被覆処理温度は３０℃とした。
[Example 1]
2 g of lanthanum hexaboride fine particles, 10 g of methyltrimethoxysilane, 50 g of ethanol as a solvent, and an aqueous solution in which 7 g of boric acid was dissolved in 31 g of water were stirred and mixed, and this was subjected to a dispersion treatment to obtain an average dispersed particle size of 100 nm. A surface-coated lanthanum hexaboride fine particle dispersion was prepared. The coating temperature at this time was 30 ° C.
この分散液を溶媒のエタノールで８００倍に希釈し、可視光透過率を測定したところ６７.０５％であった。上記基準例に比べて可視光透過率の上昇は２.０７ポイントと僅かであり、被覆処理中の六ホウ化ランタンの溶解が抑制されていることが分かった。 This dispersion was diluted 800 times with ethanol as a solvent, and the visible light transmittance was measured to be 67.05%. The increase in visible light transmittance was only 2.07 points compared to the above reference example, indicating that dissolution of lanthanum hexaboride during the coating process was suppressed.
次に、この分散液３ｇを紫外線硬化樹脂（ＵＶ３７０１）４ｇと混合し、塗布液とした。この塗布液を、厚さ５０μｍのＰＥＴフィルム上にバーコーターを用いて塗布成膜し、７０℃で１分間乾燥して溶媒を蒸発させた後、高圧水銀ランプを用いて紫外線を照射し、膜を硬化させた。 Next, 3 g of this dispersion was mixed with 4 g of an ultraviolet curable resin (UV3701) to obtain a coating solution. This coating solution was coated on 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 light using a high-pressure mercury lamp. Was cured.
得られた被膜とＰＥＴフィルムの合計の可視光透過率は７２.０％、ヘイズは０.９％であった。また、これを６０℃で湿度９０％の環境に４日間放置した後、可視光透過率を測定したところ７２.６％であった。従って、透過率の上昇は０.６ポイントであり、この実施例の表面被覆六ホウ化ランタン微粒子の耐水性は良好であった。 The total visible light transmittance of the obtained coating film and PET film was 72.0%, and the haze was 0.9%. In addition, after leaving this in an environment of 90% humidity at 60 ° C. for 4 days, the visible light transmittance was measured to be 72.6%. Accordingly, the increase in transmittance was 0.6 points, and the water resistance of the surface-coated lanthanum hexaboride fine particles of this example was good.
［実施例２］
六ホウ化ランタン微粒子２ｇと、メチルトリメトキシシラン１０ｇと、溶媒としてのエタノール５２ｇと、水３１ｇにホウ酸５ｇを溶解した水溶液とを撹拌混合し、これを分散処理して平均分散粒子径１００ｎｍの表面被覆六ホウ化ランタン微粒子分散液を調製した。尚、このときの被覆処理温度は３０℃とした。
[Example 2]
2 g of lanthanum hexaboride fine particles, 10 g of methyltrimethoxysilane, 52 g of ethanol as a solvent, and an aqueous solution in which 5 g of boric acid was dissolved in 31 g of water were stirred and mixed, and this was subjected to a dispersion treatment to obtain an average dispersed particle size of 100 nm. A surface-coated lanthanum hexaboride fine particle dispersion was prepared. The coating temperature at this time was 30 ° C.
この分散液を溶媒のエタノールで８００倍に希釈し、可視光透過率を測定したところ６７.５％であった。上記基準例に比べて可視光透過率の上昇は２.５２ポイントであり、被覆処理中の六ホウ化ランタンの溶解が抑制されていることが分かった。 When this dispersion was diluted 800 times with ethanol as a solvent and the visible light transmittance was measured, it was 67.5%. The increase in visible light transmittance was 2.52 points compared to the above reference example, indicating that dissolution of lanthanum hexaboride during the coating process was suppressed.
次に、この分散液３ｇを紫外線硬化樹脂（ＵＶ３７０１）４ｇと混合し、塗布液とした。得られた塗布液を、厚さ５０μｍのＰＥＴフィルム上にバーコーターを用いて塗布成膜し、７０℃で１分間乾燥して溶媒を蒸発させた後、高圧水銀ランプを用いて紫外線を照射し、膜を硬化させた。 Next, 3 g of this dispersion was mixed with 4 g of an ultraviolet curable resin (UV3701) to obtain a coating solution. The obtained coating solution was coated on 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 light using a high-pressure mercury lamp. The film was cured.
得られた被膜とＰＥＴフィルムの合計の可視光透過率は７２.４％、ヘイズは０.９％であった。また、これを６０℃で湿度９０％の環境に４日間放置した後、可視光透過率を測定したところ７２.９％であり、透過率の上昇は０.５ポイントであり、この実施例の表面被覆六ホウ化ランタン微粒子の耐水性は良好であった。 The total visible light transmittance of the obtained coating film and PET film was 72.4%, and the haze was 0.9%. In addition, when this was left in an environment of 90% humidity at 60 ° C. for 4 days, the visible light transmittance was measured to be 72.9%, and the increase in transmittance was 0.5 points. The water resistance of the surface-coated lanthanum hexaboride fine particles was good.
［実施例３］
六ホウ化ランタン微粒子２ｇと、メチルトリメトキシシラン１０ｇと、溶媒としてのエタノール５４ｇと、水３１ｇにホウ酸３ｇを溶解した水溶液とを撹拌混合し、これを分散処理して平均分散粒子径１００ｎｍの表面被覆六ホウ化ランタン微粒子分散液を調製した。尚、このときの被覆処理温度は３０℃とした。
[Example 3]
2 g of lanthanum hexaboride fine particles, 10 g of methyltrimethoxysilane, 54 g of ethanol as a solvent, and an aqueous solution in which 3 g of boric acid was dissolved in 31 g of water were stirred and mixed, and this was subjected to a dispersion treatment to obtain an average dispersed particle size of 100 nm. A surface-coated lanthanum hexaboride fine particle dispersion was prepared. The coating temperature at this time was 30 ° C.
この分散液を溶媒のエタノールで８００倍に希釈し、可視光透過率を測定したところ６８.２６％であった。上記基準例に比べ可視光透過率の上昇は３.２８ポイントであり、被覆処理中の六ホウ化ランタンの溶解が抑制されていることが分かった。 This dispersion was diluted 800 times with ethanol as a solvent, and the visible light transmittance was measured and found to be 68.26%. The increase in visible light transmittance was 3.28 points compared to the above reference example, indicating that dissolution of lanthanum hexaboride during the coating process was suppressed.
次に、この塗布液３ｇを紫外線硬化樹脂（ＵＶ３７０１）４ｇと混合し、塗布液とした。得られた塗布液を、厚さ５０μｍのＰＥＴフィルム上にバーコーターを用いて塗布成膜し、７０℃で１分間乾燥して溶媒を蒸発させた後、高圧水銀ランプを用いて紫外線を照射し、膜を硬化させた。 Next, 3 g of this coating solution was mixed with 4 g of an ultraviolet curable resin (UV3701) to obtain a coating solution. The obtained coating solution was coated on 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 light using a high-pressure mercury lamp. The film was cured.
得られた被膜とＰＥＴフィルムの合計の可視光透過率は７３.１％、ヘイズは０.９％であった。また、これを６０℃で湿度９０％の環境に４日間放置した後、可視光透過率を測定したところ７３.６％であり、透過率の上昇は０.５ポイントであり、この実施例の表面被覆六ホウ化ランタン微粒子の耐水性は良好であった。 The total visible light transmittance of the obtained coating film and PET film was 73.1%, and the haze was 0.9%. Moreover, when this was left in an environment of 90% humidity at 60 ° C. for 4 days, the visible light transmittance was measured to be 73.6%, and the increase in transmittance was 0.5 points. The water resistance of the surface-coated lanthanum hexaboride fine particles was good.
［比較例１］
六ホウ化ランタン微粒子２ｇと、メチルトリメトキシシラン１０ｇと、溶媒としてのエタノール５７ｇと、水３１ｇを撹拌混合し、これを分散処理して平均分散粒子径１００ｎｍの六ホウ化ランタン微粒子分散液を調製した。尚、このときの被覆処理温度は３０℃とした。
[Comparative Example 1]
2 g of lanthanum hexaboride fine particles, 10 g of methyltrimethoxysilane, 57 g of ethanol as a solvent, and 31 g of water are mixed with stirring, and this is dispersed to prepare a lanthanum hexaboride fine particle dispersion having an average dispersed particle size of 100 nm. did. The coating temperature at this time was 30 ° C.
この分散液を溶媒のエタノールで８００倍に希釈し、可視光透過率を測定したところ７２.７９％であった。上記基準例に対する可視光透過率の上昇は７.８１ポイントと大きく、被覆処理中に六ホウ化ランタンの溶解が起こっていたことが分かった。 This dispersion was diluted 800 times with ethanol as a solvent, and the visible light transmittance was measured to be 72.79%. The increase in visible light transmittance with respect to the above reference example was as large as 7.81 points, and it was found that dissolution of lanthanum hexaboride occurred during the coating process.
次に、この分散液３ｇを紫外線硬化樹脂（ＵＶ３７０１）４ｇと混合して、塗布液とした。この塗布液を、厚さ５０μｍのＰＥＴフィルム上にバーコーターを用いて塗布成膜し、７０℃で１分間乾燥して溶媒を蒸発させた後、高圧水銀ランプを用いて紫外線を照射し、膜を硬化させた。 Next, 3 g of this dispersion was mixed with 4 g of an ultraviolet curable resin (UV3701) to obtain a coating solution. This coating solution was coated on 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 light using a high-pressure mercury lamp. Was cured.
得られた被膜とＰＥＴフィルムの合計の可視光透過率は７７.６％、ヘイズは０.９％であった。また、これを６０℃で湿度９０％の環境に４日間放置した後、可視光透過率を測定したところ７８.０％であり、透過率の上昇は０.４ポイントであり、この比較例の表面被覆六ホウ化ランタン微粒子の耐水性は良好であった。 The total visible light transmittance of the obtained coating film and PET film was 77.6%, and the haze was 0.9%. The visible light transmittance was measured after leaving it in an environment of 90% humidity at 60 ° C. for 4 days. The transmittance was 78.0%, and the increase in transmittance was 0.4 points. The water resistance of the surface-coated lanthanum hexaboride fine particles was good.
［実施例４］
六ホウ化ランタン微粒子２ｇと、メチルトリメトキシシラン１０ｇと、溶媒としてのエタノール５６ｇと、水３１ｇにホウ酸１ｇを溶解した水溶液とを撹拌混合し、これを分散処理して平均分散粒子径１００ｎｍの表面被覆六ホウ化ランタン微粒子分散液を調製した。尚、このときの被覆処理温度は３０℃とした。
[Example 4]
2 g of lanthanum hexaboride fine particles, 10 g of methyltrimethoxysilane, 56 g of ethanol as a solvent, and an aqueous solution in which 1 g of boric acid was dissolved in 31 g of water were stirred and mixed, and this was subjected to a dispersion treatment to obtain an average dispersed particle size of 100 nm. A surface-coated lanthanum hexaboride fine particle dispersion was prepared. The coating temperature at this time was 30 ° C.
この分散液を溶媒のエタノールで８００倍に希釈し、可視光透過率を測定したところ７１.３９％であった。上記基準例に比べ可視光透過率の上昇は６.４１ポイントであり、ホウ素を含む水溶液を添加していない上記比較例１に比べて透過率の上昇が少なく、被覆処理中の六ホウ化ランタンの溶解が抑制されていることが分かった。 When this dispersion was diluted 800 times with ethanol as a solvent and the visible light transmittance was measured, it was 71.39%. The increase in visible light transmittance is 6.41 points compared to the above reference example, and the increase in transmittance is small compared to Comparative Example 1 in which an aqueous solution containing boron is not added, and lanthanum hexaboride during coating treatment. It was found that the dissolution of was suppressed.
次に、この分散液３ｇを紫外線硬化樹脂（ＵＶ３７０１）４ｇと混合し、塗布液とした。この塗布液を、厚さ５０μｍのＰＥＴフィルム上にバーコーターを用いて塗布成膜し、これを７０℃で１分間乾燥して溶媒を蒸発させた後、高圧水銀ランプを用いて紫外線を照射し、膜を硬化させた。 Next, 3 g of this dispersion was mixed with 4 g of an ultraviolet curable resin (UV3701) to obtain a coating solution. This coating solution was coated on 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 light using a high pressure mercury lamp. The film was cured.
得られた被膜とＰＥＴフィルムの合計の可視光透過率は７６.３％、ヘイズは０.９％であった。また、これを６０℃で湿度９０％の環境に４日間放置した後、可視光透過率を測定したところ７６.７％であり、透過率の上昇は０.４ポイントであり、この実施例の表面被覆六ホウ化ランタン微粒子の耐水性は良好であった。 The total visible light transmittance of the obtained coating film and PET film was 76.3%, and haze was 0.9%. Moreover, when this was left for 4 days at 60 ° C. in an environment of 90% humidity, the visible light transmittance was measured to be 76.7%, and the increase in transmittance was 0.4 points. The water resistance of the surface-coated lanthanum hexaboride fine particles was good.
上記した基準例、実施例、及び比較例の結果を、下記表１にまとめて示した。
［比較例２］
六ホウ化ランタン微粒子２ｇと、メチルトリメトキシシラン１０ｇと、溶媒としてのエタノール４７ｇと、水３１ｇにホウ酸１０ｇを溶解した水溶液とを撹拌混合し、これを分散処理して平均分散粒子径１００ｎｍの表面被覆六ホウ化ランタン微粒子分散液を調製した。尚、このときの被覆処理温度は３０℃とした。
[Comparative Example 2]
2 g of lanthanum hexaboride fine particles, 10 g of methyltrimethoxysilane, 47 g of ethanol as a solvent, and an aqueous solution in which 10 g of boric acid was dissolved in 31 g of water were stirred and mixed, and this was subjected to a dispersion treatment to obtain an average dispersed particle size of 100 nm. A surface-coated lanthanum hexaboride fine particle dispersion was prepared. The coating temperature at this time was 30 ° C.
この分散液を溶媒のエタノールで８００倍に希釈し、可視光透過率を測定したところ６７.３２％であった。上記基準例に比べ可視光透過率の上昇は２.３４ポイントであり、被覆処理中の六ホウ化ランタンの溶解が抑制されていることが分かった。 This dispersion was diluted 800 times with ethanol as a solvent, and the visible light transmittance was measured to be 67.32%. The increase in visible light transmittance was 2.34 points compared to the above reference example, indicating that dissolution of lanthanum hexaboride during the coating process was suppressed.
しかしながら、ホウ酸の添加量が３０℃の水におけるホウ酸溶解度を超えているため、上記ホウ酸を溶解した水溶液及び上記分散液中にホウ酸の溶け残りが目視で観察された。そのため、この分散液による塗布液の調整は行わなかった。
However, since the amount of boric acid added exceeds the solubility of boric acid in water at 30 ° C., the undissolved boric acid was visually observed in the aqueous solution in which the boric acid was dissolved and the dispersion. Therefore, adjustment of the coating liquid with this dispersion liquid was not performed.
Claims (7)
The surface-coated hexaboride fine particles according to claim 6, wherein the particle diameter of the surface-coated hexaboride fine particles is 2 nm to 10 µm.
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