JP2010040397A - Conductive particulate and its manufacturing method - Google Patents
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Abstract
Description
本発明は、導電性塗料、熱線反射塗料などの塗料、着色材、帯電防止材、静電気防止材、電磁波シールド材などの機能性材料の添加剤などとして用いられる分散性の改良された導電性微粒子及びその製造方法に関する。 The present invention relates to conductive fine particles having improved dispersibility used as additives for functional materials such as conductive paints, paints such as heat ray reflective paints, coloring materials, antistatic materials, antistatic materials, and electromagnetic shielding materials. And a manufacturing method thereof.
近年、電子材料、触媒、医薬・化粧品等の幅広い分野でナノオーダーの微粒子を製造する技術へのニーズが高まっている。例えば、プラズマディスプレイに使用されている蛍光材料では、蛍光粒子を数十ナノメートルのサイズにすることにより、解像度の向上だけでなく、光の散乱を減らしエネルギー効率を高めることもできる。
また、ＩＴＯ（錫ドープ酸化インジウム）を主成分とするナノオーダーの導電性酸化物微粒子は、透明導電性膜への利用が盛んになっている。この導電性酸化物微粒子を透明導電性皮膜とする方法としては、例えば、一次粒子径約０．１μｍ以下の導電性酸化物微粒子の粉末を、溶媒とバインダー樹脂とからなる溶液中に分散させ、これを、ガラス、プラスチック等の基材に塗布、印刷、浸漬、スピンコート或いは噴霧などの手段で塗工し、乾燥する方法がある。
こうして作製した透明導電膜は、ガラス、プラスチック等の帯電防止やほこりの付着防止に有効であり、例えば、ディスプレイや計測器の窓ガラスの帯電防止やほこりの付着防止に利用されている。
さらに、導電性酸化物微粒子は、ＩＣパッケージ回路、クリーンルーム内装材、塗布型透明電極あるいは赤外線遮蔽材料などの用途に利用されはじめてきている。
In recent years, there is a growing need for technologies for producing nano-order fine particles in a wide range of fields such as electronic materials, catalysts, pharmaceuticals and cosmetics. For example, in a fluorescent material used for a plasma display, by setting the size of fluorescent particles to several tens of nanometers, not only the resolution can be improved, but also light scattering can be reduced and energy efficiency can be increased.
In addition, nano-order conductive oxide fine particles mainly composed of ITO (tin-doped indium oxide) are actively used for transparent conductive films. As a method for making the conductive oxide fine particles into a transparent conductive film, for example, a powder of conductive oxide fine particles having a primary particle diameter of about 0.1 μm or less is dispersed in a solution composed of a solvent and a binder resin. There is a method in which this is applied to a substrate such as glass or plastic by means such as coating, printing, dipping, spin coating or spraying, and then dried.
The transparent conductive film produced in this way is effective for preventing charging of glass, plastics and the like and preventing dust adhesion, and is used, for example, for preventing charging of window glass of displays and measuring instruments and preventing dust adhesion.
Furthermore, conductive oxide fine particles have begun to be used for applications such as IC package circuits, clean room interior materials, coated transparent electrodes, and infrared shielding materials.
これらのＩＴＯ微粒子などの導電性酸化物微粒子は、通常、溶液法で製造されているが、この溶液法で製造された導電性酸化物微粒子は、溶液に対する分散性に劣るため、得られる導電性酸化物微粒子の皮膜（導電性皮膜）は、導電性にバラツキが生じ、またヘーズが劣るという問題があった。
このような導電性が良好なＩｎ含有酸化物微粉末を得るためには、これまで一般的な製造方法として、２種以上の原料遷移金属イオンを含有する水溶液（例えば、ＩＴＯ粉末の場合、ＳｎとＩｎを塩化物又は硝酸塩として溶解した水溶液）をアルカリ水溶液と反応させて、原料金属の水酸化物を共沈させ、この共沈水酸化物を出発原料として、これを大気中で加熱処理して酸化物に変換させる方法がある（特許文献１参照）。さらに導電性を高めるために、焼成雰囲気の酸素分圧を制御したり、あるいは還元性の気流で焼成することも述べられている。
また、共沈によって得られた原料を不活性ガスの加圧下、密閉して焼成する等の工夫をして低抵抗化を図ることも知られている（特許文献２参照）。
しかし、このような溶液系を用いた製造方法では廃液処理が必要であり環境負荷が多大でありかつ製造コストも高価になる。また水素による還元処理などが必要であるため、爆発の危険性があり装置も大掛かりなものとなり、コストがかかるという問題点がある。
These conductive oxide fine particles such as ITO fine particles are usually produced by a solution method, but the conductive oxide fine particles produced by this solution method are inferior in dispersibility with respect to the solution, and thus the obtained conductivity. The oxide fine particle film (conductive film) has a problem that the conductivity varies and the haze is inferior.
In order to obtain such an In-containing oxide fine powder having good electrical conductivity, an aqueous solution containing two or more raw material transition metal ions (for example, Sn powder in the case of ITO powder) has been used as a general production method. And an aqueous solution in which In is dissolved as a chloride or nitrate) are reacted with an alkaline aqueous solution to co-precipitate a hydroxide of a raw material metal, and this co-precipitated hydroxide is used as a starting material, and this is heated in the atmosphere. There is a method of converting to an oxide (see Patent Document 1). Furthermore, in order to increase the conductivity, it is also described that the oxygen partial pressure in the firing atmosphere is controlled or the firing is performed in a reducing air flow.
It is also known to reduce the resistance by devising the raw material obtained by coprecipitation under an inert gas pressurization and sealing (see Patent Document 2).
However, in the manufacturing method using such a solution system, waste liquid treatment is required, the environmental load is great, and the manufacturing cost is expensive. Further, since reduction treatment with hydrogen is necessary, there is a risk of explosion, and the apparatus becomes large, and there is a problem that costs are increased.
一方、従来より知られている大気中で２種類以上の原料を混合し、大気中で焼成して反応させた後粉砕し微粉を得るというブレークダウン的な方法では良好な導電性が得られないという課題があったが、本発明者らは物理的方法による超微粒子を不活性ガス存在下で作製することにより高い導電性を得る方法を見出し特許出願している（特許文献３、４）。 On the other hand, good conductivity cannot be obtained by a conventional breakdown method in which two or more kinds of raw materials are mixed in the air, fired in the air, reacted and then pulverized to obtain fine powder. However, the present inventors have found a method for obtaining high conductivity by producing ultrafine particles by a physical method in the presence of an inert gas and have applied for a patent (Patent Documents 3 and 4).
しかしながら上述の特許文献３、４に記載の方法では、高導電化と微粒子化は用途によっては必ずしも十分ではなかった。 However, in the methods described in Patent Documents 3 and 4 described above, high conductivity and fine particles are not always sufficient depending on the application.
本発明はかかる問題を解決するためになされたものであり、高い電気伝導性と超微粒子領域の粒径を有し、ヘイズの小さい導電性皮膜を与える導電性酸化物微粒子及び安全な不活性ガス下での低温加熱処理によっても該導電性酸化物微粒子を得る製造方法を提供することを目的とする。 The present invention has been made to solve such a problem, and has a conductive oxide fine particle and a safe inert gas which have a high electrical conductivity, a particle size in the ultrafine particle region, and provide a conductive film with a small haze. It aims at providing the manufacturing method which obtains this electroconductive oxide microparticles | fine-particles also by the low temperature heat processing under.
本発明者らは、かかる課題を解決するために鋭意研究したところ、溶液系を用いなくても、金属酸化物原料にホウ酸を添加し不活性ガス中で低温加熱処理を行うことにより良好な導電性を有し、粒子の成長が抑制された超微粒子であって、ヘイズの小さい導電性皮膜を与える導電性酸化物微粒子が得られることを見出し、本発明を完成した。 The inventors of the present invention have made extensive studies to solve such problems, and it is preferable to add boric acid to a metal oxide raw material and perform low-temperature heat treatment in an inert gas without using a solution system. The inventors have found that conductive oxide fine particles that have conductivity and suppress the growth of particles and give a conductive film having a small haze can be obtained, and the present invention has been completed.
すなわち、本発明は、
１．導電性材料と、ホウ素元素０．００１〜１質量％とを含有し、且つ、重量平均粒径が０．１μｍ以下であることを特徴とする導電性微粒子、
２．前記導電性材料がインジウム、錫及び亜鉛の少なくとも一種の酸化物を含有する上記１記載の導電性微粒子、
３．９．８１ＭＰａ加圧時の電気伝導度が０．１Ｓ／ｃｍ以上である上記１又は２記載の導電性微粒子、
４．上記１〜３のいずれかに記載の導電性微粒子を溶媒中に分散させてなる導電性微粒子分散液、
５．上記４記載の導電性微粒子分散液を含有することを特徴とする導電性微粒子含有塗料、及び
６．インジウム、錫及び亜鉛の少なくとも一種の酸化物を含有する導電性材料粉末と、ホウ酸とを混合し、不活性ガス下で加熱処理することを特徴とする上記１〜３のいずれかに記載の導電性微粒子の製造方法、
を提供するものである。
That is, the present invention
1. Conductive fine particles containing a conductive material and 0.001 to 1% by mass of boron element, and having a weight average particle size of 0.1 μm or less,
2. 2. The conductive fine particles according to 1 above, wherein the conductive material contains at least one oxide of indium, tin and zinc;
3. The electroconductive fine particles according to 1 or 2 above, wherein the electrical conductivity at the time of pressurization of 3.9.81 MPa is 0.1 S / cm or more,
4). Conductive fine particle dispersion obtained by dispersing the conductive fine particles according to any one of the above 1 to 3 in a solvent,
5). 5. A conductive fine particle-containing paint comprising the conductive fine particle dispersion described in 4 above, and 4. The conductive material powder containing at least one oxide of indium, tin and zinc and boric acid are mixed and heat-treated under an inert gas, Production method of conductive fine particles,
Is to provide.
本発明によれば、導電性を損なうことなく、アルコールなどの溶媒に対する分散性が良好で、かつ安価な導電性微粒子及びその製造方法を提供することができる。 According to the present invention, it is possible to provide conductive fine particles that have good dispersibility in a solvent such as alcohol and are inexpensive without impairing conductivity, and a method for producing the same.
本発明に係る導電性微粒子は、導電性材料と、ホウ素元素０．００１〜１質量％とを含有し、且つ、重量平均粒径が０．１μｍ以下である。
上記導電性材料としては、酸化インジウム、酸化錫、酸化亜鉛、酸化マグネシウム、酸化ニッケル、酸化チタンなどの導電性酸化物が挙げられ、これらを単独で用いてもよく、また、通常、導電性酸化物として用いられるＳｎ含有Ｉｎ2Ｏ3（ＩＴＯ）、Ｚｎ含有Ｉｎ2Ｏ3（ＩＺＯ）、Ｉｎ2Ｏ3の共置換化合物（４価元素と２価元素を３価のＩｎに置換した酸化物）、Ｓｂ含有ＳｎＯ2（ＡＴＯ）、ＺｎＯ、Ａｌ含有ＺｎＯ（ＡＺＯ）、Ｇａ含有ＺｎＯ（ＧＺＯ）の組成になるように２種以上を組み合わせたものを用いることもできる。上記導電性材料の中でも、インジウム、錫及び亜鉛の少なくとも一種の酸化物を含有するものが好ましく用いられる。
The conductive fine particles according to the present invention contain a conductive material and 0.001 to 1% by mass of a boron element, and have a weight average particle size of 0.1 μm or less.
Examples of the conductive material include conductive oxides such as indium oxide, tin oxide, zinc oxide, magnesium oxide, nickel oxide, and titanium oxide. These may be used alone, and usually conductive oxide. Sn-containing In 2 O 3 (ITO), Zn-containing In 2 O 3 (IZO), and In 2 O 3 co-substituted compounds (oxides in which tetravalent and divalent elements are substituted with trivalent In) ), Sb-containing SnO 2 (ATO), ZnO, Al-containing ZnO (AZO), and a combination of two or more of them so as to have a composition of Ga-containing ZnO (GZO) can also be used. Among the conductive materials, those containing at least one oxide of indium, tin, and zinc are preferably used.
本発明の導電性微粒子が含有するホウ素元素の原料としては、例えば、ホウ酸、ホウ化炭素などが挙げられ、価格、取り扱い易さの観点から、ホウ酸が好ましい。
本発明の導電性微粒子におけるホウ素元素の含有量は、導電性微粒子全体に対する割合で、０．００１〜１質量％であり、０．００５〜１質量％であると好ましく、０．０１〜０．５質量％であるとより好ましい。ホウ素元素の含有量が０．００１質量％未満であると、導電性を向上させる効果が十分ではなく、他方、ホウ素の含有量が１質量％を超えると導電性が逆に低下する。この理由としてはホウ素が多くなると絶縁性のＩｎＢＯ3が生成してＩｎを消費しまうからと思われる。そして、ホウ素元素を上記含有量の割合で含有することにより、窒素などの不活性ガス中での焼成を行っても、導電性微粒子の導電性を向上させることができる。
Examples of the raw material for the boron element contained in the conductive fine particles of the present invention include boric acid and carbon boride, and boric acid is preferable from the viewpoint of cost and ease of handling.
The content of boron element in the conductive fine particles of the present invention is 0.001 to 1% by mass, preferably 0.005 to 1% by mass with respect to the entire conductive fine particles, and 0.01 to 0.00%. More preferably, it is 5 mass%. If the boron element content is less than 0.001% by mass, the effect of improving the conductivity is not sufficient. On the other hand, if the boron content exceeds 1% by mass, the conductivity decreases. The reason for this seems to be that when boron increases, insulating InBO 3 is generated and In is consumed. And by containing a boron element in the ratio of the said content, even if it bakes in inert gas, such as nitrogen, the electroconductivity of electroconductive fine particles can be improved.
導電性微粒子の重量平均粒径は、導電性微粒子を含有するペーストや分散液として用いる観点から、０．１μｍ以下であり、０．０７μｍ以下であると好ましい。その下限については特に制限はないが、凝集の防止及び生産性の観点から、１０ｎｍ程度である。
導電性微粒子の導電性は、高い方が好ましいが、９．８１ＭＰａの加圧時の電気伝導度が、０．０１Ｓ／ｃｍ以上であれば、導電性微粒子としての機能を有する。
前記電気伝導度は、０．１Ｓ／ｃｍ以上であることがより好ましい。
The weight average particle diameter of the conductive fine particles is 0.1 μm or less and preferably 0.07 μm or less from the viewpoint of use as a paste or dispersion containing the conductive fine particles. The lower limit is not particularly limited, but is about 10 nm from the viewpoint of preventing aggregation and productivity.
The conductivity of the conductive fine particles is preferably higher, but if the electrical conductivity at the time of pressurization of 9.81 MPa is 0.01 S / cm or more, it has a function as the conductive fine particles.
The electrical conductivity is more preferably 0.1 S / cm or more.
本発明はまた、上記導電性微粒子を溶媒中に分散させてなる導電性微粒子分散液も提供する。
前記溶媒としては、水、有機溶媒を用いることができる。有機溶媒としては、メタノール、エタノール、ｎ−プロパノール、イソプロパノール、エチレングリコール、ジエチレングリコール、トリエチレングリコール、プロピレングリコール、グリセリンなどのアルコール類、アセトン、メチルエチルケトン、シクロヘキサン等のケトン類、トルエン、キシレンなどの芳香族溶媒などがある。これらは、１種を単独で用いてもよく、２種以上を組み合わせて用いても良い。
さらに、必要に応じて、スルホン酸アミド系、ε-カプトラクトン系、ハイドロステアリン酸系、ポリカルボン酸系、ポリエステル系などの分散剤を使用することも可能である。
The present invention also provides a conductive fine particle dispersion obtained by dispersing the conductive fine particles in a solvent.
As the solvent, water or an organic solvent can be used. Organic solvents include methanol, ethanol, n-propanol, isopropanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerol and other alcohols, acetone, methyl ethyl ketone and cyclohexane ketones, and toluene and xylene aromatics. There are solvents. These may be used alone or in combination of two or more.
Furthermore, if necessary, a dispersant such as a sulfonic acid amide, ε-captolactone, hydrostearic acid, polycarboxylic acid, or polyester may be used.
本発明はさらに、上記導電性微粒子分散液を含有する導電性微粒子含有塗料も提供する。
本発明の導電性微粒子含有塗料としては、上述の導電性微粒子分散液をそのまま用いてもよく、この導電性微粒子分散液に、塗膜形成成分として、ポリエステル樹脂、アクリル樹脂、エポキシ樹脂、アルキド樹脂、シリコン樹脂などを加えて、得られたものを導電性微粒子含有塗料として用いることもできる。
The present invention further provides a conductive fine particle-containing coating containing the conductive fine particle dispersion.
As the conductive fine particle-containing coating of the present invention, the above-mentioned conductive fine particle dispersion may be used as it is, and a polyester resin, acrylic resin, epoxy resin, alkyd resin is used as a coating film forming component in this conductive fine particle dispersion. In addition, a resin obtained by adding silicon resin or the like can also be used as a coating material containing conductive fine particles.
次に、本発明に係る導電性微粒子の製造方法について説明する。
本発明に係る導電性微粒子の製造方法は、インジウム、錫及び亜鉛の少なくとも一種の酸化物を含有する導電性材料粉末と、ホウ酸とを混合し、不活性ガス下で加熱処理することを特徴とする。
導電性材料粉末としては、前記したインジウム、錫及び亜鉛の少なくとも一種の酸化物を含有する導電性材料の粉末状のものが用いられる。
Next, a method for producing conductive fine particles according to the present invention will be described.
The method for producing conductive fine particles according to the present invention is characterized in that a conductive material powder containing at least one oxide of indium, tin and zinc and boric acid are mixed and heat-treated in an inert gas. And
As the conductive material powder, powdered conductive material containing at least one oxide of indium, tin and zinc is used.
ホウ酸は、溶媒に溶解させて溶液状態のものを用いることで、原料の導電性材料粉末及びこの粉砕物の表面に均一にホウ素を付着させ、その後の加熱処理により、導電性微粒子とホウ素を反応させることが容易となる。
ホウ酸の配合量は、得られる導電性微粒子がホウ素元素を０．００１〜１質量％含有する量であればよく、具体的には、導電性材料粉末１００質量部に対して０．０１〜５質量部であると好ましく、０．０５〜３質量部であるとより好ましい。
また、ホウ酸に加えてハロゲン化合物を添加すると、さらに溶媒への分散性が向上するため好ましい。
前記ハロゲン化合物としては、溶媒に溶解するハロゲン化合物が好ましく、加熱処理により揮発する成分を含むハロゲン化合物がより好ましい。
これらの観点から、前記ハロゲン化合物としては、ハロゲン化アンモニウムが好ましく、特に、臭化アンモニウムが好ましい。
Boric acid is dissolved in a solvent and used in a solution state, so that boron is uniformly attached to the surface of the raw material conductive material powder and this pulverized product, and then the conductive fine particles and boron are removed by heat treatment. It becomes easy to make it react.
The compounding quantity of boric acid should just be the quantity in which the electroconductive fine particles obtained contain the boron element 0.001-1 mass%, specifically, 0.01-0.1 with respect to 100 mass parts of electroconductive material powder. It is preferable in it being 5 mass parts, and it is more preferable in it being 0.05-3 mass parts.
Further, it is preferable to add a halogen compound in addition to boric acid because dispersibility in a solvent is further improved.
As the halogen compound, a halogen compound dissolved in a solvent is preferable, and a halogen compound containing a component that volatilizes by heat treatment is more preferable.
From these viewpoints, the halogen compound is preferably ammonium halide, and particularly preferably ammonium bromide.
前記ハロゲン化合物の添加量及び溶媒に対するハロゲン化合物の割合は、加熱処理条件等を考慮して決定されるが、例えば、ハロゲン化合物として、ハロゲン化アンモニウムを用いた場合、その添加量は、導電性材料粉末１００質量部に対して、例えば、０．０５〜１０質量部、好ましくは０．５〜５質量部である。
前記溶媒としては、水、アセトン、アルコールなどの溶媒を用いることができる。
The addition amount of the halogen compound and the ratio of the halogen compound to the solvent are determined in consideration of heat treatment conditions and the like. For example, when ammonium halide is used as the halogen compound, the addition amount is determined by the conductive material. It is 0.05-10 mass parts with respect to 100 mass parts of powders, Preferably it is 0.5-5 mass parts.
As the solvent, a solvent such as water, acetone or alcohol can be used.
原料の導電性材料粉末と、ホウ酸とを混合する方法は、特に限定されず、通常の混合方法を採用することができ、混合と同時に原料の導電性材料粉末を粉砕する混合方法を採用することが特に好ましい。
例えば、遊星ボールミルによる混合は、粉砕効果にも優れ、原料の導電性材料粉末と前記ホウ酸とを混合すると同時に導電性材料粉末を粉砕することができるので、有用な方法である。
また、混合温度は、通常、常温でよく、混合時間は、導電性材料粉末の粒径、目的とする導電性微粒子の粒径などを考慮して適宜決定することができ、原料の導電性材料粉末の粒径にもよるが、例えば、１〜２４時間混合する。
その後、得られた混合粉体を加熱処理することにより、ホウ素元素を０．００１〜１質量％含有する本発明の導電性微粒子が得られる。
A method of mixing the raw material conductive material powder and boric acid is not particularly limited, and a normal mixing method can be adopted, and a mixing method of pulverizing the raw material conductive material powder simultaneously with the mixing is adopted. It is particularly preferred.
For example, mixing by a planetary ball mill is a useful method because it has an excellent pulverization effect, and the conductive material powder can be pulverized at the same time as mixing the raw material conductive material powder and the boric acid.
The mixing temperature is usually normal temperature, and the mixing time can be appropriately determined in consideration of the particle size of the conductive material powder, the particle size of the target conductive fine particles, and the like. Depending on the particle size of the powder, for example, it is mixed for 1 to 24 hours.
Then, the conductive fine particles of the present invention containing 0.001 to 1% by mass of boron element are obtained by heat-treating the obtained mixed powder.
加熱処理は、通常の電気炉やマイクロ波加熱炉などを用いて行うことができる。
加熱処理における加熱温度、加熱時間は、特に限定されないが、加熱温度としては、原料の種類にもよるが、例えば、３００℃以上、好ましくは４００℃以上、より好ましくは５００℃以上である。
この加熱温度が高いと、加熱により粒成長が激しくなり超微粒子を得られない場合があり、導電性微粒子の種類にもよるが、例えば、加熱温度は、１０００℃未満にすることが好ましく、特に、９００℃以下が好ましい。
The heat treatment can be performed using a normal electric furnace, a microwave heating furnace, or the like.
The heating temperature and heating time in the heat treatment are not particularly limited, but the heating temperature is, for example, 300 ° C. or higher, preferably 400 ° C. or higher, more preferably 500 ° C. or higher, although it depends on the type of raw material.
When this heating temperature is high, grain growth becomes intense due to heating and ultrafine particles may not be obtained. Depending on the type of conductive fine particles, for example, the heating temperature is preferably less than 1000 ° C. 900 ° C. or less is preferable.
また、加熱時間としては、例えば、１〜１２０分、好ましくは、５〜９０分、より好ましくは１０〜６０分である。
加熱時間が長くなると、微粒子が成長する傾向にあるが、加熱温度ほどには微粒子の成長に影響しないようである。
The heating time is, for example, 1 to 120 minutes, preferably 5 to 90 minutes, and more preferably 10 to 60 minutes.
As the heating time becomes longer, the fine particles tend to grow, but it does not seem to affect the growth of the fine particles as much as the heating temperature.
さらに、加熱雰囲気としては、大気中でも可能であるが、より高い導電性を得るためには、低酸素雰囲気などが好ましく、低酸素雰囲気における酸素濃度は１体積％以下が好ましく、より好ましくは０．１体積％以下である。 Furthermore, the heating atmosphere is possible even in the air, but in order to obtain higher conductivity, a low oxygen atmosphere or the like is preferable, and the oxygen concentration in the low oxygen atmosphere is preferably 1% by volume or less, more preferably 0. 1% by volume or less.
さらに、必要に応じて、加熱処理を行う前に、得られた混合粉体を乾燥することができる。
乾燥温度、乾燥時間は、特に限定されないが、例えば、６０〜１２０℃で、１〜１０時間行うことができる。
Furthermore, the obtained mixed powder can be dried before heat treatment, if necessary.
Although a drying temperature and drying time are not specifically limited, For example, it can carry out at 60-120 degreeC for 1 to 10 hours.
以下、導電性微粒子として、ＩＴＯ組成の導電性微粒子を例にして、本発明をさらに説明する。
ＩＴＯ組成の導電性微粒子を作製する場合、原料として、酸化インジウム粉末と酸化第二錫粉末とを用いることができる。
この場合、加熱処理の雰囲気にもよるが、窒素ガス雰囲気の場合、３００℃以上で酸化インジウムと酸化錫の反応が開始する。また、４００℃以上では、反応がさらに進み、得られる導電性微粒子の導電性が向上する。さらに、７００℃以上では、微粒子の成長が顕著になり、得られる導電性微粒子の導電性がさらに向上する。
Hereinafter, the present invention will be further described using conductive fine particles having an ITO composition as an example of conductive fine particles.
When producing conductive fine particles having an ITO composition, indium oxide powder and stannic oxide powder can be used as raw materials.
In this case, although depending on the atmosphere of the heat treatment, in the case of a nitrogen gas atmosphere, the reaction between indium oxide and tin oxide starts at 300 ° C. or higher. Moreover, at 400 degreeC or more, reaction advances further and the electroconductivity of the electroconductive fine particles obtained improves. Furthermore, at 700 ° C. or higher, the growth of fine particles becomes remarkable, and the conductivity of the obtained conductive fine particles is further improved.
このように、加熱処理の温度は、高いほど導電性が向上するものであるが、加熱温度を高くしても、一定温度以上では、導電性は飽和傾向になり、その温度以上で処理しても粒子同士が焼結しはじめ、数μｍの大粒径となり、導電性微粒子には適さなくなる。また、エネルギーの利用効率の点からも好ましくない。
加熱処理雰囲気としては、導電性向上には水素などの還元性雰囲気が優れることもあるが、安全上の問題、価格の問題、さらには粉体が濃褐色に着色するという問題があり、窒素などの不活性ガス雰囲気での焼成が望ましい。
窒素ガス雰囲気での焼成では水素などの還元性雰囲気の場合に比べ、粒子の成長が抑制され、粒子の着色も少ない。しかし低温での加熱処理では導電性が十分得られないことがあるが、ホウ酸を共存させることにより５００℃程度の低温加熱でも高い導電性を得ることができる。
Thus, the higher the temperature of the heat treatment, the better the conductivity. However, even if the heating temperature is increased, the conductivity tends to saturate at a certain temperature or higher, and the heat treatment is performed at that temperature or higher. However, the particles begin to sinter and have a large particle size of several μm, making them unsuitable for conductive fine particles. Moreover, it is not preferable also from the point of the utilization efficiency of energy.
As a heat treatment atmosphere, a reducing atmosphere such as hydrogen may be excellent for improving conductivity, but there are safety problems, price problems, and problems that the powder is colored dark brown, such as nitrogen Firing in an inert gas atmosphere is desirable.
Firing in a nitrogen gas atmosphere suppresses particle growth and reduces particle coloring compared to a reducing atmosphere such as hydrogen. However, sufficient heat conductivity may not be obtained by heat treatment at a low temperature, but high conductivity can be obtained even by low temperature heating at about 500 ° C. by coexisting boric acid.
以下、実施例及び比較例により、本発明をさらに具体的に説明する。
表１に、実施例及び比較例におけるＩｎ：Ｓｎ比、加熱温度、得られた導電性微粒子のホウ素含有量、重量平均粒径、電気伝導度、格子定数及び導電性皮膜のヘイズの測定結果を示す。
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
Table 1 shows the measurement results of In: Sn ratio, heating temperature, boron content of the obtained conductive fine particles, weight average particle size, electrical conductivity, lattice constant, and haze of the conductive film in Examples and Comparative Examples. Show.
＜測定方法＞
（１）ホウ素含有量：
導電性微粒子におけるホウ素含有量は、ＩＣＰ−ＭＳ（高周波誘導結合プラズマ質量分析装置：ＳＩＩ社製ＳＰＱ９１００）を用いて測定した。
（２）重量平均粒径：
導電性微粒子の平均粒径は、ＢＥＴ法（一点法）による窒素吸着比表面積（ｍ2／ｇ）から測定した。
（３）電気伝導度（σ）：
導電性微粒子の電気伝導度（σ）は、粉体抵抗システム（株式会社ダイアインスツルメント社製）を用い、加圧しながら測定し、圧力−電気伝導度のグラフから９．８１ＭＰａでの電気伝導度により測定した。
（４）ヘイズ：
ヘイズは、スガ試験機株式会社製ヘーズメーターを用いて測定した。
（５）格子定数：Ｘ線回折測定からもとめた。
<Measurement method>
(1) Boron content:
The boron content in the conductive fine particles was measured using ICP-MS (High Frequency Inductively Coupled Plasma Mass Spectrometer: SPQ9100 manufactured by SII).
(2) Weight average particle diameter:
The average particle diameter of the conductive particles was measured from the BET method specific surface area by nitrogen adsorption according to (single point method) (m 2 / g).
(3) Electrical conductivity (σ):
The electric conductivity (σ) of the conductive fine particles was measured while applying pressure using a powder resistance system (Diainstrument Co., Ltd.), and the electric conduction at 9.81 MPa from the pressure-electric conductivity graph. Measured by degree.
(4) Haze:
The haze was measured using a haze meter manufactured by Suga Test Instruments Co., Ltd.
(5) Lattice constant: determined from X-ray diffraction measurement.
実施例１
まず、原料である純度９９．９％の酸化インジウム粉末（添川化学株式会社製）９４．６ｇを秤量し、これをメノウ乳鉢に入れ、次いで、原料である純度９８％の酸化第二錫粉末（日本化学工業株式会社製）５．４ｇを秤量し、これを前記メノウ乳鉢に入れた。
次に、ホウ酸０．３ｇを溶解させた水溶液２０ｇを前記メノウ乳鉢に添加して、原料粉末を混合、粉砕した。
その後、さらなる混合、粉砕をするために、遊星ボールミルで６時間混合、粉砕し、混合粉体を得た。
Example 1
First, 94.6 g of a 99.9% pure indium oxide powder (Zoekawa Chemical Co., Ltd.) as a raw material was weighed and placed in an agate mortar, and then 98% pure stannic oxide powder (as a raw material) 5.4 g (manufactured by Nippon Chemical Industry Co., Ltd.) was weighed and placed in the agate mortar.
Next, 20 g of an aqueous solution in which 0.3 g of boric acid was dissolved was added to the agate mortar, and the raw material powder was mixed and pulverized.
Thereafter, in order to further mix and pulverize, the mixture was mixed and pulverized in a planetary ball mill for 6 hours to obtain a mixed powder.
次に、得られた混合粉体を９０℃で３時間乾燥させ、乾燥後、この混合粉体をアルミナボートに入れ、このアルミナボートを管状炉の中に挿入し、処理雰囲気として、窒素ガスとするために窒素ガスを０．５リットル／分の流量で流した。そして、加熱温度を６００℃、加熱時間を３０分とするために、室温から６００℃まで約２０分間かけて昇温し、６００℃で３０分間保持し、その後加熱を止め、アルミナボートを取り出して急冷し、薄褐色の粉体を得た。 Next, the obtained mixed powder is dried at 90 ° C. for 3 hours, and after drying, this mixed powder is put into an alumina boat, this alumina boat is inserted into a tubular furnace, and nitrogen gas and In order to achieve this, nitrogen gas was flowed at a flow rate of 0.5 l / min. Then, in order to set the heating temperature to 600 ° C. and the heating time to 30 minutes, the temperature was raised from room temperature to 600 ° C. over about 20 minutes, held at 600 ° C. for 30 minutes, then the heating was stopped, and the alumina boat was taken out. Quenching was performed to obtain a light brown powder.
〔ホウ素含有量〕
この褐色の粉体について、ホウ素含有量をＩＣＰ−ＭＳにより測定したところ、０．０５０質量％であった。
〔重量平均粒径〕
この褐色の粉体について、ＢＥＴ法により比表面積の測定し、重量平均粒径を求めたところ、重量平均粒径は３７ｎｍであった。
〔電気伝導度〕
この褐色の粉体について、電気伝導度（σ）を測定したところ、９．８１ＭＰａの加圧時の電気伝導度は、８．２Ｓ／ｃｍであり、電気伝導性が良好であった。
〔格子定数〕
この褐色の粉体について、格子定数を測定した。結果を表１に示す。粉体の格子定数はホウ酸の添加量によって増加することが明らかになった。ホウ素のイオン半径はＩｎに比べて非常に小さいので、Ｉｎ元素などを置換するのではなく、格子間に入っているものと思われる。
[Boron content]
About this brown powder, when boron content was measured by ICP-MS, it was 0.050 mass%.
[Weight average particle size]
About this brown powder, when the specific surface area was measured by BET method and the weight average particle diameter was calculated | required, the weight average particle diameter was 37 nm.
[Electric conductivity]
When the electric conductivity (σ) of this brown powder was measured, the electric conductivity at the time of pressurization of 9.81 MPa was 8.2 S / cm, and the electric conductivity was good.
[Lattice constant]
The lattice constant of this brown powder was measured. The results are shown in Table 1. It became clear that the lattice constant of the powder increased with the amount of boric acid added. Since the ionic radius of boron is much smaller than that of In, it is considered that the boron is not interstitial but substituted in the lattice.
〔導電性分散液の調製〕
この薄褐色の粉体である導電性微粒子をシクロヘキサノン溶媒に入れ、導電性微粒子を２０質量％含有する導電性微粒子分散液を作製した。
さらに、この導電性微粒子分散液に、導電性微粒子１００質量部に対して、３質量部の分散剤（ビッグケミージャパン社製、ＤＩＳＰＥＲＢＹＫ−２０９５）と２質量部のポリエステル樹脂とを添加し、ビーズミルを用いて３時間混合し導電性微粒子分散液を調製した。
(Preparation of conductive dispersion)
The conductive fine particles, which are a light brown powder, were put in a cyclohexanone solvent to prepare a conductive fine particle dispersion containing 20% by mass of conductive fine particles.
Further, 3 parts by mass of a dispersant (manufactured by Big Chemie Japan, DISPERBYK-2095) and 2 parts by mass of a polyester resin are added to the conductive fine particle dispersion with respect to 100 parts by mass of the conductive fine particles. Was mixed for 3 hours to prepare a conductive fine particle dispersion.
この導電性微粒子分散液を導電性微粒子含有塗料として用い、バーコーターによりガラス基板上に塗布し、１５０℃で１時間乾燥させて、厚さ約１μｍの導電性皮膜を得た。
この導電性皮膜について、ヘイズメーターによりヘイズを測定した結果、導電性皮膜のヘイズは４％であり、この薄褐色の粉体である導電性微粒子は、良好な電気伝導度と分散性を有することがわかった。
This conductive fine particle dispersion was used as a conductive fine particle-containing coating, applied onto a glass substrate with a bar coater, and dried at 150 ° C. for 1 hour to obtain a conductive film having a thickness of about 1 μm.
As a result of measuring the haze of this conductive film with a haze meter, the haze of the conductive film is 4%, and the conductive fine particles as the light brown powder have good electrical conductivity and dispersibility. I understood.
実施例２
酸化インジウム粉末の量を７８．６５ｇ、酸化第二錫粉末を２１．３５ｇ、ホウ酸０．１ｇを溶解させた水溶液２０ｇとした以外は、実施例１と同様の条件で実施し、薄褐色の粉体を得た。
また、この褐色の粉体のホウ素含有量、重量平均粒径、電気伝導度、格子定数及び導電性皮膜のヘイズを測定した結果を表１に示す。
その結果、この薄褐色の粉体である導電性微粒子は、良好な電気伝導度と分散性を有することがわかった。
Example 2
The procedure was the same as in Example 1 except that the amount of indium oxide powder was 78.65 g, stannic oxide powder was 21.35 g, and boric acid 0.1 g was dissolved in 20 g. A powder was obtained.
Table 1 shows the results of measuring the boron content, weight average particle diameter, electrical conductivity, lattice constant, and haze of the conductive coating of the brown powder.
As a result, it was found that the conductive fine particles, which are a light brown powder, have good electrical conductivity and dispersibility.
実施例３
ホウ酸１．０ｇを溶解させた水溶液２０ｇとした以外は、実施例２と同様の条件で実施し、薄褐色の粉体を得た。
また、この薄褐色の粉体のホウ素含有量、重量平均粒径、電気伝導度、格子定数及び導電性皮膜のヘイズを測定した結果を表１に示す。
その結果、この薄褐色の粉体である導電性微粒子は、良好な電気伝導度と分散性を有することがわかった。
Example 3
A light brown powder was obtained under the same conditions as in Example 2 except that 20 g of an aqueous solution in which 1.0 g of boric acid was dissolved was used.
Table 1 shows the results of measuring the boron content, weight average particle diameter, electrical conductivity, lattice constant, and haze of the conductive film of the light brown powder.
As a result, it was found that the conductive fine particles, which are a light brown powder, have good electrical conductivity and dispersibility.
実施例４
加熱温度を７００℃、加熱時間を３０分とし、ホウ酸０．３ｇを溶解させた水溶液２０ｇとした以外は、実施例２と同様の条件で実施し、薄黄緑色の粉体を得た。
また、この薄黄緑色の粉体のホウ素含有量、重量平均粒径、電気伝導度、格子定数及び導電性皮膜のヘイズを測定した結果を表１に示す。
その結果、この薄黄緑色の粉体である導電性微粒子は、良好な電気伝導度と分散性を有することがわかった。
Example 4
The procedure was the same as in Example 2 except that the heating temperature was 700 ° C., the heating time was 30 minutes, and 20 g of an aqueous solution in which 0.3 g of boric acid was dissolved.
Table 1 shows the results of measuring the boron content, weight average particle diameter, electrical conductivity, lattice constant, and haze of the conductive coating of the light yellow green powder.
As a result, it was found that the conductive fine particles, which are this pale yellow green powder, have good electrical conductivity and dispersibility.
実施例５
加熱温度を５００℃、加熱時間を３０分とし、ホウ酸０．５ｇを溶解させた水溶液２０ｇとした以外は、実施例２と同様の条件で実施し、薄褐色の粉体を得た。
また、この薄褐色の粉体のホウ素含有量、重量平均粒径、電気伝導度、格子定数及び導電性皮膜のヘイズを測定した結果を表１に示す。
その結果、この薄褐色の粉体である導電性微粒子は、良好な電気伝導度と分散性を有することがわかった。
Example 5
A light brown powder was obtained under the same conditions as in Example 2, except that the heating temperature was 500 ° C., the heating time was 30 minutes, and 20 g of an aqueous solution in which 0.5 g of boric acid was dissolved was used.
Table 1 shows the results of measuring the boron content, weight average particle diameter, electrical conductivity, lattice constant, and haze of the conductive film of the light brown powder.
As a result, it was found that the conductive fine particles, which are a light brown powder, have good electrical conductivity and dispersibility.
実施例６
ホウ酸０．３ｇに加え、臭化アンモニウムを１ｇを溶解させた水溶液２０ｇとし、加熱温度を７００℃、加熱時間を３０分とした以外は、実施例２と同様の条件で実施し、薄黄緑色の粉体を得た。
また、この薄褐色の粉体のホウ素含有量、重量平均粒径、電気伝導度、格子定数及び導電性皮膜のヘイズを測定した結果を表１に示す。
その結果、この薄褐色の粉体である導電性微粒子は、良好な電気伝導度と分散性を有することがわかった。
Example 6
Except for 0.3 g of boric acid, 20 g of an aqueous solution in which 1 g of ammonium bromide was dissolved, heating temperature was set to 700 ° C., and heating time was set to 30 minutes. A green powder was obtained.
Table 1 shows the results of measuring the boron content, weight average particle diameter, electrical conductivity, lattice constant, and haze of the conductive film of the light brown powder.
As a result, it was found that the conductive fine particles, which are a light brown powder, have good electrical conductivity and dispersibility.
比較例１
ホウ酸を添加しなかった以外は、実施例２と同じ条件で実施し、褐色の粉体を得た。
また、この褐色の粉体の重量平均粒径、電気伝導度、格子定数及び導電性皮膜のヘイズを測定した結果を表１に示す。
表１に示すように、重量平均粒径は３９ｎｍと小さいものの、電気伝導性は低く１０の−４乗（Ｓ／ｃｍ）のオーダーであり、導電性皮膜のヘイズも２２と大きく、導電性皮膜は透明性が悪く、分散性も悪くなっていた。
Comparative Example 1
The procedure was the same as in Example 2 except that boric acid was not added, to obtain a brown powder.
Table 1 shows the results of measuring the weight average particle diameter, electrical conductivity, lattice constant, and haze of the conductive film of the brown powder.
As shown in Table 1, although the weight average particle size is as small as 39 nm, the electrical conductivity is low and is on the order of 10 −4 (S / cm), and the haze of the conductive film is as large as 22, Had poor transparency and dispersibility.
比較例２
加熱温度を７００℃、加熱時間を３０分とした以外は比較例２と同じ条件で実施し、褐色の粉体を得た。また、この褐色の粉体の重量平均粒径、電気伝導度及び導電性皮膜のヘイズを測定した結果を表１に示す。
表１に示すように、重量平均粒径は４２ｎｍと小さいものの、電気伝導性は低く１０の−２乗（Ｓ／ｃｍ）のオーダーであり、導電性皮膜のヘイズも３２と大きく、導電性皮膜は透明性が悪く、分散性も悪くなっていた。
Comparative Example 2
A brown powder was obtained under the same conditions as in Comparative Example 2 except that the heating temperature was 700 ° C. and the heating time was 30 minutes. Table 1 shows the results of measuring the weight average particle diameter, electrical conductivity, and haze of the conductive coating of the brown powder.
As shown in Table 1, although the weight average particle size is as small as 42 nm, the electrical conductivity is low and is on the order of 10 −2 (S / cm), and the haze of the conductive film is as large as 32. Had poor transparency and dispersibility.
本発明の導電性および分散性の改良された導電性微粒子は、アルコールなどの溶媒に対する分散性に優れているため、導電性塗料、熱線反射塗料などの塗料、着色、帯電防止、静電気防止、電磁シールドなどの機能性材料の添加剤などとして好適に用いられる。 The conductive fine particles having improved conductivity and dispersibility according to the present invention have excellent dispersibility in solvents such as alcohol, and therefore, paints such as conductive paints and heat ray reflective paints, coloring, antistatic, antistatic, electromagnetic It is suitably used as an additive for functional materials such as shields.
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