JP4274822B2 - Method for manufacturing membrane covering - Google Patents

Description

【００２９】
式（１）に従って計算される緩衝液のイオン強度は、１．４１〜５．０であることが好ましい。より好ましくは、１．５〜３．５である。なお、式（１）において、例えば［Ｋ⁺］はＫ⁺イオンのモル濃度を示す。
【００３０】
本発明に用いる基体の形状としては、特に限定されず、平面板状のものでも、粉体（粒子）状のものでも構わないが、特に、粉体（粒子）状のものを用いる際に本発明の有用性が顕著となる。
基体が粉体の場合、その形状の詳細としては、球体、亜球状態、正多面体等の等方体、直方体、回転楕円体、菱面体、板状体、針状体（円柱、角柱）などの多面体、さらに粉砕物のような全く不定形な粉体も使用可能である。これらの基体は、粒径については特に限定するものでないが、０．０１μｍ〜数ｍｍの範囲のものが好ましい。また、基体粒子の比重としては、０．１〜１０．５の範囲のものが用いられるが、分散液媒等に分散等をさせる場合に流動性、浮遊性の面から０．１〜５．５が好ましく、より好ましくは０．１〜２．８の範囲である。基体の比重が０．１未満では分散液媒中の浮力が大きすぎ、膜を多層あるいは非常に厚くする必要があり、不経済である。一方、１０．５を超えると、浮遊させるための膜が厚くなり、同様に不経済である。
【００３１】
また、本発明に用いる基体の材質としては、特に限定されず、無機物でも、有機物でもよいが、膜被覆体に多機能性を持たせるためには、磁性体、誘電体および導電体等が主に用いられる。基体が金属の場合、鉄、ニッケル、クロム、チタン、アルミニウム等、どのような金属でもよいが、その磁性を利用するものにおいては、鉄、コバルト、ニッケル等磁性を帯びるものが好ましい。これらの金属は合金でも良く、前記の磁性を有するものであるときには、強磁性合金を使用することが好ましい。また、その基体が金属化合物の場合には、その代表的なものとして前記した金属の酸化物が挙げられるが、例えば、鉄、ニッケル、クロム、チタン、アルミニウム、ケイ素等の外、カルシウム、マグネシウム、バリウム等の酸化物、あるいはこれらの複合酸化物でも良い。さらに、金属酸化物以外の金属化合物としては、金属窒化物、金属炭化物等を挙げることができる。
【００３２】
さらに、基体として、金属以外では、半金属、非金属の化合物、特に酸化物、炭化物、窒化物であり、シリカ、ガラスビーズ等を使用することができる。その他の無機物としてはシラスバルーン（中空ケイ酸粒子）などの無機中空粒子、微小炭素中空球（クレカスフェアー）、電融アルミナバブル、アエロジル、ホワイトカーボン、シリカ微小中空球、炭酸カルシウム微小中空球、炭酸カルシウム、パーライト、タルク、ベントナイト、合成雲母、白雲母など雲母類、カオリン等を用いることができる。
【００３３】
有機物としては、樹脂が好ましい。樹脂の具体例としては、セルロースパウダー、酢酸セルロースパウダー、ポリアミド、エポキシ樹脂、ポリエステル、メラミン樹脂、ポリウレタン、酢酸ビニル樹脂、ケイ素樹脂、アクリル酸エステル、メタアクリル酸エステル、スチレン、エチレン、プロピレン及びこれらの誘導体の重合または共重合により得られるものなどが挙げられる。特に好ましい樹脂はアクリル酸またはメタアクリル酸エステルの重合により得られる球状のアクリル樹脂である。但し、樹脂を基体とする場合、乾燥における加熱温度は樹脂の融点以下でなければならない。
【００３４】
本発明における炭酸系緩衝液をもちいて形成する膜としては、特に限定されないが、金属酸化物膜、金属水酸化物膜、金属チッ化物膜、金属膜等が挙げられるが、金属酸化物膜、金属水酸化物膜が特に好適である。
また、基体の表面に膜を形成するための上記炭酸緩衝液中での反応としては、特に限定されないが、金属塩からの反応等が挙げられる。
【００３５】
本発明において、金属塩として使用される金属には、鉄、ニッケル、クロム、チタン、亜鉛、アルミニウム、カドミウム、ジルコニウム、ケイ素、錫、鉛、リチウム、インジウム、ネオジウム、ビスマス、セリウム、アンチモン等の他、カルシウム、マグネシウム、バリウム等が挙げられる。また、これら金属の塩としては、硫酸、硝酸、塩酸、シュウ酸、炭酸やカルボン酸の塩が挙げられる。さらにまた、前記金属のキレート錯体も含まれる。本発明において使用される金属塩の種類は、その基体の表面に付与しようとする性質や製造に際して適用する手段に応じてそれに適するものが選択される。
【００３６】
これらの金属塩の反応により形成される金属酸化物等の膜は、複数層形成してもよく、またそれらの金属酸化物等の膜の上に、必要により金属アルコキシドの加水分解による金属酸化物等、また他の製膜方法による膜を形成することもできる。このようにして、基体の上に多層の膜を形成することができ、しかもその際、各層の厚さが所定の厚さをもつように形成条件を設定することにより、目的とする特性を得ることが可能である。また簡単な操作でかつ安価な原料である金属塩を用いて金属酸化物等の膜を多層に形成することができる。
【００３７】
本発明の膜被覆体を製造する方法では、多層被覆膜を連続した工程として製作しても良く、また、各被覆膜を１層ずつ製作、あるいは単層製作と複層連続製作を組み合わせるなど種々の方法で製作することができる。
本発明において、その１回に形成させる金属酸化物膜等の膜の厚さとしては、５ｎｍ〜１０μｍの範囲とすることが可能であり、従来の形成法より厚くすることができる。
本発明においては、上記粉体基体を屈折率が互いに異なる複数の被膜層を用い、各被膜層の屈折率及び層厚を適宜選択して被覆することにより、その干渉色により着色しかつ可視光域および可視光域以外に特異的な干渉反射ピークを発現する粉体とすることができる。
【００３８】
例えば、基体の表面に、屈折率の異なる被覆を、膜の物質の屈折率と膜の厚さとの積が電磁波の４分の１に相当する厚さだけ設けると、干渉により光は大部分反射（フレネル反射）され、この作用を利用し、染料や顔料を用いずとも着色することができる。
詳細には、基体の表面に、屈折率の異なる交互被覆膜を、次の式（２）を満たすように、被膜を形成する物質の屈折率ｎと可視光の波長の４分の１の整数ｍ倍に相当する厚さｄを有する交互膜を適当な厚さと膜数設けると、特定の波長λの光（フレネルの干渉反射を利用したもの）が反射または吸収される。
【００３９】
ｎｄ＝ｍλ／４ （２）
【００４０】
この作用を利用して、基体粒子の表面に目標とする可視光の波長に対し、式（２）を満たすような膜の厚みと屈折率を有する被膜を製膜し、さらにその上に屈折率の異なる膜を被覆することを１度あるいはそれ以上交互に繰り返すことにより可視光域に反射ピークを有する膜が形成される。このとき製膜する物質の順序は次のように決める。まず核となる基体の屈折率が高いときには第１層目が屈折率の低い膜、逆の関係の場合には第１層目が屈折率の高い膜とすることが好ましい。
【００４１】
膜厚は、膜屈折率と膜厚の積である光学膜厚の変化を分光光度計などで反射波形として測定、制御するが、反射波形が最終的に必要な波形になるように各層の膜厚を設計する。例えば、多層膜を構成する各単位被膜の反射波形のピーク位置を特定の波長に精密に合わせると、染料や顔料を用いずとも青、緑、黄色などのの単色の着色粉体とすることができる。
ただし、実際の基体の場合、基体の粒径、形状、膜物質および基体物質の相互の界面での位相ずれ及び屈折率の波長依存性によるピークシフトなどを考慮して設計する必要がある。例えば、基体表面にある酸化物層のためのピークシフトや屈折率の波長依存性によるピークシフトも加味することが好ましい。
【００４２】
また、金属や減衰係数の大きい基体あるいは膜を用いる場合についても、金属面減衰係数の大きい物質表面での反射光が楕円偏光する等、位相ずれが起こり、この干渉が核粒子と多層膜それぞれの粒子相互の位相に影響を及ぼすため、それを考慮する事が好ましい。
幾何学的な膜厚だけを合わせてもピーク位置がずれるため、特にシアン色系に着色する際に色が淡くなる。これを防ぐためには、すべての膜に対する位相ずれの影響を加味し、コンピュータシミュレーションであらかじめ膜厚の組合せが最適になるように設計する。
さらに、基体表面にある酸化物層のための位相ずれや、屈折率の波長依存性によるピークシフトがある。これらを補正するためには、分光光度計などで、反射ピークが最終目的膜数で目標波長になるよう最適の条件を見出すことが必要である。
【００４３】
球状粉体などの曲面に形成された膜の干渉は平板と同様に起こり、基本的にはフレネルの干渉原理に従う。したがって、着色方法も特定の色系に設計することができる。ただし曲面の場合には、粉体に入射し反射された光が複雑に干渉を起こす。これらの干渉波形は膜数が少ない場合には平板とほぼ同じである。しかし、膜数が増えると多層膜内部での干渉がより複雑になる。多層膜の場合もフレネル干渉に基づいて、反射分光曲線をコンピュータシミュレーションであらかじめ膜厚の組合せが最適になるよう設計することができる。特に基体粒子表面への被膜形成の場合、基体粒子表面とすべての膜に対する位相ずれの影響を加味し、コンピュータシミュレーションであらかじめ膜厚の組合せが最適になるよう設計する。さらに、基体粒子表面にある酸化物層のためのピークシフトや屈折率の波長依存性によるピークシフトも加味する。実際のサンプル製造では設計した分光曲線を参考にし、実際の膜においてこれらを補正するために、分光光度計などで反射ピークが最終目的膜数で目標波長になるよう膜厚を変えながら最適の条件を見出さねばならない。
【００４４】
また、金属や減衰係数の大きい核粒子あるいは膜を用いる場合についても、金属面減衰係数の大きい物質表面での反射光が楕円偏光する等、位相ずれが起こり、この干渉が核粒子と多層膜それぞれの粒子相互の位相に影響を及ぼすため、それぞれを最適化し、目標波形を得ることは非常に複雑であり、最適干渉反射波形を得るために、前記のように核粒子および多層膜各膜の物質の光学物性値を求め、それを基にコンピュータシミュレーションであらかじめ目標波形が得られる膜厚および膜の組合せを求めておかなければならない。
不定形状の粉末に着色する場合も多層膜による干渉が起こり、球状粉体の干渉多層膜の条件を参考にし基本的な膜設計を行う。上記の多層膜を構成する各単位被膜のピーク位置は各層の膜厚により調整することができ、膜厚は基体粒子の表面に金属酸化物等の固相成分を形成させる被覆形成条件中、原料組成、固相析出速度および基体量などを制御することにより、精度良く膜厚を制御でき、均一な厚さの被膜を形成することができ、所望の色系に着色することができる。
【００４５】
以上のように、反射スペクトルのピーク、バレー波長が最終目的膜数で目標波長になるよう膜形成溶液などの製膜条件を変えながら最適の条件を見出すことにより、特定の色系の膜被覆体を得ることができる。また、多層膜を構成する物質の組合せおよび各単位被膜の膜厚を制御することにより多層膜干渉による発色を調整することができる。これにより、染料や顔料を用いなくても膜被覆体を所望の色系に鮮やかに着色することができる。
また、カラーシフトを最大にするためには鋭い反射ピーク波長およびピークの数を最適化することが必要であり、各層の膜厚制御の最適化を行う。
【００４６】
また、カラーシフトによる色変化は、下記式３あるいは式３及び式４の組合せにおいて、入射角を変えた場合のピーク位置の計算値から予測することができる。
本発明に用いる膜被覆粉体を製造するにあたり、予め、基体の材質、基体粒子の粒径、被覆層の数、各被覆層の被覆順序、各被覆層の材質、所望の反射光波長を選定する必要がある。
特に、基体粒子および各被覆層の材質を選定するということは、それらの屈折率を自ずと特定することとなる。
基体粒子および各被覆層の屈折率の特定は、各層間のフレネル反射係数、振幅反射強度の算出に関与する。
【００４７】
基体粒子の粒径を選定することにより、基体粒子および多層膜の曲率を特定する。曲率が特定されなければ、後述する膜厚監視用分光光度特性の補正が困難になる。
被覆層の数を選定することにより、後述するＲ_flat値の特定に関与する。
基体粒子が平板体の場合の多層膜反射強度Ｒ_flatは、予め選定された基体粒子の材質（屈折率）、被覆層数、各被覆層の被覆順序、各被覆層の材質（屈折率）、所望の反射光波長を、下記漸化式３に当てはめて解くことにより求められる。
【００４８】
【数２】

【００４９】
（式中、Ｒ_j+1,j：下から第ｊ番目の層とその直上の層との間の振幅反射強度、
ｊ：１以上の整数（ｊ−１＝０は基盤を示す）、
ｉ：虚数単位、
ｒ_j+1,j：下から第ｊ番目の層とその直上の層との間の界面のフレネル反射係数、
Ｒ_j,j-1：下から第ｊ−１番目の層とその直上の層との間の振幅反射強度、
２δ_j：下から第ｊ番目の層における位相差、
λ：所望の反射光波長、
ｎ_j：下から第ｊ番目の層の屈折率、
ｄ_j：下から第ｊ番目の層の膜厚、
φ_j：下から第ｊ番目の層への光の入射角。）
【００５０】
上記の様にして得られた多層膜反射強度Ｒ_flatを基体粒子の形状により補正する手法としては特に限定されないが、該Ｒ_flat値をさらに下記式４
【００５１】
【数３】

【００５２】
（式中、θ：最外層への入射角を示す）
に適用させ、Ｒ（λ）値が所望の波長で最大値または最小値になるように各被覆層の膜厚を求めることにより行う手法が好ましい。
Ｒ_flat値を上記式４に適用させるということは、多層膜被覆粉体への光入射角の角度分布を１個の被覆半球への光入射角度分布に近似することにより上記式３の解を補正することを意味する。
この各被覆膜の膜厚を求める場合には、コンピュータによるシミュレーションで行うことが効率的である。
【００５３】
次いで、各被覆膜を、上記のようにして求められた膜厚になるように、基体粒子上に製膜する。
但し、先にも述べたが、多層膜被覆粉体における実際の製膜作業においては、設計値通りの膜厚になるまで実膜厚を直接監視しながら行うことは不可能であり、そのため、製膜作業中の膜厚の監視は、各被覆層を被覆した被覆物体の反射強度が最大値または最小値になる波長を分光光度計にて測定し、該膜厚に相対する最大または最小反射波長値に達した時点で製膜作業を終了させることが考えられる。
しかしながら基材が粉体の場合においては、その粒子形状および粒子径に依存する各被覆層の曲率によって、最大または最小反射波長測定値と膜厚との関係に狂いが生じ、分光光度計にて測定される最大または最小反射波長が所望の値になるように製膜すると、最終的に得られる多層膜被覆粉体が、所望の波長で所望の反射強度とならないという問題が生じる。
そのため、基体粒子の形状および粒子径に依存する各被覆層の曲率による補正が必要になる。
【００５４】
この補正手法としては、特に限定されないが、選定した基体粒子上に選定した各被覆層を段階的に数種類に膜厚を変えて被覆して粒径補正用膜被覆粉体とし、該粒径補正用膜被覆粉体の各被覆層の実膜厚値（ｄ_M）を測定し、また、該膜被覆粉体のそれぞれを分光光度計にて測定し、それぞれの粒径補正用膜被覆粉体における各被覆層の光学膜厚（ｎｄ）を求め、各粒径補正用膜被覆粉体の各被覆層の実膜厚値と屈折率（ｎ）との積（ｎｄ_M）に対する各被覆層の光学膜厚（ｎｄ）の比（ｎｄ／ｎｄ_M）を求め、多層膜反射強度を求める上記漸化式３の２δ_jに上記比（ｎｄ／ｎｄ_M）値を乗じて各被覆層を有する粉体の分光光度特性を補正し、該補正分光光度特性になるように各被覆層を製膜することにより行うことが好ましい。
【００５５】
なお、上記粒径補正用膜被覆粉体の各被覆層の実膜厚値（ｄ_M）を測定するさいの手法としては、特に限定されないが、該粒径補正用膜被覆粉体のそれぞれを切断しその切断面から測定することにより行うことが好ましい。また、前記粒径補正用膜被覆粉体を切断する際には、集束イオンビーム（ＦＩＢ）加工により行うことが、その切断面が明瞭になり、各被覆層の実膜厚値（ｄ_M）を測定に好適である。
【００５６】
次に一例として、炭酸系緩衝液を用いて、高屈折率の金属酸化物と低屈折率の金属酸化物の交互多層膜を形成する方法について具体的に説明する。まず、酸化チタンあるいは酸化ジルコニウムなどの高屈折率被膜を形成する場合、炭酸水素ナトリウム／炭酸ナトリウム系等の緩衝液中に基体を浸漬し分散し、チタンあるいはジルコニウムなどの金属塩である塩化チタン、塩化ジルコニウム等を原料とし、これら金属塩の水溶液を反応系に緩やかに滴下し、生成する金属水酸化物あるいは金属酸化物を基体のまわりに析出させることにより行うことができる。この滴下反応の間、ｐＨは上記緩衝液のｐＨ（９．２）に保持される。反応終了後、この基体を固液分離し、洗浄・乾燥後、熱処理を施す。乾燥手段としては真空乾燥、自然乾燥のいずれでもよい。また、不活性雰囲気中で噴霧乾燥機などの装置を用いることも可能である。なお、金属塩にＴｉＣｌ₃を使用した場合の被覆膜である酸化チタンの形成は下記の反応式で示される。
【００５７】
２ＴｉＣｌ₃ ＋３Ｈ₂Ｏ → ２Ｔｉ₂Ｏ₃ ＋６ＨＣｌ
【００５８】
続いて、酸化ケイ素あるいは酸化アルミニウムなどの低屈折率被膜を形成する場合、炭酸水素ナトリウム／炭酸ナトリウム系等の緩衝液中に上記のチタニアコート粒子を浸漬し分散し、ケイ素あるいはアルミニウムなどの金属塩であるケイ酸ナトリウム、塩化アルミニウム等を原料とし、これら金属塩の水溶液を反応系に緩やかに滴下し、生成する金属水酸化物あるいは金属酸化物を基体のまわりに析出させることにより行うことができる。この滴下反応の間、ｐＨは上記緩衝液のｐＨ（９．２）に保持される。反応終了後、この基体を固液分離し、洗浄・乾燥後、熱処理を施す。基体の表面に屈折率の異なる２層の金属酸化物膜を形成する操作を繰り返すことにより、多層の金属酸化物膜をその表面上に有する膜被覆体が得られる。なお、この場合の被覆膜である酸化ケイ素の形成は下記の反応式で示される。
【００５９】
Ｎａ₂Ｓｉ× Ｏ₂×₊₁＋Ｈ₂Ｏ → ＸＳｉＯ₂＋２Ｎａ⁺＋２ＯＨ^-
【００６０】
次に、上記例において使用する原料、特に金属塩について説明する。高屈折率の膜を製膜するのに使用する原料としては、酸化チタン膜用には、チタンのハロゲン化物、硫酸塩等、酸化ジルコニウム膜用には、ジルコニウムのハロゲン化物、硫酸塩、カルボン酸塩、シュウ酸塩、キレート錯体等、酸化セリウム膜用には、セリウムのハロゲン化物、硫酸塩、カルボン酸塩、シュウ酸塩等、酸化ビスマス膜用には、ビスマスのハロゲン化物、硝酸塩、カルボン酸塩等、酸化インジゥム膜用には、インジウムのハロゲン化物、硫酸塩等が好ましい。また、低屈折率の膜を製膜するのに使用する原料としては、酸化ケイ素膜用には、ケイ酸ソーダ、水ガラス、ケイ素のハロゲン化物、アルキルシリケート等の有機ケイ素化合物とその重合体等、酸化アルミニウム膜用には、アルミニウムのハロゲン化物、硫酸塩、キレート錯体等、酸化マグネシウム膜用には、マグネシウムの硫酸塩、ハロゲン化物等が好ましい。また、例えば酸化チタン膜の場合には、塩化チタンに硫酸チタンを混合すると、より低温で屈折率の高いルチル型の酸化チタン膜になる等の効果がある。
【００６１】
また、被覆の際の反応温度は各金属塩の種類に適した温度に管理して被覆することにより、より良質な酸化物膜を製作することができる。水系溶媒中での基体の表面への被膜形成反応（固層析出反応）が遅すぎる場合には、反応系を加熱して固層析出反応を促進することもできる。但し、加熱の熱処理が過剰であると、該反応速度が速すぎて、過飽和な固層が膜にならず、水溶液中に析出し、ゲルあるいは微粒子を形成し、膜厚制御が困難になる。被覆膜は製作後、蒸留水を加えながら傾斜洗浄を繰り返して、電解質を除去した後、乾燥・焼成等の熱処理を施し、固相中に含まれた水を除去して、完全に酸化物膜とすることが好ましい。また、製膜後の粉体を回転式チューブ炉などで熱処理することにより、固着を防ぐことができ、分散された粒子を得ることができる。
【００６２】
水酸化物膜あるいは酸化物膜等を形成し、それを熱処理するには、各層を被覆する毎に熱処理しても良く、また、目的の多層膜を完成後最後に熱処理しても良い。熱処理条件は反応系により異なるが、熱処理温度は２００〜１３００℃であることが好ましく、４００〜１１００℃であることがより好ましい。２００℃以下では塩類や水分が残ってしまうことがあり、１３００℃を超えて高くなると、膜と基体が反応し別の物質となることがあり、共に不適当である。熱処理時間は０．１〜１００時間が好ましく、０．５〜５０時間がより好ましい。
【００６３】
【実施例】
本発明を以下の実施例によりさらに詳細に説明するが、本発明はこれらの実施例により限定されるものではない。
【００６４】
［実施例１〜７］
（シリカ膜被覆球状鉄粉の作成）
（基体粒子懸濁緩衝液の調製）
脱イオン水に炭酸ナトリウム試薬（関東化学）、炭酸水素ナトリウム試薬（関東化学）、塩化カリウム試薬（関東化学）を加え溶解することにより緩衝液を調製した。炭酸ナトリウム、炭酸水素ナトリウム、塩化カリウムの濃度を下記の表に示す。
【００６５】
【表１】

【００６６】
この緩衝液に平均粒径３．３μｍ（ＢＡＳＦ社測定）を有する球状鉄粉（ＢＡＳＦ社製、商品名ＥＳ）２０ｇを懸濁させ、基体粒子懸濁緩衝液を得た。
【００６７】
（シリカ膜被覆工程）
前記基体粒子懸濁緩衝液を１０００ｒｐｍで撹拌しながら、５ｗｔ％のケイ酸ナトリウム水溶液１５０ｇを１．００ｍｌ／ｍｉｎの供給速度で全量滴下投入し、１時間熟成した。これにより、液中のケイ酸ナトリウムからのシリカの析出が基体粒子表面で起こり、基体粒子へのシリカ膜被覆が行われた。
熟成後、撹拌を止めて懸濁液中の粉体を静置沈降させ、上清液を除去した。上清液は無色透明であった。
さらに、脱イオン水による傾斜洗浄（デカンテーション）を行った後、１２０℃で２時間乾燥し、シリカ膜被覆球状鉄粉を得た。
【００６８】
［実施例８］
（チタニア膜被覆球状鉄粉の作成）
（滴下液の調整）
２０％塩化チタン［III］溶液（関東化学社製、鹿１級試薬）１０．０ｇ、２８％アンモニア水（関東化学社製、鹿１級試薬）２０．５ｇ、３１％過酸化水素水（関東化学社製、特級試薬）１０．０ｇを混合することによって、ペルオキソチタン酸を含有する黄色透明の滴下液を得た。この滴下液のｐＨは１０．０であった。
（基体粒子懸濁緩衝液の調製）
上記実施例７で得られた緩衝液に平均粒径３．３μｍ（ＢＡＳＦ社測定）を有する球状鉄粉（ＢＡＳＦ社製、商品名ＥＳ）４０ｇを懸濁させ、基体粒子懸濁緩衝液を得た。
【００６９】
（チタニア膜被覆）
前記基体粒子懸濁緩衝液を１０００ｒｐｍにて撹拌しながら、滴下液を１．５ｍｌ／ｍｉｎの速さで全量滴下投入し、２時間熟成した。これにより、液中のペルオキソチタン酸からのチタニアの析出が基体粉表面で起こり、基体粒子へのチタニア膜被覆が行われた。
熟成後、撹拌を止めて懸濁液中の粉体を静置沈降させ、上液を除去した。上液は無色透明であった。
さらに、脱イオン水による傾斜洗浄（デカンテーション）を行った後、１２０℃で２時間乾燥し、チタニア膜被覆球状鉄粉を得た。
【００７０】
［実施例９］
（シリカ膜被覆パーマロイ粉を作成）
（基体粒子懸濁緩衝液の調製）
上記実施例７で得られた緩衝液に平均粒径１５．３μｍ（ＨＯＮＥＹＷＥＬＬ社製、９３２０−Ｘ１００型マイクロトラックＨＲＡ粒度分析計で測定）を有するフレーク状パーマロイ粉（福田金属箔粉工業社製、商品名７８パーマロイフレーク）１８．５ｇを懸濁させ、基体粒子懸濁緩衝液を得た。
【００７１】
（シリカ膜被覆）
前記基体粒子懸濁緩衝液を１０００ｒｐｍにて撹拌しながら、５質量％のケイ酸ナトリウム水溶液１２０ｇを１．００ｍｌ／ｍｉｎの供給速度で全量滴下投入し、１時間熟成した。これにより、液中のケイ酸ナトリウムからのシリカの析出が基体粒子表面で起こり、基体粒子へのシリカ膜被覆が行われた。
熟成後、撹拌を止めて懸濁液中の粉体を静置沈降させ、上清液を除去した。上清液は無色透明であった。
さらに、脱イオン水による傾斜洗浄（デカンテーション）を行った後、１２０℃で２時間乾燥し、シリカ膜被覆パーマロイ粉を得た。
【００７２】
【発明の効果】
本発明の膜被覆体、膜被覆方法および膜被覆体の製造方法は、基体の表面の膜を炭酸緩衝液中での反応により形成することにより、生じる廃液の廃水基準が緩く廃液処理コストが低くできるものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film covering, a film covering method, and a method for manufacturing a film covering, and more specifically, a film covering, a film covering method, and a method for manufacturing a film covering, with good waste water quality and low waste liquid treatment costs. It is about.
[0002]
[Prior art]
With the progress of science and technology, there is an increasing demand for powders with unique properties, especially metal powders or metal compound powders, and properties that only powders, particularly metal powders or metal compound powders, have. In addition to the above, there is a demand for powders having other properties and having combined functions. In order to meet this demand, attempts have been made to improve the properties of the powder or to provide diversity in the properties by coating the surface of the powder with a film of another substance.
[0003]
For example, the present inventors have found that the reflected light interference waveform of the multilayer film can be adjusted by controlling the combination and film thickness of the multilayer film, and acrylic resin particles or inorganic hollows can be used without using dyes or pigments. Specific gravity of particles such as 0.3 to 2.8 g / cm^ThreeBlue, green, yellow colored with a powder having a plurality of thin coating films (titanium dioxide film, titania film, polystyrene film, metallic silver film, etc.) having different refractive indexes on the surface of the substrate. It has been disclosed that pigments for monochromatic color inks and fillers for plastics and paper can be designed, and pigment powders having a stable color tone can be provided even during long-term storage (see, for example, Patent Document 1).
[0004]
In addition, various means have been proposed as a method for realizing a powder having a composite function. For example, as a coating technique for forming a film on the surface of an object for protection or decoration, many means such as a coating method, a deposition method, a sputtering method, a vacuum deposition method, an electrodeposition method and an anodizing method are known. . However, it is difficult to make the film thickness uniform by a coating method or a deposition method, and it is difficult to obtain a thick film by sputtering or vacuum deposition. In addition, the electrodeposition method and the anodic oxidation method have a problem that they are not suitable for the processing of powder because of using the workpiece as an electrode.
[0005]
First, the inventors of the present invention have a composite property that can meet the new requirements as described above, and a metal oxide for providing a powder, particularly a metal or metal compound powder that can perform a composite function. As a useful forming method, a metal powder or metal oxide powder is dispersed in a metal alkoxide solution, and the metal alkoxide is hydrolyzed to form a metal oxide film. Invented a powder having a metal oxide film whose component is a metal different from the metal constituting the substrate, having a uniform thickness of 0.01 to 20 μm on the surface of the substrate (see, for example, Patent Document 2) .
[0006]
In this powder, when a plurality of the metal oxide films are provided, a special function can be given by adjusting the thickness of each layer of the film. For example, if a coating film having a different refractive index is provided on the surface of the substrate with a thickness corresponding to a quarter wavelength of light, all the light is reflected. When this means is applied to a material based on a magnetic material such as iron, cobalt, nickel, or other metal powder, metal alloy powder, or iron nitride powder, the magnetic toner for magnetic toners shines white by totally reflecting light. A powder can be obtained. Furthermore, it is disclosed that a color magnetic toner can be obtained if a colored layer is provided on the powder and a resin layer is provided thereon. In addition, the present inventors further improved the above-mentioned powder, and disclosed a powder in which a plurality of metal oxide films and metal films are alternately provided instead of a metal oxide film alone (for example, a patent) Reference 3). This has excellent properties as a color magnetic toner or the like.
[0007]
Further, as a method for forming a metal oxide coating film on the powder in water, an aqueous nickel compound solution is added to an alkaline suspension of powder mainly composed of iron oxyhydroxide or iron oxide, Next, an aqueous silicon compound solution is added, and the nickel compound is deposited as nickel hydroxide on the surface of the powder particles, and then the solution is neutralized to further deposit the silicon compound on the surface of the powder particles. A method for producing a metal magnetic powder that is sequentially deposited on the surface of powder particles is disclosed (for example, see Patent Document 4).
[0008]
Furthermore, the present inventors have noted that the metal oxide film obtained by the hydrolysis method of the metal alkoxide is extremely dense, inert, and preferable from the viewpoint of durability. A film-coated powder was proposed. In this multilayer film-coated powder, the powder is coated with a dense metal oxide film by a metal alkoxide hydrolysis method, and then a metal oxide film is formed using a precipitation method from a metal salt aqueous solution. Yes. Since the powder is covered with a dense metal oxide film by the metal alkoxide hydrolysis method, even if it is immersed in the metal salt aqueous solution, it is not attacked, and the precipitation method from the metal salt aqueous solution is used. The metal oxide film thus formed can be formed (for example, see Patent Document 5).
[0009]
Next, the present inventors avoided the use of expensive metal alkoxides or highly flammable organic solvents in the above-mentioned metal alkoxide hydrolysis method, and used metal alkoxides in the same manner as when metal alkoxides were used. A method for forming a metal oxide film having the following film quality was proposed. In this method, after a powder is dispersed in a buffer solution, a solution of a metal salt that is a film component raw material is dropped into the buffer solution. Moreover, the boric acid type | system | group is used for a buffer solution (for example, refer patent document 6).
[0010]
The metal oxide film forming method using the metal salt aqueous solution does not use an expensive compound metal alkoxide or a highly flammable organic solvent, and has a film quality equivalent to that when using a metal alkoxide. A film can be obtained, which is an excellent method.
In this method, an aqueous solution of a metal salt as a film component raw material is dropped into a buffer solution in which powder is dispersed. At this time, the amount of the buffer solution used is several times larger than the amount of the dropping solution. For this reason, sufficient consideration is necessary regarding the manufacturing cost of the buffer solution and the waste liquid treatment after use.
[0011]
[Patent Document 1]
International Publication No. 96/28269 Pamphlet
[Patent Document 2]
JP-A-6-228604
[Patent Document 3]
JP-A-7-90310
[Patent Document 4]
JP 59-31003 A
[Patent Document 5]
JP-A-10-001702
[Patent Document 6]
JP-A-11-131102
[0012]
[Problems to be solved by the invention]
In recent years, the boric acid used in the buffer solution has a stricter wastewater standard, and there is a problem that the waste solution treatment after use of the boric acid buffer solution is costly.
An object of the present invention is to provide a membrane coating body, a membrane coating method, and a manufacturing method of the membrane coating body that can overcome the above-mentioned problems of the prior art and can reduce waste water standards and reduce waste liquid treatment costs.
[0013]
[Means for Solving the Problems]
The above-mentioned problem uses a sodium hydrogen carbonate / sodium carbonate buffer solution as a reaction solvent, disperses the powder in a buffer solution adjusted in pH, and suspends an aqueous solution of a metal salt as a membrane component raw material in the powder It has been found that a film covering can be produced by dropping it into a buffer solution, and the present invention has been achieved.
That is, the present invention is as follows.
[0014]
(1) In the method of manufacturing a film covering for forming a film on the surface of a powder, at least one layer of the film is immersed in the powder, KCl, NaCl or LiClAlkali metal saltContains ionic strength of 1.41-5.0A method for producing a membrane covering, comprising adding a metal salt aqueous solution, which is a membrane component raw material, to a carbonate buffer solution and forming a reaction from the metal salt.
(2) The carbonate buffer is Na₂CO₃And NaHCO₃The method for producing a film-coated body according to the above (1), comprising:Law.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, by using a carbonic acid buffer solution capable of keeping the pH constant as the membrane-forming reaction solvent, the solid phase film can be uniformly formed on the surface of the substrate without precipitating only the solid phase in the liquid phase. A film can be formed. During the film-forming reaction, using a carbonate buffer as a reaction solvent and precipitating at an appropriate speed at a certain pH, the deposition of a solid phase that does not become a film is suppressed, and a film with a uniform thickness is formed. , Can be formed with a desired thickness. In addition, by keeping the pH constant and maintaining the surface charge of the membrane coating body constant, even when the substrate is a powder, there is no aggregation of the membrane coating powder and the particles are dispersed by the action of the electric double layer. It can be in the state. In order to make use of the function of the electric double layer, the appropriate pH varies depending on the combination of the substance of the substrate and the type of metal compound formed in the liquid by the film-forming reaction, and it is preferable to avoid the isoelectric point of both.
[0021]
According to the present invention, the film covering body having a uniform thickness and a desired film thickness can be easily produced by the above-described mechanism of action, regardless of the use of the water-soluble raw material. In addition, by using a carbonate buffer as a solvent, it is possible to obtain an effect that the waste water standard is looser than the borate buffer, the environmental load is small, and the film can be formed at low cost.
[0022]
The basic composition of the carbonate buffer used in the present invention is not particularly limited, but Na₂CO_ThreeAnd NaHCO_Three, K₂CO_ThreeAnd KHCO_ThreeNaHCO_ThreeAnd NaOH, etc.₂CO_Three-NaHCO_ThreeIt is preferred to use a system.
[0023]
In addition, the carbonate buffer used in the present invention may contain an electrolyte for the purpose of adjusting the ionic strength. Although it does not specifically limit as electrolyte contained in this carbonate type buffer solution, KCl, NaCl, LiCl, etc. are mentioned. Of these, KCl or NaCl is more preferably used, and KCl is most preferably used.
[0024]
When a powdery substrate is used, it is important that the carbonate buffer solution can sufficiently disperse the substrate powder. At the same time, the film-coated powder in which the film substance is deposited on the surface of the substrate also functions as an electric double layer. And the concentration, pH, and ionic strength are adjusted so that a dense film can be formed by a slow dropping reaction described later.
[0025]
The concentration of the buffer solution is Na with electrolyte as KCl.₂CO_Three-NaHCO_ThreeIn the case of a system buffer solution, the KCl concentration is 0.2 to 1.1 mol / liter, Na₂CO_ThreeConcentration of 0.01 to 0.5 mol / liter, NaHCO_ThreeThe concentration is preferably 0.2 to 1.2 mol / liter, but is not limited to this range, and can be determined as appropriate depending on the type of substrate and coating film. Na₂CO_ThreeAnd NaHCO_ThreeIf the concentration of is extremely low, the buffer capacity decreases, which is not preferable.
[0026]
Usually, a buffer having a pH of 8.5 to 10.0 is preferably used. However, the buffer is not limited to this range, and is appropriately determined in consideration of the type of substrate and coating film. It is done.
[0027]
The ionic strength of the buffer is, for example, Na₂CO_Three-NaHCO_ThreeWhen KCl is used as the electrolyte in the system, it is defined by the following formula (1).
[0028]
[Expression 1]

[0029]
The ionic strength of the buffer solution calculated according to the formula (1) is preferably 1.41 to 5.0. More preferably, it is 1.5-3.5. In Equation (1), for example, [K⁺] Is K⁺Indicates the molar concentration of ions.
[0030]
The shape of the substrate used in the present invention is not particularly limited and may be a flat plate shape or a powder (particle) shape. The usefulness of the invention becomes remarkable.
When the substrate is powder, details of its shape include, for example, spheres, subspheres, isotropic bodies such as regular polyhedrons, rectangular parallelepipeds, spheroids, rhombohedrals, plate-like bodies, needle-like bodies (columns, prisms), etc. It is also possible to use a polyhedron, a completely irregular powder such as a pulverized product. These substrates are not particularly limited in terms of particle size, but those in the range of 0.01 μm to several mm are preferable. The specific gravity of the substrate particles is in the range of 0.1 to 10.5. When the dispersion medium is dispersed or the like, 0.1 to 5. 5 is preferable, and more preferably in the range of 0.1 to 2.8. If the specific gravity of the substrate is less than 0.1, the buoyancy in the dispersion medium is too large, and the film needs to be multilayered or very thick, which is uneconomical. On the other hand, if it exceeds 10.5, the film for floating becomes thick, which is similarly uneconomical.
[0031]
The material of the substrate used in the present invention is not particularly limited and may be inorganic or organic. However, in order to provide the film covering with multifunctionality, a magnetic material, a dielectric material, a conductor, and the like are mainly used. Used for. When the substrate is a metal, any metal such as iron, nickel, chromium, titanium, and aluminum may be used. However, in the case of utilizing the magnetism, those having magnetism such as iron, cobalt, and nickel are preferable. These metals may be alloys, and when they have the above magnetism, it is preferable to use a ferromagnetic alloy. In addition, when the substrate is a metal compound, typical examples thereof include the above-described metal oxides, for example, iron, nickel, chromium, titanium, aluminum, silicon, etc., calcium, magnesium, An oxide such as barium or a composite oxide thereof may be used. Furthermore, examples of metal compounds other than metal oxides include metal nitrides and metal carbides.
[0032]
Further, as the substrate, other than metals, semi-metal and non-metallic compounds, particularly oxides, carbides and nitrides, silica, glass beads and the like can be used. Other inorganic substances include inorganic hollow particles such as shirasu balloon (hollow silicic acid particles), fine carbon hollow spheres (clecas spheres), fused alumina bubbles, aerosil, white carbon, silica fine hollow spheres, calcium carbonate fine hollow spheres, Mica such as calcium carbonate, pearlite, talc, bentonite, synthetic mica, muscovite, kaolin and the like can be used.
[0033]
As the organic substance, a resin is preferable. Specific examples of the resin include cellulose powder, cellulose acetate powder, polyamide, epoxy resin, polyester, melamine resin, polyurethane, vinyl acetate resin, silicon resin, acrylic ester, methacrylic ester, styrene, ethylene, propylene, and these Examples thereof include those obtained by polymerization or copolymerization of derivatives. A particularly preferred resin is a spherical acrylic resin obtained by polymerization of acrylic acid or methacrylic acid ester. However, when a resin is used as a substrate, the heating temperature in drying must be equal to or lower than the melting point of the resin.
[0034]
The film formed using the carbonate buffer in the present invention is not particularly limited, and examples thereof include a metal oxide film, a metal hydroxide film, a metal nitride film, and a metal film. Metal hydroxide films are particularly suitable.
In addition, the reaction in the carbonate buffer for forming a film on the surface of the substrate is not particularly limited, and examples thereof include a reaction from a metal salt.
[0035]
In the present invention, the metal used as the metal salt includes iron, nickel, chromium, titanium, zinc, aluminum, cadmium, zirconium, silicon, tin, lead, lithium, indium, neodymium, bismuth, cerium, antimony, etc. , Calcium, magnesium, barium and the like. Examples of these metal salts include sulfuric acid, nitric acid, hydrochloric acid, oxalic acid, carbonic acid and carboxylic acid salts. Furthermore, chelate complexes of the above metals are also included. The type of metal salt used in the present invention is selected according to the properties to be imparted to the surface of the substrate and the means applied during production.
[0036]
The metal oxide film formed by the reaction of these metal salts may be formed in a plurality of layers, and if necessary, a metal oxide by hydrolysis of metal alkoxide on the metal oxide film or the like. It is also possible to form a film by other film forming methods. In this way, a multilayer film can be formed on the substrate, and at that time, by setting the formation conditions so that the thickness of each layer has a predetermined thickness, desired characteristics can be obtained. It is possible. In addition, a metal oxide or the like film can be formed in multiple layers by using a metal salt which is a simple operation and inexpensive.
[0037]
In the method of manufacturing a film coating according to the present invention, a multilayer coating film may be manufactured as a continuous process, or each coating film is manufactured one layer at a time, or single layer manufacturing and multi-layer continuous manufacturing are combined. It can be manufactured by various methods.
In the present invention, the thickness of the metal oxide film or the like to be formed at one time can be in the range of 5 nm to 10 μm, and can be made thicker than the conventional forming method.
In the present invention, the powder substrate is coated with a plurality of coating layers having different refractive indexes, and each coating layer is appropriately selected for the refractive index and the layer thickness to be colored by the interference color and visible light. It can be set as the powder which expresses a specific interference reflection peak other than a visible region and a visible light region.
[0038]
For example, if a coating having a different refractive index is provided on the surface of the substrate so that the product of the refractive index of the material of the film and the thickness of the film corresponds to a quarter of the electromagnetic wave, the light is mostly reflected by interference. (Fresnel reflection), and using this action, coloring can be performed without using dyes or pigments.
Specifically, an alternating coating film having a different refractive index is formed on the surface of the substrate so that the refractive index n of the substance forming the film and the wavelength of visible light are one-fourth so as to satisfy the following formula (2). When an alternating film having a thickness d corresponding to an integer m times is provided with an appropriate thickness and the number of films, light having a specific wavelength λ (using Fresnel interference reflection) is reflected or absorbed.
[0039]
nd = mλ / 4 (2)
[0040]
Using this action, a film having a film thickness and a refractive index satisfying the formula (2) is formed on the surface of the base particle with respect to the target visible light wavelength, and the refractive index is further formed thereon. A film having a reflection peak in the visible light region is formed by repeating coating of different films once or more alternately. At this time, the order of substances to be formed is determined as follows. First, when the refractive index of the substrate serving as the nucleus is high, the first layer is preferably a film having a low refractive index, and in the opposite case, the first layer is preferably a film having a high refractive index.
[0041]
The film thickness is measured and controlled as a reflected waveform using a spectrophotometer, etc., as the change in the optical film thickness, which is the product of the film refractive index and the film thickness. Design the thickness. For example, if the peak position of the reflection waveform of each unit film constituting the multilayer film is precisely matched to a specific wavelength, it can be made into a single color powder such as blue, green, yellow, etc. without using a dye or pigment. it can.
However, in the case of an actual substrate, it is necessary to design in consideration of the particle size and shape of the substrate, the phase shift at the interface between the film material and the substrate material, and the peak shift due to the wavelength dependence of the refractive index. For example, it is preferable to take into account the peak shift due to the oxide layer on the substrate surface and the peak shift due to the wavelength dependence of the refractive index.
[0042]
In addition, when using a metal or a substrate or film having a large attenuation coefficient, a phase shift occurs such that the reflected light on the surface of the material having a large metal surface attenuation coefficient is elliptically polarized. Since it affects the phase between particles, it is preferable to consider it.
Even if only the geometric film thickness is combined, the peak position is shifted, so that the color becomes light particularly when coloring in a cyan color system. In order to prevent this, the influence of the phase shift on all the films is taken into consideration, and the combination of film thicknesses is designed in advance by computer simulation so as to be optimized.
Furthermore, there is a phase shift due to the oxide layer on the substrate surface and a peak shift due to the wavelength dependence of the refractive index. In order to correct these, it is necessary to find an optimal condition with a spectrophotometer or the like so that the reflection peak reaches the target wavelength by the final target film number.
[0043]
Interference of a film formed on a curved surface such as a spherical powder occurs in the same manner as a flat plate, and basically follows the Fresnel interference principle. Therefore, the coloring method can also be designed to a specific color system. However, in the case of a curved surface, the light incident on and reflected by the powder causes complicated interference. These interference waveforms are almost the same as the flat plate when the number of films is small. However, interference within the multilayer film becomes more complex as the number of films increases. Also in the case of a multilayer film, based on Fresnel interference, the reflection spectral curve can be designed in advance by computer simulation so that the combination of film thicknesses is optimized. In particular, in the case of forming a film on the surface of the substrate particles, the influence of the phase shift on the surface of the substrate particles and all the films is taken into account, and the design is made so as to optimize the combination of film thicknesses in advance by computer simulation. Furthermore, the peak shift for the oxide layer on the surface of the substrate particles and the peak shift due to the wavelength dependence of the refractive index are taken into account. In actual sample production, in order to correct these in the actual film with reference to the designed spectroscopic curve, the optimum conditions are adjusted while changing the film thickness so that the reflection peak reaches the target wavelength with the final target film number with a spectrophotometer. Must be found.
[0044]
In addition, when using metal or a core particle or film having a large attenuation coefficient, a phase shift occurs, for example, the reflected light on the surface of the material having a large metal surface attenuation coefficient is elliptically polarized. It is very complicated to obtain the target waveform by optimizing each of the particles in order to obtain the optimum interference reflection waveform, as described above. It is necessary to obtain the optical property values of the film thickness and to obtain the film thickness and the combination of the films from which the target waveform can be obtained in advance by computer simulation.
Interference with the multilayer film also occurs when the powder of irregular shape is colored, and the basic film design is performed with reference to the condition of the interference multilayer film of spherical powder. The peak position of each unit film constituting the multilayer film can be adjusted by the film thickness of each layer, and the film thickness is the raw material in the coating forming conditions for forming a solid phase component such as a metal oxide on the surface of the base particle. By controlling the composition, the solid phase deposition rate, the amount of the substrate, and the like, the film thickness can be controlled with high accuracy, a film having a uniform thickness can be formed, and a desired color system can be colored.
[0045]
As described above, by finding the optimum conditions while changing the film forming conditions such as the film forming solution so that the peak and valley wavelengths of the reflection spectrum become the target wavelength by the final target film number, the film covering of a specific color system Can be obtained. Further, the color development due to multilayer film interference can be adjusted by controlling the combination of substances constituting the multilayer film and the thickness of each unit film. Accordingly, the film covering can be vividly colored in a desired color system without using a dye or a pigment.
Further, in order to maximize the color shift, it is necessary to optimize the sharp reflection peak wavelength and the number of peaks, and the film thickness control of each layer is optimized.
[0046]
The color change due to the color shift can be predicted from the calculated value of the peak position when the incident angle is changed in the following formula 3 or the combination of formula 3 and formula 4.
In manufacturing the film-coated powder used in the present invention, the substrate material, the particle size of the substrate particles, the number of coating layers, the coating order of each coating layer, the material of each coating layer, and the desired reflected light wavelength are selected in advance. There is a need to.
In particular, selecting the material of the base particles and the respective coating layers naturally identifies their refractive index.
The specification of the refractive index of the base particle and each coating layer is involved in the calculation of the Fresnel reflection coefficient and the amplitude reflection intensity between the respective layers.
[0047]
By selecting the particle size of the substrate particles, the curvature of the substrate particles and the multilayer film is specified. If the curvature is not specified, it becomes difficult to correct the spectrophotometric characteristic for film thickness monitoring described later.
By selecting the number of coating layers, R described later_flatInvolved in identifying values.
Multi-layer film reflection intensity R when substrate particles are flat_flatApplies the recurrence formula 3 below to the previously selected base particle material (refractive index), number of coating layers, coating order of each coating layer, material of each coating layer (refractive index), and desired reflected light wavelength. It is calculated by solving.
[0048]
[Expression 2]

[0049]
(Wherein R_{j + 1, j}: Amplitude reflection intensity between the j-th layer from the bottom and the layer immediately above it,
j: an integer greater than or equal to 1 (j-1 = 0 indicates a base),
i: imaginary unit,
r_{j + 1, j}: Fresnel reflection coefficient of the interface between the jth layer from the bottom and the layer immediately above it,
R_{j, j-1}: Amplitude reflection intensity between the j-1st layer from the bottom and the layer immediately above it,
2δ_j: Phase difference in the j-th layer from the bottom,
λ: desired reflected light wavelength,
n_j: Refractive index of the jth layer from the bottom,
d_j: The film thickness of the jth layer from the bottom,
φ_j: The incident angle of light from the bottom to the j-th layer. )
[0050]
Multilayer film reflection intensity R obtained as described above_flatIs not particularly limited as a method for correcting the shape of the substrate by the shape of the base particles._flatThe value is further expressed by the following formula 4
[0051]
[Equation 3]

[0052]
(Where θ represents the angle of incidence on the outermost layer)
It is preferable to apply this method to obtain the film thickness of each coating layer so that the R (λ) value becomes the maximum value or the minimum value at a desired wavelength.
R_flatApplying the value to Equation 4 above corrects the solution of Equation 3 above by approximating the angle distribution of the light incident angle on the multilayer coated powder to the light incident angle distribution on one coated hemisphere. Means that.
When determining the film thickness of each coating film, it is efficient to carry out by computer simulation.
[0053]
Next, each coating film is formed on the base particles so as to have the film thickness obtained as described above.
However, as described above, in the actual film-forming operation in the multilayer-coated powder, it is impossible to directly monitor the actual film thickness until the film thickness reaches the designed value. The film thickness is monitored during film formation by measuring the wavelength at which the reflection intensity of the coated object covering each coating layer reaches the maximum or minimum value with a spectrophotometer, and measuring the maximum or minimum reflection relative to the film thickness. It can be considered that the film forming operation is terminated when the wavelength value is reached.
However, when the substrate is a powder, the curvature of each coating layer depending on the particle shape and particle diameter causes a deviation in the relationship between the measured maximum or minimum reflected wavelength and the film thickness. When the film is formed so that the maximum or minimum reflection wavelength to be measured becomes a desired value, there arises a problem that the finally obtained multilayer film-coated powder does not have a desired reflection intensity at a desired wavelength.
Therefore, it is necessary to correct the curvature of each coating layer depending on the shape and particle diameter of the base particles.
[0054]
The correction method is not particularly limited, but the coating layer selected on the selected substrate particles is coated with various thicknesses in stages to form a coating powder for particle size correction. Actual film thickness value of each coating layer (d)_M), And each of the film-coated powders is measured with a spectrophotometer to determine the optical film thickness (nd) of each coating layer in each particle-size correcting film-coated powder. Product (nd) of actual film thickness value and refractive index (n) of each coating layer of correction coating powder_M) Ratio of optical film thickness (nd) of each coating layer to (nd / nd)_M2) of the above recurrence formula 3 for obtaining the multilayer film reflection intensity._jTo the above ratio (nd / nd_M) Value is preferably corrected to correct the spectrophotometric characteristics of the powder having each coating layer, and each coating layer is preferably formed to have the corrected spectrophotometric characteristics.
[0055]
In addition, the actual film thickness value (d_M) Is not particularly limited, but it is preferable to measure by cutting each of the particle-correcting film-coated powders and measuring from the cut surface. Further, when cutting the particle-correcting film-coated powder, it is performed by focused ion beam (FIB) processing, the cut surface becomes clear, and the actual film thickness value (d of each coating layer)_M) Is suitable for measurement.
[0056]
Next, as an example, a method for forming an alternating multilayer film of a high refractive index metal oxide and a low refractive index metal oxide using a carbonate buffer solution will be specifically described. First, when forming a high refractive index film such as titanium oxide or zirconium oxide, the substrate is immersed in and dispersed in a buffer solution such as sodium bicarbonate / sodium carbonate, and titanium chloride which is a metal salt such as titanium or zirconium, Zirconium chloride or the like is used as a raw material, and an aqueous solution of these metal salts is slowly dropped into the reaction system, and the resulting metal hydroxide or metal oxide is precipitated around the substrate. During this dropwise reaction, the pH is maintained at the pH of the buffer (9.2). After completion of the reaction, the substrate is separated into solid and liquid, washed and dried, and then subjected to heat treatment. The drying means may be either vacuum drying or natural drying. It is also possible to use a device such as a spray dryer in an inert atmosphere. In addition, TiCl is added to the metal salt_ThreeThe formation of titanium oxide, which is a coating film when using, is shown by the following reaction formula.
[0057]
2TiCl_Three+ 3H₂O → 2Ti₂O_Three+ 6HCl
[0058]
Subsequently, when a low refractive index film such as silicon oxide or aluminum oxide is formed, the above titania-coated particles are immersed and dispersed in a buffer solution such as sodium hydrogen carbonate / sodium carbonate, and a metal salt such as silicon or aluminum. It can be carried out by using sodium silicate, aluminum chloride, etc. as raw materials, slowly dropping an aqueous solution of these metal salts into the reaction system, and precipitating the resulting metal hydroxide or metal oxide around the substrate. . During this dropwise reaction, the pH is maintained at the pH of the buffer (9.2). After completion of the reaction, the substrate is separated into solid and liquid, washed and dried, and then subjected to heat treatment. By repeating the operation of forming two layers of metal oxide films having different refractive indexes on the surface of the substrate, a film covering having a multilayer metal oxide film on the surface can be obtained. In this case, the formation of silicon oxide as the coating film is represented by the following reaction formula.
[0059]
Na₂Si x O₂×₊₁+ H₂O → XSiO₂+ 2Na⁺+ 2OH^-
[0060]
Next, raw materials used in the above examples, particularly metal salts, will be described. Raw materials used to form a film with a high refractive index include titanium halides and sulfates for titanium oxide films, and zirconium halides, sulfates and carboxylic acids for zirconium oxide films. Salts, oxalates, chelate complexes, etc., for cerium oxide films, cerium halides, sulfates, carboxylates, oxalates, etc., for bismuth oxide films, bismuth halides, nitrates, carboxylic acids For indium oxide films such as salts, indium halides, sulfates and the like are preferred. In addition, as a raw material used to form a film having a low refractive index, for silicon oxide films, organic silicon compounds such as sodium silicate, water glass, silicon halide, alkyl silicate, and polymers thereof are used. For aluminum oxide films, aluminum halides, sulfates, chelate complexes, etc. are preferred, and for magnesium oxide films, magnesium sulfates, halides, etc. are preferred. Further, for example, in the case of a titanium oxide film, mixing titanium sulfate with titanium chloride has an effect of becoming a rutile type titanium oxide film having a higher refractive index at a lower temperature.
[0061]
Further, by controlling the reaction temperature at the time of coating to a temperature suitable for the type of each metal salt, it is possible to produce a higher quality oxide film. When the film formation reaction (solid layer deposition reaction) on the surface of the substrate in the aqueous solvent is too slow, the solid layer deposition reaction can be promoted by heating the reaction system. However, if the heat treatment for heating is excessive, the reaction rate is too high, and the supersaturated solid layer does not become a film, but precipitates in an aqueous solution, forms gels or fine particles, and film thickness control becomes difficult. After the production of the coating film, repeated washing with tilted water while adding distilled water to remove the electrolyte, followed by heat treatment such as drying and baking, removing the water contained in the solid phase to completely remove the oxide. A film is preferred. Further, by heat-treating the powder after film formation in a rotary tube furnace or the like, sticking can be prevented and dispersed particles can be obtained.
[0062]
In order to form a hydroxide film or an oxide film and heat-treat it, it may be heat-treated every time each layer is coated, or may be finally heat-treated after the target multilayer film is completed. Although the heat treatment conditions vary depending on the reaction system, the heat treatment temperature is preferably 200 to 1300 ° C, and more preferably 400 to 1100 ° C. Below 200 ° C., salts and moisture may remain, and when it exceeds 1300 ° C., the film and the substrate may react with each other to form different substances, both of which are inappropriate. The heat treatment time is preferably 0.1 to 100 hours, more preferably 0.5 to 50 hours.
[0063]
【Example】
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
[0064]
[Examples 1-7]
(Preparation of silica film-coated spherical iron powder)
(Preparation of substrate particle suspension buffer)
A buffer solution was prepared by adding and dissolving sodium carbonate reagent (Kanto Chemical), sodium hydrogen carbonate reagent (Kanto Chemical), and potassium chloride reagent (Kanto Chemical) in deionized water. The concentrations of sodium carbonate, sodium bicarbonate and potassium chloride are shown in the table below.
[0065]
[Table 1]

[0066]
In this buffer, 20 g of spherical iron powder (BASF, trade name ES) having an average particle size of 3.3 μm (measured by BASF) was suspended to obtain a substrate particle suspension buffer.
[0067]
(Silica film coating process)
While stirring the substrate particle suspension buffer at 1000 rpm, 150 g of a 5 wt% aqueous sodium silicate solution was added dropwise at a supply rate of 1.00 ml / min and aged for 1 hour. As a result, precipitation of silica from the sodium silicate in the liquid occurred on the surface of the substrate particles, and the silica particles were coated on the substrate particles.
After aging, stirring was stopped and the powder in the suspension was allowed to settle and the supernatant was removed. The supernatant was colorless and transparent.
Furthermore, after carrying out the inclination washing | cleaning (decantation) by deionized water, it dried at 120 degreeC for 2 hours, and obtained the silica membrane coating spherical iron powder.
[0068]
[Example 8]
(Creation of titania film coated spherical iron powder)
(Adjustment of dripping liquid)
20% titanium chloride [III] solution (Kanto Chemical Co., Ltd., deer grade 1 reagent) 10.0 g, 28% ammonia water (Kanto Chemical Co., Ltd., deer grade 1 reagent) 20.5 g, 31% hydrogen peroxide solution (Kanto) A yellow transparent drop containing peroxotitanic acid was obtained by mixing 10.0 g of a chemical reagent (special grade reagent). The pH of this dropping liquid was 10.0.
(Preparation of substrate particle suspension buffer)
In the buffer obtained in Example 7, 40 g of spherical iron powder (BASF, trade name ES) having an average particle size of 3.3 μm (measured by BASF) was suspended to obtain a substrate particle suspension buffer. It was.
[0069]
(Titania film coating)
While stirring the substrate particle suspension buffer at 1000 rpm, the dropping solution was added dropwise at a rate of 1.5 ml / min and aged for 2 hours. As a result, precipitation of titania from the peroxotitanic acid in the liquid occurred on the surface of the substrate powder, and the substrate particles were coated with the titania film.
After aging, stirring was stopped and the powder in the suspension was allowed to settle and settle, and the upper liquid was removed. The upper liquid was colorless and transparent.
Furthermore, after carrying out the inclination washing | cleaning (decantation) by deionized water, it dried at 120 degreeC for 2 hours, and obtained the titania film-coated spherical iron powder.
[0070]
[Example 9]
(Create silica film-coated permalloy powder)
(Preparation of substrate particle suspension buffer)
Flaky permalloy powder (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.) having an average particle size of 15.3 μm (produced by HONEYWELL, measured with 9320-X100 type Microtrac HRA particle size analyzer) in the buffer obtained in Example 7 above. 18.5 g (trade name 78 Permalloy Flakes) was suspended to obtain a substrate particle suspension buffer.
[0071]
(Silica film coating)
While stirring the substrate particle suspension buffer at 1000 rpm, 120 g of a 5 mass% sodium silicate aqueous solution was added dropwise at a supply rate of 1.00 ml / min, and aged for 1 hour. As a result, precipitation of silica from the sodium silicate in the liquid occurred on the surface of the substrate particles, and the silica particles were coated on the substrate particles.
After aging, stirring was stopped and the powder in the suspension was allowed to settle and the supernatant was removed. The supernatant was colorless and transparent.
Furthermore, after carrying out the inclination washing | cleaning (decantation) by deionized water, it dried at 120 degreeC for 2 hours, and obtained the silica membrane coating | cover permalloy powder.
[0072]
【The invention's effect】
The membrane coating body, the membrane coating method, and the manufacturing method of the membrane coating body according to the present invention are formed by forming a film on the surface of the substrate by a reaction in a carbonate buffer solution, resulting in a low waste water standard for waste liquid generated and a low waste liquid treatment cost. It can be done.

Claims (2)

In the method of manufacturing a film covering for forming a film on the surface of a powder, at least one layer of the film contains an alkali metal salt such as KCl, NaCl, or LiCl in which the powder is immersed, and has an ionic strength of 1. A method for producing a membrane-coated body, comprising adding a metal salt aqueous solution as a membrane component raw material to a carbonate buffer solution of 41 to 5.0, and forming a reaction from the metal salt. Producing how the film-coated member according to claim 1 wherein said carbonate buffer is characterized in that it consists of _Na 2 CO ₃ and NaHCO ₃ Prefecture.