JP4233295B2 - Method for producing powder coated with titanium oxide film - Google Patents

Description

【００４０】
（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。）
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３
【００４１】
【式２】

【００４２】
（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３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２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。
【００４３】
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。
【００４４】
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。
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の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２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わうことが好ましい。
【００４５】
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。
【００４６】
本発明の方法で得られる酸化チタン膜被覆粉体は、表面に被覆された酸化チタン膜による光学的干渉作用により、青色や赤紫色を呈するものであり、カラーインキ、プラスチック、紙用カラーフィラー、カラートナー、インクジェットプリンター用カラーインク等多種の目的に用いることができる。
【００４７】
本発明の方法で得られる酸化チタン膜被覆粉体を含有する塗料組成物を調製する場合のうち、（１）各特定色系インキあるいは塗料様組成物（流体）および（２）各特定色系トナー、各特定色系乾式インキ様組成物（粉体）について詳しく説明する。
【００４８】
（１）本発明において特定の色系インキあるいは塗料様組成物（流体）の媒質（ビヒクル）としては、カラー印刷用、カラー磁気印刷用、カラー磁気塗料用に用いられる、従来公知のワニスを用いることができ、例えば液状ポリマー、有機溶媒に溶解したポリマーやモノマーなどを粉体の種類やインキの適用方法、用途に応じて適宜に選択して使用することができる。
上記液状ポリマーとしては、ポリペンタジエン、ポリブタジエン等のジエン類、ポリエチレングリコール類、ポリアミド類、ポリプロピレン類、ワックス類あるいはこれらの共重合体編成体等を挙げることができる。
【００４９】
有機溶媒に溶解するポリマーとしては、オレフィン系ポリマー類、オリゴエステルアクリレート等のアクリル系樹脂類、ポリエステル類、ポリアミド類、ポリイソシアネート類、アミノ樹脂類、キシレン樹脂類、ケトン樹脂類、ジエン系樹脂類、ロジン変性フェノール樹脂、ジエン系ゴム類、クロロプレン樹脂類、ワックス類あるいはこれらの変性体や共重合体などを挙げることができる。
有機溶媒に溶解するモノマーとしては、スチレン、エチレン、ブタジエン、プロピレンなどを挙げることができる。
有機溶媒としては、エタノール、イソプロパノール、ノルマルプロパノール等のアルコール類、アセトン等のケトン類、ベンゼン、トルエン、キシレン、ケロシン、ベンジン炭化水素類、エステル類、エーテル類あるいはこれらの変性体や共重合体などを挙げることができる。
【００５０】
（２）特定色系トナー、特定色系乾式インキ、特定色系乾式塗料様組成物（粉体）は、上記特定色系多層膜被覆粉体を、樹脂とあるいは必要に応じて調色材とを、スクリュー型押出機、ロールミル、ニーダなどで直接混練し、ハンマミル、カッターミルで粗粉砕したあと、ジェットミルなどで微粉砕し、エルボージェットなどで必要な粒度に分級することにより粉体状シアン色色材組成物を得ることができる。また、乳化重合法や懸濁重合法などの重合法を用いて、特定色系多層膜被覆粉体を粉体状特定色系塗料組成物とすることもできる。
さらに、特定色系多層膜被覆粉体と樹脂、調色剤などの添加剤および溶剤をコロイドミルや３本ロールで液状化しインキ塗料などの液状特定色系塗料組成物とすることもできる。
【００５１】
明度を上げるための調色材としては、白色顔料（展色材）である、例えば、酸化チタン、酸化亜鉛、酸化錫、酸化珪素、酸化アンチモン、酸化鉛等あるいはこれらの複合酸化物類、また炭酸カルシウム、炭酸マグネシウム、炭酸バリウム等の炭酸塩、あるいは硫酸バリウム、硫酸カルシウムのような硫酸塩類、硫酸亜鉛のような硫化物あるいは前記酸化物や炭酸塩および硫酸塩を焼結した複合酸化物、複合含水酸化物類が挙げられる。
【００５２】
彩度、色相を調整するため、特にフルカラー用混色で色再現用に使用する場合の調色材としては、青色顔料である（有機染料・顔料）アルカリブルーレーキ、ピーコックレーキ、ピーコックレーキブルー等のレーキ染料およびレーキ顔料、オイルブルー等、オイル染料顔料、アルコールブルー等のアルコール染料、フタロシアニン、銅フタロシアニン等のフタロシアニン系顔料等、（無機顔料）ウルトラマリン等の酸化物硫化物複合顔料、鉄青、ミロリーブルー等の銅系群青紺青顔料類、コバルトブルー、セルリアンブルー等の酸化コバルト系複合酸化物類青色顔料、青色系有機染料および顔料および青色無機顔料アルカリブルーレーキ、ピーコックブルーレーキ等のレーキ染料、レーキ系顔料無金属フタロシアニン、銅フタロシアニン等のフタロシアニン系染顔料 および緑色顔料であるクロームグリーン、ジンクグリーン、酸化クロム、含水クロム（ビリジアン）等のクロム系酸化物および含水酸化物、エメラルドグリーン等の銅系酸化物、コバルトグリーン等のコバルト系酸化物等の無機顔料あるいは、ピグメントグリーン、ナフトールグリーンなどのニトロソ顔料、グリーンゴールド等のアゾ系顔料、フタロシアニングリーン、ポリクロム銅フタロシアニン等のフタロシアニン系顔料、マラカイトグリーンレーキ、アシッドグリーンレーキなどのレーキ系、オイルグリーン等、オイル染料顔料アルコールブルー等のアルコール染料顔料等有機染顔料が挙げられる。しかし本発明はこれらのみに限定されるものではない。
【００５３】
さらに、微妙な色調制御においては青色、黄色、赤紫色などの顔料や染料を用いて調色することが必要な場合は、これらの顔料を添加することにより最適の特定色とすることが好ましい。
この粉体状特定色系塗料組成物の場合、（ａ）上記粉砕法で製造する場合の樹脂としては、特に限定されるものではないが、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、ブタジエン、プロピレン及びこれらの誘導体の重合体または共重合体などが挙げられる。
（ｂ）重合法の場合、エステル、ウレタン、酢酸ビニル、有機ケイ素、アクリル酸、メタアクリル酸、スチレン、エチレン、ブタジエン、プロピレン等のうち１種あるいは複数の混合物から重合を開始させ、重合体あるいはこれらの共重合体などが形成される。
【００５４】
本発明の膜被覆粉体を含有する塗料組成物は上記のように、（１）各特定色系インキあるいは塗料様組成物（流体）および（２）各特定色系トナー、各特定色系乾式インキ様組成物（粉体）の形をとることができる。
また、流体状の場合には、特定色系インキ、塗料等であり、前記調色材、乾燥の遅い樹脂には固化促進剤、粘度を上げるために増粘剤、粘性を下げるための流動化剤、粒子同志の分散のために分散剤などの成分を含ませることができる。
一方、粉体の場合には、（ａ）粉砕法で粉体を製造する場合には、前記調色材、乾燥の遅い樹脂には固化促進剤、混練の際の粘性を下げるためには流動化剤、粒子同志の分散のためには分散剤、紙等への定着のための電荷調整剤、ワックスなどの成分を含ませることができる。
（ｂ）重合法を用いる場合には、前記調色材、重合開始剤、重合促進剤、粘度を上げるためには増粘剤、粒子同志の分散のためには分散剤、紙等への定着のための電荷調整剤、ワックスなどの成分を含ませることができる。
本発明の多層膜被覆粉体は、単一の粉体ないしは分光特性の異なる複数の粉体の組み合せにより、湿式および乾式カラー印刷や湿式および乾式カラー磁気印刷に適用できるほか、３原色の粉体を用いて、可視光、非可視光（紫外域およびシアン外域）、蛍光発色および磁気、さらに電気（電場の変化）の６種の組合せの識別機能を持ち、印刷物の偽造防止用カラー磁性インキなどセキュリティ機能を必要とする他の用途に適用することができる。
【００５５】
前記本発明の被覆粉体を各特定色系インキあるいは塗料様組成物または各特定色系トナー、各特定色系乾式インキ様組成物、各特定色系乾式塗料組成物として、基材に印刷、溶融転写または被塗装体に塗布する場合、塗料組成物中の各特定色系多層膜被覆粉体と樹脂の含有量の関係は、体積比で１：０．５〜１：１５である。媒質の含有量が少な過ぎると塗布した膜が被塗装体に固着しない。また、多過ぎると顔料の色が薄くなりすぎ良いインキまたは塗料といえない。 また、各色系インキあるいは塗料組成物中の各色系色材および樹脂を合わせた量と溶剤の量との関係は、体積比で１：０．５〜１：１０であり、溶剤の量が少な過ぎると塗料の粘度が高く、均一に塗布できない。また、溶剤の量が多過ぎると塗膜の乾燥に時間を要し塗布作業の能率が極端に低下する。
【００５６】
また、基材に印刷、溶融転写または被塗装体に塗料を塗布した際の塗膜の色の濃度は、被塗装体の単位面積当たりに載った顔料の量によって決まる。塗料が乾燥した後の被塗装体上の本発明の膜被覆粉体の量は、均一に塗布した場合の面積密度で１平方メートルあたり０．１〜３００ｇであり、好ましくは０．１〜１００ｇであれば良好な塗装色が得られる。面積密度が前記の値より小さければ被塗装体の地の色が現れ、前記の値より大きくても塗装色の色濃度は変わらないので不経済である。すなわち、ある厚さ以上に顔料を被塗装体上に載せても、塗膜の下側の顔料にまでは光りが届かない。かかる厚さ以上に塗膜を厚くすることは、塗料の隠蔽力を越えた厚さであるので塗装の効果がなく不経済である。ただし、塗膜の磨耗を考慮し、塗膜の厚さが摩り減るため厚塗りする場合はこの限りではない。また特定の意匠等を部分的に形成する場合にもこの限りではない。
【００５７】
【実施例】
以下、本発明を実施例によりさらに具体的に説明するが、本発明の範囲はこれらに限定されるものではない。
【００５８】
実施例１：マグネタイト粉末粒子の青色化、水系２層被覆
[第１層シリカ膜被覆操作]
（１）緩衝液の調整
イオン交換水３００ミリリットルに塩化カリウム（関東化学社製試薬特級）の２９．８２ｇ（０．４モル量）とホウ酸（関東化学社製試薬特級）の２４．２３ｇ（０．４モル量）を溶解し、イオン交換水で１０００ミリリットルにメスアップしてＡ溶液とした。
イオン交換水３００ミリリットルに水酸化ナトリウム（関東化学社製試薬特級）の１６．０ｇ（０．４モル量）を溶解し、イオン交換水で１０００ミリリットルにメスアツプしてＢ溶液とした。
上記Ａ溶液の２５０ミリリットルとＢ溶液の１１５ミリリットルを混合し、緩衝液Ｃとした。この緩衝液ＣのｐＨは９．１であった。
（２）ケイ酸ナトリウム水溶液（水ガラス溶液）の調整
ケイ酸ナトリウム溶液（関東化学社製試薬）の１００．０ｇをイオン交換水で全量が１０００．０ｇになるように希釈して、１０重量％ケイ酸ナトリウム水溶液を調整した。
【００５９】
（３）シリカ膜被覆
基材粉体として１０グラムのマグネタイト粉末（平均粒径０．７μｍ）を、予め用意しておいた上記緩衝液Ｃの５４０ミリリットルに投入し、よく分散させた、この懸濁液の入った容器（１０００ミリリットルガラスビーカー）を、６００Ｗ、２８ｋＨｚの超音波洗浄槽（（株）井内盛栄堂ＵＳ−６型）水槽に浸け、５５０ｒｐｍにて攪拌する。攪拌開始と同時に、超音波を照射する。
次に、１０重量％ケイ酸ナトリウム水溶液の所定量９０グラムを、１．３４ミリリットル／分の滴下速度で、先の攪拌している懸濁液中に滴下する。滴下終了後、さらに１時間攪拌を続け、原料マグネタイト表面にシリカ膜被覆を行う。
所定時間経過後、シリカ膜被覆された粉体を含むスラリーを十分なイオン交換水にてデカンテーションを繰り返し、洗浄した。洗浄操作後、シリカ膜被覆された粉体を含むスラリーを１１０℃にて８時間乾燥させ、シリカ膜被覆されたマグネタイト粉Ｄ₁を得た。このシリカ膜被覆されたマグネタイト粉Ｄ₁の分光特性を分光光度計（日本分光社製Ｕｂｅｓｔ５５０）にて測定した結果、茶色を呈し、ＣＩＥ（１９７６）Ｌ^*ａ^*ｂ^*表色系ではＬ^*＝３４．９、ａ^*＝０．４、ｂ^*＝−１．４であった。
【００６０】
[第２層酸化チタン膜被覆操作]
（１）ペルオキソチタン溶液の調整
塩化チタン（IV）溶液（和光純薬社製試薬）２．２ミリリットル（ＴｉＯ₂量０．８８グラム（０．０１１モル））を、イオン交換水にて１０倍に希釈した。
次に、この塩化チタン（IV）水溶液にアンモニア水（関東化学社製試薬特級）５．３４グラムを添加し、水酸化チタンスラリー液を作る。
次に、この水酸化チタンスラリー液に過酸化水素水（関東化学社製試薬特級）１０．０グラムをゆっくりと添加し、十分に攪拌して水酸化チタンを溶解させ、黄色透明のペルオキソチタン溶液を得る。この黄色透明のペルオキソチタン溶液のｐＨは９．０程度であった。
最後に、ｐＨ調整としてアンモニア水（関東化学社製試薬特級）０．５０グラムを添加してｐＨを９．３程度のアルカリ性とした。ペルオキソチタン溶液Ｅ₁を得る。
【００６１】
（２）酸化チタン膜被覆
上記シリカ膜被覆されたマグネタイト粉Ｄ₁６．０グラムを第１層シリカ膜被覆操作で用いたのと同じ緩衝液Ｃの５６０グラムに懸濁させた。この懸濁液の入った容器（１０００ミリリットルセパラブルフラスコ）を、５０℃に保温した恒温水槽に浸け、７００ｒｐｍにて攪拌する。
懸濁液の液温が５０℃になったところで、上記ペルオキソチタン溶液Ｅ₁の所定量３９グラム（３８ミリリットル）を１．８ミリリットル／分の滴下速度で滴下する。滴下終了後、さらに１２０分攪拌を続け、原料であるシリカ膜被覆されたマグネタイト粉Ｄ₁上に酸化チタン膜被覆を行う。所定時間経過後、酸化チタン膜被覆された粉体を含むスラリーを十分なイオン交換水にてデカンテーションを繰り返し、洗浄した。洗浄操作終了後、酸化チタン膜被覆された粉体を含むスラリーを１２０℃にて２時間乾燥させ、酸化チタン膜被覆されたマグネタイト粉Ｆ₁を得た。得られた酸化チタン膜被覆されたマグネタイト粉Ｆ₁を分光光度計（日本分光社製Ｕｂｅｓｔ５５０）にて分光特性を測定した結果を表１及び図１に示すが、３５０ｎｍ付近に反射ピーク（λ／４ピーク）を持ち、ＣＩＥ（１９７６）Ｌ^*ａ^*ｂ^*表色系ではＬ^*＝３５．９、ａ^*＝−０．４、ｂ^*＝−５．９の青色を呈した。
【００６２】
実施例２：マグネタイト粉末粒子の赤紫色化、水系２層被覆
[第１層シリカ膜被覆操作]
実施例１と同じ操作によりシリカ膜被覆されたマグネタイト粉Ｄ₁を得た。
【００６３】
[第２層酸化チタン膜被覆操作]
（１）ペルオキソチタン溶液の調整
塩化チタン（IV）溶液（和光純薬社製試薬）４．４ミリリットル（ＴｉＯ₂量１．７６グラム（０．０２２モル））を、イオン交換水にて１０倍に希釈した。
次に、この塩化チタン（ｌＶ）水溶液にアンモニア水（関東化学社製試薬特級）１０．６９グラムを添加し、水酸化チタンスラリー液を作る。
次に、この水酸化チタンスラリー液に過酸化水素水（関東化学社製試薬特級）２０．０グラムをゆっくりと添加し、十分に攪拌して水酸化チタンを溶解させ、黄色透明のペルオキソチタン溶液を得る。この黄色透明のペルオキソチタン溶液のｐＨは９．０程度であった。
最後に、ｐＨ調整としてアンモニア水（関東化学社製試薬特級）１．００グラムを添加してｐＨを９．３程度のアルカリ性とした。ペルオキソチタン溶液Ｅ₂を得る。
【００６４】
（２）酸化チタン膜被覆
上記シリカ膜被覆されたマグネタイト粉Ｄ₁６．０グラムを第１層シリカ膜被覆操作で用いたのと同じ緩衝液Ｃの５６０グラムに懸濁させた。この懸濁液の入った容器（１０００ミリリットルセパラブルフラスコ）を、５０℃に保温した恒温水槽に浸け、７００ｒｐｍにて攪拌する。
懸濁液の液温が５０℃になったところで、上記ペルオキソチタン溶液Ｅ₂の所定量７８ｇ（７６ミリリットル）を２．０ミリリットル／分の滴下速度で滴下する。滴下終了後、さらに１２０分攪拌を続け、原料であるシリカ膜被覆されたマグネタイト粉Ｄ₁上に酸化チタン膜被覆を行う。所定時間経過後、酸化チタン膜被覆された粉体を含むスラリーを十分なイオン交換水にてデカンテーションを繰り返し、洗浄した。洗浄操作終了後、酸化チタン膜被覆された粉体を含むスラリーを１２０℃にて２時間乾燥させ、酸化チタン膜被覆されたマグネタイト粉Ｆ₂を得た。得られた酸化チタン膜被覆されたマグネタイト粉Ｆ₂を分光光度計（日本分光社製Ｕｂｅｓｔ５５０）にて分光特性を測定した結果を表１及び図１の分光反射率曲線に示すが、３５０ｎｍ付近（３λ／４ピーク）と６３０ｎｍ付近（λ／４ピーク）に二つの反射ピークを持ち、ＣＩＥ（１９７６）Ｌ^*ａ^*ｂ^*表色系ではＬ^*＝３７．１、ａ^*＝１．２、ｂ^*＝−０．８の赤紫色を呈した。
【００６５】
実施例３：パーマロイ粉末粒子への酸化チタン膜被覆
[酸化チタン膜被覆操作]
（１）ペルオキソチタン溶液の調整
実施例１と同じ操作によりペルオキソチタン溶液Ｅ₁を得る。
（２）緩衝液の調整
イオン交換水３００ミリリットルに塩化カリウム（関東化学社製試薬特級）の２９．８２ｇ（０．４モル量）とホウ酸（関東化学社製試薬特級）の２４．２３ｇ（０．４モル量）を溶解し、イオン交換水で１０００ミリリットルにメスアップしてＡ溶液とした。
イオン交換水３００ミリリットルに水酸化ナトリウム（関東化学社製試薬特級）の１６．０ｇ（０．４モル量）を溶解し、イオン交換水で１０００ミリリットルにメスアップしてＢ溶液とした。
上記Ａ溶液の２５０ミリリットルとＢ溶液の１１５ミリリットルを混合し、緩衝液Ｃとした。この緩衝液ＣのｐＨは９．１であった。
【００６６】
（３）酸化チタン膜被覆
基材粉体として２９グラムのパーマロイ粉末（平均粒径１６．７μｍ）を、予め用意しておいた上記緩衝液Ｃの２８０ミリリットルに投入し、よく分散させた。この懸濁液の入った容器を２３℃に保温した恒温水槽に浸け、７００ｒｐｍにて攪拌した。
次に、上記ペルオキソチタン溶液Ｅ₁の所定量３９グラム（３８ミリリットル）を１．８ミリリットル／分の滴下速度で滴下する。滴下終了後、さらに１２０分攪拌を続け、原料パーマロイ粉上に酸化チタン膜被覆を行う。所定時間経過後、酸化チタン膜被覆された粉体を含むスラリーを十分なイオン交換水にてデカンテーションを繰り返し、洗浄した。洗浄操作終了後、酸化チタン膜被覆された粉体を含むスラリーを１２０℃にて２時間乾燥させ、酸化チタン膜被覆されたパーマロイ粉Ｇ₁を得た。得られた酸化チタン膜被覆されたパーマロイ粉Ｇ₁を分光光度計（日本分光社製Ｕｂｅｓｔ５５０）にて分光特性を測定した結果を表１及び図２の分光反射率曲線に示すが、３３０ｎｍ付近に反射ピーク（２λ／４ピーク）を持ち、ＣＩＥ（１９７６）Ｌ^*ａ^*ｂ^*表色系ではＬ^*＝ ４５．２、ａ^*＝５．４、ｂ^*＝−３．７の紫色を呈した。
【００６７】
実施例４：パーマロイ粉末粒子への酸化チタン膜被覆
[酸化チタン膜被覆操作]
（１）ペルオキソチタン溶液の調整
塩化チタン（IV）溶液（和光純薬社製試薬）２．９３ミリリットル（ＴｉＯ₂量１．１７グラム（０．０１５モル））を、イオン交換水にて１０倍に希釈した。
次に、この塩化チタン（IV）水溶液にアンモニア水（関東化学社製試薬特級）７．１２グラムを添加し、水酸化チタンスラリー液を作る。
次に、この水酸化チタンスラリー液に過酸化水素水（関東化学社製試薬特級）２０．０グラムをゆっくりと添加し、十分に攪拌して水酸化チタンを溶解させ、黄色透明のペルオキソチタン溶液を得る。この黄色透明のペルオキソチタン溶液のｐＨは９．０程度であった。
最後に、ｐＨ調整としてアンモニア水（関東化学社製試薬特級）１．００グラムを添加してｐＨを９．３程度のアルカリ性とした、ペルオキソチタン溶液Ｅ₃を得る。
【００６８】
（２）緩衝液の調整
イオン交換水３００ミリリットルに塩化カリウム（関東化学社製試薬特級）の２９．８２ｇ（０．４モル量）とホウ酸（関東化学社製試薬特級）の２４．２３ｇ（０．４モル量）を溶解し、イオン交換水で１０００ミリリットルにメスアップしてＡ溶液とした。
イオン交換水３００ミリリットルに水酸化ナトリウム（関東化学社製試薬特級）の１６．０ｇ（０．４モル量）を溶解し、イオン交換水で１０００ミリリットルにメスアップしてＢ溶液とした。
上記Ａ溶液の２５０ミリリットルとＢ溶液の１１５ミリリットルを混合し、緩衝液Ｃとした。この緩衝液ＣのｐＨは９．１であった。
【００６９】
（３）酸化チタン膜被覆
基材粉体として２９グラムのパーマロイ粉末（平均粒径１６．７μｍ）を、予め用意しておいた上記緩衝液Ｃの２８０ミリリットルに投入し、よく分散させた。この懸濁液の入った容器を２３℃に保温した恒温水槽に浸け、７００ｒｐｍにて攪拌した。
次に、上記ペルオキソチタン溶液Ｅ₃の所定量５９グラム（５８ミリリットル）を２．０ミリリットル／分の滴下速度で滴下する。滴下終了後、さらに１２０分攪拌を続け、原料パーマロイ粉上に酸化チタン膜被覆を行う。所定時間経過後、酸化チタン膜被覆された粉体を含むスラリーを十分なイオン交換水にてデカンテーションを繰り返し、洗浄した。洗浄操作終了後、酸化チタン膜被覆された粉体を含むスラリーを１２０℃にて２時間乾燥させ、酸化チタン膜被覆されたパーマロイ粉Ｇ₂を得た。得られた酸化チタン膜被覆されたパーマロイ粉Ｇ₂を分光光度計（日本分光社製Ｕｂｅｓｔ５５０）にて分光特性を測定した。結果を表１及び図２の分光反射率曲線に示すが、４００ｎｍ付近に反射ピーク（２λ／４ピーク）を持ち、ＣＩＥ（１９７６）Ｌ^*ａ^*ｂ^*表色系ではＬ^*＝５２．５、ａ^*＝−１．７、ｂ^*＝−１１．０の青色を呈した。
【００７０】
比較例１
[酸化チタン膜被覆]
（１）ペルオキソチタン溶液の調整
塩化チタン（IV）溶液（和光純薬社製試薬）２．２ミリリットル（ＴｉＯ₂量０．８８グラム（０．０１１モル））を、イオン交換水にて１０倍に希釈した。
次に、過酸化水素水（関東化学社製試薬特級）１０．０グラムをゆっくりと添加し、橙赤色の過チタン酸溶液Ｅ₄を得た。この溶液のｐＨは１．３程度であった。
【００７１】
（２）酸化チタン膜被覆
実施例３の滴下液を橙赤色の過チタン酸溶液Ｅ₄とした以外は同じ操作を行った。結果は、滴下液の全量を滴下した後の反応液のｐＨは２．２付近にまで低下し、酸化チタンの微粒子が形成され、反応液が薄黄色に濁っていた。また、反応液中のパーマロイ粉を十分なイオン交換水にてデカンテーションを繰り返し、洗浄した。洗浄操作終了後、パーマロイ粉を含むスラリーを１２０℃にて２時間乾燥させた後、結果を観察した。この方法では酸化チタン膜は全く被覆されていなかった。
【００７２】
【表１】

【００７３】
【発明の効果】
本発明によれば、基材金属粉体に対して塩化チタン（IV）溶液を使用して酸化チタン膜を被覆させる際に、反応液のｐＨを７以上のアルカリ牲とすることができ、より多くの基材金属粉体を溶解させることなく使用できるようになった。また、製膜反応を短時間に、効率よく、しかも低い温度で行うことが可能となった。
【００７４】
さらに、一回の酸化チタン膜の被覆操作で、光学的干渉作用を生じさせるに十分な厚さの酸化チタン膜を、その膜厚を容易に調節して被覆させることができ、酸化チタン膜を破覆させた基材粉体に高い光学的干渉作用を生じさせることが可能となった。そのため、青色や赤紫色の着色磁性粉体を製造することが可能となった。
【図面の簡単な説明】
【図１】実施例１と実施例２で得られた酸化チタン膜被覆シリカコートマグネタイト粉の分光反射率曲線を示す図である。
【図２】実施例３と実施例４で得られた酸化チタン膜被覆パーマロイ粉の分光反射率曲線を示す図である。[0001]
BACKGROUND OF THE INVENTION
  The present invention is a titanium oxide film-coated powder.the body'sIt relates to a manufacturing method. This titanium oxide film-coated powder is colored blue or magenta due to the optical interference effect of the titanium oxide film coated on the surface. Color ink, plastic, color filler for paper, color toner, ink jet The present invention relates to a colored powder used for various purposes such as color ink for printers and a method for producing the same.
[0002]
[Prior art]
In the past, the inventors have applied a method of coating a titanium oxide film using a metal alkoxide (Patent Document 1 (Japanese Patent Laid-Open No. 06-228604) or the like) or a titanium oxide film using a titanyl sulfate solution. A coating method (Patent Document 2 (JP 2000-345072 A) and the like) has been developed. Furthermore, using these titanium oxide film coating methods, a method of coating an interference film made of silica / titanium oxide on black magnetic powder and coloring the black magnetic powder has been developed and disclosed (Patent Document 3). (Japanese Patent Laid-Open No. 10-330644).
[0003]
On the other hand, as a method of coating a titanium oxide film, there is known a method using a titanium (IV) chloride solution in addition to the above titanium raw material, and these are disclosed in Patent Document 4 (Japanese Patent Laid-Open No. 2000-86292) and A large number of documents and patents such as Patent Document 5 (Japanese Patent Laid-Open No. 5-286738) are disclosed.
Furthermore, in Patent Document 6 (Japanese Patent Application Laid-Open No. 01-224220), a peroxotitanium solution is prepared from a titanium (IV) chloride solution, and the peroxotitanium solution is heated in the presence of a base material powder to thereby form the base material. A method of coating a titanium oxide film on the powder surface has been disclosed.
In Patent Document 7 (Japanese Patent Laid-Open No. 09-71418) and Patent Document 8 (Japanese Patent Laid-Open No. 10-67516), a basic substance such as aqueous ammonia is added to a titanium-containing liquid such as a titanium (IV) chloride solution. To precipitate titanium hydroxide gel, and the precipitate is filtered and washed to form a dispersion, and a hydrogen peroxide solution is added thereto to form a peroxotitanium solution, and the powder is surface-treated with the peroxotitanium solution. The method is public.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 06-228604
[Patent Document 2]
JP 2000-345072 A
[Patent Document 3]
Japanese Patent Laid-Open No. 10-330644
[Patent Document 4]
JP 2000-86292 A
[Patent Document 5]
Japanese Patent Laid-Open No. 5-286638
[Patent Document 6]
JP-A-01-224220
[Patent Document 7]
JP 09-71418 A
[Patent Document 8]
JP 10-67516 A
[0005]
[Problems to be solved by the invention]
However, it has been found that there are various problems with the titanium oxide film coating methods known so far.
First, when a metal alkoxide is used as a titanium oxide film coating raw material, the metal alkoxide is unstable and its hydrolysis reaction is very fast, so that the reaction system must be performed at constant temperature and humidity, and further the reaction Must be carried out in an organic solvent such as alcohol, which complicates the reaction apparatus.
[0006]
In addition, as a problem when a titanyl sulfate solution is used as a raw material for coating a titanium oxide film, it takes a long time for the film forming operation because the reaction of titanyl sulfate is slow, and the titanium oxide film that can be coated by one film forming operation When there is a limit to the thickness, and it is necessary to increase the thickness of the titanium oxide film, it is necessary to divide the titanium oxide film coating operation into a plurality of times.
The titanium oxide film coating method using a titanium (IV) chloride solution can significantly reduce the reaction time compared with the case of using a titanyl sulfate solution, and can be considerably performed by a single titanium oxide film coating operation. A thick titanium oxide film can be coated. However, the conventional titanium oxide film coating method using the above titanyl sulfate solution or titanium (IV) chloride solution is acidic with a pH of 7 or less in the reaction solution. In the case of a body, there is an influence such as dissolution of the base powder, and it is difficult to apply.
[0007]
Furthermore, in the method for producing a titanium oxide film-coated powder disclosed in Patent Document 6 (Japanese Patent Laid-Open No. 01-224220), the produced peroxotitanium solution is heated to 95 ° C. or higher in the presence of a base material powder. This is a method of covering the surface of the substrate powder with the titanium oxide film by holding it for 8 hours or more, and cannot be said to be a method of easily covering the surface of the powder with the titanium oxide film in a short time. Met.
In addition, the titanium oxide film coating method disclosed in Patent Document 6 (Japanese Patent Laid-Open No. 01-224220), Patent Document 7 (Japanese Patent Laid-Open No. 09-71418), etc. describes surface treatment of powder as an application. However, in order to obtain a peroxotitanium solution that is a coating raw material solution, the precipitate after adding a basic substance to the titanium-containing liquid must be filtered and washed, and then hydrogen peroxide solution must be added. That is, how much thickness of the titanium oxide film can be coated on the base powder by one operation of coating the titanium oxide film, that is, on the target base powder Since a method for coating a titanium oxide film has not been introduced, it is difficult to coat a titanium oxide film having a thickness that causes an optical interference action.
[0008]
In addition, the applicants have developed a method for coating a titanium oxide film on a base powder using a titanium (III) chloride solution (Japanese Patent Application No. 2001-308682). In this method, it has become possible to produce a titanium oxide film coating with greater ease than before. However, in this method, foaming frequently occurs at the stage of adding peroxide to the titanium (III) chloride solution in the process of peroxolating the titanium (III) chloride solution, so a peroxotitanium solution is prepared. It was not so easy. Therefore, a method for producing a highly accurate titanium oxide-coated powder more easily and quickly has been demanded.
[0009]
[Means for Solving the Problems]
As a result of diligent efforts, the authors can solve the above-described problems by using a titanium (IV) chloride solution and a process for producing a peroxotitanic acid solution. The present inventors have found a method capable of coating a titanium oxide film on a metal powder. This method made it possible to coat the titanium oxide film in a short time and at a low temperature.
[0010]
  Such a method means:
(1) An excess of a basic substance is added to the titanium (IV) chloride solution, and then a peroxide is added to form a basic peroxotitanium solution. The peroxotitanium solution is dropped into the base powder suspension. A method of producing a titanium oxide film-coated powder by coating a titanium oxide film on a substrate powder.
(2) The method for producing a titanium oxide film-coated powder according to (1), wherein the substrate powder suspension is an alkaline buffer having a pH of 8 or more and a pH of 10 or less.
(3) The method for producing a titanium oxide film-coated powder according to (1), wherein the titanium oxide film coating reaction according to (1) is performed at a reaction temperature of 15 ° C. or higher and 65 ° C. or lower.
(4) The method for producing a titanium oxide film-coated powder according to (1), wherein the titanium oxide film coating reaction according to (1) is performed for a reaction time of 1 hour to 6 hours.Law.
It is.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention
(A) Add an excess of basic substance to the titanium (IV) chloride solution,
(B) A peroxide is then added to form a basic peroxotitanium solution;
(C) The peroxotitanium solution is dropped into the substrate powder suspension.
The present invention relates to a method for producing a titanium oxide film-coated powder by coating a titanium oxide film on a substrate powder including a process.
According to the present invention, a basic substance and a peroxide are sequentially added to a titanium (IV) chloride solution, which is a titanium source, and the reaction liquid is simply dropped onto the base particle dispersion, whereby the base particles can be easily formed. In addition, a titanium oxide film can be formed. In the present invention, it is possible to easily form a titanium oxide film without going through complicated steps that require time for filtration, washing, heating, and standing for a long time.
Below, the manufacturing method of this invention is demonstrated in detail.
[0012]
(A) A step of adding an excess of a basic substance to a titanium (IV) chloride solution
In the present invention, a commercially available titanium (IV) chloride solution can be used, but a titanium (IV) chloride solution having a Ti concentration of 9% by mass to 20% by mass is preferably used. More preferably, a titanium (IV) chloride solution having a Ti concentration of 14% by mass or more and 18% by mass or less is used. As such a titanium (IV) chloride solution, commercially available products such as a reagent manufactured by Wako Pure Chemical Industries, Ltd. can be used.
[0013]
In the present invention, the basic substance added to the titanium (IV) chloride solution is not particularly limited as long as it forms a precipitate of titanium hydroxide gel by adding to the titanium chloride (IV) solution. For example, Examples include aqueous solutions of alkali metal hydroxides such as aqueous ammonia and aqueous sodium hydroxide. Preferably, aqueous ammonia having an ammonia concentration of 9 to 35% by mass is used. As such ammonia water, for example, a commercially available product such as a reagent special grade manufactured by Kanto Chemical Co., Inc. can be used. These basic substances can also be used as a mixture.
[0014]
The amount of the basic substance added to the titanium (IV) chloride solution is an excessive amount with respect to the titanium chloride (IV) solution, and is not particularly limited as long as a precipitate of titanium hydroxide gel can be formed. The solution is added so that the pH is preferably 7.5 or more, more preferably pH 8 or more and pH 11 or less. Preferably, it is desirable to add an amount containing 4 times or more moles of basic substance relative to titanium oxide in the titanium (IV) chloride solution, more preferably 8 times or more moles of basic substance. By adding an excessive amount of the basic substance in this manner, the pH of the resulting titanium hydroxide gel solution is increased, the pH of the peroxotitanium solution obtained after the addition of the peroxide is increased, and as a result, the substrate is weak against low pH. Films can also be formed on particles.
[0015]
The speed and temperature at which the basic substance is added are not particularly limited, but it is preferable not to perform heating or cooling in order to simplify the production process. More preferably, the reaction solution is preferably added at 5 to 50 ° C, more preferably 10 to 40 ° C.
[0016]
The peroxide added after adding the basic substance to the titanium (IV) chloride solution is not particularly limited as long as the precipitate of titanium hydroxide gel can be dissolved into a peroxo complex, but preferably the peroxide is oxidized. Hydrogen peroxide water having a hydrogen concentration of 25% by mass to 40% by mass is used. As such a peroxide, for example, a commercially available product such as a reagent special grade manufactured by Kanto Chemical Co., Inc. can be used.
[0017]
(B) A step of adding a peroxide to form a basic peroxotitanium solution
The amount of peroxide added is not particularly limited as long as the precipitate of titanium hydroxide gel can be dissolved into a peroxo complex, but preferably 3 times the number of moles of titanium oxide in the titanium (IV) chloride solution. It is desirable to add 15 times mole number, more preferably 5 times mole number to 10 times mole number of peroxide. If the amount added is small, the titanium hydroxide gel will not be sufficiently re-dissolved, resulting in a precipitate of titanium hydroxide gel. Also, if the amount of hydrogen peroxide added is too large, the excess of the added peroxide will be decomposed and bubbles will be generated due to the bubbles generated, producing a precipitate of peroxotitanium hydrate. To do.
[0018]
In the method of adding the peroxide, the speed and temperature of addition are not particularly limited, but it is preferable not to perform heating or cooling in order to simplify the production process. More preferably, the reaction solution is preferably added at 5 to 50 ° C, more preferably 10 to 40 ° C.
After the peroxide is added to form a peroxo complex solution, a basic substance can be further added to adjust the pH. Although there is no restriction | limiting in particular in the solvent which adjusts pH, It is preferable to add basic solvents, such as aqueous ammonia. Here, when adding a basic solvent, the pH of the peroxotitanium solution after addition of peroxide obtained by adjusting as described above is increased to 9 to 10, more preferably to pH 9.2 to pH 9.5. It is preferable to add a sufficient amount.
[0019]
(C) Dropping the peroxotitanium solution into the substrate powder suspension
The dropping speed when dropping the peroxotitanium solution into the base powder suspension is preferably a speed at which a predetermined amount of the peroxotitanium solution is completed within 20 to 60 minutes, more preferably 20 to 40 minutes. A rate of completion in about minutes is preferred. When the dropping speed is shorter than 20 minutes, precipitation of titanium oxide occurs abruptly, making it difficult to coat a smooth titanium oxide film. When the dropping speed is longer than 60 minutes, the property of the titanium oxide film to be coated is almost the same as when the dropping speed is 20 to 60 minutes, so that the coating operation time is merely lengthened.
[0020]
Although the base powder suspension to which the peroxotitanium solution is dropped is not particularly limited, specifically, Tris-based, boric acid-based, borate-based, phosphate-based, phosphate-based, glycine-based, Examples include carbonates. The pH of the suspension is preferably pH 8 to pH 10, more preferably pH 9.0 to pH 9.2. Under pH conditions lower than this, titanium oxide particles are rapidly precipitated from the dropped peroxotitanium solution, making it difficult to smoothly coat the titanium oxide film on the substrate powder. At the time of dropping, the reaction temperature of the reaction system is preferably between 15 ° C and 65 ° C, and more preferably between 20 ° C and 55 ° C. When the reaction temperature of the reaction system is too low, the reaction rate of the peroxotitanium solution becomes slow, and it becomes difficult to coat the titanium oxide film having the target thickness. This is because the reaction of the peroxotitanium solution becomes too fast under conditions where the reaction temperature is too high, and it becomes difficult to coat a smooth titanium oxide film.
[0021]
The substrate powder to be coated with a titanium film in the present invention is not particularly limited, but the substrate particles may be inorganic materials including metals, organic materials, magnetic materials, dielectric materials, conductors, insulators, and the like. Good. 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, a material having magnetism such as iron is 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 powder substrate is a metal compound, typical examples thereof include the above-mentioned metal oxides, such as iron, nickel, chromium, titanium, aluminum, silicon, etc., calcium Further, oxides such as magnesium and barium, or composite oxides thereof may be used. Furthermore, examples of metal compounds other than metal oxides include metal nitrides, metal carbides, metal sulfides, metal fluorides, metal carbonates, and metal phosphates.
[0022]
Further, as the base particles, other than metals, they are semi-metallic and non-metallic compounds, particularly oxides, carbides and nitrides, and 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.
[0023]
As the organic substance, resin particles are preferable. Specific examples of the resin particles 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. And spherical or crushed particles obtained by polymerization or copolymerization. Particularly preferred resin particles are spherical acrylic resin particles obtained by polymerization of acrylic acid or methacrylic acid ester.
Unlike the prior art, the film forming method of the present invention can be used which is weak against acid, and therefore, it is preferable to use the manufacturing method of the present invention for a substrate which is weak against acid. Examples of the substrate that is weak against acid include metal powder, particularly iron powder and iron-containing alloy powder.
[0024]
In addition, the film forming method for coating the substrate particles of the present invention with a titanium oxide film can be combined with a film forming method for another substrate to produce particles having a plurality of films.
When using the film forming method of the present invention in combination with other film forming methods, for example, when forming a titanium oxide film using the film forming method of the present invention on a powder coated by another film forming method, The powder coated by the film forming method can be treated as the above-mentioned substrate particles. Similarly, a powder coated with a titanium oxide film by the method of the present invention can be used as a base particle to coat another film.
[0025]
As the shape of the substrate, a sphere, a subsphere, an isotropic body such as a regular polyhedron, a rectangular parallelepiped, a spheroid, a rhombohedron, a plate, a needle, etc. A completely amorphous powder can also be used. 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.
[0026]
(D) Other processes
It is preferable to further provide an aging step in which the reaction product is allowed to stand after the dropwise addition of (C) into the substrate powder suspension.
The temperature during aging is preferably between 15 ° C. and 65 ° C., more preferably between 20 ° C. and 55 ° C.
The aging time is preferably between 30 minutes and 6 hours, more preferably between 1 hour and 3 hours. When the total of the reaction time and the aging time is too short, the reaction of the dropped peroxotitanium solution becomes insufficient, and the titanium oxide film having the desired thickness may not be coated. If it is too long, the reaction of the dropped peroxotitanium solution has already been completed, so that the coating operation time is merely lengthened.
[0027]
In the film forming method of the present invention, the thickness of the titanium oxide film formed on the substrate particles can be adjusted by optimizing the material ratio.
[0028]
When producing a powder coated with a plurality of films using the film-forming method of the present invention together with other film-forming methods, by adjusting the thickness of each layer of the film involved in optical interference, Can give function. For example, an alternating coating film having a different refractive index on the surface of the base particle is an integer that is a quarter of the refractive index n of the substance forming the coating and the wavelength of visible light so as to satisfy the following formula (1): If an alternating film having a thickness d corresponding to 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.
[0029]
nd = mλ / 4 (1)
[0030]
Using this action, a film having a film thickness and a refractive index satisfying the formula (1) 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 the 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.
[0031]
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 particle 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 for the oxide layer on the surface of the substrate particles and the peak shift due to the wavelength dependence of the refractive index.
[0032]
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 preferable to take this into consideration because it affects the phase between particles.
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.
[0033]
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.
[0034]
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.
[0035]
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.
[0036]
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, Obtainable. 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. Thereby, the powder 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. In particular, when the reflection peak appears in the visible range by changing the viewing angle from the outside of the visible range, or conversely, when the reflection peak in the visible range appears by changing the viewing angle, the sharp reflection peak is slightly By changing the viewing angle, the color can be changed at the same time, which is effective.
[0037]
Further, 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 formula 1 or the combination of the formula 1 and the formula 2 below.
In manufacturing the film-coated powder, it is necessary to select in advance the material of the base particles, the particle size of the base 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. is there. 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.
[0038]
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 following recurrence formula 2 to the material (refractive index) of the base particles, the number of coating layers, the coating order of each coating layer, the material (refractive index) of each coating layer, and the desired reflected light wavelength. It is calculated by solving.
[0039]
[Formula 1]

[0040]
(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. )
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 calculated by the following formula 3
[0041]
[Formula 2]

[0042]
(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 3 above corrects the solution of Equation 2 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.
[0043]
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.
[0044]
Therefore, it is necessary to correct the curvature of each coating layer depending on the shape and particle diameter of the base particles.
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 film-coated powder is measured with a spectrophotometer to determine the optical film thickness (nd) of each coating layer of each particle-size correcting film-coated powder. Product (nd) of actual film thickness value of each coating layer and refractive index (n)_M) Ratio of optical film thickness (nd) of each coating layer to (nd / nd)_M2) of the above recurrence formula 2 for calculating the multilayer film reflection intensity._jTo the above ratio (nd / nd_MThis is preferably performed by correcting the spectrophotometric characteristic of the powder having each coating layer by multiplying the value and forming each coating layer so as to obtain the corrected spectrophotometric characteristic.
[0045]
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.
[0046]
The titanium oxide film-coated powder obtained by the method of the present invention exhibits a blue or reddish purple color due to optical interference caused by the titanium oxide film coated on the surface, and is a color ink, plastic, color filler for paper, It can be used for various purposes such as color toners and color inks for inkjet printers.
[0047]
Among the cases where a coating composition containing a titanium oxide film-coated powder obtained by the method of the present invention is prepared, (1) each specific color ink or paint-like composition (fluid) and (2) each specific color system The toner and each specific color dry ink-like composition (powder) will be described in detail.
[0048]
(1) In the present invention, a conventionally known varnish used for color printing, color magnetic printing, and color magnetic paint is used as a medium (vehicle) for a specific color ink or paint-like composition (fluid) in the present invention. For example, a liquid polymer, a polymer or a monomer dissolved in an organic solvent, and the like can be appropriately selected and used depending on the kind of powder, the ink application method, and the use.
Examples of the liquid polymer include dienes such as polypentadiene and polybutadiene, polyethylene glycols, polyamides, polypropylenes, waxes, and copolymer knitted bodies thereof.
[0049]
Polymers that are soluble in organic solvents include olefin polymers, acrylic resins such as oligoester acrylates, polyesters, polyamides, polyisocyanates, amino resins, xylene resins, ketone resins, and diene resins. Rosin-modified phenolic resins, diene rubbers, chloroprene resins, waxes, modified products and copolymers thereof, and the like.
Examples of the monomer that can be dissolved in the organic solvent include styrene, ethylene, butadiene, and propylene.
Examples of organic solvents include alcohols such as ethanol, isopropanol, and normal propanol, ketones such as acetone, benzene, toluene, xylene, kerosene, benzine hydrocarbons, esters, ethers, and modified products and copolymers thereof. Can be mentioned.
[0050]
(2) The specific color toner, the specific color dry ink, and the specific color dry paint-like composition (powder) include the specific color multilayer coating powder, a resin, or a toning material as necessary. Is directly kneaded with a screw type extruder, roll mill, kneader, etc., coarsely pulverized with a hammer mill or cutter mill, then finely pulverized with a jet mill, etc., and classified to the required particle size with an elbow jet etc. A color material composition can be obtained. Further, the specific color multilayer coating powder can be made into a powder specific color coating composition by using a polymerization method such as an emulsion polymerization method or a suspension polymerization method.
Further, the specific color multilayer coating powder, resin, additives such as toning agents, and solvent can be liquefied with a colloid mill or three rolls to obtain a liquid specific color coating composition such as an ink coating.
[0051]
As the color-adjusting material for increasing the brightness, it is a white pigment (color developing material), for example, titanium oxide, zinc oxide, tin oxide, silicon oxide, antimony oxide, lead oxide or the like, or complex oxides thereof, Carbonates such as calcium carbonate, magnesium carbonate, barium carbonate, sulfates such as barium sulfate and calcium sulfate, sulfides such as zinc sulfate, or composite oxides obtained by sintering the oxides, carbonates and sulfates, A composite hydrous oxide is mentioned.
[0052]
In order to adjust the saturation and hue, especially as a toning material for color reproduction with full color mixing, blue pigments (organic dyes / pigments) such as alkali blue lake, peacock lake, peacock lake blue, etc. Lake dyes and lake pigments, oil blue, oil dye pigments, alcohol dyes such as alcohol blue, phthalocyanine pigments such as phthalocyanine and copper phthalocyanine, (inorganic pigments) oxide sulfide composite pigments such as ultramarine, iron blue, Copper group blue and blue pigments such as milory blue, cobalt oxide complex oxides such as cobalt blue and cerulean blue, blue pigments, blue organic dyes and pigments, and blue inorganic pigments rake dyes such as alkali blue lakes and peacock blue lakes, lakes Pigments such as metal-free phthalocyanine and copper phthalocyanine Chromium oxides and hydrous oxides such as chromium green, zinc green, chromium oxide, hydrous chromium (viridian), and green oxides such as talocyanine dyes and green pigments, copper oxides such as emerald green, and cobalt oxides such as cobalt green Inorganic pigments such as pigments, nitroso pigments such as pigment green and naphthol green, azo pigments such as green gold, phthalocyanine pigments such as phthalocyanine green and polychrome copper phthalocyanine, lake systems such as malachite green lake and acid green lake, oil Examples include organic dyes such as green, oil dye pigments, alcohol dyes such as alcohol blue, and the like. However, the present invention is not limited to these.
[0053]
Furthermore, when it is necessary to adjust colors using pigments or dyes such as blue, yellow, and reddish purple in delicate color tone control, it is preferable to add these pigments to obtain an optimum specific color.
In the case of this powdery specific color coating composition, (a) the resin for production by the above pulverization method is not particularly limited, but polyamide, epoxy resin, polyester, melamine resin, polyurethane, acetic acid Examples thereof include vinyl resins, silicon resins, acrylic acid esters, methacrylic acid esters, styrene, ethylene, butadiene, propylene, and polymers or copolymers of these derivatives.
(B) In the case of a polymerization method, polymerization is started from one or a mixture of esters, urethane, vinyl acetate, organic silicon, acrylic acid, methacrylic acid, styrene, ethylene, butadiene, propylene, etc. These copolymers are formed.
[0054]
As described above, the coating composition containing the film-coated powder of the present invention comprises (1) each specific color ink or paint-like composition (fluid) and (2) each specific color toner, each specific color dry type. It can take the form of an ink-like composition (powder).
In the case of fluid, it is a specific color ink, paint, etc., the toning material, a slow-drying resin, a solidification accelerator, a thickener to increase the viscosity, and a fluidization to decrease the viscosity In order to disperse the agent and particles, a component such as a dispersant can be included.
On the other hand, in the case of powder, (a) when powder is produced by a pulverization method, the toning material, a slow-drying resin, a solidification accelerator, and a fluid to reduce the viscosity during kneading. In order to disperse the agent and the particles, a component such as a dispersant, a charge adjusting agent for fixing on paper or the like, and a wax can be included.
(B) When a polymerization method is used, the toning material, the polymerization initiator, the polymerization accelerator, a thickener for increasing the viscosity, and a dispersing agent for fixing particles, fixing to paper, etc. Ingredients such as a charge control agent and wax may be included.
The multilayer coated powder of the present invention can be applied to wet and dry color printing and wet and dry color magnetic printing by combining a single powder or a plurality of powders having different spectral characteristics. Has a distinguishing function of six types of combination of visible light, invisible light (ultraviolet and cyan outside), fluorescent color and magnetism, and electricity (change in electric field), and color magnetic ink for preventing counterfeiting of printed matter, etc. It can be applied to other uses requiring a security function.
[0055]
The coating powder of the present invention is printed on a substrate as each specific color ink or paint-like composition or each specific color toner, each specific color dry ink-like composition, each specific color dry paint composition, In the case of melt transfer or application to an object to be coated, the relationship between the specific color multilayer coating powder and the resin content in the coating composition is 1: 0.5 to 1:15 in volume ratio. When the content of the medium is too small, the applied film does not adhere to the object to be coated. On the other hand, if the amount is too large, the color of the pigment becomes too thin to be a good ink or paint. Further, the relationship between the amount of each color-based color material and resin in each color-based ink or coating composition and the amount of solvent is 1: 0.5 to 1:10 in volume ratio, and the amount of solvent is small. If it is too high, the viscosity of the paint is so high that it cannot be applied uniformly. Moreover, when there is too much quantity of a solvent, time will be required for drying of a coating film, and the efficiency of an application | coating operation will fall extremely.
[0056]
In addition, the color density of the coating film when printing, melt transfer, or coating on the substrate is determined by the amount of pigment placed per unit area of the substrate. The amount of the film-coated powder of the present invention on the object to be coated after the paint is dried is 0.1 to 300 g per square meter in area density when uniformly coated, preferably 0.1 to 100 g. If it is, a good paint color can be obtained. If the area density is smaller than the above value, the ground color of the object to be coated appears, and if it is larger than the above value, the color density of the painted color does not change, which is uneconomical. That is, even if the pigment is placed on the object to be coated more than a certain thickness, the light does not reach the pigment below the coating film. Making the coating film thicker than this thickness is uneconomical because it has a coating thickness that exceeds the hiding power of the coating material and has no coating effect. However, in consideration of wear of the coating film, the thickness of the coating film is worn down. This is not the case when a specific design or the like is partially formed.
[0057]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but the scope of the present invention is not limited thereto.
[0058]
Example 1: Bluening of magnetite powder particles, aqueous two-layer coating
[First-layer silica film coating operation]
(1) Adjustment of buffer solution
To 300 ml of ion-exchanged water, 29.82 g (0.4 mole amount) of potassium chloride (Kanto Chemical Co., Ltd. reagent grade) and 24.23 g (0.4 mole amount) of boric acid (Kanto Chemical Co., Ltd. reagent grade) are added. Dissolved and made up to 1000 ml with ion-exchanged water to make solution A.
13.0 g (0.4 mol amount) of sodium hydroxide (special grade reagent manufactured by Kanto Chemical Co., Inc.) was dissolved in 300 ml of ion-exchanged water, and made up to 1000 ml with ion-exchanged water to obtain a solution B.
The buffer solution C was prepared by mixing 250 ml of the solution A and 115 ml of the solution B. The pH of this buffer C was 9.1.
(2) Preparation of sodium silicate aqueous solution (water glass solution)
A 10 wt% sodium silicate aqueous solution was prepared by diluting 100.0 g of a sodium silicate solution (reagent manufactured by Kanto Chemical Co., Inc.) with ion-exchanged water so that the total amount becomes 1000.0 g.
[0059]
(3) Silica film coating
As a base powder, 10 grams of magnetite powder (average particle size 0.7 μm) was put into 540 ml of the above-mentioned buffer C prepared in advance and well dispersed in a container containing this suspension. (1000 ml glass beaker) is immersed in a 600 W, 28 kHz ultrasonic cleaning tank (Inoue Seieido US-6 type) water tank and stirred at 550 rpm. Simultaneously with the start of stirring, ultrasonic waves are applied.
Next, 90 grams of a predetermined amount of 10% by weight aqueous sodium silicate solution is dropped into the agitated suspension at a drop rate of 1.34 ml / min. After completion of the dropping, stirring is further continued for 1 hour, and the surface of the raw material magnetite is coated with a silica film.
After a predetermined time, the slurry containing the silica film-coated powder was repeatedly decanted with sufficient ion exchange water and washed. After the washing operation, the slurry containing the silica film-coated powder is dried at 110 ° C. for 8 hours, and the silica film-coated magnetite powder D₁Got. This silica film-coated magnetite powder D₁As a result of measuring the spectral characteristics of the sample with a spectrophotometer (Ubest 550 manufactured by JASCO Corporation), the product exhibits a brown color and exhibits CIE (1976) L^*a^*b^*L in the color system^*= 34.9, a^*= 0.4, b^*= -1.4.
[0060]
[Second-layer titanium oxide film coating operation]
(1) Preparation of peroxotitanium solution
Titanium (IV) chloride solution (reagent manufactured by Wako Pure Chemical Industries) 2.2 ml (TiO₂An amount of 0.88 grams (0.011 mol) was diluted 10 times with ion-exchanged water.
Next, 5.34 grams of aqueous ammonia (special grade reagent manufactured by Kanto Chemical Co., Inc.) is added to the aqueous titanium chloride (IV) solution to form a titanium hydroxide slurry.
Next, 10.0 grams of hydrogen peroxide (Kanto Chemical Co., Ltd. reagent grade) is slowly added to the titanium hydroxide slurry, and the mixture is thoroughly stirred to dissolve the titanium hydroxide. Get. The yellow transparent peroxotitanium solution had a pH of about 9.0.
Finally, 0.50 grams of aqueous ammonia (special grade reagent manufactured by Kanto Chemical Co., Inc.) was added to adjust the pH to an alkalinity of about 9.3. Peroxotitanium solution E₁Get.
[0061]
(2) Titanium oxide film coating
Magnetite powder D coated with silica film₁6.0 grams was suspended in 560 grams of the same buffer C used in the first layer silica membrane coating operation. A container (1000 ml separable flask) containing this suspension is immersed in a constant temperature water bath kept at 50 ° C. and stirred at 700 rpm.
When the temperature of the suspension reaches 50 ° C., the peroxotitanium solution E₁A predetermined amount of 39 grams (38 ml) is dropped at a drop rate of 1.8 ml / min. After completion of dropping, stirring is continued for 120 minutes, and the raw material magnetite powder D coated with silica film is used.₁A titanium oxide film is coated thereon. After a predetermined time, the slurry containing the powder coated with the titanium oxide film was repeatedly decanted with sufficient ion exchange water and washed. After completion of the washing operation, the slurry containing the powder coated with the titanium oxide film is dried at 120 ° C. for 2 hours to obtain a magnetite powder F coated with the titanium oxide film.₁Got. Obtained magnetite powder F coated with titanium oxide film₁Table 1 and FIG. 1 show the results of measuring spectral characteristics with a spectrophotometer (Ubest 550 manufactured by JASCO Corporation), and have a reflection peak (λ / 4 peak) near 350 nm, and CIE (1976) L^*a^*b^*L in the color system^*= 35.9, a^*= −0.4, b^*= -5.9 blue.
[0062]
Example 2: Magnetite powder particle reddish purple, aqueous two-layer coating
[First-layer silica film coating operation]
Magnetite powder D coated with a silica film by the same operation as in Example 1₁Got.
[0063]
[Second-layer titanium oxide film coating operation]
(1) Preparation of peroxotitanium solution
Titanium (IV) chloride solution (reagent manufactured by Wako Pure Chemical Industries) 4.4 ml (TiO₂An amount of 1.76 grams (0.022 mol) was diluted 10 times with ion-exchanged water.
Next, 10.69 grams of aqueous ammonia (special grade reagent manufactured by Kanto Chemical Co., Inc.) is added to the aqueous titanium chloride (1V) solution to make a titanium hydroxide slurry.
Next, 20.0 grams of hydrogen peroxide (Kanto Chemical Co., Ltd. reagent grade) is slowly added to the titanium hydroxide slurry, and the mixture is thoroughly stirred to dissolve the titanium hydroxide. Get. The yellow transparent peroxotitanium solution had a pH of about 9.0.
Finally, as pH adjustment, 1.00 g of ammonia water (special grade reagent manufactured by Kanto Chemical Co., Inc.) was added to make the pH alkaline with about 9.3. Peroxotitanium solution E₂Get.
[0064]
(2) Titanium oxide film coating
Magnetite powder D coated with silica film₁6.0 grams was suspended in 560 grams of the same buffer C used in the first layer silica membrane coating operation. A container (1000 ml separable flask) containing this suspension is immersed in a constant temperature water bath kept at 50 ° C. and stirred at 700 rpm.
When the temperature of the suspension reaches 50 ° C., the peroxotitanium solution E₂A predetermined amount of 78 g (76 ml) is dropped at a drop rate of 2.0 ml / min. After completion of dropping, stirring is continued for 120 minutes, and the raw material magnetite powder D coated with silica film is used.₁A titanium oxide film is coated thereon. After a predetermined time, the slurry containing the powder coated with the titanium oxide film was repeatedly decanted with sufficient ion exchange water and washed. After completion of the washing operation, the slurry containing the powder coated with the titanium oxide film is dried at 120 ° C. for 2 hours to obtain a magnetite powder F coated with the titanium oxide film.₂Got. Obtained magnetite powder F coated with titanium oxide film₂The results of measuring the spectral characteristics using a spectrophotometer (Ubest 550 manufactured by JASCO Corporation) are shown in the spectral reflectance curves of Table 1 and FIG. ) Has two reflection peaks, CIE (1976) L^*a^*b^*L in the color system^*= 37.1, a^*= 1.2, b^*A reddish purple color of −0.8 was exhibited.
[0065]
Example 3: Titanium oxide film coating on permalloy powder particles
[Titanium oxide film coating operation]
(1) Preparation of peroxotitanium solution
The peroxotitanium solution E was prepared in the same manner as in Example 1.₁Get.
(2) Adjustment of buffer solution
To 300 ml of ion-exchanged water, 29.82 g (0.4 mole amount) of potassium chloride (Kanto Chemical Co., Ltd. reagent grade) and 24.23 g (0.4 mole amount) of boric acid (Kanto Chemical Co., Ltd. reagent grade) are added. Dissolved and made up to 1000 ml with ion-exchanged water to make solution A.
16.0 g (0.4 molar amount) of sodium hydroxide (special grade reagent manufactured by Kanto Chemical Co., Inc.) was dissolved in 300 ml of ion-exchanged water, and made up to 1000 ml with ion-exchanged water to obtain a solution B.
The buffer solution C was prepared by mixing 250 ml of the solution A and 115 ml of the solution B. The pH of this buffer C was 9.1.
[0066]
(3) Titanium oxide film coating
As a base powder, 29 grams of permalloy powder (average particle size 16.7 μm) was put into 280 ml of the buffer C prepared in advance and well dispersed. The container containing the suspension was immersed in a constant temperature water bath kept at 23 ° C. and stirred at 700 rpm.
Next, the peroxotitanium solution E₁A predetermined amount of 39 grams (38 ml) is dropped at a drop rate of 1.8 ml / min. After completion of the dropping, stirring is further continued for 120 minutes, and a titanium oxide film is coated on the raw material permalloy powder. After a predetermined time, the slurry containing the powder coated with the titanium oxide film was repeatedly decanted with sufficient ion exchange water and washed. After completion of the washing operation, the slurry containing the powder coated with the titanium oxide film is dried at 120 ° C. for 2 hours to obtain a permalloy powder G coated with the titanium oxide film.₁Got. Obtained permalloy powder G coated with titanium oxide film₁The spectral characteristics measured with a spectrophotometer (Ubest 550 manufactured by JASCO Corporation) are shown in the spectral reflectance curves of Table 1 and FIG. 1976) L^*a^*b^*L in the color system^*= 45.2, a^*= 5.4, b^*= -3.7 A purple color was exhibited.
[0067]
Example 4: Titanium oxide film coating on permalloy powder particles
[Titanium oxide film coating operation]
(1) Preparation of peroxotitanium solution
Titanium (IV) chloride solution (reagent manufactured by Wako Pure Chemical Industries) 2.93 ml (TiO₂An amount of 1.17 g (0.015 mol) was diluted 10 times with ion-exchanged water.
Next, 7.12 grams of aqueous ammonia (special grade reagent manufactured by Kanto Chemical Co., Inc.) is added to the aqueous titanium chloride (IV) solution to form a titanium hydroxide slurry.
Next, 20.0 grams of hydrogen peroxide (Kanto Chemical Co., Ltd. reagent grade) is slowly added to the titanium hydroxide slurry, and the mixture is thoroughly stirred to dissolve the titanium hydroxide. Get. The yellow transparent peroxotitanium solution had a pH of about 9.0.
Finally, 1.00 g of ammonia water (special grade reagent manufactured by Kanto Chemical Co., Ltd.) was added for pH adjustment to make the pH alkaline with a pH of about 9.3._ThreeGet.
[0068]
(2) Adjustment of buffer solution
To 300 ml of ion-exchanged water, 29.82 g (0.4 mole amount) of potassium chloride (Kanto Chemical Co., Ltd. reagent grade) and 24.23 g (0.4 mole amount) of boric acid (Kanto Chemical Co., Ltd. reagent grade) are added. Dissolved and made up to 1000 ml with ion-exchanged water to make solution A.
16.0 g (0.4 molar amount) of sodium hydroxide (special grade reagent manufactured by Kanto Chemical Co., Inc.) was dissolved in 300 ml of ion-exchanged water, and made up to 1000 ml with ion-exchanged water to obtain a solution B.
The buffer solution C was prepared by mixing 250 ml of the solution A and 115 ml of the solution B. The pH of this buffer C was 9.1.
[0069]
(3) Titanium oxide film coating
As a base powder, 29 grams of permalloy powder (average particle size 16.7 μm) was put into 280 ml of the buffer C prepared in advance and well dispersed. The container containing the suspension was immersed in a constant temperature water bath kept at 23 ° C. and stirred at 700 rpm.
Next, the peroxotitanium solution E_ThreeA predetermined amount of 59 grams (58 milliliters) is dropped at a drop rate of 2.0 milliliters / minute. After completion of the dropping, stirring is further continued for 120 minutes, and a titanium oxide film is coated on the raw material permalloy powder. After a predetermined time, the slurry containing the powder coated with the titanium oxide film was repeatedly decanted with sufficient ion exchange water and washed. After completion of the washing operation, the slurry containing the powder coated with the titanium oxide film is dried at 120 ° C. for 2 hours to obtain a permalloy powder G coated with the titanium oxide film.₂Got. Obtained permalloy powder G coated with titanium oxide film₂The spectral characteristics were measured with a spectrophotometer (Ubest 550 manufactured by JASCO Corporation). The results are shown in the spectral reflectance curves of Table 1 and FIG. 2, and have a reflection peak (2λ / 4 peak) near 400 nm, and CIE (1976) L^*a^*b^*L in the color system^*= 52.5, a^*= -1.7, b^*A blue color of = -11.0 was exhibited.
[0070]
Comparative Example 1
[Titanium oxide coating]
(1) Preparation of peroxotitanium solution
Titanium (IV) chloride solution (reagent manufactured by Wako Pure Chemical Industries) 2.2 ml (TiO₂An amount of 0.88 grams (0.011 mol) was diluted 10 times with ion-exchanged water.
Next, 10.0 grams of hydrogen peroxide (Kanto Chemical Co., Ltd. reagent grade) was slowly added to the orange-red pertitanate solution E._FourGot. The pH of this solution was about 1.3.
[0071]
(2) Titanium oxide film coating
The dripping liquid of Example 3 was changed to orange-red pertitanic acid solution E._FourThe same operation was performed except that. As a result, the pH of the reaction solution after dropping the entire amount of the dropping solution was lowered to around 2.2, fine particles of titanium oxide were formed, and the reaction solution was light yellow. Further, the permalloy powder in the reaction solution was repeatedly decanted with sufficient ion exchange water and washed. After completion of the washing operation, the slurry containing permalloy powder was dried at 120 ° C. for 2 hours, and the result was observed. In this method, the titanium oxide film was not covered at all.
[0072]
[Table 1]

[0073]
【The invention's effect】
According to the present invention, when the titanium oxide film is coated on the base metal powder using the titanium chloride (IV) solution, the pH of the reaction solution can be made 7 or more alkaline, Many base metal powders can be used without dissolving them. Further, it has become possible to perform the film forming reaction in a short time, efficiently and at a low temperature.
[0074]
Furthermore, it is possible to easily coat the titanium oxide film having a sufficient thickness to cause an optical interference effect by a single coating operation of the titanium oxide film. It has become possible to produce a high optical interference effect on the crushed substrate powder. For this reason, it has become possible to produce colored magnetic powders of blue or reddish purple.
[Brief description of the drawings]
1 is a diagram showing spectral reflectance curves of titanium oxide film-coated silica-coated magnetite powders obtained in Example 1 and Example 2. FIG.
2 is a diagram showing spectral reflectance curves of titanium oxide film-coated permalloy powders obtained in Example 3 and Example 4. FIG.

Claims (4)

  Adding an excess of a basic substance to the titanium (IV) chloride solution, then adding a peroxide to form a basic peroxotitanium solution, and dropping the peroxotitanium solution into the substrate powder suspension; A method of producing a titanium oxide film-coated powder by coating a titanium oxide film on a substrate powder.   2. The method for producing a titanium oxide film-coated powder according to claim 1, wherein the substrate powder suspension is an alkaline buffer having a pH of 8 or more and a pH of 10 or less.   The method for producing a titanium oxide film-coated powder according to claim 1, wherein the titanium oxide film coating reaction according to claim 1 is performed at a reaction temperature of 15 ° C to 65 ° C. Claim 1 titanium oxide film coating reactions described, producing how titanium oxide film-coated powder according to claim 1, wherein a carried out in a reaction time of 6 hours or more 1 hour.

Images