JP4450424B2 - Cerium-based abrasive and its raw materials - Google Patents

Description

【００６３】
各実施例、参考例および比較例で得られたセリウム系研摩材を用いて、平均粒径（Ｄ_５０）、ＢＥＴ法比表面積（ＢＥＴ）および回折Ｘ線強度（Intensity）を測定した。また、各実施例、参考例および比較例で得られたセリウム系研摩材を用いて研摩試験を行い、研摩値（研摩速度）、得られた研摩面の傷評価および付着性（洗浄性）について評価を行った。測定方法、研摩試験方法、各種研摩特性の評価方法を次に説明する。なお、測定値および評価結果については後掲の表２に示す。
【００６４】
平均粒径（Ｄ _５０ ）の測定
レーザ回折・散乱法粒度分布測定装置（（株）島津製作所製：ＳＡＬＤ−２０００Ａ）を使用してセリウム系研摩材の粒度分布を測定し、平均粒径（Ｄ₅₀：小粒径側からの累積体積５０wt％における粒径）を求めた。
【００６５】
ＢＥＴ法比表面積（ＢＥＴ）：ＪＩＳ Ｒ １６２６-1996（ファインセラミックス粉体の気体吸着ＢＥＴ法による比表面積の測定方法）の「６．２ 流動法 の（３．５）一点法」に準拠して測定を行った。その際、キャリアガスであるヘリウムと、吸着質ガスである窒素の混合ガスを使用した。
【００６６】
Ｘ線回折測定
Ｘ線回折装置（マックサイエンス（株）製、ＭＸＰ１８）を用いて、セリウム系研摩材についてＸ線回折分析を行い、回折Ｘ線強度を測定した。本測定では、銅（Ｃｕ）ターゲットを使用しており、Ｃｕ−Ｋα線を照射して得られたＣｕ−Ｋα_１線による回折Ｘ線パターンのうち回折角（２θ）が２０°〜３０°に出現したピークについて解析した。なお、その他の測定条件は、管電圧４０ｋＶ、管電流１５０ｍＡ、測定範囲２θ＝５°〜８０°、サンプリング幅０．０２°、走査速度４°／ｍｉｎであった。そして、得られたＸ線回折測定結果から、酸化セリウム（ＣｅＯ_２）のＸ線回折ピーク強度、ランタノイドオキシフッ化物（ＬｎＯＦ）のＸ線回折ピーク強度およびランタノイドフッ化物（ＬｎＦ_３）のＸ線回折ピーク強度を読み取り、各Ｘ線回折ピーク強度比（ＬｎＯＦ／ＣｅＯ_２、ＬｎＦ_３／ＣｅＯ_２）を求めた。
【００６７】
研摩試験
研摩機として、研摩試験機（ＨＳＰ−２Ｉ型、台東精機（株）製）を用意した。この研摩試験機は、研摩対象面に研摩材スラリーを供給しながら研摩パッドで研摩対象面を研摩するものである。研摩パッドはポリウレタン製のものであり、当該研摩試験では１回（２４時間程度の研摩時間）毎に新品に交換した。そして、研摩対象物として６５ｍｍφの平面パネル用ガラスの用意した。また、粉末状のセリウム系研摩材粉末と純水を混合して、固形分濃度が１５重量wt％である研摩材スラリーを５０Ｌ調製した。この研摩材スラリーを用いて平面パネル用ガラスの表面を研摩した。本研摩試験では、研摩材スラリーを５リットル／分の割合で供給することとし、研摩材スラリーを循環使用した。また、研摩面に対する研摩パッドの圧力を９．８ｋＰａ（１００ｇ／ｃｍ²）とし、研摩試験機の回転速度を１００ｒｐｍに設定した。
【００６８】
研摩値（研摩速度）の評価
研摩開始３０分後、研摩対象の平面パネル用ガラスを交換した。なお、交換した平面パネル用ガラスは重量測定済みのものである。そして、平面パネル用ガラス交換後１０分間研摩を行って、研摩によるガラス重量の減少量を求め、この値に基づき「研摩値１」を求めた。なお、比較例１の研摩材の研摩値を基準（１００）とした。
【００６９】
最初の３０分間とその後の１０分間の合計４０分間の研摩終了後、新しい平面パネル用ガラスに交換して、２３時間２０分（合計２４時間）の間、研摩を行い、その後、研摩対象の平面パネル用ガラスを交換した。なお、交換した平面パネル用ガラスは重量測定済みのものである。そして、平面パネル用ガラス交換後１０分間研摩を行って、研摩によるガラス重量の減少量を求め、この値に基づき「研摩値２」を求めた。ここでは、比較例１の研摩材の研摩値１を基準（１００）として研摩値２を求めた。
【００７０】
そして、「研摩値１」および「研摩値２」に基づいて「研摩値比（研摩値２／研摩値１）」を求め、「研摩値１」、「研摩値２」および「研摩値比」を用いてセリウム系研摩材の研摩値（研摩速度）を評価した。
【００７１】
研摩傷の評価
また、研摩終了後、研摩した平面パネル用ガラスを、純水で洗浄し、無塵状態で乾燥させた研摩面について傷評価を行った。傷評価は、３０万ルクスのハロゲンランプを光源として用いる反射法でガラス表面を観察し、大きな傷および微細な傷の数を点数化し、１００点を満点として減点評価する方式で行った。この傷評価では、ハードディスク用あるいはＬＣＤ用のガラス基板の仕上げ研摩で要求される研摩精度を判断基準とした。具体的には表２および表５中、「◎」は、９８点以上（ＨＤ用・ＬＣＤ用ガラス基板の仕上げ研摩に非常に好適）であることを、「○」は、９８点未満９５点以上（ＨＤ用・ＬＣＤ用ガラス基板の仕上げ研摩に好適）であることを、「△」は、９５点未満９０点以上（ＨＤ用・ＬＣＤ用ガラス基板の仕上げ研摩に使用可能）であることを、そして「×」は、９０点未満（ＨＤ用・ＬＣＤ用ガラス基板の仕上げ研摩に使用不可）であることを示す。
【００７２】
付着性試験
また、研摩材の付着性（洗浄性）について試験を行った。試験では、まず、洗浄・乾燥された光学顕微鏡観察用のスライドグラスを、研摩材スラリー中に浸漬すると共に引き上げて５０℃で一旦乾燥させ、その後、純水入りの容器に浸漬させて超音波洗浄を５分間行い、超音波洗浄後、容器から取り出したスライドグラスを純水で流水洗して観察対象のスライドグラスを得た。その後、スライドグラス表面に残存する研摩材粒子の残存量を光学顕微鏡で観察することで付着性を評価した。具体的には、表２および表５中、「○」は、研摩材粒子の残存が観察されず仕上げ研摩用として非常に好適であることを、「△」は、研摩材粒子の残存が観察されたがわずかであり仕上げ研摩用として好適であることを、「×」は、研摩材粒子の残存が非常に多く観察され仕上げ研摩用として不適であることを示す。
【００７３】
【表２】

【００７４】
表２に示されるように、実施例１、参考例２〜３の研摩材は、研摩開始直後（３０分後）の研摩値（研摩値１）が高く、そして、長時間循環使用した後においても比較的高い研摩値（研摩値２）を有しており、使用による研摩値の低下が比較的小さかった（研摩値比＝０．６６〜０．７８）。つまり、研摩開始後の急激な研摩値（研摩速度）の低下が防止され、より高い研摩値がより長い間維持された。そして、実施例１、参考例２〜３の研摩材とも、研摩傷が発生しにくく、研摩面に付着しにくいという点で優れていた。また、表２に示されるように、実施例、参考例の研摩材は、全て研摩特性に優れていたが、中でも実施例１の研摩材が最も研摩特性に優れていた。これに対し、比較例１〜３の研摩材は、研摩値２が著しく低く、使用により急激に研摩力が低下した（研摩値比＝０．２３〜０．３２）。また、研摩傷が発生しやすく、研摩面に付着しやすいという不具合が見られた。
【００７５】
そこで、表１に示されるデータについて各実施例、参考例と比較例のデータについて検討したところ、次のようなことが解った。
【００７６】
セリウム系研摩材としては、ＴＲＥＯが９０wt％以上のものが好ましく、９２wt％以上がより好ましい。そして、ＴＲＥＯに占める酸化セリウムの重量の割合（ＣｅＯ_２／ＴＲＥＯ）が５０wt％以上であるものが好ましい。また、各実施例、参考例と比較例２から、セリウム系研摩材としては、ＴＲＥＯに占める酸化ネオジムの重量の割合（Ｎｄ_２Ｏ_３／ＴＲＥＯ）が１６wt％以下が好ましい。さらに、各実施例、参考例と比較例３から、セリウム系研摩材としては、ＴＲＥＯに占める酸化ネオジムの重量の割合（Ｎｄ_２Ｏ_３／ＴＲＥＯ）が少なくとも１０wt％以上が好ましい。
【００７７】
そして、セリウム系研摩材としては、ＴＲＥＯに占める酸化ランタンの重量の割合（Ｌａ_２Ｏ_３／ＴＲＥＯ）が３０wt％以下が好ましい。
【００７８】
また、各実施例、参考例および比較例のデータ（表１）について別の観点で比較したところ、セリウム系研摩材としては、酸化ランタン（Ｌａ_２Ｏ_３）と酸化ネオジム（Ｎｄ_２Ｏ_３）との重量比（Ｌａ_２Ｏ_３／Ｎｄ_２Ｏ_３）が１．４以上のものが好ましく（各実施例と比較例２との比較）、２．８以下のものが好ましい（各実施例と比較例1，３との比較）。
【００７９】
さらに、セリウム系研摩材としては、ＴＲＥＯに占める酸化ランタンおよび酸化ネオジムの合計重量の割合（（Ｌａ_２Ｏ_３＋Ｎｄ_２Ｏ_３）／ＴＲＥＯ）が２５wt％〜５０wt％であるものが好ましい。また、実施例１および実施例２〜３、参考例３〜４を比較したところ、セリウム系研摩材としては、ＴＲＥＯと、フッ素含有量の重量比（Ｆ／ＴＲＥＯ）が４．０wt％〜９．０wt％であるものがより好ましい。
【００８０】
また、セリウム系研摩材としては、ＴＲＥＯと、ウランおよびトリウムの合計重量の重量比（（Ｕ＋Ｔｈ）／ＴＲＥＯ）が０．０５wt％以下のものが好ましい。そして、実施例１、参考例１〜２と比較例１〜３を比較したところ、上記Ｘ線回折ピーク強度比（ＬｎＯＦ／ＣｅＯ_２）は０．４〜０．７が好ましい。
【００８１】
さらに、各実施例、参考例から、研摩材粒子の平均粒径（Ｄ₅₀）が０．７μｍ〜１．６μｍであるものがより好ましく、ＢＥＴ法比表面積が２．０ｍ^２／ｇ〜５．０ｍ^２／ｇであることがより好ましい。
【００８２】
また、表２に示されるように、実施例１および実施例２〜３、参考例３〜４の研摩材は、いずれも、研摩値１が高く、且つ比較的高い研摩値２を有しており、使用による研摩値の低下が比較的小さかった（研摩値比＝０．６６〜０．７８）。つまり、研摩開始後に急激に研摩値（研摩速度）が低下するようなことが防止されており、より高い研摩値がより長い間維持されていた。ただし、参考例３の研摩材は、実施例１などと比べると、やや研摩値１および研摩値２が低く、付着性が若干あった。これは、実施例１などと比べて、ＴＲＥＯ量とフッ素量の重量比（Ｆ／ＴＲＥＯ）が小さく、またＸ線回折ピーク強度比（ＬｎＯＦ／ＣｅＯ_２）が小さいからであると考えられる。また、参考例４の研摩材は、実施例１などと比べると、やや研摩傷が発生しやすく付着性が若干あった。これは、実施例１などと比べて、Ｘ線回折ピーク強度比（ＬｎＯＦ／ＣｅＯ_２やＬｎＦ_３／ＣｅＯ_２）が大きいからであると考えられる。
【００８３】
そして、表２に示されるように、実施例１、４および５の研摩材は、研摩値１が高く、そして研摩値２も比較的高く、使用による研摩値の低下が比較的小さかった（研摩値比＝０．７２〜０．７８）。つまり、研摩開始後に急激に研摩値（研摩速度）が低下するようなことが防止されており、より高い研摩値がより長い間維持されていた。この結果、本発明の研摩材用原料を用いて研摩材を製造する場合、焙焼温度が８００℃〜１２００℃（より好ましくは８５０℃〜１１００℃）であれば、研摩値（研摩速度）の低下が少ない（研摩値比が大きい）研摩材を製造できることが解った。
【００８４】
第２実施形態
次に、炭酸セリウム、炭酸ランタン、炭酸プラセオジム、炭酸ネオジムを各々個別に仮焼（焙焼）した後、混合して原料を調製し、調製した原料を用いてセリウム系研摩材を製造した実施例、参考例および比較例について説明する。
【００８５】
まず、高純度の炭酸セリウム（ＴＲＥＯ：４５wt％、ＣｅＯ_２／ＴＲＥＯ：９９．９wt％以上）、炭酸ランタン（ＴＲＥＯ：が４５wt％、Ｌａ_２Ｏ_３／ＴＲＥＯ：９９．９wt％以上）、炭酸プラセオジム（ＴＲＥＯ：４５wt％、Ｐｒ_６Ｏ_１１／ＴＲＥＯ：９９．９wt％以上）、炭酸ネオジム（ＴＲＥＯ：４５wt％、Ｎｄ_２Ｏ_３／ＴＲＥＯ：９９．９wt％以上）を用意して、各々別個に仮焼（焙焼）した。仮焼温度は６００℃、仮焼時間は１２時間であった。そして、仮焼によって、炭酸セリウム仮焼品（ＴＲＥＯ：８３wt％、ＣｅＯ_２／ＴＲＥＯ：９９．９wt％以上、強熱減量：１７wt％）、炭酸ランタン仮焼品（ＴＲＥＯ：８５wt％、Ｌａ_２Ｏ_３／ＴＲＥＯ：９９．９wt％以上、強熱減量：１５wt％）、炭酸プラセオジム仮焼品（ＴＲＥＯ：８６wt％、Ｐｒ_６Ｏ_１１／ＴＲＥＯ：９９．９wt％以上、強熱減量：１４wt％）、炭酸ネオジム仮焼品（ＴＲＥＯ：８２wt％、Ｎｄ_２Ｏ_３／ＴＲＥＯ：９９．９wt％以上、強熱減量：１８wt％）を得た。
【００８６】
そして、このようにして得られた各仮焼品を混合して、次に説明する各実施例、参考例および各比較例で用いるセリウム系研摩材原料（中間原料）を調製した。各実施例、参考例および比較例で用いたセリウム系研摩材原料（中間原料）の組成を表３に示す。また、これらの混合して調製した中間原料５種類の（Ｕ＋Ｔｈ）／ＴＲＥＯ重量比は、いずれも０．０００５wt％未満であり、（Ｃａ＋Ｂａ＋Ｆｅ＋Ｐ）／ＴＲＥＯ重量比は、０．１wt％未満であった。
【００８７】
【表３】

【００８８】
実施例６、参考例５〜８および比較例６〜９：調製したセリウム系研摩材用原料（中間原料＝希土類炭酸塩仮焼品（混合品））と当該原料重量の２倍の重量の純水とを混合し、湿式ボールミル（粉砕媒体は直径５ｍｍのジルコニアボール）にて８時間湿式粉砕を行って原料スラリーを得た。得られた粉砕品のＤ_５０は、０．８μｍであった。そして得られたスラリーに対してフッ化処理（参考例１での処理と同じ）を行った。フッ化処理後の「Ｆ／ＴＲＥＯ」は８．０wt％であった。その後、固形分を沈降させて上澄み液を抜出し、純水を加えるという、いわゆるリパルプ洗浄を行い、洗浄後のスラリーをフィルタプレス法にて濾過した。そして、得られた濾過品に対して、乾燥、焙焼、粉砕、分級の各工程を順次行ってセリウム系研摩材を得た。なお、乾燥以降の各工程の条件は参考例１と同じであった。
【００８９】
上記実施例、参考例および比較例６〜９で得られたセリウム系研摩材のフッ素含有率、ＴＲＥＯ、ＴＲＥＯ中の各希土類酸化物の重量の割合などの値を表４に示す。また、これらの研摩材の（Ｃａ＋Ｂａ＋Ｆｅ＋Ｐ）／ＴＲＥＯ重量比は、０．１wt％未満であった。
【００９０】
【表４】

【００９１】
各実施例、参考例および比較例で得られたセリウム系研摩材を用いて、平均粒径（Ｄ_５０）、ＢＥＴ法比表面積（ＢＥＴ）および回折Ｘ線強度（Intensity）を測定した。また、各実施例、参考例および比較例で得られたセリウム系研摩材を用いて研摩試験を行い、研摩値（研摩速度）、得られた研摩面の傷評価および付着性（洗浄性）について評価を行った。測定法および試験法は先に説明した通りである。測定値および評価結果を表５に示す。
【００９２】
【表５】

【００９３】
表５に示されるように、各実施例、参考例の研摩材は、未使用状態での研摩値（研摩値１）が高く、そして、使用済み状態においても比較的高い研摩値（研摩値２）を有しており、使用による研摩値の低下が比較的小さかった（研摩値比＝０．６７〜０．７９）。また、各実施例、参考例の研摩材とも、研摩傷が発生しにくく、研摩面に付着しにくいという点で優れていた。なお、実施例６、参考例５〜８の中では、実施例６の研摩材が最も研摩特性に優れていた。これに対し、各比較例の研摩材は、研摩値２が著しく低く、使用により急激に研摩値（研摩速度）が低下した（ただし比較例９は除く）。また、研摩傷が発生しやすく、研摩面に付着しやすいという不具合が見られた。
【００９４】
そして、表４に示されるデータについて、各実施例、参考例と比較例８、９とを比較したところ、セリウム系研摩材としては、ＴＲＥＯに占める酸化セリウムの重量の割合（ＣｅＯ_２／ＴＲＥＯ）が４５wt％〜７０wt％であるものが好ましいことが解った。また、各実施例、参考例と比較例６、７とを比較したところ、セリウム系研摩材としては、ＴＲＥＯに占める酸化ネオジムの重量の割合（Ｎｄ_２Ｏ_３／ＴＲＥＯ）が１０wt％〜１６wt％であるものが好ましいことが解った。また、表５に示されるように、セリウム系研摩材としては、Ｘ線回折ピーク強度比（ＬｎＯＦ／ＣｅＯ_２）が０．４〜０．７であるものがより好ましいことが解った。
また、表４に示される実施例、参考例と比較例のデータを別の観点で比較したところ、ＴＲＥＯ中の酸化ランタン（Ｌａ_２Ｏ_３）と酸化ネオジム（Ｎｄ_２Ｏ_３）の重量比（Ｌａ_２Ｏ_３／Ｎｄ_２Ｏ_３）については、実施例、参考例と比較例７との比較から１．４以上が好ましく、各実施例、参考例と比較例６との比較から２．８以下が好ましいことが解った。そして、参考例７，８から、酸化ランタンと酸化ネオジムの重量バランスを整えると、ＴＲＥＯに占める酸化ネオジムの重量の割合（Ｎｄ_２Ｏ_３／ＴＲＥＯ）が９wt％や１７wt％であっても実用的な研摩材が得られることが解った。
【００９５】
【産業上の利用の可能性】
以上の説明から解るように、本発明に係るセリウム系研摩材は、傷の発生が少なく、また高い研摩力が長い間維持されるものである。したがって、本発明に係るセリウム系研摩材を用いれば、傷が少なく研摩材の付着が少ない高品質の研摩面をより短時間で得ることができる。つまり、本発明によれば、光ディスクや磁気ディスク用ガラス基板の研摩など、高精度の表面研摩性能が要求される分野において好適なセリウム系研摩材を提供できる。[0001]
【Technical field】
  The present invention relates to a so-called cerium-based abrasive containing cerium oxide as a main component and its raw material.
[0002]
[Background]
    In general, cerium-based abrasives are used for ore raw materials such as bastonite concentrate, monazite concentrate, and Chinese complex ore concentrate. (See JP-A-9-183966, JP-A-2002-97457, JP-A-2002-224949). Among the exemplified raw materials, bust nesite concentrate contains rare earth elements such as cerium, lanthanum, and neodymium and fluorine, and is considered as one of suitable raw materials for cerium-based abrasives.
[0003]
  For example, a typical bastonite concentrate has a weight ratio of the total rare earth oxide equivalent weight (hereinafter sometimes referred to as TREO) of about 68 to 73 wt%, fluorine is about 6 wt%, and is ignitable. The weight loss (1000 ° C.) is about 20 wt%. The breakdown of TREO is cerium oxide (CeO).₂Etc.) about 50 wt%, lanthanum oxide (La₂O₃Etc.) about 35 wt%, neodymium oxide (Nd₂O₃Etc.) is about 11 wt%, praseodymium oxide (Pr)₆O₁₁Etc.) is about 4 wt%.
[0004]
  By the way, as the polishing material, a material having excellent polishing characteristics, such as being hard to cause polishing scratches, is required. In order to efficiently manufacture a product manufactured through the polishing process, it is preferable that the time required for the polishing process is as short as possible. For this reason, as a cerium-based abrasive, one having as high a polishing rate as possible (one having a high polishing value) is required.
[0005]
  In recent years, cerium-based abrasives are used for glass substrates for optical disks and magnetic disks, active matrix LCDs (Liquid Crystal Displays), color filters for liquid crystal TVs, clocks, calculators, LCDs for cameras, solar cells, etc. In addition, it is used for polishing glass substrates such as glass substrates for LSI photomasks or optical lenses, and optical lenses. In such fields, it is possible to perform surface polishing with higher precision and polishing. There is a need for higher speed cerium-based abrasives.
[0006]
  However, in the conventional polishing using a cerium-based abrasive, scratches having a size that does not satisfy the polishing accuracy required for polishing optical disks, glass substrates for magnetic disks, and the like have occurred. In addition, after the start of polishing, the polishing speed decreased rapidly and the polishing efficiency decreased rapidly as polishing was continued. Thus, the conventional cerium-based abrasives cannot sufficiently meet the demands in the above fields.
[0007]
DISCLOSURE OF THE INVENTION
  In view of such problems, it is an object of the present invention to provide a cerium-based abrasive having excellent polishing characteristics such as fewer scratches and a higher polishing speed.
[Means for Solving the Problems]
[0008]
  The cerium-based abrasive according to the first invention for solving the above-mentioned problem is a cerium-based abrasive containing at least cerium oxide, lanthanum oxide, and neodymium oxide as rare earth oxides, and containing fluorine, in terms of total rare earth oxides. The weight (TREO) is 90 wt% or more, and the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is 50 wt% to 65 wt%, and the ratio of the weight of neodymium oxide in the TREO (Nd₂O₃/ TREO) is 10 wt% to 16 wt%.
[0009]
  When the cerium-based abrasive is used, the generation of polishing scratches is small, and the required highly accurate polished surface (polished surface) can be obtained. Further, it is possible to prevent the polishing rate from rapidly decreasing after the start of polishing, and to maintain a higher polishing rate for a longer time. The reason for having such excellent polishing characteristics is not necessarily clear, but it is thought that the main factor is that the ratio of neodymium (neodymium oxide) in the abrasive is increased. Conventional cerium-based abrasives have a neodymium oxide ratio of about 5.0 wt% in TREO. When polishing with such cerium-based abrasives, as described above, scratches occur and the polishing speed is increased. This is because of a sharp drop.
[0010]
  In cerium-based abrasives, the amount of rare earth elements in the abrasive is generally examined by TREO. In the abrasive containing the fluorine as in the abrasive according to the present invention, the rare earth element is present in the abrasive in various forms such as oxide, oxyfluoride or fluoride. However, if TREO is used, The amount of rare earth elements can be examined relatively easily.
[0011]
  In the abrasive according to the present invention, TREO is 90 wt% or more, more preferably 92 wt% or more. This is because when the ratio of each rare earth element in the polishing material is constant, the higher the ratio of TREO, the higher the ratio of cerium oxide that contributes to polishing among the rare earth oxides, thereby ensuring a high polishing rate. . Moreover, it is because the content rate of the impurity which is one of the causes of generation | occurrence | production of a crack will be low, and a crack generation | occurrence | production will be prevented more reliably.
[0012]
  However, the ratio of the weight of cerium oxide in TREO (CeO₂As / TREO) increases, scratches are more likely to occur, and when the upper limit is exceeded, abrasive scratches that are unacceptable in the above-described fields where high-precision polishing is required tend to occur. On the other hand, the lower the ratio, the lower the polishing speed as described above. If the ratio is less than the lower limit, a sufficient polishing speed cannot be ensured. Considering both of these aspects, the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is more preferably 50 wt% to 60 wt%.
[0013]
  And the ratio of the weight of neodymium oxide in TREO (Nd₂O₃The higher the / TREO), the lower the polishing speed. If the upper limit is exceeded, a sufficient polishing speed cannot be secured. On the other hand, the lower the ratio of neodymium oxide, the easier it is for scratches to occur. When the ratio is less than the lower limit, abrasive scratches that are unacceptable in the aforementioned fields where high-precision polishing is required tend to occur. Therefore, in consideration of these two sides, the ratio of the weight of neodymium oxide in the TREO (Nd₂O₃/ TREO) is more preferably 11 wt% to 15 wt%, further preferably 12 wt% to 14 wt%.
[0014]
  Further, as the cerium-based abrasive according to the present invention, the ratio of the weight of lanthanum oxide to the total rare earth oxide equivalent weight (La₂O₃/ TREO) is preferably 22 wt% to 30 wt%. This is because the polishing rate decreases as the proportion of lanthanum oxide increases, and if the upper limit is exceeded, a sufficient polishing rate cannot be ensured. When the proportion of lanthanum oxide increases, the proportion of cerium oxide decreases accordingly, and the polishing rate is considered to decrease. On the other hand, as the ratio of lanthanum oxide decreases, scratches are more likely to occur. When the ratio is below the lower limit, abrasive scratches that are unacceptable in the above-described fields where high-precision polishing is required tend to occur. Considering these two aspects, the proportion of lanthanum oxide in TREO is more preferably 24 wt% to 28 wt%.
[0015]
  Furthermore, the cerium-based abrasive according to the present invention contains praseodymium oxide, and the ratio of praseodymium oxide in the weight of TREO (Pr₆O₁₁/ TREO) is more preferably 2.0 wt% to 8.0 wt%.
[0016]
  As will be understood from the description so far, in the abrasive, not only cerium but also lanthanum and neodymium contribute to the polishing, and the polishing state varies depending on the content of lanthanum and neodymium. Then, when the relationship between the content of lanthanum and neodymium and polishing was further examined, the inventors came up with a second invention different from the first invention.
[0017]
  That is, the cerium-based abrasive according to the second invention is a cerium-based abrasive containing at least cerium oxide, lanthanum oxide, and neodymium oxide as rare earth oxides, and containing fluorine, and the total rare earth oxide equivalent weight ( Ratio of the weight of cerium oxide in the TREO) (CeO₂/ TREO) is 45 wt% to 70 wt%, and lanthanum oxide (La₂O₃) And neodymium oxide (Nd)₂O₃) Weight ratio (La₂O₃/ Nd₂O₃) Is 1.4 to 2.8. Thus, an abrasive in which the weight ratio of lanthanum oxide to neodymium oxide in TREO is in the above range has a good balance between the amount of lanthanum and the amount of neodymium in the abrasive, and as a result, is considered to have excellent polishing characteristics. It is done.
[0018]
  In the abrasive according to the present invention, the weight ratio of lanthanum oxide and neodymium oxide (La₂O₃/ Nd₂O₃) Becomes too large or too small, the polishing speed decreases, and a sufficient polishing speed cannot be secured. For this reason, the weight ratio (La₂O₃/ Nd₂O₃) Is more preferably 1.6 to 2.6.
  Furthermore, the ratio of the total weight of lanthanum oxide and neodymium oxide in TREO ((La₂O₃+ Nd₂O₃) / TREO) is more preferably 25 wt% to 50 wt%. If the balance between lanthanum oxide and neodymium oxide is good, the preferred range for the ratio of the total weight of lanthanum oxide and neodymium oxide is further expanded. The reason why this range is preferable is that the polishing rate decreases as the ratio increases, and if the upper limit is exceeded, a sufficient polishing rate cannot be ensured. It is considered that when the proportion of lanthanum oxide increases, the proportion of cerium oxide decreases accordingly, and as a result, the polishing rate decreases. On the other hand, scratches are more likely to occur as the ratio decreases, and if the ratio is less than the lower limit value, scratches that are unacceptable in the above-described fields where high-precision polishing is required tend to occur. Considering these two sides, the above ratio ((La₂O₃+ Nd₂O₃) / TREO) is more preferably 30 wt% to 45 wt%.
[0019]
  And if the content of examination up to here is integrated, the following cerium-based abrasive (third invention) is preferable. That is, it is a cerium-based abrasive containing at least cerium oxide, lanthanum oxide and neodymium oxide as rare earth oxides and containing fluorine, and the total rare earth oxide equivalent weight (TREO) is 90 wt% or more, and the oxidation occupies in TREO Cerium weight ratio (CeO₂/ TREO) is 45 wt% to 70 wt%, and the ratio of the weight of neodymium oxide in the TREO (Nd₂O₃/ TREO) is 10 wt% to 16 wt%, and lanthanum oxide (La₂O₃) And neodymium oxide (Nd)₂O₃) Weight ratio (La₂O₃/ Nd₂O₃) Is preferably 1.4 to 2.8. Furthermore, it is such an abrasive, and the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is more preferably 50 wt% to 65 wt%, and the ratio of the weight of lanthanum oxide in TREO (La₂O₃/ TREO) is more preferably 22 wt% to 30 wt%, and the ratio of the total weight of lanthanum oxide and neodymium oxide in TREO ((La₂O₃+ Nd₂O₃) / TREO) is more preferably 25 wt% to 50 wt%.
[0020]
  Further, the improvement of the polishing characteristics was further studied, and the following results were obtained. That is, as the abrasive according to each of the above inventions, regardless of the abrasive according to any of the inventions, the weight ratio (F / TREO) of the fluorine amount to the total rare earth oxide equivalent weight is 4.0 wt% to 9 wt%. A content of 0.0 wt% is preferable. As the proportion of fluorine increases, the polishing characteristics deteriorate, such as the roughened polishing surface. If the upper limit is exceeded, the polishing surface becomes unacceptably rough in the above fields where high-precision polishing is required. It is. It is thought that this is the result of excessive chemical amount due to excessive amount of fluorine. On the other hand, the polishing rate decreases as the proportion of fluorine decreases, and if it is less than the lower limit, a sufficient polishing rate cannot be ensured. This is probably because the amount of fluorine is small and chemical action contributing to polishing does not occur so much. Considering these two surfaces, the weight ratio of fluorine to TREO (F / TREO) is more preferably 5.0 wt% to 8.0 wt%. In the fluorine-containing cerium-based abrasive, a part (or all) of the rare earth element is present not as a rare earth oxide but as an oxyfluoride or a fluoride. Therefore, the total rare earth oxide equivalent weight (TREO) of the fluorine-containing cerium-based abrasive is the total rare earth oxide equivalent weight obtained by converting that all rare earth elements are present as rare earth oxides. In addition, the fluorine content here is the fluorine content in the cerium-based abrasive that is the measurement target of TREO.
[0021]
  And as a cerium type abrasive | polishing material which concerns on said each invention, the weight ratio ((U + Th) / TREO) of the total amount of uranium and thorium with respect to the total rare earth oxide conversion weight is 0.05 wt% or less. This is because it is preferable that the radioactive material such as thorium and uranium contained in the cerium-based abrasive is as small as possible. Therefore, the weight ratio is more preferably 0.005 wt% or less, and further preferably 0.0005 wt% or less.
[0022]
  In addition, as the cerium-based abrasive according to each of the above inventions, the weight ratio ((TREO + F) / abrasive weight) of the abrasive weight to the total weight of the TREO and fluorine content of the abrasive is 95 wt% to 105 wt%. % Is preferred. This is because as the weight ratio increases, the polishing characteristics deteriorate such that the polished surface becomes rough. When the upper limit is exceeded, the polished surface becomes unacceptably rough in the above-described field. When the weight ratio is high, the amount of fluorine is excessive, and it is considered that the polished surface becomes rough as a result of strong chemical action. On the other hand, the lower the weight ratio, the easier it is for abrasive scratches to occur. When the weight ratio is less than the lower limit, abrasive scratches that are unacceptable in the above-mentioned field are likely to occur. The main reason why the weight ratio is low is considered to be that many impurities are contained, and as a result, scratches are likely to occur. Considering these two surfaces, the weight ratio is more preferably 98 wt% to 104 wt%.
[0023]
  Furthermore, when the cerium-based abrasive according to each of the above inventions was examined by analysis by X-ray diffraction, the following results were obtained. As the cerium-based abrasive according to each of the above inventions, Cu-Kα ray or Cu-Kα as an X-ray source₁X-ray diffraction peak intensity of rare earth oxyfluoride (LnOF) among X-ray diffraction peaks appearing in the range of 2θ (diffraction angle) = 20 ° to 30 ° as measured by X-ray diffraction method using X-ray. Strongest X-ray diffraction peak intensity and cerium oxide (CeO₂) X-ray diffraction peak intensity with respect to the strongest X-ray diffraction peak intensity (LnOF / CeO)₂) Is preferably 0.4 to 0.7.
  This is because the greater the X-ray diffraction peak intensity ratio, the easier it is for abrasive flaws to occur, and when the upper limit is exceeded, abrasive flaws that are unacceptable in the above-mentioned field will occur. On the other hand, the polishing rate decreases as the X-ray diffraction peak intensity ratio decreases, and if it is less than the lower limit, a sufficient polishing rate cannot be ensured. Considering these two surfaces, the X-ray diffraction peak intensity ratio is more preferably 0.45 to 0.65.
[0024]
  And as a cerium type abrasive | polishing material which concerns on said each invention, as a X-ray source, it is Cu-K alpha ray or Cu-K alpha.₁Rare earth fluoride (LnF) appearing in the range of 2θ = 24.2 ° ± 0.5 ° among the X-ray diffraction peaks appearing by measurement by X-ray diffraction method using X-rays₃The intensity ratio (LnF) of the strongest X-ray diffraction peak intensity and the strongest X-ray diffraction peak intensity of cerium oxide.₃/ CeO₂) Is more preferably 0.1 or less. Here, rare earth fluoride (LnF₃) Is produced, for example, when the raw material contains a rare earth oxide and the raw material is subjected to a fluorination treatment in the abrasive production stage.
[0025]
  Therefore, the case where the X-ray diffraction peak intensity ratio exceeds the above upper limit is the case where rare earth fluoride remains with little conversion from rare earth fluoride to rare earth oxyfluoride due to insufficient roasting, or Although roasting is sufficient, there is a limit to the conversion from rare earth fluoride to rare earth oxyfluoride, and the rare earth fluoride remains because the amount of fluorine is excessive with respect to the rare earth element. Abrasive materials that are insufficiently roasted are not preferable because a sufficient polishing speed cannot be secured. On the other hand, an abrasive that has been sufficiently roasted but has an excessive amount of fluorine contains a relatively large amount of coarse particles that cause abrasive scratches, which is also not preferable. Abrasives that contain a relatively large amount of fluorine are those in which chemical action by fluorine is likely to proceed during the roasting stage during the production of abrasives, and the cause of abrasive scratches due to excessive progress of sintering of abrasive particles It is thought that coarse particles were generated. In addition, since the amount of fluorine in the abrasive is relatively excessive, even if the coarse particles are sufficiently reduced by pulverization and classification after roasting, the polishing surface is excessive in the polishing using the abrasive. It is considered that the polished surface is unacceptably rough in the above-described field where high-precision polishing is required.
[0026]
  In addition, cerium oxide (CeO) used for the calculation of the peak intensity ratio.₂The X-ray diffraction peak of the rare earth oxide containing cerium as the main component is an X-ray diffraction peak appearing in the range of 2θ = 28.1 ° ± 1.0 °. It is.
[0027]
  In addition, cerium oxide (CeO) here₂More specifically, the X-ray diffraction peak intensity of) is a cubic rare earth oxide (Ln) mainly composed of cerium._xO_y) Diffraction X-ray diffraction peak intensity. Ln_xO_yIs usually 1.5 ≦ y / x ≦ 2, for example CeO₂, Ce_0.5Nd_0.5O_1.75Or Ce_0.75Nd_0.25O_1.875Identified. However, Nd₂O₃Even if it is an abrasive with a small / TREO, it may be identified as a Ce—Nd—O-based compound, and hence it is presumed to be an oxide containing rare earth elements (La and the like) other than Ce and Nd. As can be seen from the above, with respect to X-ray diffraction, cerium oxide (CeO₂), For example, CeO in TREO₂In the case of CeO₂Unlike pure cerium oxide, does not have to be pure cerium oxide.
[0028]
  And the average particle diameter (D of the abrasive particle in the cerium-type abrasive | polishing material which concerns on said each invention (D₅₀) Is preferably 0.7 μm to 1.6 μm. Here, the average particle diameter (D₅₀The following values were used as That is, the particle size of the particles in which the cumulative volume from the small particle size side becomes 50 wt% in the particle size distribution of the cerium-based abrasive measured by the laser diffraction / scattering particle size distribution measurement method. Average particle size (D₅₀) Becomes more likely to occur, and if the upper limit is exceeded, abrasive scratches that are unacceptable in the aforementioned fields where high-precision polishing is required tend to occur. On the other hand, the average particle size (D₅₀) Decreases, the polishing speed decreases, and if it is less than the lower limit, a sufficient polishing speed cannot be secured. Considering these both sides, the average particle size (D₅₀) Is more preferably 0.8 μm to 1.4 μm.
[0029]
  Further, as the cerium-based abrasive according to each of the above inventions, the BET method specific surface area is 2.0 m.²/G-5.0m²/ G is preferred. This is because the polishing rate decreases as the BET method specific surface area increases, and if the upper limit is exceeded, a sufficient polishing rate cannot be ensured. On the other hand, as the BET method specific surface area becomes smaller, scratches are more likely to occur. When the BET method specific surface area is less than the above lower limit value, scratches that are unacceptable in the above-described fields where high-precision polishing is required tend to occur. Considering these two surfaces, the BET specific surface area is 2.5 m.²/G-4.0m²/ G is more preferable.
[0030]
  Next, raw materials for cerium-based abrasives were examined.
  Among the abrasives according to the invention, the weight ratio of the total rare earth oxide equivalent weight (TREO) is 90 wt% or more, and the proportion of cerium oxide in the TREO (CeO₂/ TREO) is 50 wt% to 65 wt%, and the ratio of neodymium oxide in the TREO (Nd₂O₃As a raw material (fourth invention), a cerium-based abrasive containing at least cerium, lanthanum, and neodymium as rare earth elements is used for the cerium-based abrasive (first invention) having 10/16% by weight / TREO) Ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is 50 wt% to 65 wt%, and the ratio of the weight of neodymium oxide in the TREO (Nd₂O₃/ TREO) is preferably 10 wt% to 16 wt%, and the weight ratio of the total amount of uranium and thorium to TREO ((U + Th) / TREO) is preferably 0.05 wt% or less.
[0031]
  In the raw material for cerium-based abrasives, the proportion of cerium oxide in TREO (CeO₂As the / TREO) increases, scratches are easily produced in the manufactured abrasive, and if the above upper limit is exceeded, unacceptable abrasive scratches occur in the aforementioned fields where high-precision polishing is required. It becomes easy. On the other hand, the lower the ratio of cerium oxide, the lower the polishing rate of the manufactured abrasive, and if it is less than the lower limit, it is difficult to ensure a sufficient polishing rate. Therefore, considering these two sides, the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is more preferably 50 wt% to 60 wt%. On the other hand, in the case of neodymium oxide, the polishing rate of the polishing material produced decreases as the weight ratio increases. When the upper limit is exceeded, it is difficult to ensure a sufficient polishing rate. On the other hand, the lower the ratio of neodymium oxide, the easier it is for the abrasive to be produced to be scratched, and if it is less than the above lower limit value, abrasive scratches that are unacceptable in the aforementioned fields where high-precision polishing is required are likely to occur. Therefore, taking these two aspects into consideration, the ratio of the weight of neodymium oxide to the content of TREO (Nd₂O₃/ TREO) is more preferably 11 wt% to 15 wt%, further preferably 12 wt% to 14 wt%.
[0032]
  The reason why the weight ratio of TREO to the total weight of uranium and thorium ((U + Th) / TREO) is preferably within the above range is that it is preferable that the amount of radioactive substances such as uranium and thorium is as small as possible. Ore such as bastonite concentrate, monazite concentrate, Chinese complex ore concentrate (especially monazite concentrate and Chinese complex ore concentrate) contains a lot of thorium, and it is an abrasive without removing uranium and thorium It is not preferable to use it as a raw material. Therefore, a raw material with the weight ratio ((U + Th) / TREO) being 0.005 wt% or less is more preferable, and a raw material with 0.0005 wt% or less is more preferable.
[0033]
  The ratio of the weight of lanthanum oxide in TREO (La₂O₃/ TREO) is more preferably 22 wt% to 30 wt%. And the thing whose said ratio is 24 wt%-28 wt% is still more preferable. The lower the ratio of lanthanum oxide, the greater the amount of fluorine released during roasting. If it is less than the above lower limit value, the amount of fluorine released will be too high, making it difficult to control the amount of fluorine in the cerium-based abrasive during roasting. Because it becomes.
[0034]
  Among the abrasives according to the invention, cerium oxide (CeO) with respect to the total rare earth oxide equivalent weight (TREO)₂) Weight ratio (CeO₂/ TREO) is 45 wt% to 70 wt%, and lanthanum oxide (La₂O₃) And neodymium oxide (Nd)₂O₃) Weight ratio (La₂O₃/ Nd₂O₃) Is 1.4 to 2.8, the raw material (the fifth invention) is a cerium-based abrasive containing at least cerium, lanthanum and neodymium as rare earth elements. Ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is 45 wt% to 70 wt%, and the weight ratio of lanthanum oxide and neodymium oxide in TREO (La₂O₃/ Nd₂O₃) Is preferably 1.4 to 2.8.
[0035]
  In the cerium-based abrasive raw material, the ratio of the weight of cerium oxide in TREO (CeO₂When the / TREO) is increased, the manufactured abrasive is likely to be damaged, and when the upper limit is exceeded, unacceptable abrasive scratches are likely to occur in the above-described fields where high-precision polishing is required. On the other hand, the lower the ratio of cerium oxide, the lower the polishing speed of the manufactured abrasive. If it is less than the lower limit, it is difficult to ensure a sufficient polishing speed. Therefore, considering these two sides, the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is more preferably 50 wt% to 60 wt%. The weight ratio of lanthanum oxide to neodymium oxide (La₂O₃/ Nd₂O₃) Becomes too large or too small, the polishing speed of the produced abrasive material decreases, and a sufficient polishing speed cannot be secured. Therefore, the weight ratio of lanthanum oxide and neodymium oxide in TREO (La₂O₃/ Nd₂O₃) Is more preferably 1.6 to 2.6.
[0036]
  A weight ratio of TREO to the total weight of uranium and thorium ((U + Th) / TREO) is preferably 0.05 wt% or less. This is because it is preferable that the amount of radioactive materials such as uranium and thorium be as small as possible. Ore such as bastonite concentrate, monazite concentrate, Chinese complex ore concentrate (especially monazite concentrate and Chinese complex ore concentrate) contains a lot of thorium, and it is an abrasive without removing uranium and thorium It is not preferable to use it as a raw material. Therefore, a raw material with the weight ratio ((U + Th) / TREO) being 0.005 wt% or less is more preferable, and a raw material with 0.0005 wt% or less is more preferable.
[0037]
  The ratio of the total weight of lanthanum oxide and neodymium oxide in TREO ((La₂O₃+ Nd₂O₃) / TREO) is more preferably 25 wt% to 50 wt%. The lower the ratio, the more easily the amount of fluorine released at the time of roasting. If the ratio is less than the above lower limit value, the amount of fluorine released is likely to be released too much, making it difficult to control the amount of fluorine in the cerium-based abrasive during roasting. Because.
[0038]
  Further, among the abrasives according to the above invention, the rare earth oxide contains at least cerium oxide, lanthanum oxide and neodymium oxide and contains fluorine, and has a total rare earth oxide equivalent weight (TREO) of 90 wt. % Or more and the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is 45 wt% to 70 wt%, and the ratio of the weight of neodymium oxide in the TREO (Nd₂O₃/ TREO) is 10 wt% to 16 wt%, and lanthanum oxide (La₂O₃) And neodymium oxide (Nd)₂O₃) Weight ratio (La₂O₃/ Nd₂O₃) Is 1.4 to 2.8, the raw material (sixth invention) is a cerium-based abrasive containing at least cerium, lanthanum and neodymium as rare earth elements. A raw material for which TREO is 90 wt% or more, and the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is 45 wt% to 70 wt%, and the ratio of the weight of neodymium oxide in the TREO (Nd₂O₃/ TREO) is 10 wt% to 16 wt%, and lanthanum oxide (La₂O₃) And neodymium oxide (Nd)₂O₃) Weight ratio (La₂O₃/ Nd₂O₃) Is preferably 1.4 to 2.8. Furthermore, it is such a raw material, and the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is more preferably 50 wt% to 65 wt%, and the ratio of the weight of lanthanum oxide in TREO (La₂O₃/ TREO) is more preferably 22 wt% to 30 wt%, and the ratio of the total weight of lanthanum oxide and neodymium oxide in TREO ((La₂O₃+ Nd₂O₃) / TREO) is more preferably 25 wt% to 50 wt%. Also in this raw material, for the same reason as described above, it is preferable that the weight ratio ((U + Th) / TREO) of TREO to the total weight of uranium and thorium is 0.05 wt% or less, and 0.005 wt% The raw material which is below is more preferable, and the raw material which is 0.0005 wt% or less is further preferable.
[0039]
  Furthermore, as a raw material for cerium-based abrasives according to the above-mentioned invention, regardless of the raw material according to any of the inventions, the ratio of the weight of praseodymium oxide in TREO (Pr₆O₁₁More preferably, / TREO) is 2.0 wt% to 8.0 wt%.
[0040]
  In addition, the radioactive materials such as uranium and thorium that may be contained in the raw material have been mentioned above. However, in addition to these, the ore used as the raw material for the abrasive material includes calcium (Ca), barium (Ba), iron ( It may contain a lot of elements such as Fe) and phosphorus (P). The abrasive produced from the ore (raw material) containing such many elements contains many of these components as impurities. When an abrasive containing a large amount of these impurities is used, abrasive scratches are likely to occur, and the polishing speed may be reduced. If these impurities (particularly iron) remain on the polished surface or the like, the electrical or magnetic characteristics of the object to be polished may be degraded. In that sense, regardless of which of the inventions related to the above raw materials, the cerium-based abrasive raw material and the cerium-based abrasive according to the present invention include TREO and the total weight of calcium, barium, iron and phosphorus. The weight ratio ((Ca + Ba + Fe + P) / TREO) is preferably 2.0 wt% or less, more preferably 1.0 wt% or less, and even more preferably 0.5 wt% or less, and the weight ratio ((Ca + Ba + Fe + P) / (TREO) is preferably 2.0 wt% or less, more preferably 1.0 wt% or less, and further preferably 0.5 wt% or less.
[0041]
  As a manufacturing method of the raw material for cerium-based abrasives, there is generally the following method (first manufacturing method of raw material).
  First, concentrates such as bastonite concentrate are decomposed by sulfuric acid decomposition method or alkali decomposition method, and fractional precipitation and fractional dissolution are performed to reduce impurities such as uranium, thorium, calcium, barium, iron and phosphorus. -A rare earth solution is obtained by removing. And the composition of the rare earth component of the obtained rare earth solution is adjusted (rare earth composition adjustment). Then, mix the rare earth solution whose composition is adjusted and the precipitating agent (for example, ammonium hydrogen carbonate, ammonium carbonate, sodium hydrogen carbonate, sodium carbonate, aqueous ammonia, oxalic acid, ammonium oxalate, sodium oxalate, urea, etc.) A precipitate of a rare earth compound (for example, carbonate, basic carbonate, monooxy carbonate, hydroxide, oxalate, etc.) is produced, and this is filtered and washed with water to obtain the cerium-based abrasive raw material according to the present invention. It is a method of obtaining.
[0042]
  There are a solvent extraction method and an addition method as the composition adjustment method of the rare earth solution performed after the reduction / removal of impurities during the production of the cerium-based abrasive material. In the solvent extraction method, impurities other than rare earth elements can be reduced to some extent depending on the application method. The solvent extraction method and the addition method may be combined.
[0043]
  First, the solvent extraction method will be described. For example, the ratio of neodymium in the solution before solvent extraction (Nd₂O₃/ TREO) is high, or the weight ratio of lanthanum oxide to neodymium oxide in the solution (La₂O₃/ Nd₂O₃) Is small, the following two methods can be cited as solvent extraction methods. That is, a method of extracting a part of neodymium from an aqueous rare earth solution into an organic solvent, or after extracting almost all of the rare earth element into an organic solvent, the organic solvent is brought into contact with an aqueous solution for back extraction, and neodymium is added to the organic solvent. In this method, most of the other rare earth elements are back-extracted into an aqueous solution while leaving a part of the above. By such a method, the proportion of neodymium is reduced and adjusted to a proportion suitable for the present invention. Conversely, the proportion of neodymium in the solution before solvent extraction (Nd₂O₃/ TREO) is low or the weight ratio of lanthanum oxide to neodymium oxide in the solution (La₂O₃/ Nd₂O₃) Is large, examples of the solvent extraction method used include the following methods. That is, after extracting other rare earth elements into an organic solvent while leaving a part of lanthanum or cerium in the aqueous solution, it is brought into contact with the aqueous solution for back extraction, and almost all of the rare earth elements extracted into the organic solvent are put into the aqueous solution. This is a back extraction method. By such a method, the proportion of neodymium is increased and adjusted to a proportion suitable for the present invention.
[0044]
  In addition, although each solvent extraction method demonstrated here is a method when the organic solvent which is easy to extract as a heavy rare earth element is used as an organic solvent, the organic solvent which is easy to extract as a light rare earth element can also be used. . In addition, the extraction amount and back extraction amount of the target substance in each extraction step and back extraction step of the solvent extraction method depend on conditions such as which invention the raw material for the abrasive material to be manufactured is a raw material according to which invention. As appropriate.
  Next, the addition method will be described. Ratio of neodymium in the solution before adjusting the rare earth composition (Nd₂O₃/ TREO) is high or the weight ratio of lanthanum oxide to neodymium oxide in the solution before solvent extraction (La₂O₃/ Nd₂O₃) Is a small amount of addition method using an aqueous solution of a compound containing a large amount of lanthanum or cerium as a rare earth element (for example, carbonate, hydroxide, chloride, oxide, etc.) The solution dissolved in (1) is added and mixed to reduce the ratio of neodymium, and adjust to a ratio suitable for the present invention. Conversely, the ratio of neodymium in the solution before adjusting the rare earth composition (Nd₂O₃/ TREO) is low, or the weight ratio of lanthanum oxide to neodymium oxide in the solution before solvent extraction (La₂O₃/ Nd₂O₃) Is a method in which an aqueous solution of a compound containing a large amount of neodymium as a rare earth element is added and mixed to increase the proportion of neodymium and adjust the proportion to suit the present invention.
[0045]
  The amount of the aqueous solution added in the above addition method is appropriately determined depending on conditions such as whether the raw material for the abrasive to be produced is a raw material according to any of the above inventions.
[0046]
  As a method for producing a cerium-based abrasive raw material, there is the following method (second raw material production method).
  For example, among the abrasives according to the present invention, the total rare earth oxide equivalent weight (TREO) is 90 wt% or more, and the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is 50 wt% to 65 wt%, and the ratio of the weight of neodymium oxide in the TREO (Nd₂O₃In the case of producing a cerium-based abrasive (first invention) having a ratio of / TREO) of 10 wt% to 16 wt%, first, the following are prepared as raw materials for the abrasive material. Specifically, the content of elements such as uranium, thorium, potassium, barium, iron, and phosphorus is sufficiently reduced.₂/ TREO "and" Nd₂O₃A plurality of “/ TREO” values not necessarily within the above-mentioned preferred range (for example, carbonate, basic carbonate, monooxycarbonate, hydroxide, oxalate, oxide, etc.) are prepared. Then, the cerium-based abrasive material according to the present invention is manufactured by mixing these plural materials (abrasive material) and adjusting the content of cerium and neodymium (mixing step).
[0047]
  Further, for example, among the abrasives according to the invention, cerium oxide (CeO) relative to the total rare earth oxide equivalent weight (TREO)₂) Weight ratio (CeO₂/ TREO) is 45 wt% to 70 wt%, and lanthanum oxide (La₂O₃) And neodymium oxide (Nd)₂O₃) Weight ratio (La₂O₃/ Nd₂O₃In the case of producing a cerium-based abrasive (second invention) having 1.4 to 2.8, first, the following materials are prepared as raw materials for the abrasive. Specifically, the content of elements such as uranium, thorium, potassium, barium, iron, and phosphorus is sufficiently reduced.₂/ TREO "and" La₂O₃/ Nd₂O₃The value of “is not necessarily within the above-mentioned preferred range (for example, carbonate, basic carbonate, monooxycarbonate, hydroxide, oxalate, oxide, etc.) are prepared. Then, the cerium-based abrasive material according to the present invention is manufactured by mixing these plural materials (abrasive material) and adjusting the content of cerium and neodymium (mixing step).
[0048]
  In addition, the mixing process demonstrated by the said 2nd manufacturing method should just be performed before the baking process performed by manufacture of a cerium type abrasive. That is, the mixing step is a step that may be performed at any stage in the production process of the cerium-based abrasive raw material. For example, a plurality of raw materials (raw material for abrasive materials) as described above may be separately pulverized and subjected to a fluorination treatment, followed by a mixing step. In addition, as a plurality of raw materials used for mixing (raw material of abrasive materials), there may be one or more high-purity materials in which the ratio of one kind of rare earth oxide in TREO is 99 wt% or more. If a high-purity material is used, the composition can be easily adjusted, but a high-purity material is expensive.
[0049]
  Various abrasive materials have been described so far, but calcined products obtained by calcining the cerium-based abrasive materials (for example, rare earth carbonates, basic carbonates, monooxy carbonates, hydroxides, oxalates). An oxide obtained by calcining a raw material such as an acid salt or an intermediate between the oxide and the raw material) can also be used as the cerium-based abrasive raw material according to the present invention. Here, the raw material for abrasives means that a roasting step is required at the time of producing the abrasives in order to produce an abrasive from the raw material. In other words, the raw materials for cerium-based abrasives here include raw materials before the pulverization process performed at the initial stage of the production of the abrasives, and raw materials before being subjected to the roasting process during the production of the cerium-based abrasives. (Intermediate raw materials) are included. Therefore, even if the above-mentioned abrasive raw material described so far is pulverized and / or fluorinated, and further dried and / or pulverized, cerium is only roasted. What becomes the system abrasive (that is, before the roasting step in the production of the abrasive) is the cerium-based abrasive material (intermediate material) referred to herein.
[0050]
  In the cerium-based abrasive raw materials and cerium-based abrasives according to each of the above inventions, “F / TREO”, “(U + Th) / TREO”, and “(Ca + Ba + Fe + P) / TREO” are abrasive raw materials and abrasives. Is the weight ratio of the weight of “F”, the weight of “U + Th” or the weight of “Ca + Ba + Fe + P” with respect to the total rare earth oxide equivalent weight (TREO), and the weight of “F” in “TREO”, “U + Th” It is not the ratio of the weight or the weight of “Ca + Ba + Fe + P”. “TREO” does not contain “F”, “U + Th”, “Ca + Ba + Fe + P”, and the ratio of the weight of “F”, the weight of “U + Th” or the weight of “Ca + Ba + Fe + P” in “TREO” is basically 0% by weight. Therefore, when “F / TREO”, “(U + Th) / TREO” or “(Ca + Ba + Fe + P) / TREO” of an abrasive material or abrasive is required, “TREO (total rare earth oxidation) of the abrasive material or abrasive is required. (Weight in terms of product) ”,“ F ”,“ U + Th ”and“ (Ca + Ba + Fe + P) ”are measured separately, and“ TREO ”is converted to 100 wt% by calculation. For example, when the abrasive “TREO” is 90.0 wt% and the abrasive “F” is 6.3 wt%, the “F / TREO” of the abrasive is 6.3 (wt%) ÷ 90. 0 (wt%) × 100 (wt%) = 7.0 (wt%).
[0051]
BEST MODE FOR CARRYING OUT THE INVENTION
  Hereinafter, preferred embodiments of the cerium-based abrasive according to the present invention will be described.
[0052]
First embodiment
  First, a rare earth chloride (from India) was prepared. The composition is that the total rare earth oxide equivalent weight (hereinafter referred to as TREO) is 46.0 wt%, CeO.₂/ TREO is 50.3wt%, La₂O₃/ TREO is 23.7wt%, Nd₂O₃/ TREO is 20.0wt%, Pr₆O₁₁/ TREO was 5.2 wt%, (U + Th) / TREO was less than 0.0005 wt%, and (Ca + Ba + Fe + P) / TREO was 0.6 wt%. This rare earth chloride is pulverized from monazite concentrate (produced in India), alkali decomposition using concentrated NaOH aqueous solution (140 ° C., 3 hours), hydrothermal treatment for dissolving phosphoric acid component in aqueous solution, filtration, pH 3 Separation and dissolution using hydrochloric acid adjusted to 0.5 to 4.0 (dissolving rare earth elements and leaving uranium (U) and thorium (Th) in the hydroxide precipitate), filtration, solvent extraction, evaporation and concentration In addition, each process of standing to cool and solidify is obtained sequentially.
[0053]
Reference example 1: A cerium-based abrasive material (intermediate material) was produced using the prepared rare earth chloride. First, the prepared rare earth chloride and 0.1 mol / L dilute hydrochloric acid were mixed and dissolved to prepare a rare earth chloride solution, the prepared solution was filtered, and the filtered solution was subjected to solvent extraction. In the solvent extraction, as an organic solvent, an extractant (PC-88A: manufactured by Daihachi Chemical Industry Co., Ltd.) and a diluent (Ipsol: manufactured by Idemitsu Petrochemical Co., Ltd.) that are more easily extracted as heavy rare earth elements are in a liquid volume ratio (extractant / diluent). The agent was mixed at a ratio of 1/2. Then, the organic solvent and the rare earth chloride solution (TREO 210 g / L) are brought into countercurrent multistage contact (30 stages) in a state where the flow ratio (organic solvent / diluted chloride chloride solution) is 8/1. Was extracted into an organic solvent. In this process, a sodium hydroxide aqueous solution in an amount necessary and sufficient to extract almost all of the rare earth element in the rare earth chloride solution was added during the countercurrent multistage extraction with the organic solvent to be used. Thereafter, the organic solvent containing the rare earth element and the 3 mol / L hydrochloric acid aqueous solution are brought into countercurrent multistage contact (30 stages) in a state where the flow ratio (organic solvent / hydrochloric acid aqueous solution) is 8 / 1.4, and praseodymium and neodymium Most of the rare earth elements (samarium (Sm) to heavy rare earth and yttrium (Y)) that are more easily extracted into organic solvents than neodymium are left in the organic solvent, and most of lanthanum and cerium, and one of praseodymium and neodymium. Part was back-extracted into an aqueous hydrochloric acid solution to obtain a rare earth solution (purified solution).
[0054]
  After solvent extraction, the resulting rare earth solution and aqueous ammonium hydrogen carbonate solution (precipitant) are mixed to form a rare earth carbonate precipitate, which is then filtered and washed (washed with water) using a centrifuge. A rare earth carbonate as an abrasive material (intermediate material) was obtained. The composition was that TREO was 44 wt%. In addition, the ratio of the weight of each rare earth element in TREO was the same as that of the obtained cerium-based abrasive (see Table 1). Moreover, F / TREO was less than 0.1 wt%, (U + Th) / TREO was less than 0.0005 wt%, and (Ca + Ba + Fe + P) / TREO was less than 0.4 wt%.
[0055]
  The rare earth carbonate prepared in this way (intermediate raw material) and pure water having twice the weight of the raw material are mixed, and wet pulverized for 8 hours with a wet ball mill (grinding medium is zirconia ball having a diameter of 5 mm). The raw material slurry was obtained. D of the obtained pulverized product₅₀Was 0.8 μm. Then, 10 wt% hydrofluoric acid was added to the obtained slurry to prepare a weight ratio (F / TREO) of fluorine components in the slurry, and this slurry was subjected to a stirring treatment for 30 minutes (hereinafter simply referred to as “fluid”). Is referred to as processing). “F / TREO” after the fluorination treatment was 8.0 wt%. In addition, the alkali concentration, hot water extraction, and the fluorine ion electrode method were used for the measurement of fluorine concentration. Thereafter, so-called repulp washing, in which the solid content was settled, the supernatant liquid was extracted, and pure water was added, was performed, and the washed slurry was filtered by a filter press method. The obtained filter cake was dried at 140 ° C. for 48 hours. Furthermore, the obtained dried cake was pulverized with a sample mill, and the obtained pulverized product was roasted (roasting temperature 1000 ° C., roasting time 12 hours). After roasting, the obtained roasted product was further pulverized by a sample mill and classified by a turbo classifier (the classification point was set to 5 μm) to obtain a cerium-based abrasive.
[0056]
Example 1, Reference Example 2: These examplesReference examplesThen, the flow rate ratio between the organic solvent and the hydrochloric acid aqueous solution in the step of back-extracting the rare earth element such as lanthanum into the hydrochloric acid aqueous solution by bringing the organic solvent containing the rare earth element into contact with the 3 mol / L hydrochloric acid aqueous solution in a countercurrent multistage contact. Hydrochloric acid solution)Reference example 1And different. In addition,Example 1The flow rate ratio (organic solvent / hydrochloric acid aqueous solution) is 8 / 1.3,Reference example 2The flow rate ratio (organic solvent / hydrochloric acid aqueous solution) was 8 / 1.2. Other conditions areReference example 1Since this is the same, the description is omitted. In addition, the TREO of the rare earth carbonate (intermediate raw material) produced in Example 1 is 46 wt%,Reference example 2The TREO of the rare earth carbonate (intermediate raw material) produced in step 4 was 43 wt%. The ratio of the weight of each rare earth element in TREOReference examplesBoth were the same as the finally manufactured cerium-based abrasive (see Table 1). Also, any exampleReference examplesIn both cases, F / TREO was less than 0.1 wt%, (U + Th) / TREO was less than 0.0005 wt%, and (Ca + Ba + Fe + P) / TREO was less than 0.4 wt%.
[0057]
Comparative Example 1: US-made bastonite concentrate was prepared as a raw material. Its composition (weight ratio) is 70 wt% TREO, CeO₂/ TREO is 49.3wt%, La₂O₃/ TREO is 34.0wt%, Nd₂O₃/ TREO is 11.3 wt%, Pr₆O₁₁/ TREO 4.0 wt%, F / TREO 8.0 wt%, (U + Th) / TREO) 0.1 wt%, and (Ca + Ba + Fe + P) / TREO 6.8 wt%. Then, the prepared raw material (bust nesite concentrate) and pure water having twice the weight of the raw material are mixed, and wet pulverized with a wet ball mill (grinding medium is zirconia ball having a diameter of 5 mm) for 8 hours. A raw slurry was obtained. And the cerium type abrasive | polishing material was obtained by performing sequentially each process of repulp washing | cleaning, filtration, drying, roasting, grinding | pulverization, and classification with respect to the obtained raw material slurry. The conditions of each process after repulp washing areReference example 1Was the same.
[0058]
Comparative Examples 2 and 3In these comparative examples, the conditions for the step of back-extracting a rare earth element such as lanthanum into an aqueous hydrochloric acid solution by contacting the organic solvent containing the rare earth element with a 3 mol / L hydrochloric acid aqueous solution in a countercurrent multistage contactReference example 1Is different. In Comparative Example 2, the flow ratio of the organic solvent to the aqueous hydrochloric acid solution (organic solvent / aqueous hydrochloric acid solution) was 8 / 1.6, and almost all of the rare earth elements in the organic solvent were back extracted into the aqueous hydrochloric acid solution to extract the rare earth. A solution (purified solution) was obtained. The flow rate ratio (organic solvent / hydrochloric acid aqueous solution) in Comparative Example 3 was 8 / 1.1. Other conditions areReference example 1Was the same. The TREO of the rare earth carbonate (intermediate raw material) produced in Comparative Example 2 was 42 wt%, and the TREO of the rare earth carbonate (intermediate raw material) produced in Comparative Example 3 was 46 wt%. The ratio of the weight of each rare earth element in TREO was the same as that of the finally produced cerium-based abrasive in all the comparative examples (see Table 1). In any of the comparative examples, F / TREO was less than 0.1 wt%, (U + Th) / TREO was less than 0.0005 wt%, and (Ca + Ba + Fe + P) / TREO was less than 0.4 wt%.
[0059]
Examples 2-3 and Reference Examples 3-4: ExamplesReference examplesThen, except that the conditions of fluorination treatment are different,Example 1A cerium-based abrasive was produced under the same conditions. In addition, "F / TREO" after fluorination treatment isReference example 3Then 4.0 wt%,Example 2Then 5.5 wt%,Example 3Then, 11 wt%,Reference example 4It was 15 wt%.
[0060]
Examples 4 and 5: In each example, except that the baking temperature in the baking process is different,Example 1A cerium-based abrasive was produced under the same conditions. The roasting temperature isExample 4Is 850 ° C,Example 9Then, it was 1100 degreeC.
[0061]
  Each of the above examplesReference examplesTable 1 shows values such as the fluorine content, the ratio of the weight of each rare earth oxide in TREO, and TREO of the cerium-based abrasives obtained in the respective comparative examples. In addition, (Ca + Ba + Fe + P) / TREO was 6.2 wt% for the abrasive of Comparative Example 1 and less than 0.4 wt% for the other abrasives.
[0062]
[Table 1]

[0063]
  ExamplesReference examplesAnd using the cerium-based abrasive obtained in the comparative example, the average particle size (D₅₀), BET specific surface area (BET) and diffraction X-ray intensity (Intensity) were measured. In addition, each exampleReference examplesAlso, a polishing test was performed using the cerium-based abrasive obtained in the comparative example, and the polishing value (polishing speed), the scratch evaluation of the obtained polished surface, and the adhesion (cleanability) were evaluated. A measuring method, a polishing test method, and evaluation methods for various polishing characteristics will be described below. The measured values and evaluation results are shown in Table 2 below.
[0064]
Average particle size (D ₅₀ ) Measurement
  The particle size distribution of the cerium-based abrasive was measured using a laser diffraction / scattering particle size distribution measuring device (manufactured by Shimadzu Corporation: SALD-2000A), and the average particle size (D₅₀: The particle size at a cumulative volume of 50 wt% from the small particle size side).
[0065]
BET specific surface area (BET): Measured in accordance with “6.2 Flow Method (3.5) Single Point Method” in JIS R 1626-1996 (Method for Measuring Specific Surface Area of Fine Ceramics Powder by Gas Adsorption BET Method). At that time, a mixed gas of helium as a carrier gas and nitrogen as an adsorbate gas was used.
[0066]
X-ray diffraction measurement
  Using an X-ray diffractometer (manufactured by Mac Science Co., Ltd., MXP18), the cerium-based abrasive was subjected to X-ray diffraction analysis and the diffraction X-ray intensity was measured. In this measurement, a copper (Cu) target is used, and Cu—Kα obtained by irradiating Cu—Kα rays.₁Analysis was performed on the peak where the diffraction angle (2θ) appeared in the range of 20 ° to 30 ° in the X-ray diffraction pattern. Other measurement conditions were tube voltage 40 kV, tube current 150 mA, measurement range 2θ = 5 ° to 80 °, sampling width 0.02 °, and scanning speed 4 ° / min. And from the obtained X-ray diffraction measurement result, cerium oxide (CeO₂) X-ray diffraction peak intensity, lanthanoid oxyfluoride (LnOF) X-ray diffraction peak intensity and lanthanoid fluoride (LnF)₃) X-ray diffraction peak intensity, and each X-ray diffraction peak intensity ratio (LnOF / CeO)₂, LnF₃/ CeO₂)
[0067]
Polishing test
  A polishing tester (HSP-2I type, manufactured by Taito Seiki Co., Ltd.) was prepared as a polishing machine. This polishing tester polishes the surface to be polished with a polishing pad while supplying an abrasive slurry to the surface to be polished. The polishing pad was made of polyurethane, and was replaced with a new one every time (about 24 hours polishing time) in the polishing test. And 65 mmφ glass for a flat panel was prepared as an object to be polished. Further, 50 L of an abrasive slurry having a solid content concentration of 15 wt% was prepared by mixing powdered cerium-based abrasive powder and pure water. The surface of the glass for flat panels was polished using this abrasive slurry. In this polishing test, the abrasive slurry was supplied at a rate of 5 liters / minute, and the abrasive slurry was circulated and used. Further, the pressure of the polishing pad against the polishing surface is 9.8 kPa (100 g / cm²) And the rotational speed of the polishing tester was set to 100 rpm.
[0068]
Evaluation of polishing value (polishing speed)
  After 30 minutes of polishing, the flat panel glass to be polished was replaced. The replaced flat panel glass has been weighed. Then, polishing was performed for 10 minutes after the replacement of the glass for the flat panel, and the amount of reduction in the glass weight due to the polishing was determined. Based on this value, the “polishing value 1” was determined. The polishing value of the polishing material of Comparative Example 1 was used as the reference (100).
[0069]
  After the first 30 minutes and the subsequent 10 minutes of polishing for a total of 40 minutes, the glass is replaced with a new flat panel glass and polished for 23 hours and 20 minutes (total 24 hours). Panel glass was replaced. The replaced flat panel glass has been weighed. Then, polishing was performed for 10 minutes after the replacement of the glass for the flat panel, and the amount of reduction in the glass weight due to the polishing was determined. Based on this value, the “polishing value 2” was determined. Here, the polishing value 2 was determined with the polishing value 1 of the polishing material of Comparative Example 1 as the reference (100).
[0070]
  Then, “abrasion value ratio (abrasion value 2 / abrasion value 1)” is obtained based on “abrasion value 1” and “abrasion value 2”, and “abrasion value 1”, “abrasion value 2”, and “abrasion value ratio”. Was used to evaluate the polishing value (polishing rate) of the cerium-based abrasive.
[0071]
Evaluation of abrasive scratches
  Further, after polishing, the polished flat panel glass was cleaned with pure water, and scratches were evaluated on the polished surface which was dried in a dust-free state. Scratch evaluation was performed by observing the glass surface by a reflection method using a 300,000 lux halogen lamp as a light source, scoring the number of large scratches and fine scratches, and evaluating 100 points as a perfect score. In this scratch evaluation, the polishing accuracy required for finish polishing of a glass substrate for hard disk or LCD was used as a criterion. Specifically, in Tables 2 and 5, “◎” indicates 98 points or more (very suitable for finishing polishing of glass substrates for HD and LCD), and “◯” indicates 95 points less than 98 points. That it is above (suitable for finishing polishing of HD / LCD glass substrates), and “△” is less than 95 points and 90 points or more (can be used for finishing polishing of HD / LCD glass substrates). "X" indicates that it is less than 90 points (cannot be used for finish polishing of glass substrates for HD and LCD).
[0072]
Adhesion test
  In addition, a test was conducted on the adhesiveness (cleanability) of the abrasive. In the test, first, the cleaned and dried slide glass for optical microscope observation was immersed in the abrasive slurry and pulled up and dried at 50 ° C., and then immersed in a container containing pure water for ultrasonic cleaning. After performing ultrasonic cleaning, the slide glass taken out from the container was washed with pure water to obtain a slide glass to be observed. Thereafter, the adhesiveness was evaluated by observing the remaining amount of abrasive particles remaining on the surface of the slide glass with an optical microscope. Specifically, in Tables 2 and 5, “◯” indicates that the remaining abrasive particles are not observed and is very suitable for finishing polishing, and “△” indicates that the remaining abrasive particles are observed. “×” indicates that a large amount of residual abrasive particles are observed and unsuitable for finishing polishing.
[0073]
[Table 2]

[0074]
  As shown in Table 2,Example 1, Reference Examples 2-3The polishing material of No. 1 has a high polishing value (polishing value 1) immediately after the start of polishing (after 30 minutes), and has a relatively high polishing value (polishing value 2) even after long-term circulation. The decrease in the polishing value due to use was relatively small (polishing value ratio = 0.66 to 0.78). That is, a sharp decrease in the polishing value (polishing speed) after the start of polishing was prevented, and a higher polishing value was maintained for a longer time. AndExample 1, Reference Examples 2-3Both of these abrasives were excellent in that they were less likely to be scratched and adhered to the polished surface. Also, as shown in Table 2, the examplesReference examplesAll of the abrasives were excellent in abrasive properties,Example 1The abrasive material of No. 1 had the best polishing characteristics. On the other hand, the polishing materials of Comparative Examples 1 to 3 had a remarkably low polishing value of 2, and the polishing force suddenly decreased with use (polishing value ratio = 0.23 to 0.32). In addition, there was a defect that the abrasive flaws were likely to occur and were likely to adhere to the polished surface.
[0075]
  Therefore, each example of the data shown in Table 1Reference examplesWhen the data of the comparative example were examined, the following was found.
[0076]
  The cerium-based abrasive preferably has a TREO of 90 wt% or more, more preferably 92 wt% or more. And the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) is preferably 50 wt% or more. In addition, each exampleReference examplesFrom Comparative Example 2, as the cerium-based abrasive, the ratio of the weight of neodymium oxide in TREO (Nd₂O₃/ TREO) is preferably 16 wt% or less. Furthermore, each exampleReference examplesFrom Comparative Example 3, as the cerium-based abrasive, the ratio of the weight of neodymium oxide in TREO (Nd₂O₃/ TREO) is preferably at least 10 wt% or more.
[0077]
  As the cerium-based abrasive, the ratio of the weight of lanthanum oxide in TREO (La₂O₃/ TREO) is preferably 30 wt% or less.
[0078]
  In addition, each exampleReference examplesWhen the data of the comparative example (Table 1) were compared from different viewpoints, the cerium-based abrasive was lanthanum oxide (La₂O₃) And neodymium oxide (Nd)₂O₃) Weight ratio (La₂O₃/ Nd₂O₃) Is preferably 1.4 or more (comparison between each example and comparative example 2), and preferably 2.8 or less (comparison between each example and comparative examples 1 and 3).
[0079]
  Further, as the cerium-based abrasive, the ratio of the total weight of lanthanum oxide and neodymium oxide in TREO ((La₂O₃+ Nd₂O₃) / TREO) is preferably 25 wt% to 50 wt%. Also,Example 1 and Examples 2-3 and Reference Examples 3-4As a cerium-based abrasive, it is more preferable that the weight ratio (F / TREO) of TREO and fluorine content is 4.0 wt% to 9.0 wt%.
[0080]
  The cerium-based abrasive preferably has a weight ratio of TREO to the total weight of uranium and thorium ((U + Th) / TREO) of 0.05 wt% or less. AndExample 1, Reference Examples 1-2And Comparative Examples 1 to 3 were compared, the X-ray diffraction peak intensity ratio (LnOF / CeO₂) Is preferably 0.4 to 0.7.
[0081]
  Furthermore, each exampleReference examplesFrom the average particle size of the abrasive particles (D₅₀) Is more preferably 0.7 μm to 1.6 μm, and the BET specific surface area is 2.0 m.²/G-5.0m²/ G is more preferable.
[0082]
  Also, as shown in Table 2,Example 1 and Examples 2-3 and Reference Examples 3-4All of the abrasives had a high polishing value of 1 and a relatively high polishing value of 2, and the decrease in the polishing value due to use was relatively small (Abrasive value ratio = 0.66 to 0.78). ). In other words, the sharpening value (polishing rate) is prevented from suddenly decreasing after the start of polishing, and a higher polishing value is maintained for a longer time. However,Reference example 3The abrasive ofExample 1As compared with the above, the polishing value 1 and the polishing value 2 were slightly lower, and there was some adhesion. this is,Example 1The weight ratio (F / TREO) between the amount of TREO and the amount of fluorine (F / TREO) is smaller than that of the X-ray diffraction peak intensity ratio (LnOF / CeO).₂) Is small. Also,Reference example 4The abrasive ofExample 1Compared to the above, abrasive scratches were likely to occur, and there was some adhesion. this is,Example 1X-ray diffraction peak intensity ratio (LnOF / CeO₂And LnF₃/ CeO₂) Is large.
[0083]
  And as shown in Table 2,Examples 1, 4 and 5The polishing material had a high polishing value of 1 and a relatively high polishing value of 2, and the decrease in the polishing value due to use was relatively small (polishing value ratio = 0.72 to 0.78). In other words, the sharpening value (polishing rate) is prevented from suddenly decreasing after the start of polishing, and a higher polishing value is maintained for a longer time. As a result, in the case of producing an abrasive using the raw material for an abrasive of the present invention, if the roasting temperature is 800 ° C. to 1200 ° C. (more preferably 850 ° C. to 1100 ° C.), the polishing value (polishing speed) is obtained. It has been found that an abrasive with a small decrease (a large polishing value ratio) can be produced.
[0084]
Second embodiment
  Next, cerium carbonate, lanthanum carbonate, praseodymium carbonate, neodymium carbonate were each calcined (roasted) individually, mixed to prepare raw materials, and cerium-based abrasives were produced using the prepared raw materials.Reference examplesA comparative example will be described.
[0085]
  First, high purity cerium carbonate (TREO: 45 wt%, CeO₂/ TREO: 99.9 wt% or more), lanthanum carbonate (TREO: 45 wt%, La₂O₃/ TREO: 99.9 wt% or more), praseodymium carbonate (TREO: 45 wt%, Pr)₆O₁₁/ TREO: 99.9 wt% or more), neodymium carbonate (TREO: 45 wt%, Nd₂O₃/ TREO: 99.9 wt% or more) were prepared and calcined (roasted) separately. The calcination temperature was 600 ° C. and the calcination time was 12 hours. And by calcining, cerium carbonate calcined product (TREO: 83 wt%, CeO₂/ TREO: 99.9 wt% or more, loss on ignition: 17 wt%), calcined lanthanum carbonate (TREO: 85 wt%, La₂O₃/ TREO: 99.9 wt% or more, loss on ignition: 15 wt%), praseodymium carbonate calcined product (TREO: 86 wt%, Pr₆O₁₁/ TREO: 99.9 wt% or more, loss on ignition: 14 wt%), neodymium carbonate calcined product (TREO: 82 wt%, Nd₂O₃/ TREO: 99.9 wt% or more, loss on ignition: 18 wt%).
[0086]
  And each calcined product obtained in this way is mixed, and each example explained belowReference examplesAnd the cerium-type abrasive raw material (intermediate raw material) used by each comparative example was prepared. ExamplesReference examplesTable 3 shows the composition of the cerium-based abrasive raw material (intermediate raw material) used in the comparative examples. In addition, the (U + Th) / TREO weight ratio of the five kinds of intermediate materials prepared by mixing them was less than 0.0005 wt%, and the (Ca + Ba + Fe + P) / TREO weight ratio was less than 0.1 wt%. .
[0087]
[Table 3]

[0088]
Example 6, Reference Examples 5 to 8 and Comparative Examples 6 to 9: The prepared raw material for cerium-based abrasive (intermediate raw material = rare earth carbonate calcined product (mixed product)) and pure water having twice the weight of the raw material are mixed, and a wet ball mill (the grinding medium is 5 mm in diameter) A raw slurry was obtained by wet grinding with zirconia balls) for 8 hours. D of the obtained pulverized product₅₀Was 0.8 μm. The resulting slurry is fluorinated (Reference example 1The same processing as in the above. “F / TREO” after the fluorination treatment was 8.0 wt%. Thereafter, so-called repulp washing, in which the solid content was settled, the supernatant liquid was extracted, and pure water was added, was performed, and the washed slurry was filtered by a filter press method. Then, the obtained filtered product was sequentially subjected to drying, roasting, pulverization, and classification steps to obtain a cerium-based abrasive. In addition, the conditions of each process after drying areReference example 1Was the same.
[0089]
  Example aboveReference examplesTable 4 shows values such as the fluorine content of the cerium-based abrasives obtained in Comparative Examples 6 to 9, and the weight ratio of each rare earth oxide in TREO and TREO. Further, the weight ratio of (Ca + Ba + Fe + P) / TREO of these abrasives was less than 0.1 wt%.
[0090]
[Table 4]

[0091]
  ExamplesReference examplesAnd using the cerium-based abrasive obtained in the comparative example, the average particle size (D₅₀), BET specific surface area (BET) and diffraction X-ray intensity (Intensity) were measured. In addition, each exampleReference examplesAlso, a polishing test was performed using the cerium-based abrasive obtained in the comparative example, and the polishing value (polishing speed), the scratch evaluation of the obtained polished surface, and the adhesion (cleanability) were evaluated. The measurement method and test method are as described above. Table 5 shows the measured values and the evaluation results.
[0092]
[Table 5]

[0093]
  As shown in Table 5, each exampleReference examplesThe polishing material of No. 1 has a high polishing value (abrasion value 1) in an unused state, and has a relatively high polishing value (abrasion value 2) even in a used state. It was relatively small (abrasive value ratio = 0.67-0.79). In addition, each exampleReference examplesBoth of these abrasives were excellent in that they were less likely to be scratched and adhered to the polished surface. In addition,Example 6, Reference Examples 5-8InExample 6The abrasive material of No. 1 had the best polishing characteristics. On the other hand, the polishing material of each comparative example had a remarkably low polishing value of 2, and the polishing value (polishing speed) was rapidly reduced by use (except for comparative example 9). In addition, there was a defect that the abrasive flaws were likely to occur and were likely to adhere to the polished surface.
[0094]
  For the data shown in Table 4, each exampleReference examplesAnd Comparative Examples 8 and 9 show that, as a cerium-based abrasive, the ratio of the weight of cerium oxide in the TREO (CeO₂/ TREO) has been found to be preferably 45 wt% to 70 wt%. In addition, each exampleReference examplesAnd Comparative Examples 6 and 7 show that as a cerium-based abrasive, the ratio of the weight of neodymium oxide in TREO (Nd₂O₃/ TREO) has been found to be preferably 10 wt% to 16 wt%. Further, as shown in Table 5, as the cerium-based abrasive, the X-ray diffraction peak intensity ratio (LnOF / CeO₂) Is more preferably 0.4 to 0.7.
  Examples shown in Table 4Reference examplesAnd the data of the comparative example were compared from another point of view, it was found that lanthanum oxide (La₂O₃) And neodymium oxide (Nd)₂O₃) Weight ratio (La₂O₃/ Nd₂O₃) For exampleReference examples1.4 or more is preferable from comparison with Comparative Example 7, and each ExampleReference examplesFrom a comparison with Comparative Example 6, it was found that 2.8 or less is preferable. AndReference examples 7 and 8When the weight balance between lanthanum oxide and neodymium oxide is adjusted, the ratio of the weight of neodymium oxide in TREO (Nd₂O₃It was found that a practical abrasive can be obtained even if / TREO) is 9 wt% or 17 wt%.
[0095]
[Possibility of industrial use]
  As can be understood from the above description, the cerium-based abrasive according to the present invention has few scratches and maintains a high polishing force for a long time. Therefore, by using the cerium-based abrasive according to the present invention, it is possible to obtain a high-quality polished surface with less scratches and less adherence of the abrasive in a shorter time. That is, according to the present invention, it is possible to provide a cerium-based abrasive suitable for use in fields where high-precision surface polishing performance is required, such as polishing of a glass substrate for optical disks and magnetic disks.

Claims (6)

In the cerium-based abrasive containing at least cerium oxide, lanthanum oxide and neodymium oxide as the rare earth oxide and containing fluorine,
The total rare earth oxide equivalent weight (TREO) is 90 wt% or more, and the ratio of the weight of cerium oxide to the total rare earth oxide equivalent weight (CeO ₂ / TREO) is 50 wt% to 65 wt%. The ratio of the weight of neodymium oxide to the weight (Nd ₂ O ₃ / TREO) is 12 wt% to 14 wt%,
The weight ratio (La ₂ O ₃ / Nd ₂ O ₃ ) of lanthanum oxide (La ₂ O ₃ ) to neodymium oxide (Nd ₂ O ₃ ) in the total rare earth oxide equivalent weight is 1.4 to 2.8,
The ratio of the total weight of lanthanum oxide and neodymium oxide ((La ₂ O ₃ + Nd ₂ O ₃ ) / TREO) in the total rare earth oxide equivalent weight is 25 wt% to 50 wt%,
Among the X-ray diffraction peaks appearing in the range of 2θ (diffraction angle) = 20 ° to 30 ° as measured by the X-ray diffraction method using Cu—Kα ray or Cu—Kα ₁ ray as the X-ray source, rare earth oxyfluoride Intensity ratio between the X-ray diffraction peak intensity of (LnOF) and the strongest X-ray diffraction peak intensity and the X-ray diffraction peak intensity of cerium oxide (CeO ₂ ) and the strongest X-ray diffraction peak intensity ( LnOF / CeO ₂ ) is 0.4 to 0.7,
Further, the average particle size (D ₅₀₎ of abrasive particles, a cerium-based abrasive which is a 0.7Myuemu～1.6Myuemu. _2. The cerium-based abrasive according to claim 1, wherein a ratio of the weight of lanthanum oxide to the total rare earth oxide equivalent weight (La ₂ O ₃ / TREO) is 22 wt% to 30 wt%.   The cerium-based abrasive according to claim 1 or 2, wherein a weight ratio (F / TREO) of fluorine amount to total rare earth oxide equivalent weight is 4.0 wt% to 9.0 wt%.   The cerium-based abrasive according to any one of claims 1 to 3, wherein a weight ratio ((U + Th) / TREO) of a total amount of uranium and thorium to a total rare earth oxide equivalent weight is 0.05 wt% or less. BET specific surface area of ^cerium-based abrasive as claimed in any one of claims 4 a 2.0m ² /g~5.0m 2 / g. A cerium-based abrasive raw material for producing the cerium-based abrasive according to claim 1 ,
The total rare earth oxide equivalent weight (TREO) is 90 wt% or more, and the ratio of the weight of cerium oxide to the total rare earth oxide equivalent weight (CeO ₂ / TREO) is 50 wt% to 65 wt%. The ratio of the weight of neodymium oxide to the weight (Nd ₂ O ₃ / TREO) is 12 wt% to 14 wt% ,
The ratio of the total weight of lanthanum oxide and neodymium oxide ((La ₂ O ₃ + Nd ₂ O ₃ ) / TREO) in the total rare earth oxide equivalent weight is 25 wt% to 50 wt% . the weight ratio of lanthanum oxide _(La 2 _{O 3)} and neodymium oxide _{(Nd 2 O 3) (La} 2 O 3 / Nd 2 O 3) is 1.4 to 2.8,
Furthermore, the total amount of the weight ratio of uranium and thorium to the total rare earth oxide equivalent weight ((U + Th) / TREO ) is 0.05 wt% or less der Ru cerium-raw material.