JP2004277543A - Method for producing phosphor particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inexpensively producing fine phosphor nano particles capable of forming a homogeneous dense high-luminance fluorescent film when used in cathode-ray tubes, fluorescent lamps, PDPs and the like, and having high purity, a uniform chemical composition and excellent luminous characteristics. <P>SOLUTION: The method comprises the steps of spraying a solution comprising a phosphor raw material containing a phosphor constituent metal element and a dispersing medium component into an entraining gas to form liquid droplets comprising the phosphor raw material and the dispersing medium component, heating the liquid droplets, directly or after drying, at a temperature where the dispersing medium component substantially remains unmelted to subject the liquid droplets to pyrolysis to obtain primary pyrolysis particles comprising phosphor precursor particles and the dispersing medium component, reheating the primary pyrolysis particles at a temperature where the dispersing medium component is not substantially melted, and removing the dispersing medium component to obtain phosphor particles. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、ブラウン管、蛍光ランプ、プラズマディスプレーパネル（ＰＤＰ）などに用いることが可能な微小蛍光体粒子の製造方法に関し、特にその１次粒子径が１００ｎｍ以下のナノ粒子蛍光体の製造法に関する。
【０００２】
【従来の技術】
ブラウン管、蛍光ランプやＰＤＰなどに用いられる蛍光体は、従来、原料粉末を混合したものを坩堝などの焼成容器に入れた後、高温で長時間加熱することにより固相反応を起こさせ、それをボールミルなどで微粉砕することにより製造されてきた。
【０００３】
しかし、この方法で製造された蛍光体は、不規則形状粒子が凝集した粉末からなるため、この蛍光体を塗布して得られる蛍光膜は不均質で充填密度の低いものとなり、発光特性が低かった。また、固相反応後のボールミルなどによる微粉砕処理中に蛍光体に物理的及び化学的な衝撃が加えられるために、粒子内や表面に欠陥が発生して発光強度が低下するという不都合もあった。さらには、坩堝などの焼成容器に入れて高温で長時間加熱するために、坩堝からの不純物が混入して発光特性が低下したり、原料粉末の粒度によっては固相反応が十分に進行せずに不純物相が混在して発光特性の低下を招くことがあった。また、高温で長時間加熱すると、消費エネルギーが大きくなり、蛍光体の製造コストを高くする要因となっていた。
【０００４】
これらの問題を解消するために、蛍光体の構成金属元素含有溶液を超音波ネブライザーで同伴気体中に噴霧して微液滴を形成した後、これを乾燥して金属塩粒子や金属錯体粒子とし、この金属塩粒子や金属錯体粒子を同伴気体とともに熱分解合成炉に導入して加熱することにより、熱分解合成を行って蛍光体を得る方法が提案されている。しかしながら、この方法では、熱分解合成炉内での滞留時間を十分に長く取れないために、蛍光体の結晶性が低い上に付活剤イオンを結晶内に均一に付活することができず、結果として発光特性の良好な蛍光体を得られないという問題があった。
【０００５】
そこで、この問題を解消するために、金属塩粒子又は金属錯体粒子を比較的低温で短時間熱分解して所望の結晶相からなる粉末を得て、これを一旦捕集した後、この粉末を比較的高温で長時間再加熱処理して最終的に蛍光体を得るという、２段階加熱処理法が提案された。この方法は、熱分解により得られる粒子の結晶性を更に高めると同時に付活剤イオンを結晶内に均一に付活できるため、発光特性の良好な球状蛍光体を得ることができる。しかしながら、比較的低温で短時間の噴霧で結晶相を得た後、通常１０００〜１６００℃を超える比較的高温で長時間熱処理することが必要であり、この場合、結晶は大きく成長し、蛍光体の結晶性は良好となるが、大きな焼結した粒子となり、一次粒子が１００ｎｍ以下のような微細なナノ粒子を得ることができなかった。
【０００６】
また、蛍光体の構成金属元素と融点以上の高温反応時にフラックス成分として働く分散媒体成分を含有する溶液を用いて液滴を形成し、分散媒体の融点以上で加熱して金属塩を熱分解して蛍光体のナノ粒子を得ることが知られているが、多量の上記分散媒体をフラックスとして融点以上で反応させるので、電気炉の炉心管と溶融化合物が反応したり、分散媒体の蒸気圧がその融点以上では大きく上昇し、電気炉内で蒸気成分が反応し、炉心管を傷めたり、炉心管―反応蒸気の関係が炉の使用頻度毎に変化してしまうため、得られる蛍光体の特性が不安定になるといった問題点を有していた。（例えば、非特許文献１や非特許文献２参照。）
さらに、量産用の熱分解炉は、通常大きな口径の炉心管を用いており、液滴を同伴した気流の炉心管の直径方向の温度分布は、管径が大きくなればなるほど広くなり、均一の合成状況を実現できず安定した蛍光特性が得られない問題点を有していた。
【０００７】
また、上記のフラックス成分を用いて融点を大きく超える温度以上で合成した場合、得られる蛍光体のナノ粒子が凝結体となってしまい、粒径が１００ｎｍ以下の微小な蛍光体を得がたい場合があった。
さらに、蛍光体の場合、その粒子径と発光特性の間には相関関係があり、通常ＴＶ用等に用いられる２〜４μｍの蛍光体のＵＶ励起による輝度１００とした時、ナノ粒子のＵＶ輝度は通常３０％程度以下であった。従ってナノ粒子の場合、いかに高い発光特性を実現するかその手法の開発が求められている。
【０００８】
【非特許文献１】奥山喜久夫，ウレットレンゴロー セラミックス，３４，１０１−１０５（１９９９）
【非特許文献２】Ｂｉｎ Ｘｉａ， Ｗｕｌｅｄ Ｌｅｎｇｇｏｒｏ，奥山喜久夫 Ｍａｔｅｒｉａｌ Ｉｎｔｅｇｒａｔｉｏｎ，１４（１２），２５−２９（２００１）
【０００９】
【発明が解決しようとする課題】
本発明は、上記の問題を解消し、結晶性が高く、分散しやすいナノ粒子からなるため、ブラウン管、蛍光ランプやＰＤＰなどに用いる際に均質で緻密な高輝度蛍光膜を形成することが可能で、しかも、高純度で化学組成が均一で発光特性に優れた微小ナノ蛍光体粒子を安価に製造できる方法を提供しようとするものである。
【００１０】
【課題を解決するための手段】
本発明者らは、上記課題を解決すべく鋭意検討を重ねた結果、蛍光体の構成金属元素及び分散媒体成分を含有する溶液を同伴気体中に噴霧して微液滴を形成し、特定の温度で熱分解、及び、再加熱処理を行い、その後分散媒体成分を除去することにより、高純度で化学組成が均一で発光特性に優れた、粒径が微小な蛍光体粒子を得ることを見出し、それに基づいて本発明を完成した。
【００１１】
即ち、本発明の要旨は、蛍光体の構成金属元素及び分散媒体成分を含有する溶液を同伴気体中に噴霧して微液滴を形成し、分散媒体成分が実質的に溶融しない温度で加熱することで熱分解を行って前駆体粒子を形成した後、分散媒体成分が実質的に溶融しない温度で再加熱処理を行い、その後分散媒体成分を除去して蛍光体粒子を得ることを特徴とする蛍光体粒子の製造方法、に存する。
【００１２】
【発明の実施の形態】
以下、本発明を更に詳細に説明する。
本発明の蛍光体粒子の製造方法において、蛍光体の構成金属元素を含有する蛍光体原料は、水に可溶性を有するものであり、高温に加熱するときに酸化物や硫化物を生成し得る塩化物や硝酸塩や硫酸塩等の無機塩や有機金属化合物などを使用することができる。また、蛍光体の構成金属元素の酸化物を酸に溶解して使用することも可能である。本発明では、蛍光体の合成を容易にするために、蛍光体の構成金属元素の硝酸塩を使用することが好ましい。硝酸塩粒子は、加熱により容易に分解して蛍光体を生成しやすいからである。それ故、溶液に溶解されている金属塩の１０重量％以上が硝酸塩であることが好ましい。また、溶液に溶解されている金属塩の５０重量％以上が硝酸塩であることがより好ましい。
【００１３】
また、蛍光体の構成金属元素としては、特に制限はないが、Ｓｒ，Ｃａ，Ｂａ、Ｍｇ、Ａｌ、Ｙ、Ｖ、Ｚｎ、Ｅｕ、Ｔｍ、Ｔｂ、Ｎｄ、Ｄｙ、Ｇｄ、Ｍｎ等が挙げられる。
なお、良好な発光特性を得るためには、キラーセンターとなる鉄やニッケルなどの不純物元素の含有量の少ない蛍光体原料を使用することが好ましい。
蛍光体の構成金属元素を含有する蛍光体原料は、通常、水や酸に投入して攪拌して十分に溶解し、蛍光体原料溶液として使用される。溶液内の蛍光体原料構成金属元素濃度は、水溶液内の金属元素の溶質濃度Ｃが０．０１≦Ｃ≦５の範囲にあることが好ましい。ここで、Ｃは、水溶液１リットルに含有される全ての金属元素の合計のモル数である。溶質濃度が低すぎると、乾燥除去される水分量に対して合成できる蛍光体量が少ないために生産性が低くなる傾向にある。一方、溶質濃度が高すぎると、後に製造する微液滴が生成しにくくなる。
【００１４】
蛍光体原料溶液のｐＨは７以下に調整することが好ましく、特に５以下に調整することがより好ましい。この溶液のｐＨを７以下に適切に調整すると、均質な水溶液が形成され、噴霧により均質な液滴を形成することができるため、均質な蛍光体粒子を合成しやすい。溶液のｐＨが７を越えると、水酸化物が多量に沈殿する傾向にある。その結果、噴霧する水溶液中の蛍光体の構成金属元素の含有量が低下し、微液滴中の蛍光体原料の組成が変動するため、蛍光体結晶核が均一に発生せず蛍光体の組成が変動したり、粒径が変動する要因となり、均質で発光特性の高い蛍光体粒子を得ることができにくい。溶液に固形分が混在する場合でも、その混在割合は１０重量％以下であることが好ましく、１重量％以下がより好ましい。
【００１５】
分散媒体成分としては、分散媒体成分の融点以上の温度での高温反応時にフラックスとして作用する成分であり、具体的にはＬｉ、Ｋ、Ｎａ、Ｒｂ等のアルカリ金属のハロゲン化物、Ｍｇ、Ｂａ、Ｃａ、Ｓｒ等のアルカリ土類金属のハロゲン化物、ハロゲン化亜鉛、及び前記のアルカリ金属の硫化物の群から選ばれる少なくとも一種の化合物を使用することができ、その中でもアルカリ金属のハロゲン化物、ベリリウムを除くアルカリ土類金属の塩化物、臭化マグネシウム、フッ化亜鉛、硫化リチウム、硫化ナトリウム、及び硫化カリウムの群から選ばれる少なくとも一種の無機塩化合物を使用することが好ましい。
【００１６】
蛍光体原料及び分散媒体成分を含有する溶液は、通常、蛍光体原料溶液と分散媒体成分を混合して調整される。
分散媒体成分は、その固体の体積割合が、所望の蛍光体粒子の固体体積に対して、通常５〜１００倍となる割合で使用するのが好ましい。体積割合が小さい、すなわち、分散媒体量が少ないと凝集を招きやすくなりフラックス成分を除去しても、最初に噴霧された液滴の形骸を有した凝集した球形状粒子が得られ、１００ｎｍ以下のような微細なナノ粒子は得られにくい。また、体積割合が大きいと、フラックス成分を除去した後の蛍光体成分の割合が低下するので、体積割合は５〜２０倍が好ましく、５〜１５倍がさらに好ましい。
【００１７】
本発明の蛍光体の製造方法は、蛍光体原料及び分散媒体成分を含有し、それらが溶解された溶液を同伴気体中に噴霧し、得られた微液滴を同伴気体と共に、通常、熱分解合成炉に導入して、加熱、熱分解して所望の蛍光体を合成する際、まず、用いる分散媒体成分が実質的に溶融しない温度で熱分解を行い、多量の分散媒体成分中に、蛍光体の構成金属元素で構成される蛍光体前駆体粒子である結晶核前駆体もしくは所望の蛍光体の結晶核を形成させる。その後、分散媒体成分が実質的に溶融しない温度で再加熱処理を行い、結晶核を成長させ、結晶性を向上させて、蛍光特性に優れた微少なナノ領域（＜１００ｎｍ）の蛍光体を得るものである。
【００１８】
尚ここで、蛍光体の構成金属元素及び分散媒体成分を共に含有しそれらが溶解された溶液を同伴気体中に噴霧し、得られた微液滴を乾燥させる工程処理を行い、乾燥して得られた微粉体と同伴気体を熱分解炉に導入し熱分解をしてもよい。
同伴気体中で蛍光体原料溶液を微液滴にする方法としては、以下の方法を採用できる。例えば、加圧空気で液体を吸い上げながら噴霧して１〜５０μｍの液滴を形成する方法、圧電結晶からの２ＭＨｚ程度の超音波を利用して４〜１０μｍの液滴を形成する方法、穴径が１０〜２０μｍのオリフィスが振動子により振動し、そこへ一定の速度で供給される液体が振動数に応じて一定量ずつ穴から放出され５〜５０μｍの液滴を形成する方法、回転している円板上に液を一定速度で落下させて遠心力によって２０〜１００μｍの液滴を形成する方法、液体表面に高い電圧を引加して０．５〜１０μｍの液滴を発生する方法などが挙げられる。
【００１９】
同伴気体としては、空気、酸素、窒素、水素、少量の一酸化炭素や水素や硫化水素を含む窒素やアルゴンなどとそれらの混合気体が使用できる。良好な発光特性を得るためには、蛍光体の化学組成と発光に関与する付活剤イオンの種類により気体を選択することが重要である。例えば、酸化雰囲気で原子価を保ちやすいＥｕ^３＋等を付活イオンとする酸化物を主相とする蛍光体を合成する場合には、空気や酸素などの酸化性ガスが好ましく、還元雰囲気で原子価を保ちやすいＥｕ^２＋等を付活イオンとする酸化物を主相とする蛍光体を合成する場合には、水素、少量の水素を含む窒素やアルゴンなどの還元性ガスが好ましい。また、硫化物蛍光体や酸硫化物蛍光体を合成する際には、硫化水素を含有する同伴気体を使用することが好ましい。
【００２０】
熱分解合成炉での蛍光体の生産効率を上げるために、分級器を使用して液滴同伴気体の単位体積当たりの液滴体積を濃縮することが好ましい。分級器としては、重力分級器、遠心分級器、慣性分級器などが使用し得る。しかし、微液滴を同伴した気体から、気体の一部と共に上記の液滴径の下限未満の微液滴を除去して、液滴同伴気体の単位体積当たりの液滴体積を濃縮するためには、慣性分級器が好適である。
【００２１】
微液滴は、直接、熱分解に供してもよく、予め乾燥してもよい。熱分解の前に、微液滴を乾燥させる場合、微液滴の乾燥方法としては、凍結乾燥、減圧乾燥、拡散乾燥、加熱乾燥などが採用できる。しかし、凍結乾燥や減圧乾燥などと比較して加熱乾燥が工業的生産性において優れている。尚、乾燥は、微液滴を熱分解温度まで昇温する過程において行ってもよい。乾燥して得られる分散媒体成分を含む固体状蛍光体原料粒子の温度は、熱分解前に１００℃以上に保持することが好ましい。この温度が熱分解前に１００℃未満になると乾燥時に発生した水蒸気が凝縮して固体状蛍光体原料を部分的に再溶解するため、所望の形状や粒径の蛍光体粒子を得ることができない。また、乾燥と熱分解を同時に連続的に電気炉内で実施する手法が、より生産性が向上する観点からより好ましい。
【００２２】
熱分解においては、分散媒体成分が実質的に溶融しない温度で加熱するが、炉内の滞留時間は通常１秒程度以下と非常に短いので実質的に溶融しない温度とは、融点をＴｍ（℃）とした場合、（Ｔｍ＋３０）℃程度が上限である。さらに蛍光体の前駆体粒子である、結晶核前駆体もしくは結晶核を形成させるためには、熱分解温度Ｔ１（℃）は、通常、融点Ｔｍ（℃）を基準にして（Ｔｍ−２００）℃以上、好ましく（Ｔｍ−１００）℃以上、更に好ましくは（Ｔｍ−５０）℃以上であり、上限は、（Ｔｍ＋３０）℃以下、好ましくはＴｍ（℃）以下の温度である。
【００２３】
熱分解炉での最高温度域での熱分解反応時間は、通常、０．０１秒間以上１分間以下の範囲内の時間で行われる。中でも下限としては０．０３秒間以上、上限としては１０秒間以下の時間で行うのが好ましい。短すぎると、結晶核前駆体や結晶核が生成しにくく、長すぎると、粒径が成長し、例えば一次粒子径が１００ｎｍ以上となりナノ粒子が得難くなる。
【００２４】
噴霧熱分解工程において、前記分散媒体の融点以上で反応処理を実施した場合、温度が高いほど、電気炉の炉心管と分散媒体フラックス溶融化合物粒子が反応し、炉心管に付着物を形成したり、激しい場合は、炉心管が目詰まりを起こしたり、また、蒸気圧が融点以上では大きく上昇して電気炉内で蒸気成分が反応し、炉心管を傷めたり、炉心管−蒸気の間の化学反応の状況が、炉の使用頻度毎に変化し、得られる蛍光体の発光特性が不安定になるといった問題点があるが、この手法を採用することによってこれらの問題を解決できる。
【００２５】
前記噴霧熱分解により得られた蛍光体前駆体粒子と分散媒体成分を含む１次熱分解粒子は、電気集塵器などで捕集した後、分散媒体成分が実質的に溶融しない温度で再加熱処理を行う。
再加熱処理温度Ｔ２（℃）は、分散媒体成分が実質的に溶融しない温度で行われるが、具体的には、分散媒体成分の融点Ｔｍ（℃）を基準にして、通常（Ｔｍ−２００）℃以上、好ましくは（Ｔｍ−５０）℃以上、さらに好ましくは（Ｔｍ−３０）℃以上であり、上限は、通常（Ｔｍ＋３０）℃以下、好ましくはＴｍ（℃）以下である。
【００２６】
再加熱処理時間は、通常、１秒以上、好ましくは３０秒以上であり、上限は通常１時間以下、好ましくは３０分以下である。短すぎると、結晶核前駆体もしくは結晶核の成長が十分ではなく、長すぎると粒成長が促進され、例えば一次粒径が１００ｎｍ以上となり、ナノ粒子を得難くなる。
融点近傍付近の状態を利用して、分散媒体を介しての原子の拡散状態を向上せしめることによって、上記の状態の分散媒体中に存在する蛍光体の前駆体粒子である、結晶核前駆体もしくは結晶核の成長を促進させ、その結晶性を向上させて従来の融点以上の噴霧熱分解法によって得られる蛍光体ナノ粒子に比べて発光性能の優れた蛍光体ナノ粒子を合成することが可能である。
【００２７】
分散媒体として水溶性の無機塩を使用するときには、分散媒体中で蛍光体を合成した後、水系溶液で分散媒体を溶解して容易に除去する。また、有機溶媒に可溶な無機塩を使用する場合は、当該無機塩に溶解可溶な有機溶媒を用いて分散媒体を除去してもよい。
本発明で得られる蛍光体としては、Ｅｕ、Ｔｍ、Ｔｂ、Ｎｄ、Ｇｄ、Ｄｙ、Ｍｎ等で付活してなるＹ_２Ｏ_３系蛍光体、Ｙ_２Ｏ_２Ｓ系蛍光体、ＺｎＳ系蛍光体、ＣａＳ系蛍光体、ＢａＡｌ_１２Ｏ_１９系蛍光体、ＢａＭｇＡｌ_１０Ｏ_１７系蛍光体、ＣａＡｌ_２Ｏ_４系蛍光体、ＳｒＡｌ_２Ｏ_４系蛍光体、Ｓｒ_４Ａｌ_１４Ｏ_２５系蛍光体等があり、一次粒子の粒径が通常１〜１００ｎｍの蛍光体粒子となる。
【００２８】
【実施例】
以下、本発明を実施例により更に詳細に説明する。
（実施例１）
蛍光体の化学組成が（Ｙ_０．９４，Ｅｕ_０．０６）_２Ｏ_３となるように酸化イットリウムＹ_２Ｏ_３と酸化ユーロピウムＥｕ_２Ｏ_３を硝酸水溶液にまず溶解し、さらに（Ｙ_０．９４，Ｅｕ_０．０６）_２Ｏ_３蛍光体の固体体積に対して１０倍の固体体積となるように分散媒体成分である塩化カリウム（融点：７７６℃）を添加し溶解、硝酸イットリウムユーロピウムとして溶質濃度Ｃが０．１モル／ｋｇの均質な水溶液を調製した。
【００２９】
同伴気体として空気を使用し、この水溶液を１．７ＭＨｚの振動子を有する超音波噴霧器に入れて噴霧を行い平均粒径５μｍの微液滴を形成させた。
この微液滴を縦型管状型電気炉の中に同伴気体とともに導入し、最高温度７００℃にて０．３秒間、噴霧熱分解して蛍光体前駆体粒子及び分散媒体成分の混合物粉体粒子（１次熱分解粒子）を得た。得られた粒子は−１８ｋｖの高電圧を印加して電気集塵機にて捕集した。
【００３０】
その後、電気集塵器で捕集し得られた上記粉体を７７０℃で１分間再加熱処理を行った。得られた微粉末中の分散媒体成分を水洗除去処理した後、粉末Ｘ線回折を行った所、分散媒体成分等不純物相のない所望の（Ｙ_０．９４，Ｅｕ_{０．０ ６}）_２Ｏ_３結晶のみが観測された。得られた微細粒子はＴＥＭ・ＳＥＭを用いて一次粒子の大きさを観察した。
【００３１】
この蛍光体について、波長２５４ｎｍの紫外線を照射して発光スペクトルを測定した。
発光強度（ＵＶ輝度）は、市販の一次粒子径３μｍの同組成の物を標準サンプルとして用いて測定し比較した。その結果を表−１に示す。
【００３２】
この噴霧実験を繰り返して行ったが、炉心管等との反応は観測されなかった。
（実施例２）
蛍光体の化学組成が（Ｙ_０．９４，Ｅｕ_０．０６）_２Ｏ_３となるように酸化イットリウムＹ_２Ｏ_３と酸化ユーロピウムＥｕ_２Ｏ_３を硝酸水溶液にまず溶解し、さらに（Ｙ_０．９４，Ｅｕ_０．０６）_２Ｏ_３蛍光体の固体体積に対して１０倍の固体体積となるように分散媒体成分である塩化ナトリウム（融点：８０１℃）を添加し溶解、硝酸イットリウムユーロピウムとして溶質濃度Ｃが０．１モル／ｋｇの均質な水溶液を調製した。
【００３３】
同伴気体として空気を使用し、この水溶液を１．７ＭＨｚの振動子を有する超音波噴霧器に入れて噴霧を行い平均粒径５μｍの微液滴を形成させた。
この微液滴を縦型管状型電気炉の中に同伴気体とともに導入し、最高温度８００℃にて０．２８秒間、噴霧熱分解して蛍光体前駆体粒子及び分散媒体成分の混合物粉体粒子（１次熱分解粒子）を得た。得られた粒子は−１８ｋｖの高電圧を印加して電気集塵機にて捕集した。
【００３４】
その後、電気集塵器で捕集し得られた上記粉体を７７０℃で１分間再加熱処理を行った。得られた微粉末中の分散媒体成分を水洗除去処理した後、粉末Ｘ線回折を行った所、分散媒体成分等不純物相のない所望の（Ｙ_０．９４，Ｅｕ_０．０６）_２Ｏ_３結晶のみが観測された。得られた微細粒子を実施例１と同様にして評価した。
【００３５】
この噴霧実験を繰り返しおこなったが、炉心管等との反応は観測されなかった。
（比較例１）
実施例１と同様にして微液滴を形成させ、この微液滴を縦型管状型電気炉の中に同伴気体とともに導入し、最高温度７００℃にて０．３秒間、噴霧熱分解して蛍光体粒子及び分散媒体成分の混合物粉体粒子を得た。得られた粒子は−１８ｋｖの高電圧を印加して電気集塵機にて捕集した。
【００３６】
得られた粉体中の分散媒体成分を水洗除去処理した後、粉末Ｘ線回折を行った所、分散媒体成分等不純物相のない所望の（Ｙ_０．９４，Ｅｕ_０．０６）_２Ｏ_３結晶のみが観測された。得られた微細粒子を、実施例１と同様に評価した。
この実験を繰り返して行ったところ、炉心管等との反応は観測されなかった。
（比較例２）
実施例１と同様にして微液滴を形成させ、この微液滴を縦型管状型電気炉の中に同伴空気とともに導入し、最高温度１０００℃にて０．２４秒間、噴霧熱分解して蛍光体粒子及び分散媒体成分の混合物粉体粒子を得た。得られた粒子は−１８ｋｖの高電圧を印加して電気集塵機にて捕集した。
【００３７】
得られた粉体中の分散媒体成分を水洗除去処理した後、粉末Ｘ線回折を行った所、分散媒体成分や不純物相のない所望の（Ｙ_０．９４，Ｅｕ_０．０６）_２Ｏ_３結晶のみが観測された。得られた微細粒子を、実施例１と同様に評価した。
この実験を繰り返して行ったところ、炉心管に分散媒体成分由来の付着物が多量について成長してくることを確認した。
【００３８】
ＳＥＭ、ＴＥＭを用い一次粒子の大きさを調べたところ、実施例１、２と比較例１では５０ｎｍ以下のナノ粒子であったが、比較例２では、４０〜１００ｎｍ、１００ｎｍ以上のものも混在していた。ＵＶ輝度評価は、市販のＥｕ＝６ｍｏｌ％で付活したＹ_２Ｏ_３蛍光体（同一組成品）で粒径３μｍのものの輝度を１００％として比較した。
表−１に示すように実施例１、２は比較例１〜２に比べて高い発光特性を示した。
【００３９】
【表１】

【００４０】
【発明の効果】
本発明は、上記の構成を採用することにより、電気炉等合成装置を傷めることなく、結晶性に優れて、凝集粒子が少なく、高純度で化学組成が均一で、発光特性の優れた１００ｎｍ以下の微小蛍光体粒子を得ることが可能となり、ブラウン管、蛍光ランプやＰＤＰなどに適用するときに均質で緻密な高輝度蛍光膜を安価に提供できる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing fine phosphor particles that can be used for a cathode ray tube, a fluorescent lamp, a plasma display panel (PDP), and the like, and particularly relates to a method for producing nanoparticle phosphors having a primary particle diameter of 100 nm or less.
[0002]
[Prior art]
Conventionally, phosphors used in cathode ray tubes, fluorescent lamps, PDPs, etc., are prepared by mixing raw material powders in a firing vessel such as a crucible and then heating at a high temperature for a long time to cause a solid phase reaction. It has been manufactured by finely pulverizing with a ball mill or the like.
[0003]
However, since the phosphor produced by this method is composed of a powder in which irregularly shaped particles are aggregated, the phosphor film obtained by applying this phosphor has a non-uniform and low packing density, and has low light emission characteristics. Was. In addition, since a physical and chemical impact is applied to the phosphor during the fine pulverization treatment by a ball mill or the like after the solid-phase reaction, defects are generated in the particles and on the surface, and the emission intensity is reduced. Was. In addition, since it is placed in a firing vessel such as a crucible and heated at a high temperature for a long time, impurities from the crucible are mixed and the light emission characteristics are reduced, or the solid phase reaction does not proceed sufficiently depending on the particle size of the raw material powder. In some cases, the impurity phase is mixed, resulting in deterioration of the light emission characteristics. Further, heating at a high temperature for a long time increases energy consumption, which is a factor that increases the manufacturing cost of the phosphor.
[0004]
To solve these problems, a solution containing the metal elements of the phosphor is sprayed into the accompanying gas with an ultrasonic nebulizer to form fine droplets, which are then dried to form metal salt particles or metal complex particles. A method has been proposed in which a phosphor is obtained by performing pyrolysis synthesis by introducing the metal salt particles and metal complex particles together with accompanying gas into a pyrolysis synthesis furnace and heating. However, in this method, since the residence time in the pyrolysis synthesis furnace cannot be sufficiently long, the crystallinity of the phosphor is low and activator ions cannot be uniformly activated in the crystal. As a result, there is a problem that a phosphor having good emission characteristics cannot be obtained.
[0005]
Therefore, in order to solve this problem, a metal salt particle or a metal complex particle is thermally decomposed at a relatively low temperature for a short time to obtain a powder having a desired crystal phase. A two-stage heat treatment method has been proposed in which a phosphor is finally obtained by reheating at a relatively high temperature for a long time. According to this method, activator ions can be uniformly activated in the crystal at the same time as the crystallinity of the particles obtained by thermal decomposition is further increased, so that a spherical phosphor having good emission characteristics can be obtained. However, after obtaining a crystal phase by spraying at a relatively low temperature for a short time, it is necessary to perform a heat treatment at a relatively high temperature usually exceeding 1000 to 1600 ° C. for a long time. Although the crystallinity was good, large sintered particles were obtained, and it was not possible to obtain fine nanoparticles having primary particles of 100 nm or less.
[0006]
In addition, droplets are formed using a solution containing a dispersing medium component that acts as a flux component during a high-temperature reaction with the constituent metal elements of the phosphor and a melting point or higher, and the metal salt is thermally decomposed by heating at a temperature equal to or higher than the melting point of the dispersing medium. It is known to obtain phosphor nanoparticles, but since a large amount of the dispersion medium is reacted as a flux at a temperature equal to or higher than the melting point, the furnace furnace tube of the electric furnace reacts with the molten compound, or the vapor pressure of the dispersion medium decreases. Above its melting point, the temperature rises significantly, and the vapor component reacts in the electric furnace, damaging the furnace tube, and the relationship between the furnace tube and the reaction vapor changes with each use of the furnace. However, there was a problem that the data became unstable. (For example, see Non-Patent Document 1 and Non-Patent Document 2.)
Furthermore, pyrolysis furnaces for mass production generally use large-diameter core tubes, and the temperature distribution in the diametrical direction of the core flow of the air flow accompanied by droplets becomes wider as the tube diameter increases, and becomes uniform. There was a problem that a synthesis state could not be realized and stable fluorescent characteristics could not be obtained.
[0007]
Also, when the above-mentioned flux component is used to synthesize at a temperature much higher than the melting point, the resulting phosphor nanoparticles become aggregates, and it may be difficult to obtain a fine phosphor having a particle size of 100 nm or less. Was.
Further, in the case of a phosphor, there is a correlation between the particle diameter and the emission characteristics. When the luminance of a phosphor of 2 to 4 μm usually used for TV and the like is set to 100 by UV excitation, the UV luminance of nanoparticles is Was usually about 30% or less. Therefore, in the case of nanoparticles, it is required to develop a method for achieving high emission characteristics.
[0008]
[Non-Patent Document 1] Kikuo Okuyama, Uret Lengolo ceramics, 34, 101-105 (1999)
[Non-Patent Document 2] Bin Xia, Wuled Lengoro, Kikuo Okuyama Material Integration, 14 (12), 25-29 (2001)
[0009]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems, and since it is composed of nanoparticles having high crystallinity and being easily dispersed, it is possible to form a uniform and dense high-luminance phosphor film when used in a cathode ray tube, a fluorescent lamp, a PDP, or the like. Another object of the present invention is to provide a method for inexpensively producing fine nanophosphor particles having a high purity, a uniform chemical composition, and excellent emission characteristics.
[0010]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, sprayed a solution containing the constituent metal elements of the phosphor and the dispersion medium component into the accompanying gas to form fine droplets, By conducting thermal decomposition and reheating at a temperature, and then removing the dispersing medium component, we found that phosphor particles with high purity, uniform chemical composition, excellent emission characteristics, and small particle size can be obtained. Based on this, the present invention has been completed.
[0011]
That is, the gist of the present invention is that a solution containing the constituent metal element of the phosphor and the dispersion medium component is sprayed into the accompanying gas to form fine droplets, and heating is performed at a temperature at which the dispersion medium component does not substantially melt. After the precursor particles are formed by performing thermal decomposition by performing the reheating treatment at a temperature at which the dispersion medium component does not substantially melt, and thereafter, the dispersion medium component is removed to obtain phosphor particles. A method for producing phosphor particles.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail.
In the method for producing the phosphor particles of the present invention, the phosphor raw material containing the constituent metal elements of the phosphor is soluble in water, and is capable of forming oxides and sulfides when heated to a high temperature. Inorganic salts such as substances, nitrates and sulfates, and organic metal compounds can be used. Further, it is also possible to use the oxide of the metal element constituting the phosphor dissolved in an acid. In the present invention, it is preferable to use a nitrate of a metal element constituting the phosphor in order to facilitate the synthesis of the phosphor. This is because nitrate particles are easily decomposed by heating to easily generate a phosphor. Therefore, it is preferable that 10% by weight or more of the metal salt dissolved in the solution is a nitrate. More preferably, 50% by weight or more of the metal salt dissolved in the solution is a nitrate.
[0013]
The constituent metal elements of the phosphor are not particularly limited, but include Sr, Ca, Ba, Mg, Al, Y, V, Zn, Eu, Tm, Tb, Nd, Dy, Gd, Mn, and the like. .
Note that, in order to obtain good emission characteristics, it is preferable to use a phosphor raw material having a small content of impurity elements such as iron and nickel serving as a killer center.
The phosphor raw material containing the constituent metal element of the phosphor is usually put into water or an acid, stirred and sufficiently dissolved to be used as a phosphor raw material solution. The concentration of the metal element constituting the phosphor raw material in the solution is preferably such that the solute concentration C of the metal element in the aqueous solution is in the range of 0.01 ≦ C ≦ 5. Here, C is the total number of moles of all metal elements contained in one liter of the aqueous solution. If the solute concentration is too low, the productivity tends to be low because the amount of phosphor that can be synthesized with respect to the amount of water to be dried and removed is small. On the other hand, when the solute concentration is too high, it is difficult to generate fine droplets to be manufactured later.
[0014]
The pH of the phosphor raw material solution is preferably adjusted to 7 or less, more preferably to 5 or less. When the pH of this solution is appropriately adjusted to 7 or less, a homogeneous aqueous solution is formed, and uniform droplets can be formed by spraying, so that uniform phosphor particles are easily synthesized. When the pH of the solution exceeds 7, a large amount of hydroxide tends to precipitate. As a result, the content of the constituent metal elements of the phosphor in the aqueous solution to be sprayed is reduced, and the composition of the phosphor raw material in the fine droplets fluctuates. Of the phosphor particles and the variation of the particle diameter, and it is difficult to obtain uniform phosphor particles having high emission characteristics. Even when the solid content is mixed in the solution, the mixing ratio is preferably 10% by weight or less, more preferably 1% by weight or less.
[0015]
The dispersion medium component is a component that acts as a flux during a high-temperature reaction at a temperature equal to or higher than the melting point of the dispersion medium component. Specifically, halides of alkali metals such as Li, K, Na, and Rb, Mg, Ba, At least one compound selected from the group consisting of halides of alkaline earth metals such as Ca and Sr, zinc halides, and sulfides of the aforementioned alkali metals can be used. Among them, alkali metal halides, beryllium It is preferable to use at least one inorganic salt compound selected from the group consisting of alkaline earth metal chlorides, magnesium bromide, zinc fluoride, lithium sulfide, sodium sulfide, and potassium sulfide, excluding the following.
[0016]
The solution containing the phosphor material and the dispersion medium component is usually prepared by mixing the phosphor material solution and the dispersion medium component.
The dispersing medium component is preferably used in such a proportion that the volume ratio of the solid is usually 5 to 100 times the solid volume of the desired phosphor particles. Even when the volume ratio is small, that is, when the amount of the dispersion medium is small, aggregation is likely to occur and the flux component is removed, aggregated spherical particles having the shape of droplets sprayed first are obtained, and the particle size is 100 nm or less. Such fine nanoparticles are difficult to obtain. Further, if the volume ratio is large, the ratio of the phosphor component after removing the flux component decreases, so the volume ratio is preferably 5 to 20 times, more preferably 5 to 15 times.
[0017]
The method for producing a phosphor of the present invention comprises the steps of: containing a phosphor raw material and a dispersion medium component; spraying a solution in which these are dissolved in an entrained gas; When introduced into a synthesis furnace and heated and thermally decomposed to synthesize a desired phosphor, first, thermal decomposition is performed at a temperature at which the dispersing medium component to be used does not substantially melt, and a large amount of fluorescent medium is dispersed in the dispersing medium component. A crystal nucleus precursor, which is a phosphor precursor particle composed of a constituent metal element of the body, or a crystal nucleus of a desired phosphor is formed. Thereafter, a reheating treatment is performed at a temperature at which the dispersion medium component does not substantially melt to grow crystal nuclei, improve crystallinity, and obtain a fine nano-range (<100 nm) phosphor excellent in fluorescence characteristics. Things.
[0018]
Here, a process in which both the constituent metal element of the phosphor and the dispersing medium component are contained and the solution in which they are dissolved is sprayed into the accompanying gas, and the resulting fine droplets are subjected to a process treatment for drying, and then dried. The obtained fine powder and accompanying gas may be introduced into a pyrolysis furnace to perform pyrolysis.
The following method can be employed as a method for forming the phosphor raw material solution into fine droplets in the accompanying gas. For example, a method of forming droplets of 1 to 50 μm by spraying while sucking up liquid with pressurized air, a method of forming droplets of 4 to 10 μm using ultrasonic waves of about 2 MHz from a piezoelectric crystal, a hole diameter A method in which an orifice of 10 to 20 μm is vibrated by a vibrator, and a liquid supplied thereto at a constant speed is discharged from a hole by a constant amount according to the frequency to form a droplet of 5 to 50 μm, A method in which a liquid is dropped at a constant speed on a circular plate to form droplets of 20 to 100 μm by centrifugal force, a method of applying a high voltage to the surface of the liquid to generate droplets of 0.5 to 10 μm, etc. Is mentioned.
[0019]
As the entrained gas, air, oxygen, nitrogen, hydrogen, a small amount of carbon monoxide, hydrogen, or nitrogen or argon containing hydrogen sulfide, and a mixed gas thereof can be used. In order to obtain good emission characteristics, it is important to select a gas according to the chemical composition of the phosphor and the type of activator ions involved in emission. For example, in the case of synthesizing a phosphor having an oxide having a main phase of Eu ³⁺ or the like as an activating ion which easily maintains a valence in an oxidizing atmosphere, an oxidizing gas such as air or oxygen is preferable. In the case of synthesizing a phosphor whose main phase is an oxide having Eu ²⁺ or the like as an activating ion, which is easy to maintain its value, hydrogen, a reducing gas such as nitrogen or argon containing a small amount of hydrogen is preferable. Further, when synthesizing a sulfide phosphor or an oxysulfide phosphor, it is preferable to use an accompanying gas containing hydrogen sulfide.
[0020]
In order to increase the production efficiency of the phosphor in the pyrolysis synthesis furnace, it is preferable to use a classifier to concentrate the droplet volume per unit volume of the droplet-entrained gas. As a classifier, a gravity classifier, a centrifugal classifier, an inertial classifier, or the like can be used. However, in order to concentrate the droplet volume per unit volume of the droplet-entrained gas by removing the droplets having a diameter smaller than the lower limit of the droplet diameter together with a part of the gas from the gas accompanied by the droplets, Is preferably an inertial classifier.
[0021]
The microdroplets may be directly subjected to thermal decomposition or may be dried in advance. When the microdroplets are dried before the thermal decomposition, freeze drying, reduced-pressure drying, diffusion drying, heat drying, and the like can be adopted as a method for drying the microdroplets. However, heat drying is superior to freeze drying and reduced pressure drying in terms of industrial productivity. The drying may be performed in the process of raising the temperature of the microdroplets to the thermal decomposition temperature. The temperature of the solid phosphor raw material particles containing the dispersion medium component obtained by drying is preferably maintained at 100 ° C. or higher before thermal decomposition. If the temperature is lower than 100 ° C. before the thermal decomposition, water vapor generated during drying condenses and partially redissolves the solid phosphor raw material, so that phosphor particles having a desired shape and particle size cannot be obtained. . Further, a method in which drying and thermal decomposition are simultaneously and continuously performed in an electric furnace is more preferable from the viewpoint of further improving productivity.
[0022]
In the thermal decomposition, heating is performed at a temperature at which the dispersion medium component does not substantially melt. However, since the residence time in the furnace is very short, usually about 1 second or less, the melting temperature is defined as Tm (° C.). ), The upper limit is about (Tm + 30) ° C. Further, in order to form a crystal nucleus precursor or a crystal nucleus, which is a phosphor precursor particle, the thermal decomposition temperature T1 (° C) is usually (Tm-200) ° C based on the melting point Tm (° C). The temperature is preferably (Tm-100) ° C or higher, more preferably (Tm-50) ° C or higher, and the upper limit is (Tm + 30) ° C or lower, preferably Tm (° C) or lower.
[0023]
The pyrolysis reaction time in the highest temperature range in the pyrolysis furnace is usually performed in a time period within a range from 0.01 seconds to 1 minute. Above all, it is preferable to perform the treatment for a time of 0.03 seconds or more as a lower limit and 10 seconds or less as an upper limit. If the length is too short, a crystal nucleus precursor or a crystal nucleus is not easily generated, and if it is too long, the particle size grows, for example, the primary particle size becomes 100 nm or more, making it difficult to obtain nanoparticles.
[0024]
In the spray pyrolysis step, when the reaction treatment is carried out at a temperature equal to or higher than the melting point of the dispersion medium, the higher the temperature, the more the furnace core tube of the electric furnace and the dispersion medium flux molten compound particles react to form deposits on the furnace core tube. In severe cases, the core tube may be clogged, and if the vapor pressure is higher than the melting point, the steam component reacts in the electric furnace to damage the core tube, or the chemical between the core tube and steam may be damaged. There is a problem that the state of the reaction changes every time the furnace is used, and the emission characteristics of the obtained phosphor become unstable. These problems can be solved by employing this method.
[0025]
The primary pyrolysis particles containing the phosphor precursor particles and the dispersion medium component obtained by the spray pyrolysis are collected by an electrostatic precipitator and then reheated at a temperature at which the dispersion medium component does not substantially melt. Perform processing.
The reheating temperature T2 (° C.) is performed at a temperature at which the dispersing medium component does not substantially melt. Specifically, the reheating temperature T2 (° C.) is usually (Tm−200) based on the melting point Tm (° C.) of the dispersing medium component. ° C or higher, preferably (Tm-50) ° C or higher, more preferably (Tm-30) ° C or higher, and the upper limit is usually (Tm + 30) ° C or lower, preferably Tm (° C) or lower.
[0026]
The reheating time is usually at least 1 second, preferably at least 30 seconds, and the upper limit is usually at most 1 hour, preferably at most 30 minutes. If it is too short, the growth of the crystal nucleus precursor or crystal nucleus is not sufficient, and if it is too long, the grain growth is promoted, for example, the primary particle size becomes 100 nm or more, and it becomes difficult to obtain nanoparticles.
By utilizing the state in the vicinity of the melting point, by improving the diffusion state of atoms through the dispersion medium, the precursor particles of the phosphor present in the dispersion medium in the above state, a crystal nucleus precursor or By promoting the growth of crystal nuclei and improving its crystallinity, it is possible to synthesize phosphor nanoparticles with superior luminescence performance compared to phosphor nanoparticles obtained by the conventional spray pyrolysis method above the melting point. is there.
[0027]
When a water-soluble inorganic salt is used as the dispersion medium, the phosphor is synthesized in the dispersion medium, and then the dispersion medium is dissolved in an aqueous solution and easily removed. When an inorganic salt soluble in an organic solvent is used, the dispersion medium may be removed using an organic solvent soluble in the inorganic salt.
The phosphor obtained in the present invention, Eu, Tm, Tb, Nd , Gd, Dy, activated to become _Y 2 _{O 3} phosphor in Mn or the _like, Y _{2 O} 2 S phosphor, ZnS-based fluorescent body, CaS-based _{phosphor, BaAl} 12 _{O 19} phosphor, _BaMgAl 10 _{O 17} phosphor, CaAl ₂ O ₄ phosphor, SrAl ₂ O _{4 phosphor,} Sr _{4 Al} 14 _{O 25} phosphor and the like Yes, the primary particles are usually phosphor particles having a particle size of 1 to 100 nm.
[0028]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples.
(Example 1)
Yttrium oxide Y ₂ O ₃ and europium oxide Eu ₂ O ₃ are first dissolved in a nitric acid aqueous solution so that the chemical composition of the phosphor becomes (Y _0.94 , Eu _0.06 ) ₂ O _3, and then (Y _{0. 94} , Eu _0.06 ) ₂ O ₃ Phosphor is added and dissolved by adding potassium chloride (melting point: 776 ° C.) as a dispersing medium component so as to have a solid volume 10 times as large as the solid volume of the phosphor. A homogeneous aqueous solution having a concentration C of 0.1 mol / kg was prepared.
[0029]
Using air as an entrained gas, this aqueous solution was put into an ultrasonic atomizer having a 1.7 MHz vibrator and sprayed to form fine droplets having an average particle size of 5 μm.
The fine droplets are introduced into a vertical tubular electric furnace together with the accompanying gas, and spray pyrolysis is performed at a maximum temperature of 700 ° C. for 0.3 seconds to obtain a mixture of phosphor precursor particles and a dispersion medium component powder particles. (Primary pyrolysis particles) were obtained. The obtained particles were collected with an electric dust collector by applying a high voltage of -18 kv.
[0030]
Thereafter, the powder collected by the electrostatic precipitator was reheated at 770 ° C. for 1 minute. The resulting was washed with water removal treatment the dispersing medium component in the fine powder, and by performing powder X-ray diffraction, dispersion media components such impurity phases without the desired _{(Y 0.94, Eu 0.0 6)} 2 O Only _three crystals were observed. The size of the primary particles of the obtained fine particles was observed using a TEM / SEM.
[0031]
This phosphor was irradiated with ultraviolet light having a wavelength of 254 nm, and the emission spectrum was measured.
The emission intensity (UV luminance) was measured using a commercially available product of the same composition having a primary particle diameter of 3 μm as a standard sample and compared. Table 1 shows the results.
[0032]
This spraying experiment was repeated, but no reaction with the furnace tube or the like was observed.
(Example 2)
Yttrium oxide Y ₂ O ₃ and europium oxide Eu ₂ O ₃ are first dissolved in a nitric acid aqueous solution so that the chemical composition of the phosphor becomes (Y _0.94 , Eu _0.06 ) ₂ O _3, and then (Y _0. Sodium chloride (melting point: 801 ° C.) as a dispersing medium component is added and dissolved so that the solid volume becomes 10 times the solid volume of the ₉₄ , Eu _0.06 ) ₂ O ₃ phosphor, and the solute is converted into yttrium europium nitrate. A homogeneous aqueous solution having a concentration C of 0.1 mol / kg was prepared.
[0033]
Using air as an entrained gas, this aqueous solution was put into an ultrasonic atomizer having a 1.7 MHz vibrator and sprayed to form fine droplets having an average particle size of 5 μm.
The fine droplets are introduced into a vertical tubular electric furnace together with the accompanying gas, and spray pyrolysis is performed at a maximum temperature of 800 ° C. for 0.28 seconds to obtain a mixture of phosphor precursor particles and a dispersion medium component powder particles. (Primary pyrolysis particles) were obtained. The obtained particles were collected with an electric dust collector by applying a high voltage of -18 kv.
[0034]
Thereafter, the powder collected by the electrostatic precipitator was reheated at 770 ° C. for 1 minute. After the dispersion medium component in the obtained fine powder was washed and removed with water, powder X-ray diffraction was performed. As a result, desired (Y _0.94 , Eu _0.06 ) ₂ O _{3 having} no impurity phase such as the dispersion medium component was _observed . Only crystals were observed. The obtained fine particles were evaluated in the same manner as in Example 1.
[0035]
This spraying experiment was repeated, but no reaction with the furnace tube or the like was observed.
(Comparative Example 1)
Fine droplets were formed in the same manner as in Example 1, and the fine droplets were introduced together with the accompanying gas into a vertical tubular electric furnace, and spray pyrolyzed at a maximum temperature of 700 ° C. for 0.3 seconds. Mixture powder particles of the phosphor particles and the dispersion medium component were obtained. The obtained particles were collected with an electric dust collector by applying a high voltage of -18 kv.
[0036]
After the dispersion medium component in the obtained powder was washed with water and removed, powder X-ray diffraction was performed. As a result, desired (Y _0.94 , Eu _0.06 ) ₂ O _{3 having} no impurity phase such as the dispersion medium component was _observed . Only crystals were observed. The obtained fine particles were evaluated in the same manner as in Example 1.
When this experiment was repeated, no reaction with the furnace tube or the like was observed.
(Comparative Example 2)
Fine droplets were formed in the same manner as in Example 1, and the fine droplets were introduced into a vertical tubular electric furnace together with entrained air, and subjected to spray pyrolysis at a maximum temperature of 1000 ° C. for 0.24 seconds. Mixture powder particles of the phosphor particles and the dispersion medium component were obtained. The obtained particles were collected with an electric dust collector by applying a high voltage of -18 kv.
[0037]
After the dispersion medium component in the obtained powder was washed with water and removed, the powder was subjected to X-ray diffraction. As a result, the desired (Y _0.94 , Eu _0.06 ) ₂ O ₃ free of the dispersion medium component and the impurity phase was obtained. Only crystals were observed. The obtained fine particles were evaluated in the same manner as in Example 1.
By repeating this experiment, it was confirmed that a large amount of deposits derived from the dispersion medium component grew on the furnace tube.
[0038]
When the size of the primary particles was examined using SEM and TEM, the nanoparticles were 50 nm or less in Examples 1 and 2 and Comparative Example 1, but those of 40 to 100 nm and 100 nm or more were mixed in Comparative Example 2. Was. The UV luminance was evaluated by comparing the luminance of a commercially available Y ₂ O ₃ phosphor (of the same composition) activated with Eu = 6 mol% with a particle size of 3 μm as 100%.
As shown in Table 1, Examples 1 and 2 exhibited higher emission characteristics than Comparative Examples 1 and 2.
[0039]
[Table 1]

[0040]
【The invention's effect】
The present invention adopts the above configuration, without damaging the synthesizing apparatus such as an electric furnace, is excellent in crystallinity, has few agglomerated particles, is highly pure, has a uniform chemical composition, and has excellent emission characteristics of 100 nm or less. Can be obtained, and when applied to a cathode ray tube, a fluorescent lamp, a PDP, or the like, a uniform and dense high-luminance fluorescent film can be provided at low cost.

Claims (5)

蛍光体の構成金属元素を含有する蛍光体原料、及び分散媒体成分を含有する溶液を同伴気体中に噴霧して蛍光体原料と分散媒体成分を含有する微液滴を形成し、該微液滴を直接又は乾燥後、分散媒体成分が実質的に溶融しない温度で加熱することで熱分解を行って蛍光体前駆体粒子と分散媒体成分を含む１次熱分解粒子を得、該１次熱分解粒子を分散媒体成分が実質的に溶融しない温度で再加熱処理を行い、その後分散媒体成分を除去して蛍光体粒子を得ることを特徴とする蛍光体粒子の製造方法。A solution containing a phosphor material containing a metal element constituting the phosphor and a dispersion medium component is sprayed into an accompanying gas to form fine droplets containing the phosphor material and a dispersion medium component, Is directly or dried, and then heated at a temperature at which the dispersion medium component does not substantially melt, thereby performing thermal decomposition to obtain primary pyrolyzed particles containing the phosphor precursor particles and the dispersion medium component. A method for producing phosphor particles, wherein the particles are subjected to a reheating treatment at a temperature at which the dispersion medium component does not substantially melt, and then the dispersion medium component is removed to obtain phosphor particles. 熱分解する温度Ｔ１（℃）が、分散媒体成分の融点Ｔｍ（℃）に対して、Ｔｍ−２００≦Ｔ１≦Ｔｍ＋３０であることを特徴とする請求項１に記載の蛍光体粒子の製造方法。2. The method for producing phosphor particles according to claim 1, wherein the temperature T1 (° C.) at which the thermal decomposition is performed is Tm−200 ≦ T1 ≦ Tm + 30 with respect to the melting point Tm (° C.) of the dispersion medium component. 再加熱処理温度Ｔ２（℃）が、分散媒体成分の融点Ｔｍ（℃）に対して、Ｔｍ−２００≦Ｔ２≦Ｔｍ＋３０であることを特徴とする請求項１又は２に記載の蛍光体粒子の製造方法。3. The phosphor particles according to claim 1, wherein the reheating temperature T2 (° C.) is Tm−200 ≦ T2 ≦ Tm + 30 with respect to the melting point Tm (° C.) of the dispersion medium component. Method. 所望の蛍光体粒子の固体体積に対して、分散媒体成分の体積が５〜１００倍であることを特徴とする請求項１〜３のいずれか１つに記載の蛍光体粒子の製造方法。The method for producing phosphor particles according to any one of claims 1 to 3, wherein the volume of the dispersion medium component is 5 to 100 times the solid volume of the desired phosphor particles. 蛍光体粒子の一次粒子が１００ｎｍ以下であることを特徴とする請求項１〜４のいずれか１つに記載の蛍光体粒子の製造方法。The method for producing phosphor particles according to any one of claims 1 to 4, wherein the primary particles of the phosphor particles are 100 nm or less.