JP4023184B2 - Luminescent particles, production method thereof and use thereof - Google Patents

Description

【００６０】
本発明においては、セラミックス膜の耐湿膜としての機能及び硬度の点から、側鎖が全て水素であるペルヒドロポリシラザンが好ましい。側鎖に有機基を有するポリシラザンは、硬化後も有機基が残存するため、緻密性に乏しいものとなる。ペルヒドロポリシラザンの製造法は例えば特公昭６３−１６３２５号公報、D. Seyferth らCommunication of Am. Cer. Soc., C-13, January 1983. に報告されている。ペルヒドロポリシラザンは直鎖構造と６および８員環を中心とする環構造が存在した構造と推定されている。その分子量は、数平均分子量（Ｍｎ）で１００〜５００００である。用いるポリシラザンの分子量が小さすぎると、硬化時の収率が低く、実用的でない。一方分子量が大きすぎると溶液の安定性が低く、緻密な膜が得られない。これらの理由から、用いるポリシラザンの分子量は数平均分子量で下限は１００であり、好ましくは３００、より好ましくは５００である。上限は５万であり、好ましくは２万、より好ましくは１０，０００である。
【００６１】
これらは、有機溶媒に溶解した溶液状態で、例えばキシレンで希釈されたポリシラザン（ＳｉＨ₂ＮＨ）ｎ（東燃株式会社製）、ポリ（１、１−ジメチルシラザン）テロマー（アズマックス株式会社製）、ペルヒドロシラザン（クラリアントジャパン株式会社製）等が使用できる。
【００６２】
溶剤としては、脂肪族炭化水素、脂環式炭化水素、芳香族炭化水素の炭化水素溶媒、ハロゲン化メタン、ハロゲン化エタン、ハロゲン化ベンゼン等のハロゲン化炭化水素、脂肪族エーテル、脂環式エーテル等のエーテル類が使用できる。好ましい溶媒は、塩化メチレン、クロロホルム、四塩化炭素、ブロモホルム、塩化エチレン、塩化エチリデン、トリクロロエタン、テトラクロロエタン等のハロゲン化炭化水素、エチルエーテル、イソプロピルエーテル、エチルブチルエーテル、ジブチルエーテル、１，２−ジオキシエタン、ジオキサン、ジメチルジオキサン、テトラヒドロフラン、テトラヒドロピラン、セロソルブアセテート、カルビトールアセテート等のエーテル類、ペンタンヘキサン、イソヘキサン、メチルペンタン、ヘプタン、イソヘプタン、オクタン、イソオクタン、シクロペンタン、メチルシクロペンタン、シクロヘキサン、メチルシクロヘキサン、ベンゼン、トルエン、キシレン、エチルベンゼン等の炭化水素等である。これらの中でも、溶解性、安定性、均一被膜性の点からキシレン、ジブチルエーテルが特に好ましい。
【００６３】
これらの溶剤を使用する場合、ポリシラザンの溶解度や溶剤の蒸発速度を調節するために、２種類以上の溶剤を混合してもよい。溶剤の使用量（割合）は採用する被覆方法により作業性がよくなるように、また必要な膜厚により選択され、またポリシラザンの平均分子量、分子量分布、その構造によって異なるので、被膜形成用組成物中溶剤は９９．９９質量％程度まで混合することができ、好ましくは固形分濃度が０．１〜５０質量％の範囲で混合することができる。固形分濃度が０．１質量％未満では、シリカ被膜の形成速度が極めて遅く実用的ではない。また、５０質量％を越えると、被膜を形成せずにシリカ粒子が組成物中に生成する場合があるため好ましくない。
【００６４】
ポリシラザンは、前述のとおり、セラミック前駆体ポリマーであり、これを用いてシリカ膜を形成するには、４００℃以上で大気焼成して、例えば（式２）に示す反応でＳｉＯ₂を得ることが通常行われるが、被覆発光体の場合、４００℃以上では、付活剤及び共付活剤の局在化により初期ルミネッセンス光度の低下を来してしまうため好ましくない。
【００６５】
【化２】

【００６６】
一方、ポリシラザンのウェット状態の被膜を、触媒存在下に水蒸気酸化を組み合わせることで１００℃以下でも緻密なシリカ膜が得られ、上述のごとく本被覆発光体のような耐熱性の低い基材にも成膜できるため、初期ルミネッセンス光度の低下を引き起こさない。
【００６７】
特に、ポリシラザン中に炭素（Ｃ）成分を含有していないものは、下地の第一被膜とは濡れ性がよく（なじみやすい）緻密な膜を形成する。また、アルコシド系を使用するゾルゲル膜のような熱分解中に膜の収縮や残留炭素の問題も発生せずクラックが入ったりしない。
【００６８】
触媒としてはアミン又は金属イオン触媒を使用することができ、両者を組み合わせて使用してもよい。
アミンの種類は特に限定されないが、例えば、トリエチルアミン、トリメチルアミン、ジエチルアミン、モノエタノールアミン、ジエタノールアミン、トリエタノールアミン、ｎ−エキシルアミン、ｎ−ブチルアミン、トリ−ｎ−ブチルアミン、グアニジン、ピグアニン、イミダゾール等のアミン類を使用することができる。それら中でも、トリメチルアミン、トリエチルアミンが溶解性、均一被覆性、低温硬化性の点で好ましい。シリカ被膜形成用組成物中の濃度は、０．１〜１０質量％であり、好ましくは１〜８質量％、より好ましくは１〜５質量％である。０．１質量％以下では、シリカへの転化速度が遅く経済的でなく、１０質量％以上では、シリカ転化速度が速くなりすぎ均一被膜性を損ねたり、発光体粒子同士の固着を引き起こし分散性を損ねたりする。例えばポリシラザンにトリエチルアミンを加えた組成物を発光粒子に塗布、噴霧又は含浸により接触させた後、９５℃、８０％ＲＨ雰囲気下に３ｈｒ程度保持したりすることにより緻密なシリカ被膜が形成される。また、トリメチルアミンを含む水溶液の蒸気（無相）にＭｎが１００〜５００００のポリシラザンを塗布した発光粒子を２５℃で２ｍｉｎ程度気相接触後、９５℃、８０％ＲＨ雰囲気下に３ｈｒ程度保持することにより緻密なシリカ被膜が形成される。
【００６９】
また、金属イオンを触媒とする場合は、金属としてＡｇ、Ａｕ、Ｐｄ、Ｎｉ等が挙げられる。中でもＰｄが均一被覆性、低温硬化性の点で好ましい。シリカ被膜形成用組成物中の濃度は、０．１〜１０質量％であり、好ましくは１〜５質量％、より好ましくは１〜３質量％である。０．１質量％以下では、シリカへの転化速度が遅く経済的でなく、５質量％以上では、シリカ転化速度が速くなりすぎ均一被膜性を損ねたり、発光体粒子同士の固着を引き起こし分散性を損ねたりする。例えばＭｎが１００〜５００００のポリシラザンにＰｄを加えた組成物を発光粒子に塗布、噴霧又は含浸により接触させた後、乾燥し、１００〜３５０℃で低温焼成することでも緻密なシリカ被膜が得られる。
【００７０】
シリカ被膜形成用組成物には、さらに必要に応じて、レベリング剤、消泡剤、帯電防止剤、紫外線吸収剤、ｐＨ調整剤、分散剤、表面改質剤、流れ止め剤等を加えてもよい。
【００７１】
また、第一被膜無し、つまり未被覆発光粒子に直接ポリシラザン由来のシリカ被膜を施した場合には、粒子との密着性が不十分であり、均一な被膜状態が得られず耐湿性の向上が認められなかった。つまり、第一被膜の存在によりポリシラザン由来の第二被膜の充分な密着性を確保することができ、且つ、低膜厚な第二被膜においても相乗的な耐湿性向上が可能になる。
【００７２】
また、本発明のシリカ被膜発光体粒子はその表面が疎水化されていてもよい。疎水化のためにはその表面をオルガノシロキサン類、シリコーン樹脂類で被覆することがあげられる。オルガノシロキサン類、シリコーン樹脂類の例としては、メチルハイドロジェンポリシロキサン、ジメチルポリシロキサン、メチルフェニルポリシロキサン、ビフェニルポリシロキサン、アルキル変性シリコーンアルコキシ変性シリコーン、トリメチルシロキシケイ酸、アクリルシリコーン、シリコーンレジン等があげられ、また、これらのオルガノシロキサン類、シリコーン樹脂類とシランカップリング剤、アルミニウムカップリング剤等を同時に用いることもできる。好ましいオルガノシロキサン類、シリコーン樹脂類はメチルハイドロジェンポリシロキサン、ジメチルポリシロキサンである。
【００７３】
これらの被覆処理は、湿式法、乾式法、メカノケミカル法等のいずれでもよい。この疎水化によって、発光体の耐湿性をよりいっそう高めることができる。これら被覆量としては、被覆発光体粒子に対して０．１〜５質量％、好ましくは０．１〜２質量％である。０．１質量％以下では疎水性が低く、５質量％以上では、初期ルミネッセンス光度の低下を伴う場合があるため好ましくない。
【００７４】
本発明のシリカ被膜発光体粒子の一次粒子径は特に限定されるものではないが、好ましくは０．１〜１００μｍ、好ましくは１〜８０μｍ、さらに好ましくは１〜５０μｍである。一次粒子径が１００μｍより大きいと、例えばエレクトロルミネッセンスにおいて薄い発光体層の形成が困難となり、且つ発光体の分布が不均一になる場合がある。一次粒子が０．１μｍ未満では、粒子が凝固して易流動性が低下する傾向にあり、好ましくない。
【００７５】
なお、本発明でいう「一次粒子」は、久保輝一郎他編「粉体」ｐ５６〜６６，１９７９年発行により定義されているものをいう。
【００７６】
また、発光体粒子の粒子径はゾルーゲル法による超微粒子（粒径０．５μｍ以下）や粒径０．５〜１００μｍ程度のものが好ましく使用できる。
【００７７】
本発明においてシリカ膜の膜厚、屈折率は、シリカ被膜発光体粒子を合成する際に同時に系内に浸漬したシリコンウエハー上に形成されるシリカ膜を用いて測定することができる。このシリコンウエハーには、発光体粒子上と同じシリカ被膜が形成されている。シリカ膜の屈折率は、エリプソメーター（ＵＬＶＡＣ製；ＬＡＳＳＥＲ ＥＬＬＩＰＳＯＭＥＴＥＲ ＥＳＭ−１Ａ）により測定できる。膜厚測定には段差計を用いることができる。
【００７８】
シリカ被膜発光体粒子のシリカ膜の透過赤外吸収スペクトル（日本分光製ＦＴ−ＩＲ−８０００）は、ＫＢｒ法を用いて測定することができる。シリカ被膜発光体粒子の１次粒子径及びシリカ膜厚は、透過型電子顕微鏡又は走査型電子顕微鏡像から求めることができる。
【００７９】
また、本発明における第一、第二被膜の構造はＸ線回折、ＥＰＭＡ（電子プローブマイクロアナリシス）による面分析で約１μｍ深さの表面層組織、表面元素分布を確認できる。
【００８０】
【実施例】
以下、本発明の実施例について詳細に説明する。ただし、本発明はこれら実施例によりなんら限定されるものではない。
【００８１】
実施例において用いた初期ルミネッセンス光度測定、耐湿性試験、分散性試験、屈折率測定、シリカ被膜厚測定、赤外吸収スペクトル測定は、以下の方法により行った。
【００８２】
（初期エレクトロルミネッセンス光度測定）
発光体粒子５０質量部をシアノエチルセルロース１５質量部、ジメチルホルムアミド３５質量部に混合した分散体１を得る。チタン酸バリウムとシアノエチルセルロースからなる絶縁体層をアルミニウム背面電極に形成後、分散体１を自動塗工機にて５０μｍ厚みで塗布、乾燥後、ＩＴＯ（酸化インジウムスズ）透明電極ではさみ、分散型ＥＬ（エレクトロルミネッセンス）素子を構成した。相対湿度１０％、温度２５℃、電圧１００Ｖ、振動数４００Ｈｚでの発光光度を測定した。未被覆処理発光体粒子の発光光度を１００として各実施例の被覆発光体粒子の発光光度の相対値（ＩＢｅ）を算出した。
【００８３】
（エレクトロルミネッセンス耐湿性試験）
発光体粒子５０質量部をシアノエチルセルロース１５質量部、ジメチルホルムアミド３５質量部に混合した分散体１を得る。チタン酸バリウムとシアノエチルセルロースからなる絶縁体層をアルミニウム背面電極に形成後、分散体１を自動塗工機にて５０μｍ厚みで塗布、温風乾燥機にて８０℃、１ｈｒ乾燥後、ＩＴＯ透明電極ではさみ、分散型ＥＬ素子を構成した。相対湿度９０％、温度４０℃、電圧１００Ｖ、振動数４００Ｈｚでの１００時間連続発光における発光光度の残存率（ＲＢｅ）を求めた。
【００８４】
（分散性試験）
発光体粒子５０質量部をシアノエチルセルロース１５質量部、ジメチルホルムアミド３５質量部に混合した分散体１を得る。分散体１を沈降管にいれ、静置して、発光体粒子が沈降する様子を目視で観察し、分散度を評価した。
【００８５】
分散度の判断は、以下の基準で行った。
【００８６】
静置直後に沈降する場合を−２、静置後１時間後に沈降する場合を−１、静置後３時間後に沈降する場合を０、静置後９時間後に沈降する場合を＋１、静置後１日後にも沈降しない場合を＋２とする。
【００８７】
（屈折率測定）
シリカ被膜発光体粒子を合成する際に系内に浸漬したシリコンウエハー上に形成されるシリカ膜を用いて、エリプソメーター（ＵＬＶＡＣ社製；ＬＡＳＳＥＲ ＥＬＬＩＰＳＯＭＥＴＥＲ ＥＳＭ−１Ａ）により測定した。
【００８８】
（膜厚測定）
シリカ被膜発光体粒子を合成する際に系内に浸漬したシリコンウエハー上に形成されるシリカ膜を用いて、段差計（ＳＬＯＡＮ社製、ＤＥＫＴＡＫ３０３０）により測定した。シリコンウエハーの一部をテープで覆い、その部分をはがすことにより、段差ブランクとする。シリカ被膜部とブランク部の段差を測定する。
また、シリカ被膜発光体粒子そのものを透過型電子顕微鏡（日本電子（株）製ＪＥＭ２０１０、加速電圧２００Ｖ）により観察し、粒子表面のシリカ被膜（基材に対して、基材を覆うように認められる、薄いコントラストを有する膜部）の厚み観察によっても測定することができ、段差計による測定値とほぼ一致する値が得られる。
【００８９】
（ＩＲスペクトル測定）
シリカ被膜発光体粒子のシリカ膜の透過赤外吸収スペクトル（日本分光（株）製ＦＴ−ＩＲ−８０００）は、ＫＢｒ法（発光粒子とＫＢｒの各粉体の混合比は、発光粒子／ＫＢｒ質量比が１／３２）を用いて測定した。１１５０〜１２５０ｃｍ^-1と１０００〜１１００ｃｍ^-1における赤外吸収スペクトルの透過率より吸収ピークの吸光度を算出し、吸収ピーク強度の比Ｉ（Ｉ＝Ｉ₁／Ｉ₂：Ｉ₁は１１５０〜１２５０ｃｍ^-1の吸収ピークの吸光度、Ｉ₂は１０００〜１１００ｃｍ^-1の吸収ピークの吸光度）を求める。
【００９０】
（実施例１）
（第一被膜の合成）
５Ｌ反応器に脱イオン水４４０ｍＬ、エタノール（純正化学株式会社製）１８６０ｍＬ及び２５質量％アンモニア水４０ｍｌ（大盛化工社製）を混合し、その中に蛍光体粒子（ＨＡＮＥＹＷＥＬＬ製 ＬＵＭＩＬＵＸ ＢｌｕｅＥＬ（登録商標）：ＺｎＳ系エレクトロルミネッセンス粒子；平均粒径Ｄ₅₀２５μｍ）２００ｇを分散させ、懸濁液１を調製した。次に、テトラエトキシシラン（ナカライテスク製）２０ｍＬ、エタノール２５０ｍＬを混合し、溶液１を調製した。
【００９１】
マグネチックスターラーで撹拌している懸濁液１に、溶液１を１２時間かけて一定速度で加えた後、１２時間熟成した。成膜、熟成は２５℃にて行った。その後固形分を遠心濾過にて分離し、エタノール２００ｍｌでリンスした後、湿体固形分を回収した。湿体固形分を８０℃で１２時間真空乾燥してシリカ第一被膜を施した蛍光体粒子を得た。
【００９２】
（第二被膜の合成）
５Ｌ反応器にキシレン（和光純薬株式会社製）１６００ｇ、トリエチルアミン（和光純薬株式会社製）６ｇを混合し、その中に、上記のごとくシリカ第一被膜を施した蛍光体粒子１６０ｇを分散させ、懸濁液２を調製した。次に、ペルヒドロポリシラザン（クラリアントジャパン株式会社製 ＮＬ−１１０−２；酸化物換算２０質量％のペルヒドロポリシラザンを含むキシレン溶液）２０ｇ、脱水キシレン（和光純薬株式会社製）１６０ｇを混合し、溶液２を調製した。
【００９３】
マグネチックスターラーで撹拌している懸濁液２に、溶液２を２０時間かけて一定速度で加えた後、１２時間熟成した。成膜、熟成は４５℃にて行った。その後固形分を遠心濾過にて分離し、湿体固形分を回収した。湿体固形分を８０℃で１２時間真空乾燥し、更に９５℃、８０％ＲＨの雰囲気で１２ｈｒ処理した後、９５℃で１ｈｒ真空乾燥することでシリカ第二被膜を施したシリカ被覆蛍光体粒子１を得た。
【００９４】
（実施例２）
（第一被膜の合成）
５Ｌ反応器に脱イオン水４４０ｍＬ、エタノール（純正化学株式会社製）１８６０ｍＬ及び２５質量％アンモニア水４０ｍｌ（大盛化工社製）を混合し、その中に蛍光体粒子（ＨＡＮＥＹＷＥＬＬ製 ＬＵＭＩＬＵＸ ＢｌｕｅＥＬ：ＺｎＳ系エレクトロルミネッセンス粒子）２００ｇを分散させ、懸濁液３を調製した。次に、テトラエトキシシラン（ナカライテスク製）４ｍＬ、エタノール５０ｍＬを混合し、溶液３を調製した。
【００９５】
マグネチックスターラーで撹拌している懸濁液３に、溶液３を２．５時間かけて一定速度で加えた後、１２時間熟成した。成膜、熟成は２５℃にて行った。その後固形分を遠心濾過にて分離し、エタノール２００ｍｌでリンスした後、湿体固形分を回収した。湿体固形分を８０℃で１２時間真空乾燥してシリカ第一被膜を施した蛍光体粒子を得た。
【００９６】
（第二被膜の合成）
５Ｌ反応器にキシレン（和光純薬株式会社製）１６００ｇ、トリエチルアミン（和光純薬株式会社製）６ｇを混合し、その中に、上記のごとくシリカ第一被膜を施した蛍光体粒子１６０ｇを分散させ、懸濁液４を調製した。次に、ペルヒドロポリシラザン（クラリアントジャパン株式会社製 ＮＬ−１１０−２；酸化物換算２０質量％のペルヒドロポリシラザンを含むキシレン溶液）２０ｇ、脱水キシレン（和光純薬株式会社製）１６０ｇを混合し、溶液４を調製した。
【００９７】
マグネチックスターラーで撹拌している懸濁液４に、溶液４を２０時間かけて一定速度で加えた後、１２時間熟成した。成膜、熟成は４５℃にて行った。その後固形分を遠心濾過にて分離し、湿体固形分を回収した。湿体固形分を８０℃で１２時間真空乾燥し、更に９５℃、８０％ＲＨの雰囲気で１２ｈｒ処理した後、９５℃で１ｈｒ真空乾燥することでシリカ第二被膜を施したシリカ被覆蛍光体粒子２を得た。
【００９８】
（実施例３）
（第一被膜の合成）
５Ｌ反応器に脱イオン水４４０ｍＬ、エタノール（純正化学株式会社製）１８６０ｍＬ及び２５質量％アンモニア水４０ｍｌ（大盛化工社製）を混合し、その中に蛍光体粒子（ＨＡＮＥＹＷＥＬＬ製 ＬＵＭＩＬＵＸ ＢｌｕｅＥＬ：ＺｎＳ系エレクトロルミネッセンス粒子）２００ｇを分散させ、懸濁液５を調製した。次に、テトラエトキシシラン（ナカライテスク製）２０ｍＬ、エタノール２５０ｍＬを混合し、溶液５を調製した。
【００９９】
マグネチックスターラーで撹拌している懸濁液５に、溶液５を１２時間かけて一定速度で加えた後、１２時間熟成した。成膜、熟成は２５℃にて行った。その後固形分を遠心濾過にて分離し、エタノール２００ｍｌでリンスした後、湿体固形分を回収した。湿体固形分を８０℃で１２時間真空乾燥してシリカ第一被膜を施した蛍光体粒子を得た。
【０１００】
（第二被膜の合成）
５Ｌ反応器にキシレン（和光純薬株式会社製）１６００ｇ、トリエチルアミン（和光純薬株式会社製）６ｇを混合し、その中に、上記のごとくシリカ第一被膜を施した蛍光体粒子１６０ｇを分散させ、懸濁液６を調製した。次に、ペルヒドロポリシラザン（クラリアントジャパン株式会社製 ＮＬ−１１０−２；酸化物換算２０質量％のペルヒドロポリシラザンを含むキシレン溶液）５ｇ、脱水キシレン（和光純薬株式会社製）４０ｇを混合し、溶液６を調製した。
【０１０１】
マグネチックスターラーで撹拌している懸濁液６に、溶液６を５時間かけて一定速度で加えた後、１２時間熟成した。成膜、熟成は４５℃にて行った。その後固形分を遠心濾過にて分離し、湿体固形分を回収した。湿体固形分を８０℃で１２時間真空乾燥し、更に９５℃、８０％ＲＨの雰囲気で１２ｈｒ処理した後、９５℃で１ｈｒ真空乾燥することでシリカ第二被膜を施したシリカ被覆蛍光体粒子３を得た。
【０１０２】
（比較例１）
未被覆蛍光体粒子（実施例１で使用したものと同じＬＵＭＩＬＵＸ ＢｌｕｅＥＬ）そのものを比較対照体粒子１とした。
【０１０３】
（比較例２）
実施例１において、シリカ第二被膜を施さないこと以外は実施例１と同様の方法により、シリカ第一被膜蛍光体粒子（シリカ第二被膜無し）を得、これを比較対照体粒子２とした。
【０１０４】
（比較例３）
実施例１において、テトラエトキシシランを４０ｍｌとし、且つシリカ第二被膜を施さないこと 以外は実施例１と同様の方法により、シリカ第一被膜蛍光体粒子（シリカ第二被膜無し）を得、比較対照体粒子３とした。
【０１０５】
（比較例４）
実施例１において、シリカ第一被膜を施さないこと以外は実施例１と同様の方法により、ポリシラザン由来のシリカ被膜を直に蛍光体粒子に施したシリカ被覆蛍光体粒子を得、比較対照体粒子４とした。この場合は、被膜の密着性、均一被覆性が乏しいため、比較対照対粒子の表面処理状態は、シリカ微少粒子が多く存在し、且つ発光体粒子表面以外にも、単独のシリカ粒子の形成が認められた。
【０１０６】
ＫＢｒ法により、実施例１〜３で得られたシリカ被膜蛍光体粒子及び比較例２〜４の比較対照体粒子の透過赤外吸収スペクトルを測定したところ、いずれの蛍光体粒子も１０００〜１１００ｃｍ^-1にＳｉ−Ｏ−Ｓｉ伸縮振動由来の吸収が観測され、２８００〜３０００ｃｍ^-1にＣ−Ｈ伸縮振動由来の吸収は検出限界内では観測されず、生成した被膜はシリカであると同定された。
【０１０７】
さらに、シリカ第一被膜及び第二被膜のシリカ膜厚、赤外吸収スペクトルの吸収ピーク強度の比Ｉ、屈折率を測定した結果を表１にまとめた。屈折率は溶融石英ガラスの値（密度２．２ｇ／ｃｍ³、屈折率１．４６）に近い値を示しているので被膜の組成が実質的にＳｉＯ₂であることが確認された。
【０１０８】
実施例１〜３及び比較例１〜４の蛍光体粒子の初期エレクトロルミネッセンス光度（ＩＢｅ）、エレクトロルミネッセンス耐湿性（ＲＢｅ）、分散度を評価した結果を表２に示す。
【０１０９】
【表１】

【０１１０】
【表２】

【０１１１】
【発明の効果】
本発明は耐湿性に優れ、初期ルミネッセンス光度が非被覆品と同等であり、且つ被膜の緻密性、密着性が良く、粒子固着の無い分散性・成形性に優れたシリカ被膜発光体粒子を提供するものであり、該発光体粒子はエレクトロルミネッセンス素子の分散型発光層等へ使用することができる。
【０１１２】
【図面の簡単な説明】
【図１】実施例１で製造されたシリカ第一被膜を有する発光体粒子の赤外吸収スペクトル。
【図２】実施例１で製造されたシリカ第二被膜を有する発光体粒子の赤外吸収スペクトル。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to phosphor particles having excellent moisture resistance by surface treatment and having excellent dispersibility without causing a decrease in initial luminescence intensity and a method for producing the same.
[0002]
[Prior art]
Luminescent particles are used in various applications such as flat panel displays, electronic devices, lighting equipment, watches and fashion accessories, and cathode ray tubes. The phosphor particles in the present invention are fluorescent particles, phosphorescent particles, phosphorescent particles, and the like. As a stimulation method (excitation energy source) for light emission, there are ultraviolet rays, electron beams, X-rays / radiation, electric fields, and chemical reactions. Phosphors include those based on zinc sulfide (ZnS), calcium sulfide (CaS), and strontium sulfide (SrS), and for various purposes such as multicolor and high brightness, such as copper, silver, and manganese. Activators and coactivators are added.
[0003]
In putting these phosphor particles into practical use, techniques for extending the life, increasing the brightness, and imparting high dispersibility are important.
[0004]
In particular, from the viewpoint of extending the life, it is essential to improve moisture resistance. The phosphor particles generally have poor moisture resistance, and not only contact with water but also contact with water vapor in the atmosphere has a serious adverse effect on the light emission characteristics. Therefore, if it is used for a long time in a place with high humidity, the luminescence intensity will rapidly decrease with moisture absorption. Further, if the light emission is continued in the moisture absorption state, the light emitting surface suddenly becomes black and the luminance is also lowered. In particular, in electroluminescence (EL), for example, in the case of a ZnS-based phosphor, Zn is reduced and precipitated, or the binder is carbonized in the vicinity of the transparent electrode due to a kind of chemical reaction caused by moisture and electrical energy that has entered the light emitting layer. To do.
[0005]
The prior art for moisture resistance is given as an example of electroluminescence (EL).
[0006]
EL phosphor particles are generally used as a dispersion type EL device, and the basic structure thereof is that a light emitting layer formed by dispersing phosphor particles in an organic binder having a high dielectric constant such as cyanoethyl cellulose is used. A dielectric layer (insulating layer) for increasing the withstand voltage and ensuring a stable operation is overlaid, and electrodes for applying voltage (at least one is a transparent electrode) are provided on both sides of the dielectric layer.
[0007]
Therefore, in order to achieve moisture resistance, it is also possible to sheet the element with a moisture-proof film such as trifluoromonochloroethylene polymer, but the problem is that the element is thick and expensive, and further includes dark borders and delamination. have.
[0008]
Attempts have also been made to improve moisture resistance by coating the phosphor itself. JP-A-4-178486 discloses a method for producing a water-resistant phosphor by coating the phosphor surface with a phosphate of a metal such as magnesium, calcium or strontium, and then rapidly heating it by plasma treatment. Yes. However, in the coating with these phosphates, the salt is merely precipitated, and it cannot be said that the coating state is uniform. Of course, there is no denseness, and therefore a complicated and costly process such as a plasma process is required. Moreover, in order to obtain a uniform coating without pinholes by plasma treatment, the particles cannot be fixed, and the dispersibility and moldability are poor.
[0009]
Japanese Patent Laid-Open No. 4-230996 has moisture resistance and high initial luminescence by heating phosphor particles in the range of 25 ° C. to 170 ° C. and coating the oxide by CVD in the presence of an oxide precursor material. Phosphorescent particles and methods for producing the same are disclosed. However, in order to uniformly coat the oxide by the CVD method, expensive equipment is required, which is not economical. In addition, since processing time is required, interparticle adhesion is not likely to occur, and this tendency is strengthened by CVD at a low temperature. Therefore, when the phosphor particles are crushed or dispersed in an organic binder, pinholes are generated in the coating and oxide is peeled off, resulting in poor moldability.
[0010]
The fixation of the phosphor particles causes problems such as preventing the formation of a thin light emitting layer, causing nonuniform light output, and further causing poor dispersibility and sedimentation during the production of an EL element.
JP-A-8-236274 discloses that phosphor particles are coated with a ceramic film derived from polysilazane. Specifically, the zinc sulfide powder is turbid in a polysilazane solution and dried with a spray dryer to obtain coated particles. Polysilazane causes an increase in mass during silica conversion and is less likely to crack even in a thick film due to its small volume shrinkage. In addition, it is difficult to obtain a smooth coating and adhesion between particles tends to occur. For this reason, when the phosphor particles are crushed or dispersed in an organic binder, pinholes of the film are generated and the film is peeled off, resulting in poor moldability. As a result, the improvement in moisture resistance is insufficient.
[0011]
The inventor first coats with a specific dense and uniform thin-film silica, or further nitridizes or fluorinates the surface to improve the moisture resistance, and the initial luminescence intensity of the uncoated product. Disclosed is a phosphor particle that is less degraded and excellent in dispersibility. However, improvement in moisture resistance has been demanded as before. Although the moisture resistance is improved with an increase in the silica content, an excessive increase in the content causes a decrease in the initial luminance. Of course, an increase in the silica content means an increase in film thickness. However, when the film thickness is 0.5 μm or more, cracks are likely to occur due to film shrinkage during drying.
[0012]
Therefore, in the coating of phosphor particles, not only the improvement in moisture resistance, but also providing sufficient moisture resistance even with a thin film thickness that is difficult to generate cracks, or a coating that does not generate cracks even with a thick film thickness. A method is required and the initial luminescence intensity is not reduced, the particles are not fixed and there is no need for crushing, the film adhesion and particle dispersibility are excellent, and the moldability is excellent. No one has ever satisfied all of these.
[0013]
[Problems to be solved by the invention]
In addition to improving moisture resistance, the present invention is uniform and silica with an initial luminescence luminous intensity equivalent to that of an uncoated product, good adhesion of the coating (film), excellent dispersibility and moldability without particle adhesion The object is to provide new phosphor particles coated with a thin film.
[0014]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned problems, the present inventor has coated a thin film silica (first film) having a refractive index of 1.435 or more, and a refractive index derived from polysilazane is further formed on the first film. 1. Luminescent particles coated with a dense silica film of 1.45 or more (second coating), in addition to the improvement of moisture resistance, the initial luminescence intensity is equivalent to that of the uncoated product, and the coating adhesion is good. The present inventors have found that it is excellent in dispersibility and moldability without sticking, and completed the present invention. The term “luminescent particles” as used herein includes fluorescent, phosphorescent, or phosphorescent particles. Surprisingly, when only the first coating was applied, or when only the second coating was applied to the phosphor particle surface, an improvement in moisture resistance that could not be obtained was recognized.
[0016]
That is, the present invention relates to the following matters.
1) A film (first film) is coated with a thin film silica having a refractive index of 1.435 or more, and further coated with a silica film having a refractive index derived from polysilazane of 1.45 or more (second film) on the first film. Phosphor particles,
2) The phosphor particles according to 1 above, wherein the silica film of the first coating and the second coating has a thickness of 0.02 to 1 μm.
3) The phosphor particles according to 1 or 2 above, wherein the polysilazane is perhydropolysilazane,
4) The phosphor particles according to 3 above, wherein the polysilazane has a number average molecular weight in the range of 100 to 50,000,
5) The luminescence according to any one of 1 to 4 above, which is coated with a silica film having a first coating film thickness of 0.01 to 0.5 μm and a second coating film thickness of 0.01 to 0.5 μm. Body particles,
6) The film thickness is 0.01 to 0.5 μm, the refractive index is 1.45 or more, and 1150 to 1250 cm in the infrared absorption spectrum. ^-1 And 1000-1100cm ^-1 Absorption peak intensity ratio I (I = I ₁ / I ₂ : I ₁ 1150-1250cm ^-1 Absorbance of absorption peak, I ₂ Is 1000-1100cm ^-1 The phosphor particles according to any one of 1 to 5 above, which are coated with a polysilazane-derived silica film (second film) having an absorption peak absorbance of less than 0.2,
7) The film thickness is 0.01 to 0.5 μm, the refractive index is 1.435 or more, and 1150 to 1250 cm in the infrared absorption spectrum. ^-1 And 1000-1100cm ^-1 Absorption peak intensity ratio I (I = I ₁ / I ₂ : I ₁ 1150-1250cm ^-1 Absorbance of absorption peak, I ₂ Is 1000-1100cm ^-1 The phosphor particles according to any one of 1 to 6 above, which are coated with a silica film (first coating) having an absorption peak of 0.2) or more,
8) The phosphor particles according to any one of 1 to 7 above, wherein the outermost surface is hydrophobized.
9) 1) Silica acid containing no organic group and halogen, or a silicic acid precursor capable of producing silicic acid, and 2) water, 3) alkali, and 4) a composition for forming a silica film containing at least an organic solvent. A step of bringing the phosphor particles into contact with the composition for forming a silica film containing at least 1) a polysilazane and 2) an organic solvent, 3) an amine and / or a metal ion catalyst. ,
10) 1) Silica acid containing no organic group and halogen, or a silicic acid precursor capable of producing silicic acid, and 2) water, 3) alkali, 4) a phosphor film on a silica film forming composition containing at least an organic solvent. A step of contacting, and then 1) a polysilazane and 2) an organic solvent, 3) a step of bringing phosphor particles into contact with a composition for forming a silica film containing at least an amine and / or a metal ion catalyst, and bringing into contact with water vapor. Particle manufacturing method,
11) The method for producing phosphor particles according to 9 or 10 above, wherein the polysilazane is a polysilazane having a number average molecular weight of 100 to 50,000,
12) Phosphor particles in a composition for forming a silica film containing 1) silicic acid containing no organic group and halogen or a silicic acid precursor capable of producing silicic acid, and 2) water, 3) alkali, and 4) an organic solvent In this step, the water / organic solvent ratio (based on the charged volume) is used in the range of 0.1 to 10 and the silicic acid concentration is in the range of 0.0001 to 5 mol / liter. The method for producing phosphor particles according to any one of 9 to 11 above, wherein the first film is applied by selectively coating silica on the surface, and then drying.
13) The phosphor particles according to any one of 1 to 8 above, wherein the phosphor particles emit fluorescence.
14) The method for producing phosphor particles as described in any one of 9 to 12 above, wherein the phosphor particles emit fluorescence.
15) A dispersion-type light emitting device using the phosphor particles according to any one of 1 to 8 above,
16) A dispersive electroluminescence device using the phosphor particles according to any one of 1 to 8 above,
17) The luminescent material as described in any one of 1 to 8 above, wherein the phosphor particles are made from one or more selected from zinc sulfide (ZnS), calcium sulfide (CaS), and strontium sulfide (SrS). Body particles, and
18) The luminescent material as described in any one of 9 to 12 above, wherein the phosphor particles are made from one or more selected from zinc sulfide (ZnS), calcium sulfide (CaS), and strontium sulfide (SrS). A method for producing body particles.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in more detail, but the present invention is not limited to these.
[0018]
First, phosphor particles that can be used in the present invention (the phosphor particles here include fluorescent, phosphorescent, or phosphorescent particles) are not particularly limited, but are usually zinc sulfide (ZnS), calcium sulfide ( Sulfides such as CaS) and strontium sulfide (SrS), Y ₂ O ₂ S, Ln ₂ O ₂ Oxysulfides such as S (Ln is at least one selected from the group consisting of Y, Gd and La), MGa ₂ S _Four (M is at least one selected from the group consisting of Sr, Ca, Ba and Mg) and the like, (Ba, Eu) OMgO.5Al ₂ O _Three There are materials based on aluminate compounds such as Further, for example, a zinc sulfide-based electroluminescence material includes a compound of copper sulfide (CuS), zinc selenide (ZnSe), and cadmium sulfide (CdS) in a solid solution of the zinc sulfide crystal structure. Moreover, various activators and coactivators, such as copper, silver, and manganese, may be added for the purpose of increasing color and increasing brightness. For example, in zinc sulfide-based electroluminescent materials, those containing Cu and I emit blue-green, those containing Cu and Al emit green, and those containing Cu, Mn, and Cl emit yellow-orange.
[0019]
Next, the silica coating of the present invention and the production method thereof will be described.
[0020]
(First coating)
The silica-coated phosphor particles of the present invention have 1150 to 1250 cm. ^-1 And 1000-1100cm ^-1 Of the absorption peak intensity I of the infrared absorption spectrum (I = I ₁ / I ₂ : I ₁ 1150-1250cm ^-1 Absorbance of absorption peak due to Si-OH, I ₂ Is 1000-1100cm ^-1 The silica coating (first coating) has an absorption peak absorbance due to Si—O—Si of 0.2 or more and a refractive index of 1.435 or more. This first coating is a dense thin-film silica that is well applied to the complicated particle shape of the light-emitting body that is the base material, and that has good adhesion and coverage even at a very thin film thickness. “Dense” as used herein means that the formed silica film has a high density and is uniform and free from pinholes and cracks.
[0021]
The first coating in the present invention has the role of 1) a hydrophilic undercoat for ensuring the adhesion of the second coating described later. By exhibiting sufficient adhesiveness and 2) a thin film silica having a dense property, it is possible to synergistically improve moisture resistance with the second film having a low film thickness.
Usually, a silica film obtained by baking by a sol-gel method or the like or obtained by a CVD method has a thickness of 1150 to 1250 cm. ^-1 And 1000-1100cm ^-1 The ratio I of the absorption peak intensity of the infrared absorption spectrum at is generally less than 0.2. It is known that the value of I generally changes the chemical bond or functional group by firing, and changes the hydrophilic and oil-absorbing properties of the silica film. Moreover, the silica film obtained without baking by a normal sol-gel method has a refractive index of less than 1.435 and low density. Here, it is generally assumed that there is a positive correlation between the denseness of the silica film and the refractive index. (For example, C. JEFFERY BRINKER, SOL-GEL SCIENCE, 581-583, ACADEMI PRESS (1990))
In addition, when an alkali metal such as sodium is included in the coating, the silica film may be dissolved in a heated and humid atmosphere. In the present invention, the content of alkali metal such as sodium is selected by selecting the production conditions. It is also possible to obtain a silica coating with a very small amount. This means that there is almost no deterioration of the film when it is brought into contact with water vapor in the low-temperature ceramicization of the second film, which will be described later, and it can be suitably used.
[0022]
The silica-coated phosphor particles of the present invention contain silicic acid containing no organic group and halogen or a precursor capable of producing the silicic acid, and water, an alkali and an organic solvent, and the water / organic solvent ratio is 0.00 by volume. A fine thin-film silica is formed on the surface of the phosphor particles by bringing the phosphor particles into contact with a composition for forming a silica film having a silicon concentration in the range of 1 to 10 and a silicon concentration in the range of 0.0001 to 5 mol / liter. Silica-coated phosphor particles obtained by a selective deposition method.
[0023]
In particular, 1150 to 1250 cm ^-1 And 1000-1100cm ^-1 Of the absorption peak intensity I of the infrared absorption spectrum (I = I ₁ / I ₂ : I ₁ 1150-1250cm ^-1 Absorbance of absorption peak due to Si-OH, I ₂ Is 1000-1100cm ^-1 Silica-coated phosphor particles coated with dense thin-film silica having an absorption peak absorbance due to Si—O—Si of 0.2 or more and a refractive index of 1.435 or more.
[0024]
The silicic acid containing no organic group and halogen used in the composition for forming a silica film in the present invention is, for example, “silicic acid” of Chemical Dictionary (Kyoritsu Shuppan Co., Ltd. Orthosilicic acid H shown in the section _Four SiO _Four , And its polymer, metasilicic acid H ₂ SiO _Three , Mesosilicate H ₂ SiO _Five , Mesotrisilicic acid H _Four Si _Three O ₈ Mesotetrasilicic acid H ₆ Si _Four O ₁₁ Etc.
[0025]
The composition for forming a silica film is, for example, tetraalkoxysilane (Si (OR)). _Four In which R is a hydrocarbon group, in particular C ₁ ~ C ₆ A precursor capable of producing silicic acid containing no organic groups and halogen such as tetramethoxysilane, tetraethoxysilane, tetra n-propoxysilane, tetraisopropoxysilane, tetra n-butoxysilane, and the like. In addition, water, an alkali, and an organic solvent are added and stirred, and the hydrolysis reaction proceeds. This method is preferable because it is easy to handle or operate and practical. Of these, tetraethoxysilane is a preferred material.
[0026]
Formula X _n Si (OH) _4-n (Wherein X is a hydrocarbon group, halogen, hydrogen, and n is an integer of 1, 2 or 3), a compound having a hydrophobic group such as a hydrocarbon group, halogen or hydrogen represented by the present invention. It differs from the silicic acid used in Therefore, trialkoxyalkylsilanes, dialkoxyalkyldialkylsilanes, trialkoxysilanes, dialkoxysilanes, etc. are not suitable as precursors that can produce silicic acid free of organic groups and halogens.
[0027]
In addition, water, alkali, and organic solvent are added to tetrahalogenated silane and hydrolyzed, alkali and organic solvent are added to water glass, or water glass is treated with a cation exchange resin to obtain alkali, Even if it uses the method of adding an organic solvent, the composition for silica film formation containing the silicic acid which does not contain an organic group and a halogen can be obtained. Tetraalkoxysilane, tetrahalogenated silane, and water glass used as a raw material for silicic acid containing no organic group and halogen are not particularly limited, and may be those generally used for industrial use or as reagents, but preferably higher Those of purity are suitable. The composition for forming a silica film of the present composition may contain an unreacted material of the silicic acid raw material.
[0028]
The amount of silicic acid containing no organic group and halogen is not particularly limited, but is preferably in the range of 0.0001 to 5 mol / liter as the concentration of silicon atoms. More preferably, it is the range of 0.001-5 mol / liter. If the silicon concentration is less than 0.0001 mol / liter, the formation rate of the silica film is very slow and not practical. On the other hand, if it exceeds 5 mol / liter, silica particles may be formed in the composition without forming a film.
[0029]
The silicon concentration can be calculated from the amount of silicic acid raw material, for example, tetraethoxysilane, but the composition can also be measured by atomic absorption analysis. For the measurement, the spectrum of silicon having a wavelength of 251.6 nm is used as an analysis line, and the frame is preferably made of acetylene / nitrous oxide.
[0030]
The water used for the composition for forming a silica film is not particularly limited, and ion-exchanged water, distilled water, tap water, and the like can be used, but water from which particles are preferably removed by filtration or the like is preferable. If particles are contained in water, it is not preferable because they are mixed as impurities in the product.
[0031]
Water is preferably used in an amount such that the water / organic solvent ratio is in the range of 0.1 to 10 by volume. If the volume ratio of water / organic solvent is outside this range, film formation may not be possible or the film formation rate may be extremely reduced. More preferably, the water / organic solvent ratio is in the range of 0.1 to 0.5 by volume ratio. When the water / organic solvent ratio is in the range of 0.1 to 0.5 by volume ratio, the type of alkali used is not limited. When the water / organic solvent ratio is 0.5 or more, it is preferable to form a film using an alkali not containing an alkali metal, for example, ammonia, ammonium hydrogen carbonate, ammonium carbonate or the like.
[0032]
In the present invention, the alkali used in the composition for forming a silica film is not particularly limited. For example, inorganic alkalis such as ammonia, sodium hydroxide, potassium hydroxide; inorganic alkali salts such as ammonium carbonate, ammonium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate; monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, Organic alkalis such as pyridine, aniline, choline, tetramethylammonium hydroxide, guanidine; organic acid alkali salts such as ammonium formate, ammonium acetate, monomethylamine formate, dimethylamine acetate, pyridine lactic acid, guanidinoacetic acid, aniline acetate, etc. be able to.
[0033]
Among these, ammonia, ammonium carbonate, ammonium hydrogen carbonate, ammonium formate, ammonium acetate, sodium carbonate, and sodium hydrogen carbonate are particularly preferable from the viewpoint of reaction rate control. The alkali used for the composition for forming a silica film can be used alone or in combination of two or more selected from the above group.
[0034]
There is no restriction | limiting in particular in the purity of the alkali used in this invention. Any material that is generally used for industrial use or as a reagent may be used, but those having higher purity are suitable.
[0035]
In the present invention, for example, in the case of sodium carbonate, a film can be formed by adding a trace amount of about 0.002 mol / liter in the case of sodium carbonate, but a large amount of about 1 mol / liter may be added. Absent. However, it is not preferable to add a solid alkali in an amount exceeding the solubility because it is mixed as an impurity in the phosphor particles.
[0036]
By using an alkali that does not contain an alkali metal as a main component, silica-coated phosphor particles with a low alkali metal content can be produced. Among these, ammonia, ammonium carbonate, and ammonium hydrogen carbonate are particularly preferable from the viewpoint of film formation speed and ease of residue removal.
[0037]
The organic solvent used in the silica film-forming composition in the present invention is preferably such that the silica film-forming composition forms a uniform solution. For example, alcohols such as methanol, ethanol, propanol and pentanol; ethers and acetals such as tetrahydrofuran and 1,4-dioxane; ketones such as acetone, diacetone alcohol and methyl ethyl ketone; ethylene glycol, propylene glycol, diethylene glycol and the like Polyhydric alcohol derivatives and the like can be used. Among these, alcohols are preferably used from the viewpoint of reaction rate control, and ethanol is particularly preferable. As an organic solvent, 1 type selected from the said group or 2 types or more can also be mixed and used.
[0038]
There is no particular limitation on the purity of the organic solvent used in the composition for forming a silica film, and it may be industrially used or widely used as a reagent, but preferably has a higher purity.
[0039]
A general solution preparation method can be applied to the preparation of the silica film-forming composition. For example, a method of adding a predetermined amount of alkali and water to an organic solvent and stirring and then adding and stirring tetraethoxysilane can be mentioned. is there. When mixing water and tetraethoxysilane, it is preferable to dilute both with an organic solvent from the viewpoint of controllability of the reaction.
[0040]
Further, if necessary, a leveling agent, an antifoaming agent, an antistatic agent, an ultraviolet absorber, a pH adjusting agent, a dispersing agent, a surface modifying agent, a flow preventing agent and the like may be added.
[0041]
The composition for forming a silica film thus prepared is a stable composition, and substantially no deposition or precipitation occurs until it is brought into contact with the phosphor particles. After contacting the phosphor particles with the composition, silica begins to selectively deposit on the surface of the phosphor particles.
[0042]
In the present invention, the phosphor particles are immersed in the composition for forming a silica film and kept at a predetermined temperature, whereby silica is selectively deposited on the surfaces of the phosphor particles to form a silica film. it can. A method of forming a silica film by adding phosphor particles after preparing a film-forming composition in advance may be used. Alternatively, the phosphor particles may be suspended in a solvent before adding other raw material components. It may be a composition, a method of forming a silica film, or the like. That is, there is no restriction | limiting in particular in the order which throws in the raw material of the composition for film formation, and light-emitting body particle | grains, and any can form a silica film first.
[0043]
Among these methods, after preparing a suspension containing phosphor particles, water, an organic solvent, and an alkali, dropwise addition of tetraalkoxysilane diluted with an organic solvent at a constant rate gives better denseness. Since a silica film can be formed and an industrially useful continuous process can be constructed, it is preferable.
[0044]
Since the silica film grows by deposition on the surface of the phosphor particles, the film thickness can be increased by increasing the film formation time. Of course, when most of the silicic acid in the film-forming composition is consumed due to the formation of the film, the film-forming speed will decrease, but it will be put to practical use by successively adding silicic acid corresponding to the consumption. The silica film can be formed at a suitable film formation rate. In particular, the phosphor is held in a film-forming composition to which silicic acid corresponding to the desired silica film thickness is added for a predetermined time, the silica film is formed to consume silicic acid, and the silica-coated phosphor particles are taken out of the system. Then, by additionally adding silicic acid corresponding to the consumption, the composition can be subsequently used for forming a film on the next phosphor particles, and a continuous process with high economic efficiency and productivity can be constructed.
[0045]
In the case of a method of preparing a suspension containing phosphor particles, water, an organic solvent and an alkali and then dropping tetraalkoxysilane diluted with an organic solvent at a constant rate, a desired silica film thickness A solution obtained by diluting a tetraalkoxysilane corresponding to the above in an organic solvent is dropped at a constant rate corresponding to the hydrolysis rate of tetraalkoxylane, so that tetraalkoxysilane is completely consumed and a dense film having a desired film thickness is obtained. A silica film can be formed, and the resulting silica-coated phosphor particles can be taken out of the system to obtain a high-purity product free of unreacted tetraalkoxylane. Of course, the solvent after the silica-coated phosphor particles are taken out can be recycled for the subsequent film formation, and a process with high economic efficiency and productivity can be constructed.
[0046]
Although there is no limitation in particular in the temperature at the time of a silica film formation, Preferably it is the range of 10-100 degreeC, More preferably, it is the range of 20-50 degreeC. The higher the temperature, the higher the film formation rate. However, if the temperature is too high, it will be difficult to keep the solution composition constant due to volatilization of the components in the composition, and if the temperature is too low, the film formation rate will become slow and practical. Not.
[0047]
In order to increase the silica film formation rate, it is effective to increase the temperature at which the film is formed. In this case, it is preferable to use an alkali and an organic solvent that hardly volatilize and decompose at the film forming temperature.
[0048]
Moreover, the pH at the time of film formation should just be alkaline. However, when a light-emitting body whose solubility increases depending on the pH is coated with silica, it is preferable to control the pH of the film-forming composition. The preferred pH is 8-13, more preferably 9-12. The pH can be controlled by adjusting the amount added depending on the alkali species.
[0049]
After the coating is formed, the solid-liquid separation can be performed to isolate the silica-coated phosphor particles. As a method for isolation, general separation methods such as filtration, centrifugal sedimentation, and centrifugal separation can be used.
[0050]
By sufficiently drying after solid / liquid separation, silica-coated phosphor particles having high initial luminescence intensity can be obtained without being affected at all by the water environment despite wet coating. As a drying method, a general drying method such as warm air drying, vacuum drying, spray drying or the like can be used. In order to reduce the influence of loss on drying on the initial luminescence intensity and moisture resistance of the coated illuminant, a preferred drying method is vacuum drying, in which case drying is performed at 50 to 150 ° C. at 5 kPa or less for 1 to 5 hours.
[0051]
The silica-coated phosphor particles of the present invention have extremely good shape followability of the silica coating, and all the primary particles of the phosphor particles as the base material are coated with a dense silica film, and the coating adhesion thereof is strong.
[0052]
The silica film obtained by the above method is 1150 to 1250 cm. ^-1 And 1000-1100cm ^-1 Of the absorption peak intensity I of the infrared absorption spectrum (I = I ₁ / I ₂ : I ₁ 1150-1250cm ^-1 Absorbance of absorption peak due to Si-OH, I ₂ Is 1000-1100cm ^-1 (Absorbance of absorption peak due to Si—O—Si) is 0.2 or more and the refractive index is 1.435 or more. In other words, because it retains chemical bonds or functional groups of the silica film obtained when not baked by the conventional sol-gel method, it has specific physical properties different from the silica film obtained by baking in hydrophilicity and lipophilicity. Nevertheless, it is a dense and practical silica coating.
[0053]
Furthermore, the silica coating of the present invention is also good for the complicated shape of the phosphor particles of the substrate. In the neutralization deposition method from sodium silicate, silica particles are deposited on the phosphor particles to form a coating, whereas in the method of the present invention, a dense silica film is formed on the surface of the phosphor particles of the base material. The film is selectively and three-dimensionally deposited and grown, and even with a thin film of about 1 nm, it is possible to form a uniform film with good shape followability. Further, by limiting the type of alkali in the composition for forming a silica film, it is possible to obtain a silica film having a very low content of alkali metals such as sodium, so that the silica film does not dissolve even in a high-temperature and high-humidity atmosphere. It has the characteristic that the physical property of a film does not change.
[0054]
(Second coating)
Next, a dense silica coating (second coating) derived from polysilazane will be described. The silica second coating of the present invention is formed using polysilazane. The thickness of such a silica film is preferably about 0.01 to 0.5 μm, and more preferably about 0.05 to 0.25 μm. By setting it as such a film thickness, the function as a moisture-proof film becomes sufficient, and it is possible to obtain light-emitting particles with good dispersibility without causing a decrease in the initial luminescence intensity. When the film thickness is 0.01 μm or less, the function as a moisture-resistant film is insufficient, and when it is 0.5 μm or more, the initial luminous intensity is lowered and the dispersibility may be impaired.
[0055]
In addition, the silica film by the sol-gel method for obtaining a silica film by a typical wet surface treatment or the above-mentioned first film has a large mass loss due to desorption of hydroxy group and alkoxy group at the time of silica conversion. The crack is likely to occur at a film thickness of 0.5 μm or more.
[0056]
On the other hand, in silica conversion using polysilazane, due to the reaction mechanism described later, mass increase occurs during silica conversion, volume shrinkage is small, and cracks are hardly generated at a relatively low temperature during silica film conversion.
[0057]
The second film forms a dense film having a refractive index of 1.45 or more, among which 1150 to 1250 cm. ^-1 And 1000-1100cm ^-1 Of the absorption peak intensity I of the infrared absorption spectrum (I = I ₁ / I ₂ : I ₁ 1150-1250cm ^-1 Absorbance of absorption peak due to Si-OH, I ₂ Is 1000-1100cm ^-1 (Absorbance of absorption peak due to Si—O—Si) of less than 0.2 is preferable. The refractive index is that of fused silica glass (density 2.2 g / cm ^Three , Showing a value close to a refractive index of 1.46) and substantially SiO2. ₂ A film is formed.
[0058]
The polysilazane used in the present invention is a polymer having a silicon-nitrogen bond, and is composed of Si—N, Si—H, NH, etc. ₂ The ceramic precursor inorganic polymer. For example, the general formula 1 disclosed in JP-A-8-236274 (provided that R ¹ , R ² , R ^Three Are independently a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, or a group other than these groups in which the group directly connected to silicon is carbon, an alkylsilyl group, an alkylamino group, an alkoxy group, or a metal atom Represents. However, R ¹ , R ² , R ^Three At least one of them is a hydrogen atom. Those having a main skeleton composed of units represented by
[0059]
[Chemical 1]

[0060]
In the present invention, perhydropolysilazane whose side chains are all hydrogen is preferable from the viewpoint of the function and hardness of the ceramic film as a moisture-resistant film. A polysilazane having an organic group in the side chain is poor in density because the organic group remains after curing. The production method of perhydropolysilazane is reported in, for example, Japanese Patent Publication No. 63-16325, D. Seyferth et al., Communication of Am. Cer. Soc., C-13, January 1983. Perhydropolysilazane is presumed to have a linear structure and a ring structure centered on 6- and 8-membered rings. The molecular weight is 100 to 50000 in number average molecular weight (Mn). If the molecular weight of the polysilazane used is too small, the yield upon curing is low, which is not practical. On the other hand, if the molecular weight is too large, the stability of the solution is low and a dense film cannot be obtained. For these reasons, the molecular weight of the polysilazane used is a number average molecular weight and the lower limit is 100, preferably 300, more preferably 500. The upper limit is 50,000, preferably 20,000, and more preferably 10,000.
[0061]
These are in a solution state dissolved in an organic solvent, for example, polysilazane (SiH) diluted with xylene. ₂ NH) n (manufactured by Tonen Co., Ltd.), poly (1,1-dimethylsilazane) telomer (manufactured by Asmax Co., Ltd.), perhydrosilazane (manufactured by Clariant Japan Co., Ltd.) and the like can be used.
[0062]
Solvents include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbon hydrocarbon solvents, halogenated hydrocarbons such as halogenated methane, halogenated ethane, and halogenated benzene, aliphatic ethers, and alicyclic ethers. Etc. can be used. Preferred solvents are halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, bromoform, ethylene chloride, ethylidene chloride, trichloroethane, tetrachloroethane, ethyl ether, isopropyl ether, ethyl butyl ether, dibutyl ether, 1,2-dioxyethane, Ethers such as dioxane, dimethyldioxane, tetrahydrofuran, tetrahydropyran, cellosolve acetate, carbitol acetate, pentanehexane, isohexane, methylpentane, heptane, isoheptane, octane, isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, benzene , Hydrocarbons such as toluene, xylene, and ethylbenzene. Among these, xylene and dibutyl ether are particularly preferable from the viewpoint of solubility, stability, and uniform film property.
[0063]
When these solvents are used, two or more kinds of solvents may be mixed in order to adjust the solubility of polysilazane and the evaporation rate of the solvent. The amount (ratio) of the solvent used is selected so as to improve workability depending on the coating method employed, and depending on the required film thickness, and also varies depending on the average molecular weight, molecular weight distribution, and structure of the polysilazane. The solvent can be mixed up to about 99.99% by mass, preferably in the range of 0.1 to 50% by mass of the solid content concentration. When the solid content concentration is less than 0.1% by mass, the formation rate of the silica coating is extremely slow and not practical. Moreover, when it exceeds 50 mass%, since a silica particle may produce | generate in a composition, without forming a film, it is unpreferable.
[0064]
As described above, polysilazane is a ceramic precursor polymer, and in order to form a silica film using this, it is fired in the atmosphere at 400 ° C. or higher, for example, SiO 2 by the reaction shown in (Formula 2). ₂ However, in the case of a coated illuminant, if the temperature is 400 ° C. or higher, the initial luminescence intensity decreases due to localization of the activator and coactivator, which is not preferable.
[0065]
[Chemical 2]

[0066]
On the other hand, a dense silica film can be obtained at a temperature of 100 ° C. or less by combining a wet film of polysilazane with steam oxidation in the presence of a catalyst. As described above, it can be applied to a substrate having low heat resistance such as the coated phosphor. Since the film can be formed, the initial luminescence intensity is not lowered.
[0067]
In particular, a polysilazane containing no carbon (C) component forms a dense film having good wettability (easily compatible) with the underlying first film. Further, there is no problem of film shrinkage or residual carbon during thermal decomposition such as a sol-gel film using an alkoxide system, and cracks do not occur.
[0068]
As the catalyst, an amine or a metal ion catalyst can be used, or a combination of both may be used.
Although the kind of amine is not particularly limited, for example, amines such as triethylamine, trimethylamine, diethylamine, monoethanolamine, diethanolamine, triethanolamine, n-exylamine, n-butylamine, tri-n-butylamine, guanidine, piganine, imidazole, etc. Can be used. Among these, trimethylamine and triethylamine are preferable in terms of solubility, uniform coverage, and low-temperature curability. The density | concentration in the composition for silica film formation is 0.1-10 mass%, Preferably it is 1-8 mass%, More preferably, it is 1-5 mass%. If it is 0.1% by mass or less, the conversion rate to silica is slow and not economical, and if it is 10% by mass or more, the silica conversion rate becomes too high and the uniform film property is deteriorated or the phosphor particles are fixed and dispersibility. Damage. For example, a composition obtained by adding triethylamine to polysilazane is applied to the luminescent particles by contact, spraying or impregnation, and then kept at 95 ° C. and 80% RH for about 3 hours to form a dense silica film. In addition, the luminous particles obtained by applying polysilazane having a Mn of 100 to 50000 to the vapor (non-phase) of an aqueous solution containing trimethylamine are subjected to gas phase contact at 25 ° C. for about 2 minutes, and then held at 95 ° C. in an 80% RH atmosphere for about 3 hours. A dense silica coating is formed.
[0069]
When metal ions are used as a catalyst, examples of metals include Ag, Au, Pd, and Ni. Among these, Pd is preferable in terms of uniform coverage and low temperature curability. The density | concentration in the composition for silica film formation is 0.1-10 mass%, Preferably it is 1-5 mass%, More preferably, it is 1-3 mass%. If it is 0.1% by mass or less, the conversion rate to silica is slow and not economical, and if it is 5% by mass or more, the silica conversion rate becomes too high and the uniform coating property is impaired, or the phosphor particles are fixed and dispersibility. Damage. For example, a fine silica coating can be obtained by applying a composition obtained by adding Pd to polysilazane having a Mn of 100 to 50000 to a light emitting particle, bringing it into contact with spraying or impregnation, and then drying and baking at a low temperature of 100 to 350 ° C. .
[0070]
If necessary, a leveling agent, an antifoaming agent, an antistatic agent, an ultraviolet absorber, a pH adjuster, a dispersant, a surface modifier, a flow inhibitor, etc. may be added to the silica film forming composition. Good.
[0071]
Also, when there is no first coating, that is, when a silica coating derived from polysilazane is directly applied to the uncoated luminescent particles, the adhesion with the particles is insufficient, and a uniform coating state cannot be obtained, improving the moisture resistance. I was not able to admit. That is, due to the presence of the first coating, sufficient adhesion of the second coating derived from polysilazane can be secured, and a synergistic improvement in moisture resistance can be achieved even in the second coating having a small thickness.
[0072]
The silica-coated phosphor particles of the present invention may have a hydrophobic surface. In order to make the surface hydrophobic, it is possible to coat the surface with organosiloxanes or silicone resins. Examples of organosiloxanes and silicone resins include methyl hydrogen polysiloxane, dimethyl polysiloxane, methylphenyl polysiloxane, biphenyl polysiloxane, alkyl-modified silicone alkoxy-modified silicone, trimethylsiloxysilicic acid, acrylic silicone, and silicone resin. These organosiloxanes, silicone resins and silane coupling agents, aluminum coupling agents and the like can also be used simultaneously. Preferred organosiloxanes and silicone resins are methyl hydrogen polysiloxane and dimethyl polysiloxane.
[0073]
These coating treatments may be any of wet methods, dry methods, mechanochemical methods and the like. This hydrophobization can further increase the moisture resistance of the light emitter. The coating amount is 0.1 to 5% by mass, preferably 0.1 to 2% by mass with respect to the coated phosphor particles. If it is 0.1% by mass or less, the hydrophobicity is low, and if it is 5% by mass or more, the initial luminescence intensity may be lowered, which is not preferable.
[0074]
The primary particle diameter of the silica-coated phosphor particles of the present invention is not particularly limited, but is preferably 0.1 to 100 μm, preferably 1 to 80 μm, and more preferably 1 to 50 μm. When the primary particle diameter is larger than 100 μm, for example, it is difficult to form a thin light emitter layer in electroluminescence, and the distribution of the light emitters may be uneven. If the primary particles are less than 0.1 μm, the particles tend to solidify and the free-flowing property tends to decrease, which is not preferable.
[0075]
The “primary particles” as used in the present invention refers to those defined by Kuichiro Keiichiro et al., “Powder”, p. 56-66, published in 1979.
[0076]
Moreover, the particle size of the phosphor particles is preferably ultrafine particles (particle size of 0.5 μm or less) by the sol-gel method or those having a particle size of about 0.5 to 100 μm.
[0077]
In the present invention, the film thickness and refractive index of the silica film can be measured using a silica film formed on a silicon wafer immersed in the system at the same time when the silica-coated phosphor particles are synthesized. On this silicon wafer, the same silica coating as that on the phosphor particles is formed. The refractive index of the silica film can be measured by an ellipsometer (manufactured by ULVAC; LASSER ELIPSOMETER ESM-1A). A step gauge can be used for the film thickness measurement.
[0078]
The transmission infrared absorption spectrum (FT-IR-8000 manufactured by JASCO Corporation) of the silica film of the silica-coated phosphor particles can be measured using the KBr method. The primary particle diameter and the silica film thickness of the silica-coated phosphor particles can be determined from a transmission electron microscope image or a scanning electron microscope image.
[0079]
Further, the structure of the first and second coatings in the present invention can confirm the surface layer structure and surface element distribution of about 1 μm depth by surface analysis by X-ray diffraction and EPMA (Electron Probe Microanalysis).
[0080]
【Example】
Examples of the present invention will be described in detail below. However, the present invention is not limited to these examples.
[0081]
The initial luminescence photometry, moisture resistance test, dispersibility test, refractive index measurement, silica film thickness measurement, and infrared absorption spectrum measurement used in the examples were performed by the following methods.
[0082]
(Initial electroluminescence photometric measurement)
Dispersion 1 is obtained by mixing 50 parts by mass of phosphor particles with 15 parts by mass of cyanoethyl cellulose and 35 parts by mass of dimethylformamide. After forming an insulator layer composed of barium titanate and cyanoethyl cellulose on an aluminum back electrode, dispersion 1 was applied with an automatic coating machine to a thickness of 50 μm, dried, and then sandwiched with an ITO (indium tin oxide) transparent electrode. An EL (electroluminescence) element was constructed. The luminous intensity was measured at a relative humidity of 10%, a temperature of 25 ° C., a voltage of 100 V, and a vibration frequency of 400 Hz. The relative value (IBe) of the luminous intensity of the coated phosphor particles of each example was calculated with the luminous intensity of the uncoated phosphor particles as 100.
[0083]
(Electroluminescence moisture resistance test)
Dispersion 1 is obtained by mixing 50 parts by mass of phosphor particles with 15 parts by mass of cyanoethyl cellulose and 35 parts by mass of dimethylformamide. After forming an insulator layer composed of barium titanate and cyanoethyl cellulose on an aluminum back electrode, dispersion 1 was applied with an automatic coating machine to a thickness of 50 μm, dried at 80 ° C. for 1 hour with a warm air dryer, and then an ITO transparent electrode In the meantime, a dispersion type EL element was constructed. The residual ratio of light emission intensity (RBe) in continuous light emission for 100 hours at a relative humidity of 90%, a temperature of 40 ° C., a voltage of 100 V, and a vibration frequency of 400 Hz was determined.
[0084]
(Dispersibility test)
Dispersion 1 is obtained by mixing 50 parts by mass of phosphor particles with 15 parts by mass of cyanoethyl cellulose and 35 parts by mass of dimethylformamide. Dispersion 1 was placed in a settling tube, allowed to stand, and the state in which the phosphor particles settled was visually observed to evaluate the degree of dispersion.
[0085]
The degree of dispersion was determined according to the following criteria.
[0086]
-2 if settled immediately after standing, -1 if settled 1 hour after standing, 0 if settled 3 hours after standing, +1 if settled 9 hours after standing The case where it does not settle after one day later is defined as +2.
[0087]
(Refractive index measurement)
Measurement was performed with an ellipsometer (manufactured by ULVAC; LASSER ELIPSOMETER ESM-1A) using a silica film formed on a silicon wafer immersed in the system when the silica-coated phosphor particles were synthesized.
[0088]
(Film thickness measurement)
Using a silica film formed on a silicon wafer immersed in the system at the time of synthesizing silica-coated phosphor particles, measurement was performed with a step meter (DEKTAK3030, manufactured by SLOAN). A part of the silicon wafer is covered with tape, and the part is peeled off to obtain a step blank. The level difference between the silica coating part and the blank part is measured.
Further, the silica-coated phosphor particles themselves are observed with a transmission electron microscope (JEM 2010, acceleration voltage 200 V, manufactured by JEOL Ltd.), and the silica coating on the particle surface is recognized so as to cover the substrate. It can also be measured by observing the thickness of the film portion having a thin contrast), and a value almost coincident with the measured value by the step gauge can be obtained.
[0089]
(IR spectrum measurement)
The transmission infrared absorption spectrum (FT-IR-8000 manufactured by JASCO Corporation) of the silica-coated phosphor particles is the KBr method (the mixing ratio of each particle of the luminescent particles and KBr is luminescent particles / KBr mass). The ratio was measured using 1/32). 1150-1250cm ^-1 And 1000-1100cm ^-1 The absorbance of the absorption peak is calculated from the transmittance of the infrared absorption spectrum at the absorption peak intensity ratio I (I = I ₁ / I ₂ : I ₁ 1150-1250cm ^-1 Absorbance of absorption peak, I ₂ Is 1000-1100cm ^-1 (Absorbance of absorption peak).
[0090]
Example 1
(Synthesis of the first coating)
Into a 5 L reactor, 440 mL of deionized water, 1860 mL of ethanol (manufactured by Junsei Co., Ltd.) and 40 ml of 25% by mass ammonia water (manufactured by Daisei Kako) are mixed. ): ZnS-based electroluminescent particles; average particle diameter D ₅₀ Suspension 1 was prepared by dispersing 200 g of 25 μm). Next, 20 mL of tetraethoxysilane (manufactured by Nacalai Tesque) and 250 mL of ethanol were mixed to prepare Solution 1.
[0091]
Solution 1 was added to suspension 1 stirred with a magnetic stirrer at a constant rate over 12 hours, and then aged for 12 hours. Film formation and aging were performed at 25 ° C. Thereafter, the solid content was separated by centrifugal filtration, rinsed with 200 ml of ethanol, and then wet solid content was recovered. The wet solid content was vacuum-dried at 80 ° C. for 12 hours to obtain phosphor particles coated with a silica first coating.
[0092]
(Synthesis of second coating)
In a 5 L reactor, 1600 g of xylene (manufactured by Wako Pure Chemical Industries, Ltd.) and 6 g of triethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) are mixed, and 160 g of the phosphor particles coated with the silica first coating are dispersed therein. Suspension 2 was prepared. Next, 20 g of perhydropolysilazane (NL-110-2 manufactured by Clariant Japan Co., Ltd .; xylene solution containing 20% by mass of perhydropolysilazane in terms of oxide) and 160 g of dehydrated xylene (manufactured by Wako Pure Chemical Industries, Ltd.) are mixed. Solution 2 was prepared.
[0093]
The solution 2 was added to the suspension 2 stirred with a magnetic stirrer at a constant rate over 20 hours, and then aged for 12 hours. Film formation and aging were performed at 45 ° C. Thereafter, the solid content was separated by centrifugal filtration, and the wet solid content was recovered. Silica-coated phosphor particles having a wet solid content vacuum-dried at 80 ° C. for 12 hours, further treated in an atmosphere of 95 ° C. and 80% RH for 12 hours, and then vacuum-dried at 95 ° C. for 1 hour to apply a silica second coating. 1 was obtained.
[0094]
(Example 2)
(Synthesis of the first coating)
Into a 5 L reactor, 440 mL of deionized water, 1860 mL of ethanol (manufactured by Junsei Chemical Co., Ltd.) and 40 ml of 25% by mass ammonia water (manufactured by Daisei Kako Co., Ltd.) are mixed. Suspension 3 was prepared by dispersing 200 g of electroluminescent particles). Next, 4 mL of tetraethoxysilane (manufactured by Nacalai Tesque) and 50 mL of ethanol were mixed to prepare a solution 3.
[0095]
Solution 3 was added to suspension 3 stirred with a magnetic stirrer at a constant rate over 2.5 hours, and then aged for 12 hours. Film formation and aging were performed at 25 ° C. Thereafter, the solid content was separated by centrifugal filtration, rinsed with 200 ml of ethanol, and then wet solid content was recovered. The wet solid content was vacuum-dried at 80 ° C. for 12 hours to obtain phosphor particles coated with a silica first coating.
[0096]
(Synthesis of second coating)
In a 5 L reactor, 1600 g of xylene (manufactured by Wako Pure Chemical Industries, Ltd.) and 6 g of triethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) are mixed, and 160 g of the phosphor particles coated with the silica first coating are dispersed therein. Suspension 4 was prepared. Next, 20 g of perhydropolysilazane (NL-110-2 manufactured by Clariant Japan Co., Ltd .; xylene solution containing 20% by mass of perhydropolysilazane in terms of oxide) and 160 g of dehydrated xylene (manufactured by Wako Pure Chemical Industries, Ltd.) are mixed. Solution 4 was prepared.
[0097]
The solution 4 was added to the suspension 4 stirred with a magnetic stirrer at a constant rate over 20 hours, and then aged for 12 hours. Film formation and aging were performed at 45 ° C. Thereafter, the solid content was separated by centrifugal filtration, and the wet solid content was recovered. Silica-coated phosphor particles that have been dried in vacuo at 80 ° C. for 12 hours, further treated for 12 hours in an atmosphere of 95 ° C. and 80% RH, and then vacuum-dried at 95 ° C. for 1 hour to give a silica second coating. 2 was obtained.
[0098]
(Example 3)
(Synthesis of the first coating)
Into a 5 L reactor, 440 mL of deionized water, 1860 mL of ethanol (manufactured by Junsei Chemical Co., Ltd.) and 40 ml of 25% by mass ammonia water (manufactured by Daisei Kako Co., Ltd.) are mixed. Suspension 5 was prepared by dispersing 200 g of electroluminescent particles). Next, 20 mL of tetraethoxysilane (manufactured by Nacalai Tesque) and 250 mL of ethanol were mixed to prepare a solution 5.
[0099]
The solution 5 was added to the suspension 5 being stirred with a magnetic stirrer at a constant rate over 12 hours, and then aged for 12 hours. Film formation and aging were performed at 25 ° C. Thereafter, the solid content was separated by centrifugal filtration, rinsed with 200 ml of ethanol, and then wet solid content was recovered. The wet solid content was vacuum-dried at 80 ° C. for 12 hours to obtain phosphor particles coated with a silica first coating.
[0100]
(Synthesis of second coating)
In a 5 L reactor, 1600 g of xylene (manufactured by Wako Pure Chemical Industries, Ltd.) and 6 g of triethylamine (manufactured by Wako Pure Chemical Industries, Ltd.) are mixed, and 160 g of the phosphor particles coated with the silica first coating are dispersed therein. Suspension 6 was prepared. Next, 5 g of perhydropolysilazane (CL-110-2 manufactured by Clariant Japan KK; xylene solution containing 20% by mass of perhydropolysilazane in terms of oxide) and 40 g of dehydrated xylene (manufactured by Wako Pure Chemical Industries, Ltd.) are mixed. Solution 6 was prepared.
[0101]
Solution 6 was added to suspension 6 stirred with a magnetic stirrer at a constant rate over 5 hours, and then aged for 12 hours. Film formation and aging were performed at 45 ° C. Thereafter, the solid content was separated by centrifugal filtration, and the wet solid content was recovered. Silica-coated phosphor particles that have been dried in vacuo at 80 ° C. for 12 hours, further treated for 12 hours in an atmosphere of 95 ° C. and 80% RH, and then vacuum-dried at 95 ° C. for 1 hour to give a silica second coating. 3 was obtained.
[0102]
(Comparative Example 1)
Uncoated phosphor particles (the same LUMILUX Blue EL as used in Example 1) itself were used as comparative control particles 1.
[0103]
(Comparative Example 2)
In Example 1, silica first-coated phosphor particles (without silica second coating) were obtained in the same manner as in Example 1 except that the silica second coating was not applied. .
[0104]
(Comparative Example 3)
In Example 1, a silica first-coated phosphor particle (without silica second coating) was obtained in the same manner as in Example 1 except that the tetraethoxysilane was 40 ml and the silica second coating was not applied. Control particle 3 was designated.
[0105]
(Comparative Example 4)
In Example 1, silica-coated phosphor particles in which a silica film derived from polysilazane was directly applied to the phosphor particles were obtained in the same manner as in Example 1 except that the silica first film was not applied, and comparative control particles were obtained. It was set to 4. In this case, since the adhesion and uniform coverage of the film are poor, the surface treatment state of the comparative control particles is that there are many fine silica particles, and in addition to the surface of the phosphor particles, the formation of single silica particles is not possible. Admitted.
[0106]
When the transmission infrared absorption spectra of the silica-coated phosphor particles obtained in Examples 1 to 3 and the comparative control particles of Comparative Examples 2 to 4 were measured by the KBr method, all the phosphor particles were 1000 to 1100 cm. ^-1 The absorption derived from Si—O—Si stretching vibration was observed in 2800 to 3000 cm. ^-1 In addition, absorption derived from C—H stretching vibration was not observed within the detection limit, and the produced coating was identified as silica.
[0107]
Further, Table 1 summarizes the results of measuring the silica film thickness, the absorption peak intensity ratio I of the infrared absorption spectrum, and the refractive index of the silica first coating and the second coating. The refractive index is that of fused silica glass (density 2.2 g / cm ^Three The refractive index is close to 1.46), so that the coating composition is substantially SiO. ₂ It was confirmed that.
[0108]
Table 2 shows the results of evaluating the initial electroluminescence intensity (IBe), electroluminescence moisture resistance (RBe), and dispersity of the phosphor particles of Examples 1 to 3 and Comparative Examples 1 to 4.
[0109]
[Table 1]

[0110]
[Table 2]

[0111]
【The invention's effect】
The present invention provides silica-coated phosphor particles having excellent moisture resistance, initial luminescence intensity equivalent to that of non-coated products, good denseness and adhesion of the coating, and excellent dispersibility and moldability without particle adhesion. Therefore, the phosphor particles can be used for a dispersed light emitting layer of an electroluminescence element.
[0112]
[Brief description of the drawings]
FIG. 1 is an infrared absorption spectrum of phosphor particles having a silica first coating produced in Example 1. FIG.
2 is an infrared absorption spectrum of phosphor particles having a silica second coating produced in Example 1. FIG.

Claims (14)

Thickness is 0.01 to 0.5 [mu] m, the refractive index is at 1.435 or more, and the ratio I of absorption peak intensity of 1150～1250Cm ^-1 and 1000～1100Cm ^-1 in its infrared absorption spectrum ( _{I = I 1 / I 2:} I 1 is the absorbance of the absorption peak of 1150~1250cm ^-1, silica film _{I 2} is the absorbance of the absorption peak of 1000～1100Cm ^-1) is 0.2 or more (first coating) The film thickness is 0.01 to 0.5 μm, the refractive index is 1.45 or more, and 1150 to 1250 cm ⁻¹ and 1000 in the infrared absorption spectrum. ~1100cm ratio of the absorption peak intensity of _{^{-1 I (I = I 1 /}} I 2: I 1 is the absorbance of the absorption peak of 1150~1250cm ^-1, _{I 2} is 1000～1100Cm ^-1 Absorbance of absorption peak) is less than 0.2, the coated phosphor particles with silica membranes from polysilazane (second film).   The phosphor particle according to claim 1, wherein the polysilazane is perhydropolysilazane.   The phosphor particles according to claim 2, wherein the polysilazane has a number average molecular weight in the range of 100 to 50,000.   4. The phosphor particles according to claim 1, wherein the outermost surface is hydrophobized.   1) The phosphor particles are brought into contact with a silica film-forming composition containing at least an organic group and a halogen-free silicic acid or a silicic acid precursor capable of producing the silicic acid, and 2) water, 3) alkali, and 4) an organic solvent. And a step of bringing the phosphor particles into contact with a composition for forming a silica film containing at least a polysilazane and 2) an organic solvent, 3) an amine and / or a metal ion catalyst.   1) The phosphor particles are brought into contact with a silica film forming composition containing at least an organic group and a halogen-free silicic acid or a silicic acid precursor capable of producing the silicic acid, and 2) water, 3) alkali, and 4) an organic solvent. A step of contacting phosphor particles with a composition for forming a silica film containing at least 1) a polysilazane and 2) an organic solvent, 3) an amine and / or a metal ion catalyst, and then bringing the phosphor particles into contact with water vapor. Production method.   The method for producing phosphor particles according to claim 5 or 6, wherein the polysilazane is polydilazan having a number average molecular weight of 100 to 50,000.   1) The phosphor particles are brought into contact with a silica film forming composition containing at least an organic group and a halogen-free silicic acid or a silicic acid precursor capable of producing the silicic acid, and 2) water, 3) alkali, and 4) an organic solvent. In the process, the water / organic solvent ratio (based on the charged capacity) is used in the range of 0.1 to 10 and the silicic acid concentration is in the range of 0.0001 to 5 mol / liter. The method for producing phosphor particles according to any one of claims 5 to 7, wherein the silica is selectively coated, and then the first film is applied by drying.   The phosphor particles according to claim 1, wherein the phosphor particles emit fluorescence.   The method for producing phosphor particles according to any one of claims 5 to 8, wherein the phosphor particles emit fluorescence.   A dispersion-type light emitting device using the phosphor particles according to claim 1.   A dispersive electroluminescence device using the phosphor particles according to claim 5.   The phosphor according to any one of claims 1 to 4, wherein the phosphor particles are made of at least one selected from zinc sulfide (ZnS), calcium sulfide (CaS), and strontium sulfide (SrS). particle.   The phosphor according to any one of claims 5 to 8, wherein the phosphor particles are made of at least one selected from zinc sulfide (ZnS), calcium sulfide (CaS), and strontium sulfide (SrS). Particle production method.

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