JP3881876B2 - Polymer compound and organic thin film device using the same - Google Patents

Description

【００１４】
【化４】

【００１５】
式（Ｉ）及び（II）中、ｎは重合度を表す正の整数。Ｒは、水素原子、アルキル基、アルコキシ基、エステル基、シアノ基、アリール基、または、アルキル基、アルコキシ基、エステル基、シアノ基の群より選ばれる置換基を有するアリール基、または、窒素原子とアリール基からなるトリフェニルアミン誘導体を示す。Ａｒ¹は、水素原子、アルキル基、アルコキシ基、エステル基、アリール基、または、アルキル基、アルコキシ基、エステル基、シアノ基の群より選ばれる置換基を有するアリール基、または、窒素原子とアリール基からなるトリフェニルアミン誘導体を示す。Ａｒ²は、アルキル基、アルコキシ基、エステル基、アリール基、または、アルキル基、アルコキシ基、エステル基、シアノ基の群より選ばれる置換基を有するアリール基、または、窒素原子とアリール基からなるトリフェニルアミン誘導体を示す。または、機能性を有する共役性有機材料である。
この高分子化合物は、平均重合度が２〜１００００であることが望ましい。
上記高分子化合物は、有機薄膜素子、特に、有機エレクトロルミネッセンス素子の電荷輸送層や発光層、または、電子写真用感光体に好適である。
【００１６】
【発明の実施の形態】
以下に、本発明を詳細に説明する。本発明の高分子電荷輸送材料は、青色の蛍光を示すフェノキサジンにハロゲン原子を導入した誘導体を重合することにより得られるものである。例えば、ジブロモフェノキサジン誘導体をニッケル触媒を用いて重合させる、または、ジブロモフェノキサジン誘導体とジホウ酸化したフェノキサジン誘導体をパラジウム触媒を用いる鈴木カップリング法で重合させることで得ることが可能となる。
【００１７】
上記以外にフェノキサジンを主鎖骨格に有する高分子化合物を合成する方法としては、他の有機化合物と共重合させて新規の高分子化合物を得ることができる。これは、ジブロモフェノキサジン誘導体とジホウ酸化させた機能性を有する分子構造を持つ有機材料を共重合させることで、主鎖骨格にフェノキサジンと機能性を有する分子構造をもつ新規な高分子化合物を合成することが可能となる。
【００１８】
上記一般式（Ｉ）〜（II）で示される本発明の高分子化合物において、Ｒは、水素原子、アルキル基、アルコキシ基、エステル基、シアノ基、アリール基からなる群より選ばれる置換基を示す。または、アルキル基、アルコキシ基、エステル基、シアノ基からなる群より選ばれる置換基を一つあるいは複数有するアリール基でもよい。または、窒素原子とアリール基からなるトリフェニルアミン誘導体を示す。Ｒは互いに同一であっても異なっていても良い。
Ａｒ¹は、水素原子、アルキル基、アルコキシ基、エステル基、アリール基から選ばれる置換基を示す。または、アルキル基、アルコキシ基、エステル基、シアノ基からなる群より選ばれる置換基を一つあるいは複数有するアリール基を示す。または、窒素原子とアリール基からなるトリフェニルアミン誘導体を示す。
Ａｒ²は、アルキル基、アルコキシ基、エステル基、アリール基を示す。または、アルキル基、アルコキシ基、エステル基、シアノ基からなる群より選ばれる置換基を一つあるいは複数有するアリール基を示す。または、窒素原子とアリール基からなるトリフェニルアミン誘導体、または、機能性を有する共役性有機材料を示す。
【００１９】
上記のＲで示される置換基をより具体的に示す。
アルキル基には、メチル基、エチル基、イソプロピル基、ターシャリーブチル基、シクロヘキシル基、トリフルオロメチル基、ベンジル基等に代表される置換基（ここで飽和環状炭化水素基もアルキル基に含む）が挙げられる。
アルコキシ基には、メトキシ基、エトキシ基、イソプロポキシ基、ターシャリーブトキシ基、フェノキシ基、ナフトキシ基等に代表される置換基が挙げられる。
エステル基には、脂肪族および芳香族エステルを具体例として挙げることができる。
また、アリール基には、フェニル基、ナフチル基、ビフェニル基、トリフェニル基などの芳香族化合物や、ピリジン環、キノリン環、チオフェン環等に代表される酸素原子や窒素原子および硫黄原子等のヘテロ原子を一つあるいは複数含む芳香族化合物を具体例として挙げることができる。
トリフェニルアミン誘導体としては、トリフェニルアミン、ジフェニルナフチルアミン、テトラフェニルジアミノビフェニル等の正孔輸送材料として知られている三級アミン化合物が挙げられる。この三級アミン化合物はアルキル基、アルコキシ基の置換基を有していても良い。
【００２０】
上記のＡｒ¹で示される置換基を具体的に示す。
アルキル基には、メチル基、エチル基、イソプロピル基、ターシャリーブチル基、シクロヘキシル基、トリフルオロメチル基、ベンジル基等に代表される置換基（ここで飽和環状炭化水素基もアルキル基に含む）が挙げられる。
アルコキシ基には、メトキシ基、エトキシ基、イソプロポキシ基、ターシャリーブトキシ基、フェノキシ基、ナフトキシ基等に代表される置換基が挙げられる。
エステル基には、脂肪族および芳香族エステルを具体例として挙げることができる。
また、アリール基としては、フェニレン基、ナフチレン基、ビフェニレン基、トリフェニレン基などの芳香族化合物や、ピリジン環、キノリン環、チオフェン環等に代表される酸素原子や窒素原子および硫黄原子等のヘテロ原子を一つあるいは複数含む芳香族化合物を具体例として挙げることができる。
トリフェニルアミン誘導体としては、トリフェニルアミン、ジフェニルナフチルアミン、テトラフェニルジアミノビフェニル等の正孔輸送材料として知られている三級アミン化合物が挙げられる。この三級アミン化合物はアルキル基、アルコキシ基の置換基を有していても良い。
【００２１】
上記のＡｒ²で示される置換基を具体的に示す。
アルキル基には、メチル基、エチル基、イソプロピル基、ターシャリーブチル基、シクロヘキシル基、トリフルオロメチル基、ベンジル基等に代表される置換基（ここで飽和環状炭化水素基もアルキル基に含む）が挙げられる。
アルコキシ基には、メトキシ基、エトキシ基、イソプロポキシ基、ターシャリーブトキシ基、フェノキシ基、ナフトキシ基等に代表される置換基が挙げられる。
エステル基には、脂肪族および芳香族エステルを具体例として挙げることができる。
また、アリール基としては、フェニレン基、ナフチレン基、ビフェニレン基、トリフェニレン基などの芳香族化合物や、ピリジン環、キノリン環、チオフェン環等に代表される酸素原子や窒素原子および硫黄原子等のヘテロ原子を一つあるいは複数含む芳香族化合物を具体例として挙げることができる。
トリフェニルアミン誘導体としては、トリフェニルアミン、ジフェニルナフチルアミン、テトラフェニルジアミノビフェニル等の正孔輸送材料として知られている三級アミン化合物が挙げられる。この三級アミン化合物はアルキル基、アルコキシ基等の置換基を有していても良い。
【００２２】
機能性を有する有機材料の具体例としては、アントラセン、ベンゾアントラセン、フルオレン等およびフェニレンビニレンに代表される二重結合あるいは三重結合を分子構造に含む蛍光性を有する芳香族化合物、またはカルバゾール、アクリドン、クマリン等に代表される酸素原子や窒素原子および硫黄原子等のヘテロ原子を一つあるいは複数含む芳香族化合物、さらには、ハロゲン化アルキル基を有しているクマリンやＤＣＭ等に代表されるレーザー色素およびＥＬ素子に用いられているＡｌｑやジスチリルアリーレン誘導体等も具体例として挙げることができる。これらの機能性を有する有機材料は、メチル基、エチル基、イソプロピル基、ターシャリーブチル基、トリフルオロメチル基、シクロヘキシル基等のアルキル基、メトキシ基やエトキシ基、イソプロポキシ基等に代表されるアルコキシ基、シアノ基、またはフェニル基やトリル基、ナフチル基等に代表されるアリール基を置換基として有していてもよい。
【００２３】
本発明の高分子化合物は、薄膜として利用する場合の有機溶剤への溶解性および薄膜を作製するコーティング方法を考慮すると、平均重合度が２〜１０,０００であることが望ましい。１０〜１,０００であればより好ましい。
【００２４】
上述した本発明の高分子化合物は、フェノキサジンを主鎖骨格に導入されていることで高い正孔輸送性能および発光特性の発現し、有機ＥＬ素子および電子写真感光体の電荷輸送層または発光層に適用できる。
即ち、本発明の高分子化合物は、有機ＥＬ素子に適用する場合、その正孔注入輸送層または発光層のいずれかに適用でき、その場合の他方の層には、正孔注入輸送層または発光層として周知の材料を適用できる。また、本発明の高分子化合物を電子写真感光体に適用する場合、電荷発生層または電荷輸送層のいずれかに適用でき、その場合、他方の層には、電荷発生層または電荷輸送層として周知の材料を適用できる。この場合、本発明の高分子化合物は、有機ＥＬ素子においては発光層に適用することが、また、電子写真感光体においては電荷輸送層に適用することが、より顕著な作用効果を発揮するので好ましい。
また、本発明の高分子化合物は、他の電荷輸送材料や発光材料等と混合して用いることも可能である。
さらに、本発明の高分子化合物では、高い電荷発生性及び電荷輸送性を共に発揮することから、有機ＥＬ素子の正孔注入輸送層と発光層を兼用した層として用いることができ、また、電子写真感光体の電荷発生層と電荷輸送層を兼用した層として用いることも可能となる。この場合、層構成が減少するので、製造コストを大幅に削減できる。
また、薄膜形成法としては、低分子材料のような蒸着方法ではなく、より容易な湿式法、例えば、スピンコート法、キャスト法、印刷等の一般的な方法の適用が可能で、薄膜形成の容易性にも優れている。
【００２５】
さらに、高分子化合物なので耐熱性及び耐久性に優れ、また、結晶性を抑制し、ガラス転移温度を低分子化合物よりも高くすることが可能となり、熱的安定性と機械的強度が高い。従って、この高分子化合物を適用した有機ＥＬ素子や電子写真感光体の信頼性を高めることができる。また、低公害で環境上の理由からも優れている。
また、置換基を導入することで、有機溶剤に対する溶解性を向上させることも可能であり、機能性有機材料と共重合させることで、発光色や蛍光特性を変化させたり、電荷輸送特性を向上させることも可能となる。また、置換基の導入や共重合することで、高分子構造を制御することも可能となり、耐熱性の向上やスピンコート法、印刷等により作製した薄膜の安定性および機械的強度の向上、耐光性、耐酸化性等の新たな特性の付与を図ることも可能となる。
【００２６】
【実施例】
以下、本発明の実施例について説明する。
［実施例１］
不活性ガス雰囲気中で、Ｎ−（４−ブチル）フェニル−３,６−ジブロモフェノキサジン２.５ｍＭ、塩化ニッケル０.１２５ｍＭ、トリフェニルホスフィン０.２５ｍＭ、２,２'−ビピリジン０.１２５ｍＭ、亜鉛７.７５ｍＭをジメチルホルムアミド３ｍｌに加え、９０℃で２４時間反応させた。反応終了後、メタノールを加えて沈殿させ、良溶媒にクロロホルム、貧溶媒としてメタノールを用いた再沈殿法で精製した後、さらに展開溶媒にトルエン：ヘキサン（１：１）を用いたシリカゲルカラムクロマトグラフィーにより精製し、下記化学式（III）に示す黄色粉末状の高分子化合物を得た。収率は５５％であった。
【００２７】
【化５】

【００２８】
図１に、得られた高分子化合物の¹Ｈ−ＮＭＲスペクトル（日本電子（株）社製 ＪＥＯＬ Ａ−５００を使用、重クロロホルム溶媒）を示す。
¹Ｈ−ＮＭＲ（ＣＤＣｌ₃、ＴＭＳ） s（ｐｐｍ）：０.７〜１.１（３Ｈ、ＣＨ₃）、１.３〜１.５（２Ｈ，ＣＨ₂）、１.５〜１.８（２Ｈ，ＣＨ₂）、２.５〜２.８（２Ｈ，ＣＨ₂）、５.７〜６.０（２Ｈ，ＣＨ）、６.５〜６.８（２Ｈ、ＣＨ）、６.７〜７.０（２Ｈ、ＣＨ）、７.１〜７.３（２Ｈ，ＣＨ）、７.２〜７.５（２Ｈ，ＣＨ）
また、この高分子化合物について、ポンプとして日本分光工業社製の８８０−ＰＵを用い、検出器として日本分光工業社製の示差屈折計８３０−ＲＩを用い、スチレンゲルを固定相、クロロホルムを移動相としてＧＰＣ測定を行ったところ、重量平均分子量は１２,０００（昭和電工社製 標準ポリスチレン換算）であった。平均重合度は３８である。
次に、この高分子化合物について、セイコー電子工業社製のＤＳＣ２２０を用いて、窒素雰囲気下、昇温速度１０℃／ｍｉｎの条件下で融点の測定を行った結果、融点は３５９℃であり、高い耐熱性、熱的安定性を発揮するものであった。
【００２９】
さらに、この高分子化合物からなるキャスト膜を白金電極上に形成し、窒素雰囲気下、アセトニトリル中で、参照電極にＡｇ／ＡｇＣｌを用い、東方技研製ＰＳ−０６により、この高分子化合物の酸化電位を測定した結果、０.３〜０.７Ｖ付近に陽極酸化に基づくブロードな酸化波がみられ、０.６〜０.２Ｖ付近に対応する還元波がみられた。
また、このキャスト膜は掃引を繰り返し行っても酸化還元波に波形の変化はみられず、このことからこの高分子化合物は電気化学的に安定であることが分かった。フェノキサジン骨格であるＮ−（４−ブチル）フェノキサジンの陽極酸化に基づく酸化波は０.５Ｖ付近に、対応する還元波は０.４Ｖ付近にあらわれた。
また、この高分子化合物の発光特性を評価した結果、トルエン溶液中においてピーク波長が４５１ｎｍの青色、薄膜においてはピーク波長が４５９ｎｍの青色の蛍光を示すことが分かった。
【００３０】
［実施例２］
不活性ガス雰囲気中で、Ｎ−（２−エチル）ヘキソキシ−３,６−ジブロモフェノキサジン１.０ｍＭ、４,４'−ビス（４,４,５,５−テトラメチル−１,３,２−ジオキサボロラン−２−イル）ビフェニル１.０ｍＭ、テトラ（トリフェニルホスフィン）パラジウム０.０１ｍＭを２.５ｍｌのテトラヒドロフランと１.７ｍｌの炭酸カリウム水溶液に加え、６０℃で４８時間反応させた。反応終了後、メタノールを加えて沈殿させ、沈殿物を希塩酸で洗浄した後、良溶媒にクロロホルム、貧溶媒としてアセトンを用いた再沈殿法で精製した後、さらに展開溶媒にトルエン：ヘキサン（１：１）を用いたシリカゲルカラムクロマトグラフィーにより精製し、下記化学式（IV）に示す黄色粉末状の高分子化合物を得た。収率は８８％であった。
【００３１】
【化６】

【００３２】
図２に、得られた高分子化合物の¹Ｈ−ＮＭＲスペクトル（日本電子（株）社製 ＪＥＯＬ Ａ−５００を使用、重クロロホルム溶媒）を示す。
¹Ｈ−ＮＭＲ（ＣＤＣｌ₃、ＴＭＳ） s（ｐｐｍ）：０.８５〜１.０（６Ｈ、ＣＨ₃）、１.３〜１.６（８Ｈ，ＣＨ₂）、１.７〜１.８（１Ｈ，ＣＨ）、３.８〜４.０（２Ｈ，ＣＨ₂）、５.７〜６.０（２Ｈ，ＣＨ）、５.７〜６.１（２Ｈ，ＣＨ）、６.６〜８.０（８Ｈ，ＣＨ）
また、この高分子化合物について、ポンプとして日本分光工業社製の８８０−ＰＵを用い、検出器として日本分光工業社製の示差屈折計８３０−ＲＩを用い、スチレンゲルを固定相、クロロホルムを移動相としてＧＰＣ測定を行ったところ、重量平均分子量は４７,０００（昭和電工社製 標準ポリスチレン換算）であった。平均重合度は８８である。
次に、この高分子化合物について、セイコー電子工業社製のＤＳＣ２２０を用いて、窒素雰囲気下、昇温速度１０℃／ｍｉｎの条件下でガラス転移温度の測定を行った結果、ガラス転移温度は１７３℃であった。
この高分子化合物の発光特性を評価した結果、トルエン溶液中においてピーク波長が４６５ｎｍの青色、薄膜においてはピーク波長が４７６ｎｍの青色の蛍光を示すことが分かった。
【００３３】
［実施例３］
実施例１で合成した高分子化合物を用いて有機ＥＬ素子を作製した。
まず、パターンを形成したＩＴＯガラス基板上に、実施例１で合成した高分子化合物を溶かしたトルエン溶液を用いてスピンコート法により厚さ２００ｎｍの薄膜を作製した。この高分子薄膜の上に蒸着法によりフッ化リチウム層を０.５ｎｍ形成し、さらにこの上に２００ｎｍのアルミニウム層を形成し、陽極と陰極の間に実施例１の高分子化合物からなる有機層を形成した有機ＥＬ素子を作製した。
ＩＴＯ製陽極と、ＬｉＦ／Ａｌ製陰極の間に直流電流を印加すると、最高３,０００ｃｄ／ｍ²の青色（ピーク波長：４６７ｎｍ）の発光が素子から観測された。このように、本発明の有機ＥＬ素子では、その有機層が高い電荷輸送性および発光特性を発揮することから、単一層で正孔注入輸送層と発光層とを兼用することができ、層構成が簡易で生産コストの削減に大きく寄与できる。
また、この素子は、印加電圧を高くしても低分子を用いた素子とは異なり、薄膜の溶融に代表される変化はみられなかった。この結果から、この高分子化合物を用いることで素子の安定性が認められた。
尚、この実施例では正孔注入輸送層と発光層とを兼用する単一層として本発明の高分子化合物を用いたが、これに限られず、正孔注入輸送層と発光層を相違する材料で構成し、そのいずれかに本発明に係る高分子化合物を適用し、他方に正孔注入輸送層または発光層として公知の材料を適用することもできる。
【００３４】
［実施例４］
実施例１で合成した高分子化合物を用いて図４に示すような電子写真感光体を作製した。
まず、ガラス基板上にＩＴＯを成膜した導電性支持体３２上に、銅フタロシアニンからなる厚さ１００ｎｍの電荷発生層３４を成膜し、その上に、実施例１で製造した高分子化合物を溶かしたトルエン溶液を用いてスピンコート法により厚さ１５００ｎｍの電荷輸送層３６を作製して電子写真感光体を製造した。
この電子写真感光体について、その電荷輸送層３６の表面に対してコロナ放電により帯電させ、画像を露光することにより静電潜像を感光体表面に形成し、この静電潜像を潜像の電荷とは反対に帯電したトナーを用いて現像し、これを普通紙に転写して定着することにより印画を行なった。
その結果、暗所において電荷を表面に保持でき、光照射により電気抵抗が減少して速やかに表面電荷を放出させることができ、光導電性に優れているものであった。
また、クリーニングによる再利用を繰り返しても十分な耐久性を発揮した。
【００３５】
【発明の効果】
フェノキサジン誘導体を主鎖骨格に有する本発明の高分子化合物は、フェノキサジンの高い電荷輸送性および発光特性を示すと同時に、高分子化合物の特徴である高い耐熱性および熱的安定性、機械的強度、耐久性を合わせ持つ優れた材料である。この高分子材料を有機ＥＬ素子や電子写真感光体等の有機薄膜素子に用いることで、素子の電荷輸送特性、発光特性および安定性を向上できる。さらに、薄膜形成に係る製造工程の簡易化も図ることができる。また、従来一般の電荷輸送層と発光層とをもつ多層構成の有機層のいずれかの層に適用できる他、これらを兼ね備えた層として機能させて層構成の削減を図ることもできる。
また、蛍光特性を有する材料を主鎖に導入することで、発光色や蛍光特性を変化させることも可能である。
【図面の簡単な説明】
【図１】 実施例１の高分子化合物の¹Ｈ−ＮＭＲスペクトル図である。
【図２】 実施例２の高分子化合物の¹Ｈ−ＮＭＲスペクトル図である。
【図３】 有機エレクトロルミネッセンス素子の一例を示す断面図である。
【図４】 電子写真感光体の一例を示す断面図である。
【符号の説明】
１４ 陽極
１６ 正孔注入輸送層
１８ 有機発光層
２０ 有機層
２２ 陰極
３２ 支持体
３４ 電荷発生層
３６ 電荷輸送層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polymer compound having charge transport performance and light emission characteristics, and is a polymer material applicable to organic thin film elements typified by organic electroluminescence elements and electrophotographic organic photoreceptors.
[0002]
[Prior art]
At present, research and development of devices using organic thin films are carried out in a wide range of fields, and realization of devices having excellent functions is expected. One example thereof is an electroluminescence (electroluminescence; hereinafter referred to as “EL”) element.
Among them, the organic EL element is a light-emitting element using an organic material utilizing an organic electroluminescence phenomenon, and has attracted attention as a self-luminous flat display element or a flat light source. This organic EL device started from research on anthracene single crystals in the 1960s, and since the development of a thin film multilayer device by CW Tang et al. Of Eastman Kodak Company, Applied Physics Letter Vol. 51, Vol. 12 No. 913 (1987), Journal of Applied Physics Vol. 65, No. 9, No. 3610 (1989), JP-A-59-194393, JP-A-63-264692, JP-A This is disclosed in Japanese Patent Laid-Open No. 63-295695. Even now, active research and development has been conducted in a wide range of fields for this thin-film laminated organic EL element.
[0003]
As shown in FIG. 3, the basic organic EL element has a structure in which an anode 14, a hole injection transport layer 16 that is a charge transport layer, an organic light emitting layer 18, and a cathode 22 are laminated on a substrate 12 in this order. is doing. This is produced, for example, through the following steps.
First, a transparent conductive film mainly made of a composite oxide of indium and tin (hereinafter referred to as “ITO”) as an anode 14 is formed on a transparent insulating substrate 12 such as glass or a resin film by vapor deposition or sputtering. Thus, the anode 14 is formed. Next, a monolayer film or a multilayer film made of an organic hole injection / transport material typified by copper phthalocyanine or an aromatic amine compound is formed on the anode 14 by a vapor deposition method to a thickness of about 100 nm or less, The hole injection transport layer 16 is used. Further, an organic phosphor film such as tris (8-quinolinol) aluminum (hereinafter referred to as “Alq”) is formed as an organic light emitting layer 18 on the hole injecting and transporting layer 16 by a vapor deposition method with a thickness of about 100 nm or less. . Then, an organic EL element is manufactured by forming a laminated body such as an alloy such as Mg: Ag or LiF / Al with a thickness of about 200 nm on the organic light emitting layer 18 to form the cathode 22. Is done.
[0004]
By applying a DC low voltage between the electrodes of such an organic EL element, holes (positive charge) from the anode 14 and electrons (negative charge) from the cathode 22 are injected into the organic layer 20 and applied. Due to the applied electric field, the holes and electrons move inside the organic layer 20 and recombine in the organic light emitting layer 18 to excite the organic fluorescent material. An element using light emission generated when the excited organic phosphor returns to the ground state is an organic EL element. The DC voltage applied to this element is usually 20 V or less, and 10,000 cd / m for an EL element using Alq for the light emitting layer and Mg: Ag alloy for the cathode. ² The above luminance is obtained.
[0005]
[Problems to be solved by the invention]
An organic layer such as a hole injecting and transporting layer and an organic light emitting layer of such an organic EL device must have excellent charge transporting properties and light emitting characteristics. Therefore, most of these charge transport materials are mostly low molecular weight compounds having excellent charge transport properties and light emitting properties.
However, when an organic layer is formed using these low molecular weight compounds, there is a problem that heat resistance is low and thermal stability and mechanical strength are inferior due to high crystallinity and aggregation. Therefore, there is a demand for a charge transport material having insufficient element reliability and excellent heat resistance, thermal stability, and mechanical strength.
[0006]
The high molecular compound is excellent in heat resistance and low in crystallinity as compared with the low molecular compound. Furthermore, even when used as a thin film, it has advantages such as ease of forming a thin film and high mechanical strength.
For organic EL devices using such polymer compounds, a soluble precursor polymer is coated on the electrode to form a thin film, and then subjected to heat treatment to convert it into a conjugated polymer to produce the device. Beginning with a report (WO901314), many devices using conjugated polymers and polysiloxane derivatives represented by polyparaphenylene vinylene derivatives, polythiophene derivatives, polyfluorene derivatives and the like have been reported.
In addition, it is possible to change the emission color by introducing substituents and controlling the molecular structure, and research and development of polymer compounds that emit blue, green, and red light necessary for full-color display have achieved steady results.
However, such a polymer compound still has a problem that the charge transport property and the light emission property are not necessarily sufficient.
[0007]
In the electrophotographic technology, the charge transport material as described above may be used as the photoreceptor.
Regarding electrophotographic technology, since the electrophotographic copying machine using an amorphous selenium photoreceptor has been put into practical use, many inorganic and organic photoreceptor materials have been developed. In the past, inorganic photoreceptor materials such as selenium, zinc oxide, cadmium sulfide have been used as the photoreceptor material of the electrophotographic photoreceptor.
However, since some of these inorganic photoreceptor materials are toxic, it has been pointed out that they may cause environmental problems. Therefore, instead, a low-pollution organic photoreceptor material with high sensitivity and durability has been developed.
[0008]
As shown in FIG. 4, an electrophotographic photoreceptor using an organic photoreceptor material basically has a structure in which a charge generation layer 34 and a charge transport layer 36 are sequentially laminated on a conductive support 32. Yes. Here, the charge generation layer 34 is a layer having a function of generating charges by absorbing light, and the charge transport layer 36 allows the charges generated in the charge generation layer 34 to move in the photoconductor. This is a functional layer.
As described above, when an organic photoreceptor material is used for an electrophotographic photoreceptor, the risk of causing the above-described environmental problems is low. However, since there are few materials having high charge generation properties and charge transport properties at the same time, the charge generation layer is usually used. And a two-layer structure in which a charge transport layer is laminated.
[0009]
In the electrophotographic process using the electrophotographic photosensitive member constituted as described above, the electrophotographic photosensitive member is charged by corona discharge, and an image is exposed to form an electrostatic latent image on the surface of the photosensitive member. The electrostatic latent image is developed using toner charged opposite to the charge of the latent image, and this is transferred to plain paper and fixed to perform printing.
In this process, the electrophotographic photosensitive member is required to be able to hold a charge on the surface in a dark place, and to be excellent in photoconductivity that reduces the electrical resistance by light irradiation and quickly releases the surface charge. In addition, since this photoreceptor is reused by cleaning, excellent durability that can withstand repeated use is also required.
[0010]
The present invention has been made to solve the above-mentioned problems, and is a polymer compound applicable to organic thin film elements such as organic EL elements and electrophotographic photoreceptors, and has high heat resistance, thermal stability, mechanical strength. It is intended to be a polymer compound having durability, excellent charge transportability and light emission characteristics, and excellent in the ease of forming a thin film and the freedom of emission color.
[0011]
[Means for Solving the Problems]
An object of the present invention is to synthesize a polymer compound having phenoxazine in the main chain skeleton having excellent charge characteristics and light emission characteristics, and to provide an organic thin film element exhibiting excellent characteristics by using this. By using a polymer material that is less likely to cause crystallization and aggregation and has excellent thermal stability and mechanical strength, it is possible to solve the problems of low molecular materials.
[0012]
The polymer compound of the present invention is represented by the following general formula (I) or (II) having phenoxazine in the main chain skeleton.
[0013]
[Chemical 3]

[0014]
[Formula 4]

[0015]
In the formulas (I) and (II), n is a positive integer representing the degree of polymerization. R is a hydrogen atom, an alkyl group, an alkoxy group, an ester group, a cyano group, an aryl group, or an aryl group having a substituent selected from the group of an alkyl group, an alkoxy group, an ester group, and a cyano group, or a nitrogen atom And a triphenylamine derivative consisting of an aryl group. Ar ¹ Is a hydrogen atom, an alkyl group, an alkoxy group, an ester group, an aryl group, or an aryl group having a substituent selected from the group of an alkyl group, an alkoxy group, an ester group, and a cyano group, or a nitrogen atom and an aryl group The following triphenylamine derivative is shown. Ar ² Is an alkyl group, an alkoxy group, an ester group, an aryl group, or an aryl group having a substituent selected from the group of an alkyl group, an alkoxy group, an ester group, and a cyano group, or triphenyl consisting of a nitrogen atom and an aryl group An amine derivative is shown. Alternatively, it is a conjugated organic material having functionality.
The polymer compound preferably has an average degree of polymerization of 2 to 10,000.
The polymer compound is suitable for an organic thin film element, particularly a charge transport layer or a light emitting layer of an organic electroluminescence element, or an electrophotographic photoreceptor.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. The polymer charge transport material of the present invention is obtained by polymerizing a derivative in which a halogen atom is introduced into phenoxazine that exhibits blue fluorescence. For example, it can be obtained by polymerizing a dibromophenoxazine derivative using a nickel catalyst, or polymerizing a dibromophenoxazine derivative and a diborated phenoxazine derivative by a Suzuki coupling method using a palladium catalyst.
[0017]
In addition to the above, as a method of synthesizing a polymer compound having phenoxazine in the main chain skeleton, a novel polymer compound can be obtained by copolymerization with another organic compound. This is because a dibromophenoxazine derivative and a diborated organic material with a functional molecular structure are copolymerized to form a novel polymer compound having a functional molecular structure with phenoxazine in the main chain skeleton. It is possible to synthesize.
[0018]
In the polymer compound of the present invention represented by the general formulas (I) to (II), R represents a substituent selected from the group consisting of a hydrogen atom, an alkyl group, an alkoxy group, an ester group, a cyano group, and an aryl group. Show. Alternatively, it may be an aryl group having one or more substituents selected from the group consisting of an alkyl group, an alkoxy group, an ester group, and a cyano group. Alternatively, a triphenylamine derivative composed of a nitrogen atom and an aryl group is shown. R may be the same or different from each other.
Ar ¹ Represents a substituent selected from a hydrogen atom, an alkyl group, an alkoxy group, an ester group, and an aryl group. Alternatively, it represents an aryl group having one or more substituents selected from the group consisting of alkyl groups, alkoxy groups, ester groups, and cyano groups. Alternatively, a triphenylamine derivative composed of a nitrogen atom and an aryl group is shown.
Ar ² Represents an alkyl group, an alkoxy group, an ester group, or an aryl group. Alternatively, it represents an aryl group having one or more substituents selected from the group consisting of alkyl groups, alkoxy groups, ester groups, and cyano groups. Alternatively, a triphenylamine derivative including a nitrogen atom and an aryl group or a conjugated organic material having functionality is shown.
[0019]
The substituent represented by R above will be shown more specifically.
The alkyl group includes a methyl group, an ethyl group, an isopropyl group, a tertiary butyl group, a cyclohexyl group, a trifluoromethyl group, a benzyl group and the like (here, a saturated cyclic hydrocarbon group is also included in the alkyl group). Is mentioned.
Examples of the alkoxy group include substituents represented by a methoxy group, an ethoxy group, an isopropoxy group, a tertiary butoxy group, a phenoxy group, a naphthoxy group, and the like.
Specific examples of the ester group include aliphatic and aromatic esters.
Aryl groups include aromatic compounds such as phenyl, naphthyl, biphenyl, and triphenyl, and hetero atoms such as oxygen, nitrogen, and sulfur represented by pyridine, quinoline, and thiophene rings. Specific examples include aromatic compounds containing one or more atoms.
Examples of the triphenylamine derivative include tertiary amine compounds known as hole transport materials such as triphenylamine, diphenylnaphthylamine, and tetraphenyldiaminobiphenyl. This tertiary amine compound may have an alkyl group or alkoxy group substituent.
[0020]
Ar above ¹ The substituent shown by is shown concretely.
The alkyl group includes a methyl group, an ethyl group, an isopropyl group, a tertiary butyl group, a cyclohexyl group, a trifluoromethyl group, a benzyl group and the like (here, a saturated cyclic hydrocarbon group is also included in the alkyl group). Is mentioned.
Examples of the alkoxy group include substituents represented by a methoxy group, an ethoxy group, an isopropoxy group, a tertiary butoxy group, a phenoxy group, a naphthoxy group, and the like.
Specific examples of the ester group include aliphatic and aromatic esters.
The aryl group includes aromatic compounds such as phenylene group, naphthylene group, biphenylene group, and triphenylene group, and heteroatoms such as oxygen atom, nitrogen atom, and sulfur atom represented by pyridine ring, quinoline ring, thiophene ring, etc. A specific example is an aromatic compound containing one or a plurality of.
Examples of the triphenylamine derivative include tertiary amine compounds known as hole transport materials such as triphenylamine, diphenylnaphthylamine, and tetraphenyldiaminobiphenyl. This tertiary amine compound may have an alkyl group or alkoxy group substituent.
[0021]
Ar above ² The substituent shown by is shown concretely.
The alkyl group includes a methyl group, an ethyl group, an isopropyl group, a tertiary butyl group, a cyclohexyl group, a trifluoromethyl group, a benzyl group and the like (here, a saturated cyclic hydrocarbon group is also included in the alkyl group). Is mentioned.
Examples of the alkoxy group include substituents represented by a methoxy group, an ethoxy group, an isopropoxy group, a tertiary butoxy group, a phenoxy group, a naphthoxy group, and the like.
Specific examples of the ester group include aliphatic and aromatic esters.
The aryl group includes aromatic compounds such as phenylene group, naphthylene group, biphenylene group, and triphenylene group, and heteroatoms such as oxygen atom, nitrogen atom, and sulfur atom represented by pyridine ring, quinoline ring, thiophene ring, etc. A specific example is an aromatic compound containing one or a plurality of.
Examples of the triphenylamine derivative include tertiary amine compounds known as hole transport materials such as triphenylamine, diphenylnaphthylamine, and tetraphenyldiaminobiphenyl. This tertiary amine compound may have a substituent such as an alkyl group or an alkoxy group.
[0022]
Specific examples of the organic material having functionality include an anthracene, benzoanthracene, fluorene and the like, and a fluorescent aromatic compound containing a double bond or a triple bond represented by phenylene vinylene in a molecular structure, or carbazole, acridone, Aromatic compounds containing one or more hetero atoms such as oxygen atoms, nitrogen atoms and sulfur atoms typified by coumarins, and laser dyes typified by coumarins and DCMs having halogenated alkyl groups Specific examples include Alq and distyrylarylene derivatives used in EL devices. Organic materials having these functionalities are represented by alkyl groups such as methyl group, ethyl group, isopropyl group, tertiary butyl group, trifluoromethyl group, and cyclohexyl group, methoxy group, ethoxy group, isopropoxy group, and the like. An alkoxy group, a cyano group, or an aryl group represented by a phenyl group, a tolyl group, a naphthyl group, or the like may be used as a substituent.
[0023]
The polymer compound of the present invention preferably has an average degree of polymerization of 2 to 10,000 in consideration of solubility in an organic solvent when used as a thin film and a coating method for producing the thin film. More preferably, it is 10 to 1,000.
[0024]
The above-described polymer compound of the present invention exhibits high hole transport performance and light emission characteristics due to the introduction of phenoxazine into the main chain skeleton, and the charge transport layer or light emitting layer of the organic EL device and the electrophotographic photosensitive member. Applicable to.
That is, when the polymer compound of the present invention is applied to an organic EL device, it can be applied to either the hole injecting and transporting layer or the light emitting layer. In that case, the other layer has a hole injecting and transporting layer or a light emitting layer. Known materials can be applied for the layer. Further, when the polymer compound of the present invention is applied to an electrophotographic photoreceptor, it can be applied to either a charge generation layer or a charge transport layer, in which case the other layer is known as a charge generation layer or a charge transport layer. Any material can be applied. In this case, since the polymer compound of the present invention can be applied to the light-emitting layer in an organic EL device and applied to a charge transport layer in an electrophotographic photosensitive member, it can exhibit more remarkable effects. preferable.
In addition, the polymer compound of the present invention can be used by mixing with other charge transporting materials, light emitting materials and the like.
Furthermore, since the polymer compound of the present invention exhibits both high charge generation and charge transport properties, it can be used as a layer that combines the hole injection transport layer and the light emitting layer of an organic EL device, It can also be used as a layer that serves both as a charge generation layer and a charge transport layer of a photographic photoreceptor. In this case, since the layer configuration is reduced, the manufacturing cost can be greatly reduced.
In addition, as a thin film forming method, not a vapor deposition method such as a low molecular material, but an easier wet method, for example, a general method such as a spin coating method, a casting method, or printing can be applied. Easy to use.
[0025]
Furthermore, since it is a high molecular compound, it is excellent in heat resistance and durability, can suppress crystallinity, and can have a higher glass transition temperature than a low molecular compound, and has high thermal stability and mechanical strength. Therefore, the reliability of an organic EL element or an electrophotographic photosensitive member to which this polymer compound is applied can be improved. It is also low pollution and excellent for environmental reasons.
In addition, by introducing substituents, it is possible to improve solubility in organic solvents, and by copolymerizing with functional organic materials, the emission color and fluorescence characteristics can be changed, and charge transport characteristics can be improved. It is also possible to make it. In addition, by introducing or copolymerizing substituents, it is also possible to control the polymer structure, improving heat resistance, improving the stability and mechanical strength of thin films produced by spin coating, printing, etc. It is also possible to impart new characteristics such as resistance and oxidation resistance.
[0026]
【Example】
Examples of the present invention will be described below.
[Example 1]
In an inert gas atmosphere, N- (4-butyl) phenyl-3,6-dibromophenoxazine 2.5 mM, nickel chloride 0.125 mM, triphenylphosphine 0.25 mM, 2,2′-bipyridine 0.125 mM, Zinc 7.75 mM was added to 3 ml of dimethylformamide and reacted at 90 ° C. for 24 hours. After completion of the reaction, methanol was added for precipitation, and after purification by a reprecipitation method using chloroform as a good solvent and methanol as a poor solvent, silica gel column chromatography further using toluene: hexane (1: 1) as a developing solvent. To obtain a yellow powdery polymer compound represented by the following chemical formula (III). The yield was 55%.
[0027]
[Chemical formula 5]

[0028]
Fig. 1 shows the obtained polymer compound. ¹ 1 shows an H-NMR spectrum (using JEOL A-500 manufactured by JEOL Ltd., deuterated chloroform solvent).
¹ H-NMR (CDCl _Three , TMS) s (ppm): 0.7 to 1.1 (3H, CH _Three ) 1.3-1.5 (2H, CH ₂ ) 1.5-1.8 (2H, CH ₂ ) 2.5-2.8 (2H, CH ₂ ), 5.7-6.0 (2H, CH), 6.5-6.8 (2H, CH), 6.7-7.0 (2H, CH), 7.1-7.3 (2H) , CH), 7.2 to 7.5 (2H, CH)
Further, for this polymer compound, 880-PU manufactured by JASCO Corporation was used as a pump, a differential refractometer 830-RI manufactured by JASCO Corporation was used as a detector, styrene gel was used as a stationary phase, and chloroform as a mobile phase. As a result of GPC measurement, the weight average molecular weight was 12,000 (converted to standard polystyrene by Showa Denko KK). The average degree of polymerization is 38.
Next, as a result of measuring the melting point under a condition of a temperature rising rate of 10 ° C./min under a nitrogen atmosphere using DSC220 manufactured by Seiko Electronics Industry Co., Ltd., the melting point was 359 ° C. It exhibited high heat resistance and thermal stability.
[0029]
Further, a cast film made of this polymer compound was formed on a platinum electrode, and in the acetonitrile in a nitrogen atmosphere, Ag / AgCl was used as a reference electrode, and the oxidation potential of this polymer compound was measured by PS-06 made by Toho Giken. As a result, a broad oxidation wave based on anodization was observed in the vicinity of 0.3 to 0.7 V, and a corresponding reduction wave was observed in the vicinity of 0.6 to 0.2 V.
In addition, even when the cast film was repeatedly swept, the oxidation-reduction wave showed no change in waveform, which indicates that the polymer compound is electrochemically stable. An oxidation wave based on anodization of N- (4-butyl) phenoxazine, which is a phenoxazine skeleton, appeared in the vicinity of 0.5V, and a corresponding reduction wave appeared in the vicinity of 0.4V.
In addition, as a result of evaluating the light emission characteristics of the polymer compound, it was found that blue fluorescence having a peak wavelength of 451 nm in a toluene solution and blue fluorescence having a peak wavelength of 459 nm in a thin film were exhibited.
[0030]
[Example 2]
In an inert gas atmosphere, N- (2-ethyl) hexoxy-3,6-dibromophenoxazine 1.0 mM, 4,4′-bis (4,4,5,5-tetramethyl-1,3,2) -Dioxaborolan-2-yl) biphenyl 1.0 mM and tetra (triphenylphosphine) palladium 0.01 mM were added to 2.5 ml of tetrahydrofuran and 1.7 ml of an aqueous potassium carbonate solution and reacted at 60 ° C. for 48 hours. After completion of the reaction, methanol was added for precipitation, the precipitate was washed with dilute hydrochloric acid, purified by a reprecipitation method using chloroform as a good solvent and acetone as a poor solvent, and further toluene: hexane (1: Purification by silica gel column chromatography using 1) gave a yellow powdery polymer compound represented by the following chemical formula (IV). The yield was 88%.
[0031]
[Chemical 6]

[0032]
FIG. 2 shows the obtained polymer compound. ¹ 1 shows an H-NMR spectrum (using JEOL A-500 manufactured by JEOL Ltd., deuterated chloroform solvent).
¹ H-NMR (CDCl _Three , TMS) s (ppm): 0.85-1.0 (6H, CH _Three ) 1.3-1.6 (8H, CH ₂ ) 1.7-1.8 (1H, CH), 3.8-4.0 (2H, CH) ₂ ) 5.7-6.0 (2H, CH), 5.7-6.1 (2H, CH), 6.6-8.0 (8H, CH)
Further, for this polymer compound, 880-PU manufactured by JASCO Corporation was used as a pump, a differential refractometer 830-RI manufactured by JASCO Corporation was used as a detector, styrene gel was used as a stationary phase, and chloroform as a mobile phase. As a result of GPC measurement, the weight average molecular weight was 47,000 (converted to standard polystyrene by Showa Denko KK). The average degree of polymerization is 88.
Next, as a result of measuring the glass transition temperature of the polymer compound using a DSC220 manufactured by Seiko Denshi Kogyo Co., Ltd. under a nitrogen atmosphere under a temperature increase rate of 10 ° C./min, the glass transition temperature was 173. ° C.
As a result of evaluating the light emission characteristics of the polymer compound, it was found that the toluene solution showed blue fluorescence with a peak wavelength of 465 nm, and the thin film showed blue fluorescence with a peak wavelength of 476 nm.
[0033]
[Example 3]
An organic EL device was produced using the polymer compound synthesized in Example 1.
First, a thin film having a thickness of 200 nm was prepared on a patterned ITO glass substrate by a spin coating method using a toluene solution in which the polymer compound synthesized in Example 1 was dissolved. A lithium fluoride layer of 0.5 nm is formed on this polymer thin film by vapor deposition, and an aluminum layer of 200 nm is further formed thereon, and an organic layer composed of the polymer compound of Example 1 between the anode and the cathode. An organic EL element having the structure was prepared.
When a direct current is applied between the ITO anode and the LiF / Al cathode, the maximum is 3,000 cd / m. ² Blue light (peak wavelength: 467 nm) was observed from the device. As described above, in the organic EL device of the present invention, the organic layer exhibits high charge transportability and light emission characteristics, so that the hole injection transport layer and the light emitting layer can be used in a single layer, and the layer configuration Is simple and can greatly contribute to the reduction of production costs.
In addition, even if the applied voltage was increased, this element did not show a change represented by melting of the thin film, unlike the element using low molecules. From this result, the stability of the device was recognized by using this polymer compound.
In this example, the polymer compound of the present invention was used as a single layer that combines the hole injection transport layer and the light emitting layer. However, the present invention is not limited to this, and the hole injection transport layer and the light emitting layer are made of different materials. The polymer compound according to the present invention can be applied to any one of them, and a known material can be applied to the other as a hole injecting and transporting layer or a light emitting layer.
[0034]
[Example 4]
Using the polymer compound synthesized in Example 1, an electrophotographic photoreceptor as shown in FIG. 4 was produced.
First, a 100 nm-thick charge generation layer 34 made of copper phthalocyanine is formed on a conductive support 32 in which ITO is formed on a glass substrate, and the polymer compound produced in Example 1 is formed thereon. Using the dissolved toluene solution, a charge transport layer 36 having a thickness of 1500 nm was produced by a spin coating method to produce an electrophotographic photosensitive member.
About this electrophotographic photosensitive member, the surface of the charge transport layer 36 is charged by corona discharge, and an image is exposed to form an electrostatic latent image on the surface of the photosensitive member. Development was performed using toner charged opposite to the charge, and this was transferred to plain paper and fixed to perform printing.
As a result, the charge can be held on the surface in a dark place, the electric resistance can be reduced by light irradiation, and the surface charge can be quickly released, and the photoconductivity is excellent.
In addition, sufficient durability was exhibited even after repeated reuse by cleaning.
[0035]
【The invention's effect】
The polymer compound of the present invention having a phenoxazine derivative in the main chain skeleton exhibits the high charge transport property and light emission property of phenoxazine, and at the same time, the high heat resistance and thermal stability, mechanical properties that are characteristic of the polymer compound. It is an excellent material that combines strength and durability. By using this polymer material for an organic thin film element such as an organic EL element or an electrophotographic photosensitive member, the charge transport characteristics, light emission characteristics and stability of the element can be improved. Furthermore, the manufacturing process for forming a thin film can be simplified. In addition, the present invention can be applied to any one of the organic layers having a multilayer structure having a conventional charge transport layer and a light emitting layer, and the layer structure can be reduced by functioning as a layer having both of them.
In addition, it is possible to change the emission color and the fluorescence characteristics by introducing a material having fluorescence characteristics into the main chain.
[Brief description of the drawings]
FIG. 1 shows the polymer compound of Example 1. ¹ It is a H-NMR spectrum figure.
FIG. 2 shows the polymer compound of Example 2. ¹ It is a H-NMR spectrum figure.
FIG. 3 is a cross-sectional view showing an example of an organic electroluminescence element.
FIG. 4 is a cross-sectional view showing an example of an electrophotographic photosensitive member.
[Explanation of symbols]
14 Anode
16 Hole injection transport layer
18 Organic light emitting layer
20 Organic layer
22 Cathode
32 Support
34 Charge generation layer
36 Charge transport layer

Claims (8)

A polymer compound represented by the following general formula (I) having phenoxazine in the main chain skeleton.

(In the formula, n is a positive integer representing the degree of polymerization. R is a hydrogen atom, alkyl group, alkoxy group, ester group, cyano group, aryl group, or alkyl group, alkoxy group, ester group, cyano group. An aryl group having a substituent selected from the above, or a triphenylamine derivative consisting of a nitrogen atom and an aryl group, Ar ¹ represents a hydrogen atom, an alkyl group, an alkoxy group, an ester group, an aryl group, or an alkyl group, An aryl group having a substituent selected from the group consisting of an alkoxy group, an ester group and a cyano group, or a triphenylamine derivative comprising a nitrogen atom and an aryl group is shown.) A polymer compound represented by the following general formula (II) having phenoxazine in the main chain skeleton.

(In the formula, n is a positive integer representing the degree of polymerization. R is a hydrogen atom, alkyl group, alkoxy group, ester group, cyano group, aryl group, or alkyl group, alkoxy group, ester group, cyano group. An aryl group having a substituent selected from the above, or a triphenylamine derivative consisting of a nitrogen atom and an aryl group, Ar ¹ represents a hydrogen atom, an alkyl group, an alkoxy group, an ester group, an aryl group, or an alkyl group, An aryl group having a substituent selected from the group consisting of an alkoxy group, an ester group and a cyano group, or a triphenylamine derivative comprising a nitrogen atom and an aryl group, Ar ² represents an alkyl group, an alkoxy group, an ester group, an aryl group Group, or an aryl group having a substituent selected from the group consisting of an alkyl group, an alkoxy group, an ester group, and a cyano group, Represents a triphenylamine derivative composed of a nitrogen atom and an aryl group.) 3. The polymer compound according to claim ² , wherein Ar ² is a conjugated organic material having functionality. 4. The polymer compound according to claim 1, wherein the average degree of polymerization is 2 to 10,000. An organic thin film element using the polymer compound according to claim 1. An organic electroluminescence device using the polymer compound according to claim 1 as a charge transport layer. An organic electroluminescence device using the polymer compound according to claim 1 as a light emitting layer. An electrophotographic photoreceptor using the polymer compound according to claim 1.

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