JP4025259B2 - Light emitting layer forming ink for LED element and LED element - Google Patents

Description

【０００９】
上記式（４）に示す希土類錯体は、配位子がフェナントロリンとβジケトンから構成される。フェナントロリンが光を吸収して励起状態となり、３重項励起状態から中心のユーロピウムにエネルギー移動が起こり、ユーロピウム特有の６１２ｎｍの発光が得られる。
【００１０】
この希土類錯体は、フェナントロリンで光吸収するため、吸光係数が大きく、発光強度が大きくなる。このような希土類錯体からなる蛍光体は、一般の有機化合物からなる蛍光体と比較して、以下に示すような利点を有する。
【００１１】
１）発光波長は希土類特有のものであり、色素濃度や分散するポリマーの種類の影響を受けず、蛍光スペクトルは安定している。
【００１２】
２）配位子は有機化合物であるが、配位子が光を吸収して励起状態になると、中心元素に対するエネルギー移動によって基底状態に戻るため、励起状態から不可逆的な化学変化を起す機会が減少する。従って、紫外線に対する耐久性を期待することが出来る。
【００１３】
しかし、希土類錯体からなる蛍光体は、溶媒に対する溶解性、樹脂に対する分散性が悪いという問題がある。
【００１４】
これに対し、フェナントロリンを持たない、βジケトンのみを配位子とする、下記式（５）に示す希土類錯体からなる蛍光体は、溶媒に対する溶解性に優れており、かつ樹脂中に分散又は溶解することが可能である（例えば、特許文献２，３参照）。これは、フェナントロリンを配位子として持たないために生じた効果である。しかしながら、フェナントロリンを持たない結果として、光吸光係数が小さく、発光強度が弱いという欠点がある。
【００１５】
【化７】

【００１６】
（式中、Ｒ_９及びＲ_１０は、同一又は異なる、水素原子を含まないＣ１−Ｃ２２の脂肪族基、水素原子を含まない芳香族基または水素原子を含まないヘテロ環基である。）
上述した式（４）に示すような希土類錯体をポリマーに分散して発光層を形成し、ＬＥＤ素子を実現する場合、用いるポリマーは以下に示す特性を満たす必要がある。
【００１７】
１）可視・近紫外領域における光透過率が大きいこと。
【００１８】
２）光化学的に安定であること。
【００１９】
３）酸化反応を起し難いこと。
【００２０】
４）ガラス転移点が大きいこと（好ましくは１００℃以上であること）。
【００２１】
５）酸素遮断性が大きいこと。
【００２２】
６）防湿性が大きいこと。
【００２３】
７）Ｃ−Ｈ結合及びＯ−Ｈ結合が無いか、少ないこと。
【００２４】
これら１）−７）の条件を満たすポリマーとして、ある種のフッ素系ポリマーが考えられる。しかしながら、フッ素系ポリマーは一般にフッ素系の溶媒以外には溶解せず、一方、フッ素系の溶媒には色素のような極性化合物は溶解しないため、フッ素系ポリマー中に希土類錯体を均一に分散することは困難である。
【００２５】
【特許文献１】
特開２００２−１７３６２２公報
【００２６】
【特許文献２】
特開平１１−８０１６５号公報
【００２７】
【特許文献３】
特開２０００−６３６８２号公報
【００２８】
【発明が解決しようとする課題】
本発明は、上記事情に鑑み、希土類錯体及びフッ素系ポリマーをともに溶媒に溶解してなる、色純度、演色性、耐久性に優れたＬＥＤ素子を提供する、ＬＥＤ素子の発光層形成用インク、及びＬＥＤ素子を提供することを目的とする。
【００２９】
【課題を解決するための手段】
上記課題を解決するため、本発明者らは、鋭意検討した結果、３環以上の縮合環およびこの誘導体を配位子として有する希土類錯体が、特定の分子構造を有するフッ素系ポリマーに分散できるとともに、これら希土類錯体及びフッ素系ポリマーが、フッ素置換溶媒とフッ素非置換溶媒の混合溶媒に溶解又は分散可能であることを見出し、本発明を成すに至った。
【００３０】
即ち、本願発明は、３環以上の縮合環又はその誘導体を配位子として有する希土類錯体、及び水素原子の少なくとも一部がフッ素原子に置換されたフッ素系ポリマーを、水素原子の一部がフッ素原子に置換されたフッ素置換溶媒、及びフッ素原子を含まないフッ素非置換溶媒に、溶解又は分散してなり、前記フッ素系ポリマーが、下記に挙げるものであることを特徴とするＬＥＤ素子の発光層形成用インクを提供する。
【００３１】
以上のように構成される本発明のＬＥＤ素子の発光層形成用インクでは、溶媒として、フッ素置換溶媒とフッ素非置換溶媒の混合溶媒を用いているため、希土類錯体とフッ素系ポリマーの双方が、十分に溶解又は分散されており、その結果、このインクを用いて発光層を形成することにより、色純度、演色性、耐久性に優れたＬＥＤ素子を実現することが可能である。
【００３２】
本発明のＬＥＤ素子の発光層形成用インクに含まれる希土類錯体は、３環以上の縮合環又はその誘導体を配位子として有するものでなければならない。２環の縮合環又はその誘導体を配位子として有するものでは、十分な発光強度及び寿命のＬＥＤ素子を得ることが出来ない。
【００３３】
また、フッ素置換溶媒は、水素原子の一部がフッ素原子に置換されたものでなければならない。水素原子のすべてがフッ素原子に置換されたものでは、十分な発光強度のＬＥＤ素子を得ることが出来ない。
【００３４】
本発明に用いるフッ素非置換溶媒として、テトラヒドロフラン，アセトン、ジメチルスルホキシド、クロロホルム、ジクロロメタン、酢酸エチル、酢酸ブチル及びこれらの重水素置換体からなる群から選択される少なくとも１種を挙げることが出来る。
【００３５】
また、本発明に用いるフッ素置換溶媒としては、例えば直鎖又は枝分かれ構造を有するアルカン又はアルケン等の水素原子の少なくとも一部がフッ素原子に置換されたものを用いることが出来る。
【００３６】
本発明のＬＥＤ素子の発光層形成用インクは、希土類錯体に加え、更に無機蛍光体微粒子を含んでもよい。
【００３７】
本発明に用いるフッ素系ポリマーは、下記一般式（１）で表される分子構造を有するものであることが望ましい。
【００３８】
【化８】

【００３９】
（式中、ｍ,ｎは整数、Ｒｆ１,Ｒｆ２は分子構造中に少なくとも一つのフッ素原子を有する炭素数２０以下の直鎖又は枝分かれ構造を有するアルキル基である。）
また、 本発明に用いるフッ素系ポリマーは、下記一般式（２）で表される分子構造を有するものであることが望ましい。
【００４０】
【化９】

【００４１】
（式中、ｐ,ｑ は整数である。）
また、フッ素系ポリマーの例として、フルオロエチレン、フルオロプロピレン及びビニリデンフロライドを含むコポリマー、或いはフッ素含有エチレンビニールアセテートを挙げることが出来る。
【００４２】
本発明において、希土類錯体は、フェナントロリン骨格を有する第１の配位子と、βジケトン骨格を有する第２の配位子を有するものであることが望ましい。
【００４３】
或いは、希土類錯体は、下記式（３）により表される構造を有するものであることが望ましい。
【００４４】
【化１０】

【００４５】
（式中、Ｌｎは希土類原子、Ｒ１及びＲ２は、同一又は異なる、炭素原子数２０以下の直鎖若しくは枝分かれ構造を有するアルキル基又はアルコキシ基、フェニル基、ビフェニル基、ナフチル基、ヘテロ環基、及びこれらの置換体からなる群から選ばれる基であり、Ｒ３ないしＲ８は、水素原子、重水素原子、炭素原子数２０以下の直鎖若しくは枝分かれ構造を有するアルキル基又はアルコキシ基、フェニル基、ビフェニル基、ナフチル基、ヘテロ環基、及びこれらの置換体からなる群から選ばれた基であり、ｒ,ｓは０ないし３の整数であり、環Ａ及びＣはヘテロ環である。）
なお、希土類錯体の希土類原子は、ユーロピウム、テルビウム、及びエルビウムからなる群から選ばれた元素とすることが出来る。
【００４６】
本発明の発光層形成用インクにおいて、フッ素置換溶媒とフッ素非置換溶媒の合計に対するフッ素置換溶媒の比率は、１５重量％以上、９０重量％以下であることが好ましい。溶媒全体に占めるフッ素系溶媒の比率が１５重量％未満では、フッ素系ポリマーの溶解が困難となり、一方、９０重量％を越えると、希土類錯体の溶解が困難となる。
【００４７】
また、固形分の割合が２重量％以上、４０重量％以下の範囲であることが好ましい。固形分の割合が２重量％未満では、溶媒の量が多すぎてＬＥＤチップに対する発光層の成膜が困難になり、一方、４０重量％を越えると、インクの粘度が大きくなり、やはり成膜が困難となる。
【００４８】
また、フッ素系ポリマーに対する希土類錯体の割合が０．３重量％以上、８０重量％以下であることが好ましい。希土類錯体の割合が０．３重量％未満では、十分な発光強度を得ることが困難となり、８０重量％を越えると、平坦な薄膜を形成することが困難となる。
【００４９】
また、本発明は、３環以上の縮合環又はその誘導体を配位子として有する希土類錯体が、下記一般式（１）で表される分子構造を有するポリマーと、下記一般式（２）で表される分子構造を有するポリマーと、フルオロエチレン、フルオロプロピレン及びビニリデンフロライドを含むコポリマーと、フッ素含有エチレンビニールアセテートからなる群から選ばれたフッ素系ポリマーに溶解または分散してなる発光層を具備するＬＥＤ素子を提供する。
【００５０】
【化１１】

【００５１】
（式中、ｍ,ｎは整数、Ｒｆ１,Ｒｆ２は分子構造中に少なくとも一つのフッ素原子を有する炭素数２０以下の直鎖又は枝分かれ構造を有するアルキル基である。）
【化１２】

【００５２】
（式中、ｐ,ｑ は整数である。）
なお、本発明にいう３環以上の縮合環の形状としては、直線状、「くの字」状、複数の「くの字」の組み合わせ、または隣接する環の２辺以上が接する平板状等が考えられる。
【００５３】
本発明の発光層形成用インクは、これを例えばバーコード状に印刷することにより、可視光では視認できないが紫外光照射により鮮明に視認識できる所謂セキュリティーインクとして使用することができる。
【００５４】
【発明の実施の形態】
以下、本発明の種々の実施例及び比較例を示すが、本発明は、これら実施例によってなんら制限されるものではない。
【００５５】
実施例１
上述した式（４）に示す希土類錯体と、上記式（１）の一例としてのフッ素系ポリマー（テフロンＡＦ：商品名、デュポン社製）を、フッ素置換溶媒としてのフッ素系溶媒（バートレルＸＦ：商品名、デュポン社製、直鎖状アルカンの水素原子の少なくとも一部がフッ素原子に置換されたもの）と、フッ素非置換溶媒としてのテトラヒドロフランの１０：３混合溶媒に溶解し、インクを作成した。ここで、インクの固形分（乾燥した時に残存する成分）の割合は、２．５重量％であった。
【００５６】
このようにして調製した溶液を、図１に示すように、ＬＥＤチップ１（発光波長：３９５ｎｍ、ＩｎＧａＮ）を備えるセル内４に収容し、窒素雰囲気中で加熱乾燥して発光層２を形成して、ＬＥＤ素子３を製造した。図１において、参照符号５，６は、それぞれ電極端子である。
【００５７】
このＬＥＤ素子３について、ＬＥＤチップ１を発光させ、発光強度及び輝度半減寿命を測定した。発光強度及び輝度半減寿命は、ＬＥＤチップ１を２０ｍＡ、３．４３Ｖの条件で発光させ、積分球光度計を用いて測定した。発光強度は、光束（ｌｍ）又は光度（ｍｃｄ）を用いて評価し、また、輝度半減寿命は、発光により輝度が半減する時間（ｈ）を用いて評価した。
【００５８】
その結果、良好なレッドの発光が得られ、下記表１に示すような測定値を得た。下記表１から明らかなように、本実施例に係るＬＥＤ素子３によると、発光強度は良好であり、輝度半減寿命は３００００時間と優れていた。
【００５９】
比較例１
希土類錯体として下記式（６）に示す化合物を用いた以外は、実施例１と同様にしてＬＥＤ素子を作成した。このＬＥＤ素子について発光強度及び輝度半減寿命を測定したところ、下記表１に示すように、発光強度は、実施例１のＬＥＤ素子を１００とした場合に１１と非常に低く、輝度半減寿命は５０００時間と実施例１のＬＥＤ素子に比べ大幅に減少した。
【００６０】
このように発光強度が低いのは、式（６）に示す希土類錯体は遷移確率が小さく、吸光係数が小さいことが原因であると思われる。また、輝度半減寿命が短いのは、式（６）に示す希土類錯体に空気中の水が配位し、Ｏ−Ｈ結合による振動失活が生じたことが原因であると思われる。
【００６１】
【化１３】

【００６２】
比較例２
上述した式（４）に示す希土類錯体と、フッ素系ポリマー（テフロンＡＦ：商品名、デュポン社製）を、フッ素置換溶媒としてのフッ素系溶媒（フロリナート：商品名、デュポン社製）と混合した。この混合物を窒素雰囲気下で加熱したが、溶解することはなく、微粒子分散状態であった。
【００６３】
このようにして調製した分散液を用いて、実施例１と同様にしてＬＥＤ素子を製造した。このＬＥＤ素子について、ＬＥＤチップを発光させ、発光強度及び輝度半減寿命を測定したところ、下記表１に示すように、輝度半減寿命は２５０００時間と良好であったが、発光強度は、実施例１のＬＥＤ素子を１００とした場合に５０と低いものであった。
【００６４】
これは、希土類錯体がフッ素系ポリマー中で粒径が大きい凝集体として存在することが原因であると思われる。
【００６５】
実施例２
フッ素系ポリマーとして、上記式（２）の一例であるサイトップ（商品名、旭硝子社製）を用いた以外は、実施例１と同様にしてＬＥＤ素子を作成した。このＬＥＤ素子について、ＬＥＤチップを発光させ、発光強度及び輝度半減寿命を測定したところ、下記表１に示すように、発光強度は、実施例１のＬＥＤ素子を１００とした場合に９５であり、輝度半減寿命は２５０００時間と、いずれもやや低いが、実用上、ほぼ満足し得る結果を得た。
【００６６】
実施例３
希土類錯体として、下記（７）に示す化合物を用いた以外は、実施例１と同様にしてＬＥＤ素子を作成した。このＬＥＤ素子について、ＬＥＤチップを発光させ、発光強度及び輝度半減寿命を測定したところ、下記表１に示すように、発光強度は、実施例１のＬＥＤ素子を１００とした場合に１１０と高く、輝度半減寿命も３５０００時間と、いずれも優れた結果を得た。
【００６７】
【化１４】

【００６８】
実施例４
実施例１で用いたレッドの希土類錯体と、グリーン(InGaN, 520 nm)及びブルー(InGaN, 450nm)の無機蛍光体を実施例１で用いたポリマーに分散し、実施例１と同様にして、有機―無機ハイブリッドタイプの白色ＬＥＤ素子を製造した。
【００６９】
この白色ＬＥＤ素子について、実施例１と同様にして輝度半減寿命を測定したところ、下記表１に示すように、３５０００時間と優れた結果を得た。
【００７０】
実施例５
希土類錯体として、下記（８）に示すエルビウム錯体を用いた以外は、実施例１と同様にしてＬＥＤ素子を作成した。このＬＥＤ素子について、ＬＥＤチップを発光させ、発光強度及び輝度半減寿命を測定したところ、下記表１に示すように、発光強度は１０５、輝度半減寿命は３００００時間と、いずれも実施例１と同等の優れた結果を得た。
【００７１】
【化１５】

【００７２】
実施例６
希土類錯体として、下記式（９）に示すエルビウム錯体を用いた以外は、実施例１と同様にしてＬＥＤ素子を作成した。このＬＥＤ素子について、ＬＥＤチップを発光させ、発光強度及び輝度半減寿命を測定したところ、下記表１に示すように、発光強度は１０５、輝度半減寿命は３００００時間と、いずれも実施例１と同等の優れた結果を得た。
【００７３】
【化１６】

【００７４】
実施例７
フッ素系ポリマーとして、フルオロエチレン、フルオロプロピレン及びビニリデンフロライドを含むコポリマーであるダイニオンＴＨＶ２２０（商品名、住友スリーエム株式会社製）を用い、フッ素非置換溶媒として酢酸エチルを用いる他は、実施例１と同様にしてＬＥＤ素子を作成した。このＬＥＤ素子について、ＬＥＤチップを発光させ、発光強度及び輝度半減寿命を測定したところ、下記表１に示すように、発光強度は１２０、輝度半減寿命は３００００時間と、いずれも良好な結果を得た。
【００７５】
実施例８
フッ素系ポリマーとして、フッ素含有エチレンビニールアセテートを用いた以外は、実施例１と同様にしてＬＥＤ素子を作成した。このＬＥＤ素子について、ＬＥＤチップを発光させ、発光強度及び輝度半減寿命を測定したところ、下記表１に示すように、発光強度は１２５、輝度半減寿命は２５０００時間と、いずれも良好な結果を得た。
【００７６】
比較例３
希土類錯体として、下記式（１０）に示す２環の縮合環を有するエルビウム錯体を用いた以外は、実施例１と同様にしてＬＥＤ素子を作成した。このＬＥＤ素子について発光強度及び輝度半減寿命を測定したところ、下記表１に示すように、発光強度は７０と低く、輝度半減寿命は５０００時間と実施例１のＬＥＤ素子に比べ大幅に減少した。
【００７７】
【化１７】

【００７８】
【表１】

【００７９】
なお、本発明は上記実施形態そのままに限定されるものではなく、実施段階ではその要旨を逸脱しない範囲で構成要素を変形して具体化できる。また、上記実施形態に開示されている複数の構成要素の適宜な組み合わせにより、種々の発明を形成できる。例えば、実施形態に示される全構成要素から幾つかの構成要素を削除してもよい。さらに、異なる実施形態にわたる構成要素を適宜組み合わせてもよい。
【００８０】
【発明の効果】
以上、詳細に説明したように、本発明によると、３環以上の縮合環又はその誘導体を配位子として有する希土類錯体と、水素原子のすべてまたは一部がフッ素原子に置換されたポリマーが、フッ素置換溶媒とフッ素非置換溶媒の混合溶媒に溶解又は分散されてなるインクが提供され、このインクで発光層を形成することにより、色純度、演色性、耐久性に優れたＬＥＤ素子を実現することが可能である。
【図面の簡単な説明】
【図１】 本発明の一実施形態に係るＬＥＤ素子の概略を示す図。
【符号の説明】
１・・・ＬＥＤチップ、２・・・発光媒体、３・・・ＬＥＤ素子、４・・・セル、５，６・・・電極端子。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting layer forming ink for an LED element that provides an LED element excellent in color purity, color rendering, and durability, and an LED element.
[0002]
[Prior art]
At present, the luminous efficiency of inorganic LEDs is dramatically improved, and in particular, white LEDs are said to surpass the luminous efficiency of fluorescent lamps in the future.
[0003]
However, when an LED is used in a lighting device, there are many applications that need to have excellent color rendering properties as well as luminous efficiency. Currently, LEDs using only inorganic phosphors cannot satisfy all of these characteristics. LEDs using organic phosphors are already known. However, since organic phosphors have the following problems, they are not yet put into practical use for illumination.
[0004]
1) In particular, in the case of ELDs using near-ultraviolet LEDs, which are now becoming mainstream, and using organic phosphors of R, G, and B, organic compounds are generally vulnerable to ultraviolet rays, so the degradation of organic phosphors due to ultraviolet rays is remarkable. It is. In particular, when there is absorption based on the n-π * transition in the near ultraviolet region, the deterioration is fast.
[0005]
2) The fluorescence spectrum of an organic phosphor may change depending on its concentration, and spectrum control is difficult. Further, the fluorescence intensity is also concentration dependent, and concentration quenching occurs in a high concentration region.
[0006]
3) The fluorescence spectrum changes depending on the type of polymer in which the organic phosphor is dispersed.
[0007]
In general, a phosphor made of a rare earth complex can have the following advantages compared to a general organic phosphor. An example of a rare earth complex used for a low molecular organic EL element is shown in the following formula (4) (see, for example, Patent Document 1).
[0008]
[Chemical 6]

[0009]
In the rare earth complex represented by the above formula (4), the ligand is composed of phenanthroline and β-diketone. Phenanthroline absorbs light and enters an excited state, energy transfer occurs from the triplet excited state to the central europium, and emission of 612 nm peculiar to europium is obtained.
[0010]
Since this rare earth complex absorbs light with phenanthroline, it has a large extinction coefficient and a high emission intensity. A phosphor made of such a rare earth complex has the following advantages as compared with a phosphor made of a general organic compound.
[0011]
1) The emission wavelength is unique to rare earths, and is not affected by the dye concentration or the type of polymer dispersed, and the fluorescence spectrum is stable.
[0012]
2) The ligand is an organic compound, but when the ligand absorbs light and enters the excited state, it returns to the ground state by energy transfer to the central element, so there is an opportunity to cause an irreversible chemical change from the excited state. Decrease. Therefore, durability against ultraviolet rays can be expected.
[0013]
However, phosphors composed of rare earth complexes have a problem of poor solubility in solvents and dispersibility in resins.
[0014]
On the other hand, a phosphor comprising a rare earth complex represented by the following formula (5) having no phenanthroline and having only a β-diketone as a ligand is excellent in solubility in a solvent and is dispersed or dissolved in a resin. (See, for example, Patent Documents 2 and 3). This is an effect caused by not having phenanthroline as a ligand. However, as a result of not having phenanthroline, there are disadvantages that the light absorption coefficient is small and the emission intensity is weak.
[0015]
[Chemical 7]

[0016]
(In the formula, R ₉ and R ₁₀ are the same or different, a C1-C22 aliphatic group containing no hydrogen atom, an aromatic group containing no hydrogen atom, or a heterocyclic group containing no hydrogen atom.)
When a light emitting layer is formed by dispersing a rare earth complex as shown in the above formula (4) in a polymer to realize an LED element, the polymer used needs to satisfy the following characteristics.
[0017]
1) High light transmittance in the visible / near ultraviolet region.
[0018]
2) Photochemically stable.
[0019]
3) It is difficult to cause an oxidation reaction.
[0020]
4) The glass transition point is large (preferably 100 ° C. or higher).
[0021]
5) The oxygen barrier property is large.
[0022]
6) High moisture resistance.
[0023]
7) No or few C—H bonds and O—H bonds.
[0024]
As the polymer that satisfies the conditions 1) -7), a certain kind of fluorine-based polymer can be considered. However, fluorine-based polymers generally do not dissolve other than fluorine-based solvents. On the other hand, polar compounds such as pigments do not dissolve in fluorine-based solvents, so the rare earth complex is uniformly dispersed in the fluorine-based polymer. It is difficult.
[0025]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-173622
[Patent Document 2]
Japanese Patent Laid-Open No. 11-80165
[Patent Document 3]
Japanese Patent Laid-Open No. 2000-63682
[Problems to be solved by the invention]
In light of the above circumstances, the present invention provides a light emitting layer forming ink for an LED element, which provides an LED element excellent in color purity, color rendering, and durability, which is obtained by dissolving a rare earth complex and a fluoropolymer in a solvent. And it aims at providing an LED element.
[0029]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have made extensive studies and, as a result, a rare earth complex having three or more condensed rings and this derivative as a ligand can be dispersed in a fluorine-based polymer having a specific molecular structure. The present inventors have found that these rare earth complexes and fluorine-based polymers can be dissolved or dispersed in a mixed solvent of a fluorine-substituted solvent and a fluorine-non-substituted solvent, and have achieved the present invention.
[0030]
That is, the present invention relates to a rare earth complex having three or more condensed rings or derivatives thereof as a ligand, and a fluorine-based polymer in which at least part of hydrogen atoms are substituted with fluorine atoms, and part of hydrogen atoms is fluorine. fluorinated solvents are substituted with atom, and a fluorine-unsubstituted solvent containing no fluorine atom, becomes dissolved or dispersed, the fluorine-based polymer, luminescence of the LED element, characterized in der Rukoto those listed below A layer forming ink is provided.
[0031]
In the light emitting layer forming ink of the LED element of the present invention configured as described above, since a mixed solvent of a fluorine-substituted solvent and a fluorine-unsubstituted solvent is used as a solvent, both the rare earth complex and the fluorine-based polymer are As a result, it is possible to realize an LED element excellent in color purity, color rendering properties and durability by forming a light emitting layer using this ink.
[0032]
The rare earth complex contained in the light emitting layer forming ink of the LED element of the present invention must have three or more condensed rings or derivatives thereof as a ligand. An LED element having sufficient light emission intensity and lifetime cannot be obtained if it has two condensed rings or derivatives thereof as a ligand.
[0033]
In addition, the fluorine-substituted solvent must be one in which a part of hydrogen atoms is replaced with fluorine atoms. If all of the hydrogen atoms are replaced with fluorine atoms, an LED element with sufficient emission intensity cannot be obtained.
[0034]
Examples of the fluorine non-substituted solvent used in the present invention include at least one selected from the group consisting of tetrahydrofuran, acetone, dimethyl sulfoxide, chloroform, dichloromethane, ethyl acetate, butyl acetate, and their deuterium substitutes.
[0035]
In addition, as the fluorine-substituted solvent used in the present invention, for example, a solvent in which at least a part of hydrogen atoms such as alkane or alkene having a linear or branched structure is substituted with fluorine atoms can be used.
[0036]
The ink for forming a light emitting layer of the LED element of the present invention may further contain inorganic phosphor fine particles in addition to the rare earth complex.
[0037]
The fluorine-based polymer used in the present invention desirably has a molecular structure represented by the following general formula (1).
[0038]
[Chemical 8]

[0039]
(In the formula, m and n are integers, and Rf1 and Rf2 are alkyl groups having a linear structure or a branched structure having 20 or less carbon atoms and having at least one fluorine atom in the molecular structure.)
Moreover, it is desirable that the fluoropolymer used in the present invention has a molecular structure represented by the following general formula (2).
[0040]
[Chemical 9]

[0041]
(In the formula, p and q are integers.)
Examples of the fluorine-based polymer include a copolymer containing fluoroethylene, fluoropropylene and vinylidene fluoride, or fluorine-containing ethylene vinyl acetate.
[0042]
In the present invention, the rare earth complex desirably has a first ligand having a phenanthroline skeleton and a second ligand having a β-diketone skeleton.
[0043]
Alternatively, the rare earth complex desirably has a structure represented by the following formula (3).
[0044]
Embedded image

[0045]
(Wherein Ln is a rare earth atom, R1 and R2 are the same or different, an alkyl or alkoxy group having a straight chain or branched structure having 20 or less carbon atoms, a phenyl group, a biphenyl group, a naphthyl group, a heterocyclic group, And R3 to R8 are a hydrogen atom, a deuterium atom, an alkyl group or an alkoxy group having a straight or branched structure having 20 or less carbon atoms, a phenyl group, a biphenyl group. A group selected from the group consisting of a group, a naphthyl group, a heterocyclic group, and a substituent thereof, r and s are integers of 0 to 3, and rings A and C are heterocyclic.)
The rare earth atom of the rare earth complex can be an element selected from the group consisting of europium, terbium, and erbium.
[0046]
In the light emitting layer forming ink of the present invention, the ratio of the fluorine-substituted solvent to the total of the fluorine-substituted solvent and the fluorine-unsubstituted solvent is preferably 15% by weight or more and 90% by weight or less. If the ratio of the fluorinated solvent in the total solvent is less than 15% by weight, it will be difficult to dissolve the fluorinated polymer, while if it exceeds 90% by weight, it will be difficult to dissolve the rare earth complex.
[0047]
Moreover, it is preferable that the ratio of solid content is 2 to 40 weight%. If the solid content is less than 2% by weight, it is difficult to form a light emitting layer on the LED chip because the amount of the solvent is too large. On the other hand, if it exceeds 40% by weight, the viscosity of the ink increases and the film is formed. It becomes difficult.
[0048]
Moreover, it is preferable that the ratio of the rare earth complex with respect to a fluorine-type polymer is 0.3 to 80 weight%. When the ratio of the rare earth complex is less than 0.3% by weight, it is difficult to obtain sufficient light emission intensity, and when it exceeds 80% by weight, it is difficult to form a flat thin film.
[0049]
In the present invention, a rare earth complex having a condensed ring of three or more rings or a derivative thereof as a ligand has a molecular structure represented by the following general formula (1) and the following general formula (2). A light emitting layer formed by dissolving or dispersing in a fluorine-based polymer selected from the group consisting of a polymer having a molecular structure, a copolymer containing fluoroethylene, fluoropropylene and vinylidene fluoride, and a fluorine-containing ethylene vinyl acetate. An LED element is provided.
[0050]
Embedded image

[0051]
(In the formula, m and n are integers, and Rf1 and Rf2 are alkyl groups having a linear structure or a branched structure having 20 or less carbon atoms and having at least one fluorine atom in the molecular structure.)
Embedded image

[0052]
(In the formula, p and q are integers.)
In addition, as the shape of the condensed ring of 3 or more rings referred to in the present invention, a linear shape, a “shape”, a combination of a plurality of “shapes”, or a plate shape in which two or more sides of adjacent rings are in contact, etc. Can be considered.
[0053]
The ink for forming a light emitting layer of the present invention can be used as a so-called security ink that is not visible with visible light but can be clearly recognized by irradiation with ultraviolet light, for example, by printing it in a barcode form.
[0054]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although various Examples and comparative examples of the present invention are shown, the present invention is not limited at all by these Examples.
[0055]
Example 1
The rare earth complex represented by the above formula (4) and a fluorine polymer (Teflon AF: trade name, manufactured by DuPont) as an example of the above formula (1) are used as a fluorine-substituted solvent (Bertrel XF: product). Name, manufactured by DuPont, in which at least part of hydrogen atoms of a linear alkane is substituted with fluorine atoms) and a 10: 3 mixed solvent of tetrahydrofuran as a fluorine non-substituted solvent, to prepare an ink. Here, the ratio of the solid content of the ink (the component remaining when dried) was 2.5% by weight.
[0056]
As shown in FIG. 1, the solution thus prepared is accommodated in a cell 4 having an LED chip 1 (emission wavelength: 395 nm, InGaN), and is heated and dried in a nitrogen atmosphere to form a light emitting layer 2. Thus, the LED element 3 was manufactured. In FIG. 1, reference numerals 5 and 6 are electrode terminals, respectively.
[0057]
For this LED element 3, the LED chip 1 was caused to emit light, and the light emission intensity and the luminance half life were measured. The light emission intensity and the luminance half life were measured using an integrating sphere photometer after causing the LED chip 1 to emit light at 20 mA and 3.43 V. The emission intensity was evaluated using the luminous flux (lm) or the luminous intensity (mcd), and the luminance half-life was evaluated using the time (h) during which the luminance was reduced by half.
[0058]
As a result, good red light emission was obtained, and the measured values shown in Table 1 below were obtained. As is apparent from Table 1 below, according to the LED element 3 according to this example, the light emission intensity was good and the luminance half-life was 30000 hours.
[0059]
Comparative Example 1
An LED element was produced in the same manner as in Example 1 except that the compound represented by the following formula (6) was used as the rare earth complex. The light emission intensity and the luminance half life of this LED element were measured. As shown in Table 1 below, the light emission intensity was as extremely low as 11 when the LED element of Example 1 was 100, and the luminance half life was 5000. Compared with the time and the LED element of Example 1, it decreased significantly.
[0060]
The low emission intensity is considered to be caused by the rare earth complex represented by formula (6) having a low transition probability and a low extinction coefficient. Further, the reason why the luminance half-life is short is considered that water in the air is coordinated with the rare earth complex represented by the formula (6) and vibrational deactivation due to the O—H bond occurs.
[0061]
Embedded image

[0062]
Comparative Example 2
The rare earth complex represented by the above formula (4) and a fluorine-based polymer (Teflon AF: trade name, manufactured by DuPont) were mixed with a fluorine-based solvent (Fluorinert: trade name, manufactured by DuPont) as a fluorine substitution solvent. This mixture was heated in a nitrogen atmosphere, but did not dissolve and was in a fine particle dispersed state.
[0063]
An LED element was produced in the same manner as in Example 1 using the dispersion thus prepared. With respect to this LED element, the LED chip was allowed to emit light and the emission intensity and luminance half-life were measured. As shown in Table 1, the luminance half-life was as good as 25,000 hours. When the number of LED elements was 100, the value was as low as 50.
[0064]
This seems to be because the rare earth complex exists as an aggregate having a large particle size in the fluoropolymer.
[0065]
Example 2
An LED element was produced in the same manner as in Example 1 except that Cytop (trade name, manufactured by Asahi Glass Co., Ltd.), which is an example of the above formula (2), was used as the fluoropolymer. About this LED element, when the LED chip was made to emit light and the emission intensity and luminance half-life were measured, as shown in Table 1 below, the emission intensity was 95 when the LED element of Example 1 was 100, The luminance half-life was 25,000 hours, which was a little low, but practically satisfactory results were obtained.
[0066]
Example 3
An LED element was produced in the same manner as in Example 1 except that the compound shown in the following (7) was used as the rare earth complex. For this LED element, the LED chip was allowed to emit light and the emission intensity and luminance half-life were measured. As shown in Table 1 below, the emission intensity was as high as 110 when the LED element of Example 1 was 100, The luminance half-life was 35000 hours, and excellent results were obtained.
[0067]
Embedded image

[0068]
Example 4
The red rare earth complex used in Example 1 and the inorganic phosphors of green (InGaN, 520 nm) and blue (InGaN, 450 nm) were dispersed in the polymer used in Example 1, and in the same manner as in Example 1, An organic-inorganic hybrid type white LED element was manufactured.
[0069]
When the luminance half life of this white LED element was measured in the same manner as in Example 1, as shown in Table 1 below, an excellent result of 35000 hours was obtained.
[0070]
Example 5
An LED element was produced in the same manner as in Example 1 except that the erbium complex shown in the following (8) was used as the rare earth complex. With respect to this LED element, the LED chip was caused to emit light and the emission intensity and luminance half-life were measured. As shown in Table 1 below, the emission intensity was 105 and the luminance half-life was 30000 hours, both of which were equivalent to Example 1. Excellent results were obtained.
[0071]
Embedded image

[0072]
Example 6
An LED element was produced in the same manner as in Example 1 except that an erbium complex represented by the following formula (9) was used as the rare earth complex. With respect to this LED element, the LED chip was caused to emit light and the emission intensity and luminance half-life were measured. As shown in Table 1 below, the emission intensity was 105 and the luminance half-life was 30000 hours, both of which were equivalent to Example 1. Excellent results were obtained.
[0073]
Embedded image

[0074]
Example 7
Example 1 except that Dion THV220 (trade name, manufactured by Sumitomo 3M Limited), which is a copolymer containing fluoroethylene, fluoropropylene and vinylidene fluoride, is used as the fluorine-based polymer, and ethyl acetate is used as the fluorine-unsubstituted solvent. Similarly, an LED element was prepared. With respect to this LED element, the LED chip was made to emit light, and the emission intensity and luminance half-life were measured. As shown in Table 1, the emission intensity was 120 and the luminance half-life was 30000 hours. It was.
[0075]
Example 8
An LED element was prepared in the same manner as in Example 1 except that fluorine-containing ethylene vinyl acetate was used as the fluorine polymer. With respect to this LED element, the LED chip was made to emit light, and the emission intensity and luminance half-life were measured. As shown in Table 1 below, the emission intensity was 125 and the luminance half-life was 25000 hours. It was.
[0076]
Comparative Example 3
An LED element was produced in the same manner as in Example 1 except that an erbium complex having two condensed rings represented by the following formula (10) was used as the rare earth complex. When the light emission intensity and the luminance half-life of this LED element were measured, as shown in Table 1 below, the light emission intensity was as low as 70, and the luminance half-life was significantly reduced to 5000 hours as compared with the LED element of Example 1.
[0077]
Embedded image

[0078]
[Table 1]

[0079]
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.
[0080]
【The invention's effect】
As described above in detail, according to the present invention, a rare earth complex having three or more condensed rings or derivatives thereof as a ligand, and a polymer in which all or part of hydrogen atoms are substituted with fluorine atoms, Provided is an ink that is dissolved or dispersed in a mixed solvent of a fluorine-substituted solvent and a fluorine-non-substituted solvent. By forming a light emitting layer with this ink, an LED element having excellent color purity, color rendering properties, and durability is realized. It is possible.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an LED element according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... LED chip, 2 ... Luminescent medium, 3 ... LED element, 4 ... Cell, 5, 6 ... Electrode terminal.

Claims (13)

A rare earth complex having three or more condensed rings or derivatives thereof as a ligand, and a fluorine-based polymer in which at least some of the hydrogen atoms are substituted with fluorine atoms, and fluorine in which some of the hydrogen atoms are substituted with fluorine atoms An LED element comprising a substituted solvent and a fluorine non-substituted solvent not containing a fluorine atom dissolved or dispersed, wherein the fluoropolymer has a molecular structure represented by the following general formula (1): Ink for forming a light emitting layer.

(In the formula, m and n are integers, and Rf1 and Rf2 are alkyl groups having a linear structure or a branched structure having 20 or less carbon atoms and having at least one fluorine atom in the molecular structure.) A rare earth complex having three or more condensed rings or derivatives thereof as a ligand, and a fluorine-based polymer in which at least some of the hydrogen atoms are substituted with fluorine atoms, and fluorine in which some of the hydrogen atoms are substituted with fluorine atoms An LED element, wherein the fluorine polymer has a molecular structure represented by the following general formula (2), which is dissolved or dispersed in a substitution solvent and a fluorine non-substitution solvent not containing a fluorine atom. Ink for forming a light emitting layer.

(In the formula, p and q are integers.)   A rare earth complex having three or more condensed rings or derivatives thereof as a ligand, and a fluorine-based polymer in which at least some of the hydrogen atoms are substituted with fluorine atoms, and fluorine in which some of the hydrogen atoms are substituted with fluorine atoms An LED element, wherein the fluorine polymer is a copolymer containing fluoroethylene, fluoropropylene, and vinylidene fluoride, wherein the fluorine polymer is dissolved or dispersed in a substituted solvent and a fluorine non-substituted solvent not containing a fluorine atom. The light emitting layer forming ink.   A rare earth complex having three or more condensed rings or derivatives thereof as a ligand, and a fluorine-based polymer in which at least some of the hydrogen atoms are substituted with fluorine atoms, and fluorine in which some of the hydrogen atoms are substituted with fluorine atoms An ink for forming a light emitting layer of an LED element, wherein the ink is dissolved or dispersed in a substitution solvent and a fluorine non-substitution solvent containing no fluorine atom, and the fluorine-based polymer is fluorine-containing ethylene vinyl acetate.   2. The fluorine non-substituted solvent is at least one selected from the group consisting of tetrahydrofuran, acetone, dimethyl sulfoxide, chloroform, dichloromethane, ethyl acetate, butyl acetate, and their deuterium substitutes. The ink for light emitting layer formation of the LED element in any one of -4.   The ink for forming a light emitting layer of an LED element according to any one of claims 1 to 5, further comprising fine inorganic phosphor particles.   The light emission of the LED element according to claim 1, wherein the rare earth complex has a first ligand having a phenanthroline skeleton and a second ligand having a β-diketone skeleton. Layer forming ink. The said rare earth complex has a structure represented by following formula (3), The light emitting layer forming ink of the LED element in any one of Claims 1-6 characterized by the above-mentioned.

(Wherein Ln is a rare earth atom, R ₁ and R ₂ are the same or different, an alkyl group or an alkoxy group having a straight chain or branched structure having 20 or less carbon atoms, a phenyl group, a biphenyl group, a naphthyl group, a heterocyclic ring And a group selected from the group consisting of these substituents, and R ₃ to R ₈ are a hydrogen atom, a deuterium atom, an alkyl group or an alkoxy group having a straight chain or branched structure having 20 or less carbon atoms, A group selected from the group consisting of a phenyl group, a biphenyl group, a naphthyl group, a heterocyclic group, and substituents thereof, r and s are integers of 0 to 3, and rings A and C are heterocyclic rings. .)   The ink for forming a light emitting layer of an LED element according to any one of claims 1 to 8, wherein the rare earth element of the rare earth complex is an element selected from the group consisting of europium, terbium, and erbium.   The ratio of the said fluorine substitution solvent with respect to the sum total of the said fluorine substitution solvent and a fluorine non-substitution solvent is 15 weight% or more and 90 weight% or less, The LED element in any one of Claims 1-9 characterized by the above-mentioned. Ink for forming a light emitting layer.   The solid content is in the range of 2% by weight to 40% by weight, and the ratio of the rare earth complex to the fluoropolymer is 0.3% by weight to 80% by weight. Item 11. A light emitting layer forming ink for an LED element according to any one of Items 1 to 10. A rare earth complex having three or more condensed rings or derivatives thereof as a ligand has a polymer having a molecular structure represented by the following general formula (1) and a molecular structure represented by the following general formula (2). An LED device comprising a light emitting layer formed by dissolving or dispersing in a fluorine-based polymer selected from the group consisting of a polymer, a copolymer containing fluoroethylene, fluoropropylene and vinylidene fluoride, and fluorine-containing ethylene vinyl acetate.

(In the formula, m and n are integers, and Rf1 and Rf2 are alkyl groups having a linear structure or a branched structure having 20 or less carbon atoms and having at least one fluorine atom in the molecular structure.)

(In the formula, p and q are integers.)   The LED device according to claim 12, further comprising a light emitting layer in which the rare earth complex and the inorganic phosphor fine particles are dissolved or dispersed in the fluorine polymer.

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