JP3899011B2 - Surface emitter - Google Patents

Description

【００６７】
（式中、置換基Ｘ^１、Ｘ^２、Ｘ^３およびＸ^４は水素、ハロゲン（例えば塩素、フッ素等）、１価の炭化水素基、ＯＲ（Ｒは１価の炭化水素基である）で表されるアルコキシ基およびＯＨで表される水酸基から選択される基であり、これらは相互に異なっても、部分的に異なっても、あるいは全部同じであってもよく、これらの少なくとも２つは、それぞれアルコキシ基および水酸基から選択される基である。）
で表されるシラン化合物である。このシラン化合物は、、少なくとも２つ、好ましくは３つ、より好ましくは４つの同じまたは異なるアルコキシル基および／もしくは水酸基を有する。バインダー形成材料は、シラン化合物の少なくとも１つのアルコキシル基が加水分解されているものであってもよい。
【００６８】
別の態様では、バインダー形成材料は、上記シラン化合物の１種またはそれ以上が、加水分解可能な場合には加水分解した後、縮合することによって生成するシロキサン化合物またはポリシロキサン化合物である。尚、ポリシロキサン化合物とは２以上のシロキサン結合を有する化合物を意味する。この（ポリ）シロキサン化合物は、少なくとも２つのアルコキシ基および／または水酸基を置換基として有するのが好ましい。
【００６９】
尚、上述のシラン化合物および（ポリ）シロキサン化合物は、アルコキシル基を有する場合、アルコキシル基が加水分解して生成する水酸基を有することができる。その結果、これらのシラン化合物および（ポリ）シロキサン化合物も、コーティング材組成物を塗布して乾燥するに際して、少なくとも部分的に縮合して架橋し、バインダーとしての多孔質シリカを形成できる。（ポリ）シロキサン化合物が、アルコキシ基および／または水酸基を置換基を有さない場合であっても、コーティング材組成物を塗布して乾燥するに際して、多孔質のバインダーを形成できる。
【００７０】
特に好ましいシリカ多孔質体は、ＳｉＸ_４（Ｘは例えば炭素数１〜４の加水分解可能置換基、例えば炭素数１〜５のアルコキシル基である）で表される、珪素元素に４個の加水分解可能置換基を有する４官能加水分解性オルガノシロキサンの部分加水分解物あるいは完全加水分解物が縮重合して得られる、ポリシロキサン化合物（本明細書において、このポリシロキサン化合物を「シリコーンレジン−Ｍ」と呼ぶ）をバインダー形成材料として使用するコーティング材組成物を塗布して塗膜を乾燥することによって得られる。尚、一般的に「シリコーン樹脂」として知られているものと区別するために、このバインダー形成材料としてのポリシロキサン化合物を、本明細書ではこのように「シリコーンレジン−Ｍ」（SILICONE RESIN-M）と特に呼ぶことにしている。そのような「シリコーンレジン−Ｍ」は、一般的にシリコーン樹脂として知られているものと同じである必要はない。
このシリコーンレジン−Ｍは、それ自体が加水分解可能置換基を有してもよく、その場合は、シリコーンレジン−Ｍがバインダーを形成するに際して、加水分解して縮合することによってより大きい分子量のシリコーンレジン−Ｍとしてバインダーを形成する。シリコーンレジン−Ｍがそのような置換基を有さない場合は、シリコーンレジン−Ｍがそのままバインダーを形成する。
【００７１】
従って、コーティング材組成物に上述のようなバインダー形成材料を充填剤と一緒に含ませ、基材に塗布して塗膜を乾燥することによってバインダー中に充填剤が分散した複合薄膜を得ることができる。バインダーとしてのこのようなシリカ多孔質体の屈折率は、充填剤とバインダー形成材料の重量比率を種々変えることによって所望の値にすることができる。
【００７２】
シリカ多孔質体を形成するこのようなシリコーンレジン−Ｍは、複合被膜の機械的強度が要求される場合は、その重量平均分子量が約２００〜２０００であるのが好ましく、６００〜１２００であるのがより好ましい。この範囲の分子量は、複合被膜の強度の向上およびバインダーの多孔率（即ち、バインダー中の空隙の割合）の増加を達成しやすい傾向にある。また、シリコーンレジン−Ｍは、複合被膜に大きな機械的強度が要求されない場合は、その重量平均分子量が約２０００以上であるのが好ましく、３０００以上であるのがより好ましく、例えば、３０００〜５０００である。
【００７３】
尚、シリコーンレジン−Ｍを用いて形成された複合被膜は、必要に応じて、好ましくは１００〜３００℃、より好ましくは５０〜１５０℃で５〜３０分熱処理してよく、複合被膜の機械的強度を向上させることができる。
【００７４】
別の態様では、シリカ多孔質体はシリカエアロゲルである。このバインダーとしてのエアロゲルは、先に説明したようなアルコキシシラン（シリコンアルコキシド、特に上述の４官能アルコキシシラン）の加水分解・重合反応、珪酸ナトリウム水溶液のゲル化反応等によって得られるゲル状化合物をコーティング材組成物に含まれるバインダー形成材料として用い、コーティング材組成物を塗布して塗膜を得、これを乾燥することによって充填剤を保持する状態で形成できる。従って、この場合では、バインダー形成材料は、アルコキシシラン、その加水分解物（必ずしも全部のアルコキシル基が加水分解している必要はなく、一部分のアルコキシル基だけが加水分解している部分加水分解物も含む）および加水分解物の縮合物の少なくとも１種である。一般的に、バインダー形成材料は、加水分解物の縮合物であるのが好ましい。そのようなシリカエアロゲルについては先に説明したようにして得ることができる。湿潤状態のゲル状化合物に充填剤を混入してこれを乾燥すれば、シリカエアロゲル中に充填剤が分散した状態の複合薄膜を得ることができる。従って、コーティング剤組成物は、湿潤状態のゲル状化合物および充填剤を含んで成る。
【００７５】
バインダーとしてのこのようなエアロゲルの屈折率は、原料溶液の調合比、乾燥方法等を選択することによって所望の値にすることができる。
【００７６】
（２−３）バインダーとしての金属酸化物について
本発明の複合薄膜保持基板の複合薄膜のバインダーとして、金属酸化物を使用できる。この場合、コーティング材組成物中にバインダー形成材料として含まれている金属酸化物前駆体が、コーティング材組成物を塗布して得られる塗膜を乾燥するに際してバインダーとしての金属酸化物に変化する。使用するのが好ましいそのような金属酸化物前駆体の例としては、シリカ、シリカ／チタニア複合酸化物等を例示できる。バインダーとしての金属酸化物の屈折率は、金属酸化物をもたらすその物質の構成元素種を種々選択することによって所望の値にすることができる。
【００７７】
本発明の複合被膜保持基板では、上述の屈折率の関係を満足するように先に説明した充填剤とバインダーとの組み合わせを選択すればよい。尚、このような充填剤とバインダーとの組み合わせから形成される複合薄膜の屈折率（即ち、複合膜の全体としての屈折率）は、充填剤の屈折率、バインダーの屈折率、および形成される薄膜における充填剤／バインダーの割合から理論的に算出される屈折率より通常、小さい。それは、形成される複合薄膜のバインダーには、バインダーの材料自体に固有に存在し得る空隙（例えばバインダーの多孔性故の空隙部）に加えて、充填剤を構成する微粒子同士の間に空隙が存在し得、また、充填剤の微粒子とバインダーとの間に空隙が存在し得るからであり、実際、充填剤とバインダー形成材料を混合して複合被膜を形成する場合には、そのような他の空隙も複合薄膜に含まれ、そのような空隙は、複合薄膜の屈折率を下げる効果を有する。本明細書において、複合薄膜の屈折率とは、そのような他の空隙の効果をも含む総括的な屈折率を意味する。
【００７８】
本発明のコーティング材組成物を用いて形成された複合被膜において、充填剤の周囲に存在してマトリクスとして作用するバインダーはその中に微細な空隙を多数含む状態を意味する。従って、バインダーの見かけ比重がバインダーを構成する材料自体（即ち、空隙が実質的に存在しない場合の材料）の真比重より小さい。バインダーの真比重に対するバインダーの見かけ比重の割合は、好ましくは０．９０以下、より好ましくは０．７５以下であり、例えば０．５０〜０．７５である。尚、この割合は、複合被膜が上述の「他の空隙」を含む場合、そのような空隙の体積をも含んで算出される値である。尚、バインダー内の空隙は、通常、被膜の周辺気体を含む。
【００７９】
１つの例では、屈折率１．４５のバインダーとしての４官能シリコーンレジン（即ち、シリコーンレジン−Ｍ）および屈折率１．３２の充填剤としてのシリカ中空微粒子を、バインダー／充填剤の体積比０．１〜０．３で含む複合薄膜の平均屈折率は１．２６〜１．３５となり得る。
【００８０】
他の例では、屈折率１．２０のバインダーとしてのシリカエアロゲルおよび屈折率１．５９の充填剤としてのアクリルポリマー微粒子を、バインダー／充填剤の体積比０．５〜０．７５で含む複合薄膜の平均屈折率は１．３０〜１．４０となり得る。
【００８１】
更にもう１つの他の例では、屈折率１．５９のバインダーとしてのアクリルポリマーおよび屈折率１．６の充填剤としてのシリカ／チタニア複合酸化物微粒子を、バインダー／充填剤の体積比０．０５〜０．１５で含む複合薄膜の平均屈折率は１．３５〜１．４０となり得る。この複合薄膜の場合は、複合被膜の見掛け体積とバインダーおよび充填剤の重量に基づいて計算すると、複合薄膜の体積の約４０％が空隙によって占められていることになり、それ故に、複合薄膜の平均屈折率は、充填剤の屈折率より小さく、また、バインダーの屈折率より小さくなっている。
【００８２】
以下、添付図面を参照して、本発明の実施の形態を説明する。
【００８３】
図１（ａ）は、第１の要旨の複合薄膜保持基板Ａの１つの形態を断面図にて模式的に示す。図示した形態では、基材１の表面に、充填剤２とバインダー３によって構成された複合薄膜４が形成されている。この複合薄膜４は、充填材とバインダー形成材料との混合物である液状コーティング材組成物を基材１上に塗布して乾燥することによって得られたものである。図示した態様において、この充填剤２の屈折率は、基材１の屈折率より低く、形成されたバインダー３の屈折率は、充填剤２の屈折率より高い。尚、基材１については、先に説明した通りである。
【００８４】
また、充填剤２の屈折率は、基材１の屈折率よりも低ければよく、特に限定されるものではないが、通常１．３５よりも低い、好ましくは１．３よりも低い屈折率であることが、複合薄膜４の平均屈折率を低くするうえで望ましい。充填剤２の屈折率は低い程望ましいので、下限は理想的には１．０であるが、実用的には１．００３であり、一般的には下限は、１．１であってよい。バインダーの屈折率は、充填剤の屈折率より高ければよく、特に限定されるものではないが、通常１．５よりも低く、好ましくは１．４６よりも低い屈折率であることが、複合薄膜４の平均屈折率を低くするうえで望ましい。
【００８５】
基材１の屈折率より低い屈折率を有する充填剤２としては、例えば上述のエアロゲル微粒子、中空シリカ微粒子、ポリマー製中空微粒子等を挙げることができる。
【００８６】
充填剤２のエアロゲル微粒子としてシリカエアロゲル微粒子を用いる場合、その屈折率は、シリカエアロゲルの透明性等の性能を確保するためには、好ましくは１．００８〜１．１８の範囲に、より好ましくは１．１〜１．３の範囲内となるように調整するのが好ましい。
【００８７】
充填剤２として中空シリカ微粒子を使用する場合、その屈折率が、好ましくは１．２〜１．３５、より好ましくは１．２〜１．３の範囲内となるように調整するのが好ましい。
【００８８】
充填剤２としてポリマー製中空微粒子を使用する場合、その屈折率が、好ましくは１．２〜１．４、より好ましくは１．２〜１．３の範囲内となるように調整するのが好ましい。
【００８９】
上述の低屈折率の充填剤２としては、粒径が５ｎｍ〜２μｍの範囲のものが好ましく、特に２０ｎｍ〜５００ｎｍのものがより好ましい。充填剤が中空微粒子の場合、その外殻の厚さは、５ｎｍ〜２０ｎｍであるのが好ましい。充填剤２は粒径が小さいほど、複合薄膜４の平均屈折率（即ち、複合薄膜の全体としての屈折率）を低くする効果が高く、また透明性に優れた複合薄膜４が得られ、その結果、光の取出効率を大きくすることができる。逆に、粒径が大きいほど、複合薄膜４内での散乱効果が大きくなって光の導波を抑制する効果が大きいので、光の取出効率を大きくすることができる。この両者の効果を併せ持たせるために、充填剤２の粒径は上述の範囲が好ましく、充填剤２の粒径は複合薄膜４を構成するバインダー３の屈折率、発光素子の種類および厚み等に応じて、上記の範囲で適宜適切なものを選択できる。尚、本明細書において記載する粒子径は一次粒子径のことを指し、粒子径は、透過型電子顕微鏡観察等の目視観察により計測される。
【００９０】
一方、充填剤２より屈折率が高いバインダー３は、透明性のコーティング材組成物中に含まれるバインダー形成材料から生成する有機ポリマーあるいは金属酸化物であるのが好ましい。バインダー３の屈折率が充填剤２より高いものであれば、バインダーは、上述の有機ポリマー、金属酸化物等のバインダーであって、その屈折率が充填剤の屈折率より大きければ、その種類は特に限定されない。バインダー形成材料として使用するのが好ましい材料としては、バインダーとしての有機ポリマーの場合、メチルメタクリレート等のアクリル系ポリマー、エポキシ系ポリマー、フッ素系ポリマー、スチレン系ポリマー等を例示でき、これらを用いて形成されるバインダーの屈折率は、通常、１．４〜１．６５であり、好ましくは１．４５〜１．６である。また、バインダー形成材料として使用するのが好ましい材料としては、バインダーとしての金属酸化物の場合、シリカ、酸化インジウム錫、チタニア、シリカ／チタニア複合酸化物、ジルコニア等を例示でき、これらを用いて形成されるバインダーの屈折率は、通常、１．４５〜３．０であり、好ましくは１．４５〜２．５である。
【００９１】
特に、コーティング材組成物において一緒に使用する充填剤２の分散性が良好なバインダー形成材料を選定するのが望ましい。中でも、充填剤２としてシリカ系のものを用いる場合には、先に説明したＳｉＸ₄（Ｘは例えば炭素数１〜４のアルコキシル基）で表される４官能加水分解性オルガノシロキサンの部分加水分解物あるいは完全加水分解物が縮重合して得られるシリコーンレジン−Ｍをバインダー３として用いるのが最も好ましい。上述のように、このシリコーンレジン−Ｍは、それ自体が加水分解可能置換基を有してもよく、あるいはシリコーンレジン−Ｍがそのような置換基を有さなくてもよい。このようにシリコーンレジン−Ｍによって形成されるバインダー３の屈折率は、通常、１．３〜１．５０であり、好ましくは１．３〜１．４５である。
【００９２】
複合薄膜４において、充填剤２とバインダー３の存在比率は、それぞれの屈折率の比や密度の比によって変動するが、充填剤２の質量比率が４０〜９５質量％であることが好ましく、その場合、複合薄膜４の平均屈折率は通常１．２〜１．４好ましくは１．２０〜１．３５である。低屈折率の充填剤２の比率が４０質量％よりも低いと、複合薄膜４の平均屈折率が大きくなってしまい、また９５質量％よりも高いと、複合薄膜４の強度や基材１への密着性が低くなる等の実用性が不十分なものになるおそれがあり、いずれも好ましくない。尚、本明細書を通じて、複合被膜の平均屈折率は、後述の実施例にて説明するようにして測定される屈折率を意味する。
【００９３】
基材１の表面に複合薄膜４を形成するにあたっては、充填剤２とバインダー３を溶媒に混合して溶解および／または分散させて液体のコーティング材組成物を調製し、このコーティング材組成物を基材１の表面に塗布した後、乾燥することによって液体を除去して複合薄膜４として被膜を残す。このような乾燥に際して、必要に応じて加熱してよい。更に、必要に応じて得られた被膜を更に熱処理することによって焼成してもよい。塗布方法としてはスピンコート、ディップコート、フローコート、ロールコート、バーコート等のいずれの適当な方法を採用してもよい。複合薄膜４の厚み、基材１の大きさ、種類等に応じて適当な塗布方法を選定できる。
【００９４】
本発明の第１の要旨において、上述のようにして形成される複合薄膜の平均屈折率は、一般的に基材の屈折率より小さく、例えば０．０１〜０．５、好ましくは０．０５〜０．３小さいのが望ましい。複合薄膜の平均屈折率自体は、通常１．２〜１．４であり、好ましくは１．２０〜１．３５であり、より好ましくは１．２５〜１．３である。しかしながら、充填剤２が複合薄膜４を通過する光を拡散できるので、複合薄膜の平均屈折率より少し大きくてもよく、例えば１．３５〜１．４５程度に大きくてもよい。
【００９５】
図１（ｂ）は、図１（ａ）の複合薄膜保持基板Ａを用い、基材１が位置する側とは反対側の複合薄膜４の側に薄膜の発光素子１５を設けた面発光体Ａを断面図にて概念的に示す。図示した形態では、発光素子１５で発光した光は、矢印で示すように、複合薄膜４及び基材１を通過して基材１の表面から取り出される。複合薄膜４は、屈折率のより低い充填剤２と屈折率のより高いバインダー３の複合層であり、複合薄膜４の平均屈折率は基材１の屈折率より好ましくは小さい。光は発光素子１５と複合薄膜４の界面及び複合薄膜４内で拡散され、拡散光として基材１を通過する。この際に、複合薄膜４から基材１に入射する光の入射角度は小さくなり、その結果、基材１の表面と空気との界面で反射される光の量を少なくして基材１内での導波を減少させることができ、好ましい場合には、殆ど存在しないようにすることができる。
【００９６】
また、発光素子１５内を導波し得る光成分も存在するが、発光素子１５と複合薄膜４の界面は充填剤の影響によって、模式的に図示するように平坦性が減少しているので、界面での散乱によってこの導波が減少し得る。更に、発光素子１５の厚みはせいぜいサブミクロンオーダー（例えば０．０５〜１μｍ）であるので、導波光が発光素子１５と複合薄膜４との界面に当たる回数は著しく多く、導波光のほぼ全量が最終的には複合薄膜４の側へ透過できる。このように基材１に複合薄膜４を設けることによって光の導波を低減することができ、基材１の表面からの光の取出効率を向上させることができる。
【００９７】
この複合薄膜４において、充填剤２とバインダー３の屈折率の差が大きいほど、光の取出効率を高めることができ、具体的には、この差は、好ましくは少なくとも０．０１、より好ましくは少なくとも０．０５である。また、発光素子１５を配置する複合薄膜４の表面は、発光素子１５が形成できる限り、粗度が大きいほうが好ましい。
【００９８】
尚、上記の複合薄膜４中の充填剤の粒子２同士の間は、バインダー３によって完全に埋められている必要は必ずしもなく、その間に空隙部（これを、気泡と呼ぶこともできる）が存在してよい。空隙部には、通常周辺気体（一般的には空気）が含まれており、従って、空隙部は、充填剤２と同様に低屈折率であるか、あるいはそれより低い屈折率である。そのため、充填剤２の間に空隙部が残ると、空隙部は充填剤２とほぼ同様に作用し、その結果、光の取出効率が向上する。尚、複合薄膜４全体の平均屈折率は、基材１の屈折率より低いことが望ましいが、基材１より多少高くてもよい。
【００９９】
図２（ａ）は、第２の要旨の複合薄膜保持基板Ａの１つの形態を断面図にて模式的に示す。図示した形態では、基材１の表面に、充填剤２とバインダー３によって構成された複合薄膜４が形成されている。この複合薄膜４は、充填材２とバインダー形成材料との混合物であるコーティング材組成物を塗布して乾燥することによって得られたものである。図示した態様において、形成されたバインダー３の屈折率は基材１の屈折率より低く、充填剤２の屈折率はバインダー３の屈折率より高い。
【０１００】
基材１の屈折率より低い屈折率のバインダー３としては、基材１より屈折率が低い透光性のものであれば特に限定されないが、中でも上述のシリカ多孔質体、エアロゲル（例えばシリカエアロゲル）等であるのが好ましい。複合薄膜４の平均屈折率を低くするには、一般的にバインダー３の屈折率が１．３より低い、好ましくは１．２５より低い屈折率であることが望ましい。
【０１０１】
バインダー３としてシリカ多孔質体を用いる場合、その屈折率が、好ましくは１．２〜１．４５の範囲に、より好ましくは１．２〜１．３５の範囲内となるようにバインダー形成材料を選択するのが好ましい。
【０１０２】
バインダー３としてエアロゲルを用いる場合、その屈折率が、好ましくは１．００５〜１．３の範囲に、より好ましくは１．１〜１．３の範囲内となるようにバインダー形成材料を選択するのが好ましい。
【０１０３】
バインダー３の屈折率より高い屈折率の充填剤２としては、上述のシリカ、チタニア等の金属酸化物の微粒子、シリコーンに代表される有機ポリマーの微粒子等の中空シリカ微粒子を用いることができる。この充填剤２の屈折率は、バインダー３の屈折率より高ければ特に限定されないものであるが、一般的に、１．４以上、好ましくは１．４６以上、より好ましくは１．５以上のものが用いられる。
【０１０４】
充填剤２として金属酸化物の微粒子を用いる場合、その屈折率が、好ましくは１．４６〜３．０の範囲に、より好ましくは１．５〜２．５の範囲内となるように金属酸化物の微粒子を選択するのが好ましい。
【０１０５】
充填剤２として有機ポリマーの微粒子を用いる場合、その屈折率が、好ましくは１．４９〜１．７の範囲に、より好ましくは１．５〜１．６７の範囲内となるように有機ポリマーの微粒子を選択するのが好ましい。
【０１０６】
充填剤２として中空シリカ微粒子を用いる場合、その屈折率が、好ましくは１．３〜１．４の範囲に、より好ましくは１．３２〜１．３７の範囲内となるように中空シリカ微粒子を選択するのが好ましい。
【０１０７】
上述の充填剤２としては、粒径が５ｎｍ〜２μｍの範囲のものが好ましく、特に２０ｎｍ〜５００ｎｍのものがより好ましい。充填剤が中空微粒子の場合、その外殻の厚さは、５ｎｍ〜２０ｎｍであるのが好ましい。充填剤２はそのかさ比重が小さいほど、すなわち中空粒子においては粒子内の空隙率が大きいほど複合薄膜４の平均屈折率（即ち、複合薄膜の全体としての屈折率）を低くする効果が高く、またその粒子径は小さいほど透明性に優れた複合薄膜４が得られ、その結果、光の取出効率を大きくすることができる。逆に、粒径が大きいほど、複合薄膜４内での散乱効果が大きくなって光の導波を抑制する効果が大きいので、光の取出効率を大きくすることができる。この両者の効果を併せ持たせるために、充填剤２の粒径は上述の範囲が好ましく、充填剤２の粒径は複合薄膜４を構成するバインダー３の屈折率、発光素子の種類および厚み等に応じて、上記の範囲で適宜適切なものを選択できる。
【０１０８】
形成される複合薄膜において、バインダー３と充填剤２の存在比率は、これらの材料の屈折率、密度、意図する複合薄膜の平均屈折率等に応じて変えてよいが、一般的にはバインダー３の質量比率が４０〜９５質量％であり、充填剤の質量比率が５〜６０質量％であることが好ましい。低屈折率のバインダー３の比率が４０質量％よりも低いと、複合薄膜４の平均屈折率が大きくなってしまい、また９５質量％よりも高いと、複合薄膜４の膜としての強度が不十分になるなど、場合によって目的を達成できないおそれがあり、いずれも好ましくない場合がある。
【０１０９】
そして、基材１の表面に複合薄膜４を形成するにあたっては、充填剤２とバインダー形成材料を溶媒に混合・分散させた液状のコーティング材組成物を既述のように基材１の表面に塗布して塗膜を得た後、これを乾燥し、必要に応じて熱処理して焼成する。また、バインダー３としてエアロゲルを用いる場合には、必要に応じて超臨界乾燥法で乾燥を行なってもよい。
【０１１０】
本発明の第２の要旨において、上述のようにして形成される複合薄膜の平均屈折率は、一般的に基材の屈折率より小さく、例えば０.０１〜０.５、好ましくは０.０５〜０.３小さいのが望ましい。複合薄膜の平均屈折率自体は、通常１.１〜 １.４であり、好ましくは１.１〜１.３５であり、より好ましくは１.２〜１.３である。
【０１１１】
図２（ｂ）は、図２（ａ）の複合薄膜保持基板Ａを用い、基材１が位置する側とは反対側の複合薄膜４の側に薄膜の発光素子１５を設けた面発光体Ａを断面図にて概念的に示す。図示した形態では、発光素子１５で発光した光は、矢印で示すように、複合薄膜４及び基材１を通過して基材１の表面から取り出される。複合薄膜４は、屈折率のより低いバインダー３と屈折率のより高い充填剤２の複合層であり、複合薄膜４の平均屈折率は基材１の屈折率より小さい。光は発光素子１５と複合薄膜４の界面及び複合薄膜４内を通過し、さらに基材１を通過する。この際に、複合薄膜は基材１よりも屈折率が小さいため、複合薄膜４から基材１に入射する光の入射角度は小さくなり、その結果、基材１の表面と空気との界面で反射される光の量を少なくして基材１内での導波を減少させことができ、好ましい場合には、殆ど存在しないようにすることができる。
【０１１２】
また、発光素子１５内を導波し得る光成分も存在するが、発光素子１５と複合薄膜４の界面は充填剤の影響によって、模式的に図示するように平坦性が減少しているので、界面での散乱によってこの導波が減少する場合もある。更に、発光素子１５の厚みはせいぜいミクロンオーダー（例えば０.０５〜１μｍ）であるので、導波光が発光素子１５と複合薄膜４との界面に当たる回数は著しく多く、導波光のほぼ全量が最終的には複合薄膜４の側へ透過できる。このように基材１に複合薄膜４を設けることによって光の導波を低減することができ、基材１の表面からの光の取出効率を向上させることができる。
【０１１３】
この複合薄膜４において、充填剤２とバインダー３の屈折率の差は適宜設計され、具体的には、この差は、好ましくは少なくとも０.０１、より好ましくは少なくとも０.１である。また、発光素子１５を配置する複合薄膜４の表面は、本来高い平坦性を有することが好ましいが、その粗度は充填剤の粒径と充填量により設計される。しかし一方で、粗度が大きくなる場合にはその界面での拡散による導波成分の減少が期待でき、その粗度は発光素子１５が連続的な膜として形成できる範囲である必要性がある。
【０１１４】
尚、上記の複合薄膜４中の充填剤の粒子２同士の間は、バインダー３によって完全に埋められている必要は必ずしもなく、その間に空隙部（これを、気泡と呼ぶこともできる）が存在してよい。空隙部には、通常周辺気体（一般的には空気）が含まれており、従って、空隙部は、バインダー３と同様に低屈折率であるか、あるいはそれより低い屈折率である。そのため、充填剤２の間に空隙部が残ると、空隙部はバインダー３とほぼ同様に作用し、その結果、光の取出効率がより高くなる。尚、複合薄膜４全体の屈折率は、基材１の屈折率より低いことが望ましいが、基材１より多少高くてもよい。
【０１２５】
図１（ａ）および図２（ａ）の複合薄膜保持基板Ａにあって、基材１に設けた複合薄膜４の表面（即ち、基材１の側と反対の側の表面）の粗度が大き過ぎる場合には、複合薄膜４の基材１と反対側の表面に平滑化下地層を設け、複合薄膜４の表面の凹凸を埋めて平滑にするのが好ましい。このような平滑化下地層６を、図１（ａ）の複合薄膜保持基板Ａに、また、図２（ａ）の複合薄膜保持基板Ａに設けた形態を、それぞれ図３（ａ）および図３（ｂ）に模式的に断面図にて示す。このように平滑化下地層６を設けることによって、有機エレクトロルミネッセンス素子等のように薄膜間の平滑性、厚みの高度な均一性等が必要とされるものを複合薄膜４の上に形成することが容易になる。
【０１２６】
この平滑化下地層６を構成する材料は特に限定されるものではないが、平滑化下地層６の上に形成される薄膜等の層の屈折率に近い屈折率を有するものが好ましい。具体的には、シリカ、窒化珪素、アルミナ、窒化アルミニウム、チタニア等の金属酸化物および金属窒化物、フッ化マグネシウム、フッ素系ポリマー等のフッ素化物、アクリル系ポリマー、エポキシ系ポリマー、パリレン等を用いることができる。平滑化下地層６を形成する方法としては、真空蒸着、スパッタリング、ＣＶＤ等の気相成長法、複合薄膜４上に塗膜として形成した後に揮発分を乾燥除去するコーティング法等を挙げることができる。
【０１２７】
上述のように形成した複合薄膜保持基板Ａの表面上であって、基板が位置する側と反対側に透明導電性膜を形成してよい。この際、複合薄膜の露出表面が平坦でない場合、上述のように、複合薄膜の上に平滑化下地層６を形成し、その上に透明導電性膜を形成してよい。
【０１２８】
このように透明導電性膜を形成した形態を図４に断面図にて模式的に示す。図４に示す形態は、上述のようにして形成される複合薄膜保持基板Ａの複合薄膜４の上に透明導電性膜５を設けて形成される透明導電性膜保持基板Ｂを示すものである。尚、図４の形態では、複合薄膜４の基材１と反対側の表面に平滑化下地層６を設け、この平滑化下地層６の上に透明導電性膜５を形成している。図４（ａ）は、図３（ａ）の複合薄膜保持基板Ａに透明導電性膜５を設けたものを、図４（ｂ）は図３（ｂ）の複合薄膜保持基板Ａに透明導電性膜５を設けたものをそれぞれ示す。このように平滑化下地層６の上に透明導電性膜５を形成することによって、表面が平滑で厚みの均一性が高い薄膜に透明導電性膜５を形成することが容易になる。
【０１２９】
この透明導電性膜５は、後述のようにエレクトロルミネッセンス素子を形成する場合に陽極として使用できるものであってよい。その場合、透明導電性膜５の材料としては、酸化インジウム錫（ＩＴＯ）、酸化亜鉛、酸化錫、酸化インジウム亜鉛（ＩＺＯ）、導電性ポリマー等を例示できるが、特に限定されるものではない。透明導電性膜５を形成する方法としても、平滑化下地層６の場合と同様に、気相成長法、コーティング法等を適宜選択することができる。
【０１３０】
尚、透明導電性膜５の種類およびその形成方法によっては、下地の平滑性が低くても表面が平滑な透明導電性膜５を形成することが可能である。その場合には、平滑化下地層６を設ける必要なく、複合薄膜４の上に透明導電性膜５を直接形成することができる。例えば、ＩＺＯに代表されるアモルファス系の金属酸化物を気相成長法で製膜して透明導電性膜５を形成する場合、導電性ポリマー、ＩＴＯ微粒子をコーティング法で製膜して透明導電性膜５を形成する場合等がこれに該当する。
【０１３１】
図５の実施の形態は、上述のようにして製造した複合薄膜保持基板Ａにおいて、複合薄膜４の上に蛍光体の薄膜７を設けた面発光体Ｃを模式的に断面図にて示す。図５の形態では、複合薄膜４の基材１と反対側の表面に直接、蛍光体の薄膜７を設けている。この薄膜７は、紫外線の照射や電子線の照射によって励起されて発光する有機又は無機の蛍光体を含んで成り、フォトルミネッセンス素子として面発光体Ｃを形成する。この面発光体ＣはＣＲＴ、ＦＥＤ、ＰＤＰ等の自発光型ディスプレイにおいて特に有用である。図５（ａ）は図１（ａ）の複合薄膜保持基板Ａに蛍光体の薄膜７を設けたものを、図５（ｂ）は図２（ａ）の複合薄膜保持基板Ａに蛍光体の薄膜７を設けたものをそれぞれ示す。蛍光体の薄膜７がこのように複合薄膜４の表面に接していることによって、充填剤２の存在による複合薄膜４の表面の凹凸で光取出効率が向上する。
【０１３２】
蛍光体の材料としては特に限定されるものではなく、フォトルミネッセンス素子において従来から使用されている有機あるいは無機の任意の材料を用いることができる。蛍光体の薄膜７の形成方法としては、無機蛍光体の場合にはスパッタリング法、ＭＯＣＶＤ法（有機金属気相成長法）等の気相成長法を、低分子有機蛍光体の場合には真空蒸着法を、高分子有機蛍光体の場合にはスピンコーティング、インクジェットコーティング等のコーティング法を挙げることができる。
【０１３３】
図６の実施の形態は、上述の透明導電性膜保持基板Ｂにおいて、透明導電性膜５の上に発光層８および金属電極９を積層してエレクトロルミネッセンス素子１０を形成するようにした面発光体Ｄを断面図にて模式的に示す。即ち、複合薄膜保持基板Ａ上に素子１０が形成されている。エレクトロルミネッセンス素子１０は、陽極としての透明導電性膜５および陰極としての金属薄膜の金属電極９を有して成り、この陽極と陰極の間に発光層８を積層して形成されている。図６の形態は、有機エレクトルミネッセンス素子１０を示し、陽極となる透明導電性膜５と発光層８との間にホール輸送層１９が、そして、発光層８と陰極となる金属電極９との間に電子輸送層２０が必要に応じて積層されている。無機エレクトロルミネッセンス１０の場合には、発光層８の片面あるいは両面に誘電層が積層される。これらの発光層８、金属電極９、ホール輸送層１９、電子輸送層２０の材料としては、エレクトロルミネッセンスの製造に従来から使用されているものをそのまま用いることができる。
【０１３４】
尚、図６（ａ）は図４（ａ）の透明導電性膜保持基板Ｂに有機エレクトロルミネッセンス素子１０を設けたものを、図６（ｂ）は図４（ｂ）の透明導電性膜保持基板Ｂに有機エレクトロルミネッセンス素子１０を設けたものをそれぞれ示す。有機エレクトロルミネッセンス素子１０は、陽極となる透明導電性膜５に正電圧を、陰極となる金属電極９に負電圧を印加すると、電子輸送層２０を介して発光層８に注入された電子と、ホール輸送層１９を介して発光層８に注入されたホールとが、発光層８内にて再結合して発光が起こる。
【０１３５】
【実施例】
次に、本発明を実施例によってより具体的に説明する。重量平均分子量はＧＰＣ（ゲルパーミエーションクロマトグラフィー）により、測定機として東ソー（株）のＨＬＣ８０２０を用いて、標準ポリスチレンで検量線を作成し、その換算値として測定した。
【０１３６】
（実施例１）
テトラエトキシシラン２０８質量部にメタノール３５６質量部を加え、さらに水１８質量部及び０．０１Ｎの塩酸１８質量部を加え、ディスパーを用いてよく混合することによって溶液を得た。得られた溶液を２５℃恒温槽中で２時間攪拌し、重量平均分子量が８５０のバインダー形成材料としてのシリコーンレジン−Ｍ（テトラエトキシシランが加水分解して縮重合したもの）を得た。次に、このシリコーンレジン−Ｍに、中空シリカ微粒子としての中空シリカＩＰＡ分散ゾル（固形分：２０質量％、分散媒：イソプロピルアルコール、平均一次粒子径：約３５ｎｍ、外殻厚み：約８ｎｍ、触媒化成工業株式会社製）を、中空シリカ微粒子／シリコーンレジン−Ｍ（縮合化合物換算）の固形分質量基準で８０／２０となるように添加し、全固形分が１０質量％になるようにメタノールで希釈して、中空シリカ微粒子を含有するコーティング材組成物を得た。尚、「縮合化合物換算」とは、例えばテトラアルコキシシラン（この場合テトラエトキシシラン）の場合は存在するＳｉがＳｉＯ_２であるとしての重量、トリアルコキシシランの場合は、ＳｉＯ_１．５であるとしての重量である。
【０１３７】
次に、基材としてガラス板を用い、ガラス板の表面にこの得られたコーティング材組成物をスピンコータによって１０００ｒｐｍの条件で塗布して乾燥して被膜を得、これを２００℃で１０分間焼成することによって熱処理し、図１（ａ）のような構造を有する複合薄膜保持基板を製造した。尚、ガラス板の屈折率は１．５２、中空シリカ微粒子の屈折率は１．２５、シリコーンレジン−Ｍのみを塗布して乾燥させて熱処理したものの屈折率、即ち、バインダーの屈折率は１．４５であった。
【０１３８】
（実施例２）
テトラメトキシシラン１５２質量部にメタノール６４質量を加え、ディスパーを用いてよく混合することによって、シリカエアロゲルバインダーを形成するバインダー形成材料の溶液を得た。この溶液２１６質量部に対してメタノール６４質量部、水３６質量部、２８質量％濃度のアンモニア水０．６質量部、及びポリスチレン微粒子分散ゾル（固形分：１質量％、平均一次粒子径：約１００ｎｍ、Ｄｕｋｅ Ｓｃｉｅｎｔｉｆｉｃ社製）を５０倍濃縮したものを添加して混合し、混合物中におけるポリスチレン微粒子の割合を１０質量％に調製したポリスチレン微粒子を含有するコーティング材組成物を得た。
【０１３９】
次に、基材としてガラス板を用い、ガラス板の表面にこのコーティング材組成物をスピンコータにより１０００ｒｐｍの条件で塗布して塗膜を形成し、塗膜のゲル化後、８０℃、１６０ｋｇ／ｃｍ^２の条件で超臨界乾燥することによって、図２（ａ）のような構成の複合薄膜保持基板を作製した。ここで、ガラス板の屈折率は１．５２、ポリスチレン微粒子の屈折率は１．５９、超臨界乾燥後のバインダーの屈折率は１．１８である。
【０１４０】
（比較例１）
実施例１および２で用いたガラス板を未処理のまま用いて、これを比較例１とした。
【０１４１】
（比較例２）
実施例１および２で用いたガラス板に、実施例１で得たシリコーンレジン−Ｍのみ（従って、中空シリカ微粒子含有せず）を、実施例１と同様にコーティングし、これを比較例２とした。
【０１４２】
実施例１および２、ならびに比較例１および２で得た基板について、全光線透過率および複合薄膜の平均屈折率を測定した。ここで、全光線透過率の測定は、分光光度計（日立製作所製「Ｕ−３４００」）を用い、波長５５０ｎｍの全光線透過率を計測して行なった。また、複合薄膜の平均屈折率の測定は、走査型電子顕微鏡で基板の破断面を観察して複合薄膜の膜厚を測定した後、エリプソメーター（ＵＬＶＡＣ社製「ＥＭＳ−１」）で屈折率を計測して行なった。これらの結果を表１に示す。
【０１４３】
尚、実施例１および２で得た基板の複合薄膜の鉛筆硬度を測定したところ、実施例１の場合には鉛筆硬度が２Ｈ、実施例２の場合には、鉛筆硬度が５Ｈを示し、これらは、実質的には十分に取り扱える強度であった。尚、シリカエアロゲルのみからなる、屈折率１．２の低屈折率薄膜の場合は、鉛筆硬度はＢより柔らかい硬度であり、非常に傷つき易く取扱いの困難さを伴うものであった。
【０１４４】
【表１】

【０１４５】
（実施例３）
実施例１で得た複合薄膜保持基板を用い、複合薄膜の上にテトラエトキシシランをソースとしたプラズマＣＶＤを３００℃の条件で行ない、１００ｎｍの膜厚のＳｉＯ₂膜からなる平滑化下地層を複合薄膜の表面に形成した。次に、この平滑化下地層の上に２００℃の条件でＲＦスパッタリングすることにより、１００ｎｍの膜厚のＩＴＯ薄膜からなる透明導電性膜を形成し、図４（ａ）のような透明導電性膜保持基板を作製した。
【０１４６】
（実施例４）
実施例２で得た複合薄膜保持基板を用い、複合薄膜の上にＳｉＨ_４ガス及びＮ_２ガスをソースとしたプラズマＣＶＤを３００℃の条件で行ない、１００ｎｍの膜厚のＳｉＮ膜からなる平滑化下地層を複合薄膜の表面に形成した。次にこの平滑化下地層の上に２００℃の条件でＲＦスパッタリングすることにより、１００ｎｍの膜厚のＩＺＯ薄膜からなる透明導電性膜を形成し、図４（ｂ）のような透明導電性膜保持基板を作製した。
【０１４７】
（比較例３）
実施例１および２で用いたガラス板の表面に直接、実施例３と同様にしてＩＴＯ薄膜からなる透明導電性膜を形成し、これを比較例３とした。
【０１４８】
（比較例４）
実施例１および２で用いたガラス板の表面に直接、実施例４と同様にしてＩＺＯ薄膜からなる透明導電性膜を形成し、これを比較例４とした。
【０１４９】
実施例３および４ならびに比較例３および４で得た透明導電性膜保持基板について、全光線透過率と、透明導電性膜のシート抵抗値を測定した。ここで、シート抵抗値の測定は、ホール効果測定装置（アクセントオプティカルテクノロジー社製「ＨＬ５５００」）を用いて行なった。結果を表２に示す。
【０１５０】
【表２】

【０１５１】
（実施例５）
実施例１で得た複合薄膜保持基板を用い、複合薄膜の上に蛍光体の薄膜として、トリス（８−ヒドロキノリン）アルミニウム（同仁化学研究所製「Ａｌｑ３」）を１００ｎｍの厚みで製膜し、フォトルミネッセンス素子として図５（ａ）のような面発光体を作製した。
【０１５２】
（実施例６）
実施例２で得た複合薄膜保持基板を用い、複合薄膜の上に実施例５と同様にして蛍光体の薄膜を製膜し、フォトルミネッセンス素子として図５（ｂ）のような面発光体を作製した。
【０１５３】
（比較例５）
実施例１および２で用いたガラス板の表面に直接、実施例５と同様にして蛍光体の薄膜を製膜し、フォトルミネッセンス素子として面発光体を作製した。
【０１５４】
実施例５および６ならびに比較例５で得た面発光体について、蛍光体薄膜に２０Ｗの紫外線蛍光灯を照射し、ガラス基板の表面の輝度を輝度計（ミノルタ社製「ＬＳ−１１０」）を用いて測定した。結果を表３に示す。
【０１５５】
【表３】

【０１５６】
（実施例７）
実施例３で得た透明導電性膜保持基板を用い、透明導電性膜の上に、真空蒸着法によって、Ｎ，Ｎ−ジフェニル−Ｎ，Ｎ−ビス−３−メチルフェニル−１，１−ジフェニル−４，４−ジアミン（α−ＮＰＤ）を５０ｎｍ厚みで、トリス（８−ヒドロキノリン）アルミニウム（Ａｌｑ３）を５０ｎｍの厚みで、Ａｌを１００ｎｍの厚みで製膜して、ホール輸送層、発光層、金属電極を積層し、有機エレクトロルミネッセンス素子を形成して図６（ａ）のような面発光体を作製した。
【０１５７】
（実施例８）
実施例４で得た透明導電性膜保持基板を用い、実施例７と同様にして、有機エレクトロルミネッセンス素子を形成して図６（ｂ）のような面発光体を作製した。
【０１５８】
（比較例６）
比較例３で得た透明導電性膜保持基板を用い、実施例７と同様にして、有機エレクトロルミネッセンス素子を形成して面発光体を作製した。
【０１５９】
（比較例７）
比較例４で得た透明導電性膜保持基板を用い、実施例７と同様にして、有機エレクトロルミネッセンス素子を形成して面発光体を作製した。
【０１６０】
実施例７および８ならびに比較例６および７で得た面発光体について、透明導電性膜とＡｌ膜の金属電極の間に１０Ｖの直流電源を接続して発光させ、ガラス基板の表面の輝度を輝度計（ミノルタ社製「ＬＳ−１１０」）を用いて測定した。結果を表４に示す。
【０１６１】
【表４】

【０１６２】
【発明の効果】
本発明の第１の要旨の複合薄膜保持基板において、基材の表面に、基材の屈折率よりも屈折率の小さい充填剤を有することで、基板内での光の導波成分を低減させることができ、光の取り出し効率を大きくすることができる。また、基材の屈折率より低い屈折率の充填剤と、充填剤の屈折率より屈折率の高いバインダーとからなる複合薄膜が形成されている場合、屈折率が異なる充填剤とバインダーからなる複合薄膜を通過する際に光は一部散乱される。その相乗効果により、この基板の複合薄膜上に発光素子を設ける場合、発光素子内を導波する光が少なくなり、複合薄膜を通過する光は基材から外部（大気）への取出効率が高くなる。
【０１６３】
本発明の第２の要旨の複合薄膜保持基板において、基材の表面に、基材の屈折率より低い屈折率のバインダーと、バインダーの屈折率より屈折率の高い充填剤とからなる複合薄膜が形成されている場合についても同様である。
【０１６５】
第１の要旨の複合薄膜保持基板において、基材より屈折率の低い充填剤が、エアロゲル微粒子、中空シリカ微粒子およびポリマー製中空微粒子から選ばれるものであり、この充填剤より屈折率の高いバインダーが、有機ポリマーおよび金属酸化物から選ばれるものである場合、充填剤とバインダーからなる複合薄膜による外部への光の取出効率を高める効果を向上させることができる。
【０１６６】
第２の要旨の複合薄膜保持基板において、基材より屈折率の低いバインダーがエアロゲルであり、このバインダーより屈折率の高い充填剤が有機ポリマーおよび金属化合物から選ばれる微粒子である場合、バインダーと充填剤からなる複合薄膜による外部への光の取出効率を高める効果を向上させることができる。
【０１６７】
上述の複合薄膜保持基板のいずれかにおいて、基材より屈折率の低いものの屈折率が１．３５以下である場合、複合薄膜の平均屈折率を低く形成することができ、外部への光の取出効率をより一層高めることができる。
【０１６８】
上述のいずれかに記載の複合薄膜保持基板の複合薄膜の上に透明導電性膜を形成した透明導電性膜保持基板の場合は、外部への光の取出効率が高い透明導電性膜保持基板を得ることができる。
【０１６９】
この透明導電性膜保持基板において、複合薄膜の上に平滑化下地層を形成し、その上に透明導電性膜を形成する場合、表面が平滑で厚みの均一性が高い薄膜として透明導電性膜を形成することができ、また、外部への光の取出効率が高い透明導電性膜保持基板を得ることができる。
【０１７０】
本発明の面発光体は、複合薄膜保持基板の複合薄膜の上に、紫外線又は電子線によって励起されて発光する有機又は無機の蛍光体の薄膜が形成されており、外部への光の取出効率が高い面発光体を得ることができる。
【０１７１】
本発明のもう１つの面発光体は、透明導電性膜保持基板の透明導電性膜の上に発光層と金属電極がこの順に積層されてエレクトロルミネッセンス素子が形成されており、外部への光の取出効率が高い面発光体を得ることができる。
【図面の簡単な説明】
【図１】（ａ）および（ｂ）は、本発明の複合薄膜保持基板の形態の一例を模式的に示す断面図であり、（ｂ）では発光素子が設けられている。
【図２】（ａ）および（ｂ）は、本発明の複合薄膜保持基板の形態のもう一つの例を模式的に示す断面図であり、（ｂ）では発光素子が設けられている。
【図３】（ａ）および（ｂ）は、図１（ａ）および図２（ａ）の複合薄膜保持基板上に平滑化下地層を設けた形態を模式的に示す断面図である。
【図４】（ａ）および（ｂ）は、図３（ａ）および図３（ｂ）の複合薄膜保持基板上に透明導電性膜を設けた形態を模式的に示す断面図である。
【図５】（ａ）および（ｂ）は、図１（ａ）および図２（ａ）の複合薄膜保持基板上に蛍光体薄膜を設けた形態を模式的に示す断面図である。
【図６】（ａ）および（ｂ）は、図３（ａ）および図３（ｂ）の複合薄膜保持基板上にエレクトロルミネッセンス素子を設けた形態を模式的に示す断面図である。
【図７】従来の発光体の一例を示す断面図である。
【図８】従来の発光体の別の一例を示す断面図である。
【図９】従来の発光体の更に別の一例を示す断面図である。
【符号の説明】
１ 基材
２ 充填剤
３ バインダー
４ 複合薄膜
５ 透明導電性膜
６ 平滑化下地層
７ 蛍光体薄膜
８ 発光層、
９ 金属電極
１０ エレクトロルミネッセンス素子[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to surface emission used in various displays, display elements, backlights for liquid crystals,To the bodyRelated.
[0002]
[Prior art]
In recent years, various displays have been developed with the progress of the information society. As a typical thin film type light emitting element used for such a display, for example, there is an organic electroluminescence (EL) light emitter.
[0003]
FIG. 7 schematically shows a cross-sectional view of the structure of an organic electroluminescent luminescent material formed by providing a light emitting element 15 on a translucent substrate 1. The light emitted from the light emitting element 15 is extracted from the exposed surface of the base material 1 through the base material 1, thereby being extracted to the outside. As shown by the arrows in FIG. 7, some light that enters the interface between the surface of the base material 1 and air at a small incident angle is emitted to the outside from the exposed surface of the base material 1, but much of the light is Reflected at the interface between the exposed surface of the base material 1 and air and guided in the direction toward the edge of the substrate within the base material 1, in fact, only about 20% of the emitted light is exposed to the base material 1. Does not come out of the surface. This phenomenon is one of the major causes that keeps the extraction efficiency of the thin film light emitting element low.
[0004]
In view of this, various attempts have been made to avoid such a phenomenon and increase the light extraction efficiency from the exposed surface of the substrate 1. For example, as schematically shown in a sectional view in FIG. 8, the exposed surface of the substrate 1 is finely processed to form a diffusion layer 16, and light is diffused by the diffusion layer 16 of the substrate 1. The waveguide in the substrate 1 is reduced, and the efficiency of extracting light from the exposed surface of the substrate 1 to the outside is increased. This fine processing includes microlens processing and diffusion processing.
[0005]
However, in the case of FIG. 8, since the thickness of the base material 1 is generally in the order of millimeters, the number of times the light in the wave guide hits the diffusion layer 16 is small, and the effect of suppressing the wave guide and increasing the extraction efficiency is sufficient. It cannot be said. In addition, since the light is diffused by the diffusion layer 16, when it is necessary to recognize light emission as an image as in a display or the like, it becomes difficult to obtain a clear contrast by mixing the light. There is also a problem.
[0006]
In another aspect, as schematically shown in a cross-sectional view in FIG. 9, a low refractive index layer 17 (for example, having a refractive index of 1.. 3 or less). In this case, light is refracted at the interface between the low refractive index layer 17 and the base material 1, and the incident angle of the light incident on the interface between the exposed surface of the base material 1 and air is reduced. The amount of light reflected at the interface between the exposed surface of the material 1 and the air is reduced, the wave guide in the substrate 1 is suppressed, and the efficiency of extracting light from the surface of the substrate 1 to the outside increases.
[0007]
In the case of FIG. 9, it is possible to substantially eliminate the waveguide in the substrate 1 by inserting the low refractive index layer 17, and as a result, the light extraction efficiency can be increased. However, when the thickness of the light emitting element 15 having a refractive index higher than the refractive index of the low refractive index layer 17 is large, reflection of light at the interface between the light emitting element 15 and the low refractive index layer 17 increases, and the light emitting element 15 There is a possibility that the wave guide inside increases, and there is a problem that the thickness design of the light emitting element 15 needs to be devised.
[0008]
As described above, in a thin-film light-emitting element, it is difficult to improve extraction efficiency when the emitted light is extracted outside (in the atmosphere), and improvement of extraction efficiency is a problem.
[0009]
In general, the extraction rate η at which light generated inside a light emitter having a surface light emitting element is extracted to the outside of the light emitter is based on the law of classical optics, and the refractive index from a medium having a refractive index n. It is determined by the critical angle θc of total reflection when emitted into air of 1.0.
[0010]
From the law of refraction, this critical angle θc is given by the following equation (1).
[0011]
sin θc = 1 / n (1)
The extraction rate η is calculated from the ratio of the amount of light passing from the medium of refractive index n to the air and the total amount of light generated (the sum of the amount of light totally reflected at the interface between the medium and air and the amount of light passing through the air). (2).
[0012]
η = 1− (n²-1)^1/2/ N (2)
When the refractive index n of the medium is larger than 1.5, the following approximate expression (3) can be used. When the refractive index n of the medium is very close to 1.00, the above expression (2 ) Must be used.
[0013]
η = 1 / (2n²(3)
Here, in a thin film type light emitter such as an electroluminescence (EL) element, the thickness of the surface light emitting element portion is smaller than the wavelength of light, so that the refractive index of the base material mainly determines the extraction rate η. Usually, the refractive index n of glass, plastic film or the like used as a substrate is generally about 1.5 to 1.6. Therefore, from the formula (3), the extraction rate η is about 0.2 (about 20%). That is, the remaining 80% is lost as guided light due to total reflection at the interface between the substrate and air.
[0014]
An organic EL element is a typical thin film light emitter, but the same applies to a PL light emitting element using a PL (photoluminescence) light emitting layer as the light emitter. In a PL light emitting element, a PL light emitting layer is formed in a structure laminated on a substrate. In this element, when light such as ultraviolet rays is irradiated to the PL light emitting layer, the PL light emitting layer emits light, and the light is emitted from the substrate. In this element as well, since the light emitter is usually formed on the base material, the extraction rate η is low and much light is lost as guided light.
[0015]
In view of the above, Patent Document 1 discloses that a light-emitting body is formed on a base material having a surface layer with a low refractive index to reduce the light guide loss at the base material. Therefore, the light extraction efficiency is improved by forming the thin film light emitter on a thin film having a low refractive index. In an illuminant having a thickness smaller than the wavelength of light, wave guiding in the luminescent layer is limited, and thus the amount of light that can be emitted to the surface of the luminescent layer increases. Specifically, when the thickness of the light-emitting layer (including the thickness of the transparent conductive film in the case of organic EL) is about 200 nm or less, the phenomenon of waveguide restriction is significant, Applied Physics Letters, Volume 78, No. 13, p. 1927 and the like.
[0016]
Considering the above contents, when forming a light emitting body by forming a certain light emitting layer on the surface of the substrate, it is more efficient to form it on the substrate having a surface layer having a low refractive index. It is clear that it becomes higher, and the following formula (4):
n2 <n1 (4)
(In the formula, n1 is the refractive index of the substrate, and n2 is the refractive index of the low refractive index surface layer formed in advance on the surface of the substrate on the light emitting layer forming side.)
It is advantageous for the formation of the luminous body to form a thin film surface layer satisfying the above relationship on the substrate. Generally, a glass or plastic film is used for the substrate, and its refractive index is about 1.5 to 1.6.
[0017]
It can be said that there are virtually infinite combinations of the types of base materials that satisfy the relationship of formula (4) and the types of thin films provided on the surface thereof. Actually, by appropriately selecting the refractive index of the light emitting layer itself, the conditions for forming the light emitting layer (for example, temperature, process), etc., the light extraction efficiency of the light emitting body can be improved compared to the case where no thin film is provided on the substrate surface Can be improved. Patent Document 1 proposes to provide a thin film having a refractive index of 1.003 to 1.300 on the surface on the assumption that a general substrate is used, and specifically, it is represented by silica airgel. A porous thin film is formed. However, since the low refractive index thin film formed here is porous, its strength is not always sufficient.
[0018]
[Patent Document 1]
JP 2001-202827 A
[0019]
[Problems to be solved by the invention]
Therefore, regardless of the type of the substrate, by forming a thin film on the surface, an effect of improving the luminous efficiency can be expected as compared with the known techniques as described above, and preferably, A thin layer having sufficient strength and handleability for formation is desired.
[0020]
  Therefore, the present invention has a higher efficiency of extracting light to the outside than a conventional substrate having a thin layer.BoardConfigured withSurfaceAn object is to provide a light emitter.
[0021]
[Means for Solving the Problems]
  The object as described above is a composite thin film holding substrate having a base material and a composite thin film disposed on the surface thereof, the composite thin film comprising a filler and a binder, and the refractive index (Nf) of the filler. ) And the refractive index (Nb) of the binder are smaller than the refractive index (Ns) of the base material.UsingHas been found to be achieved. The other of the refractive index (Nf) of the filler and the refractive index (Nb) of the binder is smaller than the other.
[0022]
  Therefore, in the composite thin film holding substrate of the present invention, the relationship between the refractive indexes is A and B in the following two cases:
      Case A: Nf <Ns and Nf <Nb
      Case B: Nb <Ns and Nb <Nf
[0023]
  BookIn the invention, the composite thin film is a film that remains on the substrate by applying a liquid coating material composition comprising a filler and a binder-forming material to the substrate to form a coating film, and then drying the coating film. Drying means removing a liquid component (or volatile component) from the coating film to leave a solid coating, and may be heated as necessary during drying. In addition, after drying and obtaining a film, the film may be heated and heat-treated, or the film may be heat-treated by continuing heating during drying.
[0024]
In a composite thin film, fillers are dispersed in a binder formed from a binder forming material, and these form different phases from each other. In this sense, the term “composite” is used. The binder restrains and holds the filler in a dispersed state therein. The binder is formed from the binder-forming material by drying the coating material composition in the form of a film. During this drying, the binder-forming material may or may not be chemically changed. The state of being dissolved and / or dispersed in the material composition is converted into a solid in a layer form as a whole. The coating material composition is usually a liquid solvent and / or a dispersion medium (for example, water, alcohol (for example, methanol, ethanol, isopropyl alcohol, etc.), toluene, xylene in order to make it a liquid state that can be applied to the substrate. Organic solvent such as methyl ethyl ketone) and other components may be included as required. Examples of such other components include leveling agents for forming a smooth coating film typified by acrylic polymers, ethylene glycol derivatives such as ethylene glycol, ethylene glycol monobutyl ether, and ethylene glycol monoethyl ether acetate, Examples thereof include a thickener for film thickness control represented by diethylene glycol derivatives such as diethylene glycol and diethylene glycol monobutyl ether, a high boiling point solvent, and a silane coupling agent for imparting adhesion to a substrate.
[0025]
In the composite thin film holding substrate of the present invention, it is preferable that both the refractive index (Nf) of the filler and the refractive index (Nb) of the binder are smaller than the refractive index (Ns) of the substrate. At least one of Nf) and the refractive index (Nb) of the binder may be the same as or larger than the refractive index (Ns) of the substrate.
[0026]
  Therefore, in the first aspect, the present invention provides the composite thin film holding substrate of Case A.The surface emitter usedA composite thin film holding substrate comprising a substrate and a composite thin film disposed on a surface thereof, wherein the composite thin film comprises a filler and a binder, and the refractive index (Nf) of the filler is A composite thin film holding substrate that is smaller than the refractive index (Nb) of the binder and smaller than the refractive index (Ns) of the base material.The surface emitter usedprovide.
[0027]
In the first aspect, the filler is preferably at least one selected from, for example, airgel fine particles, hollow silica fine particles and polymer hollow fine particles, and the binder is at least one selected from organic polymers and metal oxides. Preferably it is a seed.
[0028]
  Accordingly, in the second aspect, the present invention provides the composite thin film holding substrate of Case B.The surface emitter usedProviding a composite thin film holding substrate comprising a substrate and a composite thin film disposed on the surface thereof, wherein the composite thin film comprises a filler and a binder, and the refractive index (Nb) of the binder is: A composite thin film holding substrate that is smaller than the refractive index (Nf) of the filler and smaller than the refractive index (Ns) of the base material.The surface emitter usedprovide.
[0029]
In the second aspect, the binder is preferably a silica porous material, for example, a silicone resin-M described later (if it is polycondensable, it may be a polycondensate), airgel, etc. The filler is preferably at least one kind of fine particles selected from organic polymer fine particles, metal compound fine particles and hollow silica fine particles.
[0032]
  In the first aspect, the refractive index of the filler having a refractive index lower than the refractive index of the base material is generally 1.35 or less, preferably 1.30 or less. In this case, the refractive index of the binder having a refractive index lower than that of the substrate is generally 1.45 or less, preferably 1.30 or less..
  In the present invention, the transparent conductive film holding substrate has a transparent conductive film formed on the composite thin film of the composite thin film holding substrate described above. In this transparent conductive film holding substrate, a very thin (for example, about 10 to 100 nm thick) smoothing underlayer is formed on the composite thin film, and the transparent conductive film is formed on the smoothing underlayer. It's okay.
  In the present invention, a thin film of an organic or inorganic phosphor that emits light when excited by ultraviolet rays or an electron beam is formed on the composite thin film of the above-described composite thin film holding substrate.
  In the present invention, another surface light emitter has a light emitting layer and a metal electrode 9 laminated in this order on the transparent conductive film of the transparent conductive film holding substrate, thereby forming an electroluminescence element. ing.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0037]
  Composite thin film of the present inventionfilmIn the holding substrate, the base material can be used without particular limitation as long as it is translucent, and is usually in the form of a sheet or a plate. A base material may be a transparent glass plate, a transparent plastic plate, etc., for example, and will not be restrict | limited especially if generally used as a translucent board. In many cases, the refractive index of the substrate 1 is in the range of 1.46 to 1.6.
[0038]
  Composite thin of the present inventionfilmExamples of materials that can be used for the filler in the holding substrate include airgel fine particles, hollow silica fine particles, polymer hollow fine particles, organic polymer fine particles, and metal oxide fine particles. Moreover, as a material which can be used for a binder, an organic polymer, a metal oxide, a silica porous body (especially silicone resin-M mentioned later, silica airgel, etc.) etc. can be illustrated. A combination of a filler and a binder may be selected from these usable materials so as to satisfy the above-described refractive index relationship. Next, the filler and binder will be described.
[0039]
Unless otherwise specified, in the present specification, the refractive index means a refractive index obtained as follows:
(Refractive index of filler)
Regarding the refractive index of the filler, whether the fine particles as the filler are solid, porous or hollow (including the case where the outer shell is porous) Can be obtained in this way.
[0040]
The refractive index and specific gravity of the sol in which the filler is dispersed in a solvent typified by water or alcohol are measured, and the refractive index and specific gravity of the solvent constituting the sol, and the true specific gravity of the substance forming the filler and Calculate with the following formula using the refractive index:
Refractive index-1 of the filler is n,
n = n₀(PN₀-P₀N) / {n₀(PP₀) + P₀(N₀-N)}
Thus, the refractive index of the filler is n + 1.
[0041]
In the above formula, symbols are as shown below, and the above formula is derived from the following formulas (a), (b) and (c).
[0042]
Here, the formulas (a) and (b) are formulas showing the relationship between the refractive index and the specific gravity of a mixture obtained by uniformly mixing two substances, which are obvious to those skilled in the art. On the other hand, for a filler as a porous material having fine voids whose dimensions (generally the diameter) are sub-micron level or less, the refractive index of the porous material is that of the solid portion and the void portion in the porous body. It is determined by the volume ratio. Between the refractive index of the porous body and the solid filling rate in the porous body (ie, 1-porosity of the porous body), [refractive index-1 of the porous body] is solid-filled. It is generally known that it is proportional to the rate. Based on this fact, the true specific gravity (p₀) And the original refractive index of the substance-1 (refractive index of the solid pure substance constituting the porous body-1: n₀) And the bulk specific gravity (p) of the porous body, [refractive index of the porous body −1], that is, the formula for calculating n is (c), which is also a formula well known to those skilled in the art. is there. The formula (c) is originally applied to the filler of the porous body, but can also be applied to the hollow body fine particles (including the case where the outer shell is porous). By making the true specific gravity and the bulk specific gravity the same, and making the refractive index of the filler equal to the refractive index of the material constituting the filler, the formula (c) applies even if the filler is solid, and therefore Needless to say, the refractive index of the filler can be obtained by the above formula.
[0043]
Sol refractive index (measured value) = N + 1
Refractive index of solvent = N₀+1
Refractive index of the material constituting the filler = n₀+1
Specific gravity of sol (measured value) = P
Specific gravity of solvent = P₀
True specific gravity of the material constituting the filler = p₀
Bulk specific gravity of filler = p
Occupied volume ratio of filler in sol = V
V = (N−N₀) / (N-N₀(A)
V = (PP₀) / (P-P₀(B)
n = pn₀/ P₀                    (C)
(Binder refractive index)
Refractive index measured by ellipsometry for a coating obtained as follows; a binder mixture is dissolved and / or dispersed in a suitable solvent (eg, alcohol such as methanol, isopropyl alcohol, etc.) to form a liquid mixture. A film that remains on the substrate by applying it to a substrate to obtain a coating film, removing liquid (or volatiles) from the coating film and drying. In addition, this film comprises the binder part in the composite film of the present invention.
[0044]
(1-1) About airgel fine particles as a filler
Examples of the airgel fine particles include silica airgel fine particles, composite airgel fine particles such as silica / alumina airgel, and organic airgel fine particles such as melamine airgel. Silica aerogels are used to hydrolyze and condense alkoxysilanes (also referred to as silicon alkoxides or alkyl silicates), as described, for example, in U.S. Pat. By dispersing a gel compound in a wet state composed of a silica skeleton obtained by a polymerization reaction in a solvent (dispersion medium) such as alcohol or carbon dioxide and drying it in a supercritical state above the critical point of this solvent. Can be manufactured. In supercritical drying, for example, a gel compound is immersed in liquefied carbon dioxide, and all or part of the solvent previously contained in the gel compound is replaced with liquefied carbon dioxide having a lower critical point than that solvent. Thereafter, it can be carried out by drying under supercritical conditions of a single system of carbon dioxide or a mixed system of carbon dioxide and a solvent.
[0045]
Alternatively, silica aerogels can be produced in the same manner as described above, starting from sodium silicate as described in US Pat. Nos. 5,137,279 and 5,124,364.
[0046]
In producing silica aerogel, as disclosed in JP-A-5-279011 and JP-A-7-138375, a gel-like material obtained as described above by hydrolysis and condensation polymerization of alkoxysilane. It is preferable to impart hydrophobicity to the silica airgel by hydrophobizing the compound. Thus, the hydrophobic silica aerogel to which hydrophobicity is imparted can prevent moisture, water and the like from entering, and can prevent the performance of the silica aerogel such as the refractive index and light transmittance from deteriorating. This hydrophobization treatment step can be performed before or during supercritical drying of the gel compound.
[0047]
The hydrophobizing treatment is performed by reacting the hydroxyl group of the silanol group present on the surface of the gel compound with the functional group of the hydrophobizing agent and replacing the silanol group with the hydrophobic group of the hydrophobizing agent. As a method for performing the hydrophobization treatment, for example, the gel is immersed in a hydrophobization treatment solution in which the hydrophobization treatment agent is dissolved in a solvent, and the hydrophobization treatment agent is permeated into the gel by mixing or the like. There is a method in which the hydrophobization reaction is performed by heating accordingly. Examples of the solvent used for the hydrophobizing treatment include methanol, ethanol, isopropanol, xylene, toluene, benzene, N, N-dimethylformamide, hexamethyldisiloxane and the like. The solvent is not limited to these as long as the hydrophobizing agent is easily dissolved and can be replaced with the solvent contained in the gel before the hydrophobizing treatment.
[0048]
When supercritical drying is performed in a step after the hydrophobizing treatment, the solvent used for the hydrophobizing treatment is a medium that is easily supercritically dried (for example, methanol, ethanol, isopropanol, liquid carbon dioxide, etc.), or Those that can be substituted are preferred. Examples of hydrophobizing agents include hexamethyldisilazane, hexamethyldisiloxane, trimethylmethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, trimethylethoxysilane, dimethyldiethoxysilane, and methyltriethoxysilane. Can be mentioned.
[0049]
In the present invention, the airgel fine particles used as the filler can be obtained, for example, by pulverizing the silica airgel prepared in advance as described above. Alternatively, the wet gel before drying can be obtained by pulverizing and then drying. Moreover, when manufacturing it using sodium silicate as a raw material, airgel microparticles | fine-particles can be obtained by atomizing at the time of suspension polymerization. In addition, the refractive index of the silica airgel obtained by making it above can be made into a desired value by selecting variously the kind of raw material, compounding ratio, etc. which are used for manufacture of a silica airgel.
[0050]
(1-2) Hollow silica fine particles as a filler
As the hollow silica fine particles that can be used as the filler, there can be used a hollow silica sol produced by the method described in JP-A-2001-233611 and other commercially available hollow silica powders. Throughout this specification, the hollow fine particles are fine particles having a hollow portion surrounded by an outer shell, and any appropriate known hollow silica fine particles may be used. In the hollow silica fine particles, the outer shell is composed of a silica-based inorganic oxide. Particularly preferred hollow silica particulates to use are, for example:
The outer shell (shell) made of silica-based inorganic oxide is (A) a single layer of silica, (B) a single layer of a composite oxide made of silica and an inorganic oxide other than silica, and (C) the above (A ) Layer and (B) layer. The outer shell may be porous with pores, or the pores may be closed and the cavity sealed with respect to the outside of the outer shell. The outer shell is preferably a plurality of silica-based coating layers including an inner first silica coating layer and an outer second silica coating layer. By providing the second silica coating layer on the outer side, it is possible to obtain fine hollow silica fine particles that close the fine pores of the outer shell to make the outer shell dense, and further seal the inner cavity.
[0051]
The thickness of the outer shell is preferably in the range of 1 to 50 nm, particularly 5 to 20 nm. If the thickness of the outer shell is less than 1 nm, the hollow fine particles may not maintain a predetermined particle shape. On the other hand, when the thickness of the outer shell exceeds 50 nm, the cavities in the hollow silica fine particles are small, and as a result, the ratio of the cavities may decrease and the refractive index may not be sufficiently lowered. Furthermore, the thickness of the outer shell is preferably in the range of 1/50 to 1/5 of the average particle diameter of the hollow fine particles. When the first silica coating layer and the second silica coating layer are provided as outer shells as described above, the total thickness of these layers may be in the range of 1 to 50 nm. For the outer shell, the thickness of the second silica coating layer is preferably in the range of 20 to 40 nm.
[0052]
In addition, the solvent used when preparing the hollow silica fine particles and / or the gas that enters during drying may be present in the hollow portion. Moreover, the precursor substance for forming the cavity mentioned later may remain in the cavity. The precursor material may remain slightly attached to the outer shell or may occupy most of the interior of the cavity. Here, the precursor material is a porous material that remains after a part of the constituent components of the core particle is removed from the core particle surrounded by the outer shell. As the core particles, porous composite oxide particles composed of silica and an inorganic oxide other than silica are used. As an inorganic oxide, Al₂O₃, B₂O₃TiO₂, ZrO₂, SnO₂, Ce₂O₃, P₂O₅, Sb₂O₃, MoO₃ZnO₃, WO₃1 type, or 2 or more types, etc. can be mentioned. TiO as two or more inorganic oxides₂-Al₂O₃TiO₂-ZrO₂Etc. can be illustrated. The solvent or gas may be present in the pores of the porous material. When the removal amount of the constituent components of the core particles at this time increases, the volume of the cavity increases and hollow silica fine particles having a low refractive index are obtained. The transparent coating obtained by blending the hollow silica fine particles reflects with a low refractive index. Excellent prevention performance.
[0053]
In the present invention, the average particle diameter of the hollow silica fine particles is preferably in the range of 5 nm to 2 μm. If the average particle size is smaller than 5 nm, the effect of lowering the refractive index due to hollowness is small. Conversely, if the average particle size is larger than 2 μm, the transparency becomes extremely poor, and contribution is due to diffuse reflection (Anti-Glare). Will become bigger. In the present invention, the composite thin film is required to have high transparency, for example, there is an antireflection application such as the outermost surface of the display. For this purpose, it is preferable that the hollow silica fine particles used have a particle diameter in the range of 5 to 100 nm. In addition, the particle diameter used in this specification is a number average particle diameter by transmission electron microscope observation.
[0054]
The method for producing hollow silica fine particles as described above is known as described in detail in JP-A-2001-233611, and a commercial product produced by this method is provided. Can be obtained and used.
[0055]
The refractive index of the hollow silica fine particles can be set to a desired value by variously adjusting the thickness and particle diameter of the outer shell at the production stage of the hollow fine particles.
[0056]
As for the hollow silica fine particles, the outer shell may be a dense layer or a porous layer, but it is preferable that the distribution of particle diameter and outer shell thickness is uniform. This is because the volume ratio of the hollow fine particles in the particle diameter and the composite thin film determines the refractive index of the composite thin film.
[0057]
(1-3) About polymer hollow fine particles as filler
As the filler for the composite thin film of the composite thin film holding substrate of the present invention, polymer hollow fine particles can be used. The outer shell of the fine particles is made of a polymer material such as a fluorine-based polymer. Various such fine particles are disclosed in, for example, Japanese Patent Laid-Open No. 10-142402, and the content of this patent publication constitutes a part of this specification by this reference. The polymer hollow microparticles that are particularly preferably used are fluoropolymers, and the use of this makes it possible to easily reduce the refractive index of the composite thin film.
[0058]
The refractive index of the polymer hollow fine particles can be set to a desired value by variously selecting the particle diameter and the polymer material.
[0059]
(1-4) Organic polymer fine particles as a filler
Organic polymer fine particles can be used as a filler for the composite thin film of the composite thin film holding substrate of the present invention. Examples of the organic polymer include silicone resin, acrylic resin, and styrene resin. Such an organic polymer can be obtained as a filler in the form of fine particles by suspension polymerization, supercritical polymerization or the like, but may be fine particles produced by another method as long as fine particles are obtained. The refractive index of the organic polymer fine particles can be set to a desired value by selecting various polymer materials.
[0060]
(1-5) Metal oxide fine particles as filler
Metal oxide fine particles can be used as a filler for the composite thin film of the composite thin film holding substrate of the present invention. Examples of the metal oxide include titania fine particles, indium tin oxide fine particles, silica fine particles, and alumina fine particles. These are mixed into the coating material composition using a sol that is commercially available as a dispersion sol. As the metal oxide fine particles that are particularly preferable to be used, titania fine particles and indium tin oxide fine particles can be exemplified when selecting those having a large refractive index, and silica can be exemplified when selecting those having a small refractive index. . The refractive index of the metal oxide fine particles can be set to a desired value by variously selecting the material itself.
[0061]
(2-1) Organic polymer as binder
An organic polymer can be used as a binder for the composite thin film of the composite thin film holding substrate of the present invention. This organic polymer may be the same as the polymer constituting the organic polymer fine particles described above. Accordingly, such a polymer is in a dissolved and / or dispersed state in the liquid coating material composition, and is applied and dried to form a solid film containing the filler in a dispersed state. That is, in this case, the organic polymer itself is a binder forming material and a binder. As another example of such a polymer, an acrylic resin, a fluorine resin, or the like that is excellent in transparency is preferable, but it may be one generally used as an optical thin film coating.
[0062]
In another aspect, when the coating film obtained by applying the coating material composition is dried, the binder-forming material may be chemically changed to a binder. For example, the binder-forming material may be a reactive (eg, crosslinkable, polycondensable, etc.) organic monomer, organic oligomer, or organic prepolymer, which reacts to become an organic polymer as a binder. Good. Accordingly, such an organic monomer, organic oligomer or organic prepolymer is dissolved and / or dispersed as a reactive binder forming material in the liquid coating material composition. Examples of such organic monomer, organic oligomer or organic prepolymer that are preferably used include epoxy monomers, oligomers, prepolymers and the like.
[0063]
The refractive index of the organic polymer can be set to a desired value by variously selecting the organic polymer, the organic monomer, the organic oligomer, and the organic prepolymer that provide the organic polymer.
[0064]
(2-2) Silica porous body as binder
A porous silica material can be used as a binder for the composite thin film of the composite thin film holding substrate of the present invention. Here, the silica porous body means a material in which silica as a binder for holding the filler in a dispersed state includes a large number of fine voids. Such a porous silica material is preferably used when a silica-based material is used as a filler.
[0065]
A binder-forming material that can be used to form a particularly preferred porous silica is represented by the general formula (1):
[0066]
[Chemical 1]

[0067]
(Wherein the substituent X¹, X², X³And X⁴Is a group selected from hydrogen, halogen (eg, chlorine, fluorine, etc.), a monovalent hydrocarbon group, an alkoxy group represented by OR (R is a monovalent hydrocarbon group), and a hydroxyl group represented by OH These may be different from each other, partially different from each other, or all the same, and at least two of these are groups selected from an alkoxy group and a hydroxyl group, respectively. )
It is a silane compound represented by these. The silane compound has at least 2, preferably 3, and more preferably 4 identical or different alkoxyl and / or hydroxyl groups. The binder forming material may be one in which at least one alkoxyl group of the silane compound is hydrolyzed.
[0068]
In another aspect, the binder-forming material is a siloxane compound or a polysiloxane compound that is formed by condensing one or more of the silane compounds, if hydrolyzable, after hydrolysis. The polysiloxane compound means a compound having two or more siloxane bonds. This (poly) siloxane compound preferably has at least two alkoxy groups and / or hydroxyl groups as substituents.
[0069]
In addition, when the above-mentioned silane compound and (poly) siloxane compound have an alkoxyl group, they can have a hydroxyl group produced by hydrolysis of the alkoxyl group. As a result, these silane compounds and (poly) siloxane compounds can also be at least partially condensed and cross-linked when the coating composition is applied and dried to form porous silica as a binder. Even when the (poly) siloxane compound does not have an alkoxy group and / or a hydroxyl group as a substituent, a porous binder can be formed when the coating material composition is applied and dried.
[0070]
Particularly preferred porous silica is SiX.₄(X is a hydrolyzable substituent having 1 to 4 carbon atoms, for example, an alkoxyl group having 1 to 5 carbon atoms), and tetrafunctional hydrolysis having 4 hydrolyzable substituents on silicon element A polysiloxane compound obtained by condensation polymerization of a partially hydrolyzed product or a completely hydrolyzed product of a functional organosiloxane (this polysiloxane compound is referred to as “silicone resin-M” in this specification) is used as a binder forming material. It is obtained by applying a coating material composition to be applied and drying the coating film. In addition, in order to distinguish from what is generally known as “silicone resin”, the polysiloxane compound as the binder-forming material is referred to as “silicone resin-M” (SILICONE RESIN-M) in this specification. ). Such “silicone resin-M” need not be the same as what is generally known as a silicone resin.
This silicone resin-M may itself have a hydrolyzable substituent, in which case, when the silicone resin-M forms a binder, it hydrolyzes and condenses to give a higher molecular weight silicone. A binder is formed as Resin-M. When Silicone Resin-M does not have such a substituent, Silicone Resin-M forms a binder as it is.
[0071]
Therefore, a composite thin film in which the filler is dispersed in the binder can be obtained by including the binder-forming material as described above in the coating material composition together with the filler, and applying it to the substrate and drying the coating film. it can. The refractive index of such a porous silica as a binder can be set to a desired value by variously changing the weight ratio between the filler and the binder-forming material.
[0072]
When such a silicone resin-M that forms a porous silica is required to have a mechanical strength of the composite coating, it preferably has a weight average molecular weight of about 200 to 2000, preferably 600 to 1200. Is more preferable. A molecular weight in this range tends to easily improve the strength of the composite coating and increase the porosity of the binder (ie, the proportion of voids in the binder). Silicone resin-M has a weight average molecular weight of preferably about 2000 or more, more preferably 3000 or more, for example, 3000 to 5000 when the composite coating does not require high mechanical strength. is there.
[0073]
In addition, the composite film formed using the silicone resin-M may be heat-treated at 100 to 300 ° C., more preferably at 50 to 150 ° C. for 5 to 30 minutes as necessary. Strength can be improved.
[0074]
In another aspect, the silica porous body is a silica airgel. The airgel as the binder is coated with a gel-like compound obtained by hydrolysis / polymerization reaction of alkoxysilane (silicon alkoxide, especially the above-mentioned tetrafunctional alkoxysilane) as described above, gelation reaction of sodium silicate aqueous solution, etc. It can be used as a binder-forming material contained in the material composition, applied to the coating material composition to obtain a coating film, and dried to form a filler. Therefore, in this case, the binder-forming material is an alkoxysilane or a hydrolyzate thereof (not necessarily all the alkoxyl groups are hydrolyzed, but a partial hydrolyzate in which only a part of the alkoxyl groups is hydrolyzed is also included. And a hydrolyzate condensate. In general, the binder-forming material is preferably a hydrolyzate condensate. Such silica airgel can be obtained as described above. When a filler is mixed in a wet gel compound and dried, a composite thin film in which the filler is dispersed in silica aerogel can be obtained. Accordingly, the coating composition comprises a wet gel compound and a filler.
[0075]
The refractive index of such an airgel as a binder can be set to a desired value by selecting a blending ratio of raw material solutions, a drying method, and the like.
[0076]
(2-3) Metal oxide as binder
A metal oxide can be used as a binder for the composite thin film of the composite thin film holding substrate of the present invention. In this case, the metal oxide precursor contained in the coating material composition as a binder forming material changes to a metal oxide as a binder when the coating film obtained by applying the coating material composition is dried. Examples of such metal oxide precursors that are preferably used include silica and silica / titania composite oxide. The refractive index of the metal oxide as the binder can be set to a desired value by variously selecting the constituent element species of the substance that provides the metal oxide.
[0077]
In the composite film holding substrate of the present invention, the combination of the filler and the binder described above may be selected so as to satisfy the above-described refractive index relationship. Note that the refractive index of the composite thin film formed from the combination of the filler and the binder (that is, the refractive index of the composite film as a whole) is the refractive index of the filler, the refractive index of the binder, and formed. The refractive index is usually smaller than the theoretically calculated refractive index from the filler / binder ratio in the thin film. In the composite thin film binder to be formed, in addition to voids that may exist inherently in the binder material itself (for example, voids due to the porosity of the binder), there are voids between the fine particles constituting the filler. This is because there may be voids between the filler fine particles and the binder. In fact, when the filler and the binder-forming material are mixed to form a composite film, such other These voids are also included in the composite thin film, and such voids have the effect of lowering the refractive index of the composite thin film. In the present specification, the refractive index of the composite thin film means a general refractive index including the effect of such other voids.
[0078]
In the composite film formed using the coating material composition of the present invention, the binder existing around the filler and acting as a matrix means a state containing a large number of fine voids therein. Therefore, the apparent specific gravity of the binder is smaller than the true specific gravity of the material constituting the binder itself (that is, the material in the case where voids are not substantially present). The ratio of the apparent specific gravity of the binder to the true specific gravity of the binder is preferably 0.90 or less, more preferably 0.75 or less, for example 0.50 to 0.75. In addition, this ratio is a value calculated also including the volume of such a space | gap, when a composite film contains the above-mentioned "other space | gap". In addition, the space | gap in a binder contains the surrounding gas of a film normally.
[0079]
In one example, a tetrafunctional silicone resin as a binder with a refractive index of 1.45 (ie, Silicone Resin-M) and hollow silica fine particles as a filler with a refractive index of 1.32 are combined with a binder / filler volume ratio of 0. The average refractive index of the composite thin film including 0.1 to 0.3 can be 1.26 to 1.35.
[0080]
In another example, a composite thin film comprising silica airgel as a binder with a refractive index of 1.20 and acrylic polymer fine particles as a filler with a refractive index of 1.59 in a binder / filler volume ratio of 0.5 to 0.75. The average refractive index of can be 1.30 to 1.40.
[0081]
In still another example, an acrylic polymer as a binder having a refractive index of 1.59 and silica / titania composite oxide fine particles as a filler having a refractive index of 1.6 are mixed with a binder / filler volume ratio of 0.05. The average refractive index of the composite thin film comprising ˜0.15 can be 1.35 to 1.40. In the case of this composite thin film, when calculated based on the apparent volume of the composite film and the weight of the binder and the filler, about 40% of the volume of the composite thin film is occupied by voids. The average refractive index is smaller than the refractive index of the filler and smaller than the refractive index of the binder.
[0082]
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0083]
Fig.1 (a) shows typically one form of the composite thin film holding | maintenance board | substrate A of a 1st summary with sectional drawing. In the illustrated form, a composite thin film 4 composed of a filler 2 and a binder 3 is formed on the surface of a substrate 1. The composite thin film 4 is obtained by applying a liquid coating material composition, which is a mixture of a filler and a binder forming material, onto the substrate 1 and drying it. In the illustrated embodiment, the refractive index of the filler 2 is lower than the refractive index of the substrate 1, and the refractive index of the formed binder 3 is higher than the refractive index of the filler 2. In addition, about the base material 1, it is as having demonstrated previously.
[0084]
Moreover, the refractive index of the filler 2 should just be lower than the refractive index of the base material 1, and it is not specifically limited, Usually, it is lower than 1.35, Preferably it is lower than 1.3. It is desirable to lower the average refractive index of the composite thin film 4. Since the refractive index of the filler 2 is preferably as low as possible, the lower limit is ideally 1.0, but is practically 1.003, and generally the lower limit may be 1.1. The refractive index of the binder is not particularly limited as long as it is higher than the refractive index of the filler, but it is usually lower than 1.5, preferably lower than 1.46. 4 is desirable for lowering the average refractive index.
[0085]
Examples of the filler 2 having a refractive index lower than that of the substrate 1 include the above-mentioned airgel fine particles, hollow silica fine particles, and polymer hollow fine particles.
[0086]
When silica airgel fine particles are used as the airgel fine particles of the filler 2, the refractive index is preferably in the range of 1.008 to 1.18, more preferably in order to ensure performance such as transparency of the silica airgel. It is preferable to adjust so that it may become in the range of 1.1-1.3.
[0087]
When hollow silica fine particles are used as the filler 2, the refractive index is preferably adjusted to be in the range of 1.2 to 1.35, more preferably 1.2 to 1.3.
[0088]
When the polymer hollow fine particles are used as the filler 2, the refractive index is preferably adjusted to be in the range of 1.2 to 1.4, more preferably 1.2 to 1.3. .
[0089]
As the low refractive index filler 2 described above, those having a particle diameter in the range of 5 nm to 2 μm are preferable, and those having a particle diameter of 20 nm to 500 nm are more preferable. When the filler is hollow fine particles, the thickness of the outer shell is preferably 5 nm to 20 nm. The smaller the particle diameter of the filler 2, the higher the effect of lowering the average refractive index of the composite thin film 4 (that is, the refractive index of the composite thin film as a whole), and the composite thin film 4 having excellent transparency is obtained. As a result, the light extraction efficiency can be increased. Conversely, the larger the particle size, the greater the scattering effect in the composite thin film 4 and the greater the effect of suppressing light guiding, so that the light extraction efficiency can be increased. In order to have both effects, the particle size of the filler 2 is preferably in the above-mentioned range, and the particle size of the filler 2 is the refractive index of the binder 3 constituting the composite thin film 4, the type and thickness of the light emitting element, and the like. Depending on the above, an appropriate one can be selected within the above range. In addition, the particle diameter described in this specification refers to the primary particle diameter, and the particle diameter is measured by visual observation such as observation with a transmission electron microscope.
[0090]
On the other hand, the binder 3 having a refractive index higher than that of the filler 2 is preferably an organic polymer or metal oxide generated from a binder forming material contained in the transparent coating material composition. If the refractive index of the binder 3 is higher than that of the filler 2, the binder is a binder such as the above-mentioned organic polymer, metal oxide, etc. If the refractive index is larger than the refractive index of the filler, the type is There is no particular limitation. In the case of an organic polymer as a binder, examples of materials that are preferably used as a binder forming material include acrylic polymers such as methyl methacrylate, epoxy polymers, fluorine polymers, styrene polymers, and the like. The refractive index of the binder is usually 1.4 to 1.65, preferably 1.45 to 1.6. In addition, as a material preferably used as a binder forming material, in the case of a metal oxide as a binder, silica, indium tin oxide, titania, silica / titania composite oxide, zirconia, etc. can be exemplified and formed using these The refractive index of the binder is usually 1.45 to 3.0, preferably 1.45 to 2.5.
[0091]
In particular, it is desirable to select a binder-forming material with good dispersibility of the filler 2 used together in the coating material composition. Among these, when silica-based one is used as the filler 2, the SiX described above is used._FourSilicone resin-M obtained by condensation polymerization of a partially hydrolyzed or fully hydrolyzed tetrafunctional organosiloxane represented by the formula (X is, for example, an alkoxyl group having 1 to 4 carbon atoms) is used as the binder 3. Is most preferred. As mentioned above, the silicone resin-M may itself have hydrolyzable substituents, or the silicone resin-M may not have such substituents. Thus, the refractive index of the binder 3 formed of the silicone resin-M is usually 1.3 to 1.50, preferably 1.3 to 1.45.
[0092]
In the composite thin film 4, the abundance ratio of the filler 2 and the binder 3 varies depending on the refractive index ratio and density ratio, but the mass ratio of the filler 2 is preferably 40 to 95 mass%, In this case, the average refractive index of the composite thin film 4 is usually 1.2 to 1.4, preferably 1.20 to 1.35. When the ratio of the low refractive index filler 2 is lower than 40% by mass, the average refractive index of the composite thin film 4 becomes large, and when it is higher than 95% by mass, the strength of the composite thin film 4 and the base material 1 are increased. There is a possibility that the practicality such as low adhesiveness may be insufficient, which is not preferable. In addition, throughout this specification, the average refractive index of a composite film means the refractive index measured as demonstrated in the below-mentioned Example.
[0093]
In forming the composite thin film 4 on the surface of the substrate 1, a filler 2 and a binder 3 are mixed in a solvent and dissolved and / or dispersed to prepare a liquid coating material composition. After coating on the surface of the substrate 1, the liquid is removed by drying to leave a film as the composite thin film 4. During such drying, heating may be performed as necessary. Furthermore, you may bake by further heat-processing the film obtained as needed. As a coating method, any suitable method such as spin coating, dip coating, flow coating, roll coating, and bar coating may be employed. An appropriate coating method can be selected according to the thickness of the composite thin film 4, the size and type of the substrate 1, and the like.
[0094]
In the first aspect of the present invention, the average refractive index of the composite thin film formed as described above is generally smaller than the refractive index of the substrate, for example, 0.01 to 0.5, preferably 0.05. It is desirable that it be smaller by ~ 0.3. The average refractive index of the composite thin film itself is usually 1.2 to 1.4, preferably 1.20 to 1.35, more preferably 1.25 to 1.3. However, since the filler 2 can diffuse the light passing through the composite thin film 4, it may be slightly larger than the average refractive index of the composite thin film, for example, about 1.35 to 1.45.
[0095]
FIG. 1B shows a surface light emitter using the composite thin film holding substrate A of FIG. 1A, and a thin film light emitting element 15 provided on the side of the composite thin film 4 opposite to the side on which the base material 1 is located. A is conceptually shown in a sectional view. In the illustrated form, the light emitted from the light emitting element 15 passes through the composite thin film 4 and the base material 1 and is extracted from the surface of the base material 1 as indicated by an arrow. The composite thin film 4 is a composite layer of the filler 2 having a lower refractive index and the binder 3 having a higher refractive index, and the average refractive index of the composite thin film 4 is preferably smaller than the refractive index of the substrate 1. Light is diffused in the interface between the light emitting element 15 and the composite thin film 4 and in the composite thin film 4 and passes through the substrate 1 as diffused light. At this time, the incident angle of light incident on the base material 1 from the composite thin film 4 is reduced, and as a result, the amount of light reflected at the interface between the surface of the base material 1 and air is reduced, and the inside of the base material 1 is reduced. Can be reduced and, if desired, can be made almost nonexistent.
[0096]
In addition, although there is an optical component that can be guided in the light emitting element 15, the flatness of the interface between the light emitting element 15 and the composite thin film 4 is reduced due to the influence of the filler, as schematically illustrated. This waveguiding can be reduced by scattering at the interface. Further, since the thickness of the light emitting element 15 is at most in the submicron order (for example, 0.05 to 1 μm), the number of times that the guided light hits the interface between the light emitting element 15 and the composite thin film 4 is extremely large, and almost all of the guided light is finally obtained. Specifically, the light can be transmitted to the composite thin film 4 side. Thus, by providing the composite thin film 4 on the base material 1, the waveguide of light can be reduced, and the light extraction efficiency from the surface of the base material 1 can be improved.
[0097]
In this composite thin film 4, the greater the difference in refractive index between the filler 2 and the binder 3, the higher the light extraction efficiency. Specifically, this difference is preferably at least 0.01, more preferably At least 0.05. Further, it is preferable that the surface of the composite thin film 4 on which the light emitting element 15 is disposed has a large roughness as long as the light emitting element 15 can be formed.
[0098]
Note that the filler particles 2 in the composite thin film 4 do not necessarily have to be completely filled with the binder 3, and there are voids (also referred to as bubbles) between them. You can do it. The void portion usually contains ambient gas (generally air), and therefore the void portion has a low refractive index or a refractive index lower than that of the filler 2. Therefore, when a void portion remains between the fillers 2, the void portion acts almost in the same manner as the filler 2, and as a result, the light extraction efficiency is improved. The average refractive index of the entire composite thin film 4 is preferably lower than the refractive index of the substrate 1, but may be slightly higher than that of the substrate 1.
[0099]
FIG. 2A schematically shows one form of the composite thin film holding substrate A of the second gist in a sectional view. In the illustrated form, a composite thin film 4 composed of a filler 2 and a binder 3 is formed on the surface of a substrate 1. The composite thin film 4 is obtained by applying and drying a coating material composition that is a mixture of the filler 2 and the binder forming material. In the illustrated embodiment, the refractive index of the formed binder 3 is lower than the refractive index of the substrate 1, and the refractive index of the filler 2 is higher than the refractive index of the binder 3.
[0100]
The binder 3 having a refractive index lower than the refractive index of the substrate 1 is not particularly limited as long as it has a light-transmitting property lower than that of the substrate 1. Among them, the above-described porous silica and airgel (for example, silica aerogel). Etc.). In order to lower the average refractive index of the composite thin film 4, it is generally desirable that the refractive index of the binder 3 is lower than 1.3, preferably lower than 1.25.
[0101]
When a silica porous body is used as the binder 3, the binder forming material is adjusted so that its refractive index is preferably in the range of 1.2 to 1.45, more preferably in the range of 1.2 to 1.35. It is preferable to select.
[0102]
When airgel is used as the binder 3, the binder forming material is selected so that the refractive index is preferably in the range of 1.005 to 1.3, more preferably in the range of 1.1 to 1.3. Is preferred.
[0103]
As the filler 2 having a refractive index higher than the refractive index of the binder 3, hollow silica fine particles such as fine particles of metal oxides such as silica and titania as described above and fine particles of organic polymer typified by silicone can be used. The refractive index of the filler 2 is not particularly limited as long as it is higher than the refractive index of the binder 3, but is generally 1.4 or more, preferably 1.46 or more, more preferably 1.5 or more. Is used.
[0104]
When metal oxide fine particles are used as the filler 2, the metal oxide is oxidized so that its refractive index is preferably in the range of 1.46 to 3.0, more preferably in the range of 1.5 to 2.5. It is preferable to select fine particles.
[0105]
When organic polymer fine particles are used as the filler 2, the refractive index of the organic polymer is preferably in the range of 1.49 to 1.7, more preferably in the range of 1.5 to 1.67. It is preferable to select fine particles.
[0106]
When hollow silica fine particles are used as the filler 2, the hollow silica fine particles are adjusted so that the refractive index is preferably in the range of 1.3 to 1.4, more preferably in the range of 1.32 to 1.37. It is preferable to select.
[0107]
  As the above-mentioned filler 2, those having a particle diameter in the range of 5 nm to 2 μm are preferable, and those having a particle diameter of 20 nm to 500 nm are particularly preferable. When the filler is hollow fine particles, the thickness of the outer shell is preferably 5 nm to 20 nm. Filler 2 has a smaller bulk specific gravity.ButThat is, in hollow particles, the effect of lowering the average refractive index of the composite thin film 4 (that is, the refractive index of the composite thin film as a whole) is higher as the porosity in the particles is larger, and the transparency is better as the particle diameter is smaller. As a result, the light extraction efficiency can be increased. Conversely, the larger the particle size, the greater the scattering effect in the composite thin film 4 and the greater the effect of suppressing light guiding, so that the light extraction efficiency can be increased. In order to have both effects, the particle size of the filler 2 is preferably in the above-mentioned range, and the particle size of the filler 2 is the refractive index of the binder 3 constituting the composite thin film 4, the type and thickness of the light emitting element, and the like. Depending on the above, an appropriate one can be selected within the above range.
[0108]
In the composite thin film to be formed, the abundance ratio of the binder 3 and the filler 2 may be changed according to the refractive index and density of these materials, the average refractive index of the intended composite thin film, and the like. Is preferably 40 to 95% by mass, and the mass ratio of the filler is preferably 5 to 60% by mass. When the ratio of the binder 3 having a low refractive index is lower than 40% by mass, the average refractive index of the composite thin film 4 becomes large, and when it is higher than 95% by mass, the strength of the composite thin film 4 is insufficient. In some cases, the purpose may not be achieved.
[0109]
And in forming the composite thin film 4 on the surface of the base material 1, the liquid coating material composition in which the filler 2 and the binder forming material are mixed and dispersed in the solvent is applied to the surface of the base material 1 as described above. After coating to obtain a coating film, this is dried, and if necessary, heat treated and fired. Moreover, when using airgel as the binder 3, you may dry by a supercritical drying method as needed.
[0110]
In the second aspect of the present invention, the average refractive index of the composite thin film formed as described above is generally smaller than the refractive index of the substrate, for example, 0.01 to 0.5, preferably 0.05. It is desirable to be smaller by about 0.3. The average refractive index itself of the composite thin film is usually 1.1 to 1.4, preferably 1.1 to 1.35, and more preferably 1.2 to 1.3.
[0111]
FIG. 2B shows a surface light emitter using the composite thin film holding substrate A of FIG. 2A and having a thin film light emitting element 15 on the side of the composite thin film 4 opposite to the side on which the base material 1 is located. A is conceptually shown in a sectional view. In the illustrated form, the light emitted from the light emitting element 15 passes through the composite thin film 4 and the base material 1 and is extracted from the surface of the base material 1 as indicated by an arrow. The composite thin film 4 is a composite layer of a binder 3 having a lower refractive index and a filler 2 having a higher refractive index, and the average refractive index of the composite thin film 4 is smaller than the refractive index of the substrate 1. The light passes through the interface between the light emitting element 15 and the composite thin film 4 and the composite thin film 4, and further passes through the substrate 1. At this time, since the composite thin film has a refractive index smaller than that of the base material 1, the incident angle of light incident on the base material 1 from the composite thin film 4 becomes small. As a result, at the interface between the surface of the base material 1 and air. The amount of reflected light can be reduced to reduce the waveguiding in the substrate 1 and, if preferred, can be substantially absent.
[0112]
In addition, although there is an optical component that can be guided in the light emitting element 15, the flatness of the interface between the light emitting element 15 and the composite thin film 4 is reduced due to the influence of the filler, as schematically illustrated. This guided wave may be reduced by scattering at the interface. Furthermore, since the thickness of the light emitting element 15 is at most a micron order (for example, 0.05 to 1 μm), the number of times the guided light hits the interface between the light emitting element 15 and the composite thin film 4 is extremely large, and almost all of the guided light is finally obtained. Can be transmitted to the composite thin film 4 side. Thus, by providing the composite thin film 4 on the base material 1, the waveguide of light can be reduced, and the light extraction efficiency from the surface of the base material 1 can be improved.
[0113]
In this composite thin film 4, the difference in refractive index between the filler 2 and the binder 3 is appropriately designed. Specifically, this difference is preferably at least 0.01, more preferably at least 0.1. In addition, the surface of the composite thin film 4 on which the light emitting element 15 is disposed preferably has high flatness originally, but the roughness is designed by the particle size and the filling amount of the filler. However, on the other hand, when the roughness increases, it can be expected that the waveguide component decreases due to diffusion at the interface, and the roughness needs to be within a range in which the light emitting element 15 can be formed as a continuous film.
[0114]
Note that the filler particles 2 in the composite thin film 4 do not necessarily have to be completely filled with the binder 3, and there are voids (also referred to as bubbles) between them. You can do it. The void portion usually contains ambient gas (generally air), and therefore the void portion has a low refractive index as in the binder 3 or a lower refractive index. Therefore, if a void portion remains between the fillers 2, the void portion acts almost in the same manner as the binder 3, and as a result, the light extraction efficiency becomes higher. The refractive index of the composite thin film 4 as a whole is preferably lower than the refractive index of the substrate 1, but may be slightly higher than that of the substrate 1.
[0125]
In the composite thin film holding substrate A of FIGS. 1A and 2A, the roughness of the surface of the composite thin film 4 provided on the substrate 1 (that is, the surface opposite to the substrate 1 side) Is too large, it is preferable to provide a smoothing underlayer on the surface of the composite thin film 4 opposite to the substrate 1 and fill the unevenness on the surface of the composite thin film 4 to make it smooth. Such a smoothing underlayer 6 is provided on the composite thin film holding substrate A of FIG. 1A and on the composite thin film holding substrate A of FIG. 3 (b) schematically shows a cross-sectional view. By providing the smoothing underlayer 6 in this way, an organic electroluminescence element or the like that requires smoothness between thin films, high uniformity in thickness, etc. is formed on the composite thin film 4. Becomes easier.
[0126]
Although the material which comprises this smoothing base layer 6 is not specifically limited, What has a refractive index close | similar to the refractive index of layers, such as a thin film formed on the smoothing base layer 6, is preferable. Specifically, metal oxides and metal nitrides such as silica, silicon nitride, alumina, aluminum nitride, and titania, fluorides such as magnesium fluoride and fluorine polymers, acrylic polymers, epoxy polymers, and parylene are used. be able to. Examples of the method for forming the smoothing underlayer 6 include vapor deposition methods such as vacuum deposition, sputtering, and CVD, and a coating method in which volatile components are removed by drying after being formed as a coating film on the composite thin film 4. .
[0127]
A transparent conductive film may be formed on the surface of the composite thin film holding substrate A formed as described above on the side opposite to the side where the substrate is located. At this time, if the exposed surface of the composite thin film is not flat, as described above, the smoothing underlayer 6 may be formed on the composite thin film, and the transparent conductive film may be formed thereon.
[0128]
The form in which the transparent conductive film is formed in this way is schematically shown in a sectional view in FIG. The form shown in FIG. 4 shows a transparent conductive film holding substrate B formed by providing a transparent conductive film 5 on the composite thin film 4 of the composite thin film holding substrate A formed as described above. . In the embodiment shown in FIG. 4, a smoothing underlayer 6 is provided on the surface of the composite thin film 4 opposite to the substrate 1, and the transparent conductive film 5 is formed on the smoothing underlayer 6. 4 (a) shows the composite thin film holding substrate A of FIG. 3 (a) provided with the transparent conductive film 5, and FIG. 4 (b) shows the transparent conductive film on the composite thin film holding substrate A of FIG. 3 (b). Each provided with the conductive film 5 is shown. By forming the transparent conductive film 5 on the smoothing underlayer 6 in this way, it becomes easy to form the transparent conductive film 5 on a thin film having a smooth surface and high thickness uniformity.
[0129]
The transparent conductive film 5 may be used as an anode when an electroluminescent element is formed as described later. In that case, examples of the material of the transparent conductive film 5 include indium tin oxide (ITO), zinc oxide, tin oxide, indium zinc oxide (IZO), and a conductive polymer, but are not particularly limited. As a method for forming the transparent conductive film 5, as in the case of the smoothing underlayer 6, a vapor phase growth method, a coating method, and the like can be appropriately selected.
[0130]
Depending on the type of transparent conductive film 5 and the method for forming the same, it is possible to form the transparent conductive film 5 having a smooth surface even if the smoothness of the base is low. In that case, the transparent conductive film 5 can be directly formed on the composite thin film 4 without providing the smoothing underlayer 6. For example, when the transparent conductive film 5 is formed by depositing an amorphous metal oxide represented by IZO by vapor deposition, the conductive polymer and ITO fine particles are deposited by a coating method to form a transparent conductive film. This is the case when the film 5 is formed.
[0131]
The embodiment of FIG. 5 schematically shows a cross-sectional view of a surface light emitter C in which a phosphor thin film 7 is provided on a composite thin film 4 in the composite thin film holding substrate A manufactured as described above. In the form of FIG. 5, a phosphor thin film 7 is provided directly on the surface of the composite thin film 4 on the side opposite to the substrate 1. The thin film 7 includes an organic or inorganic phosphor that emits light when excited by irradiation with ultraviolet rays or electron beams, and forms a surface light emitter C as a photoluminescence element. This surface light emitter C is particularly useful in a self-luminous display such as CRT, FED, PDP and the like. 5A shows the composite thin film holding substrate A shown in FIG. 1A provided with the phosphor thin film 7. FIG. 5B shows the composite thin film holding substrate A shown in FIG. Each provided with a thin film 7 is shown. Since the phosphor thin film 7 is in contact with the surface of the composite thin film 4 in this manner, the light extraction efficiency is improved by the unevenness of the surface of the composite thin film 4 due to the presence of the filler 2.
[0132]
The material for the phosphor is not particularly limited, and any organic or inorganic material conventionally used in photoluminescence elements can be used. As a method of forming the phosphor thin film 7, vapor deposition methods such as sputtering and MOCVD (metal organic chemical vapor deposition) are used in the case of inorganic phosphors, and vacuum deposition is used in the case of low molecular organic phosphors. Examples of the method include a coating method such as spin coating and ink jet coating in the case of a polymer organic phosphor.
[0133]
In the embodiment of FIG. 6, in the above-described transparent conductive film holding substrate B, the surface light emission in which the light emitting layer 8 and the metal electrode 9 are laminated on the transparent conductive film 5 to form the electroluminescence element 10. The body D is schematically shown in a sectional view. That is, the element 10 is formed on the composite thin film holding substrate A. The electroluminescence element 10 includes a transparent conductive film 5 as an anode and a metal thin film metal electrode 9 as a cathode, and is formed by laminating a light emitting layer 8 between the anode and the cathode. The form of FIG. 6 shows the organic electroluminescent element 10, wherein a hole transport layer 19 is provided between the transparent conductive film 5 serving as the anode and the light emitting layer 8, and the light emitting layer 8 and the metal electrode 9 serving as the cathode. An electron transport layer 20 is laminated between the layers as necessary. In the case of the inorganic electroluminescence 10, a dielectric layer is laminated on one side or both sides of the light emitting layer 8. As materials for the light emitting layer 8, the metal electrode 9, the hole transport layer 19, and the electron transport layer 20, those conventionally used in the production of electroluminescence can be used as they are.
[0134]
6 (a) shows the transparent conductive film holding substrate B of FIG. 4 (a) provided with the organic electroluminescence element 10, and FIG. 6 (b) shows the transparent conductive film holding of FIG. 4 (b). The thing which provided the organic electroluminescent element 10 in the board | substrate B is shown, respectively. When a positive voltage is applied to the transparent conductive film 5 serving as an anode and a negative voltage is applied to the metal electrode 9 serving as a cathode, the organic electroluminescent element 10 has electrons injected into the light emitting layer 8 through the electron transport layer 20, The holes injected into the light emitting layer 8 through the hole transport layer 19 recombine in the light emitting layer 8 to emit light.
[0135]
【Example】
Next, the present invention will be described more specifically with reference to examples. The weight average molecular weight was measured by GPC (Gel Permeation Chromatography) using a standard polystyrene with a calibration curve using HLC8020 manufactured by Tosoh Corporation as a measuring instrument.
[0136]
Example 1
A solution was obtained by adding 356 parts by mass of methanol to 208 parts by mass of tetraethoxysilane, further adding 18 parts by mass of water and 18 parts by mass of 0.01N hydrochloric acid, and mixing well using a disper. The obtained solution was stirred for 2 hours in a 25 ° C. constant temperature bath to obtain a silicone resin-M (condensation polymerized by hydrolysis of tetraethoxysilane) as a binder-forming material having a weight average molecular weight of 850. Next, to this silicone resin-M, hollow silica IPA dispersion sol (solid content: 20% by mass, dispersion medium: isopropyl alcohol, average primary particle size: about 35 nm, outer shell thickness: about 8 nm, catalyst) Kasei Kogyo Co., Ltd.) is added so as to be 80/20 based on the solid mass of hollow silica fine particles / silicone resin-M (condensed compound equivalent), and methanol is used so that the total solid content becomes 10% by mass. Dilution was performed to obtain a coating material composition containing hollow silica fine particles. In addition, “condensation compound conversion” means, for example, in the case of tetraalkoxysilane (in this case, tetraethoxysilane), the existing Si is SiO.₂In the case of trialkoxysilane,_1.5It is the weight as it is.
[0137]
Next, a glass plate is used as a substrate, and the obtained coating material composition is applied to the surface of the glass plate with a spin coater at 1000 rpm and dried to obtain a film, which is baked at 200 ° C. for 10 minutes. The composite thin film holding substrate having the structure as shown in FIG. The refractive index of the glass plate is 1.52, the refractive index of the hollow silica fine particles is 1.25, only the silicone resin-M is applied, dried, and heat-treated, that is, the refractive index of the binder is 1. 45.
[0138]
(Example 2)
A solution of a binder forming material for forming a silica airgel binder was obtained by adding 64 masses of methanol to 152 mass parts of tetramethoxysilane and mixing well using a disper. 64 parts by mass of methanol, 36 parts by mass of water, 0.6 parts by mass of 28% by mass ammonia water, and polystyrene fine particle dispersed sol (solid content: 1% by mass, average primary particle size: about 216 parts by mass of this solution) A coating material composition containing polystyrene fine particles prepared by adding 50-fold concentrated 100 nm, manufactured by Duke Scientific Co., Ltd., and mixing them to obtain a polystyrene fine particle ratio of 10% by mass in the mixture was obtained.
[0139]
Next, a glass plate is used as a substrate, and this coating material composition is applied to the surface of the glass plate with a spin coater at 1000 rpm to form a coating film. After the coating film is gelled, 80 ° C., 160 kg / cm²The composite thin film holding substrate having the structure as shown in FIG. 2A was produced by supercritical drying under the above conditions. Here, the refractive index of the glass plate is 1.52, the refractive index of the polystyrene fine particles is 1.59, and the refractive index of the binder after supercritical drying is 1.18.
[0140]
(Comparative Example 1)
The glass plate used in Examples 1 and 2 was used untreated, and this was designated as Comparative Example 1.
[0141]
(Comparative Example 2)
The glass plate used in Examples 1 and 2 was coated with only the silicone resin-M obtained in Example 1 (therefore not containing hollow silica fine particles) in the same manner as in Example 1. did.
[0142]
With respect to the substrates obtained in Examples 1 and 2 and Comparative Examples 1 and 2, the total light transmittance and the average refractive index of the composite thin film were measured. Here, the total light transmittance was measured by measuring the total light transmittance at a wavelength of 550 nm using a spectrophotometer (“U-3400” manufactured by Hitachi, Ltd.). The average refractive index of the composite thin film is measured by observing the fracture surface of the substrate with a scanning electron microscope and measuring the film thickness of the composite thin film, and then using an ellipsometer ("EMS-1" manufactured by ULVAC). Was performed. These results are shown in Table 1.
[0143]
When the pencil hardness of the composite thin film of the substrate obtained in Examples 1 and 2 was measured, the pencil hardness was 2H in the case of Example 1, and the pencil hardness was 5H in the case of Example 2. Was sufficiently strong to handle. Incidentally, in the case of a low refractive index thin film having a refractive index of 1.2 consisting only of silica airgel, the pencil hardness is softer than B, which is very fragile and difficult to handle.
[0144]
[Table 1]

[0145]
(Example 3)
Using the composite thin film holding substrate obtained in Example 1, plasma CVD using tetraethoxysilane as a source was performed on the composite thin film under the condition of 300 ° C.₂A smoothing underlayer composed of a film was formed on the surface of the composite thin film. Next, a transparent conductive film made of an ITO thin film having a thickness of 100 nm is formed on this smoothed underlayer by RF sputtering at 200 ° C., and the transparent conductive film as shown in FIG. A film holding substrate was produced.
[0146]
(Example 4)
Using the composite thin film holding substrate obtained in Example 2, SiH was formed on the composite thin film.₄Gas and N₂Plasma CVD using a gas as a source was performed at 300 ° C. to form a smoothing underlayer made of a SiN film having a thickness of 100 nm on the surface of the composite thin film. Next, a transparent conductive film made of an IZO thin film having a thickness of 100 nm is formed on this smoothed underlayer by RF sputtering at 200 ° C., and the transparent conductive film as shown in FIG. A holding substrate was produced.
[0147]
(Comparative Example 3)
A transparent conductive film made of an ITO thin film was formed directly on the surface of the glass plate used in Examples 1 and 2 in the same manner as in Example 3, and this was designated as Comparative Example 3.
[0148]
(Comparative Example 4)
A transparent conductive film composed of an IZO thin film was formed directly on the surface of the glass plate used in Examples 1 and 2 in the same manner as in Example 4, and this was designated as Comparative Example 4.
[0149]
For the transparent conductive film holding substrates obtained in Examples 3 and 4 and Comparative Examples 3 and 4, the total light transmittance and the sheet resistance value of the transparent conductive film were measured. Here, the sheet resistance value was measured using a Hall effect measuring device (“HL5500” manufactured by Accent Optical Technology Co., Ltd.). The results are shown in Table 2.
[0150]
[Table 2]

[0151]
(Example 5)
Using the composite thin film holding substrate obtained in Example 1, a film of tris (8-hydroquinoline) aluminum (“Alq3” manufactured by Dojindo Laboratories) having a thickness of 100 nm was formed on the composite thin film as a phosphor thin film. A surface light emitter as shown in FIG. 5A was prepared as a photoluminescence element.
[0152]
(Example 6)
Using the composite thin film holding substrate obtained in Example 2, a phosphor thin film was formed on the composite thin film in the same manner as in Example 5, and a surface light emitter as shown in FIG. 5B was used as a photoluminescence element. Produced.
[0153]
(Comparative Example 5)
A thin phosphor film was formed directly on the surface of the glass plate used in Examples 1 and 2 in the same manner as in Example 5 to produce a surface light emitter as a photoluminescence element.
[0154]
For the surface light emitters obtained in Examples 5 and 6 and Comparative Example 5, the phosphor thin film was irradiated with a 20 W ultraviolet fluorescent lamp, and the luminance of the surface of the glass substrate was measured with a luminance meter (“LS-110” manufactured by Minolta). And measured. The results are shown in Table 3.
[0155]
[Table 3]

[0156]
(Example 7)
Using the transparent conductive film holding substrate obtained in Example 3, N, N-diphenyl-N, N-bis-3-methylphenyl-1,1-diphenyl was formed on the transparent conductive film by vacuum deposition. -4,4-diamine (α-NPD) is formed to a thickness of 50 nm, tris (8-hydroquinoline) aluminum (Alq3) is formed to a thickness of 50 nm, and Al is formed to a thickness of 100 nm. Then, metal electrodes were laminated to form an organic electroluminescence element, and a surface light emitter as shown in FIG.
[0157]
(Example 8)
Using the transparent conductive film holding substrate obtained in Example 4, an organic electroluminescence element was formed in the same manner as in Example 7 to produce a surface light emitter as shown in FIG.
[0158]
(Comparative Example 6)
Using the transparent conductive film holding substrate obtained in Comparative Example 3, an organic electroluminescence element was formed in the same manner as in Example 7 to produce a surface light emitter.
[0159]
(Comparative Example 7)
Using the transparent conductive film holding substrate obtained in Comparative Example 4, an organic electroluminescence element was formed in the same manner as in Example 7 to produce a surface light emitter.
[0160]
For the surface light emitters obtained in Examples 7 and 8 and Comparative Examples 6 and 7, a 10 V DC power source was connected between the transparent conductive film and the metal electrode of the Al film to emit light, and the luminance of the surface of the glass substrate was increased. The luminance was measured using a luminance meter (“LS-110” manufactured by Minolta). The results are shown in Table 4.
[0161]
[Table 4]

[0162]
【The invention's effect】
In the composite thin film holding substrate according to the first aspect of the present invention, a light guide component of light in the substrate is reduced by having a filler having a refractive index smaller than that of the base material on the surface of the base material. And the light extraction efficiency can be increased. In addition, when a composite thin film composed of a filler having a refractive index lower than the refractive index of the substrate and a binder having a refractive index higher than the refractive index of the filler is formed, a composite composed of a filler and a binder having different refractive indexes. When passing through the thin film, part of the light is scattered. Due to the synergistic effect, when the light emitting element is provided on the composite thin film of the substrate, the light guided in the light emitting element is reduced, and the light passing through the composite thin film has a high extraction efficiency from the base material to the outside (atmosphere). Become.
[0163]
In the composite thin film holding substrate according to the second aspect of the present invention, a composite thin film comprising a binder having a refractive index lower than the refractive index of the base material and a filler having a refractive index higher than the refractive index of the binder is formed on the surface of the base material. The same applies to the case where it is formed.
[0165]
In the composite thin film holding substrate of the first aspect, the filler having a refractive index lower than that of the base material is selected from airgel fine particles, hollow silica fine particles, and polymer hollow fine particles, and a binder having a higher refractive index than the filler is used. In the case of being selected from organic polymers and metal oxides, it is possible to improve the effect of increasing the light extraction efficiency to the outside by the composite thin film comprising the filler and the binder.
[0166]
In the composite thin film holding substrate of the second aspect, when the binder having a refractive index lower than that of the base material is an airgel and the filler having a refractive index higher than that of the binder is fine particles selected from an organic polymer and a metal compound, the binder and the packing The effect of increasing the light extraction efficiency to the outside by the composite thin film made of the agent can be improved.
[0167]
In any of the above-described composite thin film holding substrates, when the refractive index is lower than that of the base material but is 1.35 or less, the composite thin film can be formed with a low average refractive index, and light is extracted to the outside. Efficiency can be further increased.
[0168]
  A transparent conductive film is formed on the composite thin film of the composite thin film holding substrate described above.ToruBright conductive film holding substratein the case ofCan obtain a transparent conductive film holding substrate having high light extraction efficiency.
[0169]
  ThisIn the transparent conductive film holding substrate, when a smoothing underlayer is formed on a composite thin film and a transparent conductive film is formed thereon, the transparent conductive film is a thin film having a smooth surface and high thickness uniformity. In addition, a transparent conductive film holding substrate with high light extraction efficiency can be obtained.
[0170]
In the surface light emitter of the present invention, a thin film of an organic or inorganic phosphor that emits light by being excited by ultraviolet rays or an electron beam is formed on a composite thin film of a composite thin film holding substrate. Can be obtained.
[0171]
In another surface light emitter of the present invention, a light emitting layer and a metal electrode are laminated in this order on a transparent conductive film of a transparent conductive film holding substrate to form an electroluminescence element. A surface light emitter with high extraction efficiency can be obtained.
[Brief description of the drawings]
FIGS. 1A and 1B are cross-sectional views schematically showing an example of a form of a composite thin film holding substrate of the present invention. In FIG. 1B, a light emitting element is provided.
FIGS. 2A and 2B are cross-sectional views schematically showing another example of the form of the composite thin film holding substrate of the present invention, and FIG. 2B is provided with a light emitting element.
FIGS. 3A and 3B are cross-sectional views schematically showing a form in which a smoothing underlayer is provided on the composite thin film holding substrate of FIGS. 1A and 2A. FIGS.
4A and 4B are cross-sectional views schematically showing a mode in which a transparent conductive film is provided on the composite thin film holding substrate of FIGS. 3A and 3B. FIG.
5 (a) and 5 (b) are cross-sectional views schematically showing a mode in which a phosphor thin film is provided on the composite thin film holding substrate of FIGS. 1 (a) and 2 (a).
6A and 6B are cross-sectional views schematically showing a mode in which an electroluminescent element is provided on the composite thin film holding substrate of FIGS. 3A and 3B. FIG.
FIG. 7 is a cross-sectional view showing an example of a conventional light emitter.
FIG. 8 is a cross-sectional view showing another example of a conventional light emitter.
FIG. 9 is a cross-sectional view showing still another example of a conventional light emitter.
[Explanation of symbols]
1 Base material
2 Filler
3 Binder
4 Composite thin film
5 Transparent conductive film
6 Smoothing underlayer
7 Phosphor thin film
8 Light emitting layer,
9 Metal electrode
10 Electroluminescence element

Claims (7)

Excited by ultraviolet light or electron beam directly on the composite thin film of the composite thin film holding substrate having the base material and the composite thin film arranged on the surface thereof or through a smoothing underlayer having a thickness of 10 to 100 nm A surface light emitter comprising a thin film of an organic or inorganic phosphor that emits light, wherein the composite thin film restrains and holds a filler composed of fine particles having a particle diameter of 5 nm to 2 μm in a dispersed state. consists binder, the refractive index of the filler (Nf), the refractive index of the binder (Nb) from small and refractive index of the substrate (Ns) is smaller than the surface emitter. A transparent conductive film is formed directly on the composite thin film of the composite thin film holding substrate having the base material and the composite thin film disposed on the surface thereof or through a smoothing underlayer having a thickness of 10 to 100 nm . In addition, the light emitting layer and the metal electrode are laminated in this order on the transparent conductive film, and the transparent conductive film, the light emitting layer, and the metal electrode are a surface light emitter constituting an electroluminescence element, and the composite thin film has a grain shape. diameter consists binder to hold and restrain a dispersed state fillers and filler made of fine particles of 5 nm to 2 [mu] m, the refractive index of the filler (Nf), the refractive index of the binder (Nb) from small and group A surface light emitter that is smaller than the refractive index (Ns) of the material. A transparent conductive film is formed directly on the composite thin film of the composite thin film holding substrate having the base material and the composite thin film arranged on the surface thereof or through a smoothing underlayer having a thickness of 10 to 100 nm . In addition, a light emitting layer and a metal electrode are laminated in this order on a transparent conductive film, and the transparent conductive film, the light emitting layer, and the metal electrode are a surface light emitter that constitutes an electroluminescence element, and the composite thin film has a grain shape. diameter consists binder to hold and restrain a dispersed state fillers and filler made of fine particles of 5 nm to 2 [mu] m, the refractive index of the binder (Nb) is less than the refractive index of the filler (Nf), and group A surface light emitter that is smaller than the refractive index (Ns) of the material. Excited by ultraviolet rays or electron beam directly on the composite thin film of the composite thin film holding substrate having the base material and the composite thin film arranged on the surface thereof or through a smoothing underlayer having a thickness of 10 to 100 nm. a formed Ru surface emitter with a thin film of a light emitting organic or inorganic phosphors, the composite thin film by restraining the filler and filler particle size is from microparticles 5nm~2μm in a dispersed state holding consists binders, refractive index of the binder (Nb), the refractive index of the filler (Nf) smaller than, and the refractive index of the substrate (Ns) is smaller than the surface emitter. The surface light emitter according to claim 1 or 2 , wherein the filler is selected from airgel fine particles, hollow silica fine particles, and polymer hollow fine particles, and the binder is selected from an organic polymer and a metal oxide. The surface light emitter according to claim 3 or 4 , wherein the binder is a porous silica, and the filler is selected from organic polymer fine particles, metal compound fine particles, and hollow silica fine particles. The surface light emitter according to claim 5 or 6 , wherein the composite thin film has a refractive index of 1.4 or less .

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