JP3734376B2 - Radio wave transmissive wavelength selective glass and manufacturing method thereof - Google Patents

Description

【００１３】
ここで、
λ ：電波透過性波長選択ガラスに入射する電磁波の波長
Ｒ_ｄｐ：電波透過性波長選択ガラスの反射率
Ｉ_ｓｒ：エアーマス１.０における太陽の放射強度
また、本発明の電波透過性波長選択ガラスの製法は、スパッタリング法によりガラス基板表面、またはガラス基板上にＡｌＮ層（窒化アルミ層）を被覆した表面に連続層よりなるＡｇ層を成膜したのち、熱処理をすることにより、Ａｇ粒子より構成されるＡｇ層を生成させてなることを特徴とする電波透過性波長選択ガラスの製法である。
【００１４】
【発明の実施の形態】
本発明の電波透過性波長選択ガラスは、ガラス基板表面、またはガラス基板上にＡｌＮ層（窒化アルミ層）を被覆した表面に、Ａｇ粒子より構成されるＡｇ層を被覆してなるものであり、その代表的な製法としては、スパッタリング法により、ガラス基板表面、またはガラス基板上にＡｌＮ層（窒化アルミ層）を被覆した表面に連続層のＡｇよりなるＡｇ層を成膜したのち、熱処理をすることにより、該連続層のＡｇよりなるＡｇ層中のＡｇをＡｇ粒子に変化させて作製することができる。
【００１５】
得られた波長選択ガラスは、ＴＶ放送、衛星放送、携帯電話それぞれの周波数帯域の電波に対して反射率を低減させて、電波障害を防止するとともに、充分な日射遮蔽性能と可視光線透過性を有する電波透過性波長選択ガラスである。
【００１６】
前記波長選択ガラスの反射率（Ｒ_ｄｐ）は、下記（２）式で示されるような理論式により、銀の形状から算出することができる。
（この理論式は、本発明者が、Ｊｏｕｒｎａｌ ｏｆ Ａｐｐｌｉｅｄ Ｐｈｙｓｉｃｓ Ｖｏｌｕｍｅ ８４， Ｎｕｍｂｅｒ １１， ６２８５−８２９０（１９９８）ですでに発表している。）
【００１７】
【式２】

【００１８】
ここで、
Ｒ_ｄｐ： 電波透過性波長選択ガラスの反射率
λ ： 電波透過性波長選択ガラスに入射する電磁波の波長［ｎｍ］
ＡＲ： Ａｇ粒子が占める面積率
Ｒ_ｍｓ： 厚みＤのＡｇ粒子の反射率
Ｄ ： Ａｇ粒子の平均厚み ［ｎｍ］
Ｅ_ｓｇ： 分割係数
（板ガラス基板、または誘電体膜上に無限繰り返しに配列した
完全導体からなる正方形セグメントの長さと入射光の波長の
比がＬ_ｉ／λ、前記セグメントが占める面積率がＡＲの系の
反射率）
Ｌ_ｉ： Ａｇ粒子の粒径 ［ｎｍ］
Ｓ_ｒ： 粒径Ｌ_ｉのＡｇ粒子の面積率
ｎi： 粒径Ｌ_ｉのＡｇ微粒子の数
以下に、本発明の波長選択ガラスの反射率（Ｒ_ｄｐ）が、上記（２）式で示される理論式により、銀の形状から算出することができることを、以下に示す式（３）〜（１４）により説明する。
【００１９】
以下、順を追って、完全導体セグメントを誘電体基板上に周期的に固定した系の反射率を算出する電気的な積分方程式を導く方法について説明する。
先ず、理論式による分割係数Ｅ_ｓｇの求め方について説明する。
（１）誘起電流分布
下記の計算では、導電体セグメントおよび誘電体基板からの放射が電磁界を誘起すると仮定する。
【００２０】
ここで論ずる周期アレーと電磁波の状態を図１に幾何学的に示す。ｘ軸、ｙ軸の周期単位ａ、ｂそれぞれの無限周期アレーを誘電体基板上に固定する。基板の厚さはｄ、誘電率はεｒである。（θ_ｉ，φ_ｉ）方向から伝搬してきた電界強度Ｅ_iの入射平面波で、周波数選択スクリーンを照射すると仮定する。αは、（θ_ｉ，φ_ｉ）面内での偏波角である。
【００２１】
【式３】

【００２２】
電流Ｊｃは、入射波によって導電体表面に誘起されると仮定する。この電流は入射波の位相に比例する。そして構造が周期的であるので、電流はフーリエ級数展開が可能である。従って、電流分布は次のように表現できる。
【００２３】
【式４】

【００２４】
【式５】

【００２５】
【式６】

【００２６】
任意形状の導電体はワイヤーセグメントで電気的に近似できる。
電流分布は区分的正弦波（ＰＷＳ）函数で表現できる。
【００２７】
【式７】

【００２８】
【式８】

【００２９】
（２）放射界（反射電界と反射磁界）
散乱体表面の誘起磁流・誘起電流が放射する電界を反射電界という。この反射電界は、グリーン函数を用いると式（９）で表現できる。
【００３０】
【式９】

【００３１】
（３）電力反射率
【００３２】
【式１０】

【００３３】
【式１１】

【００３４】
【式１２】

【００３５】
以上、分割係数Ｅ_ｓｇの求め方について説明した。
次に、（２）式の粒径分布（Ａｇ粒子の粒径、面積率、粒子の数）について求める。
（４）Ａｇ粒子の平均粒径
【００３６】
【式１３】

【００３７】
Ａｇ粒子の平均粒径（ｌ）は次のように計算できる。
【００３８】
【式１４】

【００３９】
後述の実施例２で述べるように、近赤外域の遮蔽効率が０．３以上を確保するためには、Ａｇ粒子の平均粒径が１０ｎｍ以上およびＡｇ粒子の厚みが５ｎｍ以上であることが好ましい。なお、Ａｇ粒子の平均粒径が０．５ｍｍ以上になると電波障害の問題が発生するので好ましくない。
次に、前記で示した分割係数Ｅ_ｓｇと粒径分布から反射率を求める方法について説明する。
（５）Ａｇ粒子より構成されるＡｇ層を積層したＡｌＮ層の反射率の理論式
Ａｇ層の反射率は、銀原子のプラズマ振動の影響を受ける。それ故、銀を分散させたＡｌＮ層の反射率（Ｒ_ｄｐ）は表面抵抗率（Ｒ_ｓｑ）、入射波の波長（λ）と銀の粒径に依存する。Ｒ_ｄｐに対する粒径の影響を、分割係数（Ｅ_ｓｇ）の項で表現する。
【００４０】
厚さ４０ｎｍのＡｌＮ層上に完全導体の正方形セグメントを周期的に固定した系の反射率の理論値をＥ_ｓｇと定義する。理論値は、式（１２）を用いて算出する。この係数は、Ｌ／λと面積率（ＡＲ）に依存する。Ｌ／λは、セグメントの大きさ（Ａｇ粒子の粒径に対応する）と図２に示した入射光の波長の比である。なお、図２は、ＡＲ＝２^２／３²の分割係数（Ｅ_ｓｇ）とＬ／λ（セグメントの大きさと入射光の波長の比を示す図である。
【００４１】
ＡＲは、Ｌ／ａ、すなわちセグメントの面積と図１に示した単位セル（最小繰り返し単位）の面積の比である。ＡＲ＝２／３（＝０．４４４）にもかかわらず、図２のＥ_ｓｇはＬ／λ＝０．５２５で、１．０に近づく。これは、導体のＲ_ｓｑと基板の誘電損率が無視できるほどに小さい場合、共鳴周波数において入射波のエネルギーが単位セル上の誘起電流に全て変換されることに起因する。
Ｒ_ｄｐは、Ｒ _ｍｓ とＥ_ｓｇの積に等しいと仮定して、Ｒ_ｄｐを求める式（２）を提案する。Ｒ _ｍｓ はＡｌＮ(３０ｎｍ)/Ａｇ(Ｄｎｍ)/ＡｌＮ(１０ｎｍ)多層膜の反射率である。なお、ＤはＡｇ粒子の平均厚みである。
【００４２】
【式２】

【００４３】
ここで、
Ｒ _ｄｐ ： 電波透過性波長選択ガラスの反射率
λ ： 電波透過性波長選択ガラスに入射する電磁波の波長［ｎｍ］
ＡＲ： Ａｇ粒子が占める面積率
Ｒ _ｍｓ ： 厚みＤの銀膜の反射率
Ｄ ： Ａｇ粒子の平均厚み ［ｎｍ］
Ｅ_ｓｇ ： 分割係数
（板ガラス基板、または誘電体膜上に無限繰り返しに配列した
完全導体からなる正方形セグメントの長さと入射光の波長の
比がＬ _ｉ ／λ、前記セグメントが占める面積率がＡＲの系の
反射率）
Ｌ _ｉ ：Ａｇ粒子の粒径 ［ｎｍ］
Ｓ _ｒ ：粒径Ｌ_ｉ のＡｇ粒子の面積率
ｎ i ：粒径Ｌ _ｉ のＡｇ微粒子の数
【００４４】
【式１５】

【００４５】
ここで、ＡＲ_oは、薄膜の全面積に対するＡｇ粒子の占める割合である。Ｒ_ｍｓはＲ_ｓｑとλの函数である。そして、Ｅ_ｓｑはＬ／λに依存するので、式（２）は、Ｒ_ｄｐがＲ_ｓｑ、λとＬに依存することを示している。Σの項はＡｇ粒子の粒径分布のＲ_ｄｐへの影響を描写している。 図２に示したように、Ｌ／λの増大に対するＥ_ｓｑの変化が非線形のため、Σの項が必要である。
【００４６】
ＡｌＮ層中のＡｇの全重量は、Ａｇ層の熱処理の間一定に保たれるので、ＤとＬは、式（１６）と（１７）で表現できる。
【００４７】
【式１６】

【００４８】
【式１７】

【００４９】
ここで、Ｌm は、セグメントの平均長さ、Ｄ₀は、成膜直後の多層膜中のＡｇ層の厚さである。
なお、Ａｇは紫外線領域にプラズマ振動数が存在し、さらに、この周波数の低周波数側に、「銀の窓」と呼ばれるＡｇの消衰係数が無限小になる領域があるので、Ａｇ粒子の厚みと、誘電体干渉膜の膜厚を制御すれば、可視光の透過性が確保できる。
【００５０】
加熱によりＡｇ層は、粒子状に分散した状態に変化する。この粒径は、前記した０.５ｍｍよりはるかに小さく、また、Ａｇ膜の厚み、熱処理条件などを制御することより、近赤外線を選択的に反射するガラスが得られる。
【００５１】
【実施例】
以下、本発明の実施の１例を述べる。但し、本発明は、これに限定するものではない。
実施例１
電波透過性波長選択ガラスは、ＤＣマグネトロン・スパッタリング法により成膜した。
（１）スパッタリング前に、真空槽を２×１０^-4Ｐａまで真空引きした。
なお、スパッタリング中、ターゲット−ガラス基板間の距離は９０ｍｍに固定した。
（２）最下層のＡｌＮ層は、純Ａｌターゲット（直径１２９ｍｍ、厚み１０ｍｍ）を用いて、反応スパッタで堆積させた。なお、異常放電を防止するために、周波数１０ｋＨｚの矩形パルス波をカソードに印加した。スパッタリング中、Ｎ２／Ａｒガス流量比を２０／８０に調整する方法で混合ガスの圧力を０．７Ｐａに制御した。
（３）アルゴンのガス圧０．７Ｐａで、純Ａｇターゲット（直径１２９ｍｍ、厚み５ｍｍ）を用いて、中間層のＡｇ層を堆積させた。
（４） 最上段のＡｌＮ層を積層する前に、スパッタリング真空槽内で、成膜直後のＡｌＮ／Ａｇ層を２×１０^-4Ｐａ、２００℃で加熱処理した。
（５）最上層のＡｌＮ層は、最下層のＡｌＮ層と同じ方法により、純Ａｌターゲット（直径１２９ｍｍ、厚み１０ｍｍ）を用いて、反応スパッタで堆積させた。
【００５２】
前記（３）或いは（４）の工程を終了したガラス基板／ＡｌＮ層／Ａｇ層からなるサンプルについて、下記に示す方法により、Ａｇ粒子の粒径分布の測定を行った。
Ａ.Ａｇ粒子の粒径分布
（４）の工程を終了したガラス基板／ＡｌＮ層／Ａｇ層からなるサンプルの表面の状態を、日立Ｓ−４１５を用いた走査型電子顕微鏡（ＳＥＭ）で観察した結果を図３に示す。
なお、図３の各粒子の大きさをＭａｒｔｉｎ法で読み取った粒径分布を表１に示す。
【００５３】
結果、面積比（Ａｇ粒子が占める面積と全面積の比と定義）は０.２０であった。
表１の粒径（ｌ）と数（ｎ）を式（１３）と（１４）に代入した結果、平均粒径は８７ｎｍとなった。粒径分布は、表２にＳ_ｒの関数として示す。
【００５４】
（４）の工程を終了したガラス基板／ＡｌＮ層／Ａｇ層からなるサンプルの表面の状態を、セイコ製ＳＰＡー２５０を用いた原子間力顕微鏡（ＡＦＭ）にて観察した結果、平均粒子径は１６８ｎｍで、面積率は０.３８であった。
【００５５】
【表１】

【００５６】
【表２】

【００５７】
Ｂ.結晶の配向性
前記（３）および（４）の工程を終了したガラス基板／ＡｌＮ層／Ａｇ層からなるサンプルについて、銀結晶の配向性を評価した。なお、測定は、ＣｕＫαの特性Ｘ線を用い理学製ＲＩＮＴ−１５００のＸ線回折（ＸＲＤ）法で測定した。
【００５８】
結果、（３）の工程が終了した成膜直後のガラス基板／ＡｌＮ層／Ａｇ層のサンプルにおけるＡｇ層は、基板に平行にＡｇ（１１１）面が成長した多結晶銀を含むことを示している。また、（４）の工程の熱処理を行うことにより、前記図３で示すようにＡｇ連続層が不連続な粒子に変化すると、Ａｇ（２００）面の回折ピークの強度は多少増加した。また、表３は、Ａｇ（１１１）面の面間隔が２時間の熱処理の結果、２３６.６から２３５.９ｐｍに減少することを示している。ピークの半値幅もまた減少する傾向を示した。
【００５９】
【表３】

【００６０】
Ｃ.反射率
（３）の工程が完了した成膜直後の試料と、（４）の工程を完了した熱処理試料の反射率スペクトルを測定した。
なお、反射スペクトルは日立製３４０分光光度計を用いて、室温で、３５０から１８００ｎｍの範囲で測定した結果を図４に示す。
【００６１】
Ａｇ層の厚さを（３）の工程が完了した成膜直後の試料の反射率曲線から求める。４端子マトリックス法で計算した反射率の理論曲線は、図５に示したように、成膜直後のＡｇ層の厚さが８ｎｍのとき、測定値とよく一致した。
なお、図５は、成膜直後の試料の実験値（○）と理論値（ー）との反射スペクトルの比較を示した図である。理論値は、Ａｇ層の厚さを８ｎｍと仮定して計算した。
【００６２】
一方、表３で、加熱時間が０時間のＡｇ（１１１）ピークの半値幅を式（１８）［Ｓｃｈｅｒｒｅｒの式］に代入して成膜直後のＡｇ層中の結晶の厚みを求めた結果、その値は１０ｎｍとなった。Ａｇ層の厚さは、結晶の大きさに等しいことになる。すなわち、Ａｇ層は基板に平行なＡｇ（１１１）面が成長した多結晶銀から構成されていることを示している。
【００６３】
【式１８】

【００６４】
ここで、ＣＴ ： 結晶の厚み ［Å］
λ ： 照射Ｘ線の波長［Å］
Δ（２θ）： 半値幅 ［ｒａｄｉａｎ］
θ ： Ｘ線の入射角度［ｒａｄｉａｎ］
図４に示した（４）の工程を完了した熱処理試料の反射率曲線から、Ａｇ層の熱処理によって波長が７８０ｎｍより小さい入射波の反射率は増大し、７８０ｎｍより長い入射波の反射率は減少することが示された。この現象は、粒径が入射波の波長より小さいＡｇ粒子の分散によると考えられる。
図６に示した曲線は、Ａｇ粒子の面積平均粒径１３０ｎｍ、Ａｇ粒子の厚み１８ｎｍ、面積率０．４４４の波長選択膜の反射率について３５０ｎｍ〜１８００ｎｍの波長範囲で、理論式（２）から求めた理論曲線である。この曲線は、図６に黒丸で示した実施例の値とよく一致している。ところが、表４に示したように、ＳＥＭで観測した平均粒径は、理論粒径より小さい値である。この差は、ＳＥＭ観察では銀の粒径を過小に見積もることに原因がある。すなわち、Ａｇ層の厚さ約３ｎｍの粒子の裾野から散乱された２次電子の強度は弱いので、粒子の裾野として検出できなかったためと考えられる。また、表４に示したようにＡｇ層の厚みはＸ線的に求めた測定値と一致する。本実施例で、理論式（２）の妥当性が証明できた。
【００６５】
【表４】

【００６６】
実施例２
実施例１で、理論式（２）の妥当性が証明できたので、式（２）の理論値から、波長選択膜に適したＡｇ粒子の形状を求める。
先ず、Ａｇ粒子より構成されるＡｇ層の遮弊効率（Ｅs）は式（１）で定義される。
式（２）のＳ_ｒはセグメントの種々の平均サイズ（Ｌi）に対して一定であると仮定して、ＡＲ＝０.４４４、Ｄ_０＝８nmのＡｇ粒子系の最大遮蔽効率を式（２）で計算する。図７に示したようにＬ_ｉ＝３７５nmのとき、可視光および放送波領域で、断熱ガラスの透明性を確保しながら、遮蔽効率は最大となる。
なお図７は、Ａｇ粒子系の遮弊効率とセグメントの平均サイズを示す図である。遮弊効率は、ＡＲ＝２^２／３^２、Ｄｉ＝１８ｎｍと仮定して、式（２）から算出した。
Ｄｉ＝３７５ｎｍの反射スペクトルの理論曲線を図９に示す。
Ａｇ粒子分散ＡｌＮ膜で、３７５ｎｍの理論反射スペクトル（−）とＬｍ＝１３０ｎｍの測定反射スペクトル（●）の比較を示す図である。理論値はＡＲ＝２^２／３^２、Ｌ_ｉ＝１８ｎｍと仮定して、式（２）から算出した。
【００６７】
Ｌ_ｍ＝Ｌ_ｉが１３０ｎｍから３７５ｎｍまで増大することにより、反射が最大となる位置は、長波長側にシフトする。これは、近赤外線のみを反射する波長選択スクリーンはＡｇ粒子の大きさを調整することにより設計できることを示している。
反射率の理論値は、８００ｎｍ以下の波長域で５〜６箇所鋭く減少している。セグメントは周期的に配列されているので、図２の場合、Ｌ／λ＝０．６２６で反射率が鋭く減少する。
【００６８】
次に、代表例として、Ａｇ粒子の平均粒径が３７５ｎｍの場合の波長選択ガラスの近赤外域の遮蔽効率および可視光の透過率のＡｇ粒子の厚み依存性を理論式（２）から求めた結果を表５と表６に示す。なお、面積率は、代表値として０．４４４と０．８２６を用いた。
【００６９】
表５と表６より、近赤外域の遮蔽効率が０．３以上を確保するためには、Ａｇ粒子の厚みが５ｎｍ以上必要であることがわかる。一方、Ａｇ粒子の厚みが３０ｎｍを越えると近赤外域の遮蔽効率は、可視光の透過性を有しながら飽和に達する。
【００７０】
式（１８）のＳｃｈｅｒｒｅｒの式から求められるＡｇ層の厚さは、Ａｇの（１１１）面の回折ピークの半値幅に逆比例するので、Ａｇ層の厚さの測定限界は、半値幅の検出限界値で決まる。この値は、現在のＸ線回折装置では、０．０１度程度である。この値を式（１８）に代入すると、１μｍとなる。すなわち、Ｓｃｈｅｒｒｅｒの式は、Ａｇ層の厚さが１μｍ以下の場合にのみ適応できる。従って、Ａｇ層の好ましい厚みは、５ｎｍ〜１μｍの範囲である。なお、ＣｕＫαの特性Ｘ線の波長は、１．５４０５Å、Ａｇの（１１１）面に対応するＸ線の入射角度は、３８．１２／２度である。
【００７１】
【表５】

【００７２】
【表６】

【００７３】
代表例として、Ａｇ粒子の厚みが２０ｎｍの場合の波長選択ガラスの近赤外域の遮蔽効率および可視光透過率のＡｇ粒子の面積平均粒径依存性を理論式（２）から求めた結果を表７と表８に示す。表７、および表８より、近赤外域の遮蔽効率が０．３以上を確保するためには、Ａｇ粒子の粒径が１００ｎｍ以上必要であることがわかる。粒径の増大に伴い遮蔽効率は増大するが、面積率によって異なるが、ある粒径以上になると減少する。しかし、遮蔽効率が０．３以下にはならない。ところが、粒径が、現在使用されている放送波の内、最も波長の短い衛星放送波の波長の１／２０以上になると電波障害が問題となる（特許登録番号２６２０４５６参照）ので、Ａｇ粒子の粒径は０．５ｍｍ以下が望ましい。
【００７４】
【表７】

【００７５】
【表８】

【００７６】
【発明の効果】
本発明は、ＴＶ放送、衛星放送、携帯電話それぞれの周波数帯域の電波に対して反射率を低減させるとともに、充分な日射遮蔽性能と可視光線透過性を有するので、ＴＶ画面にゴーストを発生させたり、携帯電話が通じなくなったり、或いはガラスアンテナの利得が悪くなったり等の電波障害がなく、且つ日射を充分に遮蔽される等快適な生活をすることが可能である。
【図面の簡単な説明】
【図１】散乱体の幾何学的図面を示す。
【図２】ＡＲ＝２^２／３^２の分割係数（Ｅ_ｓｇ）とＬ／λ（セグメントの大きさと入射光の波長の比）との関係を示す図である。
【図３】銀分散ＡｌＮ層のＳＥＭ顕微鏡写真を示す図である。
【図４】熱処理前後の反射率を示す図である。
【図５】成膜直後の試料の実験（○）と理論（−）反射スペクトルの比較を示す図である。
【図６】銀分散ＡｌＮ膜の反射スペクトルの実験値（●）と理論値（−）比較を示す図である。
【図７】Ａｇ粒子系の遮蔽効果とセグメントの平均サイズとの関係を示す図である。
【図８】Ａｇ粒子分散ＡｌＮ膜で、Ｌｍ＝３７５ｎｍの理論反射スペクトル（−）と
Ｌｍ＝１３０ｎｍの測定反射スペクトル（●）の比較を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wavelength-selective glass that can efficiently transmit radio waves and visible rays arriving on a window glass of a building, an automobile, etc., and can exhibit sufficient heat insulation properties by reflecting solar heat rays.
[0002]
[Prior art]
In recent years, for the purpose of shielding solar radiation, window glass coated with a conductive thin film or attached with a film containing the conductive thin film has begun to spread. When such a window glass is applied to a high-rise building, radio waves in the TV frequency band are reflected, causing a ghost on the TV screen and making it difficult to receive satellite broadcasts with an indoor antenna. In addition, when used as a window glass for a house or a window glass for an automobile, there is a possibility that the mobile phone may become difficult to communicate, or the gain of the glass antenna may be deteriorated.
[0003]
Under such circumstances, at present, the glass substrate is covered with a transparent heat ray reflective film having a relatively high electrical resistance to partially transmit visible light and to reduce radio wave reflection to prevent radio interference. Has been done.
[0004]
In the case of glass with a conductive film, the length of the conductive film parallel to the direction of the electric field of the incident radio wave is 1/20 times or less the wavelength of the radio wave. Japanese Patent No. 2620456 discloses that it is divided into two parts to prevent radio interference.
[0005]
[Problems to be solved by the invention]
However, the conventional method of coating a transparent heat ray reflective film having a relatively high electrical resistance can reduce radio wave reflection and prevent radio wave interference, but the heat ray shielding performance is not sufficient, and the comfort of life There was a problem. In addition, the method of dividing the conductive film disclosed in Japanese Patent No. 2620456 is much longer than the wavelength of visible light and near infrared light that occupy most of sunlight, so that these light beams are divided. However, there is a problem in that visible light transmittance cannot be secured, although a radio wave transmissive wavelength selection screen glass having sufficient solar radiation shielding performance and preventing radio wave interference can be obtained. Furthermore, in a large window such as the size of the opening of 2 m × 3 m, for example, in order to transmit satellite broadcast waves, 1/20 of the wavelength of satellite broadcast is about 1/20, at least the conductive film is 1.25 mm square, Preferably it must be cut to 0.5 mm square. In order to cut a large-area conductive film into such small segments with, for example, an yttrium-aluminum-garnet laser, there is a problem that it takes a long time and is not practical.
[0006]
[Means for Solving the Problems]
The present invention has been studied in view of the above-mentioned conventional problems, and reduces the reflectance with respect to radio waves in each frequency band of TV broadcasting, satellite broadcasting, and mobile phones, and prevents radio interference, An object of the present invention is to provide a radio wave transmissive wavelength selective glass having sufficient solar radiation shielding performance and visible light transmittance.
That is, a radio wave transmitting wavelength selective glasses of the present invention, the glass substrate surface or AlN layer on a glass substrate to the coated surface (aluminum nitride layer), made by stacking Ag layer composed of Ag particles, Ag particles, the average particle size 100Nm～0. 5 mm, radio wave transmitting wavelength selective glass, characterized in that the range of thickness 5nm~1μm of Ag layer.
[0008]
[0009]
Further, the Ag layer composed of Ag particles is preferably formed by forming an Ag layer consisting of a continuous layer by sputtering and then changing it to Ag particles by heat treatment. Ag of the Ag particles produced by heat-treating the Ag layer is made by reducing the half-value width of the Ag (111) plane identified by the X-ray diffraction method to 85% or less as compared with Ag before heat treatment. It is preferable.
[0010]
Furthermore, an AgN layer (aluminum nitride layer) may be coated on an Ag layer composed of Ag particles , and the reflectivity of the radio wave transmissive wavelength selective glass has a maximum value in a wavelength range of 600 nm to 1500 nm. It is preferable to have.
[0011]
Moreover, it is preferable that the shielding efficiency (Es) of the near-infrared region defined by Formula (1) is 0.3 or more.
[0012]
[Formula 1]

[0013]
here,
λ: Wavelength of electromagnetic wave incident on radio wave transmission wavelength selection glass R _dp : Reflectance of radio wave transmission wavelength selection glass I _sr : Radiation intensity of the sun at air mass 1.0 Further, the radio wave transmission wavelength selection glass of the present invention The manufacturing method is composed of Ag particles by forming an Ag layer composed of a continuous layer on the surface of the glass substrate by sputtering or coating the AlN layer (aluminum nitride layer) on the glass substrate, followed by heat treatment. that is a process for preparing a radio wave transmitting wavelength selective glasses Ag layer to generate characterized by comprising.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The radio wave transmitting wavelength-selective glass of the present invention is obtained by coating an Ag layer composed of Ag particles on a glass substrate surface or a surface coated with an AlN layer (aluminum nitride layer) on a glass substrate, As a typical production method, an Ag layer made of continuous Ag is formed on the surface of the glass substrate or the surface of the glass substrate coated with an AlN layer (aluminum nitride layer) by sputtering, and then heat treatment is performed. Thus, the Ag in the Ag layer made of Ag in the continuous layer can be produced by changing to Ag particles .
[0015]
The resulting wavelength selective glass reduces the reflectivity of radio waves in each frequency band of TV broadcast, satellite broadcast, and mobile phone to prevent radio wave interference, as well as sufficient solar radiation shielding performance and visible light transmittance. It has a radio wave transmission wavelength selection glass.
[0016]
The reflectance (R _dp ) of the wavelength selective glass can be calculated from the shape of silver by a theoretical formula as shown by the following formula (2).
(This theoretical formula has already been published by the inventor in Journal of Applied Physics Volume 84, Number 11, 6285-8290 (1998).)
[0017]
[Formula 2]

[0018]
here,
R _dp: reflectance of a radio wave transmitting wavelength selective glass lambda: the wavelength of electromagnetic wave incident on the radio wave transmitting wavelength selective glass [nm]
AR: Area ratio occupied by Ag particles R _ms : Reflectance of Ag particles of thickness D: Average thickness of Ag particles [nm]
E _sg : Division factor
(Arranged infinitely on a flat glass substrate or dielectric film.
Of the length of the square segment consisting of a perfect conductor and the wavelength of the incident light
The ratio is L _i / λ, and the area ratio occupied by the segment is AR.
Reflectivity)
L _i : Ag particle diameter [nm]
S _r: the area ratio of Ag particles having a particle size _{L i}
ni: Number of Ag fine particles having a particle diameter L _i Below, the reflectance (R _dp ) of the wavelength selective glass of the present invention can be calculated from the shape of silver by the theoretical formula shown by the above formula (2). Will be described by the following formulas (3) to (14).
[0019]
In the following, a method for deriving an electrical integral equation for calculating the reflectance of a system in which perfect conductor segments are periodically fixed on a dielectric substrate will be described.
First, how to obtain the division coefficient _Esg using a theoretical formula will be described.
(1) Induced Current Distribution In the following calculation, it is assumed that radiation from the conductor segment and the dielectric substrate induces an electromagnetic field.
[0020]
The periodic array and electromagnetic wave state discussed here are shown geometrically in FIG. An infinite periodic array of x-axis and y-axis period units a and b is fixed on the dielectric substrate. The thickness of the substrate is d, and the dielectric constant is εr. Assume that the frequency selective screen is irradiated with an incident plane wave of electric field strength E _i propagating from the (θ _i , φ _i ) direction. α is a polarization angle in the (θ _i , φ _i ) plane.
[0021]
[Formula 3]

[0022]
It is assumed that the current Jc is induced on the conductor surface by the incident wave. This current is proportional to the phase of the incident wave. And since the structure is periodic, the current can be expanded in Fourier series. Therefore, the current distribution can be expressed as follows.
[0023]
[Formula 4]

[0024]
[Formula 5]

[0025]
[Formula 6]

[0026]
Arbitrary shaped conductors can be electrically approximated by wire segments.
The current distribution can be expressed by a piecewise sine wave (PWS) function.
[0027]
[Formula 7]

[0028]
[Formula 8]

[0029]
(2) Radiation field (reflected electric field and reflected magnetic field)
The electric field radiated by the induced magnetic current / induced current on the scatterer surface is called a reflected electric field. This reflected electric field can be expressed by Equation (9) using the Green function.
[0030]
[Formula 9]

[0031]
(3) Power reflectivity [0032]
[Formula 10]

[0033]
[Formula 11]

[0034]
[Formula 12]

[0035]
The method for _obtaining the division coefficient E _sg has been described above.
Next, it calculates | requires about the particle size distribution (The particle size of Ag particle , an area rate, the number of particles) of (2) Formula.
(4) Average particle diameter of Ag particles
[Formula 13]

[0037]
The average particle diameter (l) of Ag particles can be calculated as follows.
[0038]
[Formula 14]

[0039]
As described in Example 2 below, in order to shield the efficiency of the near-infrared region to secure a 0.3 or higher, it is preferable that the thickness of the average particle diameter of 10nm or more and Ag particles Ag particles is 5nm or more . Note that if the average particle size of Ag particles is 0.5 mm or more, a problem of radio interference occurs, which is not preferable.
Next, a method for obtaining the reflectance from the above-described division coefficient _Esg and particle size distribution will be described.
(5) Theoretical formula of the reflectance of the AlN layer in which an Ag layer composed of Ag particles is laminated The reflectance of the Ag layer is affected by the plasma vibration of silver atoms. Therefore, the reflectance (R _dp ) of the AlN layer in which silver is dispersed depends on the surface resistivity (R _sq ), the wavelength (λ) of the incident wave, and the silver particle size. The influence of the particle size on R _dp is expressed in terms of the division factor (E _sg ).
[0040]
The theoretical value of the reflectance of a system in which a square segment of a complete conductor is periodically fixed on an AlN layer having a thickness of 40 nm is defined as E _sg . The theoretical value is calculated using Equation (12). This coefficient depends on L / λ and the area ratio (AR). L / λ is the ratio of the segment size (corresponding to the particle size of the Ag particles ) and the wavelength of the incident light shown in FIG. Incidentally, FIG. 2 is a diagram showing the ratio of the wavelength of the AR ^{= 2} 2/3 ² of division factor _{(E sg)} and L / lambda (segment size and the incident light.
[0041]
AR is L / a, that is, the ratio of the area of the segment to the area of the unit cell (minimum repeating unit) shown in FIG. Despite AR = 2/3 (= 0.444), E _sg in FIG. 2 is L / λ = 0.525, which approaches 1.0. This is because when the R _sq of the conductor and the dielectric loss factor of the substrate are small enough to be ignored, the energy of the incident wave is completely converted into the induced current on the unit cell at the resonance frequency.
R _{dp is} assumed to be equal to the product of _{R ms} and _{E sg,} we propose a formula (2) for obtaining the _{R dp.} R _ms is the reflectivity of the AlN (30 nm) / Ag (D nm) / AlN (10 nm) multilayer film. D is the average thickness of Ag particles.
[0042]
[Formula 2]

[0043]
here,
R _dp : reflectance of radio wave transmitting wavelength selective glass
λ: Wavelength [nm] of electromagnetic wave incident on radio wave transmissive wavelength selective glass
AR: Area ratio occupied by Ag particles
R _ms : reflectivity of silver film with thickness D
D: Average thickness of Ag particles [Nm]
E _sg : Division factor
(Arranged infinitely on a flat glass substrate or dielectric film.
Of the length of the square segment consisting of a perfect conductor and the wavelength of the incident light
The ratio is L _i / λ, and the area ratio occupied by the segment is AR.
Reflectivity)
L _i : Particle diameter of Ag particles [Nm]
S _r: the area ratio of Ag particles having a particle size L _i
n i : Number of Ag fine particles having a particle diameter L _i
[Formula 15]

[0045]
Here, AR _o is the ratio of Ag particles to the total area of the thin film. R _ms is a function of R _sq and λ. Since E _sq depends on L / λ, equation (2) shows that R _dp depends on R _sq , λ, and L. The term Σ depicts the effect of the Ag particle size distribution on R _dp . As shown in FIG. 2, since the change in E _sq with respect to the increase in L / λ is non-linear, a Σ term is necessary.
[0046]
Since the total weight of Ag in the AlN layer is kept constant during the heat treatment of the Ag layer, D and L can be expressed by equations (16) and (17) .
[0047]
[Formula 16]

[0048]
[Formula 17]

[0049]
Here, Lm is the average length of the segment, D ₀ is the thickness of the Ag layer in the multilayer film immediately after deposition.
Since Ag has a plasma frequency in the ultraviolet region, and there is a region called “silver window” where the extinction coefficient of Ag is infinitesimal on the lower frequency side of this frequency, the thickness of Ag particles If the film thickness of the dielectric interference film is controlled, it is possible to ensure visible light transmission.
[0050]
By heating, the Ag layer changes to a dispersed state in the form of particles. The particle size, the above-mentioned much smaller than 0.5 mm, The thickness of the Ag film, than to controlling the heat treatment conditions, glass is obtained which selectively reflects near infrared.
[0051]
【Example】
An example of the implementation of the present invention will be described below. However, the present invention is not limited to this.
Example 1
The radio wave transmissive wavelength selective glass was formed by a DC magnetron sputtering method.
(1) The vacuum chamber was evacuated to 2 × 10 ⁻⁴ Pa before sputtering.
During sputtering, the distance between the target and the glass substrate was fixed at 90 mm.
(2) The lowermost AlN layer was deposited by reactive sputtering using a pure Al target (diameter 129 mm, thickness 10 mm). In order to prevent abnormal discharge, a rectangular pulse wave with a frequency of 10 kHz was applied to the cathode. During sputtering, the pressure of the mixed gas was controlled to 0.7 Pa by adjusting the N2 / Ar gas flow rate ratio to 20/80.
(3) An intermediate Ag layer was deposited using a pure Ag target (diameter: 129 mm, thickness: 5 mm) at an argon gas pressure of 0.7 Pa.
(4) Before laminating the uppermost AlN layer, the AlN / Ag layer immediately after film formation was heat-treated at 2 × 10 ⁻⁴ Pa and 200 ° C. in a sputtering vacuum chamber.
(5) The uppermost AlN layer was deposited by reactive sputtering using a pure Al target (diameter 129 mm, thickness 10 mm) by the same method as the lowermost AlN layer.
[0052]
About the sample which consists of the glass substrate / AlN layer / Ag layer which completed the process of said (3) or (4), the particle size distribution of Ag particle | grains was measured by the method shown below.
A. Particle size distribution of Ag particles The state of the surface of the sample consisting of the glass substrate / AlN layer / Ag layer after the step (4) was observed with a scanning electron microscope (SEM) using Hitachi S-415. The results are shown in FIG.
The particle size distribution obtained by reading the size of each particle in FIG.
[0053]
As a result, the area ratio (defined as the ratio of the area occupied by Ag particles to the total area) was 0.20.
As a result of substituting the particle size (l) and the number (n) in Table 1 into the formulas (13) and (14), the average particle size was 87 nm. The particle size distribution, as a function of S _r in Table 2.
[0054]
As a result of observing the surface state of the sample consisting of the glass substrate / AlN layer / Ag layer after the step (4) with an atomic force microscope (AFM) using a Seiko SPA-250, the average particle size is At 168 nm, the area ratio was 0.38.
[0055]
[Table 1]

[0056]
[Table 2]

[0057]
B. Crystal orientation The silver crystal orientation was evaluated for the sample consisting of the glass substrate / AlN layer / Ag layer after the steps (3) and (4). In addition, the measurement was performed by the X-ray diffraction (XRD) method of RINT-1500 made by Rigaku using the characteristic X-ray of CuKα.
[0058]
As a result, it is shown that the Ag layer in the glass substrate / AlN layer / Ag layer sample immediately after film formation after the step (3) includes polycrystalline silver having an Ag (111) plane grown parallel to the substrate. Yes. Further, when the Ag continuous layer was changed to discontinuous particles as shown in FIG. 3 by performing the heat treatment in the step (4), the intensity of the diffraction peak on the Ag (200) plane slightly increased. Table 3 also shows that the spacing of the Ag (111) plane decreases from 236.6 to 235.9 pm as a result of heat treatment for 2 hours. The half width of the peak also showed a tendency to decrease.
[0059]
[Table 3]

[0060]
C. Reflectance The reflectance spectra of the sample immediately after film formation after the step (3) and the heat-treated sample after the step (4) were measured.
In addition, the reflection spectrum measured in the range of 350 to 1800 nm at room temperature using a Hitachi 340 spectrophotometer is shown in FIG.
[0061]
The thickness of the Ag layer is obtained from the reflectance curve of the sample immediately after film formation after the step (3) is completed. The theoretical curve of the reflectance calculated by the four-terminal matrix method agreed well with the measured value when the thickness of the Ag layer immediately after film formation was 8 nm, as shown in FIG.
FIG. 5 is a diagram showing a comparison of reflection spectra between the experimental value (◯) and the theoretical value (−) of the sample immediately after film formation. The theoretical value was calculated on the assumption that the thickness of the Ag layer was 8 nm.
[0062]
On the other hand, in Table 3, the half width of the Ag (111) peak with a heating time of 0 hour was substituted into Equation (18) [Scherrer's equation] to determine the thickness of the crystal in the Ag layer immediately after film formation. The value was 10 nm. The thickness of the Ag layer is equal to the crystal size. That is, the Ag layer is composed of polycrystalline silver grown with an Ag (111) plane parallel to the substrate.
[0063]
[Formula 18]

[0064]
Where CT: crystal thickness [Å]
λ: wavelength of irradiated X-ray [Å]
Δ (2θ): Half width [radian]
θ: X-ray incident angle [radian]
From the reflectance curve of the heat-treated sample that has completed step (4) shown in FIG. 4, the reflectance of incident waves having a wavelength smaller than 780 nm increases and the reflectance of incident waves longer than 780 nm decreases due to the heat treatment of the Ag layer. Was shown to do. This phenomenon is considered to be due to dispersion of Ag particles whose particle size is smaller than the wavelength of the incident wave.
The curve shown in FIG. 6 is from the theoretical formula (2) in the wavelength range of 350 nm to 1800 nm with respect to the reflectance of the wavelength selective film of Ag particle area average particle size 130 nm, Ag particle thickness 18 nm, and area ratio 0.444. It is the calculated theoretical curve. This curve is in good agreement with the values of the example shown by the black circles in FIG. However, as shown in Table 4, the average particle diameter observed by SEM is smaller than the theoretical particle diameter. This difference is caused by the underestimation of the silver particle size in SEM observation. That is, it is considered that the secondary electrons scattered from the bottom of the particle having a thickness of about 3 nm of the Ag layer were weak and could not be detected as the bottom of the particle. Further, as shown in Table 4, the thickness of the Ag layer coincides with the measured value obtained by X-ray. In this example, the validity of the theoretical formula (2) was proved.
[0065]
[Table 4]

[0066]
Example 2
In Example 1, since the validity of the theoretical formula (2) was proved, the shape of Ag particles suitable for the wavelength selective film is obtained from the theoretical value of the formula (2).
First, the shielding efficiency (Es) of an Ag layer composed of Ag particles is defined by equation (1).
Assuming that S _{r in} equation (2) is constant for various average sizes (Li) of the segments, the maximum shielding efficiency of an Ag particle system with AR = 0.444, D ₀ = 8 nm is given by equation (2) ) To calculate. As shown in FIG. 7, when L _i = 375 nm, the shielding efficiency is maximized while ensuring the transparency of the heat insulating glass in the visible light and broadcast wave regions.
FIG. 7 is a graph showing the shielding efficiency and average segment size of the Ag particle system. Saegihei ^efficiency, assuming ^{AR = 2 2/3 2,} Di = 18nm, was calculated from the equation (2).
The theoretical curve of the reflection spectrum at Di = 375 nm is shown in FIG.
It is a figure which shows the comparison of the theoretical reflection spectrum (-) of 375 nm and the measurement reflection spectrum (-) of Lm = 130 nm with an Ag particle-dispersed AlN film . Theoretical values assuming _{^{AR = 2 2/3 2,}} L i = 18nm, was calculated from the equation (2).
[0067]
As L _m = L _i increases from 130 nm to 375 nm, the position where the reflection is maximized is shifted to the long wavelength side. This indicates that a wavelength selection screen that reflects only near infrared rays can be designed by adjusting the size of Ag particles.
The theoretical value of the reflectance decreases sharply in 5 to 6 places in the wavelength region of 800 nm or less. Since the segments are periodically arranged, in the case of FIG. 2, the reflectance decreases sharply at L / λ = 0.626.
[0068]
Next, as a typical example, to obtain an average particle size of thickness dependence of shielding efficiency and the visible light transmittance of the Ag particles in the near-infrared region of the wavelength selective glass in the case of 375nm of Ag particles from the theoretical formula (2) The results are shown in Tables 5 and 6. In addition, the area ratio used 0.444 and 0.826 as a representative value.
[0069]
From Tables 5 and 6, it can be seen that the thickness of the Ag particles needs to be 5 nm or more in order to ensure the shielding efficiency in the near infrared region of 0.3 or more. On the other hand, when the thickness of the Ag particles exceeds 30 nm, the shielding efficiency in the near infrared region reaches saturation while having visible light transmittance.
[0070]
Since the thickness of the Ag layer obtained from the Scherrer equation of equation (18) is inversely proportional to the half width of the diffraction peak of the (111) plane of Ag , the measurement limit of the thickness of the Ag layer is the detection of the half width. Determined by the limit value. This value is about 0.01 degrees in the current X-ray diffractometer. Substituting this value into equation (18) yields 1 μm. That is, Scherrer's equation is applicable only when the thickness of the Ag layer is 1 μm or less. Therefore, the preferable thickness of the Ag layer is in the range of 5 nm to 1 μm. The wavelength of the characteristic X-ray of CuKα is 1.5405 mm, and the incident angle of the X-ray corresponding to the (111) plane of Ag is 38.12 / 2 degrees.
[0071]
[Table 5]

[0072]
[Table 6]

[0073]
As a representative example, the results of calculating the near-infrared shielding efficiency and the visible light transmittance dependency of the area average particle size of Ag particles from the theoretical formula (2) when the thickness of the Ag particles is 20 nm are shown. 7 and Table 8. From Table 7 and Table 8, it can be seen that the Ag particle size needs to be 100 nm or more in order to secure the shielding efficiency in the near infrared region of 0.3 or more. The shielding efficiency increases as the particle size increases, but it varies depending on the area ratio, but decreases when the particle size exceeds a certain particle size. However, the shielding efficiency does not become 0.3 or less. However, particle size, of the broadcast wave currently being used, since radio interference becomes a problem becomes the most 1/20 or less of the wavelength of the satellite wave wavelengths (see Patent Registration No. 2620456), the Ag particles The particle size is desirably 0.5 mm or less.
[0074]
[Table 7]

[0075]
[Table 8]

[0076]
【The invention's effect】
The present invention reduces the reflectance with respect to radio waves in the frequency bands of TV broadcasting, satellite broadcasting, and mobile phones, and has sufficient solar shading performance and visible light transmission, so that ghosts are generated on the TV screen. It is possible to have a comfortable life, such as being free from radio interference such as a cellular phone becoming inaccessible or a gain of a glass antenna being deteriorated, and being sufficiently shielded from sunlight.
[Brief description of the drawings]
FIG. 1 shows a geometric drawing of a scatterer.
2 is a diagram showing the relationship between the AR ⁼ 2 ^{2/3 2} of division factor _{(E sg)} and L / lambda (the ratio of the wavelength of the segment size and the incident light).
FIG. 3 is a view showing an SEM micrograph of a silver-dispersed AlN layer.
FIG. 4 is a diagram showing reflectivity before and after heat treatment.
FIG. 5 is a diagram showing a comparison between an experiment (◯) and a theoretical (−) reflection spectrum of a sample immediately after film formation.
FIG. 6 is a diagram showing a comparison between an experimental value (●) and a theoretical value (−) of a reflection spectrum of a silver-dispersed AlN film.
FIG. 7 is a diagram showing the relationship between the shielding effect of an Ag particle system and the average size of segments.
FIG. 8 is a diagram showing a comparison between a theoretical reflection spectrum (−) at Lm = 375 nm and a measured reflection spectrum (●) at Lm = 130 nm in an Ag particle-dispersed AlN film.

Claims (7)

The surface of the glass substrate or an AlN layer on a glass substrate coated surface (aluminum nitride layer), made by stacking Ag layer composed of Ag particles, Ag particles have an average particle size 100nm~0. 5mm, Ag A radio wave-transmitting wavelength-selective glass characterized by having a layer thickness in the range of 5 nm to 1 μm . Ag layer composed of Ag particles, according to claim 1, wherein the mixture was allowed to deposit a Ag layer of a continuous layer by sputtering, in which was varied generated Ag particles by heat treatment Radio wave transmission wavelength selective glass. Ag of Ag particles generated by heat-treating an Ag layer composed of a continuous layer has a half-value width of the Ag (111) plane identified by X-ray diffractometry reduced to 85% or less compared to Ag before heat treatment. The radio wave transmitting wavelength selective glass according to claim 1, wherein The radio wave transmissive wavelength selective glass according to any one of claims 1 to 3, wherein an AlN layer (aluminum nitride layer) is further coated on an Ag layer composed of Ag particles . Light reflectance, a radio wave transmitting wavelength selective glass according to any one of claims 1 to 4 wavelength and having a maximum value in the range of 600Nm～1500nm. The radio wave transmission wavelength selective glass according to any one of claims 1 to 5, wherein a shielding efficiency (Es) in a near infrared region defined by the formula (1) is 0.3 or more.
[Formula 1]

Where λ is the wavelength of the electromagnetic wave incident on the radio wave transmission wavelength selection glass
R _dp : reflectivity of radio wave transmitting wavelength selective glass
I _sr : Solar radiation intensity at air mass 1.0 An Ag layer composed of Ag particles is formed by performing a heat treatment after forming an Ag layer made of a continuous layer on a glass substrate surface or a surface coated with an AlN layer (aluminum nitride layer) on the glass substrate by sputtering. The method for producing a radio wave transmissive wavelength selective glass according to any one of claims 1 to 5, wherein a layer is formed.

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