【０００１】
【発明の属する技術分野】
本発明は、車両用の窓ガラス、建築用の窓ガラス、鏡、ショーウィンドウ、テレビジョン用のディスプレーガラス、太陽電池用ガラス基板、レンズ等の光学部品等に供される低反射物品に関する。
【０００２】
【従来の技術】
従来、パソコン、ワープロ、テレビ、プラズマディスプレー等のディスプレー、車両用窓、建築用窓には、無機又は有機のガラス基材が使用されてきた。ガラス基材を通して文字、図形、物体等の視覚情報を観察・認識する場合、基材表面で外光が反射して内部の視覚情報が見え難くなるという問題があるので、基材上に低反射膜を形成し低反射物品としてきた。
【０００３】
前記低反射膜には、無機化合物微粒子で表面に微細な凹凸を設けてなる低反射膜が、反射率の角度依存性が小さく、経済性に優れるので広く利用されている。
例えば、特許文献１には、シリカ微粒子、アルコキシシラン、及びアルコールからなる塗布液を基材に塗布してなる低反射物品が開示されている。しかし、該文献で開示されている低反射物品の低反射性は十分ではなく、低反射膜と基材との密着力も弱い。
【０００４】
無機化合物微粒子で表面に微細な凹凸を設けてなる低反射膜の低反射特性を改善するために、特許文献２では、基材上にチタニア等の高屈折率膜を形成し、その高屈折率膜上に無機化合物微粒子で表面に微細な凹凸を設けてなる低屈折率膜を形成してなる低反射物品が開示されている。該低反射物品は、干渉による効果と表面の微細な凹凸構造の効果で垂直光に対する低反射特性が優れるようになるが、反射率の角度依存性が発生するようになる。加えて、使用時に低反射膜が磨耗した場合に、干渉による低反射効果の有効波長が変化する。部分的に低屈折率膜がなくなった場合に、高屈折率膜が表層に露出し傷として認識しやすくなり、磨耗部の低反射特性が著しく劣化する。
【０００５】
特許文献３には、表層に凹凸を有する被膜の膜厚方向の屈折率を連続的に変化させてなる低反射物品が開示されている。しかしながら、該低反射物品は無機化合物微粒子による被膜ではなく、屈折率を連続的に変化させために蒸着装置等の大掛かりな装置が必要であった。
【０００６】
【特許文献１】
特開昭６３−１９３１０１号公報
【特許文献２】
特開平６−１８６４０１号公報
【特許文献３】
特開２００１−４８５９３号公報
【０００７】
【本発明が解決しようとする課題】
本発明では、微粒子によって形成される膜表層の微細な凹凸構造を有する低反射膜と基材とからなる低反射物品の低反射性及び低反射膜と基材の密着性を向上させ、且つ使用時の磨耗によって低反射特性の劣化が少ない低反射物品、及び該低反射物品を経済的に優れる方法で作製できる製法を提供することを課題とする。
【０００８】
【課題を解決するための手段】
本発明の低反射物品は、微粒子によって形成される膜表層の微細な凹凸構造を有する低反射膜を基材に被覆してなる低反射物品であり、該低反射膜が該基材の屈折率値以下の屈折率値を有する無機化合物微粒子と無機化合物バインダーとからなり、該膜の表層側に存在する微粒子の平均粒径が５０ｎｍ以上１００ｎｍ以下であり、該膜の基材側に存在する微粒子の平均粒径が５ｎｍ以上５０ｎｍ未満であることを特徴とする。前記低反射膜は、無機化合物微粒子が充填してなる膜であり、微粒子間、又は微粒子と基材とが無機化合物バインダーによって接合されている。尚、本発明での平均粒径は、走査型電子顕微鏡観察によって倍率１０万倍で膜の断面の観察を行った時に、１μｍ平方の範囲内に存在する全ての該粒子の粒径を目視で読みとり、その平均値を算出する。この算出を２０回繰り返して得られた各値の平均値で定義される。
【０００９】
無機化合物微粒子によって形成される膜表層の微細な凹凸構造を有する低反射膜の低反射性は、膜表層部に露出される無機化合物微粒子の平均粒径に影響される。低反射性を大きくするためには、低反射物品の無機化合物微粒子による光散乱に起因する白濁化が生じない範囲で平均粒径が大きい程良いが、平均粒径を大きくすると微粒子間の接触面積、微粒子と基材との接触面積が小さくなり、膜強度が小さくなる。
【００１０】
膜の基材側に存在する微粒子の粒径を小さく、膜表層に存在する微粒子の粒径を大きく設定することによって、基材と膜との接合が改善され、且つ表層側のより大きな微粒子は、膜中の基材側に存在する微粒子と接合することになる。従って、高強度な低反射特性に優れる膜を得ることが容易となる。前記点を鑑み、膜の表層側に存在する無機化合物微粒子の平均粒径は、低反射物品の白濁化を起こさずに透視性を確保することが可能な５０ｎｍ以上１００ｎｍ以下とする。又、膜の基材側に存在する無機化合物微粒子の平均粒径は、５ｎｍ以上５０ｎｍ未満とする。
【００１１】
表層側に存在する微粒子の平均粒径と基材側に存在する微粒子の平均粒径との関係は、基材側に存在する微粒子の平均粒径に対し、５倍以上１０倍以下とすると、低反射膜の強度をより高めることができるので好ましい。
【００１２】
本発明の低反射物品の低反射膜は、少なくとも２層の多層構造を有し、各層に配される無機化合物微粒子の平均粒径が層毎で異なるものとすることができる。本発明のように微粒子が充填されてなる膜の場合、無機化合物微粒子の平均粒径が大きい程空隙率が高くなるので、屈折率は小さくなる。低反射膜を前記構造とすると層毎の屈折率が異なるので、低反射膜の低反射特性が向上する。しかも使用される微粒子は基材よりも屈折率の低いものでなので、膜中の各層は基材よりも屈折率が低く、膜が磨耗性した際の低反射特性の著しい劣化を防げるようになる。該効果は、２層あれば十分であり、経済性を考慮すると２層とすることがより好ましい。又、経済性と低反射性の観点から前記無機化合物微粒子及び前記無機化合物バインダーをシリカとすることが好ましい。
【００１３】
前記低反射膜を、波長６３３ｎｍで、１．４〜２．０、好ましくは１．５〜１．７の屈折率の基材に被覆して低反射物品とすることができ、低反射物品は、塗布液を基材に塗布し該基材を焼成することによって得られる。前期塗布液は、無機化合物微粒子及び無機化合物バインダーの前駆体、及び溶媒とからなる少なくとも２種の塗布液であり、それぞれの塗布液中に存在する無機化合物粒子の平均粒径が異なるように調製される。各塗布液を逐次基材に塗布する際に、各塗布液を基材に塗布した後に、乾燥又は焼成を行わずに、別の塗布液を塗布することで効率的に本発明の低発射物品を作製することができる。
【００１４】
又、塗布液を調製する際の無機化合物微粒子量は無機化合物バインダーの前駆体に対して、重量比で１倍量以上２０倍量以下とすることが好ましい。１倍未満では、得られる膜の低反射特性が十分ではなく、２０倍超では、得られるの膜の強度が低くなるからである。
【００１５】
【発明の実施の形態】
低反射物品を構成する無機化合物の微粒子には、平均粒径が５ｎｍ〜１００ｎｍ（但し、膜表層に使用する微粒子の平均粒径は、５０ｎｍ〜１００ｎｍとする）の球状のシリカ、弗化マグネシウム、アルミナ、鎖状のシリカ等を使用することができる。これらの中で、経済性と低反射性を鑑み、無機化合物には、コロイダルシリカとして入手が容易な球状シリカを使用することが好ましい。
【００１６】
又、無機化合物バインダーは、前記微粒子を微粒子又は基材と接合させ、膜強度を高めるものであり、そのようなバインダーには、シリカ、アルミナ、珪酸ナトリウム等があげられ、中でも経済性に優れ、屈折率が低く、優れた低反射特性が得られるシリカが好ましい。これらバインダーは、前駆体より形成され、シリカ、アルミナの前駆体には、エトキシド、メトキシド等のアルコキシド化合物、オキシハロゲン化合物、酢酸化合物等、珪酸ナトリウムには、水ガラス等を使用することができる。
【００１７】
低反射膜の総厚は、低反射を鑑み６０ｎｍ〜２１０ｎｍとすることが好ましい。基材よりも小さい屈折率（ｎ）の低反射膜の膜厚ｄ、入射光の波長λ、光の入射角αとは、［ｄ＝λ／４（ｎ２ーｓｉｎ２α）１／２］の関係で表さる。本発明の低反射膜の屈折率は１．３から１．４の範囲であるため、この式から、垂直入射する可視光線の反射率を最小にする膜厚は、太陽光の放射強度の高い波長５５０ｎｍの光を対象にすると、膜厚は９８〜１０６ｎｍとすることが好適と導かれる。同波長光の入射角が６０度の場合、好適な膜厚は１２５〜１４２ｎｍとなる。
【００１８】
対象波長光を３８０ｎｍとした場合、垂直入射光に対する好適な膜厚は、６８〜７３ｎｍ、６０度入射光に対して好適な膜厚は８６〜９８ｎｍと導かれ、対象波長光を７８０ｎｍとした場合、垂直入射光に対する好適な膜厚は１３９〜１５０ｎｍ、６０度入射光に対して好適な膜厚は１７７〜２０１ｍと導かれる。
【００１９】
少なくとも２層有する構造の低反射膜を得るために、表層側用に微粒子として平均粒径が５０〜１００ｎｍの球状シリカ、基材側層には、平均粒径が５ｎｍ以上５０ｎｍ未満の球状シリカを使用し、バインダーとしてシリカを使用すると、屈折率が１．３〜１．４５の範囲で膜厚方向に分布した膜が得られる。この場合、基材側層の膜厚を１０ｎｍ〜７０ｎｍとすることが好ましい。基材側層の膜厚が７０ｎｍ超だと膜全体の屈折率低減効果が小さく、１０ｎｍ未満だと膜強度が低下するからである。
【００２０】
低反射物品を構成する基材には、波長６３３ｎｍで、１．４〜２．０、好ましくは１．５〜１．７の屈折率を有するガラスやプラスチック基材を使用でき、例えば、ソーダ石灰ガラス、アルカリ硼珪酸塩ガラス、無アルカリガラス、石英ガラス、ポリカーボネートやポリエチレンテレフタレートなどの樹脂ガラス等のディスプレー、レンズ、窓、液晶表示基板、光電変換装置用基板等に使用される基材を使用することができる。
【００２１】
本発明の低反射物品は、塗布液を基材に塗布し該基材を焼成することによって得られる。前期塗布液は、無機化合物微粒子及び無機化合物バインダーの前駆体、及び溶媒とからなる少なくとも２種の塗布液であり、それぞれの塗布液中に存在する無機化合物粒子の平均粒径が異なるように調製される。例えば、２層構造の低反射膜を作製するにあたり、表層側の微粒子を５０ｎｍ〜１００ｎｍの平均粒径の無機化合物微粒子とした場合、一つの塗布剤は、該微粒子、無機化合物バインダーの前駆体、及び溶媒からなり、もう一つの塗布剤は、５ｎｍ〜４０ｎｍの平均粒径を有する無機化合物微粒子、無機化合物バインダーの前駆体、及び溶媒からなるものとする。
【００２２】
又、前記溶媒には、メタノール、エタノール、メチルエチルケトンやイソプロピルアルコール等のアルコール類やエチレングリコールなどのグリコール類等を使用することができる。
【００２３】
各塗布液を逐次基材に塗布する際に、各塗布液を基材に塗布した後に、乾燥又は焼成を行わずに、別の塗布液を塗布することで効率的に本発明の低発射物品を作製することができる。塗布液を基材に塗布する方法としては、ディッピング法、スピンコート法、ロールコート法、カーテンフローコート法、スクリーン印刷法、フレキソ印刷法等の公知の方法を使用することができる。
【００２４】
【実施例】
以下、実施例により本発明を具体的に説明する。なお、本実施例で得られたサンプルの品質評価は以下に示す方法で行った。
【００２５】
〔外観評価〕：サンプルの外観、透過性、クラックの有無を目視で評価し、問題がないものを合格とした。
【００２６】
〔耐テーバー磨耗性〕：Ｔａｂｅｒ社の５１３０型テーバー試験機を用いた。サンプルの低反射膜を磨耗輪（ＣＦ−１０Ｆ）に接触させ、４．９Ｎ／ｃｍ２の荷重をかけながら１００回転実施した後の膜剥離の有無を目視評価し、膜剥離なきものを合格（○）とした。
【００２７】
〔耐トラバース磨耗性〕：荷重４．９Ｎ／４ｃｍ２で１００番のネル布を押し付け、距離１０ｃｍを毎分３０往復の速度で１０００往復させた時の外観変化を目視評価し、膜剥離なきものを合格（○）とした。
【００２８】
〔反射低減効果〕：瞬間マルチ測光システム（大塚電子社製ＭＣＰＤ−７０００型）を用いて入射角６０度での裏面反射を含めた可視光反射率を測定した。光源はＤ６５とした。低反射膜を被覆していない基材の反射率と低反射膜を被覆した低反射物品の反射率との差（ΔＲｆ）が、５．０％以上のものを合格とした。
【００２９】
〔屈折率・膜厚〕：エリプソメーター（溝尻光学工業所製ＤＶＡ−ＦＬ３Ｇ型）を用いて、屈折率と膜厚を測定した。低反射膜の屈折率が１．３〜１．４の範囲にあるものを合格とした。
【００３０】
実施例１
〔基材の準備〕
基材としては、フロート法による厚さ３．４ｍｍ、２００ｍｍ四方のソーダ石灰ケイ酸塩ガラスを使用した。基板表面をセリア微粒子で研磨し、ブラッシング洗浄を行った。
【００３１】
〔基板層側用の塗布液の準備〕
平均粒径１０ｎｍのシリカ微粒子が分散している２．３４ｇのコロイダルシリカ分散液（日産化学社製、ＩＰＡ−ＳＴ−Ｓ）、０．８ｇの精製水、及び２．６ｇの１−メトキシ−２−プロパノール（以下ＭＦＧ）を５分間攪拌混合した溶液に、０．３６ｇのケイ酸エチル、及び０．１２ｇの０．１規定塩酸を添加し、さらに３０分間攪拌混合した。この混合液に２３．０８ｇのＭＦＧを加えて３０分間攪拌混合し、母液とした。この母液２０ｇにメチルエチルケトン（キシダ化学社製、以下ＭＥＫ）４０ｇとイソプロパノール（キシダ化学社製、以下ＩＰＡ）４０ｇを加えて２時間攪拌し塗布液を得た。
【００３２】
〔表層側用塗布液の準備〕
シリカ微粒子源を平均粒径５０ｎｍのシリカ微粒子が分散している２ｇのコロイダルシリカ分散液（日産化学社製、ＭＡ−ＳＴ−Ｌ）２ｇ、ＴＥＯＳを０．３６ｇ量とした以外は上記〔基板層側用の塗布液の準備〕と同様の操作で塗布液を得た。
【００３３】
〔低反射膜の形成〕
基材層側用塗布液を、上記で準備した基材にスピンコーティング法により塗布し、次いで、表層側用塗布液を同様の操作で塗布した。塗布液が塗布された基材を１５０℃に保持されたの電気炉に３０分間入れ、低反射物品を作製した。品質評価結果を表１に示す。この低反射物品の膜厚は１３０ｎｍ（基材側層３０ｎｍ）、屈折率は１．３２で、外観、耐テーバー磨耗性、耐トラバース磨耗性、反射低減効果及び屈折率・膜厚の全ての項目に合格した。
【００３４】
【表１】
【００３５】
実施例２
表層側用塗布液のシリカ微粒子源を平均粒径１００ｎｍのシリカ微粒子が分散している２．３４ｇのコロイダルシリカ分散液（日産化学社製、ＩＰＡ−ＳＴ−ＺＬ）とした以外は、実施例１と同様の操作で低反射物品を得た。得られた低反射物品の膜厚は、１４０ｎｍ（基材側層３０ｎｍ）、膜の屈折率は１．３１、外観、耐テーバー磨耗性、耐トラバース磨耗性、反射低減効果及び屈折率・膜厚の全ての項目に合格した。
【００３６】
実施例３
各塗布液の固形分濃度で制御し、膜厚を１７０ｎｍ（基材層側５０ｎｍ）とした以外は実施例１と同様の操作で膜の屈折率が１．３３の低反射物品を得た。外観、耐テーバー磨耗性、耐トラバース磨耗性、反射低減効果及び屈折率・膜厚の全ての項目に合格した。
【００３７】
実施例４
各塗布液の固形分濃度で制御し、膜厚を２００ｎｍ（表層側３０ｎｍ）とした以外は実施例２と同様の操作で膜の屈折率が１．３２低反射物品を得た。外観、耐テーバー磨耗性、耐トラバース磨耗性、反射低減効果及び屈折率・膜厚の全ての項目に合格した。
【００３８】
実施例５
各塗布液の固形分濃度で制御し、膜厚を６０ｎｍ（基材層側１０ｎｍ）とした以外は実施例１と同様の操作で膜の屈折率が１．３３の低反射物品を得た。外観、耐テーバー磨耗性、耐トラバース磨耗性、反射低減効果及び屈折率・膜厚の全ての項目に合格した。
【００３９】
比較例１
実施例１での表層側用塗布液を基材層側用塗布液とし、実施例１での基材層側用塗布液を表層側用塗布液とした以外は実施例１と同様の操作で膜厚１３０ｎｍ（基材層側５０ｎｍ）、膜の屈折率１．４２の低反射物品を得た。反射低減効果は３．５％と悪くが不合格であった。
【００４０】
比較例２
表層側用塗布液のシリカ微粒子源を平均粒径１５０ｎｍのシリカ微粒子が分散している１．００ｇのコロイダルシリカ分散液（扶桑化学社製、ＰＬ−１０）とした以外は、実施例１と同様の操作で低反射物品を得た。得られた低反射物品の膜厚は、３００ｎｍ（基材側層５０ｎｍ）、膜の屈折率は１．３３で、耐テーパー磨耗試験、耐トラバース磨耗性試験にて膜が剥離した。
【００４１】
比較例３
実施例１での基材側用塗布液にシリカ微粒子を加えなかった以外は実施例１と同様の操作で低反射物品を得た。膜厚３００ｎｍ（基材層側５０ｎｍ）、膜の屈折率１．３９で、反射低減効果が不合格であった。
【００４２】
比較例４
実施例１での表層側用塗布液を基材層側用塗布液とし、比較例３での基材層側用塗布液を表層側用塗布液とした以外は実施例１と同様の操作で膜厚１００ｎｍ（基材層側５０ｎｍ）、膜の屈折率１．４５の低反射物品を得た。反射低減効果が不合格であった。
【００４３】
【発明の効果】
本発明の低反射物品は、低反射性に優れるとともに低反射性の角度依存性が小さく、また、長期使用にあっては、低反射膜と基材との密着性に優れるので耐久性が高く、且つ使用時の磨耗によって低反射特性の劣化が少ない特性を有しているので、ディスプレー、車両用窓、建築用窓等への使用に奏功する。さらには、係る低反射物品を経済的に優れる方法で作製することができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a low-reflection article to be used for a window glass for a vehicle, a window glass for a building, a mirror, a show window, a display glass for a television, a glass substrate for a solar cell, an optical component such as a lens, and the like.
[0002]
[Prior art]
Conventionally, inorganic or organic glass base materials have been used for personal computers, word processors, televisions, displays such as plasma displays, vehicle windows, and architectural windows. When observing and recognizing visual information such as characters, figures, and objects through a glass substrate, there is a problem that external light is reflected on the substrate surface, making it difficult to see the internal visual information. A film is formed to produce a low reflection article.
[0003]
As the low-reflection film, a low-reflection film formed by providing fine irregularities on the surface with inorganic compound fine particles is widely used because the angle dependence of the reflectance is small and the economy is excellent.
For example, Patent Literature 1 discloses a low-reflection article obtained by applying a coating liquid composed of silica fine particles, alkoxysilane, and alcohol to a substrate. However, the low-reflection article disclosed in this document does not have sufficient low reflectivity, and the adhesion between the low-reflection film and the substrate is weak.
[0004]
In order to improve the low-reflection characteristics of a low-reflection film formed by providing fine irregularities on the surface with inorganic compound fine particles, in Patent Document 2, a high-refractive-index film such as titania is formed on a substrate, There is disclosed a low-reflection article formed by forming a low-refractive-index film in which fine irregularities are provided on the surface with inorganic compound fine particles on the film. The low-reflection article has excellent low-reflection characteristics for vertical light due to the effect of interference and the effect of the fine uneven structure on the surface, but the angle dependence of the reflectance occurs. In addition, when the low reflection film is worn during use, the effective wavelength of the low reflection effect due to interference changes. When the low-refractive-index film is partially removed, the high-refractive-index film is exposed on the surface layer, is easily recognized as a scratch, and the low-reflection characteristics of the worn portion are significantly deteriorated.
[0005]
Patent Literature 3 discloses a low-reflection article in which the refractive index in the thickness direction of a coating having irregularities on the surface layer is continuously changed. However, the low-reflection article is not a coating of inorganic compound fine particles, but requires a large-scale apparatus such as a vapor deposition apparatus to continuously change the refractive index.
[0006]
[Patent Document 1]
JP-A-63-193101 [Patent Document 2]
JP-A-6-186401 [Patent Document 3]
JP 2001-48593 A
[Problems to be solved by the present invention]
In the present invention, the low-reflection article of a low-reflection article comprising a substrate and a low-reflection film having a fine uneven structure of a film surface layer formed by fine particles, and the adhesion between the low-reflection film and the substrate are improved and used. It is an object of the present invention to provide a low-reflection article in which the low-reflection property is hardly degraded due to abrasion at the time, and a method for manufacturing the low-reflection article by a method which is economically excellent.
[0008]
[Means for Solving the Problems]
The low-reflection article of the present invention is a low-reflection article obtained by coating a substrate with a low-reflection film having a fine uneven structure of a film surface layer formed by fine particles, and the low-reflection film has a refractive index of the substrate. Particles comprising an inorganic compound fine particle having a refractive index value of not more than a value and an inorganic compound binder, the average particle diameter of the fine particles present on the surface layer side of the film is 50 nm or more and 100 nm or less, and the fine particles present on the substrate side of the film Has an average particle diameter of 5 nm or more and less than 50 nm. The low-reflection film is a film filled with inorganic compound fine particles, and the fine particles and the base material are bonded to each other by the inorganic compound binder. Incidentally, the average particle size in the present invention, when the cross section of the film was observed at a magnification of 100,000 times by scanning electron microscope observation, the particle size of all the particles present within a range of 1 μm square visually. Read and calculate the average value. This calculation is defined as an average value of each value obtained by repeating the calculation 20 times.
[0009]
The low reflectivity of the low-reflection film having a fine uneven structure on the film surface layer formed by the inorganic compound fine particles is affected by the average particle diameter of the inorganic compound fine particles exposed on the film surface layer portion. In order to increase the low reflectivity, the average particle size is preferably as large as possible within a range in which white turbidity due to light scattering by the inorganic compound fine particles of the low reflective article does not occur. In addition, the contact area between the fine particles and the substrate is reduced, and the film strength is reduced.
[0010]
By setting the particle size of the fine particles present on the substrate side of the film to be small and the particle size of the fine particles present on the surface of the film to be large, the bonding between the substrate and the film is improved, and the larger fine particles on the surface layer are Then, the particles are bonded to the fine particles existing on the substrate side in the film. Therefore, it becomes easy to obtain a film having high strength and excellent low reflection characteristics. In view of the above, the average particle size of the inorganic compound fine particles present on the surface layer side of the film is set to 50 nm or more and 100 nm or less, which can ensure transparency without causing clouding of the low reflection article. The average particle diameter of the inorganic compound fine particles present on the substrate side of the film is 5 nm or more and less than 50 nm.
[0011]
The relationship between the average particle size of the fine particles present on the surface side and the average particle size of the fine particles present on the base material side is 5 to 10 times the average particle size of the fine particles present on the base material side, This is preferable because the strength of the low reflection film can be further increased.
[0012]
The low-reflection film of the low-reflection article of the present invention has a multilayer structure of at least two layers, and the average particle size of the inorganic compound fine particles disposed in each layer can be different for each layer. In the case of a film filled with fine particles as in the present invention, the porosity increases as the average particle size of the inorganic compound fine particles increases, so that the refractive index decreases. When the low-reflection film has the above structure, the refractive index of each layer is different, so that the low-reflection film has improved low-reflection characteristics. In addition, since the fine particles used have a lower refractive index than the base material, each layer in the film has a lower refractive index than the base material, thereby preventing significant deterioration of the low reflection characteristics when the film is abraded. . The effect is sufficient if two layers are provided, and it is more preferable to use two layers in consideration of economy. In addition, it is preferable that the inorganic compound fine particles and the inorganic compound binder are silica from the viewpoint of economy and low reflectivity.
[0013]
The low-reflection film can be coated on a substrate having a refractive index of 1.4 to 2.0, preferably 1.5 to 1.7 at a wavelength of 633 nm to form a low-reflection article. It is obtained by applying a coating solution to a substrate and baking the substrate. The coating liquid is at least two kinds of coating liquids composed of inorganic compound fine particles and a precursor of an inorganic compound binder, and a solvent, and is prepared so that the average particle diameter of the inorganic compound particles present in each coating liquid is different. Is done. When sequentially applying each coating solution to the base material, after applying each coating solution to the base material, without drying or baking, efficiently applying another coating solution to the low firing article of the present invention Can be produced.
[0014]
Further, the amount of the fine particles of the inorganic compound when preparing the coating liquid is preferably 1 to 20 times the weight of the precursor of the inorganic compound binder by weight. If the ratio is less than 1, the low reflection characteristics of the obtained film will not be sufficient, and if it exceeds 20, the strength of the obtained film will be low.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Fine particles of the inorganic compound constituting the low-reflection article include spherical silica and magnesium fluoride having an average particle diameter of 5 nm to 100 nm (however, the average particle diameter of the fine particles used for the film surface layer is 50 nm to 100 nm). Alumina, chain silica and the like can be used. Among them, spherical silica, which is easily available as colloidal silica, is preferably used as the inorganic compound in view of economic efficiency and low reflectivity.
[0016]
Further, the inorganic compound binder is to bond the fine particles to the fine particles or the substrate, and to increase the film strength, such binders include silica, alumina, sodium silicate, etc. Silica having a low refractive index and capable of obtaining excellent low reflection characteristics is preferable. These binders are formed from precursors, and alkoxide compounds such as ethoxide and methoxide, oxyhalogen compounds, acetic acid compounds and the like can be used as precursors for silica and alumina, and water glass and the like can be used for sodium silicate.
[0017]
The total thickness of the low reflection film is preferably 60 nm to 210 nm in view of low reflection. The thickness d of the low reflection film having a refractive index (n) smaller than that of the base material, the wavelength λ of the incident light, and the incident angle α of the light are [d = λ / 4 (n 2 −sin 2 α) 1/2 ]. Since the refractive index of the low-reflection film of the present invention is in the range of 1.3 to 1.4, from this equation, the film thickness that minimizes the reflectance of vertically incident visible light has a high radiation intensity of sunlight. For light having a wavelength of 550 nm, it is suggested that the film thickness is preferably 98 to 106 nm. When the incident angle of the light of the same wavelength is 60 degrees, a preferable film thickness is 125 to 142 nm.
[0018]
When the target wavelength light is 380 nm, a preferable film thickness for vertically incident light is 68 to 73 nm, and a preferable film thickness for 60 degree incident light is 86 to 98 nm, and when the target wavelength light is 780 nm. The preferred film thickness for vertically incident light is 139 to 150 nm, and the preferred film thickness for 60 degree incident light is 177 to 201 m.
[0019]
In order to obtain a low-reflection film having a structure having at least two layers, spherical silica having an average particle diameter of 50 to 100 nm is used as fine particles for the surface layer, and spherical silica having an average particle diameter of 5 nm to less than 50 nm is used for the substrate side layer. When silica is used as the binder, a film having a refractive index in the range of 1.3 to 1.45 distributed in the film thickness direction can be obtained. In this case, it is preferable that the thickness of the substrate side layer be 10 nm to 70 nm. If the thickness of the substrate side layer exceeds 70 nm, the effect of reducing the refractive index of the entire film is small, and if it is less than 10 nm, the film strength is reduced.
[0020]
A glass or plastic base material having a refractive index of 1.4 to 2.0, preferably 1.5 to 1.7 at a wavelength of 633 nm can be used as a base material constituting the low reflection article. For example, soda lime can be used. Uses substrates used for displays such as glass, alkali borosilicate glass, alkali-free glass, quartz glass, resin glass such as polycarbonate and polyethylene terephthalate, lenses, windows, liquid crystal display substrates, substrates for photoelectric conversion devices, etc. be able to.
[0021]
The low reflection article of the present invention is obtained by applying a coating liquid to a substrate and baking the substrate. The coating liquid is at least two kinds of coating liquids composed of inorganic compound fine particles and a precursor of an inorganic compound binder, and a solvent, and is prepared so that the average particle diameter of the inorganic compound particles present in each coating liquid is different. Is done. For example, in producing a low-reflection film having a two-layer structure, when the fine particles on the surface layer are inorganic compound fine particles having an average particle size of 50 nm to 100 nm, one coating agent is a precursor of the fine particles, a precursor of the inorganic compound binder, And a solvent, and the other coating agent is composed of inorganic compound fine particles having an average particle diameter of 5 nm to 40 nm, a precursor of an inorganic compound binder, and a solvent.
[0022]
As the solvent, alcohols such as methanol, ethanol, methyl ethyl ketone and isopropyl alcohol, and glycols such as ethylene glycol can be used.
[0023]
When sequentially applying each coating solution to the base material, after applying each coating solution to the base material, without drying or baking, efficiently applying another coating solution to the low firing article of the present invention Can be produced. As a method of applying the coating solution to the substrate, a known method such as a dipping method, a spin coating method, a roll coating method, a curtain flow coating method, a screen printing method, a flexographic printing method, or the like can be used.
[0024]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples. In addition, the quality evaluation of the sample obtained in this example was performed by the following method.
[0025]
[Evaluation of Appearance]: Appearance, permeability, and the presence or absence of cracks of the sample were visually evaluated.
[0026]
[Taber abrasion resistance]: A Taber 5130 type Taber tester was used. The low-reflection film of the sample was brought into contact with an abrasion wheel (CF-10F) and visually checked for film peeling after 100 rotations while applying a load of 4.9 N / cm 2. ○).
[0027]
[Traverse abrasion resistance]: No. 100 flannel cloth was pressed with a load of 4.9 N / 4 cm 2 , and the appearance change when 1000 reciprocations were performed at a speed of 30 reciprocations per minute at a distance of 10 cm per minute was visually evaluated. Was passed (o).
[0028]
[Reflection reduction effect]: Using an instantaneous multi-photometry system (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.), the visible light reflectance including the back surface reflection at an incident angle of 60 degrees was measured. The light source was D65. A sample having a difference (ΔRf) of 5.0% or more between the reflectance of a substrate not coated with a low-reflection film and the reflectance of a low-reflection article coated with a low-reflection film was judged as acceptable.
[0029]
[Refractive index / film thickness]: The refractive index and the film thickness were measured using an ellipsometer (DVA-FL3G type manufactured by Mizojiri Optical Industrial Co., Ltd.). Those whose refractive index of the low reflection film was in the range of 1.3 to 1.4 were regarded as acceptable.
[0030]
Example 1
(Preparation of base material)
As the substrate, a soda-lime silicate glass having a thickness of 3.4 mm and a square of 200 mm by a float method was used. The substrate surface was polished with ceria fine particles, and brushing cleaning was performed.
[0031]
(Preparation of coating liquid for substrate layer side)
2.34 g of a colloidal silica dispersion (IPA-ST-S, manufactured by Nissan Chemical Industries, Ltd.) in which silica fine particles having an average particle diameter of 10 nm are dispersed, 0.8 g of purified water, and 2.6 g of 1-methoxy-2 -To a solution obtained by stirring and mixing propanol (hereinafter, MFG) for 5 minutes, 0.36 g of ethyl silicate and 0.12 g of 0.1 N hydrochloric acid were added, and further stirred and mixed for 30 minutes. To this mixture, 23.08 g of MFG was added and mixed by stirring for 30 minutes to obtain a mother liquor. 40 g of methyl ethyl ketone (manufactured by Kishida Chemical Co., hereinafter referred to as MEK) and 40 g of isopropanol (manufactured by Kishida Chemical Co., hereinafter referred to as IPA) were added to 20 g of the mother liquor and stirred for 2 hours to obtain a coating solution.
[0032]
(Preparation of coating liquid for surface layer)
The above [substrate layer] except that the silica fine particle source was 2 g of a colloidal silica dispersion (MA-ST-L, manufactured by Nissan Chemical Industries, Ltd., 2 g) in which silica fine particles having an average particle diameter of 50 nm were dispersed, and the TEOS was 0.36 g Preparation of Coating Solution for Side] to obtain a coating solution.
[0033]
(Formation of low reflection film)
The substrate layer-side coating liquid was applied to the substrate prepared above by a spin coating method, and then the surface layer-side coating liquid was applied by the same operation. The base material coated with the coating solution was placed in an electric furnace maintained at 150 ° C. for 30 minutes to produce a low-reflection article. Table 1 shows the quality evaluation results. The film thickness of this low-reflection article is 130 nm (base layer 30 nm), the refractive index is 1.32, and all items of appearance, Taber abrasion resistance, traverse abrasion resistance, reflection reduction effect, refractive index and film thickness Passed.
[0034]
[Table 1]
[0035]
Example 2
Example 1 except that the silica fine particle source of the coating solution for the surface layer was 2.34 g of a colloidal silica dispersion (Nissan Chemical Industries, IPA-ST-ZL) in which silica fine particles having an average particle diameter of 100 nm were dispersed. A low-reflection article was obtained by the same operation as described above. The film thickness of the obtained low-reflection article is 140 nm (substrate side layer 30 nm), the refractive index of the film is 1.31, the appearance, the resistance to Taber abrasion, the resistance to traverse abrasion, the reflection reducing effect, and the refractive index and film thickness. All items passed.
[0036]
Example 3
A low-reflection article having a film refractive index of 1.33 was obtained in the same manner as in Example 1 except that the solid content of each coating solution was controlled and the film thickness was 170 nm (50 nm on the base material layer side). All items of appearance, Taber abrasion resistance, traverse abrasion resistance, reflection reduction effect, refractive index and film thickness were passed.
[0037]
Example 4
The same procedure as in Example 2 was carried out except that the solid content of each coating solution was controlled and the film thickness was set to 200 nm (30 nm on the surface side) to obtain a 1.32 low-reflection article with a film refractive index. All items of appearance, Taber abrasion resistance, traverse abrasion resistance, reflection reduction effect, refractive index and film thickness were passed.
[0038]
Example 5
A low reflection article having a film refractive index of 1.33 was obtained in the same manner as in Example 1 except that the solid content of each coating solution was controlled and the film thickness was set to 60 nm (10 nm on the base layer side). All items of appearance, Taber abrasion resistance, traverse abrasion resistance, reflection reduction effect, refractive index and film thickness were passed.
[0039]
Comparative Example 1
The same operation as in Example 1 was performed except that the surface-layer-side coating liquid in Example 1 was used as the substrate-layer-side coating liquid, and the substrate-layer-side coating liquid in Example 1 was used as the surface-layer-side coating liquid. A low-reflection article having a film thickness of 130 nm (base layer side 50 nm) and a film refractive index of 1.42 was obtained. The reflection reduction effect was 3.5%, which was poor, but was rejected.
[0040]
Comparative Example 2
Same as Example 1 except that the silica fine particle source of the coating liquid for the surface layer was 1.00 g of a colloidal silica dispersion (PL-10, manufactured by Fuso Chemical Co., Ltd.) in which silica fine particles having an average particle size of 150 nm were dispersed. By the operation described above, a low reflection article was obtained. The film thickness of the obtained low-reflection article was 300 nm (substrate side layer 50 nm), the refractive index of the film was 1.33, and the film was peeled off in a taper wear resistance test and a traverse wear resistance test.
[0041]
Comparative Example 3
A low-reflection article was obtained in the same manner as in Example 1, except that the silica fine particles were not added to the coating solution for the substrate side in Example 1. The film had a thickness of 300 nm (50 nm on the side of the base material layer) and a refractive index of 1.39.
[0042]
Comparative Example 4
The same operation as in Example 1 was performed, except that the coating solution for the surface layer in Example 1 was used as the coating solution for the base layer, and the coating solution for the base layer in Comparative Example 3 was used as the coating solution for the surface layer. A low-reflection article having a thickness of 100 nm (substrate layer side 50 nm) and a refractive index of the film of 1.45 was obtained. The reflection reduction effect was rejected.
[0043]
【The invention's effect】
The low-reflective article of the present invention has excellent low reflectivity and low angle dependence of low reflectivity, and, in long-term use, has high durability because of excellent adhesion between the low-reflection film and the substrate. In addition, since it has a characteristic that the low reflection characteristic is hardly deteriorated due to abrasion during use, it is effective for use in displays, vehicle windows, architectural windows, and the like. Furthermore, such a low-reflection article can be manufactured by a method that is economically excellent.
