JP3856227B2

JP3856227B2 - Matte colored clear painted stainless steel sheet

Info

Publication number: JP3856227B2
Application number: JP2003010140A
Authority: JP
Inventors: 和美松原; 修一杉田; 謙一大久保; 浩治森
Original assignee: Nisshin Steel Co Ltd
Current assignee: Nippon Steel Nisshin Co Ltd
Priority date: 2003-01-17
Filing date: 2003-01-17
Publication date: 2006-12-13
Anticipated expiration: 2023-01-17
Also published as: JP2004216834A

Description

【０００１】
【産業上の利用分野】
本発明は、基材の金属光沢を活かした色調を呈し、表面欠陥が目立ちにくい艶消し着色クリア塗装ステンレス鋼板に関する。
【０００２】
【従来の技術】
家電製品，ＯＡ機器等の表装材として、クリア塗装を施した塗装金属板が使用され始めている。クリア塗装金属板は、金属素地の光沢を活用した外観を呈することから、従来の着色塗装金属板では得られない雰囲気を醸し出す。
クリア塗装金属板は、着色剤を配合したクリア塗料を塗装原板表面に塗布し、焼付け乾燥することによって製造される。着色剤に染料を使用すると焼付け時に変色しやすく色調が安定しないので、通常は有機顔料が使用される。
【０００３】
有機顔料を配合したカラークリア塗膜では、入射光の特定波長成分が有機顔料に吸収され、残りの入射光が下地金属板の表面で反射され、吸収波長成分を除く反射光により特定の色調が発現する。しかし、有機顔料に吸収される光量はクリア塗膜に含まれている有機顔料の量，換言すれば塗膜の厚みによって異なり、厚い塗膜ほど吸収量が大きく、薄い塗膜ほど吸収量が少ない。そのため、発現する色調の膜厚依存性が高く、僅かな膜厚変動によっても色調が微妙に変動しやすい。色調の変動は、製造ロットの異なるクリア塗装金属板を突き合わせて施工する場合に色ムラとして強調される。
【０００４】
【発明が解決しようとする課題】
膜厚に応じた色調の変動は、光の干渉を利用した発色顔料を有機顔料に代えてクリア塗膜に分散させることにより防止できる。本発明者等は、発色顔料で発現する色調に着目し、透明又は半透明鱗片状無機基質を透明又は半透明金属酸化物で被覆した発色顔料をクリア塗膜に分散させたクリア塗装金属板を特願2002−188364号で提案した。
発色顔料を分散させたクリア塗膜の表面状態を更に調査・研究する過程で、有機顔料で色調を付与したクリア塗装金属板に比較し、発色顔料で色調を付与したクリア塗装金属板では塗膜欠陥部が目立ちやすいことが判った。塗膜欠陥部の高い視認性は、次のように推察される。
【０００５】
基材・金属板１の表面にあるクリア塗膜２に分散している鱗片状発色顔料３は、大半が基材・金属板１の沿面方向に配向しているが、クリア塗膜２から突出する発色顔料３p（顔料立ち）もある（図１）。塗装条件によってはクリア塗膜２の表面にワキ４が発生し、異物５がクリア塗膜２の表面に付着することもある。金属光沢が高い基材・金属板１の上に透明度の高いクリア塗膜２を設けているクリア塗装金属板では、入射光が基材・金属板１の表面で正反射し、発色顔料３pの突出部，ワキ４，異物５で拡散反射するため、顔料立ち３p，ワキ４，異物５が際立って塗膜欠陥部として視認される。
【０００６】
顔料立ち３pやワキ４に起因する塗膜欠陥部はクリア塗膜２の上にトップクリア塗膜６を積層することにより改善されるが、トップクリア塗膜６の形成用に塗装ラインを変更する必要がある。トップクリア塗膜６を形成しても、異物５に起因する塗膜欠陥部はトップクリア塗膜６を透過して視認される。着色クリア塗装金属板では、発色顔料による色調に加えて塗膜の表面状態が重視され、塗膜欠陥部の有無は商品価値に大きく影響する。
【０００７】
【課題を解決するための手段】
本発明は、このような問題を解消すべく案出されたものであり、発色顔料と共に無色透明の粒状艶消し剤をクリア塗膜に分散させることにより、着色クリア塗膜で目立ちがちな塗膜欠陥部の視認性を下げ、美麗な色調を呈する艶消し着色クリア塗装ステンレス鋼板を提供することを目的とする。
【０００８】
本発明の艶消し着色クリア塗装ステンレス鋼板は、金属光沢をもつステンレス鋼板の表面にアクリル系又はポリエステル系の有機樹脂からなるクリア塗膜が形成されており、鱗片状透明無機基質を透明の金属酸化物で被覆した透明又は半透明の発色顔料及び無色透明の粒状艶消し剤が前記クリア塗膜に分散し、当該クリア塗膜の６０度鏡面光沢度が２０〜８０％に調整されていることを特徴とする。クリア塗膜の形成に先立ち、発色顔料を含まないプライマクリア塗膜を金属基材の表面に形成しても良い。
【０００９】
透明又は半透明鱗片状無機基質にはマイカフレーク，ガラスフレーク，シリカフレーク等が使用され、ＴｉＯ₂，ＳｉＯ₂，ＺｒＯ₂，Ｆｅ₂Ｏ₃，ＳｎＯ₂，Ｆｅ₃Ｏ₄，Ｃｒ₂Ｏ₃，ＺｎＯ，Ａｌ₂Ｏ₃等の透明又は半透明金属酸化物で被覆することにより発色顔料が用意される。金属酸化物は単層で或いは２種以上を複層として鱗片状無機基質に設けられ、金属酸化物皮膜の膜厚に応じて発色を調整できる。
【００１０】
無色透明の粒状艶消し剤としては、シリカ，ガラス，ナイロン，尿素樹脂，アクリル樹脂，フッ素樹脂，ポリエチレン樹脂，ポリプロピレン樹脂等が単独で又は２種以上を複合して使用される。クリア塗膜を適度の粗面化する上では、粒径：１〜１０μｍの艶消し剤が好ましい。なお、本件明細書では、塗装原板の上に設けた膜厚１０μｍの艶消し剤無添加のクリア塗膜及び艶消し剤を１０質量％添加したクリア塗膜の色調をJIS Z8741に準拠して測定し、両者の色差ΔＥが２以下となる艶消し剤を無色透明な艶消し剤としている。
【００１１】
【作用】
本発明に従ったクリア塗装金属板では、基材・金属板１の表面に設けられているクリア塗膜２に発色顔料３，粒状艶消し剤７が分散している（図２）。発色顔料３は、透明又は半透明鱗片状無機基質３aの表面に透明又は半透明金属酸化物皮膜３bを単層（図３ａ）又は複層（図３ｂ）設けた顔料である。
発色顔料３が分散しているクリア塗膜２に入射した光Ｌ_inは、発色顔料３の隙間を縫って或いは透過して基材・金属板１の表面に達し、基材・金属板１の表面で反射された反射光及び発色顔料３の表面で反射された反射光Ｌ₁〜Ｌ₃になる。反射光Ｌ₁〜Ｌ₃の間に生じる光路差ΔＬに応じて干渉色が発現する。クリア塗膜２に分散している粒状艶消し剤７を反射光Ｌ_out，入射光Ｌ_inが透過するので、反射光Ｌ_outの合計強度が入射光Ｌ_inの強度にほぼ等しく、明度低下や膜厚依存性のない色調が得られる。
【００１２】
粒状艶消し剤７の分散によって塗膜欠陥部の視認性が低下する理由は，次のように推察され、後述の実施例でも支持される。
艶消し剤７自体は、無色透明であることから多少の屈折があるものの光の拡散反射をほとんど生じさせない。粒状艶消し剤７がクリア塗膜２の表面近傍に分布すると、塗膜表面で適度の拡散反射が生じる程度にクリア塗膜２を粗面化する。クリア塗膜２の内部に分布する粒状艶消し剤７では多少の屈折を除き光の直進性が保たれ、入射光Ｌ_inにほぼ等しい強度の反射光Ｌ_outが得られる。
粒状艶消し剤７で粗面化されたクリア塗膜２の表面で入射光Ｌ_inが拡散反射し、顔料立ち３p，ワキ４，異物５での拡散反射との差が少なくなることから、塗膜欠陥部が目立たなくなる。塗膜内部に分散している粒状艶消し剤７でクリア塗膜２を透過する入射光Ｌ_in，反射光Ｌ_outの光路が複雑屈折することも、視認性低下に寄与しているものと考えられる。
【００１３】
【実施の形態】
基材・金属板１としては、光沢のある金属表面が観察される製品形態で使用されることから、ステンレス鋼が使用される。基材・金属板１には、クリア塗膜２の形成に先立って脱脂・酸洗，クロメート処理，リン酸塩処理，クロムフリー処理等、適宜の塗装前処理が施される。
クリア塗膜２を形成するためのクリア塗料には、透明度の高いアクリル系又はポリエステル系の有機樹脂や，或いはこれらの縮み模様を形成する樹脂や無機系ポリマーを配合した有機樹脂も使用できる。また、透明性を損なわない範囲で、防錆顔料，着色顔料，染料等を必要に応じて添加しても良い。
【００１４】
発色顔料３を分散させたクリア塗膜２の形成に先立って、基材・金属板１に対する密着性を改善するため発色顔料３を含まないプライマクリア塗膜を形成しても良い。プライマクリア塗膜形成用の塗料は、塗料種に特段の制約が加わるものではなく、エポキシ樹脂，エポキシ変性ポリエステル樹脂，ウレタン樹脂，ウレタン変性エポキシ樹脂等が使用され、クロメート処理等の塗装前処理を施した基材・金属板１とクリア塗膜２との密着性が一層向上する。プライマクリア塗膜を形成する場合、プライマクリア塗膜の膜厚を１〜１０μｍにすることが好ましい。プライマクリア塗料には、透明感を損なわない範囲で防錆顔料，着色顔料，染料等を必要に応じて添加することも可能である。
【００１５】
クリア塗装金属板はクリア塗膜２を形成した後で製品形状に加工されることもあるので、基材・金属板１に対する密着性，塗膜自体の柔軟性に富むことがクリア塗膜２に要求される。また、柔軟性に相反する機能として耐疵付き性が要求されることもある。このような目的に応じた特性を考慮してクリア塗料の樹脂系が選択され、たとえばメラミン，イソシアネート等の硬化剤を適宜配合してクリア塗膜２を形成することも可能である。
【００１６】
クリア塗料に配合される発色顔料３は、マイカ，ガラスフレーク，アルミナフレーク，シリカフレーク等の透明又は半透明鱗片状無機基質３aに湿式法，ＣＶＤ法，粉末スパッタリング法等で金属酸化物皮膜３bの単層又は複層被覆を形成することにより製造される。
基材・金属板１の表面に沿った方向に鱗片状無機基質３aを配向させるほど発色顔料３の表面で入射光Ｌ_inが反射する確率が高くなるので、鱗片状無機基質３aのアスペクト比（厚みに対する最大径の比率）が大きなものほど好ましい。具体的には、アスペクト比が６０以上になると、大半の鱗片状無機基質３aが基材・金属板１の表面と平行又はほぼ平行な配向性をもってクリア塗膜２に分散し、透明の金属酸化物皮膜３bの干渉色が強く発現して鮮やかな色調となり光輝感も強くなる。
【００１７】
マイカを鱗片状無機基質３aとして使用し、湿式法でＴｉＯ₂被覆する場合、種々の方法を採用できる。たとえば、希薄なチタン酸水溶液にマイカを懸濁させて７０〜１００℃に加温し、チタン塩の加水分解生成物である水和酸化チタン粒子をマイカ表面に析出させた後、７００〜１０００℃で高温焼成することによりＴｉＯ₂被覆が形成される。ＴｉＯ₂被覆の膜厚は、チタン塩の濃度，懸濁液の温度，処理時間等の処理条件によって制御できる。
粉末スパッタリング法で発色顔料３を製造する場合、マイカ，ガラスフレーク等の鱗片状無機基質３aを回転ドラムに入れ、Ｔｉをターゲットとする反応性雰囲気下でスパッタリングすることにより、鱗片状無機基質３aの表面にＴｉＯ₂被覆が形成される。
【００１８】
屈折率が異なる複数の金属酸化物層３b，３cを鱗片状無機基質３aの表面に設ける場合、一層目の金属酸化物層３bを形成した後、被覆原料を代えて一層目と同じ方法又は異なる方法で２層目の金属酸化物層３cを形成する。
たとえば、ＴｉＯ₂被覆にＦｅ₂Ｏ₃被覆を積層する場合、ＴｉＯ₂被覆顔料を懸濁させた水溶液を７０〜１００℃に加温し、鉄塩水溶液を添加して水酸化鉄を析出させた後、１５０〜２００℃で乾燥することによりＴｉＯ₂被覆にＦｅ₂Ｏ₃被覆が積層される。Ｆｅ₂Ｏ₃被覆の膜厚は、鉄塩水溶液の濃度，懸濁液の温度，処理時間等によって制御できる。
【００１９】
透明な金属酸化物皮膜３b，３cで鱗片状無機基質３aを被覆した発色顔料３は、そのままでクリア塗料用樹脂に添加することも可能であるが、必要に応じて適宜の表面処理を施すことができる。表面処理では、クロム酸系，リン酸系，アルミナ系，ジルコニア系，セリウム系等の無機質表面処理剤や各種シランカップリング剤，チタネートカップリング剤，有機モノマー系等の有機質表面処理剤が使用される。表面処理により、クリア塗料用樹脂に対する発色顔料３の分散性及び隣接樹脂層との層間密着性が改善される。
【００２０】
クリア塗料に配合される艶消し剤７には、粒径：１〜１０μｍのシリカ，ガラス，ナイロン，尿素樹脂，アクリル樹脂，フッ素樹脂，ポリエチレン樹脂，ポリプロピレン樹脂等がある。艶消し剤７は、クリア塗膜２が適度に粗面化する程度、具体的には６０度鏡面光沢度が２０〜８０％となる割合で配合される。過剰量の艶消し剤７を配合するとクリア塗膜２が過度に粗面化されて６０度鏡面光沢度が２０％を下回り、発色顔料３の干渉色が発現しがたくなる。逆に艶消し剤７の配合量が不足するとクリア塗膜２の粗面化が不十分となって６０度鏡面光沢度が８０％を超え、塗膜欠陥部が目立ちやすくなる。
【００２１】
クリア塗膜２の表面粗さは、艶消し剤７の粒径にも影響される。艶消し剤７の粒径を１〜１０μｍの範囲に収めると、クリア塗膜２への分散性が良くクリア塗膜２が適度に粗面化され、加工性も確保される。粒径が小さすぎる艶消し剤７では、クリア塗料中で凝集しやすく、表面粗さも調整しがたくなる。逆に粒径が１０μｍを超える艶消し剤７がクリア塗膜２に分散すると、艶消し剤７自体が異物５として観察され、塗膜の加工性も低下する。
【００２２】
発色顔料３，艶消し剤７を配合したクリア塗料を塗装原板に塗布した後、クリア塗料の樹脂種や塗布量にもよるが２００〜４００℃で３０〜１２０秒加熱することによってクリア塗膜２が基材・金属板１に焼き付けられる。得られたクリア塗装金属板を観察すると、基材・金属板１の金属光沢が活かされ、クリア塗装金属板にありがちな顔料立ち３p，ワキ４，異物５等に起因する塗膜欠陥部が観察されない美麗な表面性状を呈する。
ワキ４，異物５等に由来する塗膜欠陥部は、クリア塗膜２の膜厚を２０μｍ以下に抑えることによっても抑制される。しかし、薄すぎるクリア塗膜２では膜厚制御，着色，製造性に問題を生じるので、クリア塗膜２の膜厚を３〜２０μｍの範囲に調整することが好ましい。
【００２３】
【実施例１】
板厚０.４ｍｍのＳＵＳ４３０ステンレス鋼板を塗装原板に使用した。塗装原板を２％塩酸で酸洗し、酸系の表面処理を施した後、クロム換算付着量２０ｍｇ／ｍ²の塗布型クロメート処理を施した。
クリア塗料としては、高分子ポリエステル系クリア樹脂塗料（PM5000：日本ペイント株式会社製）に発色顔料３を４％，所定量（表２）の艶消し剤７を配合することにより用意した。発色顔料３には、膜厚５０〜１４０ｎｍのＴｉＯ₂被覆を形成したアスペクト比１５０，中心粒径３０μｍのマイカフレークを使用した。
【００２４】
使用した艶消し剤７の材質，粒径，透明度を表１に示す。表中、ΔＥは、塗装原板の上に設けた膜厚１０μｍのクリア塗膜及び艶消し剤：１０質量％含有クリア塗膜の色調をJIS Z8741に準拠して測定し、クリア塗膜と艶消し剤含有クリア塗膜との色差ΔＥで表した。
【００２５】

【００２６】
ＴｉＯ₂被覆は、次の手順でマイカフレークの表面に形成した。
マイカフレーク１００ｇを水２リットルに懸濁させて７５℃に加温した後、ＴｉＣｌ₄溶液及びゼラチン溶液を懸濁液に添加し、ＮａＯＨ溶液で懸濁液のｐＨを６.０に調整した。懸濁液を１５分間攪拌した後、マイカフレークを濾過分離し、塩分がなくなるまでマイカフレークを洗浄した。次いで、１００℃で乾燥し、窒素雰囲気中８５０℃で焼成することにより、ＴｉＯ₂被覆をマイカフレーク表面に形成した。
【００２７】
クリア塗料を塗装原板に塗布して乾燥した後、２３０℃に６０秒加熱することにより基材・金属板１に焼き付け、膜厚１０μｍのクリア塗膜２を形成した。
得られたクリア塗装ステンレス鋼板について、分光測色計（CM−3700d：ミノルタ株式会社製）を用いてJIS Z8737で規定する色差表示法に従って明度（Ｌ値）を測定した。測定結果を顔料で着色したクリア塗装ステンレス鋼板の明度と比較すると格段に高くなっており、ステンレス鋼板本来の暗く冷たい金属感が和らげられたマイルドな色調を呈していた。
【００２８】
次いで、顔料立ち３p，ワキ４，異物５等に起因する塗膜欠陥部に及ぼす艶消し剤７の影響を調査するため、同じＴｉＯ₂被覆マイカフレークを４％配合したクリア塗料に分散させる艶消し剤７の粒径及び配合量を種々変更し、同様な条件下でステンレス鋼板の表面にクリア塗膜２を形成した。得られたクリア塗装ステンレス鋼板は、何れも発色顔料特有の色調を呈した。
各クリア塗装ステンレス鋼板から試験片を切り出し、クリア塗膜２の６０度鏡面光沢度を測定すると共に、塗膜欠陥部の有無を調査した。
【００２９】
クリア塗膜２の６０度鏡面光沢度は、デジタル光沢計（GM−3D：株式会社村上色彩研究所製）で測定した。クリア塗膜２の表面粗さは、表面形状測定器（Dektak 3030：日本真空技術株式会社製）を用い、塗膜面に対して垂直方向の形状を測定し、平均粗さ（全体の平均線を求め、平均線からの標準偏差）を指標とした。同じ艶消し剤７を用いた場合、クリア塗膜２への添加量を増加させると光沢度が低下し、平均粗さが増大する相関関係にあった。
【００３０】
塗膜欠陥部は、視認性評価に拠った。まず、艶消し剤７を添加していないクリア塗膜２の１００ｍｍ角の表面域にある欠陥の個数を目視観察でカウントする作業をクリア塗膜２の異なる３箇所で繰り返し、平均欠陥部数を算出した。艶消し剤７を添加したクリア塗膜２についても同じ方法で平均欠陥部数を求め、艶消し剤無添加の塗膜に比較して艶消し剤添加塗膜の欠陥部数が半分以下を良好，半分を超える場合を不良と評価した。
【００３１】
表２の調査結果にみられるように、艶消し剤７をクリア塗膜２に分散させたクリア塗装ステンレス鋼板では、クリア塗膜２の６０度鏡面光沢度が２０〜８０％に収まっており、発色顔料特有の色調を損なうことなく塗膜欠陥部が抑えられた膜面性状であった。なかでも、粒径：１〜１０μｍの艶消し剤７を分散させると、比較的厚膜のクリア塗膜２でも塗膜欠陥部を視認できなかった。
他方、艶消し剤７を含まないクリア塗膜２では、６０度鏡面光沢度が１５０と高く、入射光が顔料立ち３p、ワキ４、異物５で拡散反射することに起因する塗膜欠陥部が際立っていた。艶消し剤７を配合した場合でも、クリア塗膜２の６０度鏡面光沢度が適正範囲から外れると塗膜欠陥部が観察された。
【００３２】

【００３３】
【発明の効果】
以上に説明したように、発色顔料で色調を発現させるクリア塗膜に無色透明の艶消し剤を分散させてクリア塗膜を粗面化すると、塗膜表面で入射光が適度の拡散反射し、顔料立ち，ワキ，異物等での拡散反射との間の差が少なくなる。その結果、金属素地外観を活用した色調付与にも拘らず、顔料立ち，ワキ，異物等に由来する塗膜欠陥部が目立たなくなる。このようにして塗膜欠陥部の視認性が低下された艶消し着色クリア塗装金属板は、光の干渉による発色で色調が付与された高級感のある外観を呈し、家電機器，ＯＡ機器，厨房機器等の広範な分野で表装材，内装材として使用される。
【図面の簡単な説明】
【図１】有機顔料を配合したクリア塗膜で塗膜欠陥部が目立つことを説明する図
【図２】発色顔料と共に艶消し剤を分散させたクリア塗膜で塗膜欠陥部の視認性が低下することを説明する図
【図３】金属酸化物で単層被覆した発色顔料（ａ）及び異種の金属酸化物で複層被覆した発色顔料（ｂ）を分散させたクリア塗膜で干渉色が発現する機構の説明図
【符号の説明】
１：基材・金属板２：クリア塗膜３：発色顔料３p：クリア塗膜から突出した発色顔料（顔料立ち）３a：鱗片状無機基質３b，３c：金属酸化物被覆４：ワキ５：異物６：トップクリア塗膜７：粒状艶消し剤
Ｌ_in：入射光Ｌ_out：反射光[0001]
[Industrial application fields]
The present invention relates to a matte-colored clear-coated stainless steel sheet that exhibits a color tone utilizing the metallic luster of a base material and in which surface defects are hardly noticeable.
[0002]
[Prior art]
As a cover material for home appliances, OA equipment, etc., a painted metal plate with a clear coating has begun to be used. The clear painted metal plate exhibits an appearance that utilizes the gloss of the metal substrate, and thus creates an atmosphere that cannot be obtained with conventional colored painted metal plates.
The clear painted metal plate is manufactured by applying a clear paint blended with a colorant to the surface of the painted original plate and baking and drying. When a dye is used as a colorant, an organic pigment is usually used because it tends to change color during baking and the color tone is not stable.
[0003]
In a color clear coating film containing an organic pigment, a specific wavelength component of incident light is absorbed by the organic pigment, the remaining incident light is reflected by the surface of the base metal plate, and a specific color tone is obtained by the reflected light excluding the absorption wavelength component. To express. However, the amount of light absorbed by the organic pigment varies depending on the amount of organic pigment contained in the clear coating, in other words, the thickness of the coating. . For this reason, the color tone to be developed is highly dependent on the film thickness, and the color tone is likely to fluctuate slightly even with slight film thickness fluctuations. The variation in the color tone is emphasized as color unevenness when the clear painted metal plates having different production lots are put together.
[0004]
[Problems to be solved by the invention]
Variation in color tone according to the film thickness can be prevented by dispersing a coloring pigment utilizing light interference in a clear coating instead of an organic pigment. The present inventors focused on the color tone expressed by the coloring pigment, and provided a clear painted metal plate in which a coloring pigment coated with a transparent or semi-transparent scale-like inorganic substrate with a transparent or semi-transparent metal oxide was dispersed in a clear coating film. Proposed in Japanese Patent Application No. 2002-188364.
In the process of further investigating and studying the surface condition of the clear paint film in which the color pigment is dispersed, the paint film is applied to the clear paint metal plate to which the color tone is given in comparison with the clear paint metal plate to which the color tone is given by the organic pigment It was found that the defective part was easily noticeable. The high visibility of a coating-film defect part is guessed as follows.
[0005]
Most of the scaly coloring pigment 3 dispersed in the clear coating 2 on the surface of the base material / metal plate 1 is oriented in the creeping direction of the base material / metal plate 1 but protrudes from the clear coating film 2. There is also a coloring pigment 3p (pigment standing) (FIG. 1). Depending on the coating conditions, the edge 4 may be generated on the surface of the clear coating 2, and the foreign matter 5 may adhere to the surface of the clear coating 2. In a clear painted metal plate with a highly transparent clear coating 2 provided on a substrate / metal plate 1 with a high metallic luster, the incident light is regularly reflected on the surface of the substrate / metal plate 1 and the colored pigment 3p Because of the diffuse reflection of the protruding portion, the armpit 4 and the foreign material 5, the pigment standing 3p, the armpit 4 and the foreign material 5 are conspicuously recognized as a coating film defect portion.
[0006]
The coating defect due to pigment standing 3p and armpit 4 is improved by laminating the top clear coating 6 on the clear coating 2, but the coating line is changed to form the top clear coating 6. There is a need. Even when the top clear coating film 6 is formed, the coating film defect portion caused by the foreign matter 5 is visible through the top clear coating film 6. In a colored clear painted metal plate, the surface condition of the coating film is emphasized in addition to the color tone of the coloring pigment, and the presence or absence of a coating film defect part greatly affects the commercial value.
[0007]
[Means for Solving the Problems]
The present invention has been devised to solve such a problem, and by dispersing a colorless transparent granular matting agent together with a coloring pigment in the clear coating film, the coating film tends to be noticeable in the colored clear coating film. An object of the present invention is to provide a matte-colored clear-coated stainless steel sheet that reduces the visibility of defective portions and exhibits a beautiful color tone.
[0008]
The matte colored clear painted stainless steel sheet of the present invention has a clear coating formed of an acrylic or polyester organic resin on the surface of a stainless steel sheet having a metallic luster, and a transparent metal oxide is formed on a scaly transparent inorganic substrate. that particulate matting agent coated transparent or translucent color pigments and colorless, transparent objects is dispersed in the clear coating film, 60 degree specular gloss of the clear coating film is adjusted to 20-80% Features. Prior to the formation of the clear coating film, a primer clear coating film containing no coloring pigment may be formed on the surface of the metal substrate.
[0009]
Mica flakes, glass flakes, silica flakes and the like are used as the transparent or translucent scaly inorganic substrate, and include TiO ₂ , SiO ₂ , ZrO ₂ , Fe ₂ O ₃ , SnO ₂ , Fe ₃ O ₄ , Cr ₂ O ₃ , A coloring pigment is prepared by coating with a transparent or translucent metal oxide such as ZnO or Al ₂ O ₃ . The metal oxide is provided on the scaly inorganic substrate as a single layer or as two or more layers, and the color development can be adjusted according to the thickness of the metal oxide film.
[0010]
As the colorless and transparent granular matting agent, silica, glass, nylon, urea resin, acrylic resin, fluorine resin, polyethylene resin, polypropylene resin and the like are used alone or in combination of two or more. A matting agent having a particle size of 1 to 10 μm is preferable for appropriately roughening the clear coating film. In addition, in this specification, the color tone of a clear coating film with a 10 μm-thick matting agent additive and a clear coating film added with 10% by mass of a matting agent provided on a coating original plate is measured according to JIS Z8741. The matting agent having a color difference ΔE of 2 or less is a colorless and transparent matting agent.
[0011]
[Action]
In the clear coated metal plate according to the present invention, the coloring pigment 3 and the granular matting agent 7 are dispersed in the clear coating film 2 provided on the surface of the substrate / metal plate 1 (FIG. 2). The coloring pigment 3 is a pigment in which a transparent or translucent scale-like inorganic substrate 3a is provided with a single layer (FIG. 3a) or multiple layers (FIG. 3b) of a transparent or translucent metal oxide film 3b.
Light L _in the color pigment 3 is incident on the clear coating film 2 are dispersed is weaving through color pigment 3 or transmitted to reach the surface of the substrate, the metal plate 1, the base-metal plate 1 The reflected light reflected on the surface and the reflected light L _{1 to} L ₃ reflected on the surface of the coloring pigment ₃ are obtained. The interference color appears according to the optical path difference ΔL generated between the reflected lights L _{1 to} L ₃ . Clearcoats reflected light granular matting agent 7 dispersed in 2 L _out, the incident light L _in is transmitted, substantially equal, Ya brightness decrease the intensity of the total intensity incident light L _in the reflected light L _out A color tone that does not depend on the film thickness can be obtained.
[0012]
The reason why the visibility of the coating film defect portion decreases due to the dispersion of the granular matting agent 7 is presumed as follows, and is supported in the examples described later.
The matting agent 7 itself is colorless and transparent, and therefore has little refraction, but hardly causes diffuse reflection of light. When the granular matting agent 7 is distributed in the vicinity of the surface of the clear coating film 2, the clear coating film 2 is roughened to such an extent that moderate diffuse reflection occurs on the coating film surface. Clear straightness of except light refraction somewhat the particulate matting agent 7 distributed in the interior of the coating film 2 is maintained, reflected light L _out of about equal intensity to the incident light L _in is obtained.
The incident light L _in the surface of the clear coating film 2 roughened by particulate matting agent 7 is diffusely reflected, pigments Standing 3p, Waki 4, since the difference between the diffuse reflection in the foreign matter 5 is reduced, the coating Film defects become inconspicuous. The complex refraction of the incident light L _in and reflected light L _out transmitted through the clear coating film 2 by the granular matting agent 7 dispersed inside the coating film also contributes to a decrease in visibility. It is done.
[0013]
Embodiment
As the substrate / metal plate 1, stainless steel is used because it is used in a product form in which a glossy metal surface is observed. Prior to the formation of the clear coating film 2, the base material / metal plate 1 is subjected to appropriate pretreatments such as degreasing / pickling, chromate treatment, phosphate treatment, and chromium-free treatment.
The clear paint for forming the clear coating film 2, high or acrylic or polyester organic resin transparency, or an organic resin containing a resin or inorganic polymers that form these shrinkage patterns can also be used. Moreover, you may add an antirust pigment, a coloring pigment, dye, etc. as needed in the range which does not impair transparency.
[0014]
Prior to the formation of the clear coating film 2 in which the coloring pigment 3 is dispersed, a primer clear coating film that does not contain the coloring pigment 3 may be formed in order to improve the adhesion to the substrate / metal plate 1. The paint for forming the primer clear coating does not impose any particular restrictions on the type of paint. Epoxy resin, epoxy-modified polyester resin, urethane resin, urethane-modified epoxy resin, etc. are used, and coating pretreatment such as chromate treatment is performed. The adhesion between the applied substrate / metal plate 1 and the clear coating film 2 is further improved. When forming a primer clear coating film, it is preferable to make the film thickness of a primer clear coating film into 1-10 micrometers. It is also possible to add a rust preventive pigment, a color pigment, a dye or the like to the primer clear coating as needed within a range that does not impair the transparency.
[0015]
Since the clear painted metal plate may be processed into a product shape after the clear coating 2 is formed, the clear coating 2 has excellent adhesion to the substrate / metal plate 1 and the flexibility of the coating itself. Required. In addition, as a function that contradicts flexibility, wrinkle resistance may be required. The resin system of the clear paint is selected in consideration of the characteristics according to the purpose. For example, the clear coating film 2 can be formed by appropriately blending a curing agent such as melamine or isocyanate.
[0016]
The coloring pigment 3 blended in the clear paint is formed on a transparent or translucent scale-like inorganic substrate 3a such as mica, glass flakes, alumina flakes, silica flakes, etc. by a wet method, CVD method, powder sputtering method, etc. Manufactured by forming a single or multi-layer coating.
Since the probability of the incident light L _in the surface of the color pigment 3 enough to orient the scale-like inorganic substrates 3a in a direction along the surface of the substrate, the metal plate 1 is reflected increases, the aspect ratio of the scaly inorganic substrates 3a ( The larger the ratio of the maximum diameter to the thickness, the better. Specifically, when the aspect ratio is 60 or more, most of the scaly inorganic substrate 3a is dispersed in the clear coating film 2 with an orientation parallel or almost parallel to the surface of the base material / metal plate 1, and transparent metal oxidation. The interference color of the material film 3b strongly develops to become a vivid color tone, and the brightness is also enhanced.
[0017]
When mica is used as the scaly inorganic substrate 3a and TiO _{2 is} coated by a wet method, various methods can be employed. For example, after suspending mica in a dilute titanic acid aqueous solution and heating to 70 to 100 ° C. to precipitate hydrated titanium oxide particles, which are hydrolysis products of titanium salts, on the mica surface, 700 to 1000 ° C. TiO ₂ coating is formed by baking at a high temperature. The film thickness of the TiO ₂ coating can be controlled by processing conditions such as the concentration of titanium salt, the temperature of the suspension, and the processing time.
When the coloring pigment 3 is produced by the powder sputtering method, the scaly inorganic substrate 3a such as mica and glass flakes is placed in a rotating drum and sputtered in a reactive atmosphere using Ti as a target, thereby forming the scaly inorganic substrate 3a. A TiO ₂ coating is formed on the surface.
[0018]
When a plurality of

metal oxide layers

3b and 3c having different refractive indexes are provided on the surface of the scaly inorganic substrate 3a, after forming the first metal oxide layer 3b, the coating raw material is changed and the same method or different from the first layer. A second metal oxide layer 3c is formed by the method.
For example, the case of laminating the Fe ₂ O ₃ coated on TiO ₂ coating, the aqueous suspension of TiO ₂ coated pigment was heated to 70 to 100 ° C., to precipitate iron hydroxide by adding an iron salt solution Thereafter, the Fe ₂ O ₃ coating is laminated on the TiO ₂ coating by drying at 150 to 200 ° C. The film thickness of the Fe ₂ O ₃ coating can be controlled by the concentration of the aqueous iron salt solution, the temperature of the suspension, the treatment time, and the like.
[0019]
The coloring pigment 3 in which the scaly inorganic substrate 3a is coated with the transparent

metal oxide films

3b and 3c can be added to the clear coating resin as it is, but an appropriate surface treatment is performed if necessary. Can do. In the surface treatment, inorganic surface treatment agents such as chromic acid, phosphoric acid, alumina, zirconia, cerium, etc., and various surface treatment agents such as various silane coupling agents, titanate coupling agents, and organic monomers are used. The By the surface treatment, the dispersibility of the coloring pigment 3 with respect to the clear coating resin and the interlayer adhesion with the adjacent resin layer are improved.
[0020]
Examples of the matting agent 7 blended in the clear paint include silica, glass, nylon, urea resin, acrylic resin, fluororesin, polyethylene resin, and polypropylene resin having a particle size of 1 to 10 μm. The matting agent 7 is blended to such an extent that the clear coating film 2 is appropriately roughened, specifically, at a ratio that the 60 ° specular gloss is 20 to 80%. When an excessive amount of matting agent 7 is blended, the clear coating film 2 is excessively roughened, the 60 ° specular glossiness is less than 20%, and the interference color of the coloring pigment 3 is hardly developed. On the contrary, when the blending amount of the matting agent 7 is insufficient, the rough coating of the clear coating film 2 is insufficient, and the 60 ° specular glossiness exceeds 80%, and the coating film defect portion is easily noticeable.
[0021]
The surface roughness of the clear coating film 2 is also affected by the particle size of the matting agent 7. When the particle size of the matting agent 7 falls within the range of 1 to 10 μm, the dispersibility in the clear coating film 2 is good, the clear coating film 2 is appropriately roughened, and processability is ensured. The matting agent 7 having a particle size that is too small tends to aggregate in the clear paint, and the surface roughness is difficult to adjust. Conversely, when the matting agent 7 having a particle size exceeding 10 μm is dispersed in the clear coating film 2, the matting agent 7 itself is observed as the foreign material 5, and the processability of the coating film also decreases.
[0022]
After applying clear paint containing coloring pigment 3 and matting agent 7 to the coating original plate, clear coating 2 is heated at 200-400 ° C for 30-120 seconds, depending on the resin type and coating amount of the clear paint. Is baked onto the substrate / metal plate 1. Observing the resulting clear-painted metal plate, the metallic luster of the substrate / metal plate 1 is utilized, and defects in the paint film due to pigment standing 3p, armpits 4, foreign objects 5 etc., which are often found in clear-painted metal plates, are observed. Exhibits beautiful surface properties that are not possible.
The coating film defect part originating in the armpit 4, the foreign material 5, etc. is suppressed also by suppressing the film thickness of the clear coating film 2 to 20 micrometers or less. However, since the clear coating film 2 that is too thin causes problems in film thickness control, coloring, and manufacturability, it is preferable to adjust the film thickness of the clear coating film 2 in the range of 3 to 20 μm.
[0023]
[Example 1]
A SUS430 stainless steel plate having a thickness of 0.4 mm was used as a coating original plate. The coated original plate was pickled with 2% hydrochloric acid and subjected to an acid-based surface treatment, followed by a coating-type chromate treatment with a chromium equivalent adhesion amount of 20 mg / m ² .
The clear paint was prepared by blending 4% of the coloring pigment 3 and a predetermined amount (Table 2) of the matting agent 7 into a high molecular weight polyester clear resin paint (PM5000: manufactured by Nippon Paint Co., Ltd.). As the coloring pigment 3, mica flakes having an aspect ratio of 150 and a center particle size of 30 μm formed with a TiO ₂ coating having a thickness of 50 to 140 nm were used.
[0024]
Table 1 shows the material, particle size, and transparency of the matting agent 7 used. In the table, ΔE is a clear coating film with a film thickness of 10 μm and matting agent provided on the coating original plate: The color tone of the clear coating film containing 10% by mass is measured according to JIS Z8741, It was represented by a color difference ΔE with the agent-containing clear coating film.
[0025]

[0026]
A TiO ₂ coating was formed on the surface of mica flakes by the following procedure.
After 100 g of mica flakes were suspended in 2 liters of water and heated to 75 ° C., TiCl ₄ solution and gelatin solution were added to the suspension, and the pH of the suspension was adjusted to 6.0 with NaOH solution. After the suspension was stirred for 15 minutes, the mica flakes were separated by filtration and washed until the salt content disappeared. Then dried at 100 ° C., by baking at 850 ° C. in a nitrogen atmosphere to form a TiO ₂ coated mica flakes surface.
[0027]
The clear paint was applied to the coating original plate, dried, and then heated to 230 ° C. for 60 seconds to be baked onto the base material / metal plate 1 to form a clear coating film 2 having a thickness of 10 μm.
About the obtained clear coating stainless steel plate, the lightness (L value) was measured according to the color difference display method prescribed | regulated by JISZ8737 using the spectrocolorimeter (CM-3700d: product made by Minolta Co., Ltd.). Compared with the brightness of the clear-coated stainless steel plate colored with pigment, the measurement result was much higher, and it exhibited a mild color tone that softened the original dark and cold metal feeling of the stainless steel plate.
[0028]
Next, in order to investigate the influence of the matting agent 7 on the coating film defect due to the pigment standing 3p, the armpit 4, the foreign matter 5, etc., the matte dispersed in a clear paint containing 4% of the same TiO ₂ coated mica flake The particle size and blending amount of the agent 7 were variously changed, and the clear coating film 2 was formed on the surface of the stainless steel plate under the same conditions. All of the clear coated stainless steel sheets obtained exhibited a color tone peculiar to a coloring pigment.
A test piece was cut out from each clear-coated stainless steel plate, the 60-degree specular gloss of clear coating film 2 was measured, and the presence or absence of a coating film defect portion was investigated.
[0029]
The 60-degree specular gloss of clear coating film 2 was measured with a digital gloss meter (GM-3D: manufactured by Murakami Color Research Co., Ltd.). The surface roughness of the clear coating film 2 is measured by measuring the shape in the direction perpendicular to the coating film surface using a surface shape measuring instrument (Dektak 3030: manufactured by Nippon Vacuum Technology Co., Ltd.). The standard deviation from the mean line) was used as an index. When the same matting agent 7 was used, when the amount added to the clear coating film 2 was increased, the glossiness decreased and the average roughness increased.
[0030]
The coating film defect part was based on visibility evaluation. First, the work of counting the number of defects in the surface area of 100 mm square of the clear coating film 2 to which the matting agent 7 is not added is visually observed at three different locations of the clear coating film 2 to calculate the average number of defective parts. did. For the clear coating 2 with the matting agent 7 added, the average number of defective parts is obtained by the same method. Compared with the coating film without the matting agent, the number of defective parts of the matting agent-added coating is less than half. The case where it exceeded was evaluated as bad.
[0031]
As can be seen from the survey results in Table 2, in the clear coated stainless steel plate in which the matting agent 7 is dispersed in the clear coating 2, the 60 degree specular gloss of the clear coating 2 is within 20 to 80%. It was a film surface property in which a defective portion of the coating film was suppressed without impairing the color tone peculiar to the coloring pigment. In particular, when the matting agent 7 having a particle size of 1 to 10 μm was dispersed, even a relatively thick clear coating film 2 could not be visually recognized.
On the other hand, the clear coating film 2 that does not contain the matting agent 7 has a high 60 ° specular gloss of 150, and there is a coating film defect caused by diffuse reflection of incident light by the pigment standing 3p, the armpit 4 and the foreign material 5. It stood out. Even when the matting agent 7 was blended, a coating film defect portion was observed when the 60-degree specular gloss of the clear coating film 2 was out of the proper range.
[0032]

[0033]
【The invention's effect】
As explained above, when the clear coating film is roughened by dispersing a colorless and transparent matting agent in the clear coating film that expresses the color tone with the coloring pigment, the incident light is appropriately diffusely reflected on the coating film surface, Differences from diffuse reflection due to pigment standing, armpits, and foreign matter are reduced. As a result, in spite of imparting a color tone utilizing the appearance of the metal substrate, the defective portion of the coating film derived from pigment stand, armpit, foreign matter, etc. becomes inconspicuous. In this way, the matte colored clear painted metal plate with reduced visibility of the defective portion of the coating film has a high-grade appearance with color tone due to light interference, and is used in home appliances, OA devices, kitchens. Used as a cover material and interior material in a wide range of equipment.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating that a coating film defect portion is noticeable in a clear coating film containing an organic pigment. FIG. 2 is a clear coating film in which a matting agent is dispersed together with a color pigment and the visibility of the coating film defect section is high. FIG. 3 shows interference color in a clear coating film in which a coloring pigment (a) coated with a single layer of a metal oxide and a coloring pigment (b) coated with a layer of a different metal oxide are dispersed. Explanatory diagram of the mechanism of expression [Explanation of symbols]
1: Base material / metal plate 2: Clear coating 3: Color developing pigment 3p: Color developing pigment protruding from clear coating (pigment standing) 3a: Scale-like

inorganic substrate

3b, 3c: Metal oxide coating 4: Waki 5: Foreign matter 6: Top clear coating film 7: Granular matting agent L _in : incident light L _out : reflected light

Claims

A transparent coating made of an acrylic or polyester organic resin is formed on the surface of a stainless steel plate having a metallic luster, a transparent or translucent coloring pigment coated with a transparent metal oxide on a scaly transparent inorganic substrate, and colorless granular matting agent for transparent dispersed in the clear coating film, matte colored clear coating stainless steel plate, wherein a 60 ° specular gloss of the clear coating film is adjusted to 20-80%.

The matte colored clear painted stainless steel sheet according to claim 1, wherein the granular matting agent is one or more selected from silica, glass, nylon, urea resin, acrylic resin, fluororesin, polyethylene resin and polypropylene resin.

The matte colored clear painted stainless steel sheet according to claim 1 or 2, wherein a granular matting agent having a particle size of 1 to 10 µm is dispersed in the clear coating film.