JP2004224017A

JP2004224017A - Painted steel sheet with high cooling power

Info

Publication number: JP2004224017A
Application number: JP2003045482A
Authority: JP
Inventors: Hirokazu Yano; 矢野　　宏和; Katsumi Owa; 尾和　　克美; Koji Mori; 浩治森
Original assignee: Nisshin Steel Co Ltd
Current assignee: Nippon Steel Nisshin Co Ltd
Priority date: 2002-11-25
Filing date: 2003-02-24
Publication date: 2004-08-12
Anticipated expiration: 2023-02-24
Also published as: JP4252818B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a painted steel sheet efficiently absorbing a heat from a heating component and adapting to suppressing a temperature rising at the heating component. <P>SOLUTION: The painted steel strip comprises a plated steel sheet or a stainless steel sheet as a substrate 1 and a heat absorbing painted film 2 with a heat reflectance of ≤0.35 in a wave length range of 3-30 μm formed on at least one face of the substrate. In the case of use as a heating equipment, a casing of a component or a peripheral component, the heat absorbing painted film 2 is arranged so as to face the heating member. For lowering the heat reflectance of the heat absorbing painted film 2, lowering a lightness L of the heat absorbing painted film to ≤50 is preferred by dispersing a hyperchromic pigment. To form an acrylic painted film wherein a color pigment or a coloring pigment is dispersed at an opposite side of the heat absorbing painted film 2 is preferred. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【産業上の利用分野】
本発明は、熱発生源に近接配置される構造部材に好適な高い冷却能を呈する塗装鋼板に関する。
【０００２】
【従来技術及び問題点】
ＣＰＵ，パワートランジスタ，ディスクドライブ，電源，光源等の発熱器具は、稼動時に発熱して昇温する。高温は、発熱器具，部品の使用者にとって危険であるばかりでなく、発熱器具，部品の故障や誤動作の原因にもなる。温度上昇に起因するトラブルは、発熱器具，部品を小型化，高密度化するほど大きな問題となる。
【０００３】
昇温による発熱器具の故障や誤動作を防止するため、ファン等で冷風を発熱器具，部品に吹き付けて冷却する方法が採用されている。しかし、冷却装置を組み込む設計では、発熱器具，部品の小型化，高密度化に十分対応できない。ドラフト作用をもつ筐体で発熱器具，部品を覆う方法も採用されているが、ドラフト作用のために通風孔を筐体に形成する必要があり、気密性や電磁シールド性に劣る筐体になる。
【０００４】
小型化，高密度化の要求に応え、気密性，電磁シールド性も良好な筐体を得る上では、筐体を構成する材料自体の放熱特性を向上させることが必要である。筐体構成材料の材質選択，表面状態等について種々の調査・研究がこれまで報告されているが、小型化，高性能化が著しい電気・電子部品に適した特性をもつ筐体構成材料は実用に供されていない。
材料自体の優れた放熱特性は、電気・電子機器用の筐体に限らず、蛍光灯を始めとする各種照明器具の反射板に使用した場合でも照明器具の発光効率や寿命が高まること等、種々の用途で要求される特性である。
【０００５】
【課題を解決するための手段】
本発明は、このような要求に応えるべく案出されたものであり、めっき鋼板又はステンレス鋼板の表面に熱吸収性塗膜を設けることにより、発熱を効率よく吸収して外部に放散させる作用を呈する塗装鋼板を提供することを目的とする。
【０００６】
本発明の塗装鋼板は、その目的を達成するため、めっき鋼板又はステンレス鋼板を基材とし、３〜３０μｍの波長域における熱反射率が０．３５以下に抑えられた熱吸収性塗膜が基材の少なくとも一面に形成されていることを特徴とする。
熱吸収性塗膜の熱反射率を低下させるためには、濃色顔料の分散によって熱吸収性塗膜の明度Ｌ値を５０以下に下げることが好ましい。熱吸収性塗膜を設けた基材表面が発熱源側に臨むように使用されるが、反対表面には同様な熱反射率の低い塗膜、或いは着色顔料や発色顔料を分散させたクリア塗膜等の意匠性塗膜の何れを設けても良い。
【０００７】
【実施の形態】
本発明の塗装鋼板は、めっき鋼板又はステンレス鋼板を金属基材１とし、金属基材１の一面に熱吸収性塗膜２，他面に下塗り塗膜３を介して上塗り塗膜４を設けている（図１）。下塗り塗膜３，上塗り塗膜４に代えて、着色顔料又は発色顔料を分散させたクリア塗膜を形成しても良い。何れの場合も、塗膜形成に先立ち脱脂，酸洗，クロメート処理，リン酸塩処理，クロムフリー処理等の塗装前処理を必要に応じて施し、塗膜密着性の向上に有効な化成処理皮膜５を金属基材１の表面に設けることが好ましい。
【０００８】
金属基材１には、Ｚｎ，Ｚｎ−Ａｌ，Ｚｎ−Ａｌ−Ｍｇ，Ｚｎ−Ｎｉ，Ａｌ，Ａｌ−Ｓｉ等のめっき層６を設けためっき鋼板や無垢のステンレス鋼板が使用される。基材表面で乱反射を促進させて熱吸収効率を向上させる上では、表面粗さの大きな基材ほど好ましい。なかでも、波長域３〜３０μｍの入射光では表面粗さによる熱反射の抑制効果が顕著になる。熱吸収性塗膜２は、赤外線，可視光を含む３〜３０μｍの波長域における熱反射率が０．３５以下に調整されている。
当該塗装鋼板で発熱機器周辺の構造部材を作製する場合、熱吸収性塗膜２が発熱機器側となるように塗装鋼板を配置する。
【０００９】
光照射に起因する熱吸収は、波長域３〜３０μｍの光で最も促進され、３μｍ未満又は３０μｍを超える波長域では熱吸収に及ぼす光照射の影響が小さい。波長域３〜３０μｍでの熱反射率が０．３５以下になると、発熱器具，部品で発生した熱の大半が熱吸収性塗膜２に伝達され、発熱器具，部品の昇温が大幅に抑制される。熱吸収性塗膜２に伝達された熱は、熱伝導性の良好な金属基材１全体に広がった後、外部に放散される。
熱反射率０．３５以下は、濃色顔料を分散させて熱吸収性塗膜２の明度Ｌ値を５０以下に下げることにより達成される。
【００１０】
熱吸収性塗膜２は、ポリエステル，エポキシ，エポキシ変性ポリエステル，アクリル，ポリエーテルサルフォン，ポリオルガノシロキサン，シリコン変性アクリル，フッ素樹脂等の樹脂塗料を金属基材１に塗布・焼付けすることにより形成される。必要な熱吸収特性を確保する上で膜厚５μｍ以上で熱吸収性塗膜２を形成することが好ましいが、厚すぎる熱吸収性塗膜２では加工性，塗膜密着性が低下する傾向がみられるので好ましくは膜厚の上限を１５μｍに設定する。
【００１１】
熱吸収性塗膜２に分散させる濃色顔料には、カーボンブラック，黒鉛粉末，セラミック粉末，遷移金属酸化物粉末，複合酸化物粉末等から熱吸収能の高い顔料が選択される。セラミック粉末にはＳｉＣ，リン鉄等、遷移金属酸化物粉末にはＣｕ−Ｃｒ，Ｃｕ−Ｃｒ−Ｍｎ，Ｃｕ−Ｆｅ−Ｍｎ，Ｃｏ−Ｆｅ−Ｃｒ，Ｆｅ−Ｚｎ，Ｆｅ−Ｚｎ−Ｃｒ，Ｃｏ−Ａｌ，Ｃｏ−Ａｌ−Ｃｒ，Ｔｉ−Ｃｏ−Ｎｉ−Ｚｎ，Ｃｏ−Ａｌ−Ｃｒの複合酸化物等が挙げられる。その他、アニリンブラック，シアニンブルー等の有機顔料も使用可能である。
【００１２】
下塗り塗膜３，上塗り塗膜４は常法に従って形成される塗膜であるが、下塗り塗膜３，上塗り塗膜４に代えて発熱機器の反対側表面にも熱吸収性塗膜２を形成できる。しかし、用途，嗜好等に応じた意匠を筐体外面に付与するため、好ましくは膜厚７〜３０μｍの上塗り塗膜４を設ける場合が多い。下塗り塗膜３は、好ましくは１〜１０μｍの膜厚をもち、必要に応じ着色顔料，体質顔料，防錆顔料等を分散させている。
下塗り塗膜３，上塗り塗膜４に代えて、着色顔料や発色顔料を分散させたクリア塗膜を設けることにより、塗装鋼板の意匠性を高めることもできる。クリア塗膜の形成には、高分子ポリエステル樹脂，ポリエステル樹脂，エポキシ変性ポリエステル樹脂，アクリル樹脂，アクリルシリコーン樹脂，フッ素樹脂，エポキシ樹脂等をベース樹脂とし、各種着色又は発色顔料を配合しクリア塗料が使用される。
【００１３】
着色顔料には、カーボンブラック，鉄黒，酸化チタン，亜鉛華，シアニンブルー，シアニングリーン，酸化鉄イエロー，チタンイエロー，ハンザエロー，グリーンゴールド，フラバンスロンエロー，酸化鉄レッド，ベンガラ，キナクリドンレッド，パーマネントレッド，ウォチングレッド，ボンマルーンライト，ジオキサジンバイオレット，Ｃｕ−Ｃｒ系複合酸化物顔料，Ｃｕ−Ｃｒ−Ｍｎ系複合酸化物顔料，Ｃｕ−Ｆｅ−Ｍｎ系複合酸化物顔料，Ｃｏ−Ｆｅ−Ｃｒ系複合酸化物顔料，Ｆｅ−Ｚｎ系複合酸化物顔料，Ｆｅ−Ｚｎ−Ｃｒ系複合酸化物顔料，Ｃｏ−Ａｌ系複合酸化物顔料，Ｃｏ−Ａｌ−Ｃｒ系複合酸化物顔料，Ｔｉ−Ｃｏ−Ｎｉ−Ｚｎ系複合酸化物顔料，Ｃｏ−Ａｌ−Ｃｒ系複合酸化物顔料等がある。
【００１４】
発色顔料には、鱗片状無機基質を透明又は半透明金属酸化物皮膜で被覆し、光の干渉によって発色する顔料が使用される。鱗片状無機基質には、ガラスフレーク，マイカフレーク，アルミナフレーク，シリカフレーク，アルミニウムフレーク，グラファイトフレーク等がある。金属酸化物皮膜にはＴｉＯ_２，ＳｉＯ_２，ＺｒＯ_２，Ｆｅ_２Ｏ_３，ＳｎＯ_２，Ｆｅ_３Ｏ_４，Ｃｒ_２Ｏ_３，ＺｎＯ，Ａｌ_２Ｏ_３等があり、湿式法，乾式法等で無機基質上に設けられる。アルミニウムフレークを始めとする金属フレーク等のメタリック顔料を適宜配合することも可能である。
クリア塗膜は好ましくは２〜３０μｍの膜厚で形成されるが、クリア塗膜の形成で熱吸収性塗膜２の特性が大きく変わることがない。
【００１５】
波長域３〜３０μｍにおける熱反射率０．３５以下にした熱吸収性塗膜２を形成すると、発熱器具，部品から放出された熱が熱吸収性塗膜２に効率よく吸収され、金属基材１を介し外部に放散される。熱放射率は放射率計により測定でき、濃色顔料の材質，分散量等によって調整できる。具体的には、熱吸収性塗膜２の明度Ｌ値が５０以下となる配合量で濃色顔料を分散させることにより、熱反射率０．３５以下の熱吸収性塗膜２が得られる。
【００１６】
塗膜２〜４が設けられた金属基材１は、曲げ，絞り加工等で製品形状に成型加工され、発熱器具，部品の筐体や周辺部材として使用される。そのため、塗膜２〜４としては、成形加工時に剥離，亀裂等の欠陥が発生しない加工性が要求される。塗膜２〜４の形成には、ポリエステル，エポキシ，エポキシ変性ポリエステル，アクリル，ポリエーテルサルフォン，ポリオルガノシロキサン，シリコン変性アクリル，フッ素樹脂等の樹脂塗料を単独で又は複合して使用できる。
【００１７】
樹脂塗料には、通常使用されている着色顔料，Ｃｒ系又はＣｒフリー系防錆顔料，導電性付与剤，ワックス，メタリック顔料，パール顔料，体質顔料等を必要に応じて濃色顔料と共に複合添加しても良い。熱吸収性塗膜２用の塗料には、濃色顔料の他に、アース性，溶接性を付与するためにＮｉ粉等の金属粉やリン鉄を始めとする各種導電性付与剤が必要に応じて添加される。
【００１８】
【実施例１】
樹脂１００重量部に対し２０重量部のメラミン硬化剤，４０重量部のカーボンブラックを数平均分子量３０００のポリエステル樹脂に配合した黒色塗料及び１００重量部の白色酸化チタンを同じポリエステル樹脂に配合した白色塗料を用意した。黒色塗料，白色塗料を種々の割合で混練して明度Ｌ値の異なる塗料組成物を調合した後、１０重量部のストロンチウムクロメートを添加して熱吸収性塗膜２用の塗料を調整した。
下塗り塗膜３の形成には２０重量部のストロンチウムクロメートを配合したエポシキ変性高分子ポリエステル樹脂系プライマ，上塗り塗膜４の形成には市販の黒色系艶消しメタリック高分子ポリエステル塗料を使用した。
【００１９】
塗装原板として板厚０．５ｍｍの溶融亜鉛めっき鋼板を使用し、Ｎｉ析出型の表面調整処理，塗布型クロメート処理を順次施した。表面調整された塗装原板に各種塗料を塗布し、最高到達板温２１５℃で４０秒焼き付けることにより、膜厚５μｍの下塗り塗膜３，膜厚１３μｍの上塗り塗膜４を塗装原板の一面に、膜厚５μｍの熱吸収性塗膜２を他面に形成した。
作製された各塗装鋼板の熱吸収性塗膜２側で熱放射率計（ＤａｎｄＳＡＥＲＤ）により熱放射率を測定し、熱放射が熱吸収によるものと仮定し、熱反射率＝（１−放射率の測定値）として熱反射率を算出した。表１の調査結果にみられるように、明度Ｌ値が高いほど熱反射率が高くなっていた。
【００２０】

【００２１】
次いで、Ｎｏ．１の塗装鋼板から長さ２８５ｍｍ，幅１５０ｍｍの試験片を切り出し、放熱試験に供した。放熱試験では、上部が開放され断熱材でライニングした試験ボックス１１にヒータ１２を収容し、ヒータ１２から試験片１０までの距離を２０ｍｍに設定して試験片１０を試験ボックス１１の上部開口に固定した（図２）。試験片１０の固定に際しては、熱吸収性塗膜２を試験ボックス１１内側に向けた。ヒータ１２に投入する電力を一定値０．５ｋＷに維持し、電力投入開始から試験ボックス１１内の温度を熱電対１３で連続測定した。
【００２２】
図３の測定結果にみられるように、熱反射率０．１３の熱吸収性塗膜２を形成した塗装鋼板Ｎｏ．１では、塗膜を設けていない無垢の亜鉛めっき鋼板に比較して温度上昇に最大で２０℃近くの差があり、２時間連続加熱した後でも試験ボックス１１内の温度が７０℃を超えなかった。試験ボックス１１内の昇温が抑制されていることは、ヒータ１２で発生した熱量が熱吸収性塗膜２に効率よく吸収され、金属基材１を熱伝導して外部に放散されたことを示す。その結果、熱吸収性塗膜２に面している発熱部品が比較的低温に維持され、故障や寿命低下の原因となる昇温が少ないことが理解される。
【００２３】
熱反射率０．３５以下の熱吸収性塗膜２を設けた塗装鋼板Ｎｏ．１〜４は、何れも塗装鋼板Ｎｏ．１と同様な昇温特性を呈し、発熱部品の昇温を抑制できた。他方、熱反射率が０．６４と高い塗膜を設けた塗装鋼板Ｎｏ．６は、無垢の亜鉛めっき鋼板と同様な昇温特性を呈し、昇温抑制に有効でなかった。Ｎｏ．６に比較して熱反射率が０．４５と若干低い塗装鋼板Ｎｏ．５でも、十分な昇温抑制ができなかった。
【００２４】
【実施例２】
樹脂１００重量部に対し２０重量部のメラミン硬化剤，１０重量部のカーボンブラック，３０重量部のＣｕ−Ｆｅ−Ｍｎ系複合酸化物（黒色顔料）を数平均分子量３０００のポリエステル樹脂に配合した黒色塗料及び１００重量部の白色酸化チタンを配合した白色塗料を用意した。黒色塗料，白色塗料を種々の割合で混練して明度Ｌ値の異なる塗料組成物を調合した後、平均粒径５μｍのＮｉ粉（導電性付与剤）を１０重量部，カルシウムシリケート（防錆顔料）を１０重量部添加して熱吸収性塗膜２形成用の塗料を調整した。
【００２５】
下塗り塗膜３の形成には１０重量部のカルシウムクロメートを配合したエポキシ変性高分子ポリエステル樹脂系プライマ，上塗り塗膜４の形成にはアクリルビーズを分散させた黒色系艶消しメタリック高分子ポリエステル塗料を使用した。
実施例１と同様に表面調整された塗装原板に各種塗料を塗布し、最高到達板温２１５℃で４０秒焼き付けることにより、膜厚５μｍの下塗り塗膜３，膜厚１３μｍの上塗り塗膜４を塗装原板の一面に、膜厚５μｍの熱吸収性塗膜２を他面に形成した。
作製された塗装鋼板の熱反射率を実施例１と同様に求めたところ、本例でも明度Ｌ値が高いほど大きな熱反射率が示され、表２に示すように明度Ｌ値を５０以下に下げたときに熱反射率が０．３５以下になった。
【００２６】

【００２７】
【実施例３】
基材の一面に熱吸収性塗膜２（実施例２の試験Ｎｏ．１）を、他面に着色顔料，発色顔料を分散させたクリア塗膜を設けた。
着色顔料にはカーボンブラックを、発色顔料には酸化チタンをコーティングしたガラスフレークを用い、分子量１２０００の高分子ポリエステル樹脂１００質量部に対し２０質量部のメラミン硬化剤を添加した樹脂をベースとする塗料組成物にそれぞれ２質量％，６質量％配合した。実施例１と同じ条件下で塗料組成物を塗布・焼付けすることにより、膜厚１２μｍのクリア塗膜を形成した。
熱吸収性塗膜２，クリア塗膜が形成された塗装鋼板の熱反射率を実施例２と同じ条件下で測定したところ、０．１４と低い熱反射率が示され、下塗り塗膜３，上塗り塗膜４に代えてクリア塗膜を形成しても優れた熱吸収特性が維持されることが判った。しかも、着色顔料又は発色顔料が分散したクリア塗膜のため、金属光沢が活かされ、しかも淡い色調の外観を呈した。
【００２８】
【発明の効果】
以上に説明したように、本発明の塗装鋼板は、少なくとも一面に熱反射率を低下させた熱吸収性塗膜を設けている。該塗装鋼板で発熱器具，部品の筐体や周辺部材を作製するとき、発熱器具，部品に熱吸収性塗膜を臨ませると、発熱器具，部品からの熱が熱吸収性塗膜に効率よく吸収され、金属基材を熱伝導して外部に放散される。そのため、昇温に起因した発熱器具，部品の故障や寿命低下が防止され、発熱器具，部品自体の信頼性向上に適した構造部材が得られる。また、熱吸収性塗膜と反対側に設けたクリア塗膜を製品外側に使用すると、金属光沢が活かされ淡い色調が付与された意匠性の高い製品となる。
【図面の簡単な説明】
【図１】本発明に従った塗装鋼板の層構成を示す模式図
【図２】塗装鋼板の吸熱・放熱特性が筐体内部の温度上昇に及ぼす影響を調査した試験装置
【図３】熱吸収性塗膜を設けた塗装鋼板で作製した筐体内部の昇温特性を無垢の亜鉛めっき鋼板製筐体内部と比較したグラフ
【符号の説明】
１：金属基材２：熱吸収性塗膜３：下塗り塗膜４：意匠塗膜５：化成処理皮膜６：めっき層[0001]
[Industrial applications]
TECHNICAL FIELD The present invention relates to a coated steel sheet exhibiting a high cooling ability suitable for a structural member arranged close to a heat generation source.
[0002]
[Prior art and problems]
Heating appliances such as a CPU, a power transistor, a disk drive, a power supply, and a light source generate heat and increase in temperature during operation. The high temperature is not only dangerous for the user of the heating device or component, but also causes a failure or malfunction of the heating device or component. The trouble caused by the rise in temperature becomes a serious problem as the size and the density of the heating equipment and components are reduced.
[0003]
In order to prevent a failure or malfunction of the heating device due to a rise in temperature, a method is employed in which cooling is performed by blowing cool air onto the heating device and components with a fan or the like. However, a design incorporating a cooling device cannot sufficiently cope with miniaturization and high-density of a heating device and components. A method of covering heat-generating appliances and parts with a casing having a draft action is also adopted, but a ventilation hole must be formed in the casing for the draft action, resulting in a casing with poor airtightness and electromagnetic shielding properties. .
[0004]
In order to meet the demand for miniaturization and high density, and to obtain a housing with good airtightness and electromagnetic shielding properties, it is necessary to improve the heat radiation characteristics of the material itself constituting the housing. Various investigations and studies have been reported on the material selection and surface condition of the housing component material, but a housing component material with characteristics suitable for electrical and electronic components with remarkable miniaturization and high performance has been practically used. Has not been offered.
The excellent heat dissipation characteristics of the material itself are not limited to the housings for electric and electronic equipment, but also increase the luminous efficiency and life of lighting equipment even when used for reflectors of various lighting equipment such as fluorescent lamps. This is a characteristic required for various uses.
[0005]
[Means for Solving the Problems]
The present invention has been devised to meet such a demand, and by providing a heat-absorbing coating on the surface of a plated steel plate or a stainless steel plate, an effect of efficiently absorbing heat and dissipating it to the outside. It is intended to provide a coated steel sheet to be presented.
[0006]
In order to achieve the object, the coated steel sheet of the present invention is based on a heat-absorbing coating film having a base material of a plated steel sheet or a stainless steel sheet and having a heat reflectance of 0.35 or less in a wavelength range of 3 to 30 μm. It is characterized by being formed on at least one surface of the material.
In order to reduce the heat reflectance of the heat-absorbing coating film, it is preferable to lower the lightness L value of the heat-absorbing coating film to 50 or less by dispersing a dark pigment. It is used so that the surface of the substrate provided with the heat-absorbing coating faces the side of the heat source. On the opposite surface, a similar coating with low heat reflectance or a clear coating in which color pigments or coloring pigments are dispersed. Any of decorative coatings such as a film may be provided.
[0007]
Embodiment
The coated steel sheet of the present invention comprises a plated steel sheet or a stainless steel sheet as the metal substrate 1, and a heat-absorbing coating film 2 on one surface of the metal substrate 1, and an overcoat film 4 on the other surface via an undercoat film 3. (Fig. 1). Instead of the undercoating film 3 and the topcoating film 4, a clear coating film in which a coloring pigment or a coloring pigment is dispersed may be formed. In any case, prior to coating film formation, a pre-coating treatment such as degreasing, pickling, chromate treatment, phosphate treatment, chromium-free treatment, etc. is applied as necessary, and a chemical conversion coating effective for improving coating adhesion. 5 is preferably provided on the surface of the metal substrate 1.
[0008]
As the metal substrate 1, a plated steel plate provided with a plated layer 6 of Zn, Zn-Al, Zn-Al-Mg, Zn-Ni, Al, Al-Si, or the like, or a solid stainless steel plate is used. In order to enhance the heat absorption efficiency by promoting diffuse reflection on the surface of the substrate, a substrate having a larger surface roughness is more preferable. Above all, the effect of suppressing heat reflection due to surface roughness is remarkable for incident light in a wavelength range of 3 to 30 μm. The heat-absorbing coating film 2 is adjusted to have a heat reflectance of 0.35 or less in a wavelength range of 3 to 30 μm including infrared light and visible light.
When manufacturing a structural member around a heating device with the coated steel plate, the coated steel plate is arranged so that the heat-absorbing coating film 2 is on the heating device side.
[0009]
Heat absorption due to light irradiation is most promoted by light in a wavelength range of 3 to 30 μm, and in a wavelength range of less than 3 μm or more than 30 μm, the influence of light irradiation on heat absorption is small. When the heat reflectance in the wavelength range of 3 to 30 μm becomes 0.35 or less, most of the heat generated in the heat-producing device and components is transmitted to the heat-absorbing coating film 2, and the temperature rise of the heat-producing device and components is largely suppressed. Is done. The heat transmitted to the heat-absorbing coating film 2 spreads throughout the metal substrate 1 having good heat conductivity, and is then radiated to the outside.
The heat reflectance of 0.35 or less is achieved by dispersing a dark pigment to lower the lightness L value of the heat-absorbing coating film 2 to 50 or less.
[0010]
The heat-absorbing coating film 2 is formed by applying and baking a resin paint such as polyester, epoxy, epoxy-modified polyester, acrylic, polyethersulfone, polyorganosiloxane, silicon-modified acrylic, or fluororesin on the metal substrate 1. Is done. It is preferable to form the heat-absorbing coating film 2 with a film thickness of 5 μm or more in order to secure necessary heat-absorbing characteristics. However, if the heat-absorbing coating film 2 is too thick, processability and coating film adhesion tend to be reduced. Therefore, the upper limit of the film thickness is preferably set to 15 μm.
[0011]
As the dark pigment to be dispersed in the heat-absorbing coating film 2, a pigment having high heat-absorbing ability is selected from carbon black, graphite powder, ceramic powder, transition metal oxide powder, composite oxide powder and the like. For ceramic powders, such as SiC and phosphorus iron, and for transition metal oxide powders, Cu-Cr, Cu-Cr-Mn, Cu-Fe-Mn, Co-Fe-Cr, Fe-Zn, Fe-Zn-Cr, Co -Al, Co-Al-Cr, Ti-Co-Ni-Zn, and a composite oxide of Co-Al-Cr. In addition, organic pigments such as aniline black and cyanine blue can be used.
[0012]
The undercoat film 3 and the overcoat film 4 are formed according to a conventional method, but the heat-absorbing film 2 is also formed on the opposite surface of the heating device in place of the undercoat film 3 and the overcoat film 4. it can. However, in order to provide a design corresponding to the use, taste, and the like to the outer surface of the housing, the top coat 4 preferably having a thickness of 7 to 30 μm is often provided in many cases. The undercoat 3 preferably has a film thickness of 1 to 10 μm, and a coloring pigment, an extender pigment, a rust preventive pigment, and the like are dispersed as necessary.
By providing a clear coating film in which a coloring pigment or a coloring pigment is dispersed instead of the undercoating film 3 and the topcoating film 4, the design of the coated steel sheet can be enhanced. For the formation of the clear coating film, high-molecular polyester resin, polyester resin, epoxy-modified polyester resin, acrylic resin, acrylic silicone resin, fluororesin, epoxy resin, etc. are used as the base resin, and various coloring or coloring pigments are blended to form a clear coating. used.
[0013]
Color pigments include carbon black, iron black, titanium oxide, zinc white, cyanine blue, cyanine green, iron oxide yellow, titanium yellow, hansa yellow, green gold, flavanthrone yellow, iron oxide red, bengala, quinacridone red, and permanent red. , Watching Red, Bon Maroon Light, Dioxazine Violet, Cu-Cr-based composite oxide pigment, Cu-Cr-Mn-based composite oxide pigment, Cu-Fe-Mn-based composite oxide pigment, Co-Fe-Cr-based composite Oxide pigment, Fe-Zn-based composite oxide pigment, Fe-Zn-Cr-based composite oxide pigment, Co-Al-based composite oxide pigment, Co-Al-Cr-based composite oxide pigment, Ti-Co-Ni- There are a Zn-based composite oxide pigment and a Co-Al-Cr-based composite oxide pigment.
[0014]
As the color-forming pigment, a pigment that is formed by coating a scaly inorganic substrate with a transparent or translucent metal oxide film and that develops color by light interference is used. The scaly inorganic substrate includes glass flake, mica flake, alumina flake, silica flake, aluminum flake, graphite flake and the like. Metal oxide films include TiO ₂ , SiO ₂ , ZrO ₂ , Fe ₂ O ₃ , SnO ₂ , Fe ₃ O ₄ , Cr ₂ O ₃ , ZnO, Al ₂ O _3, etc. Provided on an inorganic substrate. Metallic pigments such as aluminum flakes and other metal flakes can be appropriately compounded.
The clear coating film is preferably formed with a thickness of 2 to 30 μm, but the properties of the heat-absorbing coating film 2 do not significantly change by the formation of the clear coating film.
[0015]
When the heat-absorbing coating film 2 having a heat reflectance of 0.35 or less in a wavelength range of 3 to 30 μm is formed, the heat released from the heating equipment and components is efficiently absorbed by the heat-absorbing coating film 2, and the metal substrate 1 to the outside. The thermal emissivity can be measured by an emissivity meter, and can be adjusted by the material and the amount of dispersion of the dark pigment. Specifically, by dispersing the dark color pigment in a blending amount at which the lightness L value of the heat absorbing coating film 2 becomes 50 or less, the heat absorbing coating film 2 having a heat reflectance of 0.35 or less can be obtained.
[0016]
The metal substrate 1 on which the coating films 2 to 4 are provided is formed into a product shape by bending, drawing, or the like, and is used as a heating device, a housing of components, or a peripheral member. For this reason, the coating films 2 to 4 are required to have workability in which defects such as peeling and cracking do not occur during molding. In forming the coating films 2 to 4, resin coatings such as polyester, epoxy, epoxy-modified polyester, acrylic, polyethersulfone, polyorganosiloxane, silicon-modified acrylic, and fluororesin can be used alone or in combination.
[0017]
To the resin coating, commonly used coloring pigments, Cr-based or Cr-free rust-preventive pigments, conductivity-imparting agents, waxes, metallic pigments, pearl pigments, extender pigments, etc. are added in combination with dark pigments as necessary. You may. In the paint for the heat-absorbing coating film 2, in addition to the dark-colored pigment, metal powder such as Ni powder and various conductivity-imparting agents such as phosphorous iron are required in order to impart earthing property and weldability. Will be added accordingly.
[0018]
Embodiment 1
A black paint in which 20 parts by weight of a melamine curing agent and 40 parts by weight of carbon black are mixed with a polyester resin having a number average molecular weight of 3,000 with respect to 100 parts by weight of a resin, and a white paint in which 100 parts by weight of white titanium oxide is mixed with the same polyester resin. Was prepared. A black paint and a white paint were kneaded in various ratios to prepare paint compositions having different lightness L values, and then 10 parts by weight of strontium chromate was added to prepare a paint for the heat-absorbing coating film 2.
For the formation of the undercoat film 3, an epoxy modified polymer polyester resin primer containing 20 parts by weight of strontium chromate was used. For the formation of the overcoat film 4, a commercially available black matte metallic polymer polyester paint was used.
[0019]
A hot-dip galvanized steel sheet having a thickness of 0.5 mm was used as a coating base sheet, and was subjected to a Ni precipitation type surface conditioning treatment and a coating type chromate treatment in this order. Various paints are applied to the surface-adjusted coating base plate and baked at a maximum reaching plate temperature of 215 ° C. for 40 seconds, so that a 5 μm-thick undercoating film 3 and a 13 μm-thick top coating film 4 are coated on one surface of the coating base plate. A heat-absorbing coating film 2 having a thickness of 5 μm was formed on the other surface.
The thermal emissivity was measured by a thermal emissivity meter (DandSAERD) on the heat-absorbing coating film 2 side of each of the prepared coated steel sheets, and it was assumed that the thermal radiation was due to thermal absorption. The heat reflectance was calculated as a measured value of the rate). As can be seen from the investigation results in Table 1, the higher the lightness L value, the higher the thermal reflectance.
[0020]

[0021]
Then, No. A test piece having a length of 285 mm and a width of 150 mm was cut out from the coated steel sheet 1 and subjected to a heat radiation test. In the heat radiation test, the heater 12 is housed in a test box 11 which is open at the top and lined with a heat insulating material, and the distance from the heater 12 to the test piece 10 is set to 20 mm and the test piece 10 is fixed to the upper opening of the test box 11. (Fig. 2). When fixing the test piece 10, the heat-absorbing coating film 2 was directed inside the test box 11. The power supplied to the heater 12 was maintained at a constant value of 0.5 kW, and the temperature in the test box 11 was continuously measured by the thermocouple 13 from the start of power supply.
[0022]
As can be seen from the measurement results of FIG. 3, the coated steel sheet No. having the heat-absorbing coating film 2 having a heat reflectance of 0.13 was formed. In No. 1, there is a maximum difference of about 20 ° C. in the temperature rise as compared with a pure galvanized steel sheet having no coating film, and the temperature in the test box 11 does not exceed 70 ° C. even after continuous heating for 2 hours. Was. The suppression of the temperature rise in the test box 11 means that the amount of heat generated by the heater 12 was efficiently absorbed by the heat-absorbing coating film 2 and was conducted to the metal substrate 1 to be radiated to the outside. Show. As a result, it is understood that the temperature of the heat-generating component facing the heat-absorbing coating film 2 is maintained at a relatively low temperature, and the temperature rise that causes failure and shortens the life is small.
[0023]
The coated steel sheet No. provided with the heat-absorbing coating film 2 having a heat reflectance of 0.35 or less. No. 1 to 4 are all coated steel sheet Nos. It exhibited the same temperature rise characteristics as Example 1, and the temperature rise of the heat-generating component could be suppressed. On the other hand, a coated steel sheet No. having a coating film having a high thermal reflectance of 0.64 was prepared. No. 6 exhibited the same temperature raising characteristics as a solid galvanized steel sheet and was not effective in suppressing the temperature rise. No. Coated steel sheet No. 6 having a slightly lower thermal reflectance of 0.45 than that of No. 6 Even with No. 5, it was not possible to sufficiently suppress the temperature rise.
[0024]
Embodiment 2
20 parts by weight of a melamine curing agent, 10 parts by weight of carbon black, and 30 parts by weight of a Cu—Fe—Mn-based composite oxide (black pigment) with respect to 100 parts by weight of a resin are mixed with a polyester resin having a number average molecular weight of 3,000 to obtain a black color. A white paint containing the paint and 100 parts by weight of white titanium oxide was prepared. A black paint and a white paint are kneaded at various ratios to prepare paint compositions having different lightness L values. Then, 10 parts by weight of Ni powder (conductivity imparting agent) having an average particle size of 5 μm, calcium silicate (rust preventive pigment) ) Was added in an amount of 10 parts by weight to prepare a paint for forming the heat-absorbing coating film 2.
[0025]
For forming the undercoat 3, an epoxy-modified high-molecular polyester resin-based primer containing 10 parts by weight of calcium chromate, and for forming the overcoat 4, a black matte metallic high-molecular polyester paint in which acrylic beads are dispersed are used. used.
Various paints were applied to the original plate whose surface was adjusted in the same manner as in Example 1, and baked at a maximum temperature of 215 ° C. for 40 seconds to obtain a 5 μm thick undercoat 3 and a 13 μm thick overcoat 4. A heat-absorbing coating film 2 having a thickness of 5 μm was formed on one surface of the original coating plate.
The heat reflectance of the produced coated steel sheet was determined in the same manner as in Example 1. In this example as well, the higher the lightness L value, the larger the heat reflectance was shown. As shown in Table 2, the lightness L value was reduced to 50 or less. When lowered, the heat reflectance became 0.35 or less.
[0026]

[0027]
Embodiment 3
A heat-absorbing coating film 2 (Test No. 1 of Example 2) was provided on one surface of the substrate, and a clear coating film in which a coloring pigment and a coloring pigment were dispersed was provided on the other surface.
A paint based on a resin in which carbon black is used as a coloring pigment and glass flakes coated with titanium oxide are used as a coloring pigment, and 20 parts by weight of a melamine curing agent is added to 100 parts by weight of a high molecular weight polyester resin having a molecular weight of 12,000. 2% by mass and 6% by mass of the composition were mixed. The coating composition was applied and baked under the same conditions as in Example 1 to form a clear coating film having a thickness of 12 μm.
When the heat reflectance of the coated steel sheet on which the heat-absorbing coating film 2 and the clear coating film were formed was measured under the same conditions as in Example 2, the heat reflectance was as low as 0.14. It was found that excellent heat absorption characteristics were maintained even when a clear coating film was formed instead of the top coating film 4. In addition, because of the clear coating film in which the coloring pigment or the coloring pigment was dispersed, the metallic luster was utilized and the appearance of a light color tone was exhibited.
[0028]
【The invention's effect】
As described above, the coated steel sheet of the present invention has at least one surface provided with a heat-absorbing coating film having reduced heat reflectance. When making a heat-generating device, component housing or peripheral members with the coated steel sheet, if a heat-absorbing coating is exposed to the heat-generating device or component, the heat from the heat-generating device or component will be efficiently applied to the heat-absorbing coating. Absorbed, thermally conducted through the metal substrate and radiated to the outside. For this reason, a failure and a shortened life of the heat-generating device and components due to the temperature rise are prevented, and a structural member suitable for improving the reliability of the heat-generating device and components themselves can be obtained. When a clear coating film provided on the side opposite to the heat-absorbing coating film is used on the outer side of the product, a product having a high designability with a light color tone imparted by utilizing the metallic luster.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a layer structure of a coated steel sheet according to the present invention. FIG. 2 is a test apparatus for examining the effect of heat absorption and heat radiation characteristics of the coated steel sheet on temperature rise inside a housing. FIG. Graph comparing the temperature rise characteristics inside a housing made of a coated steel sheet with a conductive coating with those inside a solid zinc-coated steel sheet [Explanation of symbols]
1: metal base material 2: heat-absorbing coating film 3: undercoat coating film 4: decorative coating film 5: chemical conversion coating film 6: plating layer

Claims

A heat-absorptive coating in which the heat reflectance in a wavelength range of 3 to 30 μm is suppressed to 0.35 or less, based on a plated steel plate or a stainless steel plate, is formed on at least one surface of the substrate. Painted steel plate with high cooling ability.

The coated steel sheet according to claim 1, wherein the lightness L value of the heat-absorbing coating film is reduced to 50 or less by the dispersion of the dark pigment.

The coated steel sheet according to claim 1, wherein a clear coating film in which a coloring pigment or a coloring pigment is dispersed is formed on the surface of the base material opposite to the heat absorbing coating film.