【考案の詳細な説明】
〈技術分野〉
本考案は、電子レンジのオーブンに関し、特に
オーブン壁内面に彩色仕上げの塗膜を形成するも
のの改良に関する。
〈従来技術〉
従来、電子レンジのオーブン壁に塗装を行う場
合、耐食品汚染性、耐熱性、耐腐食性などを考慮
した溶剤型アクリル−メラミン系樹脂塗料、エポ
キシ系樹脂粉体塗料を下塗、上塗ともに指定色調
にして塗装仕上げを行う。また、指定色調の下塗
電着塗料を電着塗装して焼付硬化乾燥後指定色調
の溶剤型アクリル−メラミン樹脂系上塗塗料を塗
装焼付乾燥し、オープン壁塗膜としていた。しか
し、近年、従来のものでは耐腐食性が長期間安定
せず、溶剤型塗装では、塗膜の発泡、“タレ”や
“スケ”が出やすく不良率が10〜30％も出る。そ
して、電子レンジのオーブン内面の塗装であるた
め、ロボツト、レシプロケーター、ロータリー式
塗装装置などの自動化塗装装置を設置しても、人
手による手吹き塗装が数人（４〜５人）いる。手
吹き作業者も塗料の吹付けによる“はね返り”を
あびて、塗料霧の汚染を受ける。粉体塗装による
オープン壁は前記、溶剤型塗装と同じく“スケ”
や“タマリ”がでたり、粉体塗装独特の間隙部不
連続塗装膜（ブリツヂ）が出来て見苦しい外観を
示す。そして、塗装膜厚も40〜50ミクロン以上の
100ミクロンとか200ミクロンになつて、電波もれ
を生じやすい問題がある。そして、機械加工組立
などによる塗油がオーブン継目から出て来て、粉
体塗装膜をはじかせるという表面仕上肌のきたな
い状態が（塗布する油の量が多いとひんぱんに）
生じる。さらに、下塗を電着で上塗を溶剤型アク
リル系焼付塗装の場合、従来から実施しているの
は下塗の電着にアニオン系の無公害元素（Pb，
Crの入らない塗料）を使用したクリーム色など
の彩色電着塗料を20〜30μ塗着させ焼付後、オー
ブン内面に指定彩色（クリーム色）のアクリル系
焼付硬化型の溶剤型塗料を20〜30μ塗着し、焼付
硬化させて成膜オーブン壁としている。この電着
−溶剤型アクリルの塗装では耐腐食性に劣り、
“折り曲げ”や“へこみ”の外傷で“キレツ”が
入る。上塗と下塗を同一色にしてスケを防止して
いるが上塗の塗膜厚み管理が塗装工程の吹付量と
塗装手順で管理することになるため、スケていて
もわからず製品になつてから耐食品汚染に劣る不
良がでている。これは、下塗として用いる電着塗
料のアニオン系無公害アクリル樹脂系、エポキシ
樹脂系の彩色塗料が塗膜形成完了後、耐汚染性に
よくないものであるから（電着用塗料樹脂でいま
だみつかつていない）、電着塗装後上塗に耐食品
汚染の優れた溶剤型アクリル系の塗料を塗布し、
成膜させても焼付硬化時150〜230℃の温度がかか
ると下塗の電着塗料樹脂成分が軟化して上塗の塗
料中にわずか溶出移行して、上塗の塗装膜厚がう
すいと顕著にあらわれて、100℃前後の単機能電
子レンジ作動で食品汚染が起こるようになる。即
ち、実際の調理で、食品が付着し加熱により高温
になつて固化あるいは炭化し、オーブン壁の清掃
後塗膜面の汚れが目立つか否かの食品汚染が生じ
て見苦しい状態になる。この原因は、上塗に耐食
品性のよいアクリル−メラミン系塗料を使用して
いるにもかかわらず下塗である電着塗料の上に塗
る上塗塗料の塗膜厚みがうすいことにある。即
ち、下塗の電着塗料は現在、食品汚染性に耐える
ものがなく、染色しやすい電着塗料の上に20μ以
下の塗膜で上塗が形成されていると、上塗の塗膜
を通して下塗の電着塗膜に食品中の有機染色物質
が到達し、染色するからである。電着塗料の彩用
は、効率よく塗着し、自動化ができ、廉価に仕上
げられること、及び耐腐食性の優れた塗膜を形成
するからである。しかし、現状は、前記した原因
で、市販品の中に汚染するものが多く存在する。
なぜ、耐食品汚染不良が起るかと言えば、食品汚
染性の悪い下塗電着塗料と食品汚染性の良い上塗
塗料とが同一色で仕上げられているため、仕上げ
終了完成品の塗膜の上塗がうすくても不良の見分
けがつかないためである。
〈目的〉
本考案は上記に鑑みてなされたもので、下塗の
色調と上塗の色調とを異ならしめることによつ
て、上塗の膜厚管理を行ないやすい電子レンジの
オーブンの提供を目的とするものである。
〈実施例〉
本考案の実施例として、第１図及び第２図に示
すように扉２、外箱３、オーブン４、機構部品５
（図示せず）などから構成する単機能電子レンジ
１のオーブン４において、第３図及び第４図に示
すオーブン内表面に天板６、胴板７、背板８、前
板９、外表面の天板６′、胴板７′、背板８′、前
板９′を塗装する。素地として、冷間圧延鋼板、
合金化溶融亜鉛めつき鋼板などの安価な鋼板を用
いて、第３図に示すオーブンを機械加工組立を行
い、このオーブン４を脱脂−水洗−化成被膜処理
−水洗−純水洗滌−水切乾燥などの塗装前処理工
程でリン酸鉄皮膜処理或はリン酸亜鉛皮膜処理を
行い、エポキシ樹脂を主成分とするPb，Cr，
Cd，Asなどの含有しない無公害で食品衛生法に
合格する黒色のカチオン電着塗料沿中に浸漬、通
電し、オーブン４の内外面と接合間隙に至る全表
面を20〜30μの塗膜・厚みに電着させ、水洗後焼
付硬化約160〜180℃20分行う。
上記、実施例の電着塗料は、表−１に示す関西
ペイントK.Kカチオン電着塗料商品名エレクロン
No.9210のエポキシ−ポリアミド系樹脂に硬化剤と
してブロツクイソシアネート樹脂を用いた黒色カ
チオン電着塗料である。
【表】
次に、オーブン４の背板外表面８′をそのまま
の黒色にするため、第５図のマスキング用キヤツ
プを背板外表面８′にかぶせて、指定色彩色の上
塗塗料を第３図に示すオーブン内面６，７，８と
前板９の壁面に表−２のピンキーホワイトのアク
リル−メラミン系樹脂塗料を約10±5μ位にうす
く塗布し、数分間室内放置して、表面にぬれがな
くなつた時に、表−３の指定色彩色のクリーミイ
ホワイト色アクリル−メラミン系樹脂塗料を約15
±5μの塗膜厚に塗布し、約160〜180℃、20分間
焼付を行う。
【表】
【表】
以上のようにして、仕上げた塗装膜は第１図か
ら第４図に示すように、オーブン４の内表面６，
７，８と前板９はクリーミイホワイト色、背板外
表面（うしろ）８′は黒色のツートンカラーにな
つて、オーブン外表面６′，７′，９′は黒色でわ
ずか上塗のクリーミイホワイトの塗料霧がかかつ
た、“しもふり”状態となつている。この６′，
７′，９′は第１図、第２図に示すように外箱３を
取付け組立するとかくれてしまう。背板外表面
８′は第１図のように外観部品として見えるので
意匠性が要求される。だから、第５図のマスキン
グキヤツプ１１を用いて６′，７′，９′のような
“しもふり”状態を避ける必要がある。また、第
５図のマスキングキヤツプに穴を無数にあけて、
一定のパターンを示す“水玉模様”や細い溝を適
宜設けて“ストライプ模様”を形成してもよい。
６′，７′，９′の“しもふり”は一定した模様に
ならず、みにくいパターンを形成するので背板外
表面８′には不向きである。
さらに、他の方法として、第１図、第２図の扉
２をオーブン４と同様、電着の黒色とし、オーブ
ン４の前板９をマスキングをして、黒色とした
２，９，８′が黒で、オーブン内表面６，７，８
をクリーミイホワイトにした“ツートンカラー”
も意匠性とあいまつて、扉２と前板９が黒である
ことからドアー開閉のくり返しで傷付きが目立ち
難くなり、同質であることから耐衝撃剥離にも耐
久性が向上する。さらに、ドアー開閉による塗装
面の耐久性を向上させようとすると、４フツ化ポ
リエチレン樹脂などの粉体を10％以下の量で黒色
アクリル−メラミン系樹脂塗料に配合して、塗装
した扉２の面にするとよい。
〈効果〉
本考案によれば、下塗として電着塗装をし、上
塗として溶剤型アクリル−メラミン系塗装を行う
ことによつて、耐食品汚染性の品質安定を図ると
共に下塗の電着塗装を外観面とすることによつ
て、余分の上塗塗料が不要となり、経済的な２色
塗装仕上げを得ることができる。 [Detailed Description of the Invention] <Technical Field> The present invention relates to a microwave oven, and particularly relates to an improvement in a microwave oven in which a colored coating film is formed on the inner surface of the oven wall. <Prior art> Conventionally, when painting the oven wall of a microwave oven, a solvent-based acrylic-melamine resin paint or an epoxy resin powder paint was used as an undercoat, taking into consideration food stain resistance, heat resistance, corrosion resistance, etc. Both top coats are painted in the specified color and finished. Further, an undercoating electrodeposition paint of a specified color was electrodeposited, baked to harden and dried, and then a solvent-based acrylic-melamine resin top coat of a specified color was baked and dried to form an open wall coating. However, in recent years, the corrosion resistance of conventional coatings has not been stable over a long period of time, and with solvent-based coatings, the paint film tends to foam, sag, and flake, resulting in a defective rate of 10 to 30%. Since the interior surface of the microwave oven is painted, even if automated painting equipment such as robots, reciprocators, and rotary painting equipment is installed, several people (4 to 5 people) are still involved in the hand-spraying process. Hand-spraying workers are also exposed to "splash" from spraying paint and are contaminated by paint mist. Powder coating on open walls is similar to solvent-based coating, as mentioned above.
This creates an unsightly appearance due to the appearance of smudges and discontinuous paint film (brittle) that is unique to powder coatings. And the coating film thickness is 40 to 50 microns or more.
There is a problem with radio wave leakage at 100 or 200 microns. Additionally, the oil applied during assembly and machining comes out of the oven joints, causing the powder coating film to repel, resulting in an unsightly surface finish (this happens frequently when a large amount of oil is applied).
arise. Furthermore, when the undercoat is electrodeposited and the topcoat is a solvent-based acrylic baking paint, the conventional method is to electrodeposit the undercoat using anionic non-polluting elements (Pb,
Apply 20 to 30μ of colored electrodeposition paint such as cream color using Cr-free paint, and after baking, apply 20 to 30μ of acrylic bake-curable solvent-based paint of specified color (cream color) on the inside of the oven. It is applied and baked to harden to form a film oven wall. This electrodeposition-solvent acrylic coating has poor corrosion resistance,
“Kiretsu” occurs due to trauma such as “bending” or “denting”. The top coat and undercoat are made the same color to prevent scratches, but since the thickness of the top coat is controlled by the amount of spray and the painting procedure during the painting process, you won't know if there is any scratches, and you will have to worry about the durability of the product. There are defects that are inferior to food contamination. This is because the anionic non-polluting acrylic resin-based and epoxy resin-based colored paints used as undercoats do not have good stain resistance after the coating film has been formed. After electrodeposition coating, a solvent-based acrylic paint with excellent food stain resistance is applied as the top coat.
Even if a film is formed, if a temperature of 150 to 230°C is applied during baking and curing, the resin component of the electrodeposition paint in the undercoat will soften and be slightly eluted into the topcoat, which will become noticeable if the topcoat film is thin. Therefore, food contamination occurs when a single-function microwave oven operates at temperatures around 100℃. That is, during actual cooking, food adheres to the oven and becomes heated to a high temperature, solidifying or carbonizing, and after cleaning the oven wall, contamination of the food is caused by conspicuous stains on the coating surface, resulting in an unsightly condition. The reason for this is that, although an acrylic-melamine paint with good food resistance is used as the top coat, the film thickness of the top coat applied over the electrodeposition paint, which is the base coat, is thin. In other words, there is currently no undercoat electrodeposition paint that is resistant to food contamination, and if a top coat is formed with a coating film of 20μ or less on top of an electrodeposition paint that is easily dyed, the undercoat voltage will pass through the top coat film. This is because the organic dyeing substance in the food reaches the deposited coating and stains it. Electrodeposition paints are used for coloring because they can be applied efficiently, can be automated, can be finished at low cost, and form coatings with excellent corrosion resistance. However, at present, many commercially available products are contaminated due to the causes mentioned above.
The reason why defects in food contamination resistance occur is that the undercoat electrodeposition paint, which has poor food contamination properties, and the top coat paint, which has good food contamination properties, are finished in the same color. This is because it is difficult to distinguish between defects even if they are thin. <Purpose> The present invention was made in view of the above, and aims to provide a microwave oven in which the thickness of the top coat can be easily controlled by making the color tone of the undercoat different from the color tone of the top coat. It is. <Example> As an example of the present invention, as shown in FIGS. 1 and 2, a door 2 , an outer box 3 , an oven 4 , and a mechanical part 5 are
In the oven 4 of the single-function microwave oven 1 consisting of (not shown), etc., the inner surface of the oven shown in FIGS. Paint the top plate 6', body plate 7', back plate 8', and front plate 9'. As a base material, cold rolled steel plate,
The oven shown in Fig. 3 is machined and assembled using inexpensive steel plates such as alloyed hot-dip galvanized steel plates, and the oven 4 is subjected to degreasing, washing with water, chemical conversion coating treatment, washing with water, washing with pure water, draining and drying, etc. In the pre-painting process, iron phosphate film treatment or zinc phosphate film treatment is performed to remove Pb, Cr, and
The entire surface of the oven 4 , including the inner and outer surfaces and the bonding gap, is coated with a coating film of 20 to 30 μm by dipping it in a black cationic electrodeposition paint that does not contain Cd, As, etc. and is pollution-free and passes the Food Sanitation Law. Electrodeposit to a certain thickness, wash with water, and bake at 160-180°C for 20 minutes. The electrocoating paints used in the above examples are Kansai Paint KK cationic electrocoating paints (trade name: Elekron) shown in Table 1.
This is a black cationic electrodeposition paint using No. 9210 epoxy-polyamide resin and blocking isocyanate resin as a curing agent. [Table] Next, in order to make the outer surface 8' of the back plate of the oven 4 black, cover the outer surface 8' of the back plate with the masking cap shown in Fig. 5, and apply a third coat of top coat in the specified color. Apply a thin layer of Pinky White acrylic-melamine resin paint shown in Table 2 to the walls of the oven inner surfaces 6, 7, 8 and front plate 9 shown in the figure to a thickness of approximately 10±5μ, and leave it indoors for several minutes to coat the surface. When the wetness is gone, apply approximately 15 cm of creamy white acrylic-melamine resin paint of the specified color in Table 3.
Apply to a coating thickness of ±5μ and bake at approximately 160 to 180℃ for 20 minutes. [Table] [Table] As shown in FIGS. 1 to 4 , the finished coating film is as shown in FIGS.
7, 8 and the front plate 9 are a creamy white color, the outer surface (back) of the back plate 8' is a two-tone black color, and the outer surface of the oven 6', 7', 9' is black with a slight creamy white coating. The paint is foggy and looks like it's in a ``shimofuri'' state. This 6′,
7' and 9' are hidden when the outer box 3 is attached and assembled as shown in FIGS. 1 and 2. Since the outer surface 8' of the back plate is visible as an external part as shown in FIG. 1, it is required to have a good design. Therefore, it is necessary to use the masking cap 11 shown in FIG. 5 to avoid the "flip-flop" situations such as those shown at 6', 7', and 9'. Also, make countless holes in the masking cap shown in Figure 5,
A "polka dot pattern" showing a certain pattern or a "stripe pattern" may be formed by appropriately providing thin grooves.
The "shimofuri" patterns 6', 7', and 9' do not have a uniform pattern and form an ugly pattern, so they are not suitable for the outer surface of the back plate 8'. Furthermore, as another method, the door 2 in FIGS. 1 and 2 may be made black by electrodeposition like the oven 4 , and the front plate 9 of the oven 4 may be made black by masking . , 9, 8' are black, and the oven inner surface 6, 7, 8
“Two-tone color” with creamy white
In addition to the design, since the door 2 and front plate 9 are black, scratches from repeated opening and closing of the door are less noticeable, and since they are of the same material, durability against impact peeling is improved. Furthermore, in an attempt to improve the durability of the painted surface when the door is opened and closed, powders such as tetrafluoroethylene resin are added to the black acrylic-melamine resin paint in an amount of less than 10 %. It is best to face it. <Effects> According to the present invention, by applying electrodeposition coating as the undercoat and solvent-based acrylic-melamine coating as the topcoat, it is possible to stabilize the quality of food stain resistance and improve the appearance of the electrodeposition coating as the undercoat. By applying it as a surface, no extra top coat is required and an economical two-color paint finish can be obtained.
【図面の簡単な説明】[Brief explanation of drawings]
第１図は本考案の電子レンジ１の側方斜視図
で、黒色扉２、外箱３、オーブン４の背板外表面
８′（黒色）を示す。第２図は第１図同様電子レ
ンジ１の斜視図で、扉２、外箱３、オーブン４の
内表面、胴板７、背板８、前板９のクリーミイホ
ワイト色を示す。第３図は、本考案のオーブン４
の斜視図で、天板６、胴板７、背板８、前板９は
クリーミイホワイト色で、胴板の外面７′は黒と
クリーミイホワイト色の“シモフリ模様”を示
す。第４図はオーブン４の後方からの斜視図で、
背板８′は黒色で、６′，７′，９′は黒とクリーミ
イホワイト色の“シモフリ模様”を示す。第５図
は背板８′のマスキングキヤツプ１１の斜視図で
ある。
FIG. 1 is a side perspective view of the microwave oven 1 of the present invention, showing the black door 2 , the outer box 3 , and the outer surface 8' of the back plate of the oven 4 (black). FIG. 2 is a perspective view of the microwave oven 1 similar to FIG. 1, showing the creamy white color of the door 2 , the outer box 3 , the inner surface of the oven 4 , the body plate 7, the back plate 8, and the front plate 9. Figure 3 shows the oven 4 of the present invention.
In this perspective view, the top plate 6, body plate 7, back plate 8, and front plate 9 are creamy white, and the outer surface 7' of the body plate shows a "shimofuri pattern" of black and creamy white. FIG. 4 is a perspective view of the oven 4 from the rear.
The back plate 8' is black, and the panels 6', 7', and 9' have a "shimofuri pattern" of black and creamy white. FIG. 5 is a perspective view of the masking cap 11 of the back plate 8'.