Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
2000-09-08
2001-10-09
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S328000, C428S336000, C428S457000, C428S458000, C428S467000, C428S323000, C106S403000, C106S404000, C524S441000, C523S200000
Reexamination Certificate
active
06299993
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a metallic coating composition capable of providing a metallic coating which provides a metal-surface-like luster exhibiting some specular reflection as exhibited by metal foil or metal plating surfaces, and also to a method of forming a multilayer coating utilizing the metallic coating.
2. Description of Related Art
Known metallic coatings contain metal flakes, such as aluminum flakes, and are typically applied to automobile bodies. Such metallic coatings for typical application to automobile bodies provide a unique designing, e.g., sparkling effect.
There are known electrical appliance and automobile parts which provide a metal-surface-like luster such as provided by a metal surface, which is different in nature from the sparkling luster provided by the aforementioned metallic coatings. Such parts with the metal-surface-like luster generally have a surface covered with a metal foil such as an aluminum foil. Alternatively, a thin film of meal is deposited on the surface by means of plating or vapor deposition.
However, in the technique of covering a substrate surface with the metal foil, a problem arises when the substrate has a complicated configuration having irregular surfaces. In such a case, localized wrinkling occurs in the foil to result in uneven coverage of the surface with the foil. Where the plating technique is utilized, the substrate is limited to electrically conductive materials. Otherwise, a conductive layer must be provided on the substrate surface. Also, the requirement of dipping the whole substrate in a plating bath complicates a manufacturing process and constrains plant design. When utilizing the vapor deposition technique, the substrate must be placed in a vacuumed or pressure-reduced container, making difficult to apply the technique to large-sized substrates. The requirement of pressure reduction also imposes a practical limitation on a manufacturing process. The practice of the aforementioned conventional techniques, which involve either adhesion of a metal foil or deposition of a metallic thin film by means of plating or vapor deposition, produces metallic coats which sometimes provide excessively intense gross, i.e., specular gloss. In such an instance, a special processing, such as surface roughening, is further required to reduce the gloss.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a metallic coating composition capable of producing a metallic coating which provides an appropriate metal-surface-like luster, as well as a method of forming a multilayer coating utilizing the metallic coating composition.
The metallic coating composition of the present invention is characterized as containing bright pigments in the form of metal flakes produced by finely dividing a vapor-deposited metal layer.
The bright pigment for use in the present invention is not particularly limited, so long as it is in the form of a metal flake produced by finely dividing a vapor-deposited metal layer. Such bright pigments are obtainable generally by vapor depositing a metal, layer on a base film, separating the metal layer from the base film, and finely dividing the vapor-deposited metal layer into metal flakes. The thickness of the vapor-deposited metal layer, i.e., the thickness of the metal flake obtained by finely dividing the film is preferably in the range of 100-1000 Å. It is also preferred that the finely divided metal flake has a particle diameter ranging from about 5 &mgr;m to about 100 &mgr;m.
The material types of the vapor-deposited metal layer are not particularly limited, and include aluminum, gold, silver, copper, brass, titanium, chromium, nickel, nickel chrome, and stainless steel, for example.
Since the bright pigment for use in the present invention is in the form of the metal flake produced by finely dividing the vapor-deposited metal layer, its thickness is very small. Accordingly, the hereinafter-described planar orientation of the bright pigments results in formation of a flat-surfaced metallic coating layer which provides for the metal-surface-like luster. On the other hand, metal flakes, such as aluminum flakes, employed for formulation of conventional metallic coating compositions are generally produced by pulverizing metallic particles or foils as by a ball mill. Such metal flakes are relatively thick and have irregular surfaces. Accordingly, the planar orientation of these metal flakes fails to produce a flat surface, i.e., fails to provide for the metal-surface-like luster which is attainable by the present invention.
The bright pigment for use in the present invention can be manufactured by using the techniques such as disclosed in Japanese Patent Laid-open No. 02-8268 and International Publication No. WO 93/23481. For example, a plastic film, such as an OPP (oriented polypropylene), CPP (crystalline polypropylene) or PET (polyethylene terephthalate) film, is employed as a base film to which a release coating is applied. A metal layer is deposited on the release coating. After deposition of the metal layer, a top coating may be applied to an outside surface of the metal layer to prevent oxidation thereof. Examples of applicable release and top coatings include resins, such as acrylic resin, vinyl resin, nitrocellulose, cellulosic resin, polyamide resin, polyester resin, EVA resin, chlorinated PP resin, chlorinated EVA resin, and petroleum resin.
The vapor-deposited metal layer is separated from the base film for subsequent comminution into metal flakes. The residual release and/or top coatings that may remain on the metal flake dissolve in a solvent generally used in metallic coating compositions.
The metallic coating composition of the present invention can be formulated by mixing the bright pigments obtainable by the method as stated above, a solvent, and an additive(s) when needed. For the metallic coating produced from the composition of the present invention, the pigment weight concentration (PWC) of the bright pigment in the coating composition is preferably controlled at as high a level as possible. It is preferably at least 15%, more preferably at least 50%, and still more preferably at least 70%. In the most preferred embodiment of the present invention, the metallic coating composition consists essentially of the bright pigments and the solvent. By “the metallic coating composition consists essentially of the bright pigments and the solvent”, it is meant that the metallic coating composition either contains no ingredient other than the bright pigments and the solvent, or contains a small amount of resin or additive in addition to the bright pigments and the solvent, i.e., exhibits the PWC of at least 95%. The increased level of PWC for the metallic coating is effective to promote the planar orientation of the bright pigments in the resulting metallic coating, which serves to reduce sparkling effect of the bright pigments, leading to an increased tendency of imparting more appropriate metal-surface-like luster to the resulting metallic coating.
The type of the solvent for inclusion in the metallic coating composition of the present invention can be suitably chosen depending upon the types of the release and top coatings employed for manufacturing the bright pigments, and the type of an undercoating over which the metallic coating is applied. Examples of suitable solvents include toluene, xylene, n-hexane, cyclohexane, methyl acetate, ethyl acetate, isopropyl acetate, n-propyl acetate, n-butyl acetate, isobutyl acetate, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, acetone, methylethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether, propylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, and hydrocarbon solvents such as
Nakasuji Hiroyuki
Terada Sadao
Jones Deborah
McNeil Jennifer
Nippon Paint Co. Ltd.
Townsend & Banta
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