Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2000-12-18
2003-12-16
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S328000, C428S411100
Reexamination Certificate
active
06663951
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to curable effect providing coating systems and more particularly to two layer effect providing coating systems.
BACKGROUND OF THE INVENTION
Coatings have long been used to provide a protective finish for vulnerable or exposed substrates. Such systems typically provide protection from the effects of outdoor exposure and use as well as resistance to corrosion and chemicals such as acids, solvents and the like. However, the atheistic visual appearance or effect provided by a coating composition or system is equally important, particularly in the automotive industry.
Although automotive basecoats and topcoats were once primarily relied upon to provide a single color effect, more recent years have seen the introduction of metallic, pearlescent and opalescent color effects. Metallic effects, in which the appearance of sparkle is imparted to a finished film, are achieved by the introduction of finely divided metallic flake or mica particles into one or more layers of the coating system. Typical systems of this type are disclosed in U.S. Pat. Nos. 4,048,136; 4,499,143; and 4,605,687. Pearlescent or opalescent color effects have been achieved by the introduction of particles of mica which have previously been encapsulated in a thin layer of a metal oxide into one or more layers of the coating system. Typical systems of this type are disclosed in U.S. Pat. Nos. 4,530,258; 4,457,410; 4,551,491; 4,598,015; 4,498,020; and 4,615,940.
While many of these systems provide unique and desirable color and special appearance effects, improvements in visual appearance are constantly being sought. Improvements and new effects that are ever more lustrous, satiny or liquid in appearance are desired, especially with improved depth and clarity as well as special color highlights, hues and shifts. The most desirable appearance effects are those which make traditional colors such as white, beige, gray and the like, more interesting and appealing to the consumer.
Thus, more dramatic hue shifts, particularly in the angle of viewing available to the casual observer, i.e., a 25° angle to 75° angle of viewing, are especially desired. For example, an observer of a coated surface would initially percieve a first color or effect when said coated surface is viewed at a 0° angle, i.e., perpendicular to the observers' eye or directly opposite the observer's line of sight. However, when the coated surface is slowly moved so as to be oblique to the observer's line of sight, i.e., at a 25° to 75° angle of viewing, the observer would like to see a dramatic hue or color shift relative that first perceived color or effect. Thus, what is desired is a particular color effect which is dependent upon the angle of viewing. Such particularly desired hue shifts can provide highlight colors of red, blue, green, gold, violet, or orange to a coating system, resulting in a more aesthetically appealing appearance and effect.
While the use of metal oxide coated micas is known in coatings, i.e., see U.S. Pat. Nos. 3,087,829, 4,456,486, 4,551,491, 4,598,015, and 5,741,355, such compositions have failed to provide dramatic color shifts at the various angles of viewing. This is especially true in regards to unique appearance effects in white and/or pastel automotive body colors.
Moreover, the prior art has failed to date to provide such visual effect improvements in commercially feasible effect providing coating systems. Those prior art special effect coating systems which do provide prior art visual appearance effects generally require multilayer applications. The prior art has utilized such multilayer systems in order to balance appearance considerations with durability and protection requirements.
For example, U.S. Pat. Nos. 4,539,258 and 4,615,940 describe a multilayer coating system wherein a least three coating layers must be used to provide the desired opalescent effects. In such systems, the opalescent effect derives from the use of a primer layer or intermediate layer containing metal oxide encapsulated mica particles in addition to a basecoat and a clearcoat. The desired visual effects are obtained only with the use of the disclosed third layer. Failure to use the required third layer in conjunction with both a basecoat and a transparent topcoat results in a nondesireable visual appearance.
BASF Corporation of Southfield, Mich. provides a commerically available ivory three-layer coating system wherein a transparent topcoat is applied over an intermediate layer comprising metal oxide encapsulated micas. The intermediate layer is applied over a pigmented basecoat which has been tinted to match the “flop” or hue shift of the intermediate layer.
However, the application of a third effect providing coating layer is greatly disfavored in view of practical manufacturing considerations. The application of a three-layer effect providing coating system requires more space, equipment, time, and/or expense than that required to apply a two-layer effect providing coating system. It may also result in the discharge of greater amounts of volatile organic solvents as a result of the additional application step. Thus, most automotive manufacturers require the use of no more than a two-layer effect providing coating system. That is, the desired appearance must be provided by either a single topcoat or a two-coat composite system, the latter highly favored and most often being a pigmented basecoat followed by a transparent clearcoat.
Finally, many of the prior art effect providing coating systems suffer from mottling, a visual defect which detracts from the appearance of the finished film. Mottling may generally be described as an undesirable variation in the visual appearance and color at a particular angle of viewing. Mottling is believed to be a function of the varied orientation of flaked pigments in a coating, usually a basecoat, and can occur as a result of various application problems, or as a result of an inherently weak basecoat rheology system.
Mottling can sometimes be fixed by improving basecoat application or rheology. In other systems, the only possibility is to change the flake or pigment system of the basecoat or surrounding coatings, especially transparent or semi-transparent flake containing coatings. It would be advantageous to provide an effect providing coating system which provides a pearlescent or luminescent appearance and which is less likely to exhibit mottling relative to prior art effect providing coating systems.
Thus, it is an object of the instant invention to provide a two-layer coating system which provides a visual appearance and effect previously obtainable only with the use of a three layer effect providing coating system.
It is another object of the instant invention to provide a two-layer coating system which provides improvements in visual appearance and effect relative to that previously obtainable with prior art three-layer effect providing coating systems.
It is a particular object of the invention to provide a two-layer coating system that provides dramatic improvements in hue shift at viewing angles of from 25° to 75° degrees.
Another desired object of the invention is provide such dramatic hue shifts in conjunction with traditional colors such as white, beige, gray and the like so as to provide heretofore unknown visual effects in a two-layer coating system.
SUMMARY OF THE INVENTION
These and other objects have been achieved with the instant invention. It has unexpectedly been found that the use of certain metal oxide encapsulated mica pigments in a particular two-layer coating system results in new and improved visual effects while maintaining the performance requirements and characteristics of a commercially acceptable three-layer effect providing coating system.
The curable effect providing coating system of the invention consists essentially of a first layer consisting of a first coating composition (a), and a transparent second layer applied directly to the first layer and consisting of a second coating composition (b) comprising an effe
Ahmed Sheeba
BASF Corporation
Thibodeau Paul
LandOfFree
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